ANALYSIS AND DESIGN OF NUMERICAL SCHEMES FOR GAS-DYNAMICS .1. ARTIFICIAL DIFFUSION, UPWIND BIASING, LIMITERS AND THEIR EFFECT ON ACCURACY AND MULTIGRID CONVERGENCE

The theory of non-oscillatory scalar schemes is developed in this paper in terms of the local extremum diminishing (LED) principle that maxima should not increase and minima should not decrease. This principle can be used for multi-dimensional problems on both structured and unstructured meshes, while it is equivalent to the total variation diminishing (TVD) principle for one-dimensional problems. A new formulation of symmetric limited positive (SLIP) schemes is presented, which can be generalized to produce schemes with arbitrary high order of accuracy in regions where the solution contains no extrema, and which can also be implemented on multi-dimensional unstructured meshes. Systems of equations lead to waves travelling with distinct speeds and possibly in opposite directions. Alternative treatments using characteristic splitting and scalar diffusive duxes are examined, together with a modification of the scalar diffusion through the addition of pressure differences to the momentum equations to produce full upwinding in supersonic how. This convective upwind and split pressure (CUSP) scheme exhibits very rapid convergence in multigrid calculations of transonic Bow, and provides excellent shock resolution at very Mach numbers.