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Tarr SW, Brunner JS, Soto D, Goldman DI. Probing Hydrodynamic Fluctuation-Induced Forces with an Oscillating Robot. PHYSICAL REVIEW LETTERS 2024; 132:084001. [PMID: 38457731 DOI: 10.1103/physrevlett.132.084001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/14/2023] [Accepted: 01/16/2024] [Indexed: 03/10/2024]
Abstract
We study the dynamics of an oscillating, free-floating robot that generates radially expanding gravity-capillary waves at a fluid surface. In open water, the device does not self-propel; near a rigid boundary, it can be attracted or repelled. Visualization of the wave field dynamics reveals that when near a boundary, a complex interference of generated and reflected waves induces a wave amplitude fluctuation asymmetry. Attraction increases as wave frequency increases or robot-boundary separation decreases. Theory on confined gravity-capillary wave radiation dynamics developed by Hocking in the 1980s captures the observed parameter dependence due to these "Hocking fields." The flexibility of the robophysical system allows detailed characterization and analysis of locally generated nonequilibrium fluctuation-induced forces [M. Kardar and R. Golestanian, Rev. Mod. Phys. 71, 1233 (1999)RMPHAT0034-686110.1103/RevModPhys.71.1233].
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Affiliation(s)
- Steven W Tarr
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, Georgia 30332, USA
| | - Joseph S Brunner
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, Georgia 30332, USA
- Department of Radiation Medicine, University of Kentucky, 800 Rose Street, Lexington, Kentucky 40536, USA
| | - Daniel Soto
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, Georgia 30332, USA
| | - Daniel I Goldman
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, Georgia 30332, USA
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A Hydrodynamic Analog of the Casimir Effect in Wave-Driven Turbulent Flows. FLUIDS 2022. [DOI: 10.3390/fluids7050155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We present experimental results on a fluctuation-induced force observed in Faraday wave-driven turbulence. As recently reported, a long-range attraction force arises between two walls that confine the wave-driven turbulent flow. In the Faraday waves system, the turbulent fluid motion is coupled with the disordered wave motion. This study describes the emergence of the fluctuation-induced force from the viewpoint of the wave dynamics. The wave amplitude is unaffected by the confinement while the wave erratic motion is. As the wall spacing decreases, the wave motion becomes less energetic and more anisotropic in the cavity formed by the walls, giving rise to a stronger attraction. These results clarify why the modelling of the attraction force in this system cannot be based on the wave amplitude but has to be built upon the wave-fluid motion coupling. When the wall spacing is comparable to the wavelength, an intermittent wave resonance is observed, and it leads to a complex short-range interaction. These results contribute to the study of aggregation processes in the presence of turbulence and its related problems such as the accumulation of plastic debris in coastal marine ecosystems or the modelling of planetary formation.
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Davoodianidalik M, Punzmann H, Kellay H, Xia H, Shats M, Francois N. Fluctuation-Induced Interaction in Turbulent Flows. PHYSICAL REVIEW LETTERS 2022; 128:024503. [PMID: 35089756 DOI: 10.1103/physrevlett.128.024503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 10/11/2021] [Accepted: 12/15/2021] [Indexed: 06/14/2023]
Abstract
Fluctuation-induced forces are observed in numerous physical systems spanning from quantum to macroscopic scale. However, there is as yet no experimental report of their existence in hydrodynamic turbulence. Here, we present evidence of an attraction force mediated via turbulent fluctuations by using two walls locally confining 2D turbulence. This long-range interaction is a function of the wall separation and the energy injection rate in the turbulent flow. As the wall spacing decreases, the confined flow becomes less energetic and more anisotropic in the bounded domain, producing stronger attraction. The mechanism of force generation is rooted in a nontrivial fluid-wall coupling where coherent flow structures are guided by the cavity walls. For the narrowest cavities studied, a resonance phenomenon at the flow forcing scale leads to a complex short-range interaction. The results could be relevant to problems encountered in a range of fields from industrial multiphase flows to modeling of planetary formation.
