[{"project":[{"_id":"25152F3A-B435-11E9-9278-68D0E5697425","call_identifier":"FP7","name":"Decoding the complexity of turbulence at its origin","grant_number":"306589"},{"name":"Eliminating turbulence in oil pipelines","grant_number":"737549","call_identifier":"H2020","_id":"25104D44-B435-11E9-9278-68D0E5697425"}],"publication":"Journal of Fluid Mechanics","status":"public","ec_funded":1,"date_published":"2019-05-25T00:00:00Z","year":"2019","isi":1,"external_id":{"arxiv":["1807.05357"],"isi":["000462606100001"]},"related_material":{"record":[{"status":"public","relation":"dissertation_contains","id":"7258"}],"link":[{"url":"https://doi.org/10.1017/jfm.2019.191","relation":"supplementary_material"}]},"page":"934-948","main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/1807.05357"}],"quality_controlled":"1","doi":"10.1017/jfm.2019.191","article_processing_charge":"No","publisher":"Cambridge University Press","date_updated":"2024-03-25T23:30:20Z","_id":"6228","type":"journal_article","oa":1,"language":[{"iso":"eng"}],"citation":{"ista":"Scarselli D, Kühnen J, Hof B. 2019. Relaminarising pipe flow by wall movement. Journal of Fluid Mechanics. 867, 934–948.","chicago":"Scarselli, Davide, Jakob Kühnen, and Björn Hof. “Relaminarising Pipe Flow by Wall Movement.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2019. <a href=\"https://doi.org/10.1017/jfm.2019.191\">https://doi.org/10.1017/jfm.2019.191</a>.","mla":"Scarselli, Davide, et al. “Relaminarising Pipe Flow by Wall Movement.” <i>Journal of Fluid Mechanics</i>, vol. 867, Cambridge University Press, 2019, pp. 934–48, doi:<a href=\"https://doi.org/10.1017/jfm.2019.191\">10.1017/jfm.2019.191</a>.","apa":"Scarselli, D., Kühnen, J., &#38; Hof, B. (2019). Relaminarising pipe flow by wall movement. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2019.191\">https://doi.org/10.1017/jfm.2019.191</a>","ama":"Scarselli D, Kühnen J, Hof B. Relaminarising pipe flow by wall movement. <i>Journal of Fluid Mechanics</i>. 2019;867:934-948. doi:<a href=\"https://doi.org/10.1017/jfm.2019.191\">10.1017/jfm.2019.191</a>","short":"D. Scarselli, J. Kühnen, B. Hof, Journal of Fluid Mechanics 867 (2019) 934–948.","ieee":"D. Scarselli, J. Kühnen, and B. Hof, “Relaminarising pipe flow by wall movement,” <i>Journal of Fluid Mechanics</i>, vol. 867. Cambridge University Press, pp. 934–948, 2019."},"user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","arxiv":1,"month":"05","department":[{"_id":"BjHo"}],"intvolume":"       867","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."}],"publication_status":"published","publication_identifier":{"eissn":["14697645"],"issn":["00221120"]},"author":[{"last_name":"Scarselli","full_name":"Scarselli, Davide","id":"40315C30-F248-11E8-B48F-1D18A9856A87","first_name":"Davide","orcid":"0000-0001-5227-4271"},{"last_name":"Kühnen","full_name":"Kühnen, Jakob","id":"3A47AE32-F248-11E8-B48F-1D18A9856A87","orcid":"0000-0003-4312-0179","first_name":"Jakob"},{"orcid":"0000-0003-2057-2754","first_name":"Björn","id":"3A374330-F248-11E8-B48F-1D18A9856A87","full_name":"Hof, Björn","last_name":"Hof"}],"scopus_import":"1","day":"25","title":"Relaminarising pipe flow by wall movement","oa_version":"Preprint","volume":867,"date_created":"2019-04-07T21:59:14Z"},{"oa":1,"language":[{"iso":"eng"}],"issue":"11","citation":{"mla":"Kühnen, Jakob, et al. “Relaminarization of Pipe Flow by Means of 3D-Printed Shaped Honeycombs.” <i>Journal of Fluids Engineering</i>, vol. 141, no. 11, 111105, ASME, 2019, doi:<a href=\"https://doi.org/10.1115/1.4043494\">10.1115/1.4043494</a>.","apa":"Kühnen, J., Scarselli, D., &#38; Hof, B. (2019). Relaminarization of pipe flow by means of 3D-printed