Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session H07: Suspensions: FluidParticle Interactions 
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Chair: Shankar Subramaniam, Iowa State University Room: North 122 C 
Monday, November 22, 2021 8:00AM  8:13AM 
H07.00001: Singlecamera 3D particle tracking and application to shearinduced migration John T Antolik, Amanda Howard, Daniel M Harris In the experimental investigation of suspension flows, it is important to be able to precisely track suspended particles over a wide field of view. We present a costeffective method for singlecamera 3D particle tracking using digital image correlation and demonstrate its application to studying shearinduced migration. A speckle pattern is imaged through transparent spherical particles suspended in a viscous fluid and the resulting pattern distortion is used to deduce the particles’ 3D positions. Using this method, we examine the irreversible migration of millimeterscale particles at low Reynolds number in an oscillatory, rectangular channel flow. We report measurements of the migration dynamics and track interparticle contacts which are generally understood to be the source of irreversibility. 
Monday, November 22, 2021 8:13AM  8:26AM 
H07.00002: Effects of gravitydriven drainage on particle filtration during dip coating Connor B Copeland, Joshua B Bostwick When a solid substrate is withdrawn from a liquid bath at velocity V, a coating of thickness h is deposited according to the classical Landau Levich Derjaguin model. For a particleladen suspension, it has been recently demonstrated by Sauret et al. (2019, 2020) that particles whose size is smaller than the resulting film thickness can be filtered. This mechanism is both tunable and relevant to numerous industrial and medical applications. Here, we perform an experimental study of particle filtration during dip coating using a large range of particle sizes and fluid viscosities, such that our flow is in the gravitydriven drainage regime. Low volume fraction suspensions are utilized in order to minimize changes to the rheology of the fluid and clumping of particles. The filter is tuned by altering the withdraw velocity and data is collected on the thickness of the coating using gravimetric methods while particle entrainment is measured though imaging. Our extensive data set allows us to understand this soft particle filtering process over a wide range of flow conditions. 
Monday, November 22, 2021 8:26AM  8:39AM 
H07.00003: Shearmigration in dense suspensions from the point of view of physicsinformed neural networks Daihui Lu, Ivan C Christov Phillips et al. [Phys. Fluids A 4 (1992) 30] proposed a phenomenological model for the shearinduced migration of particles in a lowReynoldsnumber flow. Since then, the model has been the workhorse for continuum modeling of migration phenomena in suspensions. However, being phenomenological, the model has only been calibrated for certain geometries. It is not clear if the model's parameters, determined by visually matching concentration profiles, for one flow scenario are valid in others. To address this knowledge gap, we apply the physicsinformed neural networks (PINNs) approach. Specifically, the NN is constrained via the Phillips et al. model, and a suitable momentum equation for the unidirectional flow of the suspension. The NN is then trained against different experiments from the literature. We first verify the PINN approach for solving the inverse problem of radial particle migration in a nonBrownian suspension in an annular Couette flow. Then, we apply the PINN approach to analyze experiments on particle migration in both nonBrownian and Brownian suspensions in Poiseuille slot flow. For the latter, there is an additional model parameter, which has not been calibrated in prior literature, that we identify using the PINN. Significantly different values for the model parameters are obtained via the PINN upon analyzing Poiseuille flow experiments, although the parameters match Phillips et al. for the classical of an annular Couette flow. The PINN results also show that the bestfit model parameters vary with the Péclet number and the particle bulk volume fraction, instead of being constant as previously assumed. 
Monday, November 22, 2021 8:39AM  8:52AM 
H07.00004: Fluidmediated sources to granular temperature in homogeneous fluidization AARON M LATTANZI, Vahid Tavanashad, Shankar Subramaniam, Jesse S Capecelatro The present study considers analytical solutions for hydrodynamic sources and sinks to granular temperature in homogeneous suspensions of elastic particles at finite Reynolds numbers and solids volume fraction. We model the neighborinduced drag disturbances with an acceleration Langevin, which allows an exact solution for the joint fluctuating accelerationvelocity distribution function $P\left(v^{\prime},a^{\prime};t\right)$. The quadrant conditioned covariance integrals of $P\left(v^{\prime},a^{\prime};t\right)$ are derived, allowing direct computation of the hydrodynamic source and sink that dictate the evolution of granular temperature. Analytical predictions agree with benchmark data obtained from particleresolved direct numerical simulations. Furthermore, the theory correctly predicts saturation of steady granular temperature at small particlefluid density ratios $\rho_p/\rho_f \ll 1$, and thus, shows promise as a general theory from gassolid to bubbly flows. 
