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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Analysis of 7- X 10-foot high speed wind tunnel shaft loads in support of fan blade failure investigation

This is a report of the investigation of the High-Speed 7- X 10-Foot Wind Tunnel at NASA Langley Research Center, which experienced a catastrophic failure of all 18 Sitka spruce fan blades during operation at 0.8 Mach number on 2 July 1985. The High-Speed Tunnel, a closed-circuit/single-return atmospheric wind tunnel, had been operated since 1945 to support a wide range of subsonic aerodynamic tests and studies. The failed blade set had been in use since 1975. In addition to blade loss, the most significant damage was a bent main drive shaft for a total estimated damage loss of 1.7 million dollars. An analysis of the natural frequency characteristics as well as loads, reactions, stresses, and deflections of the fan drive system resulting from steady-state and dynamic loads due to unbalance was performed. Transient load cases were simulated by step input and ramp input loading functions intended to simulate the loss of one to nine blades (maximum unbalance forces).

Faison, Richard W.↗
NASA NTRS1975

Heat-flux gage measurements on a flat plate at a Mach number of 4.6 in the VSD high speed wind tunnel, a feasibility test (LA28)

The feasibility of employing thin-film heat-flux gages was studied as a method of defining boundary layer characteristics at supersonic speeds in a high speed blowdown wind tunnel. Flow visualization techniques (using oil) were employed. Tabulated data (computer printouts), a test facility description, and photographs of test equipment are given.

Source record↗
NASA NTRS2019

High-Speed Wind Tunnel Tests of a Full-Scale Proprotor on the Tiltrotor Test Rig

The Tiltrotor Test Rig (TTR) is a NASA project, joint with the U.S. Army and Air Force, to develop a new, large scale proprotor test system for the National Full-Scale Aerodynamics Complex (NFAC). The first wind-tunnel entry was completed in November 2018 with a modern, 26-ft diameter proprotor. The primary purpose was to complete the development of the TTR, including systems integration with the NFAC. The TTR and rotor were tested up to 273 knots in axial flow. This is the highest airspeed ever achieved by a full-scale proprotor in any wind tunnel. Extensive conversion-mode data were also acquired, and hover/climb conditions were explored. Additional testing included aerodynamic tares, motor tests, thermal tests, modal vibration tests, and other checkout activities. This paper summarizes the results of the test, including examples of the most significant data.

Wind Tunnel Tests↗
NASA NTRS1967

Jet engine powers large, high-temperature wind tunnel

Wind tunnel for large component testing uses a jet engine with afterburner to provide high temperatures /1200 degrees to 2000 degrees F/ and controlled high velocity gas. This economical wind tunnel can accommodate parts ten feet by ten feet or larger, and is a useful technique for qualitative information.

Benham, T. F.↗
NASA NTRS1994

Ionospheric projections of magnetospheric regions under low and high solar wind pressure conditions

The projection of magnetospheric regions into the dayside ionosphere as determined by particle precipitation characteristics was studied for dependence on solar wind parameters. It was found that the solar wind kinetic pressure p dramatically affected the map of magnetospheric projections. Under the constraint that p greater than or equal 4 nPa(yielding (p) = 5.9 nPa), the area of the cusp (magnetic latitude times magnetic local time extent) was 4.83 degree-hours; whereas under the constraint that p greater than or equal 2 nPa (yielding (p) = 1.5 nPa), the cusp area was only 1.01 degree-hours. The ionospheric footprint of the low-latitude boundary layer was similarly affected. Various possible correlations of p with other solar wind variables, including n, v, and absolute value of B(sub z), proved unable to account for the pressure effect. Because one criterion for identifying the cusp is high fluxes, the effect of nv was investigated with particular care, both in examples and statistically. Again, p itself had by far the most striking effect. Thus we concluded that some physical mechanism is needed to account for the pressure effect. One possibility is that increased direct solar wind plasma penetration of the magnetopause occurs under high-p conditions in the manner suggested by various proponents of impulsive penetration models. An alternative, which we find promising, is that, regardless of the original interplanetary magnetic field (IMF) strength, a high-p solar wind leads to a large compression factor for the magnetosheath field, which is the field actually in contact with the magnetosphere. From this latter viewpoint, the chief effect of high particle pressure is simply to enhance the effectiveness of the interaction of the IMF with the magnetosphere.

Newell, Patrick T.↗
NASA NTRS2000

Fine Structure in the Corona and Solar Wind at High Heliographic Latitudes at Solar Maximum

Microstreams and pressure balance structures in fast solar wind were more easily detected at Ulysses at 2.2 AU over the poles than at Helios at 0.3 AU. This is because solar rotation brings sources of fast solar wind beneath sources of slow solar wind at a rate that depends on latitude, for the same size features. Dynamic interaction between the fast and slow wind tends to mix the flows and make features more difficult to detect with increasing distance from the Sun. A given sized feature takes proportionally longer to pass a longitude when it is at 80 degrees latitude than when it is at the equator. At solar maximum, Ulysses will mainly be sampling solar wind coming from above streamers and from near streamers. The data will provide information on fine structure at the tops of streamers - the stalks - and on the source of slow solar wind, The visibility of the boundaries between fast and slow wind and of the stalk will increase with increasing latitude. We will present quantitative calculations of the visibility of various sized features, with various differences in flow speed, at the location of Ulysses when it is over the south (in 2000) and north (in 2001) polar regions of the Sun.

