Results for “Wind Direction” — Page 58

NASA NTRS1985

Sound propagation studies for a large horizontal axis wind turbine

Systematic noise measurements in three directions with respect to the wind vector, over a range of distances to 1050 m, over a range of frequencies from 8 Hz to 2000 Hz, and for a stable wind turbine noise source (WTS-4) in windy conditions (V = 9.4 to 13.0 m/s) are presented. At frequencies above 63 Hz in the downwind and crosswind directions the sound pressure levels decay with distance according to predictions based on atmospheric absorption and spherical spreading, assuming no excess attenuation due to ground effects. In the upwind direction there is excess attenuation due to an acoustic shadow zone. The assumption of a distributed noise source leads to better noise estimates in the upwind direction. For very low frequencies 8 to 16 Hz no excess attenuation was observed in the upwind direction at distances up to 1050 m and a sound pressure level decay rate of approximately 3 dB per doubling of distance was observed in the downwind direction.

Shepherd, K. P.↗

NASA NTRS2001

Combining TOPEX and SeaWinds Data to Refine Models for Ocean Surface Emissivity: Wind Vector Signatures at 18, 21 and 37 GHz

TOPEX Microwave Radiometer (TMR) brightness temperature observations at 18, 21, and 37 GHz have been collocated with near-simultaneous SeaWinds wind vector data as well as with a monthly SST climatological product. The combined data set allows us to study the dependence of ocean surface emissivity (at each frequency) upon both wind speed. Results show clear two-branch wind speed dependence; weak and linear below 6 m/s with an abrupt increase in sensitivity above that point. The analysis also shows that the zenith-directed ocean surface emissivity is polarization dependent above wind speeds of 5-6 m/s with an azimuthal variation related to the wind direction. This last result accords with recent polarimetric radiometer observations collected from aircraft. Implications of these observations to water vapor retrieval algorithms, nadir-viewing polarimetry, and ocean emission modeling will be discussed.

Vandemark, D.↗

NASA NTRS2004

Circular Data Images for Directional Data

Directional data includes vectors, points on a unit sphere, axis orientation, angular direction, and circular or periodic data. The theoretical statistics for circular data (random points on a unit circle) or spherical data (random points on a unit sphere) are a recent development. An overview of existing graphical methods for the display of directional data is given. Cross-over occurs when periodic data are measured on a scale for the measurement of linear variables. For example, if angle is represented by a linear color gradient changing uniformly from dark blue at -180 degrees to bright red at +180 degrees, the color image will be discontinuous at +180 degrees and -180 degrees, which are the same location. The resultant color would depend on the direction of approach to the cross-over point. A new graphical method for imaging directional data is described, which affords high resolution without color discontinuity from "cross-over". It is called the circular data image. The circular data image uses a circular color scale in which colors repeat periodically. Some examples of the circular data image include direction of earth winds on a global scale, rocket motor internal flow, earth global magnetic field direction, and rocket motor nozzle vector direction vs. time.

Morpet, William J.↗

NASA NTRS2005

Seasat--A 25-Year Legacy of Success

Thousands of scientific publications and dozens of textbooks include data from instruments derived from NASA's Seasat. The Seasat mission was launched on June 26, 1978, on an Atlas-Agena rocket from Vandenberg Air Force Base. It was the first Earth-orbiting satellite to carry four complementary microwave experiments--the Radar Altimeter (ALT) to measure ocean surface topography by measuring spacecraft altitude above the ocean surface; the Seasat-A Satellite Scatterometer (SASS), to measure wind speed and direction over the ocean; the Scanning Multichannel Microwave Radiometer (SMMR) to measure surface wind speed, ocean surface temperature, atmospheric water vapor content, rain rate, and ice coverage; and the Synthetic Aperture Radar (SAR), to image the ocean surface, polar ice caps, and coastal regions. While originally designed for remote sensing of the Earth's oceans, the legacy of Seasat has had a profound impact in many other areas including solid earth science, hydrology, ecology and planetary science.

