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 S37: Particle Laden Flows: Simulations |
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Chair: Jesse Capecelatro, University of Michigan, Ann Arbor Room: 619 |
Tuesday, November 26, 2019 10:31AM - 10:44AM |
S37.00001: Particle number decomposition DEM parallel algorithm for particle laden flows Zhengping Zhu, Xiaojing Zheng, Lian Shen Domain decomposition is the most commonly used parallel algorithm in simulations of particle laden flows. However, there are two limitations of this algorithm. Firstly, particles are generally distributed unevenly over the different sub-domains in anisotropic flows, leading to problems of loading balance, especially when gravity effect is strong. Secondly, as particles naturally cross borders between sub-domains, passing values between sub-domains can be complicated. In this study, we develop a new particle number decomposition algorithm to overcome these two limitations. In this method, each core deals with almost the same number of particles to achieve excellent loading balance. We further develop a low storage method that can effectively store the particles information in each core, while substantially reducing the complexity of passing values among different cores. The new algorithm is easy to implement, and existing serial DEM algorithms remain unchanged in the parallel version. It also has high parallel efficiency and can compute millions of fully resolved particles. [Preview Abstract] |
Tuesday, November 26, 2019 10:44AM - 10:57AM |
S37.00002: Optimization of Finite Element Simulations of Colliding, Particle-laden Flows on Unstructured Grids Grant Rydquist, Mahdi Esmaily When simulating fluid systems in complex geometries, it is often necessary to discretize the system using a large number of unstructured elements to achieve accurate results. However, this can pose a number of problems when the simulation must also include Lagrangian particles. In such simulations, it is necessary to search for the element that contains a particle at each time step in order to accurately interpolate fluid properties to the location of the particle. While this operation is inexpensive for structured grids, in unstructured grids a standard implementation of this search algorithm requires $O(N_{p}N_{el})$ operations, and can become prohibitively expensive for fine grids with many particles. A second situation which can lead to increased computational cost in simulations with Lagrangian particles is when binary collisions between particles must be captured. In general, each particle must be checked against every other particle to check for potential collisions, resulting in $O(N_{p}^2)$ calculations. In this work, we present a new technique to drastically reduce the computational cost in both of these situations through an optimization problem. In both of these cases, application of this optimization problem has led to a cost that is $O(N_{p})$. [Preview Abstract] |
Tuesday, November 26, 2019 10:57AM - 11:10AM |
S37.00003: Numerical modeling of inertial particles in under-expanded jets Yuan Yao, Jason Rabinovitch, Jesse Capecelatro Inertial particle dynamics in flows that exhibit strong gas-phase compressibility and turbulence is crucial to many practical engineering applications. Such examples include coal dust explosions, shock wave lithotripsy, combustion/detonation, etc. Compared to their low-speed counterpart, particle-laden compressible flows like the examples listed here typically introduce new length- and time-scales and additional physics that further complicate modeling efforts. In this presentation, we perform three-dimensional Eulerian-â€“Lagrangian simulations of particle-laden under-expanded jets to study the dynamics of inertial particles in compressible flows. The gas-phase equations are solved using a high-order, energy stable finite difference discretization. A combined ghost-point / direct-forcing immersed boundary method is employed to model the nozzle geometry. The focus of the present work is to assess the ability of existing drag models to capture particle dynamics through a series of compression and expansion waves (Mach diamonds). Particle trajectories and velocity distribution together with DMD modes are compared between different drag models and experiments. Two-way coupling effects on the structure of the Mach diamonds are also reported. [Preview Abstract] |
Tuesday, November 26, 2019 11:10AM - 11:23AM |
S37.00004: Particle Scale Heat Transfer Calculations and Flow Characteristics in a Fluidized Bed with Immersed Tube by CFD-DEM Approach Naveen Raj Nannamkeril, Danesh K Tafti, S Vengadesan A combined approach of discrete element method and computational fluid dynamics is used to study the heat transfer behaviour in a fluidised bed with an immersed tube. A method to resolve particle-particle and particle-wall unsteady conduction heat transfer is developed within the framework of the soft sphere collision model. The unsteady heat transfer model is incorporated into an existing CFD-DEM framework. The model is derived from the analytical solution of one-dimensional unsteady heat conduction between two semi-infinite objects. The model considers the area and time of contact with appropriate scaling for compatibility with the soft sphere model. The model is validated against experimental data available from the literature. The model is applied to a fluidized bed with an immersed tube to characterize the heat transfer mechanisms and the effective heat transfer coefficient. The relative importance of various heat transfer mechanisms is analysed. The requirement of the coarse grid for coupled CFD-DEM near the boundaries are overcome with a particle grid formulation. Hence the dynamic large eddy simulation turbulence model resolved the boundary layer precisely around the tube surface. The continuity in void fraction near the wall is also retained. [Preview Abstract] |
