Finite difference computation of the aerodynamic interference of wing—pylon—store combinations at transonic speeds

Abstract

In this paper a computational method is described for calculating aerodynamic interference of a wing—pylon—store combination. This method is based on the mixed finite difference method presented first by Murman and Cole in 1971 [1]. The governing equation is a steady flow transonic small disturbance potential equation. It differs from that of [1] in that the transonic small disturbance potential equation is derived from the exact potential equations without the assumption of small disturbance in the x (longitudinal) direction. The flow field around the wing is described by Cartesian coordinates and around the store by cylindrical coordinates. The effect of the pylon is taken into account together with its vortex sheet. The boundary condition on the surface of the wing—pylon—store combination is satisfied. On the vortex sheets the Kutta condition is satisfied. The potential value in the far field is approximated by integrating the linearized potential equation. The program is written for the TQ-6 computer. It can calculate all the flow field requirements including the perturbation potential ϑ, the down wash speed ϑy, the side wash speed ϑz, the pressure distributions and the aerodynamic coefficients. Three examples of computation are presented in the paper. They indicate the convergence and level of agreement with wind tunnel test values.