--- _id: '1021' abstract: - lang: eng text: Most flows in nature and engineering are turbulent because of their large velocities and spatial scales. Laboratory experiments on rotating quasi-Keplerian flows, for which the angular velocity decreases radially but the angular momentum increases, are however laminar at Reynolds numbers exceeding one million. This is in apparent contradiction to direct numerical simulations showing that in these experiments turbulence transition is triggered by the axial boundaries. We here show numerically that as the Reynolds number increases, turbulence becomes progressively confined to the boundary layers and the flow in the bulk fully relaminarizes. Our findings support that turbulence is unlikely to occur in isothermal constant-density quasi-Keplerian flows. article_processing_charge: No author: - first_name: Jose M full_name: Lopez Alonso, Jose M id: 40770848-F248-11E8-B48F-1D18A9856A87 last_name: Lopez Alonso orcid: 0000-0002-0384-2022 - first_name: Marc full_name: Avila, Marc last_name: Avila citation: ama: Lopez Alonso JM, Avila M. Boundary layer turbulence in experiments on quasi Keplerian flows. Journal of Fluid Mechanics. 2017;817:21-34. doi:10.1017/jfm.2017.109 apa: Lopez Alonso, J. M., & Avila, M. (2017). Boundary layer turbulence in experiments on quasi Keplerian flows. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2017.109 chicago: Lopez Alonso, Jose M, and Marc Avila. “Boundary Layer Turbulence in Experiments on Quasi Keplerian Flows.” Journal of Fluid Mechanics. Cambridge University Press, 2017. https://doi.org/10.1017/jfm.2017.109. ieee: J. M. Lopez Alonso and M. Avila, “Boundary layer turbulence in experiments on quasi Keplerian flows,” Journal of Fluid Mechanics, vol. 817. Cambridge University Press, pp. 21–34, 2017. ista: Lopez Alonso JM, Avila M. 2017. Boundary layer turbulence in experiments on quasi Keplerian flows. Journal of Fluid Mechanics. 817, 21–34. mla: Lopez Alonso, Jose M., and Marc Avila. “Boundary Layer Turbulence in Experiments on Quasi Keplerian Flows.” Journal of Fluid Mechanics, vol. 817, Cambridge University Press, 2017, pp. 21–34, doi:10.1017/jfm.2017.109. short: J.M. Lopez Alonso, M. Avila, Journal of Fluid Mechanics 817 (2017) 21–34. date_created: 2018-12-11T11:49:44Z date_published: 2017-04-25T00:00:00Z date_updated: 2023-09-22T09:39:46Z day: '25' department: - _id: BjHo doi: 10.1017/jfm.2017.109 external_id: isi: - '000398179100006' intvolume: ' 817' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1608.05527 month: '04' oa: 1 oa_version: Submitted Version page: 21 - 34 project: - _id: 255008E4-B435-11E9-9278-68D0E5697425 grant_number: RGP0065/2012 name: Information processing and computation in fish groups publication: Journal of Fluid Mechanics publication_identifier: issn: - '00221120' publication_status: published publisher: Cambridge University Press publist_id: '6371' quality_controlled: '1' scopus_import: '1' status: public title: Boundary layer turbulence in experiments on quasi Keplerian flows type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 817 year: '2017' ... --- _id: '792' abstract: - lang: eng text: The chaotic dynamics of low-dimensional systems, such as Lorenz or Rössler flows, is guided by the infinity of periodic orbits embedded in their strange attractors. Whether this is also the case for the infinite-dimensional dynamics of Navier–Stokes equations has long been speculated, and is a topic of ongoing study. Periodic and relative periodic solutions have been shown to be involved in transitions to turbulence. Their relevance to turbulent dynamics – specifically, whether periodic orbits play the same role in high-dimensional nonlinear systems like the Navier–Stokes equations as they do in lower-dimensional systems – is the focus of the present investigation. We perform here a detailed study of pipe flow relative periodic orbits with energies and mean dissipations close to turbulent values. We outline several approaches to reduction of the translational symmetry of the system. We study pipe flow in a minimal computational cell at Re=2500, and report a library of invariant solutions found with the aid of the method of slices. Detailed study of the unstable manifolds of a sample of these solutions is consistent with the picture that relative periodic orbits are embedded in the chaotic saddle and that they guide the turbulent dynamics. article_processing_charge: No author: - first_name: Nazmi B full_name: Budanur, Nazmi B id: 3EA1010E-F248-11E8-B48F-1D18A9856A87 last_name: Budanur orcid: 0000-0003-0423-5010 - first_name: Kimberly full_name: Short, Kimberly last_name: Short - first_name: Mohammad full_name: Farazmand, Mohammad last_name: Farazmand - first_name: Ashley full_name: Willis, Ashley last_name: Willis - first_name: Predrag full_name: Cvitanović, Predrag last_name: Cvitanović citation: ama: Budanur NB, Short K, Farazmand M, Willis A, Cvitanović P. Relative periodic orbits form the backbone of turbulent pipe flow. Journal of Fluid Mechanics. 2017;833:274-301. doi:10.1017/jfm.2017.699 apa: Budanur, N. B., Short, K., Farazmand, M., Willis, A., & Cvitanović, P. (2017). Relative periodic orbits form the backbone of turbulent pipe flow. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2017.699 chicago: Budanur, Nazmi B, Kimberly Short, Mohammad Farazmand, Ashley Willis, and Predrag Cvitanović. “Relative Periodic Orbits Form the Backbone of Turbulent Pipe Flow.” Journal of Fluid Mechanics. Cambridge University Press, 2017. https://doi.org/10.1017/jfm.2017.699. ieee: N. B. Budanur, K. Short, M. Farazmand, A. Willis, and P. Cvitanović, “Relative periodic orbits form the backbone of turbulent pipe flow,” Journal of Fluid Mechanics, vol. 833. Cambridge University Press, pp. 274–301, 2017. ista: Budanur NB, Short K, Farazmand M, Willis A, Cvitanović P. 2017. Relative periodic orbits form the backbone of turbulent pipe flow. Journal of Fluid Mechanics. 833, 274–301. mla: Budanur, Nazmi B., et al. “Relative Periodic Orbits Form the Backbone of Turbulent Pipe Flow.” Journal of Fluid Mechanics, vol. 833, Cambridge University Press, 2017, pp. 274–301, doi:10.1017/jfm.2017.699. short: N.B. Budanur, K. Short, M. Farazmand, A. Willis, P. Cvitanović, Journal of Fluid Mechanics 833 (2017) 274–301. date_created: 2018-12-11T11:48:32Z date_published: 2017-12-25T00:00:00Z date_updated: 2023-09-27T12:17:35Z day: '25' department: - _id: BjHo doi: 10.1017/jfm.2017.699 external_id: isi: - '000414641700001' intvolume: ' 833' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1705.03720 month: '12' oa: 1 oa_version: Submitted Version page: 274 - 301 project: - _id: 25636330-B435-11E9-9278-68D0E5697425 grant_number: 11-NSF-1070 name: ROOTS Genome-wide Analysis of Root Traits publication: Journal of Fluid Mechanics publication_identifier: issn: - '00221120' publication_status: published publisher: Cambridge University Press publist_id: '6862' quality_controlled: '1' scopus_import: '1' status: public title: Relative periodic orbits form the backbone of turbulent pipe flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 833 year: '2017' ... --- _id: '824' abstract: - lang: eng text: 'In shear flows at transitional Reynolds numbers, localized patches of turbulence, known as puffs, coexist with the laminar flow. Recently, Avila et al. (Phys. Rev. Lett., vol. 110, 2013, 224502) discovered two spatially localized relative periodic solutions for pipe flow, which appeared in a saddle-node bifurcation at low Reynolds number. Combining slicing methods for continuous symmetry reduction with Poincaré sections for the first time in a shear flow setting, we compute and visualize the unstable manifold of the lower-branch solution and show that it extends towards the neighbourhood of the upper-branch solution. Surprisingly, this connection even persists far above the bifurcation point and appears to mediate the first stage of the puff generation: amplification of streamwise localized fluctuations. When the state-space trajectories on the unstable manifold reach the vicinity of the upper branch, corresponding fluctuations expand in space and eventually take the usual shape of a puff.' article_number: R1 article_processing_charge: No author: - first_name: Nazmi B full_name: Budanur, Nazmi B id: 3EA1010E-F248-11E8-B48F-1D18A9856A87 last_name: Budanur orcid: 0000-0003-0423-5010 - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Budanur NB, Hof B. Heteroclinic path to spatially localized chaos in pipe flow. Journal of Fluid Mechanics. 2017;827. doi:10.1017/jfm.2017.516 apa: Budanur, N. B., & Hof, B. (2017). Heteroclinic path to spatially localized chaos in pipe flow. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2017.516 chicago: Budanur, Nazmi B, and Björn Hof. “Heteroclinic Path to Spatially Localized Chaos in Pipe Flow.” Journal of Fluid Mechanics. Cambridge University Press, 2017. https://doi.org/10.1017/jfm.2017.516. ieee: N. B. Budanur and B. Hof, “Heteroclinic path to spatially localized chaos in pipe flow,” Journal of Fluid Mechanics, vol. 827. Cambridge University Press, 2017. ista: Budanur NB, Hof B. 2017. Heteroclinic path to spatially localized chaos in pipe flow. Journal of Fluid Mechanics. 827, R1. mla: Budanur, Nazmi B., and Björn Hof. “Heteroclinic Path to Spatially Localized Chaos in Pipe Flow.” Journal of Fluid Mechanics, vol. 827, R1, Cambridge University Press, 2017, doi:10.1017/jfm.2017.516. short: N.B. Budanur, B. Hof, Journal of Fluid Mechanics 827 (2017). date_created: 2018-12-11T11:48:42Z date_published: 2017-08-18T00:00:00Z date_updated: 2023-09-26T16:17:43Z day: '18' department: - _id: BjHo doi: 10.1017/jfm.2017.516 external_id: isi: - '000408326300001' intvolume: ' 827' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1703.10484 month: '08' oa: 1 oa_version: Submitted Version publication: Journal of Fluid Mechanics publication_identifier: issn: - '00221120' publication_status: published publisher: Cambridge University Press publist_id: '6824' quality_controlled: '1' scopus_import: '1' status: public title: Heteroclinic path to spatially localized chaos in pipe flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 827 year: '2017' ... --- _id: '745' abstract: - lang: eng text: 'Fluid flows in nature and applications are frequently subject to periodic velocity modulations. Surprisingly, even for the generic case of flow through a straight pipe, there is little consensus regarding the influence of pulsation on the transition threshold to turbulence: while most studies predict a monotonically increasing threshold with pulsation frequency (i.e. Womersley number, ), others observe a decreasing threshold for identical parameters and only observe an increasing threshold at low . In the present study we apply recent advances in the understanding of transition in steady shear flows to pulsating pipe flow. For moderate pulsation amplitudes we find that the first instability encountered is subcritical (i.e. requiring finite amplitude disturbances) and gives rise to localized patches of turbulence (''puffs'') analogous to steady pipe flow. By monitoring the impact of pulsation on the lifetime of turbulence we map the onset of turbulence in parameter space. Transition in pulsatile flow can be separated into three regimes. At small Womersley numbers the dynamics is dominated by the decay turbulence suffers during the slower part of the cycle and hence transition is delayed significantly. As shown in this regime thresholds closely agree with estimates based on a quasi-steady flow assumption only taking puff decay rates into account. The transition point predicted in the zero limit equals to the critical point for steady pipe flow offset by the oscillation Reynolds number (i.e. the dimensionless oscillation amplitude). In the high frequency limit on the other hand, puff lifetimes are identical to those in steady pipe flow and hence the transition threshold appears to be unaffected by flow pulsation. In the intermediate frequency regime the transition threshold sharply drops (with increasing ) from the decay dominated (quasi-steady) threshold to the steady pipe flow level.' article_processing_charge: No author: - first_name: Duo full_name: Xu, Duo id: 3454D55E-F248-11E8-B48F-1D18A9856A87 last_name: Xu - first_name: Sascha full_name: Warnecke, Sascha last_name: Warnecke - first_name: Baofang full_name: Song, Baofang last_name: Song - first_name: Xingyu full_name: Ma, Xingyu id: 34BADBA6-F248-11E8-B48F-1D18A9856A87 last_name: Ma orcid: 0000-0002-0179-9737 - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Xu D, Warnecke S, Song B, Ma X, Hof B. Transition to turbulence in pulsating pipe flow. Journal of Fluid Mechanics. 