Quantification of airborne odor plumes using planar laser-induced fluorescence

Abstract

Planar laser-induced fluorescence (PLIF) is used to quantify spatiotemporal structure of gaseous scalar plumes (Sc $$\approx 1.5$$ ) in a benchtop-scale low-speed wind tunnel. The study is motivated by a desire to understand variations in information content in odor plumes used by animals for navigation. Acetone vapor is used as a fluorescent odor surrogate and is released isokinetically to form a neutrally buoyant plume. Three cases are investigated: a near-bed scalar release at 10 cm/s, a freestream scalar release at 10 cm/s, and a second freestream scalar release at 20 cm/s. PLIF image data are collected at 15 Hz and processed to provide distributions of instantaneous concentrations. Spatial distributions of mean concentration, root-mean-square fluctuations, and concentration intermittency are presented, along with probability density functions of concentrations at select locations. The results demonstrate significant differences in spatiotemporal structure of the scalar plumes across the three tested cases. In particular, the near-bed plume is markedly different from those released in the freestream. The results have important implications for understanding gaseous plume structure. Specifically, the results suggest that different flow and release conditions control constraints and opportunities for animals using odor plumes for navigational purposes.