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At least 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Non-steady wind turbine response to daytime atmospheric turbulence

Relevant to drivetrain bearing fatigue failures, we analyse non-steady wind turbine responses from interactions between energy-dominant daytime atmospheric turbulence eddies and the rotating blades of a GE 1.5 MW wind turbine using a unique dataset from a GE field experiment and computer simulation. Time-resolved local velocity data were collected at the leading and trailing edges of an instrumented blade together with generator power, revolutions per minute, pitch and yaw. Wind velocity and temperature were measured upwind on a meteorological tower. The stability state and other atmospheric conditions during the field experiment were replicated with a large-eddy simulation in which was embedded a GE 1.5 MW wind turbine rotor modelled with an advanced actuator line method. Both datasets identify three important response time scales: advective passage of energy-dominant eddies (≈25–50 s), blade rotation (once per revolution (1P), ≈3 s) and sub-1P scale (<1 s) response to internal eddy structure. Large-amplitude short-time ramp-like and oscillatory load fluctuations result in response to temporal changes in velocity vector inclination in the aerofoil plane, modulated by eddy passage at longer time scales. Generator power responds strongly to large-eddy wind modulations. Lastly, we show that internal dynamics of the blade boundary layer near the trailing edge is temporally modulated by the non-steady external flow that was measured at the leading edge, as well as blade-generated turbulence motions.

17 WIND ENERGY↗
NASA NTRS1985

Deformation of the heliospheric current sheet

A kinematic analysis of the previously neglected effect of velocity inhomogeneity on the topology of the heliospheric current sheet in a radially flowing solar wind shows how the originally smooth current sheet becomes 'ruffled'. In the highly idealized case of a totally uniform, radial, steady solar wind, the shape of the current sheet is independent of distance from the sun. However, the real solar wind is inhomogeneous; the velocity varies from point to point along the current sheet, causing a distortion in the current sheet of progressively greater amplitude with increasing distance from the sun. This is true even for purely radial flow. Significant and observable distortion is produced by relatively small gradients in velocity; thus to predict or understand the shape of the heliospheric current sheet it is essential to know the solar wind in which the current sheet is embedded. Examples are given of mild velocity gradients which demonstrate the principles, the magnitude, and the character of the effect; deformation of the actual heliospheric current sheet in the highly variable solar wind is expected to be of far greater amplitude and complexity than in the simplified, tutorial examples. A new expression for the inclination of the current sheet as a function of velocity inhomogeneity and distance from the sun that is easily applied to the interpretation of solar wind data is also derived.

Suess, S. T.↗
DOE OSTI2015

Spatially extended NA i D resonant emission and absorption in the galactic wind of the nearby infrared-luminous quasar F05189-2524

Emission from metal resonant lines has recently emerged as a potentially powerful probe of the structure of galactic winds at low and high redshift. In this work, we present only the second example of spatially resolved observations of Na i D emission from a galactic wind in a nearby galaxy (and the first 3D observations at any redshift). F05189-2524, a nearby (z = 0.0428) ultraluminous infrared galaxy powered by a quasar, was observed with the integral field unit on the Gemini Multi-Object Spectrograph at Gemini South. Na i D absorption in the system traces dusty filaments on the near side of an extended, active galactic nucleus-driven galactic wind (with projected velocities up to 2000 km s{sup −1}). These filaments (A{sub V}≲4 and N(H)≲10{sup 22} cm{sup −2}) simultaneously obscure the stellar continuum and Na i D emission lines. The Na i D emission lines serve as a complementary probe of the wind: they are strongest in regions of low foreground obscuration and extend up to the limits of the field of view (galactocentric radii of 3 kpc). An azimuthally symmetric Sérsic model extincted by the same foreground screen as the stellar continuum reproduces the Na i D emission line surface brightness distribution except in the inner regions of the wind, where some emission-line filling of absorption lines may occur. The presence of detectable Na i D emission in F05189-2524 may be due to its high continuum surface brightness at the rest wavelength of Na i D. These data uniquely constrain current models of cool gas in galactic winds and serve as a benchmark for future observations and models.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1991

