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.

Marangoni convection. Part 1. A cavity with differentially heated sidewalls

Abstract: Marangoni convection in a cavity with differentially heated sidewalls has been investigated. The analysis includes the complete effects of interface deformation. The results determined for large Biot and zero Marangoni (zero Prandtl) numbers show that steady convection may exist for Reynolds numbers Re larger than, and for capillary numbers Ca and cavity lengths L smaller than, certain critical values. The main factor limiting the existence of steady convection involves the interface becoming tangential to the hot wall at the contact point (tangency condition). Unsteady analysis shows that the tangency condition defines the limit point for the system; its violation is most likely to lead to the formation of a dry spot at the hot wall. The critical values of Re, Ca, and L are mutually dependent and change with the heating rate (they reach a minimum for instantaneous heating). For a certain range of parameters, multiple (i.e. steady and oscillatory) states are possible. The oscillatory state has a form consisting of the steady mode with a simple harmonic sloshing motion superposed on it. A reduction in the heating rate permits heating of the liquid without triggering the oscillatory state. Transition between the steady and the oscillatory states involves a nonlinear instability process.

Bursting of Dilute Emulsion-Based Liquid Sheets Driven by a Marangoni Effect.

Abstract: We study the destabilization mechanism of thin liquid sheets expanding in air and show that dilute oil-in-water emulsion-based sheets disintegrate through the nucleation and growth of holes that perforate the sheet. The velocity and thickness fields of the sheet outside the holes are not perturbed by holes, and hole opening follows the Taylor-Culick law. We find that a prehole, which widens and thins out the sheet with time, systematically precedes the hole nucleation. The growth dynamics of the prehole follows the law theoretically predicted for a liquid spreading on another liquid of higher surface tension due to Marangoni stresses. Classical Marangoni spreading experiments quantitatively corroborate our findings.

Drops, liquid layers and the marangoni effect

Abstract: An overview is given of recent results about the onset and development of steady and timedependent flow motions past an instability threshold induced by the Marangoni effect. First, I consider the ...

Bénard-Marangoni convection in a differentially heated cylindrical cavity

Abstract: The work described in this paper concerns the study of a Benard–Marangoni convection problem in a differentially heated cylindrical cavity. The study had two main aims; first to justify from a numerical point of view the transitions that have been reported in several experiments as the aspect ratio is varied and, second, to study both theoretically and experimentally the role of vertical and horizontal temperature differences in lateral heating convection. Initially, we analyzed the role of the aspect ratio in layers where a dynamic flow is imposed through a nonzero temperature gradient at the bottom. The basic solutions are linear or return flows depending on different parameters. Depending on the vertical temperature difference and other heat-related parameters, the problem bifurcates either to stationary or oscillatory structures. Competing solutions at codimension two bifurcation points were found: stationary radial rolls with different wavenumbers and radial rolls together with hydrothermal waves. For small aspect ratios it was found that the Biot number does not influence the bifurcations, whereas for large aspect ratios it does. In the second part we present experimental results obtained at larger aspect ratios and for stronger surface tension effects. The role of horizontal gradients to determine the type of bifurcation both in experiments and in numerics approaching experimental conditions are discussed along with the role of vertical temperature gradients in comparison with previous theoretical works. Good agreement was obtained in terms of patterns, bifurcation sequences, and thresholds between theory, where eigenfunctions are obtained by tuning two parameters in a linear stability analysis, and experiments, where patterns are due to a nonlinear secondary bifurcation sequence caused by increasing one of the parameters.

The effect of support fibers on micro-convection in droplet combustion experiments

Abstract: This study reports experimental evidence of gas phase micro-convection induced by support fibers used in droplet combustion experimentation. Soot aggregates formed during combustion of n-octane and n-decane droplets (initial diameters ranging from 0.5 mm to 5 mm) provide natural seeds to reveal the thermal and flow asymmetries involved. The experiments are carried out in an environment that reduces the influence of forced and buoyant convection for both free-floating (unsupported) and fiber-supported droplets. Under these conditions, the soot trapping patterns (due to a balance of thermophoretic and flow-induced drag) would be spherical. However, this situation is only observed for unsupported droplets, or for fiber-supported droplets when the fiber is small relative to the droplet diameter. For Do 1 mm the International Space Station provided capabilities for anchoring test droplets onto a single 80 μm SiC fiber, and for deploying unsupported droplets. Results clearly indicate that a non-symmetric gas flow field exists in some cases (i.e., for 1 mm < Do < 3 mm, with an 80 μm fiber) near to where the fiber enters the droplet. This gas motion originates from the presence of the fiber that introduces asymmetries in the temperature and flow fields resulting in localized force imbalances on the soot particles, which cause vortical flow patterns near the fiber. This may in part be explained by flow asymmetries induced by droplet shape distortions coupled with heat exchanges between the fiber and surrounding gas and conduction into the droplet, resulting in a Marangoni flow near the droplet surface. For very small fibers (or for unsupported droplets) spherical soot shells are found suggesting that no thermal and flow asymmetries exist.