Experimental Study On Internal Wave Generated By Tidal Flow Over Topography

Internal waves are widely distributed in the global stratified ocean and seen in thecoastal areas. The internal wave generation and mixing caused by internal wave arewidespread phenomenon. When barotropic tidal currents flow over submarine ridge,especially after the steep submarine ridge will generate obvious internal tide, sosubmarine ridge is pretty important to the generation of internal tide, energy transferand conversion in the process is very important to explore energy transfer amonglarge scale, mesoscale, and small scale in the ocean.According to the relationship between ω/Nand topography slope sinα, thesupercritical, critical and subcritical cases are divided. In this paper we will show theinternal wave generation process of supercritical, critical and subcritical cases inlinear and nonlinear density stratification.In some particular conditions, internal tide generated by barotropic tidal currentsflow over submarine ridge will excite internal solitary wave, which can be seenoffshore usually. Internal solitary wave is one kind of non-linear internal waves, withlarger amplitude, higher speed and shorter period than internal wave in general. Thereare two kinds of the appearance form of internal solitary wave, one is single internalsolitary wave; another is internal solitary wave train. Internal solitary wave has a hugeinfluence and threats to communication and transportation and marine engineeringbuilding (such as oil, gas pipelines, cables and oil platforms, etc.). Therefore,Research on internal solitary wave is very significant for human life.At present, the generation mechanism of internal solitary wave in the ocean canroughly be summed up in two kinds (Fang Xinhua and Du Tao,2005): one is internaltide mechanism; Another is lee wave mechanism. This experiment will launch a seriesof experiments for both internal solitary wave generation mechanisms respectively.In order to simulate barotropic tidal current precisely in this experiment, wepressure tide process within a submarine terrain generation and formation mechanism,the solitary wave in the lab, using back-and-forth flow through the ridge and verticalslab to simulate the Marine topography process of barotropic tide. Three types of internal wave experiments were conducted:In this paper, the process of internal waves generated by tidal flow over criticaltopography was examined in laboratory using Particle Image Velocimetry (PIV) andsynthetic schlieren methods in synchrony. Finally, by choosing uniformly-spacedfourteen vertical profiles in the x-z plane, we constructed perturbation fields of densityand velocity fields. Thus, available potential energy, kinetic energy and energy fluxeswere determined quantitatively. The distribution of baroclinic energy and energyfluxes are constructed exactly and all of them focused on the positions that theinternal wave rays exist. Total energy and energy fluxes away from the topographywere all larger than those above the topography.