Experimental Study On The Internal Waves Induced By Artificial Disturbance In The Stratified Ocean

Oceanic internal waves(OIWs)are fluctuations that occur inside the ocean of stable density stratification.The OIWs have the characteristics of large amplitude,long period and slow wave speed,which contain violent energy and could impact on the marine environment and ecosystem,vertical exchange of nutrients in the ocean and marine sediments,etc.In the natural ocean,the sources of OIWs are complex and result in an intense randomness of their locality and propagation.Therefore,the key point to the process of converting the hazard of OIWs into advantages is to generate OIWs by artificial disturbance,and it is of great significance to further the investigation on the topic deeply.In order to explore the most efficient,feasible and economic artificial means of disturbance,this paper undertook a physical experimental study on the artificially induced OIWs.The main contents are as follows:(1)On the basis of summarizing the theoretical analyses,experimental researches and numerical simulation results of domestic and foreign scholars,the generation mechanism and propagation characteristics of the OIWs have been analyzed.Combined with the distribution of density thermocline and the seabed topographic features of the South China Sea,the feasibility of utilizing artificially induced OIWs has been demonstrated in the paper.(2)A new sort of OIWs experimental facility was designed and applied to simulate the generation,propagation and evolution of artificially induced OIWs under the background shear flow in the ocean.And a set of optical instruments were used to precisely record and measure the interfacial waves in the laboratory stratified fluid.(3)Five different types of artificial disturbance modes were proposed and contrast experiments of the suspending cylinder,traversing membrane,striking slab,collapsing airbag and sliding wedge were then conducted.By changing parameters such as the velocity,direction of the disturbing objects as well as the upper layer water depth,the effects and regularities of the interfacial waves induced by different ways of disturbance were studied systematically.The experimental results indicate that the interfacial waves with largest amplitude are induced by the striking slab,and that the most effective method of artificial disturbance is the suspending cylinder.(4)According to the feasible scenarios of artificial disturbance obtained in the laboratory experiments,three kinds of artificial disturbance structures were devised,and the specific structure of the tubular airbag,the flexible membrane as well as the current-propelled slab were illustrated in detail.The installation and operation techniques and main advantages of the structures were also analyzed.