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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1940

Boundary-Layer Transition on the N.A.C.A. 0012 and 23012 Airfoils in the 8-Foot High-Speed Wind Tunnel, Special Report

Determinations of boundary-layer transition on the NACA 0012 and 2301 airfoils were made in the 8-foot high-speed wind tunnel over a range of Reynolds Numbers from 1,600,000 to 16,800,000. The results are of particular significance as compared with flight tests and tests in wind tunnels of appreciable turbulence because of the extremely low turbulence in the high-speed tunnel. A comparison of the results obtained on NACA 0012 airfoils of 2-foot and 5-foot chord at the same Reynolds Number permitted an evaluation of the effect of compressibility on transition. The local skin friction along the surface of the NACA 0012 airfoil was measured at a Reynolds Number of 10,000,000. For all the lift coefficient at which tests were made, transition occurred in the region of estimated laminar separation at the low Reynolds Numbers and approach the point of minimum static pressure as a forward limit at the high Reynolds Numbers. The effect of compressibility on transition was slight. None of the usual parameters describing the local conditions in the boundary layer near the transition point served as an index for locating the transition point. As a consequence of the lower turbulence in the 8-foot high-speed tunnel, the transition points occurred consistently farther back along the chord than those measured in the NACA full-scale tunnel. An empirical relation for estimating the location of the transition point for conventional airfoils on the basis of static-pressure distribution and Reynolds Number is presented.

Becker, John V.↗
NASA NTRS1998

Application of Rapid Prototyping Methods to High-Speed Wind Tunnel Testing

This study was undertaken in MSFC's 14-Inch Trisonic Wind Tunnel to determine if rapid prototyping methods could be used in the design and manufacturing of high speed wind tunnel models in direct testing applications, and if these methods would reduce model design/fabrication time and cost while providing models of high enough fidelity to provide adequate aerodynamic data, and of sufficient strength to survive the test environment. Rapid prototyping methods utilized to construct wind tunnel models in a wing-body-tail configuration were: fused deposition method using both ABS plastic and PEEK as building materials, stereolithography using the photopolymer SL-5170, selective laser sintering using glass reinforced nylon, and laminated object manufacturing using plastic reinforced with glass and 'paper'. This study revealed good agreement between the SLA model, the metal model with an FDM-ABS nose, an SLA nose, and the metal model for most operating conditions, while the FDM-ABS data diverged at higher loading conditions. Data from the initial SLS model showed poor agreement due to problems in post-processing, resulting in a different configuration. A second SLS model was tested and showed relatively good agreement. It can be concluded that rapid prototyping models show promise in preliminary aerodynamic development studies at subsonic, transonic, and supersonic speeds.

Springer, A. M.↗
NASA NTRS1992

Development of an optical flameout detection system for High Temperature Wind Tunnels

This paper outlines the design and development of a flameout detection system for future use in the 8-Foot High Temperature Wind Tunnel (8' HTT) at the NASA Langley Research Center. The proposed system is required to function reliably in an oxidizing environment with pressures up to 28 MPa (4,000 psi), survive temperatures reaching 1700 C (3100 F), and respond with a shut-down signal upon flameout in less than 100 milliseconds. The 7-Inch High Temperature Pilot Tunnel (7" HTT), a one-twelfth scale version of the 8' HTT, was used to develop a prototype system and to obtain data on the spectral content of the flame during combustion. The design and development of the spectral data acquisition system for the 7" HTT is presented here.

Borg, Stephen E.↗
NASA NTRS1994

Coronal mass ejections in the solar wind at high solar latitudes: An overview

Ulysses provided the first direct measurements of coronal mass ejections (CME's) in the solar wind at high heliographic latitudes. An overview of new results from the plasma experiment on Ulysses and magnetic field measurements, during the spacecraft's first excursion to high solar latitudes are summarized. A striking aspect of the high-latitude CME's observed is that they all had high speeds, with the overall average speed being 730 km/sec. A new class of forward-reverse shock pairs, associated with expansion of CME's was discovered at high latitudes. Of six certain CME's observed at high latitudes, three have associated shock pairs of this nature. Combined Ulysses and Yohkoh observations suggest that the flux rope topology characteristic of some CME's results from reconnection within the legs of neighboring magnetic loops embedded within the escaping CME's.

