Search NASA⌕ Search

SEARCH · Search NASA

Results for “Fluid”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Dynamics of two fluids under periodic acceleration

The evolution of the interface between two fluids confined in a rectangular cavity is investigated numerically to predict its transient behavior. These computations address mixing characteristics of fluids under microgravity conditions, particularly g-jitter conditions resulting from aircraft vibration or crew motion, and have applications in solution crystal growth. The two-dimensional formulation employs the Boussinesq approximation and treats the mixing of two fluids as an initial value problem with a prescribed concentration field. For fluid mixing of practical applications inside a cavity, it is shown that nonlinear convective transport can dominate over both viscous and molecular diffusion. However, viscous diffusion can become important for low Reynolds number or certain cavity sizes. A stacking phenomenon is shown to occur for aspect ratios (Ar) approximately between 5 to 10. For aspect ratios in the neighborhood of 0.1 to 0.2, inner cells evolve at the interface with increasing time. For a square cavity of Ar = 1, chaotic mixing of the fluid appears to occur for a Stokes-Reynolds number greater than about 5.

Duval, Walter M. B.↗
NASA NTRS1988

Working fluid selection for space-based two-phase heat transport systems

The working fluid for externally-mounted, space-based two-phase heat transport systems is considered. A sequence of screening criteria involving freezing and critical point temperatures and latent heat of vaporization and vapor density are applied to a data base of 860 fluids. The thermal performance of the 52 fluids which pass this preliminary screening are then ranked according to their impact on the weight of a reference system. Upon considering other nonthermal criteria (flammability, toxicity, and chemical stability) a final set of 10 preferred fluids is obtained. The effects of variations in system parameters is investigated for these 10 fluids by means of a factorial design.

Mclinden, Mark O.↗
NASA NTRS1988

Characteristics and carbon stable isotopes of fluids in the Southern Kerala granulites and their bearing on the source of CO2

Carbon dioxide-rich inclusions commonly occur in the banded charnockites and khondalites of southern Kerala as well as in the incipient charnockites formed by desiccation of gneisses along oriented zones. The combined high density fluid inclusion isochores and the range of thermometric estimates from mineral assemblages indicate entrapment pressures in the range of 5.4 to 6.1 Kbar. The CO2 equation of state barometry closely compares with the 5 plus or minus 1 Kbar estimate from mineral phases for the region. The isochores for the high density fluid inclusions in all the three rock types pass through the P-T domain recorded by phase equilibria, implying that carbon dioxide was the dominating ambient fluid species during peak metamorphic conditions. In order to constrain the source of fluids and to evaluate the mechanism of desiccation, researchers undertook detailed investigations of the carbon stable isotope composition of entrapped fluids. Researchers report here the results of preliminary studies in some of the classic localities in southern Kerala namely, Ponmudi, Kottavattom, Manali and Kadakamon.

Santosh, M.↗
NASA NTRS1988

Nature and interpretation of fluid inclusions in granulites

Many granulites contain CO2 rich high density fluid inclusions (carbonic fluids). This observation has led to the concept of carbonic metamorphism, the dry character of granulites being less explained by the absence of water (vapor absent metamorphism) than by the presence of a CO2-rich fluid phase which dilutes the water and lowers considerably its partial pressure. Recent observations have indicated that the situation is much more complicated than initially assumed and that any interpretation must be carefully evaluated and discussed against other, independent evidence. The nature of fluid inclusions and the interpretation of fluid inclusion densities are discussed.

Touret, Jacques L. R.↗
NASA NTRS1989

On the performance of finite journal bearings lubricated with micropolar fluids

A study of the performance parameters for a journal bearing of finite length lubricated with micropolar fluids is undertaken. Results indicate that a significantly higher load carrying capacity than the Newtonian fluids may result depending on the size of material characteristics length and the coupling number. It is also shown that although the frictional force associated with micropolar fluid is, in general, higher than that of a Newtonian fluid, the friction coefficient of micropolar fluids tends to be lower than that of the Newtonian.

