Momentum transport and bed shear stress distribution in a meandering bend: Experimental analysis in a laboratory flume

• Estimation of terms in the depth-averaged momentum equations using a detailed dataset.
• Role of momentum transport by cross-circulation in bed shear stress distribution.
• Interdependence cross-circulation momentum transport/velocity non-uniformity.
• Equation to describe feedback cross-circulation momentum transport/downstream velocity.

The paper concerns the mechanisms underlying the distribution of the bed shear stress in meandering bends. Literature indicates that cross-stream circulation strongly affects the redistribution of the downstream velocity, but the feedback between them is still poorly understood. The aim of this paper is to gain some insight into how the momentum transport by cross-stream circulation contributes to the bed shear stress redistribution. Experimental analysis, based on a detailed dataset collected in a large-amplitude meandering laboratory flume, is presented. From these data an evaluation is made of the terms in the depth-averaged momentum equations and the analysis is especially devoted to terms including the momentum transport by cross-sectional motion. Results confirm that these terms exert an important role in bed shear stress estimation and, thus, they have to be adequately included in the depth-averaged models. Based on measured data, an equation expressing the interrelation between the cross-sectional momentum and the downstream velocity is also introduced.