[{"status":"public","intvolume":"       974","type":"journal_article","day":"10","file_date_updated":"2024-02-15T09:05:21Z","publication":"Journal of Fluid Mechanics","language":[{"iso":"eng"}],"publisher":"Cambridge University Press","article_type":"original","date_published":"2023-11-10T00:00:00Z","month":"11","date_created":"2023-10-30T09:32:28Z","file":[{"creator":"dernst","file_id":"14996","content_type":"application/pdf","relation":"main_file","success":1,"date_updated":"2024-02-15T09:05:21Z","access_level":"open_access","date_created":"2024-02-15T09:05:21Z","checksum":"17c64c1fb0d5f73252364bf98b0b9e1a","file_name":"2023_JourFluidMechanics_Marensi.pdf","file_size":2804641}],"department":[{"_id":"GradSch"},{"_id":"BjHo"}],"has_accepted_license":"1","author":[{"id":"0BE7553A-1004-11EA-B805-18983DDC885E","orcid":"0000-0001-7173-4923","full_name":"Marensi, Elena","last_name":"Marensi","first_name":"Elena"},{"last_name":"Yalniz","full_name":"Yalniz, Gökhan","orcid":"0000-0002-8490-9312","first_name":"Gökhan","id":"66E74FA2-D8BF-11E9-8249-8DE2E5697425"},{"first_name":"Björn","orcid":"0000-0003-2057-2754","last_name":"Hof","full_name":"Hof, Björn","id":"3A374330-F248-11E8-B48F-1D18A9856A87"}],"keyword":["turbulence","transition to turbulence","patterns"],"abstract":[{"text":"The first long-lived turbulent structures observable in planar shear flows take the form of localized stripes, inclined with respect to the mean flow direction. The dynamics of these stripes is central to transition, and recent studies proposed an analogy to directed percolation where the stripes’ proliferation is ultimately responsible for the turbulence becoming sustained. In the present study we focus on the internal stripe dynamics as well as on the eventual stripe expansion, and we compare the underlying mechanisms in pressure- and shear-driven planar flows, respectively, plane-Poiseuille and plane-Couette flow. Despite the similarities of the overall laminar–turbulence patterns, the stripe proliferation processes in the two cases are fundamentally different. Starting from the growth and sustenance of individual stripes, we find that in plane-Couette flow new streaks are created stochastically throughout the stripe whereas in plane-Poiseuille flow streak creation is deterministic and occurs locally at the downstream tip. Because of the up/downstream symmetry, Couette stripes, in contrast to Poiseuille stripes, have two weak and two strong laminar turbulent interfaces. These differences in symmetry as well as in internal growth give rise to two fundamentally different stripe splitting mechanisms. In plane-Poiseuille flow splitting is connected to the elongational growth of the original stripe, and it results from a break-off/shedding of the stripe's tail. In plane-Couette flow splitting follows from a broadening of the original stripe and a division along the stripe into two slimmer stripes.","lang":"eng"}],"publication_status":"published","citation":{"ama":"Marensi E, Yalniz G, Hof B. Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows. <i>Journal of Fluid Mechanics</i>. 2023;974. doi:<a href=\"https://doi.org/10.1017/jfm.2023.780\">10.1017/jfm.2023.780</a>","mla":"Marensi, Elena, et al. “Dynamics and Proliferation of Turbulent Stripes in Plane-Poiseuille and Plane-Couette Flows.” <i>Journal of Fluid Mechanics</i>, vol. 974, A21, Cambridge University Press, 2023, doi:<a href=\"https://doi.org/10.1017/jfm.2023.780\">10.1017/jfm.2023.780</a>.","short":"E. Marensi, G. Yalniz, B. Hof, Journal of Fluid Mechanics 974 (2023).","ista":"Marensi E, Yalniz G, Hof B. 2023. Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows. Journal of Fluid Mechanics. 974, A21.","apa":"Marensi, E., Yalniz, G., &#38; Hof, B. (2023). Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2023.780\">https://doi.org/10.1017/jfm.2023.780</a>","ieee":"E. Marensi, G. Yalniz, and B. Hof, “Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows,” <i>Journal of Fluid Mechanics</i>, vol. 974. Cambridge University Press, 2023.","chicago":"Marensi, Elena, Gökhan Yalniz, and Björn Hof. “Dynamics and Proliferation of Turbulent Stripes in Plane-Poiseuille and Plane-Couette Flows.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2023. <a href=\"https://doi.org/10.1017/jfm.2023.780\">https://doi.org/10.1017/jfm.2023.780</a>."