11th World Congress on Computational Mechanics (WCCM XI) 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI) E. O˜ nate, J. Oliver and A. Huerta (Eds) MODELLING SURFACE TENSION DOMINATED MULTIPHASE FLOWS USING THE VOF APPROACH JOHAN A. HEYNS ∗ AND OLIVER F. OXTOBY † Council for Scientific and Industrial Research (CSIR) P.O. Box 395, Pretoria, South Africa e-mail: ∗ jheyns@csir.co.za and † ooxtoby@csir.co.za Key words: Volume-of-fluid, Low-capillary number flows, Surface tension, Multiphase. Abstract. This study considers enhancements to the volume-of-fluid (VOF) approach to allow for the accurate modelling of low capillary or surface tension dominated flows. Conservative VOF approaches tend to result in the formation of spurious or parasitic currents due to sharp changes in gradient over the interface. With the aim of reducing this imbalance between the fluid pressure and the surface tension forces an alternative pressure interpolation scheme is evaluated. Furthermore, the continuum surface forces (CSF) method is extended to use a smoothed volume fraction field which is computed using an implicit diffusion-type algorithm. 1 INTRODUCTION Low-capillary number or surface tension dominated flows are found in a number appli- cations, ranging from small scale microfluidics up to larger scale analysis of microgravity sloshing. This paper evaluates the possibility of modelling of surface tension dominated multiphase flows using an Eulerian volume-of-fluid (VOF) approach with high-resolution surface capturing. With the aim of improved stability and computational efficiency, a conservative formulation is implemented that ensures parasitic currents are negligibly small. Level-set (LS) and VOF methods are extensively used in modelling multiphase flows as these approaches are easily extended to arbitrary unstructured three-dimensional meshes and allow for efficient scaling in parallel computation. When modelling surface tension dominated problems, LS methods allow for an accurate approximation of the curvature as it is based on a smooth, continuous approximation of the Heaviside equation. LS methods are, however, found to be non-conservative [2, 16] and require the reinitialisation of the distance function at regular time intervals to ensure a well maintained gradient [21]. It is noted that a number of studies suggested corrections to the LS approach to improve mass 1