Zero-gravity Field Research Articles

Solidification of Undercooled Liquid under Supergravity Field by Phase-Field Crystal Approach

Solidification under a supergravity field is an effective method to control the solidified microstructure, which can be used to prepare materials with excellent comprehensive properties. In order to explore the influence of supergravity on the solidification behavior, a phase-field crystal model for the solidification under supergravity fields is developed and utilized to study the supergravity-controlled solidification behaviors. The results show that the grains in the solidification structures are refined in a supergravity field. The grain size in a zero-gravity field is uniformly distributed in the sample, but gradually decreases along the direction of the supergravity, showing a graded microstructure. The simulations show real-time images of the nucleation and growth of grains during solidification. In a supergravity field, solidification occurs preferentially in the liquid subject to greater gravity and advances in the opposite direction of supergravity with the time evolution. In addition, the driving force of crystallization in liquid is calculated to explain the effect of the supergravity field on the solidification structure from a thermodynamic point of view. Our findings are expected to provide a new approach and insight for understanding the solidification behaviors under supergravity.

Three-pronged convection in a cubic cavity under modulating gravity

Three-dimensional thermal convection in a cubic cavity heated from one wall and chilled from its opposite wall in the terrestrial-gravity and zero-gravity fields with and without a sinusoidal modulation is investigated numerically. The gravity and its modulation are parallel to the temperature gradient. An incompressible fluid with Prandtl number Pr = 7.1 (water) is considered and hence the Boussinesq approximation is used. The gravity-modulation parameters are a vibrational Rayleigh number Raη and a non-dimentional gravity-modulation frequency ω. Here the authors report a novel ‘trident’ flow structure in laminar and steady thermal convection, which consists of a point-symmetric pair of three-pronged flows, namely, three ascending streams and three descending streams in the cube. This flow structure is stable and persistent in the sense that it is observed in all three situations: a stationary cube under the terrestrial gravity, an oscillating cube under the terrestrial gravity, and an oscillating cube under zero gravity. A POD analysis confirmed this observation. Tested parameters are Rayleigh number Ra = 8.0 × 104 in the terrestrial-gravity field without the gravity modulation or Ra = 1.0 × 104; and the gravity modulation in the terrestrial-gravity field Raη = 1.0 × 105 and ω = 5.0 in the terrestrial-gravity field and Raη = 1.1 × 105 and ω = 5.0 in the zero-gravity field.

Sculpture in Space: Flotation and Levitation in Postwar Art

The idea of sculpture with no visible contact with the earth, hovering in space without the usual vertical and horizontal orientation, arose in contemporary art practice during the postwar decades, amid the Cold War race for space. In Milan, Paris, Düsseldorf and New York, an array of floating art projects were attempted both inside—and outside—the art gallery. These artistic experiments offered a counterpoint to the first satellites and manned spacecraft, using simple technologies including magnets and balloons to address complex aesthetic issues raised by the outer-space environment and, in particular, the zero-gravity field. By the late 1960s, free-floating “aerial” and “pneumatic” art had become an international trend, reflecting a new conception of art’s meaning during a time of cultural and technological change.

PREPARATION OF ION-EXCHANGE SOILS BASED ON WEEK DISSOCIATING FIBROUS ION EXCHANGERS

The perspectives of using ion-exchange soils for growing plants in zero-gravity field are described. Standard methods for obtaining ion-exchange soils are not suitable for weakly dissociating ion-exchangers. Methods for obtaining ion-exchange soil based on weakly dissociating fibrous ion exchangers are proposed. The method using concentrated solutions made it possible to obtain ion-exchange soils with a larger content of deficient ions (K+ , NO3 – ). The suitability of the obtained ion-exchange soils was confirmed by a biological experiment.

Three-dimensional Numerical Simulation of Thermal and Solutal Marangoni Convection in a Liquid Bridge under Zero-gravity Field

Three-dimensional Numerical Simulation of Thermal and Solutal Marangoni Convection in a Liquid Bridge under Zero-gravity Field

Vibrational Effect on Entropy Generation in a Square Porous Cavity

We investigate the nature of entropy generation for natural convection in a two-dimensional square section enclosure vibrating sinusoidally perpendicular to the applied temperature gradient in a zero-gravity field. The enclosure is assumed to fill with porous media. The Darcy momentum equation is used to model the porous media. The full governing differential equations are simplified with the Boussinesq approximation and solved by a finite volume method. Whereas the Prandtl number Pr is fixed to 1.0. Results are presented in terms of average Nusselt number (Nuav), entropy generation number (Nsav), Bejan number (Beav), and kinetic energy (KEav).

Vibrational effects on convection in a square cavity at zero gravity

In this numerical study, we investigate natural convection in a two-dimensional square-section enclosure vibrating sinusoidally parallel to the applied temperature gradient in a zero-gravity field. The full Navier–Stokes equations are simplified with the Boussinesq approximation and solved by a finite difference method. Whereas the Prandtl number Pr is fixed to 7.1 (except for some test cases with Pr = 7.0, 6.8), the vibrational Rayleigh number Ra based on acceleration amplitude is varied from 1.0 × 104 to 1.0 × 105, and dimensionless angular frequency ω is varied from 1.0 × 100 to 1.0 × 103. In the tested range, time evolutions exhibit synchronous, 1/2-subharmonic and non-periodic responses, and flow patterns are characterized mainly by one- or two-cell structures. Flow-regime diagrams show considerable differences from results in a non-zero-mean-gravity field even at large acceleration amplitudes, and suggest that some parts of non-periodic-response regimes may be related to transitions between flow patterns. The amplitude of fluctuations in spatially averaged kinetic energy density K (equal to the difference between maximum and minimum kinetic energies over a cycle) tends to be large when fluid is stationary everywhere over some interval of time during each period, and has a peak when fluid begins to move continuously throughout one period. Such peaks are caused by impulsively started convection, and are not connected to resonant oscillations in a constant-gravity field.

