Search NASA⌕ Search

SEARCH · Search NASA

Results for “wind generator”

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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

A wall interference assessment/correction system

A Wall Signature method originally developed by Hackett has been selected to be adapted for the Ames 12-ft Wind Tunnel WIAC system in the project. This method uses limited measurements of the static pressure at the wall, in conjunction with the solid wall boundary condition, to determine the strength and distribution of singularities representing the test article. The singularities are used in turn for estimating blockage wall interference. The lifting interference will be treated separately by representing in a horseshoe vortex system for the model's lifting effects. The development and implementation of a working prototype will be completed, delivered and documented with a software manual. The WIAC code will be validated by conducting numerically simulated experiments rather than actual wind tunnel experiments. The simulations will be used to generate both free-air and confined wind-tunnel flow fields for each of the test articles over a range of test configurations. Specifically, the pressure signature at the test section wall will be computed for the tunnel case to provide the simulated 'measured' data. These data will serve as the input for the WIAC method--Wall Signature method. The performance of the WIAC method then may be evaluated by comparing the corrected data with those of the free-air simulation.

Lo, Ching F.↗
NASA NTRS1993

A wall interference assessment/correction system

A Wall Signature method originally developed by Hackett was selected to be adapted for the Ames 12-ft Wind Tunnel Wall Interference Assessment/Correction (WIAC) System in the project. This method uses limited measurements of the static pressure at the wall, in conjunction with the solid wall boundary condition, to determine the strength and distribution of singularities representing the test article. The singularities are used in turn for estimating wall interference at the model location. The lifting interference will be treated separately by representing in a horseshoe vortex system for the model's lifting effects. The development and implementation of a working prototype will be completed, delivered, and documented with a software manual. The WIAC code will be validated by conducting numerically simulated experiments rather than actual wind tunnel experiments. The simulations will be used to generate both free-air and confined wind-tunnel flow fields for each of the test articles over a range of test configurations. Specifically, the pressure signature at the test section wall will be computed for the tunnel case to provide the simulated 'measured' data. These data will serve as the input for the WIAC method - Wall Signature method. The performance of the WIAC method then may be evaluated by comparing the corrected parameters with those for the free-air simulation. The following two additional tasks are included in the supplement No. 1 to the basic Grant. On-line wall interference calculation: The developed wall signature method (modified Hackett's method) for Ames 12-ft Tunnel will be the pre-computed coefficients which facilitate the on-line calculation of wall interference; and support system effects estimation: The effects on the wall pressure measurements due to the presence of the model support systems will be evaluated.

Lo, Ching F.↗
NASA NTRS1994

A wall interference assessment/correction system

A Wall Signature method originally developed by Hackett has been selected to be adapted for the Ames 12-ft Wind Tunnel WIAC system in the project. This method uses limited measurements of the static pressure at the wall, in conjunction with the solid wall boundary condition, to determine the strength and distribution of singularities representing the test article. The singularities are used in turn for estimating wall interference at the model location. The development and implementation of a working prototype will be completed, delivered and documented with a software manual. The WIAC code will be validated by conducting numerically simulated experiments rather than actual wind tunnel experiments. The simulations will be used to generate both free-air and confined wind-tunnel flow fields for each of the test articles over a range of test configurations. Specifically, the pressure signature at the test section wall will be computed for the tunnel case to provide the simulated 'measured' data. These data will serve as the input for the WIAC method--Wall Signature method. The performance of the WIAC method then may be evaluated by comparing the corrected parameters with those for the free-air simulation. The following two additional tasks are included: (1) On-line wall interference calculation: The developed wall signature method (modified Hackett's method) for Ames 12-ft Tunnel will be the pre-computed coefficients which facilitate the on-line calculation of wall interference, and (2) Support system effects estimation: The effects on the wall pressure measurements due to the presence of the model support systems will be evaluated.