Scanning Multichannel Microwave Radiometer↗

NASA NTRS1969

Direct measurements of interplanetary magnetic fields and plasmas.

Solar wind existence verified by direct measurements of interplanetary magnetic field and plasma, reviewing solar corona studies by satellites and space probes

Ness, N. F.↗

DOE OSTI2018

Additive Manufacturing: A New Paradigm for the Next Generation of High-Power-Density Direct-Drive Electric Generators

In recent years, there has been a growing demand for high-power-density direct-drive generators in the wind industry owing to their high reliability, torque per unit volume, and conversion efficiencies. However, direct-drive wind turbine generators are very large, low-speed electric machines, which pose remarkable design and manufacturing issues that challenge their upscaling potential and cost of implementation. With air-gap tolerance as the main design driver, the need for high stiffness shifts the focus toward support-structure design that forms a significant portion of the generator's total mass. Existing manufacturing processes allow the use of segmented-steel-weldment disk or spoke-arm assemblies that yield stiffer structures per unit mass but tend to be heavier and more expensive to build. As a result, there is a need for a transformative approach to realize lightweight designs that can also facilitate series production at competitive costs. Inspired by recent developments in metal additive manufacturing (AM), we explore a new freedom in the structural design space with a high potential for weight savings in direct-drive generators. This includes the feasibility of using nonconventional complex geometries, such as lattice-based structures as structurally efficient options. Powder-binder jetting of a sand-cast mold was identified as the most feasible AM technology to produce large-scale generator rotor structures with complex geometry. A parametric optimization study was performed and optimized results within deformation and mass constraints were found for each design. The response to the maximum Maxwell stress due to unbalanced magnetic pull was also explored for each design. Further, a topology optimization was applied for each parameter-optimized design to validate results and provide insights into further mass reduction. These novel designs catered for AM are compared in both deflection and mass to conventional rotor designs using NREL's systems engineering design tool, GeneratorSE. The optimized lattice design with a U-beam truss resulted in a 24% reduction in structural mass of the rotor and 60% reduction in radial deflection. It is demonstrated that additive manufacturing shifts the focus from manufacturability constraints toward lower mass.

17 WIND ENERGY↗

DOE OSTI2018

Additive Manufacturing: A New Paradigm for the Next Generation of High-Power-Density Direct-Drive Electric Generators: Preprint

In recent years, there has been a growing demand for high-power-density direct-drive generators in the wind industry owing to their high reliability, torque per-unit volume, and conversion efficiencies. However, direct-drive wind turbine generators are very large, low-speed electric machines, which pose remarkable design and manufacturing issues that challenge their upscaling potential and cost of implementation. With air-gap tolerance as the main design driver, the need for high stiffness shifts the focus toward support-structure design that forms a significant portion of the generator's total mass. Existing manufacturing processes allow the use of segmented-steel-weldment disk or spoke-arm assemblies that yield stiffer structures per unit mass but tend to be heavier and more expensive to build. As a result, there is a need for a transformative approach to realize lightweight designs that can also facilitate series production at competitive costs. Inspired by recent developments in metal additive manufacturing (AM), we explore a new freedom in the structural design space with a high potential for weight savings in direct-drive generators. This includes the feasibility of using nonconventional complex geometries, such as lattice-based structures as structurally efficient options. Powder-binder jetting of a sand-cast mold was identified as the most feasible AM technology to produce large-scale generator rotor structures with complex geometry. A parametric optimization study was performed and optimized results within deformation and mass constraints were found for each design. The response to the maximum Maxwell stress due to unbalanced magnetic pull was also explored for each design. Further, a topology optimization was applied for each parameter-optimized design to validate results and provide insights into further mass reduction. These novel designs catered for AM are compared in both deflection and mass to conventional rotor designs using NREL's systems engineering design tool, GeneratorSE. The optimized lattice design with a Ubeam truss resulted in a 24% reduction in structural mass of the rotor and 60% reduction in radial deflection. It is demonstrated that additive manufacturing shifts the focus from manufacturability constraints toward lower mass.

