Investigation on Hydraulic Characteristics of Turbine-Type Manhole Cover

Manhole cover is an important device of urban drainage infrastructures. The hydraulic characteristics of turbine-type manhole covers were studied through numerical simulations and physical experiments. The flow field characteristics and water surface were investigated. The drainage process is divided into two parts: free flow regime and submerged flow regime. Numerical and experimental results are in good agreement. It is indicated that the depth of water is constant in the later stage of unstable free drainage, while it changes with time and determines the discharge under the subsequent unstable submerged drainage condition. The influence of the depth on discharge is mainly reflected in the submerged drainage stage, in which period the discharge is linearly related to the square root of the depth. While in free flow regime, the discharge is affected by volume fraction of water with second order. The correlation between the depth and the discharge in the process of submerged flow is proposed based on dimensional harmony principle. With the characteristic of massive discharge, the design of turbine-type manhole cover provides one more choice in urban drainage construction.