Showing papers on "Marangoni effect published in 1983"
TL;DR: In this paper, a discussion is presented concerning the motion of droplets in a surrounding fluid induced by a temperature gradient, which is characterized as the tangential stress at the interface that is induced by the temperature gradient's variation of interfacial tension, causing motion in neighboring fluid both inside and outside the droplet.
73 citations
TL;DR: In this article, a boudnary-layer analysis is performed that is valid for large Marangoni numbers M and Prandtl numbers P for the horizontal heat transport.
Abstract: A liquid, contained in a quarter plane, undergoes steady motion due to thermocapillary forcing on its upper boundary, a free surface separating the liquid from a passive gas. The rigid vertical sidewall has a strip whose temperature is elevated compared with the liquid at infinity. A boudnary-layer analysis is performed that is valid for large Marangoni numbers M and Prandtl numbers P. It is found that the Nusselt number N for the horizontal heat transport satisfies N proportional to min (M to the 1 2/7/power, M to the 1 1/5/power, M to the 1 1/10/power) Generalizations are discussed.
29 citations
TL;DR: In this paper, a microvisual study of residual oil mobilization using a relatively simple chemical system consisting of water, n-propanol, and cyclohexane is presented, and two different classes of experiments are performed to determine the sensitivity of the capillary number required to displace a particular residual oil globule from chemical equilibrium.
Abstract: A microvisual study of residual oil mobilization that uses a relatively simple chemical system consisting of water, n-propanol, and cyclohexane is presented. Two different classes of experiments were performed to determine the sensitivity of the capillary number required to displace a particular residual oil globule from chemical equilibrium. It was found that under certain circumstances the capillary number required to mobilize the oil drop could be reduced greatly if the displacing phase contained more alcohol than it would in equilibrium with the trapped phase. Experiments clearly demonstrated that spontaneous emulsification by a diffusion and stranding mechanism could not account for the differences between equilibrium and nonequilibrium capillary numbers. Experimental observations did correlate well with the development of interfacial turbulence (Marangoni effect). Variations that, according to theory, tended to enhance the level of interfacial turbulence between the equilibrium and nonequilibrium capillary numbers were observed. The importance of the Marangoni effect relative to laboratory oil recovery experiments is discussed. A second class of experiments consisted of observing the displacement of residual oil globules that had been increased in volume (swollen) by mass transfer from a continuous phase flowing too slowly to displace the drop. Once the residual oil globule attained equilibrium withmore » the continuous phase, the flooding velocity was increased until the swollen globule was displaced.« less
27 citations
TL;DR: An infinite at both ends closed cylindrical free surface liquid column is subjected to various instationary axial temperature timewise periodic fields, such as linear, parabolic, sinusoidal and exponential temperature changes, which are imposed at the free liquid surface as mentioned in this paper.
Abstract: An infinite at both ends closed cylindrical free surface liquid column is subjected to various instationary axial temperature timewise periodic fields, such as linear, parabolic, sinusoidal and exponential temperature changes, which are imposed at the free liquid surface.
25 citations
Journal Article•
24 citations
01 Jul 1983
TL;DR: In this article, an analytical solution leading to the magnification functions and their phases is presented for an arbitrary axial temperature field for a linear and a quadratic temperature field numerical results are presented.
Abstract: Time-wise fluctuating temperature gradients induce, due to the variation of surface tension, oscillation of the free surface of the liquid sphere, which may in or close to resonance with the surface waves lead to large amplitudes, capable to disintegrate the liquid system. An analytical solution leading to the magnification functions and their phases is presented for an arbitrary axial temperature field. For a linear and a quadratic temperature field numerical results are presented.
19 citations
TL;DR: In this article, a minute drop evaporating on a plate surface is visualized through two methods: solid suspension and laser shadowgraphy, and the effects of drop motion, liquid properties and air-liquid interfacial geometry on both the interfacial and internal flow structures are determined and the consequences of the evaporation rate are discussed.
19 citations
TL;DR: The authors found that bubble surface life increases in magnitude with decreasing humidity and increasing speed of the air over the surface of the water, which appears to be caused by a salinity gradient along the bubble cap.
Abstract: The time an air bubble persists at a seawater surface is a function of many factors, including the relative humidity and speed of the air over the surface of the water. We find that bubble surface life increases in magnitude with decreasing humidity and increasing speed of the air. This appears to be caused by a salinity gradient along the bubble cap. This produces a surface tension gradient (Marangoni effect) that increases bubble surface life.
18 citations
TL;DR: In this article, the authors show that changing the imposed angular temperature distribution suddenly into another angular temperature yields a transient convection due to the thermal Marangoni effect inside the liquid column until the final velocity distribution is reached.
Abstract: Changing the imposed angular temperature distribution suddenly into another angular temperature yields a transient convection due to the thermal Marangoni effect inside the liquid column until the final velocity distribution is reached. This transient has been determined analytically for a liquid bridge, for which no axial dependency exists,i.e. for the two-dimensional case. The method may also be applied to time-periodic temperature fields.
