Abstract
Vegetation or pile dikes in a river may affect 3-D flow structures and can control the local scour and deposit in curved open channels. In this study, three-dimensional mean flow structures were measured in a curved open channel with various arrangements of cylindrical roughness elements. Furthermore, experiments were conducted in a movable bed and the effects of roughness on the local scour were examined. Some outer-bank arrangements of roughness can reduce the bed evolution. The secondary flow cell is generated over whole section through the roughness area and the spanwise deference of primary mean velocity becomes small in the case of submerged roughness. The streamwise variation of bed share stress indicatcs charactcristic behaviors affected by the arrangement of the roughness area, and it gives an explanation for the tendency of bed evolution.
