Experimental study on pressure characteristics in stilling basin of stepped spillway

To study the pressure characteristics in the stilling basin of a stepped spillway without anti-arc, we chose a reservoir and used the physical model test method to study the pressure characteristics including time-average pressure, fluctuating pressure intensity, and peak pressure pulsation in the stilling basin of a stepped spillway. The results showed that all the time-average pressure was positive in the stilling basin. When the flow regime was skimming flow and transition flow, the time-average pressure became large in the flow impact area, reaching a maximum of 0.926 kPa; it reached the minimum in the downstream rebound zone. The time-average pressure varied slightly when the flow regime was nappe flow, and increased with the increase of flow. The variation patterns of the fluctuating pressure intensity and peak pressure were basically consistent. They both increased with the flow on the whole. The maximum value appeared in the flow impact zone. The maximum fluctuating pressure was 1.198 kPa. It then decreased gradually in the downstream direction until it became stable. The step size hardly affected the time-average pressure and fluctuating pressure on the floor of the stilling basin. The dominant frequencies of fluctuations in the stilling basin were 0.01 – 4 HZ, which belonged to the low-frequency vibration and will not endanger the safety of drainage buildings.

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