| Summary: | 碩士 === 國立中山大學 === 海洋環境及工程學系研究所 === 95 === Internal solitary waves (ISW) have been detected on the interface of a stratified water column in the ocean. It is believed that ISW could affect oil drilling operations, nutrient pumping, and acoustic signal obstruction. In the ocean, the thickness of a pycnocline is finite which differs with the theoretical assumption as being a thin layer. This thesis reports the effect of an ISW propagation in various pycnocline thicknesses.
Laboratory experiments were conducted in an internal wave flume (0.5×0.7×12m) at the National Sun Yat-sen University, Kaohsiung, Taiwan. ISW in depression or elevation type were generaled using a stratified two-layer fresh/brine water system with a total depth of 50 cm in the flume. Upon creating an ISW propagating on a flat bed or over a triangular obstacle later, several physical parameters of the ISW (i.e. wave amplitude, phase speed, characteristic wave length, and wave energy) were measured or calculated for different thicknesses of the pycnocline.
The major controlling factors in the experiments included the depth ratio of the upper to lower layer H1/H2, interface displacement η0 between the wave generating chamber and the main flume, and the thickness of the pycnocline. The thickness of the pycnocline was estimated from the result of density profile in the vertical direction in the flume, experiments under the same H1/H2 and η was terminated when the pycnocline thickness became large enough.
As the thickness of the pycnoline increased, the values of all the physical parameters (including wave amplitude, phase speed, and wave energy) under consideration decreased. Their reduction rates were more significant in the case of small interface displacement (η0=10cm) than that with large η0=15cm. On the other hand, the changes in the physical variables associated with a depression ISW were more significant than those in an elevation ISW.
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