A Thermocapillary Convection Experiment in Microgravity

1995 ◽  
Vol 117 (3) ◽  
pp. 611-618 ◽  
Author(s):  
Y. Kamotani ◽  
S. Ostrach ◽  
A. Pline
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Temperature Distribution ◽  
Laser Beam ◽  
Thermocapillary Convection ◽  
Silicone Oil ◽  
Free Surfaces ◽  
Numerical Predictions ◽  
Liquid Free Surface ◽  
Infrared Imager

Results are reported of the Surface Tension Driven Convection Experiment (STDCE) aboard the USML-1 Spacelab, which was launched on June 25, 1992. In the experiment, 10 cSt silicone oil was placed in an open 10-cm-dia circular container, which was 5 cm deep. The fluid was heated either by a cylinderical heater (1.11 cm diameter) located along the container centerline or by a CO2 laser beam to induce thermocapillary flow. Several thermistor probes were placed in the fluid to measure the temperature distribution. The temperature distribution along the liquid-free surface was measured by an infrared imager. Tests were conducted over a range of heating powers, laser-beam diameters, and free surface shapes. An extensive numerical modeling of the flow was conducted in conjunction with the experiments. Some results of the temperature measurements with flat free surfaces are presented in this paper and they are shown to agree well with the numerical predictions.

Thermocapillary Convection With Undeformable Curved Surfaces in Open Cylinders

2001 ◽  
Author(s):  
Bok-Cheol Sim ◽  
Abdelfattah Zebib
Keyword(s):  
Free Surface ◽  
Critical Frequency ◽  
Thermocapillary Convection ◽  
Three Dimensional ◽  
Quantitative Agreement ◽  
Fluid Volume ◽  
Uniform Heat Flux ◽  
Free Surfaces ◽  
Space Experiments ◽  
Steady Convection

Abstract Thermocapillary convection driven by a uniform heat flux in an open cylindrical container of unit aspect ratio is investigated by two- and three-dimensional numerical simulations. The undeformable free surface is either flat or curved as determined by the fluid volume (V ≤ 1) and the Young-Laplace equation. Convection is steady and axisymmetric at sufficiently low values of the Reynolds number (Re) with either flat or curved interfaces. Only steady convection is possible in strictly axisymmetric computations. Transition to oscillatory three-dimensional motions occurs as Re increases beyond a critical value dependent on Pr and V. With a flat free surface (V = 1), two-lobed pulsating waves are found on the free surface and prevail with increasing Re. While the critical Re increases with increasing Pr, the critical frequency decreases. In the case of a concave surface, four azimuthal waves are found rotating clockwise on the surface. The critical Re decreases with increasing fluid volume, and the critical frequency is found to increase. The numerical results with either flat or curved free surfaces are in good quantitative agreement with space experiments.

Stability Analysis of Thermocapillary Convection of B2O3/Sapphire Melt in an Annular Pool

2021 ◽  
Vol 1036 ◽  
pp. 175-184
Author(s):  
Dong Ming Mo
Keyword(s):  
Stability Analysis ◽  
Temperature Distribution ◽  
Thermocapillary Convection ◽  
Silicone Oil ◽  
Liquid Interface ◽  
Sapphire Crystal ◽  
Neutral Stability ◽  
Unstable Flow ◽  
Fluid Layers ◽  
Lower Fluid

Aiming at the thermocapillary convection stability of sapphire crystal grown by liquid-encapsulated Czochralski method, by non-linear numerical simulation, obtained the flow function and temperature distribution of R-Z cross section, as well as the velocity and temperature distribution at liquid-liquid interface and monitoring point of B2O3/sapphire melt in annular two liquid system, covered with solid upper wall and in microgravity. By means of linear stability analysis, obtained the neutral stability curve and critical stability parameters of the system, and revealed the temperature fluctuation of the liquid-liquid interface. The calculated results of B2O3/sapphire melt were compared with 5cSt silicone oil/HT-70. The results show that under the same geometrical conditions, the flow of B2O3/sapphire melt system is more unstable than 5cSt silicone oil/HT-70, there are two unstable flow patterns, radial three-dimensional steady flow cell and hydrothermal waves near the hot wall. The larger the ratio of Pr number of upper and lower fluid layers is, the better the effect of restraining the flow of lower fluid layers is.

