Numerical Simulation On The Interaction Between Internal Solitary Waves And Submerged Body In The Ocean

Internal solitary wave(ISW)is a kind of fluctuation that occurs in stratified seawater,and it often appears in the actual ocean environment.ISWs carry huge energy during propagation to induce strong convergence and divergence of water bodies and sudden strong currents,which have an important impact on the ecological environment of the sea,the exploitation of oil and gas resources,and the safety of submerged bodies.For the investigation of interaction between ISWs and the submerged body,a numerical model of ISWs in continuously stratified fluid,and the interaction between ISWs and moving submerged body,is developed based on the characteristics of the actual marine environment.The model is applied to study suspended submersible body and self-propelled submersible body encountering ISWs respectively,and the ISWs generated by the moving submerged body.The main research contents and results are as follows.(1)A numerical model of ISWs in continuously stratified fluid isdeveloped.The model is established by introducing a density transport equation to the three-dimensional Navier-Stokes equation and adopting the fully nonlinear theoretical solution of ISW to obtain the initial field of the ISW.The model can accurately simulate the propagation and evolution of ISW,the breaking phenomenon of ISW,the evolution of vortex structure,waveform inversion,and the propagation and evolution of the wave train generated by waveform inversion.The developed model provides a numerical simulation tool for the study of ISWs in the real marine environment.The model code based on Open FOAM has passed the review and is open source in Zenodo Library(DOI:10.5281/zenodo.5069480).(2)Based on the established numerical model of ISWs in continuously stratified fluid,taking the SUBOFF standard submarine model as an example,the load variation of fixed submersible body encountering ISWs at different submergence depths and the influence of the rotation center position on the moment are studied and analyzed,and the most dangerous working condition of submersible body encountering ISWs is given.Through a series of numerical simulation results,the optimal rotation centre position ranges for the standard submarine can be recommended as 0.46-0.48 for a bare hull and 0.45-0.49 for a fully appended hull.When the submerged body encounters the ISWs in the ocean and the rotation center is within the range of the optimal rotation center,the moment of the submerged body is relatively small,which is convenient for the underwater manoeuvring of the submerged body.(3)A numerical model of the interaction of ISWs and moving submerged body in continuously stratified fluid is established.The model is developed by combing the rigid body motion equation and the overset method,based on the established numerical model of ISW in continuously stratified fluid.The model established is applied to study suspended submersible body and self-propelled submersible body encountering ISWs respectively,the load and motion response are given,the motion response of the emergency floating of the submersible body under different escape measures is systematically analyzed,and the escape plan through discharging ballast water is given.(4)The established model is used to study the ISWs generated by the moving submerged body,which traverses the continuously stratified at different angles and different submergence depths.The mechanism of the ISW generated by the motion of the submerged body and the law of ISW propagation and evolution are given.The results show that with the increase of the angle of the motion path,the ISWs height generated by the submersible body increases gradually,and the second ISW has the largest amplitude.The ISWs generated by the oblique moving submarine body finally propagate outward in a V shape with an angle of about 60° in front and rear of the submarine body.