Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session H34: Thin Film Theory II |
Hide Abstracts |
Chair: Marie-Jean Thoraval, Xi'an Jiaotong University Room: 616 |
Monday, November 25, 2019 8:00AM - 8:13AM |
H34.00001: On the dynamics of air sheet contraction Peng DENG, Zhen JIAN, Marie-Jean THORAVAL We have investigated the contraction of a thin air sheet by direct numerical simulations with the open source code Basilisk. An initially stationary thin air sheet starts to contract under capillary force. The contraction dynamics is dominated by the competition between capillary force and viscous dissipation. Three different regimes have been identified as a function of the Ohnesorge number of the sheet. For high Oh ($Oh \gg 1$), viscous effect dominates the dynamics. The rim of the sheet retracts under a nearly constant velocity after a rapid transition. For intermediate Oh ($0.1 < Oh < 1$), the contraction velocity decreases in time under a power-law scaling. For low Oh ($Oh < 0.1$), some vortices are shed behind the rim of the air sheet forcing its vertical oscillations. The air sheet can be even pinched off for smaller Oh ($Oh<0.01$). [Preview Abstract] |
Monday, November 25, 2019 8:13AM - 8:26AM |
H34.00002: Three-dimensional Numerical Simulations of Annular Falling Film Wave Dynamics in the Presence of Soluble Surfactants Assen Batchvarov, Lyes Kahouadji, Cristian Constante-Amores, Richard Craster, Omar Matar Falling film reactors are a key unit operation for the production of surfactants. This work focuses on numerical investigations into the effect of soluble and insoluble surfactants on the wave dynamics of annular falling films. We carry out three-dimensional direct numerical simulations of the film dynamics using a hybrid front-tracking/level-set solver, where surfactant effects are modelled using a couple of convective-diffusion transport equations for the interfacial and bulk species (Shin {\it et al.}, J. Comp. Phys., 359, 409-435, 2018). The influence of surfactant diffusivity, elasticity, and solubility on the wave dynamics, characterised by the shape of the emergent coherent structures, and their speed, is investigated as part of this work. [Preview Abstract] |
Monday, November 25, 2019 8:26AM - 8:39AM |
H34.00003: Flow stability of a liquid film partially wetting a substrate with rectangular trenches Dionysis Pettas, George Karapetsas, Yiannis Dimakopoulos, John Tsamopoulos We investigate the hydrodynamic stability of a Newtonian liquid film flowing down an inclined, solid substrate featuring periodic rectangular trenches. We focus on cases where the film fails to thoroughly wet the topography forming air inclusions inside the structure of the substrate. We solve the two-dimensional Navier–Stokes equations and develop a finite element model to accurately describe the exact configuration of all liquid-gas interfaces at steady state. To determine the linear stability, we consider perturbations around this base state and employ Floquet-Bloch theory to account for disturbances of arbitrary wavelengths, i.e. not necessarily matching the periodicity of the substrate. Through numerical simulations, we highlight the effect of inertia, viscous, and capillary forces on the stability of the fluid flow and also examine in detail the effect of substrate wettability, orientation with respect to gravity and geometric characteristics of the substrate. Moreover, the existence of the freely moving contact lines inside the cavity gives rise to multiple steady states which are analyzed for their stability. The role of air inclusions in the stabilization of the liquid film and the related mechanism will be discussed. [Preview Abstract] |
Monday, November 25, 2019 8:39AM - 8:52AM |
H34.00004: Fantastic Fluted Films Matthew Jones, Nathan Speirs, Mohammad Mansoor, Jesse Belden, Tadd Truscott When the rear end of a jet exits a pipe various beautiful shapes emerge. As the water flows through the pipe, the no-slip condition at the wall forms a thin boundary layer. Upon tube exit this slower moving fluid at the tube walls creates a thin tubular film, trailing behind the main water mass and connecting it to the tube exit. This film can morph into various shapes including fluted champagne glasses, bubbles, bells, jets, and crowns. We experimentally examine the regimes of this phenomenon and attempt to elucidate the physics behind how and why they occur. [Preview Abstract] |
Monday, November 25, 2019 8:52AM - 9:05AM |
H34.00005: Roll wave instability in Guinness beer Tomoaki Watamura, Kazuyasu Sugiyama, Fumiya Iwatsubo, Kenichiro Yamamoto, Yuko Yotsumoto, Takashi Shiono To gain the insight into the texture formation in a glass of Guinness beer, we performed experiments on the bubble distribution in Guinness poured in an inclined container, and observed how the texture forms. We also report the texture-formation in controllable experiments using particle suspensions with precisely specified diameters and volume-concentrations. The hydrodynamic condition for the texture-formation is analogous to the critical point of the roll-wave instability in a fluid film at Froude number $Fr$ > 1. We conclude that the roll-wave instability of the gravity current is responsible for the texture-formation in a glass of Guinness beer. [Preview Abstract] |
Monday, November 25, 2019 9:05AM - 9:18AM |
