Compressibility effects on the vortical flow over a 65° sweep delta wing

Abstract

The aim of this study is to investigate numerically the compressibility effects on the vortical flow developing over the VFE-2 delta wing. This wing is equipped with a sharp leading-edge and a sweep angle equal to 65°. The angle of attack is set equal to 25.5°, and two different freestream Mach numbers are considered: M∞=0.4 and M∞=0.8. The simulations are based on a turbulent modeling coupling Delayed Detached Eddy Simulation and Zonal Detached Eddy Simulation approaches, allowing a faster decay of the eddy-viscosity in Large Eddy Simulation regions. Such a method allows a good agreement with available experimental data. These computations highlight a modification of the flow behavior with an increase in the freestream Mach number. Indeed, the leading-edge vortex moves toward the wing and its core is dilated. Moreover, it is demonstrated in this study that the leading-edge vortex interacts with shock wave at midchord. This interaction induces a decay of the Rossby number in the leading-edge region and then an earlier breakdown in the transonic regime than in the subsonic one. Furthermore, several cross-flow shock waves deeply alter the aerodynamic field, in particular, a shock wave sitting beneath the leading-edge vortex. It is shown that this cross-flow shock wave moves in the lateral direction and that the frequency of this shock unsteadiness corresponds to the one classically encountered in shock-induced separation problems. As a result, the probability density function of the lateral location of the vortex core is altered in comparison with the subsonic case.