Application of two-thirds law to plume rise from industrial-sized sources

Plume rise measurements from industrial-sized sources (F < 100m⁴sec^-3), including those experiencing stack-tip downwash, were compared to the plume-rise predictions from the " 2 3 law". When stack-tip downwash was not significant, plume rises for sources having a buoyancy flux less than 100 m⁴ s^-3 were typically 70-75 % of that predicted by the 2 3 law. Plume rises for sources experiencing severe stack-tip downwash were on the average 44 % of that predicted by the 2 3 law; however, most plume rises were 12 to 50% of the predicted values, and some were negative. Reduced rise and weakened correlation of rise with buoyancy flux indicated that factors other than buoyancy flux-such as downwash, increased entrainment, and turbulence controlled termination-significantly controlled plume rise.