Simulations of surfactant-laden drops rising in a density-stratified medium
Phys. Rev. Fluids 2, 023602 – Published 27 February, 2017
DOI: https://doi.org/10.1103/PhysRevFluids.2.023602
Abstract
We present simulations of the effects of insoluble surfactant on drops rising in unstratified media and density-stratified media. We consider an oil drop rising in water, and we track surfactant concentration on the drop surface. We first consider a drop coated with insoluble surfactant rising through an unstratified ambient. The drop speed is computed for various Marangoni numbers, and inertial and surface diffusion effects are also examined. In the second setup, we compare clean and contaminated drops rising through a linear density-stratified fluid. The entrained buoyancy is computed for various density gradients, and the effects of inertia and Marangoni number are characterized. We find that the entrained fluid slows the drop in a manner comparable to a vertical shift in the ambient density gradient.