Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session Q31: Computational Fluid Dynamics: Lattice Boltzmann and Smoothed Particle Hydrodynamics MethodsCFD
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Chair: Amir Barati Farimani, Stanford University Room: 108 |
Tuesday, November 21, 2017 12:50PM - 1:03PM |
Q31.00001: Modelling of Dispersed Gas-Liquid Flow using LBGK and LPT Approach Alankar Agarwal, Akshay Prakash, B. Ravindra The dynamics of gas bubbles play a significant, if not crucial, role in a large variety of industrial process that involves using reactors. Many of these processes are still not well understood in terms of optimal scale-up strategies.An accurate modeling of bubbles and bubble swarms become important for high fidelity bioreactor simulations. This study is a part of the development of robust bubble fluid interaction modules for simulation of industrial-scale reactors. The work presents the simulation of a single bubble rising in a quiescent water tank using current models presented in the literature for bubble-fluid interaction. In this multiphase benchmark problem, the continuous phase (water) is discretized using the Lattice Bhatnagar-Gross and Krook (LBGK) model of Lattice Boltzmann Method (LBM), while the dispersed gas phase (i.e. air-bubble) modeled with the Lagrangian particle tracking (LPT) approach. The cheap clipped fourth order polynomial function is used to model the interaction between two phases. The model is validated by comparing the simulation results for terminal velocity of a bubble at varying bubble diameter and the influence of bubble motion in liquid velocity with the theoretical and previously available experimental data. [Preview Abstract] |
Tuesday, November 21, 2017 1:03PM - 1:16PM |
Q31.00002: Discrete Boltzmann model of shallow water equations with polynomial equilibria Jianping Meng, Xiao-Jun Gu, David Emerson, Yong Peng, Jianming Zhang A hierarchy of discrete Boltzmann model is proposed for simulating shallow water flows. By using the Hermite expansion and Gauss-Hermite quadrature, the conservation laws are automatically satisfied without extra effort. Moreover, the expansion order and quadrature can be chosen flexibly according to the problem for striking the balance of accuracy and efficiency. The models are then tested using the classical one-dimensional dam-breaking problem, and successes are found for both supercritical and subcritical flows. [Preview Abstract] |
Tuesday, November 21, 2017 1:16PM - 1:29PM |
Q31.00003: ABSTRACT WITHDRAWN |
Tuesday, November 21, 2017 1:29PM - 1:42PM |
Q31.00004: Axisymmetric Lattice Boltzmann Model of Droplet Impact on Solid Surfaces Hussein Dalgamoni, Xin Yong Droplet impact is a ubiquitous fluid phenomena encountered in scientific and engineering applications such as ink-jet printing, coating, electronics manufacturing, and many others. It is of great technological importance to understand the detailed dynamics of drop impact on various surfaces. The lattice Boltzmann method (LBM) emerges as an efficient method for modeling complex fluid systems involving rapidly evolving fluid-fluid and fluid-solid interfaces with complex geometries. In this work, we model droplet impact on flat solid substrates with well-defined wetting behavior using a two-phase axisymmetric LBM with high density and viscosity contrasts. We extend the two-dimensional Lee and Liu model to capture axisymmetric effect in the normal impact. First we compare the 2D axisymmetric results with the 2D and 3D results reported by Lee and Liu to probe the effect of axisymmetric terms. Then, we explore the effects of Weber number, Ohnesorge number, and droplet-surface equilibrium contact angle on the impact. The dynamic contact angle and spreading factor of the droplet during impact are investigated to qualitatively characterize the impact dynamics. [Preview Abstract] |
Tuesday, November 21, 2017 1:42PM - 1:55PM |
Q31.00005: Numerical Modeling of Non-Newtonian and Viscoelastic Flows using Central Moment Lattice Boltzmann Approach Saad Adam, Kannan Premnath Non-Newtonian fluid flows with nonlinear rheological behavior occur in a number of applications such as in chemical, biological and materials processing contexts. In addition, viscoelastic fluids exhibit peculiar normal stress and memory effects. Lattice Boltzmann (LB) methods involving the use of central moments provide improved numerical stability and better physical coherence. Here, first, we present a LB model based on central moments with extended moment equilibria involving strain rates and an adjustable parameter to represent non-Newtonian power-law fluids in three-dimensions, and its numerical validation for flows encompassing both shear thinning and shear thickening fluids. Next, we discuss a LB scheme using central moments and a source term to represent the evolution of the viscoelastic stresses modeled using the upper convected Oldroyd-B model, which transform objectively -- a key physical requirement. The viscoelastic stresses are then coupled to the LB flow solver as additional contributions to the latter's second order moment equilibria in the collision step. The resulting scheme is validated for various viscoelastic benchmark flows for which prior analytical and/or numerical solutions available at different Weissenberg numbers and viscosity ratios. [Preview Abstract] |