shaped honeycombs. <i>Journal of Fluids Engineering</i>. ASME. <a href=\"https://doi.org/10.1115/1.4043494\">https://doi.org/10.1115/1.4043494</a>","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.","chicago":"Kühnen, Jakob, Davide Scarselli, and Björn Hof. “Relaminarization of Pipe Flow by Means of 3D-Printed Shaped Honeycombs.” <i>Journal of Fluids Engineering</i>. ASME, 2019. <a href=\"https://doi.org/10.1115/1.4043494\">https://doi.org/10.1115/1.4043494</a>.","short":"J. Kühnen, D. Scarselli, B. Hof, Journal of Fluids Engineering 141 (2019).","ieee":"J. Kühnen, D. Scarselli, and B. Hof, “Relaminarization of pipe flow by means of 3D-printed shaped honeycombs,” <i>Journal of Fluids Engineering</i>, vol. 141, no. 11. ASME, 2019.","ama":"Kühnen J, Scarselli D, Hof B. Relaminarization of pipe flow by means of 3D-printed shaped honeycombs. <i>Journal of Fluids Engineering</i>. 2019;141(11). doi:<a href=\"https://doi.org/10.1115/1.4043494\">10.1115/1.4043494</a>"},"user_id":"4359f0d1-fa6c-11eb-b949-802e58b17ae8","month":"11","arxiv":1,"department":[{"_id":"BjHo"}],"article_number":"111105","intvolume":"       141","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"}],"publication_identifier":{"eissn":["1528901X"],"issn":["00982202"]},"publication_status":"published","author":[{"first_name":"Jakob","orcid":"0000-0003-4312-0179","full_name":"Kühnen, Jakob","id":"3A47AE32-F248-11E8-B48F-1D18A9856A87","last_name":"Kühnen"},{"first_name":"Davide","orcid":"0000-0001-5227-4271","last_name":"Scarselli","id":"40315C30-F248-11E8-B48F-1D18A9856A87","full_name":"Scarselli, Davide"},{"first_name":"Björn","orcid":"0000-0003-2057-2754","id":"3A374330-F248-11E8-B48F-1D18A9856A87","full_name":"Hof, Björn","last_name":"Hof"}],"scopus_import":"1","day":"01","oa_version":"Preprint","title":"Relaminarization of pipe flow by means of 3D-printed shaped honeycombs","volume":141,"article_type":"original","date_created":"2019-05-26T21:59:13Z","project":[{"_id":"25152F3A-B435-11E9-9278-68D0E5697425","call_identifier":"FP7","name":"Decoding the complexity of turbulence at its origin","grant_number":"306589"}],"publication":"Journal of Fluids Engineering","status":"public","ec_funded":1,"date_published":"2019-11-01T00:00:00Z","year":"2019","isi":1,"external_id":{"arxiv":["1809.07625"],"isi":["000487748600005"]},"related_material":{"record":[{"id":"7258","status":"public","relation":"dissertation_contains"}]},"main_file_link":[{"url":"https://arxiv.org/abs/1809.07625","open_access":"1"}],"quality_controlled":"1","doi":"10.1115/1.4043494","article_processing_charge":"No","publisher":"ASME","date_updated":"2024-03-25T23:30:20Z","_id":"6486","type":"journal_article"},{"department":[{"_id":"BjHo"}],"month":"01","citation":{"ieee":"J. Kühnen <i>et al.</i>, “Destabilizing turbulence in pipe flow,” <i>Nature Physics</i>, vol. 14. Nature Publishing Group, pp. 386–390, 2018.","short":"J. Kühnen, B. Song, D. Scarselli, N.B. Budanur, M. Riedl, A. Willis, M. Avila, B. Hof, Nature Physics 14 (2018) 386–390.","ama":"Kühnen J, Song B, Scarselli D, et al. Destabilizing turbulence in pipe flow. <i>Nature Physics</i>. 2018;14:386-390. doi:<a href=\"https://doi.org/10.1038/s41567-017-0018-3\">10.1038/s41567-017-0018-3</a>","apa":"Kühnen, J., Song, B., Scarselli, D., Budanur, N. B., Riedl, M., Willis, A., … Hof, B. (2018). Destabilizing turbulence in pipe flow. <i>Nature Physics</i>. Nature Publishing Group. <a href=\"https://doi.org/10.1038/s41567-017-0018-3\">https://doi.org/10.1038/s41567-017-0018-3</a>","mla":"Kühnen, Jakob, et al. “Destabilizing Turbulence in Pipe Flow.” <i>Nature Physics</i>, vol. 14, Nature Publishing Group, 2018, pp. 386–90, doi:<a href=\"https://doi.org/10.1038/s41567-017-0018-3\">10.1038/s41567-017-0018-3</a>.","chicago":"Kühnen, Jakob, Baofang Song, Davide Scarselli, Nazmi B Budanur, Michael Riedl, Ashley Willis, Marc Avila, and Björn Hof. “Destabilizing Turbulence in Pipe Flow.” <i>Nature Physics</i>. Nature Publishing Group, 2018. <a href=\"https://doi.org/10.1038/s41567-017-0018-3\">https://doi.org/10.1038/s41567-017-0018-3</a>.","ista":"Kühnen J, Song B, Scarselli D, Budanur NB, Riedl M, Willis A, Avila M, Hof B. 2018. Destabilizing turbulence in pipe flow. Nature Physics. 