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 Q36: Porous Media Flows II |
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Chair: Bryan Quaife, Florida State University Room: Georgia World Congress Center B408 |
Tuesday, November 20, 2018 12:50PM - 1:03PM |
Q36.00001: Compressional dynamics of fibrous porous media I: from the coffee press to industrial machinery Daniel Paterson, Duncan R Hewitt, Thomas Eaves, Neil J Balmforth, Mark Martinez We present an experimental and theoretical investigation of compressional dewatering of dense porous fibre suspensions. Fixed rate, uniaxial compression experiments are performed for a variety of compression rates for comparison to a 1D two-phase model, for both nylon and cellulose pulp fibres suspended in viscous fluid. The constitutive functions representing the solid network’s compressive yield stress and permeability are calibrated using independent experiments. Comparisons are made between the model and experiment of both the compressional load and the solid phase velocity. It is found that reasonable representation of nylon fibre suspensions is achieved by a traditional plasticity model for the solid phase, however a strain-rate-dependent extension to the solid network stress in the model is necessary for agreement with cellulose pulp suspensions. The source of this rate-dependent stress is attributed to the hollow, porous-wall structure of cellulose pulp fibres. The model for pulp suspensions can be compared to results found on a pilot-scale Twin Roll Press, for which reduction of a 2D version of the model yields a similar set of equations as the uniaxial compression tests. |
Tuesday, November 20, 2018 1:03PM - 1:16PM |
Q36.00002: Compressional dynamics of fibrous porous media II: gelling and Freeness Thomas Eaves, Daniel Paterson, Duncan R Hewitt, Neil J Balmforth, Mark Martinez We present a model for flow-induced compaction of a fibrous porous medium near its gel point, that is, the smallest solid fraction at which fibres (on average) interact mechanically. The solid network’s compressive yield stress and permeability is calibrated experimentally for a particular cellulose pulp suspension in the low-solidity limit, and the effect of rate-dependence is elucidated via a comparison of the two-phase model to experimental PIV measurements of the solid-phase velocity. A standardised industrial testing device for examining pulp suspensions at low solid-fractions called the “Canadian Standard Freeness” tester and the corresponding “freeness score” is described. The model results compare well with the device, and the dependence of the freeness score on the material properties of the pulp network is elucidated and compared to the freeness scores of a catalogue of pulps whose properties are only known at higher solid-fractions. |
Tuesday, November 20, 2018 1:16PM - 1:29PM |
Q36.00003: Hollow Fibres CFD modelling Gustavo Alonso Patino, Rafael Gioria, Julio Romano Meneghini This work deals with the numerical implementation of a multi-component diffusion model in a selective permeability membrane. The tools developed allow to establish a complete numerical methodology for the analysis of the mechanism of selective permeability in the separation of gases in the CO2 , CH4 mixture. Additionally, we implemented a boundary condition on the membrane surface to model the concentration polarization. The main consequence of the concentration polarization is the reduction of the permeate flow, increasing the osmotic pressure on the feed side of the membrane owing to the surface layer. |
Tuesday, November 20, 2018 1:29PM - 1:42PM |
Q36.00004: Buoyant convection in porous media: Multiple layers with inclined permeability jump* Bharath S. Kattemalalawadi, Chunendra K. Sahu, Morris R Flynn We report upon an experimental study of a filling box flow in a heterogeneous porous medium comprised of two layers of greater (upper layer) and lesser (lower layer) permeability. The associated permeability jump is inclined and the flow, which derives from a discrete line source, has modest Reynolds number but large Peclet number. When plume that issues from the source strikes the permeability jump, a significant fraction of the plume fluid is discharged into an unequal pair of (primary) interfacial gravity currents. These primary gravity currents suffer from drainage loss into the lower layer, as a result they each reach a terminal runout length. We model the associated dynamics using a sharp interface model. Analytical model results predict the time evolution of the gravity currents and their runout lengths. Results are validated with experimental data conducted for different permeability jump angles. Of course, experiments are characterized by perimetric boundaries such that the later time dynamics are of the filling-box variety. Thus the later propagation of primary gravity currents are dictated by the gravity current in the lower layer. We furthermore discuss the nature of filling of upper and lower regions for different plume density. |
