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.

Stability analysis of Benard-Marangoni convection in fluids with internal heat generation

Abstract: The effect of uniform distribution of internal heat generation on the stability of the Benard-Marangoni convection in a horizontal fluid layer with a deformable upper free surface is investigated. The stability analysis in this study is based on the linear stability theory. The eigenvalue equations obtained from the analysis are solved by using the fourth-order Runge-Kutta-Gill method with the shooting technique. The results indicate that the stability of Benard-Marangoni convection is significantly affected by internal heat generation in the fluid layer and by surface tension at the upper free surface. There are two different kinds of instability mode: the thermal mode and the surface tensile mode. At lower values of the Crispation number C, the instability is dominated by the thermal mode. At higher values of C, the system becomes more unstable and creates the surface tensile mode, which is induced by the surface tensile effect. The Crispation number C at the transition between the thermal and the surface tensile modes decreases as the value of internal heat generation increases and that of thermal buoyance decreases. The bond number Bo at the mode transition increases due to the existence of the internal heat generation. In addition, the system becomes more stable when the Biot number Bi of the upper free surface increases.

Dewetting of ultrathin surfactant-covered films

Abstract: Many industrially and technologically important situations involve thin films covered with either pre-existing or introduced surfactant, which can potentially affect dewetting and spreading processes. The two-dimensional dewetting dynamics of ultrathin liquid films are studied here in the presence of insoluble surfactant; surfactants can drive a flow due to surface tension gradients and additionally the coefficients of the intermolecular potential, which are usually assumed to be constant, can depend on the surfactant concentration. Coupled evolution equations for the film height and surfactant concentration are derived using lubrication theory. These equations are parameterized by a Marangoni parameter, M, and the equilibrium film thickness, lc, obtained by setting the intermolecular potential to zero. A linear stability analysis of these equations shows that the presence of surfactant can widen the band of unstable wave numbers and that, for relatively large lc, the selected wave number is minimized for...

Marangoni convection in binary mixtures with Soret eect

Abstract: Marangoni convection in a dierentially heated binary mixture is studied numerically by continuation. The fluid is subject to the Soret eect and is contained in a twodimensional small-aspect-ratio rectangular cavity with one undeformable free surface. Either or both of the temperature and concentration gradients may be destabilizing; all three possibilities are considered. A spectral-element time-stepping code is adapted to calculate bifurcation points and solution branches via Newton’s method. Linear thresholds are compared to those obtained for a pure fluid. It is found that for large enough Soret coecient, convection is initiated predominantly by solutal eects and leads to a single large roll. Computed bifurcation diagrams show a marked transition from a weakly convective Soret regime to a strongly convective Marangoni regime when the threshold for pure fluid thermal convection is passed. The presence of many secondary bifurcations means that the mode of convection at the onset of instability is often observed only over a small range of Marangoni number. In particular, two-roll states with up-flow at the centre succeed one-roll states via a well-dened sequence of bifurcations. When convection is oscillatory at onset, the limit cycle is quickly destroyed by a global (innite-period) bifurcation leading to subcritical steady convection.

Auto-oscillation of surface tension.

Abstract: Long-time auto-oscillation of the surface tension can evolve when in an aqueous system a diethyl phthalate droplet is placed under the free water surface. The experimental conditions for development of surface tension auto-oscillations are described. Based on a theoretical analysis the mechanism of these auto-oscillations is proposed. The mechanism of the auto-oscillations results from a switching between diffusion and convection transfer of diethyl phthalate in the solution. A periodic Marangoni flow on the water surface resulting from a surface layer instability is discussed. The solubility of the amphiphile in the water and its surface activity are the main characteristics that determine the system behavior.