Research On Characteristics Of Wake Internal Wave And Sound Field Of Underwater Moving Objects

Affected by light,ocean currents,tides and vortices,the density and thermocline are widely distributed in the ocean.The abundant and diverse densities in the ocean provide indispensable conditions for the generation of internal waves.When the underwater vehicle moves in densely layered seawater,it will produce continuous internal waves in the area behind its tail.With the perturbation and evolution of the internal wave field,it will change the motion state of the flow field behind the underwater vehicle,reshape the local density and thermocline,and then affect the propagation of sound waves in seawater.First,the paper studies the feasibility and reliability of the finite element method in the calculation of the density stratified fluid and the vector sound field propagation characteristics.The sound field propagation of the continuous density stratified flow and the shallow sea Pekeris waveguide model on the elastic seabed are respectively studied.The comparison and analysis of simulation and calculation results with existing experimental results show that the finite element method is effective in the calculation of high Froude number fluid and the calculation of sound field propagation of low-frequency signals in shallow seas.The verification results are the following mixed layered form Density stratified flow calculation and acoustic signal propagation research on horizontal elastic seabed provide theoretical basis and reference.Second,the paper refers to the China Sea Cline data of the Marine Meteorological and Hydrological Center,and uses the shallow cline of the South China Sea as the research background to construct a mixed-layered density-layered flow model close to the actual marine environment.The real-scale model of the underwater vehicle in the shape of the body is used as the research object to study the density of the surrounding fluid in the rear area of the underwater vehicle under different navigation speeds,different density gradients,and different positions relative to the density jumper.The vertical distribution characteristics of the far-field temperature under the disturbance of the wave field in the wake.Finally,based on the vertical distribution of temperature in the far field of the underwater vehicle,the paper constructs a sound signal propagation model of the horizontal elastic seabed in the shallow sea range,and converts the vertical distribution of temperature into a sound velocity gradient according to the empirical formula of sound velocity in seawater.Change,by changing the emission frequency and depth position of the sound source to study the influence of the wave field in the wake of an underwater vehicle on the propagation of acoustic signals,including sound pressure propagation loss,seabed propagation loss curve,sound energy flow intensity,sound energy flow.The deflection angle and the sound intensity level curve of the seabed and the time when the sound signal reaches the receiver.The research results show that the speed of the underwater vehicle has a great influence on the disturbance of the wave field in the wake.The reshaping degree of the vertical temperature distribution in the far field will increase with the increase of the speed,and the influence of the density gradient is relatively.As the sailing speed is slightly weaker,the effect of sailing depth is not obvious.The increase of navigation speed will cause the difference of propagation loss at a certain distance,the increase of sound source frequency will cause the change of sound energy flow intensity and deflection angle,different sound source frequency will affect the wave field of wake at different navigation speed and its corresponding.There is a difference in the perception ability of the sound vector field.