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.

Evaporation and Marangoni driven convection in small heated water droplets.

Abstract: Evaporation dynamics of small sessile water droplets under microgravity conditions is investigated numerically. The water-air interface is free, and the surrounding air is assumed to be quasisteady. The droplet is described by Navier-Stokes and heat equations and its surrounding water/air gaseous phase with Laplace equation. In the thermodynamic conditions of the simulations presented herein, the evaporative mass flow is nonlinear. It shows a minimum that indicates the existence of qualitative changes in the evaporative regimes although the droplet is sessile. Due to temperature gradients on the free interface, Marangoni motion occurs and generates inside the droplet convection cells that furthermore exhibit small fluctuating motion as evaporation goes on.

Suppression of the coffee ring effect by hydrosoluble polymer additives.

Abstract: A simple and novel method has been demonstrated for avoiding coffee ring structure based on hydrosoluble polymer additives during droplet evaporation. The polymer additives lead to the motion of the contact line (CL) resulted from the viscosity and Marangoni effect. The viscosity provides a large resistance to the radially outward flow. It results in a small amount of spheres deposited at droplet edge, which do not facilitate the pinning of the CL. The Marangoni effect resulted from the variation of polymer concentration at droplet edge during droplet evaporation contributes to the motion of the CL. Thus, uniform and ordered macroscale SiO2 microspheres deposition is achieved. What’s more, the coffee ring effect can be eliminated by different hydrosoluble polymer. This method will be applicable to a wide of aqueous system and will be of great significance for extensive applications of droplet deposition in biochemical assays and material deposition.

Impact of Binary Chemical Reaction and Activation Energy on Heat and Mass Transfer of Marangoni Driven Boundary Layer Flow of a Non-Newtonian Nanofluid

Abstract: The flow and heat transfer of non-Newtonian nanofluids has an extensive range of applications in oceanography, the cooling of metallic plates, melt-spinning, the movement of biological fluids, heat exchangers technology, coating and suspensions. In view of these applications, we studied the steady Marangoni driven boundary layer flow, heat and mass transfer characteristics of a nanofluid. A non-Newtonian second-grade liquid model is used to deliberate the effect of activation energy on the chemically reactive non-Newtonian nanofluid. By applying suitable similarity transformations, the system of governing equations is transformed into a set of ordinary differential equations. These reduced equations are tackled numerically using the Runge–Kutta–Fehlberg fourth-fifth order (RKF-45) method. The velocity, concentration, thermal fields and rate of heat transfer are explored for the embedded non-dimensional parameters graphically. Our results revealed that the escalating values of the Marangoni number improve the velocity gradient and reduce the heat transfer. As the values of the porosity parameter increase, the velocity gradient is reduced and the heat transfer is improved. Finally, the Nusselt number is found to decline as the porosity parameter increases.

Dynamic Surface Tension Effects in Impact of a Drop with a Solid Surface

Abstract: Recent research on free surface flows in the presence of surface-active species in which a fluid interface undergoes very large deformations, e.g., as in the deformation and breakup of drops in extensional flows under conditions of Stokes flow (Stone, H. A., and Leal, L. G., J. Fluid Mech. 220, 161 (1990)) (19) and the formation of drops from capillaries (Zhang, X., and Basaran, O. A., Phys. Fluids 7, 1184 (1995)) (20) has shown that dynamic surface tension (DST) effects can radically alter the dynamics compared to situations in which the fluid interface is clean. In this paper, we present results of an experimental study that examines the impact with a solid substrate of drops of Newtonian liquids containing two commonly used surfactants. In the experiments, an ultra high-speed video and associated image analysis system is used to monitor the dynamics of the impact process. On account of the extremely large deformations that a drop exhibits and the large-amplitude oscillations that it undergoes upon impacting and spreading on the substrate, DST plays a complex and dominant role in determining the dynamics and the asymptotic state that is approached at large times. A major consequence of the presence of surfactant is that on the one hand its accumulation on the fluid interface reduces the surface tension and thereby enhances the spreading of the drop across the substrate. On the other hand, the non-uniform distribution of surfactant along the fluid interface gives rise to Marangoni stresses that inhibit drop spreading. Given the fact that many liquids used in atomization coating applications ranging from the spraying of agricultural chemicals to painting of substrates contain surfactants and/or other surface-active species, the fundamental results to be reported in this paper have important practical ramifications.

Radar signatures of oil films floating on the sea surface and the Marangoni effect

Abstract: Airborne radar backscattering experiments carried out recently by Singh et al. (1986) over sea surfaces covered with mineral oil films show that the radar cross section depression has a maximum as a function of incidence angle. In this paper we show that Singh et al.'s measurements can be explained by the Marangoni effect if the assumption is made that the mineral oil spill contained surface active material as “impurities.” The Marangoni effect causes a resonance-type wave damping in the short gravity wave region when the sea surface is covered with a viscoelastic film. Maximum wave damping was observed by Singh et al. (1986) at frequencies around 8 Hz. Marangoni theory predicts such a maximum for surface active compounds of medium to low wave damping ability with a dilational modulus of the order of 0.01 Nm−1 Furthermore, it is demonstrated that the Ku band and C band radar backscattering depression curves do not contradict each other. It is pointed out that when converting the radar data into information on depression of spectral energy density of short surface waves, one has to take into account that the radar backscattering at low incidence angles is dominated by specular reflection, while at intermediate incidence angles it is dominated by Bragg scattering.