逆向傅里叶衍射定理快速预报水下目标三维声散射指向分布

提出逆向运用傅里叶衍射定理预报水下弱散射目标三维声散射指向分布的快速计算方法。依据目标形状、周围介质的密度和声速构建三维声场图像模型,建立散射远场积分结果与图像频域幅值的关系式,提取频域中半径为水中波数k;的球型表面上的幅值,获得精细化的宽带、全方位散射声压指向特性。数值计算表明:将傅里叶衍射定理逆向运用于解决声学正问题,适用于分层的、不均匀的、非规则及多体弱散射目标散射声场的求解。通过插值提取频域样本获得远场声压的方法,避免了有限元法(3D-FEM)所必须的大规模的网格划分和迭代运算,可以有效地减少计算成本并拓展散射频率响应的带宽。在水池中完成两种具有不同声学参数和形状目标指向性测试实验,得到散射声压指向性幅度函数与理论预报相一致。 

Fast prediction of 3D acoustic scattering directional distribution of underwater target based on fourier diffraction theorem

An efficient method for predicting the acoustic scattering of weakly scattering targets using the Fourier diffraction theorem in reverse is proposed.According to the target shape,the density and sound velocity of the surrounding medium,a three-dimensional image of sound field is constructed,and the relationship between the scattered far field and the image frequency domain samples is established.The directional distribution of scattering field in refined broadband is obtained by taking samples on a spherical surface whose radius is k;in the frequency domain.The numerical results show that Fourier's diffraction theorem is used to solve the acoustic forward problem,which is suitable for solving the scattering sound field of layered,non-uniform and arbitrary shape fluid objects.The far-field sound pressure is obtained by sampling in frequency domain by interpolation method,which avoids the large-scale meshing and iterative computation necessary by 3D-FEM,and can effectively reduce the computational cost and expand the bandwidth of scattering frequency response.The experiment is completed in the water tank of two targets with different acoustic parameters and shapes,the results show that the amplitude function of the directivity of scattered sound pressure was consistent with the theoretical prediction.