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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

High pressure hypervelocity electrothermal wind tunnel performance study and subscale tests

The feasibility of a Mach 10 to 20, high pressure electrothermal wind tunnel was assessed. A heater based on a continuous high power electric arc discharge capable of heating air to temperatures above 10,000 K and pressures of 15,000 atm is the key element of this wind tunnel. Results of analytical study indicate that the facility is capable of simulation conditions suitable for hypervelocity airbreathing propulsion testing up to Mach 16. In this case simulation was limited by pressure containment, high nozzle throat heat flux rates, and chemical freezing in the nozzle. The high total pressure capability improved the recombination chemistry in the facility nozzle as chemical equilibrium prevailed to the freezing point. Steady arc discharges were observed with liquid nitrogen flowing into the arc chamber during tests based on the two millisecond test facility. The measured steady pressure in the arc chamber was 4559 psi, which is two times greater than maximum total pressure obtainable in conventional arc heaters.

Rizkalla, Oussama F.↗
NASA NTRS2006

A Summary of the Experimental Results for a Generic Tractor-Trailer in the Ames Research Center 7- by 10-Foot and 12-Foot Wind Tunnels

Experimental measurements of a generic tractor-trailer were obtained in two wind tunnels at Ames Research Center. After a preliminary study at atmospheric conditions in the 7- by 10-Foot Wind Tunnel, additional testing was conducted at Reynolds numbers corresponding to full-scale highway speeds in the 12-Foot Pressure Wind Tunnel. To facilitate computational modeling, the 1:8-scale geometry, designated the Generic Conventional Model, included a simplified underbody and omitted many small-scale details. The measurements included overall and component forces and moments, static and dynamic surface pressures, and three-component particle image velocimetry. This summary report highlights the effects of numerous drag reduction concepts and provides details of the model installation in both wind tunnels. To provide a basis for comparison, the wind-averaged drag coefficient was tabulated for all configurations tested. Relative to the baseline configuration representative of a modern class-8 tractor-trailer, the most effective concepts were the trailer base flaps and trailer belly box providing a drag-coefficient reduction of 0.0855 and 0.0494, respectively. Trailer side skirts were less effective yielding a drag reduction of 0.0260. The database of this experimental effort is publicly available for further analysis.

Storms, Bruce L.↗
NASA NTRS2013

Stratified Magnetically Driven Accretion-Disk Winds and Their Relations To Jets

We explore the poloidal structure of two-dimensional magnetohydrodynamic (MHD) winds in relation to their potential association with the X-ray warm absorbers (WAs) and the highly ionized ultra-fast outflows (UFOs) in active galactic nuclei (AGNs), in a single unifying approach. We present the density n(r, theta), ionization parameter xi(r, theta), and velocity structure v(r, theta) of such ionized winds for typical values of their fluid-to-magnetic flux ratio, F, and specific angular momentum, H, for which wind solutions become super-Alfvenic. We explore the geometrical shape of winds for different values of these parameters and delineate the values that produce the widest and narrowest opening angles of these winds, quantities necessary in the determination of the statistics of AGN obscuration. We find that winds with smaller H show a poloidal geometry of narrower opening angles with their Alfv´en surface at lower inclination angles and therefore they produce the highest line of sight (LoS) velocities for observers at higher latitudes with the respect to the disk plane. We further note a physical and spatial correlation between the X-ray WAs and UFOs that form along the same LoS to the observer but at different radii, r, and distinct values of n, xi, and v consistent with the latest spectroscopic data of radio-quiet Seyfert galaxies. We also show that, at least in the case of 3C 111, the winds' pressure is sufficient to contain the relativistic plasma responsible for its radio emission. Stratified MHD disk winds could therefore serve as a unique means to understand and unify the diverse AGN outflows.

accretion↗
NASA NTRS1976

Wind-tunnel testing with a rotary-balance apparatus to simulate aircraft spin motions

Experiments have been conducted in the Ames 12-Foot Pressure Wind Tunnel on a simple airplane-like model using a rotary-balance apparatus to simulate a steady spin motion at high angles of attack. Tests were run at Mach numbers of 0.1 and 0.25 over a wide Reynolds number range with the angle of attack varying from 45 to 90 deg. During previous tests of the same research model, some difficulties were experienced with measurement accuracy in the low-to-medium range of Reynolds number because of limitations in the sensitivity of selected force balances. For the present tests, special balances were built to provide accurate measurements of the nose and tail contributions to spin motions and improvements were made to the overall test apparatus. The results of this test, including some interesting hysteresis effects with spin rate, are described. Some of the problems associated with rotary-balance tests at high Reynolds numbers are discussed. A new large-scale rotary apparatus now nearing completion for use in the Ames 12-Foot and 11- by 11-Foot Wind Tunnels is described briefly.