H34.00006: Experiments on the Dynamic Wetting of Growing Ice John Ladan, Stephen W. Morris The morphology of ice formed from liquid water flowing over a growing surface presents a challenging free-boundary problem. We present experimental measurements of water flow on the surface of a growing icicle. The liquid water contains Sodium Fluorescein in concentrations below 168 ppm. Icicles exhibit ripples around their circumference with a near universal wavelength of 1 cm. Experiments have shown that the rippling instability is associated with small levels of impurities and is not present for sufficiently pure water. Existing models of icicle growth assume that the icicle is covered completely by a thin film of flowing water. In our experiment, the dye acts both as the instability-triggering impurity and the liquid indicator. We can clearly observe where liquid lies on the surface, and the presence of non-fluorescing dye trapped inside the ice. The icicle surface is not entirely covered by a water film, but rather is only partially wetted. The coverage and speed of the dynamic wetting depends on the topography and impurity dependent surface properties. Water flows much more readily over previously wetted areas. This incomplete coverage appears to affect the morphology of the growing icicle and may be an important component of the mechanism of ripple formation. [Preview Abstract] |
Monday, November 25, 2019 9:18AM - 9:31AM |
H34.00007: Bistability in the Flow of Polymer Solutions in Porous Media Christopher Browne, Audrey Shih, Sujit Datta Polymer solutions are often injected in porous media to improve oil recovery or groundwater remediation, but applications are limited by an incomplete understanding of the underlying physics. In a tortuous pore space, the flow becomes unstable at sufficiently large injection rates. However, how the spatio-temporal characteristics of this flow state depend on pore geometry is poorly understood. We shed light on this question by systematically varying the spacing between pores. When the pore spacing is large, unstable eddies form upstream of each pore, similar to the case of an isolated pore. By contrast, when the pore spacing is sufficiently small, the flow exhibits a surprising bistability, stochastically switching between two distinct flow states. We hypothesize that this unusual behavior arises from the interplay between the retention of polymer strain between pores, hysteresis in polymer conformations, and fluctuations in the flow. Consistent with this idea, the mean flow state can be tuned by the imposed flow rate. Moreover, we find that while flow state is correlated between neighboring pores, these correlations do not persist long-range. Our results thus help to elucidate the rich array of flow behaviors that can arise in polymer solution flow through porous media. [Preview Abstract] |
Monday, November 25, 2019 9:31AM - 9:44AM |
H34.00008: Elastic and Shear thinning instabilities for the flow of polymer solutions through microtubes Bidhan Chandra, Viswanathan Shankar It is well known that the flow of dilute polymer solution through tubes undergoes a non-linear subcritical transition at Re slightly higher than 2000. However, when the polymer concentration is increased beyond a threshold concentration, the instability occurs at a Re much lower than 2000. The instability occurring at Re lower than 2000 at higher polymer concentration (hence higher elasticity) is a linear instability. A recent article by Poole, 2016, shows that if the polymer solution prepared is sufficiently shear thinning in nature, an instability occurs at very low inertia (Re\textasciitilde 50). We explore the possibility of very low Re instability for the flow of concentrated polymer solutions through micro-tubes. High concentration of polymer solution coupled with small tube diameters enable us to reach high elasticity numbers. We observe that the polymer solution destabilize at very low Re (Re\textasciitilde 10). The nature of instability is also observed to be very different as compared to elasto-inertial instability as observed from the scaling relationships. [Preview Abstract] |
Monday, November 25, 2019 9:44AM - 9:57AM |
H34.00009: Soft Cell: Flow-induced deformation of a compliant Hele-Shaw cell Finn Box, Gunnar Peng, Anne Juel, Draga Pihler-Puzovic We present an experimental study of the flow-induced deformation of a compliant Hele-Shaw cell, comprising a soft substrate and a rigid upper boundary separated by a thin gap. An axisymmetric displacement flow is formed by injecting viscous fluid, at a constant volumetric flux, into the center of the cell, which is pre-filled with the same fluid. By measuring the surface deflection of the substrate, we find that the deformation profile is self-similar during a period of transient growth before rapidly attaining a steady shape determined by the logarithmic profile of the fluid pressure within the cell. We discuss how the deformed substrate influences the motion of the advancing front between injected and resident fluid in the cell. [Preview Abstract] |
Monday, November 25, 2019 9:57AM - 10:10AM |
H34.00010: Control of Radial Miscible Viscous Fingering Using a Finite Blob-An Experimental Study. Sada Nand, Vandita Sharma, Manoranjan Mishra We experimentally demonstrate the control of miscible viscous fingering instability in a novel way. We consider the less viscous fluid initially in a circular blob of finite radius r$_{\mathrm{0}}$ displacing the surrounding more viscous fluid in the radial Hele-Shaw cell. Experiments only with a point source (r$_{\mathrm{0}} \quad =$0) are available in the literature. Getting initial finite circular blob is a huge experimental challenge. For each r$_{\mathrm{0}}$, a flow rate is wisely calculated so as to have a stable displacement up to radius r$_{\mathrm{0}}$. Also, a diligently designed T- junction is utilized in the Hele-Shaw experimental set-up to ease the fluid injection. The experiments depict the initial radius of the circular blob (r$_{\mathrm{0}}_{\thinspace })$ as a controlling parameter. A delay in instability is observed for experiments with non-zero r$_{\mathrm{0}}$ in comparison to those performed with a point source. Further, a reduced instability is evident with an increase in r$_{\mathrm{0}}$, which is in agreement with the numerical simulations performed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700