Effects of the relative humidity on the particle-laden jet with crossflow

Particle-laden airflows are attracting more attention driven by the on-going environmental issues. Our previous studies have shown that the particle-laden jet under a crossflow, being governed by the organized vortices, demonstrate different particle dispersion pattern according to the velocity ratio (R) between the jet and crossflow. Meanwhile, the relative humidity (RH) of the background airflow changes significantly depending on the time and space; however, the mechanism of the particle dynamics driven by the RH change has not yet been elucidated. In the present study, we experimentally investigate the particle concentration and dispersion by controlling the air RH within the range of 30 – 70 % in the particle-laden jet with crossflow. The R (jet/crossflow) is 1.1 – 2.85. Considering the wettability of particles as a major factor, we used hydrophilic particles of Silicon (contact angle (CA) ~ 33⁰) and hydrophobic particles of PTFE (CA ~ 100⁰). As a result, the concentration of the hydrophilic particles decays more rapidly for lower RH and low R. Conversely, the concentration decay rate of hydrophobic particles is independent of the RH.