Thesis (M.Eng.) - Asian Institute of Technology, 1993

A thesis submited in partial fulfillment of the requirements for the degree of Master of Engineering.

The suspended sedimentation has been studied by numerous researchers, but they assume the sand diametereither is a constant or presented by a single diameter, although the practical beach consists of non-uniform sand. Therefore this study will be concerned with the suspension of mixed sand. A numerical model k-e model was used to simulate the suspension of mixed sand under wave motion, alsointhis study the wall function method which oneofboundaryconditions was introduced. The computed fluid field by this k-E model has been compared with Jonsson's & Carlsen's (1976) data and good agreement is found, and the friction factor criteria is proposed if the wall function method were used under wave motion. Also the computed results of suspension under the uniform sand assumption have been compared with Chen's (1992) data, and good agreement is found in the lower part near bed region. The computed results of suspension ofmixed sand have been compared with Kajima's & Saito's (1971) data, for small grain size the computed concentration will be underestimated and for large grain size the good agreement is found. The difference of computed concentration of mixed sand and uniform sand in Kajima & Saito (1971) case is small, and mixed sand concentration is slight larger than the concentration ofuniform sand.Foreach grain size concentration profile, their shapes are quite similar with each other, its slope is the function of sand diameter and sand fraction under the same wave conditions.