Lo, C. F.↗
NASA NTRS2000

The Surface Pressure Response of a NACA 0015 Airfoil Immersed in Grid Turbulence: Characteristics of the Turbulence - Volume 1

Two grids have been developed for the Virginia Tech 6 ft x 6 ft Stability wind tunnel for the purpose of generating homogeneous isotropic turbulent flows for the study of unsteady airfoil response. The first, a square bi-planar grid with a 12" mesh size and an open area ratio of 69.4%, was mounted in the wind tunnel contraction. The second grid, a metal weave with a 1.2 in. mesh size and an open area ratio of 68.2% was mounted in the tunnel test section. Detailed statistical and spectral measurements of the turbulence generated by the two grids are presented for wind tunnel free stream speeds of 10, 20, 30 and 40 m/s. These measurements show the flows to be closely homogeneous and isotropic. Both grids produce flows with a turbulence intensity of about 4% at the location planned for the airfoil leading edge. Turbulence produced by the large grid has an integral scale of some 3.2 inches here. Turbulence produced by the small grid is an order of magnitude smaller. For wavenumbers below the upper limit of the inertial subrange, the spectra and correlations measured with both grids at all speeds can be represented using the von Karman interpolation formula with a single velocity and length scale. The spectra maybe accurately represented over the entire wavenumber range by a modification of the von Karman interpolation formula that includes the effects of dissipation. These models are most accurate at the higher speeds (30 and 40 m/s).

Bereketab, Semere↗
NASA NTRS1991

Twin-Mirrored-Galvanometer Laser-Light-Sheet Generator

Multiple, rotating laser-light sheets generated to illuminate flows in wind tunnels. Designed and developed to provide flexibility and adaptability to wide range of applications. Design includes capability to control size and location of laser-light sheet in real time, to generate horizontal or vertical sheets, to sweep sheet repeatedly through volume, to generate multiple sheets with controllable separation, and to rotate single or multiple laser-light sheets. Includes electronic equipment and laser mounted on adjustable-height platform. Twin-mirrored galvanometer unit supported by tripod to reduce vibration. Other possible applications include use in construction industry to align beams of building. Artistic or display applications also possible.

Rhodes, David B.↗
NASA NTRS2020

Evaluation of a Method to Retrieve Temperature and Wind Velocity Profiles of the Venusian Nightside Mesosphere from Mid-Infrared CO2 Absorption Line Observed by Heterodyne Spectroscopy

We evaluated a method for retrieving vertical temperature and Doppler wind velocity profiles of the Venusian nightside mesosphere from the CO2 absorption line resolved by mid-infrared heterodyne spectroscopy. The achievable sensitive altitude and retrieval accuracy were derived with multiple model spectra generated from various temperature and wind velocity profiles with several noise levels. The temperature profiles were retrieved at altitudes of 70–100 km with a vertical resolution of 5 km and a retrieval accuracy of ±15 K. The wind velocity was also retrieved at an altitude of approximately 85 km with a vertical resolution of 10 km and a retrieval accuracy of ± 25–50 m/s. In addition, we studied an event and applied our method to spectra obtained by the HIPWAC instrument attached to the NASA/IRTF 3-m telescope on May 19–22, 2012. Retrieved wind velocities in a latitude of 33° S at 3:00 LT were interpreted as subsolar-to-antisolar (SS-AS) flows at altitudes of 84 ±6 km and 94 ±7 km, and they were stronger than expected. This result suggested that the transition between the retrograde super rotational zonal (RSZ) wind and SS-AS flow may occur at altitudes below 90 km which previously was predicted to be the transition region. This work provides a basis for our analysis of further observations obtained by a mid-infrared heterodyne spectrometer MILAHI attached to the Tohoku University 60-cm telescope at Haleakalā, Hawaii.

