Jean Koster | University of Colorado, Boulder (original) (raw)
Papers by Jean Koster
Sky and Telescope, Dec 1, 1988
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Published for the American Astronautical Society by Univelt eBooks, 1987
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Measurement Science and Technology, Jun 1, 1995
ABSTRACT Particle displacement tracking velocimetry is used to obtain full-field minimally invasi... more ABSTRACT Particle displacement tracking velocimetry is used to obtain full-field minimally invasive velocity measurement of natural convective flow in multiple immiscible liquid layers. The quality of the obtained signals depends very much on the particles used. The objective was to improve the quality of the system by designing neutrally buoyant spherical and highly reflective tracer particles. This work provides a laboratory manual for fabrication of silver-coated neutrally buoyant spherical particles of high reflectivity in any specific fluid volume subjected to temperature differences.
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Various papers on low-gravity fluid dynamics and transport phenomena are presented. Individual to... more Various papers on low-gravity fluid dynamics and transport phenomena are presented. Individual topics addressed include: fluid management in low gravity, nucleate pool boiling in variable gravity, application of energy-stability theory to problems in crystal growth, thermosolutal convection in liquid HgCdTe near the liquidus temperature, capillary surfaces in microgravity, thermohydrodynamic instabilities and capillary flows, interfacial oscillators, effects of gravity jitter on typical fluid science experiments and on natural convection in a vertical cylinder. Also discussed are: double-diffusive convection and its effects under reduced gravity, segregation and convection in dendritic alloys, fluid flow and microstructure development, analysis of convective situations with the Soret effect, complex natural convection in low Prandtl number metals, separation physics, phase partitioning in reduced gravity, separation of binary alloys with miscibility gap in the melt, Ostwald ripening in liquids, particle cloud combustion in reduced gravity, opposed-flow flame spread with implications for combustion at microgravity.
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Crystal Research and Technology, Nov 1, 1999
ABSTRACT Eutectic gallium-indium is studied in a horizontal Bridgman furnace geometry. Differenti... more ABSTRACT Eutectic gallium-indium is studied in a horizontal Bridgman furnace geometry. Differential temperature gradients are applied to solidify and melt the alloy while observing in-situ the interface morphology and the chemical segregation in the melt and in the solid as well. Upon cooling, a wedge-type indium-rich mushy zone develops at the cold wall. The melt is initially stirred by convective flow. After solidification starts the roll cell recedes to be replaced by a chemically layered conductive melt that eventually solidifies with rather uniform eutectic structure. Upon re-melting, the morphology of the interface adopts a profile that is predetermined by the original solid structure. Those patterns, as well as the flow, are different from single element solid melting experiments and have yet to be modeled. Under high thermal gradient the convective flow mixes the binary melt and the visualized density pattern eventually becomes that of a homogeneous melt.
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Physics of fluids, Aug 1, 1993
Thermocapillary convection is studied in two immiscible liquid layers with one free surface, one ... more Thermocapillary convection is studied in two immiscible liquid layers with one free surface, one liquid/liquid interface, and differential heating applied parallel to the interfaces. An analytical solution is introduced for infinite horizontal layers. The defining parameter for the flow pattern is λ, the ratio of the temperature coefficient of the interfacial tension to that of the surface tension. Four different flow patterns exist under zero gravity conditions. ‘‘Halt’’ conditions which halt the fluid motion in the lower encapsulated liquid layer have been found. A numerical experiment is carried out to study effects of vertical end walls on the double layer convection in a two-dimensional cavity. The halt condition obtained from the analytical study is found to be valid in the limit of small Reynolds numbers. The flow in the encapsulated liquid layer can be suppressed substantially.
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Published for the American Astronautical Society by Univelt eBooks, 1987
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ABSTRACT
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JOM, Mar 1, 1997
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International Journal of Heat and Mass Transfer, Aug 1, 1997
... convection problem is an extension of the broadly studied problem of natural convection in a ... more ... convection problem is an extension of the broadly studied problem of natural convection in a ... in two-layers which parallels CLI's exhaustive inves-tigation of single layer convection in a ...Temperature of the side-wall boundaries is ramped to specific temperature differences [AT] at ...
