Hydraulics of Wedge-shaped Flip Bucket to Investigate Flow Pattern with Retracted Bottom Plate

Abstract

This study analyzed the flow pattern of a wedge-shaped flip bucket with a retracted bottom plate (WFB-R) that is quite different from conventional flip buckets. The flow pattern of the free jet release from WFB-R is determined by the relationship between water depth at the exit and wedge height. If the water depth is less than or equal to the wedge height, the free jet appears narrow and long, whereas if the water depth is greater, the free jet appears like a hammer. Hence, WFB-R offers the advantage of extending the free jet longitudinally, but its longitudinal length can be controlled, which allows it to avoid hitting the bank of the plunge pool. The experimental results indicate that, compared to constant-width flip buckets with retracted bottom plates (CFB-R), WFB-R reduces the maximum impact pressure on the plunge pool bottom to 70–86% of what it originally was. In addition, the flow structure of free jets issued from WFB-R was modeled using the k-ε turbulence model. The numerical results show that in the case of WFB-R, the shrinkage ratio should be less than or equal to a critical shrinkage ratio (0.63 for the present case) in order to stretch a free jet longitudinally. The length of the retracted bottom plate affects the longitudinal extension of the free jet. The longer the retracted bottom plate, the better the longitudinal stretching effect. The flow pattern is determined by the relationship between water depth at the exit of WFB-R and wedge height. Based on the projectile theory, a novel method was developed to predict the trajectory of free jets released from WFB-R by incorporating the average velocity, takeoff velocity coefficient, and takeoff angle coefficient. The Yangfanggou high dam project illustrates the application of WFB-R.