--- _id: '5943' abstract: - lang: eng text: The hairpin instability of a jet in a crossflow (JICF) for a low jet-to-crossflow velocity ratio is investigated experimentally for a velocity ratio range of R ∈ (0.14, 0.75) and crossflow Reynolds numbers ReD ∈ (260, 640). From spectral analysis we characterize the Strouhal number and amplitude of the hairpin instability as a function of R and ReD. We demonstrate that the dynamics of the hairpins is well described by the Landau model, and, hence, that the instability occurs through Hopf bifurcation, similarly to other hydrodynamical oscillators such as wake behind different bluff bodies. Using the Landau model, we determine the precise threshold values of hairpin shedding. We also study the spatial dependence of this hydrodynamical instability, which shows a global behaviour. article_processing_charge: No article_type: original author: - first_name: Lukasz full_name: Klotz, Lukasz id: 2C9AF1C2-F248-11E8-B48F-1D18A9856A87 last_name: Klotz orcid: 0000-0003-1740-7635 - first_name: Konrad full_name: Gumowski, Konrad last_name: Gumowski - first_name: José Eduardo full_name: Wesfreid, José Eduardo last_name: Wesfreid citation: ama: Klotz L, Gumowski K, Wesfreid JE. Experiments on a jet in a crossflow in the low-velocity-ratio regime. Journal of Fluid Mechanics. 2019;863:386-406. doi:10.1017/jfm.2018.974 apa: Klotz, L., Gumowski, K., & Wesfreid, J. E. (2019). Experiments on a jet in a crossflow in the low-velocity-ratio regime. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2018.974 chicago: Klotz, Lukasz, Konrad Gumowski, and José Eduardo Wesfreid. “Experiments on a Jet in a Crossflow in the Low-Velocity-Ratio Regime.” Journal of Fluid Mechanics. Cambridge University Press, 2019. https://doi.org/10.1017/jfm.2018.974. ieee: L. Klotz, K. Gumowski, and J. E. Wesfreid, “Experiments on a jet in a crossflow in the low-velocity-ratio regime,” Journal of Fluid Mechanics, vol. 863. Cambridge University Press, pp. 386–406, 2019. ista: Klotz L, Gumowski K, Wesfreid JE. 2019. Experiments on a jet in a crossflow in the low-velocity-ratio regime. Journal of Fluid Mechanics. 863, 386–406. mla: Klotz, Lukasz, et al. “Experiments on a Jet in a Crossflow in the Low-Velocity-Ratio Regime.” Journal of Fluid Mechanics, vol. 863, Cambridge University Press, 2019, pp. 386–406, doi:10.1017/jfm.2018.974. short: L. Klotz, K. Gumowski, J.E. Wesfreid, Journal of Fluid Mechanics 863 (2019) 386–406. date_created: 2019-02-10T22:59:15Z date_published: 2019-03-25T00:00:00Z date_updated: 2023-08-24T14:43:13Z day: '25' department: - _id: BjHo doi: 10.1017/jfm.2018.974 ec_funded: 1 external_id: arxiv: - '1902.07931' isi: - '000526029100016' intvolume: ' 863' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1902.07931 month: '03' oa: 1 oa_version: Preprint page: 386-406 project: - _id: 260C2330-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '754411' name: ISTplus - Postdoctoral Fellowships publication: Journal of Fluid Mechanics publication_status: published publisher: Cambridge University Press quality_controlled: '1' scopus_import: '1' status: public title: Experiments on a jet in a crossflow in the low-velocity-ratio regime type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 863 year: '2019' ... --- _id: '5878' abstract: - lang: eng text: We consider the motion of a droplet bouncing on a vibrating bath of the same fluid in the presence of a central potential. We formulate a rotation symmetry-reduced description of this system, which allows for the straightforward application of dynamical systems theory tools. As an illustration of the utility of the symmetry reduction, we apply it to a model of the pilot-wave system with a central harmonic force. We begin our analysis by identifying local bifurcations and the onset of chaos. We then describe the emergence of chaotic regions and their merging bifurcations, which lead to the formation of a global attractor. In this final regime, the droplet’s angular momentum spontaneously changes its sign as observed in the experiments of Perrard et al. article_number: '013122' article_processing_charge: No article_type: original 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: Marc full_name: Fleury, Marc last_name: Fleury citation: ama: 'Budanur NB, Fleury M. State space geometry of the chaotic pilot-wave hydrodynamics. Chaos: An Interdisciplinary Journal of Nonlinear Science. 2019;29(1). doi:10.1063/1.5058279' apa: 'Budanur, N. B., & Fleury, M. (2019). State space geometry of the chaotic pilot-wave hydrodynamics. Chaos: An Interdisciplinary Journal of Nonlinear Science. AIP Publishing. https://doi.org/10.1063/1.5058279' chicago: 'Budanur, Nazmi B, and Marc Fleury. “State Space Geometry of the Chaotic Pilot-Wave Hydrodynamics.” Chaos: An Interdisciplinary Journal of Nonlinear Science. AIP Publishing, 2019. https://doi.org/10.1063/1.5058279.' ieee: 'N. B. Budanur and M. Fleury, “State space geometry of the chaotic pilot-wave hydrodynamics,” Chaos: An Interdisciplinary Journal of Nonlinear Science, vol. 29, no. 1. AIP Publishing, 2019.' ista: 'Budanur NB, Fleury M. 2019. State space geometry of the chaotic pilot-wave hydrodynamics. Chaos: An Interdisciplinary Journal of Nonlinear Science. 29(1), 013122.' mla: 'Budanur, Nazmi B., and Marc Fleury. “State Space Geometry of the Chaotic Pilot-Wave Hydrodynamics.” Chaos: An Interdisciplinary Journal of Nonlinear Science, vol. 29, no. 1, 013122, AIP Publishing, 2019, doi:10.1063/1.5058279.' short: 'N.B. Budanur, M. Fleury, Chaos: An Interdisciplinary Journal of Nonlinear Science 29 (2019).' date_created: 2019-01-23T08:35:09Z date_published: 2019-01-22T00:00:00Z date_updated: 2023-08-25T10:16:11Z day: '22' department: - _id: BjHo doi: 10.1063/1.5058279 external_id: arxiv: - '1812.09011' isi: - '000457409100028' intvolume: ' 29' isi: 1 issue: '1' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1812.09011 month: '01' oa: 1 oa_version: Preprint publication: 'Chaos: An Interdisciplinary Journal of Nonlinear Science' publication_identifier: eissn: - 1089-7682 issn: - 1054-1500 publication_status: published publisher: AIP Publishing quality_controlled: '1' related_material: link: - relation: erratum url: https://aip.scitation.org/doi/abs/10.1063/1.5097157 scopus_import: '1' status: public title: State space geometry of the chaotic pilot-wave hydrodynamics type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 29 year: '2019' ... --- _id: '6413' abstract: - lang: eng text: Phase-field methods have long been used to model the flow of immiscible fluids. Their ability to naturally capture interface topological changes is widely recognized, but their accuracy in simulating flows of real fluids in practical geometries is not established. We here quantitatively investigate the convergence of the phase-field method to the sharp-interface limit with simulations of two-phase pipe flow. We focus on core-annular flows, in which a highly viscous fluid is lubricated by a less viscous fluid, and validate our simulations with an analytic laminar solution, a formal linear stability analysis and also in the fully nonlinear regime. We demonstrate the ability of the phase-field method to accurately deal with non-rectangular geometry, strong advection, unsteady fluctuations and large viscosity contrast. We argue that phase-field methods are very promising for quantitatively studying moderately turbulent flows, especially at high concentrations of the disperse phase. article_processing_charge: No article_type: original author: - first_name: Baofang full_name: Song, Baofang last_name: Song - first_name: Carlos full_name: Plana, Carlos last_name: Plana - 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: Song B, Plana C, Lopez Alonso JM, Avila M. Phase-field simulation of core-annular pipe flow. International Journal of Multiphase Flow. 2019;117:14-24. doi:10.1016/j.ijmultiphaseflow.2019.04.027 apa: Song, B., Plana, C., Lopez Alonso, J. M., & Avila, M. (2019). Phase-field simulation of core-annular pipe flow. International Journal of Multiphase Flow. Elsevier. https://doi.org/10.1016/j.ijmultiphaseflow.2019.04.027 chicago: Song, Baofang, Carlos Plana, Jose M Lopez Alonso, and Marc Avila. “Phase-Field Simulation of Core-Annular Pipe Flow.” International Journal of Multiphase Flow. Elsevier, 2019. https://doi.org/10.1016/j.ijmultiphaseflow.2019.04.027. ieee: B. Song, C. Plana, J. M. Lopez Alonso, and M. Avila, “Phase-field simulation of core-annular pipe flow,” International Journal of Multiphase Flow, vol. 117. Elsevier, pp. 14–24, 2019. ista: Song B, Plana C, Lopez Alonso JM, Avila M. 2019. Phase-field simulation of core-annular pipe flow. International Journal of Multiphase Flow. 117, 14–24. mla: Song, Baofang, et al. “Phase-Field Simulation of Core-Annular Pipe Flow.” International Journal of Multiphase Flow, vol. 117, Elsevier, 2019, pp. 14–24, doi:10.1016/j.ijmultiphaseflow.2019.04.027. short: B. Song, C. Plana, J.M. Lopez Alonso, M. Avila, International Journal of Multiphase Flow 117 (2019) 14–24. date_created: 2019-05-13T07:58:35Z date_published: 2019-08-01T00:00:00Z date_updated: 2023-08-25T10:19:55Z day: '01' department: - _id: BjHo doi: 10.1016/j.ijmultiphaseflow.2019.04.027 external_id: arxiv: - '1902.07351' isi: - '000474496000002' intvolume: ' 117' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1902.07351 month: '08' oa: 1 oa_version: Preprint page: 14-24 publication: International Journal of Multiphase Flow publication_identifier: issn: - '03019322' publication_status: published publisher: Elsevier quality_controlled: '1' scopus_import: '1' status: public title: Phase-field simulation of core-annular pipe flow type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 117 year: '2019' ... --- _id: '6978' abstract: - lang: eng text: In pipes and channels, the onset of turbulence is initially dominated by localizedtransients, which lead to sustained turbulence through their collective dynamics. In thepresent work, we study numerically the localized turbulence in pipe flow and elucidate astate space structure that gives rise to transient chaos. Starting from the basin boundaryseparating laminar and turbulent flow, we identify transverse homoclinic orbits, thepresence of which necessitates a homoclinic tangle and chaos. A direct consequence ofthe homoclinic tangle is the fractal nature of the laminar-turbulent boundary, which wasconjectured in various earlier studies. By mapping the transverse intersections between thestable and unstable manifold of a periodic orbit, we identify the gateways that promote anescape from turbulence. acknowledged_ssus: - _id: ScienComp article_processing_charge: No article_type: original 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: Akshunna full_name: Dogra, Akshunna last_name: Dogra - 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, Dogra A, Hof B. Geometry of transient chaos in streamwise-localized pipe flow turbulence. Physical Review Fluids. 