Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session F36: ParticleLaden Flows: Experimental TechniquesExperimental Particles

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Chair: Laura Villafane, Stanford University Room: 302 
Monday, November 20, 2017 8:00AM  8:13AM 
F36.00001: Measurements of gas temperature in a radiatively heated particle laden turbulent duct flow Ji Hoon Kim, Andrew Banko, Laura Villafane, Chris Elkins, John Eaton Predicting the absorption of radiation through a turbulent, particle laden flow is relevant in atmospheric sciences, turbulent combustion, and in the design of a particle solar receivers. In order to better understand the coupling between the particle phase, the turbulent fluid phase, and the incident radiation, the effects of radiation absorption by disperse inertial particles in a turbulent duct flow was studied experimentally. A fullydeveloped turbulent duct flow at Reynolds numbers of $O$(10$^{\mathrm{4}})$, laden with particles at mass loading ratios of 0.10.8, was subject to infrared radiation at varying incident powers. The particle Stokes number based on the Kolmogorov length scale was approximately 12, resulting in a preferentially concentrated particle phase. Measurements of the mean and fluctuating components of the gas phase temperature were made along the wall bisector. Results from mean temperature traverses of the gas phase show that a onedimensional model can account for much of the mean gas temperature rise. Temperature fluctuations due to preferential concentration are significant and can reach approximately 50{\%} of the mean temperature rise. [Preview Abstract] 
Monday, November 20, 2017 8:13AM  8:26AM 
F36.00002: Effects of preferential concentration on direct radiation transmission in a turbulent duct flow Laura Villafane, Andrew Banko, Ji Hoon Kim, Chris Elkins, John Eaton Inertial particles in turbulent flows preferentially concentrate, giving rise to spatial and temporal fluctuations of particle number density that affect radiation transmission through the medium. Positive particle correlations enhance direct transmission when compared to the exponential attenuation predicted by the Beer's Law for randomly distributed particles. In the context of a particle based solar receiver, this work studies the effects of preferential concentration and optical depth on direct transmission through a particle laden turbulent duct flow. Time resolved measurements of transmission through the mixture were performed for various particle loadings and Reynolds numbers, thus varying particle correlation lengths, optical depth and concentration fluctuations. These measurements were made using a photodiode to record the transmission of a collimated laser beam along the wall bisector of the duct. A synchronized highspeed camera provided particle positions along most of the beam path. Average and fluctuating radiation transmission results are compared to predictions derived from the imaged number density fields and to simplified analytical models. Simplified models are able to capture the correct trends with varying loading and preferential concentration. [Preview Abstract] 
Monday, November 20, 2017 8:26AM  8:39AM 
F36.00003: Evaluating the influence of particulate matter on spectroscopic measurements of a combusting flow Jonathan Herlan, Nathan Murray An adiabatic tabletop burner has been used to develop a method for estimating the temperature and concentration of OH in a measurement volume of a nonpremixed, hydrogenair flame. The estimation method uses a nonlinear curvefitting routine to compare experimental absorption spectra with a model derived, using statistical mechanics, from the BeerLambert law. With the aim of applying this method to the analysis of rocket exhaust plumes, this study evaluates whether or not it provides faithful estimates of temperature and OH concentration when the combusting flow contains particulate mattersuch as soot or tracers used for particle image velocimetry (PIV) measurements. The hydrogen line of the tabletop burner will be seeded with alumina, Al$_{2}$O$_{3}$, particles and their influence on spectroscopic measurements elucidated. [Preview Abstract] 
Monday, November 20, 2017 8:39AM  8:52AM 
