Study on the Effects of a Wing Dihedral for the Reduction of Sonic Boom Intensity

Abstract

The effects of a wing dihedral on sonic boom reduction are systematically studied for a realistic supersonic transport. The LM1021, which was designed in detail by Lockheed Martin Corporation (U.S.A.), is used as the baseline analysis model. The aerodynamic coefficients and near-field pressure signatures are obtained using CFD for inviscid flows, and then the sonic boom intensity on the ground is calculated with the pressure wave propagation analysis by solving the augmented Burger's equation. The ‘Xnoise’ code developed by JAXA is used for the wave propagation analysis. The results clearly show a reduction in the sonic boom intensity not only on the undertrack, but also on the off-track. One representative result is that the pressure peak of the tail boom at the flight Mach number of 1.6 is reduced more than 15% by a 10-deg dihedral compared to a 0-deg dihedral at the cost of a 2% increase in drag. Variations of the lateral/directional static stability are also studied, and the results show improved lateral stability while there are mild directional instabilities caused by the dihedral.