2017;831:418-432. doi:10.1017/jfm.2017.620 apa: Xu, D., Warnecke, S., Song, B., Ma, X., & Hof, B. (2017). Transition to turbulence in pulsating pipe flow. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2017.620 chicago: Xu, Duo, Sascha Warnecke, Baofang Song, Xingyu Ma, and Björn Hof. “Transition to Turbulence in Pulsating Pipe Flow.” Journal of Fluid Mechanics. Cambridge University Press, 2017. https://doi.org/10.1017/jfm.2017.620. ieee: D. Xu, S. Warnecke, B. Song, X. Ma, and B. Hof, “Transition to turbulence in pulsating pipe flow,” Journal of Fluid Mechanics, vol. 831. Cambridge University Press, pp. 418–432, 2017. ista: Xu D, Warnecke S, Song B, Ma X, Hof B. 2017. Transition to turbulence in pulsating pipe flow. Journal of Fluid Mechanics. 831, 418–432. mla: Xu, Duo, et al. “Transition to Turbulence in Pulsating Pipe Flow.” Journal of Fluid Mechanics, vol. 831, Cambridge University Press, 2017, pp. 418–32, doi:10.1017/jfm.2017.620. short: D. Xu, S. Warnecke, B. Song, X. Ma, B. Hof, Journal of Fluid Mechanics 831 (2017) 418–432. date_created: 2018-12-11T11:48:17Z date_published: 2017-11-25T00:00:00Z date_updated: 2023-09-27T12:28:12Z day: '25' department: - _id: BjHo doi: 10.1017/jfm.2017.620 ec_funded: 1 external_id: isi: - '000412934800005' intvolume: ' 831' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1709.03738 month: '11' oa: 1 oa_version: Submitted Version page: 418 - 432 project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin publication: Journal of Fluid Mechanics publication_identifier: issn: - '00221120' publication_status: published publisher: Cambridge University Press publist_id: '6922' quality_controlled: '1' scopus_import: '1' status: public title: Transition to turbulence in pulsating pipe flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 831 year: '2017' ... --- _id: '673' abstract: - lang: eng text: We present a numerical study of wavy supercritical cylindrical Couette flow between counter-rotating cylinders in which the wavy pattern propagates either prograde with the inner cylinder or retrograde opposite the rotation of the inner cylinder. The wave propagation reversals from prograde to retrograde and vice versa occur at distinct values of the inner cylinder Reynolds number when the associated frequency of the wavy instability vanishes. The reversal occurs for both twofold and threefold symmetric wavy vortices. Moreover, the wave propagation reversal only occurs for sufficiently strong counter-rotation. The flow pattern reversal appears to be intrinsic in the system as either periodic boundary conditions or fixed end wall boundary conditions for different system sizes always result in the wave propagation reversal. We present a detailed bifurcation sequence and parameter space diagram with respect to retrograde behavior of wavy flows. The retrograde propagation of the instability occurs when the inner Reynolds number is about two times the outer Reynolds number. The mechanism for the retrograde propagation is associated with the inviscidly unstable region near the inner cylinder and the direction of the global average azimuthal velocity. Flow dynamics, spatio-temporal behavior, global mean angular velocity, and torque of the flow with the wavy pattern are explored. article_number: '053103' article_processing_charge: No author: - first_name: Sebastian full_name: Altmeyer, Sebastian id: 2EE67FDC-F248-11E8-B48F-1D18A9856A87 last_name: Altmeyer orcid: 0000-0001-5964-0203 - first_name: Richard full_name: Lueptow, Richard last_name: Lueptow citation: ama: Altmeyer S, Lueptow R. Wave propagation reversal for wavy vortices in wide gap counter rotating cylindrical Couette flow. Physical Review E. 2017;95(5). doi:10.1103/PhysRevE.95.053103 apa: Altmeyer, S., & Lueptow, R. (2017). Wave propagation reversal for wavy vortices in wide gap counter rotating cylindrical Couette flow. Physical Review E. American Physical Society. https://doi.org/10.1103/PhysRevE.95.053103 chicago: Altmeyer, Sebastian, and Richard Lueptow. “Wave Propagation Reversal for Wavy Vortices in Wide Gap Counter Rotating Cylindrical Couette Flow.” Physical Review E. American Physical Society, 2017. https://doi.org/10.1103/PhysRevE.95.053103. ieee: S. Altmeyer and R. Lueptow, “Wave propagation reversal for wavy vortices in wide gap counter rotating cylindrical Couette flow,” Physical Review E, vol. 95, no. 5. American Physical Society, 2017. ista: Altmeyer S, Lueptow R. 2017. Wave propagation reversal for wavy vortices in wide gap counter rotating cylindrical Couette flow. Physical Review E. 95(5), 053103. mla: Altmeyer, Sebastian, and Richard Lueptow. “Wave Propagation Reversal for Wavy Vortices in Wide Gap Counter Rotating Cylindrical Couette Flow.” Physical Review E, vol. 95, no. 5, 053103, American Physical Society, 2017, doi:10.1103/PhysRevE.95.053103. short: S. Altmeyer, R. Lueptow, Physical Review E 95 (2017). date_created: 2018-12-11T11:47:50Z date_published: 2017-05-10T00:00:00Z date_updated: 2023-10-10T13:30:03Z day: '10' department: - _id: BjHo doi: 10.1103/PhysRevE.95.053103 intvolume: ' 95' issue: '5' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/pdf/physics/0505164.pdf month: '05' oa: 1 oa_version: Submitted Version publication: Physical Review E publication_identifier: issn: - 2470-0045 publication_status: published publisher: American Physical Society publist_id: '7049' scopus_import: '1' status: public title: Wave propagation reversal for wavy vortices in wide gap counter rotating cylindrical Couette flow type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 95 year: '2017' ... --- _id: '463' abstract: - lang: eng text: We investigate transient behaviors induced by magnetic fields on the dynamics of the flow of a ferrofluid in the gap between two concentric, independently rotating cylinders. Without applying any magnetic fields, we uncover emergence of flow states constituted by a combination of a localized spiral state (SPIl) in the top and bottom of the annulus and different multi-cell flow states (SPI2v, SPI3v) with toroidally closed vortices in the interior of the bulk (SPIl+2v = SPIl + SPI2v and SPIl+3v = SPIl + SPI3v). However, when a magnetic field is presented, we observe the transient behaviors between multi-cell states passing through two critical thresholds in a strength of an axial (transverse) magnetic field. Before the first critical threshold of a magnetic field strength, multi-stable states with different number of cells could be observed. After the first critical threshold, we find the transient behavior between the three- and two-cell flow states. For more strength of magnetic field or after the second critical threshold, we discover that multi-cell states are disappeared and a localized spiral state remains to be stimulated. The studied transient behavior could be understood by the investigation of various quantities including a modal kinetic energy, a mode amplitude of the radial velocity, wavenumber, angular momentum, and torque. In addition, the emergence of new flow states and the transient behavior between their states in ferrofluidic flows indicate that richer and potentially controllable dynamics through magnetic fields could be possible in ferrofluic flow. article_number: '113112' article_processing_charge: No article_type: original author: - first_name: Sebastian full_name: Altmeyer, Sebastian id: 2EE67FDC-F248-11E8-B48F-1D18A9856A87 last_name: Altmeyer orcid: 0000-0001-5964-0203 - first_name: Younghae full_name: Do, Younghae last_name: Do - first_name: Soorok full_name: Ryu, Soorok last_name: Ryu citation: ama: Altmeyer S, Do Y, Ryu S. Transient behavior between multi-cell flow states in ferrofluidic Taylor-Couette flow. Chaos. 2017;27(11). doi:10.1063/1.5002771 apa: Altmeyer, S., Do, Y., & Ryu, S. (2017). Transient behavior between multi-cell flow states in ferrofluidic Taylor-Couette flow. Chaos. AIP Publishing. https://doi.org/10.1063/1.5002771 chicago: Altmeyer, Sebastian, Younghae Do, and Soorok Ryu. “Transient Behavior between Multi-Cell Flow States in Ferrofluidic Taylor-Couette Flow.” Chaos. AIP Publishing, 2017. https://doi.org/10.1063/1.5002771. ieee: S. Altmeyer, Y. Do, and S. Ryu, “Transient behavior between multi-cell flow states in ferrofluidic Taylor-Couette flow,” Chaos, vol. 27, no. 11. AIP Publishing, 2017. ista: Altmeyer S, Do Y, Ryu S. 2017. Transient behavior between multi-cell flow states in ferrofluidic Taylor-Couette flow. Chaos. 