Tuesday, November 20, 2018 1:42PM - 1:55PM |
Q36.00005: Effect of dispersion on convective mixing in porous media Marc A Hesse, David DiCarlo, Baole Wen, Yu Liang, Kyung-Won Andre Chang Solutal convection in porous media is thought to be controlled by the molecular Rayleigh number, Ra_{m}, the ratio of the buoyant driving force over diffusive dissipation. The mass flux should increase linearly with $Ra_m$ and the finger spacing should decrease as Ra_{m}^{-1/2}. Instead our experiments find that flux levels off at large Ra_{m} and finger spacing increases with Ra_{m}. Here we show that the convective pattern is controlled by a dispersive Rayleigh number, Ra_{d}, balancing buoyancy and dispersion. Increasing the bead size of the porous medium increases Ra_{m} but decreases Ra_{d} and hence coarsens the pattern. While the flux is predominantly controlled by Ra_{m}, the anisotropy of mechanical dispersion leads to an asymmetry in the pattern that limits the flux at large bead sizes. |
Tuesday, November 20, 2018 1:55PM - 2:08PM |
Q36.00006: Simulations of convection, phase change and solute fluxes in a porous mushy layer James RG Parkinson, Dan Martin, Rich F Katz, Andrew J Wells Sea ice is a reactive porous material composed of ice crystals and an interstitial saline fluid (or 'brine'); a so-called mushy layer. Dense brine tends to sink through the ice, driving convection. Downwelling at the edge of convective cells leads to the development of narrow, entirely liquid channels, through which saline brine is efficiently rejected into the underlying ocean. |
Tuesday, November 20, 2018 2:08PM - 2:21PM |
Q36.00007: Adjoint Formulation and Sensitivity Analysis for Flows through Porous Media with Adsorption. João Brasil Lima, Bruno Galelli Chieregatti, Ernani Vitillo Volpe, Marcelo Tanaka Hayashi Adsorbed Natural Gas (ANG) technology has gained importance, lately, in storage applications due to the development of more effective adsorbent materials. However, its widespread use still poses a few challenges. Among them, the exothermic character of the adsorption process is no small matter. For a temperature rise will hinder the adhesion of gas molecules to the adsorbent bed, thus diminishing its storage capacity altogether. Under these circumstances, the thermal management of adsorption is an attractive proposal. While for small tanks that may be accomplished by passive devices, larger ANG reservoirs may require active thermal management systems, comprising heat exchangers and more sophisticated control of the transient filling process. In order to address those questions, with especial emphasis on active systems, we derive a continuous form of the adjoint problem to porous media flows with adsorption. Our approach allows for the computation of sensitivities with respect to both device geometry and operational conditions. This work focuses on the later case, presenting sensitivity calculations which enables future optimizations cases. |
Tuesday, November 20, 2018 2:21PM - 2:34PM |
Q36.00008: Quantitative prediction of oxygen diffusion resistance and porous characters under capillary condensation of water in the mesoporous cathode catalyst layer of polymer electrolyte fuel cell Toshihiro Kaneko, Yuta Yoshimoto, Takuma Hori, Shu Takagi, Ikuya Kinefuchi In the mesoporous cathode catalyst layer of polymer electrolyte fuel cell, water arises as the electrical power generation process goes on through O_{2} + 4H^{+} + 4e^{−} -> 2H_{2}O. It is known that the generated water fills the catalyst layer through capillary condensation that results in a reduction of power generation performance due to a significant increase in the oxygen diffusion resistance, but little is known about the quantitative relation among the oxygen diffusion resistance, the mesoporous characters and the amount of condensed water. A porosity and tortuosity are important parameters to characterize porous structures. In the case of the cathode catalyst layer, the porosity changes through capillary condensation of water and this effect must be considered appropriately. Our group developed coupled analysis simulation of lattice density functional theory and gas transport simulation of Knudsen flow region and applied to the porous media composed of randomly packed spheres [Yoshimoto, Hori, Kinefuchi, and Takagi, Phys. Rev. E, 2017]. In this work, we applied this approach for the actual structure of the mesoporous cathode catalyst layer obtained by scanning electron microscope. |
Tuesday, November 20, 2018 2:34PM - 2:47PM |
