Showing papers on "Marangoni effect published in 1985"

Interfacial Phenomena: Equilibrium and Dynamic Effects

Abstract: FUNDAMENTALS OF INTERFACIAL TENSION Introduction to Interfacial Phenomena Interfacial Tension: Qualitative Considerations Interfacial Tension: Thermodynamic Approach Interfacial Tension: Mechanical Approach Density and Concentration Profiles Equilibrium Shapes of Fluid Interfaces Methods of Measuring Interfacial Tension Surface Tension of Binary Mixtures Surfactants Solid-Fluid Interfaces FUNDAMENTALS OF WETTING, CONTACT ANGLE, AND ADSORPTION Young's Equation Work of Adhesion and Work of Cohesion Phenomenological Theories of Equilibrium Contact Angles Acid-Base Interaction Contact Angle Hysteresis Adsorption Density Profiles in Liquid Films on Solids Characterizing Solid Surfaces COLLOIDAL DISPERSIONS Attractive Forces Electrical Interaction Colloids of All Shapes and Sizes Combined Attractive and Electrical Interaction: DLVO Theory Effect of Polymer Molecules on the Stability of Colloidal Dispersions Kinetics of Coagulation SURFACTANTS Micelle Formation Variation of CMC for Pure Surfactants and Surfactant Mixtures Other Phases Involving Surfactants Formation of Complexes Between Surfactants and Polymers Surface Films of Insoluble Substrates Solubilization and Microemulsions Phase Behavior and Interfacial Tension for Oil-Water-Surfactant Systems Effect of Composition Changes Thermodynamics of Microemulsions Applications of Surfactants: Emulsions Applications of Surfactants: Detergency Chemical Reactions in Micellar Solutions and Microemulsions INTERFACES IN MOTION: STABILITY AND WAVE MOTION Linear Analysis of Interfacial Stability Damping of Capillary Wave Motion by Insoluble Surfactants Instability of Fluid Cylinders or Jets Oscillating Jet Stability and Wave Motion of Thin Liquid Films: Foams Energy and Force Methods for Thermodynamic Stability of Interfaces Interfacial Stability for Fluids in Motion: Kelvin-Helmholtz Instability Waves on a Falling Liquid Film TRANSPORT EFFECTS ON INTERFACIAL PHENOMENA Interfacial Tension Variation Interfacial Species Mass Balance and Energy Balance Interfacial Instability for a Liquid Heated from Below or Cooled from Above Interfacial Instability During Mass Transfer Other Phenomena Influenced by Marangoni Flow Nonequilibrium Interfacial Tensions Effect of Surfactant Transport on Wave Motion Stability of Moving Interfaces with Phase Transformation Stability of Moving Interfaces with Chemical Reaction Intermediate Phase Formation Transport-Related Spontaneous Emulsification Interfacial Mass Transfer Resistance Other Interfacial Phenomena Involving Dispersed Phase Formation DYNAMIC INTERFACES Surfaces Basic Equations of Fluid Mechanics Flow Past a Droplet Asymptotic Analysis Dip Coating Spherical Drop Revisited Surface Rheology Drainage of Thin Liquid Films Dynamic Contact Lines Slip Thin and Ultrathin Films SIZE, SHAPE, STRUCTURE, DIFFUSIVITY, AND MASS TRANSFER Probing with Light More Light Diffraction Diffusion Dynamic Light Scattering NMR Self-Diffusion Coefficient *Each chapter provides an Introduction, General Topic and Text References, and Problems. Worked examples also appear throughout the chapters.

High Marangoni number convection in a square cavity

Abstract: Steady thermocapillary flow is examined in a square two‐dimensional cavity with a single free surface and differentially heated side walls. The numerical solutions are obtained with a finite difference method applied to a streamfunction‐temperature formulation. This work investigates the Prandtl number dependence, structure, and stability of high Marangoni number flow. It is found that the character of thermocapillary flow is highly sensitive to the value of the Prandtl number over a range of Marangoni numbers exceeding 1×105 for 1≤Pr≤50, the magnitude of the flow showing nonmonotonic dependence on the Marangoni number for Pr≤∼10. A complete structural analogy is observed between flow in a cavity driven by a moving lid and thermocapillary flow in the boundary layer limit, and it is found that all the solutions, spanning a wide range of Marangoni and Prandtl numbers, are linearly stable to a restricted class of disturbances.

