Annular Aerators in Tunnels with Horse shoe section

Aeration is one of the most practical and economical methods for prevention of cavitation attack inhigh speed flows. Many research works are conducted on aerators. Although a general method is notavailable for aerator design, many aerators are designed and constructed all over the world. Cavitationdanger in tunnels also makes the designers to consider aerators for tunnels. Since tunnel sections areusually circular or horse shoe, a specific type of aerator is required for tunnels. Lack of information onapplication of aerators in tunnels makes some of designers to change the tunnel section to rectangularby subsequent concrete operation and then design the same type of aerators used in spillways. Thismethod is expensive and time consuming. In the present work, annular aerators are studied in aphysical model of a tunnel with horse shoe section. The effect of aerator geometry on jet length andspray formation is studied. Experimental results showed that to reduce spray formation, the aeratorgeometry should follow the tunnel section. It was also concluded that to reduce spray formation in therange of Froude numbers tested, it is better to keep the ramp angle less than 5 degrees. To increase thejet length and efficiency of the aerator, the ramp height should also be increased.