Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session T32: Porous Media Flows: Mass and Heat Transfer II |
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Chair: Simon Toedtli, Johns Hopkins University Room: 158AB |
Monday, November 20, 2023 4:25PM - 4:38PM |
T32.00001: Rayleigh-Taylor instability in confined porous media: pore-scale simulations and experiments Marco DePaoli, Christopher J Howland, Roberto Verzicco, Detlef Lohse We analyse the convective mixing due to Rayleigh-Taylor instability in homogeneous and isotropic porous media. Convection originates by solute-induced density differences. We investigate the flow at the scale of the pores using numerical simulations, experimental measurements, and physical modelling. Simulations and experiments have been designed to mimic the same flow properties in terms of medium porosity, Schmidt and Rayleigh numbers, and fluids density. We characterise the evolution of the flow via the mixing length, which grows linearly in time. The centre-line mean wavelength is observed to grow, in quantitative agreement with theoretical predictions. Finally, we analyse the mixing dynamics via the mean scalar dissipation: Three mixing regimes are observed. First, the evolution is controlled by diffusion. When the horizontal interfacial diffusive layer is sufficiently thick, it becomes unstable, forming finger-like structures and driving the system into a convection-dominated phase. Finally, when the fingers grow sufficiently to touch the horizontal boundaries of the domain, the mixing reduces dramatically due to the absence of fresh unmixed fluid. We further elucidated the physics of the observed phenomena with the aid of a simple physical model. |
Monday, November 20, 2023 4:38PM - 4:51PM |
T32.00002: Pattern Formation of Refrozen Melt Structures in Snowpack Nathan D Jones, Adrian Moure, Xiaojing Fu Infiltration of surface-generated meltwater into snowpack is a spatially heterogeneous process due to the gravity fingering instability. Upon contact with deeper and colder snow, melt can refreeze into solid structures during infiltration. Refrozen meltwater forms as one of two primary structures within snowpack: (1) horizontal frozen structures that act as a barrier for infiltration, and (2) vertical frozen structures which may facilitate deeper meltwater infiltration. These two types of refrozen structures have been observed in the field and have profound effects on how meltwater and its residual thermal content distributes into the snowpack. However, a more detailed physics-based understanding of these structures has not yet been posed. |
Monday, November 20, 2023 4:51PM - 5:04PM |
T32.00003: Heat transfer analysis in a porous microchannel heat sink with variable permeability Ian Guillermo Monsivais Montoliu, Edgar Ali Ramos, Federico Mendez, Jose Lizardi In this study, the heat transfer of a Newtonian fluid flowing through a porous microchannel with constant permeability and different models of variable permeability is analyzed numerically. In addition a conjugate heat transfer analysis in the microchannel walls is considered. The governing equations were solved using the finite element method under the variational approach for the momentum equation, energy conservation equation and the coupled heat conduction equation. Temperature field results were obtained at the thermally thick and thermally thin asymptotic limits in the fluid and at the thermally thin limit in the wall for visualization of longitudinal heat conduction effects. The results indicate that the temperature field is strongly influenced by the velocity field and the variable permeability function of each case studied. Also, it could be observed that the temperature varies as a function of the Brinkman number (Br), which represents the effect of viscous dissipation. However, there were no significant changes of the fluid and temperature and wall temperature profiles as a function of the Darcy number. Finally, the model in which the largest temperature difference was experienced compared to the case with constant permeability was the potential model, which had a 66.7% higher fluid temperature at the outlet and in the center of the microchannel and a 45.7% higher wall temperature, for Br= 1.0 and taking into account the longitudinal effects of heat conduction in the wall. |
Monday, November 20, 2023 5:04PM - 5:17PM |
