The Effect On Underwater Acoustic Environment Of A Stratified Fluid When A Submerged Body Presented

Acoustic method is one of the most effective means known for underwater submerged body detection. However, the sound wave propagation in the ocean when influenced by many environmental factors such as water temperature, density, velocity stratification, where the affection of the distribution of seawater temperature on the propagation velocity of acoustic waves is most significant. Since the underwater acoustic propagation environment is changed by the flow around the submerged body and vortex shedding phenomena when the submerged body presented, it results in abnormal received signal. However, this change of the underwater acoustic environment can be used to predict underwater submerged body, which provides a new way for underwater target detection. Therefore, the research on that the effect on underwater acoustic environment of a stratified fluid when submerged body presented is necessary. In view of this, in the paper, by the use of computational fluid dynamics software,simulations were carried out on the underwater acoustic environment of a stratified fluid when submerged body presented.CFD is an important law of fluid motion in a stratified fluid. Therefore, in this paper, its basic theories were firstly introduced, and its discrete manner of control equations and turbulence model were discussed. And further, the stability conditions in a stratified fluid motion were derived. Secondly, based on the stability criterion of layered interface, a simulation study of the two layers of fluid when no submerged body under various conditions was carried out, obtained the temperature contours of the fluid and velocity vectors at different temperatures, density, velocity gradient.Again, a finite element model of two layer of fluid when submerged body presented was established and studied, obtained the pattern of the variation of temperature distribution and the change of hierarchical interface under different conditions.Then, the paper analyzed the effect on the fluid movement and the appearance of interface waves that caused by the flow around the submerged body and vortex shedding phenomena at different temperatures,density and velocity gradient. And by comparing the situation of no submerged body, the paper illustrated the influence of submerged body in the two layer of fluid on the underwater acoustic environment.Finally, a simulation study was carried out on the fluid movement when a submerged body in continuously stratified fluid. And a finite element model of standard SUBOFF was established. By analyzing of the simulation results, obtained the temperature contours when a submerged body moving in the ocean under typical operating conditions. Further, analyzed the moving pattern of fluid particles.