Evaluation of methods for predicting complex aircraft flowfields

Abstract

Reliable methods for predicting external aircraft flowfields are required for airframe/engine and aircraft/store integrations, as well as for predicting store trajectories. Several analytical techniques exist that can predict the flowfield about complete aircraft configurations. Three of these - the PAN AIR panel method, the Boppe transonic small disturbance code, and the influence function method (IFM) technique - are examined in this paper. All three methods have certain advantages and disadvantages. The PAN AIR method has the greatest geometric flexibility, but only gives consistently good results at subsonic speeds and lacks an integrated boundary layer calculation. The Boppe code gives a better prediction of wing-induced flowfield effects at all Mach numbers but cannot properly account for body-induced effects. The IFM method has the best ability to predict aircraft flowfield effects but requires store grid force and moment data in a horizontal traverse to make the flowfield predictions.