Numerical simulation of transonic flow over wing-mounted twin-engine transport aircraft

A numerical method has been developed for computing the flowfield around advanced transport aircraft with wing-mounted nacelles. The method is based on a multiblock point-matched grid-generation approach combined with zonal solving strategy for complex flowfield. In this study the flowfield is divided into a number of nonover-lapped blocks by a cutout technique. II-type grids are generated independently in each block using an elliptic grid-generation method, in which the control of the grid quality is accomplished by the forcing-function technique of Hilgenstock. The flowfield is simulated by solving the Euler equations. An explicit three-stage Runge-Kutta algorithm based on the Jameson's finite volume scheme for the Euler equations has been developed that is applied to the multiregion II-type grids. The present method has been applied to isolated powered engine nacelles and complex transport aircrafts consisting of low-wing/fuselage with wing-mounted pylon/nacelles. On the wing surfaces the viscous effects are simulated by the employment of the viscous/inviscid interaction (VII) technique of two-dimensional strip boundary layer. In this study the boundary-layer program uses an integral method to calculate turbulent boundary layers. With the concept of an equivalent inviscid flow, the model of blowing velocity is employed in the VII technique. The effect of the boundary layer on the outer inviscid flow is represented through a transpiration boundary condition derived from the boundary-layer parameters. The main benefit of this treatment is that the grid is generated only once in overall computing procedure. Computational results and comparisons with experimental data are presented. The good agreement indicates that the present method is effective in predicting the flows about powered engine nacelles and/or complex transport aircrafts.