Influence of different skew angles of the submerged vane on pressure flushing performance

Siltation significantly threatens a reservoir’s original storage capacity and lifespan. Pressure flushing is an effective measure against siltation through the partial drawdown of the reservoir water level with limited flushed cone volumes in front of the bottom outlet. In this study, a novel configuration with submerged vanes has been proposed and tested experimentally to increase the flushed sediment volume during pressure flushing. In the new configuration, submerged vanes aligned with ten skew angles (θ) of 10°, 20°, 30°, 45°, 70°, 110°, 135°, 150°, 160°, and 170° to the flow direction in noncohesive sediment bed materials were used. The results showed that increasing the skew angle at 45° ≤ θ ≤ 160° increased the flushing cone geometry. The minimum and maximum flushing cone dimensions and volume occurred at skew angles of θ = 45° and 135° ≤ θ ≤ 160° around the bottom outlet. The sediment flushing volume in the presence of submerged vanes at 135° ≤ θ ≤ 160° increased 25 times compared to tests without submerged vanes. Eventually, nonlinear regression analysis yielded an equation for estimating flushing cone volumes. The developed equation was tested in real case studies of a target reservoir, and an acceptable correlation between the calculated and experimental results was obtained.