Research Of Acoustic Scattering Characteristics Of Underwater Moving Sphere

At present,sound is the most frequently used medium in underwater communication and object detection.However,there exist many obstacles underwater.As a result,it is of great significance to study the sound scattering characteristics of objects,especially those moving ones.This paper presents a novel sound scattering model of moving sphere based on the flow-sound splitting method,which can provide a guide to sound scattering calculation of underwater moving objects..Firstly,based on the spherical harmonic expansion method,the external sound scattering field of a rigid sphere and a bubble under the incident of the plane wave are deduced respectively.In addition,the inside sound field of the bubble is also deduced.After that,a code based on C++ is proposed.Its accuracy is validated by comparing with VirtualLab,which is based on Boundary Element Method.Subsequently,an error analysis of the program is performed.It shows that one can get a more accurate result by truncating more series in a certain range.In addition,more items are needed to get a good result if the sound wave number is relatively large.Then,the characteristics of the external sound scattering field of the rigid ball and the bubble and sound field inside the bubble are analyzed in detail.Then,the sound scattering model of moving sphere is proposed.The sound scattering field at any time can get after the trajectory of the scatterer gotten from theoretical formula and SPH based on fluid-solid coupling.The sound fields of a bubble in a centrifugal motion,a rigid sphere subsides freely and a bubble floating in water under the incident of plane waves are analyzed in detail.The results show that the far field directivity of these three moving spheres is different from that of immobile one.The scattering energy is concentrated on the front side of the sound source no matter how large the relative frequency is.While for the case of immovable sphere,the scattering energy is concentrated on the front side when the relative frequency is low and on the other side when the relative frequency is large.Finally,a GPU acceleration technique based on CUDA(Compute Unified Device Architecture)is adopted.Since it is time-consuming in obtaining a fine sound field,this method can greatly accelerate the speed of calculation.Its accuracy is validated and various factors including the number of truncated items and computing platforms are discussed.The results show that GPU acceleration technique can achieve a speedup of nearly 200 times under certain conditions,which can greatly shorten the calculation time.It can serve as a reference to the engineering application of actual undersea sound scattering calculation.