Time-Averaged Distributions of Velocity and Sediment-Concentration under Irregular Waves and Currents

The velocity and sediment-concentration distributions in the case of irregular waves and currents are studied by using the theoretical model developed by means of a mixing-length concept for sediment-laden flow, and by improving the sediment-concentration formula based on the same hypothesis. The predicted results are compared with a set of velocity and sediment-concentration data collected previously in a recirculating wave flume. The time-averaging procedure is adopted, since it eliminates the random scatter of the instantaneous components of velocities and concentration. The general characteristic of the time-averaged velocity is greatly affected by the significant-wave height and the flow direction to the generated waves, although the mixing length is a function of the sediment concentration. To compute the time-averaged vertical distribution of suspended sediment, two different formulae are proposed. The agreement between the simulated velocity and concentration profiles and the measured ones is satisfactory for the flow containing fine sands.