16 citations
TL;DR: In this paper, the influence of various factors (dynamic interfacial tension, Marangoni instability, and natural convection) have to produce spontaneous pulsation of liquid drops in binary systems and to influence the kinetics of their dissolution is discussed.
14 citations
TL;DR: In this paper, numerical calculations of the flow caused by thermocapillary forces at the free surface in NaNO3 and Si melts in an open boat geometry have been carried out.
Abstract: Numerical calculations of the flow caused by thermocapillary forces at the free surface in NaNO3 and Si melts in an open boat geometry have been carried out. The results agree well with measured flow velocities in model experiments for crystal growth configurations with NaNO3 melts. For Si melts a transition to a more complicated multiple eddy flow occurs. The projection-iteration method used for the calculations is much more effective than the finite difference methods applied until now and is especially advantageous for more complicated flow patterns.
Numerische Berechnungen der durch thermokapillare Krafte an der freien Oberflache hervorgerufenen Stromung in NaNO3 und Si-Schmelzen in einer open „boat” Geometrie wurden durchgefuhrt. Die Resultate stimmen gut mit gemessenen Stromungsgeschwindigkeiten in Modellexperimenten fur Kristallzuchtanordnungen mit NaNO3-Schmelzen uberein. Fur Si-Schmelzen erscheint ein Ubergang zu einer komplizierten Mehrwirbelstromung. Die fur die Berechnungen benutzte Projektions-Iterations-Methode ist wesentlich effektiver als die bisher verwendeten endlichen Differenzenverfahren und ist vor allem fur kompliziertere Stromungsformen vorteilhaft.
TL;DR: In this paper, the role of film rheology, Marangoni effects, van der Waals forces, electrical interactions, and asymmetry on the stretching and squeezing modes of instability was examined.
Abstract: The linear stability of thin films has many interesting biological and industrial applications. This article has focused only on the biological applications. Considering a membrane to be an isotropic and transversely isotropic film on the order of 10 nm in thickness, we have examined the role of film rheology, Marangoni effects, van der Waals forces, electrical interactions, and asymmetry on the stretching and squeezing modes of instability. The results are in general agreement with the experimental data available. 16 references.
01 May 1983
TL;DR: In this article, the authors investigated the Marangoni flow caused by interfacial tension gradients in the case of an undeformable free drop suspended in an immiscible liquid.
Abstract: The Marangoni flow caused by interfacial tension gradients is experimentally and theoretically investigated in the case of an undeformable free drop suspended in an immiscible liquid. The spreading of the surfactant on the interface—as a result of the Marangoni effect—is approximated to a succession of quasisteady states; integration of the hydrodynamic equations proposed in the authors' theoretical model yields the velocities in the outer liquid, in the inner one, and on the surface of the drop. Experimentally, as much undeformable free drops are obtained if, made of paraffin oil and immersed in an ethanol-water or methanol-water equidense mixture, they also have large viscosities (36–80 cP) as compared with that of the continuous medium (1–3 cP). The interfacial tension differences of only 2.3–6.7 dyn cm −1 have been established by injecting with a surfactant (propanol-water or isopropanol-water mixture dyed with methylene blue). The advance velocities of the surfactant front have been determined by filming (with 500 images/sec) and they satisfactorily agree with the theoretical values, particularly for high grades of covering of the drop surface.
TL;DR: The radial Si distrinution in Fe-3wt%Si crystals grown by floating zone melting with induction heating differes remarkably from that with electron beam heating as mentioned in this paper, and the change of the flow direction is explained by the action of electrodynamic forces driving the melt convection in the opposite direction from that driven by Marangoni forces.
01 Jun 1983
TL;DR: In this article, a two-chamber reaction cell was used to control the strength and duration of interfacial turbulence in a high-temperature liquid tin/indium-fused sodium chloride system.
TL;DR: In this paper, an electric field when applied across liquid-liquid interface was found to cause, due to different susceptibilities of the two phases, what the authors would term as Marangoni "type" of instabilities, that resulted in the generation of bubbles/drops and caused the movement of the interface countering gravity.
TL;DR: The effect of the configuration and the convection in microgravity on crystal growth was discussed in this article, where the fluid flow driven by surface tension and by buoyancy force was visualized and measured.
TL;DR: In this paper, the authors described the bubble motion as a function of thermal variation of surface tension of a bubble, temperature gradient, gravity, bubble diameter, viscosity and density.
TL;DR: In this paper, the inversion of surface movement with increasing T o n the surface of an aqueous fatty alcohol solution was studied. But the authors focused on the case where T o(T) presents a minimum for all studied alcohols a t sufficient concentrations.
