Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session E3: Porous Media Flows III: Mixing and Transport |
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Chair: Petr Denissenko, University of Warwick Room: 3004 |
Sunday, November 23, 2014 4:45PM - 4:58PM |
E3.00001: The Impact of Miscible Viscous Fingering on Mixing Jane Chui, Pietro de Anna, Ruben Juanes Viscous fingering is a hydrodynamic instability that occurs when a less viscous fluid displaces a more viscous one. Instead of progressing as a uniform front, the less viscous fluid forms fingers that vary in size and shape to create complex patterns. The interface created from these patterns affects mixing between the two fluids, and therefore understanding how these patterns evolve in time is of critical importance in applications such as enhanced oil recovery and microfluidics. In this work, we focus on experimentally quantifying the impact of miscible viscous fingering on mixing. We use a radial Hele-Shaw cell as an analog of radial flows in porous media, and the local concentration field is measured temporally and spatially with the use of a fluorescein tracer. We first observe two distinct growth regimes in the evolution of the diffuse invading front: an initial regime of rapid growth due to the viscous fingering instability, and a latter regime of growth equivalent to a stable uniform displacement. We propose a scaling framework that predicts the time of transition between these two regimes, and subsequently the total length of the invading front. This framework will help to accurately determine the interface available for mixing when viscous fingering is observed. [Preview Abstract] |
Sunday, November 23, 2014 4:58PM - 5:11PM |
E3.00002: Statistics of admixture distribution in flows through rigid foams Petr Denissenko, Pierre Le Fur, Jozef Vlaskamp, Mark Williams, Xiaolei Fan, Alexei Lapkin Diffusion and dispersion of admixture in flows through rigid foams need to be accounted for when modelling catalytic reactions on the foam surface. We study diffusion of admixture and scaling exponents of admixture concentration both experimentally and by numerical simulations. A liquid admixture was continuously released from a point source at the upstream boundary of a block of rigid SiC foam. Foam thickness was varied from 20 to 80 average pore sizes. A flow with Re of up to 300 based on the pore size was imposed by a progressive cavity pump. The distribution of the tracer at the exit from the foam was measured using LIF and the concentration moments have been calculated. Numerical simulation of the flow in laminar regime has been performed within OpenFoam for the Re from 1 to 100. Geometry of the sample was acquired by Micro Computed Tomography scanning of the actual foam sample. A steady-state SIMPLE method was used to solve the incompressible steady flow in the volume of 20x20x40 average pore sizes. Diffusion and dispersion of passive scalar has been studied by following individual streamlines. Results are interpreted in terms of mixing, heat transfer, and selectivity of catalytic reactions at the foam surface. [Preview Abstract] |
Sunday, November 23, 2014 5:11PM - 5:24PM |
E3.00003: Mixing-Scale Dependent Dispersion For Transport in Heterogeneous Flows Marco Dentz, Felipe P.J. de Barros Dispersion quantifies the impact of microscale velocity fluctuations on the effective movement of particles and the evolution of scalar distributions in heterogeneous flows. It depends on the interaction between the velocity fluctuation scales and the scale on which the scalar is homogenized. The mixing, or coarse grained scale is the characteristic length below which the scalar is well mixed. It evolves in time as a result of dispersion and deformation of material fluid elements in the heterogeneous flow. We propose to use the mixing scale as a natural coarse graining scale for dispersion in heterogeneous flows. Using a stochastic modeling approach, we derive explicit expressions for the mixing-scale dependent dispersion coefficients and their variance. The fundamental mechanisms of local dispersion and compression of material fluid elements on evolving velocity scales determine the evolution of mixing-scale dependent dispersion and its self-averaging behavior. [Preview Abstract] |
Sunday, November 23, 2014 5:24PM - 5:37PM |
E3.00004: Direct Numerical Simulation of turbulent flow in a porous, face centered cubic cell Xiaoliang He, Sourabh Apte, Brian Wood DNS of flow through a 3D, periodic, face centered cubic (FCC) unit cell geometry at $Re = 300$, $550$, and $950$ based on diameter is performed. This low porosity arrangement of spheres is characterized by rapid flow expansions and contractions, and thus features an early onset to turbulence. The simulations are performed using a fictitious domain approach [Apte et al, J. Comp. Physics 2009], which uses non-body conforming Cartesian grids, with resolution up to $D/\Delta=250$ ($354^3$ cells total). The results are used to investigate the structure of turbulence in the Eulerian and Lagrangian frames, the distribution and budget of turbulent kinetic energy, and the characteristics of the energy spectrum in complex packed beds and porous media. The porescale flow physics, which are important to properties such as bulk mixing performance and permeability, are investigated. Specifically, the data generated is being used to understand the important turbulence characteristics in low porosity packed beds of relevance for heat tranfer applications in chemical/nuclear reactors. [Preview Abstract] |
Sunday, November 23, 2014 5:37PM - 5:50PM |
E3.00005: Modeling of nanoparticle transport and deposition in a porous medium: Effects of pore surface heterogeneity Ngoc Pham, Dimitrios Papavassiliou Pore surface charge heterogeneity has been found to affect particle retention in flow through porous media. In this study, retention of nanoparticles under different surface blocking conditions is numerically investigated. Micro-CT scanning is used to reconstruct the 3D geometry of sandstone and image-based analysis is used to characterize the pore space and the mineral composition of the rock. Flow of water through the sample is simulated with the lattice Boltzmann method. The motion of nanoparticles is modeled by injection of particles moving under convection and molecular diffusion and recording their trajectories in time [1,2]. When interacting with the pore surface, particles can be retained onto the surface with a particular deposition rate. As deposited particles hinder the retention of other particles by blocking occupied sites, the deposition is considered to be a second order process. Particle breakthrough under different modeled and real distributions of surface heterogeneity as a function of various surface blocking conditions is investigated. The effect is stronger when parts of the surface are much more favorable for deposition than others. \\[4pt] [1] Voronov, R.S., VanGordon, S., Sikavitsas, V.I., Papavassiliou, D.V., \textit{Int. J. Num. Metods in Fluids,} \textbf{67,} 501, 2011\\[0pt] [2] Pham, N., Swatske, D.E., Harwell, J.H., Shiau, B.-J., Papavassiliou, D.V., \textit{Int. J. Heat {\&} Mass Transf.}, \textbf{72, }319, 2014 [Preview Abstract] |
Sunday, November 23, 2014 5:50PM - 6:03PM |
E3.00006: Advective-diffusive transport in microflows Patrick Anderson, Michel Speetjens, Oleksandr Gorodetskyi Advective-diffusive transport in microflows is studied by means of the diffusive mapping method, a recent extension of the mapping method by Gorodetskyi et al. (Phys. Fluids 24, 2012) that includes molecular diffusion. This greatly expands the application area of the mapping technique and makes the powerful concepts of eigenmode decomposition and spectral analysis of scalar transport accessible to an important class of flows: inline micromixers with diffusion. The staggered herringbone micro-mixer is adopted as a prototypical three-dimensional micro mixer. Simulations with the diffusive mapping method are in close agreement with experimental observations in literature and expose a strong impact of diffusion on the transport. Diffusion enables crossing of Lagrangian transport barriers and thus smoothens concentration gradients and accelerates homogenization. Spectral analysis of the mapping matrix reveals this already occurs on a modal level in that individual eigenmodes progressively smoothen and spread out across transport barriers with stronger diffusion. Concurrently, the corresponding eigenvalues diminish and thus fundamentally alter the mixing process by invariably causing homogenization, irrespective of the Lagrangian flow structure. [Preview Abstract] |
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