--- _id: '328' abstract: - lang: eng text: The drag of turbulent flows can be drastically decreased by adding small amounts of high molecular weight polymers. While drag reduction initially increases with polymer concentration, it eventually saturates to what is known as the maximum drag reduction (MDR) asymptote; this asymptote is generally attributed to the dynamics being reduced to a marginal yet persistent state of subdued turbulent motion. Contrary to this accepted view, we show that, for an appropriate choice of parameters, polymers can reduce the drag beyond the suggested asymptotic limit, eliminating turbulence and giving way to laminar flow. At higher polymer concentrations, however, the laminar state becomes unstable, resulting in a fluctuating flow with the characteristic drag of the MDR asymptote. Our findings indicate that the asymptotic state is hence dynamically disconnected from ordinary turbulence. © 2018 American Physical Society. acknowledged_ssus: - _id: SSU acknowledgement: The authors thank Philipp Maier and the IST Austria workshop for their dedicated technical support. article_number: '124501' article_processing_charge: No author: - first_name: George H full_name: Choueiri, George H id: 448BD5BC-F248-11E8-B48F-1D18A9856A87 last_name: Choueiri - 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: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Choueiri GH, Lopez Alonso JM, Hof B. Exceeding the asymptotic limit of polymer drag reduction. Physical Review Letters. 2018;120(12). doi:10.1103/PhysRevLett.120.124501 apa: Choueiri, G. H., Lopez Alonso, J. M., & Hof, B. (2018). Exceeding the asymptotic limit of polymer drag reduction. Physical Review Letters. American Physical Society. https://doi.org/10.1103/PhysRevLett.120.124501 chicago: Choueiri, George H, Jose M Lopez Alonso, and Björn Hof. “Exceeding the Asymptotic Limit of Polymer Drag Reduction.” Physical Review Letters. American Physical Society, 2018. https://doi.org/10.1103/PhysRevLett.120.124501. ieee: G. H. Choueiri, J. M. Lopez Alonso, and B. Hof, “Exceeding the asymptotic limit of polymer drag reduction,” Physical Review Letters, vol. 120, no. 12. American Physical Society, 2018. ista: Choueiri GH, Lopez Alonso JM, Hof B. 2018. Exceeding the asymptotic limit of polymer drag reduction. Physical Review Letters. 120(12), 124501. mla: Choueiri, George H., et al. “Exceeding the Asymptotic Limit of Polymer Drag Reduction.” Physical Review Letters, vol. 120, no. 12, 124501, American Physical Society, 2018, doi:10.1103/PhysRevLett.120.124501. short: G.H. Choueiri, J.M. Lopez Alonso, B. Hof, Physical Review Letters 120 (2018). date_created: 2018-12-11T11:45:51Z date_published: 2018-03-19T00:00:00Z date_updated: 2023-10-10T13:27:44Z day: '19' department: - _id: BjHo doi: 10.1103/PhysRevLett.120.124501 ec_funded: 1 external_id: isi: - '000427804000005' intvolume: ' 120' isi: 1 issue: '12' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1703.06271 month: '03' oa: 1 oa_version: Preprint project: - _id: 25681D80-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '291734' name: International IST Postdoc Fellowship Programme - _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: '7537' quality_controlled: '1' scopus_import: '1' status: public title: Exceeding the asymptotic limit of polymer drag reduction type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 120 year: '2018' ... --- _id: '136' abstract: - lang: eng text: Recent studies suggest that unstable, nonchaotic solutions of the Navier-Stokes equation may provide deep insights into fluid turbulence. In this article, we present a combined experimental and numerical study exploring the dynamical role of unstable equilibrium solutions and their invariant manifolds in a weakly turbulent, electromagnetically driven, shallow fluid layer. Identifying instants when turbulent evolution slows down, we compute 31 unstable equilibria of a realistic two-dimensional model