Study of Hydraulic Jump Characteristics in Diverging Stilling Basins with Square Bars Roughness

Hydraulic jump is the most important phenomenon in the rapid variable flow is of interest to hydraulic engineers. It has been used for dissipation of kinetic energy downstream of hydraulic structures such as spillways¡ chutes and gates to protect stilling basin. This study the roughness of the bed and the divergence of basin have studied simultaneously. The experiments have done with the walls diverging angles of 0¡ 2¡ 4¡ 6 and 8 degrees for six different Froude numbers. In total¡ 190 tests were performed in the range of 5 to 8 Froude numbers. The relative depth reduction of jump in the angles of 0¡ 2¡ 4¡ 6 and 8 degrees have obtained 10¡ 17.2¡ 22¡ 25 and 25.5% respectively. The average reduction of length jump¡ T¡ for the angles of 0¡ 2¡ 4¡ 6 and 8 degrees with the rough bed have obtained 45.5¡ 55¡ 56.1¡ 64 and 66.2% respectively. The man reduction of length jump for the cube bars is 60.3%. The loss of energy in the jump EL is equal to the difference between the specific energy before and after the jump¡ E2 - E1. The relative energy loss¡ EL/E1¡ for the angles of 0¡ 2¡ 4¡ 6 and 8 degrees have obtained 58.5¡ 62.4¡ 64.1¡ 65.9 and 67% respectively. In this study¡ the effect of the square ribs bed on hydraulic jumps was investigated. The divergence of basin without roughness effect also has influenced on reducing the relative length of jump about 37 to 47% and the relative length of jump is proportional to the angle of divergence basin. The results show that both the divergence angle of stilling basin wall and bed roughness of bed have reduced the length and depth of hydraulic jump. This makes it more economical to build a basin and control of jump is better.