Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session B15: Bubbles, Interfaces & Porous Media |
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Sponsoring Units: DFD Chair: C. Maldarelli, City University of New York Room: 304 |
Monday, March 3, 2014 11:15AM - 11:27AM |
B15.00001: Attraction of Two Floating Spheres at a Viscous Oil-Water Interface Archit Dani, Geoff Keiser, Mohsen Yeganeh, Charles Maldarelli The aggregation rate of floating particles at a fluid/fluid interface by capillary forces has drawn significant interest. This 2D phenomenon plays a critical role in self-assembly arrangement relevant to pollination processes in biological contexts, the formation of dense particle laden interfaces for stabilizing emulsions in colloid science and in the bottom up assembly of materials in nanotechnologies. We present the first experiments on the merging of two Teflon particles at an interface between a mineral oil and an aqueous phase for a series of particle pairs, interfacial tension and oil viscosity. The separation distance as a function of time and pair aggregation time are both measured by optically following the movement of the particles. The experimental results are in excellent agreement with our theoretical formulation in which a drag correction accounts for the variation in particle depth of immersion. [Preview Abstract] |
Monday, March 3, 2014 11:27AM - 11:39AM |
B15.00002: Computational Fluid Dynamics of Acoustically Driven Bubble Systems Connor Glosser, Jie Lie, Daniel Dault, Shanker Balasubramaniam, Carlo Piermarocchi The development of modalities for precise, targeted drug delivery has become increasingly important in medical care in recent years. Assemblages of microbubbles steered by acoustic pressure fields present one potential vehicle for such delivery. Modeling the collective response of multi-bubble systems to an intense, externally applied ultrasound field requires accurately capturing acoustic interactions between bubbles and the externally applied field, and their effect on the evolution of bubble kinetics. In this work, we present a methodology for multiphysics simulation based on an efficient transient boundary integral equation (TBIE) coupled with molecular dynamics (MD) to compute trajectories of multiple acoustically interacting bubbles in an ideal fluid under pulsed acoustic excitation. For arbitrary configurations of spherical bubbles, the TBIE solver self-consistently models transient surface pressure distributions at bubble-fluid interfaces due to acoustic interactions and relative potential flows induced by bubble motion. Forces derived from the resulting pressure distributions act as driving terms in the MD update at each timestep. The resulting method efficiently and accurately captures individual bubble dynamics for clouds containing up to hundreds of bubbles. [Preview Abstract] |
Monday, March 3, 2014 11:39AM - 11:51AM |
B15.00003: Soap Film Hydrodynamics: In Color, and In Black and White Collin Pearsall, Yiran Zhang, Jana Rush, Subinuer Yilixiati, Vivek Sharma Iridescent colors of soap bubbles or films arise due to interference between light reflected from two surfactant-laden surfaces that are $\sim$ 100 nm - 10 micron apart. Sandwiched between these interfacial layers is a fluid that drains primarily under the influence of gravitational and capillary or interfacial forces, including disjoining pressure. Below 50 nm the thin films appear as black. We experimentally follow the drainage kinetics of soap films using imaging {\&} color science and UV-Visible spectroscopy. We find fascinating examples of two-dimensional hydrodynamics and unexplained, if not unprecedented, drainage kinetics. [Preview Abstract] |
Monday, March 3, 2014 11:51AM - 12:03PM |
B15.00004: Atomistic simulations of surfactant adsorption kinetics at interfaces Eugeniya Iskrenova, Soumya Patnaik Heat transfer control and enhancement is an important and challenging problem in a variety of industrial and technological applications including aircraft thermal management. The role of additives in nucleate boiling and phase change in general has long been recognized and studied experimentally and modeled theoretically but in-depth description and atomistic understanding of the multiscale processes involved are still needed for better prediction and control of the heat transfer efficiency. Surfactant additives have been experimentally observed to either enhance or inhibit the boiling heat transfer depending on the surfactant concentration and chemistry and, on a molecular level, their addition leads to dynamic surface tension and changes in interfacial and transfer properties, thus contributing to the complexity of the problem. We present our atomistic modeling study of the interfacial adsorption kinetics of aqueous surfactant (sodium dodecyl sulfate) systems at a range of concentrations at room and boiling temperatures. Classical molecular dynamics and Umbrella Sampling simulations were used to study the surfactant transport properties and estimate the adsorption and desorption rates at liquid-vacuum and liquid-solid interfaces. [Preview Abstract] |
Monday, March 3, 2014 12:03PM - 12:15PM |
B15.00005: ABSTRACT WITHDRAWN |
Monday, March 3, 2014 12:15PM - 12:27PM |
B15.00006: Experimental Study of the Hydrodynamic Resistance of Liquid Droplets in Polycarbonate Microchannels Zeyad Almutairi, Carolyn Ren, David Johnson The presence of liquid droplets in a microchannel adds excess hydrodynamic resistance to the flow compared to single phase flow. The hydrodynamic resistance of liquid droplets is a function of fluid properties (viscosity ratios $\frac{\mu_d}{\mu_c}$, interfacial tension $\gamma$), geometrical properties of the droplet and the confining channel (droplet length $L_d$, microchannel width and height), and flow condition (Ca, Re). This work presents the results of an experimental examination of the transport properties of liquid droplets in a microchannel. Focus was given to the hydrodynamic resistance of droplets with lengths comparable or greater than the channel width ($L_d \ga W_{ch}$. Experiments were performed in surface modified polycarbonate microchannels since they will reduce measurement uncertainties associated with channel swelling in soft materials such as PDMS. For the droplets sizes that were examined results confirm the relation between the hydrodynamic resistance of liquid droplets and the Capillary number (Ca). It was also observed that droplet slip ($\beta = \frac{u_d}{u_{c,avg}}$) is less than 1 in all the experiments performed. [Preview Abstract] |
