Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session L46: ParticleLaden Flows: Modeling and Theory II 
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Chair: Abhilash Reddy Malipeddi, University of Michigan Room: 209BC 
Monday, November 20, 2023 8:00AM  8:13AM 
L46.00001: EulerLagrange scheme for modeling particleladen flows in medical imagebased geometries Abhilash Reddy Malipeddi, C. Alberto Figueroa, Jesse Capecelatro We describe the implementation of a coupled computational fluid dynamics  discrete element method (CFDDEM) approach for modeling particleladen biological flows in patientspecific geometries. There have been significant advances in the EulerLagrange modeling paradigm in recent years, but this has been largely restricted to studying engineering problems on structured grids. Here, we extend the CRIMSON cardiovascular flow framework to model Lagrangian particles that interact with each other and are coupled with the fluid. The incompressible NavierStokes equations are solved using a stabilized finiteelement method on an unstructured grid. Rigid particle collisions are modeled using a damped softsphere approach. We employ an efficient hashtable based celllist to accelerate particle collision detection in complex domains. Particlefluid coupling is performed using a twostage procedure that decouples the particle sizes from the mesh element size. The resulting process is a consistent, conservative and convergent method that naturally handles complex geometries. These improvements contrast with prior approaches on unstructured grids. The method developed here is used to study benign paroxysmal positional vertigo which is caused by particles settling in the semicircular canals of the inner ear. 
Monday, November 20, 2023 8:13AM  8:26AM 
L46.00002: Filtered volume fraction fluctuations: a measure to model clustering in dilute, noncollisional particleladen flow John Wakefield, Jesse Capecelatro, Shankar Subramaniam Turbulent particleladen flows are known to give rise to spatial heterogeneity (e.g. clustering) characterized by twopoint statistics. However, most coarsegrained models only solve for onepoint moments, challenging their ability to accurately reproduce important twophase flow statistics. In this talk, we present a new set of equations describing the evolution of these flows that include fluctuating components of filtered fields that describe the level of clustering present in these flows. We demonstrate that for dilute heavy particles settling in homogeneous isotropic turbulence, the averaged filtered drag and filtered Reynoldsstress like term that dictates enhanced settling is correlated to this description of volume fraction fluctuation. A datadriven approach that efficiently traverses parameter space in direct numerical simulations to inform closures is proposed, providing both descriptive insights and directions for future modeling. The evolution of the fluctuation of filtered volume fraction is shown to be valuable in that it may enable better fits for unclosed quantities related to particle drag and particlephase momentum flux in coarsegrained simulations. 
Monday, November 20, 2023 8:26AM  8:39AM 
L46.00003: Chaotic Behaviour of Multiple Immersed Ellipsoids Andrew Boyd, Prashant Valluri, David Scott, Mark Sawyer, Rama Govindarajan Building on previous work (Essmann et al, 2020) exploring the complex dynamics of a single immersed ellipsoid, we investigate the dynamics of multiple immersed ellipsoids under both inviscid and viscous environments. Earlier, using our inhouse fullycoupled 6DoF solidfluid DNS solver, GISS (https://github.com/eessmann/GISS, Essmann et al 2020), we showed that a single body can present chaotic motions even under viscous environments under certain conditions due to vortex shedding. Here, we extend Kirchoff’s equations to multiple bodies under inviscid conditions, using Lamb (1932) as a starting point. Analytical solutions for added mass and inertia are no longer available for multiple bodies, and so we solve for the potential flow using boundary integral equations (BIE), and resolve for the forces on the bodies by evaluating the flow using a regularisation of the hypersingular BIE (Toh et al, 1994). Calculations are carried out in Rust and are parallelised with a high degree of efficiency. Rotational motion is represented using quaternions. Using recurrence quantification and crosscorrelation analyses (Marwan et al, 2007), we will present how we can characterise chaos and how the number of solids affects chaos. 
Monday, November 20, 2023 8:39AM  8:52AM 
L46.00004: Determination of the probability of randomly forced pointparticle tracers Daniel DominguezVazquez, Sergio B CastiblancoBallesteros, Daniel M Tartakovsky, Gustaaf B Jacobs A method is proposed that determines the probability of the location and velocity of a randomly forced, Lagrangian pointparticle trace. Randomness naturally describes deviations from the exact Stokes drag law of a spherical shaped pointparticle for different shapes and physical conditions. A hyperbolic PDE model is derived that propagates this randomness into its joint PDF solution that governs the particle phase. A Method of Characteristics (MoC) solves the PDE locally and thus determines the probability of a single trace. The traces seeded at a tensorial grid of Jacobi quadrature points at initial time and computed over a finite time yield a highorder flow map. This flow map is used to determine marginals and moments of the PDF. The MoC approach is not subject to grid based numerical inaccuracies and instabilities in the solution of Eulerian form such as spatial approximation errors and Gibbs oscillations. We validate this novel framework with several tests and show that the MoC is accurate and computationally more efficient than the Eulerian method and Monte Carlo (MC) based methods. 
