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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 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Turbofan Noise Reduction Associated With Increased Bypass Nozzle Flow

An advanced 22-in. scale model turbofan, typical of a current-generation aircraft engine design by GE Aircraft Engines, was tested in NASA Glenn Research Center s 9- by 15- Foot Low-Speed Wind Tunnel to explore the far-field acoustic effects of an increased bypass nozzle area at simulated aircraft speeds of takeoff, approach, and landing. The wind-tunnel-scale model consisted of the bypass stage fan, stators, and nacelle (including the fan exit nozzle) of a typical turbofan. This fan-stage test was part of the NASA Glenn Fan Broadband Source Diagnostic Test, second entry, which acquired aeroacoustic results over a range of test conditions. A baseline nozzle was selected, and the nozzle area was chosen for maximum performance at sea-level conditions. Two additional nozzles were also tested--one with a 5.4-percent increase in nozzle area over the baseline nozzle (sized for design point conditions), corresponding to a 5-percent increase in fan weight flow, and another nozzle with a 10.9-percent increase in nozzle area over the baseline nozzle (sized for maximum weight flow at sea-level conditions), corresponding to a 7.5 percent increase in fan weight flow. Measured acoustic benefits with increased nozzle area were very encouraging, showing overall sound power level reductions of 2 dB or more (left graph) while the stage adiabatic efficiency (right graph) and thrust (final graph) actually increased by several percentage points. These noise-reduction benefits were seen to include both rotor-interaction tones and broadband noise, and were evident throughout the range of measured sideline angles.

Woodward, Richard P.↗
DOE OSTI2020

Future projections of wind patterns in California with the variable-resolution CESM: a clustering analysis approach

Wind energy production is expected to be affected by shifts in wind patterns that will accompany climate change. However, many questions remain on the magnitude and character of this impact, especially on regional scales. In this study, clustering is used to group and analyze large-scale wind patterns in California using model simulations from the variable-resolution Community Earth System Model (VR-CESM). Specifically, simulations have been produced that cover historical (1980–2000), mid-century (2030–2050), and end-of-century (2080–2100) time periods. Once clustered, observed changes to wind patterns can be analyzed in terms of both the change in frequency of those clusters and changes to winds within-clusters. Statistically significant capacity factors changes have been found at all five wind plant sites. Further, decomposition of the capacity factor changes into frequency changes and within-cluster changes enables a better understanding of their drivers. A further examination of the synoptic-scale fields associated with each cluster then provides a better understanding of how changes to large-scale meteorological fields are important for driving changes in localized wind speeds.

17 WIND ENERGY↗
DOE OSTI2020

Effects of Different Types of Entrances on Natural Ventilation in a Subway Station

In this study, the natural ventilation of a horizontal entrance of a typical subway station is investigated based on numerical simulations and experiments. In addition, a renormalization group k-e model (RNG k-e model) is applied to compute both the internal and external airflow patterns. Computational fluid dynamics (CFD) simulations are validated based on the experimental results. Furthermore, a multiple variable regression model is employed to study how the different parameters affect the internal airflow rates of the subway station statistically, according to the experimental results. For this typical model, the parameter importance can be ranked as follows: (1) outdoor wind speed; (2) flow resistance of the subway station; (3) height of the wind catcher; and (4) length of the wind catcher. To understand the detailed pressure distribution of the horizontal entrance of the subway station with and without the wind catcher, 3D numerical simulations are conducted for different scenarios. We attempt to alter the size of the wind catcher (including the length and height) to study the characteristics of the pressure on the horizontal entrance of the subway station under outdoor wind-driven conditions. The pressure distributions for the entrance for different scenarios are compared and analyzed. Finally, the interactions between the internal and external flows are investigated by changing the resistance of the subway station. When the internal flow resistance is changed, the pressure coefficient (Cp) of the entrance is different as well. Hence, the Cp is not only affected by the outdoor environment, but is also influenced by the internal airflows.

