Experiments on Spray Interactions in the Wake of a Bluff Body

Abstract

The dynamics of spray drop interaction within the turbulent wake of a bluff body were investigated using the Aerometrics Phase Doppler Particle Analyzer, which determines both drop size and velocity. Detailed measurements obtained included spray drop size, axial and radial velocity, angle of trajectory, and size-velocity correlations. The gas-phase flow field was also ascertained via the behavior of the smallest drops. Results showed dramatic differences in drop behavior when interacting with turbulence for the various size classes. Small drops were recirculated in a pair of toroidal vortices located behind the bluff body, whereas the larger drops followed the general direction of the spray cone angle. This was documented via backlit photography. Local changes in number density were produced as a result of lateral convection and streamwise accelerations and decelerations of various drop size classes. The spray field interaction illustrated by these data effectively reveals the complexity associated with the development of the spray and casts some doubts toward attempting to describe sprays via simple integral quantities such as the Sauter mean diameter.