2D Static Droplet Simulation with Shan-Chen Multiphase Lattice Boltzmann Model Bagdagul Dauyeshova*, Ernesto Monaco † , Luis R. Rojas-Solórzano * * Nazarbayev University, School of Engineering, Bldg. 6, 53 Kabanbay batyr ave., Astana, Kazakhstan, 010000. † Department of Mathematics, 11 Cauerstrasse, Erlangen, Germany, 91058. Corresponding author: bagdagul.dauyeshova@nu.edu.kz Keywords: Lattice Boltzmann, Multiphase flow, Shan-Chen model, Spurious currents, Density ratio. Abstract This paper presents the assessment of the capability of Shan- Chen (SC) Multiphase Lattice Boltzmann Model (LBM) to accurately predict the liquid-gas interface in multiphase flow. Multiphase flow can be found in various applications, as for example, in CO 2 sequestration. One of the challenges for numerical models of such multiphase flows is being able to capture correctly the interface where liquid/gas phase transition happens. In this study, we analyse how parameters such as density ratio and temperature range affect the magnitude of unphysical velocity fields at the interface. The assessment of the model is performed by observing the change in unphysical velocity at the vicinity of the interface under input variations and as the result of domain discretization limits. Several static droplet tests were performed with different conditions of input variables using DL_MESO Lattice Boltzmann Equation (LBE). The SC model is found to present numerical instability for liquid-gas density ratios above 33 and at reduced temperature of below 0.67, and the magnitude of unphysical velocity also increases dramatically. The results of the assessment demonstrate the current limitations of SC LBM when used in the simulation of liquid/gas flows at moderate or low temperatures and high liquid-gas density ratios. 1. Introduction Multiphase flow in porous media is found in many applications, including oil recovery, geological sequestration of CO 2 , underground pollutant remedy and proton exchange membrane fuel cell (PMEFC). CO 2 is mainly formed during combustion of fossil fuels for energy and power generation. Especially, in some countries which heavily rely on conventional sources of energy such as oil and coal, CO 2 can be produced excessively [1]. CO 2 sequestration (storage) is a part of current undergoing major Carbon Dioxide Capture and Storage (CCS) projects. CCS is considered to be one of the most promising solutions to the need of decreasing CO 2 emissions, which are mostly produced during power generation [2]. As part of one of the most effective CO 2 sequestration strategies, it is essential to investigate and model CO 2 and brine (resident fluid) multiphase flow in deep porous underground and predict the proper conditions for safe and efficient CO 2 storage in these formations. Modeling the multiphase flow in such complex geometries involving small-scale pores represents an important challenge in computational fluid dynamics (CFD) based on solution of Navier-Stokes equations [3]. Therefore, Lattice Boltzmann Methods (LBM) have arisen as a meso-scale CFD method capable of dealing with the complexity of micro-scales correctly, while reproducing the macro-scales typically depicted by a significant number of different flows. Nevertheless, even though LBM has shown potential to be applied successfully for simulation of CO 2 -brine multiphase flow in deep underground porous media, the method has still the challenge of treating large density and viscosity ratios between the fluid phases present in the flow [3]. Indeed, to date multiphase LBMs are known for their limitations when applied for simulation of multiphase flows with high density ratio, as this leads to increase in spurious currents (unphysical velocity at the vicinity of phase interface) [3]. Strong unphysical currents around the fluid interfaces are undesirable, especially for flows with low velocity magnitudes. In fact, if the magnitude of the spurious currents at the interface are of the same order as the magnitude of local flow velocity, this can eventually lead to meaningless results [3]. Therefore, before applying a multiphase LBM to a complex system such as CO 2 simulation in porous media, a number of tests need to be done to ensure that the model is able to handle the interface between the phases (fluid-fluid interaction). Shan-Chen (SC) is a multiphase LBMs that has been successfully used in numerous studies [4, 5, 6]. SC LBM has proven to lead to accurate results when set up correctly [7]. In SC model, interactions between fluid particles are handled by adding a force term that takes into account phase separation and also surface tension effects [8]. In this paper we focus on fluid-fluid interaction by analysing the phase interface. In doing so, one of the first steps is to look at the static droplet case. In this paper, we use SC multiphase LBM to analyse static interface and give detailed description of the method used and report its limitations, as well as potential improvements to better apply it to the case of interest.