Transport of Fine Sands by Currents and Waves

Abstract

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 μm and a medium‐fine sand with a diameter of 200 μm. 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 depth. 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.