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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Air-Sea Interaction During Cold Air Outbreaks

The NOAA P-3 1-sec and 20 Hz gust probe data, dropsonde measurements, and lidar data were combined to study the organized convection and the effects of the coastal shape and the sea surface temperature (SST) pattern on the development of the marine atmospheric boundary layer (MABL) during cold air outbreaks. The preliminary analysis indicated that the SST pattern and the coastal shape caused the MABL to deepen eastward and southward, which is in good agreement with the suggestion of Atlas et al. (1983). Also, good agreements were found between the lidar data and the NOAA P-3 and dropsonde date, e.g., the boundary heights, the dominant scales of motion, and the heat flux ratio between the top of MABL and the sea surface. The planetary boundary layer (PBL) height measured by lidar was found to be in good agreement with that measured by the dropsonde temperature profile. Assuming a linear heat flux profile in the clear PBL, the heat flux ratio between the PBL top and the surface may be estimated from the ratio of the entrainment zone to the completely mixed boundary layer height. The heat flux ratio estimated by lidar measurements was found to be in good agreement with that derived from the gust probe data.

Chou, S.↗
NASA NTRS1985

Characterization of erosion of metallic materials under cavitation attack in a mineral oil

Cavitation erosion and erosion rates of eight metallic materials representing three crystal structures were studied. The erosion experiments were conducted with a 20-kHz ultrasonic magnetostrictive oscillator in a viscous mineral oil. The erosion rates of the metals with an fcc matrix were 10 to 100 times higher than that of an hop-matrix titanium alloy. The erosion rates of iron and molybdenum, with bcc matrices, were higher than that of the titanium alloy but lower than those of those of the fcc materials. Studies with scanning electron microscopy indicated that the cavitation pits were initially formed at the grain boundaries and precipitates and that the pits formed at the junction of grain boundaries grew faster than the others. Transcrystalline craters formed by cavitation attack over the surface of grains and roughened the surfaces by multiple slip and twinning. Surface roughness measurements showed that the pits that formed over the grain boundaries deepened faster than pits. Computer analysis revealed that a geometric expression describes the nondimensional erosion curves during the time period 0.5 t (sub 0) t 2.5 t (sub 0), where t (sub 0) is the incubation period. The fcc metals had very short incubation periods; the titanium alloy had the longest incubation period.

Rao, B. C. S.↗
NASA NTRS1985

A survey of major east coast snowstorms, 1960-1983. Part 2. Summary of surface and upperlevel characteristics

Surface and upper-level characteristics of selected meteorological fields are summarized. Two major types of sea level development are described and applied to the cases at hand, with a few storm systems showing characteristics of both types. Aspects such as rapid sea level deepening, coastal frontogenesis, cold air damming, low level jet formation, the development of an S-shaped isotherm pattern, diffluence downwind of a negatively tilted upper level trough axis, upper level confluence and an increase of geopotential heights at the base of the upper level trough characterized the pre-cyclogenetic and cyclogenetic periods of many of the storm systems. Large variability was also observed, especially with regard to the spatial dimensions of the surface and upper level systems, as well as variations in trough/ridge amplification and the evolution of upper level jet streak systems. The influence of transverse circulations associated with a confluent jet streak entrance region and the diffluent exit region of a jet streak/trough system on the production of snowfall is also discussed.

Kocin, P. J.↗
NASA NTRS1984

Wave CISK and mesoscale convective systems

An examination is conducted of the basic assumptions of conventional wave-CISK theory, against observational data on mesoscale-organized convective systems. In response to the inadequacy of the quasi-equilibrium assumption, a nonequilibrium model of clouds actively responding to mesoscale low level mass fluxes in a preexisting and conditionally unstable atmosphere is formulated. The structures obtained for the propagating and growing waves are noted to be comparable with observations of midlatitude mesoscale convective systems. An examination is made of the energetics of this modified wave-CISK model, in order to deepen understanding of its instability and scale selection.

Xu, Q.↗
NASA NTRS1985

Properties of the lithosphere and asthenosphere deduced from geoid observations

Data from the GEOS-3 and SEASAT Satellites provided a very accurate geoid map over the oceans. Broad bathymetric features in the oceans such as oceanic swells and plateaus are fully compensated. It is shown that the geoid anomalies due to the density structures of the lithosphere are proportional to the first moment of the density distribution. The deepening of the ocean basins is attributed to thermal isostasy. The thickness of the oceanic lithosphere increases with age due to the loss of heat to the sea floor. Bathymetry and the geoid provide constraints on the extent of this heat loss. Offsets in the geoid across major fracture zones can also be used to constrain this problem. Geoid bathymetry correlations show that the Hawaiian and Bermuda swells and the Cape Verde Rise are probably due to lithospheric thinning.

