Unsteady High-Angle-Of-Attack Flowfield Simulation Around the F-18 Aircraft

Abstract

This paper describes a numerical procedure for simulating the unsteady viscous flow around the F-18 aircraft at high angles of attack. A generalized overset zonal grid scheme is used to decompose the computational space around the complete aircraft, including deflected control surfaces. The grids around various components of the aircraft are created numerically using a three-dimensional hyperbolic grid generation procedure. The Reynolds-averaged Navier-Stokes equations are integrated using a time-accurate, implicit procedure. Turbulent flowfield results at 30 degrees angle of attack show the details of the flowfield structure, including the unsteadiness created by the vortex breakdown and the resulting fluctuating airloads exerted on the vertical tail. The computed results agree fairly well with flight data for surface pressure, surface flow pattern, vortex breakdown location, and tail load fluctuations frequency.