Abstract
The flow characteristics of the undular jumps in smooth trapezoidal channels have been investigated systematically. The flow conditions of the undular jump have been divided into four types on the basis of the cross point of the shock waves and the surface profile along the channels. Also, the flow conditions have been characterized by the first wave height, the wave length and the angle of the lateral shock wave. The hydraulic condition required to form each flow condition have been determined by the slope of the side walls, the aspect ratio and the inflow Froude number.
