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This paper presented results of a numerical study on seven designs of T shape fishways. The trajectory equation of the maximum velocity line and the V/Va equation of the T shape fishways were obtained from the results. It was found that a width of 1.5bs for the T lateral baffle, a width of 5bs and a length of 6.25bs for the pools were very satisfactory for the dimensional design of T shape fishways, where bs was the slot width. From the seven designs studied, design 3 (D3, D denotes "design") was recommended for practical use.(2) the main flow travels from one slot to the next through the pool as a two-dimensional curved flow with gentle slope (S≤10%), where S is the slope of the fishway [9], [12].This paper aims to understand the hydraulics of the T shape fishway, to develop simpler pool designs by means of numerical simulation.

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Pressure flow generally exists in water conservancy projects and pipelines. The flow boundary of the contraction section faces a potential risk of cavitation erosion under high velocity. However, there is a lack of effective methods to suppress cavitation in engineering practices with pressure flow, posing a challenge to the operational safety of discharge structures and pipeline devices. The purpose of this paper was to realize the application of air entrainment in a plug-type contraction section of pressure flow. It was found that a single air vent and a low air flow rate could achieve complete vena contracta aeration. The pressure profiles of the vena contracta were investigated, and the results showed that the pressure distribution allowed the entrained air to diffuse laterally and convectively. Finally, we proposed a fitting algorithm to predict the air concentration in the vena contracta. These conclusions are of great significance for improving the safety and cavitation resistance of the contraction section of pressure flow.