Search NASA⌕ Search

SEARCH · Search NASA

Results for “consequence”

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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The hydrodynamics of magnetic nonequilibrium

Because the dynamical nonequilibrium of closely packed twisted flux tubes is essentially the problem of two-dimensional MHD turbulence, the extensive literature on two-dimensional turbulence represents the hydrodynamics of magnetic nonequilibrium. Many features of the turbulence can conversely be understood as a consequence of the dynamical nonequilibrium. Attention is presently given to the dynamics of the strong fluid jets, issuing from reconnection points, that are exhibited by numerical simulations of two-dimensional turbulence. Simple examples are given which show that the uniformity of jet width observed is a consequence of the form of the pressure of the magnetic fields between which the jets are confined. The general hydrodynamics of a layer of fluid confined by steady pressures is reducible to a quadrature, so that a variety of effects may be considered, including gravitation. The dissipation of the solar corona is discussed.

Parker, E. N.↗
NASA NTRS1983

Design procedures for compressor blades

The conventional methods for the design of the blades in the case of axial turbomachines are considered, taking into account difficulties concerning the determination of optimal blade profiles. These difficulties have been partly overcome as a consequence of the introduction of new numerical methods during the last few years. It is pointed out that, in the case of the subsonic range, a new procedure is now available for the determination of the form of blade profile on the basis of a given velocity distribution on the profile surface. The search for a profile form with favorable characteristics is consequently transformed into a search for a favorable velocity or pressure distribution on the blade. The distribution of velocities depends to a large degree on the characteristics of the profile boundary layers. The considered concept is not new. However, its practical implementation has only recently become possible. The employment of the new design procedure is illustrated with the aid of an example involving a concrete design problem.

Starken, H.↗
NASA NTRS1984

CAD/CAM and scientific data management at Dassault

The history of CAD/CAM and scientific data management at Dassault are presented. Emphasis is put on the targets of the now commercially available software CATIA. The links with scientific computations such as aerodynamics and structural analysis are presented. Comments are made on the principles followed within the company. The consequences of the approximative nature of scientific data are examined. Consequence of the new history function is mainly its protection against copy or alteration. Future plans at Dassault for scientific data appear to be in opposite directions compared to some general tendencies.

Bohn, P.↗
NASA NTRS1983

Meteorological and dynamical requirements for MST radar networks: Waves

Studies of wave motions using the MST radar have concentrated on single station time series analyses of gravity waves and tides. Since these radars collect high time resolution data they have the potential to become a significant tool for mesoscale research. In addition, radars are operated almost continuously unattended and, consequently, data sets are available for analyzing longer period wave motions such as tides and planetary scale waves. Although there is much to learn from single station data, the possibilities of new knowledge from a network of radars is exciting. The scales of wave motions in the atmosphere cover a broad range. Consequently the choice of a radar network depends to a large extent on the types of wave motions that are studied. There are many outstanding research problems that would benefit from observations from a MST radar network. In particular, there is a strong need for measurements of gravity wave parameters and equatorial wave motions. Some of the current problems in wave dynamics are discussed.

Avery, S. K.↗
NASA NTRS1984

Models of Rapid Solidification

Laser annealing studies provide much information on various consequences of rapid solidification, including the trapping of impurities in the crystal, the generation of vacancies and twins, and on the fundamental limits to the speed of the crystal-melt interface. Some results obtained by molecular dynamics methods of the solidification of a Lennard-Jones liquid are reviewed. An indication of the relationship of interface speed to undercooling for certain materials can be derived from this model. Ising model simulations of impurity trapping in silicon are compared with some of the laser annealing results. The consequences of interface segregation and atomic strain are discussed.

Gilmer, G. H.↗
NASA NTRS1983

Luminosity correlations in quasars

Simulations are conducted with and without flux thresholds in an investigation of quasar luminosity correlations by means of a Monte Carlo analysis, for various model distributions of quasars in X-rays and optical luminosity. For the case where the X-ray photons are primary, an anticorrelation between X-ray-to-optical luminosity ratio and optical luminosity arises as a natural consequence which resembles observations. The low optical luminosities of X-ray selected quasars can be understood as a consequence of the same effect, and similar conclusions may hold if the X-ray and optical luminosities are determined independently by a third parameter, although they do not hold if the optical photons are primary. The importance of such considerations is demonstrated through a reanalysis of the published X-ray-to-optical flux ratios for the 3CR sample.