Tuesday, November 21, 2017 1:55PM - 2:08PM |
Q31.00006: From Lattice Boltzmann to hydrodynamics in dissipative relativistic fluids Alessandro Gabbana, Miller Mendoza, Sauro Succi, Raffaele Tripiccione Relativistic fluid dynamics is currently applied to several fields of modern physics, covering many physical scales, from astrophysics, to atomic scales (e.g. in the study of effective 2D systems such as graphene) and further down to subnuclear scales (e.g. quark-gluon plasmas). This talk focuses on recent progress in the largely debated connection between kinetic transport coefficients and macroscopic hydrodynamic parameters in dissipative relativistic fluid dynamics. We use a new relativistic Lattice Boltzmann method (RLBM), able to handle from ultra-relativistic to almost non-relativistic flows, and obtain strong evidence that the Chapman-Enskog expansion provides the correct pathway from kinetic theory to hydrodynamics. This analysis confirms recently obtained theoretical results, which can be used to obtain accurate calibrations for RLBM methods applied to realistic physics systems in the relativistic regime. Using this calibration methodology, RLBM methods are able to deliver improved physical accuracy in the simulation of the physical systems described above. [Preview Abstract] |
Tuesday, November 21, 2017 2:08PM - 2:21PM |
Q31.00007: Random Walk Particle Tracking For Multiphase Heat Transfer Aaron Lattanzi, Xiaolong Yin, Christine Hrenya As computing capabilities have advanced, direct numerical simulation (DNS) has become a highly effective tool for quantitatively predicting the heat transfer within multiphase flows. Here we utilize a hybrid DNS framework that couples the lattice Boltzmann method (LBM) to the random walk particle tracking (RWPT) algorithm. The main challenge of such a hybrid is that discontinuous fields pose a significant challenge to the RWPT framework and special attention must be given to the handling of interfaces. We derive a method for addressing discontinuities in the diffusivity field, arising at the interface between two phases. Analytical means are utilized to develop an interfacial tracer balance and modify the RWPT algorithm. By expanding the modulus of the stochastic (diffusive) step and only allowing a subset of the tracers within the high diffusivity medium to undergo a diffusive step, the correct equilibrium state can be restored (globally homogeneous tracer distribution). The new RWPT algorithm is implemented within the SUSP3D code and verified against a variety of systems: effective diffusivity of a static gas-solids mixture, hot sphere in unbounded diffusion, cooling sphere in unbounded diffusion, and uniform flow past a hot sphere. [Preview Abstract] |
Tuesday, November 21, 2017 2:21PM - 2:34PM |
Q31.00008: Effective Simulation Strategy of Multiscale Flows using a Lattice Boltzmann model with a Stretched Lattice Eman Yahia, Kannan Premnath Resolving multiscale flow physics (e.g. for boundary layer or mixing layer flows) effectively generally requires the use of different grid resolutions in different coordinate directions. Here, we present a new formulation of a multiple relaxation time (MRT)-lattice Boltzmann (LB) model for anisotropic meshes. It is based on a simpler and more stable non-orthogonal moment basis while the use of MRT introduces additional flexibility, and the model maintains a stream-collide procedure; its second order moment equilibria are augmented with additional velocity gradient terms dependent on grid aspect ratio that fully restores the required isotropy of the transport coefficients of the normal and shear stresses. Furthermore, by introducing additional cubic velocity corrections, it maintains Galilean invariance. The consistency of this stretched lattice based LB scheme with the Navier-Stokes equations is shown via a Chapman-Enskog expansion. Numerical study for a variety of benchmark flow problems demonstrate its ability for accurate and effective simulations at relatively high Reynolds numbers. The MRT-LB scheme is also shown to be more stable compared to prior LB models for rectangular grids, even for grid aspect ratios as small as 0.1 and for Reynolds numbers of 10000. [Preview Abstract] |
Tuesday, November 21, 2017 2:34PM - 2:47PM |
