Aerators are critical devices in preventing cavitation damage in high-velocity spillway structures. However

under the conditions of low Froude numbers and mild slopes

cavity backwater is prone to obstruct aeration holes

affecting aeration effectiveness. Therefore

introducing a flow resistance slope downstream of the aerator is considered as a measure to effectively mitigate the adverse effects of backwater. This paper develops a mathematical model for predicting the volume of water accumulation associated with varying flow resistance slopes through theoretical analysis and experimental tests on a 1:25 scale model

and examines the impact of these slopes on cavity water accumulation in mild slope spillways. This study indicates a flow resistance slope affects water accumulation in the cavity through changing the jet nappe impact angle . For a mild slope spillway

if the effect of the slope change on cavity water accumulation is considered

the cavity conditions can be categorized into three phases: overflow phase

water-blocking optimization phase

and clean cavity phase. In the experimental conditions

when both the blocking and aeration effects are taken into account

the optimal angle occurs in the water-blocking optimization phase (21% < < 41%)

where a stable cavity forms under the jet and the contact between water and air is sufficiently enhanced. This study helps optimize the design of aerators on mild slope spillways under low Froude number conditions.