Ripple damping on water surface covered by a spreading film: Theory and experiment

Abstract: The results of point-by-point laboratory dampingvs. frequency measurements using mechanically generated ripples on a water surface covered by monomolecular film of oleic alcohol are discussed in terms of a theory that takes into account coupling of Laplace and Marangoni modes.

Combined Residual Natural and Marangoni Convection in a Liquid Sphere Subjected to a Constant and Variable Micro‐Gravity Field

Abstract: The combined effect of thermal Marangoni convection induced by a gradient of temperature imposed upon the free surface of a liquid sphere and the residual natural convection steming from the still existing micro-gravity field in an orbiting space laboratory has been investigated The case of a constant and linearly dependent axial residual gravity field has been considered, for which the Stokes equation in the approximation of Boussinesq have been solved By the introduction of a dynamic Bond-number derived as the ratio of the Grashof number to the Reynoldsnumber based upon the Marangoni flow the predominance of Marangoni- (for Bo 0) or natural convection (for Bo ∞) could be determined Streamlines, radial- and angular velocity distributions have been obtained analytically The combined effect of Marangoni- and natural convection is of importance for space processings In addition the isothermal lines are presented for various imposed temperature distributions at the free surface of the liquid sphere Es wird das Zusammenwirken thermischer Marangonikonvektion und der von der Restschwere in einem Weltraumlabor herruhrenden naturlichen Residualkonvektion in einer Flussigkeitskugel bestimmt Dabei wird die Oberflache der Kugel (Schmelze) einer axialsymmetrischen Temperatur ausgesetzt und in einem konstanten und linear variablen Mikrogravitationsfeld behandelt Stromfunktion und Geschwindigkeitsverteilung werden aus der Stokesgleichung in der Approximation von Boussinesq analytisch gelost Der Einflus des Residualschwerefeldes im Raumfluglabor wird durch das Einfuhren der dynamischen Bondzahl angegeben, wobei diese aus dem Verhaltnis der Grashofzahl zur Reynoldszahl, welche auf der Marangonikonvektion basiert, abgeleitet wird Fur verschwindende Bondzahlen dominiert die Marangonikonvektion, wahrend fur sehr grose Bondzahlen die naturliche Konvektion vorherrscht Fur lineare und quadratische Temperaturverteilungen werden die Stromlinien numerisch bestimmt

Marangoni convection in liquid films with a deformable open surface

Abstract: For a liquid film with an open deformable surface like a tear film, sufficient conditions are given for the onset of Marangoni convection when there is simultaneous heat and mass transport across the layer. It is shown that although temperature gradients in the film may not be responsible for convection they may, however, contribute to a drastic lowering of the solute (mucin) gradients needed for the instability. The convective threshold values are also given in terms of a capillary number, i.e., in terms of the deformation of the open surface. Our theoretical predictions are expected to be useful in fields ranging from dacriology to crystal growth and metal-semiconductor physical chemistry.

マランゴニ効果を利用した溶液中への蒸気吸収の促進 : 第1報,高級アルコールの添加による吸収促進効果とマランゴニ対流の発生機構

Abstract: This study explores the mechanism of the steam absorption enhancement by the addition of small amount of n-octanol (C8 H17 OH) into the aqueous solution of LiBr. Both the visualization by holographic interferometer and the temperature measurements in the solution indicate clearly that the steam absorption processes are classified into three representative cases by the amount of n-octanol addition. The violent Marangoni convection is recognized shortly after the steam absorption starts in the addition range of 00.1∼2 mass %. Especially in case of 0.1mass%, the heat input by the steam absorption increases to almost 400% compared with the one without the addition. Furthermore the measurements of the surface tension and the observations on the solution surface are made in order to investigate the basic mechanism for the generation of the Marangoni convection. It is the surface of the solution.