17 WIND ENERGY↗

NASA NTRS2009

Infrared Heterodyne Spectroscopy and its Unique Application to Planetary Studies

Since the early 1970's the infrared heterodyne technique has evolved into a powerful tool for the study of molecular constituents, temperatures, and dynamics in planetary atmospheres. Its extremely high spectral resolution (Lambda/(Delta)Lambda/>10(exp 6)) and highly accurate frequency measurement (to 1 part in 10(exp 8)) enabled the detection of nonthermal/natural lasing phenomena on Mars and Venus; direct measurements of winds on Venus, Mars, and Titan; study of mid-infrared aurorae on Jupiter; direct measurement of species abundances on Mars (ozone, isotopic CO2), hydrocarbons on Jupiter, Saturn., Neptune, and Titan, and stratospheric composition in the Earth's stratosphere (O3, CIO, N2O, CO2 ....). Fully resolved emission and absorption line shapes measured by this method enabled the unambiguous retrieval of molecular abundances and local temperatures and thermal structure in regions not probed by other techniques. The mesosphere of Mars and thermosphere of Venus are uniquely probed by infrared heterodyne spectroscopy. Results of these studies tested and constrained photochemical and dynamical theoretical models describing the phenomena measured. The infrared heterodyne technique will be described. Highlights in its evolution to today's instrumentation and resultant discoveries will be presented, including work at Goddard Space Flight Center and the University of Koln. Resultant work will include studies supporting NASA and ESA space missions and collaborations between instrumental and theoretical groups.

Kostiuk, Theodore↗

NASA NTRS1981

Applications of the DOE/NASA wind turbine engineering information system

A statistical analysis of data obtained from the Technology and Engineering Information Systems was made. The systems analyzed consist of the following elements: (1) sensors which measure critical parameters (e.g., wind speed and direction, output power, blade loads and component vibrations); (2) remote multiplexing units (RMUs) on each wind turbine which frequency-modulate, multiplex and transmit sensor outputs; (3) on-site instrumentation to record, process and display the sensor output; and (4) statistical analysis of data. Two examples of the capabilities of these systems are presented. The first illustrates the standardized format for application of statistical analysis to each directly measured parameter. The second shows the use of a model to estimate the variability of the rotor thrust loading, which is a derived parameter.

Neustadter, H. E.↗

NASA NTRS1984

Review of the DOE/NASA wind turbine engineering information system

A statistical analysis of data obtained from the Technology and Engineering Information Systems was made. The systems analyzed consist of the following elements: (1) sensors which measure critical parameters (e.g., wind speed and direction, output power, blade loads and component vibrations); (2) remote multiplexing units (RMUs) on each wind turbine which frequency-modulate, multiplex and transmit sensor outputs; (3) on-site instrumentation to record, process and display the sensor output; and (4) statistical analysis of data. Two examples of the capabilities of these systems are presented. The first illustrates the standardized format for application of statistical analysis to each directly measured parameter. The second shows the use of a model to estimate the variability of the rotor thrust loading, which is a derived parameter. Previously announced in STAR as N82-23696

