--- _id: '12165' abstract: - lang: eng text: It may come as a surprise that a phenomenon as ubiquitous and prominent as the transition from laminar to turbulent flow has resisted combined efforts by physicists, engineers and mathematicians, and remained unresolved for almost one and a half centuries. In recent years, various studies have proposed analogies to directed percolation, a well-known universality class in statistical mechanics, which describes a non-equilibrium phase transition from a fluctuating active phase into an absorbing state. It is this unlikely relation between the multiscale, high-dimensional dynamics that signify the transition process in virtually all flows of practical relevance, and the arguably most basic non-equilibrium phase transition, that so far has mainly been the subject of model studies, which I review in this Perspective. article_processing_charge: No article_type: original author: - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Hof B. Directed percolation and the transition to turbulence. Nature Reviews Physics. 2023;5:62-72. doi:10.1038/s42254-022-00539-y apa: Hof, B. (2023). Directed percolation and the transition to turbulence. Nature Reviews Physics. Springer Nature. https://doi.org/10.1038/s42254-022-00539-y chicago: Hof, Björn. “Directed Percolation and the Transition to Turbulence.” Nature Reviews Physics. Springer Nature, 2023. https://doi.org/10.1038/s42254-022-00539-y. ieee: B. Hof, “Directed percolation and the transition to turbulence,” Nature Reviews Physics, vol. 5. Springer Nature, pp. 62–72, 2023. ista: Hof B. 2023. Directed percolation and the transition to turbulence. Nature Reviews Physics. 5, 62–72. mla: Hof, Björn. “Directed Percolation and the Transition to Turbulence.” Nature Reviews Physics, vol. 5, Springer Nature, 2023, pp. 62–72, doi:10.1038/s42254-022-00539-y. short: B. Hof, Nature Reviews Physics 5 (2023) 62–72. date_created: 2023-01-12T12:10:18Z date_published: 2023-01-01T00:00:00Z date_updated: 2023-08-01T12:50:48Z day: '01' department: - _id: BjHo doi: 10.1038/s42254-022-00539-y external_id: isi: - '000890148700002' intvolume: ' 5' isi: 1 keyword: - General Physics and Astronomy language: - iso: eng month: '01' oa_version: None page: 62-72 publication: Nature Reviews Physics publication_identifier: eissn: - 2522-5820 publication_status: published publisher: Springer Nature quality_controlled: '1' scopus_import: '1' status: public title: Directed percolation and the transition to turbulence type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 5 year: '2023' ... --- _id: '12105' abstract: - lang: eng 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. 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)." article_number: A10 article_processing_charge: Yes (via OA deal) article_type: original author: - first_name: Elena full_name: Marensi, Elena id: 0BE7553A-1004-11EA-B805-18983DDC885E last_name: Marensi - first_name: Gökhan full_name: Yalniz, Gökhan id: 66E74FA2-D8BF-11E9-8249-8DE2E5697425 last_name: Yalniz orcid: 0000-0002-8490-9312 - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 - first_name: Nazmi B full_name: Budanur, Nazmi B id: 3EA1010E-F248-11E8-B48F-1D18A9856A87 last_name: Budanur orcid: 0000-0003-0423-5010 citation: ama: Marensi E, Yalniz G, Hof B, Budanur NB. Symmetry-reduced dynamic mode decomposition of near-wall turbulence. Journal of Fluid Mechanics. 2023;954. doi:10.1017/jfm.2022.1001 apa: Marensi, E., Yalniz, G., Hof, B., & Budanur, N. B. (2023). Symmetry-reduced dynamic mode decomposition of near-wall turbulence. Journal of Fluid Mechanics. Cambridge University Press. https://doi.org/10.1017/jfm.2022.1001 chicago: Marensi, Elena, Gökhan Yalniz, Björn Hof, and Nazmi B Budanur. “Symmetry-Reduced Dynamic Mode Decomposition of near-Wall Turbulence.” Journal of Fluid Mechanics. Cambridge University Press, 2023. https://doi.org/10.1017/jfm.2022.1001. ieee: E. Marensi, G. Yalniz, B. Hof, and N. B. Budanur, “Symmetry-reduced dynamic mode decomposition of near-wall turbulence,” Journal of Fluid Mechanics, vol. 954. Cambridge University Press, 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. mla: Marensi, Elena, et al. “Symmetry-Reduced Dynamic Mode Decomposition of near-Wall Turbulence.” Journal of Fluid Mechanics, vol. 954, A10, Cambridge University Press, 2023, doi:10.1017/jfm.2022.1001. short: E. Marensi, G. Yalniz, B. Hof, N.B. Budanur, Journal of Fluid Mechanics 954 (2023). date_created: 2023-01-08T23:00:53Z date_published: 2023-01-10T00:00:00Z