基于增广Burgers方程的音爆远场计算及应用

Accurate simulation of sonic boom is of great importance for the study of low-boom design. It is hard to conduct direct full-field simulation of sonic boom at the cruising altitude of supersonic aircraft due to limitation of computing capacity. Current methods for sonic boom prediction usually have two steps. Firstly, the near field over-pressure is obtained according to the supersonic linearized theory or computational fluid dynamics. Then the near field signal is advanced to the far field using acoustic methods to get the ground pressure signature of aircraft. During the calculation of the far field, the traditional waveform parameter method does not take into consideration the loss of sound energy resulting from classical attenuation or molecular relaxation effect in propagation, so that the final shock waves obtained do not have thickness, making the far field sound pressure level inaccurate. This paper, based on the splitting method, investigates the numerical methods of the augmented Burgers equation in nonlinear acoustics. Two standard numerical examples published in the SBPW-2 are calculated, verifying that the method proposed can accurately predict the ground signature. It can be found that adding a zero-amplitude buffer signal to the near field signal is very effective to improve the simulation accuracy in the rising of 'N' wave. A study of mesh convergence demonstrates that it is useful to refine the grid density properly. A study of atmospheric sound absorption finds that the effect of relaxation effect is stronger than classical attenuation. Dry and cold atmosphere is found to have adverse effect on over-pressure of sonic boom signal based on an analysis of influence of humidity and temperature on ground pressure signature.