2019;4(10):102401. doi:10.1103/PhysRevFluids.4.102401 apa: Budanur, N. B., Dogra, A., & Hof, B. (2019). Geometry of transient chaos in streamwise-localized pipe flow turbulence. Physical Review Fluids. American Physical Society. https://doi.org/10.1103/PhysRevFluids.4.102401 chicago: Budanur, Nazmi B, Akshunna Dogra, and Björn Hof. “Geometry of Transient Chaos in Streamwise-Localized Pipe Flow Turbulence.” Physical Review Fluids. American Physical Society, 2019. https://doi.org/10.1103/PhysRevFluids.4.102401. ieee: N. B. Budanur, A. Dogra, and B. Hof, “Geometry of transient chaos in streamwise-localized pipe flow turbulence,” Physical Review Fluids, vol. 4, no. 10. American Physical Society, p. 102401, 2019. ista: Budanur NB, Dogra A, Hof B. 2019. Geometry of transient chaos in streamwise-localized pipe flow turbulence. Physical Review Fluids. 4(10), 102401. mla: Budanur, Nazmi B., et al. “Geometry of Transient Chaos in Streamwise-Localized Pipe Flow Turbulence.” Physical Review Fluids, vol. 4, no. 10, American Physical Society, 2019, p. 102401, doi:10.1103/PhysRevFluids.4.102401. short: N.B. Budanur, A. Dogra, B. Hof, Physical Review Fluids 4 (2019) 102401. date_created: 2019-11-04T10:04:01Z date_published: 2019-10-01T00:00:00Z date_updated: 2023-08-30T07:20:03Z day: '01' department: - _id: BjHo doi: 10.1103/PhysRevFluids.4.102401 external_id: arxiv: - '1810.02211' isi: - '000493510400001' intvolume: ' 4' isi: 1 issue: '10' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1810.02211 month: '10' oa: 1 oa_version: Preprint page: '102401' publication: Physical Review Fluids publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Geometry of transient chaos in streamwise-localized pipe flow turbulence type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 4 year: '2019' ... --- _id: '7397' abstract: - lang: eng text: Polymer additives can substantially reduce the drag of turbulent flows and the upperlimit, the so called “maximum drag reduction” (MDR) asymptote is universal, i.e. inde-pendent of the type of polymer and solvent used. Until recently, the consensus was that,in this limit, flows are in a marginal state where only a minimal level of turbulence activ-ity persists. Observations in direct numerical simulations using minimal sized channelsappeared to support this view and reported long “hibernation” periods where turbu-lence is marginalized. In simulations of pipe flow we find that, indeed, with increasingWeissenberg number (Wi), turbulence expresses long periods of hibernation if the domainsize is small. However, with increasing pipe length, the temporal hibernation continuouslyalters to spatio-temporal intermittency and here the flow consists of turbulent puffs sur-rounded by laminar flow. Moreover, upon an increase in Wi, the flow fully relaminarises,in agreement with recent experiments. At even larger Wi, a different instability is en-countered causing a drag increase towards MDR. Our findings hence link earlier minimalflow unit simulations with recent experiments and confirm that the addition of polymersinitially suppresses Newtonian turbulence and leads to a reverse transition. The MDRstate on the other hand results from a separate instability and the underlying dynamicscorresponds to the recently proposed state of elasto-inertial-turbulence (EIT). article_processing_charge: No article_type: original 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: George H full_name: Choueiri, George H id: 448BD5BC-F248-11E8-B48F-1D18A9856A87 last_name: Choueiri - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Lopez Alonso JM, Choueiri GH, Hof B. Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit. Journal of Fluid Mechanics. 2019;874:699-719. doi:10.1017/jfm.2019.486 apa: Lopez Alonso, J. M., Choueiri, G. H., & Hof, B. (2019). Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit. Journal of Fluid Mechanics. CUP. https://doi.org/10.1017/jfm.2019.486 chicago: Lopez Alonso, Jose M, George H Choueiri, and Björn Hof. “Dynamics of Viscoelastic Pipe Flow at Low Reynolds Numbers in the Maximum Drag Reduction Limit.” Journal of Fluid Mechanics. CUP, 2019. https://doi.org/10.1017/jfm.2019.486. ieee: J. M. Lopez Alonso, G. H. Choueiri, and B. Hof, “Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit,” Journal of Fluid Mechanics, vol. 874. CUP, pp. 699–719, 2019. ista: Lopez Alonso JM, Choueiri GH, Hof B. 2019. Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit. Journal of Fluid Mechanics. 874, 699–719. mla: Lopez Alonso, Jose M., et al. “Dynamics of Viscoelastic Pipe Flow at Low Reynolds Numbers in the Maximum Drag Reduction Limit.” Journal of Fluid Mechanics, vol. 874, CUP, 2019, pp. 699–719, doi:10.1017/jfm.2019.486. short: J.M. Lopez Alonso, G.H. Choueiri, B. Hof, Journal of Fluid Mechanics 874 (2019) 699–719. date_created: 2020-01-29T16:05:19Z date_published: 2019-09-10T00:00:00Z date_updated: 2023-09-06T15:36:36Z day: '10' department: - _id: BjHo doi: 10.1017/jfm.2019.486 external_id: arxiv: - '1808.04080' isi: - '000475349900001' intvolume: ' 874' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1808.04080 month: '09' oa: 1 oa_version: Preprint page: 699-719 publication: Journal of Fluid Mechanics publication_identifier: eissn: - 1469-7645 issn: - 0022-1120 publication_status: published publisher: CUP quality_controlled: '1' scopus_import: '1' status: public title: Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 874 year: '2019' ... --- _id: '6957' abstract: - lang: eng text: "In many shear flows like pipe flow, plane Couette flow, plane Poiseuille flow, etc. turbulence emerges subcritically. Here, when subjected to strong enough perturbations, the flow becomes turbulent in spite of the laminar base flow being linearly stable. The nature of this instability has puzzled the scientific community for decades. At onset, turbulence appears in localized patches and flows are spatio-temporally intermittent. In pipe flow the localized turbulent structures are referred to as puffs and in planar flows like plane Couette and channel flow, patches arise in the form of localized oblique bands. In this thesis, we study the onset of turbulence in channel flow in direct numerical simulations from a dynamical system theory perspective, as well as by performing experiments in a large aspect ratio channel.\r\n\r\nThe aim of the experimental work is to determine the critical Reynolds number where turbulence first becomes sustained. Recently, the onset of turbulence has been described in analogy to absorbing state phase transition (i.e. directed percolation). In particular, it has been shown that the critical point can be estimated from the competition between spreading and decay processes. Here, by performing experiments, we identify the mechanisms underlying turbulence proliferation in channel flow and find the critical Reynolds number, above which turbulence becomes sustained. Above the critical point, the continuous growth at the tip of the stripes outweighs the stochastic shedding of turbulent patches at the tail and the stripes expand. For growing stripes, the probability to decay decreases while the probability of stripe splitting increases. Consequently, and unlike for the puffs in pipe flow, neither of these two processes is time-independent i.e. memoryless. Coupling between stripe expansion and creation of new stripes via splitting leads to a significantly lower critical point ($Re_c=670+/-10$) than most earlier studies suggest. \r\n\r\nWhile the above approach sheds light on how turbulence first becomes sustained, it provides no insight into the origin of the stripes themselves. In the numerical part of the thesis we investigate how turbulent stripes form from invariant solutions of the Navier-Stokes equations. The origin of these turbulent stripes can be identified by applying concepts from the dynamical system theory. In doing so, we identify the exact coherent structures underlying stripes and their bifurcations and how they give rise to the turbulent attractor in phase space. We first report a family of localized nonlinear traveling wave solutions of the Navier-Stokes equations in channel flow. These solutions show structural similarities with turbulent stripes in experiments like obliqueness, quasi-streamwise streaks and vortices, etc. A parametric study of these traveling wave solution is performed, with parameters like Reynolds number, stripe tilt angle and domain size, including the stability of the solutions. These solutions emerge through saddle-node bifurcations and form a phase space skeleton for the turbulent stripes observed in the experiments. The lower branches of these TW solutions at different tilt angles undergo Hopf bifurcation and new solutions