TY - JOUR T1 - Numerical Study of Surfactant-Laden Drop-Drop Interactions AU - Jian-Jun Xu, Zhilin Li, John Lowengrub & Hongkai Zhao JO - Communications in Computational Physics VL - 2 SP - 453 EP - 473 PY - 2011 DA - 2011/10 SN - 10 DO - http://doi.org/10.4208/cicp.090310.020610a UR - https://global-sci.org/intro/article_detail/cicp/7450.html KW - AB -

In this paper, we numerically investigate the effects of surfactant on drop-drop interactions in a 2D shear flow using a coupled level-set and immersed interface approach proposed in (Xu et al., J. Comput. Phys., 212 (2006), 590–616). We find that surfactant plays a critical and nontrivial role in drop-drop interactions. In particular, we find that the minimum distance between the drops is a non-monotone function of the surfactant coverage and Capillary number. This non-monotonic behavior, which does not occur for clean drops, is found to be due to the presence of Marangoni forces along the drop interfaces. This suggests that there are non-monotonic conditions for coalescence of surfactant-laden drops, as observed in recent experiments of Leal and co-workers. Although our study is two-dimensional, we believe that drop-drop interactions in three-dimensional flows should be qualitatively similar as the Maragoni forces in the near contact region in 3D should have a similar effect.