The rotary flow spillway tunnel with blocking was proposed for meeting the requirement of energy dissipation in high dam.The hydraulic characteristics of rotary flow in tunnel with different blocking,such as flow pattern,discharge,wall pressure,cavity diameter,rotational flow angle,and velocity were studied by experimentation,and then the velocity distribution was analyzed by quasi-free-vortex hypothesis.The results showed that the possibility of cavitation would decrease with the increase of wall pressure due to the blocking, and the energy dissipation would increase significantly with the increase of rotational flow angle and intense turbulence flow in the blocking.The disadvantage was that the discharge would be decreased.By the analysis of flow mechanism and measured velocity,the tangential velocity distribution along radial direction was studied by quasi-free-vortex hypothesis.The relation among wall pressure,rotational flow angle,cavity diameter,discharge and parameters of tangential velocity distribution was established, and the axial velocity expression was built.Then the expressions were verified and characteristics of flow motion were proved by experimentation.The results could provide references for the research and application of the tunnel.
