均匀各向同性大气湍流对声爆传播特性的影响

基于离散Fourier模态有限和生成的随机大气湍流场,采用修正波形参数方法,开展了均匀各向同性大气湍流对典型超声速客机声爆传播特性的影响分析。计算采用的超声速客机模型为自行生成的简化超声速公务机模型。首先,应用航空工业空气动力研究院自主研制的CFD软件ARI_Overset在三维空间求解Navier-Stokes方程,得到作为声爆远场传播初始值的近场空间压力分布;其次,基于Von Karman能量谱,采用离散Fourier模态有限和形式生成随机均匀各向同性大气湍流场;最后,采用修正波形参数方法模拟了声爆信号在随机速度湍流场中的传播过程。数值结果表明：各向同性大气湍流对于地面声爆特征有重要影响。与无湍流状态相比,均匀各向同性大气湍流使得地面声爆特征增强的概率约为55%,使得地面声爆特征减弱的概率约为45%,故总体而言大气湍流效应更倾向于增强地面声爆特征;均匀各向同性大气湍流对于声爆传播路径影响相对较小,但是这一变化仍会导致地面信号接收点的不确定性。

Homogeneous isotropic atmospheric turbulence effects on sonic boom propagation

Based on the finite sum of discrete Fourier modes and the modified waveform parameter method, the effect of homogeneous isotropic atmospheric turbulence on sonic boom propagation is studied. The model used during CFD simulation is a self-generated simplified supersonic business aircraft. First, the flow field is obtained by solving the three dimensional Navier-Stokes equations using ARI_Overset in-house CFD solver developed by AVIC Aerodynamics Research Institute, and the near-field pressure is then extracted from the CFD results. Second, based on the Von Karman energy spectrum, a random velocity field of homogeneous isotropic atmospheric turbulence is calculated from the finite sum of discrete Fourier modes. Finally, the sonic boom signature on the ground is calculated by the modified waveform parameter method. The results indicated that the atmospheric turbulence has a marked influence on sonic boom overpressure during its propagation to the ground. The sonic boom increased in 55% of the cases and decreased in 45% of the cases. Compared to the no-turbulence condition, the turbulence seems to favor an increase rather than a decrease in boom overpressure. Although the turbulence has a small effect on the propagation path from the flight altitude to the ground, it may result in a variability of the point where the sonic boom reaches on the ground.