Some Problems Of Shock Wave And Contraction Type Energy Dissipators

As the dam construction technology develops and the great dams higher than 300 meters are built, the problem of energy dissipation with high water head, large discharge and narrows gorge has become more serious. Thus more attentions have been paid on the research of the contraction energy dissipators. This paper presents the hydraulic characteristic of the contraction energy dissipators and revises Ippen's theory of shock wave by a series of model experiments in laboratory together with academic analyses. The result from this study can be summarized as follows:(1) This study gives up the assumption of the hydrostatic pressure in Ippen's theory and explores the characteristics of the shock waves on the horizontal slope with a short but abruptly deflected channel wall. A correction coefficient of the hydrodynamic pressure is introduced and calculated by the governing equation and the model experiments. As a result it has been proved that the relative error of the result calculated by the revised theory is much smaller than that obtained from Ippen theory.(2) Based on the model experiments for the effect on the shock waves by the slope and the corresponding academic analysis, a computing method has been introduces and the calculated outcome is close to the experimental data. It has been testified that the angle of the shock wave and the water depth behind the shock wave are no longer constant if the bottom is not horizontal. The former will decrease along the wave, but the later will increase along the wave on the contrary.(3)The characteristics of the flow in the slit-bucket with straight wall have been studied according to the 1-D non uniform flow. Some hydraulic parameters have been calculated such as the water surface profile in the slit-bucket, the lengths of the lower and upper jet trajectory pressures on the slit-bucket bottom, intersection point of the shock wave, and the maximum depth of scour depths, etc. The range of contraction ratio of width, the deflection angle of the side walls, the terminal position and the takeoff vertical angle of the slit-type bucket are obtained.(4)Based on the analysis, the calculated intersection point of the junction of shock wave behind flaring-tail pier has been compared with the experimental one, and the method to calculate the water flow and velocity of a point at the upstream of the intersection point of shock wave behind flaring-tail pier is deduced theoretically. Moreover, the theoretical formula to calculate the critical contraction ratio is presented, and the results of the suggested formula...