Droplet behavior in the presence of insoluble surfactants

The time-dependent behavior of droplets in the presence of insoluble surfactants, i.e., droplet elongation in supercritical flow (capillary number Ca=0.1) and droplet breakup in a quiescent matrix, is studied using a finite element method. The interfacial tension coefficient sigma as a function of the surfactant concentration Gamma is described using the Langmuir equation of state, sigma=sigma(0)+RTGamma(infinity) ln(1-Gamma/Gamma(infinity)). For droplets in an equal viscosity system, the influence of parameters Gamma, Gamma(infinity), and the Peclet number (ratio between surfactant convection and diffusion rate) on the elongation behavior has been investigated, whereas droplet breakup is considered for various values of the Peclet number for trace concentrations Gamma