branches of relative periodic orbits emerge. These RPO solutions do not belong to the same family and therefore the routes to chaos for different angles are different. \r\n\r\nIn shear flows, turbulence at onset is transient in nature. \ Consequently,turbulence can not be tracked to lower Reynolds numbers, where the dynamics may simplify. Before this happens, turbulence becomes short-lived and laminarizes. In the last part of the thesis, we show that using numerical simulations we can continue turbulent stripes in channel flow past the 'relaminarization barrier' all the way to their origin. Here, turbulent stripe dynamics simplifies and the fluctuations are no longer stochastic and the stripe settles down to a relative periodic orbit. This relative periodic orbit originates from the aforementioned traveling wave solutions. Starting from the relative periodic orbit, a small increase in speed i.e. Reynolds number gives rise to chaos and the attractor dimension sharply increases in contrast to the classical transition scenario where the instabilities affect the flow globally and give rise to much more gradual route to turbulence." alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Chaitanya S full_name: Paranjape, Chaitanya S id: 3D85B7C4-F248-11E8-B48F-1D18A9856A87 last_name: Paranjape citation: ama: Paranjape CS. Onset of turbulence in plane Poiseuille flow. 2019. doi:10.15479/AT:ISTA:6957 apa: Paranjape, C. S. (2019). Onset of turbulence in plane Poiseuille flow. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:6957 chicago: Paranjape, Chaitanya S. “Onset of Turbulence in Plane Poiseuille Flow.” Institute of Science and Technology Austria, 2019. https://doi.org/10.15479/AT:ISTA:6957. ieee: C. S. Paranjape, “Onset of turbulence in plane Poiseuille flow,” Institute of Science and Technology Austria, 2019. ista: Paranjape CS. 2019. Onset of turbulence in plane Poiseuille flow. Institute of Science and Technology Austria. mla: Paranjape, Chaitanya S. Onset of Turbulence in Plane Poiseuille Flow. Institute of Science and Technology Austria, 2019, doi:10.15479/AT:ISTA:6957. short: C.S. Paranjape, Onset of Turbulence in Plane Poiseuille Flow, Institute of Science and Technology Austria, 2019. date_created: 2019-10-22T12:08:43Z date_published: 2019-10-24T00:00:00Z date_updated: 2023-09-07T12:53:25Z day: '24' ddc: - '532' degree_awarded: PhD department: - _id: BjHo doi: 10.15479/AT:ISTA:6957 file: - access_level: closed checksum: 7ba298ba0ce7e1d11691af6b8eaf0a0a content_type: application/zip creator: cparanjape date_created: 2019-10-23T09:54:43Z date_updated: 2020-07-14T12:47:46Z file_id: '6962' file_name: Chaitanya_Paranjape_source_files_tex_figures.zip file_size: 45828099 relation: source_file - access_level: open_access checksum: 642697618314e31ac31392da7909c2d9 content_type: application/pdf creator: cparanjape date_created: 2019-10-23T10:37:09Z date_updated: 2020-07-14T12:47:46Z file_id: '6963' file_name: Chaitanya_Paranjape_Thesis.pdf file_size: 19504197 relation: main_file file_date_updated: 2020-07-14T12:47:46Z has_accepted_license: '1' keyword: - Instabilities - Turbulence - Nonlinear dynamics language: - iso: eng month: '10' oa: 1 oa_version: Published Version page: '138' publication_identifier: eissn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria status: public supervisor: - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 title: Onset of turbulence in plane Poiseuille flow type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2019' ... --- _id: '7197' abstract: - lang: eng text: During bacterial cell division, the tubulin-homolog FtsZ forms a ring-like structure at the center of the cell. This Z-ring not only organizes the division machinery, but treadmilling of FtsZ filaments was also found to play a key role in distributing proteins at the division site. What regulates the architecture, dynamics and stability of the Z-ring is currently unknown, but FtsZ-associated proteins are known to play an important role. Here, using an in vitro reconstitution approach, we studied how the well-conserved protein ZapA affects FtsZ treadmilling and filament organization into large-scale patterns. Using high-resolution fluorescence microscopy and quantitative image analysis, we found that ZapA cooperatively increases the spatial order of the filament network, but binds only transiently to FtsZ filaments and has no effect on filament length and treadmilling velocity. Together, our data provides a model for how FtsZ-associated proteins can increase the precision and stability of the bacterial cell division machinery in a switch-like manner. acknowledged_ssus: - _id: LifeSc - _id: Bio article_number: '5744' article_processing_charge: No article_type: original author: - first_name: Paulo R full_name: Dos Santos Caldas, Paulo R id: 38FCDB4C-F248-11E8-B48F-1D18A9856A87 last_name: Dos Santos Caldas orcid: 0000-0001-6730-4461 - first_name: Maria D full_name: Lopez Pelegrin, Maria D id: 319AA9CE-F248-11E8-B48F-1D18A9856A87 last_name: Lopez Pelegrin - first_name: Daniel J. G. full_name: Pearce, Daniel J. G. last_name: Pearce - 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: Jan full_name: Brugués, Jan last_name: Brugués - first_name: Martin full_name: Loose, Martin id: 462D4284-F248-11E8-B48F-1D18A9856A87 last_name: Loose orcid: 0000-0001-7309-9724 citation: ama: Dos Santos Caldas PR, Lopez Pelegrin MD, Pearce DJG, Budanur NB, Brugués J, Loose M. Cooperative ordering of treadmilling filaments in cytoskeletal networks of FtsZ and its crosslinker ZapA. Nature Communications. 2019;10. doi:10.1038/s41467-019-13702-4 apa: Dos Santos Caldas, P. R., Lopez Pelegrin, M. D., Pearce, D. J. G., Budanur, N. B., Brugués, J., & Loose, M. (2019). Cooperative ordering of treadmilling filaments in cytoskeletal networks of FtsZ and its crosslinker ZapA. Nature Communications. Springer Nature. https://doi.org/10.1038/s41467-019-13702-4 chicago: Dos Santos Caldas, Paulo R, Maria D Lopez Pelegrin, Daniel J. G. Pearce, Nazmi B Budanur, Jan Brugués, and Martin Loose. “Cooperative Ordering of Treadmilling Filaments in Cytoskeletal Networks of FtsZ and Its Crosslinker ZapA.” Nature Communications. Springer Nature, 2019. https://doi.org/10.1038/s41467-019-13702-4. ieee: P. R. Dos Santos Caldas, M. D. Lopez Pelegrin, D. J. G. Pearce, N. B. Budanur, J. Brugués, and M. Loose, “Cooperative ordering of treadmilling filaments in cytoskeletal networks of FtsZ and its crosslinker ZapA,” Nature Communications, vol. 10. Springer Nature, 2019. ista: Dos Santos Caldas PR, Lopez Pelegrin MD, Pearce DJG, Budanur NB, Brugués J, Loose M. 2019. Cooperative ordering of treadmilling filaments in cytoskeletal networks of FtsZ and its crosslinker ZapA. Nature Communications. 10, 5744. mla: Dos Santos Caldas, Paulo R., et al. “Cooperative Ordering of Treadmilling Filaments in Cytoskeletal Networks of FtsZ and Its Crosslinker ZapA.” Nature Communications, vol. 10, 5744, Springer Nature, 2019, doi:10.1038/s41467-019-13702-4. short: P.R. Dos Santos Caldas, M.D. Lopez Pelegrin, D.J.G. Pearce, N.B. Budanur, J. Brugués, M. Loose, Nature Communications 10 (2019). date_created: 2019-12-20T12:22:57Z date_published: 2019-12-17T00:00:00Z date_updated: 2023-09-07T13:18:51Z day: '17' ddc: - '570' department: - _id: MaLo - _id: BjHo doi: 10.1038/s41467-019-13702-4 ec_funded: 1 external_id: isi: - '000503009300001' file: - access_level: open_access checksum: a1b44b427ba341383197790d0e8789fa content_type: application/pdf creator: dernst date_created: 2019-12-23T07:34:56Z date_updated: 2020-07-14T12:47:53Z file_id: '7208' file_name: 2019_NatureComm_Caldas.pdf file_size: 8488733 relation: main_file file_date_updated: 2020-07-14T12:47:53Z has_accepted_license: '1' intvolume: ' 10' isi: 1 language: - iso: eng license: https://creativecommons.org/licenses/by/4.0/ month: '12' oa: 1 oa_version: Published Version project: - _id: 2595697A-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '679239' name: Self-Organization of the Bacterial Cell - _id: 260D98C8-B435-11E9-9278-68D0E5697425 name: Reconstitution of Bacterial Cell Division Using Purified Components publication: Nature Communications publication_identifier: issn: - 2041-1723 publication_status: published publisher: Springer Nature quality_controlled: '1' related_material: record: - id: '8358' relation: dissertation_contains status: public scopus_import: '1' status: public title: Cooperative ordering of treadmilling filaments in cytoskeletal networks of FtsZ and its crosslinker ZapA 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: 10 year: '2019' ... --- _id: '6069' abstract: - lang: eng text: Electron transport in two-dimensional conducting materials such as graphene, with dominant electron–electron interaction, exhibits unusual vortex flow that leads to a nonlocal current-field relation (negative resistance), distinct from the classical Ohm’s law. The transport behavior of these materials is best described by low Reynolds number hydrodynamics, where the constitutive pressure–speed relation is Stoke’s law. Here we report evidence of such vortices observed in a viscous flow of Newtonian fluid in a microfluidic device consisting of a rectangular cavity—analogous to the electronic system. We extend our experimental observations to elliptic cavities of different eccentricities, and validate them by numerically solving bi-harmonic equation obtained for the viscous flow with no-slip boundary conditions. We verify the existence of a predicted threshold at which vortices appear. Strikingly, we find that a two-dimensional theoretical model captures the essential features of three-dimensional Stokes flow in experiments. article_number: '937' article_processing_charge: No author: - first_name: Jonathan full_name: Mayzel, Jonathan last_name: Mayzel - first_name: Victor full_name: Steinberg, Victor last_name: Steinberg - first_name: Atul full_name: Varshney, Atul id: 2A2006B2-F248-11E8-B48F-1D18A9856A87 last_name: Varshney orcid: 0000-0002-3072-5999 citation: ama: Mayzel J, Steinberg V, Varshney A. Stokes flow analogous to viscous electron current in graphene. Nature Communications. 