Study of dynamic characteristics of laminar flow zone in overland flow

To improve the basic theoretical research of overland flow,this researcher used a fixed-bed flume test and ultrasonic sensor measurement technology to study the hydrodynamic characteristics of laminar flow and roll waves on the slope surface. Glycerol solution was used as test fluid and combined tests were performed under four levels of roughness,five slope gradients and 13 single-width flow conditions. The results show that the flow index fluctuates around the theoretical value of 0.33 for Reynolds numbers ranging from 8 to 160. It first increases and then decreases as the roughness increases. The roughness is around 0.10 mm. The peak is reached,and the drag coefficient is significantly affected by the slope and roughness,which can be expressed as the relationship between slope,roughness and Reynolds number;as the Reynolds number increases,the roll wave velocity and the peak value increase in the form of a power function. There is no readily visible change in the magnitude of the rolling cycle;the increase in the slope causes the layer to lose stability and the critical single-width flow gradually decreases. The increase of the roughness causes the critical Froude number to decrease. The research results can provide theoretical basis for the development of hydraulics and hillside hydrology.