T32.00004: Flows in a freezing soap foam Thomas Seon, Krishan Bumma, Juliette Pierre, Axel Huerre The manufacture of a solid foam, widely used for its mechanical, thermal, or acoustic properties, always begins with the solidification of a liquid foam. By placing a model aqueous foam in contact with a cold surface, we observe that, as it freezes, the foam undergoes a drastic change in volume, revealing important water and air migration in the foam. We start by looking at the freezing dynamics and show that the ice front always begins by following a self-similar diffusive dynamics. We propose a 1D diffusion model, using a new expression for the foam conductivity, that enables to predict this dynamics. Based on this model, we highlight a cryosuction phenomenon, where water flows towards the solidification front, and propose a prediction of the vertical profile of the solid fraction in the solid foam. Next, we present scaling laws for the collapse velocity of the foam and for its final volume, which depend on the size of the liquid films and the substrate temperature. Finally, based on these results and the observation of bubbles behaviour at the solidification front, we discuss mechanisms to explain the gas and liquid flows. These results improve our understanding of the mechanisms involved in foam solidification, in particular the flows generated by the presence of a solidification front. More generally, they shed new light on the cryosuction phenomena that occur in many contexts, from soil solidification to the cryopreservation of living organisms. |
Monday, November 20, 2023 5:17PM - 5:30PM |
T32.00005: Flow- and interface-driven compaction of a confined soft porous medium: When does friction matter? Callum Cuttle, Christopher W MacMinn, Térence Desclaux The compaction of soft, porous media holds relevance for a host of problems in engineering, geoscience, and biology. Recent and classical studies have considered the compaction of sponges or hydrogel beads, among other model systems, confined in cylinders or Hele-Shaw cells with fluid-permeable boundaries at the outlet of the cell. A well-known qualitative feature of these systems is that, when compacted by a piston, the equilibrium state is homogeneously stressed along the axis, while flow-driven compaction results in a gradient in solid stress along the direction of flow due to the viscous pressure gradient within the pore space. In the latter scenario, solid stresses are greatest at the permeable outlet. |
Monday, November 20, 2023 5:30PM - 5:43PM |
T32.00006: On the spatial structure of reaction fronts in reactive porous media. Danielle V Bullamore, Sam Pegler, Sandra Piazolo The flow of reactive fluids in porous media generates changes in porosity and permeability. This phenomenon occurs in various contexts, such as flows in the Earth's mantle and crust, and in the formation of karst topography. |
Monday, November 20, 2023 5:43PM - 5:56PM |
T32.00007: Condensation, Evaporation and Moisture Content in Porous Media Alex J Warhover, Marc Guasch, Michael F Schatz, Roman O Grigoriev There are numerous examples of porous media, both natural ones such as soil and wood as well as synthetic ones such as catalytic converters and filters. At ambient conditions, water vapor tends to condense inside the pores impeding a variety of important transport processes. Hence, it is natural to ask how quickly the moisture can be removed from a porous material. A significant amount of work has been done on diffusive transport of moisture inside the pores. None of the existing model, however, properly account for mass and heat transport, both of which can play an important role under nonequilibrium conditions. We present a comprehensive coarse-grained model of porous media that accounts for the transport of water, in both vapor and liquid form, heat, as well as phase change. A numerical implementation of the model allows us to investigate the dependence of drying time on various parameters such as the initial temperature and moisture content of the porous material as well as the relative humidity and velocity of the air flowing past it. |
Monday, November 20, 2023 5:56PM - 6:09PM |
T32.00008: A macroscopic model for inertial flows through thin permeable membranes Kevin Wittkowski, Alberto Ponte, Pier Giuseppe Ledda, François Gallaire, Giuseppe Antonio Zampogna Porous membranes are thin solids that allow fluid to flow through their pores. In many natural and industrial situations, inertial effects at the pore scale play a relevant role, and the fluid and solute flow cannot be described by usual inertia-less, linear, models. In the present contribution, we develop a macroscopic predictive model describing the solvent and solute flow fields via a homogenization-based methodology in the presence of inertial effects. We homogenize the Navier-Stokes and advection-diffusion equations to obtain effective stress and flux jump conditions across the membrane, modelled as an interface separating two fluid sub-domains. The jump conditions rely on several coefficients, which stem from the solution of non-linear problems in the microscopic periodic cell, the elementary brick of the membrane structure. Because of the above-mentioned non-linearity, the microscopic and the macroscopic problems are coupled and a strategy to pass information from the macro- to the microscopic world is implemented using an iterative fixed-point scheme. The accuracy of the present method is assessed by comparison with full-scale direct numerical simulations of the solvent and solute flow, showing a substantial improvement with respect to the classic linear theory. |
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