14, 386–390."},"user_id":"c635000d-4b10-11ee-a964-aac5a93f6ac1","oa":1,"language":[{"iso":"eng"}],"volume":14,"date_created":"2018-12-11T11:46:36Z","scopus_import":"1","day":"08","author":[{"orcid":"0000-0003-4312-0179","first_name":"Jakob","full_name":"Kühnen, Jakob","id":"3A47AE32-F248-11E8-B48F-1D18A9856A87","last_name":"Kühnen"},{"full_name":"Song, Baofang","last_name":"Song","first_name":"Baofang"},{"orcid":"0000-0001-5227-4271","first_name":"Davide","last_name":"Scarselli","full_name":"Scarselli, Davide","id":"40315C30-F248-11E8-B48F-1D18A9856A87"},{"orcid":"0000-0003-0423-5010","first_name":"Nazmi B","last_name":"Budanur","id":"3EA1010E-F248-11E8-B48F-1D18A9856A87","full_name":"Budanur, Nazmi B"},{"last_name":"Riedl","full_name":"Riedl, Michael","id":"3BE60946-F248-11E8-B48F-1D18A9856A87","first_name":"Michael","orcid":"0000-0003-4844-6311"},{"first_name":"Ashley","last_name":"Willis","full_name":"Willis, Ashley"},{"last_name":"Avila","full_name":"Avila, Marc","first_name":"Marc"},{"orcid":"0000-0003-2057-2754","first_name":"Björn","full_name":"Hof, Björn","id":"3A374330-F248-11E8-B48F-1D18A9856A87","last_name":"Hof"}],"title":"Destabilizing turbulence in pipe flow","oa_version":"Preprint","publication_status":"published","intvolume":"        14","abstract":[{"text":"Turbulence is the major cause of friction losses in transport processes and it is responsible for a drastic drag increase in flows over bounding surfaces. While much effort is invested into developing ways to control and reduce turbulence intensities, so far no methods exist to altogether eliminate turbulence if velocities are sufficiently large. We demonstrate for pipe flow that appropriate distortions to the velocity profile lead to a complete collapse of turbulence and subsequently friction losses are reduced by as much as 90%. Counterintuitively, the return to laminar motion is accomplished by initially increasing turbulence intensities or by transiently amplifying wall shear. Since neither the Reynolds number nor the shear stresses decrease (the latter often increase), these measures are not indicative of turbulence collapse. Instead, an amplification mechanism                      measuring the interaction between eddies and the mean shear is found to set a threshold below which turbulence is suppressed beyond recovery.","lang":"eng"}],"publist_id":"7360","isi":1,"year":"2018","related_material":{"record":[{"id":"12726","status":"public","relation":"dissertation_contains"},{"id":"14530","status":"public","relation":"dissertation_contains"},{"id":"7258","relation":"dissertation_contains","status":"public"}]},"external_id":{"isi":["000429434100020"]},"ec_funded":1,"date_published":"2018-01-08T00:00:00Z","acknowledgement":"We acknowledge the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement 306589, the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 737549) and the Deutsche Forschungsgemeinschaft (Project No. FOR 1182) for financial support. We thank our technician P. Maier for providing highly valuable ideas and greatly supporting us in all technical aspects. We thank M. Schaner for technical