28-08-2017, 01:24 PM
Stilling buckets are used to dissipate high velocity water energy to minimize the effects of washing that can occur downstream of the flow. This may be due to water falling from the top of a dam or near a hydraulic jump. Local washing occurs immediately downstream of the catchment basins and is inevitable because the local water velocity exceeds the incipient sediment movement velocity. This leads to a difference between the concrete floor level of the basin and the river bed. In such cases, different basin designs may be used to protect against the development of a clearing hole that could destabilise the structure and cause widespread damage to the region. Fixing basins are designed with special accessories that help direct the flow and maximize the efficiency of the structure. Depending on the properties of the incoming flow, the kicks, thresholds and baffles can be designed to trigger a hydraulic jump for the required tail water condition. Chute Blocks are used to form a toothed device at the entrance to the quiescent basin. They operate to feed the incoming jet, thus lifting a portion of the landfill floor to create a shorter hydraulic hop length. The crossbar is located at the end of the basin and acts to reduce the length of the hydraulic jump and minimize runoff. The baffle springs are blocks placed in the middle through the floor of the basin and function to dissipate energy through the action of the impact of the flow. They are useful in small structures with low inlet velocities, but are inadequate when high velocity flows can induce cavitation. For a properly designed catch basin, the velocity leaving the basin is equal to the velocity of the inlet channel.