Search NASA⌕ Search

SEARCH · Search NASA

Results for “Streaming”

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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Modeling ice streams: Derived quantities

The model addressed is a finite-element, map-plane, time-dependent, column-averaged continuity equation solver. The key to the fitting process involves the balance between ice motion dominated by flow in internal layers, and ice motion dominated by sliding at the bed. The fitting process involves an iterative process carried out in the time domain. Beginning with the portion of the ice sheet being modeled identical to the present ice sheet with uniform flow, sliding, and fraction specified at nominal values, the model monitors each nodal point surface elevation. As the calculated surface elevation deviates from the present surface, a correction proportional to the difference is applied to selected parameter sets. This correction is in a sense that would tend to improve the fit at the particular nodal point. A calculated surface elevation that was higher than the present surface would result in an increased fraction, which would tend to lower the calculated surface (if the flow or sliding constant were being used as the fitting parameter, they would be lowered to improve the fit). This process is allowed to proceed as long as is necessary for the situation to stabilize. Typically, this takes tens of thousands of model years, but the rate is dependent on other external forcings such as the accumulation rate. The primary result is that while a typical sample of ice streams from around Antarctica can be fitted quite reasonably using only the fraction of the velocity due to sliding, a different mechanism seems to be in play along the Siple Coast, where reduced sliding constants are required to attain a reasonable fit. Flow is more strongly channelized in this region, and velocities are, in general, higher than are observed in other regions. It is unlikely that the mechanism that controls the ice movement along the Siple Coast is exactly similar to the mechanisms in the other ice streams. The concept of deformable sediments and their contribution to the fast flow along the Siple Coast may have limited applicability to other Antarctic ice streams.

Fastook, James↗
NASA NTRS1992

SAR observations of the Gulf Stream during SWADE

The Surface Wave Dynamics Experiment (SWADE) has gathered SAR observations of the Gulf Stream that show a change in ocean surface brightness; this may be due to the effects of a change in air-sea temperature difference across the observed edge, where the boundary is defined by warm, quickly flowing Gulf Stream water and cooler, relatively stationary shelf water. The two images discussed indicate the possibility of deepening understanding of Gulf Stream front dynamics by using the abundant spatial data of SAR imagery, in conjunction with more conventional (point-like) data on hydrography and currents.

Vachon, Paris W.↗
NASA NTRS1952

Solutions of laminar-boundary-equations which result in specific-weight-flow profiles locally exceeding free-stream values

Revised solutions of the laminar-boundary-layer equations for cases which involved cooling at the wall combined with large pressure gradients in the main stream produced specific-weight-flow profiles which locally exceeded free-stream values. Heat-transfer and friction coefficients, boundary-layer thicknesses, and velocity, temperature, and specific-weight-flow distributions resulting from the revised solutions are presented for Euler numbers of 0.5 and 1, stream-to-wall temperature ratios of 2 and 4, and cooling-air flow rates through porous walls designated by flow parameters of 0, -0.5, and -1.

HEAT TRANSFER, AERODYNAMIC↗
NASA NTRS1950

Free-flight Performance of 16-inch-diameter Supersonic Ram-jet Units II : Five Units Designed for Combustion-chamber-inlet Mach Number of 0.16 at Free-stream Mach Number of 1.60 (units B-1, B-2, B-3, B-4, and B-5) /c Wesley E. Messing and Scott H. S

Free-flight performance of five 16-inch-diameter ram-jet units was determined over range of free-stream Mach numbers of 0.50 to 1.86 and gas total-temperature ratios between 1.0 and 6.1 Time histories of performance data are presented for each unit. Correlations illustrate effect of free-stream Mach number and gas total-temperature ratio on diffuser total-pressure recovery, net-thrust coefficient, and external drag coefficient. One unit had smooth steady burning throughout the entire flight and encountered a maximum free-stream Mach number of 1.86 with a net acceleration of approximately 4.2 g's.

