Hydrodynamic analysis of one deformed double emulsion droplet under shear

Abstract

The hydrodynamics of one double emulsion droplet under shear is investigated on the basis of a computational fluid dynamic simulation with the volume-of-fluid (VOF) method. The morphological features of the deformed double emulsion droplet at steady state are quantitatively characterized by the deformation and tilt angles, and the potential mechanisms are explored through analyzing pressure and flow information. The existence of the inner droplet engenders two effects (namely enhancing effect and restraining effect) on the outer droplet deformation D out, determined by which mechanism in a dominant position. With the increase in k, the character of the inner droplet on D out transforms from enhancing effect into restraining effect under smaller Ca out, while under larger Ca out the restraining effect is presented in the leading role that inner droplet with different k all inhibits the outer droplet deformation. As the interfacial tension ratio increases under constant Ca out, the higher-pressure region at the tip of the inner droplet turning to the “throat” region and the tilt angle θ in enlarging both restrain the deformation D out. In addition, with the increasing viscosity ratio λ 12, the outer droplet deformation D out increases whereas the inner droplet gets smaller deformation; the tilt angles θ in and θ out both increase and their tilt angle difference gradually increases.