2019;10. doi:10.1038/s41467-019-08916-5 apa: Mayzel, J., Steinberg, V., & Varshney, A. (2019). Stokes flow analogous to viscous electron current in graphene. Nature Communications. Springer Nature. https://doi.org/10.1038/s41467-019-08916-5 chicago: Mayzel, Jonathan, Victor Steinberg, and Atul Varshney. “Stokes Flow Analogous to Viscous Electron Current in Graphene.” Nature Communications. Springer Nature, 2019. https://doi.org/10.1038/s41467-019-08916-5. ieee: J. Mayzel, V. Steinberg, and A. Varshney, “Stokes flow analogous to viscous electron current in graphene,” Nature Communications, vol. 10. Springer Nature, 2019. ista: Mayzel J, Steinberg V, Varshney A. 2019. Stokes flow analogous to viscous electron current in graphene. Nature Communications. 10, 937. mla: Mayzel, Jonathan, et al. “Stokes Flow Analogous to Viscous Electron Current in Graphene.” Nature Communications, vol. 10, 937, Springer Nature, 2019, doi:10.1038/s41467-019-08916-5. short: J. Mayzel, V. Steinberg, A. Varshney, Nature Communications 10 (2019). date_created: 2019-03-05T13:18:30Z date_published: 2019-02-26T00:00:00Z date_updated: 2023-09-08T11:39:02Z day: '26' ddc: - '530' - '532' department: - _id: BjHo doi: 10.1038/s41467-019-08916-5 ec_funded: 1 external_id: isi: - '000459704600001' file: - access_level: open_access checksum: 61192fc49e0d44907c2a4fe384e4b97f content_type: application/pdf creator: dernst date_created: 2019-03-05T13:33:04Z date_updated: 2020-07-14T12:47:18Z file_id: '6070' file_name: 2019_NatureComm_Mayzel.pdf file_size: 2646391 relation: main_file file_date_updated: 2020-07-14T12:47:18Z has_accepted_license: '1' intvolume: ' 10' isi: 1 language: - iso: eng month: '02' oa: 1 oa_version: Published Version project: - _id: 260C2330-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '754411' name: ISTplus - Postdoctoral Fellowships publication: Nature Communications publication_identifier: issn: - 2041-1723 publication_status: published publisher: Springer Nature quality_controlled: '1' scopus_import: '1' status: public title: Stokes flow analogous to viscous electron current in graphene 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: 10 year: '2019' ... --- _id: '6014' abstract: - lang: eng text: Speed of sound waves in gases and liquids are governed by the compressibility of the medium. There exists another type of non-dispersive wave where the wave speed depends on stress instead of elasticity of the medium. A well-known example is the Alfven wave, which propagates through plasma permeated by a magnetic field with the speed determined by magnetic tension. An elastic analogue of Alfven waves has been predicted in a flow of dilute polymer solution where the elastic stress of the stretching polymers determines the elastic wave speed. Here we present quantitative evidence of elastic Alfven waves in elastic turbulence of a viscoelastic creeping flow between two obstacles in channel flow. The key finding in the experimental proof is a nonlinear dependence of the elastic wave speed cel on the Weissenberg number Wi, which deviates from predictions based on a model of linear polymer elasticity. article_number: '652' article_processing_charge: No article_type: original author: - first_name: Atul full_name: Varshney, Atul id: 2A2006B2-F248-11E8-B48F-1D18A9856A87 last_name: Varshney orcid: 0000-0002-3072-5999 - first_name: Victor full_name: Steinberg, Victor last_name: Steinberg citation: ama: Varshney A, Steinberg V. Elastic alfven waves in elastic turbulence. Nature Communications. 2019;10. doi:10.1038/s41467-019-08551-0 apa: Varshney, A., & Steinberg, V. (2019). Elastic alfven waves in elastic turbulence. Nature Communications. Springer Nature. https://doi.org/10.1038/s41467-019-08551-0 chicago: Varshney, Atul, and Victor Steinberg. “Elastic Alfven Waves in Elastic Turbulence.” Nature Communications. Springer Nature, 2019. https://doi.org/10.1038/s41467-019-08551-0. ieee: A. Varshney and V. Steinberg, “Elastic alfven waves in elastic turbulence,” Nature Communications, vol. 10. Springer Nature, 2019. ista: Varshney A, Steinberg V. 2019. Elastic alfven waves in elastic turbulence. Nature Communications. 10, 652. mla: Varshney, Atul, and Victor Steinberg. “Elastic Alfven Waves in Elastic Turbulence.” Nature Communications, vol. 10, 652, Springer Nature, 2019, doi:10.1038/s41467-019-08551-0. short: A. Varshney, V. Steinberg, Nature Communications 10 (2019). date_created: 2019-02-15T07:10:46Z date_published: 2019-02-08T00:00:00Z date_updated: 2023-09-08T11:39:54Z day: '08' ddc: - '530' department: - _id: BjHo doi: 10.1038/s41467-019-08551-0 ec_funded: 1 external_id: arxiv: - '1902.03763' isi: - '000458175300001' file: - access_level: open_access checksum: d3acf07eaad95ec040d8e8565fc9ac37 content_type: application/pdf creator: dernst date_created: 2019-02-15T07:15:00Z date_updated: 2020-07-14T12:47:17Z file_id: '6015' file_name: 2019_NatureComm_Varshney.pdf file_size: 1331490 relation: main_file file_date_updated: 2020-07-14T12:47:17Z has_accepted_license: '1' intvolume: ' 10' isi: 1 language: - iso: eng month: '02' oa: 1 oa_version: Published Version project: - _id: 260C2330-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '754411' name: ISTplus - Postdoctoral Fellowships publication: Nature Communications publication_identifier: issn: - 2041-1723 publication_status: published publisher: Springer Nature quality_controlled: '1' scopus_import: '1' status: public title: Elastic alfven waves in elastic turbulence 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: 10 year: '2019' ... --- _id: '6779' abstract: - lang: eng text: "Recent studies suggest that unstable recurrent solutions of the Navier-Stokes equation provide new insights\r\ninto dynamics of turbulent flows. In this study, we compute an extensive network of dynamical connections\r\nbetween such solutions in a weakly turbulent quasi-two-dimensional Kolmogorov flow that lies in the inversion symmetric subspace. In particular, we find numerous isolated heteroclinic connections between different\r\ntypes of solutions—equilibria, periodic, and quasiperiodic orbits—as well as continua of connections forming\r\nhigher-dimensional connecting manifolds. We also compute a homoclinic connection of a periodic orbit and\r\nprovide strong evidence that the associated homoclinic tangle forms the chaotic repeller that underpins transient\r\nturbulence in the symmetric subspace." article_number: '013112' article_processing_charge: No article_type: original author: - first_name: Balachandra full_name: Suri, Balachandra id: 47A5E706-F248-11E8-B48F-1D18A9856A87 last_name: Suri - first_name: Ravi Kumar full_name: Pallantla, Ravi Kumar last_name: Pallantla - first_name: Michael F. full_name: Schatz, Michael F. last_name: Schatz - first_name: Roman O. full_name: Grigoriev, Roman O. last_name: Grigoriev citation: ama: Suri B, Pallantla RK, Schatz MF, Grigoriev RO. Heteroclinic and homoclinic connections in a Kolmogorov-like flow. Physical Review E. 2019;100(1). doi:10.1103/physreve.100.013112 apa: Suri, B., Pallantla, R. K., Schatz, M. F., & Grigoriev, R. O. (2019). Heteroclinic and homoclinic connections in a Kolmogorov-like flow. Physical Review E. American Physical Society. https://doi.org/10.1103/physreve.100.013112 chicago: Suri, Balachandra, Ravi Kumar Pallantla, Michael F. Schatz, and Roman O. Grigoriev. “Heteroclinic and Homoclinic Connections in a Kolmogorov-like Flow.” Physical Review E. American Physical Society, 2019. https://doi.org/10.1103/physreve.100.013112. ieee: B. Suri, R. K. Pallantla, M. F. Schatz, and R. O. Grigoriev, “Heteroclinic and homoclinic connections in a Kolmogorov-like flow,” Physical Review E, vol. 100, no. 1. American Physical Society, 2019. ista: Suri B, Pallantla RK, Schatz MF, Grigoriev RO. 2019. Heteroclinic and homoclinic connections in a Kolmogorov-like flow. Physical Review E. 100(1), 013112. mla: Suri, Balachandra, et al. “Heteroclinic and Homoclinic Connections in a Kolmogorov-like Flow.” Physical Review E, vol. 100, no. 1, 013112, American Physical Society, 2019, doi:10.1103/physreve.100.013112. short: B. Suri, R.K. Pallantla, M.F. Schatz, R.O. Grigoriev, Physical Review E 100 (2019). date_created: 2019-08-09T09:40:41Z date_published: 2019-07-25T00:00:00Z date_updated: 2024-02-28T13:13:00Z day: '25' ddc: - '532' department: - _id: BjHo doi: 10.1103/physreve.100.013112 ec_funded: 1 external_id: arxiv: - '1907.05860' isi: - '000477911800012' intvolume: ' 100' isi: 1 issue: '1' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1907.05860 month: '07' oa: 1 oa_version: Preprint project: - _id: 25681D80-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '291734' name: International IST Postdoc Fellowship Programme publication: Physical Review E publication_identifier: eissn: - 2470-0053 issn: - 2470-0045 publication_status: published publisher: American Physical Society quality_controlled: '1' scopus_import: '1' status: public title: Heteroclinic and homoclinic connections in a Kolmogorov-like flow type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 100 year: '2019' ... --- _id: '6486' abstract: - lang: eng text: Based on a novel control scheme, where a steady modification of the streamwise velocity profile leads to complete relaminarization of initially fully turbulent pipe flow, we investigate the applicability and usefulness of custom-shaped honeycombs for such control. The custom-shaped honeycombs are used as stationary flow management devices which generate specific modifications of the streamwise velocity profile. Stereoscopic