--- _id: '513' abstract: - lang: eng text: 'We present an experimental setup that creates a shear flow with zero mean advection velocity achieved by counterbalancing the nonzero streamwise pressure gradient by moving boundaries, which generates plane Couette-Poiseuille flow. We obtain experimental results in the transitional regime for this flow. Using flow visualization, we characterize the subcritical transition to turbulence in Couette-Poiseuille flow and show the existence of turbulent spots generated by a permanent perturbation. Due to the zero mean advection velocity of the base profile, these turbulent structures are nearly stationary. We distinguish two regions of the turbulent spot: the active turbulent core, which is characterized by waviness of the streaks similar to traveling waves, and the surrounding region, which includes in addition the weak undisturbed streaks and oblique waves at the laminar-turbulent interface. We also study the dependence of the size of these two regions on Reynolds number. Finally, we show that the traveling waves move in the downstream (Poiseuille) direction.' article_number: '043904' author: - first_name: Lukasz full_name: Klotz, Lukasz id: 2C9AF1C2-F248-11E8-B48F-1D18A9856A87 last_name: Klotz orcid: 0000-0003-1740-7635 - first_name: Grégoire M full_name: Lemoult, Grégoire M id: 4787FE80-F248-11E8-B48F-1D18A9856A87 last_name: Lemoult - first_name: Idalia full_name: Frontczak, Idalia last_name: Frontczak - first_name: Laurette full_name: Tuckerman, Laurette last_name: Tuckerman - first_name: José full_name: Wesfreid, José last_name: Wesfreid citation: ama: 'Klotz L, Lemoult GM, Frontczak I, Tuckerman L, Wesfreid J. Couette-Poiseuille flow experiment with zero mean advection velocity: Subcritical transition to turbulence. Physical Review Fluids. 2017;2(4). doi:10.1103/PhysRevFluids.2.043904' apa: 'Klotz, L., Lemoult, G. M., Frontczak, I., Tuckerman, L., & Wesfreid, J. (2017). Couette-Poiseuille flow experiment with zero mean advection velocity: Subcritical transition to turbulence. Physical Review Fluids. American Physical Society. https://doi.org/10.1103/PhysRevFluids.2.043904' chicago: 'Klotz, Lukasz, Grégoire M Lemoult, Idalia Frontczak, Laurette Tuckerman, and José Wesfreid. “Couette-Poiseuille Flow Experiment with Zero Mean Advection Velocity: Subcritical Transition to Turbulence.” Physical Review Fluids. American Physical Society, 2017. https://doi.org/10.1103/PhysRevFluids.2.043904.' ieee: 'L. Klotz, G. M. Lemoult, I. Frontczak, L. Tuckerman, and J. Wesfreid, “Couette-Poiseuille flow experiment with zero mean advection velocity: Subcritical transition to turbulence,” Physical Review Fluids, vol. 2, no. 4. American Physical Society, 2017.' ista: 'Klotz L, Lemoult GM, Frontczak I, Tuckerman L, Wesfreid J. 2017. Couette-Poiseuille flow experiment with zero mean advection velocity: Subcritical transition to turbulence. Physical Review Fluids. 2(4), 043904.' mla: 'Klotz, Lukasz, et al. “Couette-Poiseuille Flow Experiment with Zero Mean Advection Velocity: Subcritical Transition to Turbulence.” Physical Review Fluids, vol. 2, no. 4, 043904, American Physical Society, 2017, doi:10.1103/PhysRevFluids.2.043904.' short: L. Klotz, G.M. Lemoult, I. Frontczak, L. Tuckerman, J. Wesfreid, Physical Review Fluids 2 (2017). date_created: 2018-12-11T11:46:54Z date_published: 2017-04-01T00:00:00Z date_updated: 2021-01-12T08:01:16Z day: '01' department: - _id: BjHo doi: 10.1103/PhysRevFluids.2.043904 intvolume: ' 2' issue: '4' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1704.02619 month: '04' oa: 1 oa_version: Preprint publication: Physical Review Fluids publication_status: published publisher: American Physical Society publist_id: '7306' quality_controlled: '1' scopus_import: 1 status: public title: 'Couette-Poiseuille flow experiment with zero mean advection velocity: Subcritical transition to turbulence' type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 2 year: '2017' ... --- _id: '651' abstract: - lang: eng text: "Superhydrophobic surfaces reduce the frictional drag between water and solid materials, but this effect is often temporary. The realization of sustained drag reduction has applications for water vehicles and pipeline flows.