Venus↗
NASA NTRS1985

Results of an observing system simulation experiment based on the proposed Windsat instrument

Two fraternal twin experiments were conducted as part of this study. A data impact experiment using real data (runs 1 and 2) was conducted to assess the impact that rawin wind observations have on both a 5-day assimilation and a single 5-day forecast generated at the end of each assimilation. An observing system simulation experiment (OSSE) using simulated observations (runs 3, 4, and 5) was conducted in order to first calibrate the OSSE results and second to use this calibration to estimate the 'real world' impact from the contribution of global 3-dimensional wind profiles generated from a space-based lidar system known as Windsat. Each of the three runs in the seond experiment were also 5-day assimilation runs with a 5-day forecast initialized from the last 6-hour update cycle of the assimilation. The data impact study revealed a consistent positive impact when rawin winds were added back into an otherwise complete FGGE data set. Both the 6-hour and 5-day forecasts were improved at all levels, in both hemispheres, and for both the wind and the geopotential height fields. Similar results were obtained from the two parallel simulation runs, 3 and 4. Together with the results from runs 1 and 2, calibration coefficients were generated so as to 'correct' the results determined from the addition of Windsat winds (run 5). The Windsat simulation showed a positive improvement in all cases studied. Even though only the tropics were enhanced with these wind observations, hemispheric rms errors were decreased in both the assimilation and 5-day forecast. The 6-hour forecasts of zonal wind from the assimilation run were improved by as much as 50 pct. on the average, and the single forecast showed an average improvement of near 30 pct. Even though these calibrated values are considered too optimistic, the skill of the forecast generated from this run extended the useful forecast period by 18-24 hours.

Arnold, Charles P., Jr.↗
NASA NTRS1979

Low-turbulence high-speed wind tunnel for the determination of cascade shock losses

A low turbulence high-speed wind tunnel, using anti-turbulence screening and a 100:1 contraction ratio, has been found suitable for high-speed smoke flow visualization. The location and strength of normal, oblique, and curved shock waves generated by transonic or supersonic wind tunnel flow over airfoils or through axial compressor cascades is determined by combined shadowgraph and smokelines visualization techniques without the interference effects caused by intrusive probes. The Reynolds number based on chord varied between 50,000 and 1,000,000. Preliminary results are compared with the relevant theory and data gathered using a total pressure probe.

Slovisky, J. A.↗
NASA NTRS1985

Generation of auroral Omega bands by shear instability of the neutral winds

Thermospheric neutral wind acceleration via ion drag in the conducting E-region of the ionosphere is greatly increased by electron precipitation associated with auroras. This increased acceleration can lead to the development of significant horizontal wind shears, which were found to be unstable to the Kelvin-Helmholtz shear instability. Numerical simulation of the neutral response to an intense, postmidnight, diffuse aurora shows tne formation of an E-region 'jet stream' within the aurora, with peak winds speeds greather than 700 m/s after one hour. It is proposed that this jet stream produces unstable Kelvin-Helmholtz waves, which can drive waves of discrete aurora along the poleward boundary of the preexisting diffuse aurora. It is suggested that such auroral waves, driven by the neutral winds, form eastward propagating waves (omega bands) occasionally observed along the poleward boundary of postmidnight diffuse auroras. It was found that neutral wind shears that develop in response to discrete auroral arcs are unstable; however, the resulting wind waves are not expected to drive significant auroral waves along discrete arcs.

Lyons, L. R.↗
NASA NTRS2017

Optical Flow for Flight and Wind Tunnel Background Oriented Schlieren Imaging

Background oriented Schlieren images have historically been generated by calculating the observed pixel displacement between a wind-on and wind-o image pair using normalized cross-correlation. This work uses optical flow to solve the displacement fields which generate the Schlieren images. A well established method used in the computer vision community, optical flow is the apparent motion in an image sequence due to brightness changes. The regularization method of Horn and Schunck is used to create Schlieren images using two data sets: a supersonic jet plume shock interaction from the NASA Ames Unitary Plan Wind Tunnel, and a transonic flight test of a T-38 aircraft using a naturally occurring background, performed in conjunction with NASA Ames and Armstrong Research Centers. Results are presented and contrasted with those using normalized cross-correlation. The optical flow Schlieren images are found to provided significantly more detail. We apply the method to historical data sets to demonstrate the broad applicability and limitations of the technique.