Analysis of turbulence in the orthonormal wavelet representation

The usefulness of the wavelet transform for the analysis of turbulent flow fields is explored by examining the wavelet transform properties of a decomposition of turbulent velocity fields into modes that exhibit the localization in a wavenumber and physical space. The calculations are performed on 3D fields from direct numerical simulations of isotropic flow and homogeneous shear flow, and from measurements in two laboratory wind-tunnel experimental velocity signals (boundary layer and wake behind a circular cylinder). The analysis confirmed that there is strong spatial intermittency in nonlinear quantities; their mean spectral behavior results from a delicate balance between large positive and negative excursions. The wavelet analysis is a way to quantify these observations in a standardized fashion by using 'flow-independent eddies' to decompose the velocity field.

Meneveau, Charles↗
NASA NTRS1982

On the preferential acceleration and heating of solar wind heavy ions

The feasibility of producing the observed velocities and temperatures of solar wind heavy ions by the resonant cyclotron interaction with left-polarized hydromagnetic waves was investigated. A "most favorable case" scenario in which the waves are parallel-propagating and dispersionless and the energy for the wave acceleration and heating is taken from saturated low-frequency Alfven waves via a cascade to higher frequencies, is incorporated into a numerical solar wind code and agreement with observation is tested. The resonant cyclotron interaction is shown to fail on at least three points, even in this most favorable case.

Isenberg, P. A.↗
DOE OSTI2026

WINDPROF: Merged Best-Estimate Wind Profile Data – Block Island (WFIP3 Campaign)

WINDPROF provides 10-minute wind and turbulence profiles that integrate a scanning Doppler lidar, a profiling lidar, a 915 MHz radar wind profiler, and a surface met station across Northeast U.S. coastal and offshore sites during the WFIP3 campaign. Variables include wind speed, wind direction, vertical velocity, turbulence intensity, and turbulent kinetic energy, each with per-instrument quality control and inter-instrument agreement validation. Profiles are mapped to a standardized height grid – a dedicated near-surface level at the 10 m surface-wind height, 20 m spacing to 100 m, and 30 m spacing above – and carry component and derived uncertainty estimates. Heights are reported above ground level; the site's ground elevation is stored separately. The Block Island dataset covers 1 February 2024 – 8 September 2025.

17 WIND ENERGY↗
DOE OSTI2019

Winds of Massive Stars: High-resolution X-Ray Spectra of Stars in NGC 3603

The cluster NGC 3603 hosts some of the most massive stars in the Galaxy. With a modest 50 ks exposure with the Chandra High Energy Grating Spectrometer, we have resolved emission lines in spectra of several of the brightest cluster members, which are of WNh and O spectral types. This observation provides our first definitive high-resolution spectra of such stars in this nearby starburst region. The stars studied have broadened X-ray emission lines, some with blueshifted centroids, and are characteristic of massive stellar winds with terminal velocities around 2000–3000 km s{sup −1}. X-ray luminosities and plasma temperatures are very high for both the WNh and O-stars studied. We conclude that their X-rays are likely the result of colliding winds.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1974

Pioneer Solar Plasma and Magnetic Field Measurements in Interplanetary Space During August 2-17, 1972

Solar wind plasma and magnetic field measurements from Pioneers 9 and 10 during August 2-17, 1972, reveal complex and large-amplitude variations on a one-hour time scale and numerous discontinuities. During this time period an approximate radial alignment of the two spacecraft as seen from the Sun occurred with heliocentric distances of 0.8 AU for Pioneer 9 and 2.2 AU for Pioneer 10, both at 45 deg east of the Earth's solar longitude. The peak hourly average solar wind proton bulk velocity measured at Pioneer 9 was 990 km sec (exp -1) during hour 0 UT of August 5. The peak hourly average proton number density was 62 cm (exp -3) during hour 11 UT of August 3. The peak solar wind speeds are generally much reduced at Pioneer 10 compared with those observes at Pioneer 9. The peak 30 minute average magnetic field magnitude was 85 gamma during 1245 - 1315 UT of August 3. The Pioneer 9 data indicate passage of four fast forward interplanetary shocks, and one slow forward interplanetary shock.

