Near-critical CO2 liquid-vapor flow in a sub-microchannel. Part I: Mean-field free-energy D2Q9 lattice Boltzmann method

The mean-field free-energy based lattice Boltzmann method (LBM) is developed for the calculation of liquid-vapor flows in channels. We show that the extensively used common bounceback boundary condition leads to an unphysical velocity at the wall in the presence of surface forces that arise from any local forces such as gravity, fluid-fluid and fluid-solid interactions. We then develop a mass-conserving velocity-boundary condition which eliminates the unphysical velocities. An important aspect of the overall LBM model is the inclusion of the correct physics to simulate different wall wettabilities and dynamic contact lines. The model is applied to static and dynamic liquid-vapor interfacial flows and compared to theory. The model shows good agreement with three well established theories of contact line dynamics.