COMBUSTION - RAM-JET ENGINES↗
NASA NTRS1957

Aerodynamic Heating and Boundary-Layer Transition on a 1/10-Power Nose Shape in Free Flight at Mach Numbers up to 6.7 and Free-Stream Reynolds Numbers up to 16 x 10(exp 6)

A modified 1/10-power nose shape has been tested in free flight at Mach numbers up to 6.7 and free - stream Reynolds numbers based on diameter up to 16 X 10(exp 6). Measured heating rates were presented and compared with calculated values. Agreement ranges from poor on the forward portion of the nose to good on the rearward portion. The local Reynolds numbers of transition based on calculated momentum thickness varied between 1, 600 and 350. Laminar flow was maintained at momentum thickness Reynolds numbers of about 1,000 until the free-stream Reynolds number based on a length of 1 foot reached about 27 X 10(exp 6). At slightly higher free-stream Reynolds numbers transition occurred at momentum thickness Reynolds numbers as low as 250.

Garland, Benjamine J↗
NASA NTRS1930

Tests of Five Metal Model Propellers with Various Pitch Distributions in a Free Wind Stream and in Combination with Model VE-7 Fuselage

This report describes the tests of five adjustable blade metal model propellers both in a free wind stream and in combination with a model fuselage with stub wings. The propellers are of the same form and cross section but have variations in radial distributions of pitch. By making a survey of the radial distribution of air velocity through the propeller plane of the model fuselage it was found that this velocity varies from zero at the hub center to approximately free stream velocity at the blade tip. The tests show that the efficiency of a propeller when operating in the presence of the airplane is, over the working range, generally less than when operating in a free wind stream, but that a propeller with a radial distribution of pitch of the same nature as the radial distribution of air velocity through the propeller plane suffers the smallest loss in efficiency.

Lesley, E P↗
NASA NTRS1952

Heat Transfer to Bodies in a High-speed Rarified-Gas Stream

Report presents the results of an investigation to determine the equilibrium temperature and heat-transfer coefficients for transverse cylinders in a high-speed stream of rarefied gas measured over a range of Knudsen numbers (ratio of molecular-mean-free path to cylinder diameter) from 0.025 to 11.8 and for Mach numbers from 2.0 to 3.3. The range of free-stream Reynolds numbers was from 0.28 to 203. The models tested were 0.0010-, 0.0050-, 0.030-, 0.051-, 0.080-, and 0.126-inch -diameter cylinders held normal to the stream.

Stalder, Jackson R↗
NASA NTRS1953

Spectrum of turbulence in a contracting stream

The spectrum concept is employed to study the selective effect of a stream contraction on the longitudinal and lateral turbulent velocity fluctuations of the stream. By a consideration of the effect of the stream contraction on a single plane sinusoidal disturbance wave, mathematically not dissimilar to a triply periodic disturbance treated by G. I. Taylor, the effect on the spectrum tensor of the turbulence and hence on the correlation tensor is determined.

Ribner, H S↗
NASA NTRS1993

Probe systems for measuring static pressure and turbulence intensity in fluid streams

A method and an apparatus for measuring time-averaged static or ambient pressure and turbulence intensity in a turbulent stream are discussed. The procedure involves placing a plurality of probes in the stream. Each probe responds in a different manner to characteristics of the fluid stream, preferably as a result of having varying cross sections. The responses from the probes are used to eliminate unwanted components in the measured quantities for accurate determination of selected characteristics.

Rossow, Vernon J.↗
NASA NTRS1994

Large and small scale circulation signatures of the ERS-1 SAR over the Gulf Stream

Since September 1991, the ERS-1 SAR (Synthetic Aperture Radar) has collected approximately 170 frames of ocean imagery on 28 passes over the western Gulf Stream in support of ESA experiment US8-2c. SAR signatures of the north wall are seen on nearly all passes, with modulation depth varying from 3% to 35% for 100 m samples. Many small and mesoscale circulation features associated with the Stream are evident. The detailed form of the signature varies considerably, however. Narrow bright or dark linear features appear to follow streamlines, and on one occasion a strong dark line was associated with an in situ measurement of a sharp current shear. Similarly, larger spatial scale changes in backscatter over the Stream were associated with in situ measurements of atmospheric stability transitions. Physical explanations for the narrow features are not so obvious. However, the accumulation of surfactants along converging current boundaries or local short wave straining and breaking appear plausible. These preliminary results strongly suggest that a wide swath (approximately 500 km) SAR with at least 100 m resolution would be a useful adjunct to existing satellite AVHRR (Advanced Very High Resolution Radiometer) imagery.

