Droplet-Laden Homogeneous Turbulent Flow Over Unheated and Heated Cylinders

The dispersal of high boiling point liquid fire suppression agents around solid obstacles is investigated to obtain a better understanding of the physical processes of droplet transport in cluttered spaces. To this end, the present experimental investigation examines the flow field dynamics of grid-generated homogeneous turbulent flow over obstacles, and spray transport in such flow fields. Transport of both water droplets and aerosol particles was characterized upstream and downstream of a cylinder using particle image velocimetry (PIV). Data were obtained for the cylinder at ambient temperature and after being heated to 423 K to estimate the effects of the hot cylinder surface on droplet transport. The results indicate that smaller droplets are entrained into the recirculation region behind the cylinder while the larger droplets impact the cylinder surface, accumulate and drip off, or are transported around the surface. The flow over the heated cylinder indicates the formation of a vapor layer on the downstream side of the cylinder in the shear region between the recirculation zone and free stream. Thus, vaporization of smaller droplets near the heated cylinder surface suggests an increased probability of vapor, and reduced probability of droplet entrainment into cylinder wake region.