ABSTRACT
It is significant in hydraulic engineering to clarify the relationship between flow structures, channel width and bed roughness. In this paper, three-dimensional numerical experiments were conducted about turbulent flows over rectangular straight rough-bed channels with different aspect ratios (0.36 ~ 1.38) and relative depths on the roughness height (3.63 ~ 12.00). Characteristics of secondary flows in rough-bed channel and mutual relations of the outer secondary flow, the inner secondary flow and the bottom secondary flow were investigated in detail. The velocity-dip phenomenon occurred when the aspect ratio was larger than 0.84 and the relative depth was smaller than 4.18, and did not occur when the aspect ratio was smaller than 0.39 and the relative depth was larger than 4.88.