Malcolm, G. N.↗
NASA NTRS1980

Evaluation of flow quality in two large NASA wind tunnels at transonic speeds

Wind tunnel testing of low drag airfoils and basic transition studies at transonic speeds are designed to provide high quality aerodynamic data at high Reynolds numbers. This requires that the flow quality in facilities used for such research be excellent. To obtain a better understanding of the characteristics of facility disturbances and identification of their sources for possible facility modification, detailed flow quality measurements were made in two prospective NASA wind tunnels. Experimental results are presented of an extensive and systematic flow quality study of the settling chamber, test section, and diffuser in the Langley 8 foot transonic pressure tunnel and the Ames 12 foot pressure wind tunnel. Results indicate that the free stream velocity and pressure fluctuation levels in both facilities are low at subsonic speeds and are so high as to make it difficult to conduct meaningful boundary layer control and transition studies at transonic speeds.

Harvey, W. D.↗
NASA NTRS1989

Experimental Aerodynamic Characteristics of a Joined-wing Research Aircraft Configuration

A wind-tunnel test was conducted at Ames Research Center to measure the aerodynamic characteristics of a joined-wing research aircraft (JWRA). This aircraft was designed to utilize the fuselage and engines of the existing NASA AD-1 aircraft. The JWRA was designed to have removable outer wing panels to represent three different configurations with the interwing joint at different fractions of the wing span. A one-sixth-scale wind-tunnel model of all three configurations of the JWRA was tested in the Ames 12-Foot Pressure Wind Tunnel to measure aerodynamic performance, stability, and control characteristics. The results of these tests are presented. Longitudinal and lateral-directional characteristics were measured over an angle of attack range of -7 to 14 deg and over an angle of sideslip range of -5 to +2.5 deg at a Mach number of 0.35 and a Reynolds number of 2.2x10(6)/ft. Various combinations of deflected control surfaces were tested to measure the effectiveness and impact on stability of several control surface arrangements. In addition, the effects on stall and post-stall aerodynamic characteristics from small leading-edge devices called vortilons were measured. The results of these tests indicate that the JWRA had very good aerodynamic performance and acceptable stability and control throughout its flight envelope. The vortilons produced a profound improvement in the stall and post-stall characteristics with no measurable effects on cruise performance.

Smith, Stephen C.↗
NASA NTRS2019

Independent Effects of Reynolds Number and Mach Number on the Aerodynamics of an Iced Swept Wing

Aerodynamic assessment of icing effects on swept wings is an important component of a larger effort to improve three-dimensional (3D) icing simulation capabilities. An understanding of ice-shape geometric fidelity and Reynolds and Mach number effects on the iced-wing aerodynamics is needed to guide the development and validation of ice-accretion simulation tools. To this end, wind tunnel testing was carried out for a 13.3-percent-scale semispan wing based upon the Common Research Model airplane configuration. The wind tunnel testing was conducted at the Office National d’Etudes et de Recherches Aérospatiales (ONERA) F1 pressurized wind tunnel with Reynolds numbers of 1.6 x 10(exp 6) to 11.9 x 10(exp 6 ) and Mach numbers of 0.09 to 0.34. Five different configurations were investigated using fully 3D, high-fidelity artificial ice shapes that maintain nearly all of the 3D ice-accretion features documented in prior icing wind tunnel tests. These large, leading-edge ice shapes were nominally based upon airplane holding in icing conditions scenarios. For three of these configurations, lower fidelity simulations were also built and tested. The results presented in this paper show that while Reynolds and Mach number effects are important for quantifying the clean-wing performance, there is very little to no effect for an iced wing with 3D, high-fidelity artificial ice shapes or 3D smooth ice shapes with grit roughness. These conclusions are consistent with the large volume of past research on iced airfoils. However, some differences were also noted for the associated stalling angle of the iced swept wing and for various lower fidelity versions of the leading-edge ice accretion. More research is planned to further investigate the key features of ice-accretion geometry that must be simulated in lower fidelity versions in order to capture the essential aerodynamics.

