Transport of fine sands by currents and waves

The transport process of fine sands in combined current and wave conditions in a flume was studied. Two types of sediment material were used, a very fine sand with a median diameter of about 100 micrometer and a medium-fine sand with a diameter of 200 micrometer. The current velocities were varied in the range of 0.1-0.5 m/s (following and opposing the waves). Irregular waves with a single-topped spectrum and peak period of 2.5 s were generated. The significant wave height varied in the range of 0.075 m to 0.18 m. The water depth was about 0.5 m in all tests. Time-averaged fluid velocities were measured by an electromagnetic current meter. Time-averaged sediment concentrations were measured by a pump sampler. The transport rate was obtained by integration of the product of velocity and concentration over the dept. The generation of waves in following or opposing currents causes a decrease of the time-averaged velocities in the near-bed region. A larger wave height results in larger concentrations and in a more uniform distribution over the depth. The influence of the current direction on the concentration profile and the transport rate is negligible.