Computational Prediction of Roll Damping for the F/A-18E at Transonic Speeds

Abstract

Computational fluid dynamics was used to predict the roll -damping characteristics for the F/A -18E Super Hornet at transonic sp eeds . The calcu lations were made for Mach 0.8 at both wind tunnel and flight conditions . Three different wing configurations were analyzed during this study. For the first two configurations, the F/A -18E Super Hornet was modeled with the pre -production wing. The first of these configurations had flap settings of 6° leading -edge flaps, 8° trailing -edge flaps and 4° aileron , while the second configuration had flap settings of 10° leading -edge flaps, 10° trailing -edge flaps and 5° aileron. The third confi guration analyzed was that of the F/A -18E with the wing developed from the Transonic Flying Qualities Improvement Program . This wing includes a sawtooth leading edge and a chordwise fence on the wing box. The sawtooth geometry eliminated the snag that exi sted on the leading edge of the pre -production wing. The flow solver used during this project was USM3D , which was developed at NASA Langley Research Center. In preparation for this study, USM3D was modified to simulate a constant -rate rolling moti on of the grid so that the roll -damping characteristics of the aircraft could be determined. With this modification to USM3D, the roll -damping characteristics at each condition could be determined at the expense of a steady -state CFD calculation . This approach to determining roll damping is much simpler and faster than the traditional approach, which required a time -accurate calculation on a moving grid. The results of this study indicate that computational fluid dynamics can be a useful analysis tool for scre ening a configuration for potential loss of roll damping and the associated deterioration of lateral handling qualities .