Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session P41: Lattice Boltzmann Method and Applications |
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Chair: Tae Hun Lee, The City College of New York Room: 6c |
Monday, November 25, 2019 5:16PM - 5:29PM |
P41.00001: Fully implicit force splitting scheme to two-phase lattice Boltzmann equation in pressure-velocity formulation Taehun Lee We present a numerical procedure for solving the lattice Boltzmann equation (LBE) in the pressure-velocity formulation with the low Mach number approximation. We propose a unique algorithm based on the Strang splitting procedure to solve LBE for immiscible incompressible flows. Our procedure includes leading order intermolecular forcing terms within the streaming step, while keeping high-order forcing terms within the collision step such that conservative moments do not change due to collision. By coupling the finite difference/element method with a stable time-stepping technique, our scheme can easily handle stiff source term or external force. We will show that the perfect shift implementation is recovered under unity CFL condition as a special case of the proposed approach. The force splitting scheme is implemented in a fully implicit manner and applied to a novel pressure-velocity formulation of LBE. We have observed that the pressure-velocity formulation offers better numerical stability at high Reynolds numbers and reduced interfacial thickness, and the implicit formulation eliminates pressure oscillations. With the hope that this technique can be used for applications in complex geometries, benchmark calculations are performed on both uniform and non-uniform meshes. [Preview Abstract] |
Monday, November 25, 2019 5:29PM - 5:42PM |
P41.00002: Streaming Formulation in Volumetric Lattice Boltzmann Method and Its Improvement Huidan (Whitney) Yu, Xiaoyu Zhang Volumetric lattice Boltzmann method (LVBM) has been specifically developed to deal with complex flow domains with or without willfully moving boundaries (Yu, \textit{et al}, PRE, 2014). In the VLBM, fluid particles are uniformly distributed in lattice cells, instead of the traditional lattice nodes. A unique parameter, which represents the ratio of solid volume over the cell volume, is introduced to distinguish three types of lattice cells: solid cell (pure solid occupation), fluid cell (pure fluid occupation), and boundary cell (partial solid and partial fluid). Through this parameter, a volumetric bounce-back mechanism is uniquely included in the formulation of streaming process. As a result, extra interpolation/extrapolation to deal with arbitrarily oriented boundaries are avoided. Such a formulation significantly eases the handling of complicated geometries and promotes the computational efficiency without compromise of accuracy. In this work, we present the original formulation of the streaming process in VLBM and its modification. Quantitative validations in 3-D pulsatile duct flows with circular and rectangle cross sections respectively demonstrate the reliability of VLBM for solving unsteady flows.. [Preview Abstract] |
Monday, November 25, 2019 5:42PM - 5:55PM |
P41.00003: Mesoscale Modelling of Nano-Particle Growth Under Flow Rohan Vernekar, Timm Kr\"uger \par Nanoparticles have wide potential for future applications, from drug delivery to surface coatings. Control over (e.g.\ silica) nanoparticle morphology, size, porosity and dispersity is crucial for realisation of their use\footnote{Hyde, E. D. E. R. et al. Colloidal Silica Particle Synthesis and Future Industrial Manufacturing Pathways: A Review. Ind. Eng. Chem. Res. 55, 8891–8913 (2016).}. The physics of growth of such particles under flow conditions is not well understood, thus making their industrial scale-up challenging.\\ \\ We present a mesoscale lattice Boltzmann (LB) algorithm that models growth of nanoparticles under particle resolved flow conditions \textit{via} chemical species deposition. The method combines fluid LB for hydrodynamics, advection-diffusion LB for species transport with resolved Newtonian nanoparticle dynamics and a novel mesoscale adsorption boundary condition for growth\footnote{Kr\"uger, T. et al. The Lattice Boltzmann Method: Principles and Practice. (Springer International Publishing, 2017).}. The algorithm is benchmarked for various 2D cases and provides excellent results. Our method enables the study of flow effects on growth, morphology and size distribution of nanoparticle suspensions, and advances nanoscale particle synthesis modelling. [Preview Abstract] |
Monday, November 25, 2019 5:55PM - 6:08PM |