particle image velocimetry and pressure drop measurements are used to investigate and capture the development of the relaminarizing flow downstream these devices. We compare the performance of straight (constant length across the radius of the pipe) honeycombs with custom-shaped ones (variable length across the radius) and try to determine the optimal shape for maximal relaminarization at minimal pressure loss. The optimally modified streamwise velocity profile is found to be M-shaped, and the maximum attainable Reynolds number for total relaminarization is found to be of the order of 10,000. Consequently, the respective reduction in skin friction downstream of the device is almost by a factor of 5. The break-even point, where the additional pressure drop caused by the device is balanced by the savings due to relaminarization and a net gain is obtained, corresponds to a downstream stretch of distances as low as approximately 100 pipe diameters of laminar flow. acknowledged_ssus: - _id: M-Shop article_number: '111105' article_processing_charge: No article_type: original author: - first_name: Jakob full_name: Kühnen, Jakob id: 3A47AE32-F248-11E8-B48F-1D18A9856A87 last_name: Kühnen orcid: 0000-0003-4312-0179 - first_name: Davide full_name: Scarselli, Davide id: 40315C30-F248-11E8-B48F-1D18A9856A87 last_name: Scarselli orcid: 0000-0001-5227-4271 - 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, Hof B. Relaminarization of pipe flow by means of 3D-printed shaped honeycombs. Journal of Fluids Engineering. 2019;141(11). doi:10.1115/1.4043494 apa: Kühnen, J., Scarselli, D., & Hof, B. (2019). Relaminarization of pipe flow by means of 3D-printed shaped honeycombs. Journal of Fluids Engineering. ASME. https://doi.org/10.1115/1.4043494 chicago: Kühnen, Jakob, Davide Scarselli, and Björn Hof. “Relaminarization of Pipe Flow by Means of 3D-Printed Shaped Honeycombs.” Journal of Fluids Engineering. ASME, 2019. https://doi.org/10.1115/1.4043494. ieee: J. Kühnen, D. Scarselli, and B. Hof, “Relaminarization of pipe flow by means of 3D-printed shaped honeycombs,” Journal of Fluids Engineering, vol. 141, no. 11. ASME, 2019. ista: Kühnen J, Scarselli D, Hof B. 2019. Relaminarization of pipe flow by means of 3D-printed shaped honeycombs. Journal of Fluids Engineering. 141(11), 111105. mla: Kühnen, Jakob, et al. “Relaminarization of Pipe Flow by Means of 3D-Printed Shaped Honeycombs.” Journal of Fluids Engineering, vol. 141, no. 11, 111105, ASME, 2019, doi:10.1115/1.4043494. short: J. Kühnen, D. Scarselli, B. Hof, Journal of Fluids Engineering 141 (2019). date_created: 2019-05-26T21:59:13Z date_published: 2019-11-01T00:00:00Z date_updated: 2024-03-27T23:30:35Z day: '01' department: - _id: BjHo doi: 10.1115/1.4043494 ec_funded: 1 external_id: arxiv: - '1809.07625' isi: - '000487748600005' intvolume: ' 141' isi: 1 issue: '11' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1809.07625 month: '11' oa: 1 oa_version: Preprint project: - _id: 25152F3A-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '306589' name: Decoding the complexity of turbulence at its origin publication: Journal of Fluids Engineering publication_identifier: eissn: - 1528901X issn: - '00982202' publication_status: published publisher: ASME quality_controlled: '1' related_material: record: - id: '7258' relation: dissertation_contains status: public scopus_import: '1' status: public title: Relaminarization of pipe flow by means of 3D-printed shaped honeycombs type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 141 year: '2019' ... --- _id: '6228' abstract: - lang: eng text: Following the recent observation that turbulent pipe flow can be relaminarised bya relatively simple modification of the mean velocity profile, we here carry out aquantitative experimental investigation of this phenomenon. Our study confirms thata flat velocity profile leads to a collapse of turbulence and in order to achieve theblunted profile shape, we employ a moving pipe segment that is briefly and rapidlyshifted in the streamwise direction. The relaminarisation threshold and the minimumshift length and speeds are determined as a function of Reynolds number. Althoughturbulence is still active after the acceleration phase, the modulated profile possessesa severely decreased lift-up potential as measured by transient growth. As shown,this results in an exponential decay of fluctuations and the flow relaminarises. Whilethis method can be easily applied at low to moderate flow speeds, the minimumstreamwise length over which the acceleration needs to act increases linearly with theReynolds number. article_processing_charge: No author: - first_name: Davide full_name: Scarselli, Davide id: 40315C30-F248-11E8-B48F-1D18A9856A87 last_name: Scarselli orcid: 0000-0001-5227-4271 - first_name: Jakob full_name: Kühnen, Jakob id: 3A47AE32-F248-11E8-B48F-1D18A9856A87 last_name: Kühnen orcid: 0000-0003-4312-0179 - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Scarselli D, Kühnen J, Hof B. Relaminarising pipe flow by wall movement. Journal of Fluid Mechanics. 2019;867:934-948. doi:10.1017/jfm.2019.191 apa: Scarselli, D., Kühnen, J., & Hof, B. (2019). Relaminarising pipe flow by wall movement. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2019.191 chicago: Scarselli, Davide, Jakob Kühnen, and Björn Hof. “Relaminarising Pipe Flow by Wall Movement.” Journal of Fluid Mechanics. Cambridge University Press, 2019. https://doi.org/10.1017/jfm.2019.191. ieee: D. Scarselli, J. Kühnen, and B. Hof, “Relaminarising pipe flow by wall movement,” Journal of Fluid Mechanics, vol. 867. Cambridge University Press, pp. 934–948, 2019. ista: Scarselli D, Kühnen J, Hof B. 2019. Relaminarising pipe flow by wall movement. Journal of Fluid Mechanics. 867, 934–948. mla: Scarselli, Davide, et al. “Relaminarising Pipe Flow by Wall Movement.” Journal of Fluid Mechanics, vol. 867, Cambridge University Press, 2019, pp. 934–48, doi:10.1017/jfm.2019.191. short: D. Scarselli, J. Kühnen, B. Hof, Journal of Fluid Mechanics 867 (2019) 934–948. date_created: 2019-04-07T21:59:14Z date_published: 2019-05-25T00:00:00Z date_updated: 2024-03-27T23:30:35Z day: '25' department: - _id: BjHo doi: 10.1017/jfm.2019.191 ec_funded: 1 external_id: arxiv: - '1807.05357' isi: - '000462606100001' intvolume: ' 867' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1807.05357 month: '05' oa: 1 oa_version: Preprint page: 934-948 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: Journal of Fluid Mechanics publication_identifier: eissn: - '14697645' issn: - '00221120' publication_status: published publisher: Cambridge University Press quality_controlled: '1' related_material: link: - relation: supplementary_material url: https://doi.org/10.1017/jfm.2019.191 record: - id: '7258' relation: dissertation_contains status: public scopus_import: '1' status: public title: Relaminarising pipe flow by wall movement type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 867 year: '2019' ... --- _id: '6508' abstract: - lang: eng text: Segregation of maternal determinants within the oocyte constitutes the first step in embryo patterning. In zebrafish oocytes, extensive ooplasmic streaming leads to the segregation of ooplasm from yolk granules along the animal-vegetal axis of the oocyte. Here, we show that this process does not rely on cortical actin reorganization, as previously thought, but instead on a cell-cycle-dependent bulk actin polymerization wave traveling from the animal to the vegetal pole of the oocyte. This wave functions in segregation by both pulling ooplasm animally and pushing yolk granules vegetally. Using biophysical experimentation and theory, we show that ooplasm pulling is mediated by bulk actin network flows exerting friction forces on the ooplasm, while yolk granule pushing is achieved by a mechanism closely resembling actin comet formation on yolk granules. Our study defines a novel role of cell-cycle-controlled bulk actin polymerization waves in oocyte polarization via ooplasmic segregation. acknowledged_ssus: - _id: Bio - _id: PreCl acknowledgement: We would like to thank Pierre Recho, Guillaume Salbreux, and Silvia Grigolon for advice on the theory, Lila Solnica-Krezel for kindly providing us with zebrafish dachsous mutants, members of the Heisenberg and Hannezo groups for fruitful discussions, and the Bioimaging and zebrafish facilities at IST Austria for their continuous support. This project has received funding from the European Union (European Research Council Advanced Grant 742573 to C.P.H.) and from the Austrian Science Fund (FWF) (P 31639 to E.H.). article_processing_charge: No article_type: original author: - first_name: Shayan full_name: Shamipour, Shayan id: 40B34FE2-F248-11E8-B48F-1D18A9856A87 last_name: Shamipour - first_name: Roland full_name: Kardos, Roland id: 4039350E-F248-11E8-B48F-1D18A9856A87 last_name: Kardos - first_name: Shi-lei full_name: Xue, Shi-lei id: 31D2C804-F248-11E8-B48F-1D18A9856A87 last_name: Xue - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 - first_name: Edouard B full_name: Hannezo, Edouard B id: 3A9DB764-F248-11E8-B48F-1D18A9856A87 last_name: Hannezo orcid: 0000-0001-6005-1561 - 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: Shamipour S, Kardos R, Xue S, Hof B, Hannezo EB, Heisenberg C-PJ. Bulk actin dynamics drive phase segregation in zebrafish oocytes. Cell. 2019;177(6):1463-1479.e18. doi:10.1016/j.cell.2019.04.030 apa: Shamipour, S., Kardos, R., Xue, S., Hof, B., Hannezo, E. B., & Heisenberg, C.-P. J. (2019). Bulk actin dynamics drive phase segregation in zebrafish oocytes. Cell. Elsevier. https://doi.org/10.1016/j.cell.2019.04.030 chicago: Shamipour, Shayan, Roland Kardos, Shi-lei Xue, Björn Hof, Edouard B Hannezo, and Carl-Philipp J Heisenberg. “Bulk Actin Dynamics Drive Phase Segregation in Zebrafish Oocytes.” Cell. Elsevier, 2019. https://doi.org/10.1016/j.cell.2019.04.030. ieee: S. Shamipour, R. Kardos, S. Xue, B. Hof, E. B. Hannezo, and C.