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  • 1
    Electronic Resource
    Electronic Resource
    Laboratory generation and propagation of ripples (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 619-624 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The generation of gravity-capillary waves (ripples) by a flap-type wavemaker is examined theoretically and experimentally. Qualitative agreement is found in the trapped wave region; measured amplitudes exceed those predicted by the linear theory and the data extend further from the wavemaker. The air–water–aluminum contact line on the paddle face appears to cause a phase shift away from the paddle in the measured results. Excellent agreement is found with the linear dispersion relation for the progressive waves when the water is scrupulously cleaned of ions and organics, and filtered of minute particles. The presence of minute particles (only) necessitates introduction of the notion of "dynamic'' surface tension which is about 30% lower than the measured static value. When particles are removed the dynamic and static values of surface tension are equivalent. The amplitudes of the progressive waves agree well with theory when the product of the wavenumber and water depth does not exceed seven, and the inviscid theory is modified to account for decay by viscosity. Agreement requires the assumption of a "fully contaminated'' surface even when the water is particle filtered. Otherwise, the viscous decay is about twice that predicted by the fully contaminated surface model. Longitudinal instabilities of the progessive waves are observed when the product of wavenumber and water depth exceeds about seven. These instabilities appear to be modeled well by the nonlinear Schrödinger equation. Transverse instabilities are also observed in the data over the full range of wave frequencies investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865453
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On the pinch-off of a pendant drop of viscous fluid (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 3188-3200 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pinch-off of a drop of viscous fluid is observed using high-speed digital imaging. The behavior seen by previous authors is observed here; namely, the filament that attaches the drop to the orifice evolves into a primary thread attached to a much thinner, secondary thread by a slight bulge. Here, we observe that the lengths of the primary and secondary threads are reproducible among experiments to within 3% and 10%. The secondary thread becomes unstable as evidenced by wave-like disturbances. The actual pinch-off does not occur at the point of attachment between the secondary thread and the drop. Instead, it occurs between the disturbances on the secondary thread. After the initial pinch-off, additional breaks occur between the disturbances, resulting in several secondary satellite drops with a broad distribution of sizes. The pinch-off of the thread at the orifice is similar to that at the drop with one main difference: there is no distinct secondary thread. Instead, the primary thread necks down monotonically until wave-like disturbances form, resulting in pinch-off at multiple sites in between. The speed of the tips of the retreating, secondary threads after pinch-off are reported and discussed in the context of various scaling laws. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869435
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  • 3
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    On the pinch-off of a pendant drop of viscous fluid (1997)
    American Institute of Physics
    Details
    Publication Date: 1997-11-01
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
    Published by American Institute of Physics
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  • 4
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    Laboratory generation and propagation of ripples (1986)
    American Institute of Physics
    Details
    Publication Date: 1986-01-01
    Print ISSN: 0031-9171
    Topics: Physics
    Published by American Institute of Physics
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  • 5
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    Linear waves at a surfactant-contaminated interface separating two fluids: Dispersion and dissipation of capillary-gravity waves (2018)
    American Institute of Physics
    Details
    Publication Date: 2018-07-01
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
    Published by American Institute of Physics
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  • 6
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    Periodic envelopes of waves over non-uniform depth (2016)
    American Institute of Physics
    Details
    Publication Date: 2016-04-01
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
    Published by American Institute of Physics
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  • 7
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    Effects of surfactants on Faraday-wave dynamics (1998)
    Cambridge University Press
    Details
    Publication Date: 1998-06-25