Chanan, G. A.↗
NASA NTRS1984

The effects of gusts on the fluctuating airloads of airfoils in transonic flow

Unsteady interactions of distributed and sharp-edged gusts with a stationary airfoil have been analyzed in two-dimensional transonic flow.A simple method of introducing such disturbances has been numerically implemented within the framework of unsteady, transonic small-disturbance theory. Representative solutions for various airfoils subjected to chordwise and transverse gusts show that the strength and unsteady motion of the shock wave on the airfoil significantly affect the flowfield development and, consequently, the dynamic airloads. Also a study was made of the reductions in the unsteady airloads that can be achieved by the proper active control motion of a trailing-edge flap, and a simple gust-alleviation strategy was developed. However, the chordwise pressure distributions associated with gusts are very different from those produced by trailing-edge flap oscillations. Consequently, the fluctuating lift and the unsteady pitching moments cannot both be eliminated simultaneously.

Mccroskey, W. J.↗
NASA NTRS1984

Properties of the Upper Tropospheres of Uranus and Neptune Derived from Observations at Visible to Near-Infrared Wavelengths

Photons at wavelengths between 0.3 and 4.5 microns penetrate the atmospheres of Uranus and Neptune to pressures between about 0.01 bar and 10 bars. This pressure range brackets the radiative convective boundary in both atmospheres and is therefore designated upper troposphere. Physical processes which govern the transfer of radiation in Uranus's and Neptune's atmospheres at these wavelengths include Rayleigh/Raman scattering by hydrogen, scattering and broadband absorption by suspended aerosol particles and absorption in discrete bands and lines by methane and hydrogen. Consequently, tropospheric properties constrained by observations at these wavelengths include optical properties and distribution of aerosol particles, methane/hydrogen ratio, and ortho/para hydrogen ratio. Recent observations of Uranus and Neptune in this spectral range, are reviewed and compared with predictions based on models of the atmospheric structures. Significant results for Uranus include the presence of an opaque lower boundary to the visible atmosphere very near the level corresponding to 2 bars pressure, and consequently a methane/hydrogen ratio no less than 3 percent.

Bergstralh, J. T.↗
NASA NTRS1984

Cosmic ray propagation in the local superbubble

It is suggested that a ring of HI gas lying in the galactic plane is part of a supershell which formed some 3 x to the 7th power years ago. The consequences of a closed magnetic supershell for cosmic ray propagation are examined and it is concluded that there is no evidence which precludes the production and trapping of cosmic rays in such a region. A consequence of superbubble confinement is that the mean age of cosmic rays would be independent of energy. This can be tested by high energy observations of the isotopic composition of Be.

Steitmatter, R. E.↗
NASA NTRS1985

Galileo internal electrostatic discharge program

The Galileo spacecraft which will orbit Jupiter in 1988 will encounter a very harsh environment of energetic electrons. These electrons will have sufficient energy to penetrate the spacecraft shielding, consequently depositing charges in the dielectric insulating materials or ungrounded conductors. The resulting electric field could exceed the breakdown strength of the insulating materials, producing discharges. The transients produced from these Internal Electrostatic Discharges (IESD) could, depending on their relative location, be coupled to nearby cables and circuits. These transients could change the state of logic circuits or degrade or even damage spacecraft components, consequently disrupting the operation of subsystems and systems of the Galileo spacecraft during its expected mission life. An extensive testing program was initiated for the purpose of understanding the potential threats associated with these IESD events. Data obtained from these tests were used to define design guidelines.

Leung, P. L.↗
NASA NTRS1985

Gravity Reception and Cardiac Function in the Spider

The following features of the arachnid gravity system were studied. (1) the absolute threshold to hyper-gz is quite low indicating fine proprioreceptive properties of the lyriform organ, the Gz/vibration detector; (2) the neurogenic heart of the spider is a good dependent variable for assessing its behavior to Gz and other stimuli which produce mechanical effects on the exoskeleton; (3) Not only is the cardiac response useful but it is now understood to be an integral part of the system which compensates for the consequences of gravity in the spider (an hydraulic leg extension); and (4) a theoretical model was proposed in which a mechanical amplifier, the leg lever, converts a weak force (at the tarsus) to a strong force (at the patella), capable of compressing the exoskeleton and consequently the lyriform receptor.

Finck, A.↗
NASA NTRS1985

Cosmic ray propagation in the local superbubble

It is suggested that a ring of HI gas lying in the galactic plane is part of a supershell which formed some 3 x 10 to the 7th power years ago. The consequences of a closed magnetic supershell for cosmic ray propagation are examined and it is concluded that there is no evidence which precludes the production and trapping of cosmic rays in such a region. A consequence of superbubble confinement is that the mean age of cosmic rays would be independent of energy. This can be tested by high energy observations of the isotopic composition of Be.

Streitmatter, R. E.↗
NASA NTRS1986

Supernova nucleosynthesis in low-metallicity populations

The mass loss rate in low-metallicity stars is discussed, and the consequences of that rate for the fate of such stars are considered. It is shown that, if radiation pressure on dust is important in driving the mass loss from red giants, and if these stars do not dredge up large amounts of processed material during their evolution, then the total amount of mass lost by Population II stars with low metallicity is small. Consequently, the rate of supernovae in populations of low metallicity is much higher than in populations of solar abundances. This conclusion leads to the prediction that the supernova rate should be high in galaxies that have some intermediate mass stars and have metallicity less than about 0.1 of the solar value.

