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Marangoni effect

About: Marangoni effect is a research topic. Over the lifetime, 5336 publications have been published within this topic receiving 98562 citations. The topic is also known as: Gibbs–Marangoni effect.


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Journal ArticleDOI
TL;DR: In this article, the surface tension of LiBr solution with surfactant decreases with increasing LiBr concentration and the Marangoni convection in this system is not essentially induced by the presence of surfactants islands on the surface of the solution as proposed by the previous workers.
Abstract: The Marangoni convection during steam absorption into aqueous LiBr solution with a small amount of surfactant was observed by Schlieren photography, and the surface tension of the absorbing solution was measured to investigate the mechanism of the convection. Also, a numerical simulation of the Marangoni convection was carried out.It is found experimentally that the surface tension of LiBr solution with surfactant decreases with increasing LiBr concentration and that the Marangoni convection in this system is not essentially induced by the presence of surfactant islands on the surface of the solution as proposed by the previous workers, but is in accordance with the general criterion of Marangoni instability. The calculated results could simulate qualitatively the initiation and growth of convection in this system.

86 citations

Journal ArticleDOI
TL;DR: In this paper, the dynamics of a bridge of a Newtonian liquid containing an insoluble surfactant are analyzed by solving numerically a one-dimensional set of equations that results from a slender-jet approximation of the Navier-Stokes system that governs fluid flow and the convection-diffusion equation that governs surface transport.
Abstract: During the emission of single drops and the atomization of a liquid from a nozzle, threads of liquid are stretched and broken. A convenient setup for studying in a controlled manner the dynamics of liquid threads is the so-called liquid bridge, which is created by holding captive a volume of liquid between two solid disks and pulling apart the two disks at a constant velocity. Although the stability of static bridges and the dynamics of stretching bridges of pure liquids have been extensively studied, even a rudimentary understanding of the dynamics of the stretching and breakup of bridges of surfactant-laden liquids is lacking. In this work, the dynamics of a bridge of a Newtonian liquid containing an insoluble surfactant are analyzed by solving numerically a one-dimensional set of equations that results from a slender-jet approximation of the Navier–Stokes system that governs fluid flow and the convection-diffusion equation that governs surfactant transport. The computational technique is based on the method-of-lines, and uses finite elements for discretization in space and finite differences for discretization in time. The computational results reveal that the presence of an insoluble surfactant can drastically alter the physics of bridge deformation and breakup compared to the situation in which the bridge is surfactant free. They also make clear how the distribution of surfactant along the free surface varies with stretching velocity, bridge geometry, and bulk and surface properties of the liquid bridge. Gradients in surfactant concentration along the interface give rise to Marangoni stresses which can either retard or accelerate the breakup of the liquid bridge. For example, a high-viscosity bridge being stretched at a low velocity is stabilized by the presence of a surfactant of low surface diffusivity (high Peclet number) because of the favorable influence of Marangoni stresses on delaying the rupture of the bridge. This effect, however, can be lessened or even negated by increasing the stretching velocity. Large increases in the stretching velocity result in interesting changes in their own right regardless of whether surfactants are present or not. Namely, it is shown that whereas bridges being stretched at low velocities rupture near the bottom disk, those being stretched at high velocities rupture near the top disk.

85 citations

Journal Article
TL;DR: In this paper, the effect of Marangoni convection on the shape of arc weld pools without a surface-active agent was investigated and it was shown that, in the absence of both a surfaceactive agent and a significant electromagnetic force, the pool bottom convexity increases with increasing Pe.
Abstract: Stationary welds of sodium nitrate (NaNO 3 , a high-Prandtl-number material) and gallium (Ga, a low-melting-point, low-Prandtl-number material) were made with a defocused CO 2 laser beam to simulate the effect of Marangoni convection on the shape of arc weld pools without a surface-active agent. A Peclet number representing the ratio of (heat transport by convection)/(heat transport by conduction) was defined as Pe = LV/a, where L is the pool surface radius, V the maximum outward surface velocity and a the thermal diffusivity. The Ga and NaNO 3 pools represented the low and high extremes of Pe, respectively, with commonly welded metals such as aluminum, steel and stainless steel falling in between. By going to these extremes, the effect of convection on the pool shape could be much more easily understood. For Ga, Pe was low because low V (weak Marangoni convection) and high a promoted conduction down into the pool, and the resultant pool bottom was concave. For NaNO 3 , however, Pe became high easily because high V (strong Marangoni convection) and very low a promoted outward convective heat transport, and the resultant pool bottom was shallow and flat. Reducing the beam diameter further increased V (even stronger Marangoni convection) and Pe. The fast outward surface flow turned and penetrated downward at the pool edge, resulting in a convex pool bottom. Both the flat and convex pool bottoms are a clear indication Marangoni convection dominated over gravity-induced buoyancy convection. It is proposed that, in the absence of both a surface-active agent and a significant electromagnetic force, the pool bottom convexity increases with increasing Pe. It was shown that, for a given material composition and welding process, the weld shape often reveals a good deal about the nature of weld pool convection.

85 citations

Journal ArticleDOI
TL;DR: In this article, a non-normal approach was used to predict the onset of instability, critical wavenumber and time in a plane liquid layer with time-dependent temperature profile by means of a general method suitable for linear stability analysis of an unsteady basic flow.
Abstract: The convective instability in a plane liquid layer with time-dependent temperature profile is investigated by means of a general method suitable for linear stability analysis of an unsteady basic flow. The method is based on a non-normal approach, and predicts the onset of instability, critical wavenumber and time. The method is applied to transient Rayleigh–Benard–Marangoni convection due to cooling by evaporation. Numerical results as well as theoretical scalings for the critical parameters as function of the Biot number are presented for the limiting cases of purely buoyancy-driven and purely surface-tension-driven convection. Critical parameters from calculations are in good agreement with those from experiments on drying polymer solutions, where the surface cooling is induced by solvent evaporation.

85 citations

Journal ArticleDOI
TL;DR: In this paper, simulations of flow fields in the weld pool resulting from different temperature dependencies of the coefficient of surface tension are presented, and the effect of the temperature-dependent coefficient is identified as one of the primary driving forces of the liquid melt.
Abstract: In welding, the resulting weld-seam geometry may vary significantly although using constant process parameters and steels with the same material number. One likely reason for this are small variations in the concentration of sulfur, phosphorus, oxygen, and other chemical elements that are well within the tolerance of the standard of a specific alloy. These substances act as surfactants and even marginal changes strongly effect the temperature-dependent coefficient of surface tension. In simulations of conventional electric arc welding and laser heat conduction welding, the effect of the temperature-dependent coefficient of surface tension (Marangoni effect) has been identified as one of the primary driving forces of the liquid melt. In laser deep penetration welding simulations this effect has been widely neglected, so far. In this contribution, simulations of flow fields in the weld pool resulting from different temperature dependencies of the coefficient of surface tension are presented. The simulations...

85 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023212
2022421
2021289
2020283
2019217
2018247