Science.gov

Sample records for maximum wind velocity

  1. Checking Wind Velocity 

    E-print Network

    Unknown

    2011-08-17

    temperature, air velocity and humidity in different zones. The results of a study of a sales area of a supermarket in Harbin are presented in this paper, including air temperature, air velocity and humidity. According to the assessment index of air flow...

  2. Maximum Possible Transverse Velocity in Special Relativity.

    ERIC Educational Resources Information Center

    Medhekar, Sarang

    1991-01-01

    Using a physical picture, an expression for the maximum possible transverse velocity and orientation required for that by a linear emitter in special theory of relativity has been derived. A differential calculus method is also used to derive the expression. (Author/KR)

  3. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 2014-01-01 false Wind velocities. 25.237 Section 25.237 Aeronautics...Handling Characteristics § 25.237 Wind velocities. (a) For land planes and amphibians...A 90-degree cross component of wind velocity, demonstrated to be safe for...

  4. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 2012-01-01 false Wind velocities. 25.237 Section 25.237 Aeronautics...Handling Characteristics § 25.237 Wind velocities. (a) For land planes and amphibians...A 90-degree cross component of wind velocity, demonstrated to be safe for...

  5. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 2013-01-01 false Wind velocities. 25.237 Section 25.237 Aeronautics...Handling Characteristics § 25.237 Wind velocities. (a) For land planes and amphibians...A 90-degree cross component of wind velocity, demonstrated to be safe for...

  6. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...2010-01-01 2010-01-01 false Wind velocities. 25.237 Section 25.237 Aeronautics...Handling Characteristics § 25.237 Wind velocities. (a) For land planes and amphibians...A 90-degree cross component of wind velocity, demonstrated to be safe for...

  7. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 2011-01-01 false Wind velocities. 25.237 Section 25.237 Aeronautics...Handling Characteristics § 25.237 Wind velocities. (a) For land planes and amphibians...A 90-degree cross component of wind velocity, demonstrated to be safe for...

  8. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Wind velocities. 25.237 Section 25.237... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Ground and Water Handling Characteristics § 25.237 Wind... wind velocity, demonstrated to be safe for takeoff and landing, must be established for dry runways...

  9. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Wind velocities. 25.237 Section 25.237... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Ground and Water Handling Characteristics § 25.237 Wind... wind velocity, demonstrated to be safe for takeoff and landing, must be established for dry runways...

  10. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Wind velocities. 25.237 Section 25.237... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Ground and Water Handling Characteristics § 25.237 Wind... wind velocity, demonstrated to be safe for takeoff and landing, must be established for dry runways...

  11. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Wind velocities. 25.237 Section 25.237... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Ground and Water Handling Characteristics § 25.237 Wind... wind velocity, demonstrated to be safe for takeoff and landing, must be established for dry runways...

  12. 14 CFR 25.237 - Wind velocities.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Wind velocities. 25.237 Section 25.237... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Ground and Water Handling Characteristics § 25.237 Wind... wind velocity, demonstrated to be safe for takeoff and landing, must be established for dry runways...

  13. Distribution of maximum velocities in avalanches near the depinning transition.

    PubMed

    LeBlanc, Michael; Angheluta, Luiza; Dahmen, Karin; Goldenfeld, Nigel

    2012-09-01

    We report exact predictions for universal scaling exponents and scaling functions associated with the distribution of the maximum collective avalanche propagation velocities v(m) in the mean field theory of the interface depinning transition. We derive the extreme value distribution P(v(m)|T) for the maximum velocities in avalanches of fixed duration T and verify the results by numerical simulation near the critical point. We find that the tail of the distribution of maximum velocity for an arbitrary avalanche duration, v(m), scales as P(v(m))~v(m)(-2) for large v(m). These results account for the observed power-law distribution of the maximum amplitudes in acoustic emission experiments of crystal plasticity and are also broadly applicable to other systems in the mean-field interface depinning universality class, ranging from magnets to earthquakes. PMID:23005300

  14. Effects of increasing tip velocity on wind turbine rotor design.

    SciTech Connect

    Resor, Brian Ray; Maniaci, David Charles; Berg, Jonathan Charles; Richards, Phillip William

    2014-05-01

    A reduction in cost of energy from wind is anticipated when maximum allowable tip velocity is allowed to increase. Rotor torque decreases as tip velocity increases and rotor size and power rating are held constant. Reduction in rotor torque yields a lighter weight gearbox, a decrease in the turbine cost, and an increase in the capacity for the turbine to deliver cost competitive electricity. The high speed rotor incurs costs attributable to rotor aero-acoustics and system loads. The increased loads of high speed rotors drive the sizing and cost of other components in the system. Rotor, drivetrain, and tower designs at 80 m/s maximum tip velocity and 100 m/s maximum tip velocity are created to quantify these effects. Component costs, annualized energy production, and cost of energy are computed for each design to quantify the change in overall cost of energy resulting from the increase in turbine tip velocity. High fidelity physics based models rather than cost and scaling models are used to perform the work. Results provide a quantitative assessment of anticipated costs and benefits for high speed rotors. Finally, important lessons regarding full system optimization of wind turbines are documented.

  15. Satellite-tracked cumulus velocities. [for determining wind velocity

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.; Pearl, E. W.; Shenk, W. E.

    1973-01-01

    The research indicates that extreme caution must be exercised in converting cloud velocities into winds. The motion of fair-weather cumuli obtained by tracking their shadows over Springfield, Missouri revealed that the standard deviation in the individual cloud motion is several times the tracking error. The motion of over-ocean cumuli near Barbados clearly indicated the complicated nature of cumulus velocities. Analysis of whole-sky images obtained near Tampa, Florida failed to show significant continuity and stability of cumulus plumes, less than 0.3 mile in diameter. Cumulus turrets with 0.3 to 2 mile in size appear to be the best target to infer the mean wind within the subcloud layers. Cumulus or stratocumulus cells consisting of x number of turrets do not always move with wind. The addition and deletion of turrets belonging to a specific cell appear to be the cause of the erratic motion of a tracer cell. It may by concluded that the accuracy of wind estimates is unlikely to be better than 2m/sec unless the physical and dynamical characteristics of cumulus motion is futher investigated.

  16. Maximum power tracking control scheme for wind generator systems 

    E-print Network

    Mena Lopez, Hugo Eduardo

    2009-05-15

    The purpose of this work is to develop a maximum power tracking control strategy for variable speed wind turbine systems. Modern wind turbine control systems are slow, and they depend on the design parameters of the turbine and use wind and/or rotor...

  17. Design of wind farm layout for maximum wind energy capture Andrew Kusiak*, Zhe Song

    E-print Network

    Kusiak, Andrew

    Design of wind farm layout for maximum wind energy capture Andrew Kusiak*, Zhe Song Intelligent Accepted 24 August 2009 Available online 22 September 2009 Keywords: Wind farm Wind turbine Layout design Optimization Evolutionary algorithms Operations research a b s t r a c t Wind is one of the most promising

  18. Maximum wind energy extraction strategies using power electronic converters

    NASA Astrophysics Data System (ADS)

    Wang, Quincy Qing

    2003-10-01

    This thesis focuses on maximum wind energy extraction strategies for achieving the highest energy output of variable speed wind turbine power generation systems. Power electronic converters and controls provide the basic platform to accomplish the research of this thesis in both hardware and software aspects. In order to send wind energy to a utility grid, a variable speed wind turbine requires a power electronic converter to convert a variable voltage variable frequency source into a fixed voltage fixed frequency supply. Generic single-phase and three-phase converter topologies, converter control methods for wind power generation, as well as the developed direct drive generator, are introduced in the thesis for establishing variable-speed wind energy conversion systems. Variable speed wind power generation system modeling and simulation are essential methods both for understanding the system behavior and for developing advanced system control strategies. Wind generation system components, including wind turbine, 1-phase IGBT inverter, 3-phase IGBT inverter, synchronous generator, and rectifier, are modeled in this thesis using MATLAB/SIMULINK. The simulation results have been verified by a commercial simulation software package, PSIM, and confirmed by field test results. Since the dynamic time constants for these individual models are much different, a creative approach has also been developed in this thesis to combine these models for entire wind power generation system simulation. An advanced maximum wind energy extraction strategy relies not only on proper system hardware design, but also on sophisticated software control algorithms. Based on literature review and computer simulation on wind turbine control algorithms, an intelligent maximum wind energy extraction control algorithm is proposed in this thesis. This algorithm has a unique on-line adaptation and optimization capability, which is able to achieve maximum wind energy conversion efficiency through continuously improving the performance of wind power generation systems. This algorithm is independent of wind power generation system characteristics, and does not need wind speed and turbine speed measurements. Therefore, it can be easily implemented into various wind energy generation systems with different turbine inertia and diverse system hardware environments. In addition to the detailed description of the proposed algorithm, computer simulation results are presented in the thesis to demonstrate the advantage of this algorithm. As a final confirmation of the algorithm feasibility, the algorithm has been implemented inside a single-phase IGBT inverter, and tested with a wind simulator system in research laboratory. Test results were found consistent with the simulation results. (Abstract shortened by UMI.)

  19. Three dimensional winds: A maximum cross-correlation application to elastic lidar data

    SciTech Connect

    Buttler, W.T.

    1996-05-01

    Maximum cross-correlation techniques have been used with satellite data to estimate winds and sea surface velocities for several years. Los Alamos National Laboratory (LANL) is currently using a variation of the basic maximum cross-correlation technique, coupled with a deterministic application of a vector median filter, to measure transverse winds as a function of range and altitude from incoherent elastic backscatter lidar (light detection and ranging) data taken throughout large volumes within the atmospheric boundary layer. Hourly representations of three-dimensional wind fields, derived from elastic lidar data taken during an air-quality study performed in a region of complex terrain near Sunland Park, New Mexico, are presented and compared with results from an Environmental Protection Agency (EPA) approved laser doppler velocimeter. The wind fields showed persistent large scale eddies as well as general terrain-following winds in the Rio Grande valley.

  20. Developing and Testing Wind Velocity Retrieval Algorithms for Doppler Wind Lidar

    NASA Astrophysics Data System (ADS)

    Wang, H.; Barthelmie, R. J.; Clifton, A.; Capaldo, N.; Pryor, S. C.

    2013-12-01

    A 3-dimensional wind lidar is being evaluated at the National Wind Technology Center (NWTC) for its applications in wind energy. The focus of the work described here is to develop algorithms that can increase data availability and accuracy in estimating wind velocity from the line of sight (los) velocity (Vlos) from Plan Position Indicator (PPI) scans. The common algorithm (AL0) starts by removing Vlos estimates that have low signal-to-noise ratio (SNR). Then, assuming a horizontally homogeneous wind field and zero vertical wind speed (w), the wind velocity is estimated by application of ordinary least square (OLS) fitting, and the results are averaged to produce the 10-minute mean wind velocity (scalar averaging) at each range-gate position. This approach has uncertainties because: (1) SNR is robust but conservative for quality control and use of any SNR threshold may result in exclusion of valid Vlos values causing low data availability. (2) While 10-minute mean w = 0 is typically valid, assuming zero w for each individual Vlos field may introduce biases. (3) The variance of Vlos changes with azimuth angle as it is the projection of the variance of the wind vector on the los. This violates the equal variance assumption in OLS fitting. The two new algorithms are developed to increase data availability and the accuracy of 10-minute mean wind velocities. Both algorithms assume that the wind velocity is normally distributed and use the maximum likelihood estimator for which the variance of Vlos changes with azimuth angle. The first algorithm (AL1) uses the 10-minute mean Vlos to estimate the 10-minute mean wind velocity. In comparison to scalar averaging, AL1 can reduce the variation in Vlos and the assumption of w = 0 is more likely to be valid. To increase data availability, Vlos with low SNR is retained if its difference from the mean is smaller than three times the standard deviation of Vlos. The second algorithm (AL2) uses the median of Vlos over 10 minutes (as opposed to the mean value as in AL1). For a normal distribution, the sample median is a robust estimate of the mean and is insensitive to outliers (e.g. incorrect measurements associated with low SNR). Thus, using the sample median allows for the use of Vlos with very low SNR and eventually increase data availability for AL2. A preliminary analysis of lidar data collected during February 15 to 26, 2013 shows that AL2 out-performs AL0 and AL1 when the resulting wind speed estimates are compared with independent data from a sonic anemometer (Table 1). Work is underway to test the performance of the three algorithms using a dataset of several months collected during spring/summer 2013 at NWTC, and the errors/uncertainties of each approach will be quantified in terms of their relationships with atmospheric conditions, such as wind shear and atmospheric stability, using the data from instrumentation deployed on the NWTC meteorological towers.Table 1 Summary of performance of the three lidar wind retrieval algorithms

  1. Wind velocity profiles measured by the smoke-trail method at the Eastern Test Range, 1964

    NASA Technical Reports Server (NTRS)

    Manning, J. C.; Rhyne, R. H.; Henry, R. M.

    1972-01-01

    Twenty-six detailed wind profiles measured by the smoke trail technique at the Eastern Test Range during the first seven months of 1964 are presented as plots of west-to-east and south-to-north velocity components at height intervals of 25 meters. The overall altitude ranges of the profiles vary from about 2.6 to 19.1 km. The wind measurements, which were made under a variety of conditions, include velocities in excess of the 90- and 95-percent highest values for the Eastern Test Range. The report also includes a listing of the wind profiles, their maximum velocities and direction of the maximum velocities, measured by the smoke trail method at the Eastern Test Range from 1962 to 1964.

  2. Wave Tank Studies of Phase Velocities of Short Wind Waves

    NASA Astrophysics Data System (ADS)

    Ermakov, S.; Sergievskaya, I.; Shchegolkov, Yu.

    Wave tank studies of phase velocities of short wind waves have been carried out using Ka-band radar and an Optical Spectrum Analyser. The phase velocities were retrieved from measured radar and optical Doppler shifts, taking into account measurements of surface drift velocities. The dispersion relationship was studied in centimetre (cm)- and millimetre(mm)-scale wavelength ranges at different fetches and wind speeds, both for a clean water surface and for water covered with surfactant films. It is ob- tained that the phase velocities do not follow the dispersion relation of linear capillary- gravity waves, increasing with fetch and, therefore, depending on phase velocities of dominant decimetre (dm)-centimetre-scale wind waves. One thus can conclude that nonlinear cm-mm-scale harmonics bound to the dominant wind waves and propagat- ing with the phase velocities of the decimetric waves are present in the wind wave spectrum. The resulting phase velocities of short wind waves are determined by re- lation between free and bound waves. The relative intensity of the bound waves in the spectrum of short wind waves is estimated. It is shown that this relation depends strongly on the surfactant concentration, because the damping effect due to films is different for free and bound waves; this results to changes of phase velocities of wind waves in the presence of surfactant films. This work was supported by MOD, UK via DERA Winfrith (Project ISTC 1774P) and by RFBR (Project 02-05-65102).

  3. Radionuclide counting technique for measuring wind velocity and direction

    NASA Technical Reports Server (NTRS)

    Singh, J. J. (inventor)

    1984-01-01

    An anemometer utilizing a radionuclide counting technique for measuring both the velocity and the direction of wind is described. A pendulum consisting of a wire and a ball with a source of radiation on the lower surface of the ball is positioned by the wind. Detectors and are located in a plane perpendicular to pendulum (no wind). The detectors are located on the circumferene of a circle and are equidistant from each other as well as the undisturbed (no wind) source ball position.

  4. A two-dimensional study of the maximum power that can be obtained from a wind turbine in a wind shear layer

    SciTech Connect

    Johansson, B.C.A.

    1981-04-01

    In 1926 Albert Betz derived a one-dimensional stream tube theory for the maximum power that can be obtained from a wind turbine in a uniform flow. However, for modern large wind turbines there is a considerable velocity gradient in the approaching flow, since the wind flow field above the ground normally is a shear layer with a velocity profile reminding of that of a boundary layer of a wing or a flat plate. The present study extends Betz' theory to a two-dimensional case, where the undisturbed velocity field is given and allowed to vary arbitrarily vertically, and the location of the wind turbine is given. The maximum power is calculated by the method of calculus of variations. It is found that for common wind velocity profiles the maximum power is only slightly larger than the power, which is obtained by a constant relative wind speed retardation, equal to Betz' retardation, while for a linear velocity profile there is a considerable difference.

  5. Analytical expressions for maximum wind turbine average power in a Rayleigh wind regime

    SciTech Connect

    Carlin, P.W.

    1996-12-01

    Average or expectation values for annual power of a wind turbine in a Rayleigh wind regime are calculated and plotted as a function of cut-out wind speed. This wind speed is expressed in multiples of the annual average wind speed at the turbine installation site. To provide a common basis for comparison of all real and imagined turbines, the Rayleigh-Betz wind machine is postulated. This machine is an ideal wind machine operating with the ideal Betz power coefficient of 0.593 in a Rayleigh probability wind regime. All other average annual powers are expressed in fractions of that power. Cases considered include: (1) an ideal machine with finite power and finite cutout speed, (2) real machines operating in variable speed mode at their maximum power coefficient, and (3) real machines operating at constant speed.

  6. Exploratory Meeting on Airborne Doppler Lidar Wind Velocity Measurements

    NASA Technical Reports Server (NTRS)

    Fichtel, G. H. (editor); Kaufman, J. W. (editor); Vaughan, W. W. (editor)

    1980-01-01

    The scientific interests and applications of the Airborne Doppler Lidar Wind Velocity Measurement System to severe storms and local weather are discussed. The main areas include convective phenomena, local circulation, atmospheric boundary layer, atmospheric dispersion, and industrial aerodynamics.

  7. Velocity Distributions and Proton Beam Production in the Solar Wind

    SciTech Connect

    Pierrard, Viviane; Voitenko, Yuriy

    2010-03-25

    Helios, Ulysses, and Wind spacecraft have observed the velocity distribution functions (VDFs) of solar wind particles deviating significantly from Maxwellians. We review recent models using different approximations and mechanisms that determine various observed characteristics of the VDFs for the electrons, protons and minor ions. A new generation mechanism is proposed for super-Alfvenic proton beams and tails that are often observed in the fast solar wind. The mechanism is based on the proton trapping and acceleration by kinetic Alfven waves (KAWs), which carry a field-aligned potential well propagating with super-Alfven velocities.

  8. Maximum velocity of self-propulsion for an active segment

    E-print Network

    Recho, Pierre

    2015-01-01

    The motor part of a crawling eukaryotic cell can be represented schematically as an active continuum layer. The main active processes in this layer are protrusion, originating from non-equilibrium polymerization of actin fibers, contraction, induced by myosin molecular motors and attachment due to active bonding of trans-membrane proteins to a substrate. All three active mechanisms are regulated by complex signaling pathways involving chemical and mechanical feedback loops whose microscopic functioning is still poorly understood. In this situation, it is instructive to take a reverse engineering approach and study a problem of finding the spatial organization of standard active elements inside a crawling layer ensuring an optimal cost-performance trade-off. In this paper we assume that (in the range of interest) the energetic cost of self-propulsion is velocity independent and adopt, as an optimality criterion, the maximization of the overall velocity. We then choose a prototypical setting, formulate the corr...

  9. Spatiotemporal Dynamics of Wind Velocity from Mini-Sodar Measurements

    NASA Astrophysics Data System (ADS)

    Krasnenko, N. P.; Tarasenkov, M. V.; Shamanaeva, L. G.

    2015-03-01

    Mini-sodar measurements of wind velocity profiles in the 20-200 m layer have demonstrated the high efficiency of the use of mini-sodars in monitoring the fine structure of the atmospheric boundary layer (ABL) and in detecting jets and wind shear. An analysis of measurements of vertical profiles of the wind velocity and its vertical and horizontal components has shown that analytical approximations of the vertical profile of the horizontal wind velocity are possible for both neutral and unstable stratifications of the atmosphere. They are well described by a logarithmic law. The approximation constants are found and the errors associated with their use are estimated. The established physical trends and the obtained constants for the horizontal and vertical components of the wind velocity allow a description of their hourly and daily dynamics and can be recommended for use in ABL models intended for prognostic calculations (forecasting). The vector representation makes it possible to visualize the spatiotemporal dynamics of the wind field in the atmospheric boundary layer, in particular to estimate the shape and size of jets and wind shear in them.

  10. Long term periodicity in solar wind velocity during the last three solar cycles

    NASA Technical Reports Server (NTRS)

    Gazis, P. R.; Richardson, J. D.; Paularena, K. I.

