Effects of Energy Dissipation Pier Arrangements on the Hydraulic Characteristics of Segmented Pier-Type Step Energy Dissipator Structures

Abstract

To make more efficient use of limited space, improve the energy dissipation effect of the step dissipator, and mitigate the effect of cavitation, we propose a segmented pier-type step dissipator structure and used a numerical simulation to study the hydraulic effects of two different arrangements of piers: a double-row arrangement and a staggered arrangement. We’ve drawn the following conclusions from our study: the segmented pier-type structure produces a large water jump at the location of the energy dissipation pier. This involves a large amount of air, promotes air-doping of the water flow in the whole section, and reduces the length of the non-air-doping zone. The staggered pier arrangement produces a better air-doping effect at the water jump and a higher air-doping concentration along the water course. The staggered arrangement also produces a better cavitation mitigation effect and is better able to stabilise the water flow; the flow velocity at the outlet is lower, so the energy dissipation effect is better. A larger positive pressure area forms at the headwater and upstream areas of the energy dissipation pier; a larger negative pressure forms at the top and backwater of the energy areas. The staggered arrangement produces a larger negative pressure; however, under various flow conditions, the difference in the energy dissipation rate between the two forms of pier arrangements is not significant. We obtained a peak energy dissipation rate of 90.04%, which represents an improved energy dissipation effect compared with the control. The step energy dissipator described here is conducive to stabilising the outlet flow, reducing cavitation damage, and improving energy dissipation. These findings provide a valuable reference for the future design of sectional pier-type step energy dissipator structures.