A COMPARATIVE-STUDY OF THE DIFFERENT CRITERIA FOR THE PHYSICAL MODELING OF BUOYANT PLUME RISE IN A NEUTRAL ATMOSPHERE

Some of the proposed criteria for physical modeling of rising stack and chimney plumes in the atmosphere are evaluated on the basis of our wind tunnel experiments. The observed jet and plume rises in a uniform cross flow follow the well-known 1 3 and the 2 3 power laws, respectively. These become independent of the stack effluent Reynolds number (Res) only when Res exceeds a certain minimum or critical value (Rec) of about 2000 and 600, respectively, for momentum jets and buoyant plumes. It is necessary to ensure a large enough Reynolds number (Res > Rec) and a large enough effluent to ambient velocity ratio (Ws/U ≥ 1.5), or the momentum flux ratio, in order to avoid any adverse effects of stack wake and downwash on plume rise in the model. The most important similarity parameter is the buoyancy-length scale to the stack diameter ratio (lb/D), which must be matched in the model and the prototype situations. The other parameters, such as the density ratio, the effluent Froude number and the velocity or momentum ration, may be slightly mismatched (say, within a factor of 2), if necessary, for buoyancy-dominated plumes. © 1990.