},"acknowledgement":"E.M. acknowledges funding from the ISTplus fellowship programme. G.Y. and B.H. acknowledge a grant from the Simons Foundation (662960, BH).","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","oa_version":"Published Version","project":[{"_id":"238598C6-32DE-11EA-91FC-C7463DDC885E","name":"Revisiting the Turbulence Problem Using Statistical Mechanics: Experimental Studies on Transitional and Turbulent Flows","grant_number":"662960"}],"quality_controlled":"1","_id":"14466","publication_identifier":{"issn":["0022-1120"],"eissn":["1469-7645"]},"volume":974,"oa":1,"date_updated":"2024-02-15T09:06:23Z","article_processing_charge":"Yes (via OA deal)","arxiv":1,"title":"Dynamics and proliferation of turbulent stripes in plane-Poiseuille and plane-Couette flows","external_id":{"isi":["001088363700001"],"arxiv":["2212.12406"]},"doi":"10.1017/jfm.2023.780","year":"2023","ddc":["530"],"article_number":"A21","isi":1,"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)"}},{"article_number":"A10","isi":1,"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)"},"ddc":["530"],"year":"2023","doi":"10.1017/jfm.2022.1001","title":"Symmetry-reduced dynamic mode decomposition of near-wall turbulence","external_id":{"arxiv":["2101.07516"],"isi":["000903336600001"]},"volume":954,"date_updated":"2023-08-01T12:53:23Z","oa":1,"article_processing_charge":"Yes (via OA deal)","arxiv":1,"acknowledgement":"E.M. acknowledges funding from the ISTplus fellowship programme. G.Y. and B.H. acknowledge\r\na grant from the Simons Foundation (662960, BH).","user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","oa_version":"Published Version","project":[{"name":"Revisiting the Turbulence Problem Using Statistical Mechanics: Experimental Studies on Transitional and Turbulent Flows","_id":"238598C6-32DE-11EA-91FC-C7463DDC885E","grant_number":"662960"}],"quality_controlled":"1","_id":"12105","publication_identifier":{"eissn":["1469-7645"],"issn":["0022-1120"]},"publication_status":"published","citation":{"apa":"Marensi, E., Yalniz, G., Hof, B., &#38; Budanur, N. B. (2023). Symmetry-reduced dynamic mode decomposition of near-wall turbulence. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2022.1001\">https://doi.org/10.1017/jfm.2022.1001</a>","ieee":"E. Marensi, G. Yalniz, B. Hof, and N. B. Budanur, “Symmetry-reduced dynamic mode decomposition of near-wall turbulence,” <i>Journal of Fluid Mechanics</i>, vol. 954. Cambridge University Press, 2023.","chicago":"Marensi, Elena, Gökhan Yalniz, Björn Hof, and Nazmi B Budanur. “Symmetry-Reduced Dynamic Mode Decomposition of near-Wall Turbulence.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2023. <a href=\"https://doi.org/10.1017/jfm.2022.1001\">https://doi.org/10.1017/jfm.2022.1001</a>.","ama":"Marensi E, Yalniz G, Hof B, Budanur NB. Symmetry-reduced dynamic mode decomposition of near-wall turbulence. <i>Journal of Fluid Mechanics</i>. 2023;954. doi:<a href=\"https://doi.org/10.1017/jfm.2022.1001\">10.1017/jfm.2022.1001</a>","mla":"Marensi, Elena, et al. “Symmetry-Reduced Dynamic Mode Decomposition of near-Wall Turbulence.” <i>Journal of Fluid Mechanics</i>, vol. 954, A10, Cambridge University Press, 2023, doi:<a href=\"https://doi.org/10.1017/jfm.2022.1001\">10.1017/jfm.2022.1001</a>.","short":"E. Marensi, G. Yalniz, B. Hof, N.B. Budanur, Journal of Fluid Mechanics 954 (2023).","ista":"Marensi E, Yalniz G, Hof B, Budanur NB. 2023. Symmetry-reduced dynamic mode decomposition of near-wall turbulence. Journal of Fluid Mechanics. 954, A10."},"author":[{"full_name":"Marensi, Elena","last_name":"Marensi","first_name":"Elena","id":"0BE7553A-1004-11EA-B805-18983DDC885E"},{"first_name":"Gökhan","orcid":"0000-0002-8490-9312","last_name":"Yalniz","full_name":"Yalniz, Gökhan","id":"66E74FA2-D8BF-11E9-8249-8DE2E5697425"},{"first_name":"Björn","full_name":"Hof, Björn","last_name":"Hof","orcid":"0000-0003-2057-2754","id":"3A374330-F248-11E8-B48F-1D18A9856A87"},{"id":"3EA1010E-F248-11E8-B48F-1D18A9856A87","first_name":"Nazmi B","full_name":"Budanur, Nazmi B","last_name":"Budanur","orcid":"0000-0003-0423-5010"}],"abstract":[{"text":"Data-driven dimensionality reduction methods such as proper orthogonal decomposition and dynamic mode decomposition have proven to be useful for exploring complex phenomena within fluid dynamics and beyond. A well-known challenge for these techniques is posed by the continuous symmetries, e.g. translations and rotations, of the system under consideration, as drifts in the data dominate the modal expansions without providing an insight into the dynamics of the problem. In the present study, we address this issue for fluid flows in