Jura, M.↗
NASA NTRS1986

Heat transport in steep temperature gradients. I - Small flaring solar loops

Results on nonlocal heat transport which properly takes into account the presence of fast electrons with mean free paths much longer than the temperature scale height L are reviewed. In terms of the mean free path for the slow bulk electrons, lambda(s), the nonlocal effects are important whenever lambda(s)/L greater than 0.001, with the following consequences. The heat flux in the hot part of the gradient is reduced relative to the Spitzer-Haerm value q(SH) which does not take into account the heat carried away by the fast electrons. The heat flux in the cold part of the gradient is enhanced relative to the value q(SH) which does not take into account the heat deposited by the fast electrons. These quite general results, which should have several applications in astrophysics, are applied to the problem of thermal hard X-ray burst models. It is shown that heat is not bottled up as effectively as in some past models, and temperatures achieved for realistic energy input rates are consequently not as high. As a result such sources can be effective only in the soft part (10-30 keV) of the hard X-ray range for energy input rates up to 6,400 ergs/cu cm s. The analysis is based on a fluid model and does not consider the X-ray signature of fast electrons which escape to distances far beyond the conduction fronts formed. It is shown that such electrons could at most be effective in the soft part of the hard X-ray range.

Smith, D. F.↗
NASA NTRS1986

The tail lobe ion spectrometer

A two-dimensional kinetic 'tail lobe ion spectrometer' model for the transport of ionospheric ions from polar cleft ionosphere into the tail lobes is developed to semiquantitatively simulate the behavior of the observed O(+) ion streams in the magnetotail lobes. The consequences of the present model include: (1) the increase in velocity of the O(+) streams away from the tail midplane; (2) the existence of 'tongues' of O(+) density from the cleft ionosphere into the tail lobes whose distribution configuration depends on the convection electric field and the source thermal energies; and (3) very low parallel thermal energies and speeds in the lobes which are correlated with the parallel ion bulk velocities. These consequences are reasonably consistent with the trends in lobe streams observed by recent spacecraft.

Horwitz, J. L.↗
NASA NTRS1986

Geometrization of spin and the Weyssenhoff fluid conjecture

It is shown that the logical treatment of spinning perfect fluids occurs in a metric-torsion space-time with or without mass conservation. The Lagrangian formulation of a spin density fluid is reviewed, concentrating on the relationship between spin and torsion for metric-torsion space-times. The significance of the mass constraint is discussed, and its consequences for the variation of the Lagrangian is given. That consequence is the geometrization of spin; that is, the Weyssenhoff form relating spin and the trace-free torsion is obtained without any ad hoc assumption.

Smalley, L. L.↗
NASA NTRS1986

Use of the Sun to determine pointing of ST radar beams

Verification of the beam pointing direction for ST (stratosphere troposphere) radars is a technically difficult problem. Consequently it is not usually done. For measurement of horizontal wind, the lack of precise knowledge of the beam pointing direction is usually of little consequence as any errors cause only a small uncertainty in the measured velocity. However, instantaneous vertical velocities are typically more than an order of magnitude less than horizontal velocities and average vertical velocities are more than two orders of magnitude less than average horizontal velocities. Hence small pointing errors for vertical beams can result in large errors due to contamination by horizontal winds. Experimental confirmation of pointing accuracy using the measured winds is difficult but has been achieved where horizontal and vertical winds are measured at the same site. Using the techniques described by Balsley and Riddle, 1984 and Riddle and Balsley, 1985, pointing accuracy was measured at Ponape, Federated States of Micronesia. The experiment is described in detail.

Riddle, A. C.↗
NASA NTRS1988

Turbulence modeling in non-inertial frames of reference

The effect of an arbitrary change of frame on the structure of turbulence models is examined from a fundamental theoretical standpoint. It is proven, as a rigorous consequence of the Navier-Stokes equations, that turbulence models must be form invariant under arbitrary translational accelerations of the reference frame and should only be affected by rotations through the intrinsic mean vorticity. A direct application of the invariance property along with the Taylor-Proudman Theorem, material frame-indifference in the limit of two-dimensional turbulence and Rapid Distortion Theory is shown to yield powerful constraints on the allowable form of turbulence models. Most of the commonly used turbulence models are demonstrated to be in serious violation of these constraints and consequently are inconsistent with the Navier-Stokes equations in non-inertial frames. Alternative models with improved non-inertial properties are developed and some simple applications to rotating turbulent flows are considered.

Speziale, Charles G.↗