Fluid dynamics and mass transfer of interacting drops -a mathematical modelling approach

Abstract

An accurate and computationally efficient description of the transport mechanisms of accelerating, interacting drops in a gaseous environment is important for the basic understanding of this particular class of two-phase flows and for the improvement/design of trace gas absorption, dense spray, and fuel droplet combustion processes. Modelling of such a complex system requires: (i) a system conceptualization which renders the multiple drop analysis mathematically tractable, (ii) the development of governing equations detailed and flexible enough to represent differential as well as integral system parameters, and (iii) an accurate and efficient numerical scheme for a useful computer simulation model. We started out with a lumped parameter approach where trace gas absorption with chemical reaction in a jet-like stream of falling drops was considered. This analysis yielded the aerodynamics of the jet-induced entrainment corridor, the velocities of the accelerating drops, and the mass transfer rate of ambient trace gases into the stream of drops. In order to gain more insight into the dynamics of interacting drops, we developed a distributed parameter model for the coupled two-phase momentum/mass transfer of spherical drops in the Reynolds number range 50 <Re <400. After model verification, the influence of major system parameters, e.g. inter-drop distance, reaction rate, Peclet numbers etc., was analyzed in well-defined computer experiments. Presently, the local two-drop analysis is being integrated into the global stream-of-drops configuration.