Aircraft icing↗
NASA NTRS1987

Wind tunnel evaluation of a truncated NACA 64-621 airfoil for wind turbine applications

An experimental program to measure the aerodynamic performance of a NACA 64-621 airfoil with a truncated trailing edge for wind turbine applications has been conducted in the Ohio State University Aeronautical and Astronautical Research Laboratory 6 in. by 21 in. pressurized wind tunnel. The blunted or trailing edge truncated (TET) airfoil has an advantage over similar trailing edge airfoils because it is able to streamline a larger spar structure, while also providing aerodynamic properties that are quite good. Surface pressures were measured and integrated to determine the lift, pressure drag, and moment coefficients over angles of attack ranging from -14 to +90 deg at Mach 0.2 and Reynolds numbers of 1,000,000 and 600,000. Results are compared to the NACA 0025, 0030, and 0035 thick airfoils with sharp trailing edges. Comparison shows that the 30 percent thick NACA 64-621-TET airfoil has higher maximum lift, higher lift curve slope, lower drag at higher lift coefficients, and higher chordwise force coefficient than similar thick airfoils with sharp trailing edges.

Law, S. P.↗
NASA NTRS1983

An evaluation of Space Shuttle Orbiter forward fuselage surface pressures - Comparison with wind tunnel and theoretical predictions

In order for ground-based pressure distribution techniques to be verified by the actual performance of the Space Shuttle Orbiter in flight, a comparative study of flight pressure data and both wind tunnel and computational data is presented. The flight pressure data, obtained from measurements on the Orbiter's surface during atmospheric reentry, are part of the overall Orbiter flight data system designated Development Flight Instrumentation. Also given is an analysis of the Orbiter pressure data system, including its transducers, their behavior, and their calibration. The two analyses are the bases of an error assessment calculation for the flight data, as well as an explanation of any discrepancies between flight and ground-based data.

Bradley, P. F.↗
NASA NTRS1992

Submillimeter heterodyne spectroscopy and remote sensing of the upper atmosphere

Submillimeter-wavelength heterodyne spectroscopy by microwave limb sounding (MLS) from orbiting satellite is a measurement technique for studying Earth's stratosphere, mesosphere and lowerr thermosphere on a global scale. Development and deployment of such tools are timely, as stratospheric ozone shileds life from solar ultraviolet radiation but is depleted by pollution from industrial activities. MLS experiments on NASA's Upper Atmosphere Research Satellite (UARS) and Earth Observing System (EOS) are now being developed and implementend for global monitoring. Atmospheric thermal-emission spectra at millimeter and submillimeter wave-lengths are measured as the instrument field of view (FOV) is scanned through the limb from above. Atmospheric profiles of molecular abundances, temperature, pressure, wind and magnetic field can be determined from the measured emission spectra. Intensity of the emission can provide abundance and temperature. Measured linewidths, and emission from temperature-insensitive O2 lines, can provide pressure. Differentitaion of measured pressure with repsect ot measured height differential (obtaiend from the instrument FOV scan encoder) can also provide temperature through atmospheric hydrostatic equilibrium (which relates temperature to pressure and height differential). Doppler shifts of spectral lines can provide wind, and Zeeman splitting of the magnetic-dipole lines of O2 can provide magnetic field.

Waters, J. W.↗
NASA NTRS1979

Design and wind tunnel tests of winglets on a DC-10 wing

Results are presented of a wind tunnel test utilizing a 4.7 percent scale semi-span model in the Langley Research Center 8-foot transonic pressure wind tunnel to establish the cruise drag improvement potential of winglets as applied to the DC-10 wide body transport aircraft. Winglets were investigated on both the DC-10 Series 10 (domestic) and 30/40 (intercontinental) configurations and compared with the Series 30/40 configuration. The results of the investigation confirm that for the DC-10 winglets provide approximately twice the cruise drag reduction of wing-tip extensions for about the same increase in bending moment at the wing fuselage juncture. Furthermore, the winglet configurations achieved drag improvements which were in close agreement to analytical estimates. It was observed that relatively small changes in wing-winglet tailoring effected large improvements in drag and visual flow characteristics. All final winglet configurations exhibited visual flow characteristics on the wing and winglets

Gilkey, R. D.↗
NASA NTRS1978

Estimating tropical cyclone central pressure and outer winds from satellite microwave data

A new technique is presented for estimating central pressure and surface winds outside of the radius of maximum winds from brightness temperatures measured by the SCAMS on Nimbus 6. The problem of estimating maximum surface winds is not treated because the spatial resolution of the radiometer is not high enough for this purpose. The technique is developed on the basis of measurements over eight typhoons and five hurricanes during 1975. It is shown that the warm 55.45-GHz brightness temperature anomaly previously observed over Typhoon June can be found over other tropical cyclones. Maximum brightness temperature anomaly correlates with central pressure with a correlation coefficient of -0.859. Outer surface wind speeds are calculated by assuming gradient balance and using the regression between brightness temperature anomaly and central pressure to estimate pressure gradients.