date_updated: 2023-08-01T12:53:23Z day: '10' ddc: - '530' department: - _id: BjHo doi: 10.1017/jfm.2022.1001 external_id: arxiv: - '2101.07516' isi: - '000903336600001' file: - access_level: open_access checksum: 9224f987caefe5dd85a70814d3cce65c content_type: application/pdf creator: dernst date_created: 2023-02-02T12:34:54Z date_updated: 2023-02-02T12:34:54Z file_id: '12489' file_name: 2023_JourFluidMechanics_Marensi.pdf file_size: 1931647 relation: main_file success: 1 file_date_updated: 2023-02-02T12:34:54Z has_accepted_license: '1' intvolume: ' 954' isi: 1 language: - iso: eng month: '01' oa: 1 oa_version: Published Version project: - _id: 238598C6-32DE-11EA-91FC-C7463DDC885E grant_number: '662960' name: 'Revisiting the Turbulence Problem Using Statistical Mechanics: Experimental Studies on Transitional and Turbulent Flows' 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: Symmetry-reduced dynamic mode decomposition of near-wall 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: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 954 year: '2023' ... --- _id: '12681' abstract: - lang: eng text: The dissolution of minute concentration of polymers in wall-bounded flows is well-known for its unparalleled ability to reduce turbulent friction drag. Another phenomenon, elasto-inertial turbulence (EIT), has been far less studied even though elastic instabilities have already been observed in dilute polymer solutions before the discovery of polymer drag reduction. EIT is a chaotic state driven by polymer dynamics that is observed across many orders of magnitude in Reynolds number. It involves energy transfer from small elastic scales to large flow scales. The investigation of the mechanisms of EIT offers the possibility to better understand other complex phenomena such as elastic turbulence and maximum drag reduction. In this review, we survey recent research efforts that are advancing the understanding of the dynamics of EIT. We highlight the fundamental differences between EIT and Newtonian/inertial turbulence from the perspective of experiments, numerical simulations, instabilities, and coherent structures. Finally, we discuss the possible links between EIT and elastic turbulence and polymer drag reduction, as well as the remaining challenges in unraveling the self-sustaining mechanism of EIT. acknowledgement: Part of the material presented here is based upon work supported by the National Science Foundation CBET (Chemical, Bioengineering, Environmental and Transport Systems) award 1805636 (to Y.D.), the Binational Science Foundation award 2016145 (to Y.D. and Victor Steinberg), a FRIA (Fund for Research Training in Industry and Agriculture) grant of the Belgian F.R.S.-FNRS (National Fund for Scientific Research) (to V.E.T.), the Marie Curie FP7 Career Integration grant PCIG10-GA-2011-304073 (to V.E.T.), and the Fonds spéciaux pour la recherche grant C-13/19 of the University of Liege (to V.E.T.). Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CECI) funded by the Belgian F.R.S.-FNRS, the Vermont Advanced Computing Center (VACC), the Partnership for Advanced Computing in Europe (PRACE), and the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles funded by the Walloon Region (grant agreement 117545). article_processing_charge: No article_type: original author: - first_name: Yves full_name: Dubief, Yves last_name: Dubief - first_name: Vincent E. full_name: Terrapon, Vincent E. last_name: Terrapon - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Dubief Y, Terrapon VE, Hof B. Elasto-inertial turbulence. Annual Review of Fluid Mechanics. 2023;55(1):675-705. doi:10.1146/annurev-fluid-032822-025933 apa: Dubief, Y., Terrapon, V. E., & Hof, B. (2023). Elasto-inertial turbulence. Annual Review of Fluid Mechanics. Annual Reviews. https://doi.org/10.1146/annurev-fluid-032822-025933 chicago: Dubief, Yves, Vincent E. Terrapon, and Björn Hof. “Elasto-Inertial Turbulence.” Annual Review of Fluid Mechanics. Annual Reviews, 2023. https://doi.org/10.1146/annurev-fluid-032822-025933. ieee: Y. Dubief, V. E. Terrapon, and B. Hof, “Elasto-inertial turbulence,” Annual Review of Fluid Mechanics, vol. 55, no. 1. Annual Reviews, pp. 675–705, 2023. ista: Dubief Y, Terrapon VE, Hof B. 2023. Elasto-inertial turbulence. Annual Review of Fluid Mechanics. 