-P. J. Heisenberg, “Bulk actin dynamics drive phase segregation in zebrafish oocytes,” Cell, vol. 177, no. 6. Elsevier, p. 1463–1479.e18, 2019. ista: Shamipour S, Kardos R, Xue S, Hof B, Hannezo EB, Heisenberg C-PJ. 2019. Bulk actin dynamics drive phase segregation in zebrafish oocytes. Cell. 177(6), 1463–1479.e18. mla: Shamipour, Shayan, et al. “Bulk Actin Dynamics Drive Phase Segregation in Zebrafish Oocytes.” Cell, vol. 177, no. 6, Elsevier, 2019, p. 1463–1479.e18, doi:10.1016/j.cell.2019.04.030. short: S. Shamipour, R. Kardos, S. Xue, B. Hof, E.B. Hannezo, C.-P.J. Heisenberg, Cell 177 (2019) 1463–1479.e18. date_created: 2019-06-02T21:59:12Z date_published: 2019-05-30T00:00:00Z date_updated: 2024-03-27T23:30:38Z day: '30' ddc: - '570' department: - _id: CaHe - _id: EdHa - _id: BjHo doi: 10.1016/j.cell.2019.04.030 ec_funded: 1 external_id: isi: - '000469415100013' pmid: - '31080065' file: - access_level: open_access checksum: aea43726d80e35ce3885073a5f05c3e3 content_type: application/pdf creator: dernst date_created: 2020-10-21T07:22:34Z date_updated: 2020-10-21T07:22:34Z file_id: '8686' file_name: 2019_Cell_Shamipour_accepted.pdf file_size: 3356292 relation: main_file success: 1 file_date_updated: 2020-10-21T07:22:34Z has_accepted_license: '1' intvolume: ' 177' isi: 1 issue: '6' language: - iso: eng main_file_link: - open_access: '1' url: https://doi.org/10.1016/j.cell.2019.04.030 month: '05' oa: 1 oa_version: Published Version page: 1463-1479.e18 pmid: 1 project: - _id: 260F1432-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '742573' name: Interaction and feedback between cell mechanics and fate specification in vertebrate gastrulation - _id: 268294B6-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: P31639 name: Active mechano-chemical description of the cell cytoskeleton publication: Cell publication_identifier: eissn: - '10974172' issn: - '00928674' publication_status: published publisher: Elsevier quality_controlled: '1' related_material: link: - description: News on IST Homepage relation: press_release url: https://ist.ac.at/en/news/how-the-cytoplasm-separates-from-the-yolk/ record: - id: '8350' relation: dissertation_contains status: public scopus_import: '1' status: public title: Bulk actin dynamics drive phase segregation in zebrafish oocytes type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 177 year: '2019' ... --- _id: '7001' acknowledged_ssus: - _id: PreCl - _id: Bio article_processing_charge: No article_type: original author: - first_name: Cornelia full_name: Schwayer, Cornelia id: 3436488C-F248-11E8-B48F-1D18A9856A87 last_name: Schwayer orcid: 0000-0001-5130-2226 - first_name: Shayan full_name: Shamipour, Shayan id: 40B34FE2-F248-11E8-B48F-1D18A9856A87 last_name: Shamipour - first_name: Kornelija full_name: Pranjic-Ferscha, Kornelija id: 4362B3C2-F248-11E8-B48F-1D18A9856A87 last_name: Pranjic-Ferscha - first_name: Alexandra full_name: Schauer, Alexandra id: 30A536BA-F248-11E8-B48F-1D18A9856A87 last_name: Schauer orcid: 0000-0001-7659-9142 - first_name: M full_name: Balda, M last_name: Balda - first_name: M full_name: Tada, M last_name: Tada - first_name: K full_name: Matter, K last_name: Matter - 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: Schwayer C, Shamipour S, Pranjic-Ferscha K, et al. Mechanosensation of tight junctions depends on ZO-1 phase separation and flow. Cell. 2019;179(4):937-952.e18. doi:10.1016/j.cell.2019.10.006 apa: Schwayer, C., Shamipour, S., Pranjic-Ferscha, K., Schauer, A., Balda, M., Tada, M., … Heisenberg, C.-P. J. (2019). Mechanosensation of tight junctions depends on ZO-1 phase separation and flow. Cell. Cell Press. https://doi.org/10.1016/j.cell.2019.10.006 chicago: Schwayer, Cornelia, Shayan Shamipour, Kornelija Pranjic-Ferscha, Alexandra Schauer, M Balda, M Tada, K Matter, and Carl-Philipp J Heisenberg. “Mechanosensation of Tight Junctions Depends on ZO-1 Phase Separation and Flow.” Cell. Cell Press, 2019. https://doi.org/10.1016/j.cell.2019.10.006. ieee: C. Schwayer et al., “Mechanosensation of tight junctions depends on ZO-1 phase separation and flow,” Cell, vol. 179, no. 4. Cell Press, p. 937–952.e18, 2019. ista: Schwayer C, Shamipour S, Pranjic-Ferscha K, Schauer A, Balda M, Tada M, Matter K, Heisenberg C-PJ. 2019. Mechanosensation of tight junctions depends on ZO-1 phase separation and flow. Cell. 179(4), 937–952.e18. mla: Schwayer, Cornelia, et al. “Mechanosensation of Tight Junctions Depends on ZO-1 Phase Separation and Flow.” Cell, vol. 179, no. 4, Cell Press, 2019, p. 937–952.e18, doi:10.1016/j.cell.2019.10.006. short: C. Schwayer, S. Shamipour, K. Pranjic-Ferscha, A. Schauer, M. Balda, M. Tada, K. Matter, C.-P.J. Heisenberg, Cell 179 (2019) 937–952.e18. date_created: 2019-11-12T12:51:06Z date_published: 2019-10-31T00:00:00Z date_updated: 2024-03-27T23:30:38Z day: '31' ddc: - '570' department: - _id: CaHe - _id: BjHo doi: 10.1016/j.cell.2019.10.006 ec_funded: 1 external_id: isi: - '000493898000012' pmid: - '31675500' file: - access_level: open_access checksum: 33dac4bb77ee630e2666e936b4d57980 content_type: application/pdf creator: dernst date_created: 2020-10-21T07:09:45Z date_updated: 2020-10-21T07:09:45Z file_id: '8684' file_name: 2019_Cell_Schwayer_accepted.pdf file_size: 8805878 relation: main_file success: 1 file_date_updated: 2020-10-21T07:09:45Z has_accepted_license: '1' intvolume: ' 179' isi: 1 issue: '4' language: - iso: eng month: '10' oa: 1 oa_version: Submitted Version page: 937-952.e18 pmid: 1 project: - _id: 260F1432-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '742573' name: Interaction and feedback between cell mechanics and fate specification in vertebrate gastrulation publication: Cell publication_identifier: eissn: - 1097-4172 issn: - 0092-8674 publication_status: published publisher: Cell Press quality_controlled: '1' related_material: link: - description: News auf IST Website relation: press_release url: https://ist.ac.at/en/news/biochemistry-meets-mechanics-the-sensitive-nature-of-cell-cell-contact-formation-in-embryo-development/ record: - id: '7186' relation: dissertation_contains status: public - id: '8350' relation: dissertation_contains status: public scopus_import: '1' status: public title: Mechanosensation of tight junctions depends on ZO-1 phase separation and flow type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 179 year: '2019' ... --- _id: '6189' abstract: - lang: eng text: 'Suspended particles can alter the properties of fluids and in particular also affect the transition fromlaminar to turbulent flow. An earlier study [Mataset al.,Phys. Rev. Lett.90, 014501 (2003)] reported howthe subcritical (i.e., hysteretic) transition to turbulent puffs is affected by the addition of particles. Here weshow that in addition to this known transition, with increasing concentration a supercritical (i.e.,continuous) transition to a globally fluctuating state is found. At the same time the Newtonian-typetransition to puffs is delayed to larger Reynolds numbers. At even higher concentration only the globallyfluctuating state is found. The dynamics of particle laden flows are hence determined by two competinginstabilities that give rise to three flow regimes: Newtonian-type turbulence at low, a particle inducedglobally fluctuating state at high, and a coexistence state at intermediate concentrations.' article_number: '114502' article_processing_charge: No author: - first_name: Nishchal full_name: Agrawal, Nishchal id: 469E6004-F248-11E8-B48F-1D18A9856A87 last_name: Agrawal - first_name: George H full_name: Choueiri, George H id: 448BD5BC-F248-11E8-B48F-1D18A9856A87 last_name: Choueiri - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Agrawal N, Choueiri GH, Hof B. Transition to turbulence in particle laden flows. Physical Review Letters. 2019;122(11). doi:10.1103/PhysRevLett.122.114502 apa: Agrawal, N., Choueiri, G. H., & Hof, B. (2019). Transition to turbulence in particle laden flows. Physical Review Letters. American Physical Society. https://doi.org/10.1103/PhysRevLett.122.114502 chicago: Agrawal, Nishchal, George H Choueiri, and Björn Hof. “Transition to Turbulence in Particle Laden Flows.” Physical Review Letters. American Physical Society, 2019. https://doi.org/10.1103/PhysRevLett.122.114502. ieee: N. Agrawal, G. H. Choueiri, and B. Hof, “Transition to turbulence in particle laden flows,” Physical Review Letters, vol. 122, no. 11. American Physical Society, 2019. ista: Agrawal N, Choueiri GH, Hof B. 2019. Transition to turbulence in particle laden flows. Physical Review Letters. 