Based on the quasi-geostrophic vorticity equation, the present peper simulates the water mxing process in the formation Of ocean shear waves using large eddy simulation methods. From Lagrangian tracing, we study the o...Based on the quasi-geostrophic vorticity equation, the present peper simulates the water mxing process in the formation Of ocean shear waves using large eddy simulation methods. From Lagrangian tracing, we study the ocean shear wave's changing from wave character to vortex character. The distance between tracer groups increases near the ocean shear wave area, and decreases between ocean shear waves. The tracers that are uniformally distributed in space do not retain the uniform character in the mixing process. The frequency shift of the perturbation waves is caused by their nonlinear interaction. The wave number ratio and phase lag of the initial perturbation waves affect the mixing process, but the results show little difference. The increase of the viscosity coefficient will restrain the mixing process.展开更多
A comprehensive field study has been undertaken to investigate sediment resuspension dynamics in the Moreton Bay, a large semi-enclosed bay situated in South East Queensland, Australia. An instrumented tripod, which h...A comprehensive field study has been undertaken to investigate sediment resuspension dynamics in the Moreton Bay, a large semi-enclosed bay situated in South East Queensland, Australia. An instrumented tripod, which housed three current meters, three OBS sensors and one underwater video camera, was used to collect the field data on tides, currents, waves and suspended sediment concentrations at four sites （Sites 1, 2, 4, and 5） in the bay. Site 1 was located at the main entrance, Site 2 at the central bay in deep water, and Sites 4 and 5 at two small bays in shallow water. The bed sediment was fine sand （ d5o = 0.2 ram） at Site 1, and cohesive sediment at the other three sites. Based on the col- lected field data, it is found that the dominant driving forces for sediment resuspension are a combination of ocean swell and tidal currents at Site 1, tidal currents at Site 2, and wind-waves at Sites 4 and 5. The critical bed shear stress for cohesive sediment resuspension is determined as 0.079 Pa in unidirectional flow at Site 2, and 0. 076 Pa in wave-induced oscillatory flow at Site 5.展开更多
In order to evaluate bed-load sediment transport in an irregular wave-current coexistent field, a series of experiments were completed in laboratory with an irregularly oscillating tray, which is designed to simulate ...In order to evaluate bed-load sediment transport in an irregular wave-current coexistent field, a series of experiments were completed in laboratory with an irregularly oscillating tray, which is designed to simulate the irregular wave-current coexistent field. The initial motion of sediment and the rates of transport over flat horizontal bed were tested. Comparison between experimental results of initial motion and modified Shields curve indicates that the Shields curve is still valid for the case of irregular wave-current coexistent field. Analysis of flow regime shows that initial conditions fall within smooth-turbulent transitional region. The results of transport rate show that net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress and mean shear stress. A dimensionless formula is proposed on the basis of the mechanisms of waves erode sediments and tides transport sediments.展开更多
文摘Based on the quasi-geostrophic vorticity equation, the present peper simulates the water mxing process in the formation Of ocean shear waves using large eddy simulation methods. From Lagrangian tracing, we study the ocean shear wave's changing from wave character to vortex character. The distance between tracer groups increases near the ocean shear wave area, and decreases between ocean shear waves. The tracers that are uniformally distributed in space do not retain the uniform character in the mixing process. The frequency shift of the perturbation waves is caused by their nonlinear interaction. The wave number ratio and phase lag of the initial perturbation waves affect the mixing process, but the results show little difference. The increase of the viscosity coefficient will restrain the mixing process.
基金The study has been supported by the Distinguished Overseas Scholar Research Grant fromthe National Natural Sci-ence Foundation of China (Grant No4428001)
文摘A comprehensive field study has been undertaken to investigate sediment resuspension dynamics in the Moreton Bay, a large semi-enclosed bay situated in South East Queensland, Australia. An instrumented tripod, which housed three current meters, three OBS sensors and one underwater video camera, was used to collect the field data on tides, currents, waves and suspended sediment concentrations at four sites （Sites 1, 2, 4, and 5） in the bay. Site 1 was located at the main entrance, Site 2 at the central bay in deep water, and Sites 4 and 5 at two small bays in shallow water. The bed sediment was fine sand （ d5o = 0.2 ram） at Site 1, and cohesive sediment at the other three sites. Based on the col- lected field data, it is found that the dominant driving forces for sediment resuspension are a combination of ocean swell and tidal currents at Site 1, tidal currents at Site 2, and wind-waves at Sites 4 and 5. The critical bed shear stress for cohesive sediment resuspension is determined as 0.079 Pa in unidirectional flow at Site 2, and 0. 076 Pa in wave-induced oscillatory flow at Site 5.
基金Project supported by the National Natural Science Foundation of China( No.595790 1 4)
文摘In order to evaluate bed-load sediment transport in an irregular wave-current coexistent field, a series of experiments were completed in laboratory with an irregularly oscillating tray, which is designed to simulate the irregular wave-current coexistent field. The initial motion of sediment and the rates of transport over flat horizontal bed were tested. Comparison between experimental results of initial motion and modified Shields curve indicates that the Shields curve is still valid for the case of irregular wave-current coexistent field. Analysis of flow regime shows that initial conditions fall within smooth-turbulent transitional region. The results of transport rate show that net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress and mean shear stress. A dimensionless formula is proposed on the basis of the mechanisms of waves erode sediments and tides transport sediments.
