Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session D38: Flow Instability: Interfacial and Thin Film-Fingering |
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Chair: Matthew Hennessy, Imperial College London Room: Portland Ballroom 255 |
Sunday, November 20, 2016 2:57PM - 3:10PM |
D38.00001: A minimal model of solvent evaporation and absorption in thin films Giulia L. Ferretti, Matthew G. Hennessy, Joao T. Cabral, Omar K. Matar We present a minimal model of solvent evaporation and absorption in thin multicomponent films that consist of a volatile solvent and one or many non-volatile solutes. A detailed asymptotic analysis is carried out in order to (i) elucidate the key regimes that occur during evaporation and absorption and (ii) compute solutions that facilitate the extraction of physically significant model parameters from experimental data. A state diagram of the drying process is constructed and used to predict the experimental conditions that lead to the formation of a solute-rich skin below the evaporating surface. In the case of solvent absorption, the model predicts the existence of a diffuse saturation front that propagates from the film surface towards the substrate. The theoretical results are found to be in excellent agreement with data produced from dynamic vapour sorption experiments of ternary mixtures composed of an aluminum salt, glycerol, and water. Finally, we show how the model can be used to predict the drying and absorption dynamics over a wide range of experimental conditions. [Preview Abstract] |
Sunday, November 20, 2016 3:10PM - 3:23PM |
D38.00002: The effect of a blurred interface on the viscous fingering instability Thomas E. Videbaek, Thibault Guillet, Irmgard Bischofberger, Sidney R. Nagel The viscous fingering instability in a quasi-two dimensional Hele-Shaw cell provides a simple tool for studying a complex structure formation. Concentrating on the instability between pairs of miscible fluids where the interfacial tension is nearly zero, we smooth out the discontinuity in the gap-averaged viscosity at the boundary between the fluids; in this system we discover two new features. (i) We find a delay in the instability onset when we change the curvature of the finger tip by applying an oscillatory translational shear of the top plate. (ii) We observe a sharp transition in the structure of the fingers when we decrease the injection rate of the inner fluid so that diffusion smooths the interface. At this transition, there is a jump in both the wavelength and the onset radius of fingering as well as a change in the three-dimensional structure as the fingers go from half filling to fully filling the cell. These experiments indicate that, by controlling the viscosity contrast at the interface, one can alter and perhaps even completely suppress the instability. [Preview Abstract] |
Sunday, November 20, 2016 3:23PM - 3:36PM |
D38.00003: Instabilities of an immiscible reactive micellar interface in a Hele-Shaw cell Zahra Niroobakhsh, Matthew Litman, Andrew Belmonte We present the case of a micellar reaction involving two immiscible fluids, which results in the growth of a thin viscoelastic layer between them. A Hele-Shaw cell is initially filled with different oils, including oleic acid, which acts as a cosurfactant. The oil is displaced by an aqueous solution of the surfactant cetylpyridinium chloride. A rich variety of viscous fingering patterns are observed, which are different from classic Saffman-Taylor patterns. We discuss how they change with concentration, surfactant injection rate and type of oil. We also measure the viscoelastic properties of this material using an interfacial rheometer. [Preview Abstract] |
Sunday, November 20, 2016 3:36PM - 3:49PM |
D38.00004: Control of viscous fingering by chemical reactions Chinar Rana, Anne De Wit Viscous fingering is a hydrodynamic instability that occurs in porous media when a less viscous fluid displaces a more viscous one. The interface between both fluids then deforms into fingers, which leads to enhanced mixing. We investigate theoretically the possibility to control this instability thanks to chemical reactions changing the viscosity \textit{in situ}. To do so, we analyze numerically the influence of different chemical kinetics on viscous fingering, looking in particular for conditions stabilizing the instability. We show that the reaction-diffusion specificities of the chemical front can be used to tune the viscous fingering pattern. The properties of this reactive fingering are obtained by computing onset times, mixing lengths and characteristics of the nonlinear fingering dynamics as a function of the parameters of the problem which are the relative viscosity ratios of reactants and products, the Damk\"{o}hler number quantifying the ratio of hydrodynamic and chemical times scales as well as the P\'{e}clet number. [Preview Abstract] |
Sunday, November 20, 2016 3:49PM - 4:02PM |
D38.00005: Influence of chemical reaction decreasing interfacial tension on immiscible viscous fingering Reiko Tsuzuki, Masanari Fujimura, Nagatsu Yuichiro We have experimentally investigated the effects of chemical reaction on immiscible viscous fingering (VF). In the present study, we use a chemical reaction producing a surfactant leading to a decrease in interfacial tension. In our experiment, a more viscous paraffin oil containing linoleic acid is displaced by a less viscous NaOHaq in a radial Hele-Shaw cell. We have found the influence of the reaction on the VF pattern depends on the displacement flow rate. At low flow rate, the reaction makes the fingers narrower. On the other hand, at intermediate flow rate, the reaction makes the fingers wider. At high flow rate, there is little influence of the reaction. These results can be interpreted as follows; when the reaction rate is much faster than the flow rate, interfacial tension is decreased uniformly over the interface. As a result, more finger-splitting occur and the fingers become narrower. When the reaction rate and flow rate are competing, the interfacial tension gradient is formed along the interface. As a result, Marangoni convection is produced, which leads to wider fingers. When the flow rate is much faster than the reaction rate, little reaction occurs during the formation of VF. As a result, the reaction does not influence on VF pattern. [Preview Abstract] |