Neustadter, H. E.↗

NASA NTRS2010

Mixed Layer Sub-Mesoscale Parameterization - Part 1: Derivation and Assessment

Several studies have shown that sub-mesoscales (SM 1km horizontal scale) play an important role in mixed layer dynamics. In particular, high resolution simulations have shown that in the case of strong down-front wind, the re-stratification induced by the SM is of the same order of the de-stratification induced by small scale turbulence, as well as of that induced by the Ekman velocity. These studies have further concluded that it has become necessary to include SM in ocean global circulation models (OGCMs), especially those used in climate studies. The goal of our work is to derive and assess an analytic parameterization of the vertical tracer flux under baroclinic instabilities and wind of arbitrary directions and strength. To achieve this goal, we have divided the problem into two parts: first, in this work we derive and assess a parameterization of the SM vertical flux of an arbitrary tracer for ocean codes that resolve mesoscales, M, but not sub-mesoscales, SM. In Part 2, presented elsewhere, we have used the results of this work to derive a parameterization of SM fluxes for ocean codes that do not resolve either M or SM. To carry out the first part of our work, we solve the SM dynamic equations including the non-linear terms for which we employ a closure developed and assessed in previous work. We present a detailed analysis for down-front and up-front winds with the following results: (a) down-front wind (blowing in the direction of the surface geostrophic velocity) is the most favorable condition for generating vigorous SM eddies; the de-stratifying effect of the mean flow and re-stratifying effect of SM almost cancel each other out,

Canuto, V. M.↗

NASA NTRSDate not supplied

Effect of the Reynolds Number on the Freestream Disturbance Environment in a Mach 6 Nozzle

To understand the impact of unit Reynolds number on the acoustic disturbance field inside a high-speed wind tunnel, we use Direct Numerical Simulations (DNS) to model the turbulent boundary layers along the walls of a quasi-two-dimensional nozzle configuration. Intended as a stepping stone to fully three-dimensional simulations of freestream noise inside the NASA 20-Inch Mach 6 Wind Tunnel, the present simulations are based on periodic boundary conditions across the spanwise width of the computational domain that corresponds to about one third of the actual tunnel width. These simulations are performed at four different unit Reynolds numbers, ranging from 3.56e6 to 14.0e6 per meter. The predominantly hydrodynamic fluctuations inside the boundary layer are shown to be nearly unaffected by the presence of freestream forcing associated with the impinging acoustic radiation from the opposite wall. Thus, the Reynolds number trends associated with boundary-layer quantities are consistent with previously published DNS of flat-plate boundary layers at similar Mach numbers and wall temperature ratios. The unsteady disturbance environment within the nozzle core region is found to be approximately spatially homogeneous and purely acoustic in nature. The numerical results are used to make comparisons with tunnel noise measurements by Chou et al. [1,2]. Unlike previous comparisons involving static-pressure fluctuations based on the DNS and pitot-pressure fluctuations measured in the wind tunnel, direct comparisons involving the fluctuations in the same physical quantity, namely, the streamwise mass flux, have been reported for the first time. The predicted decrease in the root-mean-square fluctuations in pressure and mass flux with an increasing unit Reynolds number is in agreement with the measurements in the NASA 20-Inch Mach 6 Wind Tunnel. Additional details of the acoustic radiation field are quantified and should be useful toward a digital synthesis of the tunnel disturbance environment that would enable realistic simulations of the natural transition process.

Turbulence↗

NASA NTRSDate not supplied

Effect of the Reynolds Number on the Freestream Disturbance Environment in a Mach 6 Nozzle

To understand the impact of unit Reynolds number on the acoustic disturbance field inside a high-speed wind tunnel, we use Direct Numerical Simulations (DNS) to model the turbulent boundary layers along the walls of a quasi-two-dimensional nozzle configuration. Intended as a stepping stone to fully three-dimensional simulations of freestream noise inside the NASA 20-Inch Mach 6 Wind Tunnel, the present simulations are based on periodic boundary conditions across the spanwise width of the computational domain that corresponds to about one third of the actual tunnel width. These simulations are performed at four different unit Reynolds numbers, ranging from 3.56e6 to 14.0e6 per meter. The predominantly hydrodynamic fluctuations inside the boundary layer are shown to be nearly unaffected by the presence of freestream forcing associated with the impinging acoustic radiation from the opposite wall. Thus, the Reynolds number trends associated with boundary-layer quantities are consistent with previously published DNS of flat-plate boundary layers at similar Mach numbers and wall temperature ratios. The unsteady disturbance environment within the nozzle core region is found to be approximately spatially homogeneous and purely acoustic in nature. The numerical results are used to make comparisons with tunnel noise measurements by Chou et al. [1,2]. Unlike previous comparisons involving static-pressure fluctuations based on the DNS and pitot-pressure fluctuations measured in the wind tunnel, direct comparisons involving the fluctuations in the same physical quantity, namely, the streamwise mass flux, have been reported for the first time. The predicted decrease in the root-mean-square fluctuations in pressure and mass flux with an increasing unit Reynolds number is in agreement with the measurements in the NASA 20-Inch Mach 6 Wind Tunnel. Additional details of the acoustic radiation field are quantified and should be useful toward a digital synthesis of the tunnel disturbance environment that would enable realistic simulations of the natural transition process.

