{"article_processing_charge":"No","month":"04","date_updated":"2021-01-12T06:53:31Z","type":"journal_article","day":"08","department":[{"_id":"BjHo"}],"main_file_link":[{"url":"https://arxiv.org/abs/1508.06559","open_access":"1"}],"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"}],"date_published":"2015-04-08T00:00:00Z","publication_status":"published","issue":"5","publisher":"Cambridge University Press","scopus_import":1,"oa_version":"Preprint","oa":1,"date_created":"2018-12-11T11:54:17Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","quality_controlled":"1","title":"Subcritical versus supercritical transition to turbulence in curved pipes","status":"public","external_id":{"arxiv":["1508.06559"]},"publication":"Journal of Fluid Mechanics","author":[{"orcid":"0000-0003-4312-0179","first_name":"Jakob","last_name":"Kühnen","id":"3A47AE32-F248-11E8-B48F-1D18A9856A87","full_name":"Kühnen, Jakob"},{"last_name":"Braunshier","first_name":"P","full_name":"Braunshier, P"},{"full_name":"Schwegel, M","first_name":"M","last_name":"Schwegel"},{"last_name":"Kuhlmann","first_name":"Hendrik","full_name":"Kuhlmann, Hendrik"},{"last_name":"Hof","first_name":"Björn","id":"3A374330-F248-11E8-B48F-1D18A9856A87","full_name":"Hof, Björn","orcid":"0000-0003-2057-2754"}],"doi":"10.1017/jfm.2015.184","article_number":"R3","_id":"1837","language":[{"iso":"eng"}],"citation":{"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>.","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.","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.","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>.","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>","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>","short":"J. Kühnen, P. Braunshier, M. Schwegel, H. Kuhlmann, B. Hof, Journal of Fluid Mechanics 770 (2015)."},"article_type":"original","ec_funded":1,"year":"2015","intvolume":"       770","volume":770,"publist_id":"5265","project":[{"grant_number":"306589","name":"Decoding the complexity of turbulence at its origin","_id":"25152F3A-B435-11E9-9278-68D0E5697425","call_identifier":"FP7"}]}