The unsteady term has both explicit and implicit terms, but this is not equal to say that the time discretization is explicit, as it depends on how the convection and diffusion terms are discretized.nIn any case, based on the results that I have previously obtained, my intuition says that the UDS is not solved in the same way as the volume fraction equation for explicit VOF. I have not encountered important convergence problems in steady simulations with the UDS, while it is not possible to use a steady solver for explicit VOF.n