Abstract:

As stepped spillway has special structure and complex flow patterns, researches on the pressure in stepped spillway are not consistent. In view of this, we investigate into the effects of flow discharge, air entrainment, step size and spillway’s slope gradient on the distribution of time-averaged pressure through analysing the pressure data of skimming flow in several stepped spillways. Results reveal that big discharge per unit width leads to big time-averaged pressure. Air entrainment could effectively reduce positive time-averaged pressure and increase negative pressure. Effect of the step size is complicated: when the step size is small with gentle slope, pressure is small in the middle but large on both ends in vertical plane of the step; when step size is small with steep slope, minimum pressure occurs on the bottom and top of step in vertical plane; while when the step size is large, pressure decreases from the bottom to the top, and pressure variation intensifies with the increase of slope gradient.

Key words: stepped spillway, cavitation damage, skimming flow, time-averaged pressure, discharge per unit width, aeration