Numerical simulation of high Schmidt number flow over a droplet by using moving unstructured mesh

A direct numerical simulation code for flow over a droplet, which rises freely, deforms in shape, and dissolves into a continuous phase, was developed. A two-phase flow field was discretised by a cell-centred arbitrary Lagrangian-Eulerian finite volume formulation by using three-dimensional hybrid unstructured meshes, which consist of triangular prisms near interface for the resolution of viscous boundary layer and tetrahedrons in the other part. Since mass boundary layer is much thinner than that of momentum for high Schmidt number problems, very-thin-layer cells are generated within one layer of the prisms attached to the interface only for solving mass transfer. This can be claimed as a novelty of the present simulation method. From the simulation results, the mechanisms of shape deformation and/or oscillation, trajectory morphology, and vortex shedding are elucidated and correlated to mass transfer at moderately high Reynolds number.