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 A05: Porous Media Flows: General I |
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Chair: Saikat Mukherjee, University of Minnesota Room: North 121 C |
Sunday, November 21, 2021 8:00AM - 8:13AM |
A05.00001: The Effect of Momentum Transfer Coefficients on Turbulent Suspension Flow over porous media seyedmehdi abtahi, Marco Edoardo Rosti, Luca Brandt, Parisa Mirbod We discuss the flow of turbulent suspensions of non-Brownian, non-colloidal, rigid spherical particles in a Newtonian fluid over a porous surface. In this study, we report the effect of the momentum transfer coefficient τ on the turbulence statistics of suspension flows where the bulk particle volume fraction ranges from 0 to 0.2 for different wall porous permeability, while the thickness and porosity of the porous wall are fixed. We study three values of τ, i.e., −1, 0 and 1, because the τ of most of the porous media falls in this range that measures the transfer of stress at the porous/fluid interface and depends on the porous material and the texture of the solid interface. Direct numerical simulations (DNS) with an immersed boundary method (IBM) are employed to resolve the particles and flow phase where they coupled with the volume-averaged Navier-Stokes (VANS) to solve the flow within the porous layer. By changing τ from 0 to either 1 or -1 the velocity at the interface between the porous wall and the free fluid region increases significantly. The overall drag is found to grow by changing τ from 0 to 1 and -1 whereas the mean momentum balance analysis shows that the particle-induced stresses are the main factor for the overall drag increase for non-zero τ. |
Sunday, November 21, 2021 8:13AM - 8:26AM |
A05.00002: Effect of Permeability on the Rheology of Non-Brownian Suspensions over Porous Media Models Maryam Bagheri, Parisa Mirbod
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Sunday, November 21, 2021 8:26AM - 8:39AM |
A05.00003: Theory of Absorption Kinetics in Hygroscopic Hydrogels Carlos D Díaz-Marín, Lenan Zhang, Zhengmao Lu, Mohammed Alshrah, Jeffrey C Grossman, Evelyn N Wang Hygroscopic hydrogels have emerged as a scalable material capable of high-performance evaporative cooling and atmospheric water harvesting due to their fast kinetics and high water uptake. However, despite extensive research interest, there is a lack of understanding of the governing fluid and mass transport mechanisms within the hydrogels, which hinders the optimization of their performance. In this work, we present the first-ever model that explains the kinetics of absorption in hygroscopic hydrogels. Our model couples vapor transport within the hydrogel micropores with swelling-induced liquid transport in the polymer nanopores to accurately capture experimentally observed water uptake curves based solely on the knowledge of the hydrogel material properties. With the insights of the model, we determine the dominant properties that govern the absorption kinetics and show that mechanically stiff, thin hydrogels with optimized porosity exhibit the best kinetics. The knowledge obtained from this model can therefore guide the design of hygroscopic hydrogels and enable improved performance in atmospheric water capture and evaporative cooling. |
Sunday, November 21, 2021 8:39AM - 8:52AM |
A05.00004: On Mathematical Modeling of Erosion and Deposition in Complex Porous Media Hamad El Kahza, Pejman Sanaei Erosion and deposition are represented as the evolution of solid bodies as colloidal particles get transported within the porous media due to forces exerted by the fluid or air on the solid contact interface. These processes arise in many environmental contexts, industrial applications and are notably complicated and challenging to study in experimental endeavors. In this work, we formulate novel and idealized mathematical models to examine the internal evolution of flow networks in cylindrical channels undergoing a unidirectional flow, using asymptotic and numerical techniques. Our model captures geometry evolution as particles get eroded from or deposited into the wall of the channels. Consequently, the structure channels' radii expand and shrink, respectively, due to the interplay of erosion and deposition. Previous endeavors to model this phenomenon have revealed three different regimes within a single pore: (i) a dominant-deposition regime, (ii) a dynamic erosion-deposition regime, (iii) and a dominant-erosion regime, leading to equilibrium. In this work, we extend the parametric sweep of the physical parameters within the constructed model to trace the final configuration of the branching structure using a geometrical aspects sweep of the system. |
Sunday, November 21, 2021 8:52AM - 9:05AM |
A05.00005: Flow and transport in a pleated filter Daniel Fong, Pejman Sanaei Pleated membrane filters are used in a variety of industrial applications, since they offer more surface area to volume ratio that is not found in equivalent flat filters. A pleated membrane filter consists of a porous membrane layer which is surrounded by two supporting layers. The whole structure is pleated and placed into a cylindrical cartridge. In this work, we introduce a novel 3D model of a pleated membrane filter that consists of an empty area, a pleated region and a hollow region. The advection diffusion equation is used to model contaminant concentration in the membrane pores along with Darcy's law to model the flow within the membrane and support layers, while the Stoke's equation is used for the flow in the empty area and the hollow region. We further use the key assumptions of our model based on small aspect ratios of the filter cartridge, the support layers to simplify the governing equations such that the resulting reduced model can be solved with numerical methods. By performing these steps, we seek to discover an optimal pleat packing density to find the optimum filter performance, while not exceeding a threshold for the particle concentration at the filter outlet. |