Turcotte, D. L.↗
NASA NTRS1985

Tone excited jets. IV - Acoustic measurements

Attention is given to acoustic results from an experiment designed to deepen insight into the noise generated by a tone-excited jet, with emphasis on the mechanism of broadband jet noise amplification. Results are presented for both heated and unheated jets, with and without the effect of forward flight simulation over a range of excitation frequencies and levels, and for zero-order and first-order spinning modes. Broadband jet noise amplifications of up to 5 dB have been observed in this study. Relative velocity effects are the same for both excited and unexcited jets. It is concluded that small scale turbulence generates the additional broadband noise upon excitation of the jet by an upstream-injected discrete tone acoustic wave.

Ahuja, K. K.↗
NASA NTRS1985

Separability of boreal forest species in the Lake Jennette area, Minnesota

In order to exploit the use of thematic mapper (TM) data to obtain vegetation and net primary productivity maps in the boreal forest, three aircraft flights were undertaken over the area near Ely, MN, with the NS 001 Thematic Mapper Simulator. Attention is presently given to an analysis of these 1983 data, which attempted to separate coniferous trees from deciduous ones. Canopy reflectance models and measured optical properties of the scattering elements have been used to deepen understanding of this separability, and to relate the ratio of nadir view reflectances in TM bands 4 and 3 to the overstory leaf area index. A map that is proportional to the leaf area index for deciduous species is presented.

Shen, S. S.↗
NASA NTRS1984

A review of major east coast snowstorms

The surface and upper-level characteristics in selected wind, pressure, and temperature fields of some significant east coast cyclones are studied. The surface, 200, 300, 500, 700, and 850 mb charts of 18 case studies of storms are analyzed. The surface patterns are described in terms of the type of cyclone, the variation in rate of motion, the effect of coastal frontogenesis on the storms, sea level pressures, and the deepening rate of pressure. The influence of upper-level troughs, ridges, jet streaks, location of wind amplification, and time on cyclogenesis is examined.

Kocin, P. J.↗
NASA NTRS1986

The kinetic and available potential energy budget of a winter extratropical cyclone system

The energy budget of an extratropical cyclone system which traversed North America and intensified through the period January 9-11, 1975 is presented. The objectives of the study are: (1) to document the complete energy budget of a significant winter cyclone event, and (2) to comment on the significance of latent heat release (LHR) in the cyclone's evolution. Results reveal an overall increase in both kinetic (K) and available potential energy (A). K increases are accounted for by boundary flux convergence of K, while A increases are due to generation by LHR and K to A conversion. In addition, the general A increase is accompanied by a 24 h oscillation that is explained largely by the flux quantity in the A budget equation and is correlated with a similar fluctuation in the K to A conversion. LHR does not appear to be critical in the development of this cyclone system. Rather, LHR acts to increase the intensity of the event. It is hypothesized that the direct influence that LHR had on the deepening cyclone's reduced mass was augmented by an indirect influence, in which pre-existing dry dynamical forcing was enhanced by diabatic heating, thus leading to accelerated cyclone development at a later time.

Smith, P. J.↗
NASA NTRS1986

The possible influence of upstream upper-level baroclinic processes on the development of the QE II storm

An analysis of the QE II storm of September 9-11, 1978 presents evidence for the existence of upper-level baroclinic processes upstream of the rapidly developing cyclone. The analysis shows that a deepening shortwave trough was located 400 to 500 km upstream of the site of the storm 12 h prior to rapid cyclogenesis. The trough was associated with: (1) a polar jet marked by 65 m/s winds in its core and significant vertical and horizontal wind shear, (2) positive vorticity advection and divergence at the 300 mb level, and (3) an intense frontal zone that extended from 300 mb down to the surface. It also appears that a tropopause fold likely extruded stratospheric air down to the 700-800 mb level, 400-500 km upstream of the surface low and 12 h prior to the explosive development phase of the cyclone. These findings raise questions about Gyakum's (1983) assertion that the QE II storm developed in an area in which the baroclinic support was confined to the lower troposphere and the related assertion by Anthes et al. (1983) that upper-level forcing upstream of the area of rapid cyclogenesis was weak and apparently not important in this case.

Uccellini, L. W.↗
NASA NTRS1987

Gamma ray transients

The discovery of cosmic gamma ray bursts was made with systems designed at Los Alamos Laboratory for the detection of nuclear explosions beyond the atmosphere. HELIOS-2 was the first gamma ray burst instrument launched; its initial results in 1976, seemed to deepen the mystery around gamma ray transients. Interplanetary spacecraft data were reviewed in terms of explaining the behavior and source of the transients.

Cline, Thomas L.↗
NASA NTRS1986

Laser-induced fluorescence measurement of combustion chemistry intermediates

Laser-induced fluorescence (LIF) can measure the trace (often free radical) species encountered as intermediates in combustion chemistry; OH, CS, NH, NS, and NCO are typical of the species detected in flames by LIF. Attention is given to illustrative experiments designed to accumulate a quantitative data base for LIF detection in low pressure flow systems and flames, as well as to flame measurements conducted with a view to the detection of new chemical intermediaries that may deepen insight into the chemistry of combustion.

