Assessment of pseudo-potential lattice Boltzmann method for multiphase flows with real fluid properties

The multirange pseudo-potential lattice Boltzmann model (PP-LBM) for multiphase flows was implemented along with various strategies, including the multi-relaxation time collision operator and the so-called ??-scheme, to diminish the parasitic currents and enhance numerical stability. The PP-LBM predictions show an excellent agreement with the theoretical coexistence curve, given by Maxwell’s equal-area rule, for both Carnahan-Starling (CS) and Peng-Robinson (PR) equations of state (EOS). Increasing the isotropic order of the interaction force has a stronger impact on reducing the magnitude of the spurious velocities, as compared to the implementation of more sophisticated collision operators. Due to a satisfactory representation of the vapor-liquid coexistence curve and acentric factor dependence, the PR EOS is chosen to determine real fluid properties such as equilibrium densities and surface tension for a number of compounds, including n-alkanes (carbon number up to 10), ammonia, and hydrogen. For such paraffinic hydrocarbons, the average surface tension error lies in a range of 2.3-6.2%. Although PP-LBM suffers to accurately predict experimental equilibrium density values, the error is inherent to the PR EOS, as PP-LBM predicts well those given by Maxwell’s equal-area rule.