rectangular channels by formulating a continuous symmetry reduction method that eliminates the translations in the streamwise and spanwise directions simultaneously. We demonstrate our method by computing the symmetry-reduced dynamic mode decomposition (SRDMD) of sliding windows of data obtained from the transitional plane-Couette and turbulent plane-Poiseuille flow simulations. In the former setting, SRDMD captures the dynamics in the vicinity of the invariant solutions with translation symmetries, i.e. travelling waves and relative periodic orbits, whereas in the latter, our calculations reveal episodes of turbulent time evolution that can be approximated by a low-dimensional linear expansion.","lang":"eng"}],"department":[{"_id":"BjHo"}],"has_accepted_license":"1","file":[{"date_updated":"2023-02-02T12:34:54Z","access_level":"open_access","file_name":"2023_JourFluidMechanics_Marensi.pdf","file_size":1931647,"date_created":"2023-02-02T12:34:54Z","checksum":"9224f987caefe5dd85a70814d3cce65c","content_type":"application/pdf","relation":"main_file","creator":"dernst","file_id":"12489","success":1}],"date_created":"2023-01-08T23:00:53Z","article_type":"original","date_published":"2023-01-10T00:00:00Z","month":"01","language":[{"iso":"eng"}],"publisher":"Cambridge University Press","scopus_import":"1","file_date_updated":"2023-02-02T12:34:54Z","publication":"Journal of Fluid Mechanics","type":"journal_article","day":"10","status":"public","intvolume":"       954"},{"department":[{"_id":"GradSch"}],"date_created":"2022-03-27T22:01:45Z","article_type":"original","date_published":"2022-04-25T00:00:00Z","month":"04","language":[{"iso":"eng"}],"scopus_import":"1","publisher":"Cambridge University Press","publication":"Journal of Fluid Mechanics","type":"journal_article","day":"25","status":"public","intvolume":"       937","isi":1,"main_file_link":[{"open_access":"1","url":"https://doi.org/10.1017/jfm.2022.137"}],"article_number":"A39","doi":"10.1017/jfm.2022.137","year":"2022","title":"On the wavenumber-frequency spectrum of the wall pressure fluctuations in turbulent channel flow","external_id":{"arxiv":["2201.04702"],"isi":["000763547000001"]},"article_processing_charge":"No","oa":1,"volume":937,"date_updated":"2023-08-03T06:20:26Z","arxiv":1,"oa_version":"Published Version","quality_controlled":"1","user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","acknowledgement":"This research is supported by the NSFC Basic Science Center Program for ‘Multiscale Problems in Nonlinear Mechanics’ (no. 11988102), National Key Project (GJXM92579) and the Strategic Priority Research Program (XDB22040104).","publication_identifier":{"eissn":["1469-7645"],"issn":["0022-1120"]},"_id":"10925","citation":{"apa":"Yang, B., &#38; Yang, Z. (2022). On the wavenumber-frequency spectrum of the wall pressure fluctuations in turbulent channel flow. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2022.137\">https://doi.org/10.1017/jfm.2022.137</a>","ieee":"B. Yang and Z. Yang, “On the wavenumber-frequency spectrum of the wall pressure fluctuations in turbulent channel flow,” <i>Journal of Fluid Mechanics</i>, vol. 937. Cambridge University Press, 2022.","chicago":"Yang, Bowen, and Zixuan Yang. “On the Wavenumber-Frequency Spectrum of the Wall Pressure Fluctuations in Turbulent Channel Flow.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2022. <a href=\"https://doi.org/10.1017/jfm.2022.137\">https://doi.org/10.1017/jfm.2022.137</a>.","mla":"Yang, Bowen, and Zixuan Yang. “On the Wavenumber-Frequency Spectrum of the Wall Pressure Fluctuations in Turbulent Channel Flow.” <i>Journal of Fluid Mechanics</i>, vol. 937, A39, Cambridge University Press, 2022, doi:<a href=\"https://doi.org/10.1017/jfm.2022.137\">10.1017/jfm.2022.137</a>.","ama":"Yang B, Yang Z. On the wavenumber-frequency spectrum of the wall pressure fluctuations in turbulent channel flow. <i>Journal of Fluid Mechanics</i>. 2022;937. doi:<a href=\"https://doi.org/10.1017/jfm.2022.137\">10.1017/jfm.2022.137</a>","short":"B. Yang, Z. Yang, Journal of Fluid Mechanics 937 (2022).","ista":"Yang B, Yang Z. 2022. On the wavenumber-frequency spectrum of the wall pressure fluctuations in turbulent channel flow. Journal of Fluid Mechanics. 937, A39."