    1995-01-01

    Solar wind measurements from the Pioneer 10, Pioneer 11, Voyager 2, IMP 8, and Pioneer Venus Orbiter (PVO) spacecraft were examined to search for long-term periodicities during the last three solar cycles. For the time of the last solar maximum, these measurements confirm the existence of the periodic 1.3-year enhancements in solar wind velocity reported by Richardson et al. (1994). For most of the preceding two solar cycles, long-term velocity enhancements occurred that were similar in structure but lacked the 1.3-year periodicity. It appears that long-term enhancements in solar wind velocity, with durations on the order of a few months to a year, are a common feature throughout the heliosphere.

  11. Comparison of VLF Wave Activity in the Solar Wind During Solar Maximum and Minimum

    E-print Network

    California at Berkeley, University of

    Comparison of VLF Wave Activity in the Solar Wind During Solar Maximum and Minimum: Ulysses and intermediate speed solar wind. The maximum intensity of the electromagnetic waves for the two solar cycle are similar for the slow and intermediate solar wind in both solar maximum and minimum phases. It is also

  12. The turbulence structure of katabatic flows below and above wind-speed maximum

    NASA Astrophysics Data System (ADS)

    Grachev, Andrey; Leo, Laura; Di Sabatino, Silvana; Fernando, Harindra; Pardyjak, Eric; Fairall, Christopher

    2015-04-01

    Measurements of atmospheric small-scale turbulence made over the complex-terrain at the US Army Dugway Proving Grounds in Utah during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program are used to describe the turbulence structure of katabatic flows. Turbulent and mean meteorological data were continuously measured at multiple levels (up to seven) on four towers deployed along East lower slope (2-4 degrees) of Granite Mountain. The multi-level, multi-tower observations obtained during a 30-day long MATERHORN-Fall field campaign in September-October 2102 allow studying temporal and spatial structure of nocturnal slope flows in detail. In this study, we focus on the various statistics (fluxes, variances, spectra, cospectra, etc.) of the small-scale turbulence of katabatic winds. Observed vertical profiles of velocity, turbulent fluxes, and other quantities show steep gradients near the surface but in the layer above the slope jet these variables vary with height more slowly than near the surface. It is found that vertical momentum flux and horizontal heat (buoyancy) flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The vertical momentum flux is directed downward (upward) whereas the horizontal heat flux is downslope (upslope) below (above) the wind maximum. Our study, therefore, suggests that a position of the jet speed maximum can be derived from linear interpolation between positive and negative values of the momentum flux (or the horizontal heat flux) and determination of a height where a flux becomes zero. It is shown that the standard deviations of all wind speed components (and therefore the turbulent kinetic energy) and the dissipation rate of turbulent kinetic energy have a local minimum, whereas the standard deviation of air temperature has an absolute maximum at the height of wind speed maximum. We report several cases when the destructive effect of vertical heat (buoyancy) flux is completely cancelled by the generation of turbulence due to the horizontal heat (buoyancy) flux. Turbulence in the layer above the wind-speed maximum is decoupled from the surface and it is consistent with the classical local z-less predictions for stably stratified boundary layer.

  13. Quartz crystal microbalances to measure wind velocity and air humidity

    NASA Technical Reports Server (NTRS)

    Stephens, J. B.; Lave, E. G.

    1975-01-01

    Instrument includes four temperature-sensing, Y-cut quartz crystals to determine wind direction, velocity, and temperature. Two additional AT-cut crystals are used to determine air humidity. Entire signal processing is provided by built-in electronics circuits.

  14. Measurement of turbulent wind velocities using a rotating boom apparatus

    SciTech Connect

    Sandborn, V.A.; Connell, J.R.

    1984-04-01

    The present report covers both the development of a rotating-boom facility and the evaluation of the spectral energy of the turbulence measured relative to the rotating boom. The rotating boom is composed of a helicopter blade driven through a pulley speed reducer by a variable speed motor. The boom is mounted on a semiportable tower that can be raised to provide various ratios of hub height to rotor diameter. The boom can be mounted to rotate in either the vertical or horizontal plane. Probes that measure the three components of turbulence can be mounted at any location along the radius of the boom. Special hot-film sensors measured two components of the turbulence at a point directly in front of the rotating blade. By using the probe rotated 90/sup 0/ about its axis, the third turbulent velocity component was measured. Evaluation of the spectral energy distributions for the three components of velocity indicates a large concentration of energy at the rotational frequency. At frequencies slightly below the rotational frequency, the spectral energy is greatly reduced over that measured for the nonrotating case measurements. Peaks in the energy at frequencies that are multiples of the rotation frequency were also observed. We conclude that the rotating boom apparatus is suitable and ready to be used in experiments for developing and testing sensors for rotational measurement of wind velocity from wind turbine rotors. It also can be used to accurately measure turbulent wind for testing theories of rotationally sampled wind velocity.

  15. Measuring velocity fields in wind tunnels with holographic interferometry

    NASA Astrophysics Data System (ADS)

    Andrés, N.; Arroyo, M. P.; Hinrichs, H.; Hinsch, K.; Quintanilla, M.

    This paper investigates the feasibility of using holographic interferometry in wind tunnel flows for measuring velocity fields rather than density or temperature fields. First results were obtained in a vortex street behind a cylinder at Re=190(U?=0.7 m/s). The light scattered from an illuminated fluid plane was holographically recorded twice with the same reference beam. Using a time interval of 10?s, local fluid displacements smaller than a few microns were recorded. The holographic plate was placed in front and as close as possible to the fluid plane. The interferograms obtained from the hologram reconstruction give information about one velocity component, at 45° with the illuminated plane. The alignment of the cylinder axis with this 45° direction provided definite confirmation about the vortex street having a non-negligible axial velocity. The constant velocity fluid region has proven to be very useful for quantifying the velocity information contained in the interferogram.

  16. Velocity of Winds Aloft from Site Test Interferometer Data M.A. Holdaway

    E-print Network

    Groppi, Christopher

    Velocity of Winds Aloft from Site Test Interferometer Data M.A. Holdaway National Radio Astronomy was the velocity of the water vapor aloft. We demonstrate two quite independent methods of measuring the wind velocity aloft agree to 5­10%. Wind Velocity Aloft In MMA Memo 129 (Holdaway, et al. 1995), we showed one

  17. An experimental study of a plasma actuator in absence of free airflow: Ionic wind velocity profile

    SciTech Connect

    Mestiri, R.; Hadaji, R.; Ben Nasrallah, S.

    2010-08-15

    In this study, we are interested in the direct current electrical corona discharge created between two wire electrodes. The experimental results are related to some electroaerodynamic actuators based on the direct current corona discharge at the surface of a dielectric material. Several geometrical forms are selected for the dielectric surface, such as a plate, a cylinder, and a NACA 0015 aircraft wing. The current density-electric field characteristics are presented for different cases in order to determine the discharge regimes. The corona discharge produces nonthermal plasma, so it is called plasma discharge. Plasma discharge creates a tangential ionic wind above the surface at the vicinity of the wall. The ionic wind induced by the corona discharge is measured in absence of free external airflow. The ionic wind velocity profiles and the maximum induced tangential force are given for different surface forms, so it is possible to compare the actuators effect based on the span of the ionic wind velocity and thrust values. The higher ionic wind velocity is obtained with the NACA profile, which shows the effectiveness of this actuator for the airflow control.

  18. 1.5-?m eye-safe coherent lidar system for wind velocity measurement

    NASA Astrophysics Data System (ADS)

    Asaka, Kimio; Yanagisawa, Takayuki; Hirano, Yoshihito

    2001-02-01

    A coherent lidar is an attractive sensor for atmospheric observation because it enables the wind velocity measurement in clear air conditions. A 1.5-um eye-safe coherent lidar is more attractive than a 2-um eye-safe coherent lidar. The wavelength of 1.5-um provides a ten times higher maximum permissible exposure for human eyes than the wavelength of 2-um. In addition, optical fiber components and devices developed for optical fiber communications are easily available. We have already reported first 1.5-um coherent lidar system for wind velocity measurement, and recently completed the full system. The system has the Er,Yb:Glass pulsed laser with the output energy 10.9-mJ and the telescope with effective aperture of 100-mm. The system provides the available measurement range of 5-km (SNR>+1-dB), the detectable wind velocity range of between -50-m/sec and +50-m/sec and the range resolution of 30-m. The velocity accuracy of 0.14-m/sec (standard deviation) is obtained by measuring velocity of a non-moving hard target.

  19. Analysis of the velocity law in the wind of the Be star Lambda Pavonis

    NASA Technical Reports Server (NTRS)

    Chen, Haiqi; Ringuelet, Adela; Sahade, Jorge; Kondo, Yoji

    1989-01-01

    This paper reanalyzes the IUE spectra of Lambda Pavonis secured in 1982 (Sahade et al.). It is found that the profiles of the broad UV lines are either rotationally broadened or nonrotationally broadened and that the rotationally broadened profiles can be sorted out in two groups characterized by rotational velocity values of 170 km/s and of 210 km/s, respectively. From the analysis of the rotational and of the radial velocities it is possible to distinguish two regions in the extended atmosphere of the star, namely, a region which is rotating and a region which is expanding. In the rotating region, the radial velocities are about zero, and the rotational velocity increases from 170 km/s to 250 km/s. In the expanding region, the rotational energy dissipates, the wind is accelerated to a maximum of -155 km/s, and farther out it decelerates.

  20. The stellar wind velocity field of HD 77581

    E-print Network

    Manousakis, A

    2015-01-01

    The early acceleration of stellar winds in massive stars is poorly constrained. The scattering of hard X-ray photons emitted by the pulsar in the high-mass X-ray binary Vela X-1 can be used to probe the stellar wind velocity and density profile close to the surface of its supergiant companion HD 77581. We built a high signal-to-noise and high resolution hard X-ray lightcurve of Vela X-1 measured by Swift/BAT over 300 orbital periods of the system and compared it with the predictions of a grid of hydrodynamic simulations. We obtain a very good agreement between observations and simulations for a narrow set of parameters, implying that the wind velocity close to the stellar surface is twice larger than usually assumed with the standard beta law. Locally a velocity gradient of $\\beta\\sim0.5$ is favoured. Even if still incomplete, hydrodynamic simulations are successfully reproducing several observational properties of Vela X-1.

  1. The stellar wind velocity field of HD 77581

    NASA Astrophysics Data System (ADS)

    Manousakis, A.; Walter, R.

    2015-12-01

    Aims: The early acceleration of stellar winds in massive stars is poorly constrained. The scattering of hard X-ray photons emitted by the pulsar in the high-mass X-ray binary Vela X-1 can be used to probe the stellar wind velocity and density profile close to the surface of its supergiant companion HD 77581. Methods: We built a high signal-to-noise and high resolution hard X-ray lightcurve of Vela X-1 measured by Swift/BAT over 300 orbital periods of the system and compared it with the predictions of a grid of hydrodynamic simulations. Results: We obtain very good agreement between observations and simulations for a narrow set of parameters, implying that the wind velocity close to the stellar surface is twice higher than usually assumed with the standard beta law. Locally a velocity gradient of ? ~ 0.5 is favoured. Even if still incomplete, hydrodynamic simulations successfully reproduce several observational properties of Vela X-1.

  2. Accuracy of aircraft velocities from inertial navigation systems for application to airborne wind measurements

    NASA Technical Reports Server (NTRS)

    Rhyne, R. H.

    1980-01-01

    An experimental assessment was made of two commercially available inertial navigation systems (INS) with regard to their velocity measuring capability for use in wind, shear, and long-wavelength atmospheric turbulence research. The assessment was based on 52 sets of postflight measurements of velocity (error) during a "Schuler cycle" (84 minutes) while the INS was still operating but the airplane was motionless. Four INS units of one type and two units of another were tested over a period of 2 years after routine research flights similar to air-linetype operations of from 1 to 6 hours duration. The maximum postflight errors found for the 52 cases had a root mean square value of 2.82 m/sec with little or no correlation of error magnitude with flight duration. Using an INS for monitoring ground speed during landway in a predicted high wind shear situation could lead to landing speeds which are dangerously high or low.

  3. The Enhanced-model Ladar Wind Sensor and Its Application in Planetary Wind Velocity Measurements

    NASA Technical Reports Server (NTRS)

    Soreide, D. C.; Mcgann, R. L.; Erwin, L. L.; Morris, D. J.

    1993-01-01

    For several years we have been developing an optical air-speed sensor that has a clear application as a meteorological wind-speed sensor for the Mars landers. This sensor has been developed for aircraft use to replace the familiar, pressure-based Pitot probe. Our approach utilizes a new concept in the laser-based optical measurement of air velocity (the Enhanced-Mode Ladar), which allows us to make velocity measurements with significantly lower laser power than conventional methods. The application of the Enhanced-Mode Ladar to measuring wind speeds in the martian atmosphere is discussed.

  4. Long-term velocity enhancements in the solar wind

    NASA Technical Reports Server (NTRS)

    Gazis, P. R.; Richardson, J. D.; Paularena, K. I.

    1995-01-01

    Throughout most of the last three solar cycles, the Pioneer 10, Pioneer 11, Voyager 2, IMP 8, and Pioneer Venus Orbiter spacecraft have observed long-term enhancements in solar wind velocity. These enhancements are typically on the order of 100-200 km/s, with durations on the order of several months to over a year. They are observed over a range of heliocentric distances that ranges from 0.72 to more than 60 AU, which suggests that they are a characteristic feature throughout the entire heliosphere, at least in the vicinity of the solar equator. They appear to be related to the 'long term velocity shifts' reported by Gazis [1987], but are much more widespread. Since the last solar minimum, they have recurred with the 13-year periodicity reported by Richardson et al [1994], but prior to the last solar minimum there were long intervals were his periodicity was different or absent. We examine and characterize these long-term velocity enhancements and compare them to shorter-term variations in the solar wind such as CMEs, interaction regions, merged interaction regions (MIRs) and global merged interaction regions (GMIRs).

  5. Characteristics of Wind Velocity and Temperature Change Near an Escarpment-Shaped Road Embankment

    PubMed Central

    Kim, Young-Moon; You, Ki-Pyo; You, Jang-Youl

    2014-01-01

    Artificial structures such as embankments built during the construction of highways influence the surrounding airflow. Various types of damage can occur due to changes in the wind velocity and temperature around highway embankments. However, no study has accurately measured micrometeorological changes (wind velocity and temperature) due to embankments. This study conducted a wind tunnel test and field measurement to identify changes in wind velocity and temperature before and after the construction of embankments around roads. Changes in wind velocity around an embankment after its construction were found to be influenced by the surrounding wind velocity, wind angle, and the level difference and distance from the embankment. When the level difference from the embankment was large and the distance was up to 3H, the degree of wind velocity declines was found to be large. In changes in reference wind velocities around the embankment, wind velocity increases were not proportional to the rate at which wind velocities declined. The construction of the embankment influenced surrounding temperatures. The degree of temperature change was large in locations with large level differences from the embankment at daybreak and during evening hours when wind velocity changes were small. PMID:25136681

  6. Potential for coherent Doppler wind velocity lidar using neodymium lasers

    NASA Technical Reports Server (NTRS)

    Kane, T. J.; Byer, R. L.; Zhou, B.

    1984-01-01

    Existing techniques for the frequency stabilization of Nd:YAG lasers operating at 1.06 micron, and the high-gain amplification of radiation at that wavelength, make possible the construction of a coherent Doppler wind velocity lidar using Nd:YAG. Velocity accuracy and range resolution are better at 1.06 micron than at 10.6 microns at the same level of the SNR. Backscatter from the atmosphere at 1.06 micron is greater than that at 10.6 microns by about 2 orders of magnitude, but the quantum-limited noise is higher by 100 also. Near-field attenuation and turbulent effects are more severe at 1.06 micron. In some configurations and environments, the 1.06-micron wavelength may be the better choice, and there may be technological advantages favoring the use of solid-state lasers in satellite systems.

  7. Low-level nocturnal wind maximum over the Central Amazon Basin

    NASA Technical Reports Server (NTRS)

    Greco, Steven; Ulanski, Stanley; Garstang, Michael; Houston, Samuel

    1992-01-01

    A low-level nocturnal wind maximum is shown to exist over extensive and nearly undisturbed rainforest near the central Amazon city of Manaus. Meteorological data indicate the presence of this nocturnal wind maximum during both the wet and dry seasons of the Central Amazon Basin. Daytime wind speeds which are characteristically 3-7 m/s between 300 and 1000 m increase to 10-15 m/s shortly after sunset. The wind-speed maximum is reached in the early evening, with wind speeds remaining high until several hours after sunrise. The nocturnal wind maximum is closely linked to a strong low-level inversion formed by radiational cooling of the rainforest canopy. Surface and low-level pressure gradients between the undisturbed forest and the large Amazon river system and the city of Manaus are shown to be responsible for much of the nocturnal wind increase. The pressure gradients are interpreted as a function of the thermal differences between undisturbed forest and the river/city. The importance of both the frictional decoupling and the horizontal pressure gradient suggest that the nocturnal wind maximum does not occur uniformly over all Amazonia. Low-level winds are thought to be pervasive under clear skies and strong surface cooling and that, in many places (i.e., near rivers), local pressure gradients enhance the low-level nocturnal winds.

  8. The analysis and kinetic energy balance of an upper-level wind maximum during intense convection

    NASA Technical Reports Server (NTRS)

    Fuelberg, H. E.; Jedlovec, G. J.

    1982-01-01

    The purpose of this paper is to analyze the formation and maintenance of the upper-level wind maximum which formed between 1800 and 2100 GMT, April 10, 1979, during the AVE-SESAME I period, when intense storms and tornadoes were experienced (the Red River Valley tornado outbreak). Radiosonde stations participating in AVE-SESAME I are plotted (centered on Oklahoma). National Meteorological Center radar summaries near the times of maximum convective activity are mapped, and height and isotach plots are given, where the formation of an upper-level wind maximum over Oklahoma is the most significant feature at 300 mb. The energy balance of the storm region is seen to change dramatically as the wind maximum forms. During much of its lifetime, the upper-level wind maximum is maintained by ageostrophic flow that produces cross-contour generation of kinetic energy and by the upward transport of midtropospheric energy. Two possible mechanisms for the ageostrophic flow are considered.

  9. Analysis of spatiotemporal dynamics of the wind velocity in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Kapegesheva, O. F.; Krasnenko, N. P.; Shamanaeva, L. G.

    2014-11-01

    In the paper the spatiotemporal dynamics of the vertical and horizontal components of the wind velocity in the atmospheric boundary layer retrieved from mini-sodar measurements is analyzed. Their analytical approximations are suggested and approximation errors are estimated. The effect of the averaging time on minisodar-retrieved wind velocity components is analyzed. An example of the half-day dynamics of the wind velocity field is presented which vividly illustrates the presence of convective plumes.

  10. A multiyear global surface wind velocity dataset using SSM/I wind observations

    SciTech Connect

    Atlas, R.; Bloom, S.C.; Ardizzone, J.

    1996-05-01

    The Special Sensor Microwave Imagers (SSM/I) aboard three DMSP satellites have improved a large dataset of surface wind speeds over the global oceans from July 1987 to the present. These data are characterized by high resolution, coverage, and accuracy, but their application has been limited by the lack of directional information. In an effort to extend the applicability of these data , methodology has been developed to assign directions to the SSM/I wind speeds and to produce analyses using these data. Following extensive testing, this methodology has been used to generate a seven and one-half year dataset (from July 1987 through December 1994) of global SSM/I wind vectors. These data are currently being used in a variety of atmospheric and oceanic applications and are available to interested investigators. Recent results presented in this paper show the accuracy of the SSM/I wind velocities, the ability of these data to improve surface wind analyses, and the propagation of a synoptic-scale convergent cortex in the Tropics that can be tracked from year to year in annual mean SSM/I wind fields. 11 refs., 5 figs., 2 tabs.

  11. Determination of the Wind-Velocity Vector Above the Ocean Surface Using the Image Spectrum of a Polarimetric Radar with Synthesized Aperture

    NASA Astrophysics Data System (ADS)

    Panfilova, M. A.; Kanevsky, M. B.; Balandina, G. N.; Karaev, V. Yu.; Stoffelen, A.; Verkhoev, A.