Tuesday, November 26, 2019 11:23AM - 11:36AM |
S37.00005: CFD tools for characterizing particle passage through an idealized hydro-turbine model. Rajesh Singh, Pedro Romero-Gomez, Marshall Richmond, Samuel Harding, William Perkins The survival of fish passing through a hydroelectric power plant is a critical challenge to understand and address adverse environment impacts. Although alternative routes to bypass fish in extreme hydraulic conditions are designed in many power plants, fish bypass still remains as a critical issue. A computational fluid dynamics based tool, biological performance assessment (BioPA) method, has been developed to assess the biological performance of fish passage during the turbine design phase in new and existing turbine designs. The current work reports high fidelity turbulent flow investigations to predict the behavior, trajectories, and collisions of inertial particles in an idealized hydro-turbine model to predict the biological impact of hydro turbines on fish passage. The turbulent flow simulations were conducted using detached eddy simulation to accurately capture the flow recirculation and wake region proximate to representative geometry of the distributor of a typical hydro turbine. The flow field proximate to the distributor geometry significantly impacts the trajectory and collision of particles. Naturally buoyant spherical and cylindrical particles were released at the upstream of the distributor. The trajectory and collision rate of the particles to distributor wall is computed and further compared with corresponding experimental results for different conditions. [Preview Abstract] |
Tuesday, November 26, 2019 11:36AM - 11:49AM |
S37.00006: An AMR moving cut-cell algorithm for particle-laden flows Arthur Ghigo, Stephane Popinet, Anthony Wachs Many biomedical applications, such as targeted drug delivery, involve a large number of interactions between rigid and deformable particles. Numerical simulations of such particle-laden flows must therefore account for both complex moving embedded geometries and a wide range of spatial scales, while maintaining computational cost at a minimum. In this context, we propose an extension of the cut-cell algorithm of Johansen and Colella (Johansen and Colella, JCP 1998) to three-dimensional moving and deformable geometries. The algorithm allows for high-fidelity simulations of flows past complex moving boundaries. It is implemented in the software \textit{Basilisk} (Popinet, JCP 2009), which provides a parallel framework for adaptive mesh refinement on non-conforming Cartesian grids. The method is validated and compared with our in-house code \textit{Peligriff} (Wachs, J Eng Math 2011) on test-cases involving moving rigid particles only. We then investigate the dynamics of particle suspensions in confined geometries. [Preview Abstract] |
Tuesday, November 26, 2019 11:49AM - 12:02PM |
S37.00007: Resolution analysis of particle transport dynamics for the Lattice-Boltzmann Method Cosimo Livi, Gianluca Di Staso, Herman J.H. Clercx, Federico Toschi The capability to simulate a two-way coupled interaction between an arbitrary-shape colloidal particle and a fluid is important for a range of practical applications, however the computational cost can become burdensome. We propose a systematic error analysis of finite-size particle dynamics using the Hermite regularized Lattice Boltzmann method, for different particles resolution, addressing translational and rotational systems separately. The motivation is the understanding of the degree of accuracy provided by different boundary condition models at the fluid-solid interface, with a focus on cases where particles are discretized using few lattice grid points. We show that through a second-order accurate interpolated bounce-back scheme a strong error suppression can be achieved with respect to the standard first-order accurate approach, allowing to simulate smaller particles and thus improving computational performances. An improved version of the former interpolation scheme is developed in order to compute particle boundary position also when the particle is crossing a link between two fluid nodes, showing that the capability to resolve non-spherical particles is further enhanced. [Preview Abstract] |
Tuesday, November 26, 2019 12:02PM - 12:15PM |
S37.00008: Qualitative Benchmarking of a Developmental CFD-DEM Code William Fullmer, Jordan Musser, Ann Almgren, Michele Rosso, Oscar Antepara, Roberto Porcu, Johannes Blaschke \\MFiX-Exa is a new code being developed by the National Energy Technology Laboratory and Lawrence Berkeley National Laboratory as part of the U.S. Department of Energy's Exascale Computing Project. MFiX-Exa originated by combining the discrete element method (DEM) modules of the classic MFiX code (mfix.netl.doe.gov) with a modern low Mach number projection method for the continuous fluid phase. The new algorithm is implemented using the AMReX software framework for massively parallel block-structured applications (amrex-codes.github.io). This work utilizes a set of qualitative benchmarks which emphasize the phenomenology of a given problem rather than averaged statistical measures typically used in fluid-particle validation studies. The following cases are considered: 1) clustering of inelastic particles in the gas-solid homogeneous cooling system, 2) granular Rayleighâ€“Taylor instability of particles draining into a gas, 3) rapid injection of a single bubble into a particle bed at incipient fluidization, 4) ordered left-right bubbling pattern of a periodically fluidized bed, 5) segregation of "Brazil nuts" to the top of a small bed, 6) axial banding (segregation) of bi-disperse rotating tumbler. A range of agreement with the expected phenomena is observed and reported. [Preview Abstract] |
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