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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.

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At least 937 records · Page 52

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NASA NTRS1971

A numerical solution of the Navier-Stokes equations for supercritical fluid thermodynamic analysis

An explicit numerical solution of the compressible Navier-Stokes equations is applied to the thermodynamic analysis of supercritical oxygen in the Apollo cryogenic storage system. The wave character is retained in the conservation equations which are written in the basic fluid variables for a two-dimensional Cartesian coordinate system. Control-volume cells are employed to simplify imposition of boundary conditions and to ensure strict observance of local and global conservation principles. Non-linear real-gas thermodynamic properties responsible for the pressure collapse phenomonon in supercritical fluids are represented by tabular and empirical functions relating pressure and temperature to density and internal energy. Wall boundary conditions are adjusted at one cell face to emit a prescribed mass flowrate. Scaling principles are invoked to achieve acceptable computer execution times for very low Mach number convection problems. Detailed simulations of thermal stratification and fluid mixing occurring under low acceleration in the Apollo 12 supercritical oxygen tank are presented which model the pressure decay associated with de-stratification induced by an ordinary vehicle maneuver and heater cycle operation.

Heinmiller, P. J.↗

NASA NTRS1973

Self-cycling fluid heater

A self-cycling fluid heater is described which includes a high temperature upstream preheater for elevating the stream temperature. A high intensity jet arc heater heats the preheated fluid stream to ultrahigh reaction temperatures and discharges the stream into an electric resistance tubular heat exchanger. The heat exchanger has variations in wall thickness at measured intervals along its length to control the temperature of the fluid passing through the heat exchanger for desired time intervals to provide the specified chemical reactions desired.

Moen, W. K.↗

NASA NTRS1973

Foot pedal operated fluid type exercising device

A foot pedal operated exercising device is reported that contains a dynamometer formed of a pair of cylinders each containing a piston. The pistons are linked to each other. The upper portions of the two cylinders are joined together by a common opening to provide a common fluid reservoir and each piston is provided with a one way check valve to maintain an adequate supply of working fluid. Fluid from the driven cylinder is transmitted to the other cylinder through separate constant force spring biased valves each valve takes the predominant portion of the pressure drop thereby providing a constant force hydraulic dynamometer. A device is provided to determine the amount of movement of piston travel.

Crum, G. W.↗

NASA NTRS1974

Fluid dynamic studies on scattering aerosol and its generation for application as tracer particles in supersonic flow measurements utilizing laser Doppler velocimeter

An experimental study on the particle-fluid interactions of scattering aerosols was performed using monodisperse aerosols of different particle sizes for the application of laser Doppler velocimeters in subsonic turbulence measurements. Particle response was measured by subjecting the particles to an acoustically excited oscillatory fluid velocity field and by comparing the ratio of particle velocity amplitude to the fluid velocity amplitude as a function of particle size and the frequency of oscillation. Particle velocity was measured by using a differential laser Doppler velocimeter. The test aerosols were fairly monodisperse with a mean diameter that could be controlled over the size range from 0.1 to 1.0 micron. Experimental results on the generation of a fairly monodisperse aerosol of solid particles and liquid droplets and on the aerosol response in the frequency range 100 Hz to 100 kHz are presented. It is indicated that a unit density spherical scatterer of 0.3 micron-diameter would be an optimum choice as tracer particles for subsonic air turbulence measurements.

Mazumder, M. K.↗

NASA NTRS1973

Critique of fluid theory of magnetospheric phenomena

It is pointed out that the fluid theory has been successful in magnetospheric problems (such as the shape of the magnetopause) which involve basic considerations such as the conservation of particles, of momentum, and of energy, but that it is inadequate for other problems (such as the energization of auroral particles). Difficulties arise from the fact that it is not always possible to specify 'a volume of plasma' because particles do not remain as neighbors. Misuse of the fluid theory has led to a number of fallacies, such as the idea that the causal order of physical events in cosmic electrodynamics is the reverse of that in the familiar laboratory electrodynamics. This mistaken idea comes from a confusion of a mathematical sequence of calculations with the causal order. A plea is made for a common sense approach to magnetospheric and auroral problems wherein the fluid theory is used whenever it can, but where it is not expected to be adequate for all occasions.

