| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 88 === Transport of sediment particles in water can be classified into three different modes, namely, rolling or sliding, saltation and suspended motion. The types of transport depends on the size and location of the bed materials and the flow conditions. The transport of particles by rolling, sliding and saltating is called bed-load transport and the rest is called suspended load transport. The bed-load transport is confined in a thin layer, named bed layer, near the channel bed, and hence it is very difficult to measure and to quantify. According to previous investigators (Einstein (1942), Sekine and Kikkawa (1984, 1988, 1922) and Wiberg and Smith (1988, 1989)), most of the bed load particles are transport in a saltating mode and hence is investigated in this study. A series of studies regarding the collision mechanism with the channel bed and among the saltating particles were conducted by Garcia and Nino (1994, 1998) and our group (Chen 1998, You, 1999). The simulation results are satisfactory. However, the collision models they proposed were two dimensional models and can not really reflect the three dimensional behaviors. A three dimensional flow visualization technique will be developed in this study to measure the three dimensional collision process. Basing on these measurements a three dimensional collision model will be proposed. Combing with the saltating model of our previous studies, a three dimensional saltating model for multiple sediment particles will be established. This model will be very helpful in estimating the quantity of the bed load transport rate.
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