Crosley, David R.↗
NASA NTRS1987

Low power arcjet life issues

The present evaluation of the results of arcjet engine lifetime testing attempts to deepen understanding of the electrode erosion process, with a view to its minimization. Attention is given to the compatibility of materials with N2H4, the dependence of electrode erosion on geometry and flow field, and the erosive effects associated with the arcjet power supply. Results are presented for thrusters employing either decomposed N2H4 or cold mixed gases, over a power range of 900 to 2000 W.

Simon, M. A.↗
NASA NTRS1987

Satellite-derived attributes of cloud vortex systems and their application to climate studies

Defense Meteorological Satellite Program (DMSP) visible and infrared mosaics are analyzed in conjunction with synoptic meteorological observations of sea level pressure (SLP) and upper-air height to derive composite patterns of cyclonic cloud vortices for the Northern Hemisphere. The patterns reveal variations in the structure and implied dynamics of cyclonic systems at different stages of development that include: (1) increasing vertical symmetry of the lower-level and upper-air circulations and (2) decreasing lower-tropospheric thicknesses and temperature advection, associated with increasing age of the vortex. Cloud vortices are more intense in winter than in summer and typically reach maximum intensity in the short-lived prespiral signature stage. There are major structural differences among frontal wave, polar air, and 'instant occlusion' cyclogenesis types. Cyclones in the dissipation stage may reintensify (deepen), as denoted by the appearance in the imagery of an asymmetric cloud band or a tightened spiral vortex. The satellite-derived statistics on cloud vortex intensity, which are seasonal- and latitude- as well as type-dependent, are applied to a preliminary examination of the synoptic manifestations of seasonal climate variability. An apparently close relationship is found, for two winter and spring seasons, between Northern Hemisphere cyclonic activity and variations in cryosphere variables, particularly the extent of Arctic sea ice. The results may indicate that increased snow and ice extent accompany a southward displacement of cyclonic activity and/or a predominance of deeper systems. However, there is also a strong regional dependence to the ice-synoptics feedback. This study demonstrates the utility of high resolution meteorological satellite imagery for studies of climate variations (climate dynamics).

Carleton, Andrew M.↗
NASA NTRS1987

On the relationship between scatterometer-derived convergences and atmospheric moisture

Fields of divergence calculated from the Seasat-A Satellite Scatterometer winds and fields of integrated water vapor and rainrate from the Scanning Multichannel Microwave Radiometer on Seasat are constructed for three different midlatitude cyclones. These storms include an explosively deepening cyclone that occurred in the North Atlantic (also known as the Queen Elizabeth II cyclone), a storm that occurred in the North Pacific, and a Southern Ocean storm. In all three cases, the regions of convergence and atmospheric water (vapor and rain) are consistent with each other and help to define features of each storm. The vertical distribution of moisture is inferred for one case using both the convergence pattern and the integrated water vapor field. In another, interpretation of the convergence field in a data gap region is aided by the water vapor field. In all three cases, surface low pressure centers, fronts, and even frontal waves are clearly evident as areas of convergence, and increased water vapor and rainrate.

Mcmurdie, Lynn A.↗
NASA NTRS1987

The Spaceborne Imaging Radar program: SIR-C - The next step toward EOS

The NASA Shuttle Imaging Radar SIR-C experiments will investigate earth surface and environment phenomena to deepen understanding of terra firma, biosphere, hydrosphere, cryosphere, and atmosphere components of the earth system, capitalizing on the observational capabilities of orbiting multiparameter radar sensors alone or in combination with other sensors. The SIR-C sensor encompasses an antenna array, an exciter, receivers, a data-handling network, and the ground SAR processor. It will be possible to steer the antenna beam electronically, so that the radar look angle can be varied.

Evans, Diane↗
NASA NTRS1988

Diagnostic study of explosive cyclogenesis during FGGE

Two rapidly developing extratropical maritime cyclones (one, developed during January 13-15, 1979, along an intense frontal zone south of Japan, the other, of January 26-27, 1979, in a polar mass over the North Atlantic) were investigated using the FGGE data and ECMWF level IIIb analyses to describe the structure and dynamics of these events. Although the cyclones evolved from a strong low-level baroclinic zone without initial large midtropospheric vorticity advection, thus resembling the Petterssen type A development, rapid deepening occurred in both cases when an approaching upper tropospheric jet with appreciable shear vorticity advection became favorably superposed over the surface low. During the development period, stability decreased in the low troposphere, aiding in the rapid development of an intense mass-circulation and low tropospheric vorticity production by the divergence term. The results suggest that upper-level forcing plays a greater role in the initiation of explosive oceanic development than is suggested by the Petterssen and Smebye (1971) description.

Wash, Carlyle H.↗
NASA NTRS1988

Training for 21st century space missions

Although specific recommendations are difficult to make about spacecraft and missions not yet designed, several general guidelines are presently formulated concerning the training of future, long-duration space mission crews. Training systems should be embedded in the normal controls and displays of the spacecraft used, so that critical maneuvers can be practiced as often as possible. Some system for computer-based training should be available onboard, in order to maintain the spacecraft system-knowledge of the crew at a high level and deepen understanding of malfunction responses.

Hughes, Frank E.↗