Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session D12: Drops: Bouncing, Impact and Dynamic Surface Interactions I |
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Chair: Sungyon Lee, Texas A&M University Room: 3018 |
Sunday, November 23, 2014 2:15PM - 2:28PM |
D12.00001: Hydrodynamic quantum analogs John Bush We review recent developments in our understanding of droplets walking on a vibrating fluid bath. Particular attention is given to highlighting the manner in which pilot-wave dynamics gives rise to quantization, and chaotic pilot-wave dynamics to quantum-like statistics. The first links between between pilot-wave dynamics and relativistic effects are explored, along with the relation between this hydrodynamic system and existing realist models of quantum mechanics. Future directions are discussed. [Preview Abstract] |
Sunday, November 23, 2014 2:28PM - 2:41PM |
D12.00002: Diffraction of walking droplets Daniel M. Harris, Giuseppe Pucci, John W.M. Bush We present results from our revisitation of the experiment of a walking droplet passing through a single slit, originally investigated by Couder \& Fort (PRL, 2006). On each passage, the walker's trajectory is deviated as a result of the spatial confinement of its guiding wave. We explore the role of the droplet size and the bath's vibration amplitude on both the dynamics and statistics. We find the behavior to be remarkably sensitive to these control parameters. A complex physical picture emerges. [Preview Abstract] |
Sunday, November 23, 2014 2:41PM - 2:54PM |
D12.00003: Hydrodynamic Spin States Anand Oza, Rodolfo Rosales, John Bush We present the results of a theoretical investigation of droplets walking on a vibrating fluid bath. The droplet's trajectory is described in terms of an integro-differential equation that incorporates the influence of the propulsive force generated by its monochromatic guiding wave. A stability analysis of orbital solutions shows that walkers may execute stable circular orbits in the absence of an external force. When subjected to rotation, these hydrodynamic spin states exhibit a macroscopic analogue of Zeeman splitting. We conclude by presenting the stability analysis for a pair of orbiting walkers, and compare our results to recent laboratory experiments. [Preview Abstract] |
Sunday, November 23, 2014 2:54PM - 3:07PM |
D12.00004: Droplets Walking in a 2D Coulomb Potential Lucas Tambasco, Anand Oza, John Bush We present the results of a theoretical investigation of a droplet walking on a vibrating fluid bath subject to a central two-dimensional Coulomb force. Using the Hydrogen Atom as motivation, we introduce an attractive Coulombic term to the integro-differential trajectory equation developed by Oza et al. (JFM, 2014), and analyze the behavior of the droplet's motion. Linear stability analysis of circular trajectories indicates that stable orbits have quantized radii and can only be achieved for a specific range of vibrational forcing acceleration. In unstable regions, numerical simulations of trajectories show that droplets can either collapse into the center or escape the influence of the Coulomb force. We discuss the value of this Coulombic system as a Hydrodynamic Quantum Analog, and explore its extension to 3 dimensions. [Preview Abstract] |
Sunday, November 23, 2014 3:07PM - 3:20PM |
D12.00005: Experimental test of temporal reversibility in a memory-driven system Stephane Perrard, Matthieu Labousse, Emmanuel Fort, Yves Couder A droplet bouncing sub-harmonically on a vibrated liquid bath can be self-propelled by its interaction with the waves it generates. The resulting ``walker'' is characterized by the structure of the information loop linking the particle with its pilot wave. The particle can be considered as encoding positional information in the waves it generates. These waves, being sustained for some time, superpose so that the global wave field contains a stored memory of the past trajectory. At its next bounce the drop ``reads'' this information, which will determine its next move. Is this reading process time reversal? This question is addressed using an experimental trick. A pi phase shift is imposed to the drop, so that the associated wave is reversed. The droplet then ``reads'' the path-memory phase shifted by pi, so that it comes back on its own previous trajectory. As new emitted waves are pi-shifted, they interfere destructively with the forward path, erasing progressively the recorded memory. The possible application of wave-mediated drop computation will then be discussed. [Preview Abstract] |
Sunday, November 23, 2014 3:20PM - 3:33PM |