drawings, construction and design. We thank M. Schwegel for a Matlab code to post-process experimental data.","publication":"Nature Physics","status":"public","project":[{"call_identifier":"FP7","name":"Decoding the complexity of turbulence at its origin","grant_number":"306589","_id":"25152F3A-B435-11E9-9278-68D0E5697425"},{"_id":"25104D44-B435-11E9-9278-68D0E5697425","grant_number":"737549","name":"Eliminating turbulence in oil pipelines","call_identifier":"H2020"}],"_id":"461","date_updated":"2024-03-25T23:30:20Z","type":"journal_article","article_processing_charge":"No","doi":"10.1038/s41567-017-0018-3","publisher":"Nature Publishing Group","main_file_link":[{"open_access":"1","url":"https://arxiv.org/abs/1711.06543"}],"quality_controlled":"1","page":"386-390"},{"department":[{"_id":"BjHo"}],"file":[{"file_name":"2018_FlowTurbulenceCombust_Kuehnen.pdf","content_type":"application/pdf","access_level":"open_access","relation":"main_file","checksum":"d7c0bade150faabca150b0a9986e60ca","file_size":2210020,"date_created":"2018-12-17T15:52:37Z","creator":"dernst","date_updated":"2020-07-14T12:46:25Z","file_id":"5717"}],"month":"01","citation":{"mla":"Kühnen, Jakob, et al. “Relaminarization by Steady Modification of the Streamwise Velocity Profile in a Pipe.” <i>Flow Turbulence and Combustion</i>, vol. 100, no. 4, Springer, 2018, pp. 919–42, doi:<a href=\"https://doi.org/10.1007/s10494-018-9896-4\">10.1007/s10494-018-9896-4</a>.","apa":"Kühnen, J., Scarselli, D., Schaner, M., &#38; Hof, B. (2018). Relaminarization by steady modification of the streamwise velocity profile in a pipe. <i>Flow Turbulence and Combustion</i>. Springer. <a href=\"https://doi.org/10.1007/s10494-018-9896-4\">https://doi.org/10.1007/s10494-018-9896-4</a>","chicago":"Kühnen, Jakob, Davide Scarselli, Markus Schaner, and Björn Hof. “Relaminarization by Steady Modification of the Streamwise Velocity Profile in a Pipe.” <i>Flow Turbulence and Combustion</i>. Springer, 2018. <a href=\"https://doi.org/10.1007/s10494-018-9896-4\">https://doi.org/10.1007/s10494-018-9896-4</a>.","ista":"Kühnen J, Scarselli D, Schaner M, Hof B. 2018. Relaminarization by steady modification of the streamwise velocity profile in a pipe. Flow Turbulence and Combustion. 100(4), 919–942.","short":"J. Kühnen, D. Scarselli, M. Schaner, B. Hof, Flow Turbulence and Combustion 100 (2018) 919–942.","ieee":"J. Kühnen, D. Scarselli, M. Schaner, and B. Hof, “Relaminarization by steady modification of the streamwise velocity profile in a pipe,” <i>Flow Turbulence and Combustion</i>, vol. 100, no. 4. Springer, pp. 919–942, 2018.","ama":"Kühnen J, Scarselli D, Schaner M, Hof B. Relaminarization by steady modification of the streamwise velocity profile in a pipe. <i>Flow Turbulence and Combustion</i>. 2018;100(4):919-942. doi:<a href=\"https://doi.org/10.1007/s10494-018-9896-4\">10.1007/s10494-018-9896-4</a>"},"issue":"4","user_id":"c635000d-4b10-11ee-a964-aac5a93f6ac1","oa":1,"language":[{"iso":"eng"}],"volume":100,"date_created":"2018-12-11T11:46:23Z","day":"01","scopus_import":"1","author":[{"last_name":"Kühnen","id":"3A47AE32-F248-11E8-B48F-1D18A9856A87","full_name":"Kühnen, Jakob","orcid":"0000-0003-4312-0179","first_name":"Jakob"},{"first_name":"Davide","orcid":"0000-0001-5227-4271","last_name":"Scarselli","full_name":"Scarselli, Davide","id":"40315C30-F248-11E8-B48F-1D18A9856A87"},{"last_name":"Schaner","id":"316CE034-F248-11E8-B48F-1D18A9856A87","full_name":"Schaner, Markus","first_name":"Markus"},{"full_name":"Hof, Björn","id":"3A374330-F248-11E8-B48F-1D18A9856A87","last_name":"Hof","first_name":"Björn","orcid":"0000-0003-2057-2754"}],"oa_version":"Published Version","title":"Relaminarization by steady