Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 Song Baofang 0000-0003-4469-8781 Avila Marc marc.avila@zarm.uni-bremen.de 0000-0001-5988-1090 2021 Optimal perturbation (classic, Re=2000,A=1,Wo=15): Time series of the r-theta-z-components contributions to the kinetic energy and enstrophy dataset https://doi.org/10.1594/PANGAEA.929197 2021-03-16T07:50:42 Laminar flows through pipes driven at steady, pulsatile or oscillatory rates undergo a subcritical transition to turbulence. We carry out an extensive linear non-modal stability analysis of these flows and show that for sufficiently high pulsation amplitudes the stream-wise vortices of the classic lift-up mechanism are outperformed by helical disturbances exhibiting an Orr-like mechanism. In oscillatory flow, the energy amplification depends solely on the Reynolds number based on the Stokes-layer thickness, and for sufficiently high oscillation frequency and Reynolds number, axisymmetric disturbances dominate. In the high-frequency limit, these axisymmetric disturbances are exactly similar to those recently identified by Biau (J. Fluid Mech., vol. 794, 2016, R4) for oscillatory flow over a flat plate. In all regimes of pulsatile and oscillatory pipe flow, the optimal helical and axisymmetric disturbances are triggered in the deceleration phase and reach their peaks in typically less than a period. Their maximum energy gain scales exponentially with Reynolds number of the oscillatory flow component. Our numerical computations unveil a plausible mechanism for the turbulence observed experimentally in pulsatile and oscillatory pipe flow. Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 Song Baofang 0000-0003-4469-8781 Avila Marc marc.avila@zarm.uni-bremen.de 0000-0001-5988-1090 accepted Non-modal transient growth of disturbances in pulsatile and oscillatory pipe flows journal article Journal of Fluid Mechanics 907 https://doi.org/10.1017/jfm.2020.940 not specified FLUID_SIMULATION_MODELING FSM Model simulation 134040 CC-BY-4.0 Creative Commons Attribution 4.0 International https://creativecommons.org/licenses/by/4.0/ OptimalPerturbation_classic_time_vel_vort #(k_op,m_op)=(0.00000000,1) VARIABLES = "t", "t/T", "ur", "ut", "uz", "curlr", "curlt", "curlz" ZONE T="time series", I=16755, J=1 Dimensionless time t Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 t Time by pulsation period t/T Time T http://dbpedia.org/resource/Time Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 t/T Velocity, radial ur Velocity http://dbpedia.org/resource/Velocity Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 ur u_θ, velocity, cylindrical, azimuthal component u_θ Velocity http://dbpedia.org/resource/Velocity cylindrical http://purl.obolibrary.org/obo/PATO_0001873 Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 u_θ u_z, velocity, cylindrical, axial component u_z Velocity http://dbpedia.org/resource/Velocity cylindrical http://purl.obolibrary.org/obo/PATO_0001873 Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 u_z Curl of velocity, radial direction Curl-r Velocity http://dbpedia.org/resource/Velocity Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 Curl-r Curl of velocity, azimuthal direction Curl-t Velocity http://dbpedia.org/resource/Velocity Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 Curl-t Curl of velocity, axial direction Curl-z Velocity http://dbpedia.org/resource/Velocity Xu Duo duo.xu@zarm.uni-bremen.de 0000-0001-8330-3581 Curl-z CurationLevelC Enhanced curation https://wiki.pangaea.de/wiki/Curation_levels ProcLevel2 PANGAEA data processing level 2 https://wiki.pangaea.de/wiki/Processing_levels#PANGAEA_data_processing_level_2 citable nonlinear instability transition to turbulence ZARM author70364 author78987 author78988 curlevel30 event2965167 journal8744 license21 method12075 param171174 param191429 param191432 param191433 param191434 param191463 param514817 param514818 pi78987 proclevel30 ref107573 term1074824 term43975 term43981 term67822 term67823 term71280 topotype1