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Journal of heat transfer, May 1, 1996
Two-dimensional thermal convection in a system of two immiscible liquids heated from below is stu... more Two-dimensional thermal convection in a system of two immiscible liquids heated from below is studied experimentally and numerically. Convection in the two-layer system is characterized by two distinct coupling modes between the layers. They are mechanical coupling and thermal coupling. These two coupling modes are visualized experimentally and found to be in reasonable agreement with numerical simulations. When buoyancy forces in both layers are of similar strength, thermal coupling is preferred. The mechanical coupling mode dominates when the buoyancy forces are very different in both layers.
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Crystal Research and Technology, 1998
ABSTRACT Experiments with a stoichiometric InSb compound were first performed at small temperatur... more ABSTRACT Experiments with a stoichiometric InSb compound were first performed at small temperature gradient across the crystal/melt interface of 3 °C/cm and furnace translation velocity, Vfrn, of 2 μ/sec. Known growth requirements for quality crystals were confirmed. They are, (1) the interface temperature must be close to the congruent melting temperature and, (2) the interface must be located within the adiabatic zone. These requirements can be obtained only through specific settings of the heater temperatures. An X-ray radioscopic system has been modified to accommodate real-time visualization of the crystal/melt interface during vertical Bridgman-Stockbarger growth of InSb. It is shown that asymmetric temperature settings of the heaters can be advantageously used to minimize defect formation. The interface temperature was assessed indirectly with calibrated outside thermocouples. Optical microscopy and electron microprobe analyses provided feedback on crystalline homogeneity.
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International Communications in Heat and Mass Transfer, Oct 1, 1997
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50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, Jan 9, 2012
ABSTRACT The lunar outpost has an estimated need of 12 kW power to support four astronauts, in si... more ABSTRACT The lunar outpost has an estimated need of 12 kW power to support four astronauts, in situ energy production, and a rover. An Outpost Solar Satellite Power Plant (S2P2) is proposed to provide energy from lunar orbit to the lunar outpost for life support and in situ production needs. If such a satellite system is established first before a moon landing by astronauts the development of an outpost on the surface of the moon will become easier as energy supply and some energy infrastructure is already established. This concept applies to other planets, such as Mars, targeted for outpost development as well.
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Heat and Mass Transfer, Dec 11, 1997
ABSTRACT The stability of Rayleigh-Bénard convection in a transparent model alloy was investigate... more ABSTRACT The stability of Rayleigh-Bénard convection in a transparent model alloy was investigated with holographic interferometry. The dispersed minority phase is the heavier component. The majority component is lighter. A vertical temperature difference was applied to the liquid layer keeping the hot temperature always above phase separation. The upper cold side temperature was kept above or below the phase separation temperature. Fluid separation occurs when the cold temperature drops below consolute temperature. When the liquid is kept at higher than consolute temperature, it is noticed that the stability of the layer is increased when the average temperature approaches the consolute temperature.
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Journal of Crystal Growth, Apr 1, 1997
Off-stoichiometric equilibrium crystal growth within the indium-antimony (In-Sb) system is studie... more Off-stoichiometric equilibrium crystal growth within the indium-antimony (In-Sb) system is studied during vertical Bridgman-Stockbarger crystal growth for an antimony-rich sample, In45Sb55. Real-time X-ray radioscopy tracks the crystal/melt interface position with respect to the furnace position. Calibrated temperature measurements at the ampoule outer wall provide interfacial temperatures. Results indicate substantial constitutional supercooling at the crystal/melt interface under a variety of experimental
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Journal of Crystal Growth, 1997
ABSTRACT Constitutional supercooling is studied within the semiconductor material indium antimoni... more ABSTRACT Constitutional supercooling is studied within the semiconductor material indium antimonide (InSb) during vertical crystal growth from the melt. The starting mixture is stoichiometric In50Sb50. Translation rates are as low as 2 μm/s. Solid-liquid interface morphology and axial interface positions are monitored in real-time with radioscopic X-ray visualization. The solid-liquid interface temperature is assessed from calibrated thermocouple measurements at the ampoule wall. Results indicate substantial constitutional supercooling of the melt. Elemental segregation is assessed from the visualization of the interface location in a measured temperature profile and from the phase diagram. Temperature data suggest that the interface is in contact with a melt composition close to In62Sb38 (based on the 525.7°C melting temperature of α-InSb in a specified phase diagram). That composition reflects significant gravitational segregation in the melt.
