A new method of measuring dynamic surface tension

Antoniades, Michael G.; Godwin, R. P.; Lin, S. P.

doi:10.1016/0021-9797(80)90336-7

Cited by 13 publications

(4 citation statements)

References 1 publication

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“…In the curtain, the liquid is in free fall. Dynamic surface tension can be measured by creating and measuring standing waves (Antoniades et al, 1980). The width of the curtain is maintained by two vertical metal rods approximately 1.5 millimeters in diameter; in the absence of these, surface tension causes the curtain to contract as it falls.…”

Section: Experimental Methods Observation Of Air Entrainmentmentioning

confidence: 99%

Hydrodynamic assist of dynamic wetting

1994

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IntroductionDynamic wetting is central to many physical processes. An ambient fluid, often air, in contact with a solid is displaced by a liquid. At sufficiently high displacement speeds, wetting failure occurs, and the ambient fluid is entrained between the liquid and the solid. Usually dynamic wetting failure has undesirable consequences, and in the case of coating operations, for example, air entrainment limits processing speed.Dynamic wetting has been most frequently studied by plunging a solid into a relatively large, stagnant pool of liquid (for example, Perry, 1967;Inverarity, 1969;Burley and Kennedy, 1976; Gutot'f and Kendrick, 1982;Burley and Jolly, 1984;Blake, 1988; Brache et al., 1989;Seebergh and Berg, 1992). The angle at which the interface intersects the solid, as viewed through a low-power microscope or inferred from measurement of meniscus shape or force exerted on the solid, is determined as a function of speed. At low magnification, the interface appears to intersect the solid as a line, and the angle measured through the liquid is termed the apparent or macroscopic dynamic contact angle.At the Ion est speeds, the contact angle approaches the static advancing contact angle. The contact angle increases as speed Correspondma corlcerning this article should be addressed to K. J. Ruschak.is increased, with the wetting line remaining straight and horizontal (that is, normal to the velocity of the solid). However, when the angle reaches a nominal value of 180", wetting failure occurs, and a thin film of air, on the order of a micron in thickness (Perry, 1967), forms between the liquid and solid. The wetting line moves downward, becomes unsteady, and breaks up into straight-line segments that are inclined from the horizontal. The angle of inclination increases steadily with speed. At any instant, the wetting line has the appearance of sawteeth (Burley and Kennedy, 1976;Blake and Ruschak, 1979;Burley, 1992), and air bubbles may be formed at the downstream vertices of the sawteeth and carried into the liquid. The speed at which wetting failure begins varies inversely with viscosity raised to a power of about 0.7. Speed can also vary about a factor of 5 due to the chemical and physical properties of thesolid (Buonopaneet al., 1984;Blake and Ruschak, 1994).The case where only one sawtooth, having one vertex, forms is rare but particularly instructive. The wetting line then consists of two slanted and steady straight-line segments in the shape of a "V." Blake and Ruschak (1979) showed that the component of the speed of the solid normal to the segments is a constant that they termed the maximum speed of wetting. Initially, no air bubbles are produced, but as speed and the AIChE JournalFebruary 1994 Vol. 40, No. 2 229 inclination angle increase, air bubbles begin to form at the vertex. At still higher speed, an air tube may form and persist for a significant distance before breaking up. The vertex may be several centimeters downstream of the level of the pool, and over this distance the liquid is separated fr...

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Section: Experimental Methods Observation Of Air Entrainmentmentioning

confidence: 99%

Hydrodynamic assist of dynamic wetting

1994

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“…Lin & Roberts (1981), Lin (1981) and Lin et al (1990), who analysed the growth of both temporally and spatially varying disturbances to a viscous liquid curtain, but ultimately finding excellent agreement with Brown's prediction. Motivated, in part, by Brown's criterion and observations of Taylor (1957), Antoniades et al (1980) proposed that the balance between inertia and surface tension could be exploited to determine the dynamic surface tension, σ dyn , by placing an obstacle in the curtain such that a free edge forms at an angle, θ, from vertical, emanating from the obstacle, whereby 2σ dyn = ρQv c sin 2 θ.…”

Section: Curtain Stabilitymentioning

confidence: 99%

Experimental investigation of hysteresis in the break-up of liquid curtains

Marston

Thoroddsen

Thompson

et al. 2014

Chemical Engineering Science

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Findings from an experimental investigation of the break-up of liquid curtains are reported, with the overall aim of examining stability windows for multi-layer liquid curtains comprised of Newtonian fluids, where the properties of each layer can be kept constant or varied. For a single-layer curtain it is known that the minimum flow rate required for initial stability can be violated by carefully reducing the flow rate below this point, which defines a hysteresis region. However, when two or three layers are used to form a composite curtain, the hysteresis window can be considerably reduced depending on the experimental procedure used. Extensive quantitative measurements of this hysteresis region are provided alongside an examination of the influence of physical properties such as viscosity and surface tension. The origins of curtain break-up for two different geometries are analysed; First where the curtain width remains constant, pinned by straight edge guides; Second where the curtain is tapered by angled edge guides. For both cases, the rupture speed is measured,

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“…This ribbon forms a ligament which subsequently disintegrates according to Rayleigh's capillary instability analysis. Taylor's 'edgedynamics' theory has also been employed by other authors (Brown 1961;Antoniades, Godwin & Lin 1980) to predict the breakup length of liquid curtains.…”

Section: Linear Two-dimensional Planar Sheetsmentioning

confidence: 99%

Nonlinear capillary wave distortion and disintegration of thin planar liquid sheets

Mehring

Sirignano

1999

J. Fluid Mech.

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Linear and nonlinear dilational and sinuous capillary waves on thin inviscid infinite and semi-infinite planar liquid sheets in a void are analysed in a unified manner by means of a method that reduces the two-dimensional unsteady problem to a one-dimensional unsteady problem. For nonlinear dilational waves on infinite sheets, the accuracy of the numerical solutions is verified by comparing with an analytical solution. The nonlinear dilational wave maintains a reciprocal relationship between wavelength and wave speed modified from the linear theory prediction by a dependence of the product of wavelength and wave speed on the wave amplitude. For the general dilational case, nonlinear numerical simulations show that the sheet is unstable to superimposed subharmonic disturbances on the infinite sheet. Agreement for both sinuous and dilational waves is demonstrated for the infinite case between nonlinear simulations using the reduced one-dimensional approach, and nonlinear two-dimensional simulations using a discrete-vortex method. For semi-infinite dilational and sinuous distorting sheets that are periodically forced at the nozzle exit, linear and nonlinear analyses predict the appearance of two constant-amplitude waves of nearly equal wavelengths, resulting in a sheet disturbance characterized by a long-wavelength envelope of a short-wavelength oscillation. For semi-infinite sheets with sinuous waves, qualitative agreement between the dimensionally reduced analysis and experimental results is found. For example, a half-wave thinning and a sawtooth wave shape is found for the nonlinear sinuous mode. For the semi-infinite dilational case, a critical frequency-dependent Weber number is found below which one component of the disturbances decays with downstream distance. For the semi-infinite sinuous case, a critical Weber number equal to 2 is found; below this value, only one characteristic is emitted in the positive time direction from the nozzle exit.

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A new method of measuring dynamic surface tension

Cited by 13 publications

References 1 publication

Hydrodynamic assist of dynamic wetting

Hydrodynamic assist of dynamic wetting

Experimental investigation of hysteresis in the break-up of liquid curtains

Nonlinear capillary wave distortion and disintegration of thin planar liquid sheets

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