P41.00004: Simulation of Scalar Transport in a Non-Reacting Turbulent Jet using the Lattice Boltzmann Method Chong Wu, Wai Lee Chan In this work, numerical simulations of a non-reacting turbulent jet was performed with a lattice Boltzmann (LB) solver that is based on the open-source Palabos framework. The computational domain consists of a square nozzle, from which a free jet of Reynolds number of 10,000 was injected into a three-dimensional, open quiescent space. A scalar distribution function was introduced to describe the mixture fraction, with its transport properties extracted from a flamelet library. Subgrid-scale turbulence was described by another independent distribution function that closes the Smagorinsky model. To this end, the LB simulations are being run to a statistically-steady state, from which results can be verified with analytical scaling of turbulence theories. Meanwhile, the scalar mixing profile at different axial locations will be investigated as it is critical to the implementation of flamelet-type combustion model. In addition, computational performance and simulation results of the LB method will be compared against that of large-eddy simulations, focusing in particular on the scalability of LB method. [Preview Abstract] |
Monday, November 25, 2019 6:08PM - 6:21PM |
P41.00005: Phase-field Modeling and Simulation of Surfactant-Laden Multiphase Flows using a Central Moment Lattice Boltzmann Method Farzaneh Hajabdollahi, Kannan Premnath, Samuel Welch Surfactants modulate interfacial flows in numerous multiphase dispersed systems. We will present a robust computational technique based on unified cascaded lattice Boltzmann methods (LBMs) for two-phase flows at high density ratios, and for the capturing of the interfacial motions and surfactant dynamics. The cascaded LBM for two-phase flows, which computes the pressure and velocity fields, is based on a discretized modified continuous Boltzmann equation, where the effect of collisions is modeled by relaxation of different central moments to their equilibria and includes source terms for surface tension effects. The interfacial dynamics is represented by a conservative Allen-Cahn equation which is solved by another cascaded LBM. The transport of the surfactant concentration field, based on a free-energy functional and accounts for the energetic preference of surfactants to get adsorbed on interfaces, is evolved via yet another cascaded LBM. The effect of surfactants, i.e., the lowering of the local surface tension and the generation of Marangoni stresses, are introduced via a nonlinear interface equation of state based on the Langmuir isotherm. We will demonstrate the potential of our proposed formulation for various surfactant-laden two-phase flow cases. [Preview Abstract] |
Monday, November 25, 2019 6:21PM - 6:34PM |
P41.00006: An improved coupled Immersed-Boundary-Lattice-Boltzmann solver for the simulation of particulate flows Emmanouil Falagkaris, Timm Krueger Our present understanding of the fundamental physical mechanisms of particle-fluid interactions is far from complete. We focus on the accurate computation of the hydrodynamic forces and the no slip condition on the boundary using the lattice-Boltzmann method for the solution of the flow field and a multi-direct forcing (MDF) immersed-boundary method for the fluid-structure interaction. We found that certain MDF schemes can become unstable after a certain number of iterations. The source of the instability has been identified in the iterative computation of the boundary force. We propose an alternative iterative scheme that significantly enhances the numerical stability by allowing the boundary force computation to relax at a different rate. The numerical accuracy and stability of the proposed scheme is demonstrated by simulating flows laden with moving finite-size particles, including a particle in shear flow and the sedimentation of single spherical and non-spherical particles in a cavity, demonstrating the importance of the accurate boundary force computation on the particle motion and dynamics. Good agreement between the present results and other schemes is obtained. [Preview Abstract] |
Monday, November 25, 2019 6:34PM - 6:47PM |
P41.00007: An IB-LBM for modeling heat transfer and bushfire Fang-Bao Tian, Li Wang, Jason John Sharples Catastrophic bushfire has happened many times over the world in the last two decades, destroying many assets and multiple facilities. The most devastating bushfires normally involve wind and terrain interactions. In order to predict the spreading process of bushfire in various geographical and weather conditions, it is necessary to improve understanding of the physical mechanisms of bushfire—terrain—wind interaction. In this work, an immersed boundary method is developed for the numerical simulation of bushfire spreading mechanisms over complex terrains under different wind conditions. In this method, the lattice-Boltzmann method is used for the fluid dynamics. Large eddy simulation and wall model have been incorporated to handle the turbulence. The heat transfer is solved by using a finite difference method. The complex terrain is modeled by using an immersed boundary method. The numerical solver is validated by several benchmark cases, including heat transfer around a cylinder in a uniform flow, flow around a sphere at Re=10,000, and bushfire burning over a lee slope which is a typical terrain configuration. [Preview Abstract] |
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