Turbulent structural analysis of the combined fishway with vertical seam and bottom hole

The three-dimensional flow velocities within the typical pool chamber of the rectangular fishway were measured in a vertical slit bottom-hole combination fishway by a hydraulic model test using an acoustic Doppler velocimeter (ADV). This was aimed to analyze the effect of eddy structures within the pool chamber of the fishway on fish migration. Based on this, a numerical simulation study was conducted using the Reynolds mean model (RNG k-ε) and large eddy simulation (LES). Additionally, the omega (Ω) eddy identification method was used to identify the eddy structure within the pool chamber of the fishway and dissect the flow characteristics of the water body within the pool chamber. The findings revealed that longitudinal flow velocity dominated the flow in the lower bottom layer of the pond. Moreover, the flow in the middle and upper layers was more turbulent and there is a phenomenon of backflow upstream, and the flow at the orifice was a divergent jet with the main flow slightly to the right bank, forming two vortices in opposite directions on both sides of the orifice. The fish passage mainly displayed the turbulent vortex structure, which can effectively slow down the water flow and provide a resting place for migratory fish. The vortex identification method can more accurately identify the vortex structure inside the flow field.