High density ratio lattice Boltzmann method simulations of multicomponent multiphase transport of H2O in air

In this paper we investigate the ability of the internode interaction force based multiphase lattice Boltzmann method to realistically model the coexistence of the gas and liquid phases of H2O at low temperatures. Additionally this method is expanded to include a gas mixture of O2 and N2 into the multiphase H2O systems. We begin with examining the phase transition region described by the current implementation of the multiphase internode interaction force lattice Boltzmann model. Next, we thoroughly investigated a modified form of the pressure term with the use of a scalar multiplier κ for the Peng-Robinson equation of state. This method proves to be very effective at enabling numerically stable simulations at low temperatures with large density ratios. We find that for decreasing values of κ, this model leads to an increase in multiphase interface thickness and a reduction in maximum spurious velocities. We show that although low temperatures and large density ratios are attainable using these modifications, the lowest temperature results should be discarded due to the non-physical density variations along the phase interface. Building on this insight we are able to simulate a liquid droplet of H2O at 73°C surrounded by humidified air (a mixture of H2O, O2, and N2) with realistic density ratios.