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Journal of Crystal Growth, Jul 1, 1994
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Sky and Telescope, Dec 1, 1988
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Published for the American Astronautical Society by Univelt eBooks, 1987
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Measurement Science and Technology, Jun 1, 1995
ABSTRACT Particle displacement tracking velocimetry is used to obtain full-field minimally invasi... more ABSTRACT Particle displacement tracking velocimetry is used to obtain full-field minimally invasive velocity measurement of natural convective flow in multiple immiscible liquid layers. The quality of the obtained signals depends very much on the particles used. The objective was to improve the quality of the system by designing neutrally buoyant spherical and highly reflective tracer particles. This work provides a laboratory manual for fabrication of silver-coated neutrally buoyant spherical particles of high reflectivity in any specific fluid volume subjected to temperature differences.
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Various papers on low-gravity fluid dynamics and transport phenomena are presented. Individual to... more Various papers on low-gravity fluid dynamics and transport phenomena are presented. Individual topics addressed include: fluid management in low gravity, nucleate pool boiling in variable gravity, application of energy-stability theory to problems in crystal growth, thermosolutal convection in liquid HgCdTe near the liquidus temperature, capillary surfaces in microgravity, thermohydrodynamic instabilities and capillary flows, interfacial oscillators, effects of gravity jitter on typical fluid science experiments and on natural convection in a vertical cylinder. Also discussed are: double-diffusive convection and its effects under reduced gravity, segregation and convection in dendritic alloys, fluid flow and microstructure development, analysis of convective situations with the Soret effect, complex natural convection in low Prandtl number metals, separation physics, phase partitioning in reduced gravity, separation of binary alloys with miscibility gap in the melt, Ostwald ripening in liquids, particle cloud combustion in reduced gravity, opposed-flow flame spread with implications for combustion at microgravity.
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Crystal Research and Technology, Nov 1, 1999
ABSTRACT Eutectic gallium-indium is studied in a horizontal Bridgman furnace geometry. Differenti... more ABSTRACT Eutectic gallium-indium is studied in a horizontal Bridgman furnace geometry. Differential temperature gradients are applied to solidify and melt the alloy while observing in-situ the interface morphology and the chemical segregation in the melt and in the solid as well. Upon cooling, a wedge-type indium-rich mushy zone develops at the cold wall. The melt is initially stirred by convective flow. After solidification starts the roll cell recedes to be replaced by a chemically layered conductive melt that eventually solidifies with rather uniform eutectic structure. Upon re-melting, the morphology of the interface adopts a profile that is predetermined by the original solid structure. Those patterns, as well as the flow, are different from single element solid melting experiments and have yet to be modeled. Under high thermal gradient the convective flow mixes the binary melt and the visualized density pattern eventually becomes that of a homogeneous melt.
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Physics of fluids, Aug 1, 1993
Thermocapillary convection is studied in two immiscible liquid layers with one free surface, one ... more Thermocapillary convection is studied in two immiscible liquid layers with one free surface, one liquid/liquid interface, and differential heating applied parallel to the interfaces. An analytical solution is introduced for infinite horizontal layers. The defining parameter for the flow pattern is λ, the ratio of the temperature coefficient of the interfacial tension to that of the surface tension. Four different flow patterns exist under zero gravity conditions. ‘‘Halt’’ conditions which halt the fluid motion in the lower encapsulated liquid layer have been found. A numerical experiment is carried out to study effects of vertical end walls on the double layer convection in a two-dimensional cavity. The halt condition obtained from the analytical study is found to be valid in the limit of small Reynolds numbers. The flow in the encapsulated liquid layer can be suppressed substantially.
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Published for the American Astronautical Society by Univelt eBooks, 1987
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ABSTRACT
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JOM, Mar 1, 1997
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International Journal of Heat and Mass Transfer, Aug 1, 1997
... convection problem is an extension of the broadly studied problem of natural convection in a ... more ... convection problem is an extension of the broadly studied problem of natural convection in a ... in two-layers which parallels CLI's exhaustive inves-tigation of single layer convection in a ...Temperature of the side-wall boundaries is ramped to specific temperature differences [AT] at ...