122(11), 114502. mla: Agrawal, Nishchal, et al. “Transition to Turbulence in Particle Laden Flows.” Physical Review Letters, vol. 122, no. 11, 114502, American Physical Society, 2019, doi:10.1103/PhysRevLett.122.114502. short: N. Agrawal, G.H. Choueiri, B. Hof, Physical Review Letters 122 (2019). date_created: 2019-03-31T21:59:12Z date_published: 2019-03-22T00:00:00Z date_updated: 2024-03-27T23:30:47Z day: '22' department: - _id: BjHo doi: 10.1103/PhysRevLett.122.114502 external_id: arxiv: - '1809.06358' isi: - '000461922000006' intvolume: ' 122' isi: 1 issue: '11' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1809.06358 month: '03' oa: 1 oa_version: Preprint publication: Physical Review Letters publication_identifier: eissn: - '10797114' issn: - '00319007' publication_status: published publisher: American Physical Society quality_controlled: '1' related_material: record: - id: '9728' relation: dissertation_contains status: public scopus_import: '1' status: public title: Transition to turbulence in particle laden flows type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 122 year: '2019' ... --- _id: '291' abstract: - lang: eng text: Over the past decade, the edge of chaos has proven to be a fruitful starting point for investigations of shear flows when the laminar base flow is linearly stable. Numerous computational studies of shear flows demonstrated the existence of states that separate laminar and turbulent regions of the state space. In addition, some studies determined invariant solutions that reside on this edge. In this paper, we study the unstable manifold of one such solution with the aid of continuous symmetry reduction, which we formulate here for the simultaneous quotiening of axial and azimuthal symmetries. Upon our investigation of the unstable manifold, we discover a previously unknown traveling-wave solution on the laminar-turbulent boundary with a relatively complex structure. By means of low-dimensional projections, we visualize different dynamical paths that connect these solutions to the turbulence. Our numerical experiments demonstrate that the laminar-turbulent boundary exhibits qualitatively different regions whose properties are influenced by the nearby invariant solutions. article_number: '054401' 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. Complexity of the laminar-turbulent boundary in pipe flow. Physical Review Fluids. 2018;3(5). doi:10.1103/PhysRevFluids.3.054401 apa: Budanur, N. B., & Hof, B. (2018). Complexity of the laminar-turbulent boundary in pipe flow. Physical Review Fluids. American Physical Society. https://doi.org/10.1103/PhysRevFluids.3.054401 chicago: Budanur, Nazmi B, and Björn Hof. “Complexity of the Laminar-Turbulent Boundary in Pipe Flow.” Physical Review Fluids. American Physical Society, 2018. https://doi.org/10.1103/PhysRevFluids.3.054401. ieee: N. B. Budanur and B. Hof, “Complexity of the laminar-turbulent boundary in pipe flow,” Physical Review Fluids, vol. 3, no. 5. American Physical Society, 2018. ista: Budanur NB, Hof B. 2018. Complexity of the laminar-turbulent boundary in pipe flow. Physical Review Fluids. 3(5), 054401. mla: Budanur, Nazmi B., and Björn Hof. “Complexity of the Laminar-Turbulent Boundary in Pipe Flow.” Physical Review Fluids, vol. 3, no. 5, 054401, American Physical Society, 2018, doi:10.1103/PhysRevFluids.3.054401. short: N.B. Budanur, B. Hof, Physical Review Fluids 3 (2018). date_created: 2018-12-11T11:45:39Z date_published: 2018-05-30T00:00:00Z date_updated: 2023-09-11T12:45:44Z day: '30' department: - _id: BjHo doi: 10.1103/PhysRevFluids.3.054401 external_id: arxiv: - '1802.01918' isi: - '000433426200001' intvolume: ' 3' isi: 1 issue: '5' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1802.01918 month: '05' oa: 1 oa_version: Preprint publication: Physical Review Fluids publication_status: published publisher: American Physical Society publist_id: '7590' quality_controlled: '1' scopus_import: '1' status: public title: Complexity of the laminar-turbulent boundary in pipe flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 3 year: '2018' ... --- _id: '17' abstract: - lang: eng text: Creeping flow of polymeric fluid without inertia exhibits elastic instabilities and elastic turbulence accompanied by drag enhancement due to elastic stress produced by flow-stretched polymers. However, in inertia-dominated flow at high Re and low fluid elasticity El, a reduction in turbulent frictional drag is caused by an intricate competition between inertial and elastic stresses. Here we explore the effect of inertia on the stability of viscoelastic flow in a broad range of control parameters El and (Re,Wi). We present the stability diagram of observed flow regimes in Wi-Re coordinates and find that the instabilities' onsets show an unexpectedly nonmonotonic dependence on El. Further, three distinct regions in the diagram are identified based on El. Strikingly, for high-elasticity fluids we discover a complete relaminarization of flow at Reynolds number in the range of 1 to 10, different from a well-known turbulent drag reduction. These counterintuitive effects may be explained by a finite polymer extensibility and a suppression of vorticity at high Wi. Our results call for further theoretical and numerical development to uncover the role of inertial effect on elastic turbulence in a viscoelastic flow. article_number: '103302 ' article_processing_charge: No author: - first_name: Atul full_name: Varshney, Atul id: 2A2006B2-F248-11E8-B48F-1D18A9856A87 last_name: Varshney orcid: 0000-0002-3072-5999 - first_name: Victor full_name: Steinberg, Victor last_name: Steinberg citation: ama: Varshney A, Steinberg V. Drag enhancement and drag reduction in viscoelastic flow. Physical Review Fluids. 2018;3(10). doi:10.1103/PhysRevFluids.3.103302 apa: Varshney, A., & Steinberg, V. (2018). Drag enhancement and drag reduction in viscoelastic flow. Physical Review Fluids. American Physical Society. https://doi.org/10.1103/PhysRevFluids.3.103302 chicago: Varshney, Atul, and Victor Steinberg. “Drag Enhancement and Drag Reduction in Viscoelastic Flow.” Physical Review Fluids. American Physical Society, 2018. https://doi.org/10.1103/PhysRevFluids.3.103302. ieee: A. Varshney and V. Steinberg, “Drag enhancement and drag reduction in viscoelastic flow,” Physical Review Fluids, vol. 3, no. 10. American Physical Society, 2018. ista: Varshney A, Steinberg V. 2018. Drag enhancement and drag reduction in viscoelastic flow. Physical Review Fluids. 3(10), 103302. mla: Varshney, Atul, and Victor Steinberg. “Drag Enhancement and Drag Reduction in Viscoelastic Flow.” Physical Review Fluids, vol. 3, no. 10, 103302, American Physical Society, 2018, doi:10.1103/PhysRevFluids.3.103302. short: A. Varshney, V. Steinberg, Physical Review Fluids 3 (2018). date_created: 2018-12-11T11:44:11Z date_published: 2018-10-15T00:00:00Z date_updated: 2023-09-11T12:59:28Z day: '15' ddc: - '532' department: - _id: BjHo doi: 10.1103/PhysRevFluids.3.103302 ec_funded: 1 external_id: isi: - '000447311500001' file: - access_level: open_access checksum: e1445be33e8165114e96246275600750 content_type: application/pdf creator: system date_created: 2018-12-12T10:10:14Z date_updated: 2020-07-14T12:45:12Z file_id: '4800' file_name: IST-2018-1061-v1+1_PhysRevFluids.3.103302.pdf file_size: 1409040 relation: main_file file_date_updated: 2020-07-14T12:45:12Z has_accepted_license: '1' intvolume: ' 3' isi: 1 issue: '10' language: - iso: eng month: '10' oa: 1 oa_version: Published Version project: - _id: 260C2330-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '754411' name: ISTplus - Postdoctoral Fellowships publication: Physical Review Fluids publication_status: published publisher: American Physical Society publist_id: '8038' pubrep_id: '1061' quality_controlled: '1' scopus_import: '1' status: public title: Drag enhancement and drag reduction in viscoelastic flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 3 year: '2018' ... --- _id: '16' abstract: - lang: eng text: We report quantitative evidence of mixing-layer elastic instability in a viscoelastic fluid flow between two widely spaced obstacles hindering a channel flow at Re 1 and Wi 1. Two mixing layers with nonuniform shear velocity profiles are formed in the region between the obstacles. The mixing-layer instability arises in the vicinity of an inflection point on the shear velocity profile with a steep variation in the elastic stress. The instability results in an intermittent appearance of small vortices in the mixing layers and an amplification of spatiotemporal averaged vorticity in the elastic turbulence regime. The latter is characterized through scaling of friction factor with Wi and both pressure and velocity spectra. Furthermore, the observations reported provide improved understanding of the stability of the mixing layer in a viscoelastic fluid at large elasticity, i.e., Wi 1 and Re 1 and oppose the current view of suppression of vorticity solely by polymer additives. acknowledgement: This work was partially supported by the Israel Science Foundation (ISF; Grant No. 882/15) and the Binational USA-Israel Foundation (BSF; Grant No. 2016145). article_number: '103303' article_processing_charge: No article_type: original author: - first_name: Atul full_name: Varshney, Atul id: 2A2006B2-F248-11E8-B48F-1D18A9856A87 last_name: Varshney orcid: 0000-0002-3072-5999 - first_name: Victor full_name: Steinberg, Victor last_name: Steinberg citation: ama: Varshney A, Steinberg V. Mixing layer instability and vorticity amplification in a creeping viscoelastic flow. Physical Review Fluids. 2018;3(10). doi:10.1103/PhysRevFluids.3.103303 apa: Varshney, A., & Steinberg, V. (2018). Mixing layer instability and vorticity amplification in a creeping viscoelastic flow. Physical Review Fluids. American Physical Society. https://doi.org/10.1103/PhysRevFluids.3.103303 chicago: Varshney, Atul, and Victor Steinberg. “Mixing Layer Instability and Vorticity Amplification in a Creeping Viscoelastic Flow.” Physical Review Fluids. American Physical Society, 2018. https://doi.org/10.1103/PhysRevFluids.3.103303. ieee: A. Varshney and V. Steinberg, “Mixing layer instability and vorticity amplification in a creeping viscoelastic flow,” Physical Review Fluids, vol. 3, no. 10. American Physical Society, 2018. ista: Varshney A, Steinberg V. 2018. Mixing layer instability and vorticity amplification in a creeping viscoelastic flow. Physical Review Fluids. 