of the flow. We establish the dynamical relevance of these unstable equilibria by showing that they are closely visited by the turbulent flow. We also establish the dynamical relevance of unstable manifolds by verifying that they are shadowed by turbulent trajectories departing from the neighborhoods of unstable equilibria over large distances in state space. article_processing_charge: No author: - first_name: Balachandra full_name: Suri, Balachandra id: 47A5E706-F248-11E8-B48F-1D18A9856A87 last_name: Suri - first_name: Jeffrey full_name: Tithof, Jeffrey last_name: Tithof - first_name: Roman full_name: Grigoriev, Roman last_name: Grigoriev - first_name: Michael full_name: Schatz, Michael last_name: Schatz citation: ama: Suri B, Tithof J, Grigoriev R, Schatz M. Unstable equilibria and invariant manifolds in quasi-two-dimensional Kolmogorov-like flow. Physical Review E. 2018;98(2). doi:10.1103/PhysRevE.98.023105 apa: Suri, B., Tithof, J., Grigoriev, R., & Schatz, M. (2018). Unstable equilibria and invariant manifolds in quasi-two-dimensional Kolmogorov-like flow. Physical Review E. American Physical Society. https://doi.org/10.1103/PhysRevE.98.023105 chicago: Suri, Balachandra, Jeffrey Tithof, Roman Grigoriev, and Michael Schatz. “Unstable Equilibria and Invariant Manifolds in Quasi-Two-Dimensional Kolmogorov-like Flow.” Physical Review E. American Physical Society, 2018. https://doi.org/10.1103/PhysRevE.98.023105. ieee: B. Suri, J. Tithof, R. Grigoriev, and M. Schatz, “Unstable equilibria and invariant manifolds in quasi-two-dimensional Kolmogorov-like flow,” Physical Review E, vol. 98, no. 2. American Physical Society, 2018. ista: Suri B, Tithof J, Grigoriev R, Schatz M. 2018. Unstable equilibria and invariant manifolds in quasi-two-dimensional Kolmogorov-like flow. Physical Review E. 98(2). mla: Suri, Balachandra, et al. “Unstable Equilibria and Invariant Manifolds in Quasi-Two-Dimensional Kolmogorov-like Flow.” Physical Review E, vol. 98, no. 2, American Physical Society, 2018, doi:10.1103/PhysRevE.98.023105. short: B. Suri, J. Tithof, R. Grigoriev, M. Schatz, Physical Review E 98 (2018). date_created: 2018-12-11T11:44:49Z date_published: 2018-08-13T00:00:00Z date_updated: 2023-10-10T13:29:10Z day: '13' department: - _id: BjHo doi: 10.1103/PhysRevE.98.023105 external_id: arxiv: - '1808.02088' isi: - '000441466800010' intvolume: ' 98' isi: 1 issue: '2' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1808.02088 month: '08' oa: 1 oa_version: Submitted Version publication: Physical Review E publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Unstable equilibria and invariant manifolds in quasi-two-dimensional Kolmogorov-like flow type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 98 year: '2018' ... --- _id: '422' abstract: - lang: eng text: We show that a rather simple, steady modification of the streamwise velocity profile in a pipe can lead to a complete collapse of turbulence and the flow fully relaminarizes. Two different devices, a stationary obstacle (inset) and a device which injects fluid through an annular gap close to the wall, are used to control the flow. Both devices modify the streamwise velocity profile such that the flow in the center of the pipe is decelerated and the flow in the near wall region is accelerated. We present measurements with stereoscopic particle image velocimetry to investigate and capture the development of the relaminarizing flow downstream these devices and the specific circumstances responsible for relaminarization. We find total relaminarization up to Reynolds numbers of 6000, where the skin friction in the far downstream distance is reduced by a factor of 3.4 due to relaminarization. In a smooth straight pipe the flow remains completely laminar downstream of the control. Furthermore, we show that transient (temporary) relaminarization in a spatially confined region right downstream the devices occurs also at much higher Reynolds numbers, accompanied