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 E35: Porous Media Flows: Wicking & DryingPorous
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Chair: James Bird, Boston University Room: 301 |
Sunday, November 19, 2017 4:55PM - 5:08PM |
E35.00001: ABSTRACT WITHDRAWN |
Sunday, November 19, 2017 5:08PM - 5:21PM |
E35.00002: Effects of Surface Wettability on the Porosity and Wickability of Frost Katherine Witt, Farzad Ahmadi, Jonathan Boreyko The wicking of liquids through porous media has been studied for many materials, but never for frost, despite its implications for arctic oil spills and oil-infused surfaces. Here, we characterize silicone oils wicking up frost sheets. A layer of frost was grown on aluminum plates of varying surface wettability: superhydrophilic, hydrophilic, hydrophobic, and superhydrophobic. Once the desired frost thickness was grown, a humidity chamber was used to maintain the frost at the dew point and the bottom of the plate was dipped in a reservoir of fluorescent silicone oil. For all surfaces, the wicking rate of the oil increased with increasing wettability. For the wetting surfaces, this is manifested in the length vs. time data following the classical Washburn equation, exhibiting a power slope of about 1/2 and resulting in a larger effective pore radius with increasing wettability. However, we observed that on the non-wetting surfaces, the discrete distribution of the frosted dew droplets resulted in a new scaling law with a slope much less than 1/2, especially for the superhydrophobic surface which promoted jumping-droplet condensation. This research shows that the wicking of oil up a layer of frost can give insight into the morphology of frost. Conversely, if the underlying wettability of a frost sheet can be controlled, the spread of oil can be widely tuned. [Preview Abstract] |
Sunday, November 19, 2017 5:21PM - 5:34PM |
E35.00003: Effect of Pore Size and Pore Connectivity on Unidirectional Capillary Penetration Kinetics in 3-D Porous Media using Direct Numerical Simulation An Fu, Nikhil Palakurthi, Santosh Konangi, Ken Comer, Milind Jog The physics of capillary flow is used widely in multiple fields. Lucas-Washburn equation is developed by using a single pore-sized capillary tube with continuous pore connection. Although this equation has been extended to describe the penetration kinetics into porous medium, multiple studies have indicated L-W does not accurately predict flow patterns in real porous media. In this study, the penetration kinetics including the effect of pore size and pore connectivity will be closely examined since they are expected to be the key factors effecting the penetration process. The Liquid wicking process is studied from a converging and diverging capillary tube to the complex virtual 3-D porous structures with Direct Numerical Simulation (DNS) using the Volume-Of-Fluid (VOF) method within the OpenFOAM CFD Solver. Additionally Porous Medium properties such as Permeability ($k)$, Tortuosity ($\tau )$ will be also analyzed. [Preview Abstract] |
Sunday, November 19, 2017 5:34PM - 5:47PM |
E35.00004: The Role of Hemiwicking on the Shape of a Blood Drop Stain Samira Shiri, Kenneth Martin, James Bird Blood pattern analysis (BPA) typically assumes that an elliptical stain is due to oblique drop impact. From the eccentricity of the elliptical stain -- while also accounting for gravity and drag -- the source and trajectory of the blood drops can be estimated. Yet, these models generally neglect any fluid motion following impact that could influence the shape of the stain. Here we demonstrate that under certain conditions on certain materials, a blood drop will undergo anisotropic hemiwicking. Through systemic experiments and modeling, we aim to better understand this phenomenon with the goal of ultimately decreasing the uncertainty in crime scene reconstruction. [Preview Abstract] |
Sunday, November 19, 2017 5:47PM - 6:00PM |
E35.00005: ABSTRACT WITHDRAWN |
Sunday, November 19, 2017 6:00PM - 6:13PM |
E35.00006: Groundwater dynamics in a two-dimensional aquifer Valentin Jules, Olivier Devauchelle, Eric Lajeunesse During a rain event, water infiltrates into the ground where it flows slowly towards a river. The time scale and the geometry of this flow control the chemical composition and the discharge of the river. We use a tank filled with glass beads to simulate this process in a simplified laboratory experiment. A sprinkler pipe generates rain, which infiltrates into the porous material. Groundwater exits this laboratory aquifer through a side of the tank. Guérin et al. (2014) investigated the case of a quasi-horizontal flow. In nature, however, groundwater often follows non-horizontal flowlines. To create a vertical flow, we place the outlet of our experiment high above its bottom. We find that, during rainfall, the discharge $Q$ increases as the rainfall rate $R$ times the square root of time $t$ ($Q\propto Rt^{1/2}$). This laboratory aquifer thus responds linearly to the forcing. However, long after the rain has stopped, the discharge decreases as the inverse square of time ($Q\propto t^{-2}$), although linear systems of finite size typically relax exponentially. We investigate this surprising behavior using a combination of complex analysis and numerical methods. [Preview Abstract] |
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