    2015-09-01

    We propose a new method for determining the wind-velocity vector above the ocean surface using the data of a polarimetric synthetic aperture radar. The preliminary calculations show that for wind waves, the location of the maximum in the radar image is unambiguously related to the wind velocity, whereas the wind direction is retrieved with an uncertainty of 180°, which is related to the central symmetry of the image spectrum. To eliminate the ambiguity when determining the wind direction, a criterion based on the information on the sign of the coefficient of correlation among the complex signals on the co- and cross polarizations is used. It is shown that using the polarimetric radar, it is theoretically possible to obtain information on both the wind velocity and direction without exact radar calibration.

  12. Pulsar Wind Nebulae, Space Velocities and Supernova Remnant

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The original proposal for this LTSA grant was for X-ray studies of pulsars, and especially pulsar wind nebulae and what they could tell us about pulsar properties, especially their space velocities. By any metric, this program has been very successful. No fewer than 14 papers on directly related topics (and several dozen more on related topics) have been published in refereed journals with the PI as lead or co-author, all observational results that have had significant impact on the field. These include the first X-ray detection of the "Duck" pulsar, a clear demonstration that estimated pulsar ages can be off by over an order of magnitude (via observations of the young supernova remnant G11.2-0.3) and the detection of the first pulsar wind nebula around a millisecond pulsar. These publications have also resulted in 4 press releases. Moreover, they also represent the thesis work of two PhD students at MIT (Froney Crawford and Mike Pivovaroff) and one postdoctoral fellow, Bryan Gaensler, now Assistant Professor at Harvard.

  13. Maximum projection and velocity estimation algorithm for small moving target detection in space surveillance

    NASA Astrophysics Data System (ADS)

    Yao, Dalei; Wen, Desheng; Xue, Jianru; Chen, Zhi; Wen, Yan; Jiang, Baotan; Ma, Junyong

    2015-10-01

    The article presents a new method to detect small moving targets in space surveillance. Image sequences are processed to detect and track targets under the assumption that the data samples are spatially registered. Maximum value projection and normalization are performed to reduce the data samples and eliminate the background clutter. Targets are then detected through connected component analysis. The velocities of the targets are estimated by centroid localization and least squares regression. The estimated velocities are utilized to track the targets. A sliding neighborhood operation is performed prior to target detection to significantly reduce the computation while preserving as much target information as possible. Actual data samples are acquired to test the proposed method. Experimental results show that the method can efficiently detect small moving targets and track their traces accurately. The centroid locating precision and tracking accuracy of the method are within a pixel.

  14. Probabilistic estimates of maximum acceleration and velocity in rock in the contiguous United States

    USGS Publications Warehouse

    Algermissen, Sylvester Theodore; Perkins, D.M.; Thenhaus, P.C.; Hanson, S.L.; Bender, B.L.

    1982-01-01

    Maximum horizontal accelerations and velocities caused by earthquakes are mapped for exposure times of 10, 50 and 250 years at the 90-percent probability level of nonexceedance for the contiguous United States. In many areas these new maps differ significantly from the 1976 probabilistic acceleration map by Algermlssen and Perkins because of the increase in detail, resulting from greater emphasis on the geologic basis for seismic source zones. This new emphasis is possible because of extensive data recently acquired on Holocene and Quaternary faulting in the western United States and new interpretations of geologic structures controlling the seismicity pattern in the central and eastern United States.

  15. Effect of wind tunnel air velocity on VOC flux rates from CAFO manure and wastewater

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind tunnels and flux chambers are often used to estimate volatile organic compound (VOC) emissions from animal feeding operations (AFOs) without regard to air velocity or sweep air flow rates. Laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission ...

  16. Wind Velocities at the Chajnantor and Mauna Kea Sites and the Effect on MMA Pointing

    E-print Network

    Groppi, Christopher

    Wind Velocities at the Chajnantor and Mauna Kea Sites and the Effect on MMA Pointing M.A. Holdaway email: (mholdawa, sfoster, demerson, jcheng, fschwab)@nrao.edu August 9, 1996 Abstract We analyze wind April 1996 for the purposes of understanding the effects of the winds on pointing errors. Both

  17. Gas transfer velocities measured at low wind speed over a lake

    USGS Publications Warehouse

    Crusius, J.; Wanninkhof, R.

    2003-01-01

    The relationship between gas transfer velocity and wind speed was evaluated at low wind speeds by quantifying the rate of evasion of the deliberate tracer, SF6, from a small oligotrophic lake. Several possible relationships between gas transfer velocity and low wind speed were evaluated by using 1-min-averaged wind speeds as a measure of the instantaneous wind speed values. Gas transfer velocities in this data set can be estimated virtually equally well by assuming any of three widely used relationships between k600 and winds referenced to 10-m height, U10: (1) a bilinear dependence with a break in the slope at ???3.7 m s-1, which resulted in the best fit; (2) a power dependence; and (3) a constant transfer velocity for U10 3.7 m s-1 which, coupled with the typical variability in instantaneous wind speeds observed in the field, leads to average transfer velocity estimates that are higher than those predicted for steady wind trends. The transfer velocities predicted by the bilinear steady wind relationship for U10 < ???3.7 m s-1 are virtually identical to the theoretical predictions for transfer across a smooth surface.

  18. Radial gradient of solar wind velocity from 1 to 5 AU

    NASA Technical Reports Server (NTRS)

    Collard, H. R.; Wolfe, J. H.

    1974-01-01

    Solar wind velocities have been measured on a daily basis from data obtained by the Ames Research Center plasma analyzers on both Pioneer 10 and Pioneer 11. A comparison between the time profiles of the solar wind velocities observed at the two spacecraft shows that the solar wind has the same major features, such as high velocity streams, out to at least 5 astronomical units (AU) from the sun. Major features in the velocity time profile observed first at Pioneer 11 are seen later at Pioneer 10 with a delay consistent with the respective heliocentric longitudes of the two spacecraft, their radial distances from the sun, and the solar wind velocity. A more detailed comparison between the velocity measurements made at Pioneer 10 and Pioneer 11 shows that the range of solar wind velocities decreases with increasing radial distance from the sun. Although the average value of the solar wind velocity as measured over a sufficiently long period is approximately the same at both spacecraft, the deviations to higher and lower velocities are less at a greater radial distance from the sun.

  19. Acoustic sounding of wind velocity profiles in a stratified moving atmosphere.

    PubMed

    Ostashev, V E; Georges, T M; Clifford, S F; Goedecke, G H

    2001-06-01

    The paper deals with analytical and numerical studies of the effects of atmospheric stratification on acoustic remote sensing of wind velocity profiles by sodars. Both bistatic and monostatic schemes are considered. Formulas for the Doppler shift of an acoustic echo signal scattered by atmospheric turbulence advected with the mean wind in a stratified moving atmosphere are derived. Numerical studies of these formulas show that errors in retrieving wind velocity can be of the order of 1 m/s if atmospheric stratification is ignored. Formulas for the height at which wind velocity is retrieved are also derived. Approaches are proposed which allow one to take into account the effects of atmospheric stratification when restoring the wind velocity profile from measured values of the Doppler shift and the time interval of acoustic impulse propagation from a sodar to the scattering volume and back to the ground. PMID:11425111

  20. C. elegans maximum velocity correlates with healthspan and is maintained in worms with an insulin receptor mutation.

    PubMed

    Hahm, Jeong-Hoon; Kim, Sunhee; DiLoreto, Race; Shi, Cheng; Lee, Seung-Jae V; Murphy, Coleen T; Nam, Hong Gil

    2015-01-01

    Ageing is marked by physical decline. Caenorhabditis elegans is a valuable model for identifying genetic regulatory mechanisms of ageing and longevity. Here we report a simple method to assess C. elegans' maximum physical ability based on the worms' maximum movement velocity. We show maximum velocity declines with age, correlates well with longevity, accurately reports movement ability and, if measured in mid-adulthood, is predictive of maximal lifespan. Contrary to recent findings, we observe that maximum velocity of worm with mutations in daf-2(e1370) insulin/IGF-1 signalling scales with lifespan. Because of increased odorant receptor expression, daf-2(e1370) mutants prefer food over exploration, causing previous on-food motility assays to underestimate movement ability and, thus, worm health. Finally, a disease-burden analysis of published data reveals that the daf-2(e1370) mutation improves quality of life, and therefore combines lifespan extension with various signs of an increased healthspan. PMID:26586186

  1. C. elegans maximum velocity correlates with healthspan and is maintained in worms with an insulin receptor mutation

    PubMed Central

    Hahm, Jeong-Hoon; Kim, Sunhee; DiLoreto, Race; Shi, Cheng; Lee, Seung-Jae V.; Murphy, Coleen T.; Nam, Hong Gil

    2015-01-01

    Ageing is marked by physical decline. Caenorhabditis elegans is a valuable model for identifying genetic regulatory mechanisms of ageing and longevity. Here we report a simple method to assess C. elegans' maximum physical ability based on the worms' maximum movement velocity. We show maximum velocity declines with age, correlates well with longevity, accurately reports movement ability and, if measured in mid-adulthood, is predictive of maximal lifespan. Contrary to recent findings, we observe that maximum velocity of worm with mutations in daf-2(e1370) insulin/IGF-1 signalling scales with lifespan. Because of increased odorant receptor expression, daf-2(e1370) mutants prefer food over exploration, causing previous on-food motility assays to underestimate movement ability and, thus, worm health. Finally, a disease-burden analysis of published data reveals that the daf-2(e1370) mutation improves quality of life, and therefore combines lifespan extension with various signs of an increased healthspan. PMID:26586186

  2. An Estimate of Solar Wind Velocity Profiles in a Coronal Hole and a Coronal Streamer Area (6-40 R(radius symbol)

    NASA Technical Reports Server (NTRS)

    Patzold, M.; Tsurutani, B. T.; Bird, M. K.

    1995-01-01

    Total electron content data obtained from the Ulysses Solar Corona Experiment (SCE) in 1991 were used to select two data sets, one associated with a coronal hole and the other with coronal streamer crossings. (This is largely equatorial data shortly after solar maximum.) The solar wind velocity profile is estimated for these areas.

  3. Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Betz, A. L.; Johnson, M. A.; Mclaren, R. A.; Sutton, E. C.

    1975-01-01

    Strong 10 micrometer line emission from (C-12)(O-16)2 in the upper atmosphere of Venus was detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicate mean zonal wind velocities less than 10 m/sec in the upper atmosphere near the equator. No evidence was found of the 100 m/sec wind velocity implied by the apparent 4-day rotation period of ultraviolet cloud features.

  4. Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Betz, A. L.; Johnson, M. A.; Mclaren, R. A.; Sutton, E. C.

    1975-01-01

    Strong 10 micrometer line emission from (c-12)(o-16)2 in the upper atmosphere of Venus was detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicate mean zonal wind velocities less than 10 m/sec in the upper atmosphere near the equator. No evidence was found of the 100 m/sec wind velocity implied by the apparent 4-day rotation period of ultraviolet cloud features.

  5. RW Sextantis, a disk with a hot, high-velocity wind

    NASA Technical Reports Server (NTRS)

    Greenstein, J. L.; Oke, J. B.

    1982-01-01

    The continuum spectrum of the flickering blue variable RW Sex was observed from 10,000 to 1150 A. The star is a cataclysmic variable currently stabilized at maximum, and the spectrum is dominated by an accretion disk, with flat spectrum in the ultraviolet, except at more than 5000 A, where a blackbody near 7000 K is seen. A distance of 400 pc is derived, if the latter arises from an F type main sequence star. The accretion rate required is near 10 to the -8th solar masses per year. Only weak emission is seen, except for Lyman alpha; strong, broad UV absorption lines are seen with centers displaced up to -3000 km/s, with terminal velocities up to -4500 km/s, the velocity of escape from a white dwarf. The low X-ray flux may arise from absorption within an unusually dense, hot wind from the innermost portions of the disk. The estimated mass loss rate is nearly 10 to the -12th solar masses per year.

  6. Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison

    NASA Astrophysics Data System (ADS)

    Sime, Louise C.; Kohfeld, Karen E.; Le Quéré, Corinne; Wolff, Eric W.; de Boer, Agatha M.; Graham, Robert M.; Bopp, Laurent

    2013-03-01

    The Southern Hemisphere (SH) westerly winds are thought to be critical to global ocean circulation, productivity, and carbon storage. For example, an equatorward shift in the winds, though its affect on the Southern Ocean circulation, has been suggested as the leading cause for the reduction in atmospheric CO2 during the Last Glacial period. Despite the importance of the winds, it is currently not clear, from observations or model results, how they behave during the Last Glacial. Here, an atmospheric modelling study is performed to help determine likely changes in the SH westerly winds during the Last Glacial Maximum (LGM). Using LGM boundary conditions, the maximum in SH westerlies is strengthened by ˜+1 m s-1 and moved southward by ˜2° at the 850 hPa pressure level. Boundary layer stabilisation effects over equatorward extended LGM sea-ice can lead to a small apparent equatorward shift in the wind band at the surface. Further sensitivity analysis with individual boundary condition changes indicate that changes in sea surface temperatures are the strongest factor behind the wind change. The HadAM3 atmospheric simulations, along with published PMIP2 coupled climate model simulations, are then assessed against the newly synthesised database of moisture observations for the LGM. Although the moisture data is the most commonly cited evidence in support of a large equatorward shift in the SH winds during the LGM, none of the models that produce realistic LGM precipitation changes show such a large equatorward shift. In fact, the model which best simulates the moisture proxy data is the HadAM3 LGM simulation which shows a small poleward wind shift. While we cannot prove here that a large equatorward shift would not be able to reproduce the moisture data as well, we show that the moisture proxies do not provide an observational evidence base for it.

  7. MEASUREMENT OF MOTION CORRECTED WIND VELOCITY USING AN AEROSTAT LOFTED SONIC ANEMOMETER

    EPA Science Inventory

    An aerostat-lofted, sonic anemometer was used to determine instantaneous 3 dimensional wind velocities at altitudes relevant to fire plume dispersion modeling. An integrated GPS, inertial measurement unit, and attitude heading and reference system corrected the wind data for th...

  8. A simple method to estimate threshold friction velocity of wind erosion in the field

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nearly all wind erosion models require the specification of threshold friction velocity (TFV). Yet determining TFV of wind erosion in field conditions is difficult as it depends on both soil characteristics and distribution of vegetation or other roughness elements. While several reliable methods ha...

  9. Southern Hemisphere westerly wind changes during the Last Glacial Maximum: paleo-data synthesis

    NASA Astrophysics Data System (ADS)

    Kohfeld, K. E.; Graham, R. M.; de Boer, A. M.; Sime, L. C.; Wolff, E. W.; Le Quéré, C.; Bopp, L.

    2013-05-01

    Changes in the strength and position of Southern Hemisphere westerly winds during the Last Glacial cycle have been invoked to explain both millennial and glacial-interglacial climate fluctuations. However, neither paleo models nor paleodata agree on the magnitude, or even the sign, of the change in wind strength and latitude during the most studied glacial period, the Last Glacial Maximum (LGM), compared to the recent past. This paper synthesizes paleo-environmental data that have been used to infer changes in LGM winds. Data compilations are provided for changes in terrestrial moisture, dust deposition, sea surface temperatures and ocean fronts, and ocean productivity, and existing data on Southern Hemisphere ocean circulation changes during the LGM are summarized. We find that any hypothesis of LGM wind and climate change needs to provide a plausible explanation for increased moisture on the west coast of continents, cooler temperatures and higher productivity in the Subantarctic Zone, and reductions in Agulhas leakage around southern Africa. Our comparison suggests that an overall strengthening, an equatorward displacement, or no change at all in winds could all be interpreted as consistent with observations. If a single cause related to the southern westerlies is sought for all the evidence presented, then an equatorward displacement or strengthening of the winds would be consistent with the largest proportion of the observations. However, other processes, such as weakening or poleward shifts in winds, a weakened hydrological cycle, extended sea-ice cover, and changed buoyancy fluxes, cannot be ruled out as potential explanations of observed changes in moisture, surface temperature, and productivity. We contend that resolving the position and strength of westerly winds during the LGM remains elusive based on data reconstructions alone. However, we believe that these data reconstructions of environmental conditions can be used in conjunction with model simulations to identify which processes best represent westerly wind conditions during the LGM.

  10. Density, Velocity and Ionization Structure in Accretion-Disc Winds

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Long, Knox

    2004-01-01

    This was a project to exploit the unique capabilities of FUSE to monitor variations in the wind- formed spectral lines of the luminous, low-inclination, cataclysmic variables(CV) -- RW Sex. (The original proposal contained two additional objects but these were not approved.) These observations were intended to allow us to determine the relative roles of density and ionization state changes in the outflow and to search for spectroscopic signatures of stochastic small-scale structure and shocked gas. By monitoring the temporal behavior of blue-ward extended absorption lines with a wide range of ionization potentials and excitation energies, we proposed to track the changing physical conditions in the outflow. We planned to use a new Monte Carlo code to calculate the ionization structure of and radiative transfer through the CV wind. The analysis therefore was intended to establish the wind geometry, kinematics and ionization state, both in a time-averaged sense and as a function of time.

  11. Radial gradient of solar wind velocity from 1 to 5 AU

    NASA Technical Reports Server (NTRS)

    Collard, H. R.; Wolfe, J. H.

    1974-01-01

    Solar wind velocity measurements made by Pioneers 10 and 11 are compared to investigate radial variations in the velocity at heliocentric distances of 1 to 5 AU. Two hundred days of corresponding Pioneer 10 and 11 data are plotted, the velocity profiles for 25-day segments are compared, and the same general pattern of peaks and troughs is found in the corresponding profiles. A comparison of the relative smoothness of the profiles clearly shows that velocity amplitudes in the solar wind stream structure decrease dramatically with increasing radial distance from the sun, although the rate of decrease is not as clear. It is hypothesized that stream-stream interactions play a dominant part in inhibiting the classical radial expansion process in the solar wind and produce scattering centers which prevent the observation of a significant galactic cosmic ray gradient in this region of space.

  12. Southern Hemisphere Westerly Wind Changes during the Last Glacial Maximum: Model-Data Comparison

    NASA Astrophysics Data System (ADS)

    Sime, Louise; Kohfeld, Karen; Le Quere, Corinne; Wolff, Eric; de Boer, Agatha; Graham, Robert; Bopp, Laurent

    2013-04-01

    The Southern Hemisphere (SH) westerly winds are thought to be critical to both past and future global ocean circulation, productivity, and carbon storage. For example, an equatorward shift in the winds has been suggested as the leading cause for the reduction in atmospheric CO2 during the Last Glacial Maximum (LGM), through its affect on the Southern Ocean circulation. Despite the importance of the SH westerlies, paleo-records and modelling studies still disagree on how they behaved during the LGM. Here, a joint model-data evaluation study is performed to determine likely changes in the SH westerly winds during the LGM. HadAM3 atmospheric simulations, along with published PMIP2 coupled climate model simulations, are assessed against our newly synthesised database of moisture records for the LGM (Kohfeld et al., accepted, QSR). While moisture data are the most commonly cited evidence in support of a large equatorward shift in the SH winds during the LGM, none of the models that produce realistic LGM precipitation patterns show a large equatorward shift. In fact, the model which best simulates the moisture proxy data, our HadAM3 LGM simulation, shows a small poleward wind shift. Thus, moisture proxies do not provide a robust observational evidence base for equatorward shifted winds during the LGM (Sime et al, in press, QSR). Sensitivity simulations, featuring individual boundary condition changes, suggest that changes in sea surface temperatures are the strongest factor behind LGM wind changes, compared with sea ice and land ice effects. If the SH westerly winds were not shifted equatorward at the LGM, this raises intriguing questions regarding past and future carbon storage in the Southern Ocean.

  13. Weakest solar wind of the space age and the current 'MINI' solar maximum

    SciTech Connect

    McComas, D. J.; Angold, N.; Elliott, H. A.; Livadiotis, G.; Schwadron, N. A.; Smith, C. W.; Skoug, R. M.

    2013-12-10

    The last solar minimum, which extended into 2009, was especially deep and prolonged. Since then, sunspot activity has gone through a very small peak while the heliospheric current sheet achieved large tilt angles similar to prior solar maxima. The solar wind fluid properties and interplanetary magnetic field (IMF) have declined through the prolonged solar minimum and continued to be low through the current mini solar maximum. Compared to values typically observed from the mid-1970s through the mid-1990s, the following proton parameters are lower on average from 2009 through day 79 of 2013: solar wind speed and beta (?11%), temperature (?40%), thermal pressure (?55%), mass flux (?34%), momentum flux or dynamic pressure (?41%), energy flux (?48%), IMF magnitude (?31%), and radial component of the IMF (?38%). These results have important implications for the solar wind's interaction with planetary magnetospheres and the heliosphere's interaction with the local interstellar medium, with the proton dynamic pressure remaining near the lowest values observed in the space age: ?1.4 nPa, compared to ?2.4 nPa typically observed from the mid-1970s through the mid-1990s. The combination of lower magnetic flux emergence from the Sun (carried out in the solar wind as the IMF) and associated low power in the solar wind points to the causal relationship between them. Our results indicate that the low solar wind output is driven by an internal trend in the Sun that is longer than the ?11 yr solar cycle, and they suggest that this current weak solar maximum is driven by the same trend.

