Linear-Momentum Flux to Overbank Sections

On the basis of experiments in two joined rectangular channels, transfer of linear momentum from the major (less restricted) channel to the minor (more restricted) channel has been demonstrated. The apparent-shear stress on the junction surface was found to be of the same order of magnitude as the boundary-shear stress in the major channel. Based upon this observation, a method for engineering calculations for mean-flow characteristics in joined channels such as a river at flood stage is proposed. The steps in the proposed separate-channel method of analysis are: (1) considering the major-channel boundary including the junction plane as a solid boundary, compute the mean boundary-shear stress on the major-channel boundary; (2) compute the apparent-shear force on the junction surface using the mean boundary-shear stress of the major channel; and (3) incorporate the apparent-shear force on the junction surface as a propulsive force on the minor-channel flow.