A modified tau spectral method that eliminates spurious eigenvalues. (English) Zbl 0661.65084

The tau spectral method proposed by C. Lanczos [Applied Analysis (1956; Zbl 0074.105)] for solving eigenvalue problems in ordinary differential equations is modified so that spurious eigenvalues are eliminated. It uses a truncated series expansion of Chebyshev polynomials in a set of complete functions as an approximation for the solution of the differential equation.
The modification involves an appropriate factorization of the differential operator which removes the numerical instability. The modified tau method for a general fourth-order eigenvalue problem, for a system of fourth-order equations, and for the Orr-Sommerfeld stability equation for plane Poiseuille flow is discussed and compared with the ordinary tau method. The modified method converges at least as rapidly as the usual method. The use of the tau coefficients as identifiers of spurious eigenvalues and indicators of convergence is shown.
Reviewer: V.Burjan


65L15 Numerical solution of eigenvalue problems involving ordinary differential equations
34L99 Ordinary differential operators


Zbl 0074.105
Full Text: DOI


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