Gauge–Uzawa methods for incompressible flows with variable density

Two new Gauge–Uzawa schemes are constructed for incompressible flows with variable density. One is in the conserved form while the other is in the convective form. It is shown that the first-order versions of both schemes, in their semi-discretized form, are unconditionally stable. Numerical experiments indicate that the first-order (resp. second-order) versions of the two schemes lead to first-order (resp. second-order) convergence rate for all variables and that these schemes are suitable for handling problems with large density ratios such as in the situation of air bubble rising in water.