Coherent Disturbance Structures and Bed Topography Responses in Large Depth-to-Width Ratio River Bends With Constant Curvatures

The bed topography is the result of the dynamic response of a complex meandering river system, and is an important factor influencing the further river development. Based on meandering rivers characterized by large depth-to-width ratios, the relation between the hydraulic structure and the bed topography was explored. The flow characteristics and bed topography responses were discussed through coupling of the N-S equations, the sediment transport equations as well as the bed deformation equations, and with the perturbation method. Research results show that shallows and deep grooves present regular responses under the effects of 2D flow disturbances. For a zero curvature, the bed topography shows an anti-symmetric distribution about the channel centerline; while for a non-zero curvature, the channel centerline deviates toward the concave bank. Finally, the criteria for the judgement on the stability of the bed topography influenced by the Reynolds number, the disturbance wave number and the decay ratio of the bed topography, are given.