Fluctuating flow in a liquid layer and secondary spray created by an impacting spray

A spray impacting onto a wall produces a flow of secondary droplets. For relatively sparse spray these secondary droplets are produced by the splashing of the impacting drops and their interactions. For dense sprays, like Diesel injection sprays, these secondary droplets are created by the fluctuating liquid film created on the wall. In the present paper hydrodynamic models are presented for these two extreme cases. The velocities of the secondary droplets produced by the crown splash in a sparse spray are described theoretically. Next, the fluctuations in the motion of the liquid film created by a dense impacting spray are analyzed statistically. This motion yields the formation of finger-like jets, as observed in experiments of a Diesel spray impacting onto a rigid wall. The characteristic size and velocity of the film fluctuations are estimated. These two theoretical models are validated by comparison with the experimental data.