Gosling, Jack T.↗
NASA NTRS1993

(abstract) Ulysses Observations of Magnetic Nulls in the Solar Wind

High time resolution magnetic field measurements (1 vector/s) at radial distances out to 5.3 AU and heliographic latitudes from 0(deg) to > 35(deg) S reveal the presence of solitary pulses lasting tens of seconds in which the field magnitude approaches or reaches zero. The properties of these nulls, their spatial distribution and relation to solar wind structures and to similar-apppearing interplanetary and magnetospheric impulses will be discussed.

magnetic impulses solar wind magnetic nulls Ulysse↗
NASA NTRS1986

High speed wind tunnel tests of the PTA aircraft

Propfans, advanced highly-loaded propellers, are proposed to power transport aircraft that cruise at high subsonic speeds, giving significant fuel savings over the equivalent turbofan-powered aircraft. NASA is currently sponsoring the Propfan Test Assessment Program (PTA) to provide basic data on the structural integrity and acoustic performance of the propfan. The program involves installation design, wind-tunnel tests, and flight tests of the Hamilton Standard SR-7 propfan in a wing-mount tractor installation on the Gulfstream II aircraft. This paper reports on the high-speed wind-tunnel tests and presents the computational aerodynamic methods that were employed in the analyses, design, and evaluation of the configuration. In spite of the complexity of the configuration, these methods provide aerodynamic predictions which are in excellent agreement with wind-tunnel data.

Aljabri, A. S.↗
NASA NTRS1992

Optical spectroscopy of Z Canis Majoris, V1057 Cygni, and FU Orionis - Accretion disks and signatures of disk winds

High resolution, high SNR optical spectra have been used to investigate the hypothesis that in outburst, FU Ori objects are self-luminous accretion disks whose light dominates at optical and near-IR wavelengths. Strong evidence has been found for linewidth versus wavelength correlation in good agreement with model predictions for Z CMa and V1057 Cyg, but not for FU Ori itself. Linewidth varies continuously with wavelength at optical wavelengths in the former two objects, In the case of FU Ori, it is argued that a combination of strong wind components to spectral lines, and surface gravity possibly being lower than that of supergiants, conceals the underlying linewidth versus wavelength relationship. A marginal correlation is found between linewidth and lower excitation potential in all three objects. Synthetic disk spectra are subtracted from observed spectral, and remarkably good fits are found for all three objects for wavelengths longer than about 5000 A.

Welty, Alan D.↗
NASA NTRS1973

The results of a high-speed wind tunnel test to investigate the effects of the NASA refan JT8D engine nacelles on the stability and control characteristics of the Boeing 727 airplane

A high speed wind tunnel test was conducted to investigate the effects of the NASA Refan JT8D engine nacelles on the stability and control characteristics of the Boeing 727 airplane. The test was performed at the Calspan Corporation 8x8 ft. (2.44x2.44 m.) transonic wind tunnel. Both the 727-200 and -100 models were tested. A small nose-down pitching moment increment and a slight increase in longitudinal stability were noted due to the Refan nacelles. The directional stability of the 727-200 airplane increased up to 10 percent. A smaller improvement was observed on the 727-100 model. In general, the high speed stability and control characteristics of the basic airplane are not significantly altered by the Refan nacelle installation.

Kupcis, E. A.↗
NASA NTRS1939

An Investigation of the Drag of Windshields in the 8-Foot High-Speed Wind Tunnel

The drag of closed-cockpit and transport-type windshields was determined from tests made at speeds from 200 to 440 miles per hour in the NACA 8-foot high-speed wind tunnel. This speed range corresponds to a test Reynolds number range of 2,510,000 to 4,830,000 based on the mean aerodynamic chord of the full-span model (17.29 inches). The shapes of the windshield proper, the hood, and the tail fairing were systematically varied to include common types and a refined design. Transport types varied from a reproduction of a current type to a completely faired windshield. The results show that the drag of windshields of the same frontal area, on airplanes of small to medium size, may account for 15% of the airplane drag or may be reduced to 1%. Optimum values are given for windshield and tail-fairing lengths; the effect, at various radii is shown. The longitudinal profile of a windshield is shown to be most important and the transverse profile, to be much less important. The effects of retaining strips, of steps for telescoping hoods, and of recessed windows are determined. The results show that the drag of transport-type windshields may account for 21% of the fuselage drag or may be reduced to 2%.

Robinson, Russell G.↗
NASA NTRS1976

Results of an aerodynamic investigation of a space shuttle orbiter/747 carrier flight test configuration to determine separation characteristics utilizing 0.0125-scale models (48-0/AX1318I-1) in the LTV 4 x 4 foot high speed wind tunnel (CA26), volume 1

Results of tests conducted on a 0.0125-scale model of the Space Shuttle Orbiter and a 0.0125-scale model of the 747 CAM configuration in a 4 x 4-foot High Speed Wind Tunnel were presented. Force and moment data were obtained for each vehicle separately at a Mach number of 0.6 and for each vehicle in proximity to the other at Mach numbers of 0.3, 0.5, 0.6 and 0.7. The proximity effects of each vehicle on the other at separation distances (from the mated configuration) ranging from 1.5 feet to 75 feet were presented; 747 Carrier angles of attack from 0 deg to 6 deg and angles of sideslip of 0 deg and -5 deg were tested. Model variables included orbiter elevon, aileron and body flap deflections, orbiter tailcone on and off, and 747 stabilizer and rudder deflections.