},"publication_status":"published","author":[{"id":"71b6ff4b-15b2-11ec-abd3-aef6b028cf7e","first_name":"Bowen","full_name":"Yang, Bowen","last_name":"Yang","orcid":"0000-0002-4843-6853"},{"last_name":"Yang","full_name":"Yang, Zixuan","first_name":"Zixuan"}],"abstract":[{"text":"Direct numerical simulations (DNS) of turbulent channel flows up to  Reτ≈1000  are conducted to investigate the three-dimensional (consisting of streamwise wavenumber, spanwise wavenumber and frequency) spectrum of wall pressure fluctuations. To develop a predictive model of the wavenumber–frequency spectrum from the wavenumber spectrum, the time decorrelation mechanisms of wall pressure fluctuations are investigated. It is discovered that the energy-containing part of the wavenumber–frequency spectrum of wall pressure fluctuations can be well predicted using a similar random sweeping model for streamwise velocity fluctuations. To refine the investigation, we further decompose the spectrum of the total wall pressure fluctuations into the autospectra of rapid and slow pressure fluctuations, and the cross-spectrum between them. We focus on evaluating the assumption applied in many predictive models, that is, the magnitude of the cross-spectrum is negligibly small. The present DNS shows that neglecting the cross-spectrum causes a maximum error up to 4.7 dB in the subconvective region for all Reynolds numbers under test. Our analyses indicate that the approximation of neglecting the cross-spectrum needs to be applied carefully in the investigations of acoustics at low Mach numbers, in which the subconvective components of wall pressure fluctuations make important contributions to the radiated acoustic power.","lang":"eng"}]},{"arxiv":1,"article_processing_charge":"No","volume":951,"date_updated":"2023-08-04T08:54:16Z","oa":1,"publication_identifier":{"eissn":["1469-7645"],"issn":["0022-1120"]},"_id":"12137","oa_version":"Preprint","quality_controlled":"1","user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","acknowledgement":"K.D.’s research was supported by an Australian Research Council Discovery Early Career\r\nResearcher Award (DE170100171). B.W., R.A., F.M. and A.M. research was supported by the Spanish Ministerio de Economía y Competitivdad (grant numbers FIS2016-77849-R and FIS2017-85794-P) and Ministerio de Ciencia e Innovación (grant number PID2020-114043GB-I00) and the Generalitat de Catalunya (grant 2017-SGR-785). B.W.’s research was also supported by the Chinese Scholarship Council (grant CSC no. 201806440152).","citation":{"ista":"Wang B, Ayats López R, Deguchi K, Mellibovsky F, Meseguer A. 2022. Self-sustainment of coherent structures in counter-rotating Taylor–Couette flow. Journal of Fluid Mechanics. 951, A21.","short":"B. Wang, R. Ayats López, K. Deguchi, F. Mellibovsky, A. Meseguer, Journal of Fluid Mechanics 951 (2022).","ama":"Wang B, Ayats López R, Deguchi K, Mellibovsky F, Meseguer A. Self-sustainment of coherent structures in counter-rotating Taylor–Couette flow. <i>Journal of Fluid Mechanics</i>. 2022;951. doi:<a href=\"https://doi.org/10.1017/jfm.2022.828\">10.1017/jfm.2022.828</a>","mla":"Wang, B., et al. “Self-Sustainment of Coherent Structures in Counter-Rotating Taylor–Couette Flow.” <i>Journal of Fluid Mechanics</i>, vol. 951, A21, Cambridge University Press, 2022, doi:<a href=\"https://doi.org/10.1017/jfm.2022.828\">10.1017/jfm.2022.828</a>.","chicago":"Wang, B., Roger Ayats López, K. Deguchi, F. Mellibovsky, and A. Meseguer. “Self-Sustainment of Coherent Structures in Counter-Rotating Taylor–Couette Flow.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2022. <a href=\"https://doi.org/10.1017/jfm.2022.828\">https://doi.org/10.1017/jfm.2022.828</a>.","apa":"Wang, B., Ayats López, R., Deguchi, K., Mellibovsky, F., &#38; Meseguer, A. (2022). Self-sustainment of coherent structures in counter-rotating Taylor–Couette flow. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2022.828\">https://doi.org/10.1017/jfm.2022.828</a>","ieee":"B. Wang, R. Ayats López, K. Deguchi, F. Mellibovsky, and A. Meseguer, “Self-sustainment of coherent structures in counter-rotating Taylor–Couette flow,” <i>Journal of Fluid Mechanics</i>, vol. 951. Cambridge University Press, 2022."