Investigating the Effects of the Slope of the Reservoir Bottom on Characteristics of the Flood waves due to Dam Break in Downstream Dry Bed condition

The purpose of this study is numerical investigation of the simultaneous effect of reservoir geometric shape on the plan and its slope on the model as well as the flood wave fluctuates due to dam break. The downstream bed is considered as dry. Characteristics of flow due to dam break in two reservoirs are studied and compared under long and wide geometric shapes and reservoir bottom slopes of 0%, 2%, 3.5% and 5%. The modeling is carried out in 3D mode using Flow3D software. The results indicate that in the wide reservoir with increasing the slope of the reservoir bottom, the water level is not significantly different in the downstream and upstream of the dam, but severe variations of the water level is observed in the wide reservoir at all slopes at the downstream of the gate. The reason for these variations can be due to the shape of the tank because surges occur after the sudden opening of the gate while these waves are dissipated over the reservoir in the long reservoir. In the long reservoir and at the upstream points of the gate the level water is decreased by increasing the slope of the reservoir bottom and the lowest water level is observed for the slope of 5%. At the downstream points of the gate in the long reservoir the water level decreases with the increase in the reservoir slope and over time at t=7s the loss of water level drop for slopes of 3.5% and 5% is more than other slopes.