Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “two-component dynamics”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Dynamical modeling of a planetary wave mechanism for a Martian polar warming

The mechanisms involved in the global dust storm and polar warming seen in the Martian atmosphere by the Viking IRTM during the winter solstice of 1977 are investigated theoretically by means of numerical simulations. A two-component dynamical model (based on the combined action of a zonally symmetric 'Hadley' circulation at low and middle latitudes and a planetary-wave circulation at middle and high latitudes) is constructed by analogy to the model of Holton and Mass (1976) for terrestrial sudden stratospheric warmings. The Viking data and simulation results are presented in extensive graphs and characterized in detail. It is demonstrated that a planetary-wave mechanism, based primarily on wavenumber 1 and including a high degree of topographical or thermal wave forcing, can reproduce the observed polar warming. The roles of radiative damping, dissipation, and the transport of dust and water are explored.

Barnes, Jeffrey R.↗
NASA NTRS1986

Star-gas density waves in spiral galaxies

The steady state dynamics of spiral galaxies is analyzed as a two-component system consisting of stars and gas within the framework of the WKB density wave theory. The gravitational influence of the gas is included for the first time in a steady state calculation. The full set of equations for a star-gas galaxy is presented, and the equations are analyzed for small-amplitude forcing. Wave properties near the solar circle are examined, and it is found that the large-scale gas shock disappears for gas content above 8 percent. Instead, gas density profiles change to highly symmetric shapes as a result of the action of the gas self-gravity. The stellar wave is damped by the torque exerted by the gas.

Lubow, Stephen H.↗
NASA NTRS1990

Spray characterization and turbulence properties in an isothermal spray with swirl

In the present experimental study of the effects of swirl on the dynamic behavior of drops and on the velocity and turbulence fields of an isothermal spray, using a two-component phase Doppler particle analyzer, mean velocity and turbulence properties were obtained for the gas phase. Large differences are noted in the spatial distribution of the drops over the spray's size, velocity, and number density, when the spray in coflowing air is compared with the atomizer spraying into the swirling flow field with the same axial velocity. The turbulence properties of the swirling flow exhibit significant influence on the dynamic behavior of the drops.

Brena De La Rosa, A.↗
NASA NTRS1967

Dynamical friction.

Chandrasekhar dynamical friction theory for star in cluster adapted to Fokker-Plank electron in two-component plasma theory and including multiple encounters

STAR CLUSTER↗
NASA NTRS1986

Dynamic moduli and localized damage in composites

The scatter of elastic waves due to a thin, flat ellipsoidal inhomogeneity, either penny shaped or elliptical is discussed. An average theorem appropriate for dynamic effective mass density and effective moduli was developed via a self-consistent scheme. Effective material properties of two-component media consisting of randomly distributed spheres are given here as a special case.

Fu, L. S.↗
NASA NTRS1974

On the steady flow of gas from the nuclei of Seyfert galaxies

Heating of gas energy released during explosive events produces hot winds in Seyfert nuclei. Steady-state solutions indicate that supersonic velocities up to about 800 km per sec are obtainable. Lyman continuum radiation emitted by the wind ionizes and maintains temperature of cooler gas clouds seen in emission, and dominates energy losses during early stages of expansion. A study of stability of the thermal equilibrium state leads to a two-component model: a hot stable phase (the wind), in pressure equilibrium with a cooler stable phase (clouds). Extreme variations in cloud electron densities are a consequence of the steep decrease with radius of external pressure. Cloud dynamics are related to the radius of formation and internal parameters. Permitted lines of H are emitted by high-density clouds formed at the base of the wind, while forbidden lines arise in radially moving clouds, produced throughout the wind.