},"publication_status":"published","abstract":[{"text":"We investigate the local self-sustained process underlying spiral turbulence in counter-rotating Taylor–Couette flow using a periodic annular domain, shaped as a parallelogram, two of whose sides are aligned with the cylindrical helix described by the spiral pattern. The primary focus of the study is placed on the emergence of drifting–rotating waves (DRW) that capture, in a relatively small domain, the main features of coherent structures typically observed in developed turbulence. The transitional dynamics of the subcritical region, far below the first instability of the laminar circular Couette flow, is determined by the upper and lower branches of DRW solutions originated at saddle-node bifurcations. The mechanism whereby these solutions self-sustain, and the chaotic dynamics they induce, are conspicuously reminiscent of other subcritical shear flows. Remarkably, the flow properties of DRW persist even as the Reynolds number is increased beyond the linear stability threshold of the base flow. Simulations in a narrow parallelogram domain stretched in the azimuthal direction to revolve around the apparatus a full turn confirm that self-sustained vortices eventually concentrate into a localised pattern. The resulting statistical steady state satisfactorily reproduces qualitatively, and to a certain degree also quantitatively, the topology and properties of spiral turbulence as calculated in a large periodic domain of sufficient aspect ratio that is representative of the real system.","lang":"eng"}],"author":[{"first_name":"B.","last_name":"Wang","full_name":"Wang, B."},{"id":"ab77522d-073b-11ed-8aff-e71b39258362","last_name":"Ayats López","full_name":"Ayats López, Roger","orcid":"0000-0001-6572-0621","first_name":"Roger"},{"last_name":"Deguchi","full_name":"Deguchi, K.","first_name":"K."},{"first_name":"F.","full_name":"Mellibovsky, F.","last_name":"Mellibovsky"},{"full_name":"Meseguer, A.","last_name":"Meseguer","first_name":"A."}],"keyword":["Mechanical Engineering","Mechanics of Materials","Condensed Matter Physics","Applied Mathematics"],"isi":1,"article_number":"A21","main_file_link":[{"url":" https://doi.org/10.48550/arXiv.2207.12990","open_access":"1"}],"doi":"10.1017/jfm.2022.828","year":"2022","title":"Self-sustainment of coherent structures in counter-rotating Taylor–Couette flow","external_id":{"arxiv":["2207.12990"],"isi":["000879446900001"]},"publication":"Journal of Fluid Mechanics","day":"07","type":"journal_article","intvolume":"       951","status":"public","department":[{"_id":"BjHo"}],"date_created":"2023-01-12T12:04:17Z","month":"11","date_published":"2022-11-07T00:00:00Z","article_type":"original","scopus_import":"1","publisher":"Cambridge University Press","language":[{"iso":"eng"}]},{"publication_status":"published","citation":{"ama":"Klotz L, Pavlenko AM, Wesfreid JE. Experimental measurements in plane Couette-Poiseuille flow: Dynamics of the large- and small-scale flow. <i>Journal of Fluid Mechanics</i>. 2021;912. doi:<a href=\"https://doi.org/10.1017/jfm.2020.1089\">10.1017/jfm.2020.1089</a>","mla":"Klotz, Lukasz, et al. “Experimental Measurements in Plane Couette-Poiseuille Flow: Dynamics of the Large- and Small-Scale Flow.” <i>Journal of Fluid Mechanics</i>, vol. 912, A24, Cambridge University Press, 2021, doi:<a href=\"https://doi.org/10.1017/jfm.2020.1089\">10.1017/jfm.2020.1089</a>.","ista":"Klotz L, Pavlenko AM, Wesfreid JE. 2021. Experimental measurements in plane Couette-Poiseuille flow: Dynamics of the large- and small-scale flow. Journal of Fluid Mechanics. 912, A24.","short":"L. Klotz, A.M. Pavlenko, J.E. Wesfreid, Journal of Fluid Mechanics 912 (2021).","apa":"Klotz, L., Pavlenko, A. M., &#38; Wesfreid, J. E. (2021). Experimental measurements in plane Couette-Poiseuille flow: Dynamics of the large- and small-scale flow. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2020.1089\">https://doi.org/10.1017/jfm.2020.1089</a>","ieee":"L. Klotz, A. M. Pavlenko, and J. E. Wesfreid, “Experimental measurements in plane Couette-Poiseuille flow: Dynamics of the large- and small-scale flow,” <i>Journal of Fluid Mechanics</i>, vol. 912. Cambridge University Press, 2021.","chicago":"Klotz, Lukasz, A. M. Pavlenko, and J. E. Wesfreid. “Experimental Measurements in Plane Couette-Poiseuille Flow: Dynamics of the Large- and Small-Scale Flow.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2021. <a href=\"https://doi.org/10.1017/jfm.2020.1089\">https://doi.org/10.1017/jfm.2020.1089</a>."},"author":[{"orcid":"0000-0003-1740-7635","last_name":"Klotz","full_name":"Klotz, Lukasz","first_name":"Lukasz","id":"2C9AF1C2-F248-11E8-B48F-1D18A9856A87"},{"full_name":"Pavlenko, A. M.","last_name":"Pavlenko","first_name":"A. M."},{"last_name":"Wesfreid","full_name":"Wesfreid, J. E.","first_name":"J. E."