The Study On Hydraulic Characteristics Of Irregular Broad Tail Pier

Flood discharge and energy dissipation is always a key factor for water-control projects. As technical of dam projects develops, more water-control projects with high water level, high flow and high-power are built into use while the problem caused by flood discharge and energy dissipation has become the core problem that impacting the safety of hydraulic projects. Energy dissipation of ski-jump type is widely used for the simple construction, low investment, excellent energy dissipation effect. But in energy dissipation of ski-jump type engineering, the scour pit with flat tail pier is relatively deep and far from the downstream, while the condition of flared gate pier’s is on the opposite. Irregular broad tail pier is a special dissipater that combines the very advantages of flat tail pier and flaring gate pier which reduce the scour damage caused by the discharge flow by increasing the distance of scouring pit from downstream and reducing depth of scouring pit, which respectively belongs to the scour characteristic of flat tail pier and flaring gate pier. But the application of irregular broad tail pier isn’t that common and the research achievement is rare. It is necessary to explore the characteristics of irregular broad tail pier to provide a reference and experience for similar projects. The research contents of this paper are summarized as follows.1. Summarize the basic theory, research significance and development of flood discharge and energy dissipation. Explore the flow regime, application condition and specialty of all energy dissipation types, including energy dissipation by underflow, energy dissipation by jet trajectory, submerged bucket dissipater and bucket flow energy dissipation. Besides, the development and application of new energy dissipation used in ski-jump type projects are also mentioned.2. Summarize the empirical values and calculate formulas of hydraulic characteristic values of irregular broad tail pier, providing references to such projects. Make a contrastive analysis of addition energy rate, scour pit characteristic between irregular broad tail pier and flat tail pier, and empirical formulas related are also recommended.3. Study on hydraulic characteristics in certain engineering with the combination of irregular broad tail pier and continuous flip bucket. Contrast the variation in discharge of certain engineering which respectively use flat tail pier and irregular broad tail pier, and investigate the influence caused by irregular broad tail pier on flow capacity of overflow dam. The regularities of distribution about pressure values, flow profile and flow velocity are also concluded. Test result shows that the combination of irregular broad tail pier and continuous flip bucket may solve the scour problem downstream preferably, the depth of scour pit decreases over30%.4. Study on hydraulic characteristics based on certain engineering with the combination of irregular broad tail pier and slotted flip bucket, and test result shows that the size of scour pit decreases effectively. A comparison is made to the combination of irregular broad tail pier and continuous flip bucket. The distance of scour pit downstream increases remarkably, and the value of pit depth/distance decreases.Research shows that by combining various energy dissipaters in a project properly may bring each superiority into full play than single energy dissipater, thus improve the scour condition and lighten the adverse impact on engineering.