density -- List of fluid phases densities (this should be a vector whom dimension specify if there is one or two fluid)
sigma -- Surface tension (only when there are two fluids)
coeff_stab -- Optional argument used as coefficient for extra diffusivity added to stabilise the advection of concentration (only for two fluid problem)
solver -- possible solver are "mumps", "petsc", "scipy"
solver_options -- Optional argument to specify solver option (only when petsc is used)
solver -- possible solver are "mumps", "petsc", "petsc4py", "scipy"
solver_options -- Optional argument to specify solver option (petsc options or mumps parameters)
drag_in_stab -- States if the drag force is in the stabilisation term
drag_coefficient_factor -- Factor multiplicating the drag coefficient