Sunday, November 21, 2021 9:05AM - 9:18AM |
A05.00006: A Graphical Representation of Membrane Filtration Binan Gu, Lou Kondic, Linda J Cummings We analyze the performance of membrane filters represented by pore networks using two criteria: 1) total volumetric throughput of filtrate over the filter lifetime and 2) accumulated foulant concentration in the filtrate. We first formulate the governing equations of fluid flow on a general network, and we model transport and adsorption of particles (foulants) within the network by imposing an advection equation with a sink term on each pore (edge) as well as conservation of fluid and foulant volumetric flow rates at each pore junction (network vertex). Such a setup yields a system of partial differential equations on the network. We study the influence of three geometric network parameters on filter performance: 1) average number of neighbors of each vertex; 2) initial total void volume of the pore network; and 3) tortuosity of the network. We find that total volumetric throughput depends more strongly on the initial void volume than on average number of neighbors. Tortuosity, however, turns out to be a universal parameter, leading to almost perfect collapse of all results for a variety of different network architectures. In particular, the accumulated foulant concentration in the filtrate shows an exponential decay as tortuosity increases. |
Sunday, November 21, 2021 9:18AM - 9:31AM Not Participating |
A05.00007: Flow through a confined array of rigid hairs Emilie Dressaire, Nathan Jones, Sri Savya Tanikella A variety of aquatic organisms use appendages covered with arrays of hairs to capture food, smell, and move the fluid around them. At the hair level, the flow is characterized by a low Reynolds number (Re), whose value controls the transport through the array. The array acts either as a rake forcing the fluid around at low Re or small hair spacing or as a sieve letting the fluid through at higher Re or large hair spacing. We study the influence of confinement on the flow regimes through the finite porous structure. We investigate the flow through an array of hairs in a rectangular channel in the presence of a developed Poiseuille flow field. We vary the geometry of the array, flow rate through the channel, and confinement through numerical simulations and experiments. We show that the transition between the rake and sieve regimes depends on the geometry of the system and rationalize the results using a Darcy-Brinkman model. |
Sunday, November 21, 2021 9:31AM - 9:44AM Not Participating |
A05.00008: A homogenised model for dispersive transport and sorption in a heterogeneous porous medium Lucy C Auton, Ian M Griffiths, Mohit P Dalwadi When a fluid carrying a passive solute flows quickly through porous media, three distinct mechanisms of transport occur. These mechanisms are diffusion, advection and dispersion, all of which depend on the microstructure of the porous medium; however, this dependence remains poorly understood. For idealised microstructures, we can use the mathematical framework of homogenisation theory to examine this dependence. Here, we consider a two-dimensional microstructure comprising an array of obstacles of smooth but arbitrary shape, the size and spacing of which can vary along the length of the porous medium. We use homogenisation via the method of multiple scales to systematically upscale a novel problem involving cells of varying area to obtain effective continuum equations for macroscale flow, transport and sorption. The equations are characterized by the local porosity, a local anisotropic flow permeability, an effective local adsorption rate and an effective local anisotropic solute diffusivity. All of these macroscale properties depend nontrivially on the two degrees of microstructural geometric freedom in our problem, obstacle size and obstacle spacing. Further, the coefficient of effective diffusivity comprises the molecular diffusivity, the suppressive effect of the presence of obstacles and the promotive effect of dispersion. To illustrate the matematical model, we focus on a simple example geometry comprising circular obstacles on a hexagonal lattice, for which we numerically determine the macroscale permeability and coefficient of effective diffusivity. |
Sunday, November 21, 2021 9:44AM - 9:57AM Not Participating |
A05.00009: Redistribution of a passive tracer in a porous substrate under a surface washing flow at high Péclet number Emily Butler, Merlin A Etzold, Francesco P Contò, Stuart B Dalziel, Joel Daou, Julien R Landel We study the cleaning of a liquid chemical contaminant from the surface of a flat, wet porous medium. We focus on quantifying the extent to which cleaning the surface of the porous medium can spread the contaminant over the porous material. This modifies the concentration distribution within the porous material - potentially increasing the area that has been contaminated - compared with the case if there were no cleaning flow. To gain an understanding of this redistribution phenomenon, we propose a simple model for a shear washing flow over a small, flat drop releasing a dilute passive tracer of constant concentration, initially situated on the surface of the porous medium. As the flow progresses over the porous surface, the tracer is transported from the drop into the flow through advective and diffusive processes, while molecular diffusion across the flow-porous interface encourages mass transfer into the porous medium downstream of the drop. We will discuss an asymptotic regime, based on an intermediate time scale for high-Péclet-number flow, valid at distances downstream of the drop, that can be used to study agent redistribution in the porous substrate. To substantiate this analysis, we performed finite element simulations using COMSOL. The results of these simulations will be compared with our experimental data to confirm the mechanism redistribution of contaminant during the decontamination of porous media. |
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