A computational capability has been developed for predicting the flow field about the entire projectile, including the recirculatory base flow, at transonic speeds. Additionally, the computer code allows mass injection at the projectile base and hence is used to show the effects of base bleed on base drag. Computations have been made for a secant-ogive-cylinder projectile for a series of Mach numbers in the transonic flow regime. Computed results show the qualitative and quantitative nature of base flow with and without base bleed. The reduction in base drag with base bleed is clearly predicted for various mass injection rates and for Mach numbers .9

A three-dimensional chimera grid-embedding technique is described. The technique simplifies the construction of computational grids about complex geometries. The method subdivides the physical domain into regions which can accommodate easily generated grids. Communication among the grids is accomplished by interpolation of the dependent variables at grid boundaries. The procedures for constructing the composite mesh and the associated data structures are described. The method is demonstrated by solution of the Euler equations for transonic flow about three ellipsoid bodies in close proximity, a wing/body, and a wing/body/tail. Keywords: Grid-embedding techniques, Computational fluid dynamics, Computer programs, Chimera-grid solution, Finite-difference techniques, Transonic flow, Domain-decomposition techniques, Grid-adapting methods.