CFD↗
DOE OSTI2021

A novel network-based approach to determining measurement representation error for model evaluation of aerosol microphysical properties

Atmospheric aerosol size and abundance influence radiative effects and climate change. To date, efforts to constrain global climate models’ radiative forcing with in situ aerosol observations have been hamstrung by uncertainty. One source of error, the regional “representation error,” arises when accurate but sparse single-point measurements of atmospheric aerosol distributions are compared with a model value, assuming that the single-point measurement is representative of the model domain. The Portable Optical Particle Spectrometer network in the Southern Great Plains (POPSnet-SGP) campaign has demonstrated that a network of nearly autonomous aerosol instruments operating at ambient temperature and relative humidity (with low measurement error) may be used to quantify measurement representation error and investigate the factors introducing heterogeneity in aerosol distributions across a rural, continental background region. Measurements were made using Portable Optical Particle Spectrometer (POPS) instruments at several sites for five months across the Department of Energy’s Aerosol Radiation Measurement Southern Great Plains (ARM-SGP) User Facility in the central USA. Measurement representation error decreased with longer averaging periods (20-40 % between 1 sec and 1 day), varied between sites by 10 – 20 % for aerosol concentration 140 – 2500 nm in diameter (N_140), and was higher for aerosols > 400 nm in diameter (N_400). Our measurements also show the influence of local meteorology on aerosol surface area (A_140) and size distributions: A_140 is positively correlated with wind speed and relative humidity, negatively correlated with precipitation, and lower given westerly winds. Based on this study, we conclude that the POPSnet approach provides considerably more insight into the spatial variability in the aerosol population that can be used to constrain climate models than would be available from similar networks of PM 2.5 monitors.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Benchmarking Near-Surface Winds in the HRRR Analyses Using Multisource Observations over Complex Terrain in the Southeastern United States

Wind energy plays a crucial role in sustainable power generation, yet its full potential in the southeast United States (SEUS) remains underexplored. This study advances wind resource assessment in the SEUS using existing regional modeling and multisource observations. We find that terrain complexity, influenced by orography and forest canopy, significantly impacts the accuracy of modeled wind speed. While the High-Resolution Rapid Refresh (HRRR) model effectively simulates wind profiles over flat, nonforested terrain, larger errors are produced above forest canopies, and particularly for those stands in hilly and mountainous terrain where there are no observations aloft that could be used by HRRR’s data assimilation software. Seasonal variations, e.g., changes in the leaf area index, further complicate the relationship between terrain complexity and simulation errors. Here, our findings emphasize the critical need for comprehensive wind profile measurements, extending from below the canopy to height above the canopy and through the lower planetary boundary layer, to fully quantify model performance over and near forests, and for improving wind resource assessment, planning, and management. This study provides valuable insights not only for further model development but also for future field campaign deployment with the goal of further improving our understanding of wind resources in the region.

Complex terrain↗
DOE OSTI2024

Offshore Wind Turbine Blade (85 to120meters ultra-long blade) static and fatigue test

Offshore blades are not just longer, they are wider, heavier and more flexible. These longer blades are a key component of larger wind turbines and for turbines to be more efficient in low wind speeds. These longer blades help reduce the LCOE further and make offshore wind even more competitive. As described earlier, it is essential for the blades to be fully tested to verify and validate the blade designs and manufacturing processes to ensure a reliable product is installed in the field. Through this project WTTC developed and procured new testing equipment required to test longer blades with larger deflections and higher loads. R&D’s BCDA system commissioned was the largest fatigue test exciter system in the world and set the bar for other blade testing facilities worldwide.

17 WIND ENERGY↗
NASA NTRS1974

An analysis of the Venera 8 measurements

Analysis of the Venera 8 measurements yielded equatorial morning terminator horizontal and vertical winds which are similar to the winds obtained from the Venera 7 measurements. The lower boundary of the horizontal retrograde 4-day wind is defined by a 50-60% decrease in wind speed in the vicinity of 44 km and there exists a retrograde wind plateau of 15 to 40 m/s winds extending from 40 km down to the vicinity of 18 km where the winds decrease rapidly to the order of 0.1 m/s near the surface. Up drafts of 2 to 5 m/s exist in the vicinity of 20 to 30 km and are apparently associated with a slightly super adiabatic lapse rate. The temperature lapse-rate, surface radius, surface topography, and atmospheric structure are discussed.

