Abstract

In this study, role of internal waves in controlling stratified exchange flows between south and middle basins of Caspian Sea and energy transfer have been studied. The studies have been conducted based on field and theoretical studies based on numerical calculations. In this investigation, Caspian Sea has been considered as stratified and Boussinesq approximation has been considered. In equations governing the movement, cohesion and compressibility have been neglected. In the field studies, investigation of density profiles indicate signs of stratified structure which so far has been attributed to dual distribution convection phenomenon, but by considering density ratio profile and values of density ratio which are mostly negative numbers, the factor causing stratified structure of Caspian Sea can be attributed to existence of internal waves. Density field in these two basins indicate that the middle basin has higher average density compared to the south basin, this fact can cause creation of a gravity exchange flow. This exchange flow causes creation of internal waves in this sea that can have a modal structure towards vertical direction. In theoretical studies, the two middle and south basins of Caspian Sea are networked in two dimension x-z systems and equations governing movement are solved through a numerical method by using finite difference method and the vertical velocity values obtained in 290 points of the network was almost 10^-6 to 10^-4 m/s, meaning that vertical movements are much smaller. Values obtained for horizontal velocity are almost 10^-3 to 10^-1 m/s. Vertical and horizontal velocity profiles obtained from solution of these equations and also density profile obtained in four integration periods indicate that as a result of passage of gravity flow between the two basins, density in various points of the two basins change. The structure created from internal waves on the crest causes creation of shear strata observed. This structure can be effective in exchange of the two basins. Therefore, in transfer and energy conversion, identification of the created strata is of a high importance.

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