experimental investigation of the effect of air entrained vertical jet on the scour hole dimentions

many experimental studies have been conducted on development of the scour hole as a result of vertical jet impaction. research has shown that aeration of the nappe flow in the model is much weaker than that in the prototype. therefore, the influence of aeration on scour holes needs further study. experimental investigation of the effects of air entrainment and tail water depth on the scour hole developed by a vertical submerged jet impaction is carried out in this study. the scour holes with and without air entraining conditions were investigated while hydraulic parameters like jet velocity and tail-water depth were kept constant. the results showed that air entrainment effectively reduces the scour depth and dimension. variation of maximum relative depth and length of scouring i.e. ds/htw and ls/htw versus tail-water froude number parameter, i.e. were analyzed. by increasing the air concentration, maximum relative depth and length of scour hole reduced. the changes in scour hole dimension has a threshold. results indicated that for more than 8.78, no meaningful effect on maximum scour hole depth (ds/htw) and length (ls/htw) was seen for air concentration of less than 3.25 percent.