Experimental study on time-averaged pressures in stepped spillway

Abstract

Steps located in the non-aerated flow region of a chute are prone to cavitation damage. Two models operated with various Froude numbers and bottom slopes were employed to measure the pressure on the steps. The minimum and maximum pressures on the horizontal step surfaces occurred at the chute beginning and at the chute end, respectively. These characteristics were also found in the fully-developed flow region. The time-averaged pressure on the horizontal step surfaces is negative at the chute start, and then becomes positive along the flow direction in the non-uniform flow region. On the vertical step surfaces, the pressure is always negative at the top and remains negative along the entire vertical surface if the unit discharges are high enough in the non-uniform flow region. These results differ from the pressure characteristics in the uniform aerated flow region.

Keywords:

• Experimentation
• flow pattern
• non-aerated flow
• pressure characteristic
• stepped spillway

Acknowledgements

This project was supported by the National Key Basic Research Program of China (973 Program, grant no: 2007CB714105), the Key Projects in the National Science and Technology Pillar Program (no: 2008BAB29B04), and the Program for New Century Excellent Talents in the University (grant no: NCET-08-0378) and the Science foundation of Ministry of Education of China (no: 2008108111).