3(10), 103303. mla: Varshney, Atul, and Victor Steinberg. “Mixing Layer Instability and Vorticity Amplification in a Creeping Viscoelastic Flow.” Physical Review Fluids, vol. 3, no. 10, 103303, American Physical Society, 2018, doi:10.1103/PhysRevFluids.3.103303. short: A. Varshney, V. Steinberg, Physical Review Fluids 3 (2018). date_created: 2018-12-11T11:44:10Z date_published: 2018-10-16T00:00:00Z date_updated: 2023-09-13T08:57:05Z day: '16' ddc: - '532' department: - _id: BjHo doi: 10.1103/PhysRevFluids.3.103303 ec_funded: 1 external_id: isi: - '000447469200001' file: - access_level: open_access checksum: 7fc0a2322214d1c04debef36d5bf2e8a content_type: application/pdf creator: system date_created: 2018-12-12T10:13:56Z date_updated: 2020-07-14T12:45:04Z file_id: '5043' file_name: IST-2018-1062-v1+1_PhysRevFluids.3.103303.pdf file_size: 1838431 relation: main_file file_date_updated: 2020-07-14T12:45:04Z has_accepted_license: '1' intvolume: ' 3' isi: 1 issue: '10' language: - iso: eng month: '10' oa: 1 oa_version: Submitted Version project: - _id: 260C2330-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '754411' name: ISTplus - Postdoctoral Fellowships publication: Physical Review Fluids publication_status: published publisher: American Physical Society publist_id: '8039' pubrep_id: '1062' quality_controlled: '1' scopus_import: '1' status: public title: Mixing layer instability and vorticity amplification in a creeping viscoelastic flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 3 year: '2018' ... --- _id: '519' abstract: - lang: eng text: 'This study treats with the influence of a symmetry-breaking transversal magnetic field on the nonlinear dynamics of ferrofluidic Taylor-Couette flow – flow confined between two concentric independently rotating cylinders. We detected alternating ‘flip’ solutions which are flow states featuring typical characteristics of slow-fast-dynamics in dynamical systems. The flip corresponds to a temporal change in the axial wavenumber and we find them to appear either as pure 2-fold axisymmetric (due to the symmetry-breaking nature of the applied transversal magnetic field) or involving non-axisymmetric, helical modes in its interim solution. The latter ones show features of typical ribbon solutions. In any case the flip solutions have a preferential first axial wavenumber which corresponds to the more stable state (slow dynamics) and second axial wavenumber, corresponding to the short appearing more unstable state (fast dynamics). However, in both cases the flip time grows exponential with increasing the magnetic field strength before the flip solutions, living on 2-tori invariant manifolds, cease to exist, with lifetime going to infinity. Further we show that ferrofluidic flow turbulence differ from the classical, ordinary (usually at high Reynolds number) turbulence. The applied magnetic field hinders the free motion of ferrofluid partials and therefore smoothen typical turbulent quantities and features so that speaking of mildly chaotic dynamics seems to be a more appropriate expression for the observed motion. ' acknowledgement: S.Altmeyer is a Serra Húnter Fellow 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 citation: ama: Altmeyer S. Non-linear dynamics and alternating ‘flip’ solutions in ferrofluidic Taylor-Couette flow. Journal of Magnetism and Magnetic Materials. 2018;452:427-441. doi:10.1016/j.jmmm.2017.12.073 apa: Altmeyer, S. (2018). Non-linear dynamics and alternating ‘flip’ solutions in ferrofluidic Taylor-Couette flow. Journal of Magnetism and Magnetic Materials. Elsevier. https://doi.org/10.1016/j.jmmm.2017.12.073 chicago: Altmeyer, Sebastian. “Non-Linear Dynamics and Alternating ‘Flip’ Solutions in Ferrofluidic Taylor-Couette Flow.” Journal of Magnetism and Magnetic Materials. Elsevier, 2018. https://doi.org/10.1016/j.jmmm.2017.12.073. ieee: S. Altmeyer, “Non-linear dynamics and alternating ‘flip’ solutions in ferrofluidic Taylor-Couette flow,” Journal of Magnetism and Magnetic Materials, vol. 452. Elsevier, pp. 427–441, 2018. ista: Altmeyer S. 2018. Non-linear dynamics and alternating ‘flip’ solutions in ferrofluidic Taylor-Couette flow. Journal of Magnetism and Magnetic Materials. 452, 427–441. mla: Altmeyer, Sebastian. “Non-Linear Dynamics and Alternating ‘Flip’ Solutions in Ferrofluidic Taylor-Couette Flow.” Journal of Magnetism and Magnetic Materials, vol. 452, Elsevier, 2018, pp. 427–41, doi:10.1016/j.jmmm.2017.12.073. short: S. Altmeyer, Journal of Magnetism and Magnetic Materials 452 (2018) 427–441. date_created: 2018-12-11T11:46:56Z date_published: 2018-04-15T00:00:00Z date_updated: 2023-09-13T09:03:44Z day: '15' ddc: - '530' department: - _id: BjHo doi: 10.1016/j.jmmm.2017.12.073 external_id: isi: - '000425547700061' file: - access_level: open_access checksum: 431f5cd4a628d7ca21161f82b14ccb4f content_type: application/pdf creator: dernst date_created: 2020-05-14T14:41:17Z date_updated: 2020-07-14T12:46:37Z file_id: '7838' file_name: 2018_Magnetism_Altmeyer.pdf file_size: 17309535 relation: main_file file_date_updated: 2020-07-14T12:46:37Z has_accepted_license: '1' intvolume: ' 452' isi: 1 language: - iso: eng month: '04' oa: 1 oa_version: Submitted Version page: 427 - 441 publication: Journal of Magnetism and Magnetic Materials publication_status: published publisher: Elsevier publist_id: '7297' quality_controlled: '1' scopus_import: '1' status: public title: Non-linear dynamics and alternating ‘flip’ solutions in ferrofluidic Taylor-Couette flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 452 year: '2018' ... --- _id: '5996' abstract: - lang: eng text: 'In pipes, turbulence sets in despite the linear stability of the laminar Hagen–Poiseuille flow. The Reynolds number ( ) for which turbulence first appears in a given experiment – the ‘natural transition point’ – depends on imperfections of the set-up, or, more precisely, on the magnitude of finite amplitude perturbations. At onset, turbulence typically only occupies a certain fraction of the flow, and this fraction equally is found to differ from experiment to experiment. Despite these findings, Reynolds proposed that after sufficiently long times, flows may settle to steady conditions: below a critical velocity, flows should (regardless of initial conditions) always return to laminar, while above this velocity, eddying motion should persist. As will be shown, even in pipes several thousand diameters long, the spatio-temporal intermittent flow patterns observed at the end of the pipe strongly depend on the initial conditions, and there is no indication that different flow patterns would eventually settle to a (statistical) steady state. Exploiting the fact that turbulent puffs do not age (i.e. they are memoryless), we continuously recreate the puff sequence exiting the pipe at the pipe entrance, and in doing so introduce periodic boundary conditions for the puff pattern. This procedure allows us to study the evolution of the flow patterns for arbitrary long times, and we find that after times in excess of advective time units, indeed a statistical steady state is reached. Although the resulting flows remain spatio-temporally intermittent, puff splitting and decay rates eventually reach a balance, so that the turbulent fraction fluctuates around a well-defined level which only depends on . In accordance with Reynolds’ proposition, we find that at lower (here 2020), flows eventually always resume to laminar, while for higher ( ), turbulence persists. The critical point for pipe flow hence falls in the interval of $2020 , which is in very good agreement with the recently proposed value of . The latter estimate was based on single-puff statistics and entirely neglected puff interactions. Unlike in typical contact processes where such interactions strongly affect the percolation threshold, in pipe flow, the critical point is only marginally influenced. Interactions, on the other hand, are responsible for the approach to the statistical steady state. As shown, they strongly affect the resulting flow patterns, where they cause ‘puff clustering’, and these regions of large puff densities are observed to travel across the puff pattern in a wave-like fashion.' acknowledgement: ' We also thank Philipp Maier and the IST Austria workshop for theirdedicated technical support' article_processing_charge: No article_type: original author: - first_name: Mukund full_name: Vasudevan, Mukund id: 3C5A959A-F248-11E8-B48F-1D18A9856A87 last_name: Vasudevan - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Vasudevan M, Hof B. The critical point of the transition to turbulence in pipe flow. Journal of Fluid Mechanics. 2018;839:76-94. doi:10.1017/jfm.2017.923 apa: Vasudevan, M., & Hof, B. (2018). The critical point of the transition to turbulence in pipe flow. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2017.923 chicago: Vasudevan, Mukund, and Björn Hof. “The Critical Point of the Transition to Turbulence in Pipe Flow.” Journal of Fluid Mechanics. Cambridge University Press, 2018. https://doi.org/10.1017/jfm.2017.923. ieee: M. Vasudevan and B. Hof, “The critical point of the transition to turbulence in pipe flow,” Journal of Fluid Mechanics, vol. 839. Cambridge University Press, pp. 76–94, 2018. ista: Vasudevan M, Hof B. 2018. The critical point of the transition to turbulence in pipe flow. Journal of Fluid Mechanics. 839, 76–94. mla: Vasudevan, Mukund, and Björn Hof. “The Critical Point of the Transition to Turbulence in Pipe Flow.” Journal of Fluid Mechanics, vol. 839, Cambridge University Press, 2018, pp. 76–94, doi:10.1017/jfm.2017.923. short: M. Vasudevan, B. Hof, Journal of Fluid Mechanics 839 (2018) 76–94. date_created: 2019-02-14T12:50:50Z date_published: 2018-03-25T00:00:00Z date_updated: 2023-09-19T14:37:49Z day: '25' department: - _id: BjHo doi: 10.1017/jfm.2017.923 ec_funded: 1 external_id: arxiv: - '1709.06372' isi: - '000437858300003' intvolume: ' 839' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1709.06372 month: '03' oa: 1 oa_version: Preprint page: 76-94 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: eissn: - 1469-7645 issn: - 0022-1120 publication_status: published publisher: Cambridge University Press quality_controlled: '1' scopus_import: '1' status: public title: The critical point of the transition to turbulence in pipe flow type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 839 year: '2018' ...