by a significant local skin friction drag reduction. The underlying physical mechanism of relaminarization is attributed to a weakening of the near-wall turbulence production cycle. article_processing_charge: Yes (via OA deal) author: - first_name: Jakob full_name: Kühnen, Jakob id: 3A47AE32-F248-11E8-B48F-1D18A9856A87 last_name: Kühnen orcid: 0000-0003-4312-0179 - first_name: Davide full_name: Scarselli, Davide id: 40315C30-F248-11E8-B48F-1D18A9856A87 last_name: Scarselli orcid: 0000-0001-5227-4271 - first_name: Markus full_name: Schaner, Markus id: 316CE034-F248-11E8-B48F-1D18A9856A87 last_name: Schaner - 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, Scarselli D, Schaner M, Hof B. Relaminarization by steady modification of the streamwise velocity profile in a pipe. Flow Turbulence and Combustion. 2018;100(4):919-942. doi:10.1007/s10494-018-9896-4 apa: Kühnen, J., Scarselli, D., Schaner, M., & Hof, B. (2018). Relaminarization by steady modification of the streamwise velocity profile in a pipe. Flow Turbulence and Combustion. Springer. https://doi.org/10.1007/s10494-018-9896-4 chicago: Kühnen, Jakob, Davide Scarselli, Markus Schaner, and Björn Hof. “Relaminarization by Steady Modification of the Streamwise Velocity Profile in a Pipe.” Flow Turbulence and Combustion. Springer, 2018. https://doi.org/10.1007/s10494-018-9896-4. ieee: J. Kühnen, D. Scarselli, M. Schaner, and B. Hof, “Relaminarization by steady modification of the streamwise velocity profile in a pipe,” Flow Turbulence and Combustion, vol. 100, no. 4. Springer, pp. 919–942, 2018. ista: Kühnen J, Scarselli D, Schaner M, Hof B. 2018. Relaminarization by steady modification of the streamwise velocity profile in a pipe. Flow Turbulence and Combustion. 100(4), 919–942. mla: Kühnen, Jakob, et al. “Relaminarization by Steady Modification of the Streamwise Velocity Profile in a Pipe.” Flow Turbulence and Combustion, vol. 100, no. 4, Springer, 2018, pp. 919–42, doi:10.1007/s10494-018-9896-4. short: J. Kühnen, D. Scarselli, M. Schaner, B. Hof, Flow Turbulence and Combustion 100 (2018) 919–942. date_created: 2018-12-11T11:46:23Z date_published: 2018-01-01T00:00:00Z date_updated: 2024-03-27T23:30:36Z day: '01' ddc: - '530' department: - _id: BjHo doi: 10.1007/s10494-018-9896-4 ec_funded: 1 external_id: isi: - '000433113900004' file: - access_level: open_access checksum: d7c0bade150faabca150b0a9986e60ca content_type: application/pdf creator: dernst date_created: 2018-12-17T15:52:37Z date_updated: 2020-07-14T12:46:25Z file_id: '5717' file_name: 2018_FlowTurbulenceCombust_Kuehnen.pdf file_size: 2210020 relation: main_file file_date_updated: 2020-07-14T12:46:25Z has_accepted_license: '1' intvolume: ' 100' isi: 1 issue: '4' language: - iso: eng license: https://creativecommons.org/licenses/by/4.0/ month: '01' oa: 1 oa_version: Published Version page: 919 - 942 project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin publication: Flow Turbulence and Combustion publication_status: published publisher: Springer publist_id: '7401' quality_controlled: '1' related_material: record: - id: '7258' relation: dissertation_contains status: public scopus_import: '1' status: public title: Relaminarization by steady modification of the streamwise velocity profile in a pipe 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: 100 year: '2018' ... --- _id: '461' abstract: - lang: eng text: Turbulence is the major cause of friction losses in transport processes and it is responsible for a drastic drag increase in flows over bounding surfaces. While much effort is invested into developing ways to control and reduce turbulence intensities, so far no methods exist to altogether eliminate turbulence if velocities are sufficiently large. We demonstrate for pipe flow that appropriate distortions to the velocity profile lead to a complete collapse of turbulence and subsequently friction losses are reduced by as much as 90%. Counterintuitively, the return to