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Test functions for three-dimensional control-volume mixed finite-element methods on irregular grids

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, , and
Edited by:
Bentley L.R., Sykes J.F., Brebbia C.A., Gray W.G., and Pinder G.F.

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Abstract

Numerical methods based on unstructured grids, with irregular cells, usually require discrete shape functions to approximate the distribution of quantities across cells. For control-volume mixed finite-element methods, vector shape functions are used to approximate the distribution of velocities across cells and vector test functions are used to minimize the error associated with the numerical approximation scheme. For a logically cubic mesh, the lowest-order shape functions are chosen in a natural way to conserve intercell fluxes that vary linearly in logical space. Vector test functions, while somewhat restricted by the mapping into the logical reference cube, admit a wider class of possibilities. Ideally, an error minimization procedure to select the test function from an acceptable class of candidates would be the best procedure. Lacking such a procedure, we first investigate the effect of possible test functions on the pressure distribution over the control volume; specifically, we look for test functions that allow for the elimination of intermediate pressures on cell faces. From these results, we select three forms for the test function for use in a control-volume mixed method code and subject them to an error analysis for different forms of grid irregularity; errors are reported in terms of the discrete L2 norm of the velocity error. Of these three forms, one appears to produce optimal results for most forms of grid irregularity.

Additional Publication Details

Publication type:
Conference Paper
Publication Subtype:
Conference Paper
Title:
Test functions for three-dimensional control-volume mixed finite-element methods on irregular grids
ISBN:
9058091252
Year Published:
2000
Language:
English
Publisher location:
A.A.Balkema
Larger Work Title:
Computational methods in water resources - Volume 2 - Computational methods,surface water systems and hydrology
First page:
677
Last page:
684
Number of Pages:
8
Conference Title:
Computational Methods in Water Resources
Conference Location:
Calgary
Conference Date:
25 June 2000 through 29 June 2000