Wolfe, A. M.↗
NASA NTRS1990

Heavy rain effects on airplane performance

The objective is to determine if the aerodynamic characteristics of an airplane are altered while flying in the rain. Wind-tunnel tests conducted at the NASA Langley Research Center (LaRC) have shown losses in maximum lift, reduction in stall angle, and increases in drag when a wing is placed in a simulated rain spray. For these tests the water spray concentration used represented a very heavy rainfall. A lack of definition of the scaling laws for aerodynamic testing in a two-phase, two-component flow makes interpolation of the wind-tunnel test uncertain. Tests of a large-scale wing are to be conducted at the LaRC. The large-scale wing is mounted on top of the Aircraft Landing Dynamics Facility (ALDF) carriage. This carriage (which is 70-foot long, 30-foot wide, and 30-foot high) is propelled with the wing model attached down a 3000-foot long test track by a water jet at speeds of up to 170 knots. A simulated rain spray system has been installed along 500 feet of the test track and can simulate rain falls from 2 to 40 inches/hour. Operational checks are underway and the initial tests should be completed by the Fall of 1989.

Dunham, R. E., Jr.↗
NASA NTRS1983

Combined ultraviolet studies of astronomical sources

Ultraviolet spectra of non-radiataive shock waves grain destruction and elemental abundances in interstellar shocks, carbon abundance in M33 and M31 from supernova remnants, determination of the mass function in the large Magellanic cloud, UV spectra of white dwarf pulsars, stellar flares, availability of the double quasar Q 0957 + 56' AB, spectra of late-F dwarfs and their relation to rotation, dynamics of hot gas surrounding hybrid stars, high resolution study of epsilon coronae Austriual, active regions on solar-type dwarfs as a function of rotation rate and age, coordinated chromospheric synoptic observations of selected late-type stars, the two-component atmosphere of Lambda Andromedae, and activity in Hyades giants are discussed.

Dupree, A. K.↗
NASA NTRS1985

ICIASF '85 - International Congress on Instrumentation in Aerospace Simulation Facilities, 11th, Stanford University, CA, August 26-28, 1985, Record

Developments related to laser Doppler velocimetry are discussed, taking into account a three-component dual beam laser-Doppler-anemometer to be operated in large wind tunnels, a new optical system for three-dimensional laser-Doppler-anemometry using an argon-ion and a dye laser, and a two-component laser Doppler velocimeter by switching fringe orientation. Other topics studied are concerned with facilities, instrumentation, control, hot wire/thin film measurements, optical diagnostic techniques, signal and data processing, facilities and adaptive wall test sections, data acquisition and processing, ballistic instrument systems, dynamic testing and material deformation measurements, optical flow measurements, test techniques, force measurement systems, and holography. Attention is given to nonlinear calibration of integral wind tunnel balances, a microcomputer system for real time digitized image compression, and two phase flow diagnostics in propulsion systems.

Source record↗
NASA NTRS1972

On the exospheric temperature of hydrogen-dominated planetary atmospheres.

Results of studies of hydrogen-dominated atmospheres in which exospheric temperatures were calculated to estimate the evaporative loss rates of the constituents. Expressions are given for the exospheric temperature of a two-component diffusive equilibrium model which consists of a lighter molecule dominating the thermosphere and absorbing solar EUV, and a heavier constituent providing radiative cooling in the vicinity of the mesopause. The model approximates well the assumed atmospheres, but the resulting expressions may have wider application. The dynamics of an expanding atmosphere are discussed. A three-dimensional outflow against the back pressure of the solar wind may be configured like a comet's tail.

Gross, S. H.↗
NASA NTRS1989

An experimental study of a reattaching supersonic shear layer

A Mach 1.83 fully developed turbulent boundary layer was separated at a 25.4 mm backward step and formed a free shear layer. The incoming boundary layer thickness, momentum thickness, and Reynolds number were approximately 8 mm, 0.5 mm, and 52x10 to the 6th/m, respectively. A two-component coincident LDV system was used to take velocity measurements of the incoming boundary layer, the free shear layer, and the reattached shear layer. The results confirmed the existence of organized structures in both the free and the reattached shear layer which was reported earlier based on the authors dynamic pressure measurements and Schlieren photographs.

