FFT-LB modeling of thermal liquid-vapor systems

TL;DR

This paper introduces an improved thermal lattice Boltzmann model for multiphase flows that uses FFT for better accuracy, energy conservation, and interface sharpness, validated by phase diagram and Laplace law comparisons.

Contribution

The paper develops a novel FFT-based approach within the thermal LB model, significantly enhancing accuracy and physical fidelity in simulating liquid-vapor systems.

Findings

Reduced spurious velocities at interfaces

Enhanced energy conservation and accuracy

More consistent phase diagrams with theoretical predictions

Abstract

We further develop a thermal LB model for multiphase flows. In the improved model, we propose to use the FFT scheme to calculate both the convection term and external force term. The usage of FFT scheme is detailed and analyzed. By using the FFT algorithm spatiotemporal discretization errors are decreased dramatically and the conservation of total energy is much better preserved. A direct consequence of the improvement is that the unphysical spurious velocities at the interfacial regions can be damped to neglectable scale. Together with the better conservation of total energy, the more accurate flow velocities lead to the more accurate temperature field which determines the dynamical and final states of the system. With the new model, the phase diagram of the liquid-vapor system obtained from simulation is more consistent with that from theoretical calculation. Very sharp interfaces can be achieved. The accuracy of simulation results are also verified by the Laplace law. The FFT scheme can be easily applied to other models for multiphase flows.