Effects Of Thermocapillarity Research Articles

The effect of thermocapillarity on the flow of a thin liquid film on a rotating disc

Gradual formation of a thin liquid film on a hot/cold rotating disc under the action of thermocapillary force is studied analytically. It is found that the thermocapillary force acting on the free surface enhances the thinning rate for cooling the disc.

Two- and three-dimensional instabilities and rupture of thin liquid films falling on heated inclined plate

Long-wave instabilities in thin viscous films draining down heated inclined planes are studied. Linear stability analysis and nonlinear computations are performed via a long-wave evolution equation, which describes the effects of mass loss, wave propagation, mean flow, hydrostatic pressure, thermocapillarity, vapor recoil, and mean surface tension. Mean flow, thermocapillarity, and vapor recoil destabilize the flow, and give, respectively, surface-wave, thermocapillary, and evaporative instabilities. Nonlinear flow developments, examined by numerically integrating the evolution equation, show interesting interactions of the instabilities, including generation of longitudinal patterns.

Steady thermocapillary flows of thin liquid layers. II. Experiment

The steady thermocapillary flow of nonvolatile layers, nonuniformly heated from below, is examined. The interactions among viscous forces, thermocapillarity, and hydrostatic effects give rise to the steady-state dimpling of the interface. The steady dimpling of nonuniformly heated silicone–oil layers with mean thicknesses ranging from 0.125 to 1.684 mm is studied experimentally. The temperature distribution in the substrate is monitored by thermocouples and the interface shapes by a mechanical impedance probe. Measured steady shapes and theoretical predictions agree within 20% for moderate heating when the film is not close to rupture. When the heating rate causes the film to ‘‘dry out’’ above the hottest point on the substrate, the long-wave theory delivers a parametric index, involving thermocapillary and hydrostatic effects, which is an excellent predictor of rupture. Nonlinear long-wave theories of the type discussed here have never been tested experimentally, until now. The confirmation of this thermocapillary theory is suggestive of the validity of the previous long-wave analysis [Phys. Fluids A 2, 313 (1990)] of unsteady, evaporating/condensing liquid layers.

Buoyancy- and thermocapillary-driven flows in a shallow open cavity: Unsteady flow regimes

We consider the thermocapillarity effect on the transition from steady to unsteady buoyancy-driven flows in a shallow open cavity. Numerical simulations are done in rectangular horizontal cavity filled with low-Prandtl-number fluids. In the case of buoyancy-driven flow alone, some characteristics of the unsteady flow are given at Grashof number close to the critical value at which the unsteady flow sets up. The ability of thermocapillary forces to change the nature and the characteristics of establishing buoyancy-driven flow is shown in two cases, when thermocapillary forces act in the same sense and against the buoyancy forces. The main feature is that in each case the nature of the flow and, subsequently, the flow structure are strongly modified.

Effect of thermocapillarity on parametric excitation of surface waves

It is demonstrated that the thermocapillarity effect can either raise or lower the threshold of surface wave excitation, depending on the conditions of heating.

Combined thermocapillary and buoyant flow in a drop in a space laboratory

The problem of axially symmetric motion in a levitated drop due to a prescribed surface temperature distribution is treated. The effects of thermocapillarity as well as buoyancy due to a residual steady gravity vector aligned parallel to the axis of symmetry are included. The relevant equations are solved in the creeping flow limit wherein the convective transport of momentum as well as that of energy is neglected. Also, the solution for axially symmetric buoyant flow in a spherical container is reported in the creeping flow limit.

The effects of liquid motion induced by phase change and thermocapillarity on the thermal equilibrium of a vapour bubble

A theoretical estimate is made of the liquid motion induced in the vicinity of a vapour bubble on a heated solid surface by evaporation and condensation at the bubble surface and by thermocapillarity effects. These results are used to examine the thermal equilibrium of the vapour bubble. It is found that whilst the effects of convection induced by evaporation and condensation are small, the effects of thermocapillarity may be important in determining the temperature of the equilibrium bubble.