Q36.00009: Modeling of flow-optimal bipolar plates in a PEM fuel cell Srinivas Kosaraju The conventional proton exchange membrane (PEM) fuel cells use a graphite bipolar plate with serpentine deign of flow channels to supply hydrogen and air on each side of the plate. The channels are usually narrow and less than 1 mm wide and deep. Due to their small scale, the pressure drop across the channels is significant and fluid in the channels usually surpass the channels by flowing through a porous membrane placed on the channels. This can sometime impact the energy density of the bipolar plates due to non-uniform pressure distribution. An effort is made to design a bipolar plate using flow-optimal channels that ultimately results in uniform pressure distribution and consequently uniform energy density. A conventional serpentine channel design is compared with flow-optimal channels using numerical modeling and the results are compared for pumping power, pressure distribution, and energy density. |
Tuesday, November 20, 2018 2:47PM - 3:00PM |
Q36.00010: A study in multi-scale soft porous lubrication Zenghao Zhu, Rungun Nathan, Qianhong Wu In this paper, we report a comprehensive experimental and theoretical approach to examine soft porous lubrication on different scales. The problem is involved with a planing surface gliding over a soft porous layer at a tilted angle. Two sets of experimental setup were designed and constructed, one on the larger scale with porous layer thickness being 19 mm and another on the smaller scale with porous layer thickness being 3 mm. The distribution of the pore pressure and its contribution to the overall lift are examined, which clearly demonstrates the hydrodynamic similarity, governed by the Brinkman parameter, α=h_{2}/K_{p}^{0.5} and compression ratio, k=h_{2}/h_{1}, exists for the flow in a soft porous media. Here h_{2} and K_{p} are the thickness and Darcy permeability of the porous layer at the leading edge, h_{1} is the thickness at the trailing edge. We have further developed a theoretical model for predicting the solid phase lifting force, which, combined with the fluid pressure, provides a comprehensive method for the prediction of the pore pressure’s contribution to the overall lift, f_{air}. The approach is especially meaningful for the design of soft porous bearing with appropriate porous materials. Higher f_{air} leads to lower friction coefficient. |
Tuesday, November 20, 2018 3:00PM - 3:13PM |
Q36.00011: Viscous/Inertial Flow in Channels with Wavy Permeable Walls Immersed in Porous Medium Mojdeh Rasoulzadeh, Mikhail Panfilov The flow of a viscous fluid in a channel with wavy walls immersed in the porous medium has application to many scientific and industrial area. The Poiseuille flow in tubes and cubic law in parallel-plate channels cannot describe this problem, because of the varying cross-section and presences of inflow through the walls. The inflow and the irregular wavy geometry of the walls result in non-negligible inertial and visco-inertial effects along the channel. The asymptotic solutions of Navier-Stokes equations with slip boundary condition are obtained for axisymmetric and parallel-plate wavy channels. Two-scale homogenization technique is used to capture the effect of the corrugations on the flow. We show that the inflow through the walls creates local flow instabilities and forms reverse flow. The averaged pressure drop along the channel includes quadratic and cubic corrections to the linear law. The quadratic correction only exists in case of permeable walls. The cubic correction corresponds to the wavy geometry. In axisymmetric channels, the cubic term decreases the pressure drop as the corrugation amplitude increases, while in parallel-plate channels the cubic term is less dominant. The channel's effective permeability decreases as the amplitude of the corrugations increases. |
Tuesday, November 20, 2018 3:13PM - 3:26PM |
Q36.00012: Eulerian numerical methods for flow through poroelastic media Nicholas Derr, Christoph Weber, L. Mahadevan, Christopher Rycroft Poroelasticity, the coupling of fluid flow and solid deformation within a porous medium, describes behavior seen in a wide array of settings across biology, physics, and engineering. In this talk, we introduce an Eulerian method for the simulation of flow through an incompressible poroelastic medium. The equations of motion are time-integrated using a finite-difference method, and a combined incompressibility condition is satisfied through the application of a Chorin-type projection method. This requires the solution of a global Poisson problem at each time step. We apply this approach to an active gel model---inspired by crosslinked polymer networks under the influence of motor proteins in the Eukaryotic cytoskeleton---to investigate instabilities resulting from active contractile stresses. Simulations show the instabilities drive behaviors such as solid patch condensation and macroscopic contraction. The resulting pattern formation is shown in two and three dimensions. |
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