55(1), 675–705. mla: Dubief, Yves, et al. “Elasto-Inertial Turbulence.” Annual Review of Fluid Mechanics, vol. 55, no. 1, Annual Reviews, 2023, pp. 675–705, doi:10.1146/annurev-fluid-032822-025933. short: Y. Dubief, V.E. Terrapon, B. Hof, Annual Review of Fluid Mechanics 55 (2023) 675–705. date_created: 2023-02-26T23:01:01Z date_published: 2023-01-19T00:00:00Z date_updated: 2023-08-01T13:19:47Z day: '19' ddc: - '530' department: - _id: BjHo doi: 10.1146/annurev-fluid-032822-025933 external_id: isi: - '000915418100026' file: - access_level: open_access checksum: 2666aa3af2a25252d35eb8681d3edff7 content_type: application/pdf creator: dernst date_created: 2023-02-27T09:23:02Z date_updated: 2023-02-27T09:23:02Z file_id: '12690' file_name: 2023_AnnReviewFluidMech_Dubief.pdf file_size: 4036706 relation: main_file success: 1 file_date_updated: 2023-02-27T09:23:02Z has_accepted_license: '1' intvolume: ' 55' isi: 1 issue: '1' language: - iso: eng month: '01' oa: 1 oa_version: Published Version page: 675-705 publication: Annual Review of Fluid Mechanics publication_identifier: eissn: - 1545-4479 issn: - 0066-4189 publication_status: published publisher: Annual Reviews quality_controlled: '1' scopus_import: '1' status: public title: Elasto-inertial 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: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 55 year: '2023' ... --- _id: '12682' abstract: - lang: eng text: 'Since the seminal studies by Osborne Reynolds in the nineteenth century, pipe flow has served as a primary prototype for investigating the transition to turbulence in wall-bounded flows. Despite the apparent simplicity of this flow, various facets of this problem have occupied researchers for more than a century. Here we review insights from three distinct perspectives: (a) stability and susceptibility of laminar flow, (b) phase transition and spatiotemporal dynamics, and (c) dynamical systems analysis of the Navier—Stokes equations. We show how these perspectives have led to a profound understanding of the onset of turbulence in pipe flow. Outstanding open points, applications to flows of complex fluids, and similarities with other wall-bounded flows are discussed.' acknowledgement: 'The authors are very grateful to Laurette Tuckerman for her helpful comments. This work was supported by grants from the Simons Foundation (grant numbers 662985, D.B., and 662960, B.H.) and the Priority Programme “SPP 1881: Turbulent Superstructures” of the Deutsche Forschungsgemeinschaft (grant number AV120/3-2 to M.A.).' article_processing_charge: No article_type: original author: - first_name: Marc full_name: Avila, Marc last_name: Avila - first_name: Dwight full_name: Barkley, Dwight last_name: Barkley - first_name: Björn full_name: Hof, Björn id: 3A374330-F248-11E8-B48F-1D18A9856A87 last_name: Hof orcid: 0000-0003-2057-2754 citation: ama: Avila M, Barkley D, Hof B. Transition to turbulence in pipe flow. Annual Review of Fluid Mechanics. 2023;55:575-602. doi:10.1146/annurev-fluid-120720-025957 apa: Avila, M., Barkley, D., & Hof, B. (2023). Transition to turbulence in pipe flow. Annual Review of Fluid Mechanics. Annual Reviews. https://doi.org/10.1146/annurev-fluid-120720-025957 chicago: Avila, Marc, Dwight Barkley, and Björn Hof. “Transition to Turbulence in Pipe Flow.” Annual Review of Fluid Mechanics. Annual Reviews, 2023. https://doi.org/10.1146/annurev-fluid-120720-025957. ieee: M. Avila, D. Barkley, and B. Hof, “Transition to turbulence in pipe flow,” Annual Review of Fluid Mechanics, vol. 55. Annual Reviews, pp. 575–602, 2023. ista: Avila M, Barkley D, Hof B. 2023. Transition to turbulence in pipe flow. Annual Review of Fluid Mechanics. 55, 575–602. mla: Avila, Marc, et al. “Transition to Turbulence in Pipe Flow.” Annual Review of Fluid Mechanics, vol. 55, Annual Reviews, 2023, pp. 575–602, doi:10.1146/annurev-fluid-120720-025957. short: M. Avila, D. Barkley, B. Hof, Annual Review of Fluid Mechanics 55 (2023) 575–602. date_created: 2023-02-26T23:01:01Z date_published: 2023-01-19T00:00:00Z date_updated: 2023-08-01T13:20:30Z day: '19' ddc: - '530' department: - _id: BjHo doi: 10.1146/annurev-fluid-120720-025957 external_id: isi: - '000915418100023' file: - access_level: open_access checksum: f99ef30f76cabc9e5e1946b380c16db4 content_type: application/pdf creator: dernst date_created: 2023-02-27T09:35:52Z date_updated: 2023-02-27T09:35:52Z file_id: '12691' file_name: 2023_AnnReviewFluidMech_Avila.pdf file_size: 4769537 relation: main_file success: 1 file_date_updated: 2023-02-27T09:35:52Z has_accepted_license: '1' intvolume: ' 55' isi: 1 language: - iso: eng month: '01' oa: 1 oa_version: Published Version page: 575-602 project: - _id: 238598C6-32DE-11EA-91FC-C7463DDC885E