# Optimally blended spectral-finite element scheme for wave propagation and nonstandard reduced integration

M. Ainsworth, Hafiz Abdul Wajid

Research output: Contribution to journalArticle

43 Citations (Scopus)

### Abstract

We study the dispersion and dissipation of the numerical scheme obtained by taking a weighted averaging of the consistent (finite element) mass matrix and lumped (spectral element) mass matrix for the small wave number limit. We find and prove that for the optimum blending the resulting scheme (a) provides $2p+4$ order accuracy for $p$th order method (two orders more accurate compared with finite and spectral element schemes); (b) has an absolute accuracy which is $\mathcal{O}(p^{-3})$ and $\mathcal{O}(p^{-2})$ times better than that of the pure finite and spectral element schemes, respectively; (c) tends to exhibit phase lag. Moreover, we show that the optimally blended scheme can be efficiently implemented merely by replacing the usual Gaussian quadrature rule used to assemble the mass and stiffness matrices by novel nonstandard quadrature rules which are also derived.
Original language English 346-371 26 SIAM Journal on Numerical Analysis 48 1 https://doi.org/10.1137/090754017 Published - 16 Apr 2010

### Fingerprint

Reduced Integration
Spectral Elements
Wave propagation
Wave Propagation
Finite Element
Stiffness matrix
Phase-lag
Stiffness Matrix
Numerical Scheme
Averaging
Dissipation
Tend

### Keywords

• numerical dispersion
• numerical dissipation
• high order numerical wave propagation

### Cite this

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abstract = "We study the dispersion and dissipation of the numerical scheme obtained by taking a weighted averaging of the consistent (finite element) mass matrix and lumped (spectral element) mass matrix for the small wave number limit. We find and prove that for the optimum blending the resulting scheme (a) provides $2p+4$ order accuracy for $p$th order method (two orders more accurate compared with finite and spectral element schemes); (b) has an absolute accuracy which is $\mathcal{O}(p^{-3})$ and $\mathcal{O}(p^{-2})$ times better than that of the pure finite and spectral element schemes, respectively; (c) tends to exhibit phase lag. Moreover, we show that the optimally blended scheme can be efficiently implemented merely by replacing the usual Gaussian quadrature rule used to assemble the mass and stiffness matrices by novel nonstandard quadrature rules which are also derived.",
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Optimally blended spectral-finite element scheme for wave propagation and nonstandard reduced integration. / Ainsworth, M.; Wajid, Hafiz Abdul.

In: SIAM Journal on Numerical Analysis, Vol. 48, No. 1, 16.04.2010, p. 346-371.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Optimally blended spectral-finite element scheme for wave propagation and nonstandard reduced integration

AU - Ainsworth, M.

AU - Wajid, Hafiz Abdul

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N2 - We study the dispersion and dissipation of the numerical scheme obtained by taking a weighted averaging of the consistent (finite element) mass matrix and lumped (spectral element) mass matrix for the small wave number limit. We find and prove that for the optimum blending the resulting scheme (a) provides $2p+4$ order accuracy for $p$th order method (two orders more accurate compared with finite and spectral element schemes); (b) has an absolute accuracy which is $\mathcal{O}(p^{-3})$ and $\mathcal{O}(p^{-2})$ times better than that of the pure finite and spectral element schemes, respectively; (c) tends to exhibit phase lag. Moreover, we show that the optimally blended scheme can be efficiently implemented merely by replacing the usual Gaussian quadrature rule used to assemble the mass and stiffness matrices by novel nonstandard quadrature rules which are also derived.

AB - We study the dispersion and dissipation of the numerical scheme obtained by taking a weighted averaging of the consistent (finite element) mass matrix and lumped (spectral element) mass matrix for the small wave number limit. We find and prove that for the optimum blending the resulting scheme (a) provides $2p+4$ order accuracy for $p$th order method (two orders more accurate compared with finite and spectral element schemes); (b) has an absolute accuracy which is $\mathcal{O}(p^{-3})$ and $\mathcal{O}(p^{-2})$ times better than that of the pure finite and spectral element schemes, respectively; (c) tends to exhibit phase lag. Moreover, we show that the optimally blended scheme can be efficiently implemented merely by replacing the usual Gaussian quadrature rule used to assemble the mass and stiffness matrices by novel nonstandard quadrature rules which are also derived.

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