VARIATION OF AIR CONCENTRATION IN SKI JUMP JETS

Abstract

Scour is a significant problem for the stability and safety of a dam. Water jet issued from flip bucket of a dam creates an air-water mixture and finally plunges at the downstream of a dam. Depending on the discharge, total head, thickness of the water body, aeration conditions and geometrical features of the flip bucket, the jet is dispersed in air. It is obvious that air concentration is inversely proportional with the dynamic pressures at impingement area of the water jet coming from the flip bucket of spillway of a dam. Impact of the ski jump jet at the impingement point may be reduced depending on the air concentration of the jet. In this study, experimental and numerical assessments are performed to analyze the distribution of the air into the ski jump jet depending on the dynamic pressures at the impingement point. The impact of the ski jump jet is analyzed and air percentages are defined into the jet according to dynamic pressure measurements using pressure transmitters at the impingement area. By doing so, aeration characteristics and impact values of water jets are revealed to generate reliable scour estimations.