\r\n\r\n" author: - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: 'Hof B. Fluid dynamics: Water flows out of touch. Nature. 2017;541(7636):161-162. doi:10.1038/541161a' apa: 'Hof, B. (2017). Fluid dynamics: Water flows out of touch. Nature. Nature Publishing Group. https://doi.org/10.1038/541161a' chicago: 'Hof, Björn. “Fluid Dynamics: Water Flows out of Touch.” Nature. Nature Publishing Group, 2017. https://doi.org/10.1038/541161a.' ieee: 'B. Hof, “Fluid dynamics: Water flows out of touch,” Nature, vol. 541, no. 7636. Nature Publishing Group, pp. 161–162, 2017.' ista: 'Hof B. 2017. Fluid dynamics: Water flows out of touch. Nature. 541(7636), 161–162.' mla: 'Hof, Björn. “Fluid Dynamics: Water Flows out of Touch.” Nature, vol. 541, no. 7636, Nature Publishing Group, 2017, pp. 161–62, doi:10.1038/541161a.' short: B. Hof, Nature 541 (2017) 161–162. date_created: 2018-12-11T11:47:43Z date_published: 2017-01-11T00:00:00Z date_updated: 2021-01-12T08:07:49Z day: '11' department: - _id: BjHo doi: 10.1038/541161a intvolume: ' 541' issue: '7636' language: - iso: eng month: '01' oa_version: None page: 161 - 162 publication: Nature publication_identifier: issn: - '00280836' publication_status: published publisher: Nature Publishing Group publist_id: '7116' quality_controlled: '1' scopus_import: 1 status: public title: 'Fluid dynamics: Water flows out of touch' type: journal_article user_id: 4435EBFC-F248-11E8-B48F-1D18A9856A87 volume: 541 year: '2017' ... --- _id: '662' abstract: - lang: eng text: 'We report a direct-numerical-simulation study of the Taylor-Couette flow in the quasi-Keplerian regime at shear Reynolds numbers up to (105). Quasi-Keplerian rotating flow has been investigated for decades as a simplified model system to study the origin of turbulence in accretion disks that is not fully understood. The flow in this study is axially periodic and thus the experimental end-wall effects on the stability of the flow are avoided. Using optimal linear perturbations as initial conditions, our simulations find no sustained turbulence: the strong initial perturbations distort the velocity profile and trigger turbulence that eventually decays.' article_number: '044107' 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: Markus full_name: Rampp, Markus last_name: Rampp - first_name: Marc full_name: Avila, Marc last_name: Avila citation: ama: Shi L, Hof B, Rampp M, Avila M. Hydrodynamic turbulence in quasi Keplerian rotating flows. Physics of Fluids. 2017;29(4). doi:10.1063/1.4981525 apa: Shi, L., Hof, B., Rampp, M., & Avila, M. (2017). Hydrodynamic turbulence in quasi Keplerian rotating flows. Physics of Fluids. American Institute of Physics. https://doi.org/10.1063/1.4981525 chicago: Shi, Liang, Björn Hof, Markus Rampp, and Marc Avila. “Hydrodynamic Turbulence in Quasi Keplerian Rotating Flows.” Physics of Fluids. American Institute of Physics, 2017. https://doi.org/10.1063/1.4981525. ieee: L. Shi, B. Hof, M. Rampp, and M. Avila, “Hydrodynamic turbulence in quasi Keplerian rotating flows,” Physics of Fluids, vol. 29, no. 4. American Institute of Physics, 2017. ista: Shi L, Hof B, Rampp M, Avila M. 2017. Hydrodynamic turbulence in quasi Keplerian rotating flows. Physics of Fluids. 