ON THE USE OF ADAPTIVE HIERARCHICAL MESHES FOR NUMERICAL-SIMULATION OF SEPARATED FLOWS

This paper describes the use of adaptive hierarchical grids to predict incompressible separated flow at low Reynolds number. The grids consi st of a quadtree system of hierarchical Cartesian meshes which are gen erated by recursive subdivision about seeding points. The governing eq uations are discretized in collocated primitive variable form using fi nite volumes and solved using a pressure correction scheme. The mesh i s locally adapted at each time step, with panel division or removal de pendent on the vorticity magnitude. The resulting grids have fine loca l resolution and are economical in array size. Results are presented f or unidirectional, impulsively started flow past a circular and a squa re cylinder at various Reynolds numbers up to 5000 and 250 respectivel y. It is clear that hierarchical meshes may offer gains in efficiency when applied to complex flow domains or strongly sheared flows. Howeve r, as expected, the stepped approximation to curved boundaries resulti ng from the Cartesian quadtree representation adversely affects the ac curacy of the results for flow past a circular cylinder. (C) 1998 John Wiley & Sons, Ltd.