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 R35: Waves: Surface Waves II |
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Chair: Kianoosh Yousefi, University of Texas at Dallas Room: 355 A |
Monday, November 25, 2024 1:50PM - 2:03PM |
R35.00001: Numerical Investigations of Capillary-Gravity Wave Scattering by a Cylindrical Barrier Guoqin Liu, Likun Zhang The scattering of surface waves by structures intersecting a liquid surface has long been a focus in fluid dynamics due to its theoretical and practical implications. Historically, theoretical studies on this problem have predominantly employed idealized assumptions such as infinitesimally thin barriers, which do not fully represent real-world conditions. This project aims to extend the study by numerically investigating the scattering by a cylindrical barrier intersecting the liquid surface through a pinned contact line. Detailed numerical simulations of potential flow coupled with the surface elevation dynamics were conducted to analyze the interactions between the wave and the barrier. Parameters such as wave frequency and barrier radius were varied to examine their effects on the scattering. The results highlight how the barrier's dimensionless size and the Bond number influence the scattering, with notable findings on the dependency of the scattering efficiency on these parameters. The study elucidates the role of contact lines and barrier size in modifying the scattering and presents a comprehensive view of the scattering across different parameter ranges. |
Monday, November 25, 2024 2:03PM - 2:16PM |
R35.00002: CNN-based reconstruction of near-surface atmospheric turbulence using surface wave measurements Ahmed A Hamada, Gurpreet Singh Hora, Fabrice Veron, Kianoosh Yousefi The small-scale turbulence resulting from wind-wave interactions profoundly affects the interfacial air-sea flux exchanges and, consequently, the long-term climate trends and short-term weather events. However, the correlation between this turbulence and surface wave characteristics has yet remained challenging due to the complexity of near-surface dynamics. It is, in fact, extremely challenging to resolve the near-surface turbulence using either high-resolution experimental/field measurements or numerical techniques in most wind-wave conditions. |
Monday, November 25, 2024 2:16PM - 2:29PM |
R35.00003: Dynamic behaviour of zig-zag ladder-, double-, and broken-hexagonal superlattices in two-frequency parametric surface waves Laurette S Tuckerman, Debashis Panda, Lyes Kahouadji, Seungwon Shin, Jalel Chergui, Damir Juric, Omar K. Matar We study the nonlinear dynamics and patten formation associated with a planar interface vibrated vertically with two frequencies to form surface waves. We focus on the superlattice patterns, where a spatial mode as well as its spatial subharmonic coexist in the system. Superlattices have been studied extensively, both theoretically and experimentally [1], though focus was limited to time-independent bifurcations. Here, we ask whether the mode interactions underlying superlattices are time-dependent, and if so, how this influences the superlattice spatio-temporal evolution. Below the codimension-2 point, where the harmonic modes are unstable, we show that hexagons remain stable for a long time [1], unlike previous observations of alternating stripes and quasi-hexagons [2]. Upon increasing the forcing amplitude by 25% above its critical threshold, a series of metastable patterns are observed featuring broken- and double-hexagons resulting from mode competition between the primary harmonic mode and its spatial subharmonic. Finally, we obtain zig-zag ladder-like superlattice patterns, which is a hexagon symmetry-broken by its spatial subharmonic. To understand the dynamical behaviour of superlattices, we analyse the Fourier spectra, which shows that there are two competing routes of three-wave interactions; one involving primary mode interactions with its spatial subharmonic mode, and the other features two primary modes interacting to form the spatial subharmonic of their resultant. |
Monday, November 25, 2024 2:29PM - 2:42PM |
R35.00004: Polygonal patterns of Faraday water waves analogous to collective excitations in Bose–Einstein condensates Xinyun Liu, Xinlong Wang Since the celebrated discovery of beautiful ``crispations" on a vibrating fluid layer, Faraday experiment has been an everlasting research topic owing to its rich spectrum of wave phenomena. Here we report the observation of polygonal Faraday patterns on the water surface held in vibrating containers with parabolic and other concave bases. These patterns manifest themselves as simple geometric figures of $l$-fold symmetry, ranging from ellipse ($l = 2$) to heptagon ($l = 7$), with wavelength much longer than the capillary length. Hence, they are intrinsically different from the previously studied patterns in vibrating drops or puddles and represent a peculiar variety of nonlinear shallow-water gravity waves or tidal waves in concave basins. What is of particular interest is their resemblance to the star-shaped collective excitations recently discovered in a driven Bose-Einstein condensate, not only sharing identical square-root scaling dispersion and pattern dynamics, but also possessing similar nonlinear features like hard-spring nonlinearity. Based on the close correspondence, we propose an analogue of the patterning dynamics between the classical and quantum fluid systems subject to confinement and argue that this analogue is mathematically valid in nonlinear regime. |