Khonsari, M. M.↗
NASA NTRS1990

Fluid Phase Separation (FPS) experiment for flight on a space shuttle Get Away Special (GAS) canister

The separation of fluid phases in microgravity environments is of importance to environmental control and life support systems (ECLSS) and materials processing in space. A successful fluid phase separation experiment will demonstrate a proof of concept for the separation technique and add to the knowledge base of material behavior. The phase separation experiment will contain a premixed fluid which will be exposed to a microgravity environment. After the phase separation of the compound has occurred, small samples of each of the species will be taken for analysis on the Earth. By correlating the time of separation and the temperature history of the fluid, it will be possible to characterize the process. The experiment has been integrated into space available on a manifested Get Away Special (GAS) experiment, CONCAP 2, part of the Consortium for Materials Complex Autonomous Payload (CAP) Program, scheduled for STS-42. The design and the production of a fluid phase separation experiment for rapid implementation at low cost is presented.

Peters, Bruce↗
NASA NTRS1989

Experimental investigation of convective stability in a superposed fluid and porous layer when heated from below

Experiments have been carried out in a horizontal superposed fluid and porous layer contained in a test box 24 cm x 12 cm x 4 cm high. The porous layer consisted of 3 mm diameter glass beads, and the fluids used were water, 60 and 90 percent glycerin-water solutions, and 100 percent glycerin. The depth ratio d, which is the ratio of the thickness of the fluid layer to that of the porous layer, varied from 0 to 1.0. Fluids of increasingly higher viscosity were used for cases with larger d in order to keep the temperature difference across the tank within reasonable limits. The size of the convection cells was inferred from temperature measurements made with embedded thermocouples and from temperature distributions at the top of the layer by use of liquid crystal film. The experimental results showed: (1) a precipitous decrease in the critical Rayleigh number as the depth of the fluid layer was increased from zero, and (2) an eightfold decrease in the critical wavelength between d = 0.1 and 0.2. Both of these results were predicted by the linear stability theory reported earlier (Chen and Chen, 1988).

Chen, Falin↗
NASA NTRS1990

Telerobotic on-orbit remote fluid resupply system

The development of a telerobotic on-orbit fluid resupply demonstration system is described. A fluid transfer demonstration system was developed which functionally simulates operations required to remotely transfer fluids (liquids or gases) from a servicing spacecraft to a receiving spacecraft through the use of telerobotic manipulations. The fluid system is representative of systems used by current or planned spacecraft and propulsion stages requiring on-orbit remote resupply. The system was integrated with an existing MSFC remotely controlled manipulator arm to mate/demate couplings for demonstration and evaluation of a complete remotely operated fluid transfer system.

Source record↗
NASA NTRS1991

Transcapillary fluid shifts in head and neck tissues during and after simulated microgravity

To understand the mechanism, magnitude, and time course of facial puffiness that occurs in microgravity, seven male subjects were tilted 6 degrees head down for 8 hr, and all four Starling transcapillary pressures were directly measured before, during, and after tilt. Head-down tilt (HDT) caused facial edema and a significant elevation of microvascular pressures measured in the lower lip: capillary pressures increased from 27.2 +/- 5 mm Hg pre-HDT to 33.9 +/- 1.7 mm Hg by the end of tilt. Subcutaneous and intramuscular interstitial fluid pressures in the neck also increased as a result of HDT, while interstitial fluid colloid osmotic pressures remained unchanged. Plasma colloid osmotic pressures dropped significantly after 4 hr of HDT, suggesting a transition from fluid filtration to absorption in capillary beds between the heart and feet during HDT. After 4 hr of seated recovery from HDT, microvascular pressures remained significantly elevated by 5 to 8 mm Hg above baseline values, despite a significant HDT diuresis and the orthostatic challenge of an upright, seated posture. During the control (baseline) period, urine output was 46.7 ml/hr; during HDT, it was 126.5 ml/hr. These results indicate that facial edema resulting from HDT is primarily caused by elevated capillary pressures and decreased plasma colloid osmotic pressures. Elevation of cephalic capillary pressures sustained for 4 hr after HDT suggests that there is a compensatory vasodilation to maintain microvascular perfusion. The negativity of interstitial fluid pressures above heart level also has implications for the maintenance of tissue fluid balance in upright posture.

