Lattice Boltzmann methods for multiphase flow and phase-change heat transfer

Over the past few decades, tremendous progress has been made in the development of particle-based discrete simulation methods versus the conventional continuum-based methods. In particular, the lattice Boltzmann (LB) method has evolved from a theoretical novelty to a ubiquitous, versatile and powerful computational methodology for both fundamental research and engineering applications. It is a kinetic-based mesoscopic approach that bridges the microscales and macroscales, which offers distinctive advantages in simulation fidelity and computational efficiency. Applications of the LB method are now found in a wide range of disciplines including physics, chemistry, materials, biomedicine and various branches of engineering. The present work provides a comprehensive review of the LB method for thermofluids and energy applications, focusing on multiphase flows, thermal flows and thermal multiphase flows with phase change. The review first covers the theoretical framework of the LB method, revealing certain inconsistencies and defects as well as common features of multiphase and thermal LB models. Recent developments in improving the thermodynamic and hydrodynamic consistency, reducing spurious currents, enhancing the numerical stability, etc., are highlighted. These efforts have put the LB method on a firmer theoretical foundation with enhanced LB models that can achieve larger liquid-gas density ratio, higher Reynolds number and flexible surface tension. Examples of applications are provided in fuel cells and batteries, droplet collision, boiling heat transfer and evaporation, and energy storage. Finally, further developments and future prospect of the LB method are outlined for thermofluids and energy applications

Comparison of multiphase SPH and LBM approaches for the simulation of intermittent flows

Smoothed Particle Hydrodynamics (SPH) and Lattice Boltzmann Method (LBM) are increasingly popular and attractive methods that propose efficient multiphase formulations, each one with its own strengths and weaknesses. In this context, when it comes to study a given multi-fluid problem, it is helpful to rely on a quantitative comparison to decide which approach should be used and in which context. In particular, the simulation of intermittent two-phase flows in pipes such as slug flows is a complex problem involving moving and intersecting interfaces for which both SPH and LBM could be considered. It is a problem of interest in petroleum applications since the formation of slug flows that can occur in submarine pipelines connecting the wells to the production facility can cause undesired behaviors with hazardous consequences. In this work, we compare SPH and LBM multiphase formulations where surface tension effects are modeled respectively using the continuum surface force and the color gradient approaches on a collection of standard test cases, and on the simulation of intermittent flows in 2D. This paper aims to highlight the contributions and limitations of SPH and LBM when applied to these problems. First, we compare our implementations on static bubble problems with different density and viscosity ratios. Then, we focus on gravity driven simulations of slug flows in pipes for several Reynolds numbers. Finally, we conclude with simulations of slug flows with inlet/outlet boundary conditions. According to the results presented in this study, we confirm that the SPH approach is more robust and versatile whereas the LBM formulation is more accurate and faster

Modeling realistic multiphase flows using a non-orthogonal multiple-relaxation-time lattice Boltzmann method

In this paper, we develop a three-dimensional multiple-relaxation-time lattice Boltzmann method (MRT-LBM) based on a set of non-orthogonal basis vectors. Compared with the classical MRT-LBM based on a set of orthogonal basis vectors, the present non-orthogonal MRT-LBM simplifies the transformation between the discrete velocity space and the moment space, and exhibits better portability across different lattices. The proposed method is then extended to multiphase flows at large density ratio with tunable surface tension, and its numerical stability and accuracy are well demonstrated by some benchmark cases. Using the proposed method, a practical case of a fuel droplet impacting on a dry surface at high Reynolds and Weber numbers is simulated and the evolution of the spreading film diameter agrees well with the experimental data. Furthermore, another realistic case of a droplet impacting on a super-hydrophobic wall with a cylindrical obstacle is reproduced, which confirms the experimental finding of Liu \textit{et al.} [``Symmetry breaking in drop bouncing on curved surfaces," Nature communications 6, 10034 (2015)] that the contact time is minimized when the cylinder radius is comparable with the droplet cylinder.Comment: 19 pages, 11 figure

Simulation of droplet impacting a square solid obstacle in microchannel with different wettability by using high density ratio pseudopotential multiplerelaxation- time (MRT) lattice Boltzmann Method (LBM)