F36.00004: Stochastic Modeling of Direct Radiation Transmission in ParticleLaden Turbulent Flows Andrew Banko, Laura Villafane, Ji Hoon Kim, Mahdi Esmaily Moghadam, John K. Eaton Direct radiation transmission in turbulent flows laden with heavy particles plays a fundamental role in systems such as clouds, spray combustors, and particlesolarreceivers. Owing to their inertia, the particles preferentially concentrate and the resulting voids and clusters lead to deviations in mean transmission from the classical BeerLambert law for exponential extinction. Additionally, the transmission fluctuations can exceed those of Poissonian media by an order of magnitude, which implies a gross misprediction in transmission statistics if the correlations in particle positions are neglected. On the other hand, tracking millions of particles in a turbulence simulation can be prohibitively expensive. This work presents stochastic processes as computationally cheap reduced order models for the instantaneous particle number density field and radiation transmission therein. Results from the stochastic processes are compared to Monte Carlo Ray Tracing (MCRT) simulations using the particle positions obtained from the pointparticle DNS of isotropic turbulence at a Taylor Reynolds number of 150. Accurate transmission statistics are predicted with respect to MCRT by matching the mean, variance, and correlation length of DNS number density fields. [Preview Abstract] 
Monday, November 20, 2017 8:52AM  9:05AM 
F36.00005: Dispersion and layering of solid particles in cylindrical Couette flows Mohammad Sarabian, Mohammad Hossein Firouznia, Bloen Metzger, Sarah Hormozi Suspensions of rigid spherical particles in a cylindrical Couette flow of a Newtonian fluid is carefully studied at very low Reynolds number. We have used both Particle Tracking Velocimetry (PTV) and Particle Image Velocimetry (PIV) to examine the solid volume fraction and velocity field respectively. The experiments are carried out for a wide range of solid volume fractions (i.e., from dilute to dense suspensions). The results show that particles disperse toward the outer wall of the cylinder where a strong layering of particles occurs due to the confinement effects. ~We observe this phenomenon for the bulk volume fractions beyond 20{\%}. The particle layering enhances drastically by approaching ~the limit of dense suspensions. ~We present the comparison of both transient and steady state results with available continuum model frameworks. ~These well resolved experimental results can be used as a benchmark for fully resolved numerical simulations. [Preview Abstract] 
Monday, November 20, 2017 9:05AM  9:18AM 
F36.00006: Drag coefficient for sedimentatingrotating spherical particles in a viscoelastic fluid Alfonso Castillo, Roberto Zenit The sedimentation of a single sphere in a viscous fluid is a classical problem in fluid mechanics. Despite its apparent simplicity, the problem is full of delicate intricacies. In particular, for the case of viscoelastic fluids, the subject is still not fully resolved: it is unclear whether the drag should increase of decrease (with respect to the Newtonian case) for large values of the Weissemberg number. We study this problem with a twist, literally. To extend the range of shear rates attained for a given fluidsphere combination we make it rotate, with an external magnetic field, as it sediments. We therefore can significantly extend the range of Weissenberg numbers to well above 1. We use a Newtonian reference fluid, a Bogertype fluid and spheres of different sizes and weights. The drag coefficient, and drag correction factor are calculated for all cases. Our nonrotating results are in good agreement with those by Jones et al., 1994. We observe that for rotatingsedimenting spheres the drag is always larger than in the Newtonian case. [Preview Abstract] 
Monday, November 20, 2017 9:18AM  9:31AM 
F36.00007: Friction and drag forces on spheres propagating down inclined planes Yi Hui Tee, Ellen Longmire When a submerged sphere propagates along an inclined wall at terminal velocity, it experiences gravity, drag, lift, and friction forces. In the related equations of motion, the drag, lift and friction coefficients are unknown. Experiments are conducted to determine the friction and drag coefficients of the sphere over a range of Reynolds numbers. Through high speed imaging, translational and rotational velocities of spheres propagating along a glass plate are determined in liquids with several viscosities. The onset of sliding motion is identified by computing the dimensionless rotation rate of the sphere. Using drag and lift coefficients for Re \textless 350 obtained from numerical simulations by Rao et al. (JFM, 2012), both static and kinetic friction coefficients are calculated for several materials. The friction coefficients are then employed to estimate the drag coefficient for 350 \textless Re \textless 2000. The resulting drag curve for a sphere propagating along a wall demonstrates the importance of the frictional force over this Re range. [Preview Abstract] 
Monday, November 20, 2017 9:31AM  9:44AM 
F36.00008: Particles in shearthinning fluids Charu Datt, Gwynn Elfring The dynamics of particles in nonNewtonian fluids can be markedly different than in Newtonian fluids. In this talk, we present analytical results for the motion of spheres in weakly shearthinning fluids. The results are obtained using the reciprocal theorem of low Reynolds number hydrodynamics and demonstrate ways in which shearthinning rheology nontrivially affects the particle dynamics. [Preview Abstract] 
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