Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session R32: Particle-Laden Flows VII: Computational Methods |
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Chair: Eric C. Keaveny, Imperial College of London Room: 403 |
Tuesday, November 26, 2013 1:05PM - 1:18PM |
R32.00001: A computational scheme for simulation of dense suspensions of arbitrarily shaped rigid particles Marcos Vanella, Hussein Ez Eldin, Prateeti Mohapatra, Christopher Daley, Anshu Dubay, Elias Balaras Flows of dense particle suspensions are of great interest to engineering, science and medicine. Immerse boundary (IB) methods are commonly employed in simulations of such systems, but are usually confined to spherical particle suspensions. Extension to rigid particles of arbitrary shape introduces significant additional complexities on the IB tracking algorithms, as well as the rigid body dynamics. This increases the cost in the fluid-structure interaction (FSI) schemes employed. In this work we present a computational scheme targeted to the above problem, applicable to computations involving millions of particles on leadership high performance computing platforms. The fluid equations are discretized by standard, central, finite-differences on a staggered mesh and the equations of motion for each particle are employed on the Eulerian reference using Euler angles or quaternion variables. A Lagrangian forcing IB method is employed, using the Lagrangian particle framework of FLASH. Fluid and particle equations of motion are strongly coupled using a partitioned scheme. We present the details of the parallel implementation as well as scaling tests and results on the sedimentation of arbitrary shaped particles. [Preview Abstract] |
Tuesday, November 26, 2013 1:18PM - 1:31PM |
R32.00002: An investigation of particles suspension using smoothed particle hydrodynamics Arman Pazouki, Dan Negrut This contribution outlines a method for the direct numerical simulation of rigid body suspensions in a Lagrangian-Lagrangian framework using extended Smoothed Particle Hydrodynamics (XSPH) method. The dynamics of the arbitrarily shaped rigid bodies is fully resolved via Boundary Condition Enforcing (BCE) markers and updated according to the general Newton-Euler equations of motion. The simulation tool, refered to herien as {\textsl{Chrono::Fluid}}, relies on a parallel implementation that runs on Graphics Processing Unit (GPU) cards. The simulation results obtained for transient Poiseuille flow, migration of cylinder and sphere in Poiseuille flow, and distribution of particles at different cross sections of the laminar flow of dilute suspension were respectively within 0.1\%, 1\%, and 5\% confidence interval of analytical and experimental results reported in the literature. It was shown that at low Reynolds number, Re = O(1), the radial migration (a) behaves non-monotonically as the particles relative distance (distance over diameter) increases from zero to two; and (b) decreases as the particle skewness and size increases. The scaling of {\textsl{Chrono::Fluid}} was demonstrated in conjunction with a suspension dynamics analysis in which the number of ellipsoids went up to 3e4. [Preview Abstract] |
Tuesday, November 26, 2013 1:31PM - 1:44PM |
R32.00003: Numerical simulation of two-way coupling mechanism in particle-laden turbulent flow based on one-dimensional turbulence model Guangyuan Sun, David Lignell, John Hewson, Craig Gin We present three algorithms (type-I, type-C and type-IC) for Lagrangian particle transport within the context of the one-dimensional turbulence (ODT) approach. ODT is a stochastic model that captures the full range of length and time scales and provides statistical information on fine-scale turbulent-particle mixing and transport at low computational cost. Two of the particle transport algorithms are new as is an algorithm to provide two-way momentum and energy coupling between the particle and carrier phases. Using these methods we investigate particle-laden turbulent jet flow. In contrast to other previous particle implementation in ODT, the two new methods allow the particles to interact with multiple eddies simultaneously and evolve the particle phase continuously, and therefore are able to accurately capture turbulent mixing and fluctuation seen by inertial particles in ODT. Simulation results are compared with experimental data including the effect of two particle Stokes numbers (St $=$ 3.6 and 10.8). Turbulence modification, particle number density PDFs and particle velocity evolution are presented. [Preview Abstract] |
