Using CFD solutions as inputs of sonic boom propagation calculation

Abstract

Near-field signatures derived by equivalent area rule are traditionally used as inputs of sonic boom propagation calculation. However, CFD is more capable to present details of pressure perturbation distribution. Due to the local axisymmetric assumption in propagation calculation based on geometry acoustic theory and the asymmetry of rounding flow field, CFD solutions extracted on a cylindrical surface with radius of 1–2 times length of the projectile couldn’t be used as inputs directly. The multipole matching method proposed by Page and Plotkin was introduced to deal with this problem. At first, accuracy of CFD solutions was validated by two benchmarks, then the pressure perturbation extracted from the flow field around a 70 degrees–swept plate model was corrected before propagation calculation. Cylindrical radius and the order of expanding Fourier serials have been discussed. Ground sonic boom signatures showed that convergence was obtained with the correction.