ADVANCE IN OVERSET GRID SCHEMES - FROM CHIMERA TO DRAGON GRIDS

A new approach that uses nonstructured mesh to replace the arbitrarily overlapped structured regions of embedded grids is presented. The pre sent methodology uses the Chimera overlapped structured grids that are independently generated and body fitted, yielding a high-quality grid readily accessible for efficient solution schemes. A hybrid grid sche me is then proposed that maximizes the advantages of the Chimera schem e and adapts the strengths of the unstructured grid while at the same time keeps its weaknesses minimal. This new adaptation to the Chimera thinking is the direct replacement of arbitrary grid overlapping by no nstructured (DRAGON) grid, The nonstructured grid region sandwiched be tween the structured grids is limited in size, resulting in only a sma ll increase in memory and computational effort. The DRAGON grid method has three important advantages: 1) preserving strengths of the Chimer a grid, 2) eliminating difficulties sometimes encountered in the Chime ra scheme, and 3) making grid communication in a fully conservative an d consistent manner insofar as the governing equations are concerned. Numerical results on representative two-dimensional steady and unstead y inviscid flows are demonstrated.