Suess. S. T.↗
NASA NTRS2001

Fine Structure in the Corona and Solar Wind at High Heliographic Latitudes at Solar Maximum

Microstreams and pressure balance structures in fast solar wind were more easily detected at Ulysses at 2.2 AU over the poles than at Helios at 0.3 AU. This is because solar rotation brings sources of fast solar wind beneath sources of slow solar wind at a rate that depends on latitude, for the same size features. Dynamic interaction between the fast and slow wind tends to mix the flows and make features more difficult to detect with increasing distance from the Sun. A given sized feature takes proportionally longer to pass a longitude when it is at 80 degrees latitude than when it is at the equator. At solar maximum, Ulysses will mainly be sampling solar wind coming from above streamers and from near streamers. The data will provide information on fine structure at the tops of streamers - the stalks - and on the source of slow solar wind. The visibility of the boundaries between fast and slow wind and of the stalk will increase with increasing latitude. I will present quantitative calculations of the visibility of various sized features, with various differences in flow speed, at the location of Ulysses when it is over the south (in 2000) and north (in 2001) polar regions of the Sun.

Suess, S. T.↗
NASA NTRS1990

Evolution of atmospheric fronts over the ocean as observed with the special sensor microwave/imager and the Geosat altimeter

Integrated water vapor gradients and rain occurrence inferred from SSM/I are used to locate and trace the evolution of the atmospheric fronts for two midlatitude cyclones across the North Pacific. When compared to the NMC frontal locations advected to the time of the satellite pass, a good overall agreement is found between the SSM/I and the NMC locations of the fronts. The Geosat altimeter and the SSM/I overflew the two cyclones with several hours difference, locating the frontal positions at different times. The position of the occluded, warm, and cold fronts are detected along the altimeter track as well as regions of high wind speed associated with the cyclonic systems. These regions of high wind speeds associated with the fronts are also sensed by the SSM/I and, allowing for the time difference between the two satellites, are in good agreement with the Geosat measurements.

Mognard, Nelly M.↗
NASA NTRS1998

The Paradox of Filamented Coronal Hole Flow but Uniform High Speed Wind

Plumes and rays in coronal holes are nearly radially aligned density striations that follow the ambient magnetic field. They have long been known, but have gained new interest with growing awareness that coronal hole flow is inherently filamentary. In retrospect, filamentary flow should have been no surprise. This is because,Beta much less than 1 in coronal holes inside approximately 10 Solar radius, allowing the flow to be filamentary down to the smallest scale of photospheric magnetic activity. While the magnetic field itself is locally smooth across any height above ca. 50,000 km, SOHO/MDI has shown that the photospheric magnetic field is a complex array of rapidly evolving small bipoles that are constantly emerging, evolving, and cancelling. The resulting activity is manifested in microflares, concentrated in the magnetic network, that produce Impulsive injections at the footpoints of coronal field lines. The uneven distribution of this activity in space and time is the source of coronal hole filamentation. What is surprising is that the radial flow speed also exhibits filamentary structure. It is not well described as smooth, spherically symmetric, diverging flow, but instead ranges from 300 to over 1000 km/s at 5.5 Solar radius among field-aligned filaments like those seen in plumes and rays [Feldman et al., JGR, Dec. 1997]. This is completely unlike the constant high speed solar wind reported beyond 0.3 AU. Consequently, plumes and filamentary structure must be strongly mixed, and the mixing must be far along by 0.3 AU to be consistent with Helios observations. The paradox is what causes the mixing? Existing models of coronal heating and solar wind acceleration hardly address this issue. One possibility we are investigating is the MHD Kelvin-Helmholtz instability, to which the shear between plumes and interplume corona is expected to become unstable at 5-10 Solar radius. This instability can be simulated and followed far into the nonlinear regime and may lead to Alfvenic fluctuations like those seen at 1 AU.

Suess, Steven T.↗
NASA NTRS1978

Sequential High-Resolution Wind Profile Measurements

Tropospheric flow and lower stratospheric flow as measured by 94 sequences of high-resolution Jimsphere balloon data are presented and discussed. The 70 and 24 sequential series are presented for the Kennedy Space Center, Florida, and Point Mugu, California, areas, respectively. Supplemental data, consisting of the associative temperature profiles and surface and 200 mb synoptic maps, are also presented. The measurements are discussed relative to both the engineering and disciplinary areas. An initial subjective analysis of mesoscale features observed on some sequences is presented.

Johnson, D. L.↗
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 NTRS2005

Optically Based Flame Detection in the NASA Langley 8-ft High- Temperature Wind Tunnel

Two optically based flame-detection systems have been developed for use in NASA Langley's 8-Foot High-Temperature Tunnel (8-ft HTT). These systems are used to detect the presence and stability of the main-burner and pilot-level flames during facility operation. System design considerations will be discussed, and a detailed description of the system components and circuit diagrams will be provided in the Appendices of this report. A more detailed description of the manufacturing process used in the fabrication of the fiber-optic probes is covered in NASA TM-2001-211233.

Borg, Stephen E.↗