  14. [Measurement of path transverse wind velocity profile using light forward scattering scintillation correlation method].

    PubMed

    Yuan, Ke-E; Lü, Wei-Yu; Zheng, Li-Nan; Hu, Shun-Xing; Huang, Jian; Cao, Kai-Fa; Xu, Zhi-Hai

    2014-07-01

    A new method for path transverse wind velocity survey was introduced by analyzing time lagged covariance function of different separation sub-apertures of Hartmann wavefront sensor. A theoretical formula was logically deduced for the light propagation path transverse wind velocity profile. According to the difference of path weighting function for different sub apertures spacing, how to select reasonable path weighting functions was analyzed. Using a Hartmann wavefront sensor, the experiment for measuring path transverse velocity profile along 1 000 m horizontal propagating path was carried out for the first time to our knowledge. The experiment results were as follows. Path transverse averaged velocity from sensor had a good consistency with transverse velocity from the wind anemometer sited near the path receiving end. As the path was divided into two sections, the path transverse velocity of the first section had also a good consistency with that of the second one. Because of different specific underlaying surface of light path, the former was greater than the later over all experiment period. The averaged values were 1.273 and 0.952 m x s(-1) respectively. The path transverse velocity of second section and path transverse averaged velocity had the same trend of decrease and increase with time. The correlation coefficients reached 0.86. PMID:25269279

  15. Southern Hemisphere Westerly Wind Changes during the Last Glacial Maximum: Paleo-data Synthesis

    NASA Astrophysics Data System (ADS)

    Kohfeld, Karen; Graham, Robert; De Boer, Agatha; Sime, Louise; Wolff, Eric; Le Quéré, Corinne; Bopp, Laurent

    2013-04-01

    Changes in the strength and position of Southern Hemisphere westerly winds during the last glacial cycle have been invoked to explain glacial-interglacial climate fluctuations. However, neither paleo models nor paleodata agree on the magnitude, or even the sign, of the change in wind strength and latitude during the Last Glacial Maximum (LGM), compared to the recent past. This study synthesizes paleo-environmental data that have been used to infer changes in winds during the LGM compared with the late Holocene. These compilations include changes in terrestrial moisture, dust deposition, and ocean productivity, along with summaries of previously published information on sea surface temperatures (SSTs) and ocean dynamics in the Southern Hemisphere. Our compilations of terrestrial moisture from 94 sites and dust deposition from 87 sites show generally drier conditions for the LGM between 0 and 40°S, with wetter conditions along the west coasts and drying along the east coasts of continents. LGM dust deposition rates ranged from 2 to 4.5 times higher over the Southern Ocean and about 13 times higher over the Antarctic continent. For the oceans, reconstructed changes in SSTs show maximum cooling (>4°C) in the modern-day Subantarctic Zone, coincident with a region of enhanced export production during the LGM compared with today. We find that any hypothesis of LGM wind and climate change needs to provide a plausible explanation for increased moisture on the west coast of continents, cooler temperatures and higher productivity in the Subantarctic Zone, and reductions in Agulhas leakage around southern Africa. Our comparison suggests that an overall strengthening, an equatorward displacement, or no change at all in winds could all be interpreted as consistent with observations. If a single cause related to the southern westerlies is sought for all the evidence presented, then an equatorward displacement or strengthening of the winds would be consistent with the largest proportion of the data evidence. However, other processes, such as weakening or poleward shifts in winds, a weakened hydrological cycle, extended sea-ice cover, and changed buoyancy fluxes, cannot be ruled out as potential explanations of observed changes in moisture, surface temperature, and productivity. We contend that resolving the position and strength of westerly winds during the LGM remains elusive based on data reconstructions alone. However, we believe that these data reconstructions of environmental conditions can be used in conjunction with model simulations to identify which processes best represent westerly wind conditions during the LGM.

  16. Measurements of dust deposition velocity in a wind-tunnel experiment

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Shao, Y.; Huang, N.

    2014-09-01

    In this study, we present the results of a wind-tunnel experiment on dust deposition. A new method is proposed to derive dust deposition velocity from PDA (particle dynamics analysis) particle-velocity and particle-size measurements. This method has the advantage that the motions of individual dust particles are directly observed and all relevant data for computing dust deposition velocity is collected using a single instrument, and thus the measurement uncertainties are reduced. The method is used in the wind-tunnel experiment to measure dust deposition velocities for different particle sizes, wind speeds and surface conditions. For sticky-smooth wood and water surfaces, the observed dust deposition velocities are compared with the predictions using a dust deposition scheme, and the entire data set is compared with the data found in the literature. From the wind-tunnel experiments, a relatively reliable data set of dust deposition velocities is obtained, which is valuable for the development and validation of dust deposition schemes.

  17. Measurements of dust deposition velocity in a wind-tunnel experiment

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Shao, Y.; Huang, N.

    2014-04-01

    In this study, we present the results of a wind-tunnel experiment on dust deposition. A new method is proposed to derive dust deposition velocity from the PDA (Particle Dynamics Analysis) particle-velocity and particle-size measurements. This method has the advantage that the motions of individual dust particles are directly observed and all relevant data for computing dust deposition velocity is collected using a single instrument, and therefore the measurement uncertainties are reduced. The method is used in the wind-tunnel experiment to measure the dust deposition velocities for different particle sizes, wind speeds and surface conditions. For a sticky-smooth wood surface and a water surface, the observed dust deposition velocities are compared with the predictions using a dust deposition scheme, and the entire dataset is compared with the data found in the literature. From the wind-tunnel experiments, a relatively reliable dataset of dust deposition velocity is obtained, which is of considerable value for the development and validation of dust deposition schemes.

  18. IPS observations of the solar wind velocity and the acceleration mechanism

    NASA Technical Reports Server (NTRS)

    Ofman, L.; Davila, J. M.; Coles, W. A.; Grall, R. R.; Klinglesmith, M. T.

    1997-01-01

    Coronal holes are well know sources of high speed solar wind, however, the exact acceleration mechanism of the wind is still unknown. Interplanetary scintillation (IPS) observations indicate that the fast solar wind reaches an average velocity of 800 km s(exp -1) within several solar radii with large velocity fluctuations. However, the origin of the IPS velocity spread below 10 solar radii is unclear. A previously developed coronal home model with a more realistic initial state is applied, and time-dependent, nonlinear, resistive 2.5-DMHD equations are numerically solved. It is found that nonlinear solitary-like waves with a supersonic phase speed are generated in coronal holes by torisonal Alfven waves in the radial flow velocity. The outward propagating nonlinear waves are similar in properties to sound solitons. When these waves are present, the solar wind speed and density fluctuate considerably on a time scale of an hour and on spatial scales of several solar radii in addition to the Alfvenic fluctuations. This is in qualitative agreement with the IPS velocity observations beyond 10 solar radii.

  19. Effect of Wind Velocity on Flame Spread in Microgravity

    NASA Technical Reports Server (NTRS)

    Prasad, Kuldeep; Olson, Sandra L.; Nakamura, Yuji; Fujita, Osamu; Nishizawa, Katsuhiro; Ito, Kenichi; Kashiwagi, Takashi; Simons, Stephen N. (Technical Monitor)

    2002-01-01

    A three-dimensional, time-dependent model is developed describing ignition and subsequent transition to flame spread over a thermally thin cellulosic sheet heated by external radiation in a microgravity environment. A low Mach number approximation to the Navier Stokes equations with global reaction rate equations describing combustion in the gas phase and the condensed phase is numerically solved. The effects of a slow external wind (1-20 cm/s) on flame transition are studied in an atmosphere of 35% oxygen concentration. The ignition is initiated at the center part of the sample by generating a line-shape flame along the width of the sample. The calculated results are compared with data obtained in the 10s drop tower. Numerical results exhibit flame quenching at a wind speed of 1.0 cm/s, two localized flames propagating upstream along the sample edges at 1.5 cm/s, a single line-shape flame front at 5.0 cm/s, three flames structure observed at 10.0 cm/s (consisting of a single line-shape flame propagating upstream and two localized flames propagating downstream along sample edges) and followed by two line-shape flames (one propagating upstream and another propagating downstream) at 20.0 cm/s. These observations qualitatively compare with experimental data. Three-dimensional visualization of the observed flame complex, fuel concentration contours, oxygen and reaction rate isosurfaces, convective and diffusive mass flux are used to obtain a detailed understanding of the controlling mechanism, Physical arguments based on lateral diffusive flux of oxygen, fuel depletion, oxygen shadow of the flame and heat release rate are constructed to explain the various observed flame shapes.

  20. The Silicon and Calcium High-Velocity Features in Type Ia Supernovae from Early to Maximum Phases

    E-print Network

    Zhao, Xulin; Maeda, Keiichi; Sai, Hanna; Zhang, Tianmeng; Zhang, Jujia; Huang, Fang; Rui, Liming; Zhou, Qi; Mo, Jun

    2015-01-01

    The high-velocity features (HVFs) in optical spectra of type Ia supernovae (SNe Ia) are examined with a large sample including very early-time spectra (e.g., t < -7 days). Multiple Gaussian fits are applied to examine the HVFs and their evolutions, using constraints on expansion velocities for the same species (i.e., SiII 5972 and SiII 6355). We find that strong HVFs tend to appear in SNe Ia with smaller decline rates (e.g., dm15(B)<1.4 mag), clarifying that the finding by Childress et al. (2014) for the Ca-HVFs in near-maximum-light spectra applies both to the Si-HVFs and Ca-HVFs in the earlier phase. The Si-HVFs seem to be more common in fast-expanding SNe Ia, which is different from the earlier result that the Ca-HVFs are associated with SNe Ia having slower SiII 6355 velocities at maximum light (i.e., Vsi). This difference can be due to that the HVFs in fast-expanding SNe Ia usually disappear more rapidly and are easily blended with the photospheric components when approaching the maximum light. Mor...

  1. Combined vertical-velocity observations with Doppler lidar, cloud radar and wind profiler

    NASA Astrophysics Data System (ADS)

    Bühl, J.; Leinweber, R.; Görsdorf, U.; Radenz, M.; Ansmann, A.; Lehmann, V.

    2015-08-01

    Case studies of combined vertical-velocity measurements of Doppler lidar, cloud radar and wind profiler are presented. The measurements were taken at the Meteorological Observatory, Lindenberg, Germany. Synergistic products are presented that are derived from the vertical-velocity measurements of the three instruments: a comprehensive classification mask of vertically moving atmospheric targets and the terminal fall velocity of water droplets and ice crystals corrected for vertical air motion. It is shown that this combination of instruments can up-value the measurement values of each single instrument and may allow the simultaneous sensing of atmospheric targets and the motion of clear air.

  2. Remote Sensing of Solar Wind Velocities using Interplanetary Scintillation with MEXART and STELab Stations

    NASA Astrophysics Data System (ADS)

    Mejia-Ambriz, J. C.; Jackson, B. V.; Gonzalez-Esparza, A.; Tokumaru, M.; Yu, H.; Buffington, A.; Hick, P.

    2013-05-01

    Radio signals from compact radio sources are scattered by electron density irregularities in the solar wind. This effect is registered by radio telescopes as intensity fluctuations of the observed radio source amplitude and known as Interplanetary Scintillation (IPS). The Mexican Array Radio Telescope (MEXART) and the antennas of Solar Terrestrial Environment Laboratory (STELab) are instruments dedicated to studies of IPS signals. In this work we present a technique (Manoharan and Ananthakrishnan, 1990) used to estimate solar wind velocities applied to observations of MEXART and STELab using single station spectra. Currently STELab uses a multi-station IPS technique to determinate solar wind speeds. Here we compare velocities obtained with a single station to those obtained using the multi-station technique for a few strong radio sources using both techniques and with both instruments. At the Center for Astrophysics and Space Sciences - University of California, San Diego (CASS-UCSD), a tomography program is able to reconstruct the dynamics of the inner heliosphere globally using IPS measurements to give solar wind densities and velocities. We show the incorporation of velocities provided by MEXART into this program that has been used successfully for over a decade with STELab IPS measurements.

  3. Estimating attitude and wind velocity using biomimetic sensors on a microrobotic bee

    E-print Network

    Fuller, Sawyer Buckminster

    Estimating attitude and wind velocity using biomimetic sensors on a microrobotic bee Sawyer B discusses recent developments in sen- sors for the Harvard RoboBee. The RoboBee is a sub-100 mg flapping the ocelli on a wire-mounted RoboBee that is free to rotate about its pitch axis. These flight-weight sensors

  4. The Evolution of the Spectrum of Velocity Fluctuations in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Roberts, Dana Aaron

    2007-01-01

    Previous studies have shown that the power spectra of the magnetic field and velocity in the solar wind do not evolve in the same way with heliocentric distance. In particular, the velocity spectrum remains flatter for a substantial distance. However, Voyager observations of the velocity spectrum have demonstrated a likely asymptotic state in which the spectrum steepens to having a spectral index of -5/3, finally matching the magnetic spectrum and the theoretical expectation of Kolmogoroff turbulence. Here we examine evidence from other spacecraft, in particular studying Ulysses spectra to determine if the Voyager result, based on a very few sufficiently complete intervals, is correct. Preliminary results confirm the -5/3 slope for velocity fluctuations at -5 AU from the Sun in the ecliptic. We will examine many intervals to develop a more general picture of the spectral evolution in various conditions, and how magnetic and velocity spectra differ in these cases.

  5. Thermal creep assisted dust lifting on Mars: Wind tunnel experiments for the entrainment threshold velocity

    E-print Network

    Küpper, Markus

    2015-01-01

    In this work we present laboratory measurements on the reduction of the threshold friction velocity necessary for lifting dust if the dust bed is illuminated. Insolation of a porous soil establishes a temperature gradient. At low ambient pressure this gradient leads to thermal creep gas flow within the soil. This flow leads to a sub-surface overpressure which supports lift imposed by wind. The wind tunnel was run with Mojave Mars Simulant and air at 3, 6 and 9 mbar, to cover most of the pressure range at martian surface levels. Our first measurements imply that the insolation of the martian surface can reduce the entrainment threshold velocity between 4 % and 19 % for the conditions sampled with our experiments. An insolation activated soil might therefore provide additional support for aeolian particle transport at low wind speeds.

  6. An evaluation of errors observed in the measurement of low wind velocities

    NASA Technical Reports Server (NTRS)

    Williams, S. R.; Thomson, D. W.

    1986-01-01

    Measurements of low wind velocities (the absolute value of V sub H is approx. equal to 6 m/s) with a VHF wind profiler can be difficult if ground clutter or other biases in the system dominate in altering the position of the perceived peak in the calculated power spectrum. A variety of methods for ground clutter suppression are used in profiler systems today (Cornish, 1983). An editing method called zero suppression takes the spectral value of selectable number of points (N) on each side of 0 velocity (one point on either side, in this study) and sets them equal to the mean value of the points exterior to the specified N points on either side of 0. Analysis done with the PSU VHF(1) radar, shows that this zero-suppression method can systematically bias horizontal wings V sub H below 6 m/s. With the zero suppression, an artificial increase in absolute wind velocities occurs when the spectral peaks fall within the plus or minus N points of the FFT (personal communication, Strauch, 1985). It was also established that the method artificially decreases the absolute wind velocities inferred from spectral peaks that are outside but near the suppressed region. Comparisons of wind profiles observed with and without zero suppression are given. The range of the biased velocities extends to about plus or minus 6 m/s. Biases have been deduced to be as much as 2 m/s, but more commonly they are on the order of 1.0 m/s.

  7. THE SIMULATION OF WIND-BLOWN SAND MOVEMENT AND PROBABILITY DENSITY FUNCTION OF LIFT-OFF VELOCITIES OF SAND GRAINS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurately describing the probability density function (PDF) of lift-off or initial velocities of wind-blown sand ejecting from a sand bed is fundamental to understanding the mechanisms of wind-blown sand movement. Our objective was to investigate the efficacy of developing the PDF of lift-off veloc...

  8. Understanding the Benefits and Limitations of Increasing Maximum Rotor Tip Speed for Utility-Scale Wind Turbines

    NASA Astrophysics Data System (ADS)

    Ning, A.; Dykes, K.

    2014-06-01

    For utility-scale wind turbines, the maximum rotor rotation speed is generally constrained by noise considerations. Innovations in acoustics and/or siting in remote locations may enable future wind turbine designs to operate with higher tip speeds. Wind turbines designed to take advantage of higher tip speeds are expected to be able to capture more energy and utilize lighter drivetrains because of their decreased maximum torque loads. However, the magnitude of the potential cost savings is unclear, and the potential trade-offs with rotor and tower sizing are not well understood. A multidisciplinary, system-level framework was developed to facilitate wind turbine and wind plant analysis and optimization. The rotors, nacelles, and towers of wind turbines are optimized for minimum cost of energy subject to a large number of structural, manufacturing, and transportation constraints. These optimization studies suggest that allowing for higher maximum tip speeds could result in a decrease in the cost of energy of up to 5% for land-based sites and 2% for offshore sites when using current technology. Almost all of the cost savings are attributed to the decrease in gearbox mass as a consequence of the reduced maximum rotor torque. Although there is some increased energy capture, it is very minimal (less than 0.5%). Extreme increases in tip speed are unnecessary; benefits for maximum tip speeds greater than 100-110 m/s are small to nonexistent.

  9. Neotectonic Velocity Field of the Western United States: A new Maximum-likelihood Solution

    NASA Astrophysics Data System (ADS)

    Bird, P.

    2002-12-01

    New kinematic finite-element program NeoKinema solves for long-term-average velocity fields and fault slip rates in deforming lithosphere, based on three kinds of information: (1) geologic slip rates of an unlimited number of faults, with standard deviations (which may be large); (2) geodetic velocities of benchmarks, either in fixed or free-floating velocity reference frame, with covariance matrix; (3) stress-direction data. Faults need not be explicitly represented in the finite element grid. The geodetic data are corrected for local effects of temporary fault locking by an iterative procedure. The strain rates of non-faulting finite elements are determined by a balance between (a) minimization of viscous dissipation, and (b) conformity to principal strain rate directions interpolated from the stress-direction data. NeoKinema has been applied to model neotectonics of the western United States, from the Gorda "plate" on the west, to the Gulf of California on the south, Yellowstone on the east, and Victoria on the north. Data comes from 378 active or potentially-active faults, 298 benchmarks of the WUSC002 solution [Bennett et al., 1999], and 2080 stress directions from the World Stress Map 2000 [Mueller et al., 2000]. The F-E grid has 1813 nodes and 3468 triangular elements of 30-km and 60-km dimensions. Results of this first application are very plausible, and confirm the concept of a Sierra Nevada-Great Valley plate moving ~9 mm/a NW. After a few local artifacts are investigated and eliminated (primarily by better gridding), the model will be used to compute various measures of long-term seismic hazard. It is already apparent from the map of predicted strain rates that 20th-century seismicity levels in western Oregon, the Wasatch Front area of Utah, and the Las Vegas region have been less than their long-term-average expectations.

  10. An analysis of maximum horizontal wind speeds and associated parameters recorded at NASA's 150-Meter Ground Winds Tower facility at Kennedy Space Center, Florida

    NASA Technical Reports Server (NTRS)

    Alexander, M. B.

    1978-01-01

    Continuous horizontal wind speed measurements were processed and classified as a function of tower level (10, 18, 60, and 150 meters) and period of reference day, month, season: winter (October through March) and summer (April through September), and annual. Tabulations were made of the daily maximum horizontal wind speed, time of ocurrence, and five associated parameters: mean horizontal wind speed, maximum vertical gusts (i.e., updraft and downdraft), and mean and instantaneous directions. Analyses using these data included means, extremes, standard deviations, and frequency distributions. Comparisons of intensity of maximum horizontal wind speeds determined in this year of data are made with maximum values recorded at Kennedy Space Center during another non-hurricane-occurrence year (1967) and with values during 1966 through 1972 when six hurricanes affected the area after the Ground Winds Tower facility became operational. Wind flow in the lowest 150 meters of the atmosphere was measured for the identification of hazards involved in wind shear encounter relative to ascent and descent of the space shuttle and conventional aircraft.