Parazynski, S. E.↗
NASA NTRS1990

Creeping flow of a conducting fluid past axisymmetric bodies in the presence of an aligned magnetic field

The use of strong magnetic fields for the control of particle settling in metallic systems is investigated by altering the fluid mechanics in the melt. The fluid mechanism of particle settling is analyzed for the motion around single, axisymmetric particles in the limit of creeping flow for a fluid with a large electrical conductivity. The drag is found to increase proportionately to the intensity of the magnetic field or the Hartmann number Ha. The flowfield forms boundary layers, which thin out with increasing Ha, along the surfaces parallel to the flow. For axisymmetric bodies, the boundary layer separates as the poles of the surface are approached and encloses regions of almost stagnant fluid. These regions spread upstream and downstream along the body with increasing Ha, thereby trapping the particle in a column of stagnant fluid.

Kyrlidis, A.↗
NASA NTRS1991

The equations of nearly incompressible fluids. I - Hydrodynamics, turbulence, and waves

An attempt is made to develop a more general theory of nearly incompressible fluids that can then be applied to many different fields. A perturbation expansion is developed for the fully compressible fluid equations which, in the limit of low Mach number (sound or Alfvenic Mach number), reduce to the appropriate incompressible fluid equations. The method developed derives modified systems of fluid equations in which the compressibility effects are admitted only weakly in terms of the incompressible hydrodynamic solutions ('nearly incompressible hydrodynamics'). Molecular viscosity is included self-consistently, and the role of thermal conduction in an ideal fluid is also considered. With heat conduction included, two distinct routes to incompressibility are found to be possible, distinguished according to the relative magnitudes of the temperature, density, and pressure fluctuations.

Zank, G. P.↗
NASA NTRS1992

Near-critical point phenomena in fluids (19-IML-1)

Understanding the effects of gravity is essential if the behavior of fluids is to be predicted in spacecraft and orbital stations, and, more generally, to give a better understanding of the hydrodynamics in these systems. An understanding is sought of the behavior of fluids in space. What should emerge from the International Microgravity Lab (IML-1) mission is a better understanding of the kinetics of growth in off-critical conditions, in both liquid mixtures and pure fluids. This complex phenomenon is the object of intensive study in physics and materials sciences area. It is also expected that the IML-1 flight will procure key results to provide a better understanding of how a pure fluid can be homogenized without gravity induced convections, and to what extent the 'Piston Effect' is effective in thermalizing the compressible fluids.

Beysens, D.↗
NASA NTRS1992

Spacecraft dynamical distribution of fluid stresses activated by gravity-jitter-induced slosh waves

The dynamical behavior of fluids, in particular the effect of surface tension on partially filled rotating fluids (cryogenic liquid helium and helium vapor) in a full-scale Gravity Probe-B Spacecraft propellant Dewar tank imposed by various frequencies of gravity jitters, has been investigated. Fluid stress distribution, caused by the excitation of slosh waves and their associated large-amplitude disturbances on the liquid-vapor interface, exerted on the outer and inner walls of a rotating Dewar container also has been investigated. Results show that fluid stress distributions near the outer and inner walls of the rotating Dewar are closely related to the characteristics of slosh waves excited on the liquid-vapor interface in the rotating Dewar tank. This can provide a useful tool for managing spacecraft dynamic control leading toward the control of spacecraft imbalance caused by the uneven fluid stress distribution due to slosh wave excitations at the interface between liquid and vapor propellants.

Hung, R. J.↗
NASA NTRS1992

Fluid outflows from Venus impact craters - Analysis from Magellan data

Many impact craters on Venus have unusual outflow features originating in or under the continuous ejecta blankets and continuing downhill into the surrounding terrain. These features clearly resulted from flow of low-viscosity fluids, but the identity of those fluids is not clear. In particular, it should not be assumed a priori that the fluid is an impact melt. A number of candidate processes by which impact events might generate the observed features are considered, and predictions are made concerning the rheological character of flows produce by each mechanism. A sample of outflows was analyzed using Magellan images and a model of unconstrained Bingham plastic flow on inclined planes, leading to estimates of viscosity and yield strength for the flow materials. It is argued that at least two different mechanisms have produced outflows on Venus: an erosive, channel-forming process and a depositional process. The erosive fluid is probably an impact melt, but the depositional fluid may consist of fluidized solid debris, vaporized material, and/or melt.