27(11), 113112. mla: Altmeyer, Sebastian, et al. “Transient Behavior between Multi-Cell Flow States in Ferrofluidic Taylor-Couette Flow.” Chaos, vol. 27, no. 11, 113112, AIP Publishing, 2017, doi:10.1063/1.5002771. short: S. Altmeyer, Y. Do, S. Ryu, Chaos 27 (2017). date_created: 2018-12-11T11:46:37Z date_published: 2017-11-01T00:00:00Z date_updated: 2024-02-28T13:02:12Z day: '01' ddc: - '530' department: - _id: BjHo doi: 10.1063/1.5002771 file: - access_level: open_access checksum: 0731f9d416760c1062db258ca51f8bdc content_type: application/pdf creator: dernst date_created: 2019-10-24T15:14:30Z date_updated: 2020-07-14T12:46:32Z file_id: '6970' file_name: 2017_Chaos_Altmeyer.pdf file_size: 7714020 relation: main_file file_date_updated: 2020-07-14T12:46:32Z has_accepted_license: '1' intvolume: ' 27' issue: '11' language: - iso: eng month: '11' oa: 1 oa_version: Published Version publication: Chaos publication_identifier: issn: - '10541500' publication_status: published publisher: AIP Publishing publist_id: '7358' quality_controlled: '1' scopus_import: '1' status: public title: Transient behavior between multi-cell flow states in ferrofluidic Taylor-Couette flow type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 27 year: '2017' ... --- _id: '661' abstract: - lang: eng text: During embryonic development, mechanical forces are essential for cellular rearrangements driving tissue morphogenesis. Here, we show that in the early zebrafish embryo, friction forces are generated at the interface between anterior axial mesoderm (prechordal plate, ppl) progenitors migrating towards the animal pole and neurectoderm progenitors moving in the opposite direction towards the vegetal pole of the embryo. These friction forces lead to global rearrangement of cells within the neurectoderm and determine the position of the neural anlage. Using a combination of experiments and simulations, we show that this process depends on hydrodynamic coupling between neurectoderm and ppl as a result of E-cadherin-mediated adhesion between those tissues. Our data thus establish the emergence of friction forces at the interface between moving tissues as a critical force-generating process shaping the embryo. acknowledged_ssus: - _id: SSU author: - first_name: Michael full_name: Smutny, Michael id: 3FE6E4E8-F248-11E8-B48F-1D18A9856A87 last_name: Smutny orcid: 0000-0002-5920-9090 - first_name: Zsuzsa full_name: Ákos, Zsuzsa last_name: Ákos - first_name: Silvia full_name: Grigolon, Silvia last_name: Grigolon - first_name: Shayan full_name: Shamipour, Shayan id: 40B34FE2-F248-11E8-B48F-1D18A9856A87 last_name: Shamipour - first_name: Verena full_name: Ruprecht, Verena last_name: Ruprecht - first_name: Daniel full_name: Capek, Daniel id: 31C42484-F248-11E8-B48F-1D18A9856A87 last_name: Capek orcid: 0000-0001-5199-9940 - first_name: Martin full_name: Behrndt, Martin id: 3ECECA3A-F248-11E8-B48F-1D18A9856A87 last_name: Behrndt - first_name: Ekaterina full_name: Papusheva, Ekaterina id: 41DB591E-F248-11E8-B48F-1D18A9856A87 last_name: Papusheva - first_name: Masazumi full_name: Tada, Masazumi last_name: Tada - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 - first_name: Tamás full_name: Vicsek, Tamás last_name: Vicsek - first_name: Guillaume full_name: Salbreux, Guillaume last_name: Salbreux - first_name: Carl-Philipp J full_name: Heisenberg, Carl-Philipp J id: 39427864-F248-11E8-B48F-1D18A9856A87 last_name: Heisenberg orcid: 0000-0002-0912-4566 citation: ama: Smutny M, Ákos Z, Grigolon S, et al. Friction forces position the neural anlage. Nature Cell Biology. 2017;19:306-317. doi:10.1038/ncb3492 apa: Smutny, M., Ákos, Z., Grigolon, S., Shamipour, S., Ruprecht, V., Capek, D., … Heisenberg, C.-P. J. (2017). Friction forces position the neural anlage. Nature Cell Biology. Nature Publishing Group. https://doi.org/10.1038/ncb3492 chicago: Smutny, Michael, Zsuzsa Ákos, Silvia Grigolon, Shayan Shamipour, Verena Ruprecht, Daniel Capek, Martin Behrndt, et al. “Friction Forces Position the Neural Anlage.” Nature Cell Biology. Nature Publishing Group, 2017. https://doi.org/10.1038/ncb3492. ieee: M. Smutny et al., “Friction forces position the neural anlage,” Nature Cell Biology, vol. 19. Nature Publishing Group, pp. 306–317, 2017. ista: Smutny M, Ákos Z, Grigolon S, Shamipour S, Ruprecht V, Capek D, Behrndt M, Papusheva E, Tada M, Hof B, Vicsek T, Salbreux G, Heisenberg C-PJ. 2017. Friction forces position the neural anlage. Nature Cell Biology. 19, 306–317. mla: Smutny, Michael, et al. “Friction Forces Position the Neural Anlage.” Nature Cell Biology, vol. 19, Nature Publishing Group, 2017, pp. 306–17, doi:10.1038/ncb3492. short: M. Smutny, Z. Ákos, S. Grigolon, S. Shamipour, V. Ruprecht, D. Capek, M. Behrndt, E. Papusheva, M. Tada, B. Hof, T. Vicsek, G. Salbreux, C.-P.J. Heisenberg, Nature Cell Biology 19 (2017) 306–317. date_created: 2018-12-11T11:47:46Z date_published: 2017-03-27T00:00:00Z date_updated: 2024-03-27T23:30:38Z day: '27' department: - _id: CaHe - _id: BjHo - _id: Bio doi: 10.1038/ncb3492 ec_funded: 1 external_id: pmid: - '28346437' intvolume: ' 19' language: - iso: eng main_file_link: - open_access: '1' url: https://europepmc.org/articles/pmc5635970 month: '03' oa: 1 oa_version: Submitted Version page: 306 - 317 pmid: 1 project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin - _id: 252ABD0A-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: I 930-B20 name: Control of Epithelial Cell Layer Spreading in Zebrafish publication: Nature Cell Biology publication_identifier: issn: - '14657392' publication_status: published publisher: Nature Publishing Group publist_id: '7074' quality_controlled: '1' related_material: record: - id: '50' relation: dissertation_contains status: public - id: '8350' relation: dissertation_contains status: public scopus_import: 1 status: public title: Friction forces position the neural anlage type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 19 year: '2017' ... --- _id: '1494' abstract: - lang: eng text: Turbulence is one of the most frequently encountered non-equilibrium phenomena in nature, yet characterizing the transition that gives rise to turbulence in basic shear flows has remained an elusive task. Although, in recent studies, critical points marking the onset of sustained turbulence have been determined for several such flows, the physical nature of the transition could not be fully explained. In extensive experimental and computational studies we show for the example of Couette flow that the onset of turbulence is a second-order phase transition and falls into the directed percolation universality class. Consequently, the complex laminar–turbulent patterns distinctive for the onset of turbulence in shear flows result from short-range interactions of turbulent domains and are characterized by universal critical exponents. More generally, our study demonstrates that even high-dimensional systems far from equilibrium such as turbulence exhibit universality at onset and that here the collective dynamics obeys simple rules. acknowledgement: We thank P. Maier for providing valuable ideas and supporting us in the technical aspects. Discussions with D. Barkley, Y. Duguet, B. Eckhart, N. Goldenfeld, P. Manneville and K. Takeuchi are gratefully acknowledged. We acknowledge the Deutsche Forschungsgemeinschaft (Project No. FOR 1182), and the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement 306589 for financial support. L.S. and B.H. acknowledge research funding by Deutsche Forschungsgemeinschaft (DFG) under Grant No. SFB 963/1 (project A8). Numerical simulations were performed thanks to the CPU time allocations of JUROPA in Juelich Supercomputing Center (project HGU17) and of the Max Planck Computing and Data Facility (Garching, Germany). Excellent technical support from M. Rampp on the hybrid code nsCouette is appreciated. author: - first_name: Grégoire M full_name: Lemoult, Grégoire M id: 4787FE80-F248-11E8-B48F-1D18A9856A87 last_name: Lemoult - first_name: Liang full_name: Shi, Liang id: 374A3F1A-F248-11E8-B48F-1D18A9856A87 last_name: Shi - first_name: Kerstin full_name: Avila, Kerstin last_name: Avila - first_name: Shreyas V full_name: Jalikop, Shreyas V id: 44A1D772-F248-11E8-B48F-1D18A9856A87 last_name: Jalikop - first_name: Marc full_name: Avila, Marc last_name: Avila - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Lemoult GM, Shi L, Avila K, Jalikop SV, Avila M, Hof B. Directed percolation phase transition to sustained turbulence in Couette flow. Nature Physics. 2016;12(3):254-258. doi:10.1038/nphys3675 apa: Lemoult, G. M., Shi, L., Avila, K., Jalikop, S. V., Avila, M., & Hof, B. (2016). Directed percolation phase transition to sustained turbulence in Couette flow. Nature Physics. Nature Publishing Group. https://doi.org/10.1038/nphys3675 chicago: Lemoult, Grégoire M, Liang Shi, Kerstin Avila, Shreyas V Jalikop, Marc Avila, and Björn Hof. “Directed Percolation Phase Transition to Sustained Turbulence in Couette Flow.” Nature Physics. Nature Publishing Group, 2016. https://doi.org/10.1038/nphys3675. ieee: G. M. Lemoult, L. Shi, K. Avila, S. V. Jalikop, M. Avila, and B. Hof, “Directed percolation phase transition to sustained turbulence in Couette flow,” Nature Physics, vol. 12, no. 3. Nature Publishing Group, pp. 254–258, 2016. ista: Lemoult GM, Shi L, Avila K, Jalikop SV, Avila M, Hof B. 2016. Directed percolation phase transition to sustained turbulence in Couette flow. Nature Physics. 12(3), 254–258. mla: Lemoult, Grégoire M., et al. “Directed Percolation Phase Transition to Sustained Turbulence in Couette Flow.” Nature Physics, vol. 12, no. 3, Nature Publishing Group, 2016, pp. 254–58, doi:10.1038/nphys3675. short: G.M. Lemoult, L. Shi, K. Avila, S.V. Jalikop, M. Avila, B. Hof, Nature Physics 12 (2016) 254–258. date_created: 2018-12-11T11:52:21Z date_published: 2016-02-15T00:00:00Z date_updated: 2021-01-12T06:51:08Z day: '15' department: - _id: BjHo doi: 10.1038/nphys3675 ec_funded: 1 intvolume: ' 12' issue: '3' language: - iso: eng month: '02' oa_version: None page: 254 - 258 project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin - _id: 2511D90C-B435-11E9-9278-68D0E5697425 grant_number: SFB 963 TP A8 name: Astrophysical instability of currents and turbulences publication: Nature Physics publication_status: published publisher: Nature Publishing Group publist_id: '5685' quality_controlled: '1' scopus_import: 1 status: public title: Directed percolation phase transition to sustained turbulence in Couette flow type: journal_article user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87 volume: 12 year: '2016' ... --- _id: '1589' abstract: - lang: eng text: We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices. article_number: '18589' article_type: original author: - first_name: Sebastian full_name: Altmeyer, Sebastian id: 2EE67FDC-F248-11E8-B48F-1D18A9856A87 last_name: Altmeyer orcid: 0000-0001-5964-0203 - first_name: Younghae full_name: Do, Younghae last_name: Do - first_name: Ying full_name: Lai, Ying last_name: Lai citation: ama: Altmeyer S, Do Y, Lai Y. Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system. Scientific Reports. 2015;5. doi:10.1038/srep18589 apa: Altmeyer, S., Do, Y., & Lai, Y. (2015). Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system. Scientific Reports. Nature Publishing Group. https://doi.org/10.1038/srep18589 chicago: Altmeyer, Sebastian, Younghae Do, and Ying Lai. “Magnetic Field Induced Flow Pattern Reversal in a Ferrofluidic Taylor-Couette System.” Scientific Reports. Nature Publishing Group, 2015. https://doi.org/10.1038/srep18589. ieee: S. Altmeyer, Y. Do, and Y. Lai, “Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system,” Scientific Reports, vol. 5. Nature Publishing Group, 2015. ista: Altmeyer S, Do Y, Lai Y. 2015. Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system. Scientific Reports. 