Abstract: BCnard cells' and Marangoni convection (important in crystal growth') may be caused by a surface tension gradient (a), which, in turn, is caused by temperature (T) gradient. Such a gradient has an enhanced importance under reduced g r a ~ i t y . ~ For these reasons, it is of interest to investigate systems in which (da/dT) changes sign with increasing T and is thus zero for some temperature. Gannon and Farber observed a maximum in u near 50°C for a ~yanobiphenyl.~ Vochten and Pt t r t measured the equilibrium surface tension a of aqueous solutions of fatty alcohol as a function of T.' They found that o(T) presents a minimum for all studied alcohols a t sufficient concentrations. More recently, Motomura et al. observed the same phenomenon with an ionic surfactant solution (dodecylammonium chloride).6 The purpose of this work is to visualize the inversion of surface movement with increasing T o n the surface of an aqueous fatty alcohol solution.
17 Aug 1983
TL;DR: In this paper, a thermocapillary convection in an air-jet Marangoni flow suppressing technique was numerically simulated for flow under various conditions of fluid properties, gravity, and temperature gradient.
Abstract: Thermocapillary convection in an air-jet Marangoni flow suppressing technique was numerically simulated for flow under various conditions of fluid properties, gravity, and temperature gradient Results presented include computer generated plots of streamlines, velocities, and temperatures throughout the contained fluid flow, and plots of Marangoni flow velocities over the free surface
TL;DR: In this paper, the effects of temperature dependent surface-tensions on the growth rate of fluctuations near Benard-Marangoni's instability are examined by defining a new parameter e measuring the deviation from the marginal state.
Abstract: The effects of temperature dependent surface-tensions on the growth rate of fluctuations near Benard-Marangoni's instability are examined. This is achieved by defining a new parameter e measuring the deviation from the marginal state. The present analysis amplifies recent papers wherein surface effects were not considered. The behaviour of the growth rate in terms of the non-dimensional Rayleigh, Marangoni, Biot, and Prandtl numbers is discussed. Landau's picture is finally used to study the approach of disturbances towards equilibrium.
TL;DR: In this article, temperature gradient driven Marangoni flow has been investigated experimentally in circular disks of molten NaNO3 and the results are compared to an order of magnitude analysis and agreement is reasonably good.
Abstract: Temperature gradient driven Marangoni flow has been investigated experimentally in circular disks of molten NaNO3. 1.5 mm high by 7 mm diameter. Flow velocities were evaluated from motion picture film and temperatures were determined with a miniature thermocouple. The results are compared to an order of magnitude analysis and agreement is reasonably good.
TL;DR: In this paper, the authors measured the horizontal component of velocity on the upper surface and calculated the isotherms on the surface and the variation of temperature in the layer in the neighborhood of the threshold.
Abstract: Beyond a given threshold, a horizontal layer of liquid with a free upper surface heated uniformly from below is in convection (Binard-Marangoni convection). The aim of this work is to study the velocity of the flow, the temperature field, and the upper surface deformation. Observing the length of the trajectories of small aluminium flakes during a fixed time, we measured the horizontal component of velocity on the upper surface. Its amplitude ( A ) as a function of c (deviation from the instability threshold) is shown in FIGURE I . The equation for A is A = a + b (c em)O.Sr where a and bare constant and c, is the lowest value of E for which there is still a convection when the temperature T decreases (c, = -0.16). So, as predicted by the theory,' the bifurcation is of the inverse type, with the exponent 0.5. Using the linear theory and the experimental value of A, the isotherms on the upper surface and the variation of temperature in the layer have been calculated in the neighborhood of the threshold. These results are in good agreement with the experimental results obtained with an infrared camera or a thin thermocouple ( F I G U R E S 2 and 3) . As far as the surface deformation (FIGURE 4) is concerned, many experimental observations have been reported. In some experiments, it has been established that the surface is concave above rising warm currents at the cell centers, while the surface is convex in other experiments2 Two experimental methods were used in this work: ( I ) reflection of a laser beam on the surface, and (2) interferometry (for the magnitude of relief) and Foucault's method (for the sign of curvature). The first results show that, for a given liquid, the surface is depressed over the rising currents when the layer of liquid is thin and that the reverse is true when the layer is thick. The sign and amplitude of the relief surface depends on the relative importance of surface tension and buoyancy forces, which is governed by the depth of the pool.
TL;DR: In this paper, a 6-minutes free flight of a sounding rocket was carried out to verify the thermal Marangoni convection by flow visualisation for the first time at 10−4 g.
TL;DR: In this article, the laplace-marangoni flow in the stationary phase is attributed to the presence of surfactants (solutes or stationary or mobile phase) which causes the differences in film thickness to increase so that droplets are generated that can be washed out of the column by the liquid mobile phase.
TL;DR: In this paper, the Marangoni convection in a layer of a nonthermosensitive cholesteric has been obtained and the results obtained are discussed in terms of thermal stability of the original Cholesteric texture.
Abstract: The Marangoni convection in a layer of a nonthermosensitive cholesteric has been obtained. To induce the first stage of the convection (streaming the substance away from the “hot” area), a local heating of the layer is necessary which is from 3 to 4 times as much as that required for thermosensitive cholesterics. The CLC convection motion structures of “roll” type appeared when the layer was locally heated in a thermostat at temperatures close to the clearing point (T cl) of the cholesteric. The results obtained are discussed in terms of thermal stability of the original cholesteric texture.