Acoustics↗

NASA NTRS1973

Low-speed wind tunnel investigation of the lateral-directional characterisitcs of a large-scale variable wing-sweep fighter model in the high-lift configuration

The low-speed characteristics of a large-scale model of the F-14A aircraft were studied in tests conducted in the Ames Research Center 40- by 80-Foot Wind Tunnel. The primary purpose of the present tests was the determination of lateral-directional stability levels and control effectiveness of the aircraft in its high-lift configuration. Tests were conducted at wing angles of attack between minus 2 deg and 30 deg and with sideslip angles between minus 12 deg and 12 deg. Data were taken at a Reynolds number of 8.0 million based on a wing mean aerodynamic chord of 2.24 m (7.36 ft). The model configuration was changed as required to show the effects of direct lift control (spoilers) at yaw, yaw angle with speed brake deflected, and various amounts and combinations of roll control.

Eckert, W. T.↗

NASA NTRS1993

A monochromatic gravity wave observed by the Flatland Atmospheric Observatory

On 21 December 1991 from approximately 1300 to approximately 1600 UTC a monochromatic wave train with an 8.2-min period was observed by the suite of instruments at the Flatland Atmospheric Observatory (FAO), located in very flat terrain near Champaign-Urbana, Illinois. A 915-MHz radar measured the vertical wind velocity w every 60 s from 0.55 km MSL (0.34 km AGL) to approximately 3 km with 250-m range gates, and a 50-MHz radar measured the oblique wind in four directions, as well as w, every 130 s from 2.75 to approximately 7.25 km with 750-m range gates. A meteorological ground station measured the surface pressure P, wind speed vector u and azimuth alpha, temperature, solar insolation, etc., every 30 s. P was also measured every 120 s by six digital barograph stations within 30 km of Flatland. Using the hodograph of surface vector u and alpha and the impedance relation, we estimated the azimuthal direction of propagation phi to be 45 deg +/- 15 deg clockwise from north, the intrinsic and apparent horizontal phase speeds C(sub i) and C(sub o), respectively, (which are about equal since the direction of propagation is about normal to the mean wind) to be 21 +/- 5 m/s, and the horizontal wavelength lambda to be 10.0 +/- 2.5 km. The peak-to-peak surface horizontal perturbation velocity varied from approximately 2 to 5 m/s from cycle to cycle.

Vanzandt, T. E.↗

NASA NTRS1995

Upper Thermosphere Winds and Temperatures in the Geomagnetic Polar Cap: Solar Cycle, Geomagnetic Activity, and Interplanetary Magnetic Field Dependencies