Kidder, S. Q.↗
NASA NTRS1989

Safety and cryogenic wind tunnels

The Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT) was placed in operation at NASA's Langley Research Center in 1973 as the world's first cryogenic pressure tunnel. The 0.3-m TCT can operate from ambient to cryogenic temperatures over an absolute pressure range from about 1 to 6 atmospheres. Three major test section concepts were developed and refined in this unique facility. The 0.3-m TCT is a leader in the development of various cryogenic pressure wind tunnel experimental techniques, instrumentation, control, model technology and safety standards. The safety experience gained is examined. During this period of advanced research, new operating techniques, training policies, and procedures had to be established. The paper deals with the Do's and Don'ts of cryogenic wind tunnel testing. Hazards and safety requirements which are unique to cryogenic testing are discussed. Highlights of experience and lessons learned with the 0.3-m TCT are reviewed.

Ray, Edward J.↗
NASA NTRS1941

Wind-Tunnel Investigation of an NACA 66,2-216 Low-Drag Wing with Split Flaps of Various Sizes, Special Report

An investigation was conducted in the NACA 19-foot pressure wind tunnel of a rectangular wing having NACA 66, 2-216 low-drag airfoil sections and various sizes of simple split flaps. The purpose of the investigation was, primarily, to determine the influence of these flap installations on the aerodynamic characteristics of the wing. Complete lift, drag, and pitching-moment characteristics were determined for a range of test Reynolds numbers from about 2,600,000 to 4,600,000 for each of the installations and for the plain wing. The results of this investigation indicate that values of maximum lift coefficient similar to those of wings with conventional airfoil sections and split flaps can be expected of wings having the NACA 66,2-216 low-drag sections. The increment of maximum lift due to the split flap was found to be practically independent of the Reynolds number over the range investigated. The optimum split flap on the basis of maximum lift appears to have a chord about 20% of the wing chord and a deflection of 60 degrees. The C(sub L) max of the wing with the 0.20c partial-span flap deflected 60 degrees is 2.07 at a Reynolds number of 4,600,000 while with the full-span flap it is approximately 2.53; the increment of the maximum lift coefficient due to the flap is approximately proportional to the flap span. Although the addition of a split flap tends to hasten the stall and to cause it to occur more abruptly, little change in pattern is evidenced by observations of the behavior of wool tufts on the wing.

Muse, Thomas C.↗
NASA NTRS1941

Wind-Tunnel Investigation of an NACA Low-Drag Tapered Wing with Straight Trailing Edge and Simple Split Flaps, Special Report

An investigation was conducted in the NACA 19-foot pressure wind tunnel of a tapered wing with straight railing edge having NACA 66 series low-drag airfoil sections and equipped with full-span and partial-span simple split flaps. The airfoil sections used were the NACA 66,2-116 at the root and the 66,2-216 at the tip. The primary purpose of the investigation was to determine the effect of the split flaps on the aerodynamic characteristics of the tapered wing. Complete lift, drag, and pitching-moment coefficients were determined for the plain wing and for each flap arrangement through a Reynold number range of 2,600,000 to 4,600,000. The results of this investigation indicate that values of maximum lift coefficient comparable to values obtained on tapered wings with conventional sections and similar flap installations can be obtained from wings with the NACA low-drag sections. The increment of maximum lift due to the split flap was found to vary somewhat with Reynold number over the range investigated. The C(sub L)max of the wing alone is 1.49 at a Reynolds number of 4,600,000; whereas with the partial-span simple split flap it is 2.22 and with the full-span arrangement, 2.80. Observations of wool tufts on the wing indicate that the addition of split flaps did not appreciable alter the pattern of the stall; even though the stall did occur more abruptly than with the wing alone.

Muse, Thomas C.↗