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Computational Analysis of Binary Collisions of shear-thinning Droplets

Focke, Christian and Bothe, D. (2011):
Computational Analysis of Binary Collisions of shear-thinning Droplets.
166, In: Journal of Non-Newtonian Fluid Mechanics, (14-15), pp. 799-810, [Article]

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

Item Type: Article
Erschienen: 2011
Creators: Focke, Christian and Bothe, D.
Title: Computational Analysis of Binary Collisions of shear-thinning Droplets
Language: English
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

Journal or Publication Title: Journal of Non-Newtonian Fluid Mechanics
Volume: 166
Number: 14-15
Uncontrolled Keywords: head on collision; lamella stabilization; free surface flow; VOF method
Divisions: Exzellenzinitiative > Clusters of Excellence > Center of Smart Interfaces (CSI)
04 Department of Mathematics > Mathematical Modelling and Analysis
Zentrale Einrichtungen
04 Department of Mathematics
Exzellenzinitiative
Exzellenzinitiative > Clusters of Excellence
Exzellenzinitiative > Graduate Schools > Graduate School of Computational Engineering (CE)
Exzellenzinitiative > Graduate Schools
Date Deposited: 06 Apr 2011 12:19
Identification Number: doi:10.1016/j.jnnfm.2011.03.011 (2011
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