}],"abstract":[{"text":"In this paper we experimentally study the transitional range of Reynolds numbers in\r\nplane Couette–Poiseuille flow, focusing our attention on the localized turbulent structures\r\ntriggered by a strong impulsive jet and the large-scale flow generated around these\r\nstructures. We present a detailed investigation of the large-scale flow and show how\r\nits amplitude depends on Reynolds number and amplitude perturbation. In addition,\r\nwe characterize the initial dynamics of the localized turbulent spot, which includes the\r\ncoupling between the small and large scales, as well as the dependence of the advection\r\nspeed on the large-scale flow generated around the spot. Finally, we provide the first\r\nexperimental measurements of the large-scale flow around an oblique turbulent band.","lang":"eng"}],"oa":1,"date_updated":"2023-08-07T13:55:40Z","volume":912,"article_processing_charge":"Yes (via OA deal)","acknowledgement":"We thank Y. Duguet, S. Gomé, G. Lemoult, T. Liu, B. Semin and L.S. Tuckerman for\r\nfruitful discussions. \r\nThis work was supported by a grant, TRANSFLOW, provided by the Agence Nationale de\r\nla Recherche (ANR). A.M.P. was partially supported by the French Embassy in Russia (I.I. Mechnikov scholarship) and by the Russian Science Foundation (project no. 18-79-00189). L.K. was partially supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 754411.","user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","oa_version":"Published Version","project":[{"name":"ISTplus - Postdoctoral Fellowships","_id":"260C2330-B435-11E9-9278-68D0E5697425","call_identifier":"H2020","grant_number":"754411"}],"quality_controlled":"1","_id":"9207","publication_identifier":{"eissn":["1469-7645"],"issn":["0022-1120"]},"ec_funded":1,"year":"2021","doi":"10.1017/jfm.2020.1089","external_id":{"isi":["000618034400001"]},"title":"Experimental measurements in plane Couette-Poiseuille flow: Dynamics of the large- and small-scale flow","article_number":"A24","isi":1,"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)"},"ddc":["530"],"type":"journal_article","day":"15","status":"public","intvolume":"       912","file_date_updated":"2021-03-03T09:49:34Z","publication":"Journal of Fluid Mechanics","date_published":"2021-02-15T00:00:00Z","article_type":"original","month":"02","language":[{"iso":"eng"}],"publisher":"Cambridge University Press","scopus_import":"1","department":[{"_id":"BjHo"}],"has_accepted_license":"1","date_created":"2021-02-28T23:01:25Z","file":[{"success":1,"file_id":"9220","creator":"dernst","relation":"main_file","content_type":"application/pdf","checksum":"b8020d6338667673e34fde0608913dd2","date_created":"2021-03-03T09:49:34Z","file_size":4124471,"file_name":"2021_JourFluidMechanics_Klotz.pdf","access_level":"open_access","date_updated":"2021-03-03T09:49:34Z"}]},{"doi":"10.1017/jfm.2021.89","year":"2021","title":"Decay of streaks and rolls in plane Couette-Poiseuille flow","external_id":{"arxiv":["2008.08851"],"isi":["000629677500001"]},"isi":1,"article_number":"A65","main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/2008.08851"}],"citation":{"ieee":"T. Liu, B. Semin, L. Klotz, R. Godoy-Diana, J. E. Wesfreid, and T. Mullin, “Decay of streaks and rolls in plane Couette-Poiseuille flow,” <i>Journal of Fluid Mechanics</i>, vol. 915. Cambridge University Press, 2021.","apa":"Liu, T., Semin, B., Klotz, L., Godoy-Diana, R., Wesfreid, J. E., &#38; Mullin, T. (2021). Decay of streaks and rolls in plane Couette-Poiseuille flow. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2021.89\">https://doi.org/10.1017/jfm.2021.89</a>","chicago":"Liu, T., B. Semin, Lukasz Klotz, R. Godoy-Diana, J. E. Wesfreid, and T. Mullin. “Decay of Streaks and Rolls in Plane Couette-Poiseuille Flow.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2021. <a href=\"https://doi.org/10.1017/jfm.2021.89\">https://doi.org/10.1017/jfm.2021.89</a>.","mla":"Liu, T., et al. “Decay of Streaks and Rolls in Plane Couette-Poiseuille Flow.” <i>Journal of Fluid Mechanics</i>, vol. 915, A65, Cambridge University Press, 2021, doi:<a href=\"https://doi.org/10.1017/jfm.2021.89\">10.1017/jfm.2021.89</a>.","ama":"Liu T, Semin B, Klotz L, Godoy-Diana R, Wesfreid JE, Mullin T. Decay of streaks and rolls in plane Couette-Poiseuille flow. <i>Journal of Fluid Mechanics</i>. 2021;915. doi:<a href=\"https://doi.org/10.1017/jfm.2021.89\">10.1017/jfm.2021.89</a>","short":"T. Liu, B. Semin, L. Klotz, R. Godoy-Diana, J.E. Wesfreid, T. Mullin, Journal of Fluid Mechanics 915 (2021).","ista":"Liu T, Semin B, Klotz L, Godoy-Diana R, Wesfreid JE, Mullin T. 2021. Decay of streaks and rolls in plane Couette-Poiseuille flow. Journal of Fluid Mechanics. 