laminar motion is accomplished by initially increasing turbulence intensities or by transiently amplifying wall shear. Since neither the Reynolds number nor the shear stresses decrease (the latter often increase), these measures are not indicative of turbulence collapse. Instead, an amplification mechanism measuring the interaction between eddies and the mean shear is found to set a threshold below which turbulence is suppressed beyond recovery. acknowledgement: We acknowledge the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement 306589, the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 737549) and the Deutsche Forschungsgemeinschaft (Project No. FOR 1182) for financial support. We thank our technician P. Maier for providing highly valuable ideas and greatly supporting us in all technical aspects. We thank M. Schaner for technical drawings, construction and design. We thank M. Schwegel for a Matlab code to post-process experimental data. 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: Baofang full_name: Song, Baofang last_name: Song - first_name: Davide full_name: Scarselli, Davide id: 40315C30-F248-11E8-B48F-1D18A9856A87 last_name: Scarselli orcid: 0000-0001-5227-4271 - 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: Michael full_name: Riedl, Michael id: 3BE60946-F248-11E8-B48F-1D18A9856A87 last_name: Riedl orcid: 0000-0003-4844-6311 - first_name: Ashley full_name: Willis, Ashley last_name: Willis - 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: Kühnen J, Song B, Scarselli D, et al. Destabilizing turbulence in pipe flow. Nature Physics. 2018;14:386-390. doi:10.1038/s41567-017-0018-3 apa: Kühnen, J., Song, B., Scarselli, D., Budanur, N. B., Riedl, M., Willis, A., … Hof, B. (2018). Destabilizing turbulence in pipe flow. Nature Physics. Nature Publishing Group. https://doi.org/10.1038/s41567-017-0018-3 chicago: Kühnen, Jakob, Baofang Song, Davide Scarselli, Nazmi B Budanur, Michael Riedl, Ashley Willis, Marc Avila, and Björn Hof. “Destabilizing Turbulence in Pipe Flow.” Nature Physics. Nature Publishing Group, 2018. https://doi.org/10.1038/s41567-017-0018-3. ieee: J. Kühnen et al., “Destabilizing turbulence in pipe flow,” Nature Physics, vol. 14. Nature Publishing Group, pp. 386–390, 2018. ista: Kühnen J, Song B, Scarselli D, Budanur NB, Riedl M, Willis A, Avila M, Hof B. 2018. Destabilizing turbulence in pipe flow. Nature Physics. 14, 386–390. mla: Kühnen, Jakob, et al. “Destabilizing Turbulence in Pipe Flow.” Nature Physics, vol. 14, Nature Publishing Group, 2018, pp. 386–90, doi:10.1038/s41567-017-0018-3. short: J. Kühnen, B. Song, D. Scarselli, N.B. Budanur, M. Riedl, A. Willis, M. Avila, B. Hof, Nature Physics 14 (2018) 386–390. date_created: 2018-12-11T11:46:36Z date_published: 2018-01-08T00:00:00Z date_updated: 2024-03-27T23:30:36Z day: '08' department: - _id: BjHo doi: 10.1038/s41567-017-0018-3 ec_funded: 1 external_id: isi: - '000429434100020' intvolume: ' 14' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1711.06543 month: '01' oa: 1 oa_version: Preprint page: 386-390 project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin - _id: 25104D44-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '737549' name: Eliminating turbulence in oil pipelines publication: Nature Physics publication_status: published publisher: Nature Publishing Group publist_id: '7360' quality_controlled: '1' related_material: record: - id: '12726' relation: dissertation_contains status: public - id: '14530' relation: dissertation_contains status: public - id: '7258' relation: dissertation_contains status: public scopus_import: '1' status: public title: Destabilizing turbulence in pipe flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 14 year: '2018' ... --- _id: '1211' abstract: - lang: eng text: Systems such as fluid flows in channels and pipes or the complex Ginzburg–Landau system, defined over periodic domains, exhibit both continuous symmetries, translational and