EVALUATION OF LOCAL SCOUR DEVELOPMENT DOWNSTREAM AN APRON OF DIFFERENT ANGLES FOR AN OGEE SPILLWAY

Abstract

Local scour downstream of hydraulic structures, such as low head and high head structures, spillways, and culverts is an important research field due to its significant practical value. In this study laboratory experiments were conducted to compute the local scour downstream apron of an ogee spillway under different slopes of apron to study its effect on the characteristics of the scour. Developed physical models for spillway and aprons are installed into the water in the channel where conducted under subcritical flow and clear-water condition by using uniform cohesionless (soil) as bed material with a medium grain size (d₅₀ = 0.65 mm).

Four angles of an apron were used (0 ̊, 2.73 ̊, 5.19 ̊, and 7.43 ̊) to show the effect of the slope for apron on local scour. It is found that the slope of an apron is one of the important parameter to reduce the local scour depth and the extent of scour hole. The influence of slope for aprons angle showed a reduction of about (53, 46, and 35) % in the maximum scour depth and about (33, 49, and 33) % in the maximum scour length compared with horizontal apron for angles (2.73 ̊, 5.19 ̊, and 7.43 ̊), respectively.