Sharp interface simulations of surfactant-covered drops in electric fields

Abstract

A level-set method for computations of interfacial flows with insoluble surfactants with electric fields is presented. The discontinuities at the interface are captured in a sharp manner using the ghost-fluid method. The accuracy of the method is tested and compared to the standard level-set method. The method is then used to study the combined effect of insoluble surfactants and electric fields on the motion and deformation of a falling drop. It is found that the surfactant generally reduces the deformation and the terminal velocity of the drop. This reduction is most pronounced in the nearly spherical regime where the drop behavior is similar to a solid sphere due to the interface immobilization caused by the presence of a surfactant. The electric field increases the terminal velocity by stretching the drop in the direction of the electric field. This effect is largest for the surfactant-covered drop, which is deformed more due to the lower average interfacial tension.