Beal, R.↗
NASA NTRS1995

DE-1 observations of polar O(+) stream bulk parameters and comparison with a model of the centrifugally-accelerated polar wind

A survey of bulk parameters of analyzable O(+) outward streams in the mid-altitude (3-4.7 R(sub E) geocentric distance) polar cap magnetosphere is obtained from measurements by the Retarding Ion Mass Spectrometer (RIMS) aboard the Dynamics Explorer-1 (DE-1) spacecraft. There is wide scatter in the obtained densities, but they do display discernible trends: the average O(+) density in these streams decreases from about 60 ions/cc at 3.5 R(sub E) to about 1 ion/cc at 4.6 R(sub E). The streaming velocities are somewhat more defined, and their average increases from about 8 km/s at 3.5 R(sub E) to about 12 km/s at 4.6 R(sub E). The densities and bulk velocities are inversely correlated. We have further compared these observational trends with model profiles for the centrifugally-accelerated polar wind as recently described by Horwitz et al. (1994). The large outflow velocities observed can be understood in part as centrifugally-driven by convection with ionospheric electric field magnitudes of the order 50-70 mV/m, perhaps including plasma expansion effects.

Ho, C. Wing↗
NASA NTRS1994

X-ray bright points and high-speed wind streams: A preliminary analysis from Yohkoh and Ulysses data

The following aspect of the solar wind mass flux, and of its variation, is examined: whether coronal plumes might be responsible for the long-term variability of the mass flux in high-speed streams emanating from coronal holes. The assumption that plumes are rooted in coronal bright points (BP's) is made. The behavior of X-ray BP's, imaged by the Yohkoh soft X-ray telescope (SXT), during a seven month period when Ulysses experiments observed a series of recurrent high-speed streams, is analyzed. If plumes/BP's are sources of the wind mass flux, changes in the coronal hole BP density to mimic changes of the mass flux in high-speed streams are expected. SOHO will have the capability of measuring the solar wind speed/density at small heliocentric distances while simultaneously observing coronal BP's and coronal plumes.

Poletto, Giannina↗
NASA NTRS1995

Polarization and wavelength diversities of Gulf Stream fronts imaged by AIRSAR

During the 1990 Gulf Stream Experiment, NASA/JPL AIRSAR imaged the north edge of the Gulf Stream near the coast of Virginia. Simultaneous in-situ measurements of currents, temperatures, salinities, etc. were made for several crossings of the north edge by the R/V Cape Henlopen. Measurements identified two fronts with shearing and converging flows. The polarimetric SAR images from the fronts showed two bright linear features. One of them corresponds to the temperature front, which separated the warm Gulf Stream water to the south from a cool, freshwater filament to the north. The other line, located about 8 km north of the temperature front, is believed to correspond to the velocity front between the filament and the slope water. At these fronts, wave-current interactions produced narrow bands of steep and breaking waves manifesting higher radar returns in polarimetric SAR images. In general, our AIRSAR imagery shows that the signal-to-clutter ratio of radar cross sections for the temperature front is higher than that of the velocity front. In this paper, we study the polarization and wavelength diversities of radar response of these two fronts using the P-, L-, and C-Band Polarimetric SAR data. The north-south flight path of the AIRSAR crossed the temperature front several times and provided valuable data for analysis. Three individual passes are investigated. We found that for the temperature front, the cross-pol (HV) responses are much higher than co-pol responses (VV and HH), and that P-Band HV has the highest signal to clutter ratio. For the velocity front, the ratio is the strongest in P-Band VV, and it is indistinguishable for all polarizations in C-Band. The radar cross sections for all three polarization (HH, HV, and VV) and for all three bands are modelled using an ocean wave model and a composite Bragg scattering model. In our initial investigations, the theoretical model agrees qualitatively with the AIRSAR observations.

Lee, J. S.↗
NASA NTRS1994

Stream interfaces and energetic ions closer than expected: Analyses of Pioneers 10 and 11 observations

An empirical study of corotating interaction regions (CIRs) observed between 3.9 AU and 5.9 AU on Pioneers 10 and 11 shows that the main corotation energetic ion population (CEIP), which is associated with the trailing reverse shock, terminates within the CIR at a definite, structural boundary, which we show here is the stream interface. This new result has significant implications for solar wind and energetic particle modeling. In particular it implies either that the reverse shock forms closer to the stream interface than models suggest or that the theories that treat the generation and transport of these energetic ions, such as preshock Fermi acceleration and cross-field diffusion must be combined or extended. We test these scenarios by comparing the CEIP intensity profiles on the two sides of the stream interface. We find that while each automatically accounts for one or two aspects of the results none of them alone can account for all of our empirical results.

