Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session R3: Multiphase General II |
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Chair: Sascha Hilgenfeldt, University of Illinois at Urbana-Champaign Room: 23B |
Tuesday, November 20, 2012 1:00PM - 1:13PM |
R3.00001: Light Field Imaging of Turbulent Liquid Sheet Breakup in Air Barry Scharfman, Alexandra Techet The atomization of an unsteady turbulent sheet of water in air was analyzed using a combination of light field imaging (LFI) and synthetic aperture (SA) refocusing techniques. This sheet collides with and initially flows along a solid inclined plate, and imaging was performed in the region where breakup and separation from the plate begins. Ligaments and droplets emanate from the sheet and break off due to capillary instabilities. Image volumes consisting of these flow features, as well as segments of the liquid sheet body, were captured using a multiple CCD sensor array consisting of ten cameras arranged in three rows. Synthetic aperture refocusing techniques were applied to the raw camera array images, each with large depths of field, to obtain a stack of post-processed images, with narrow depth of field, where each image in the stack is located on a specific focal plane. Feature shapes and spatial distributions have then been extracted from the refocused image volumes. [Preview Abstract] |
Tuesday, November 20, 2012 1:13PM - 1:26PM |
R3.00002: Solid-Fluid flows using a variant of Immersed Boundary method in Gerris Pei Shui, St\'ephane Popinet, Prashant Valluri, St\'ephane Zaleski, Martin Crapper An efficient 3D Immersed Boundary solver to simulate fully coupled fluid-solid interaction with 6 degrees-of-freedom (6DOF) solid movement enabling all translational and rotational motions has been developed in the GERRIS code. Here the solids are fully immersed in a flowing fluid driven either by pressure or shear. Solid objects of any arbitrary geometry and number can be considered. Prevention of overlap between the solids and wall is enforced through a repulsive force (Glowinski et al., 2001) which is the sum of all short-range interactions. The method agrees well with Stokes' settling and is validated against experiments published in literature. The simulation also agrees well with the classical case of a neutrally buoyant solid in shear flow and the orbit tracked by it (Jeffrey, 1922). Strong hydrodynamic interaction is seen between multiple solids placed in shear flow. The interaction force is being calibrated as a function of relative distance between the solids and will be presented in the conference. Comparison with experiments of Fortes et al (1987) concerning drafting, kissing and tumbling of two spherical solids during fluidization will also be presented. [Preview Abstract] |
Tuesday, November 20, 2012 1:26PM - 1:39PM |
R3.00003: On the mixture model of two-phase proppant transport in 1D fracturing flows Weiming Li A mixture model of two-phase fluid flow is derived for proppant transport in 1D hydraulic fracturing. The governing equations of the model consists of the mass balance equations for the mixture and the proppant phase, the momentum equation for the mixture and the constitutive equation between proppant average velocity and fluid average velocity. Mass loss and momentum loss due to proppant settling are considered. One dimensional numerical simulations based on discontinuous Galerkin finite element method in space are performed. Both steady cases and transient cases are compared with available analytical solutions or manufactured solutions. Predicted numerical results agree well with exact solutions. This one dimensional two-phase model captures necessary proppant flow phenomena in hydraulic fracturing and also provides numerical efficiency and accuracy. [Preview Abstract] |
Tuesday, November 20, 2012 1:39PM - 1:52PM |
R3.00004: A GPU-accelerated interfacial flow solver with advected normals: Application to contact line problems Ashish Pathak, Mehdi Raessi Accurate curvatures are essential for modeling surface tension forces in interfacial flows. The advected normals method by Raessi \textit{et al.} yields curvatures that converge with mesh refinement. The same level of accuracy cannot be achieved with traditional approaches to calculating curvature, in which the gradient of the volume-of-fluid (VOF) or level-set functions are used. The flow solver used here is based on the VOF method and uses the two-step projection with GPU acceleration. In addition to curvature calculation, the advected normals are used for reconstructing the interface. The method has been successfully applied before to two-dimensional flow problems. We present here its extension to three dimensions. The PDE based extension of the vectors around the interface which was slow and computationally intensive in the original form has been accelerated by developing a GPU version of the extension algorithm. The advected normals method was also extended to handle contact line problems. The method has an advantage over traditional approaches to imposing contact angle. Since the normal vectors ``communicate'' with each other in this method, the effect of imposed contact angle is ``felt'' by the normal vectors in a wider region and is independent of grid resolution. [Preview Abstract] |
Tuesday, November 20, 2012 1:52PM - 2:05PM |
R3.00005: Jump Conditions for the Stokes Equations with Discontinuous Viscosity and an Incompressible Interface with Singular Forces in 3D David Salac, Prerna Gera Here the jump conditions for pressure and velocity are presented for two-phase Stokes and constant density Navier- Stokes flow with discontinuous viscosity across an incompressible interface with singular forces in three dimensions. This is necessary to accurately model systems such as vesicles or red blood cells. While jump conditions for incompressible interfaces and continuous viscosity have been published, this is the first demonstration of the jump conditions for the discontinuous viscosity situation. The derivation is based on the immersed interface method and appropriate local interface conditions. In addition to presentation of the jump conditions a simple analytic case has been created to verify the method and will be shown. [Preview Abstract] |
