CHARACTERISTICS OF RADIAL JETS AND MIXING UNDER BUOYANT CONDITIONS

This paper reports on measurements of radial jets using a laser-dopple r anemometer and compares the mixing efficiency of a single radial jet with that of a single round jet under buoyant conditions based on exp erimental data. Dimensional analysis yields two parameters for the cal culation of initial dilutions of jets and buoyant plumes. It is notice d that initial dilution of radial jets is much higher than that of rou nd jets having the same source discharge, source buoyancy flux, outlet velocity and area because of intensive entrainment of the radial jet in the zone near the discharge point. Theoretical analysis indicates t hat the central velocity of the radial jet decays with jet path at a r ate of -n (n > 1), the value of which is proportional to the relative turbulence intensity and hence is related to the geometry of the radia l jet. Experimental results show that in most situations, the value of n is approximately 1.5. Measurements also show that the ratio of half -width to distance from the virtual origin of the radial jet is given by b(w)/r(0) = 0.101 which is close to that of round jets. However vel ocity profiles of the radial jet are not completely similar, although the entrainment coefficient is basically a constant of 0.102. These re sults can help to predict correctly the flow field of the radial jet a nd its initial dilution.