Mihalov, J. D.↗
NASA NTRS1979

Radiative amplification of sound waves in the winds of O and B stars

The velocity perturbation associated with an outwardly propagating sound wave in a radiation-driven stellar wind gives rise to a periodic Doppler shifting of absorption lines formed in the flow. A linearized theory applicable to optically thin waves is used to show that the resulting fluctuation in the absorption-line force can cause the wave amplitude to grow. Detailed calculations of the acceleration due to a large number of lines indicate that significant amplification can occur throughout the high-velocity portion of winds in which the dominant force-producing lines have appreciable optical depths. In the particular case of the wind of Zeta Pup (O4f), it is found that the e-folding distance for wave growth is considerably shorter than the scale lengths over which the physical properties of the flow vary. A qualitative estimate of the rate at which mechanical energy due to nonlinear waves can be dissipated suggests that this mechanism may be important in heating the supersonic portion of winds of early-type stars.

Macgregor, K. B.↗
NASA NTRS2007

Velocity-Field Measurements of an Axisymmetric Separated Flow Subjected to Amplitude-Modulated Excitation

Active flow control was applied at the point of separation of an axisymmetric, backward-facing-step flow. The control was implemented by employing a Helmholtz resonator that was externally driven by an amplitude-modulated, acoustic disturbance from a speaker located upstream of the wind tunnel. The velocity field of the separating/reattaching flow region downstream of the step was characterized using hotwire velocity measurements with and without flow control. Conventional statistics of the data reveal that the separating/reattaching flow is affected by the imposed forcing. Triple decomposition along with conditional averaging was used to distinguish periodic disturbances from random turbulence in the fluctuating velocity component. A significant outcome of the present study is that it demonstrates that amplitude-modulated forcing of the separated flow alters the flow in the same manner as the more conventional method of periodic excitation.

Trosin, Barry James↗
NASA NTRS2014

Acoustic Measurements from Wind Tunnel Test of AMELIA - Advanced Model for Extreme Lift and Improved Aeroacoustics

A wind tunnel test has been conducted to measure the aerodynamic and acoustic performance of an active circulation-control aircraft with leading- and trailing- edge slot blowing. The 11 Advanced Model for Extreme Lift and Improved Aeroacoustics (AMELIA) model was tested in the Arnold Engineering Development Center (AEDC) National Full Scale Aerodynamics Complex (NFAC) 40- by 80-Ft wind tunnel. Forward velocities ranged from 0 to Mach 0.15 and total slot mass-flow was varied from 0 to 2.8 lbmsec. Angle-of-attack and sideslip ranges were -5 to 25 and -10 to 10, respectively.This reports summarizes acoustic measurements from the wind tunnel test and the corrections applied to the released acoustic data. The analysis focuses on measurements for the clean wing configuration (turbine propulsion simulators removed) with trailing-and leading-edge slot blowing and with trailing-edge blowing, for systematic variations in slot mass flow from nearly zero to the system maximum. The acoustic measurements from a fixed phased microphone array and seven fixed microphones were corrected for sensor directional response and atmospheric attenuation. Graphs of 13-octave spectra, narrowband spectra, and directional variations in OASPL are presented for each active lift configuration. This report is intended to document the corresponding set of corrected data that is now available for development and verification of new predictive models of the active lift source.For large slot mass flow conditions 13-octave spectral shapes were level and flat, typical of a pink noise source. Little source directivity was present in the OASPL levels for the 0 flap conditions and show only a slight downstream increase with the 60 flap configuration. For moderate to high slot mass flow conditions trailing-edge only blowing spectra were similar to leading- and trailing edge blowing cases. However for the lower mass flows variations of as much as 5 dB were observed.

