Capacitance matrix technique for avoiding spurious eigenmodes in the solution of hydrodynamic stability problems by Chebyshev collocation method
Abstract
We present a simple technique for avoiding physically spurious eigenmodes that often occur in the solution of hydrodynamic stability problems by the Chebyshev collocation method. The method is demonstrated on the solution of the OrrSommerfeld equation for plane Poiseuille flow. Following the standard approach, the original fourthorder differential equation is factorised into two secondorder equations using a vorticitytype auxiliary variable with unknown boundary values which are then eliminated by a capacitance matrix approach. However the elimination is constrained by the conservation of the structure of matrix eigenvalue problem, it can be done in two basically different ways. A straightforward application of the method results in a couple of physically spurious eigenvalues which are either huge or close to zero depending on the way the vorticity boundary conditions are eliminated. The zero eigenvalues can be shifted to any prescribed value and thus removed by a slight modification of the second approach.
 Publication:

Journal of Computational Physics
 Pub Date:
 April 2013
 DOI:
 10.1016/j.jcp.2012.12.012
 arXiv:
 arXiv:1207.0388
 Bibcode:
 2013JCoPh.238..210H
 Keywords:

 Physics  Computational Physics;
 Physics  Fluid Dynamics
 EPrint:
 10 pages, 1 figure, minor revision, to appear in J. Comp. Phys