Image processing↗
NASA NTRS2001

Non-Contact Linear Actuator Position Sensor Having a PID-Compensating Controller

A position sensor or controller generates a response signal in existing armature windings of an actuator and detects the response signal to determine the position of the armature. To generate the response signal, the actuator includes a sensor excitation winding near the armature. Two sensor excitation windings can be provided, above and below the armature, to cancel out z components and thus allow for a variable gap. The sensor excitation winding or windings are supplied with an excitation signal to induce the response signal in the armature windings. The response signal is derived by differentially amplifying and frequency filtering a raw output of the armature windings. The response signal is demodulated to determine position. If a position controller rather than a mere sensor is desired, the position signal can be buffered, PID compensated, amplified, and fed back to the armature windings.

Dean C Alhorn↗
NASA NTRS1984

Results of tests of advanced flexible insulation vortex and flow environments in the North American Aerodynamics Laboratory lowspeed wind tunnel using 0.0405-scale Space Shuttle Orbiter model 16-0 (test OA-309)

An experimental investigation (Test OA-309) was conducted using 0.0405-scale Space Shuttle Orbiter Model 16-0 in the North American Aerodynamics Laboratory 7.75 x 11.00-foot Lowspeed Wind Tunnel. The primary purpose was to locate and study any flow conditions or vortices that might have caused damage to the Advanced Flexible Reusable Surface Insulation (AFRSI) during the Space Transportation System STS-6 mission. A secondary objective was to evaluate vortex generators to be used for Wind Tunnel Test OS-314. Flowfield visualization was obtained by means of smoke, tufts, and oil flow. The test was conducted at Mach numbers between 0.07 and 0.23 and at dynamic pressures between 7 and 35 pounds per square foot. The angle-of-attack range of the model was -5 degrees through 35 degrees at 0 or 2 degrees of sideslip, while roll angle was held constant at zero degrees. The vortex generators were studied at angles of 0, 5, 10, and 15 degrees.

Marshall, B. A.↗
NASA NTRS2003

Effect of Sub-Boundary Layer Vortex Generations on Incident Turbulence

Sub-boundary layer vortex generators were tested in a wind tunnel to assess their effect on the velocity field within the wake region of a turbulent boundary layer. Both mean flow quantities and turbulence statistics were measured. Although very small relative to the boundary layer thickness, these so-called micro vortex generators were found to have a measurable effect on the power spectra and integral length scales of the turbulence at a distance many times the height of the devices themselves. In addition, the potential acoustic impact of these devices is also discussed. Measured turbulence spectra are used as input to an acoustic formulation in a manner that compares predicted sound pressure levels that result from the incident boundary-layer turbulence, with and without the vortex generators in the flow.

Casper, J.↗
NASA NTRS1983

Determining the solar wind speed above active regions using remote radio-wave observations

A new technique has made it possible to measure the velocity of portions of the solar wind during its flow outward from the sun. This analysis utilizes spacecraft (ISEE-3) observations of radio emission generated in regions of the solar wind associated with solar active regions. By tracking the source of these radio waves over periods of days, it is possible to measure the motion of the emission regions. Evidence of solar wind acceleration during this outward flow, consistent with theoretical models, has also been obtained.