rotational, as well as discrete symmetries under spatial reflections or complex conjugation. The simplest, and very common symmetry of this type is the equivariance of the defining equations under the orthogonal group O(2). We formulate a novel symmetry reduction scheme for such systems by combining the method of slices with invariant polynomial methods, and show how it works by applying it to the Kuramoto–Sivashinsky system in one spatial dimension. As an example, we track a relative periodic orbit through a sequence of bifurcations to the onset of chaos. Within the symmetry-reduced state space we are able to compute and visualize the unstable manifolds of relative periodic orbits, their torus bifurcations, a transition to chaos via torus breakdown, and heteroclinic connections between various relative periodic orbits. It would be very hard to carry through such analysis in the full state space, without a symmetry reduction such as the one we present here. acknowledgement: 'This work was supported by the family of late G. Robinson, Jr. and NSF Grant DMS-1211827. ' 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: Predrag full_name: Cvitanović, Predrag last_name: Cvitanović citation: ama: Budanur NB, Cvitanović P. Unstable manifolds of relative periodic orbits in the symmetry reduced state space of the Kuramoto–Sivashinsky system. Journal of Statistical Physics. 2017;167(3-4):636-655. doi:10.1007/s10955-016-1672-z apa: Budanur, N. B., & Cvitanović, P. (2017). Unstable manifolds of relative periodic orbits in the symmetry reduced state space of the Kuramoto–Sivashinsky system. Journal of Statistical Physics. Springer. https://doi.org/10.1007/s10955-016-1672-z chicago: Budanur, Nazmi B, and Predrag Cvitanović. “Unstable Manifolds of Relative Periodic Orbits in the Symmetry Reduced State Space of the Kuramoto–Sivashinsky System.” Journal of Statistical Physics. Springer, 2017. https://doi.org/10.1007/s10955-016-1672-z. ieee: N. B. Budanur and P. Cvitanović, “Unstable manifolds of relative periodic orbits in the symmetry reduced state space of the Kuramoto–Sivashinsky system,” Journal of Statistical Physics, vol. 167, no. 3–4. Springer, pp. 636–655, 2017. ista: Budanur NB, Cvitanović P. 2017. Unstable manifolds of relative periodic orbits in the symmetry reduced state space of the Kuramoto–Sivashinsky system. Journal of Statistical Physics. 167(3–4), 636–655. mla: Budanur, Nazmi B., and Predrag Cvitanović. “Unstable Manifolds of Relative Periodic Orbits in the Symmetry Reduced State Space of the Kuramoto–Sivashinsky System.” Journal of Statistical Physics, vol. 167, no. 3–4, Springer, 2017, pp. 636–55, doi:10.1007/s10955-016-1672-z. short: N.B. Budanur, P. Cvitanović, Journal of Statistical Physics 167 (2017) 636–655. date_created: 2018-12-11T11:50:44Z date_published: 2017-05-01T00:00:00Z date_updated: 2021-01-12T06:49:07Z day: '01' ddc: - '530' department: - _id: BjHo doi: 10.1007/s10955-016-1672-z file: - access_level: open_access checksum: 3e971d09eb167761aa0888ed415b0056 content_type: application/pdf creator: system date_created: 2018-12-12T10:18:01Z date_updated: 2020-07-14T12:44:39Z file_id: '5319' file_name: IST-2017-782-v1+1_BudCvi15.pdf file_size: 2820207 relation: main_file file_date_updated: 2020-07-14T12:44:39Z has_accepted_license: '1' intvolume: ' 167' issue: 3-4 language: - iso: eng month: '05' oa: 1 oa_version: Submitted Version page: 636-655 publication: Journal of Statistical Physics publication_status: published publisher: Springer publist_id: '6136' pubrep_id: '782' quality_controlled: '1' scopus_import: 1 status: public title: Unstable manifolds of relative periodic orbits in the symmetry reduced state space of the Kuramoto–Sivashinsky system type: journal_article user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87 volume: 167 year: '2017' ... --- _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' ... --- _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' ...