Asimow, Paul D.↗
NASA NTRS1992

Gravity jitter induced slosh waves in liquid propellant and disturbances of fluid stresses on spacecraft

The paper investigates the dynamical behavior of fluids, in particular the effect of surface tension on partially filled rotating fluids (cryogenic liquid helium and helium vapor) in a full-scale Gravity Probe-B spacecraft propellant dewar tank imposed by various frequencies of gravity jitters. Fluid stress distribution caused by the excitation of slosh waves and their associated large amplitude disturbances on the liquid-vapor interface and exerted on the outer and inner walls of a rotating dewar container are also examined. It is shown that fluid stress distributions near the outer and inner walls of the rotating dewar are closely related to the characteristics of slosh waves excited in the liquid-vapor interface in the rotating dewar tank. This can be of utility in managing spacecraft dynamic control leading to control of spacecraft imbalance caused by the uneven fluid stress distribution due to slosh wave excitations at the interface between liquid and vapor propellants.

Hung, R. J.↗
NASA NTRS1988

The development of new, low-cost perfluoroalkylether fluids with excellent low and high-temperature properties

A series of perfluoroalkylether (PFAE) fluids were synthesized by direct fluorination. Viscosity-temperature properties, oxidation stabilities, oxidation-corrosion properties, and lubricity were determined. The fluids were tested in the presence of common elastomers to check for compatibility. The bulk modulus of each was measured to determine if any could be used as nonflammable aircraft hydraulic fluid. It was determined that as the carbon to oxygen ratio decreases, the viscometric properties improve, the fluids may become poor lubricants, the bulk modulus increases, the surface tension increases, and the fluid density increases. The presence of difluoromethylene oxide units in the polymer does not seriously lower the oxidation and oxidation-corrosion stabilities as long as the difluoromethylene oxide units are separated by other units.

Bierschenk, Thomas R.↗
NASA NTRS1992

Microgravity fluid physics research in the Space Station Freedom era

Microgravity fluid physics covers an exciting range of established and potential fields of scientific research. Areas in which the Microgravity Science and Applications Division of NASA's Office of Space Science and Applications is currently supporting research include: multiphase flow and phase change heat transfer, behavior of granular media and colloids; and interface dynamics, morphological stability, and contact line phenomena. As they contribute to our knowledge of fluid behavior, advances in these areas will enhance our understanding of materials processing on Earth and in space, and will contribute to technologies as diverse as chemical extraction, the prediction of soil behavior in earthquakes, and the production of oil reservoirs. NASA' s primary platform for research in microgravity fluid physics will soon be the Fluid Physics/Dynamics Facility on Space Station Freedom. This facility shares a rack for control and utilities with the Modular Combustion Facility, and has one rack for experiment-unique instruments. It is planned to change out the content of the experiment-unique rack at intervals on the order of one year. In order to obtain a maximum return on the operation of the facility during these intervals, the research community must carefully plan and coordinate an effort that brings the efforts of many investigators to bear on problems of particular importance. NASA is currently working with the community to identify research areas in which microgravity can make a unique and valuable contribution, and to build a balanced program of research around these areas or thrusts. Selections will soon be made from our first solicitation for research in fluid dynamics and transport phenomena. These solicitations will build the research community that will make Space Station Freedom a catalyst for scientific and technological discovery, and offer U.S. scientists in many disciplines a unique opportunity to participate in space science.

Carpenter, Bradley M.↗
NASA NTRS1993

Effect of fluid compressibility on journal bearing performance

An analysis was undertaken to determine the effect of fluid film compressibility on the performance of fluid film bearings. A new version of the Reynolds equation was developed, using a polytropic expansion, for both steady-state and dynamic conditions. Polytropic exponents from 1 (isothermal) to 1000 (approaching an incompressible liquid) were evaluated for two bearing numbers, selected from a range of practical interest for cryogenic application, and without cavitation. Bearing loads were insensitive to fluid compressibility for low bearing numbers, as was expected. The effect of compressibility on attitude angle was significant, even when the bearing number was low. A small amount of fluid compressibility was enough to obtain stable running conditions. Incompressible liquid lacked stability at all conditions. Fluid compressibility can be used to control the bearing dynamic coefficients, thereby influencing the dynamic behavior of the rotor-bearing system.

Dimofte, Florin↗