Optimal perturbation (helical, Re=2000,A=1,Wo=15): Time series of the r-theta-z-components contributions to the kinetic energy and enstrophy

DOI

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.

OptimalPerturbation_helical_time_vel_vort#(k_op,m_op)=( 1.62000000,1)VARIABLES = "t", "t/T", "ur", "ut", "uz", "curlr", "curlt", "curlz"ZONE T="time series", I=11170, J=1

Identifier
DOI https://doi.org/10.1594/PANGAEA.929362
Related Identifier References https://doi.org/10.1017/jfm.2020.940
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.929362
Provenance
Creator Xu, Duo ORCID logo; Song, Baofang ORCID logo; Avila, Marc ORCID logo
Publisher PANGAEA
Publication Year 2021
Rights Creative Commons Attribution 4.0 International; https://creativecommons.org/licenses/by/4.0/
OpenAccess true
Representation
Resource Type Dataset
Format text/tab-separated-values
Size 89360 data points
Discipline Earth System Research