29(4), 044107. mla: Shi, Liang, et al. “Hydrodynamic Turbulence in Quasi Keplerian Rotating Flows.” Physics of Fluids, vol. 29, no. 4, 044107, American Institute of Physics, 2017, doi:10.1063/1.4981525. short: L. Shi, B. Hof, M. Rampp, M. Avila, Physics of Fluids 29 (2017). date_created: 2018-12-11T11:47:47Z date_published: 2017-04-01T00:00:00Z date_updated: 2021-01-12T08:08:15Z day: '01' department: - _id: BjHo doi: 10.1063/1.4981525 intvolume: ' 29' issue: '4' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1703.01714 month: '04' oa: 1 oa_version: Submitted Version project: - _id: 2511D90C-B435-11E9-9278-68D0E5697425 grant_number: SFB 963 TP A8 name: Astrophysical instability of currents and turbulences publication: Physics of Fluids publication_identifier: issn: - '10706631' publication_status: published publisher: American Institute of Physics publist_id: '7072' quality_controlled: '1' scopus_import: 1 status: public title: Hydrodynamic turbulence in quasi Keplerian rotating flows type: journal_article user_id: 4435EBFC-F248-11E8-B48F-1D18A9856A87 volume: 29 year: '2017' ... --- _id: '1160' abstract: - lang: eng text: 'We investigate fundamental nonlinear dynamics of ferrofluidic Taylor-Couette flow - flow confined be-tween two concentric independently rotating cylinders - consider small aspect ratio by solving the ferro-hydrodynamical equations, carrying out systematic bifurcation analysis. Without magnetic field, we find steady flow patterns, previously observed with a simple fluid, such as those containing normal one- or two vortex cells, as well as anomalous one-cell and twin-cell flow states. However, when a symmetry-breaking transverse magnetic field is present, all flow states exhibit stimulated, finite two-fold mode. Various bifurcations between steady and unsteady states can occur, corresponding to the transitions between the two-cell and one-cell states. While unsteady, axially oscillating flow states can arise, we also detect the emergence of new unsteady flow states. In particular, we uncover two new states: one contains only the azimuthally oscillating solution in the configuration of the twin-cell flow state, and an-other a rotating flow state. Topologically, these flow states are a limit cycle and a quasiperiodic solution on a two-torus, respectively. Emergence of new flow states in addition to observed ones with classical fluid, indicates that richer but potentially more controllable dynamics in ferrofluidic flows, as such flow states depend on the external magnetic field.' article_number: '40012' 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: 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. Dynamics of ferrofluidic flow in the Taylor-Couette system with a small aspect ratio. Scientific Reports. 2017;7. doi:10.1038/srep40012 apa: Altmeyer, S., Do, Y., & Lai, Y. (2017). Dynamics of ferrofluidic flow in the Taylor-Couette system with a small aspect ratio. Scientific Reports. Nature Publishing Group. https://doi.org/10.1038/srep40012 chicago: Altmeyer, Sebastian, Younghae Do, and Ying Lai. “Dynamics of Ferrofluidic Flow in the Taylor-Couette System with a Small Aspect Ratio.” Scientific Reports. Nature Publishing Group, 2017. https://doi.org/10.1038/srep40012. ieee: S. Altmeyer, Y. Do, and Y. Lai, “Dynamics of ferrofluidic flow in the Taylor-Couette system with a small aspect ratio,” Scientific Reports, vol. 7. Nature Publishing Group, 2017. ista: Altmeyer S, Do Y, Lai Y. 2017. Dynamics of ferrofluidic flow in the Taylor-Couette system with a small aspect ratio. Scientific Reports. 7, 40012. mla: Altmeyer, Sebastian, et al. “Dynamics of Ferrofluidic Flow in the Taylor-Couette System with a Small Aspect Ratio.” Scientific Reports, vol. 7, 40012, Nature Publishing Group, 2017, doi:10.1038/srep40012. short: S. Altmeyer, Y. Do, Y. Lai, Scientific Reports 7 (2017). date_created: 2018-12-11T11:50:28Z date_published: 2017-01-06T00:00:00Z date_updated: 2023-09-20T11:28:49Z day: '06' ddc: - '532' department: - _id: BjHo doi: 10.1038/srep40012 external_id: isi: - '000391269700001' file: - access_level: open_access checksum: 694aa70399444570825099c1a7ec91f2 content_type: application/pdf creator: system date_created: 