Ainsworth, J. E.↗
NASA NTRS1975

Venus wind and temperature structure - The Venera 8 data

Our analysis of the Venera 8 measurements yields equatorial morning terminator horizontal and vertical winds that are similar in a number of respects to the winds we obtained from our analysis of the Venera 7 measurements. The lower boundary of the horizontal retrograde '4-day' wind is defined by a 50-60% decrease in wind speed in the vicinity of 44 km, and there exists a retrograde wind 'plateau' of 15- to 40-m/s winds extending from 40 km down to the vicinity of 18 km, where the winds decrease rapidly to the order of 0.1 m/s near the surface. Updrafts of 2-5 m/s exist in the vicinity of 20-30 km and are apparently associated with a slightly superadiabatic lapse rate.

Ainsworth, J. E.↗
NASA NTRS1976

Interplanetary magnetic field power spectra - Mean field radial or perpendicular to radial

A detailed frequency analysis of Pioneer-6 interplanetary magnetic field data is carried out for 5 to 15 hour periods during which the mean interplanetary field is approximately radial or perpendicular to radial. The reason why these data sets were chosen is that by making the usual assumption that the phase speed of any wave present is much less than the mean solar wind speed, the measured frequency spectra can be interpreted in terms of the wave number parallel or perpendicular to the mean field, without such additional assumptions as isotropy or the dominance of a particular mode and without measurements of velocity and density. The details of the calculation of the magnetic field power spectra, coherencies, and correlation functions are discussed, along with results obtained directly from the data (such as spectra, slopes, anisotropies, and coherencies). The results are interpreted in terms of MHD theory, and are related to work in other areas.

Sari, J. W.↗
NASA NTRS1979

Satellite detection of a long curving cirrus plume

On August 23, 1978, a long cirrus plume, as detected by the GOES E satellite, made a sharp anticyclonic turn and traveled a total distance of 2800 km from the generating thunderstorm, as determined from satellite imagery. During a five-hour period the leading edge moved a distance of 550 km, giving a speed of 30 m/sec. This is in good agreement with the pertinent wind speeds at the presumed height of the cloud, which may indicate that cirrus evaporation may not have been too important. In a relatively dense portion of the cirrus the minimum equivalent blackbody temperature was 226 K.

Wexler, R.↗
NASA NTRS1980

Development and usage of a false color display technique for presenting Seasat-A scatterometer data

A computer generated false color program which creates digital multicolor graphics to display geophysical surface parameters measured by the Seasat-A satellite scatterometer (SASS) is described. The data is incrementally scaled over the range of acceptable values and each increment and its data points are assigned a color. The advantage of the false color display is that it visually infers cool or weak data versus hot or intense data by using the rainbow of colors. For example, with wind speeds, levels of yellow and red could be used to imply high winds while green and blue could imply calmer air. The SASS data is sorted into geographic regions and the final false color images are projected onto various world maps with superimposed land/water boundaries.

Jackson, C. B.↗
NASA NTRS1984

Wind loading on solar concentrators: Some general considerations

A survey was completed to examine the problems and complications arising from wind loading on solar concentrators. Wind loading is site specific and has an important bearing on the design, cost, performance, operation and maintenance, safety, survival, and replacement of solar collecting systems. Emphasis herein is on paraboloidal, two-axis tracking systems. Thermal receiver problems also are discussed. Wind characteristics are discussed from a general point of view. Current methods for determining design wind speed are reviewed. Aerodynamic coefficients are defined and illustrative examples are presented. Wind tunnel testing is discussed, and environmental wind tunnels are reviewed. Recent results on heliostat arrays are reviewed as well. Aeroelasticity in relation to structural design is discussed briefly.

Roschke, E. J.↗
NASA NTRS1985

Coronal temperatures, heating, and energy flow in a polar region of the sun at solar maximum

The profiles of resonantly scattered Lyman-alpha coronal radiation have been used to determine the hydrogen kinetic temperature from 1.5 to 4 solar radius from the center of the polar region of the corona observed in 1980 at solar maximum. Hydrogen temperatures derived from the line profiles were found to decrease with height from 1.2 million K at r = 1.5 solar radii to 600,000 K at r = 4 solar radius. Comparison of the measured kinetic temperatures with predictions from a semiempirical two-fluid model showed evidence of a small amount of heating or a nonthermal contribution to the motions of coronal protons between 1.5 and 4 solar radius. The widths of the profiles confirmed an upper limit of 110 + or - 15 km/s on the rms magnitude of the line-of-sight component of velocities between 1.5 and 4 solar radius. Density measurements obtained in situ in the solar wind in the ecliptic were used to locate the sources of low speed and high-speed winds in the polar region. An eclipse photograph of the corona at solar maximum is provided.

