Wind Tunnel Experiments on Cooling Tower Plumes: Part 2—In a Nonuniform Crossflow of Boundary Layer Type

The basic characteristics of plumes issuing into a boundary layer-type crossflow are reported. The flow can be considered as an interaction between two vorticity fields with different length scales and turbulence intensities. The large eddies of the oncoming boundary layer are responsible for the observed sudden changes in the plume direction. The type of structure emanating from the tower depends on the instantaneous velocity ratio. Mean velocities and normal velocity gradients are smaller than those in the case of uniform crossflow and therefore, the measured turbulence intensities are lower too. The cross-stream turbulence brings high-momentum fluid into the wake region and the velocity defect decays very rapidly. Dilution of the plumes takes place faster in the presence of external turbulence than in the case with uniform crossflow. The spreading rate is increased dramatically by the external turbulence, which causes different effects on the hydrodynamic and thermal fields.