Session MB - Drops I. Emulsions & Drops.
MIXED session, Tuesday afternoon, November 23
Grand II, Westin Seattle
We numerically investigate the rheological response of an emulsion in an oscillating extensional flow at finite Reynolds number. The rheology of an emulsion of drops is dependent on the morphology, viz. size, shape and orientation of drops. Till date, research on drop deformation and rheology has mostly been restricted to steady linear flows. We use Front-tracking method to compute deformation of a drop, and obtain excess stress by Batchelor’s formula. Drop-drop interactions are neglected. We investigate the relation between excess interfacial stress and imposed strain rate, varying interfacial tension, flow frequency, and inertia. The stress-strain relation is a function of the phase between the drop deformation and the imposed flow. At low Reynolds number, the simulation recovers the linear oscillatory rheology (loss and storage moduli) of Oldroyd and Bousmina. At low surface tension, the excess stress is predominantly elastic, while at high surface tension it is viscous. Increased drop inertia leads to resonance and complex phase in drop deformation. The resulting excess interfacial stress displays a non-monotonic variation with frequency and obtains a negative elastic modulus at low frequency.