Monday, March 3, 2014 12:27PM - 12:39PM |
B15.00007: Impact and Penetration of Nanoparticle Suspension Drops into Porous Membranes Rakesh Sahu, Alexander Yarin, Behnam Pourdeyhimi The impacts and dynamic penetration of drops with suspended nanoparticles into porous membranes are studied experimentally and theoretically. This type of penetration is radically different from the wettability-driven imbibition. Two types of membranes are used in the experiments: (i) glass fiber filter membrane (wettable) and (ii) PTFE depth filter (non-wettable). The nanoparticle entrainment and deposition inside the membrane bulk is used to mostly visualize the ultimate penetration fronts of the carrier fluid by observing the cut cross-sections of the filter membranes, albeit also provides an insight into potentially new applications like circuit printing on nonwovens. The experimental results demonstrate that during the dynamic focusing responsible for water penetration into micro- and nanopores, water can penetrate into a non-wettable porous medium (PTFE). Water also penetrates by the same focusing mechanism into the wettable glass fiber membrane, where it additionally spreads on a much longer time scale due to the wettability-driven flow. A theory explaining dynamic penetration of liquid into porous medium after drop impact is proposed. It is used to explain and predict water penetration into the non-wettable media after drop impact, and the results are compared with the experimental data. [Preview Abstract] |
Monday, March 3, 2014 12:39PM - 12:51PM |
B15.00008: Oil droplet dynamics at a porous surface in the presence of crossflow: Implications for microfiltration of oil-water dispersions Tohid Darvishzadeh, Volodymyr Tarabara, Nikolai Priezjev The behavior of an oil droplet pinned at the entrance of a micropore and subject to clossflow-induced shear is investigated numerically by solving the Navier-Stokes equation. We found that in the absence of crossflow, the critical transmembrane pressure required to force the droplet into the pore is in excellent agreement with a theoretical prediction based on the Young-Laplace equation. With increasing shear rate, the critical pressure of permeation increases, and at sufficiently high shear rates the oil droplet breaks up into two segments. It was shown that droplet breakup at the pore entrance is facilitated at lower surface tension, higher oil-to-water viscosity ratio and larger droplet size but is insensitive to the value of the contact angle. An estimate for the increase in critical pressure due to crossflow and the breakup capillary number is obtained and validated for different viscosity ratios, surface tension coefficients, contact angles, and drop-to-pore size ratios. [Preview Abstract] |
Monday, March 3, 2014 12:51PM - 1:03PM |
B15.00009: Transport and Deposition of Nanoparticles in the Pore Network of a Reservoir Rock: Effects of Pore Surface Heterogeneity and Radial Diffusion Ngoc Pham, Dimitrios Papavassiliou In this study, transport behavior of nanoparticles under different pore surface conditions of consolidated Berea sandstone is numerically investigated. Micro-CT scanning technique is applied to obtain 3D grayscale images of the rock sample geometry. Quantitative characterization, which is based on image analysis is done to obtain physical properties of the pore network, such as the pore size distribution and the type of each pore (dead-end, isolated, and fully connected pore). Transport of water through the rock is simulated by employing a 3D lattice Boltzmann method. The trajectories of nanopaticles moving under convection in the simulated flow field and due to molecular diffusion are monitored in the Lagrangian framework [1]. It is assumed in the model that the particle adsorption on the pore surface, which is modeled as a pseudo-first order adsorption, is the only factor hindering particle propagation. The effect of pore surface heterogeneity to the particle breakthrough is considered, and the role of particle radial diffusion is also addressed in details.\\[4pt] [1] Voronov, R.S., VanGordon, S., Sikavitsas, V.I., and D.V. Papavassiliou, \textit{Int. J. Num. Methods in Fluids}, \textbf{67}, 501-517, 2011 [Preview Abstract] |
Monday, March 3, 2014 1:03PM - 1:15PM |
B15.00010: Channeling and stress for fluid and suspension flows in self-affine fractures Tak S. Lo, Joel Koplik The flow of fluids and particulate suspensions in realistic models of geological fractures is investigated using lattice Boltzmann simulations. The bounding walls are self-affine fractal surfaces and combined to form a tight fracture, i.e. one in which where the particle size, the mean aperture and the surface roughness are all comparable. We consider pressure-driven flow of a viscous Newtonian liquid and model the particles as rigid non-colloidal solid spheres. Our focus is the channeling phenomena, where we compare the preferred paths for fluid flow and the suspended particles to the fracture aperture. The preferred paths are found to be somewhat similar for pure fluid and particulates, and not immediately related to the fracture aperture map. We further investigate the stress exerted on the fracture walls during flows in the irregular channel, which is useful in geological applications. Finally, we examine the spatial correlations in the stress and velocity distributions and compare to the statistics of the aperture field and identify the relationship between them. [Preview Abstract] |
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