5, 18589. mla: Altmeyer, Sebastian, et al. “Magnetic Field Induced Flow Pattern Reversal in a Ferrofluidic Taylor-Couette System.” Scientific Reports, vol. 5, 18589, Nature Publishing Group, 2015, doi:10.1038/srep18589. short: S. Altmeyer, Y. Do, Y. Lai, Scientific Reports 5 (2015). date_created: 2018-12-11T11:52:53Z date_published: 2015-12-21T00:00:00Z date_updated: 2021-01-12T06:51:48Z day: '21' ddc: - '530' - '540' department: - _id: BjHo doi: 10.1038/srep18589 file: - access_level: open_access checksum: 927e151674347661ce36eae2818dafdc content_type: application/pdf creator: system date_created: 2018-12-12T10:13:49Z date_updated: 2020-07-14T12:45:03Z file_id: '5036' file_name: IST-2016-472-v1+1_srep18589.pdf file_size: 2771236 relation: main_file file_date_updated: 2020-07-14T12:45:03Z has_accepted_license: '1' intvolume: ' 5' language: - iso: eng month: '12' oa: 1 oa_version: Published Version publication: Scientific Reports publication_status: published publisher: Nature Publishing Group publist_id: '5582' pubrep_id: '472' quality_controlled: '1' scopus_import: 1 status: public title: Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 5 year: '2015' ... --- _id: '1588' abstract: - lang: eng text: 'We investigate the Taylor-Couette system where the radius ratio is close to unity. Systematically increasing the Reynolds number, we observe a number of previously known transitions, such as one from the classical Taylor vortex flow (TVF) to wavy vortex flow (WVF) and the transition to fully developed turbulence. Prior to the onset of turbulence, we observe intermittent bursting patterns of localized turbulent patches, confirming the experimentally observed pattern of very short wavelength bursts (VSWBs). A striking finding is that, for a Reynolds number larger than that for the onset of VSWBs, a new type of intermittently bursting behavior emerges: patterns of azimuthally closed rings of various orders. We call them ring-bursting patterns, which surround the cylinder completely but remain localized and separated in the axial direction through nonturbulent wavy structures. We employ a number of quantitative measures including the cross-flow energy to characterize the ring-bursting patterns and to distinguish them from the background flow. These patterns are interesting because they do not occur in the wide-gap Taylor-Couette flow systems. The narrow-gap regime is less studied but certainly deserves further attention to gain deeper insights into complex flow dynamics in fluids.' article_number: '053018' author: - first_name: Sebastian full_name: Altmeyer, Sebastian id: 2EE67FDC-F248-11E8-B48F-1D18A9856A87 last_name: Altmeyer orcid: 0000-0001-5964-0203 - first_name: Younghae full_name: Do, Younghae last_name: Do - first_name: Ying full_name: Lai, Ying last_name: Lai citation: ama: Altmeyer S, Do Y, Lai Y. Ring-bursting behavior en route to turbulence in narrow-gap Taylor-Couette flows. Physical Review E. 2015;92(5). doi:10.1103/PhysRevE.92.053018 apa: Altmeyer, S., Do, Y., & Lai, Y. (2015). Ring-bursting behavior en route to turbulence in narrow-gap Taylor-Couette flows. Physical Review E. American Physical Society. https://doi.org/10.1103/PhysRevE.92.053018 chicago: Altmeyer, Sebastian, Younghae Do, and Ying Lai. “Ring-Bursting Behavior En Route to Turbulence in Narrow-Gap Taylor-Couette Flows.” Physical Review E. American Physical Society, 2015. https://doi.org/10.1103/PhysRevE.92.053018. ieee: S. Altmeyer, Y. Do, and Y. Lai, “Ring-bursting behavior en route to turbulence in narrow-gap Taylor-Couette flows,” Physical Review E, vol. 92, no. 5. American Physical Society, 2015. ista: Altmeyer S, Do Y, Lai Y. 2015. Ring-bursting behavior en route to turbulence in narrow-gap Taylor-Couette flows. Physical Review E. 92(5), 053018. mla: Altmeyer, Sebastian, et al. “Ring-Bursting Behavior En Route to Turbulence in Narrow-Gap Taylor-Couette Flows.” Physical Review E, vol. 92, no. 5, 053018, American Physical Society, 2015, doi:10.1103/PhysRevE.92.053018. short: S. Altmeyer, Y. Do, Y. Lai, Physical Review E 92 (2015). date_created: 2018-12-11T11:52:53Z date_published: 2015-11-24T00:00:00Z date_updated: 2021-01-12T06:51:47Z day: '24' department: - _id: BjHo doi: 10.1103/PhysRevE.92.053018 intvolume: ' 92' issue: '5' language: - iso: eng month: '11' oa_version: None publication: Physical Review E publication_status: published publisher: American Physical Society publist_id: '5583' quality_controlled: '1' scopus_import: 1 status: public title: Ring-bursting behavior en route to turbulence in narrow-gap Taylor-Couette flows type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 92 year: '2015' ... --- _id: '1664' abstract: - lang: eng text: Over a century of research into the origin of turbulence in wall-bounded shear flows has resulted in a puzzling picture in which turbulence appears in a variety of different states competing with laminar background flow. At moderate flow speeds, turbulence is confined to localized patches; it is only at higher speeds that the entire flow becomes turbulent. The origin of the different states encountered during this transition, the front dynamics of the turbulent regions and the transformation to full turbulence have yet to be explained. By combining experiments, theory and computer simulations, here we uncover a bifurcation scenario that explains the transformation to fully turbulent pipe flow and describe the front dynamics of the different states encountered in the process. Key to resolving this problem is the interpretation of the flow as a bistable system with nonlinear propagation (advection) of turbulent fronts. These findings bridge the gap between our understanding of the onset of turbulence and fully turbulent flows. acknowledgement: We acknowledge the Deutsche Forschungsgemeinschaft (Project No. FOR 1182), and the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement 306589 for financial support. B.S. acknowledges financial support from the Chinese State Scholarship Fund under grant number 2010629145. B.S. acknowledges support from the International Max Planck Research School for the Physics of Biological and Complex Systems and the Göttingen Graduate School for Neurosciences and Molecular Biosciences. We acknowledge computing resources from GWDG (Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen) and the Jülich Supercomputing Centre (grant HGU16) where the simulations were performed. author: - first_name: Dwight full_name: Barkley, Dwight last_name: Barkley - first_name: Baofang full_name: Song, Baofang last_name: Song - first_name: Mukund full_name: Vasudevan, Mukund id: 3C5A959A-F248-11E8-B48F-1D18A9856A87 last_name: Vasudevan - first_name: Grégoire M full_name: Lemoult, Grégoire M id: 4787FE80-F248-11E8-B48F-1D18A9856A87 last_name: Lemoult - first_name: Marc full_name: Avila, Marc last_name: Avila - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Barkley D, Song B, Vasudevan M, Lemoult GM, Avila M, Hof B. The rise of fully turbulent flow. Nature. 2015;526(7574):550-553. doi:10.1038/nature15701 apa: Barkley, D., Song, B., Vasudevan, M., Lemoult, G. M., Avila, M., & Hof, B. (2015). The rise of fully turbulent flow. Nature. Nature Publishing Group. https://doi.org/10.1038/nature15701 chicago: Barkley, Dwight, Baofang Song, Mukund Vasudevan, Grégoire M Lemoult, Marc Avila, and Björn Hof. “The Rise of Fully Turbulent Flow.” Nature. Nature Publishing Group, 2015. https://doi.org/10.1038/nature15701. ieee: D. Barkley, B. Song, M. Vasudevan, G. M. Lemoult, M. Avila, and B. Hof, “The rise of fully turbulent flow,” Nature, vol. 526, no. 7574. Nature Publishing Group, pp. 550–553, 2015. ista: Barkley D, Song B, Vasudevan M, Lemoult GM, Avila M, Hof B. 2015. The rise of fully turbulent flow. Nature. 526(7574), 550–553. mla: Barkley, Dwight, et al. “The Rise of Fully Turbulent Flow.” Nature, vol. 526, no. 7574, Nature Publishing Group, 2015, pp. 550–53, doi:10.1038/nature15701. short: D. Barkley, B. Song, M. Vasudevan, G.M. Lemoult, M. Avila, B. Hof, Nature 526 (2015) 550–553. date_created: 2018-12-11T11:53:20Z date_published: 2015-10-21T00:00:00Z date_updated: 2021-01-12T06:52:22Z day: '21' department: - _id: BjHo doi: 10.1038/nature15701 ec_funded: 1 intvolume: ' 526' issue: '7574' language: - iso: eng main_file_link: - open_access: '1' url: http://arxiv.org/abs/1510.09143 month: '10' oa: 1 oa_version: Preprint page: 550 - 553 project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin publication: Nature publication_status: published publisher: Nature Publishing Group publist_id: '5485' quality_controlled: '1' scopus_import: 1 status: public title: The rise of fully turbulent flow type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 526 year: '2015' ... --- _id: '1679' article_number: '091102' author: - first_name: Grégoire M full_name: Lemoult, Grégoire M id: 4787FE80-F248-11E8-B48F-1D18A9856A87 last_name: Lemoult - first_name: Philipp full_name: Maier, Philipp id: 384F7C04-F248-11E8-B48F-1D18A9856A87 last_name: Maier - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Lemoult GM, Maier P, Hof B. Taylor’s Forest. Physics of Fluids. 2015;27(9). doi:10.1063/1.4930850 apa: Lemoult, G. M., Maier, P., & Hof, B. (2015). Taylor’s Forest. Physics of Fluids. American Institute of Physics. https://doi.org/10.1063/1.4930850 chicago: Lemoult, Grégoire M, Philipp Maier, and Björn Hof. “Taylor’s Forest.” Physics of Fluids. American Institute of Physics, 2015. https://doi.org/10.1063/1.4930850. ieee: G. M. Lemoult, P. Maier, and B. Hof, “Taylor’s Forest,” Physics of Fluids, vol. 27, no. 9. American Institute of Physics, 2015. ista: Lemoult GM, Maier P, Hof B. 2015. Taylor’s Forest. Physics of Fluids. 27(9), 091102. mla: Lemoult, Grégoire M., et al. “Taylor’s Forest.” Physics of Fluids, vol. 27, no. 9, 091102, American Institute of Physics, 2015, doi:10.1063/1.4930850. short: G.M. Lemoult, P. Maier, B. Hof, Physics of Fluids 27 (2015). date_created: 2018-12-11T11:53:26Z date_published: 2015-09-24T00:00:00Z date_updated: 2021-01-12T06:52:28Z day: '24' ddc: - '532' department: - _id: BjHo doi: 10.1063/1.4930850 file: - access_level: open_access checksum: 604bba3c2496aadb3efcff77de01ce6c content_type: application/pdf creator: system date_created: 2018-12-12T10:13:35Z date_updated: 2020-07-14T12:45:12Z file_id: '5019' file_name: IST-2017-748-v1+1_1.4930850.pdf file_size: 872366 relation: main_file file_date_updated: 2020-07-14T12:45:12Z has_accepted_license: '1' intvolume: ' 27' issue: '9' language: - iso: eng month: '09' oa: 1 oa_version: Published Version publication: Physics of Fluids publication_status: published publisher: American Institute of Physics publist_id: '5469' pubrep_id: '748' quality_controlled: '1' scopus_import: 1 status: public title: Taylor's Forest tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 27 year: '2015' ... --- _id: '1804' abstract: - lang: eng text: It is known that in classical fluids turbulence typically occurs at high Reynolds numbers. But can turbulence occur at low Reynolds numbers? Here we investigate the transition to turbulence in the classic Taylor-Couette system in which the rotating fluids are manufactured ferrofluids with magnetized nanoparticles embedded in liquid carriers. We find that, in the presence of a magnetic field transverse to the symmetry axis of the system, turbulence can occur at Reynolds numbers that are at least one order of magnitude smaller than those in conventional fluids. This is established by extensive computational ferrohydrodynamics through a detailed investigation of transitions in the flow structure, and characterization of behaviors of physical quantities such as the energy, the wave number, and the angular momentum through the bifurcations. A finding is that, as the magnetic field is increased, onset of turbulence can be determined accurately and reliably. Our results imply that experimental investigation of turbulence may be feasible by using ferrofluids. Our study of transition to and evolution of turbulence in the Taylor-Couette ferrofluidic flow system provides insights into the challenging problem of turbulence control. article_number: '10781' author: - first_name: Sebastian full_name: Altmeyer, Sebastian id: 2EE67FDC-F248-11E8-B48F-1D18A9856A87 last_name: Altmeyer orcid: 0000-0001-5964-0203 - first_name: Younghae full_name: Do, Younghae last_name: Do - first_name: Ying full_name: Lai, Ying last_name: Lai citation: ama: Altmeyer S, Do Y, Lai Y. Transition to turbulence in Taylor-Couette ferrofluidic flow. Scientific Reports. 