Assessment and modification of sub-cell-fix method for re-initialization of level-set distance function

Sub-cell-fix re-initialization method was proposed by Russo and Smereka (J. Comput. Phys. 2000; 163: 51-67) as a modification to the re-distancing, algorithm Of Sussman et al. (J. Comput. Phys. 1994; 114: 146-159) that determines the distance function from an interface known as the zero level-set. The principal goal of sub-cell-fix method is to compute the distance function of the cells adjacent to the zero level-set without disturbing the original zero level-set. Following the original work of Russo and Smereka, several improved sub-cell-fix schemes were reported in the literature. In this paper, we show that in certain situations almost all the previous sub-cell-fix schemes can disturb the zero level-set, and the accuracy would not improve when the CFL numbers are decreased. Based on the scheme of Hartmann et al. (J Comput. Phys. 2008; 227:6821-6845), we propose all improved sub-cell-fix scheme that can significantly increase the accuracy of sub-cell-fix method on problems that are challenging. The scheme makes use of a combination of the points adjacent to zero level-set surfaces and preserves the interface in a second-order accuracy. The new sub-cell-fix scheme is capable of handling large local Curvature, and as a result it demonstrates satisfactory performance on several challenging test cases. Limitations of the schemes on highly stretched grids are illustrated. Copyright (C) 2009 John Wiley & Sons, Ltd.