  11. Seasonality and spatial distribution of threshold wind velocity and dust emission in Central Asia

    NASA Astrophysics Data System (ADS)

    Xi, X.; Sokolik, I. N.

    2013-12-01

    Generation of mineral dust aerosols by wind erosion exhibits strong geographic heterogeneity and seasonality, controlled by the characteristics of parent soils in dust source regions, variability of meteorological systems, and land-cover/land-use changes. These dependences can be represented in a regional dust modeling system by introducing time-varying land variables, such as soil moisture and roughness length, and source-specific soil characteristics in parameterizations of threshold wind velocities and vertical dust fluxes. The goal of this study is to examine the influence of these factors on the seasonality and spatial distribution of threshold wind velocity and dust emission in Central Asia which comprises a variety of dust sources, such as sandy deserts, solonchaks, ephemeral lakes and agricultural fields. This study focuses on two different years (1965 and 2001) with contrasting meteorological conditions and land use patterns. We use the coupled dust modeling system, WRF-Chem-DuMo, which incorporates two physically-based schemes accounting for the dependence of wind thresholds on soil moisture and surface roughness (including vegetation phenology), and the effect of size-dependent sandblasting efficiency on dust vertical fluxes. A georeferenced dataset of land surface input parameters for Asian dust sources and meteorological fields from the NCAR/NCEP reanalysis data are used in model initialization. The model also incorporates land use datasets of annual agricultural (i.e., cropland and pasture) fractions and surface water body changes to reflect the spatiotemporal changes in land cover and surface properties relevant to dust emission processes. Results will be presented on the seasonal behavior of the threshold friction velocity and threshold 10-meter wind velocity in major dust source regions in Central Asia. The relative control of soil moisture and surface roughness will be discussed. The dust vertical fluxes will be reported from two dust schemes and compared with available horizontal visibility and satellite aerosol observations.

  12. The Evolution of the Spectrum of Velocity Fluctuations in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Roberts, D. Aaron

    2010-01-01

    Recent work has shown that at 1AU from the Sun the power spectrum of the solar wind magnetic field has the -5/3 spectral slope expected for Kolmogorov turbulence, but that the velocity has closer to a -3/2 spectrum. This paper traces the changes in solar wind velocity spectra from 0.3 to 5 AU using data from the Helios and Ulysses spacecraft to show that this is a transient stage in the evolution. The spectrum of the velocity is found to be flatter than that of the magnetic field for the higher frequencies examined for all cases until the slopes become equal (at -5/3) well past 1 AU when the wind is relatively nonAlfvenic. In some respects, in particular in the evolution of the frequency at which the spectrum changes from flatter at larger scales to a traditionally turbulent spectrum at smaller scales, the velocity field evolves more rapidly that the magnetic, and this is associated with the dominance of the magnetic energy over the kinetic at "inertial range" scales. The Alfvenicity of the fluctuations, not the speed of the flow, is shown to control the rate of the spectral evolution. This study shows that, for the solar wind ., the idea of a simple "inertial range" with uniform spectral properties is not realistic, and new phenomenologies will be needed to capture the true situation. In addition a flattening of the velocity spectrum persists at times for small scales, which may provide a clue to the nature of the small-scale interactions.

  13. The Silicon and Calcium High-velocity Features in Type Ia Supernovae from Early to Maximum Phases

    NASA Astrophysics Data System (ADS)

    Zhao, Xulin; Wang, Xiaofeng; Maeda, Keiichi; Sai, Hanna; Zhang, Tianmeng; Zhang, Jujia; Huang, Fang; Rui, Liming; Zhou, Qi; Mo, Jun

    2015-09-01

    The high-velocity features (HVFs) in optical spectra of type Ia supernovae (SNe Ia) are examined with a large sample including very early-time spectra (e.g., t < -7 days). Multiple Gaussian fits are applied to examine the HVFs and their evolutions, using constraints on expansion velocities for the same species (i.e., Si ii 5972 and Si ii 6355). We find that strong HVFs tend to appear in SNe Ia with smaller decline rates (e.g., ?m15(B) ? 1.4 {mag}), clarifying that the finding by Childress et al. for the Ca-HVFs in near-maximum-light spectra applies both to the Si-HVFs and Ca-HVFs in the earlier phase. The Si-HVFs seem to be more common in rapidly expanding SNe Ia, which is different from the earlier result that Ca-HVFs are associated with SNe Ia that have slower Si ii 6355 velocities at maximum light (i.e., VSimax). Moreover, SNe Ia with both stronger HVFs at early phases and larger VSimax are found to have noticeably redder B-V colors and to occur preferentially in the inner regions of their host galaxies, while those with stronger HVFs but smaller VSimax show opposite tendencies, suggesting that these two subclasses have different explosion environments and their HVFs may have different origins. We further examine the relationships between the absorption features of Si ii 6355 and Ca ii IR lines, and find that their photospheric components are well correlated in velocity and strength but that the corresponding HVFs show larger scatter. These results cannot be explained with ionization and/or thermal processes alone, and different mechanisms are required for the creation of HVF-forming regions in SNe Ia.

  14. Long-term variations in solar wind velocity and radiation belt electrons

    NASA Astrophysics Data System (ADS)

    Reeves, Geoff; Morley, Steve; Cunningham, Greg

    2013-03-01

    In this paper we analyze the relationship between yearly variations in MeV radiation belt electron fluxes and solar wind velocity (Vsw). We find that the long-term trends have properties that are important for physical understanding of solar wind-magnetosphere coupling processes and, potentially, for improvements of short-term space weather forecasts. A statistical analysis of solar wind velocity shows that years with high average solar wind velocity are not high simply due to a larger number of days with high Vsw. Rather the entire distribution (median and percentiles) shifts along with the mean Vsw. Similar behavior is seen in the MeV geosynchronous electron fluxes. By subtracting out a 365 day running average baseline, we show that the distribution of log fluxes around the mean is remarkably stable from year to year within a solar cycle and from one solar cycle to another. In contrast, the long-term trends in the baseline show significant changes from year to year and from one solar cycle to another suggesting that solar wind coupling to radiation belt fluxes is not constant but varies over long, as well as short, time scales. In some epicycles, the mean flux is strongly dependent on Vsw while in others the dependence is weak. Similarly, a given average Vsw may produce high average fluxes in one epicycle and low average fluxes in another. Future study of these epicycles and the relative variations within them may improve both physical understanding of solar wind-magnetosphere coupling and space weather forecasting.

  15. Two-dimensional airflow modeling underpredicts the wind velocity over dunes.

    PubMed

    Michelsen, Britt; Strobl, Severin; Parteli, Eric J R; Pöschel, Thorsten

    2015-01-01

    We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune's symmetry axis - that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected. PMID:26572966

  16. Two-dimensional airflow modeling underpredicts the wind velocity over dunes

    NASA Astrophysics Data System (ADS)

    Michelsen, Britt; Strobl, Severin; Parteli, Eric J. R.; Pöschel, Thorsten

    2015-11-01

    We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune’s symmetry axis — that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected.

  17. Two-dimensional airflow modeling underpredicts the wind velocity over dunes

    PubMed Central

    Michelsen, Britt; Strobl, Severin; Parteli, Eric J. R.; Pöschel, Thorsten

    2015-01-01

    We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune’s symmetry axis — that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected. PMID:26572966

  18. Single-pulse measurement of wind velocities using an Er:Yb:glass coherent laser radar

    NASA Astrophysics Data System (ADS)

    Heintze, Matthew C.; Chang, Nick W. H.; Jeanneret, Francois; Munch, Jesper; Ottaway, David J.; Veitch, Peter J.

    2011-07-01

    Many wind-field mapping applications require range-resolved atmospheric velocity measurements at long range and/or with a temporal resolution sufficient to investigate turbulence. We argue that this capability can be achieved only by coherent laser radar systems that transmit energetic (>1mJ) pulses. We describe such a system and describe single-pulse measurement of the range-resolved line-of-sight velocities, and show that the instrument-limited reproducibility of the measurements is 0.4ms-1.

  19. The de-correlation of westerly winds and westerly-wind stress over the Southern Ocean during the Last Glacial Maximum

    SciTech Connect

    Liu, Wei; Lu, Jian; Leung, Lai-Yung R.; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang

    2015-02-22

    This paper investigates the changes of the Southern Westerly Winds (SWW) and Southern Ocean (SO) upwelling between the Last Glacial Maximum (LGM) and preindustrial (PI) in the PMIP3/CMIP5 simulations, highlighting the role of the Antarctic sea ice in modulating the wind stress effect on the ocean. Particularly, a discrepancy may occur between the changes in SWW and westerly wind stress, caused primarily by an equatorward expansion of winter Antarctic sea ice that undermines the wind stress in driving the liquid ocean. Such discrepancy may reflect the LGM condition in reality, in view of that the model simulates this condition has most credible simulation of modern SWW and Antarctic sea ice. The effect of wind stress on the SO upwelling is further explored via the wind-induced Ekman pumping, which is reduced under the LGM condition in all models, in part by the sea-ice “capping” effect present in the models.

  20. Structure of Turbulence in Katabatic Flows below and above the Wind-Speed Maximum

    E-print Network

    Grachev, Andrey A; Di Sabatino, Silvana; Fernando, Harindra J S; Pardyjak, Eric R; Fairall, Christopher W

    2015-01-01

    Measurements of small-scale turbulence made over the complex-terrain atmospheric boundary layer during the MATERHORN Program are used to describe the structure of turbulence in katabatic flows. Turbulent and mean meteorological data were continuously measured at multiple levels at four towers deployed along the East lower slope (2-4 deg) of Granite Mountain. The multi-level observations made during a 30-day long MATERHORN-Fall field campaign in September-October 2012 allowed studying of temporal and spatial structure of katabatic flows in detail, and herein we report turbulence and their variations in katabatic winds. Observed vertical profiles show steep gradients near the surface, but in the layer above the slope jet the vertical variability is smaller. It is found that the vertical (normal to the slope) momentum flux and horizontal (along the slope) heat flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The vertical momentum flux is directed...

  1. Occurrence of high-speed solar wind streams over the Grand Modern Maximum

    E-print Network

    Mursula, Kalevi; Holappa, Lauri

    2015-01-01

    In the declining phase of the solar cycle, when the new-polarity fields of the solar poles are strengthened by the transport of same-signed magnetic flux from lower latitudes, the polar coronal holes expand and form non-axisymmetric extensions toward the solar equator. These extensions enhance the occurrence of high-speed solar wind streams (HSS) and related co-rotating interaction regions in the low-latitude heliosphere, and cause moderate, recurrent geomagnetic activity in the near-Earth space. Here, using a novel definition of geomagnetic activity at high (polar cap) latitudes and the longest record of magnetic observations at a polar cap station, we calculate the annually averaged solar wind speeds as proxies for the effective annual occurrence of HSS over the whole Grand Modern Maximum (GMM) from 1920s onwards. We find that a period of high annual speeds (frequent occurrence of HSS) occurs in the declining phase of each solar cycle 16-23. For most cycles the HSS activity clearly maximizes during one year...

  2. The power associated with density fluctuations and velocity fluctuations in the solar wind

    NASA Technical Reports Server (NTRS)

    Intriligator, D. S.

    1974-01-01

    Direct observations from Pioneer 6 of solar-wind-proton fluctuations have been used to obtain the power spectra associated with solar-wind-proton number density and velocity fluctuations in the frequency range of 0.001 to 0.01 Hz, extending previous analyses by an order of magnitude at the higher frequencies. The slopes of the power spectra associated with the density fluctuations and the velocity fluctuations are similar and are in agreement with the shape of the power spectra found at the lower frequencies. The power spectra indicate that the power-law density spectrum observed at lower frequencies extends to at least 0.01 Hz. This smooth variation in the spectrum at these frequencies is consistent with previous extrapolations of both spacecraft and interplanetary scintillation observations.

  3. An investigation into the contraction of the hurricane radius of maximum wind

    NASA Astrophysics Data System (ADS)

    Kieu, Chanh Q.

    2012-01-01

    The radius of the maximum tangential wind (RMW) associated with the hurricane primary circulation has been long known to undergo continuous contraction during the hurricane development. In this study, we document some characteristic behaviors of the RMW contraction in a series of ensemble real-time simulations of Hurricane Katrina (2005) and in idealized experiments using the Rotunno and Emanuel (Mon Weather Rev 137:1770-1789, 1987) axisymmetric hurricane model. Of specific interest is that the contraction appears to slow down abruptly at the middle of the hurricane intensification, and the RMW becomes nearly stationary subsequently, despite the rapidly strengthening rotational flows. A kinematic model is then presented to examine such behaviors of the RMW in which necessary conditions for the RMW to stop contracting are examined. Further use of the Emanuel's (J Atmos Sci 43:585-605, 1986) analytical hurricane theory reveals a connection between the hurricane maximum potential intensity and the hurricane eye size, an issue that has not been considered adequately in previous studies.

  4. Development of tunable high pressure CO2 laser for lidar measurements of pollutants and wind velocities

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Guerra, M.; Javan, A.

    1980-01-01

    The problem of laser energy extraction at a tunable monochromatic frequency from an energetic high pressure CO2 pulsed laser plasma, for application to remote sensing of atmospheric pollutants by Differential Absorption Lidar (DIAL) and of wind velocities by Doppler Lidar, was investigated. The energy extraction principle analyzed is based on transient injection locking (TIL) at a tunable frequency. Several critical experiments for high gain power amplification by TIL are presented.

  5. Remote measurement of the transverse wind velocity component using a laser Doppler velocimeter

    NASA Technical Reports Server (NTRS)

    Kennedy, L. Z.; Bilbro, J. W.

    1979-01-01

    The wind speed transverse to the line-of-sight of a laser Doppler radar has been measured using the intensity fluctuations of the returned signal. These measurements were made at a range of 100 m with a CO2 CW laser Doppler velocimeter, which was simultaneously performing its design function of determining the radial velocity component. The transverse component measurements are compared with those obtained using a u, v, w Gill propeller anemometer.

  6. High altitude wind velocity at San Pedro Martir and Mauna Kea

    E-print Network

    Esperanza Carrasco; Marc Sarazin

    2003-09-03

    We analyze the monthly average wind velocity at about 12 km above sea level, between 1980 to 1995, for San Pedro Martir, Mauna Kea, another existing observatorie and some sites of interest. We compare the results obtained from two different data sets, the GGUAS and NCEP. Our results show that San Pedro Martir and Mauna Kea are comparable and are amongst the most suitable sites to apply slow wavefront corrugation correction techniques

  7. Effect on head-wind profiles and mean head-wind velocity on landing capacity flying constant-airspeed and constant-groundspeed approaches

    NASA Technical Reports Server (NTRS)

    Hastings, E. C., Jr.; Kelley, W. W.

    1979-01-01

    A study was conducted to determine the effect of head-wind profiles and mean head-wind velocities on runway landing capacity for airplanes flying constant-airspeed and constant-groundspeed approaches. It was determined that when the wind profiles were encountered with the currently used constant airspeed approach method, the landing capacity was reduced. The severity of these reductions increased as the mean head-wind value of the profile increased. When constant-groundspeed approaches were made in the same wind profiles, there were no losses in landing capacity. In an analysis of mean head winds, it was determined that in a mean head wind of 35 knots, the landing capacity using constant-airspeed approaches was 13% less than for the no wind condition. There were no reductions in landing capacity with constant-groundspeed approaches for mean head winds less than 35 knots. This same result was observed when the separation intervals between airplanes was reduced.

  8. A radionuclide counting technique for measuring wind velocity. [drag force anemometers

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Khandelwal, G. S.; Mall, G. H.

    1981-01-01

    A technique for measuring wind velocities of meteorological interest is described. It is based on inverse-square-law variation of the counting rates as the radioactive source-to-counter distance is changed by wind drag on the source ball. Results of a feasibility study using a weak bismuth 207 radiation source and three Geiger-Muller radiation counters are reported. The use of the technique is not restricted to Martian or Mars-like environments. A description of the apparatus, typical results, and frequency response characteristics are included. A discussion of a double-pendulum arrangement is presented. Measurements reported herein indicate that the proposed technique may be suitable for measuring wind speeds up to 100 m/sec, which are either steady or whose rates of fluctuation are less than 1 kHz.

  9. Vertical wind velocity measurements by a Doppler lidar and comparisons with a Doppler sodar.

    PubMed

    Congeduti, F; Fiocco, G; Adriani, A; Guarrella, C

    1981-06-15

    A Doppler lidar based on a single frequency Ar(+) laser and a spherical Fabry-Perot interferometer is used to study the vertical velocity field in the planetary boundary layer. The wind velocity information is obtained by spectral analysis of the aerosol backscatter. The internal consistency of the lidar measurements points to a precision of 0.1 msec(-1) obtained for scans of ~25-sec duration and a good level of the received signal at a height of a few hundred meters and a vertical resolution of 75 m. A Doppler sodar was simultaneously operated to provide independent measurements of vertical velocity. The tests were carried out during nights characterized by horizontal winds <1 msec(-1). The axes of the two systems were displaced by 53 m, and the two beams overlapped only above ~300 m. The values of the correlation coefficient function between the two outputs for 100 data sets were ~0.5. A comparison of the velocity power spectra provided by the two systems shows good agreement at small values of the frequency; at large values, because of the limited spatial resolution of the sodar, its readings were consistently lower than those of the lidar. PMID:20332885

  10. A method of calibrating wind velocity sensors with a modified gas flow calibrator

    NASA Technical Reports Server (NTRS)

    Stump, H. P.

    1978-01-01

    A procedure was described for calibrating air velocity sensors in the exhaust flow of a gas flow calibrator. The average velocity in the test section located at the calibrator exhaust was verified from the mass flow rate accurately measured by the calibrator's precision sonic nozzles. Air at elevated pressures flowed through a series of screens, diameter changes, and flow straighteners, resulting in a smooth flow through the open test section. The modified system generated air velocities of 2 to 90 meters per second with an uncertainty of about two percent for speeds below 15 meters per second and four percent for the higher speeds. Wind tunnel data correlated well with that taken in the flow calibrator.

  11. Kinetic Alfvén wave and ion velocity distribution functions in the solar wind

    NASA Astrophysics Data System (ADS)

    Li, X.; Lu, Q.; Chen, Y.; Li, B.; Xia, L.

    2010-12-01

    Using 1D test particle simulations, the effect of a kinetic Alfvén wave on the velocity distribution function of protons in the collisionless solar wind is investigated. We first use linear Vlasov theory to obtain the property of a kinetic Alfvén wave numerically (the wave propagates in the direction almost perpendicular to the background magnetic field). We then numerically simulate how the wave will shape the proton velocity distribution function. It is found that Landau resonance may be able to generate two components in the initially Maxwellian proton velocity distribution function: a tenuous beam component along the direction of the background magnetic field and a core component. The streaming speed of the beam relative to the core proton component is about 1.2 -- 1.3 Alfvén speed. However, no perpendicular ion heating is observed from the simulation. Reference: Li, X., Lu, Q.M., Chen, Y., Li, B., Xia, L.D., ApJ, 719, L190, 2010.

  12. Determination of vertical plasma drift and meridional wind using the Sheffield University Plasmasphere Ionosphere Model and ionospheric data at equatorial and low latitudes in Brazil: Summer solar minimum and maximum conditions

    NASA Astrophysics Data System (ADS)

    Souza, J. R.; Abdu, M. A.; Batista, I. S.; Bailey, G. J.

    2000-06-01

    The F region critical frequency f0F2 and peak height hmF2, measured simultaneously at the equatorial location Fortaleza (4°S, 38°W, magneticlatitude=3.5°S) and at the low-latitude location Cachoeira Paulista (22°S, 45°W, magnetic latitude=15°S), are compared with their values calculated by the Sheffield University Plasmasphere-Ionosphere Model (SUPIM) to determine the vertical (E×B) drift velocity at the equator and the magnetic meridional wind velocity over the two locations. The calculated and observed values of f0F2 are then matched at both Fortaleza and Cachoeira Paulista to obtain the magnetic meridional winds over their respective conjugate locations. To account for the observed f0F2 diurnal variation pattern over Cachoeira Paulista, it was found necessary to include a small source of ionization, attributable to energetic particle precipitation in the South Atlantic anomaly region. The vertical drift velocity and magnetic meridional wind velocity derived for summer months during both solar minimum and solar maximum are compared with their values given by other published models. While the diurnal variation of the modeled vertical drift velocity shows general agreement with the values based on Jicamarca radar measurements (the exception being during the sunset-midnight period at solar maximum and between 2000-2300 LT at solar minimum), the magnetic meridional wind shows significant differences with respect to the Horizontal Wind Model 1990 (HWM90) [Hedin et al., 1991] during both solar minimum and solar maximum at Fortaleza and at locations conjugate to Fortaleza and Cachoeira Paulista.

