THE EXPERIMENTAL STUDY OF THE CHARACTERISTCS ON FLOW ENERGY TRANSPORT AND DISSIPATION IN SHARPLY CURVED BENDS

In sharply curved bends, there is a nonlinear interaction between the streamwise velocity and the cross flow velocity, which leads to the adjustment of the flow energy transport, increasing the energy dissipation, and ultimately affecting the development of river bends. However, previous studies have not fully understood the mechanism of energy transport and dissipation in curved bends. In order to understand these mechanisms in depth, with the aid of detailed experimental data collected in a sharp open-channel bend, this study quantified the influence of key components in the kinetic energy equation and enstrophy equation. The results show that the component related to the transport of kinetic energy by cross-stream circulation is at least an order of magnitude larger than the other components in the kinetic energy equation, which contributes significantly to the redistribution of kinetic energy over the cross section. The component related to the production of turbulent kinetic energy in the kinetic energy equation shows the smallest order of magnitude and thus is almost negligible for the time-averaged flow field. Furthermore, over most of the measured area, the component related to the centrifugal force shows values of at least an order of magnitude larger than the other components in the enstrophy equation, which means that this component exerts the dominant influence on the energy dissipation. The results also revealed that the transformation process is insensitive to the variations in Froude number. These results are expected to improve the understanding of the complete process of energy transport and dissipation, especially the resistance caused by secondary flow in meandering rivers.