Fainberg, J.↗
NASA NTRS1986

Current wind tunnel capability and planned improvements at Lewis Research Center

As the propulsion and power generation center of NASA, Lewis has designed its wind tunnels for propulsion research. Therefore, the 8 by 6 Foot Supersonic Wind Tunnel and the 10 by 10 Foot Supersonic Wind Tunnel provide the capability to test operating propulsion systems from Mach 0.4 to 3.5. The 9 by 15 Foot Wind Tunnel can investigate propulsion installation problems at the lower takeoff and landing speeds and provides an excellent anechoic environment to measure propeller and fan noise. The Lewis Central Air System provides steady air supplies to 450 psi, and exhaust to 3 in. of mercury absolute, which are available to the wind tunnels for simulation of jets and engine induced flows. The Lewis Icing Research Tunnel is the largest in the free world that can produce icing conditions throughout the year. Rehabilitation of the Altitude Wind Tunnel at Lewis would allow testing of propulsion systems in the upper left hand corner which would be a unique capability. Also, in a mothballed state at Lewis, the Hypersonic Tunnel Facility could provide the best simulation of nonvitiated Mach 5-7 test conditions available. Studies are currently being made of the Lewis facilities to identify enhancements of their research potential for the 1990's and beyond.

Bowditch, D. N.↗
NASA NTRS1992

Hubble Space Telescope observations of the 1990 equatorial disturbance on Saturn - Zonal winds and central meridian albedos

The present comparison of two sets of HST data from August and November 1990 with Voyager 1 and 2 data acquired in 1980 and 1981 gives attention to Saturn's equatorial-region disturbance of September 1990. Longitudinal variations in the equatorial zonal winds are interpreted as evidence for interaction between the storm nucleus that was generated during the disturbance and the local wind field.

Barnet, C. D.↗
NASA NTRS1995

PARC3D calculations of the F/A-18A HARV inlet vortex generators

NASA Lewis Research Center is currently engaged in a research effort as a team member of the High Alpha Technology Program within the NASA agency. This program uses a specially-equipped F/A-18A aircraft called the High Alpha Research Vehicle (HARV), in an effort to improve the maneuverability of high performance military aircraft at low-subsonic-speed, high-angle-of-attack conditions. The overall objective of the NASA Lewis effort is to develop inlet analysis technology towards efficient airflow delivery to the engine during these maneuvers. One portion of this inlet analysis technology uses computational fluid dynamics to predict installed inlet performance. Most of the F/A-18A HARV geometry, which includes the ramp/splitter plate, side diverter and slot, inlet lip and upper diverter, and deflected leading-edge flap has been modeled. The empennage and rear fuselage have not. A pair of vortex generators located on the bottom wall of the inlet were not modeled initially. These vortex generators were installed to alleviate any flow separation that may be induced by the wheel well protrusion into the inlet wall. Calculations completed with the PARC3D code showed that the pressure recovery has been underpredicted and the flow distortion over-predicted. To improve the correlation of PARC3D predictions with flight and wind tunnel tests, the vortex generators were included in the grid geometry and the results are presented in this report. The grid totals 27 blocks or 1.3 million grid points for the half model, which includes the vortex generator grid blocks. Two flight cases were calculated, a high speed case with a Mach number of 0.8 and angle of attack of 3.4; and a low speed case with a Mach number of 0.43 and angle of attack of 32.2. The vortex generators have a significant effect on the inlet boundary layers at high speed, low angle of attack; and have no effect at low speed, high angle of attack.

Podleski, Steve D.↗
NASA NTRS2014

Anisotropic Solar Wind Sputtering of the Lunar Surface Induced by Crustal Magnetic Anomalies

The lunar exosphere is generated by several processes each of which generates neutral distributions with different spatial and temporal variability. Solar wind sputtering of the lunar surface is a major process for many regolith-derived species and typically generates neutral distributions with a cosine dependence on solar zenith angle. Complicating this picture are remanent crustal magnetic anomalies on the lunar surface, which decelerate and partially reflect the solar wind before it strikes the surface. We use Kaguya maps of solar wind reflection efficiencies, Lunar Prospector maps of crustal field strengths, and published neutral sputtering yields to calculate anisotropic solar wind sputtering maps. We feed these maps to a Monte Carlo neutral exospheric model to explore three-dimensional exospheric anisotropies and find that significant anisotropies should be present in the neutral exosphere depending on selenographic location and solar wind conditions. Better understanding of solar wind/crustal anomaly interactions could potentially improve our results.

exosphere↗