The Numerical Simulation And Analysis Of Free-surface Wake Generated By Moving Submerged Target

Modern submarine which is called “hidden killer”,has strong concealment and also is a great attacker.How to detect it in time and effectively has become an important issue at home and abroad.Although sonar and other submerged target detection technology has been fully developed,new detection methods based on submarine thermal wake,wake turbulence and free-surface wake have also received great attention.The interaction of moving submerged target and fluid will generate specific wave patterns,such as the Kelvin wave and the Bernoulli dome.The information(depth or size,speed,etc.)can be obtained indirectly through the detection.Due to the reflection of the unbiased sky radiant light through the surface of the water,a partial polarized light is formed,and the amount of polarization is related to the refractive index and incidence angle of the medium.Therefore,the polarization information of wave can be obtained by the optical polarization imaging method to calculate the wave’s shape.For this reason,the laboratory put forward the idea of research on the theory and technology of submerged target polarization imaging detection based on the specific free-surface wake,and was supported by the National Natural Science Fund.The wakes of submerged target is the key to achieve target detection,therefore mastering the characteristics of submerged target’s wake is the foundation of detection method.In view of the lack of research on detection of moving submerged targets,the paper studies the free-surface wake and its characteristics from the aspects of theoretical modeling,computer simulation and experiment.First a mathematic model is established by using the 3-D unsteady incompressible Reynolds-averaged Navier-Stokes(RANS)equations,the renormalization group(RNG)k-εturbulence model and the volume-of-fluid(VOF)method.The model and calculation domain defined by Solidworks is introduced into ICEM-CFD to complete the division and quality evaluation of the grid,then we set the boundary conditions,numerical calculation method in FLUENT,simulate the wake on free-surface of the model in different depths,different velocities and with/without the attachment.The simulation’s result in CFD-POST of the wave patterns of the submerged target at different motion parameters reveals the relationship between the parameters and the wave pattern.Then,the surface wake of the real scale submarine model is simulated,and the magnitude of wave crest&wave trough and the possible depth of detection are given,which provides the idea for subsequent image processing.Finally,the sea surface wake is simulated by using the random wave spectrum(P-M spectrum)in the environment of Matlab,which lays the foundation for the superposition of ocean waves and wakes and the image denoising / detection.The experiments data and results lay a theoretical foundation for the simulation of surface wake of full-scale targets and the further research of moving submerged target detection technology.