Bookmarks Related papers MentionsView impact
Journal of heat transfer, May 1, 1996
Two-dimensional thermal convection in a system of two immiscible liquids heated from below is stu... more Two-dimensional thermal convection in a system of two immiscible liquids heated from below is studied experimentally and numerically. Convection in the two-layer system is characterized by two distinct coupling modes between the layers. They are mechanical coupling and thermal coupling. These two coupling modes are visualized experimentally and found to be in reasonable agreement with numerical simulations. When buoyancy forces in both layers are of similar strength, thermal coupling is preferred. The mechanical coupling mode dominates when the buoyancy forces are very different in both layers.
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Crystal Research and Technology, 1998
ABSTRACT Experiments with a stoichiometric InSb compound were first performed at small temperatur... more ABSTRACT Experiments with a stoichiometric InSb compound were first performed at small temperature gradient across the crystal/melt interface of 3 °C/cm and furnace translation velocity, Vfrn, of 2 μ/sec. Known growth requirements for quality crystals were confirmed. They are, (1) the interface temperature must be close to the congruent melting temperature and, (2) the interface must be located within the adiabatic zone. These requirements can be obtained only through specific settings of the heater temperatures. An X-ray radioscopic system has been modified to accommodate real-time visualization of the crystal/melt interface during vertical Bridgman-Stockbarger growth of InSb. It is shown that asymmetric temperature settings of the heaters can be advantageously used to minimize defect formation. The interface temperature was assessed indirectly with calibrated outside thermocouples. Optical microscopy and electron microprobe analyses provided feedback on crystalline homogeneity.
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International Communications in Heat and Mass Transfer, Oct 1, 1997
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50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, Jan 9, 2012
ABSTRACT The lunar outpost has an estimated need of 12 kW power to support four astronauts, in si... more ABSTRACT The lunar outpost has an estimated need of 12 kW power to support four astronauts, in situ energy production, and a rover. An Outpost Solar Satellite Power Plant (S2P2) is proposed to provide energy from lunar orbit to the lunar outpost for life support and in situ production needs. If such a satellite system is established first before a moon landing by astronauts the development of an outpost on the surface of the moon will become easier as energy supply and some energy infrastructure is already established. This concept applies to other planets, such as Mars, targeted for outpost development as well.
Bookmarks Related papers MentionsView impact
Heat and Mass Transfer, Dec 11, 1997
ABSTRACT The stability of Rayleigh-Bénard convection in a transparent model alloy was investigate... more ABSTRACT The stability of Rayleigh-Bénard convection in a transparent model alloy was investigated with holographic interferometry. The dispersed minority phase is the heavier component. The majority component is lighter. A vertical temperature difference was applied to the liquid layer keeping the hot temperature always above phase separation. The upper cold side temperature was kept above or below the phase separation temperature. Fluid separation occurs when the cold temperature drops below consolute temperature. When the liquid is kept at higher than consolute temperature, it is noticed that the stability of the layer is increased when the average temperature approaches the consolute temperature.
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Journal of Crystal Growth, Apr 1, 1997
Off-stoichiometric equilibrium crystal growth within the indium-antimony (In-Sb) system is studie... more Off-stoichiometric equilibrium crystal growth within the indium-antimony (In-Sb) system is studied during vertical Bridgman-Stockbarger crystal growth for an antimony-rich sample, In45Sb55. Real-time X-ray radioscopy tracks the crystal/melt interface position with respect to the furnace position. Calibrated temperature measurements at the ampoule outer wall provide interfacial temperatures. Results indicate substantial constitutional supercooling at the crystal/melt interface under a variety of experimental
Bookmarks Related papers MentionsView impact
Journal of Crystal Growth, 1997
ABSTRACT Constitutional supercooling is studied within the semiconductor material indium antimoni... more ABSTRACT Constitutional supercooling is studied within the semiconductor material indium antimonide (InSb) during vertical crystal growth from the melt. The starting mixture is stoichiometric In50Sb50. Translation rates are as low as 2 μm/s. Solid-liquid interface morphology and axial interface positions are monitored in real-time with radioscopic X-ray visualization. The solid-liquid interface temperature is assessed from calibrated thermocouple measurements at the ampoule wall. Results indicate substantial constitutional supercooling of the melt. Elemental segregation is assessed from the visualization of the interface location in a measured temperature profile and from the phase diagram. Temperature data suggest that the interface is in contact with a melt composition close to In62Sb38 (based on the 525.7°C melting temperature of α-InSb in a specified phase diagram). That composition reflects significant gravitational segregation in the melt.
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Journal of Crystal Growth, Jul 1, 1994
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