Dissipative particle dynamics simulation of droplet suspension in shear flow at low Capillary number

摘要

The dissipative particle dynamics (DPD) method is used to simulate droplet suspension. The deformation of a single droplet is first studied to validate the method and a good agreement with previous theoretical, numerical and experimental results is obtained. Droplet-droplet interaction is calibrated by simulating the process of two droplets collision. A larger repulsion force is imposed between particles from different droplet to prevent two droplets from coalescing. Dilute to semi-dilute emulsions are simulated with more than a hundred droplets suspended in another immiscible fluid. Shear thinning and non-zero normal stress differences are captured in the simulations. These phenomena are related with the mean droplet deformation parameter and mean inclination angle. The droplet deformation contributes to the increasing of suspension viscosity. Decreasing the inclination angle aligns the droplets more with the flow direction, contributing more to shear thinning. Fluid inertia increases the suspension viscosity. A good agreement is achieved between our zero shear viscosity results and previous model/experimental work.