Article ID Journal Published Year Pages File Type
671003 Journal of Non-Newtonian Fluid Mechanics 2011 12 Pages PDF
Abstract

Scale-reduced models of transport processes and reactive mixing in sprays require improved closure laws, taking into account the characteristic features of elementary spray processes. The present paper investigates binary droplet collisions as such an elementary process. In the case of shear-thinning liquids considered here, this requires a profound understanding of the influence of the non-Newtonian fluid rheology on the flow inside the colliding drops and the collision complex dynamics. We employ direct numerical simulations based on the Volume-of-Fluid method to study these collisions. The results give a quantitative prediction of the resulting droplet collision diameter as well as a qualitative prediction of the complete time evolution. During collisions, extremely thin fluid lamellae appear inside the expanding complex. These have to be accounted for in a physically sound simulation and we apply a stabilization of the lamella to keep it from rupturing. The simulations show that in all considered cases an effective constant viscosity can be found a posteriori which leads to the same collision dynamics. But this effective viscosity is neither the mean nor the minimum viscosity.

► Numerical stabilization of thin fluid lamella allows for DNS of head-on collisions. ► VOF-simulations reveal an effective viscosity for shear thinning droplet collisions. ► Decomposition of total energy in DNS allows for classification of collision stages.

Related Topics
Physical Sciences and Engineering Chemical Engineering Fluid Flow and Transfer Processes
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