Q31.00009: Three-dimensional Cascaded Lattice Boltzmann Model for Thermal Convective Flows Farzaneh Hajabdollahi, Kannan Premnath Fluid motion driven by thermal effects, such as due to buoyancy in differentially heated enclosures arise in several natural and industrial settings, whose understanding can be achieved via numerical simulations. Lattice Boltzmann (LB) methods are efficient kinetic computational approaches for coupled flow physics problems. In this study, we develop three-dimensional (3D) LB models based on central moments and multiple relaxation times for D3Q7 and D3Q15 lattices to solve the energy transport equations in a double distribution function approach. Their collision operators lead to a cascaded structure involving higher order terms resulting in improved stability. This is coupled to a central moment based LB flow solver with source terms. The new 3D cascaded LB models for the convective flows are first validated for natural convection of air driven thermally on two vertically opposite faces in a cubic cavity at different Rayleigh numbers against prior numerical and experimental data, which show good quantitative agreement. Then, the detailed structure of the 3D flow and thermal fields and the heat transfer rates at different Rayleigh numbers are analyzed and interpreted. [Preview Abstract] |
Tuesday, November 21, 2017 2:47PM - 3:00PM |
Q31.00010: Hybrid fully nonlinear BEM-LBM numerical wave tank with applications in naval hydrodynamics Amin Mivehchi, Stephan T. Grilli, Jason M. Dahl, Chris M. O’Reilly, Jeffrey C. Harris, Konstantin Kuznetsov, Christian F. Janssen simulation of the complex dynamics response of ships in waves is typically modeled by nonlinear potential flow theory, usually solved with a higher order BEM. In some cases, the viscous/turbulent effects around a structure and in its wake need to be accurately modeled to capture the salient physics of the problem. Here, we present a fully 3D model based on a hybrid perturbation method. In this method, the velocity and pressure are decomposed as the sum of an inviscid flow and viscous perturbation. The inviscid part is solved over the whole domain using a BEM based on cubic spline element. These inviscid results are then used to force a near-field perturbation solution on a smaller domain size, which is solved with a NS model based on LBM-LES , and implemented on GPUs. The BEM solution for large grids is greatly accelerated by using a parallelized FMM,which is efficiently implemented on large and small clusters, yielding an almost linear scaling with the number of unknowns. A new representation of corners and edges is implemented, which improves the global accuracy of the BEM solver, particularly for moving boundaries. We present model results and the recent improvements of the BEM, alongside results of the hybrid model, for applications to problems. [Preview Abstract] |
Tuesday, November 21, 2017 3:00PM - 3:13PM |
Q31.00011: A Consistent Adaptive-resolution Smoothed Particle Hydrodynamics Method Wenxiao Pan, Wei Hu, Xiaozhe Hu, Dan Negrut We seek to accelerate and increase the size of simulations for fluid-structure interactions (FSI) by using adaptive resolutions in the spatial discretization of the equations governing the time evolution of systems displaying two-way fluid-solid coupling. To this end, we propose an adaptive-resolution smoothed particle hydrodynamics (SPH) approach, in which spatial resolutions adaptively vary according to a recovery-based error estimator of velocity gradient as flow evolves. The second-order consistent discretization of spatial differential operators is employed to ensure the accuracy of the proposed method. The convergence, accuracy, and efficiency attributes of the new method are assessed by simulating different flows. In this process, the numerical results are compared to the analytical, finite element, and consistent SPH single-resolution solutions. We anticipate that the proposed adaptive-resolution method will enlarge the class of SPH-tractable FSI applications. [Preview Abstract] |
Tuesday, November 21, 2017 3:13PM - 3:26PM |
Q31.00012: Coupling SPH with Voronoi diagrams to implement solid boundary conditions David Fernandez-Gutierrez, Tarek I. Zohdi The SPH method is well known for being able to model free surfaces undergoing large deformations. However, its consistency and implementation of boundary conditions become problematic close to solid boundaries. The new scheme presented creates a Voronoi diagram taking as cell seeds the particles within certain distance to the solid boundaries. The tessellation algorithm has been adapted to reproduce exactly planar boundaries without the need of fixed particles. Moreover, a new algorithm is presented to detect free surfaces within the Voronoi region. Following Hess \& Springel [Month. Not. Royal Astronomical Society, 406(4):2289-2311, (2010)], the dynamics of the fluid system are computed in a similar fashion than SPH, using an explicit weakly-compressible formulation. There is an overlapping region where both methods are combined such that, as the particles lay further from the boundary, they smoothly transition from Voronoi to SPH. The accuracy of the coupled scheme is discussed by analyzing the results under some well-known verification benchmarks. Results show how pressure gradient problems, such as hydrostatic conditions or sound waves, are well reproduced. [Preview Abstract] |
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