modification of the streamwise velocity profile in a pipe","file_date_updated":"2020-07-14T12:46:25Z","publication_status":"published","has_accepted_license":"1","tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png","short":"CC BY (4.0)"},"intvolume":"       100","abstract":[{"text":"We show that a rather simple, steady modification of the streamwise velocity profile in a pipe can lead to a complete collapse of turbulence and the flow fully relaminarizes. Two different devices, a stationary obstacle (inset) and a device which injects fluid through an annular gap close to the wall, are used to control the flow. Both devices modify the streamwise velocity profile such that the flow in the center of the pipe is decelerated and the flow in the near wall region is accelerated. We present measurements with stereoscopic particle image velocimetry to investigate and capture the development of the relaminarizing flow downstream these devices and the specific circumstances responsible for relaminarization. We find total relaminarization up to Reynolds numbers of 6000, where the skin friction in the far downstream distance is reduced by a factor of 3.4 due to relaminarization. In a smooth straight pipe the flow remains completely laminar downstream of the control. Furthermore, we show that transient (temporary) relaminarization in a spatially confined region right downstream the devices occurs also at much higher Reynolds numbers, accompanied by a significant local skin friction drag reduction. The underlying physical mechanism of relaminarization is attributed to a weakening of the near-wall turbulence production cycle.","lang":"eng"}],"publist_id":"7401","year":"2018","isi":1,"related_material":{"record":[{"relation":"dissertation_contains","status":"public","id":"7258"}]},"external_id":{"isi":["000433113900004"]},"ec_funded":1,"date_published":"2018-01-01T00:00:00Z","status":"public","publication":"Flow Turbulence and Combustion","project":[{"_id":"25152F3A-B435-11E9-9278-68D0E5697425","call_identifier":"FP7","name":"Decoding the complexity of turbulence at its origin","grant_number":"306589"}],"_id":"422","date_updated":"2024-03-25T23:30:20Z","type":"journal_article","article_processing_charge":"Yes (via OA deal)","doi":"10.1007/s10494-018-9896-4","publisher":"Springer","quality_controlled":"1","page":"919 - 942","ddc":["530"]},{"article_type":"original","date_created":"2018-12-11T11:54:17Z","volume":770,"oa_version":"Preprint","title":"Subcritical versus supercritical transition to turbulence in curved pipes","author":[{"orcid":"0000-0003-4312-0179","first_name":"Jakob","last_name":"Kühnen","full_name":"Kühnen, Jakob","id":"3A47AE32-F248-11E8-B48F-1D18A9856A87"},{"last_name":"Braunshier","full_name":"Braunshier, P","first_name":"P"},{"last_name":"Schwegel","full_name":"Schwegel, M","first_name":"M"},{"first_name":"Hendrik","full_name":"Kuhlmann, Hendrik","last_name":"Kuhlmann"},{"last_name":"Hof","id":"3A374330-F248-11E8-B48F-1D18A9856A87","full_name":"Hof, Björn","first_name":"Björn","orcid":"0000-0003-2057-2754"}],"scopus_import":1,"day":"08","publication_status":"published","intvolume":"       770","abstract":[{"text":"Transition to turbulence in straight pipes occurs in spite of the linear stability of the laminar Hagen-Poiseuille flow if both the amplitude of flow perturbations and the Reynolds number Re exceed a minimum threshold (subcritical transition). As the pipe curvature increases, centrifugal effects become important, modifying the basic flow as well as the most unstable linear modes. If the curvature (tube-to-coiling diameter d/D) is sufficiently large, a Hopf bifurcation (supercritical instability) is encountered