Monday, November 22, 2021 8:52AM  9:05AM 
H07.00005: Fluctuating Hydrodynamics of Granular Gases Driven by Thermal Walls Andrew Hong, Ishan Srivastava, Daniel R Ladiges, Alejandro L Garcia, John B Bell At nonequilibrium, molecular gases exhibit largescale fluctuations and longranged hydrodynamical correlations. Enhancement of these fluctuations and correlations have a significant effect on their transport and overall macroscopic behavior. However, in contrast to molecular gases, particle collisions in granular gases are inelastic. In this talk, I will describe the effect of such inelastic particle collisions on hydrodynamical fluctuations in driven granular gases, which are crucial in industry (fluidized beds and aerosols) and nature (aeolian transport and erosion). Using the direct simulation Monte Carlo method, nonequilibrium steady states of granular gases are established through thermal driving from isothermal walls. By systematically varying the magnitude of collision inelasticity, we study the spatial structure of hydrodynamical fluctuations in densityhomogeneous and clustering granular gases. 
Monday, November 22, 2021 9:05AM  9:18AM 
H07.00006: Fluid structure interaction simulations of arbitraryshaped particles settling on a flat surface Tiffany Simmons, Mohsen Daghooghi, Iman Borazjani Fluid structure interaction (FSI) of particles settling on a flat surface in a viscous fluid is simulated using a sharpinterface curvilinear immersed boundary (CURVIB) method. The dynamics of particles after the collision with the flat surface is governed by the conservation of angular and linear momentum, which are written with respect to the contact point (the instantaneous center of rotation) until a stable position is attained. A simple model based on the Stokes drag and damping is proposed to represent the FSI trend with varying Reynolds Numbers. The arbitraryshaped particles tested include cube, ellipsoid, cylinder, pyramid, and irregular shape. The accuracy of the simple model and the conditions for rebound from the flat surface are discussed. 
Monday, November 22, 2021 9:18AM  9:31AM Not Participating 
H07.00007: A hydrodynamic scaling theory for pair interaction of elastic particles V S S R K Phani Kanth Sanagavarapu, Prabhu R Nott, Ganesh Subramanian We propose a fluid lubricated extension of the Hertzian contact model supported by Finite Element Method (FEM) simulations to capture the deformation features of a pair of elastic particles interacting under constant external force, which could be due to an imposed axisymmetric compressional flow. We obtain simple scaling relations that capture the lateral dimension of the deformation (film radius), maximum dynamic pressure in the narrow gap, film thickness along the line joining the centers of the particles, minimum film thickness at the edge of the film, and the particle stresslet. The characteristic length scale chosen to obtain the scaling relations in the fluid film region is timedependent but universal, independent of the particle stiffness. A comparative study of a pair of interacting elastic particles with the droplets, capsules, and vesicles system shows that the difference in scaling relations can be attributed to the differences in the origin of the lubrication pressure that develops in the narrow gap. 
Monday, November 22, 2021 9:31AM  9:44AM Not Participating 
H07.00008: Nearwall and inertial forces on a neutrally buoyant particle in a wallbounded stagnationpoint flow Jacques J Magnaudet, Micheline Abbas

Monday, November 22, 2021 9:44AM  9:57AM 
H07.00009: Elastic sheets in shear flows, from single sheet behavior to exfoliation process: an experimental study. Hugo PERRIN, Lorenzo Botto Graphene has attracted much attention of the past decade as a candidate material for applications in a variety fields such as electronics, energy generation and storage, and biomedicine. However, the fabrication of high quality graphene at industrial scale and affordable price remains a challenge. One of the most promising techniques to produce graphene from graphite is socalled liquidphase exfoliation. In this technique, graphite is sheared in a liquid until layers of graphene detach from the bulk material. 
Monday, November 22, 2021 9:57AM  10:10AM 
H07.00010: Axisymmetric particle rotations in shear flow Davide Di Giusto, Laurence Bergougnoux, Cristian Marchioli, Elisabeth L Guazzelli We experimentally investigate the rotational dynamics of a neutrallybuoyant axisymmetric particle in a viscous shearing flow. 
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