Modulation of spray droplet number density and size distribution by an Acoustic Field

Multiple interactions may occur when a poly-disperse spray is immersed in an acoustic field. In the context of spray combustion instabilities, acoustic agglomeration, the formation of a droplet number density wave and the modulation of the droplet size distribution are important effects. A droplet number density wave, i.e. preferential concentration of droplets in space, may result from sizedependent, one-way momentum coupling between the acoustic field and the spray. The modulation of the droplet size distribution, which has been evidenced in the experimental work of Gurubaran and Sujith (AIAA 2008-1046), is then a consequence of the droplet number density wave formation. In the present work the mechanisms that produce these effects, including acoustic agglomeration, are simulated and analyzed in depth by means of CFD. The spray is modeled with both Lagrangian (particles mass-point approach) and Eulerian (continuous phase approach) descriptions. The particular Eulerian method used is the presumed density function Method of Moments, which allows to account for the effects of poly-dispersity. Both the Lagrangian and Eulerian models are validated against experimental data for spray dynamics and spray response to an acoustic field.     «

Multiple interactions may occur when a poly-disperse spray is immersed in an acoustic field. In the context of spray combustion instabilities, acoustic agglomeration, the formation of a droplet number density wave and the modulation of the droplet size distribution are important effects. A droplet number density wave, i.e. preferential concentration of droplets in space, may result from sizedependent, one-way momentum coupling between the acoustic field and the spray. The modulation of the dr...     »