CCW↗
DOE OSTI2013

ASYMMETRIC ELECTRON DISTRIBUTIONS IN THE SOLAR WIND

A plausible mechanism responsible for producing asymmetric electron velocity distribution functions in the solar wind is investigated by means of one-dimensional electrostatic particle-in-cell (PIC) simulation. A recent paper suggests that the variation in the ion-to-electron temperature ratio influences the nonlinear wave-particle dynamics such that it results in the formation of asymmetric distributions. The present PIC code simulation largely confirms this finding, but quantitative differences between the weak turbulence formalism and the present PIC simulation are also found, suggesting the limitation of the analytical method. The inter-relationship between the asymmetric electron distribution and the ion-to-electron temperature ratio may be a new useful concept for the observation.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1994

Magnetic shaping of planetary nebulae and other stellar wind bubbles

As in the case of the solar wind, the magnetic field in the wind from a magnetized, rotating star becomes increasingly toroidal with distance from the star. The strength of the magnetic field can be characterized by sigma, the ratio of toroidal magnetic energy density to kinetic energy density in the equatorial plane of the wind. A fast wind shocks against the external medium and creates a bubble whose volume is dominated by shocked gas. The toroidal magnetic field increases in the shocked bubble and can dominate the thermal pressure. Because of the low velocities in the bubble, hydrostatic equilibrium is a good approximation and allows the calculation of the thermal and magnetic pressure in the bubble, as in the model of Begelman and Li (1992) for the Crab Nebula. The structure, which is axisymmetric and extended in the polar direction, depends on two parameters: sigma nu(sub w)/w(sub 0), where nu(sub w) is the wind velocity and w(sub 0) is the shell velocity in the polar direction, and lambda = nu(sub a)/w(sub 0), where nu(sub a) is the velocity of the slow wind. For small values of lambda, there is a cusp in the shell in the equatorial plane, i.e., there is an equatorial ring. For larger values of lambda, the maximum of the surface density moves away from the equator i.e., a double ring structure. Our models should apply to planetary nebulae, if their central stars are sufficiently magnetized; the calculated shapes do resemble the observed shapes of planetaries. In all cases, our model predicts that X-ray emission from the bubble is concentrated toward the polar axis. Finally, we briefly discuss the asymmetry of the Crab Nebula and 3C 58.

Chevalier, Roger A.↗
DOE OSTI2015

Monitoring the Intensity of Ice Formation on Overhead Electric Power Lines and Contact Networks

The conditions for ice to form on a conductor are explained. A hypothesis on the existence of a functional relation between the rate of growth of a mass deposited on a non-live conductor, the dew and desublimation points, and the temperature of the wire surface when there is no wind is suggested and proved. Equations for determining the density, maximum possible mass of the coating and the intensity with which they are formed are proposed, which take into account the temperature of the conductor, the temperature and humidity of the air, the direction and velocity of the wind and the electric field strength of the conductor. The equations are the basis of a proposed thermodynamic method of monitoring the intensity of ice formation. Versions of a technical method and algorithms of the functioning of ice-formation monitoring are proposed.

42 ENGINEERING↗
NASA NTRS1961

Measured Response to Wind-Induced Dynamic Loads of a Full-Scale Scout Vehicle Mounted Vertically on a Launching Tower

Winds blowing over a vehicle mounted in the launch position may induce dynamic loads which are large enough to cause structural damage. In an attempt to prevent the formation of excessive wind-induced loads on the Scout vehicle, spoiler strips of the type used on the.Vanguard vehicle were to be mounted along the upper two stages of the Scout. These spoilers were designed to blow off shortly after launch and might hit and damage the fins at the base of the Scout. In order to determine whether the spoilers planned for installation on the Scout were needed, measurements of the response to dynamic loads imposed by winds at average velocities up to approximately 33 mph were made on a full-scale Scout vehicle mounted vertically on the launching tower at the NASA Wallops Station. From these measurements, it has been concluded that the deflections and bending moments measured in response t o wind-induced dynamic loads were small and should present no structural problems to the vehicle. No significant difference exists between the responses measured with and without spoilers of the type used on the Vanguard vehicle.