Imaging of Surface-Tension-Driven Convection Using Liquid Crystal Thermography

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
T. W. Dutton ◽  
L. R. Pate ◽  
D. K. Hollingsworth
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Liquid Crystal ◽  
Temperature Distribution ◽  
Liquid Film ◽  
Lower Boundary ◽  
Processing System ◽  
Metal Foil ◽  
Lower Boundary Condition ◽  
Liquid Crystal Thermography

Surface-tension forces can drive fluid motion within thin liquid layers with a free surface. Spatial variations in the temperature of the free surface create surface tractions that drive cellular motions. The cells are most commonly hexagonal in shape and they scale on the thickness of the fluid layer. This investigation documents the formation of cells in the liquid film in the presence of a uniform-heat-flux lower boundary condition. Liquid crystal thermography was used to image the cells and measure the temperature distribution on the lower surface of the liquid layer. A 1.1 mm deep pool of silicone oil was supported on a 50 μm thick electrically heated metal foil. The oil was retained inside an independently heated acrylic ring mounted on the top surface of the foil and a dry-ice cooling plate served as the low-temperature sink above the free surface of the oil. Color images of hexagonal convection cells were captured using liquid crystal thermography and a digital image acquisition and processing system. The temperature distribution inside a typical cell was measured using thermographic image analysis. Experimental issues, such as the use of an independently heated retaining ring to control the height of the liquid film and the utility of a flux-based Marangoni number are discussed.

scholarly journals Instability of a Two-layer System with Deformable Interfaces under Laser Beam Heating

2019 ◽  
pp. 543-550
Author(s):  
Victoria B. Bekezhanova ◽  
Olga N. Goncharova ◽  
Natalia A. Ivanova ◽  
Denis S. Klyuev
Keyword(s):  
Free Boundary ◽  
Laser Beam ◽  
Thermocapillary Convection ◽  
Silicone Oil ◽  
Numerical Study ◽  
Theoretical Data ◽  
Thermal Exposure ◽  
Local Heat ◽  
Layer System ◽  
Standard Problem

New non-standard problem of thermocapillary convection is studied to analyze the flows arising in a two- layer system under action of an intense thermal exposure on the free boundary by a laser beam. Char- acteristics of the physical experiments are presented. Parameters of the experiments are the ratio of the liquid layer thicknesses, the types of working liquids, the absorption coefficients of media. Special atten- tion is given to the study of the influence of the system geometry when changing the thickness for one of the liquid layers. Theoretical study of the thermocapillary convection includes development of the mathe- matical model tested on the basis of new physical experiment data and of the effective numerical algorithm to calculate basic characteristics. The occurrence of the decaying oscillations, which first experimentally discovered by the authors, and the evolution of the interfaces and layers are investigated. The results of numerical study of structure and nature of convective flows in the horizontal two-layer liquid – liquid systems of the type "silicone oil – glycerin", and comparison of the experimental and theoretical data allow one to validate the developed mathematical model, to analyze the peculiarities of heat and mass transfer in the two-layer system induced by the action of a local heat source at the free boundary

Numerical Simulation of Electrostatic Atomization in Spindle Mode

2010 ◽  
Author(s):  
Mohammad Passandideh Fard ◽  
Mohammad Reza Mahpeykar ◽  
Sajad Pooyan ◽  
Mortaza Rahimzadeh
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Electric Field ◽  
Stable State ◽  
Surface Shape ◽  
Liquid Jet ◽  
Perfect Conductor ◽  
Electric Force ◽  
Electrostatic Atomization ◽  
Liquid Free Surface

