Numerical Investigation of Flow over the Rectangular Compound Sharp-Crested Weir at Different Angles in Plan

Abstract

The aim of the current research is to evaluate the effect of placing a compound sharp-crested weir at different angles in the channel on its hydraulic performance. For this purpose, Flow-3D software was used to simulate the effect of the placement angle of the compound sharp-crested weir in the channel, considering four angles: zero (perpendicular to the flow pass), 15, 30, and 45 degrees. The comparison of the error percentage obtained between the results of the flow discharge and the depth of the upstream weir from the numerical results and the laboratory data was 0.39% and 2.86%, respectively. The results of the flow pattern passing through the compound sharp-crested weir showed that the flow lines are closer to each other when approaching the crest of the weir at the narrowing place, and the accumulation of flow lines increases in the place of the flow narrowing. The interference of flow lines at the narrowing place reduces the flow coefficient of the flow passing over the weir. The increase in transverse constricting and the decrease of 25 and 50% in the length of the weir crest caused a decrease in the flow discharge coefficient of 14.4 and 9.81%, respectively, compared to the sharp-crested weir of the same channel width. By creating a constant for the weir crown in the width of the compound weirs and placing them at a maximum angle of 45 degrees, the flow rate coefficient is increased 8.91% compared to the angle of the compound sharp-crested weir to the flow.

Keywords

• the compound sharp-crested weir
• discharge coefficient
• angle of weir
• transverse constriction
• numerical model