915, A65."},"publication_status":"published","author":[{"first_name":"T.","last_name":"Liu","full_name":"Liu, T."},{"first_name":"B.","last_name":"Semin","full_name":"Semin, B."},{"orcid":"0000-0003-1740-7635","full_name":"Klotz, Lukasz","last_name":"Klotz","first_name":"Lukasz","id":"2C9AF1C2-F248-11E8-B48F-1D18A9856A87"},{"full_name":"Godoy-Diana, R.","last_name":"Godoy-Diana","first_name":"R."},{"first_name":"J. E.","last_name":"Wesfreid","full_name":"Wesfreid, J. E."},{"first_name":"T.","last_name":"Mullin","full_name":"Mullin, T."}],"abstract":[{"lang":"eng","text":"We report the results of an experimental investigation into the decay of turbulence in plane Couette–Poiseuille flow using ‘quench’ experiments where the flow laminarises after a sudden reduction in Reynolds number Re. Specifically, we study the velocity field in the streamwise–spanwise plane. We show that the spanwise velocity containing rolls decays faster than the streamwise velocity, which displays elongated regions of higher or lower velocity called streaks. At final Reynolds numbers above 425, the decay of streaks displays two stages: first a slow decay when rolls are present and secondly a more rapid decay of streaks alone. The difference in behaviour results from the regeneration of streaks by rolls, called the lift-up effect. We define the turbulent fraction as the portion of the flow containing turbulence and this is estimated by thresholding the spanwise velocity component. It decreases linearly with time in the whole range of final Re. The corresponding decay slope increases linearly with final Re. The extrapolated value at which this decay slope vanishes is Reaz≈656±10, close to Reg≈670 at which turbulence is self-sustained. The decay of the energy computed from the spanwise velocity component is found to be exponential. The corresponding decay rate increases linearly with Re, with an extrapolated vanishing value at ReAz≈688±10. This value is also close to the value at which the turbulence is self-sustained, showing that valuable information on the transition can be obtained over a wide range of Re."}],"article_processing_charge":"No","volume":915,"date_updated":"2023-08-07T14:30:11Z","oa":1,"arxiv":1,"quality_controlled":"1","oa_version":"Preprint","user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","acknowledgement":"We gratefully acknowledge Joran Rolland, Yohann Duguet, Romain Monchaux, S´ebastien Gom´e, Laurette Tuckerman, Dwight Barkley, Olivier Dauchot and Sabine Bottin for fruitful discussions. We thank Xavier Benoit-Gonin, Amaury Fourgeaud, Thierry Darnige, Olivier Brouard and Justine Laurent for technical help. This work has benefited from the ANR TransFlow, and by starting grants obtained by B.S. from CNRS (INSIS) and ESPCI. T.M. was\r\nsupported by a Joliot visiting professorship grant from ESPCI.","publication_identifier":{"issn":["0022-1120"],"eissn":["1469-7645"]},"_id":"9297","article_type":"original","date_published":"2021-03-17T00:00:00Z","month":"03","language":[{"iso":"eng"}],"scopus_import":"1","publisher":"Cambridge University Press","department":[{"_id":"BjHo"}],"date_created":"2021-03-28T22:01:42Z","type":"journal_article","day":"17","status":"public","intvolume":"       915","publication":"Journal of Fluid Mechanics"},{"main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/1808.04080"}],"isi":1,"external_id":{"isi":["000475349900001"],"arxiv":["1808.04080"]},"title":"Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit","doi":"10.1017/jfm.2019.486","year":"2019","_id":"7397","publication_identifier":{"eissn":["1469-7645"],"issn":["0022-1120"]},"user_id":"c635000d-4b10-11ee-a964-aac5a93f6ac1","oa_version":"Preprint","quality_controlled":"1","arxiv":1,"oa":1,"volume":874,"date_updated":"2023-09-06T15:36:36Z","article_processing_charge":"No","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)."}],"author":[{"orcid":"0000-0002-0384-2022","full_name":"Lopez Alonso, Jose M","last_name":"Lopez Alonso","first_name":"Jose M","id":"40770848-F248-11E8-B48F-1D18A9856A87"},{"full_name":"Choueiri, George H","last_name":"Choueiri","first_name":"George H","id":"448BD5BC-F248-11E8-B48F-1D18A9856A87"},{"id":"3A374330-F248-11E8-B48F-1D18A9856A87","last_name":"Hof","full_name":"Hof, Björn","orcid":"0000-0003-2057-2754","first_name":"Björn"}],"publication_status":"published","citation":{"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.","short":"J.M. Lopez Alonso, G.H. Choueiri, B. Hof, Journal of Fluid Mechanics 874 (2019) 699–719.","mla":"Lopez Alonso, Jose M., et al. “Dynamics of Viscoelastic Pipe Flow at Low Reynolds Numbers in the Maximum Drag Reduction Limit.” <i>Journal of Fluid Mechanics</i>, vol. 874, CUP, 2019, pp. 699–719, doi:<a href=\"https://doi.org/10.1017/jfm.2019.486\">10.1017/jfm.2019.486</a>.","ama":"Lopez Alonso JM, Choueiri GH, Hof B. Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit. <i>Journal of Fluid Mechanics</i>. 2019;874:699-719. doi:<a href=\"https://doi.org/10.1017/jfm.2019.486\">10.1017/jfm.2019.486</a>","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.” <i>Journal of Fluid Mechanics</i>. CUP, 2019. <a href=\"https://doi.org/10.1017/jfm.2019.486\">https://doi.org/10.1017/jfm.2019.486</a>.","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,” <i>Journal of Fluid Mechanics</i>, vol. 874. CUP, pp. 699–719, 2019.","apa":"Lopez Alonso, J. M., Choueiri, G. H., &#38; Hof, B. (2019). Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit. <i>Journal of Fluid Mechanics</i>. CUP. <a href=\"https://doi.org/10.1017/jfm.2019.486\">https://doi.org/10.1017/jfm.2019.486</a>"},"date_created":"2020-01-29T16:05:19Z","department":[{"_id":"BjHo"}],"publisher":"CUP","scopus_import":"1","language":[{"iso":"eng"}],"month":"09","article_type":"original","date_published":"2019-09-10T00:00:00Z","publication":"Journal of Fluid Mechanics","page":"699-719","intvolume":"       874","status":"public","day":"10","type":"journal_article"},{"main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/1709.06372"}],"isi":1,"external_id":{"isi":["000437858300003"],"arxiv":["1709.06372"]},"title":"The critical point of the transition to turbulence in pipe flow","ec_funded":1,"doi":"10.1017/jfm.2017.923","year":"2018","project":[{"grant_number":"306589","_id":"25152F3A-B435-11E9-9278-68D0E5697425","name":"Decoding the complexity of turbulence at its origin","call_identifier":"FP7"}],"oa_version":"Preprint","quality_controlled":"1","acknowledgement":" We  also  thank  Philipp  Maier  and  the  IST  Austria  workshop  for  theirdedicated technical support","user_id":"c635000d-4b10-11ee-a964-aac5a93f6ac1","publication_identifier":{"issn":["0022-1120"],"eissn":["1469-7645"]},"_id":"5996","article_processing_charge":"No","volume":839,"oa":1,"date_updated":"2023-09-19T14:37:49Z","arxiv":1,"author":[{"id":"3C5A959A-F248-11E8-B48F-1D18A9856A87","first_name":"Mukund","last_name":"Vasudevan","full_name":"Vasudevan, Mukund"},{"id":"3A374330-F248-11E8-B48F-1D18A9856A87","full_name":"Hof, Björn","last_name":"Hof","orcid":"0000-0003-2057-2754","first_name":"Björn"}],"abstract":[{"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.","lang":"eng"}],"citation":{"chicago":"Vasudevan, Mukund, and Björn Hof. “The Critical Point of the Transition to Turbulence in Pipe Flow.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2018. <a href=\"https://doi.org/10.1017/jfm.2017.923\">https://doi.org/10.1017/jfm.2017.923</a>.","apa":"Vasudevan, M., &#38; Hof, B. (2018). The critical point of the transition to turbulence in pipe flow. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2017.923\">https://doi.org/10.1017/jfm.2017.923</a>","ieee":"M. Vasudevan and B. Hof, “The critical point of the transition to turbulence in pipe flow,” <i>Journal of Fluid Mechanics</i>, vol. 839. Cambridge University Press, pp. 76–94, 2018.","short":"M. Vasudevan, B. Hof, Journal of Fluid Mechanics 839 (2018) 76–94.","ista":"Vasudevan M, Hof B. 2018. The critical point of the transition to turbulence in pipe flow. Journal of Fluid Mechanics. 839, 76–94.","ama":"Vasudevan M, Hof B. The critical point of the transition to turbulence in pipe flow. <i>Journal of Fluid Mechanics</i>. 2018;839:76-94. doi:<a href=\"https://doi.org/10.1017/jfm.2017.923\">10.1017/jfm.2017.923</a>","mla":"Vasudevan, Mukund, and Björn Hof. “The Critical Point of the Transition to Turbulence in Pipe Flow.” <i>Journal of Fluid Mechanics</i>, vol. 839, Cambridge University Press, 2018, pp. 76–94, doi:<a href=\"https://doi.org/10.1017/jfm.2017.923\">10.1017/jfm.2017.923</a>."},"publication_status":"published","date_created":"2019-02-14T12:50:50Z","department":[{"_id":"BjHo"}],"language":[{"iso":"eng"}],"scopus_import":"1","publisher":"Cambridge University Press","article_type":"original","date_published":"2018-03-25T00:00:00Z","month":"03","page":"76-94","publication":"Journal of Fluid Mechanics","status":"public","intvolume":"       839","type":"journal_article","day":"25"}]