The focus of this effort is to investigate the dispersal of liquid fire suppression agents around solid obstacles, and obtain a better understanding of the physical processes of droplet transport in cluttered spaces. An experimental investigation is presented to examine the flow field dynamics of highly turbulent flow over obstacles, and spray transport in such flow fields. The obstacles of interest were a cylinder and body-centered cube (BCC) arrangement of spheres. Transport of both water droplets and seed particles was characterized upstream and downstream of these obstacles using particle image velocimetry (PIV). Data were recorded 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 disperse radially away from the surface regardless of their interaction with the cylinder. The flow over the heated cylinder indicates the formation of layer of vaporizing liquid on the downstream side of the cylinder in the shear region between the recirculation zone and free stream. In addition, surface cooling that resulted from spray impingement was around 50 % of the preset cylinder temperature. For the BCC (with a blockage ratio of about 64 %), there is both transport of droplets and seed particles around and through the BCC, as well as significantly more liquid accumulation and dripping than for the cylinder.
Citation: Special Publication (NIST SP) - 984-4
NIST Pub Series: Special Publication (NIST SP)
Pub Type: NIST Pubs