before turbulence can be excited (subcritical instability). We trace the instability thresholds in the Re - d/D parameter space in the range 0.01 ≤ d/D\\ ≤ 0.1 by means of laser-Doppler velocimetry and determine the point where the subcritical and supercritical instabilities meet. Two different experimental set-ups are used: a closed system where the pipe forms an axisymmetric torus and an open system employing a helical pipe. Implications for the measurement of friction factors in curved pipes are discussed.","lang":"eng"}],"article_number":"R3","department":[{"_id":"BjHo"}],"arxiv":1,"month":"04","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","issue":"5","citation":{"ieee":"J. Kühnen, P. Braunshier, M. Schwegel, H. Kuhlmann, and B. Hof, “Subcritical versus supercritical transition to turbulence in curved pipes,” <i>Journal of Fluid Mechanics</i>, vol. 770, no. 5. Cambridge University Press, 2015.","short":"J. Kühnen, P. Braunshier, M. Schwegel, H. Kuhlmann, B. Hof, Journal of Fluid Mechanics 770 (2015).","ama":"Kühnen J, Braunshier P, Schwegel M, Kuhlmann H, Hof B. Subcritical versus supercritical transition to turbulence in curved pipes. <i>Journal of Fluid Mechanics</i>. 2015;770(5). doi:<a href=\"https://doi.org/10.1017/jfm.2015.184\">10.1017/jfm.2015.184</a>","apa":"Kühnen, J., Braunshier, P., Schwegel, M., Kuhlmann, H., &#38; Hof, B. (2015). Subcritical versus supercritical transition to turbulence in curved pipes. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2015.184\">https://doi.org/10.1017/jfm.2015.184</a>","mla":"Kühnen, Jakob, et al. “Subcritical versus Supercritical Transition to Turbulence in Curved Pipes.” <i>Journal of Fluid Mechanics</i>, vol. 770, no. 5, R3, Cambridge University Press, 2015, doi:<a href=\"https://doi.org/10.1017/jfm.2015.184\">10.1017/jfm.2015.184</a>.","chicago":"Kühnen, Jakob, P Braunshier, M Schwegel, Hendrik Kuhlmann, and Björn Hof. “Subcritical versus Supercritical Transition to Turbulence in Curved Pipes.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2015. <a href=\"https://doi.org/10.1017/jfm.2015.184\">https://doi.org/10.1017/jfm.2015.184</a>.","ista":"Kühnen J, Braunshier P, Schwegel M, Kuhlmann H, Hof B. 2015. Subcritical versus supercritical transition to turbulence in curved pipes. Journal of Fluid Mechanics. 770(5), R3."},"language":[{"iso":"eng"}],"oa":1,"type":"journal_article","date_updated":"2021-01-12T06:53:31Z","_id":"1837","publisher":"Cambridge University Press","doi":"10.1017/jfm.2015.184","article_processing_charge":"No","quality_controlled":"1","main_file_link":[{"url":"https://arxiv.org/abs/1508.06559","open_access":"1"}],"publist_id":"5265","external_id":{"arxiv":["1508.06559"]},"year":"2015","date_published":"2015-04-08T00:00:00Z","ec_funded":1,"project":[{"grant_number":"306589","name":"Decoding the complexity of turbulence at its origin","call_identifier":"FP7","_id":"25152F3A-B435-11E9-9278-68D0E5697425"}],"publication":"Journal of Fluid Mechanics","status":"public"},{"intvolume":"       738","abstract":[{"lang":"eng","text":"The flow instability and further transition to turbulence in a toroidal pipe (torus) with curvature ratio (tube-to-coiling diameter) 0.049 is investigated experimentally. The flow inside the toroidal pipe is driven by a steel sphere fitted to the inner pipe diameter. The sphere is moved with constant azimuthal velocity from outside the torus by a moving magnet. The experiment is designed to investigate curved pipe flow by optical measurement techniques. Using stereoscopic particle image velocimetry, laser Doppler velocimetry and pressure drop measurements, the flow is measured for Reynolds numbers ranging from 1000 to 15 