Laser stripe measurement of near-wall solids distribution in channel flow with intense transport of bimodal sediment

The laser stripe method (LSM) for measuring solids distribution in sediment-laden flow has been extended to accommodate the presence of multiple sediment fractions which can differ in particle size and shape. A measurement setup with two lasers emitting green and red laser sheets was utilized to measure the vertical distribution of the near-wall concentration of a bimodal sediment mixture composed of green and red particles. The extended method was calibrated under controlled conditions in a calibration cell and was validated for measuring distributions in sediment-laden flow in a laboratory tilting flume. The results from the flume demonstrate that the extended LSM can successfully produce vertical profiles of the total concentration of all particles and the relative concentration of the two fractions. The accuracy of total concentration measurements using the extended LSM is consistent with that of the original LSM, both exhibiting an error of 0.015. The extended LSM evaluates the relative proportion of individual fractions with an error of 0.05.