Investigation of the impact of surface roughness on the flow characteristics of a broad-crested weir

Abstract

Weirs are a common hydraulic structure. The broad-crested weir's effectiveness depends on its height and surface roughness. The present study investigates the coefficient of discharge (Cd) for various broad-crested weirs in a laboratory flume. Two types of weir geometry were used and outfitted with three types of surface roughness (cement, boulders, and gravel) and the coefficient of discharge. The outcomes showed that the coefficient of discharge reduces as the surface roughness of the broad-crested weir increases for a given (H/H + P). The average value of the discharge coefficient for Group 1 (models 1, 2, and 3) was 0.66, 0.65, and 0.64, respectively. For comparison between models 1 and 2 and between models 1 and 3, the decrease in the coefficient of discharge was approximately 2 and 3.5%, respectively. Group 2 (models 4, 5, and 6) had an average value of the discharge coefficient of 0.63, 0.62, and 0.61, respectively. The decrease in the coefficient of discharge for comparison between models 4 and 5 and between models 4 and 6 was around 1.75 and 3%, respectively. Empirical equations were obtained to accurately fit the data. This study can inform the design of weirs, allowing for improved control and flow regulation in hydraulic systems.