Abstract: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.