Field Measurements of Secondary Currents in Straight Rivers

Abstract

Basic knowledge of turbulent structures in open‐channel flows are now available from accurate experimental data that were obtained using a laser Doppler anemometer in laboratory flumes. Many of these experiments have, however, been conducted at moderate Reynolds numbers. Therefore, it is not yet clear whether such laboratory data of open‐channel turbulence can be applied to river turbulence at high Reynolds numbers. In this study, velocity measurements of the Biwako‐Sosui River in Kyoto and the Aichi Irrigation Channel in Nagoya have been conducted by making use of three‐component electromagnetic flow meters. Multicellular secondary currents were evident in a wide river, whereas large‐scale free‐surface secondary currents associated with velocity‐dip phenomena were generated in a narrow river. The features of such secondary currents in rivers could be explained by theory of turbulence, and also they coincided well with the laboratory experiments and numerical calculations.