Samimy, M.↗
NASA NTRS1987

Flowfield characteristics of an axisymmetric 180-degree turnaround duct

In an attempt to provide an experimental database for computational fluid dynamics turbulence code evaluation and development, an experiment was conducted using an annular axisymmetric 180-deg turnaround passage through which air flows at close to ambient conditions. Measurements made at a nominal gap Reynolds number of 100,000 are presented; these are the static and fluctuating wall pressure distributions and the one- and two-component velocity profiles at various stations upstream, through, and downstream of the bend. Because of the large favorable pressure gradients on the inner wall up to 51 degrees, the flow experiences a large acceleration close to the wall; enhanced mixing occurs close to the outer wall. Downstream of this location, the flow close to the inner wall experiences an adverse pressure gradient before separating at about 150 degrees.

Ostermier, B. J.↗
NASA NTRS1972

A two component model of the diurnal variations in the thermospheric composition

A self-consistent, two-dimensional, two-component diffusion model is presented to describe the diurnal component of thermosphere dynamics. In the regions where oxygen and helium are the minor constituents, diffusion is shown to increase the amplitudes of these constituents and to advance the times of their diurnal maxima by several hours with respect to the gas temperature and the major species. Both effects are in basic agreement with satellite observations. The diffusion process is relatively insignificant for temperature, total mass density, and wind fields. The magnitude of the temperature-density phase delay is discussed with respect to its dependence on the electron density distribution.

Mayr, H. G.↗
NASA NTRS1973

A two-component model of the diurnal variations in the thermospheric composition.

A self consistent two-component diffusion model is presented to describe the diurnal component of the thermosphere dynamics. In the regions where oxygen and helium are the minor constituents the diffusion process is shown to increase significantly the amplitudes of these constituents and to advance the times of their diurnal maxima by several hours with respect to the gas temperature and to the major species. Both effects are in basic agreement with satellite observations. The diffusion process is however relatively insignificant for temperature, total mass density and wind fields.

Mayr, H. G.↗
NASA NTRS1986

Theory of Ostwald ripening in a two-component system

When a two-component system is cooled below the minimum temperature for its stability, it separates into two or more immiscible phases. The initial nucleation produces grains (if solid) or droplets (if liquid) of one of the phases dispersed in the other. The dynamics by which these nuclei proceed toward equilibrium is called Ostwald ripening. The dynamics of growth of the droplets depends upon the following factors: (1) The solubility of the droplet depends upon its radius and the interfacial energy between it and the surrounding (continuous) phase. There is a critical radius determined by the supersaturation in the continuous phase. Droplets with radii smaller than critical dissolve, while droplets with radii larger grow. (2) The droplets concentrate one component and reject the other. The rate at which this occurs is assumed to be determined by the interdiffusion of the two components in the continuous phase. (3) The Ostwald ripening is constrained by conservation of mass; e.g., the amount of materials in the droplet phase plus the remaining supersaturation in the continuous phase must equal the supersaturation available at the start. (4) There is a distribution of droplet sizes associated with a mean droplet radius, which grows continuously with time. This distribution function satisfies a continuity equation, which is solved asymptotically by a similarity transformation method.

Baird, J. K.↗
NASA NTRS1987

Long-period dynamic spectrograms of low-frequency interplanetary radio emissions

Dynamic spectrograms of the low-frequency interplanetary radio emissions as observed by Voyagers 1 and 2 from 1983 through mid-1986 are reported. The radio emissions were observed to be most intense in the latter portion of 1983 at 3 kHz but have also been detected at 2 kHz. The emission has been present almost continuously at either 2 or 3 kHz since late 1983. The spectrograms presented herein show that the phenomenon appears almost identically as observed by the two spacecraft separated by more than 10 AU, at least at the higher frequency. One feature revealed by the dynamic spectrograms which had not been noticed previously is a gradual rise in frequency of the 3-kHz component following the onset of the late 1983 event. These new observations reinforce the conclusion that the low-frequency emissions are freely propagating radio waves, but the two-component spectral structure implies that the previous model of emission at twice the plasma frequency at the inner heliosphere shock is inadequate to fully account for the observations. Either an additional source region or an additional source mechanism is suggested.

Kurth, W. S.↗