Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session J10: Drop: Levitation |
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Chair: John Bush, Massachusetts Institute of Technology Room: Ballroom J |
Sunday, November 24, 2024 5:50PM - 6:03PM |
J10.00001: ABSTRACT WITHDRAWN
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Sunday, November 24, 2024 6:03PM - 6:16PM |
J10.00002: Levitation of nanofluid drops Gene Patrick S Rible, Connor K Traynor, Joshua T Watkins, Syed J Raza, Hannah P Sebek, Tadd T Truscott, Andrew Dickerson In this experimental work, we investigate the influence of nanoparticle concentration and reduced surface tension on the terminal velocity and oscillation of free-falling drops. We employ a vertical wind tunnel to levitate drops of diameters 1 mm - 7 mm with silicon dioxide nanoparticle concentrations of 0.1, 0.5, and 1%m/m. The addition of 20-nm particles decreases the shape oscillation frequency observed in distilled water drops of equivalent diameter without affecting oscillation amplitude. Adding surfactant to distilled water and nanofluids stabilizes the drop by a reduction in the axis ratio oscillation, the absolute canting angle, and the absolute canting angular velocity. Surfactant produces flatter drops and a reduction in mean terminal velocity by 15\% versus distilled water drops of the same volume. Levitating drops exhibit coexisting modes of drop oscillation. The (2,0) axisymmetric mode occurs for all drops of varying sizes affirming previous studies. Smaller drop sizes introduce a (2,2) horizontal mode and a (2,1) transverse oscillation mode. In larger drops, the addition of nanoparticles introduces a (2,2) mode in addition to the (2,0) mode. |
Sunday, November 24, 2024 6:16PM - 6:29PM |
J10.00003: Droplet levitation over non-isothermal surface of evaporating liquid layer Jacob E Davis, Vladimir S Ajaev We develop a mathematical model of heat and mass transfer in a configuration which involves a spherical droplet levitating near a flat liquid layer heated from below. Analytical solutions for vapor concentration in air and the temperature distributions both inside the droplet and in moist air around it are coupled to the numerical solution for heat transfer in the liquid layer. In the limit of weak evaporation, the liquid layer surface is cooled locally due to the presence of the droplet, while the effect is reversed for strong evaporation. The latter case is also characterized by a possibility of strong temperature gradients in the droplet itself, an unexpected conclusion given the high liquid-to-air thermal conductivity ratio. The observations are explained in terms of interplay between geometric and thermal effects of the presence of the droplet. The calculation of the evaporation rate leads to determination of the flow around the droplet, treated in the Stokes flow approximation, and thus the levitation height. The latter is reduced as a result of heat transfer effects in the liquid layer. We also discuss possible mechanisms of droplet self-organization into large ordered arrays. |
Sunday, November 24, 2024 6:29PM - 6:42PM |
J10.00004: Pilot-wave hydrodynamics in confined geometries Davis Evans, Bauyrzhan K Primkulov, John W M Bush In pilot-wave hydrodynamics, a millimetric oil droplet in turn generates and is propelled by waves induced by its bouncing on a vertically vibrating liquid bath. This hydrodynamic system exhibits wave-particle duality on the macroscopic scale of a form envisaged by Louis de Broglie in his now century-old `double-solution' theory of quantum mechanics. When the droplet moves in a confined geometry (a corral), a rich set of statistical patterns emerge in the droplet's position histogram, some of which are reminiscent of those arising in the quantum corral. In the hydrodynamic corrals, the statistical behavior of the droplet can be rationalized in terms of an underlying dynamical theory. Three distinct mechanisms are detailed here, which represent the three central paradigms for emergent quantum behavior in pilot-wave hydrodynamics. In the first, droplet motion is marked by intermittent switching between unstable periodic orbits. In the second, droplet speed oscillations give rise to a coherent statistical signature. In the third, non-resonant effects between the droplet and its pilot-wave give rise to ponderomotive effects. |
Sunday, November 24, 2024 6:42PM - 6:55PM |
J10.00005: The Nusselt number of a hot sphere levitated by a volatile pool Stephen Morris The duration of the inverse Leidenfrost phenomenon depends on the Nusselt number Nu of the sphere, itself determined by the equations of motion and heat flow governing the thin film of vapour which are themselves coupled to the elliptic Laplace relation determining the shape of the entire liquid-vapour interface. In this talk, it is shown that in the limit as the ratio h/b of film thickness to sphere radius vanishes, all properties of the phenomenon, including the Nusselt number relation, can be calculated numerically using only the Laplace relation and the boundary layer equations describing the thin film; it is not necessary to introduce equations of motion and heat flow governing the outer thick region. In Morris (2024), this method is demonstrated by using it to determine Nu for a sphere sufficiently small that the acceleration g due to gravity is negligible thoughout the governing equations, except where multiplied by the density of the sphere. In addition to those results, in this talk, numerical results for Nu obtained by applying the method to larger spheres will also be described. |
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