304 無重力場での正方形容器内対流への重力変動効果に関する数値解析

304 無重力場での正方形容器内対流への重力変動効果に関する数値解析

Spacecraft capillary propellant retention and control for long-life missions.

1 2 Swalley, F. E., Ward, W. D., and Toole, L. E., Low Gravity F^id Behavior and Heat Transfer Results from the S-IVB-203 F ight, Proceedings of the Conference on Long-Term Cryo-Propellant Storage in Space, NASA Marshall Space Flight Center, Himtsville, Ala., 1966, pp. 213-232. 3 Barger, J. P., Method and Apparatus for Orienting Fluids in Zero-Gravity Fields/' U.S. Patent 3,202,160, assigned to Dynatech Corp., filed May 24, 1961, issued Aug. 24, 1965. 4 Blackman, J. B., Dielectrophoretic Propellant Orientation in Zero Gravity, Douglas Paper 1292, presented at 7th Symposium on Ballistic Missile and Space Technology, Colorado Springs, Colo., Aug. 13-16, 1962. 5 Reynolds, J. M. et al., Design Study of a Liquid Oxygen Converter for Use in Weightless Environments, TDR-63-42, Contract AF 33(657)-9423, Aerospace Medical Research Labs., Wright-Patterson Air Force Base, Ohio. 6 Melcher, J. R. and Hurwitz, M., Gradient Stabilization of Electrohydrodynamically Oriented Liquids, Journal of Spacecraft and Rockets, Vol. 4, No. 7, July 1967, pp. 864-881. 7 Stratton, J. R., Electromagnetic Theory, McGraw-Hill, New York, 1941, pp. 137-140. 8 Melcher, J. R., Field-Coupled Surface Waves, M.I.T. Press, Cambridge, Mass., 1963, pp. 22-23. 9 Reynolds, J. M. and Hurwitz, M., Electrohydrodynamic Propellant Management Systems for Cryogenic Upper Stages, Paper 66-922, 1966, AIAA. 10 Melcher, J. R. and Schwarz, W. F., Interfacial Relaxation Overs tab ility in a Tangential Electric Field, The Physics of Fluids, Vol. 11, No. 12, Dec. 1968. 11 Sumner, I. E., Experimentally Determined Pendulum Analogy of Liquid Sloshing in Spherical and Oblate-Spheroidal Tanks, TN D-2737, April 1965, NASA.

Rotation-induced, free-convection heat transfer in a zero-gravity field.

Rotation-induced, free-convection heat transfer in a zero-gravity field.

Zero-G Propellant Gauging Utilizing Radio Frequency Techniques in a Spherical Resonator

The resonant properties of a spherical cavity are described as a means of gauging liquid propellants in a zero-gravity field. The configuration of a liquid propellant in a partially filled spherical cavity have been shown to be such that a spherical vapor bubble exists in the center of the cavity. Spherical wave functions are developed and the boundary conditions applied to give an analytical expression for the cavity resonant frequency as a function of volumetric propellant loading. An aluminum scale-model, two inches in diameter, spherical cavity was constructed and loaded with varying dielectric shells to verify the mathematical predictions. Close agreement, within several percent, was obtained for three different dielectric constants, 2.5, 5, and 10.

Closure to “Discussion of ‘Transient Capillary Rise in Reduced and Zero-Gravity Fields’” (1962, ASME J. Appl. Mech., 29, pp. 445–446)

Closure to “Discussion of ‘Transient Capillary Rise in Reduced and Zero-Gravity Fields’” (1962, ASME J. Appl. Mech., 29, pp. 445–446)

Discussion: “Transient Capillary Rise in Reduced and Zero-Gravity Fields” (Siegel, Robert, 1961, ASME J. Appl. Mech., 28, pp. 165–170)

Discussion: “Transient Capillary Rise in Reduced and Zero-Gravity Fields” (Siegel, Robert, 1961, ASME J. Appl. Mech., 28, pp. 165–170)

Closure to “Discussions of ‘An Experimental Study of Boiling in Reduced and Zero Gravity Fields’” (1961, ASME J. Heat Transfer, 83, pp. 251–252)

Closure to “Discussions of ‘An Experimental Study of Boiling in Reduced and Zero Gravity Fields’” (1961, ASME J. Heat Transfer, 83, pp. 251–252)

An Experimental Study of Boiling in Reduced and Zero Gravity Fields

A pool boiling apparatus was mounted on a counterweighted platform which could be dropped a distance of nine feet. By varying the size of the counterweight, the effective gravity field on the equipment was adjusted between zero and unity. A study of boiling burnout in water indicated that a variation in the critical heat flux according to the one quarter power of gravity was reasonable. A consideration of the transient burnout process was necessary in order to properly interpret the data. A photographic study of nucleate boiling showed how the velocity of freely rising vapor bubbles decreased as gravity was reduced. The bubble diameters at the time of breakoff from the heated surface were found to vary inversely as gravity to the 1/3.5 power. Motion pictures were taken to illustrate both nucleate and film boiling in the low gravity range.

Transient Capillary Rise in Reduced and Zero-Gravity Fields

Experimental information is given on the transient “capillary” rise of water into vertical tubes subjected to reduced and zero-gravity fields. The tubes ranged in internal diameter from 0.075 to 1.295 in. The response in a low-gravity environment is of interest in studying the behavior of liquid systems for space vehicles. An approximate analysis is presented to aid in the interpretation of the data and predict the transient rise. Photographs are given which illustrate the behavior in short tubes where the water is able to move beyond the top of the tube during part of the zero-gravity period.