Monday, November 20, 2023 8:52AM  9:05AM 
L46.00005: Modeling particle dispersion in a turbulent puff Max P Herzog, Vikas Bhargav, William N McAtee, Vrishank Raghav, Jesse Capecelatro In this work we consider particle dispersion in a turbulent pulsed jet. Unresolved subgridscale velocity fluctuations in coarsegrained simulations like largeeddy simulation and Reynoldsaveraged NavierStokes play a significant role in particle dynamics. Stochastic models are commonly used to model the subgridscale velocity fluctuations 'seen' by particles as they have proven effective in recapturing onepoint and twotime statistics. However, stateoftheart continuous random walk models lack spatial correlation, leading to the loss of twopoint statistics and geometric features such as clustering and preferential concentration. We present a twopoint Lagrangian stochastic model designed to capture spatial particle distributions and maintain the onepoint and twotime capabilities of classical stochastic models. Model coefficients are chosen to reproduce the correct scaling of particlepair relative statistics. Comparisons of particle dispersion and preferential concentration between direct numerical simulations, largeeddy simulations, and experimental data demonstrate the utility of stochastic models and the need for a twopoint formulation. 
Monday, November 20, 2023 9:05AM  9:18AM Author not Attending 
L46.00006: Abstract Withdrawn

Monday, November 20, 2023 9:18AM  9:31AM 
L46.00007: Simulation and validation of a multiphase flow of hydriding ejecta particles Jonathan D Regele, Frederick Ouellet, Alan K Harrison A hydride model for solid ejecta particles has been developed and presented previously with minimal validation [Regele, J. D., Schwarzkopf, J. D., Buttler, W. T., Harrison, A. K., A simple hydride model for cerium ejecta particles, 72nd Annual Meeting of the APS Division of Fluid Dynamics, Seattle, WA 2019]. That model is revisited here with more detailed validation by simulating the experiment which motivated the model's development and analyzing the entire multiphase flow field as is done in the experiment. A detailed comparison of the total ejecta mass produced, particle sizes, velocities and particle temperatures is performed to validate the hydriding particle model. The challenges with temperature validation are highlighted and different techniques for mitigating these issues are discussed. 
Monday, November 20, 2023 9:31AM  9:44AM 
L46.00008: Large eddy simulation of turbulent gasdroplet flows using the fully Lagrangian approach Christopher Stafford, Oyuna Rybdylova The fully Lagrangian approach (FLA) is a promising means of modelling gasdroplet flows, through its representation of the droplet phase as a continuum in combination with a seeding of Lagrangian trajectories which retain the mesoscopic detail of individual droplet motion. This provides a high resolution of the droplet number density field as it undergoes clustering and segregation in response to the structural behaviour of the carrier flow, and along with the advantages in both accuracy and computational economy that the FLA offers, makes it a suitable methodology for use within turbulent flows. The present work addresses this by developing a formulation of the FLA in the framework of large eddy simulation. In keeping with the continuum representation of the FLA, droplets are tracked in the filtered turbulent velocity field, and the subgrid scale (SGS) fluid velocity is formally accounted for through the Lagrangian form of the droplet phase continuity equation. This contribution takes the form of an additional unclosed mass flux, and is modelled using a kinetic PDF approach, with the correlations between the droplet number density and SGS fluid velocity fluctuations being closed via a correlation splitting procedure that incorporates the nonlocal turbulent drift effects on the droplet phase. The evolution of the number density field calculated using this procedure is examined, and compared to the number density based on only the filtered fluid velocity field across a range of values of droplet inertia. 
Monday, November 20, 2023 9:44AM  9:57AM 
L46.00009: Comparing turbulent dispersion models for RANS simulations of particleladen flows Florian L Stoll, Cairen J Miranda, John Palmore Jr The ingestion of sandparticles into turbomachinery decreases their longevity and performance and can even lead to failure. To address these problems, studying particle deposition and erosion is of high interest in the field. For engineering design, RANS remains an important tool for analyzing turbulent flow behavior, due to low computational cost. RANS simulations solve for the time averaged velocity field. This presents an issue for particleladen flow analysis since particles are affected by the velocity fluctuations within the flow field. In order to get physical results, RANS simulations are augmented with particle dispersion models that include the influence of small scale velocity fluctuations on particle trajectory. 
Monday, November 20, 2023 9:57AM  10:10AM 
L46.00010: Analysis of Compressible ParticleParticle Interaction in Ejecta Particle Simulations Smyther Hsiao, Frederick Ouellet, Jonathan D Regele Ejecta physics play an important role in materials shocked by high explosives. When a shock impacts a surface of a solid material and melts it, the RichtmyerMeshkov instability grows perturbations on the surface until particles are ejected. After release, the ejecta travel through the postshock compressible flow. To simulate the large number of ejecta particles, an EulerLagrange approach is preferred to model the physics at a subgridscale level. If the volume fraction of the particles is high enough, one needs to resolve the particleparticle interaction. In this talk, we review efforts to model such systems, bring different force components of particle hydrodynamics to attention, and examine the relative importance of each term. 
Monday, November 20, 2023 10:10AM  10:23AM 
L46.00011: The rise of a sphere along the axis of a rotating container: Revisiting Maxworthy's 1970 experiment on a computer Jacques J Magnaudet, Tristan Aurégan, Thomas Bonometti The flow induced by a rigid particle rising along the axis of a tall cylindrical container set in rigidbody rotation is computed over a parameter range similar to that explored experimentally by Maxworthy in his famous 1970 experiment. Computations reveal how the internal characteristics of the Taylor column, those of the inertial wave pattern and the loads acting on the particle vary with the control parameters.
The drag on the particle may be much higher in rotationdominated configurations than in a nonrotating flow, but may become lower in inertiadominated configurations. Axial confinement is shown to increase dramatically the drag in rapidly rotating configurations, unless the container is unreasonably tall. Once this confinement effect is made negligibly small, the drag agrees well with semianalytical laws over a wide range of flow conditions, revealing the origin of the persistent gap between Maxworthy’s results and theoretical predictions.

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