Applied Mathematics and Mechanics (English Edition) ›› 2017, Vol. 38 ›› Issue (11): 1635-1650.doi: https://doi.org/10.1007/s10483-017-2275-9

• Articles • Previous Articles    

Algorithm for transient growth of perturbations in channel Poiseuille flow

Jianlei ZHANG1, Gang DONG1, Yi LI2   

  1. 1. National Key Laboratory of Transient Physics, Nanjing University of Science and Technology, Nanjing 210094, China;
    2. School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH, U.K
  • Received:2016-08-23 Revised:2017-05-15 Online:2017-11-01 Published:2017-11-01
  • Contact: Gang DONG E-mail:dgvehicle@yahoo.com
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No. 11372140)

Abstract:

This study develops a direct optimal growth algorithm for three-dimensional transient growth analysis of perturbations in channel flows which are globally stable but locally unstable. Different from traditional non-modal methods based on the Orr-Sommerfeld and Squire (OSS) equations that assume simple base flows, this algorithm can be applied to arbitrarily complex base flows. In the proposed algorithm, a reorthogonalization Arnoldi method is used to improve orthogonality of the orthogonal basis of the Krylov subspace generated by solving the linearized forward and adjoint Navier-Stokes (N-S) equations. The linearized adjoint N-S equations with the specific boundary conditions for the channel are derived, and a new convergence criterion is proposed. The algorithm is then applied to a one-dimensional base flow (the plane Poiseuille flow) and a two-dimensional base flow (the plane Poiseuille flow with a low-speed streak) in a channel. For one-dimensional cases, the effects of the spanwise width of the channel and the Reynolds number on the transient growth of perturbations are studied. For two-dimensional cases, the effect of strength of initial low-speed streak is discussed. The presence of the streak in the plane Poiseuille flow leads to a larger and quicker growth of the perturbations than that in the one-dimensional case. For both cases, the results show that an optimal flow field leading to the largest growth of perturbations is characterized by high- and low-speed streaks and the corresponding streamwise vortical structures. The lift-up mechanism that induces the transient growth of perturbations is discussed. The performance of the re-orthogonalization Arnoldi technique in the algorithm for both one- and two-dimensional base flows is demonstrated, and the algorithm is validated by comparing the results with those obtained from the OSS equations method and the crosscheck method.

Key words: transient growth, nonlocal field theory, localization residuals, constitutive equations, stress boundary conditions, Poiseuille flow, Krylov subspace, Arnoldi method, adjoint equation

2010 MSC Number: 

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