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.

Liquid Crystal Imaging of Surface-Tension-Driven Convection

2000 ◽  
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

Abstract 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.

Instability and Frontal Breakup in Super-Meniscus Films

1996 ◽  
Vol 464 ◽  
Author(s):  
Dawn E. Kataoka ◽  
Sandra M. Troian
Keyword(s):  
Surface Tension ◽  
Stability Analysis ◽  
Temperature Distribution ◽  
Liquid Film ◽  
Linear Stability Analysis ◽  
Surface Coverage ◽  
Flow Behavior ◽  
Leading Edge ◽  
Nonuniform Temperature ◽  
Unstable Flow

ABSTRACTSurface tension gradients created by a nonuniform temperature distribution in athin liquid film can force vertical spreading beyond the equilibrium meniscus [1]. Experiments designed to probe the flow behavior of super-meniscus films have shown that the leading edge can either spread uniformly with complete surface coverage or become corrugated and breakupinto long slender rivulets. We show that within linear stability analysis, both the conditions for unstable flow and the most unstable wavelength compare favorably with recent experiments reported in the literature.

scholarly journals On a slender dry patch in a liquid film draining under gravity down an inclined plane

2001 ◽  
Vol 12 (3) ◽  
pp. 233-252 ◽  
Author(s):  
S. K. WILSON ◽  
B. R. DUFFY ◽  
S. H. DAVIS
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Liquid Film ◽  
Similarity Solutions ◽  
Inclined Plane ◽  
First Case ◽  
Transverse Profile ◽  
Dry Patch ◽  
Strong Surface ◽  
Weak Surface

In this paper two similarity solutions describing a steady, slender, symmetric dry patch in an infinitely wide liquid film draining under gravity down an inclined plane are obtained. The first solution, which predicts that the dry patch has a parabolic shape and that the transverse profile of the free surface always has a monotonically increasing shape, is appropriate for weak surface-tension effects and far from the apex of the dry patch. The second solution, which predicts that the dry patch has a quartic shape and that the transverse profile of the free surface has a capillary ridge near the contact line and decays in an oscillatory manner far from it, is appropriate for strong surface-tension effects (in particular, when the plane is nearly vertical) and near (but not too close) to the apex of the dry patch. With the average volume flux per unit width (or equivalently with the uniform height of the layer far from the dry patch) prescribed, both solutions contain a free parameter. For each value of this parameter there is a unique solution in the first case and either no solution or a one-parameter family of solutions in the second case. The solutions capture some of the qualitative features observed in experiments.

Liquid Crystal Thermography of an On-Chip Polymerase Chain Reaction Micro-Thermocycler

2006 ◽  
Author(s):  
Tracy Helen Fung ◽  
Shih-Hui Chao ◽  
Joseph E. Peach ◽  
Deirdre R. Meldrum
Keyword(s):  
Polymerase Chain Reaction ◽  
Liquid Crystal ◽  
Temperature Distribution ◽  
Dna Amplification ◽  
Temperature Sensitive ◽  
Chain Reaction ◽  
Liquid Crystal Thermography ◽  
Polymerase Chain ◽  
On Chip

Microscale liquid crystal thermography is a technique to measure temperature distribution of microfabricated devices in real-time. This method utilizes a microscope to image the color map of a layer of temperature-sensitive encapsulated thermochromic liquid crystals (TLC) coated on a microfabricated device. This paper describes the TLC coating process on microscale devices, the characteristics of colorimetric hysteresis, and the calibration of temperature measurements. The calibrated measurements have been applied for characterization of an on-chip polymerase chain reaction (PCR) microscale thermocycler where precise and dynamic temperature control is essential for efficient DNA amplification. Tests on the micro-thermocycler were done around the ranges centered at 30 °C and 95 °C. The results illustrate the effects on the temperature distribution due to micro-thermocycler geometry, and provide important insight for micro-thermocycler design.

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.

scholarly journals Elastocapillary interactions on nematic films

2015 ◽  
Vol 112 (20) ◽  
pp. 6336-6340 ◽  
Author(s):  
Iris B. Liu ◽  
Mohamed A. Gharbi ◽  
Victor L. Ngo ◽  
Randall D. Kamien ◽  
Shu Yang ◽  
...  
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Liquid Crystal ◽  
Easy Axis ◽  
Particle Migration ◽  
Fluid Interfaces ◽  
Particle Assembly ◽  
Director Field ◽  
Liquid Crystal Films ◽  
Crystal Films

Rod-like colloids distort fluid interfaces and interact by capillarity. We explore this interaction at the free surface of aligned nematic liquid crystal films. Naive comparison of capillary and elastic energies suggests that particle assembly would be determined solely by surface tension. Here, we demonstrate that, under certain circumstances, the capillary and elastic effects are complementary and each plays an important role. Particles assemble end-to-end, as dictated by capillarity, and align along the easy axis of the director field, as dictated by elasticity. On curved fluid interfaces, however, curvature capillary energies can overcome the elastic orientations and drive particle migration along curvature gradients. Domains of dominant interaction and their transition are investigated.

scholarly journals Nonlinear two-dimensional free surface solutions of flow exiting a pipe and impacting a wedge

2021 ◽  
Vol 126 (1) ◽  
Author(s):  
Alex Doak ◽  
Jean-Marc Vanden-Broeck
Keyword(s):  
Surface Tension ◽  
Integral Equation ◽  
Free Surface ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Two Dimensional ◽  
Numerical Schemes ◽  
Additional Advantage ◽  
Infinite Wedge ◽  
Good Agreement

AbstractThis paper concerns the flow of fluid exiting a two-dimensional pipe and impacting an infinite wedge. Where the flow leaves the pipe there is a free surface between the fluid and a passive gas. The model is a generalisation of both plane bubbles and flow impacting a flat plate. In the absence of gravity and surface tension, an exact free streamline solution is derived. We also construct two numerical schemes to compute solutions with the inclusion of surface tension and gravity. The first method involves mapping the flow to the lower half-plane, where an integral equation concerning only boundary values is derived. This integral equation is solved numerically. The second method involves conformally mapping the flow domain onto a unit disc in the s-plane. The unknowns are then expressed as a power series in s. The series is truncated, and the coefficients are solved numerically. The boundary integral method has the additional advantage that it allows for solutions with waves in the far-field, as discussed later. Good agreement between the two numerical methods and the exact free streamline solution provides a check on the numerical schemes.

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