Heikkila, W. J.↗

NASA NTRS1974

Normalizing parameters for the critical flow rate of simple fluids through nozzles

It is shown that two-phase critical nozzle flow of simple fluids almost obeys the principle of corresponding states. Quantum fluid departures from the principle are resolved as a function of temperature for para-hydrogen and helium. The critical flow rates are normalized, using a normalizing parameter for which the critical flow rates of all simple fluids reduce to a single isothermal curve. The expression obtained for the normalizing parameter is shown to provide good agreement with the experiment for the critical flow rates of nitrogen, oxygen, and para-hydrogen.

Hendricks, R. C.↗

NASA NTRS1975

Analysis of Skylab fluid mechanics science demonstrations

The results of the data reduction and analysis of the Skylab fluid mechanics demonstrations are presented. All the fluid mechanics data available from the Skylab missions were identified and surveyed. The significant fluid mechanics phenomena were identified and reduced to measurable quantities wherever possible. Data correlations were performed using existing theories. Among the phenomena analyzed were: static low-g interface shapes, oscillation frequency and damping of a liquid drop, coalescence, rotating drop, liquid films and low-g ice melting. A survey of the possible applications of the results was made and future experiments are recommended.

Tegart, J. R.↗

NASA NTRS1975

Fluid manifold design for a solar energy storage tank

A design technique for a fluid manifold for use in a solar energy storage tank is given. This analytical treatment generalizes the fluid equations pertinent to manifold design, giving manifold pressures, velocities, and orifice pressure differentials in terms of appropriate fluid and manifold geometry parameters. Experimental results used to corroborate analytical predictions are presented. These data indicate that variations in discharge coefficients due to variations in orifices can cause deviations between analytical predictions and actual performance values.

Humphries, W. R.↗

NASA NTRS1974

Canonical fluid thermodynamics

The space-time integral of the thermodynamic pressure plays in a certain sense the role of the thermodynamic potential for compressible adiabatic flow. The stability criterion can be converted into a variational minimum principle by requiring the molar free-enthalpy and temperature to be generalized velocities. In the fluid context, the definition of proper-time differentiation involves the fluid velocity expressed in terms of three particle identity parameters. The pressure function is then converted into a functional which is the Lagrangian density of the variational principle. Being also a minimum principle, the variational principle provides a means for comparing the relative stability of different flows. For boundary conditions with a high degree of symmetry, as in the case of a uniformly expanding spherical gas box, the most stable flow is a rectilinear flow for which the world-trajectory of each particle is a straight line. Since the behavior of the interior of a freely expanding cosmic cloud may be expected to be similar to that of the fluid in the spherical box of gas, this suggests that the cosmic principle is a consequence of the laws of thermodynamics, rather than just an ad hoc postulate.

Schmid, L. A.↗

NASA NTRS1975

The structure and evolution of Jupiter - The fluid contraction stage

The complete evolution of a contracting star of Jovian mass consisting of a convective adiabatic homogeneous fluid is determined using stellar structure methods, improved model atmosphere calculations, and substantially improved thermodynamic properties for hydrogen and hydrogen-helium fluids. The model atmospheres are calculated in the form of time-averaged vertical temperature structures, including all relevant sources of opacity and a solar energy deposition component, and the thermodynamic properties are modified to obtain better agreement with Monte Carlo results for metallic fluids. The resultant gravitationally contracting evolutionary models are found to have two phases: an early stellar phase similar to a typical low-mass pre-main-sequence body and a later phase constituting an approach to a degenerate-dwarf cooling curve. The first phase is shown to have high luminosities and internal temperatures, while the second gives excellent agreement with the observed radius and luminosity of Jupiter. Analysis indicates that the equation of state and superadiabaticity have the strongest influence on evolution over planetary time scales.

Graboske, H. C., Jr.↗

NASA NTRS1976

Rolling-element fatigue life with two synthetic cycloaliphatic traction fluids

The life potential of two synthetic cycloaliphatic hydrocarbon traction fluids in rolling element fatigue was evaluated in a five ball fatigue tester. Life comparisons with a MIL-L-23699 qualified tetraester oil showed that the traction test oils had good fatigue life performance, comparable to that of the tetraester oil. No statistically significant life differences between the traction fluids and the tetraester oil were exhibited under the accelerated fatigue test conditions. Erratic operating behavior was occasionally encountered during tests with the antiwear additive containing traction fluid for reasons thought to be related to excessive chemical activity under high contact pressure. This behavior occasionally resulted in premature test termination due to excessive surface distress and overheating.

