Author(s): Bo Wang; Ping Wu; Yunliang Chen; Chao Wu; Qin Zhou
Linked Author(s): Wang Bo
Keywords: Stepped chute; Velocity distribution; Accelerating region; Stable region; Physical model; Numerical simulation
Abstract: The stepped chute has been used in hydraulic engineering as an energy dissipator. The interior turbulence of flow is enhanced and the frictional head loss is increased due to the concavo-convex faces of stepped chutes. As a consequence, the flow velocity is reduced. The hydraulic characteristics of channels with a small numbers of steps have been investigated in the past. With the increase in the working head of the flood discharge structure, a tendency of significant enlargement is found in the step number of stepped spillways at present. For a channel with a large number of steps, how does the flow velocity will develop? Studies on this topic are of both academic and practical values. There are forty steps on a stepped channel with constant width l = 2. 4 m and height h =1. 2 m (l/h =2). In the present research, several experimental runs were carried out on a 1: 40 scale physical model. The mean velocity and water surface profile were recorded. The simulation on the prototypical chute was done to obtain the velocity profile along the water depth by means of a three-dimensional numerical model. According to the development of flow velocity, a stepped chute is divided into two parts: accelerating region and stable region. The accelerating region is located on the upstream reach of the stepped channel, and the flow accelerates sharply in this range. The stable region is downstream of the accelerating region, and the flow velocity fluctuates slightly in this reach. The accelerating region is impacted by the inflow, and will extend towards the downstream reach as the unit discharge is increased. The flow does not accelerate any more along the whole stepped chute compared to the smooth chute. No matter what the total height of channel is, the outlet velocity will be limited to the neighbour of a constant value provided the flow enters into the stable region. This law will be a important basis for the further increase in the working head of stepped chutes.
Year: 2013