2015;5. doi:10.1038/srep10781 apa: Altmeyer, S., Do, Y., & Lai, Y. (2015). Transition to turbulence in Taylor-Couette ferrofluidic flow. Scientific Reports. Nature Publishing Group. https://doi.org/10.1038/srep10781 chicago: Altmeyer, Sebastian, Younghae Do, and Ying Lai. “Transition to Turbulence in Taylor-Couette Ferrofluidic Flow.” Scientific Reports. Nature Publishing Group, 2015. https://doi.org/10.1038/srep10781. ieee: S. Altmeyer, Y. Do, and Y. Lai, “Transition to turbulence in Taylor-Couette ferrofluidic flow,” Scientific Reports, vol. 5. Nature Publishing Group, 2015. ista: Altmeyer S, Do Y, Lai Y. 2015. Transition to turbulence in Taylor-Couette ferrofluidic flow. Scientific Reports. 5, 10781. mla: Altmeyer, Sebastian, et al. “Transition to Turbulence in Taylor-Couette Ferrofluidic Flow.” Scientific Reports, vol. 5, 10781, Nature Publishing Group, 2015, doi:10.1038/srep10781. short: S. Altmeyer, Y. Do, Y. Lai, Scientific Reports 5 (2015). date_created: 2018-12-11T11:54:06Z date_published: 2015-06-12T00:00:00Z date_updated: 2021-01-12T06:53:18Z day: '12' ddc: - '530' department: - _id: BjHo doi: 10.1038/srep10781 file: - access_level: open_access checksum: 7716f582f8c9d82d8f2bf80bf896b440 content_type: application/pdf creator: system date_created: 2018-12-12T10:17:26Z date_updated: 2020-07-14T12:45:16Z file_id: '5280' file_name: IST-2016-450-v1+1_srep10781.pdf file_size: 2449723 relation: main_file file_date_updated: 2020-07-14T12:45:16Z has_accepted_license: '1' intvolume: ' 5' language: - iso: eng month: '06' oa: 1 oa_version: Published Version publication: Scientific Reports publication_status: published publisher: Nature Publishing Group publist_id: '5306' pubrep_id: '450' quality_controlled: '1' scopus_import: 1 status: public title: Transition to turbulence in Taylor-Couette ferrofluidic flow tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 5 year: '2015' ... --- _id: '1837' abstract: - lang: eng text: 'Transition to turbulence in straight pipes occurs in spite of the linear stability of the laminar Hagen-Poiseuille flow if both the amplitude of flow perturbations and the Reynolds number Re exceed a minimum threshold (subcritical transition). As the pipe curvature increases, centrifugal effects become important, modifying the basic flow as well as the most unstable linear modes. If the curvature (tube-to-coiling diameter d/D) is sufficiently large, a Hopf bifurcation (supercritical instability) is encountered before turbulence can be excited (subcritical instability). We trace the instability thresholds in the Re - d/D parameter space in the range 0.01 ≤ d/D\ ≤ 0.1 by means of laser-Doppler velocimetry and determine the point where the subcritical and supercritical instabilities meet. Two different experimental set-ups are used: a closed system where the pipe forms an axisymmetric torus and an open system employing a helical pipe. Implications for the measurement of friction factors in curved pipes are discussed.' article_number: R3 article_processing_charge: No article_type: original author: - first_name: Jakob full_name: Kühnen, Jakob id: 3A47AE32-F248-11E8-B48F-1D18A9856A87 last_name: Kühnen orcid: 0000-0003-4312-0179 - first_name: P full_name: Braunshier, P last_name: Braunshier - first_name: M full_name: Schwegel, M last_name: Schwegel - first_name: Hendrik full_name: Kuhlmann, Hendrik last_name: Kuhlmann - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Kühnen J, Braunshier P, Schwegel M, Kuhlmann H, Hof B. Subcritical versus supercritical transition to turbulence in curved pipes. Journal of Fluid Mechanics. 2015;770(5). doi:10.1017/jfm.2015.184 apa: Kühnen, J., Braunshier, P., Schwegel, M., Kuhlmann, H., & Hof, B. (2015). Subcritical versus supercritical transition to turbulence in curved pipes. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2015.184 chicago: Kühnen, Jakob, P Braunshier, M Schwegel, Hendrik Kuhlmann, and Björn Hof. “Subcritical versus Supercritical Transition to Turbulence in Curved Pipes.” Journal of Fluid Mechanics. Cambridge University Press, 2015. https://doi.org/10.1017/jfm.2015.184. ieee: J. Kühnen, P. Braunshier, M. Schwegel, H. Kuhlmann, and B. Hof, “Subcritical versus supercritical transition to turbulence in curved pipes,” Journal of Fluid Mechanics, vol. 770, no. 5. Cambridge University Press, 2015. ista: Kühnen J, Braunshier P, Schwegel M, Kuhlmann H, Hof B. 2015. Subcritical versus supercritical transition to turbulence in curved pipes. Journal of Fluid Mechanics. 770(5), R3. mla: Kühnen, Jakob, et al. “Subcritical versus Supercritical Transition to Turbulence in Curved Pipes.” Journal of Fluid Mechanics, vol. 770, no. 5, R3, Cambridge University Press, 2015, doi:10.1017/jfm.2015.184. short: J. Kühnen, P. Braunshier, M. Schwegel, H. Kuhlmann, B. Hof, Journal of Fluid Mechanics 770 (2015). date_created: 2018-12-11T11:54:17Z date_published: 2015-04-08T00:00:00Z date_updated: 2021-01-12T06:53:31Z day: '08' department: - _id: BjHo doi: 10.1017/jfm.2015.184 ec_funded: 1 external_id: arxiv: - '1508.06559' intvolume: ' 770' issue: '5' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1508.06559 month: '04' oa: 1 oa_version: Preprint project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin publication: Journal of Fluid Mechanics publication_status: published publisher: Cambridge University Press publist_id: '5265' quality_controlled: '1' scopus_import: 1 status: public title: Subcritical versus supercritical transition to turbulence in curved pipes type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 770 year: '2015' ... --- _id: '1868' abstract: - lang: eng text: We investigate high-dimensional nonlinear dynamical systems exhibiting multiple resonances under adiabatic parameter variations. Our motivations come from experimental considerations where time-dependent sweeping of parameters is a practical approach to probing and characterizing the bifurcations of the system. The question is whether bifurcations so detected are faithful representations of the bifurcations intrinsic to the original stationary system. Utilizing a harmonically forced, closed fluid flow system that possesses multiple resonances and solving the Navier-Stokes equation under proper boundary conditions, we uncover the phenomenon of the early effect. Specifically, as a control parameter, e.g., the driving frequency, is adiabatically increased from an initial value, resonances emerge at frequency values that are lower than those in the corresponding stationary system. The phenomenon is established by numerical characterization of physical quantities through the resonances, which include the kinetic energy and the vorticity field, and a heuristic analysis based on the concept of instantaneous frequency. A simple formula is obtained which relates the resonance points in the time-dependent and time-independent systems. Our findings suggest that, in general, any true bifurcation of a nonlinear dynamical system can be unequivocally uncovered through adiabatic parameter sweeping, in spite of a shift in the bifurcation point, which is of value to experimental studies of nonlinear dynamical systems. article_number: '022906' author: - first_name: Youngyong full_name: Park, Youngyong last_name: Park - first_name: Younghae full_name: Do, Younghae last_name: Do - first_name: Sebastian full_name: Altmeyer, Sebastian id: 2EE67FDC-F248-11E8-B48F-1D18A9856A87 last_name: Altmeyer orcid: 0000-0001-5964-0203 - first_name: Yingcheng full_name: Lai, Yingcheng last_name: Lai - first_name: Gyuwon full_name: Lee, Gyuwon last_name: Lee citation: ama: Park Y, Do Y, Altmeyer S, Lai Y, Lee G. Early effect in time-dependent, high-dimensional nonlinear dynamical systems with multiple resonances. Physical Review E. 2015;91(2). doi:10.1103/PhysRevE.91.022906 apa: Park, Y., Do, Y., Altmeyer, S., Lai, Y., & Lee, G. (2015). Early effect in time-dependent, high-dimensional nonlinear dynamical systems with multiple resonances. Physical Review E. American Physical Society. https://doi.org/10.1103/PhysRevE.91.022906 chicago: Park, Youngyong, Younghae Do, Sebastian Altmeyer, Yingcheng Lai, and Gyuwon Lee. “Early Effect in Time-Dependent, High-Dimensional Nonlinear Dynamical Systems with Multiple Resonances.” Physical Review E. American Physical Society, 2015. https://doi.org/10.1103/PhysRevE.91.022906. ieee: Y. Park, Y. Do, S. Altmeyer, Y. Lai, and G. Lee, “Early effect in time-dependent, high-dimensional nonlinear dynamical systems with multiple resonances,” Physical Review E, vol. 91, no. 2. American Physical Society, 2015. ista: Park Y, Do Y, Altmeyer S, Lai Y, Lee G. 2015. Early effect in time-dependent, high-dimensional nonlinear dynamical systems with multiple resonances. Physical Review E. 91(2), 022906. mla: Park, Youngyong, et al. “Early Effect in Time-Dependent, High-Dimensional Nonlinear Dynamical Systems with Multiple Resonances.” Physical Review E, vol. 91, no. 2, 022906, American Physical Society, 2015, doi:10.1103/PhysRevE.91.022906. short: Y. Park, Y. Do, S. Altmeyer, Y. Lai, G. Lee, Physical Review E 91 (2015). date_created: 2018-12-11T11:54:27Z date_published: 2015-02-09T00:00:00Z date_updated: 2021-01-12T06:53:44Z day: '09' department: - _id: BjHo doi: 10.1103/PhysRevE.91.022906 intvolume: ' 91' issue: '2' language: - iso: eng month: '02' oa_version: None publication: Physical Review E publication_identifier: issn: - 1539-3755 publication_status: published publisher: American Physical Society publist_id: '5229' quality_controlled: '1' scopus_import: 1 status: public title: Early effect in time-dependent, high-dimensional nonlinear dynamical systems with multiple resonances type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 91 year: '2015' ... --- _id: '2030' abstract: - lang: eng text: A hybrid-parallel direct-numerical-simulation method with application to turbulent Taylor-Couette flow is presented. The Navier-Stokes equations are discretized in cylindrical coordinates with the spectral Fourier-Galerkin method in the axial and azimuthal directions, and high-order finite differences in the radial direction. Time is advanced by a second-order, semi-implicit projection scheme, which requires the solution of five Helmholtz/Poisson equations, avoids staggered grids and renders very small slip velocities. Nonlinear terms are evaluated with the pseudospectral method. The code is parallelized using a hybrid MPI-OpenMP strategy, which, compared with a flat MPI parallelization, is simpler to implement, allows to reduce inter-node communications and MPI overhead that become relevant at high processor-core counts, and helps to contain the memory footprint. A strong scaling study shows that the hybrid code maintains scalability up to more than 20,000 processor cores and thus allows to perform simulations at higher resolutions than previously feasible. In particular, it opens up the possibility to simulate turbulent Taylor-Couette flows at Reynolds numbers up to O(105). This enables to probe hydrodynamic turbulence in Keplerian flows in experimentally relevant regimes. author: - first_name: Liang full_name: Shi, Liang id: 374A3F1A-F248-11E8-B48F-1D18A9856A87 last_name: Shi - first_name: Markus full_name: Rampp, Markus last_name: Rampp - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 - first_name: Marc full_name: Avila, Marc last_name: Avila citation: ama: Shi L, Rampp M, Hof B, Avila M. A hybrid MPI-OpenMP parallel implementation for pseudospectral simulations with application to Taylor-Couette flow. Computers and Fluids. 