Dynamics of consumer sprays

The simulation of spray flows requires accurate description of the interaction of the drops with the gas phase. For this purpose there are two potential approaches. We model either the aerodynamic drag of the drops due to the motion of the drops relative to the gas phase, or, if applicable, the self-similar momentum transport in the spray flow between the liquid and the gas phases to represent the evolution of the mass and momentum fluxes. The former approach models the drag coefficient of spray drops in a group. The latter approach is restricted to self-similar spray regions. In our work we investigate the dynamics of consumer sprays from spray cans for body and textile care for predicting the transport and drying behavior of the spray drops with account for health risks from nanoparticle-laden sprays. We present an experimentally based analytical and numerical procedure to develop a model for the drop drag coefficient. The model relies on phase-Doppler measurement data revealing statistically the spray drop and gas-phase velocity evolutions in the flow field, so that the aerodynamic force can be deduced therefrom. The second approach showed that the gaseous velocity field exhibits self-similar behavior close to single-phase free jets, but with a momentum source due to the spray drops. Careful investigation of the data showed that the velocity profiles may be described as solutions of a self-similar differential equation. The two approaches combine in that the self-similar momentum source makes use of the aerodynamic drag force acting on the drops.