AIR FLOW AND DROPLET MOTIONS PRODUCED BY THE INTERACTION OF FLAT-FAN SPRAYS AND CROSS FLOWS

The interaction between the vertical flow induced by downward-pointed sprays and a horizontal cross flow was studied using a boom of overlapping flat-fan sprays in a wind tunnel. Flow patterns were visualized, and droplet fluxes, velocities, and sizes were measured 2 m downwind of the boom using line collectors and a phase-Doppler analyzer, under weak and moderate cross flows, in which the ratio of the cross-flow velocity to the maximum air entrainment velocity into the spray was respectively less and greater than unity. For weak cross flows, the spray was penetrated only in regions of low entrained air velocity, with downstream droplet fluxes and air velocity maxima corresponding to the spray edges. For moderate cross flows, the spray was penetrated everywhere across its width. Downstream flux measurements corresponded to the spray centerline, which is the origin of the highest flax of fine droplets that are "scavenged" by the mean cross flow. Drifting droplets had diameters less than 100 μm and were transported passively by the cross flow.