Optimization of Drag Minimums Including Effects of Flow Separation

Abstract

Recent work on the supersonic freestream-centered propulsive jet interaction problem has shown that minimum total afterbody drag can be achieved during power on flight with less than a full (zero annular base) boattail. In contrast to optimum power-on configurations, minimum total afterbody pressure drag for power-off (coast) flight requires, in general, a full boattail. Flow separation of the freestream on the boattail is known to occur for a wide range of flight conditions during power-on operation. This flow separation is shown herein to reduce total afterbody drag for nearly full boattails to values which approach the corresponding values for optimized configurations without separation. Thus, the possibility of reconciling flight-profile drag minimums for both power-on and power-off conditions by using afterbody separation is suggested and shown to be a feasible design consideration.