Tuesday, November 26, 2013 1:44PM - 1:57PM |
R32.00004: Incorporating Volumetric Displacement Effects In Euler-Lagrange Simulations of Particle-Laden Oscillatory Flows Sourabh Apte, Justin Finn, Andrew Cihonski Recent Euler-Lagrange discrete element modeling of a few microbubbles entrained in a traveling vortex ring (Cihonski et al., JFM, 2013) has shown that extension of the point-particle method to include local volume displacement effects is critical for capturing vortex distortion effects due to microbubbles, even in a very dilute suspension. We extend this approach to investigate particle-laden oscillatory boundary layers representative of coastal sediment environments. A wall bounded, doubly periodic domain is considered laden with a layer of sediment particles in laminar as well as turbulent oscillatory boundary layers corresponding to the experiments of Keiller and Sleath (1987) and Jensen et al. (1987). Inter-particle and particle-wall collisions are modeled using a soft-sphere model which uses a nested collision grid to minimize computational effort. The effects of fluid mass displaced by the particles on the flow statistics are quantified by comparing a standard two-way coupling approach (without volume displacement effects) with volume displacement effects to show that the latter models are important for low cases with low particle-fluid density ratios. [Preview Abstract] |
Tuesday, November 26, 2013 1:57PM - 2:10PM |
R32.00005: Fluctuating force-coupling method for simulating Brownian suspensions Eric Keaveny Brownian motion plays an important role in the dynamics of colloidal suspensions. It affects suspension rheological properties, influences the self-assembly of structures, and regulates particle transport. While including Brownian motion in simulations is necessary to reproduce and study these effects, it is computationally intensive due to the configuration dependent statistics of the particles' random motion. I will discuss recent work that speeds up this calculation for the force-coupling method (FCM), a regularized multipole approach to simulating suspensions at large-scale. I will show that by forcing the surrounding fluid with a configuration independent, white-noise stress, fluctuating FCM yields the correct particle random motion, even when higher-order terms, such as the stresslets, are included in the multipole expansion. I will present results from several simulations demonstrating the effectiveness of this approach and also discuss the extension of fluctuating FCM to dense suspension simulations. [Preview Abstract] |
Tuesday, November 26, 2013 2:10PM - 2:23PM |
R32.00006: Particle-Laden Turbulent Kolmogorov Flow Lian-Ping Wang Modulation of the carrier phase turbulence by finite-size inertial particles have been studied experimentally, but only recently it is possible to study this computationally through particle-resolved simulation methods. In addition to parameters governing the flow, the nature of modulation depends on at least four dimensionless parameters associated with the dispersed phase: the dimensionless particle size, volume fraction, particle-to-fluid density ratio, and dimensionless sedimentation velocity. Both augmentation and attenuation of the carrier phase turbulence have been reported, and the published results are often difficult to comprehend and sometime are inconsistent. Here we present results of a relatively simple setting, namely, a turbulent Kolmogorov flow laden with finite-size inertial particles. This flow setting has connection to both channel flow and homogeneous flow. We apply the lattice Boltzmann method to simulate the carrier phase turbulence and to resolve the surface of moving solid particles. Both turbulent augmentation and attenuation are found to exist, depending on the system parameters. We will report on results of large-scale energy production and local profiles near the particle surface, to help interpret the results of turbulence modulation. [Preview Abstract] |
Tuesday, November 26, 2013 2:23PM - 2:36PM |
