关键词: 水流特性, 偏流机理, PIV, 明渠扩散段, 强势回流区

Abstract: In the diffusion section of open channel, the current bias characteristics of flow is an important problem affecting the design of water diversion engineering. In this paper, based on the indoor flume test, the velocity field of the diffusion section was measured by the propeller flow velocity meter and the PIV instrument under different slow flow conditions, and the boundary layer separation, mainstream bias and the flow movement characteristics in the recirculation zone were analyzed. The results showed that the boundary layer separation occurred after the flow passed through the diffusion section, and the mainstream was squeezed to the weak recirculation zone with a small range on one side, while on the other side, a large range of strong recirculation zone formed, and then a partial flow formed randomly. The transverse distribution of the velocity was uneven and momentum cannot diffused evenly. The vertical velocity distribution of flow was different. In the bottom and middle layer of the open channel diffusion section, the bottom and middle layer of the flow was greatly affected by the side wall and the floor boundary, and the flow direction was offset, but the separation in the upper flow boundary layer was not obvious, and the degree bias induced by the flow was small.

Key words: flow characteristics, bias mechanism, PIV, diffusion section of open channel, strong flow recirculation zone