  13. Determination of the effect of wind velocity and direction changes on turbidity removal in rectangular sedimentation tanks.

    PubMed

    Khezri, Seyed Mostafa; Biati, Aida; Erfani, Zeynab

    2012-01-01

    In the present study, a pilot-scale sedimentation tank was used to determine the effect of wind velocity and direction on the removal efficiency of particles. For this purpose, a 1:20 scale pilot simulated according to Frude law. First, the actual efficiency of total suspended solids (TSS) removal was calculated in no wind condition. Then, the wind was blown in the same and the opposite directions of water flow. At each direction TSS removal was calculated at three different velocities from 2.5 to 7 m/s. Results showed that when the wind was in the opposite direction of water flow, TSS removal efficiency initially increased with the increase of wind velocity from 0 to 2.5 m/s, then it decreased with the increase of velocity to 5 m/s. This mainly might happen because the opposite direction of wind can increase particles' retention time in the sedimentation tank. However, higher wind velocities (i.e. 3.5 and 5.5 m/s) could not increase TSS removal efficiency. Thus, if sedimentation tanks are appropriately exposed to the wind, TSS removal efficiency increases by approximately 6%. Therefore, energy consumption will be reduced by a proper site selection for sedimentation tank unit in water and waste water treatment plants. PMID:23109603

  14. An empirical model to forecast solar wind velocity through statistical modeling

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Ridley, A. J.

    2013-12-01

    The accurate prediction of the solar wind velocity has been a major challenge in the space weather community. Previous studies proposed many empirical and semi-empirical models to forecast the solar wind velocity based on either the historical observations, e.g. the persistence model, or the instantaneous observations of the sun, e.g. the Wang-Sheeley-Arge model. In this study, we use the one-minute WIND data from January 1995 to August 2012 to investigate and compare the performances of 4 models often used in literature, here referred to as the null model, the persistence model, the one-solar-rotation-ago model, and the Wang-Sheeley-Arge model. It is found that, measured by root mean square error, the persistence model gives the most accurate predictions within two days. Beyond two days, the Wang-Sheeley-Arge model serves as the best model, though it only slightly outperforms the null model and the one-solar-rotation-ago model. Finally, we apply the least-square regression to linearly combine the null model, the persistence model, and the one-solar-rotation-ago model to propose a 'general persistence model'. By comparing its performance against the 4 aforementioned models, it is found that the accuracy of the general persistence model outperforms the other 4 models within five days. Due to its great simplicity and superb performance, we believe that the general persistence model can serve as a benchmark in the forecast of solar wind velocity and has the potential to be modified to arrive at better models.

  15. Wind Forcing, Stratification, and Along-channel Vertical Velocity Structure in Penobscot Bay, Maine, at Synoptic to Interannual Timescales

    NASA Astrophysics Data System (ADS)

    Knapp, S.; Dzwonkowski, B.; Pettigrew, N. R.

    2014-12-01

    Long-term observations (10 years) of current velocity, hydrographic properties, and meteorological conditions collected at the University of Maine Ocean Observing System (UMOOS) buoy F in outer western Penobscot Bay, Maine, are used to characterize flow structure and its associated dynamics in this system. The mean vertical velocity structure is primarily density-driven, with characteristic outflow typically restricted to the upper layer and inflow at middle and deep depths. At the synoptic scale, weather-based events dominate current variability; along-channel velocity at the surface and at depth is highly correlated with along-channel wind. This is typical of two-layer competition between wind forcing and pressure gradient force: wind forcing drives the surface layer, and the deeper return flow is forced by an expected sea-level setup resulting from the wind forcing. This velocity structure is modulated seasonally; during fall-winter, the surface outflow layer is deeper, and the shear at depth stronger, than during spring-summer conditions. The seasonal change in the velocity profile appears related to the seasonal change in wind conditions rather than river discharge, although seasonal stratification is linked to the restriction of shear to shallower depths in spring-summer. At interannual timescales, the same link between wind forcing and along-channel velocity is observed. These findings have important implications for key processes in the bay, such as the transport of nutrients, planktonic larvae, and pollutants.

  16. Wind velocity measurements in the neutral boundary layer above hilly prairie

    NASA Technical Reports Server (NTRS)

    Sugita, Michiaki; Brutsaert, Wilfried

    1990-01-01

    The Flint Hills region in eastern Kansas is characterized by a strongly dissected rolling to hilly terrain with an average about 25 m of relief between steep ridges and valleys, and with ridges typically separated by distances of the order of 600 m. Intensive radiosonde observations during summer and fall of 1987 allowed the determination of some aspects of the wind regime in the region. For an assumed ground-surface reference of 330 m above sea level (asl), analysis of neutral profiles yielded a value z(0) of about 1.05 m, approximately. Good agreement was obtained between the values of friction velocity derived from wind profiles and values determined independently from the corresponding humidity profiles.

  17. Lidar determination of winds by aerosol inhomogeneities: motion velocity in the planetary boundary layer.

    PubMed

    Kolev, I; Parvanov, O; Kaprielov, B

    1988-06-15

    The paper presents results from lidar measurements of wind velocity in the planetary boundary layer using correlation data processing. Two lidars are used in our experiments: a ruby lidar operating along slant paths and a YAG:Nd lidar operating for near vertical sounding used by us for the first time. On the basis of our experience the optimal sizes of aerosol inhomogeneities (30-300 m), the duration of the experiments (2-10 min), and the repetition rate of laser shots (fractions of hertz to several hertz) are determined. The results are compared to independent data obtained from anemometer measurements, theodolite- and radar-tracked pilot balloons. The range of differences is ~1-2 m/s in speed and 10-15 degrees in direction. Preliminary results from the use of lidar data to remotely sound the wind speed for various atmospheric stratifications and synoptic situations are described as well. PMID:20531786

  18. Cluster/Peace Electrons Velocity Distribution Function: Modeling the Strahl in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Figueroa-Vinas, Adolfo; Gurgiolo, Chris; Goldstein, Melvyn L.

    2008-01-01

    We present a study of kinetic properties of the strahl electron velocity distribution functions (VDF's) in the solar wind. These are used to investigate the pitch-angle scattering and stability of the population to interactions with electromagnetic (whistler) fluctuations. The study is based on high time resolution data from the Cluster/PEACE electron spectrometer. Our study focuses on the mechanisms that control and regulate the pitch-angle and stability of strahl electrons in the solar wind; mechanisms that are not yet well understood. Various parameters are investigated such as the electron heat-flux and temperature anisotropy. The goal is to check whether the strahl electrons are constrained by some instability (e.g., the whistler instability), or are maintained by other types of processes. The electron heat-flux and temperature anisotropy are determined by fitting the VDF's to a spectral spherical harmonic model from which the moments are derived directly from the model coefficients.

  19. Longitudinal spectra of wind velocity in the atmospheric surface layer perturbed by a small topographic ridge

    NASA Astrophysics Data System (ADS)

    Tampieri, F.; Mammarella, I.; Maurizi, A.

    2004-03-01

    Turbulence measurements carried out in the near neutral surface layer are presented. The wind velocity components were measured with sonic anemometers at 2 and 10 m height. Three masts are considered, placed about 4 km upwind, on the top and about 6 km downwind of Inexpressible Island, a relief 300 m high and 1 km in cross-section. Spectral features are discussed in detail. Local equilibrium is found in the inertial subrange and in (at least in part of) the intermediate range, characterized by different slopes upwind and downwind (k-1 and k -5/3, respectively) for the components parallel to the terrain.

  20. Climatologies of nighttime thermospheric winds and temperatures from Fabry-Perot interferometer measurements: From solar minimum to solar maximum

    NASA Astrophysics Data System (ADS)

    Fisher, Daniel J.; Makela, Jonathan J.; Meriwether, John W.; Buriti, Ricardo A.; Benkhaldoun, Zouhair; Kaab, Mohamed; Lagheryeb, Amine

    2015-08-01

    We present a climatology of quiet time thermospheric winds and temperatures estimated from high-resolution Fabry-Perot interferometer measurements of the 630.0 nm airglow emission spectral line shape. Three locations are examined in this long-term study: northeastern Brazil (August 2009 to August 2014), a midlatitude site in North Carolina, USA (June 2011 to December 2014), and a midlatitude site in Morocco (November 2013 to December 2014). We discuss the day-to-day, seasonal, and solar cycle trends and variations of thermospheric meridional winds, zonal winds, neutral temperatures, and for the first time vertical winds. Observations made from solar minimum to solar maximum (with F10.7 values ranging from ˜70 to ˜159 solar flux units) confirm that neutral temperatures have a strong solar cycle dependence. However, this data set shows that the neutral winds are more closely tied to the seasonal variation, rather than the solar cycle. We also present comparisons between the two midlatitude sites and include neutral wind comparisons to the updated Horizontal Wind Model 14.

  1. Retrieval and Evaluation of Wind Vectors and Advective Surface Velocities from Synthetic Aperture Radar and Infrared Radiometer Data

    NASA Astrophysics Data System (ADS)

    Carvajal, Gisela; Eriksson, Leif E. B.

    Analysis of ocean surface dynamics has been proven to be of vital importance in many areas (e.g. shipping, fishing). Two important parameters to describe the ocean dynamics are the wind velocity (speed and direction) and advective surface velocities (ocean current velocity). These parameters are currently provided operationally by forecast models, surface sensors (e.g. buoys, coastal radar) and satellite sensors. However, coverage limitations, low resolution and limited temporal availability impose a need for implementation and evaluation of new data sources and techniques for estimation of these parameters. In this paper we implement and evaluate known techniques for determination of wind and ocean current velocity from satellite data. Wind is determined from Synthetic Aperture Radar (SAR) data by applying two algo-rithms. First, the Local Gradient method is implemented to extract wind direction from the SAR data, and then the CMOD-5 Geophysical Model Function of the backscatter is inverted to obtain the wind speed as a function of the wind direction and the incidence angle. Current propagation is estimated by analyzing the Sea Surface Temperature propagation in two consec-utive infrared images of the same area from the Advanced Very High Resolution Radiometer. The evaluation shows a good agreement between estimated wind vectors from SAR and scat-terometer data. Comparison with merged ocean current estimates is addressed. The methods will be implemented in the maritime security service provided by the SECTRONIC project funded by the EU 7th framework program.

  2. Estimation of Venus wind velocities from high-resolution infrared spectra. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Smith, M. A. H.

    1978-01-01

    Zonal velocity profiles in the Venus atmosphere above the clouds were estimated from measured asymmetries of HCl and HF infrared absorption lines in high-resolution Fourier interferometer spectra of the planet. These asymmetries are caused by both pressure-induced shifts in the positions of the hydrogen-halide lines perturbed by CO2 and Doppler shifts due to atmospheric motions. Particularly in the case of the HCl 2-0 band, the effects of the two types of line shifts can be easily isolated, making it possible to estimate a profile of average Venus equatorial zonal velocity as a function of pressure in the region roughly 60 to 70 km above the surface of the planet. The mean profiles obtained show strong vertical shear in the Venus zonal winds near the cloud-top level, and both the magnitude and direction of winds at all levels in this region appear to vary greatly with longitude relative to the sub-solar point.

  3. Remote Sensing Data in Wind Velocity Field Modelling: a Case Study from the Sudetes (SW Poland)

    NASA Astrophysics Data System (ADS)

    Jancewicz, Kacper

    2014-06-01

    The phenomena of wind-field deformation above complex (mountainous) terrain is a popular subject of research related to numerical modelling using GIS techniques. This type of modelling requires, as input data, information on terrain roughness and a digital terrain/elevation model. This information may be provided by remote sensing data. Consequently, its accuracy and spatial resolution may affect the results of modelling. This paper represents an attempt to conduct wind-field modelling in the area of the ?nie?nik Massif (Eastern Sudetes). The modelling process was conducted in WindStation 2.0.10 software (using the computable fluid dynamics solver Canyon). Two different elevation models were used: the Global Land Survey Digital Elevation Model (GLS DEM) and Digital Terrain Elevation Data (DTED) Level 2. The terrain roughness raster was generated on the basis of Corine Land Cover 2006 (CLC 2006) data. The output data were post-processed in ArcInfo 9.3.1 software to achieve a high-quality cartographic presentation. Experimental modelling was conducted for situations from 26 November 2011, 25 May 2012, and 26 May 2012, based on a limited number of field measurements and using parameters of the atmosphere boundary layer derived from the aerological surveys provided by the closest meteorological stations. The model was run in a 100-m and 250-m spatial resolution. In order to verify the model's performance, leave-one-out cross-validation was used. The calculated indices allowed for a comparison with results of former studies pertaining to WindStation's performance. The experiment demonstrated very subtle differences between results in using DTED or GLS DEM elevation data. Additionally, CLC 2006 roughness data provided more noticeable improvements in the model's performance, but only in the resolution corresponding to the original roughness data. The best input data configuration resulted in the following mean values of error measure: root mean squared error of velocity = 1.0 m/s and mean absolute error of direction = 30°. The author concludes that, within specific meteorological conditions (relatively strong and constant synoptic forcing) and using the aforementioned input data, the Canyon model provides fairly acceptable results. Similarly, the quality of the presented remote sensing data is suitable for wind velocity modelling in the proposed resolution. However, CLC 2006 land use data should be first verified with a higher-resolution satellite or aerial imagery.

  4. Three-dimensional velocity measurements around a rotating vertical axis wind turbine

    NASA Astrophysics Data System (ADS)

    Coletti, Filippo; Ryan, Kevin; Dabiri, John; Eaton, John

    2013-11-01

    Vertical axis wind turbines (VAWT) can be more closely spaced than conventional horizontal axis wind turbines (HAWT), which points to a potentially greater power that can be extracted from a given wind farm footprint. In order to optimize the inter-turbine spacing and to investigate the potential for constructive aerodynamic interactions, the complex dynamics of VAWT wakes need to be analyzed. To date, only single-point or at best two-dimensional measurements of such wakes have been documented. We have measured the full three-component mean velocity field around and downstream the scaled-down model of a rotating VAWT by Magnetic Resonance Velocimetry (MRV). The high spatial resolution allows to quantitatively explore the structure of the wake, its interaction with the floor, and its development. The flow is shown to be highly three-dimensional and asymmetric for the whole investigated region (up to 7 diameters downstream of the turbine). These results can inform low-order models to predict the performance of turbine arrays.

  5. Inferring global wind energetics from a simple Earth system model based on the principle of maximum entropy production

    NASA Astrophysics Data System (ADS)

    Karkar, S.; Paillard, D.

    2015-03-01

    The question of total available wind power in the atmosphere is highly debated, as well as the effect large scale wind farms would have on the climate. Bottom-up approaches, such as those proposed by wind turbine engineers often lead to non-physical results (non-conservation of energy, mostly), while top-down approaches have proven to give physically consistent results. This paper proposes an original method for the calculation of mean annual wind energetics in the atmosphere, without resorting to heavy numerical integration of the entire dynamics. The proposed method is derived from a model based on the Maximum of Entropy Production (MEP) principle, which has proven to efficiently describe the annual mean temperature and energy fluxes, despite its simplicity. Because the atmosphere is represented with only one vertical layer and there is no vertical wind component, the model fails to represent the general circulation patterns such as cells or trade winds. However, interestingly, global energetic diagnostics are well captured by the mere combination of a simple MEP model and a flux inversion method.

  6. Horizontal forward-motion velocities of terrestrial dust devils, comparison with ambient winds, and application to Mars

    NASA Astrophysics Data System (ADS)

    Balme, M. R.; Pathare, A.; Metzger, S.; Renno, N. O.; Towner, M.; Spiga, A.; Fenton, L. K.; Michaels, T. I.; Saca, F.; Elliott, H. M.

    2011-12-01

    Dust devils are convective vortices made visible by the dust and debris they entrain. They are most common in arid environments and have been observed on Earth and Mars. Martian dust devils have been identified both in images taken at the surface and in remote sensing observations from orbiting spacecraft. Observations from orbiting instruments that can acquire multiple images in rapid succession (e.g. the ESA Mars Express High Resolution Stereo Camera) have allowed the translational forward motion of dust devils to be calculated: martian dust devils travel across the landscape at speeds of up to tens of metres per second. However, it is unclear how these velocities relate to the local ambient wind conditions, as on Earth only anecdotal evidence exists that ties dust devil forward motion with local wind speed. If dust devil translational velocity can be reliably correlated to local winds, observations of dust devils could provide a proxy for wind speed measurements on Mars, and hence provide an important tool for testing mesoscale climate models. Here we present results from a field study of terrestrial dust devils performed in the southwest USA that seeks to measure dust devil horizontal velocity as a function of wind speed. We acquired stereo images of several hundred active dust devils and hence produced multiple size and position measurements for each dust devil. We used these data to calculate dust devil translational velocity. The dust devils we measured were within a study area bounded by three 10m meteorology towers. Hence we were able to correlate dust devil speed and direction with the local ambient wind speed and direction. We found that instantaneous dust devil translational velocity correlated well with instantaneous local ambient wind velocity. Day-averaged dust devil translational velocity correlated very well with day-averaged (between 11am and 5pm) ambient wind velocity. We found that dust devil horizontal speed is about 1.2 times the ambient 10 m height wind speed. If a similar methodology and result can be applied on Mars then we suggest that dust devils can indeed be used there as proxy measurements for local wind speed.

  7. Electron Velocity Distribution Function in Magnetic Clouds in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Nieves-Chinchil, Teresa; Vinas, Adolfo F.; Bale, Stuart D.

    2006-01-01

    We present a study of the kinetic properties of the electron velocity distribution functions within magnetic clouds, since they are the dominant thermal component. The study is based on high time resolution data from the GSFC WIND/SWE electron spectrometer and the Berkeley 3DP electron plasma instruments. Recent studies on magnetic clouds have shown observational evidence of anti-correlation between the total electron density and electron temperature, which suggest a polytrope law P(sub e) = alpha(Nu(sub e) (sup gamma)) for electrons with the constant gamma approximates 0.5 < 1. This anti-correlation and small polytropic gamma-values is interpreted in the context of the presence of highly non-Maxwellian electron distributions (i.e. non-thermal) within magnetic clouds. These works suggested that the non-thermal electrons can contribute as much as 50% of the total electron pressure within magnetic clouds. We have revisited some of the magnetic cloud events previously studied and attempted to quantify the nature of the non-thermal electrons by modeling the electron velocity distribution function using a kappa distribution function to characterize the kinetic non-thermal effects. If non-thermal tail effects are the source for the anti-correlation between the moment electron temperature and density and if the kappa distribution is a reasonable representative model of non-thermal effects, then the electron velocity distribution within magnetic clouds should show indication for small K-values when gamma < 1.

  8. Two-dimensional Cascade Investigation of the Maximum Exit Tangential Velocity Component and Other Flow Conditions at the Exit of Several Turbine Blade Designs at Supercritical Pressure Ratios

    NASA Technical Reports Server (NTRS)

    Hauser, Cavour H; Plohr, Henry W

    1951-01-01

    The nature of the flow at the exit of a row of turbine blades for the range of conditions represented by four different blade configurations was evaluated by the conservation-of-momentum principle using static-pressure surveys and by analysis of Schlieren photographs of the flow. It was found that for blades of the type investigated, the maximum exit tangential-velocity component is a function of the blade geometry only and can be accurately predicted by the method of characteristics. A maximum value of exit velocity coefficient is obtained at a pressure ratio immediately below that required for maximum blade loading followed by a sharp drop after maximum blade loading occurs.

  9. The microscopic state of the solar wind: Links between composition, velocity distributions, waves and turbulence

    NASA Technical Reports Server (NTRS)

    Marsch, E.

