Numerical investigation of bed-load changes on sediment flushing cavity

Abstract

The tanks' useful life will be reduced if their sediments are not discharged with a suitable method. Various hydraulic and mechanical methods can be used in many countries to discharge sediments from reservoirs. Pressure hydraulic sediment flushing is a method of sediment flushing without lowering the water level. In the present study, using the CFD based Flow-3D software, a model has been applied to investigate the pressure hydraulic sediment flushing, and evaluate the effect of blockage phenomenon on sediment flushing efficiency. Results were compared with the available laboratory model. The dimensions of the simulated tank were 2.5 x 1.3 x 1.5 m in length, width and height, respectively, the height of the bed load was 0.4 m, and the diameter of the sediment particles was 0.3 mm according to the laboratory conditions. The average relative error for the sediment flushing cone depth was about 3%. In addition, to investigate the blocking phenomenon, the height of the bed load was considered to be 0.41, 0.45 and 0.5 meters for each simulation. The simulation results showed that when the height of the bed load increases, there is the highest sediment flushing efficiency and more sediment can be removed from the bottom outlet.

Keywords

• hydraulic sediment flushing
• numerical model
• flow-3d
• bed load height
• sediment flushing efficiency