Increased efficiency of flow energy dissipation in the downstream

Abstract

The present study assesses the efficiency of using artificial roughness as a flow energy dissipater on the spillway of a low-head concrete spillway. A comparative analysis of the effect of different types of roughness elements in the downstream is presented. Separately, the elements of resistance in the form of bottom ribs lying horizontally at the bottom of the waterfall, as well as vertically standing elements of resistance (cubes, cylinders, concrete blocks, hemispheres) are considered. The influence of the shape of the elements, their location and their distribution density per unit area is evaluated. Among the ribbed elements of roughness studied, the most promising is the double zigzag against the current. Among the vertically standing elements, it is advisable to give preference to elements with sharp edges (cubes, blocks, plates). Most of the works devoted to the study of artificial roughness is based on experiments conducted in natural or artificial channels with relatively small slopes compared to the spillway face of practical profile spillways, as well as steeply falling sections of fast currents with slopes of i>0.3. An assessment of the efficiency of the bottom ribbed elements on the model of a low- and medium-pressure concrete dam is proposed to identify the most effective structures in relation to the resistance elements often used in practice at fast currents.