    1995-01-01

    An overview is given of the microscopic state of the solar wind with emphasis on recent Ulysses high-latitude observations and previous Helios in-ecliptic observations. The possible links between composition, ionization state. velocity distribution functions of electrons, protons and heavy ions. kinetic plasma waves and MHD-scale turbulence are elaborated. Emphasis is placed on a connection of interplanetary kinetic-scale phenomena with their generating microscopic processes in the corona. The fast streams seem to consist of mesoscale pressure-balanced plasma filaments and magnetic flux tubes, reminiscent of the supergranular-size structures building the open corona, from which copious Alfven waves emanate. The wind from the magnetically structured and active corona shows developed compressive turbulence and considerable abundance and ionization state variations. Some modelling attempts to explain the observed element fractionation are briefly reviewed. The causes of the nonthermal particle features. such as proton-ion differential streaming, ion beams. temperature anisotropies, and skewed distributions associated with collisionless heat conduction, are ultimately to be searched in the fact, that the corona is never quiescent but fundamentally variable in space and time. Consequently, the radial evolution of the internal state of the wind resembles at all latitudes a complicated relaxation process, in the course of which the free (in comparison with LTE conditions) particle kinetic energy is converted into plasma waves and MHD turbulence on a wide range of scales. This leads to intermittent wave-particle interactions and unsteady anomalous transport, mixed with the weak effects of the rare Coulomb collisions. Spherical expansion and large-scale inhomogeneity forces the wind to attain microscopically a complex internal state of dynamic statistical equilibrium.

  10. Assessing Southern Hemisphere Westerly Wind Changes during the Last Glacial Maximum using Paleo-data Synthesis (Invited)

    NASA Astrophysics Data System (ADS)

    Kohfeld, K. E.; Graham, R. M.; De Boer, A. M.; Wolff, E. W.; Sime, L. C.; Le Quere, C.; Bopp, L.

    2013-12-01

    Changes in the strength and position of Southern Hemisphere westerly winds during the last glacial cycle have been invoked to explain glacial-interglacial climate fluctuations. However, neither paleo models nor paleodata agree on the magnitude, or even the sign, of the change in wind strength and latitude during the Last Glacial Maximum (LGM), compared to the recent past. This study synthesizes paleo-environmental data that have been used to infer changes in winds during the LGM compared with the late Holocene. These compilations include changes in terrestrial moisture, dust deposition, and ocean productivity, along with summaries of previously published information on sea surface temperatures (SSTs) and ocean dynamics in the Southern Hemisphere. Our compilations of terrestrial moisture from 94 sites and dust deposition from 87 sites show generally drier conditions for the LGM between 0 and 40S, with wetter conditions along the west coasts and drying along the east coasts of continents. LGM dust deposition rates ranged from 2 to 4.5 times higher over the Southern Ocean and about 13 times higher over the Antarctic continent. For the oceans, reconstructed changes in SSTs show maximum cooling (>4 °C) in the modern-day Subantarctic Zone, coincident with a region of enhanced export production during the LGM compared with today. We find that any hypothesis of LGM wind and climate change needs to provide a plausible explanation for increased moisture on the west coast of continents, cooler temperatures and higher productivity in the Subantarctic Zone, and reductions in Agulhas leakage around southern Africa. Our comparison suggests that an overall strengthening, an equatorward displacement, or no change at all in winds could all be interpreted as consistent with observations. If a single cause related to the southern westerlies is sought for all the evidence presented, then an equatorward displacement or strengthening of the winds would be consistent with the largest proportion of the data evidence. However, other processes, such as weakening or poleward shifts in winds, a weakened hydrological cycle, extended sea-ice cover, and changed buoyancy fluxes, cannot be ruled out as potential explanations of observed changes in moisture, surface temperature, and productivity. We contend that resolving the position and strength of westerly winds during the LGM remains elusive based on data reconstructions alone. However, we believe that these data reconstructions of environmental conditions can be used in conjunction with model simulations to identify which processes best represent westerly wind conditions during the LGM.

  11. Determination of the mass loss rate and the terminal velocity of stellar winds. I Genetic algorithm for automatic line profile fitting

    E-print Network

    L. Georgiev; X. Hernandez

    2005-01-28

    Terminal wind velocity and mass loss rate are the most fundamental parameters of stellar winds. Unfortunately, their determination calls for high resolution spectroscopy in a range of wavelengths spanning from the ultraviolet to the infrared. For weak and/or distant objects, this becomes unfeasible. Nevertheless, it is possible to obtain an accurate estimate of these parameters through a simplified study of the formation processes of resonant lines which show P Cyg profiles. In this case, the line profile is a complex function of 6 parameters, with the radiative transport treatment becoming relatively inexpensive. However, preforming a 6 dimensional parameter fit raises a number of problems if one seeks an objective and automatic procedure to yield the optimal values, from which wind velocities and mass loss rates can be estimated. Useing a Likelihood function to construct a well defined statistical estimator of the goodness of fit which corresponds to a given model, we turn to a genetic algorithm through which we find the global maximum of the 6 dimensional Likelihood hyper-surface. We here present the implementation of the method, its successful testing with synthetic line profiles, where the answer is known in advance, together with first results of its application to real data

  12. Design of a near-IR coherent lidar for high spatial and velocity resolution wind measurement

    NASA Technical Reports Server (NTRS)

    Grund, Christian J.; Post, Madison J.

    1992-01-01

    A coherent Doppler lidar based on a CW diode-pumped, injection seeded, Th:YAG laser operating at approx. 2.02 microns is currently under development. This system is optimized for measurements of boundary layer winds with high spatial, temporal, and velocity resolution. Initially, the system will run alongside a new high repetition rate (5-10 kHz) CO2 mini-Master Oscillator Power Amplifier (mini-MOPA) Doppler lidar, which will provide simultaneous range-resolved Differential Absorption Lidar (DIAL) water vapor measurements. Water vapor DIAL operation of the 2 micron system is being considered as a future option. The anticipated specifications and the preliminary design are discussed.

  13. Periodical oscillation of zonal wind velocities at the cloud top of Venus

    NASA Astrophysics Data System (ADS)

    Kouyama, T.; Imamura, T.; Nakamura, M.; Satoh, T.; Futaana, Y.

    2010-12-01

    Zonal wind velocity of Venus increases with height and reaches about 100 m s-1 at the cloud top level (~70km). The speed is approximately 60 times faster than the rotation speed of the solid body of Venus (~1.6 m s-1, at the equator) and this phenomenon is called a "super-rotation". From previous observations, it is known that the super-rotation changes on a long timescale. At the cloud top level, it was suggested that the super-rotation has a few years period oscillation based on observations made by Pioneer Venus orbiter of USA from 1979 to 1985 (Del Genio et al.,1990). However, the period, the amplitude, the spatial structure and the mechanism of the long period oscillation have not been understood well. Venus Express (VEX) of European Space Agency has been observing Venus since its orbital insertion in April 2006. Venus Monitoring Camera (VMC) onboard VEX has an ultra violet (UV) filter (365 nm), and VMC has taken day-side cloud images at the cloud top level with this filter. Such images exhibit various cloud features made by unknown UV absorber in the atmosphere. For investigating the characteristics of long-timescale variations of the super-rotation, we analyzed zonal velocity fields derived from UV cloud images from May 2006 to January 2010 using a cloud tracking method. UV imaging of VMC is done when the spacecraft is in the ascending portion of its elongated polar orbit. Since the orbital plane is nearly fixed in the inertial space, the local time of VMC/UV observation changes with a periodicity of one Venus year. As a result, periods when VMC observation covered day-side areas of Venus, large enough for cloud trackings, are not continuous. For deriving wind velocities we were able to use cloud images taken in 280 orbits during this period. The derived zonal wind velocity from 10°S to 40°S latitude shows a prominent year-to-year variation, and the variation is well fitted by a periodical oscillation with a period of about 260 Earth days, although not all phases of the variation were observed. The 260 day period is longer than the length of one day of Venus (~117 days) and somewhat longer than the orbital revolution period (~225 days) of Venus. In the equatorial region, the amplitude of this oscillation is about 12 m s-1 with the background zonal wind speed of about 95 m s-1. The oscillation period is shorter than the long-term oscillation reported by PVO. Such oscillation has not been reported most probably because previous Venus observations had limitations of observation chances to identify the oscillations with such a period.

  14. AXAOTHER XL -- A spreadsheet for determining doses for incidents caused by tornadoes or high-velocity straight winds

    SciTech Connect

    Simpkins, A.A.

    1996-09-01

    AXAOTHER XL is an Excel Spreadsheet used to determine dose to the maximally exposed offsite individual during high-velocity straight winds or tornado conditions. Both individual and population doses may be considered. Potential exposure pathways are inhalation and plume shine. For high-velocity straight winds the spreadsheet has the capability to determine the downwind relative air concentration, however for the tornado conditions, the user must enter the relative air concentration. Theoretical models are discussed and hand calculations are performed to ensure proper application of methodologies. A section has also been included that contains user instructions for the spreadsheet.

  15. Flying Drosophila stabilize their vision-based velocity controller by sensing wind with their antennae

    PubMed Central

    Fuller, Sawyer Buckminster; Straw, Andrew D.; Peek, Martin Y.; Murray, Richard M.; Dickinson, Michael H.

    2014-01-01

    Flies and other insects use vision to regulate their groundspeed in flight, enabling them to fly in varying wind conditions. Compared with mechanosensory modalities, however, vision requires a long processing delay (~100 ms) that might introduce instability if operated at high gain. Flies also sense air motion with their antennae, but how this is used in flight control is unknown. We manipulated the antennal function of fruit flies by ablating their aristae, forcing them to rely on vision alone to regulate groundspeed. Arista-ablated flies in flight exhibited significantly greater groundspeed variability than intact flies. We then subjected them to a series of controlled impulsive wind gusts delivered by an air piston and experimentally manipulated antennae and visual feedback. The results show that an antenna-mediated response alters wing motion to cause flies to accelerate in the same direction as the gust. This response opposes flying into a headwind, but flies regularly fly upwind. To resolve this discrepancy, we obtained a dynamic model of the fly’s velocity regulator by fitting parameters of candidate models to our experimental data. The model suggests that the groundspeed variability of arista-ablated flies is the result of unstable feedback oscillations caused by the delay and high gain of visual feedback. The antenna response drives active damping with a shorter delay (~20 ms) to stabilize this regulator, in exchange for increasing the effect of rapid wind disturbances. This provides insight into flies’ multimodal sensory feedback architecture and constitutes a previously unknown role for the antennae. PMID:24639532

  16. Maximum wind radius estimated by the 50 kt radius: improvement of storm surge forecasting over the Western North Pacific

    NASA Astrophysics Data System (ADS)

    Takagi, H.; Wu, W.

    2015-10-01

    Even though the maximum wind radius (Rmax) is an important parameter in determining the intensity and size of tropical cyclones, it has been overlooked in previous storm surge studies. This research reviewed the existing estimation methods of Rmax based on the central pressure or maximum wind speed. These over or underestimated Rmax because of the substantial variety of the data, though an average radius could be moderately estimated. Alternatively, we proposed an Rmax estimation method based on the radius of the 50 knot wind (R50). The data obtained during the passage of strong typhoons by a meteorological station network in the Japanese archipelago enabled us to derive the following formula, Rmax = 0.23R50. Although this new method substantially improved the estimation of Rmax compared to the existing models, an estimation error was unavoidable because of fundamental uncertainties regarding the typhoon's structure or insufficient number of available typhoon data. In fact, a numerical simulation from 2013 Typhoon Haiyan demonstrated a substantial difference in the storm surge height for different Rmax. Therefore, the variability of Rmax should be taken into account in storm surge simulations, independently of the model used, to minimize the risk of over or underestimation of storm surges. The proposed method is expected to increase the reliability of storm surge prediction and contribute to disaster risk management, particularly in the Western North Pacific, including countries such as Japan, China, Taiwan, Philippines, and Vietnam.

  17. Effect of Wind Tunnel Air Velocity on VOC Flux from Standard Solutions and CAFO Manure/Wastewater

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Researchers and practitioners have used wind tunnels and flux chambers to quantify the flux of volatile organic compounds (VOCs), ammonia, and hydrogen sulfide and estimate emission factors from animal feeding operations (AFOs) without accounting for effects of air velocity or sweep air flow rate. L...

  18. Effect of maximum torque according to the permanent magnet configuration of a brushless dc motor with concentrated winding

    NASA Astrophysics Data System (ADS)

    Lee, Kab-Jae; Kim, Sol; Lee, Ju; Oh, Jae-Eung

    2003-05-01

    A brushless dc (BLDC) motor, which has a permanent magnet (PM) component, is a potential candidate for hybrid or electric vehicle applications. Minimizing the BLDC motor size is an important requirement for application. This requirement is usually satisfied by adopting a high performance permanent magnet or improved winding methods. The PM configuration is also a critical point in design. This article presents the effect of the PM configuration on motor performance, especially the maximum torque. Four representative BLDC motor types are analytically investigated under the condition that the volume of the PM and magnetic material is constant. An embedded interior permanent magnet motor has the best torque performance the maximum torque of which is more than 1.5 times larger than that of the surface mounted permanent magnet motor. The performance of back electromotive force, instantaneous torques is also investigated.

  19. Covariance statistics of turbulence velocity components for wind-energy-conversion system design-homogeneous, isotropic case

    SciTech Connect

    Fichtl, G.H.

    1983-09-01

    When designing a wind energy converison system (WECS), it may be necessary to take into account the distribution of wind across the disc of rotation. The specific engineering applications include structural strength, fatigue, and control. This wind distribution consists of two parts, namely that associated with the mean wind profile and that associated with the turbulence velocity fluctuation field. The work reported herein is aimed at the latter, namely the distribution of turbulence velocity fluctuations across the WECS disk of rotation. A theory is developed for the two-time covariance matrix for turbulence velocity vector components for wind energy conversion system (WECS) design. The theory is developed for homogeneous and iotropic turbulance with the assumption that Taylor's hypothesis is valid. The Eulerian turbulence velocity vector field is expanded about the hub of the WECS. Formulae are developed for the turbulence velocity vector component covariance matrix following the WECS blade elements. It is shown that upon specification of the turbulence energy spectrum function and the WECS rotation rate, the two-point, two-time covariance matrix of the turbulent flow relative to the WECS bladed elements is determined. This covariance matrix is represented as the sum of nonstationary and stationary contributions. Generalized power spectral methods are used to obtain two-point, double frequency power spectral density functions for the turbulent flow following the blade elements. The Dryden turbulence model is used to demonstrate the theory. A discussion of linear system response analysis is provided to show how the double frequency turbulence spectra might be used to calculate response spectra of a WECS to turbulent flow. Finally the spectrum of the component of turbulence normal to the WECS disc of rotation, following the blade elements, is compared with experimental results.

  20. The Evolution of the Spectrum of Solar Wind Velocity Fluctuations from 0.3 to 5 AU

    NASA Technical Reports Server (NTRS)

    Roberts, D. Aaron

    2011-01-01

    Recent work has shown that at 1 AU from the Sun the power spectrum of the solar wind magnetic field has the -5/3 spectral slope expected for Kolmogorov turbulence, but that the velocity has closer to a -3/2 spectrum. This paper traces the changes in solar wind velocity spectra from 0.3 to 5 AU using data from the Helios and Ulysses spacecraft to show that this is a transient stage in solar-wind evolution. The spectrum of the velocity is found to be flatter than that of the magnetic field for the higher frequencies examined for all cases until the slopes become equal (at -5/3) well past 1 AU when the wind is relatively nonAlfvenic. In some respects, in particular in the evolution of the frequency at which the spectrum changes from flatter at larger scales to a "turbulent" spectrum at smaller scales, the velocity field evolves more rapidly than the magnetic, and this is associated with the dominance of the magnetic energy over the kinetic at "inertial range" scales. The speed of the flow is argued to be largely unrelated to the spectral slopes, consistent with previous work, whereas high Alfvenicity appears to slow the spectral evolution, as expected from theory. This study shows that, for the solar wind, the idea of a simple "inertial range" with uniform spectral properties is not realistic, and new phenomenologies will be needed to capture the true situation. It is also noted that a flattening of the velocity spectrum often occurs at small scales.

  1. Derivation of wind velocity standard deviation values in the urban inertial sublayer from observations in the roughness sublayer

    NASA Astrophysics Data System (ADS)

    Falabino, Simona; Trini Castelli, Silvia

    2014-05-01

    The atmospheric turbulence in the surface layer over urban and suburban areas is affected by the presence of roughness elements. The roughness sublayer (RSL) extends from the ground up to about two to five times the mean building height of the area. Within RSL, turbulence is inhomogeneous and heat and momentum turbulent fluxes are not constant with height, therefore the Monin-Obukhov Similarity Theory (MOST) is not suitable and the surface-layer parameters (friction velocity, stability parameter) are not well defined. Instead, in the inertial sublayer (ISL) above the RSL, the turbulent fluxes are constant and the MOST is still considered valid. In air pollution models, observed surface-layer parameters available from data collected at urban or suburban stations might be used as inputs. Therefore, often RSL values are used in the parameterizations of the turbulence variables, such as the wind velocity standard deviations, as they were representative of the ISL, possibly leading to a not appropriate application of the MOST. We investigate whether it is possible to derive suitable values of the wind velocity standard deviations in the ISL using RLS observed parameters, through the analysis of a sonic anemometer dataset collected in a suburban site at three levels, two in the RSL and one in the ISL. The ISL wind velocity standard deviation are evaluated as similarity-like analytical functions of the RSL friction velocity and stability parameter. The RSL surface parameters are found to be satisfying scaling parameters and the empirical coefficients in the analytical formulation are estimated from the experimental data. Then the new analytical functions for wind velocity standard deviation are tested and verified against data collected during experiments in both homogeneous and heterogeneous conditions. Such approach could be useful in air pollution modeling over urban/suburban areas when ISL data are not available.

  2. Effects of wind velocity on slant path rain-attenuation for satellite application in Malaysia

    NASA Astrophysics Data System (ADS)

    Lwas, Ali Kadhim; Islam, Md. Rafiqul; Habaebi, Mohamed Hadi; Mandeep, Singh Jit; Ismail, Ahmad Fadzil; Zyoud, Alhareth

    2015-12-01

    Earth-to-satellite signals suffer by Earth's atmosphere especially by precipitations. It is more severe in tropical climate. A reliable technique named as synthetic storm technique (SST) was proposed to predict the effects of rain on slant path. SST model uses rainfall-rate time series, velocity of wind in storm, effective length, altitude of site, and elevation angle as the main input parameters. SST was developed based on data collected from temperate regions. Since the rainfall characteristics in temperate regions differ considerably from that in tropical regions. This paper presents storm-speed effects on rain-attenuation prediction using SST based on storm speed, rain rate, and attenuation at Ku-band measurement in Malaysia. The predicted rain attenuation by SST highly overestimates for higher values of storm speed but the predicted duration is close to measurement. For lower values of storm speed, the prediction comes closer to measurement, but the duration extends much longer than the measurement. Hence, predicted rain-attenuation as a function of storm-speed variations by SST is not accurate in tropical regions.

  3. Aging of solar wind magnetic and velocity fluctuations from observations in the inner heliosphere

    NASA Astrophysics Data System (ADS)

    Ruiz, M. E.; Dasso, S.; Matthaeus, W. H.; Weygand, J. M.; Marsch, E.

    2010-12-01

    The heliosphere is a natural laboratory to study several aspects of Magnetohydrodynamic (MHD) turbulence. MHD fluctuations are ubiquitous in the solar wind (SW) and 'in situ' observations of plasma properties and magnetic field are one of the keys to unveil the secrets of MHD turbulence. In the interplanetary medium, MHD scale fluctuations are usually anisotropic, and these fluctuations frequently present different properties in regions of quasi-stationary SW with different bulk plasma parameters, or in regions associated with the presence of transients (e.g., magnetic clouds). It is known that the spatial structure of magnetic and velocity correlation functions evolves in the inner heliosphere. This evolution in terms of the aging of plasma parcels, as observed by the spacecrafts Helios 1-2, is the subject of the work presented here. Particular interest is put on the evolution of anisotropies in the integral length scale. Results are consistent with driving modes with wavevectors parallel to the direction of the local mean magnetic field near Sun, and a progressive spectral transfer of energy to modes with perpendicular wavevectors. Advances made in this direction, as those presented here, will be usefull to refine models used to describe the propagation and diffusion of charged solar and galactic energetic particles in the inner heliosphere, and will contribute to understand the MHD Alfvenic wave activity for this system.

  4. REINTERPRETATION OF SLOWDOWN OF SOLAR WIND MEAN VELOCITY IN NONLINEAR STRUCTURES OBSERVED UPSTREAM OF EARTH'S BOW SHOCK

    SciTech Connect

    Parks, G. K.; Lin, N.; Lee, E.; Hong, J.; Fu, S. Y.; McCarthy, M.; Cao, J. B.; Liu, Y.; Shi, J. K.; Goldstein, M. L.; Canu, P.; Dandouras, I.; Reme, H.

