Document Type : Research Paper
Associate Professor, Department of Civil Engineering, Faculty of Engineering, University of Maragheh
Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Iran
Department of Civil Engineering, Faculty of Engineering, University of Maragheh,, Iran
Abruptly expanding stilling basins are often used at downstream of structures such as overflows, gates and spillways to increase energy loss in hydraulic jumps. Increasing the jump length, decreasing the depth ratio and asymmetric flow are among the characteristics of jump in a sudden expanding channel. The channel bed roughness is one of the method that can reduce the secondary depth and jump length. Therefore, in this study, the effect of sand bed with median size 1.9 cm on S-jump characteristics was investigated. Whole of the experiments were performed at expansion ratios of 1, 0.67, 0.5, and 0.33 and within the range of Froud numbers;4 to 12. The results showed that the abruptly expansion stilling basins with a rough bed in all the expansion ratios reduced the depth ratio with an average of 12 to 16 percent, compared to an abruptly expansion stilling basins with smooth bed. Also, the average jump length reduction for all expansion ratio in the abruptly expanding stilling basin with the rough bed was obtained 20 percent.