Tuesday, November 20, 2012 2:05PM - 2:18PM |
R3.00006: A study of pressure-driven displacement flow of two immiscible liquids using a multiphase lattice Boltzmann approach Prasanna Redapangu, Pratap Vanka, Kirti Sahu The pressure-driven displacement of two immiscible fluids in an inclined channel in the presence of viscosity and density gradients is investigated using a multiphase lattice Boltzmann approach. The effects of viscosity ratio, Atwood number, Froude number, capillary number and channel inclination are investigated through flow structures, front velocities and fluid displacement rates. Our results indicate that increasing viscosity ratio between the fluids decreases the displacement rate. We observe that increasing the viscosity ratio has a non-monotonic effect on the velocity of the leading front; however, the velocity of the trailing edge decreases with increasing the viscosity ratio. The displacement rate of the thin-layers formed at the later times of the displacement process increases with increasing the angle of inclination because of the increase in the intensity of the interfacial instabilities. Our results also predict the front velocity of the lock-exchange flow of two immiscible fluids in the exchange flow dominated regime. [Preview Abstract] |
Tuesday, November 20, 2012 2:18PM - 2:31PM |
R3.00007: Double diffusive effects between two miscible fluid flows in a channel Manoranjan Mishra, Anne De Wit, Kirti Chandra Sahu The pressure-driven displacement flow of a less viscous fluid by a more viscous one in a horizontal channel is a stable configuration in the context of single component flows. However, we have shown by numerical simulations based on finite volume approach that the double-diffusive (DD) effects can destabilize this stably stratified system. Such effects can appear if the fluid consists of a solvent containing two solutes both influencing the viscosity of the solution and diffusing at different rates. The continuity and Navier-Stokes equations coupled to two convective-diffusion equations for the evolution of the concentration of the solutes are solved. The viscosity is assumed to depend on the concentration of both solutes, while density contrast is neglected. The results demonstrate the development of various new instability patterns in the presence of DD effects at the miscible ``interface'' separating the fluids. It is found that the intensity of the instability increases with increasing the diffusivity ratio of the solutes. This in turn increases the fluid mixing and accelerates the displacement of the fluid originally filled inside the channel. [Preview Abstract] |
Tuesday, November 20, 2012 2:31PM - 2:44PM |
R3.00008: Microscopic aspects of Liquid Foam Fracture Sascha Hilgenfeldt, Peter Stewart, Stephen Davis A layer of foam bubbles between parallel plates (a quasi-two-dimensional liquid foam) gives unique access to the details of microscopic configurations in a system whose macroscopic properties include both liquid and solid behavior. The failure of cohesion under stress in such a layer of bubbles offers a study case on fracture, which we have experimentally shown to occur both in a mode similar to fluid fingering and a mode similar to the cleavage of a solid material. Simulations elucidate the microscopic aspects and the fluid-dynamical mechanisms behind these processes, spanning a wide variety of length and time scales and incorporating both fracture modes. Aspects of microstructure and rate dependence can thus become part of a detailed study of fundamental fracture processes. [Preview Abstract] |
Tuesday, November 20, 2012 2:44PM - 2:57PM |
R3.00009: Multiphase flow of miscible liquids: drops and jets Travis Walker, Alison Logia, Gerald Fuller Drops and jets of liquids that are miscible with the surrounding bulk liquid are present in many processes. Although the interactions of immiscible drops and jets show similarities to miscible systems, the small, transient interfacial tension associated with miscible systems create distinct outcomes such as intricate droplet shapes, break-up resistant jets, and spreading sessile drops. Experiments have been conducted to understand several basic multiphase flow problems involving miscible liquids including the free-surface pendant drops resulting from drop impaction and the dissolution of sessile drops in a miscible bath. Using high-speed imaging of the morphological evolution of the flows, we show that these processes are controlled by interfacial tensions. Further multiphase flows include investigating miscible jets, which allow the creation of fibers and tubular shapes from inelastic materials that are otherwise difficult to process due to capillary breakup. This work shows that stabilization from the diminishing interfacial tensions of the miscible jets allow various elongated morphologies to be formed. When combined with a mechanism to freeze these fibers, highly oriented materials can be created. [Preview Abstract] |
Tuesday, November 20, 2012 2:57PM - 3:10PM |
R3.00010: Numerical Study of Crossflow Enhanced Microfiltration of Oil-in-Water Emulsions Tohid Darvishzadeh, Nikolai Priezjev, Volodymyr Tarabara The effective separation of dilute oil-in-water mixtures involves high flux of water through a porous membrane while maintaining high rejection rate of the oil phase. In this study, the effects of transmembrane pressure and crossflow velocity on rejection of oil droplets and thin oil films by pores of different cross-section are investigated numerically by solving the Navier-Stokes equation. We found that the presence of crossflow increases the efficiency of microfiltration by sweeping the dispersed phase away from the pore entrance at the membrane surface and thus enhancing overall water flux. With further increasing crossflow velocity, however, the shape of the droplet becomes strongly deformed near the pore entrance; and, at sufficiently high transmembrane pressures, the droplet breaks up into two fragments, one of which penetrates into the pore. The dynamics of an oil droplet near the pore entrance and the critical pressure of permeation are studied as a function of the oil viscosity, ratio of drop to pore radii, surface tension, and contact angle. [Preview Abstract] |
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