Loewenthal, S. H.↗

NASA NTRS1976

Fundamentals of fluid sealing

The fundamentals of fluid sealing, including seal operating regimes, are discussed and the general fluid-flow equations for fluid sealing are developed. Seal performance parameters such as leakage and power loss are presented. Included in the discussion are the effects of geometry, surface deformations, rotation, and both laminar and turbulent flows. The concept of pressure balancing is presented, as are differences between liquid and gas sealing. Mechanisms of seal surface separation, fundamental friction and wear concepts applicable to seals, seal materials, and pressure-velocity (PV) criteria are discussed.

Zuk, J.↗

NASA NTRS1976

The interaction between a solid body and viscous fluid by marker-and-cell method

A computational method for solving nonlinear problems relating to impact and penetration of a rigid body into a fluid type medium is presented. The numerical techniques, based on the Marker-and-Cell method, gives the pressure and velocity of the flow field. An important feature in this method is that the force and displacement of the rigid body interacting with the fluid during the impact and sinking phases are evaluated from the boundary stresses imposed by the fluid on the rigid body. A sample problem of low velocity penetration of a rigid block into still water is solved by this method. The computed time histories of the acceleration, pressure, and displacement of the block show food agreement with experimental measurements. A sample problem of high velocity impact of a rigid block into soft clay is also presented.

Cheng, R. Y. K.↗

NASA NTRS1976

Fluid handling equipment: A compilation

Devices and techniques used in fluid-handling and vacuum systems are described. Section 1 presents several articles on fluid lines and tubing. Section 2 describes a number of components such as valves, filters, and regulators. The last section contains descriptions of a number of innovative fluid-handling systems.

Source record↗

NASA NTRS1976

Noise produced by fluid inhomogeneities

In an actual engine system, one mechanism for production of hot spots is the burning of various fluid elements at various different mixture ratios. Variable mixture ratio means variable temperature, and this is the effect that has been studied insofar as a noise source is concerned. However, variable mixture ratio also implies variable molecular weight and heat capacity. The paper investigates whether either of these last two variations may be responsible for a significant noise source. The analysis is made within the context of one-dimensional unsteady flow as in the work of Candel (1972). A mixture of thermally perfect gases is assumed as the working fluid, and the fluid composition consists of species 1 and a small and variable mole fraction of species 2 which has different molecular weight and specific heats as compared with species 1. In the absence of changes in the ratio of specific heat (gamma), the entropy variations due to temperature and molecular weight variations are equivalent as a sound source. The portion of sound called 'gamma prime' noise is discussed.

Strahle, W. C.↗

NASA NTRS1976

Stability of a viscous fluid in a rectangular cavity in the presence of a magnetic field

The stability of an electrically conducting fluid subjected to two dimensional disturbance was investigated. A physical system consisting of two parallel infinite vertical plates which are thermally insulated was studied. An external magnetic field of constant strength was applied to normal plates. The fluid was heated from below so that a steady temperature gradient was maintained in the fluid. The governing equations were derived by perturbation technique, and solutions were obtained by a modified Galerkin method. It was found that the presence of the magnetic field increases the stability of the physical system and instability can occur in the form of neutral or oscillatory instability.

Liang, C. Y.↗

NASA NTRS1977

System for measuring three fluctuating velocity components in a turbulently flowing fluid

A system is described for measuring fluid velocity in a turbulently flowing fluid including a sensing apparatus for dynamically sensing the mainstream and two orthogonal cross velocity components of the fluid. A transducer operative is included to provide three electrical output signals representative of the velocity components in the mainstream, and in the cross directions. Signal processors can be utilized to derive the Reynolds stress wave and the Reynolds stress.

Cheng, D. Y.↗

NASA NTRS1977

Convection of viscous fluids: Energetics, self-similarity, experiments, geophysical applications and analogies

The main results were the formulas for the mean convection velocities, of a viscous fluid and for the mean temperature difference in the bulk of the convecting fluid. These were obtained: by scaling analysis of the Boussinesq equations, by analysis of the energetics of the process, and by using similarity and dimensional arguments. The last approach defines the criteria of similarity and allows the proposition of some self-similarity hypotheses. By several simple new ways, an expression for the efficiency coefficient gamma of the thermal convection was also obtained. An analogy is pointed out between non-turbulent convection of a viscous fluid and the structure of turbulence for scales less than Kolmogorov's internal viscous microscale of turbulence.

Golitsyn, G. S.↗