Effect of nozzle contraction angle on air entrainment rate of a vertical plunging liquid jet

The effect of nozzle contraction angle on air entrainment rate by a vertica l plunging liquid jet was investigated. The surface roughness of the jet in creases with increasing nozzle contraction angle up to about 40 degrees, an d then levels off. The volumetric air entrainment rate increases in proport ion to (sin theta)(0.21), corresponding to the increased surface roughness of the jet. The air entrainment rate is correlated with empirical equations , which cover a wider range of the nozzle geometries and operational condit ions. The relationship between the air entrainment rate per power consumpti on and nozzle contraction angle was also investigated. The power efficiency for air entrainment is found to be almost independent of the nozzle contra ction angle.