Ground-based Fabry-Perot interferometers located at Thule, Greenland (76.5 deg. N, 69.0 deg. W, lambda = 86 deg.) and at Sondre Stromfjord, Greenland (67.0 deg. N, 50.9 deg. W, lambda = 74 deg.) have monitored the upper thermospheric (approx. 240-km altitude) neutral wind and temperature over the northern hemisphere geomagnetic polar cap since 1983 and 1985, respectively. The thermospheric observations are obtained by determining the Doppler characteristics of the (OI) 15,867-K (630.0-nm) emission of atomic oxygen. The instruments operate on a routine, automatic, (mostly) untended basis during the winter observing seasons, with data coverage limited only by cloud cover and (occasional) instrument failures. This unique database of geomagnetic polar cap measurements now extends over the complete range of solar activity. We present an analysis of the measurements made between 1985 (near solar minimum) and 1991 (near solar maximum), as part of a long-term study of geomagnetic polar cap thermospheric climatology. The measurements from a total of 902 nights of observations are compared with the predictions of two semiempirical models: the Vector Spherical Harmonic (VSH) model of Killeen et al. (1987) and the Horizontal Wind Model (HWM) of Hedin et al. (1991). The results are also analyzed using calculations of thermospheric momentum forcing terms from the Thermosphere-ionosphere General Circulation Model TGCM) of the National Center for Atmospheric Research (NCAR). The experimental results show that upper thermospheric winds in the geomagnetic polar cap have a fundamental diurnal character, with typical wind speeds of about 200 m/s at solar minimum, rising to up to about 800 m/s at solar maximum, depending on geomagnetic activity level. These winds generally blow in the antisunward direction, but are interrupted by episodes of modified wind velocity and altered direction often associated with changes in the orientation of the Interplanetary Magnetic Field (IMF). The central polar cap (greater than approx. 80 magnetic latitude) antisunward wind speed is found to be a strong function of both solar and geomagnetic activity. The polar cap temperatures show variations in both solar and geomagnetic activity, with temperatures near 800 K for low K(sub p) and F(sub 10.7) and greater than about 2000 K for high K(sub p) and F(sub 10.7). The observed temperatures are significantly greater than those predicted by the mass spectrometer/incoherent scatter model for high activity conditions. Theoretical analysis based on the NCAR TIGCM indicates that the antisunward upper thermospheric winds, driven by upstream ion drag, basically 'coast' across the polar cap. The relatively small changes in wind velocity and direction within the polar cap are induced by a combination of forcing terms of commensurate magnitude, including the nonlinear advection term, the Coriolis term, and the pressure gradient force term. The polar cap thennospheric thermal balance is dominated by horizontal advection, and adiabatic and thermal conduction terms.

Killeen, T. L.↗

NASA NTRS1921

Design of Wind Tunnels and Wind Tunnel Propellers II

This report is a continuation of National Advisory Committee for Aeronautics report no. 73. The variations in velocity and direction of the wind stream were studied by means of a recording air speed meter and a recording yawmeter. The work was carried on both in a 1-foot diameter model tunnel and in a 5-foot full-size tunnel, and wherever possible comparison was made between them. It was found that placing radial vanes directly before the propeller in the exit cone increased the efficiency of the tunnel to a considerable extent and also gave a steadier flow.

Norton, F H↗

DOE OSTI2025

Frequency-domain modeling of floating wind arrays with shared mooring lines

A frequency-domain model for floating wind turbine dynamics has been extended to model floating wind farms with couplings from shared mooring systems. The model, called RAFT, could previously calculate the mean offsets and wave-induced response spectra for single floating wind turbines. Now, the model supports multiple floating wind turbines, each with their own properties and responses, along with mooring lines that run directly between floating wind turbines in the array, meaning that shared mooring lines or fully suspended dynamic power cables can be included. This capability is achieved by setting up an array-level solution of the system mean offsets and assembling the full system matrices for solving the dynamic response. The quasi-static mooring model MoorPy is used to linearize the mooring system properties. To compute the floating wind turbine relative motions, phase offsets are applied to each turbine's response as a function of wave frequency based on the wavelength and relative positions in the array. These differential motions are then applied to mooring system tension Jacobians to compute the tension loads in the shared mooring lines. Overall, the capability provides a frequency-domain analog to the modeling capabilities of the floating support structure in FAST.Farm. Mean offsets and power spectral density plots of responses are compared between RAFT and FAST.Farm to verify the implementation. The results indicate good agreement within the expectations of a frequency-domain modeling approach and suggest correct implementation of the shared mooring aspects. Additionally, a unique comb-like frequency response in the shared mooring line tensions has been observed. This phenomenon has a clear physical basis and may be an important design consideration for future shared mooring systems.

17 WIND ENERGY↗