2015;106(1):1-11. doi:10.1016/j.compfluid.2014.09.021 apa: Shi, L., Rampp, M., Hof, B., & Avila, M. (2015). A hybrid MPI-OpenMP parallel implementation for pseudospectral simulations with application to Taylor-Couette flow. Computers and Fluids. Elsevier. https://doi.org/10.1016/j.compfluid.2014.09.021 chicago: Shi, Liang, Markus Rampp, Björn Hof, and Marc Avila. “A Hybrid MPI-OpenMP Parallel Implementation for Pseudospectral Simulations with Application to Taylor-Couette Flow.” Computers and Fluids. Elsevier, 2015. https://doi.org/10.1016/j.compfluid.2014.09.021. ieee: L. Shi, M. Rampp, B. Hof, and M. Avila, “A hybrid MPI-OpenMP parallel implementation for pseudospectral simulations with application to Taylor-Couette flow,” Computers and Fluids, vol. 106, no. 1. Elsevier, pp. 1–11, 2015. ista: Shi L, Rampp M, Hof B, Avila M. 2015. A hybrid MPI-OpenMP parallel implementation for pseudospectral simulations with application to Taylor-Couette flow. Computers and Fluids. 106(1), 1–11. mla: Shi, Liang, et al. “A Hybrid MPI-OpenMP Parallel Implementation for Pseudospectral Simulations with Application to Taylor-Couette Flow.” Computers and Fluids, vol. 106, no. 1, Elsevier, 2015, pp. 1–11, doi:10.1016/j.compfluid.2014.09.021. short: L. Shi, M. Rampp, B. Hof, M. Avila, Computers and Fluids 106 (2015) 1–11. date_created: 2018-12-11T11:55:18Z date_published: 2015-01-01T00:00:00Z date_updated: 2021-01-12T06:54:51Z day: '01' department: - _id: BjHo doi: 10.1016/j.compfluid.2014.09.021 intvolume: ' 106' issue: '1' language: - iso: eng main_file_link: - open_access: '1' url: http://arxiv.org/abs/1311.2481 month: '01' oa: 1 oa_version: Preprint page: 1 - 11 publication: Computers and Fluids publication_status: published publisher: Elsevier publist_id: '5042' quality_controlled: '1' scopus_import: 1 status: public title: A hybrid MPI-OpenMP parallel implementation for pseudospectral simulations with application to Taylor-Couette flow type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 106 year: '2015' ... --- _id: '2050' abstract: - lang: eng text: The flow instability and further transition to turbulence in a toroidal pipe (torus) with curvature ratio (tube-to-coiling diameter) 0.049 is investigated experimentally. The flow inside the toroidal pipe is driven by a steel sphere fitted to the inner pipe diameter. The sphere is moved with constant azimuthal velocity from outside the torus by a moving magnet. The experiment is designed to investigate curved pipe flow by optical measurement techniques. Using stereoscopic particle image velocimetry, laser Doppler velocimetry and pressure drop measurements, the flow is measured for Reynolds numbers ranging from 1000 to 15 000. Time- and space-resolved velocity fields are obtained and analysed. The steady axisymmetric basic flow is strongly influenced by centrifugal effects. On an increase of the Reynolds number we find a sequence of bifurcations. For Re=4075±2% a supercritical bifurcation to an oscillatory flow is found in which waves travel in the streamwise direction with a phase velocity slightly faster than the mean flow. The oscillatory flow is superseded by a presumably quasi-periodic flow at a further increase of the Reynolds number before turbulence sets in. The results are found to be compatible, in general, with earlier experimental and numerical investigations on transition to turbulence in helical and curved pipes. However, important aspects of the bifurcation scenario differ considerably. article_processing_charge: No author: - first_name: Jakob full_name: Kühnen, Jakob id: 3A47AE32-F248-11E8-B48F-1D18A9856A87 last_name: Kühnen orcid: 0000-0003-4312-0179 - first_name: Markus full_name: Holzner, Markus last_name: Holzner - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 - first_name: Hendrik full_name: Kuhlmann, Hendrik last_name: Kuhlmann citation: ama: Kühnen J, Holzner M, Hof B, Kuhlmann H. Experimental investigation of transitional flow in a toroidal pipe. Journal of Fluid Mechanics. 2014;738:463-491. doi:10.1017/jfm.2013.603 apa: Kühnen, J., Holzner, M., Hof, B., & Kuhlmann, H. (2014). Experimental investigation of transitional flow in a toroidal pipe. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2013.603 chicago: Kühnen, Jakob, Markus Holzner, Björn Hof, and Hendrik Kuhlmann. “Experimental Investigation of Transitional Flow in a Toroidal Pipe.” Journal of Fluid Mechanics. Cambridge University Press, 2014. https://doi.org/10.1017/jfm.2013.603. ieee: J. Kühnen, M. Holzner, B. Hof, and H. Kuhlmann, “Experimental investigation of transitional flow in a toroidal pipe,” Journal of Fluid Mechanics, vol. 738. Cambridge University Press, pp. 463–491, 2014. ista: Kühnen J, Holzner M, Hof B, Kuhlmann H. 2014. Experimental investigation of transitional flow in a toroidal pipe. Journal of Fluid Mechanics. 738, 463–491. mla: Kühnen, Jakob, et al. “Experimental Investigation of Transitional Flow in a Toroidal Pipe.” Journal of Fluid Mechanics, vol. 738, Cambridge University Press, 2014, pp. 463–91, doi:10.1017/jfm.2013.603. short: J. Kühnen, M. Holzner, B. Hof, H. Kuhlmann, Journal of Fluid Mechanics 738 (2014) 463–491. date_created: 2018-12-11T11:55:25Z date_published: 2014-01-10T00:00:00Z date_updated: 2021-01-12T06:54:59Z day: '10' department: - _id: BjHo doi: 10.1017/jfm.2013.603 external_id: arxiv: - '1508.06546' intvolume: ' 738' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1508.06546 month: '01' oa: 1 oa_version: Submitted Version page: 463 - 491 publication: Journal of Fluid Mechanics publication_status: published publisher: Cambridge University Press publist_id: '5001' quality_controlled: '1' scopus_import: 1 status: public title: Experimental investigation of transitional flow in a toroidal pipe type: journal_article user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87 volume: 738 year: '2014' ... --- _id: '2224' abstract: - lang: eng text: This work investigates the transition between different traveling helical waves (spirals, SPIs) in the setup of differentially independent rotating cylinders. We use direct numerical simulations to consider an infinite long and periodic Taylor-Couette apparatus with fixed axial periodicity length. We find so-called mixed-cross-spirals (MCSs), that can be seen as nonlinear superpositions of SPIs, to establish stable footbridges connecting SPI states. While bridging the bifurcation branches of SPIs, the corresponding contributions within the MCS vary continuously with the control parameters. Here discussed MCSs presenting footbridge solutions start and end in different SPI branches. Therefore they differ significantly from the already known MCSs that present bypass solutions (Altmeyer and Hoffmann 2010 New J. Phys. 12 113035). The latter start and end in the same SPI branch, while they always bifurcate out of those SPI branches with the larger mode amplitude. Meanwhile, these only appear within the coexisting region of both SPIs. In contrast, the footbridge solutions can also bifurcate out of the minor SPI contribution. We also find they exist in regions where only one of the SPIs contributions exists. In addition, MCS as footbridge solution can appear either stable or unstable. The latter detected transient solutions offer similar spatio-temporal characteristics to the flow establishing stable footbridges. Such transition processes are interesting for pattern-forming systems in general because they accomplish transitions between traveling waves of different azimuthal wave numbers and have not been described in the literature yet. article_number: '025503' author: - first_name: Sebastian full_name: Altmeyer, Sebastian id: 2EE67FDC-F248-11E8-B48F-1D18A9856A87 last_name: Altmeyer orcid: 0000-0001-5964-0203 citation: ama: Altmeyer S. On secondary instabilities generating footbridges between spiral vortex flow. Fluid Dynamics Research. 2014;46(2). doi:10.1088/0169-5983/46/2/025503 apa: Altmeyer, S. (2014). On secondary instabilities generating footbridges between spiral vortex flow. Fluid Dynamics Research. IOP Publishing Ltd. https://doi.org/10.1088/0169-5983/46/2/025503 chicago: Altmeyer, Sebastian. “On Secondary Instabilities Generating Footbridges between Spiral Vortex Flow.” Fluid Dynamics Research. IOP Publishing Ltd., 2014. https://doi.org/10.1088/0169-5983/46/2/025503. ieee: S. Altmeyer, “On secondary instabilities generating footbridges between spiral vortex flow,” Fluid Dynamics Research, vol. 46, no. 2. IOP Publishing Ltd., 2014. ista: Altmeyer S. 2014. On secondary instabilities generating footbridges between spiral vortex flow. Fluid Dynamics Research. 46(2), 025503. mla: Altmeyer, Sebastian. “On Secondary Instabilities Generating Footbridges between Spiral Vortex Flow.” Fluid Dynamics Research, vol. 46, no. 2, 025503, IOP Publishing Ltd., 2014, doi:10.1088/0169-5983/46/2/025503. short: S. Altmeyer, Fluid Dynamics Research 46 (2014). date_created: 2018-12-11T11:56:25Z date_published: 2014-04-01T00:00:00Z date_updated: 2021-01-12T06:56:07Z day: '01' department: - _id: BjHo doi: 10.1088/0169-5983/46/2/025503 intvolume: ' 46' issue: '2' language: - iso: eng month: '04' oa_version: None publication: Fluid Dynamics Research publication_identifier: issn: - '01695983' publication_status: published publisher: IOP Publishing Ltd. publist_id: '4740' quality_controlled: '1' scopus_import: 1 status: public title: On secondary instabilities generating footbridges between spiral vortex flow type: journal_article user_id: 4435EBFC-F248-11E8-B48F-1D18A9856A87 volume: 46 year: '2014' ... --- _id: '2232' abstract: - lang: eng text: The purpose of this contribution is to summarize and discuss recent advances regarding the onset of turbulence in shear flows. The absence of a clear-cut instability mechanism, the spatio-temporal intermittent character and extremely long lived transients are some of the major difficulties encountered in these flows and have hindered progress towards understanding the transition process. We will show for the case of pipe flow that concepts from nonlinear dynamics and statistical physics can help to explain the onset of turbulence. In particular, the turbulent structures (puffs) observed close to onset are spatially localized chaotic transients and their lifetimes increase super-exponentially with Reynolds number. At the same time fluctuations of individual turbulent puffs can (although very rarely) lead to the nucleation of new puffs. The competition between these two stochastic processes gives rise to a non-equilibrium phase transition where turbulence changes from a super-transient to a sustained state. article_number: P02001 article_processing_charge: No article_type: original author: - first_name: Baofang full_name: Song, Baofang id: a79e57f5-e8a5-11ec-9dc9-83fb8c81cf72 last_name: Song - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Song B, Hof B. Deterministic and stochastic aspects of the transition to turbulence. Journal of Statistical Mechanics Theory and Experiment. 