2018-12-12T10:10:16Z date_updated: 2020-07-14T12:44:36Z file_id: '4802' file_name: IST-2017-743-v1+1_srep40012.pdf file_size: 4546835 relation: main_file file_date_updated: 2020-07-14T12:44:36Z has_accepted_license: '1' intvolume: ' 7' isi: 1 language: - iso: eng month: '01' oa: 1 oa_version: Published Version publication: Scientific Reports publication_identifier: issn: - '20452322' publication_status: published publisher: Nature Publishing Group publist_id: '6198' pubrep_id: '743' quality_controlled: '1' scopus_import: '1' status: public title: Dynamics of ferrofluidic flow in the Taylor-Couette system with a small aspect ratio 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: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 7 year: '2017' ... --- _id: '1087' abstract: - lang: eng text: Using extensive direct numerical simulations, the dynamics of laminar-turbulent fronts in pipe flow is investigated for Reynolds numbers between and 5500. We here investigate the physical distinction between the fronts of weak and strong slugs both by analysing the turbulent kinetic energy budget and by comparing the downstream front motion to the advection speed of bulk turbulent structures. Our study shows that weak downstream fronts travel slower than turbulent structures in the bulk and correspond to decaying turbulence at the front. At the downstream front speed becomes faster than the advection speed, marking the onset of strong fronts. In contrast to weak fronts, turbulent eddies are generated at strong fronts by feeding on the downstream laminar flow. Our study also suggests that temporal fluctuations of production and dissipation at the downstream laminar-turbulent front drive the dynamical switches between the two types of front observed up to. acknowledged_ssus: - _id: ScienComp article_processing_charge: No author: - first_name: Baofang full_name: Song, Baofang last_name: Song - first_name: Dwight full_name: Barkley, Dwight last_name: Barkley - 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: Song B, Barkley D, Hof B, Avila M. Speed and structure of turbulent fronts in pipe flow. Journal of Fluid Mechanics. 2017;813:1045-1059. doi:10.1017/jfm.2017.14 apa: Song, B., Barkley, D., Hof, B., & Avila, M. (2017). Speed and structure of turbulent fronts in pipe flow. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2017.14 chicago: Song, Baofang, Dwight Barkley, Björn Hof, and Marc Avila. “Speed and Structure of Turbulent Fronts in Pipe Flow.” Journal of Fluid Mechanics. Cambridge University Press, 2017. https://doi.org/10.1017/jfm.2017.14. ieee: B. Song, D. Barkley, B. Hof, and M. Avila, “Speed and structure of turbulent fronts in pipe flow,” Journal of Fluid Mechanics, vol. 813. Cambridge University Press, pp. 1045–1059, 2017. ista: Song B, Barkley D, Hof B, Avila M. 2017. Speed and structure of turbulent fronts in pipe flow. Journal of Fluid Mechanics. 813, 1045–1059. mla: Song, Baofang, et al. “Speed and Structure of Turbulent Fronts in Pipe Flow.” Journal of Fluid Mechanics, vol. 813, Cambridge University Press, 2017, pp. 1045–59, doi:10.1017/jfm.2017.14. short: B. Song, D. Barkley, B. Hof, M. Avila, Journal of Fluid Mechanics 813 (2017) 1045–1059. date_created: 2018-12-11T11:50:04Z date_published: 2017-02-25T00:00:00Z date_updated: 2023-09-20T11:47:22Z day: '25' department: - _id: BjHo doi: 10.1017/jfm.2017.14 ec_funded: 1 external_id: isi: - '000394376400044' intvolume: ' 813' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1603.04077 month: '02' oa: 1 oa_version: Submitted Version page: 1045 - 1059 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: '6290' quality_controlled: '1' scopus_import: '1' status: public title: Speed and structure of turbulent fronts in pipe flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 813 year: '2017' ... --- _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' ...