Deforming Grid Technique Applied to Unsteady Viscous Flow Simulation by a Fully Implicit Solver

Introduction T HE unsteady flows associated with moving boundaries have long been of interest to aerodynamic research. For most unsteady problems, the computational grid has to conform to the instantaneous shape of a moving body. Thereby, grid regeneration, or movement techniques, becomes an important issue. Rotating the grid system rigidly can easily treat rigid-body motions, but this approach is inapplicable if the body deforms, if the block boundaries have to be fixed for a multiblock grid system, or if the relative motion of a multicomponent configuration is to be considered. A simple way is to regenerate a grid at each physical time step. Obviously, this process will be very time consuming. It is a much more relatively difficult task when a three-dimensional problem must to be taken into account. An efficient grid-movement technique seems to be crucial for such problems, by which the grid system will be only deformed once per time step rather than regenerated completely in unsteady flow simulations.1 The present work attempts to develop an unsteady viscous flow simulating method for moving boundary problems with deforming grids in a multiblock grid system. The grid movement is mainly based on a transfinite interpolation (TFI) algorithm. The TFI tech-