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.