and/or face-centered values. Among the face averages to be computed arethose of the coord<strong>in</strong>ate mapp<strong>in</strong>g metric factors, whose calculation affects notonly the overall accuracy of the scheme but also freestream preservation. Thelatter is automatically achieved to mach<strong>in</strong>e roundoff by represent<strong>in</strong>g the metricfactors as exterior derivatives, whose face averages are <strong>in</strong> turn reduced toquadratures on face hyperedges. The quadratures can be performed by anyconvenient method of sufficient accuracy.To demonstrate the approach, we developed fourth-order discretizations ofprototypical elliptic and hyperbolic problems. In addition to test<strong>in</strong>g fourthorderaccuracy, the elliptic example displayed the use of an operator based ona second-order f<strong>in</strong>ite-volume discretization as a preconditioner <strong>in</strong> a conjugategradient iteration. Such strategies can be important <strong>in</strong> reduc<strong>in</strong>g the solver costof the larger stencils that <strong>in</strong>evitably accompany high-order discretizations. Inthe hyperbolic examples, we <strong>in</strong>cluded an improved nonl<strong>in</strong>ear limiter [8]. Ourresults <strong>in</strong>dicate that the limited method can achieve a fourth-order convergencerate for smooth data on mapped grids and can control oscillations fordiscont<strong>in</strong>uous data on mapped grids.Although we focused on fourth-order, f<strong>in</strong>ite-volume discretizations <strong>in</strong> this paper,higher-order discretizations are obta<strong>in</strong>able by a similar strategy. The essential<strong>in</strong>gredients are a generalization of the cell face average product formula(17), more accurate quadrature formulas for the <strong>in</strong>tegrals of metric factors overface hyperedges <strong>in</strong> (11), and a discretization of flux face averages to the desiredorder of accuracy. Further extensions <strong>in</strong>clude mov<strong>in</strong>g mapped grids, as well asgeneralization from doma<strong>in</strong>s describable by a smooth mapp<strong>in</strong>g from a s<strong>in</strong>gleCartesian computational grid to more complicated multiblock geometries.References[1] M. V<strong>in</strong>okur, An analysis of f<strong>in</strong>ite-difference and f<strong>in</strong>ite-volume formulations ofconservation laws, J. Comput. Phys. 81 (1989) 1–52.[2] D. Calhoun, R. J. LeVeque, An accuracy study of mesh ref<strong>in</strong>ement onmapped grids, <strong>in</strong>: T. Plewa (Ed.), Adaptive Mesh Ref<strong>in</strong>ement - TheoryAnd Applications: Proceed<strong>in</strong>gs of The Chicago Workshop On Adaptive MeshRef<strong>in</strong>ement <strong>Methods</strong>, Vol. 41 of Lecture Notes <strong>in</strong> Computational Science andEng<strong>in</strong>eer<strong>in</strong>g, Spr<strong>in</strong>ger Verlag, 2003, pp. 91–102.[3] D. A. Calhoun, C. Helzel, R. J. Leveque, Logically rectangular grids and f<strong>in</strong>itevolume methods for PDEs <strong>in</strong> circular and spherical doma<strong>in</strong>s, SIAM Rev. 50 (4)(2008) 723–752.[4] M. Barad, P. Colella, A fourth-order accurate local ref<strong>in</strong>ement method forPoisson’s equation, J. Comput. Phys. 209 (2005) 1–18.34
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