Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session G08: Multiphase Flows: ParticleLaden Flows I 
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Chair: Greg Voth, Wesleyan University Room: Georgia World Congress Center B213 
Monday, November 19, 2018 10:35AM  10:48AM 
G08.00001: Theoretical and Experimental Investigation of Forward Spatter of Blood from a Gunshot Patrick Comiskey, Alexander Yarin, Daniel Attinger 
(Author Not Attending)

G08.00002: Abstract Withdrawn Particle entrainment and transport under the influence of shock waves is ubiquitous in both nature and engineering. In particular, a proper understanding of the transport mechanisms of particles following a nuclear explosion is critical in mitigating damage from the blast wave. To accurately model it numerically, we use the shock produced in electrostatic discharge (ESD) experiments at the NNJIT as a surrogate for a nuclear blast wave in nonreacting dusty air. Using the U. Chicago’s code FLASH, we investigate the possible mechanisms of dust suspension and dispersion during the early phases of such flows (at Mach 1.01.5), using the 2D compressible NavierStokes equations in cylindrical geometry. The dust particles are assumed to be spherical, inert, rigid and initially at rest. The effects of particleparticle interactions, particlewall interactions, particle volume fraction and size distribution on the particle transport are taken into account. Additionally, a variation of the hard sphere model is adopted to study the particle agglomeration, which is an important aspect of the particleparticle interactions as observed in the scanning electron microscope (SEM) images in the accompanying ESD experiments with powdered glass beads (particles being 350 microns in diameter). 
Monday, November 19, 2018 11:01AM  11:14AM 
G08.00003: Particle fountains in a confined environment Martin Conrad Lippert, Andrew W Woods We present an experimental investigation of particleladen fountains in a confined environment. These experiments are complimented by simplified theoretical models which provide insight into the underlying physics. The multiphase fountains are produced by issuing a mixture of fresh water and SiliconCarbide particles upwards through a nozzle into a laterally confined water tank. The mixture issues through the nozzle as a dense particleladen jet that decelerates owing to its negative buoyancy and the entrainment of ambient liquid. The fluid rises to a finite height before falling back to the floor. 
Monday, November 19, 2018 11:14AM  11:27AM 
G08.00004: Does Lord Kelvin’s Isotropic Helicoid Exist? Greg Voth, Darci Collins, Rami J. Hamati In 1871, Lord Kelvin hypothesized the existence of a particle he called an isotropic helicoid which is chiral so that it couples translation and rotation but is isotropic in both drag and translationrotation coupling. Since then, several textbooks and theoretical papers have considered isotropic helicoids. We recently fabricated particles with a 3D printer following the isotropic helicoid design that Lord Kelvin proposed, dropped them in a quiescent fluid, and were surprised to find that they showed no rotationtranslation coupling. We then calculated the translationrotation coupling for an isotropic helicoid made of 12 oblate ellipsoids configured according to Lord Kelvin’s design. This calculation is done in Stokes flow, ignoring interparticle interactions. Again we found precisely zero rotationtranslation coupling. Numerical simulations agree with the experiments and theory. We conclude that Lord Kelvin’s particle is isotropic but does not couple translation and rotation. We conjecture that it is not possible to fabricate a particle that has isotropic but nonzero translationrotation coupling and isotropic drag. 
Monday, November 19, 2018 11:27AM  11:40AM 
G08.00005: Dispersion of Rock and CoalDust in Stratified Dust Layers Shuyue Lai, Ryan Houim, Elaine S Oran Numerical simulations of a shock wave passing over layered rock and coal investigated whether and how the presence of rock effects the entrainment of coal in an explosion. We use a multifluid granular flow model based on the Kinetic Theory for Granular Flow (KTGF) and account for multiple particle types with a binning approach. More specifically, we consider the dispersal of coal and rock dust under the action of a Mach 1.4 shock wave. The rock and coal particles have a density of 2680 kg/m^{3} and 1330 kg/m^{3}, and a diameter of 15 μm and 30 μm, respectively. When a thin layer of rock dust is initially placed on top of a thicker layer of coal particles, entrainment of the coal dust behind the shock wave is suppressed. Increasing the thickness of the rock dust shows that only the top 23 mm of the rock is entrained, and particles in the bottom layer remain stationary or become slightly compacted. We also performed simulations in which coal dust was initially placed on top of the rock dust. This configuration does not suppress entrainment of the coal particles, and particles in the dispersed region are primarily coal particles. The results are explained on the basis of the forces on the particles.

Monday, November 19, 2018 11:40AM  11:53AM 
G08.00006: Removal of fine particulate matter (PM_{2.5}) using atmospheric humidity caused by plant leaf transpiration Jeong Jae Kim, Jeongeun Ryu, Sang Joon Lee Removal of particulate matter (PM) reduction is one of the most significant challenges in public health and environment protection. To mitigate PMrelated problems and effectively remove PM_{2.5}, tree planting and afforestation have been proposed as ecofriendly strategies. However, the PM removal effect of plants and its primary mechanism remains uncertain. In this study, we experimentally investigated the PM removal performance of five species in a closed chamber and the effects of relative humidity (RH) caused by plant evapotranspiration, as a governing parameter. Based on the PM removal tests, we selected Scindapsus as a representative plant among the tested plants to identify the PM removal efficiency depending on evapotranspiration and particle type. As a result, Scindapsus showed a high PM removal efficiency for smoketype PM_{2.5} under active transpiration. We examined the correlation between PM removal and relative humidity (RH) and evaluated the effect of increased RH on PM_{2.5} removal by using a plantinspired in vitro model. These results support that the increase of RH due to plant evapotranspiration is crucial for the reduction of PM_{2.5}. 