Jones, George W., Jr.↗
NASA NTRS2011

Comparative Validation of Realtime Solar Wind Forecasting Using the UCSD Heliospheric Tomography Model

The University of California, San Diego 3D Heliospheric Tomography Model reconstructs the evolution of heliospheric structures, and can make forecasts of solar wind density and velocity up to 72 hours in the future. The latest model version, installed and running in realtime at the Community Coordinated Modeling Center(CCMC), analyzes scintillations of meter wavelength radio point sources recorded by the Solar-Terrestrial Environment Laboratory(STELab) together with realtime measurements of solar wind speed and density recorded by the Advanced Composition Explorer(ACE) Solar Wind Electron Proton Alpha Monitor(SWEPAM).The solution is reconstructed using tomographic techniques and a simple kinematic wind model. Since installation, the CCMC has been recording the model forecasts and comparing them with ACE measurements, and with forecasts made using other heliospheric models hosted by the CCMC. We report the preliminary results of this validation work and comparison with alternative models.

MacNeice, Peter↗
NASA NTRS1955

Full-scale-wind-tunnel Tests of a 35 Degree Sweptback Wing Airplane with High-velocity Blowing over the Training-edge Flaps

A wind-tunnel investigation was made to determine the effects of ejecting high-velocity air near the leading edge of plain trailing-edge flaps on a 35 degree sweptback wing. The tests were made with flap deflections from 45 degrees to 85 degrees and with pressure ratios across the flap nozzles from sub-critical up to 2.9. A limited study of the effects of nozzle location and configuration on the efficiency of the flap was made. Measurements of the lift, drag, and pitching moment were made for Reynolds numbers from 5.8 to 10.1x10(6). Measurements were also made of the weight rate of flow, pressure, and temperature of the air supplied to the flap nozzles.The results show that blowing on the deflected flap produced large flap lift increments. The amount of air required to prevent flow separation on the flap was significantly less than that estimated from published two-dimensional data. When the amount of air ejected over the flap was just sufficient to prevent flow separation, the lift increment obtained agreed well with linear inviscid fluid theory up to flap deflections of 60 degrees. The flap lift increment at 85 degrees flap deflection was about 80 percent of that predicted theoretically.With larger amounts of air blown over the flap, these lift increments could be significantly increased. It was found that the performance of the flap was relatively insensitive to the location of the flap nozzle, to spacers in the nozzle, and to flow disturbances such as those caused by leading-edge slats or discontinuities on the wing or flap surfaces. Analysis of the results indicated that installation of this system on an F-86 airplane is feasible.

Kelley, Mark W↗
DOE OSTI2013

Sulfur chemistry in the envelope of VY Canis Majoris: Detailed analysis of SO and SO{sub 2} emission

Detailed radiative transfer modeling has been carried out for SO{sub 2} and SO originating in the envelope of the O-rich supergiant star VY Canis Majoris (VY CMa). A total of 27 transitions of SO{sub 2} and 7 transitions of SO lying in the energy range 3.0-138.2 cm{sup –1} were analyzed using a new non-LTE radiative transfer code that incorporates non-spherical geometries. The spectra were primarily obtained from the Arizona Radio Observatory (ARO) 1 mm spectral survey of VY CMa, conducted with the Submillimeter Telescope; additional lines were measured with the ARO 12 m antenna at 2 and 3 mm. SO{sub 2} and SO were found to arise from five distinct outflows within the envelope, four which are asymmetric with respect to the star. Three flows arise from high-velocity red-shifted material, one from a blue-shifted wind, and the final from a classic 'spherical' expansion. In the spherical component, the peak fractional abundance, relative to H{sub 2}, of both molecules is f ∼ 2.5 × 10{sup –7} at r ∼ 25 R {sub *}, and steadily decreases outward. SO{sub 2} appears to be a 'parent' molecule, formed near the stellar photosphere. In the asymmetric outflows, both SO and SO{sub 2} are more prominent at large stellar radii in dense (10{sup 6}-10{sup 7} cm{sup –3}), clumpy material, achieving their maximum abundance between 200 and 600 R {sub *} with f ∼ 3.0 × 10{sup –8}-1.5 × 10{sup –7}. These results suggest that in the collimated outflows, both species are either produced by shock chemistry or are remnant inner shell material swept up in the high-velocity winds.

79 ASTRONOMY AND ASTROPHYSICS↗