Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session G6: CFD: Lattice Boltzmann Methods |
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Chair: Julien Favier, Aix Marseille University Room: 105 |
Monday, November 23, 2015 8:00AM - 8:13AM |
G6.00001: Simulation of immersed moving porous bodies using a coupled Immersed Boundary - Lattice Boltzmann method. Application to the control of flow separation around bluff bodies. Marianna Pepona, Julien Favier A numerical framework to simulate fluid flows in interaction with moving porous bluff bodies of complex geometry is proposed in this work. It is based on the Generalized Lattice Boltzmann method, which models the flow in the Representative Elementary Volume scale including the porous effects (porosity and the Brinkman-Forchheimer extended Darcy force model), coupled to the Immersed Boundary method to handle complex geometries and moving bodies. The coupling between both methods will be presented and the numerical results will be discussed in both porous and rigid configurations. The effect of the structure permeability on the boundary layer separation around a bluff body will be studied in the case of a static body and an oscillating one in cross-flow. A special focus will be placed on the manipulation of the vortex shedding frequency and lock-in phenomenon by a porous actuator. [Preview Abstract] |
Monday, November 23, 2015 8:13AM - 8:26AM |
G6.00002: Evaluation of the unstructured lattice Boltzmann method in porous flow simulations Marek Misztal, Rastin Matin, Anier Hernandez, Joachim Mathiesen Flows in porous media are among the most challenging to simulate using the computational fluid dynamics methods, primarily due to the complex boundaries, often characterized by a very broad distribution of pore sizes. The standard (regular grid based) lattice Boltzmann method with the multi-relaxation time (MRT) collision operator is often used to simulate such flows. However, due to the lack of coupling between the positions of the computational grid nodes and the solid boundaries, the properties of the simulated flow might unnaturally vary with the fluid's viscosity, depending on the parameters of the MRT operator. This is, for instance, the case with the otherwise popular, single-relaxation time Bhatnagar--Gross--Krook (BGK) collision operator. Our focus has been on the unstructured grid based, finite element variant of the LBM. By using such approach, we can place the computational grid nodes precisely at the solid boundary. Since there is no prior work on the accuracy of this method in simulating porous flows, we perform a thorough permeability study using both BGK and MRT operators at a wide range of viscosities. We benchmark these models on artificial samples with known solutions, and further, we demonstrate the findings of our studies in the porous networks of real rocks. [Preview Abstract] |
Monday, November 23, 2015 8:26AM - 8:39AM |
G6.00003: A Three-Dimensional Multi-Mesh Lattice Boltzmann Model for Multiphysics Simulations Amirreza Hashemi, Mohsen Eshraghi, Sergio Felicelli The lattice Boltzmann method (LBM) is known as an attractive computational method for modeling fluid flow and, more recently, transport phenomena. As any numerical method, the computational cost of LBM simulations depends on the density of the computational grids. The cost of simulations can become enormous when multiple equations are solved in three dimensions. In this work, the development of a multi-block multi-grid LBM model is discussed for three-dimensional (3D) multiphysics simulations. In a system of multiple coupled equations with different length scales, a multi-block mesh with different grids for each model would enhance the computational efficiency and stability of the model. Embedded-type grids facilitate the transfer of information between lattices while allowing larger time steps. In addition, a non-uniform mesh is considered within each mode that allows mesh refinement within each physical model when required. The multi-mesh method was developed to solve for transport phenomena including fluid flow, mass and heat transfer. The huge memory demands of LBM simulations in 3D was significantly reduced using this scheme. Moreover, by reducing the number of lattice points, cost communication in parallel processing was largely decreased. [Preview Abstract] |
Monday, November 23, 2015 8:39AM - 8:52AM |
G6.00004: Effects of viscoelasticity on droplet dynamics and break-up in microchannels : a Lattice Boltzmann study Anupam Gupta The effects of viscoelasticity on the dynamics and break-up of liquid threads in microfluidic devices, i.e., T-junctions \& Cross-Junction, are investigated using numerical simulations of dilute polymeric solutions for a wide range of Capillary numbers (Ca), i.e., changing the balance between the viscous forces and the surface tension at the interface. A Navier-Stokes (NS) description of the solvent based on the lattice Boltzmann models (LBM) is here coupled to constitutive equations for finite extensible non-linear elastic dumbbells with the closure proposed by Peterlin (FENE-P model). The various model parameters of the FENE-P constitutive equations, including the polymer relaxation time and the finite extensibility parameter, are changed to provide quantitative details on how the dynamics and break-up properties are affected by viscoelasticity. [Preview Abstract] |
Monday, November 23, 2015 8:52AM - 9:05AM |
G6.00005: ANFIS modeling for prediction of particle motions in fluid flows Arman Safdari, Kyung Chun Kim Accurate dynamic analysis of parcel of solid particles driven in fluid flow system is of interest for many natural and industrial applications such as sedimentation process, study of cloud particles in atmosphere, etc. In this paper, numerical modeling of solid particles in incompressible flow using Eulerian-Lagrangian approach is carried out to investigate the dynamic behavior of particles in different flow conditions; channel and cavity flow. Although modern computers have been well developed, the high computational time and costs for this kind of problems are still demanded. The Lattice Boltzmann Method (LBM) is used to simulate fluid flows and combined with the Lagrangian approach to predict the motion of particles in the range of masses. Some particles are selected, and subjected to Adaptive-network-based fuzzy inference system (ANFIS) to predict the trajectory of moving solid particles. Using a hybrid learning procedure from computational particle movement, the ANFIS can construct an input-output mapping based on fuzzy if-then rules and stipulated computational fluid dynamics prediction pairs. The obtained results from ANFIS algorithm is validated and compared with the set of benchmark data provided based on point-like approach coupled with the LBM method. [Preview Abstract] |
