Effect of prismatic elements as bed roughness on hydraulic jump characteristics

Abstract

The roughness bed represents structures that produce high energy dissipation. The objectives of the present experimental study were to determine the effects of using prismatic elements for two types of bed roughness, strip and staggered, on fundamental characteristics of the hydraulic jump, including sequent depth, length and energy dissipation capacity. Experiments were conducted for both smooth and rough beds in the Froude number range of 2.98 to 11.5. It was found that the sequent depth was reduced by approximately 14 to 40% for staggered roughness and 10 to 33% for strip roughness compared to a classical jump. The hydraulic jump length reduction was 52% for strip roughness and 56% for staggered roughness, compared to a classical jump. The prismatic roughness elements induced 5 to 12% more energy dissipation than that for a classical jump. Some empirical relationships for estimating the sequent depth and the energy dissipation were established. The new established formula agreed satisfactorily with the experimental data. Key words: Energy dissipator, hydraulic jump, stilling basins, prismatic roughness, rough bed.