3-D Numerical Simulation Of Suspended Sediment Under Wave And Current

Coastal and estuary regions are such regions where the interaction between land and sea is obvious and sediment is an important factor in coastal engineering research. Coastal and estuary regions are characterized by intensive interaction among wave, current, river runoff and so on. Its dynamic conditions which control the transport of suspended sediment are complicated and variable. The effect of wave (refraction, break up et al.) is very distinct in shallow water, such as the coastal and estuary zone. Therefore, the simulation of sediment with wave and current as well as their mutual interaction in coastal and continental shelf is necessary. The concentration of suspended sediment will be changed remarkably under the wind wave. A lot of effort has been made to study the impact of the wind wave on the suspended sediment, especially the one of storm wave.The major contents of this dissertation are shown as follows:1. The wind field and air pressure are simulated successfully with elements (path, center air pressure et al.) of No.9711 tropic storm using the improved elliptic wind model, and it's proved that the model works well by comparing the wind speed and air pressure of simulated ones with the observed ones.2. Using the wind speed obtained in last process as input data, the wave field of considering area is simulated by SWAN (Simulating WAves Nearshore) model employing third class nesting. And the wave elements (Hs, T et al.) of No.9711 tropic storm can be computed.3. The hydrodynamic elements are simulated by the 3-D COHERENS model, and the modeled results of water surface elevation and current in offshore area of Rizhao are compared with the measured ones by Ocean University of China in August, 2005. The COHERENS model simulated the elements over the offshore region of Rizhao realistically.4. To check degree of impact on the concentration of suspended sediment caused by wind wave, a 3-D COHERENS-SED model is established based on the validated COHERENS model. The suspended sediment is simulated under the following three conditions: 1) driven by the No.9711 tropical storm; 2) driven only by astronomic tides; 3) driven by normal condition (year by year averaged wind elements and the standard air pressure). The major conclusions of this dissertation are shown as follows:When the model is driven by both wind and tide, the concentration is much bigger than that only driven by astronomic tides (the increase is about 40%~100%), especially along the coast. When No.9711 tropical storm is taken into account, the concentration is 4 times thicker than that under the normal condition. So wind wave plays an important part in changing the suspended sediment concentration.