The behavior of a liquid jet in an electrostatic field is numerically simulated. The simulations performed correspond to a transient liquid jet leaving a capillary tube maintained at a high electric potential. The surface profile of the deforming jet is defined using the VOF scheme and the advection of the liquid free surface is performed using Youngs’ algorithm. Surface tension force is treated as a body force acting on the free surface using continuum surface force (CSF) method. To calculate the effect of the electric field on the shape of the free surface, the electrostatic potential is solved first. Next, the surface density of the electric charge and the electric field intensity are computed, and then the electric force is calculated. Liquid is assumed to be a perfect conductor, thus the electric force only acts on the liquid free surface and is treated similar to surface tension using the CSF method. To verify the simulation results, a simplified case of electrowetting phenomenon is simulated and free surface shape in stable state is compared with experimental results. Then the electrostatic atomization in spindle mode is simulated and the ability of the developed code to simulate this process is demonstrated.

Thermocapillary convection in a cylinder with a strong non-uniform axisymmetric magnetic field

1994 ◽  
Vol 276 ◽  
pp. 369-388 ◽  
Author(s):  
Yu Yu Khine ◽  
John S. Walker
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Free Surface ◽  
Magnetic Fields ◽  
Thermocapillary Convection ◽  
Hartmann Number ◽  
Asymptotic Solutions ◽  
Cylinder Wall ◽  
Axial Component ◽  
Radial Temperature

This paper treats a surface-tension-driven liquid-metal flow in a cylinder with a steady externally applied non-uniform axisymmetric magnetic field. The top boundary consists of an annular free surface around a solid disk, modelling the Czochralski growth of silicon crystals. A radial temperature gradient produces a decrease of the surface tension from the disk edge to the vertical cylinder wall. The magnetic flux density is sufficiently large that inertial effects and convective heat transfer are negligible. First we present large-Hartmann-number asymptotic solutions for magnetic fields with either a non-zero or a zero axial component at the free surface. The asymptotic solutions indicate that a purely radial magnetic field at the free surface represents a singular limit of more general magnetic fields. Secondly we present numerical solutions for arbitrary values of the Hartmann number, and we treat the evolution of the thermocapillary convection as the axial magnetic field at the free surface is changed continuously from the full field strength to zero.

The dynamics of strong turbulence at free surfaces. Part 1. Description

2001 ◽  
Vol 449 ◽  
pp. 225-254 ◽  
Author(s):  
M. BROCCHINI ◽  
D. H. PEREGRINE
Keyword(s):  
Surface Tension ◽  
Surface Roughness ◽  
Free Surface ◽  
Water Waves ◽  
Theoretical Studies ◽  
Free Surfaces ◽  
Submerged Jets ◽  
Wide Range ◽  
Experimental And Theoretical Studies ◽  
Two Parameter

A free surface may be deformed by fluid motions; such deformation may lead to surface roughness, breakup, or disintegration. This paper describes the wide range of free-surface deformations that occur when there is turbulence at the surface, and focuses on turbulence in the denser, liquid, medium. This turbulence may be generated at the surface as in breaking water waves, or may reach the surface from other sources such as bed boundary layers or submerged jets. The discussion is structured by consideration of the stabilizing influences of gravity and surface tension against the disrupting effect of the turbulent kinetic energy. This leads to a two-parameter description of the surface behaviour which gives a framework for further experimental and theoretical studies. Much of the discussion is necessarily heuristic, and is often limited by a lack of appropriate experimental observations. It is intended that such experiments be stimulated, to test the value or otherwise of our two-parameter description.

Existence of a Surface Tension Discontinuity at a Liquid Free Surface

Nature ◽  
1968 ◽  
Vol 217 (5128) ◽  
pp. 536-538 ◽  
Author(s):  
R. H. J. SELLIN
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Liquid Free Surface
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