In this paper, a pseudopotential high density ratio (DR) lattice Boltzmann Model was developed by incorporating multi-relaxation-time (MRT) collision matrix, large DR external force term, surface tension adjustment external force term and solid-liquid pseudopotential force. It was found that the improved model can precisely capture the two-phase interface at high DR. Besides, the effects of initial Reynolds number, Weber number, solid wall contact angle (CA), ratio of obstacle size to droplet diameter ( 1 χ ), ratio of channel width to droplet diameter ( 2 χ ) on the deformation and breakup of droplet when impacting on a square obstacle were investigated. The results showed that with the Reynolds number increasing, the droplet will fall along the obstacle and then spread along both sides of the obstacle. Besides, by increasing Weber number, the breakup of the liquid film will be delayed and the liquid film will be stretched to form an elongated ligament. With decreasing of the wettability of solid particle (CA→ 180°), the droplet will surround the obstacle and then detach from the obstacle. When 1 χ is greater than 0.5, the droplet will spread along both sides of the obstacle quickly; otherwise, the droplet will be ruptured earlier. Furthermore, when 2 χ decreases, the droplet will spread earlier and then fall along the wall more quickly; otherwise, the droplet will expand along both sides of the obstacle. Moreover, increasing the hydrophilicity of the microchannel, the droplet will impact the channel more rapidly and infiltrate the wall along the upstream and downstream simultaneously; on the contrary, the droplet will wet downstream only

Impact de gouttelette et changement de phase par la méthode de Boltzmann sur réseau

RÉSUMÉ Les écoulements multiphasiques avec changement de phase et transfert de chaleur interviennent dans de nombreuses applications industrielles et processus naturels. Malgré le développement rapide des outils numériques, la simulation numérique d’écoulements fluides à plusieurs phases immiscibles demeure un défi en raison de la difficulté inhérente à suivre les interfaces. Habituellement, pour résoudre ce type d’écoulement, des méthodes numériques basées sur les équations de Navier Stokes couplées à des méthodes lagrangiennes ou eulériennes sont utilisées. Cependant, ces dernières décennies, la méthode Boltzamnn sur réseau est apparue comme une méthode prometteuse pour simuler les écoulements à géométrie complexe et à plusieurs phases. Dans ce contexte, l’objectif principal de cette thèse est de développer un modèle multiphasique 3D basé sur la méthode de Boltzmann sur réseau capable d’étudier l’impact d’une gouttelette sur une surface et de traiter les changements de phase. Pour ce faire, le modèle pseudo-potentiel de Shan & Chen pour la simulation d’écoulement à plusieurs phases et plusieurs composants est utilisé comme point de départ. Cette recherche doctorale est organisée autour de trois thèmes afin de mettre en évidence les contributions. Des cas tests sont réalisés afin de valider les améliorations apportées au modèle et des applications physiques sont proposées. Le premier thème apporte une amélioration au modèle pseudo-potentiel en découplant la tension de surface et la densité. Le tenseur de pression du modèle 3D est modifié pour permettre un ajustement de la tension de surface tout en préservant la consistance thermodynamique. Dans ce thème, l’étude de l’impact d’une gouttelette sur une surface sèche et mouillée est analysée. Le thème 2 généralise la méthode de modification du tenseur de pression aux cas d’écoulements à plusieurs composants, dont la viscosité des fluides est différente. Il permet de simuler des écoulements à ratios de densité et de viscosité élevés. Enfin, le thème 3 ajoute les effets thermiques au modèle multiphasique à plusieurs composants. Le changement de phase et les échanges de chaleur entre composants sont étudiés. Pour chacun des thèmes, un article scientifique a été rédigé et soumis à un journal. ----------ABSTRACT Multiphase flows with phase change and heat transfer occur in many industrial applications and natural processes. Despite the rapid development of numerical tools, the numerical simulation of fluid flows with multiple immiscible phases remains a challenge because of the inherent difficulty for tracking the interfaces. Usually, to solve this type of flows, numerical methods based on Navier Stokes equations coupled with Lagrangian or Eulerian methods are used. However, in recent decades, the Boltzmann method has emerged as a promising approach for simulating complex geometry flows and multiphase flows. In this context, the main objective of this thesis is to develop a 3D multiphase model based on the Boltzmann method which can study droplet impingement on a surface and analyze the phase change. To do this, the pseudo-potential model of Shan & Chen for simulating multiple phases and components flows is used as a starting point. This doctoral research is organized around three themes in order to highlight the contributions of this thesis. Test cases are carried out to validate the improvements made to the model and physical applications are proposed. The first theme improves the pseudo-potential model by decoupling the surface tension and the density. The pressure tensor of the 3D model is modified to allow an adjustment of the surface tension while preserving the thermodynamic consistency. In this topic, the study of the impingement of a droplet on a dry and wet surface is analyzed. Theme 2 generalizes the modification of the pressure tensor to cases of multi-component flows with different fluid viscosities. It allows simulating flows with high density and viscosity ratios. Finally, the theme 3 adds thermal effects to the multiphase multi-component model. Phase change and heat exchanges between components are studied. For each of the themes, a scientific article was written and submitted to a journal. These articles are presented in this document as a chapter