000. Time- and space-resolved velocity fields are obtained and analysed. The steady axisymmetric basic flow is strongly influenced by centrifugal effects. On an increase of the Reynolds number we find a sequence of bifurcations. For Re=4075±2% a supercritical bifurcation to an oscillatory flow is found in which waves travel in the streamwise direction with a phase velocity slightly faster than the mean flow. The oscillatory flow is superseded by a presumably quasi-periodic flow at a further increase of the Reynolds number before turbulence sets in. The results are found to be compatible, in general, with earlier experimental and numerical investigations on transition to turbulence in helical and curved pipes. However, important aspects of the bifurcation scenario differ considerably."}],"publication_status":"published","day":"10","scopus_import":1,"author":[{"first_name":"Jakob","orcid":"0000-0003-4312-0179","last_name":"Kühnen","id":"3A47AE32-F248-11E8-B48F-1D18A9856A87","full_name":"Kühnen, Jakob"},{"full_name":"Holzner, Markus","last_name":"Holzner","first_name":"Markus"},{"first_name":"Björn","orcid":"0000-0003-2057-2754","last_name":"Hof","id":"3A374330-F248-11E8-B48F-1D18A9856A87","full_name":"Hof, Björn"},{"first_name":"Hendrik","full_name":"Kuhlmann, Hendrik","last_name":"Kuhlmann"}],"oa_version":"Submitted Version","title":"Experimental investigation of transitional flow in a toroidal pipe","volume":738,"date_created":"2018-12-11T11:55:25Z","oa":1,"language":[{"iso":"eng"}],"citation":{"ama":"Kühnen J, Holzner M, Hof B, Kuhlmann H. Experimental investigation of transitional flow in a toroidal pipe. <i>Journal of Fluid Mechanics</i>. 2014;738:463-491. doi:<a href=\"https://doi.org/10.1017/jfm.2013.603\">10.1017/jfm.2013.603</a>","short":"J. Kühnen, M. Holzner, B. Hof, H. Kuhlmann, Journal of Fluid Mechanics 738 (2014) 463–491.","ieee":"J. Kühnen, M. Holzner, B. Hof, and H. Kuhlmann, “Experimental investigation of transitional flow in a toroidal pipe,” <i>Journal of Fluid Mechanics</i>, vol. 738. Cambridge University Press, pp. 463–491, 2014.","ista":"Kühnen J, Holzner M, Hof B, Kuhlmann H. 2014. Experimental investigation of transitional flow in a toroidal pipe. Journal of Fluid Mechanics. 738, 463–491.","chicago":"Kühnen, Jakob, Markus Holzner, Björn Hof, and Hendrik Kuhlmann. “Experimental Investigation of Transitional Flow in a Toroidal Pipe.” <i>Journal of Fluid Mechanics</i>. Cambridge University Press, 2014. <a href=\"https://doi.org/10.1017/jfm.2013.603\">https://doi.org/10.1017/jfm.2013.603</a>.","mla":"Kühnen, Jakob, et al. “Experimental Investigation of Transitional Flow in a Toroidal Pipe.” <i>Journal of Fluid Mechanics</i>, vol. 738, Cambridge University Press, 2014, pp. 463–91, doi:<a href=\"https://doi.org/10.1017/jfm.2013.603\">10.1017/jfm.2013.603</a>.","apa":"Kühnen, J., Holzner, M., Hof, B., &#38; Kuhlmann, H. (2014). Experimental investigation of transitional flow in a toroidal pipe. <i>Journal of Fluid Mechanics</i>. Cambridge University Press. <a href=\"https://doi.org/10.1017/jfm.2013.603\">https://doi.org/10.1017/jfm.2013.603</a>"},"user_id":"3E5EF7F0-F248-11E8-B48F-1D18A9856A87","month":"01","arxiv":1,"department":[{"_id":"BjHo"}],"page":"463 - 491","main_file_link":[{"url":"https://arxiv.org/abs/1508.06546","open_access":"1"}],"quality_controlled":"1","article_processing_charge":"No","doi":"10.1017/jfm.2013.603","publisher":"Cambridge University Press","_id":"2050","date_updated":"2021-01-12T06:54:59Z","type":"journal_article","status":"public","publication":"Journal of Fluid Mechanics","date_published":"2014-01-10T00:00:00Z","year":"2014","external_id":{"arxiv":["1508.06546"]},"publist_id":"5001"}]