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Affiliation(s)
- M Davoodianidalik
- Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - H Punzmann
- Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - H Kellay
- Laboratoire Ondes et Matiere d'Aquitaine, UMR 5798, CNRS, Universite de Bordeaux, 33405 Talence, France
| | - H Xia
- Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - M Shats
- Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - N Francois
- Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
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Spandan V, Putt D, Ostilla-Mónico R, Lee AA. Fluctuation-induced force in homogeneous isotropic turbulence. SCIENCE ADVANCES 2020; 6:eaba0461. [PMID: 32284987 PMCID: PMC7124934 DOI: 10.1126/sciadv.aba0461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 01/13/2020] [Indexed: 06/11/2023]
Abstract
Understanding force generation in nonequilibrium systems is a notable challenge in statistical physics. We uncover a fluctuation-induced force between two plates immersed in homogeneous isotropic turbulence using direct numerical simulations. The force is a nonmonotonic function of plate separation. The mechanism of force generation reveals an intriguing analogy with fluctuation-induced forces: In a fluid, energy and vorticity are localized in regions of defined length scales. When varying the distance between the plates, we exclude energy structures modifying the overall pressure on the plates. At intermediate plate distances, the intense vorticity structures (worms) are forced to interact in close vicinity between the plates. This interaction affects the pressure in the slit and the force between the plates. The combination of these two effects causes a nonmonotonic attractive force with a complex Reynolds number dependence. Our study sheds light on how length scale-dependent distributions of energy and high-intensity vortex structures determine Casimir forces.
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Affiliation(s)
- Vamsi Spandan
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Daniel Putt
- Department of Mechanical Engineering, University of Houston, TX 77004, USA
| | | | - Alpha A. Lee
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
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Coexisting Ordered States, Local Equilibrium-like Domains, and Broken Ergodicity in a Non-turbulent Rayleigh-Bénard Convection at Steady-state. Sci Rep 2019; 9:10615. [PMID: 31337823 PMCID: PMC6650598 DOI: 10.1038/s41598-019-47127-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 07/10/2019] [Indexed: 12/12/2022] Open
Abstract
A challenge in fundamental physics and especially in thermodynamics is to understand emergent order in far-from-equilibrium systems. While at equilibrium, temperature plays the role of a key thermodynamic variable whose uniformity in space and time defines the equilibrium state the system is in, this is not the case in a far-from-equilibrium driven system. When energy flows through a finite system at steady-state, temperature takes on a time-independent but spatially varying character. In this study, the convection patterns of a Rayleigh-Bénard fluid cell at steady-state is used as a prototype system where the temperature profile and fluctuations are measured spatio-temporally. The thermal data is obtained by performing high-resolution real-time infrared calorimetry on the convection system as it is first driven out-of-equilibrium when the power is applied, achieves steady-state, and then as it gradually relaxes back to room temperature equilibrium when the power is removed. Our study provides new experimental data on the non-trivial nature of thermal fluctuations when stable complex convective structures emerge. The thermal analysis of these convective cells at steady-state further yield local equilibrium-like statistics. In conclusion, these results correlate the spatial ordering of the convective cells with the evolution of the system’s temperature manifold.
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Woodhouse FG, Ronellenfitsch H, Dunkel J. Autonomous Actuation of Zero Modes in Mechanical Networks Far from Equilibrium. PHYSICAL REVIEW LETTERS 2018; 121:178001. [PMID: 30411906 DOI: 10.1103/physrevlett.121.178001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 09/04/2018] [Indexed: 06/08/2023]
Abstract
A zero mode, or floppy mode, is a nontrivial coupling of mechanical components yielding a degree of freedom with no resistance to deformation. Engineered zero modes have the potential to act as microscopic motors or memory devices, but this requires an internal actuation mechanism that can overcome unwanted fluctuations in other modes and the dissipation inherent in real systems. In this Letter, we show theoretically and experimentally that complex zero modes in mechanical networks can be selectively mobilized by nonequilibrium activity. We find that a correlated active bath actuates an infinitesimal zero mode while simultaneously suppressing fluctuations in higher modes compared to thermal fluctuations, which we experimentally mimic by high frequency shaking of a physical network. Furthermore, self-propulsive dynamics spontaneously mobilize finite mechanisms as exemplified by a self-propelled topological soliton. Nonequilibrium activity thus enables autonomous actuation of coordinated mechanisms engineered through network topology.
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Affiliation(s)
- Francis G Woodhouse
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom
| | - Henrik Ronellenfitsch
- Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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Affiliation(s)
- Alpha A. Lee
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Jean-Pierre Hansen
- Department of Chemistry, University of Cambridge, Cambridge, UK
- Physicochimie des électrolytes et nanosystèmes interfaciaux, UMR PHENIX, Sorbonne Université, CNRS, Paris, France
| | - Olivier Bernard
- Physicochimie des électrolytes et nanosystèmes interfaciaux, UMR PHENIX, Sorbonne Université, CNRS, Paris, France
| | - Benjamin Rotenberg
- Physicochimie des électrolytes et nanosystèmes interfaciaux, UMR PHENIX, Sorbonne Université, CNRS, Paris, France
- Réseau sur le Stockage Electrochimique de l'Energie (RS2E), Amiens Cedex, France
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