Capacitance matrix technique for avoiding spurious eigenmodes in the solution of hydrodynamic stability problems by Chebyshev collocation method

J. Hagan, Janis Priede

    Research output: Contribution to journalArticle

    8 Citations (Scopus)

    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 Orr-Sommerfeld equation for plane Poiseuille flow. Following the standard approach, the original fourth-order differential equation is factorised into two second-order equations using a vorticity-type 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.
    Original languageEnglish
    Pages (from-to)210-216
    JournalJournal of Computational Physics
    Volume238
    DOIs
    Publication statusPublished - 2013

    Bibliographical note

    The full text of this item is available free from the link given. The published version can be found at: http://dx.doi.org/10.1016/j.jcp.2012.12.012 .

    Keywords

    • Chebyshev collocation method
    • hydrodynamic stability
    • spurious eigenvalue

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