Improved interface identification methods for Coupled Level-Set Volume-of-Fluid solvers

Simulations of primary atomisation must track interface evolution accurately in order to correctly model droplet dynamics. For grid-based methods such as the Volume-of-Fluid methods (VOF), interface cells must first be identified precisely, accounting for interface smearing in the VOF field. This is especially true where additional models, such as evaporation, are applied only to interface cells. The level-set field (LS) is often coupled with a VOF solver to enhance interface identification and orientation. Using a CLSVOF solver, various novel and traditional interface identification methods are compared and contrasted for different mesh resolutions, making use of both the LS and VOF fields. These include thresholds on LS and VOF fields and their gradients; direct vector bounding on LS; projected vertex bounding on LS, and LS linear interpolation. Results reveal that all level-set schemes identified a more precise thinner interface than the diffusive VOF scheme, and did not display as significant an overshoot, both for the number of cells identified and the radii of those cells. LS Interpolation was found to be the most accurate and reliable overall, but may be cost-prohibitive for rapid evaluation on larger grids. This could however be mitigated by interpolating only in cells identified as possibly interfacial by a cheaper, simpler scheme such as ‘LS Upper Bound’. Moreover, the ‘LS Projected Vertex Bound’ scheme was found to be twice as fast, with superior stability and precision, although it identified fewer cells on average. This method was found to provide the best balance between accuracy and cost.<p></p>