Monday, November 25, 2024 2:42PM - 2:55PM |
R35.00005: Marangoni-driven pattern transitions in surfactant-covered Faraday waves Debashis Panda, Lyes Kahouadji, Laurette S Tuckerman, Jalel Chergui, Seungwon Shin, Damir Juric, Omar K. Matar Parametric vibration of an interface results in the formation of standing waves of frequency half of the vibration, called Faraday waves. Owing to the capillary-gravity dispersion relation, these standing waves select a wavenumber at a certain vibrating frequency. Depending on the direction and number of unstable wave modes, N-fold symmetric patterns are usually formed, of which stripes (N=1) and squares (N=2), are the simplest. Complexities such as contact-line dissipation, viscosity, and surface contamination are well known to affect even the simplest patterns like squares. In the previous studies, surfactant-like surface contaminants are studied to elucidate the damping mechanism, wavelength selection, and the Marangoni stresses on the structure of the surface waves. However, these studies are limited to linearised, one- or two- dimensional, some of which carried out in lubrication limit [1], with a dearth of fully three-dimensional study of Marangoni stresses on the pattern formation in the strongly nonlinear regime. In this work, we report the three-dimensional spatio-temporal evolution and pattern transitions induced by Marangoni-driven surface flows. We introduce a characteristic parameter B, a ratio of Marangoni and inertial time scales, to rationalise the pivotal point of pattern transition in surfactant-covered Faraday waves. Beyond B = 1, square patterns transition to asymmetric squares, weakly wavy stripes, and beaded-squares with oscillon-like physical features, which we call bulbous structures. These newly observed structures are a consequence of the heterogenous Marangoni-driven surface backflow on the beaded stripes. With the advantage of high-fidelity direct numerical simulations, we uncover the physics of the formation of these structures and their spatio-temporal evolution. |
Monday, November 25, 2024 2:55PM - 3:08PM |
R35.00006: A Simple Model for Capillary Waves Propagating over Static Curved Surfaces Cade Steven Sbrocco, Yukun Sun, Chris Roh The distortion of propagating pure capillary waves due to curved free-surfaces, such as menisci, is an underexplored area of study. Previous works on fluid waves on curved free-surfaces focused on the interactions of gravity-capillary waves with menisci in edge constraint problems, suddenly accelerated surfaces, and the formation of parasitic capillary waves. Here, inspired by studies on Rayleigh waves propagating over curved surfaces, we present a simple inviscid model to understand how the propagation of small amplitude, high frequency capillary waves are affected by an underlying static, curved surface. Additionally, we discuss future avenues to extend our analysis to include viscous effects and relax our high frequency assumptions. |
Monday, November 25, 2024 3:08PM - 3:21PM |
R35.00007: Dispersion relation and memory effects in dynamics of viscid gravity-capillary waves João Braz, Davis A Garwood, Ian B Spielman Gravity waves and free-surface flows are of topical importance in a range of applications, the physics of which is typically addressed within the encompassing framework of the Boussinesq-type equations. Although extensions to this framework, such as capillarity, are well established, the effects of viscosity and no-slip surfaces remain elusive: a number of approaches have been developed, but a more general framework is still missing. We carry out a detailed analytical and numerical study of the interaction between the surface degrees of freedom and the vertical dynamics of the pressure and vorticity fields in the linear regime. Bypassing viscosity-perturbative and long-wavelength considerations, we identify dynamical features across a broad range of linear regimes, including the dispersion relation of viscid gravity-capillary waves as well as memory (non-instantaneous) effects. |
Monday, November 25, 2024 3:21PM - 3:34PM |
R35.00008: Abstract Withdrawn
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Monday, November 25, 2024 3:34PM - 3:47PM |
R35.00009: The effect of surface roughness induced by mean turbulent water flow on excitation of waves by wind Lev Shemer, Krishanu Kumar Mean turbulent water current has a twofold effect on the excitation and evolution of waves in a laboratory wind-wave facility: it not only modifies the dispersion relation due to current-induced Doppler shift, but also results in surface roughness. The effect of both those phenomena on the variation with fetch of the wave field excited by wind blowing steadily along or against the wind is studied experimentally. Data on diverse wave parameters such as characteristic wave amplitudes, dominant frequencies, wave spectra, etc., are accumulated for a range of well-controlled operational conditions. A more complicated case of evolution in time and in space of waves generated by impulsively applied wind over an initially rough water surface in flowing water is studied as well. Interpretation of the accumulated experimental findings in the framework of Geva and Shemer1 stochastic multiple harmonic approach sheds new light on the long-standing problem of identifying the mechanisms that govern generation of waves by wind. |
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