2014;2014(2). doi:10.1088/1742-5468/2014/02/P02001 apa: Song, B., & Hof, B. (2014). Deterministic and stochastic aspects of the transition to turbulence. Journal of Statistical Mechanics Theory and Experiment. IOP Publishing. https://doi.org/10.1088/1742-5468/2014/02/P02001 chicago: Song, Baofang, and Björn Hof. “Deterministic and Stochastic Aspects of the Transition to Turbulence.” Journal of Statistical Mechanics Theory and Experiment. IOP Publishing, 2014. https://doi.org/10.1088/1742-5468/2014/02/P02001. ieee: B. Song and B. Hof, “Deterministic and stochastic aspects of the transition to turbulence,” Journal of Statistical Mechanics Theory and Experiment, vol. 2014, no. 2. IOP Publishing, 2014. ista: Song B, Hof B. 2014. Deterministic and stochastic aspects of the transition to turbulence. Journal of Statistical Mechanics Theory and Experiment. 2014(2), P02001. mla: Song, Baofang, and Björn Hof. “Deterministic and Stochastic Aspects of the Transition to Turbulence.” Journal of Statistical Mechanics Theory and Experiment, vol. 2014, no. 2, P02001, IOP Publishing, 2014, doi:10.1088/1742-5468/2014/02/P02001. short: B. Song, B. Hof, Journal of Statistical Mechanics Theory and Experiment 2014 (2014). date_created: 2018-12-11T11:56:28Z date_published: 2014-02-01T00:00:00Z date_updated: 2022-06-10T10:13:15Z day: '01' department: - _id: BjHo doi: 10.1088/1742-5468/2014/02/P02001 external_id: arxiv: - '1403.4516' intvolume: ' 2014' issue: '2' language: - iso: eng main_file_link: - open_access: '1' url: http://arxiv.org/abs/1403.4516 month: '02' oa: 1 oa_version: Submitted Version publication: Journal of Statistical Mechanics Theory and Experiment publication_identifier: issn: - '17425468' publication_status: published publisher: IOP Publishing publist_id: '4729' quality_controlled: '1' status: public title: Deterministic and stochastic aspects of the transition to turbulence type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 2014 year: '2014' ... --- _id: '2226' abstract: - lang: eng text: Coriolis force effects on shear flows are important in geophysical and astrophysical contexts. We report a study on the linear stability and the transient energy growth of the plane Couette flow with system rotation perpendicular to the shear direction. External rotation causes linear instability. At small rotation rates, the onset of linear instability scales inversely with the rotation rate and the optimal transient growth in the linearly stable region is slightly enhanced ∼Re2. The corresponding optimal initial perturbations are characterized by roll structures inclined in the streamwise direction and are twisted under external rotation. At large rotation rates, the transient growth is significantly inhibited and hence linear stability analysis is a reliable indicator for instability. article_number: '013001' author: - first_name: Liang full_name: Shi, Liang last_name: Shi - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 - first_name: Andreas full_name: Tilgner, Andreas last_name: Tilgner citation: ama: Shi L, Hof B, Tilgner A. Transient growth of Ekman-Couette flow. Physical Review E Statistical Nonlinear and Soft Matter Physics. 2014;89(1). doi:10.1103/PhysRevE.89.013001 apa: Shi, L., Hof, B., & Tilgner, A. (2014). Transient growth of Ekman-Couette flow. Physical Review E Statistical Nonlinear and Soft Matter Physics. American Institute of Physics. https://doi.org/10.1103/PhysRevE.89.013001 chicago: Shi, Liang, Björn Hof, and Andreas Tilgner. “Transient Growth of Ekman-Couette Flow.” Physical Review E Statistical Nonlinear and Soft Matter Physics. American Institute of Physics, 2014. https://doi.org/10.1103/PhysRevE.89.013001. ieee: L. Shi, B. Hof, and A. Tilgner, “Transient growth of Ekman-Couette flow,” Physical Review E Statistical Nonlinear and Soft Matter Physics, vol. 89, no. 1. American Institute of Physics, 2014. ista: Shi L, Hof B, Tilgner A. 2014. Transient growth of Ekman-Couette flow. Physical Review E Statistical Nonlinear and Soft Matter Physics. 89(1), 013001. mla: Shi, Liang, et al. “Transient Growth of Ekman-Couette Flow.” Physical Review E Statistical Nonlinear and Soft Matter Physics, vol. 89, no. 1, 013001, American Institute of Physics, 2014, doi:10.1103/PhysRevE.89.013001. short: L. Shi, B. Hof, A. Tilgner, Physical Review E Statistical Nonlinear and Soft Matter Physics 89 (2014). date_created: 2018-12-11T11:56:26Z date_published: 2014-01-06T00:00:00Z date_updated: 2021-01-12T06:56:08Z day: '06' department: - _id: BjHo doi: 10.1103/PhysRevE.89.013001 intvolume: ' 89' issue: '1' language: - iso: eng main_file_link: - open_access: '1' url: http://arxiv.org/abs/1312.5095 month: '01' oa: 1 oa_version: Submitted Version project: - _id: 25BDE9A4-B435-11E9-9278-68D0E5697425 grant_number: SFB-TR3-TP10B name: Glutamaterge synaptische Übertragung und Plastizität in hippocampalen Mikroschaltkreisen publication: Physical Review E Statistical Nonlinear and Soft Matter Physics publication_identifier: issn: - '15393755' publication_status: published publisher: American Institute of Physics publist_id: '4737' quality_controlled: '1' scopus_import: 1 status: public title: Transient growth of Ekman-Couette flow type: journal_article user_id: 4435EBFC-F248-11E8-B48F-1D18A9856A87 volume: 89 year: '2014' ... --- _id: '2806' abstract: - lang: eng text: A novel Taylor-Couette system has been constructed for investigations of transitional as well as high Reynolds number turbulent flows in very large aspect ratios. The flexibility of the setup enables studies of a variety of problems regarding hydrodynamic instabilities and turbulence in rotating flows. The inner and outer cylinders and the top and bottom endplates can be rotated independently with rotation rates of up to 30 Hz, thereby covering five orders of magnitude in Reynolds numbers (Re = 101-106). The radius ratio can be easily changed, the highest realized one is η = 0.98 corresponding to an aspect ratio of 260 gap width in the vertical and 300 in the azimuthal direction. For η < 0.98 the aspect ratio can be dynamically changed during measurements and complete transparency in the radial direction over the full length of the cylinders is provided by the usage of a precision glass inner cylinder. The temperatures of both cylinders are controlled independently. Overall this apparatus combines an unmatched variety in geometry, rotation rates, and temperatures, which is provided by a sophisticated high-precision bearing system. Possible applications are accurate studies of the onset of turbulence and spatio-temporal intermittent flow patterns in very large domains, transport processes of turbulence at high Re, the stability of Keplerian flows for different boundary conditions, and studies of baroclinic instabilities. article_number: '065106' author: - first_name: Kerstin full_name: Avila, Kerstin last_name: Avila - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Avila K, Hof B. High-precision Taylor-Couette experiment to study subcritical transitions and the role of boundary conditions and size effects. Review of Scientific Instruments. 2013;84(6). doi:10.1063/1.4807704 apa: Avila, K., & Hof, B. (2013). High-precision Taylor-Couette experiment to study subcritical transitions and the role of boundary conditions and size effects. Review of Scientific Instruments. American Institute of Physics. https://doi.org/10.1063/1.4807704 chicago: Avila, Kerstin, and Björn Hof. “High-Precision Taylor-Couette Experiment to Study Subcritical Transitions and the Role of Boundary Conditions and Size Effects.” Review of Scientific Instruments. American Institute of Physics, 2013. https://doi.org/10.1063/1.4807704. ieee: K. Avila and B. Hof, “High-precision Taylor-Couette experiment to study subcritical transitions and the role of boundary conditions and size effects,” Review of Scientific Instruments, vol. 84, no. 6. American Institute of Physics, 2013. ista: Avila K, Hof B. 2013. High-precision Taylor-Couette experiment to study subcritical transitions and the role of boundary conditions and size effects. Review of Scientific Instruments. 84(6), 065106. mla: Avila, Kerstin, and Björn Hof. “High-Precision Taylor-Couette Experiment to Study Subcritical Transitions and the Role of Boundary Conditions and Size Effects.” Review of Scientific Instruments, vol. 84, no. 6, 065106, American Institute of Physics, 2013, doi:10.1063/1.4807704. short: K. Avila, B. Hof, Review of Scientific Instruments 84 (2013). date_created: 2018-12-11T11:59:42Z date_published: 2013-06-06T00:00:00Z date_updated: 2021-01-12T06:59:50Z day: '06' department: - _id: BjHo doi: 10.1063/1.4807704 intvolume: ' 84' issue: '6' language: - iso: eng month: '06' oa_version: None publication: Review of Scientific Instruments publication_status: published publisher: American Institute of Physics publist_id: '4081' quality_controlled: '1' scopus_import: 1 status: public title: High-precision Taylor-Couette experiment to study subcritical transitions and the role of boundary conditions and size effects type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 84 year: '2013' ... --- _id: '2811' abstract: - lang: eng text: 'In pipe, channel, and boundary layer flows turbulence first occurs intermittently in space and time: at moderate Reynolds numbers domains of disordered turbulent motion are separated by quiescent laminar regions. Based on direct numerical simulations of pipe flow we argue here that the spatial intermittency has its origin in a nearest neighbor interaction between turbulent regions. We further show that in this regime turbulent flows are intrinsically intermittent with a well-defined equilibrium turbulent fraction but without ever assuming a steady pattern. This transition scenario is analogous to that found in simple models such as coupled map lattices. The scaling observed implies that laminar intermissions of the turbulent flow will persist to arbitrarily large Reynolds numbers.' article_number: '063012' author: - first_name: Marc full_name: Avila, Marc last_name: Avila - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Avila M, Hof B. Nature of laminar-turbulence