    Description: The damping rates, natural frequencies and amplitudes of parametrically excited, standing, water waves in a partially filled, right circular cylinder are measured and compared to existing theoretical models that assume wave slopes are small. The water surfaces were covered by insoluble monomolecular (surfactant) films of oleyl alcohol, lecithin, diolein, cholesterol, and arachidyl alcohol whose concentrations were varied from zero (clean) to saturation; wave slopes were varied from about 0.1 to 1.2. Measured damping rates increased with increasing film concentration as predicted using films of oleyl alcohol, lecithin, and diolein, even when wave slopes were about one. Measured damping rates increased with increasing film concentration as predicted, using films of cholesterol and arachidyl alcohol when wave slopes were small, but not when wave slopes were large. In fact, the measured damping rates for large-slope waves on these films were equivalent to those of waves on a clean surface. Measured natural frequencies varied as predicted for all films, but were about 5% larger. Contact-line effects are incorporated, using an empirical value for contact-line speed, to account for discrepancies between measurements and predictions of damping rates and natural frequencies. Measured steady-state amplitudes agreed well with predictions that used measured damping rates and natural frequencies in the calculations for all films except lecithin and arachidyl alcohol for which there was significant disagreement.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 8
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    Progressive waves with persistent two-dimensional surface patterns in deep water (2005)
    Cambridge University Press
    Details
    Publication Date: 2005-06-10
    Description: Experiments are conducted to generate progressive wave fields in deep water with two-dimensional surface patterns for which two parameters are systematically varied: (i) the aspect ratio of the cells comprising the surface patterns and (ii) a measure of nonlinearity of the input wave field. The goal of these experiments is to determine whether these patterns persist, what their main features are, whether standard models of waves describe these features, and whether there are parameter regimes in which the patterns are stable. We find that in some parameter regimes, surface patterns in deep water do persist with little change of form during the time of the experiment. In other parameter regimes, particularly for large-amplitude experiments, the patterns evolve more significantly. We characterize the patterns and their evolutions with a list of observed features. To describe the patterns and features, we consider two models: (a) the standard (2 + 1) nonlinear Schrödinger equation and (b) coupled nonlinear Schrödinger equations for two interacting wavetrains. Exact solutions of these models provide qualitative explanations for many of the observed features. © 2005 Cambridge University Press.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 9
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    On the laboratory generation of two-dimensional, progressive, surface waves of nearly permanent form on deep water (2006)
    Cambridge University Press
    Details
    Publication Date: 2006-07-01
    Description: Recent experiments by Hammack et al. (J. Fluid Mech., vol. 532, 2005, p. 1) on deep-water waves with two-dimensional, periodic surface patterns showed several features, some of which were unsteady. Fuhrman & Madsen (J. Fluid Mech., vol. 559, 2006, p. 391) explained three of these as being the consequence of sinusoidal forcing by the wavemaker array that did not include forced harmonics, either in time or in the direction parallel to the wavemaker. They predicted that neglected third-harmonic terms cause more serious consequences than neglected second-harmonic terms when the generated wavefields have two-dimensional surface patterns. This paper presents experiments that provide strong evidence that their explanation is correct: including the third-harmonic terms in the wavemaker forcing results in wave patterns that propagate with nearly permanent form. © 2006 Cambridge University Press.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 10
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    Experiments on ripple instabilities. Part 1. Resonant triads (1987)
    Cambridge University Press
    Details
    Publication Date: 1987-11-01
    Description: Water waves for which both gravitation and surface tension are important (ripples) exhibit a variety of instabilities. Here, experimental results are presented for ripple wavetrains on deep water with frequencies greater than 19.6 Hz where a continuum of resonant triad interactions are dynamically admissible. The experimental wave-trains are indeed unstable, and the instability becomes more pronounced as non-linearity is increased. The unstable wavefield is characterized by significant spatial disorder while temporal measurements at fixed spatial locations remain quite ordered. In fact, for most experiments temporal measurements suggest that a selection process exists in which a single triad dominates evolution. The dominant triad typically does not involve a subharmonic frequency of the generated wave and persists over a wide range of amplitudes for the initial wave. Viscosity does not appear to be important in the selection process; however, it may be responsible for the lack of subsequent triad production by the excited waves of the initial triad. The presence of a selection process contradicts previous conjecture, based on the form of the interaction coefficients, that a broad-banded spectrum of waves should occur. The general absence of subharmonic growth also contradicts previously reported experiments. Results are also presented for wavetrains at the parametric boundary of 19.6 Hz and a degenerate case of resonant triads at 9.8 Hz (Wilton's ripples). In addition to resonant triads, the experiments show evidence of (generally) weaker narrow-band interactions. © 1987, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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