FLAIR - FLUX LINE-SEGMENT MODEL FOR ADVECTION AND INTERFACE RECONSTRUCTION

A computational technique for solving fluid problems with free surfaces and interfaces is presented. The conventional cell volume fraction approach is employed for tracking the interfaces. However, for surface advection and its reconstruction, a new and more accurate FLAIR (flux line-segment model for advection and interface reconstruction) algorithm is developed. The surface is approximated by a set of line segments fitted at the boundary of every two neighboring computational cells. A criterion is developed for identifying the line-segment orientation by inspecting the cell volume fractions. The new cell volume fraction field is obtained by integrating the advected area underneath the interface line-segment. As an example, this technique is applied to the capillary driven viscous flow of an initially elliptic, two-dimensional fluid zone. The problem is posed mathematically as a solution of the Navier-Stokes equations with moving free surface boundary conditions. The damping motion of the fluid zone is observed through transport of the free surface, which is related to the instantaneous internal velocity field under the influence of surface tension and viscous forces. © 1991.