Monday, November 19, 2018 11:53AM  12:06PM 
G08.00007: Effect of density ratio on velocity fluctuations in dispersed multiphase flow from particleresolved numerical simulation Vahid Tavanashad, Alberto Passalacqua, Rodney Otis Fox, Shankar Subramaniam Particleresolved direct numerical simulation of a statistically homogeneous case of a dispersed multiphase flow is used to study the velocity fluctuations in the carrier phase and dispersed phase. The simulations are presented for a fixed mean slip Reynolds number (\Re_m=20) and a wide range of dispersed phase volume fractions (0.1 < \phi < 0.4) and density ratios of the dispersed phase to the carrier phase (0.001 < \rho_p/\rho_f < 1000). The velocity fluctuations are quantified by the turbulent kinetic energy (TKE) for the carrier phase and the granular temperature for dispersed phase at statistically stationary state. The results show that the granular temperature increases and then reaches an asymptotic value with decreasing density ratio. The qualitative trend of the behavior is explained by the added mass effect. The dependence of TKE on the density ratio for all volume fractions studied here is also explained. It is also shown that the lowdensity ratio cases are less efficient in extracting energy from mean flow to fluctuations by comparing the mixture kinetic energy for different cases. 
Monday, November 19, 2018 12:06PM  12:19PM 
G08.00008: A Lattice Boltzmann Model Simulating Hydrodynamics of Particleladen Aqueous Foams and Emulsions Subhabrata Das, Zixiang Tong, Justin Heftel, Xi Chen, Raymond Farinato, D.R. Nagaraj, Joel Koplik, Charles Maldarelli, Ponisseril Somasundaran A mesoscopic two component, 2D Lattice Boltzmann Model (LBM) with longrange repulsive and frustrated shortrange attractive interactions is implemented to capture the topological changes in multiphase foams and emulsions with particles suspended within the liquid and/or vapor phases in a HeleShaw geometry. The model is first validated by simulating the dynamics of a singlesuspended particle on a planar liquidvapor interface and Poiseuille flow of liquid. Initial foam interfaces are being modeled by 2D Voronoi tessellations or images directly captured by Foam analyzer or a Flowfocusing microfludic device used to generate the monodisperse bubbles. As the fluid drains out, the wet to dry foam transition is observed with bubble deformation, coalescence and eventual collapse with the foams start breaking at the top of the cell. However, this transition and bubble coalescence process is drastically reduced in presence of particles of varied hydrophobicity. The effect of shortrange structural repulsion forces along with Vander Waals Attraction and Electrical Double layer repulsion forces in an extended DLVO theory is further investigated for particles dispersed in the foam/emulsion. 
Monday, November 19, 2018 12:19PM  12:32PM 
G08.00009: Investigation of Thermal Effects in lowRe sedimentation at anomalously large Pe James Stadler, Charles Walker, Ted Brzinski A recent metanalysis of hindered settling speeds reported in the literature showed that the data fall on two distinct branches, both of which are welldescribed by a hindered settling function of the RichardsonZaki form H(φ)=(1φ)^{n}, where φ is the particle volume fraction, but with different exponents: n≈5.5 for Brownian systems with a small Peclet number, and n≈4.5 for nonBrownian systems with large Peclet number. The critical Peclet number is Pe≈10^{8}, which is surprisingly large. We present preliminary progress in determining the grainscale, mechanistic origins of this result using a combination of lightscattering and image analysis techniques. 
Monday, November 19, 2018 12:32PM  12:45PM 
G08.00010: A Cartesian, adaptively refined and staggered grid, monolithic incompressible multiphase flow solver for high density and high shear particleladen flows Amneet Pal Singh Bhalla, Nishant Nangia, Neelesh Ashok Patankar Multiphase flows in presence of particulate matter are ubiquitous in natural and industrial processes. However, such flows are quite challenging to model computationally especially for high density and high viscosity contrasting fluids. Naive discretization of the incompressible NavierStokes (INS) equations fail miserably due to interfacial instabilities for high density and high shear flows. At the same time the spatially varying coefficients lead to a complicated linear system which is hard to solve implicitly. In this work we overcome both these limitations by employing a consistent and wellbalanced discretization of the INS equations which is solved as a monolithic system on staggered, Cartesian and adaptively refined grids. The spatiotemporal discretization remains stable for upto six order of magnitude contrast between density and viscosity coefficients. We present several convergence and orderofaccuracy results, as well as two phase and three phase fluidstructure interaction examples. The fluidfluid interface is captured on the Eulerian grid using level set method, whereas the immersed particulate matter is fully resolved via the immersed boundary method. 
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