intermittency in shear flows. Physical Review E. 2013;87(6). doi:10.1103/PhysRevE.87.063012 apa: Avila, M., & Hof, B. (2013). Nature of laminar-turbulence intermittency in shear flows. Physical Review E. American Institute of Physics. https://doi.org/10.1103/PhysRevE.87.063012 chicago: Avila, Marc, and Björn Hof. “Nature of Laminar-Turbulence Intermittency in Shear Flows.” Physical Review E. American Institute of Physics, 2013. https://doi.org/10.1103/PhysRevE.87.063012. ieee: M. Avila and B. Hof, “Nature of laminar-turbulence intermittency in shear flows,” Physical Review E, vol. 87, no. 6. American Institute of Physics, 2013. ista: Avila M, Hof B. 2013. Nature of laminar-turbulence intermittency in shear flows. Physical Review E. 87(6), 063012. mla: Avila, Marc, and Björn Hof. “Nature of Laminar-Turbulence Intermittency in Shear Flows.” Physical Review E, vol. 87, no. 6, 063012, American Institute of Physics, 2013, doi:10.1103/PhysRevE.87.063012. short: M. Avila, B. Hof, Physical Review E 87 (2013). date_created: 2018-12-11T11:59:43Z date_published: 2013-06-18T00:00:00Z date_updated: 2021-01-12T06:59:53Z day: '18' department: - _id: BjHo doi: 10.1103/PhysRevE.87.063012 ec_funded: 1 external_id: arxiv: - '1306.5890' intvolume: ' 87' issue: '6' language: - iso: eng main_file_link: - open_access: '1' url: http://arxiv.org/abs/1306.5890 month: '06' oa: 1 oa_version: Preprint project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin publication: Physical Review E publication_status: published publisher: American Institute of Physics publist_id: '4074' quality_controlled: '1' scopus_import: 1 status: public title: Nature of laminar-turbulence intermittency in shear flows type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 87 year: '2013' ... --- _id: '2813' abstract: - lang: eng text: Turbulence is ubiquitous in nature, yet even for the case of ordinary Newtonian fluids like water, our understanding of this phenomenon is limited. Many liquids of practical importance are more complicated (e.g., blood, polymer melts, paints), however; they exhibit elastic as well as viscous characteristics, and the relation between stress and strain is nonlinear. We demonstrate here for a model system of such complex fluids that at high shear rates, turbulence is not simply modified as previously believed but is suppressed and replaced by a different type of disordered motion, elasto-inertial turbulence. Elasto-inertial turbulence is found to occur at much lower Reynolds numbers than Newtonian turbulence, and the dynamical properties differ significantly. The friction scaling observed coincides with the so-called "maximum drag reduction" asymptote, which is exhibited by a wide range of viscoelastic fluids. author: - first_name: Devranjan full_name: Samanta, Devranjan last_name: Samanta - first_name: Yves full_name: Dubief, Yves last_name: Dubief - first_name: Markus full_name: Holzner, Markus last_name: Holzner - first_name: Christof full_name: Schäfer, Christof last_name: Schäfer - first_name: Alexander full_name: Morozov, Alexander last_name: Morozov - first_name: Christian full_name: Wagner, Christian last_name: Wagner - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Samanta D, Dubief Y, Holzner M, et al. Elasto-inertial turbulence. PNAS. 2013;110(26):10557-10562. doi:10.1073/pnas.1219666110 apa: Samanta, D., Dubief, Y., Holzner, M., Schäfer, C., Morozov, A., Wagner, C., & Hof, B. (2013). Elasto-inertial turbulence. PNAS. National Academy of Sciences. https://doi.org/10.1073/pnas.1219666110 chicago: Samanta, Devranjan, Yves Dubief, Markus Holzner, Christof Schäfer, Alexander Morozov, Christian Wagner, and Björn Hof. “Elasto-Inertial Turbulence.” PNAS. National Academy of Sciences, 2013. https://doi.org/10.1073/pnas.1219666110. ieee: D. Samanta et al., “Elasto-inertial turbulence,” PNAS, vol. 110, no. 26. National Academy of Sciences, pp. 10557–10562, 2013. ista: Samanta D, Dubief Y, Holzner M, Schäfer C, Morozov A, Wagner C, Hof B. 2013. Elasto-inertial turbulence. PNAS. 110(26), 10557–10562. mla: Samanta, Devranjan, et al. “Elasto-Inertial Turbulence.” PNAS, vol. 110, no. 26, National Academy of Sciences, 2013, pp. 10557–62, doi:10.1073/pnas.1219666110. short: D. Samanta, Y. Dubief, M. Holzner, C. Schäfer, A. Morozov, C. Wagner, B. Hof, PNAS 110 (2013) 10557–10562. date_created: 2018-12-11T11:59:44Z date_published: 2013-06-25T00:00:00Z date_updated: 2021-01-12T06:59:54Z day: '25' department: - _id: BjHo doi: 10.1073/pnas.1219666110 external_id: pmid: - '23757498' intvolume: ' 110' issue: '26' language: - iso: eng main_file_link: - open_access: '1' url: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3696777/ month: '06' oa: 1 oa_version: Submitted Version page: 10557 - 10562 pmid: 1 publication: PNAS publication_status: published publisher: National Academy of Sciences publist_id: '4073' quality_controlled: '1' scopus_import: 1 status: public title: Elasto-inertial turbulence type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 110 year: '2013' ... --- _id: '2829' abstract: - lang: eng text: Laminar-turbulent intermittency is intrinsic to the transitional regime of a wide range of fluid flows including pipe, channel, boundary layer, and Couette flow. In the latter turbulent spots can grow and form continuous stripes, yet in the stripe-normal direction they remain interspersed by laminar fluid. We carry out direct numerical simulations in a long narrow domain and observe that individual turbulent stripes are transient. In agreement with recent observations in pipe flow, we find that turbulence becomes sustained at a distinct critical point once the spatial proliferation outweighs the inherent decaying process. By resolving the asymptotic size distributions close to criticality we can for the first time demonstrate scale invariance at the onset of turbulence. article_number: '204502' author: - first_name: Liang full_name: Shi, Liang id: 374A3F1A-F248-11E8-B48F-1D18A9856A87 last_name: Shi - first_name: Marc full_name: Avila, Marc last_name: Avila - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Shi L, Avila M, Hof B. Scale invariance at the onset of turbulence in couette flow. Physical Review Letters. 2013;110(20). doi:10.1103/PhysRevLett.110.204502 apa: Shi, L., Avila, M., & Hof, B. (2013). Scale invariance at the onset of turbulence in couette flow. Physical Review Letters. American Physical Society. https://doi.org/10.1103/PhysRevLett.110.204502 chicago: Shi, Liang, Marc Avila, and Björn Hof. “Scale Invariance at the Onset of Turbulence in Couette Flow.” Physical Review Letters. American Physical Society, 2013. https://doi.org/10.1103/PhysRevLett.110.204502. ieee: L. Shi, M. Avila, and B. Hof, “Scale invariance at the onset of turbulence in couette flow,” Physical Review Letters, vol. 110, no. 20. American Physical Society, 2013. ista: Shi L, Avila M, Hof B. 2013. Scale invariance at the onset of turbulence in couette flow. Physical Review Letters. 110(20), 204502. mla: Shi, Liang, et al. “Scale Invariance at the Onset of Turbulence in Couette Flow.” Physical Review Letters, vol. 110, no. 20, 204502, American Physical Society, 2013, doi:10.1103/PhysRevLett.110.204502. short: L. Shi, M. Avila, B. Hof, Physical Review Letters 110 (2013). date_created: 2018-12-11T11:59:49Z date_published: 2013-05-13T00:00:00Z date_updated: 2021-01-12T07:00:00Z day: '13' department: - _id: BjHo doi: 10.1103/PhysRevLett.110.204502 ec_funded: 1 external_id: arxiv: - '1304.5446' intvolume: ' 110' issue: '20' language: - iso: eng main_file_link: - open_access: '1' url: http://arxiv.org/abs/1304.5446 month: '05' oa: 1 oa_version: Preprint project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin - _id: 2511D90C-B435-11E9-9278-68D0E5697425 grant_number: SFB 963 TP A8 name: Astrophysical instability of currents and turbulences publication: Physical Review Letters publication_status: published publisher: American Physical Society publist_id: '3970' quality_controlled: '1' scopus_import: 1 status: public title: Scale invariance at the onset of turbulence in couette flow type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 110 year: '2013' ... --- _id: '2834' abstract: - lang: eng text: Although the equations governing fluid flow are well known, there are no analytical expressions that describe the complexity of turbulent motion. A recent proposition is that in analogy to low dimensional chaotic systems, turbulence is organized around unstable solutions of the governing equations which provide the building blocks of the disordered dynamics. We report the discovery of periodic solutions which just like intermittent turbulence are spatially localized and show that turbulent transients arise from one such solution branch. article_number: '224502' author: - first_name: Marc full_name: Avila, Marc last_name: Avila - first_name: Fernando full_name: Mellibovsky, Fernando last_name: Mellibovsky - first_name: Nicolas full_name: Roland, Nicolas last_name: Roland - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Avila M, Mellibovsky F, Roland N, Hof B. Streamwise-localized solutions at the onset of turbulence in pipe flow. Physical Review Letters. 2013;110(22). doi:10.1103/PhysRevLett.110.224502 apa: Avila, M., Mellibovsky, F., Roland, N., & Hof, B. (2013). Streamwise-localized solutions at the onset of turbulence in pipe flow. Physical Review Letters. American Physical Society. https://doi.org/10.1103/PhysRevLett.110.224502 chicago: Avila, Marc, Fernando Mellibovsky, Nicolas Roland, and Björn Hof. “Streamwise-Localized Solutions at the Onset of Turbulence in Pipe Flow.” Physical Review Letters. American Physical Society, 2013. https://doi.org/10.1103/PhysRevLett.110.224502. ieee: M. Avila, F. Mellibovsky, N. Roland, and B. Hof, “Streamwise-localized solutions at the onset of turbulence in pipe flow,” Physical Review Letters, vol. 110, no. 22. American Physical Society, 2013. ista: Avila M, Mellibovsky F, Roland N, Hof B. 2013. Streamwise-localized solutions at the onset of turbulence in pipe flow. Physical Review Letters. 110(22), 224502. mla: Avila, Marc, et al. “Streamwise-Localized Solutions at the Onset of Turbulence in Pipe Flow.” Physical Review Letters, vol. 110, no. 22, 224502, American Physical Society, 2013, doi:10.1103/PhysRevLett.110.224502. short: M. Avila, F. Mellibovsky, N. Roland, B. Hof, Physical Review Letters 110 (2013). date_created: 2018-12-11T11:59:50Z date_published: 2013-05-29T00:00:00Z date_updated: 2021-01-12T07:00:05Z day: '29' department: - _id: BjHo doi: 10.1103/PhysRevLett.110.224502 ec_funded: 1 external_id: arxiv: - '1212.0230' intvolume: ' 110' issue: '22' language: - iso: eng main_file_link: - open_access: '1' url: http://arxiv.org/abs/1212.0230 month: '05' oa: 1 oa_version: Preprint project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin publication: Physical Review Letters publication_status: published publisher: American Physical Society publist_id: '3965' quality_controlled: '1' scopus_import: 1 status: public title: Streamwise-localized solutions at the onset of turbulence in pipe flow type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 110 year: '2013' ...