Monday, November 23, 2015 9:05AM - 9:18AM |
G6.00006: Reduction of the temperature jump in the immersed boundary-thermal lattice Boltzmann method Takeshi Seta, Kosuke Hayashi, Akio Tomiyama We analytically and numerically investigate the boundary errors computed by the immersed boundary-thermal lattice Boltzmann method (IB-TLBM) with the two-relaxation-time (TRT) collision operator. In the linear collision operator of the TRT, we decompose the distribution function into symmetric and antisymmetric components and define the relaxation parameters for each part. We derive the theoretical relation between the relaxation parameters for the symmetric and antisymmetric parts of the distribution function so as to eliminate the temperature jump. The simple TRT collision operator succeeds in reducing the temperature jump occurring at the high relaxation time in the IB-TLBM calculation. The porous plate problem numerically and analytically demonstrate that the velocity squared terms should be neglected in the equilibrium distribution function in order to eliminate the effect of the advection velocity on the temperature jump in the IB-TLBMs. The passive scalar model without the velocity squared terms more accurately calculates the incompressible temperature equation in the IB-TLBMs, compared to the double distribution model, which is based on the relation of the distribution function $g_{k} ={\left( {e_{k} -u} \right)^{2}f_{k} } \mathord{\left/ {\vphantom {{\left( {e_{k} -u} \right)^{2}f_{k} } 2}} \right. \kern-\nulldelimiterspace} 2$. We apply the passive scalar model without the velocity squared terms to the simulation of the natural convection between a hot circular cylinder and a cold square enclosure. The proposed method adequately sets the boundary values and provides reasonable average Nusselt numbers and maximum absolute values of the stream function. [Preview Abstract] |
Monday, November 23, 2015 9:18AM - 9:31AM |
G6.00007: Immersed boundary method implemented in lattice Boltzmann GPU code Brian DeVincentis, Kevin Smith, John Thomas Lattice Boltzmann is well suited to efficiently utilize the rapidly increasing compute power of GPUs to simulate viscous incompressible flows. Fluid-structure interaction with solids of arbitrarily complex geometry can be modeled in this framework with the immersed boundary method (IBM). In IBM a solid is modeled by its surface which applies a force at the neighboring lattice points. The majority of published IBMs require solving a linear system in order to satisfy the no-slip condition. However, the method presented by Wang et. al. (2014) is unique in that it produces equally accurate results without solving a linear system. Furthermore, the algorithm can be applied in a parallel manner over the immersed boundary and is, therefore, well suited for GPUs. Here, a 2D and 3D version of their algorithm is implemented in Sailfish CFD, a GPU-based open source lattice Boltzmann code. One issue unaddressed by most published work is how to correct force and torque calculated from IBM for translating and rotating solids. These corrections are necessary because the fluid inside the solid affects its inertia in a non-trivial manner. Therefore, this implementation uses the Lagrangian points approximation correction shown by Suzuki and Inamuro (2011) to be accurate. [Preview Abstract] |
Monday, November 23, 2015 9:31AM - 9:44AM |
G6.00008: Different Scalable Implementations of Collision and Streaming for Optimal Computational Performance of Lattice Boltzmann Simulations. Nicholas Geneva, Lian-Ping Wang In the past 25 years, the mesoscopic lattice Boltzmann method (LBM) has become an increasingly popular approach to simulate incompressible flows including turbulent flows. While LBM solves more solution variables compared to the conventional CFD approach based on the macroscopic Navier-Stokes equation, it also offers opportunities for more efficient parallelization. In this talk we will describe several different algorithms that have been developed over the past 10 plus years, which can be used to represent the two core steps of LBM, collision and streaming, more effectively than standard approaches. The application of these algorithms spans LBM simulations ranging from basic channel to particle laden flows. We will cover the essential detail on the implementation of each algorithm for simple 2D flows, to the challenges one faces when using a given algorithm for more complex simulations. The key is to explore the best use of data structure and cache memory. Two basic data structures will be discussed and the importance of effective data storage to maximize a CPU's cache will be addressed. The performance of a 3D turbulent channel flow simulation using these different algorithms and data structures will be compared along with important hardware related issues. [Preview Abstract] |
Monday, November 23, 2015 9:44AM - 9:57AM |
G6.00009: Two-dimensional plastic flow of foams and emulsions in a channel: experiments and simulations Mauro Sbragaglia In order to understand the flow profiles of complex fluids, a crucial issue concerns the emergence of spatial correlations among plastic rearrangements exhibiting cooperativity flow behaviour at the macroscopic level. In this paper, the rate of plastic events in a Poiseuille flow is experimentally measured on a confined foam in a Hele-Shaw geometry. The correlation with independently measured velocity profiles is quantified by looking at the relationship between the localisation length of the velocity profiles and the localisation length of the spatial distribution of plastic events. To complement the cooperativity mechanisms studied in foam with those of other soft glassy systems, we compare the experiments with simulations of dense emulsions based on the lattice Boltzmann method, which are performed both with and without wall friction. Finally, unprecedented results on the distribution of the orientation of plastic events show that there is a non-trivial correlation with the underlying local shear strain. These features, not previously reported for a confined foam, lend further support to the idea that cooperativity mechanisms, originally invoked for concentrated emulsions (Goyon et al., Nature, vol. 454, 2008, pp. 84–87), have parallels in the behaviour of other soft glassy ma [Preview Abstract] |
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