Numerical Study Of Effects On Internal Waves And Free Surface Flow Field Resulting From Submerged Body Moving In The Pycnocline

Due to the wide range of pycnocline in ocean, volume effect and turbulent wake effect of submerged body motion will excite internal wave. The internal waves involve wide range,long duration and it is not easy to be controlled by any method. Hence, the wide area dynamic monitoring are able to be realized without the impact of submerged body location by detecting the strength of convergence and divergence induced by internal wave combined with the characteristics of SAR imaging.This thesis studies the impact of submerged body motion on internal wave and surface wave in stratified flow based on CFD theory. Firstly, studies the relationship between steady motion of submerged body and induced internal wave. Controlling submerged body motion by programming; using dynamic layering to ensure the boundary layer will not be influenced during the motion of submerged body; Capturing the wave form of internal interface by solving the volume fraction of each fluids. For verification of internal wave calculation induced by submerged body motion by CFD method this thesis compared the calculation results to the experimental results. At different depth, the characteristics of variation in internal wave heights and lengths with densimetric Froude number are analyzed to obtain the critical densimetric Froude number, which induced the maximum internal wave heightsSecondly, studies the relationship between unsteady motion of submerged body and induced internal wave. By defining acceleration dimensionless parameters and picking different acceleration and deceleration, this thesis studies the impact of acceleration or deceleration of submerged body motion in strongly stratified fluid system on amplitude and fluctuating process of induced internal wave. The result shows that the amplitude of internal wave is volatility with the change of speed. The amplitude of internal wave located just below the submerged body has the same variation trends with speed. However, the variation trends of second hump(valley) are not only relate to the state of submerged body motion but also relate to the particularity of picking working condition. Besides, the smaller of the submerged body acceleration/deceleration is, the larger of the variation of hump/valley after motion will be.Once again, calculates the characteristics of submerged body wake in still water according to the features of pycnocline in Chinese sea area. Among the working conditions calculated, the surface wave contains divergent and transverse waves, and for internal wave divergent waves dominate, transverse waves are relatively weak. Analyses the influence of the pycnocline on surface flow field. Combining with the theory of radar detection,comparing the characteristics of surface wave and internal wave induced by submarine motion in different submergence depth and different sailing speed, and obtaining the intensity and distribution features of convergence and divergence in different working condition,which provides basic support for submarine detecting in ocean waves.Finally, calculates the modulation effect between ocean waves and surface flow for submerged body motion in stratified fluid. Obtaining the surface wave form and strength of convergence and divergence on surface flow field after modulation of surface flow field and waves combining with wave spectrum and ocean wave simulation by boundary wave making method.