grant_number: '662960' name: 'Revisiting the Turbulence Problem Using Statistical Mechanics: Experimental Studies on Transitional and Turbulent Flows' publication: Annual Review of Fluid Mechanics publication_identifier: issn: - 0066-4189 publication_status: published publisher: Annual Reviews quality_controlled: '1' scopus_import: '1' status: public title: Transition to turbulence in pipe flow tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 55 year: '2023' ... --- _id: '12172' abstract: - lang: eng text: In industrial reactors and equipment, non-ideality is quite a common phenomenon rather than an exception. These deviations from ideality impact the process's overall efficiency and the effectiveness of the equipment. To recognize the associated non-ideality, one needs to have enough understanding of the formulation of the equations and in-depth knowledge of the residence time distribution (RTD) data of real reactors. In the current work, step input and pulse input were used to create RTD data for Cascade continuous stirred tank reactors (CSTRs). For the aforementioned configuration, experiments were run at various flow rates to validate the developed characteristic equations. To produce RTD data, distilled water was utilized as the flowing fluid, and NaOH was the tracer substance. The ideal behavior of tracer concentration exits age distribution, and cumulative fraction for each setup and each input was plotted and experimental results were compared with perfect behavior. Deviation of concentration exit age distribution and cumulative fractional distribution from ideal behavior is more in pulse input as compared to a step input. For ideal cases, the exit age distribution curve and cumulative fraction curves are independent of the type of input. But a significant difference was observed for the two cases, which may be due to non-measurable fluctuations in volumetric flow rate, non-achievement of instant injection of tracer in case of pulse input, and slight variations in the sampling period. Further, with increasing flow rate, concentration, exit age, and cumulative fractional curves shifted upward, and this behavior matches with the actual case. article_processing_charge: No article_type: original author: - first_name: Bushra full_name: Khatoon, Bushra last_name: Khatoon - first_name: Shoaib full_name: Kamil, Shoaib id: 185a19af-dc7d-11ea-9b2f-8eb2201959e9 last_name: Kamil - first_name: Hitesh full_name: Babu, Hitesh last_name: Babu - first_name: M. full_name: Siraj Alam, M. last_name: Siraj Alam citation: ama: 'Khatoon B, Kamil S, Babu H, Siraj Alam M. Experimental analysis of Cascade CSTRs with step and pulse inputs. Materials Today: Proceedings. 2023;78(Part 1):40-47. doi:10.1016/j.matpr.2022.11.037' apa: 'Khatoon, B., Kamil, S., Babu, H., & Siraj Alam, M. (2023). Experimental analysis of Cascade CSTRs with step and pulse inputs. Materials Today: Proceedings. Elsevier. https://doi.org/10.1016/j.matpr.2022.11.037' chicago: 'Khatoon, Bushra, Shoaib Kamil, Hitesh Babu, and M. Siraj Alam. “Experimental Analysis of Cascade CSTRs with Step and Pulse Inputs.” Materials Today: Proceedings. Elsevier, 2023. https://doi.org/10.1016/j.matpr.2022.11.037.' ieee: 'B. Khatoon, S. Kamil, H. Babu, and M. Siraj Alam, “Experimental analysis of Cascade CSTRs with step and pulse inputs,” Materials Today: Proceedings, vol. 78, no. Part 1. Elsevier, pp. 40–47, 2023.' ista: 'Khatoon B, Kamil S, Babu H, Siraj Alam M. 2023. Experimental analysis of Cascade CSTRs with step and pulse inputs. Materials Today: Proceedings. 78(Part 1), 40–47.' mla: 'Khatoon, Bushra, et al. “Experimental Analysis of Cascade CSTRs with Step and Pulse Inputs.” Materials Today: Proceedings, vol. 78, no. Part 1, Elsevier, 2023, pp. 40–47, doi:10.1016/j.matpr.2022.11.037.' short: 'B. Khatoon, S. Kamil, H. Babu, M. Siraj Alam, Materials Today: Proceedings 78 (2023) 40–47.' date_created: 2023-01-12T12:11:26Z date_published: 2023-03-20T00:00:00Z date_updated: 2023-08-16T09:08:11Z day: '20' department: - _id: BjHo doi: 10.1016/j.matpr.2022.11.037 intvolume: ' 78' issue: Part 1 keyword: - General Medicine language: - iso: eng month: '03' oa_version: None page: 40-47 publication: 'Materials Today: Proceedings' publication_identifier: issn: - 2214-7853 publication_status: published publisher: Elsevier quality_controlled: '1' scopus_import: '1' status: public title: Experimental analysis of Cascade CSTRs with step and pulse inputs type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 78 year: '2023' ...