Intriligator, Devrie S.↗
NASA NTRS1995

Generation of Venus' nightside ionospheric structure by particle streams from cosmoids

A newly discovered source of energetic particle streams directed at Venus' nightside may cause several exosphere phenomena. The streams evolve from dispersed cosmoids, a surreptitious population of meteoroids in nearly hyperbolic orbits, measured with three dust experiments on Pioneer 10/11. Loose fragile comet-like ensembles of frozen volatile material, they are orders of magnitude more populous than short-period meteoroids. Dispersion is forced near a planet masking the meteor signature at Earth, but recently terrestrial exosphere interactions have been detected principally from VLF radar returns and as suddenly formed layers of neutral sodium and iron probed by lidar. Venus influx is estimated greater than 10(exp -14)(g)/((sq cm)(s)) with nightside directed kinetic power of greater than 0.3 (erg)/((sq cm)s)). Compared to Earth, Venus, lacking a dipole field with almost no rotation, has a readily recognized set of nightside interaction signatures of these downward energetic particle streams: i.e., density depressions of the neutral thermosphere, hydrogen and helium bulges, a non-disappearing ionosphere, electron holes, nightglows, VLF bursty signals, and local magnetic fields. From Pioneer Venus Orbiter (PVO) measurements, the cosmoid population, its temporal and solar azimuthal variation may be determined.

Dubin, M.↗
NASA NTRS1995

Stream interfaces and energetic ions II: Ulysses test of Pioneer results

Ulysses measurements of energetic and solar wind particles taken near 5 AU between 20 and 30 degrees south latitude during a well-developed recurring corotating interaction region (CIR) show that the CIR's corotating energetic ion population (CEIP) associated with the trailing reverse shock starts within the CIR at the stream interface. This is consistent with an earlier result obtained by Pioneers 10 and 11 in the ecliptic plane between 4 and 6 AU. The Ulysses/Pioneer finding is noteworthy since the stream interface is not magnetically connected to the reverse shock, but lies 12-17 corotation hours from it. Thus, the finding seems to be inconsistent with the basic model that generates CEIP particles at the reverse shock and propagates them along field lines. Eliminating the inconsistency probably entails an extension of the standard model such as cross-field diffusion or a non-shock energization process operating near the stream interface closer to the sun.

Intriligator, Devrie S.↗
NASA NTRS1995

Valve For Extracting Samples From A Process Stream

Valve for extracting samples from process stream includes cylindrical body bolted to pipe that contains stream. Opening in valve body matched and sealed against opening in pipe. Used to sample process streams in variety of facilities, including cement plants, plants that manufacture and reprocess plastics, oil refineries, and pipelines.

Callahan, Dave↗
NASA NTRS1994

The streaming-trapped ion interface in the equatorial inner magnetosphere

Spacecraft measurements of core ions on L=4-7 field-lines typically show trapped ion distributions near the magnetic equator, and frequently indicate field-aligned ion streams at higher latitudes. The nature of the transition between them may indicate both the microphysics of hot-cold plasma interactions and overall consequences for core plasma evolution. We have undertaken a statistical analysis and characterization of this interface and its relation to the equatorial region of the inner magnetosphere. In this analysis, we have characterized such features as the equatorial ion flux anisotropy, the penetration of field-aligned ionospheric streams into the equatorial region, the scale of the transition into trapped ion populations, and the transition latitude. We found that most transition latitudes occur within 13 deg of the equator. The typical values of equatorial ion anisotropies are consistent with bi-Maxwellian temperature ratios of T(sub perpendicular)/T(sub parallel) in the range of 3-5. The latitudinal scales for the edges of the trapped ion populations display a rather strong peak in the 2-3 deg range. We also found that there is a trend for the penetration ratio, the anisotropy half width, and the transition scale length to decrease with a higher equatorial ion anisotropy. We may interpret these features in terms of Liouville mapping of equatorially trapped ions and the reflection of the incoming ionospheric ion streams from the equatorial potential peaks associated with such trapped ions.

Lin, J.↗