Least squares and approximate equidistribution in multidimensions
โ Scribed by M. J. Baines
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 134 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0749-159X
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โฆ Synopsis
In this article it is shown that, under a natural condition, least squares minimization of the residual of the divergence of a vector field is equivalent to that of a least squares measure of equidistribution of the residual. More specifically, consider the conservation law div f = 0, when the vector field f is approximated by a conforming piecewise differentiable function F on a partition of a polygonal region โฆ into triangles. Then, we show that, if F has a prescribed flux across the outer boundary โโฆ of โฆ, minimization of the l 2 norm of the average residual of div F over all internal parameters of the partition (including nodal positions as well as solution amplitudes) is equivalent to minimization of the l2 norm of the differences in the average residuals of F, taken over all pairs of triangles of the partition. The result is of importance in the approximate solution of conservation laws, where alignment of the mesh is often of considerable benefit in deriving extra accuracy. The property is readily extended to systems of conservation laws. Moreover it holds for the average vorticity residual of F over a triangle as well as for l2-type norms combining both the divergence and the vorticity (as in the case of the Cauchy-Riemann equations).
๐ SIMILAR VOLUMES
Suinmary. Paired operators T = d , P + A 2 & on a HILBERT spzce are studied where P is a projector, P+Q = I , and the coefficients are linear invertible operators. The MOORE-PENXOSE inverse of T can be obtained explicitly from a factorization of the coefficients, which is equivalent to the normal so