TRANSPORT OF FINE SANDS BY CURRENTS AND WAVES .2.

The transport process of fine sand with a median diameter of about 100 mu m in combined current and wave conditions in a laboratory basin wa s studied. Irregular waves with a single-topped spectrum and peak peri od of 2.5 s were generated. The significant wave height was varied fro m 0.07 m to 0.14 m. The water depth was about 0.4 m in all tests. The depth-mean current velocities were varied from 0.1 m/s to 0.3 mis. The angles between the wave and current directions were 60 degrees, 90 de grees, and 120 degrees. Instantaneous fluid velocities were measured b y an acoustical probe and an electromagnetic probe. The acoustical pro be was also used to measure the instantaneous sand concentrations. Tim e-averaged and bed-averaged concentrations were measured by a pump sam pler. Current-related and wave-related transport rates were determined by decomposing, multiplying, and time-averaging instantaneous signals . The current-related transport rate in the main current direction was found to be largest when the waves were propagating normal to the cur rent. High-frequency wave-related transport rates were found to be dir ected onshore because of the wave asymmetry effect. Low-frequency wave -related transport rates were found to be directed offshore because of the bound long waves.