D12.00006: Repeated bouncing of drops on wetting and non-wetting surfaces mediated by a persisting thin air film Jolet de Ruiter, Rudy Lagraauw, Dirk van den Ende, Frieder Mugele Liquid drops impinging onto solid surfaces undergo a variety of impact scenarios such as splashing, sticking, and bouncing, depending on impact conditions and substrate properties. Bouncing requires efficient conversion of initial kinetic energy into surface energy and back into kinetic energy. This process is believed to be limited to non-wetting, in particular superhydrophobic surfaces, for which viscous dissipation during drop-substrate contact is minimal. Here, we report a novel bouncing mechanism that applies equally to non-wetting and wetting systems for flat surfaces with contact angles down to 10 degrees. For initial impact speeds up to about 0.5 m/s we demonstrate using dual wavelength interferometry that aqueous and non-aqueous drops remain separated from the substrate by air films of (sub)micrometer thickness at all times throughout a series of up to 16 consecutive bouncing events. We show that the purely dissipative force arising from the viscous squeeze-out of air is responsible for both the momentum transfer and for a substantial part of the residual energy dissipation. [Preview Abstract] |
Sunday, November 23, 2014 3:33PM - 3:46PM |
D12.00007: Detailed model of bouncing drops on a bounded, vibrated bath Francois Blanchette, Tristan Gilet We present a detailed model of drops bouncing on a bounded vibrated bath. These drops are known to bounce indefinitely and to exhibit complex and varied vertical dynamics depending on the acceleration of the bath. In addition, in a narrow parameter regime, these drops travel horizontally while being guided by the waves they generate. Our model tracks the drop's vertical radius and position, as well as the eigenmodes of the waves generated via ordinary differential equations only. We accurately capture the vertical dynamics, as well as some of the horizontal dynamics. Our model may be extended to account for interactions with other drops or obstacles, such as slits and corrals. [Preview Abstract] |
Sunday, November 23, 2014 3:46PM - 3:59PM |
D12.00008: Manipulation of electrically charged drops on a vibrating bath Martin Brandenbourger, St\'ephane Dorbolo The bouncing drop experiment, which allows to store small drops thanks to the vibration of a liquid interface, is sometimes linked to lab-on-a-chip applications. Unfortunately, a lot of these studies focused on the behavior of the bouncing drops instead of their handling. By electrically charging the droplet, we found that an electric field can control the displacement of a droplet stored on a vibrating bath. Even though the charged droplets seems to move with a constant speed at the bath scale, their behavior is shown to be much more complex at the droplet scale. A theoretical model, based on the movement of the droplet during one bounce, has been developed to explain these observations and to understand how to manipulate a droplet without contact with any interfaces. [Preview Abstract] |
Sunday, November 23, 2014 3:59PM - 4:12PM |
D12.00009: Walking droplets in confined geometries Boris Filoux, Olivier Mathieu, Nicolas Vandewalle When gently placing a droplet onto a vertically vibrated bath, coalescence may be avoided : the drop bounces permanently. Upon increasing forcing acceleration, a drop interacts with the wave it generates, and becomes a ``walker'' with a well defined velocity. In this work, we investigate the confinement of a walker in a mono-dimensional geometry. The system consists of linear submarine channels used as waveguides for a walker. By studying the dynamics of walkers in those channels, we discover some 1D-2D transition. We also propose a model based on an analogy with ``Quantum Wires.'' Finally, we consider the situation of a walker in a circular submarine channel, and examine the behavior of several walking droplets in this system. We show the quantization of the drop distances, and correlate it to their bouncing modes. [Preview Abstract] |
Sunday, November 23, 2014 4:12PM - 4:25PM |
D12.00010: Bouncing and coalescence of droplets on falling liquid films Zhizhao Che, Amandine Deygas, Omar Matar When a droplet impacts on a falling liquid film, the outcome depends on the fluid properties of the droplet, its speed, and angle of incidence, as well as on the film flow rate and associated flow regimes. In this study, the oblique impact of droplets on a falling liquid film is investigated experimentally. The falling film is created on an inclined substrate and the Reynolds number is varied. Droplets with different sizes and different speeds are used to study the impact process for different Weber and Ohnesorge numbers. Different phenomena of droplet impact are identified and analysed, such as bouncing, partial coalescence, total coalescence, and splashing. An impact regime map is generated, and the effects of droplet impact speed and size, and the film flow rates are studied. The propagation of waves on the liquid film post-impact is analysed. The results show that the flowing film can significantly affect the impact process of droplets, and the latter can alter the propagation of waves on the falling film. [Preview Abstract] |
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