Comment on the level-set method used in 'Numerical study onmobilization of oil slugs in capillary model with level set approach'

This is a comment on a 2014 paper by Dai and Wang. It is argued that the validation in Dai and Wang's paper is an artifact caused by the boundary conditions of the level-set function, meaning that the effects reported in their paper have little physical relevance. Simulations are presented using Dai and Wang's methods to illustrate this claim. Remarks are made on the choice of boundary conditions for the level-set function, as well as the frequency of reinitialization, both of which are important topics that are sometimes overlooked. A simple criterion is proposed for determining the appropriate reinitialization frequency in simulations of highly viscous flows.