PANGAEA_929197 Optimal perturbation (classic, Re=2000,A=1,Wo=15): Time series of the r-theta-z-components contributions to the kinetic energy and enstrophy Xu, Duo; Song, Baofang; Avila, Marc Optimal perturbation (classic, Re=2000,A=1,Wo=15): Time series of the r-theta-z-components contributions to the kinetic energy and enstrophy 2021-03-16 PANGAEA Dataset https://doi.pangaea.de/10.1594/PANGAEA.929197 Investigator Duo Xu duo.xu@zarm.uni-bremen.de Earth Science Dimensionless time Time by pulsation period Velocity, radial u_θ, velocity, cylindrical, azimuthal component u_z, velocity, cylindrical, axial component Curl of velocity, radial direction Curl of velocity, azimuthal direction Curl of velocity, axial direction geoscientificInformation FLUID_SIMULATION_MODELING FSM Model simulation nonlinear instability transition to turbulence Complete unrestricted CC-BY-4.0: Creative Commons Attribution 4.0 International English PANGAEA Data Publisher for Earth & Environmental Science https://www.pangaea.de/ Data Center Contact Michael Diepenbroek info@pangaea.de

Leobener Str.

Bremen Bremen 28359 Germany online 134040 data points text/tab-separated-values Xu, Duo; Song, Baofang; Avila, Marc (accepted): Non-modal transient growth of disturbances in pulsatile and oscillatory pipe flows. Journal of Fluid Mechanics, 907, https://doi.org/10.1017/jfm.2020.940

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. ** For all details see the full metadata description at "https://doi.pangaea.de/10.1594/PANGAEA.929197"! ** 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

https://doi.org/10.1017/jfm.2020.940 Non-modal transient growth of disturbances in pulsatile and oscillatory pipe flows DIF 9.4 2021-03-16 2026-07-15