R32.00007: Study of the Motion of Particles in Closed Streamlines Hamed Haddadi, Kevin Connington, Shahab Shojaei-Zadeh, Jeffrey Morris The behavior of neutrally-buoyant particles in the closed-streamline flows formed behind bluff bodies of various shapes is studied; the Reynolds numbers studied generate extended closed-streamline wakes but are below the transition to an unsteady wake. Experimental observations have demonstrated that the wake is depleted or completely devoid of particles. Using lattice-Boltzmann simulations, the trajectory of a single particle (small relative to the bluff body) is analyzed and shown to form a limit cycle inside the wake. With increase of the number of particles in the wake, trajectories are distorted due to interactions and particles are pushed out of the wake. Calculation of the fluid pathlines indicates that the presence of particles breaks the steadiness of the wake which results in a particle (and fluid) transfer between the wake and the free stream. The particle trajectories have also been analyzed by simulation of the flow of dilute suspensions over the circular cylindrical, square and thin rectangular (``blade'') shaped posts, for which different levels of particle depletion in the wake are seen experimentally, in order to determine the particle transfer pattern between the wake and the free stream. [Preview Abstract] |
Tuesday, November 26, 2013 2:36PM - 2:49PM |
R32.00008: A New Moving Boundary Condition in Particulate Suspensions with the Lattice Boltzmann Method Lina Xu, Laura Schaefer Particulate suspensions are common phenomena in industrial and biological fields. However, the fundamental understanding of the hydrodynamic interactions between the solid and fluid needs to be further improved. The lattice Boltzmann method has been shown to be an effective numerical method to model various fluid flows, and exhibits good performance in dealing with boundary conditions, with straightforward and easy-to-implement methods for complex solid boundaries. However, most of the previous boundary conditions used for the moving complex surface are based on the half way bounce-back boundary condition, where the geometric integrity of the body cannot be kept. In this presentation, a new boundary condition based on the Chapman-Enskog expansion is proposed for the moving complex surface, where the precise shape of the body can be preserved during the calculation. Moreover, due to the second order accuracy of the Chapman-Enskog expansion when recovering the Navier-stokes equation from the Boltzmann-BGK equation, the new boundary condition can maintain the same accuracy for the whole computational domain. [Preview Abstract] |
Tuesday, November 26, 2013 2:49PM - 3:02PM |
R32.00009: Lattice Boltzmann Method for Two-phase Flows on Unstructured Mesh Taehun Lee, Lina Baroudi, Kent Wardle A lattice Boltzmann method with Galerkin finite element discretization (FE-LBM) is proposed to simulate incompressible two-phase flows on unstructured mesh. Two-distribution functions are used to recover the transport equations for the order parameter, pressure, and momentum. Consistent treatment of streaming and intermolecular forcing terms in FE-LBM enables us to use small equilibrium interface thickness compared with the existing two-phase LBMs and thus to achieve numerical stability at higher Reynolds number and large material property contrast. Several benchmark test cases with non-trivial wall boundaries will be presented, which include turbulent free surface flow inside a concentric rotating cylinder, drop impact on patterned surfaces, and bubbly flows. [Preview Abstract] |
Tuesday, November 26, 2013 3:02PM - 3:15PM |
R32.00010: An improved lattice Boltzmann method for incompressible two-phase flows with large density differences Takaji Inamuro, Takaaki Yokoyama, Kentaro Tanaka, Motoki Taniguchi We propose a new LBM for two-phase fluid flows with high density ratios by improving the pressure computing of Inamuro et al.'s method (2004) [J. Comput. Phys. 198 (2004) 628] without solving the pressure Poisson equation. In the proposed method, the velocity and pressure fields are computed by using a single velocity distribution function even for high density ratios and by adjusting the speed of sound in a high density region to satisfy the continuity equation. In order to show the validity of the method, we apply the method to the simulations of a stationary drop, binary droplet collision, rising bubbles, and a milk crown. In a stationary drop, pressure and density profiles are computed, and the effect of a sound speed on time evolution of the pressure field in the drop. In the simulations of a binary droplet collision and rising bubbles, the computed results by the proposed method are compared with those by Inamuro et al.'s method (2004). A thin sheet and tiny drops can be computed in the simulation of a milk crown. [Preview Abstract] |
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