Quadrature-based Lattice Boltzmann model for non-equilibrium dense gas flows

TL;DR

This paper introduces a quadrature-based Lattice Boltzmann model for non-equilibrium dense gas flows, incorporating the simplified Enskog collision operator and Shakhov term to efficiently simulate non-ideal dense gases with good accuracy.

Contribution

It develops a computationally efficient Lattice Boltzmann model using a simplified Enskog operator for dense gases, improving simulation of non-equilibrium flows.

Findings

Accurately simulates sound and shock wave propagation in dense gases.

Shows good agreement with particle methods for small to moderate densities.

Offers a practical, faster alternative for dense gas flow modeling.

Abstract

The Boltzmann equation becomes invalid as the size of gas molecules is comparable with the average intermolecular distance. A better description is provided by the Enskog collision operator, which takes into account the finite size of gas molecules. This extension implies non-local collisions as well as an increase in collision frequency, making it computationally expensive to solve. An approximation of the Enskog collision operator, denoted the simplified Enskog collision operator, is used in this work to develop a quadrature-based Lattice Boltzmann model for non-ideal monatomic dense gases. The Shakhov collision term is implemented in order to fine-tune the Prandtl number. This kinetic model is shown to be able to tackle non-equilibrium flow problems of dense gases, namely the sound wave and the shock wave propagation. The results are compared systematically with the results of the more accurate but computationally intensive particle method of solving the Enskog equation. The model introduced in this paper is shown to have good accuracy for small to moderate denseness of the fluid (defined as the ratio of the molecular diameter to the mean free path) and, due to the efficiency in terms of the computational time, it is suitable for practical applications.