Suppression or control of liquid convection in float zones in a zero-gravity environment by viscous gas shear

Abstract: In the float-zone processing of materials in a zero-gravity environment, such as outer space or in orbital flight, the Marangoni flow at the free surface of the float zone is stopped by directing streams of heated, non-reactive gas(es) tangentially to the surface and in a direction and with a velocity such that counterbalancing shear forces are produced. The total resultant shear forces at the surface are therefore zero, and all Marangoni convection throughout the float zone is virtually eliminated. Alternatively, changes in the gas streams can produce any specified non-zero convection velocity in a critical region when desired. Also useful and beneficial in reducing or controlling or modifying the resultant velocity of the combined convections for float-zone processes carried out on earth. Particularly useful in the growing of improved doped semiconductor crystals, and also useful in improving the controlled solidification in float zones for the fabrication of improved glasses and metal alloys in zero gravity or on earth.

Pattern formation and Marangoni convection during oscillating glycolysis

Abstract: Spatial pattern formation during oscillating glycolysis in a thin layer of extract from yeast cells is investigated by two-dimensional spectrophotometry using video techniques and by dark-field detection of refractive index gradients. The time intervals of repetitively reappearing trans­ mission patterns coincide with the phases of maximum metabolic turnover during each glycolytic cycle. The spatial arrangement of the patterns is strongly correlated with a network of convection cells which permanently exists in the liquid layer. The patterns are generated by the coupling of reaction with Marangoni type convection due to gradients in surface tension which are mainly caused by evaporative cooling and influenced by chemical composition and reactivity.

Differences in surface tensions of non-ionic surfactant solutions as measured by the drop-volume and Wilhelmy-plate techniques

Abstract: The surface tensions of aqueous solutions of hexaethylene oxide n-dodecyl ether (C12E6) have been measured in the region of the critical micelle concentration (c.m.c.) using both the drop-volume and the Wilhelmy-plate techniques. The data obtained gave similar values for the c.m.c. (8.5 × 10–5 mol dm–3). However, significant surface-tension differences occurred in the decade of concentration below the c.m.c., the differences being manifested in apparent values for the limiting surface areas per molecule of 63 A2 molecule–1(drop-volume) and 73 A2 molecule–1(plate), or else as a surface tension difference of ca. 3 mN m–1 for 10–5 mol dm–3 solutions. The discrepancy is discussed in terms of Marangoni effects operative in the drop detachment process which modify the Harkins and Brown correction factor. The effect is expected to be important in those systems which show a high surface dilational modulus, such as non-ionics of low c.m.c. and protein solutions. The use of the drop-volume technique in such systems is unsound.

Marangoni flow regimes in liquid metals

Abstract: Marangoni flows in liquid metals are studied in two complementary ways: 1. 1. An order of magnitude analysis of the flow regimes is performed on the basis of the concepts of the boundary layer theory, as previously performed for the case of buoyancy driven flows in Bridgman solidification. This analysis is applied to the case of a planar liquid layer under 1 g conditions. Particularly, the parameter range (layer thickness d and thermal gradient G) under which pure Marangoni flows can be observed at 1 g is thus determined. 2. 2. An experimental method is developed to measure the velocities of inert particles at the surface of thin liquid metal layers at 1 g. Experimental results for liquid tin with 0.3 < H < 4 mm and 5 < G < 40 K/cm are reported, and their consistency with the predicted scaling laws is discussed.

A thermocapillary cell in a layer of a heavy fluid heated from above

Abstract: A solution is found to the problem of steady thermocapillaty convection in a thin horizontal layer of a heavy fluid with Prandtl number P ≳ 1 which is developing while being locally heated from above, for the case of large Marangoni numbers. The shape of the free surface of the fluid was determined and the structure of the convective cell was studied. The effect of the curvature of the surface on the picture of the convection was considered.

Heat Transport in a Liquid Column in Weightless Conditions Due to Thermal Marangoni

Abstract: In a circular cylindrical liquid column in zero gravity the velocity distribution due to natural and Marangoni convection is determined for the liquid surface subjected to a quadratic temperature field. The heat transport is obtained with and without the convective terms, and quite a difference appears due to the neglect of convective terms. The local temperature distribution is presented.

Theory of interfacial convection

Abstract: Using a simple thermocapillary convection problem as an example, we consider weakly nonlinear convective structures which arise near the surface of two liquids as a result of the Marangoni instability.