Withbroe, G. L.↗
NASA NTRS1991

Statistical problems of wind-generated gravity waves arising in microwave remote sensing of surface winds

The basic geometric features of a developed sea surface affecting the accuracy of wind speed measurements by satellite instruments are reviewed. Error trends in the satellite winds are shown to be correlated with various measures of wave development. For a developed sea, the influence of the equilibrium range parameters characterizing the spectrum of wind-generated waves are derived and compared with field observations. Fluctuations in the actual number of steep wavelet events which occur within a finite surface area are shown to be an important factor of the radar backscatter if the surface area, i.e., the resolution cell, is much smaller than 1 sq km. The inner scale of the equilibrium range caused by energy dissipation by breaking waves is considered to be a major factor in determining the surface's statistical geometry and, hence, its microwave returns for all satellite sensors.

Glazman, Roman E.↗
NASA NTRS1993

Solar cycle modulation of galactic cosmic rays at high heliographic latitudes - A one-dimensional simulation

Previous studies have established that large merged interaction regions (MIRs) in the outer heliosphere are the main cause of the 11-year modulation cycle of galactic cosmic rays in the ecliptic. Those simulations were successful despite their use of a constant convection speed. In this study, we show that a large rise in solar wind speed, seen at higher heliographic latitudes during 1985-1987, combined with MIRs, can generate the difference between the Voyager I and Voyager 2 count rates in this period. Also, the difference between the starting times of the new cycle at both spacecraft is directly attributable to the difference between the pattern of MIRs measured at the two spacecraft. In addition, the Voyager 2 simulation exhibits the correct behavior of the 11-year cycle in the cosmic ray radial gradients between points in the outer heliosphere.

Perko, J. S.↗
NASA NTRS1991

Hourly wind profiler observations of the jet stream - Wind shear and pilot reports of turbulence

Hourly wind profiler observations of the jet stream are reported on the basis of over 400 hr of wind and temperature data taken during two prolonged jet stream passages over western and central Pennsylvania during mid-November 1986 and mid-January 1987. The mean wind speed profile with error bars for the 79 hr that the Crown radar was determined to be 'under' the jet stream is shown. A mean speed of 83 m/s for the period was found. A plot of wind shear for the hours of interest is given. Typically, the shear was at a maximum from 3 to 4 km below the level of maximum wind. Thus, an aircraft would have to fly through potentially rough air to reach the fuel savings and relative smoothness of flight at the jet stream level. A good correlation between pilot reports of turbulence and wind shear was found.

Syrett, William J.↗
NASA NTRS1943

Drag Measurements of a Protruding .50-caliber Machine Gun with Barrel Jacket Removed

Tests were made in 8-ft high-speed wind tunnel to determine the drag reduction possible by eliminating the barrel jacket of a protruding 50-caliber aircraft gun. It was found that the drag of a standard aircraft gun protruding into the air stream at right angles to the flow can be reduced by 23% by discarding the barrel jacket. At 300 mph and sea-level conditions, this amounts to a decrease in drag of from 83 to 64 pounds. A rough surface finish on the barrel was found to have no adverse effects on the drag of the barrel, the drag being actually less at high Mach Numbers.

GUNS - DRAG↗
NASA NTRS2004

Interpretive Tools for Analysis of Coronal Images

Contents include list of publications resulting from grant: Magneto-Hydrodynamic Model of the Solar Corona and Interplanetary Medium. Coronal magnetic field topology and source of fast solar wind. Geophysical Importance of Global Magnetic Field Geometry and Density Distribution in Solar Wind Modeling. Empirical Model of the Corona-Solar Wind with Multiple Current Sheets. Model of the Solar Wind and its Comparison with ULYSSES. Physical properties of a coronal hole from a coronal diagnostic spectrometer, Mauna Loa Coronagraph, and LASCO observations during the Whole Sun Month. Semi-Empirical 2-D MHD Model of the Solar corona and Solar Wind: Energy Flow in the Corona. Source Region of High and Low Speed Wind during the Spartan. Three-dimensional coronal density structure. Cone Model for Halo CME's: Application to Space Weather Forecasting.

Ofman, Leon↗