Author(s): Masahiro Hashiba; Atsuhiro Yorozuya; Hiroshi Koseki
Linked Author(s):
Keywords: Pseudo-aDcp measuremen; Three dimensional k-epsilon model; Multi-cellular secondary currents; Discharge
Abstract: Studies on multi-cellular secondary currents have been conducted based on results from theoretical analysis and experiments using flumes and numerical simulation. Such studies have revealed the concentration variation of suspended sediment and the mechanism of sand stripes and sand ridges. However, it still remains unclear whether multi-cellular secondary currents influence water discharge measured by an a Dcp. In this study, we checked the accuracy of observed discharge by comparing it with that from numerical simulation, which used a 3-dimensional k-epsilon model with erodible bed. The discharge was measured by means of Pseudo-a Dcp measurement following the aD cp measurement principle by which the beams were slanted at 20 degrees, the a Dcp was kept free from pitches and rolls, and its head was kept upstream. The comparison between the calculated and measured results revealed the following: 1) the measured result showed the center of the secondary currents at a greater depth than the calculated result; 2) the calculated and observed depth-averaged streamwise velocities showed a very similar trend in the spanwise section while the observed spanwise and vertical velocities were larger than the calculated velocity; and 3) the trend is almost identical between the calculated and observed discharges with the maximum error rate at 1.6% and the minimum error rate at 0.6%.
Year: 2017