A Strategy to Reduce Numerical Oscillations by Aggressive Grid Stretching

Unphysical numerical oscillations arise in CFD calculations where~central difference schemes are~used~along with coarse grids. Often used remedies for such unphysical oscillations include filtering,~upwind schemes~and grid stretching/compression. While the former two approaches are known to be overly dissipative,~the latter can~many times be~expensive. In this work, we attempt to find~an optimal~mesh deployment. While~it is conventional acknowledged that~more grid points are to be used in regions where unphysical numerical oscillations are detected, our approach requires only one single refined grid in regions where drastic~acceleration/deceleration occurs, and numerical oscillations in the bulk region~are~suppressed without further mesh refinements there. The proposed grid stretching strategy is then tested in several flow~configurations, including two- and three-dimensional lid driven cavity, flow passing wall-mounted cubes, flow passing~two-/three-dimensional objects.~Two-grid-spacing~oscillations are found to be substantially suppressed in all cases. Possible use of this strategy may be in adaptive-mesh-refinement, where nowadays more grid points are immediately used~wherever the spatial gradients of, e.g., velocity~is large.