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.