Target Scattering Sound Field Simulation And Calculation Of Scatterer Size

Sound waves have unique advantage in the underwater observation and measurement.The main theory which used to carry out the underwater target survey and identification is the scattering principle of sound waves.When underwater acoustic waves encounter obstacles which will occur reflection,scattering and other phenomena,then the sound field will be changed accordingly.It is possible to infer the properties and size of the obstacle by receiving the scattered sound waves.Therefore,the study of acoustic scattering plays an important role in underwater target detection.This paper studies the rules of scattered sound field distribution of the sphere and ellipsoid.Numerical simulation is used by using finite element method,and the size of scatters is approximately calculated.The main work and related contents are as follows:(1)Firstly,the expression of the scattering field of the rigid sphere and the elastic sphere is derived by using the classical acoustic scattering theory.It is found that there is a direct relationship between the sound pressure and the radius of the sphere.Then,the finite element method was used to establish the underwater two-dimensional sphere scattering model,and to simulated the sound field distribution of plane wave incident on different materials(Aluminum,steel,glycerin and air)and the data of sound pressure and sound pressure level are extracted and compared analysis.Then calculate the radius of scattering sphere.and the sound field distribution of the aluminum sphere and the air ball with different radius is simulated.The value of the scattering sound pressure can be obtained by extracting the sound pressure distribution data on the X axis.Combined with the relationship between the scattered sound pressure and the radius,the radius of the scattered sphere can be calculated.And compared with the true given radius,the results obtained when the radius is small consistent.(2)Since the scatterer in real life cannot be absolutely spherical,the ellipsoid is closer to the shape of the scatterer.Then,based on the Helmholtz equation used the physical acoustics method to deduce the integral expression of the sound field potential function of the rigid ellipsoid.Using this formula,calculated the sound field distribution of rigid sphere which as validation.Then,the direction of the scattering field of the vertical ellipsoid is analyzed by numerical method.Compared with the rigid sphere,it is shown that the scattering field of the ellipsoid is similar to that of the sphere.And the amplitude of the sound pressure will be lower than the sphere.(3)The finite element method is used to simulate the rigid ellipsoid.The two-dimensional ellipsoidal scattering model is established to simulate the vertical distribution of the plane wave under the vertical long axis,and keep the short axis unchanged and change the length of the long axis.The data of the extracted sound pressure and sound pressure level are compared with those of the sphere.And the value of the scattered sound pressure is expressed,and the size of the scattered ellipsoid is calculated.At the end of the paper,the whole topic is summarized and forecasted.