Sunday, November 20, 2016 4:02PM - 4:15PM |
D38.00006: Inverse Saffman-Taylor instability in Hele-Shaw experiments using micro-particles Farzam Zoueshtiagh, Ilyesse Bihi, Jason Butler, Christine Faille, Michaƫl Baudoin Saffman-Taylor instability can occur when a low viscosity fluid displaces one of higher viscosity. It results from the decrease of the flow resistance as the fluid of lower viscosity replaces the more viscous one. This Saffman-Taylor instability is revisited experimentally for the inverse case of a viscous fluid displacing air when partially wetting particles are lying on the walls. Though the inverse case is otherwise stable, the presence of the particles results in a fingering instability at low capillary number. This capillary-driven instability is driven by the integration of particles into the interface which results from the minimization of the interfacial energy [1].\\ [1] Bihi et al., Phys. Rev. Lett., 117: 034501, 2016 [Preview Abstract] |
Sunday, November 20, 2016 4:15PM - 4:28PM |
D38.00007: Experimental study on viscous fingering with partial miscible fluids. Ryuta Suzuki, Yuichiro Nagatsu, Manoranjan Mishra, Takahiko Ban Viscous fingering (VF) instability occurs when a more viscous fluid is displaced by a less viscous one in porous media or Hele-Shaw cells. So far, studies of VF have focused on fluids that are either fully miscible or immiscible. However, little attention has been paid to VF in partially miscible fluids. Here, we have experimentally investigated VF in a radial Hele-Shaw cell using an aqueous two phase system (Ban et al. Soft Matter, 2012) which is an example of partially miscible fluids system. We have found novel instabilities that are counter-intuitive in miscible and immiscible systems. These include multiple droplets formation for low flow rate and widening of fingers at intermediate flow rate. The occurrence of the new instability patterns is induced by Korteweg effect in which convection is induced during phase separation in partially miscible systems. [Preview Abstract] |
Sunday, November 20, 2016 4:28PM - 4:41PM |
D38.00008: Spreading dynamics of superposed drops of two liquids on a spinning disk Subhadarshinee Sahoo, Ashish Orpe, Pankaj Doshi We have experimentally studied simultaneous spreading of two liquid drops, one engulfing the other, when rotated atop a horizontal spinning disk using flow visualization technique. A drop of high surface tension liquid is placed centrally on a horizontal disk followed by a drop of second liquid placed exactly above the first. The second liquid, of higher volume, lower surface tension and lower density than the first, engulfs the first drop completely. The disk is then rotated at a desired speed for a range of volume ratios of two liquids. The spreading behavior of both the drops is captured using a high speed camera. Such an arrangement of two liquids drops does not affect the spreading behavior of the outer liquid, but influences that of the inner liquid significantly. The drop spreads to a larger extent and breaks into more fingers as compared to the case where the same liquid is spreading in the absence of outer liquid. The fingering instability is achieved at earlier times with decreasing volume ratios, indicative of the increasing influence of the edge of outer liquid film being closer to that of the inner liquid. Further, sustained rotation of the disk leads to emanation of drops from the spreading drop travelling outwards through the fingers of outer liquid. [Preview Abstract] |
Sunday, November 20, 2016 4:41PM - 4:54PM |
D38.00009: Suppression of viscous fingering instability by a chemical reaction producing gel Yuichiro Nagatsu, Toshizo Kanbara, Masafumi Taniguchi Viscous fingering (VF) is a well-known hydrodynamic instability which is observed when a more viscous fluid is displaced by another less viscous one in porous media or Hele-Shaw cell. In such a situation, the interface between two fluids formed finger-like patterns. Recently, several techniques for suppress VF instability has been developed, which include time-dependent injection (Dias et al. PRL 2012), addition of permeability gradient (Al-Housseiny Nat. Phys. 2012), and use of viscoelastic plates of Hele-Shaw cell (Pihler-Puzovi\'{c} PRL 2012). Here, we demonstrate our trial to suppress VF by chemical reaction producing gel. We have succeeded to find a system of solutions and reaction in which the reaction producing a gel is able to completely suppress VF. In addition, we have performed rheological measurement of the gel produced at the reactive interface. The VF experiment and the rheological measurement have been performed by varying concentrations of the reactants. We show the storage modulus (G') of the gel, which corresponds to elastic response to small amplitude oscillatory shear, is responsible for the ability of suppression of VF in the present reactive system. [Preview Abstract] |
Sunday, November 20, 2016 4:54PM - 5:07PM |
D38.00010: Stabilization of miscible viscous fingering by chemical reaction decreasing viscosity Shuntaro Arai, Yuichiro Nagatsu, Priyanka Shukla, Anne De Wit Viscous fingering (VF) occurs when a more viscous fluid is displaced by a less viscous one in porous media or Hele-Shaw cells. In this study, experiment on miscible VF with chemical reaction is conducted by using a Hele-Shaw cell. Here, the chemical reaction takes place between a polymer dissolved in the more viscous solution and hydrochloric acid (HCl) dissolved in the less viscous one in the miscible interface region. The reaction decreases the viscosity of the polymer solution. The experiment shows that the reaction stabilizes VF when the flow rate is small. In the present study, the corresponding numerical simulation is also conducted. The simulation is able to reproduce the experimental results mentioned above when different diffusion coefficients are considered meaning that HCl diffuses faster than the polymer. However, the stabilization cannot be found under conditions of the same diffusivity of the reactants. These numerical results show that the different diffusivity is responsible for the stabilization of miscible VF by the chemical reaction decreasing viscosity. [Preview Abstract] |
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