Gillins, R. L.↗
NASA NTRS1977

Development of a procedure to model high-resolution wind profiles from smoothed or low-frequency data

The derivation of simulated Jimsphere wind profiles from low-frequency rawinsonde data and a generated set of white noise data are presented. A computer program is developed to model high-resolution wind profiles based on the statistical properties of data from the Kennedy Space Center, Florida. Comparison of the measured Jimsphere data, rawinsonde data, and the simulated profiles shows excellent agreement.

Camp, D. W.↗
NASA NTRS1942

An Investigation of the Drag of Windshields in the 8-foot High-Speed Wind Tunnel

Report presents the results of tests made to determine the drag of closed-cockpit and transport-type windshields. The tests were made at speeds corresponding to a Mach number range of approximately 0.25 to 0.58 in the NACA 8-foot high-speed wind tunnel. This speed range corresponds to a test Reynolds number range of 2,510,000 to 4,830,000 based on the mean aerodynamic chord of the full-span model (17.29 in.). The shapes of the windshield proper, the hood, and the tail fairing were systematically varied to include common types and refined design.

Robinson, Russell G↗
NASA NTRS1995

Acceleration phenomena of high-speed wind observed at 0.1-0.3 AU with interplanetary scintillation

The radial distance dependence of solar wind speeds, which were measured by interplanetary scintillation method, has been studied especially for a high-speed solar wind, and large increase of the IPS speeds (300 km/s) was observed at the distance range of 0.1 - 0.3 AU. When the streams are mapped back onto the source surface, they distribute in polar coronal holes or their boundaries. Since the IPS measurement can be biased by several effects such as of line-of-sight integration, strong scattering and random velocities, we examined these biasing effects and have found difficulty to explain the large IPS speed increase with the biasing effects.

Kojima, M.↗
NASA NTRS2000

A Probabilistic Technique for Improving the Mid-Swath Wind Direction Accuracy of Scanning Pencil Beam Scatterometers

The SeaWinds on QuikSCAT scatterometer is a device developed by NASA JPL to measure the speed and direction of ocean surface winds. Simulations performed in order to determine the expected performance of the instrument prior to its launch have indicated that the accuracy of the retrieved wind vectors varies across the swath. In particular the mid-swath accuracy is worse than that of the rest of the swath. This behavior is a general characteristic of scanning pencil beam scatterometers. For SeaWinds, the accuracy of the rest of the swath, and the size of the swath are such that the instrument meets its science requirements despite mid-swath shortcomings. However, by understanding the problem at mid-swath, we can improve the performance there as well, yielding even better coverage and accuracy than was originally intended. The mid-swath performance degradation is due to suboptimal viewing geometry. In particular mid-swath measurements contains measurements from two azimuths, roughly 180 degrees apart. With the standard wind retrieval technique, mid-swath root mean square (RMS) wind direction errors are approximately 30 degrees for low wind speeds (3 - 5.5 m/s) and 20 degrees for moderate to high wind speeds (5.5 - 30 m/s). We discuss the underlying causes of this phenomenon in detail and propose a modification to the wind retrieval technique in order to improve mid-swath performance. By estimating the range of likely wind directions for each measurement cell, one can optimally apply information from neighboring cells in order to reduce random wind direction errors without significantly degrading the resolution of the resultant wind field. In this manner we are able to achieve mid-swath RMS wind direction errors as low as 15 degrees for low winds and 10 degrees for moderate to high winds, while at the same time preserving high resolution structures such as cyclones and fronts. Since our results are based on simulated data, we also outline a procedure for making use of real data to optimize the technique after launch.

Stiles, Bryan↗
NASA NTRS1982

Evaluation of lightning accommodation systems for wind-driven turbine rotors

Wind-driven turbine generators are being evaluated as an alternative source of electric energy. Areas of favorable location for the wind-driven turbines (high wind density) coincide with areas of high incidence of thunderstorm activity. These locations, coupled with the 30-m or larger diameter rotor blades, make the wind-driven turbine blades probable terminations for lightning strikes. Several candidate systems of lightning accommodation for composite-structural-material blades were designed and their effectiveness evaluated by submitting the systems to simulated lightning strikes. The test data were analyzed and system design were reviewed on the basis of the analysis.

Bankaitis, H.↗