Experimental study on the influence of abrupt slope changes on flow characteristics over stepped spillways

Stepped spillways have been built since several decades in combination with roller compacted concrete dams. More recently stepped spillways are also excavated into rock along the abutments of embankment dams. According to the prevailing topography these stepped spillways are designed with variable step heights and slope changes along the channel. In his research project Dr Mohammad Javad Ostad Mirza studied for the first time systematically with laboratory tests the influence of abrupt slope changes on the flow characteristics over stepped spillways. The air-water flow behaviour was studied in detail at several cross-sections along the chute, upstream and downstream of the slope change by measuring the evolution of water surface based on the equivalent clear water depth, flow bulking, flow velocities and air concentration profiles. Furthermore, dynamic pressures were measured on both vertical and horizontal faces at several steps in the vicinity and far downstream of the slope change. The systematic experiments give new insights in the flow characteristics over stepped spillways in the vicinity of slope changes, which is helpful for practical applications.