    2013-07-10

    Two of the many features associated with nonlinear upstream structures are (1) the solar wind (SW) mean flow slows down and deviates substantially and (2) the temperature of the plasma increases in the structure. In this Letter, we show that the SW beam can be present throughout the entire upstream event maintaining a nearly constant beam velocity and temperature. The decrease of the velocity is due to the appearance of new particles moving in the opposite direction that act against the SW beam and reduce the mean velocity as computed via moments. The new population, which occupies a larger velocity space, also contributes to the second moment, increasing the temperature. The new particles include the reflected SW beam at the bow shock and another population of lower energies, accelerated nearby at the shock or at the boundary of the nonlinear structures.

  5. Influence of the tilting reflection mirror on the temperature and wind velocity retrieved by a polarizing atmospheric Michelson interferometer.

    PubMed

    Zhang, Chunmin; Li, Ying

    2012-09-20

    The principles of a polarizing atmospheric Michelson interferometer are outlined. The tilt of its reflection mirror results in deflection of the reflected beam and affects the intensities of the observed inteferogram. This effect is systematically analyzed. Both rectangular and circular apertures are considered. The theoretical expression of the modulation depth and phase of the interferogram are derived. These parameters vary with the inclination angle of the mirror and the distance between the deflection center and the optical axis and significantly influence the retrieved temperature and wind speed. If the wind and temperature errors are required to be less than 3 m/s and 5 K, the deflection angle must be less than 0.5°. The errors are also dependent on the shape of aperture. If the reflection mirror is deflected in one direction, the temperature error is smaller for a circular aperture (1.3 K) than for a rectangular one (2.6 K), but the wind velocity errors are almost the same (less than 3 m/s). If the deflection center and incident light beam are coincident, the temperature errors are 3 × 10(-4) K and 0.45 K for circular and rectangular apertures, respectively. The wind velocity errors are 1.2 × 10(-3) m/s and 0.06 m/s. Both are small. The result would be helpful for theoretical research and development of the static polarization wind imaging interferometer. PMID:23033020

  6. Effects of errors in velocity tilt on maximum longitudinal compression during neutralized drift compression of intense beam pulses

    E-print Network

    Kaganovich, Igor

    A. Startsev a , Ronald C. Davidson a , Jean-Luc Vay b , Alex Friedman c a Plasma Physics Laboratory by the beam in the induction bunching module limit the maximum longitudinal compression. It is found are small may compress to much higher values, which are determined by the initial thermal spread of the beam

  7. A New Technique using Electron Velocity Data from the Four Cluster Spacecraft to Explore Magnetofluid Turbulence in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Goldstein, Melvyn L.; Gurgiolo, C.; Fazakerley, A.; Lahiff, A.

    2008-01-01

    It is now possible in certain circumstances to use velocity moments computed from the Plasma Electron and Current Experiment (PEACE) on the four Cluster spacecraft to determine a number of turbulence properties of the solar wind, including direct measurements of the vorticity and compressibility. Assuming that the four spacecraft are not co-planar and that there is only a linear variation of the plasma variables across the volume defined by the four satellites, one can estimate the curl of the fluid velocity, i.e., the vorticity. From the vorticity it is possible to explore directly intermittent regions in the solar wind where dissipation is likely to be enhanced. In addition, one can estimate directly the Taylor microscale.

  8. Study of the wind velocity-layered structure in the stratosphere, mesosphere, and lower thermosphere by using infrasound probing of the atmosphere

    NASA Astrophysics Data System (ADS)

    Chunchuzov, I.; Kulichkov, S.; Perepelkin, V.; Popov, O.; Firstov, P.; Assink, J. D.; Marchetti, E.

    2015-09-01

    The wind velocity structure in the upper stratosphere, mesosphere, and lower thermosphere (MLT) is studied with the recently developed method of infrasound probing of the atmosphere. The method is based on the effect of infrasound scattering from highly anisotropic wind velocity and temperature inhomogeneities in the middle and upper atmosphere. The scattered infrasound field propagates in the acoustic shadow zones, where it is detected by microbarometers. The vertical profiles of the wind velocity fluctuations in the upper stratosphere (30-52 km) and MLT (90-140 km) are retrieved from the waveforms and travel times of the infrasound signals generated by explosive sources such as volcanoes and surface explosions. The fine-scale wind-layered structure in these layers was poorly observed until present time by other remote sensing methods, including radars and satellites. It is found that the MLT atmospheric layer (90-102 km) can contain extremely high vertical gradients of the wind velocity, up to 10 m/s per 100 m. The effect of a fine-scale wind velocity structure on the waveforms of infrasound signals is studied. The vertical wave number spectra of the retrieved wind velocity fluctuations are obtained for the upper stratosphere. Despite the difference in the locations of the explosive sources all the obtained spectra show the existence of high vertical wave number spectral tail with a -3 power law decay. The obtained spectral characteristics of the wind fluctuations are necessary for improvement of gravity wave drag parameterizations for numerical weather forecast.

  9. Prediction of Summer Precipitation During The Indian Monsoon Applying The Circulating Index of Wind Velocity

    NASA Astrophysics Data System (ADS)

    Sokolikhina, E.; Semenov, E.; Sokolikhina, N.

    In the MSU ECTRA model (Moscow State University empirical circulating model for the tropical atmosphere) ten action centers in the tropical atmosphere were cho- sen, which are responsible for the formation of summer monsoon rains above India. In the lower troposphere (850 hPa) the following action centers were chosen: 1 Mon- soonal depression above India. 2 Equatorial depression on the southern branch of the ITCZ (the south of the Arabian sea). 3 Equatorial depression above Indonesia. 4 Asian summer depression. 5 Subtropical anticyclone of the Southern Hemisphere. 6 North- Australian subtropical anticyclone. In the upper troposphere (200hPa) the chosen action centers are: 1 Tibet upper-level anticyclone. 2 North-African upper-level anticyclone. 3 Upper-level anticyclone above Madagascar. 4 North-Australian upper-level anticyclone. Based on NCEP/NCAR 1948-1997 reanalysis data the circulation index, i.e. the inte- gral of the wind velocity vector along contours, was calculated and the reliable con- tours' sizes and the central points were determined for each action center. In the next stage the connection between the intensity of the chosen circulating systems and sum- mer rains was assessed for five Indian regions with different precipitation regimes: 1 The coast of the Arabian Sea. 2 The southern part of India. 3 The central part of India. 4 The northern part of India. 5 The north of Bengal. The system of predictors that were found allows us to estimate the influence of each baric center in the system of summer Indian monsoon circulation and to forecast the summer rains during Indian monsoon in the future.

  10. Critical wind velocity for arresting upwind gas and smoke dispersion induced by near-wall fire in a road tunnel.

    PubMed

    Hu, L H; Peng, W; Huo, R

    2008-01-15

    In case of a tunnel fire, toxic gas and smoke particles released are the most fatal contaminations. It is important to supply fresh air from the upwind side to provide a clean and safe environment upstream from the fire source for people evacuation. Thus, the critical longitudinal wind velocity for arresting fire induced upwind gas and smoke dispersion is a key criteria for tunnel safety design. Former studies and thus, the models built for estimating the critical wind velocity are all arbitrarily assuming that the fire takes place at the centre of the tunnel. However, in many real cases in road tunnels, the fire originates near the sidewall. The critical velocity of a near-wall fire should be different with that of a free-standing central fire due to their different plume entrainment process. Theoretical analysis and CFD simulation were performed in this paper to estimate the critical velocity for the fire near the sidewall. Results showed that when fire originates near the sidewall, it needs larger critical velocity to arrest the upwind gas and smoke dispersion than when fire at the centre. The ratio of critical velocity of a near-wall fire to that of a central fire was ideally estimated to be 1.26 by theoretical analysis. Results by CFD modelling showed that the ratio decreased with the increase of the fire size till near to unity. The ratio by CFD modelling was about 1.18 for a 500kW small fire, being near to and a bit lower than the theoretically estimated value of 1.26. However, the former models, including those of Thomas (1958, 1968), Dangizer and Kenndey (1982), Oka and Atkinson (1995), Wu and Barker (2000) and Kunsch (1999, 2002), underestimated the critical velocity needed for a fire near the tunnel sidewall. PMID:17544576

  11. The magnetospheric response to a two-stream solar wind interval during solar maximum: a self-consistent magnetospheric model

    NASA Astrophysics Data System (ADS)

    Feldstein, Y.; Tsurutani, B.; Prigancova, A.; Gonzalez, W.; Levitin, A.; Kozyra, J.; Alperovich, L.; Mall, U.; Gromova, L.; Dremukhina, L.

    2003-09-01

    A two-stream solar wind interval (two interplanetary CME events) during 1-7 May 1998 is examined and the magnetospheric response to these events is modeled and compared to satellite data. The solar ejecta (CMEs) and resultant fast interplanetary streams cause magnetic storms with minimum Dst values of -75 nT and -205 nT, respectively. For the second, more intense magnetic storm, it is found that at the Earth's surface the maximum values of the disturbance fields are -208 nT for the ring current contribution (DR), 112 nT for the Chapman-Ferraro (DCF) magnetopause current system, and -161 nT for the tail current system (DT). Although DT is large, it is counterbalanced by DCF. These currents significantly modify the magnetospheric geometry and size and must be included for any accurate magnetic field representation during storm periods.

  12. Effects of errors in velocity tilt on maximum longitudinal compression during neutralized drift compression of intense beam pulses: I. general description

    SciTech Connect

    Kaganovich, Igor D.; Massidda, Scottt; Startsev, Edward A.; Davidson, Ronald C.; Vay, Jean-Luc; Friedman, Alex

    2012-06-21

    Neutralized drift compression offers an effective means for particle beam pulse compression and current amplification. In neutralized drift compression, a linear longitudinal velocity tilt (head-to-tail gradient) is applied to the non-relativistic beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam current can increase by more than a factor of 100 in the longitudinal direction. We have performed an analytical study of how errors in the velocity tilt acquired by the beam in the induction bunching module limit the maximum longitudinal compression. It is found that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may limit the compression to a factor of one hundred. However, a part of the beam pulse where the errors are small may compress to much higher values, which are determined by the initial thermal spread of the beam pulse. It is also shown that sharp jumps in the compressed current density profile can be produced due to overlaying of different parts of the pulse near the focal plane. Examples of slowly varying and rapidly varying errors compared to the beam pulse duration are studied. For beam velocity errors given by a cubic function, the compression ratio can be described analytically. In this limit, a significant portion of the beam pulse is located in the broad wings of the pulse and is poorly compressed. The central part of the compressed pulse is determined by the thermal spread. The scaling law for maximum compression ratio is derived. In addition to a smooth variation in the velocity tilt, fast-changing errors during the pulse may appear in the induction bunching module if the voltage pulse is formed by several pulsed elements. Different parts of the pulse compress nearly simultaneously at the target and the compressed profile may have many peaks. The maximum compression is a function of both thermal spread and the velocity errors. The effects of the finite gap width of the bunching module on compression are analyzed analytically.

  13. Observations of the relationship between ionospheric central polar cap and dayside throat convection velocities, and solar wind/IMF driving

    NASA Astrophysics Data System (ADS)

    Bristow, W. A.; Amata, E.; Spaleta, J.; Marcucci, M. F.

    2015-06-01

    Convection observations from the Southern Hemisphere Super Dual Auroral Radar Network are presented and examined for their relationship to solar wind and interplanetary magnetic field (IMF) conditions, restricted to periods of steady IMF. Analysis is concentrated on two specific regions, the central polar cap and the dayside throat region. An example time series is discussed in detail with specific examples of apparent direct control of the convection velocity by the solar wind driver. Closer examination, however, shows that there is variability in the flows that cannot be explained by the driving. Scatterplots and histograms of observations from all periods in the year 2013 that met the selection criteria are given and their dependence on solar wind driving is examined. It is found that on average the flow velocity depends on the square root of the rate of flux entry to the polar cap. It is also found that there is a large level of variability that is not strongly related to the solar wind driving.

  14. Some techniques for reducing the tower shadow of the DOE/NASA mod-0 wind turbine tower. [wind tunnel tests to measure effects of tower structure on wind velocity

    NASA Technical Reports Server (NTRS)

    Burley, R. R.; Savino, J. M.; Wagner, L. H.; Diedrich, J. H.

    1979-01-01

    Wind speed profile measurements to measure the effect of a wind turbine tower on the wind velocity are presented. Measurements were made in the wake of scale models of the tower and in the wake of certain full scale components to determine the magnitude of the speed reduction (tower shadow). Shadow abatement techniques tested on the towers included the removal of diagonals, replacement of diagonals and horizontals with round cross section members, installation of elliptical shapes on horizontal members, installation of airfoils on vertical members, and application of surface roughness to vertical members.

  15. THE ORIGIN OF NON-MAXWELLIAN SOLAR WIND ELECTRON VELOCITY DISTRIBUTION FUNCTION: CONNECTION TO NANOFLARES IN THE SOLAR CORONA

    SciTech Connect

    Che, H.; Goldstein, M. L.

    2014-11-10

    The formation of the observed core-halo feature in the solar wind electron velocity distribution function is a long-time puzzle. In this Letter, based on the current knowledge of nanoflares, we show that the nanoflare-accelerated electron beams are likely to trigger a strong electron two-stream instability that generates kinetic Alfvén wave and whistler wave turbulence, as we demonstrated in a previous paper. We further show that the core-halo feature produced during the origin of kinetic turbulence is likely to originate in the inner corona and can be preserved as the solar wind escapes to space along open field lines. We formulate a set of equations to describe the heating processes observed in the simulation and show that the core-halo temperature ratio of the solar wind is insensitive to the initial conditions in the corona and is related to the core-halo density ratio of the solar wind and to the quasi-saturation property of the two-stream instability at the time when the exponential decay ends. This relation can be extended to the more general core-halo-strahl feature in the solar wind. The temperature ratio between the core and hot components is nearly independent of the heliospheric distance to the Sun. We show that the core-halo relative drift previously reported is a relic of the fully saturated two-stream instability. Our theoretical results are consistent with the observations while new tests for this model are provided.

  16. Threshold wind velocities for sand movement in the Mescalero Sands of southeastern New Mexico

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind erosion activity was studied at two Chihuahuan Desert sites, the Gnome site which was contaminated with radioactivity from a nuclear device in 1961 and Near Field, a reference site. Saltation activity was measured with piezoelectric sensors, and those data were used to calculate threshold wind...

  17. Simplified equations for the rotational speed response to inflow velocity variation in fixed-pitch small wind turbines

    NASA Astrophysics Data System (ADS)

    Suzuki, H.; Hasegawa, Y.

    2015-02-01

    We propose simplified equations for the rotational speed response to inflow velocity variation in fixed-pitch small wind turbines. The present formulation is derived by introducing a series expansion for the torque coefficient at the constant tip-speed ratio. By focusing on the first- and second-order differential coefficients of the torque coefficient, we simplify the original differential equation. The governing equation based only on the first-order differential coefficient is found to be linear, whereas the second-order differential coefficient introduces nonlinearity. We compare the numerical solutions of the three governing equations for rotational speed in response to sinusoidal and normal-random variations of inflow velocity. The linear equation gives accurate solutions of amplitude and phase lag. Nonlinearity occurs in the mean value of rotational speed variation. We also simulate the rotational speed in response to a step input of inflow velocity using the conditions of two previous studies, and note that the form of this rotational speed response is a system of first-order time lag. We formulate the gain and time constant for this rotational speed response. The magnitude of the gain is approximately three when the wind turbine is operated at optimal tip-speed ratio. We discuss the physical meaning of the derived time constant.

  18. Competing mechanisms of plasma transport in inhomogeneous configurations with velocity shear: the solar-wind interaction with earth's magnetosphere.

    PubMed

    Faganello, M; Califano, F; Pegoraro, F

    2008-01-11

    Two-dimensional simulations of the Kelvin-Helmholtz instability in an inhomogeneous compressible plasma with a density gradient show that, in a transverse magnetic field configuration, the vortex pairing process and the Rayleigh-Taylor secondary instability compete during the nonlinear evolution of the vortices. Two different regimes exist depending on the value of the density jump across the velocity shear layer. These regimes have different physical signatures that can be crucial for the interpretation of satellite data of the interaction of the solar wind with the magnetospheric plasma. PMID:18232777

  19. Competing Mechanisms of Plasma Transport in Inhomogeneous Configurations with Velocity Shear: The Solar-Wind Interaction with Earth's Magnetosphere

    SciTech Connect

    Faganello, M.; Califano, F.; Pegoraro, F.

    2008-01-11

    Two-dimensional simulations of the Kelvin-Helmholtz instability in an inhomogeneous compressible plasma with a density gradient show that, in a transverse magnetic field configuration, the vortex pairing process and the Rayleigh-Taylor secondary instability compete during the nonlinear evolution of the vortices. Two different regimes exist depending on the value of the density jump across the velocity shear layer. These regimes have different physical signatures that can be crucial for the interpretation of satellite data of the interaction of the solar wind with the magnetospheric plasma.

  20. High-velocity, multistage, nozzled, ion driven wind generator and method of operation of the same adaptable to mesoscale realization

    NASA Technical Reports Server (NTRS)

    Dunn-Rankin, Derek (Inventor); Rickard, Matthew J. A. (Inventor)

    2011-01-01

    Gas flows of modest velocities are generated when an organized ion flux in an electric field initiates an ion-driven wind of neutral molecules. When a needle in ambient air is electrically charged to a potential sufficient to produce a corona discharge near its tip, such a gas flow can be utilized downstream of a ring-shaped or other permeable earthed electrode. In view of the potential practical applications of such devices, as they represent blowers with no moving parts, a methodology for increasing their flow velocities includes exploitation of the divergence of electric field lines, avoidance of regions of high curvature on the second electrode, control of atmospheric humidity, and the use of linear arrays of stages, terminating in a converging nozzle. The design becomes particularly advantageous when implemented in mesoscale domains.

  1. The Dependence of Heat and Gas Transfer Velocities on Wind-Generated and Mechanically Generated Aqueous-Phase Turbulence

    NASA Astrophysics Data System (ADS)

    Liang, H.; Mukto, M.; Loewen, M.; Zappa, C.; Litchendorf, T.; Asher, W.; Jessup, A.

    2006-12-01

    The air-sea flux, F, of a sparingly soluble nonreactive gas can be expressed as F = kG( CS-CW), where kG is the gas transfer velocity, CS is the concentration of gas that would be expected in the water if the system were in Henry`s Gas Law equilibrium, and CW is the actual concentration of the gas in the water. An analogous relationship for the net heat flux can also be written using the heat transfer velocity, kH, and the bulk-skin temperature difference in the aqueous phase. Hydrodynamical models of gas and heat exchange based on surface renewal theory predict that kG and kH will scale as the square root of the inverse of a timescale of the turbulence. Furthermore, if surface renewal provides an accurate conceptual model for both transfer processes, then both kG and kH should behave identically as turbulence conditions change. Here we report on recent laboratory experiments in which we measured turbulence, heat fluxes, kG, and kH in a 0.5 m by 0.5 m by 1 m deep tank in the presence of turbulence generated mechanically using a random synthetic jet array. The turbulence tank was embedded in a small wind tunnel so that kG and kH could be studied as a function of the mechanically generated turbulence but also turbulence generated by wind stress. Net heat transfer velocities were measured using Active Controlled Flux Technique and estimated from measurements of the latent and sensible heat fluxes combined with direct measurements of the bulk-skin temperature difference. Gas transfer velocities were determined by measuring the evasion rates of sulfur hexafluoride and helium. The length and velocity scales of the aqueous-phase turbulence were measured using a Digital Particle-Image Velocimetry system. These combined data sets are used to study how kG and kH depend on system turbulence, whether this dependence is consonant with that predicted using surface renewal, and whether there is a quantitative difference between mechanically generated turbulence and turbulence generated by the wind stress insofar as air-water exchange is concerned.

  2. Blowing in the Wind: I. Velocities of Chondrule-sized Particles in a Turbulent Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Hogan, Robert C.; Fonda, Mark (Technical Monitor)

    2003-01-01

    Small but macroscopic particles - chondrules, higher temperature mineral inclusions, metal grains, and their like - dominate the fabric of primitive meteorites. The properties of these constituents, and their relationship to the fine dust grains which surround them, suggest that they led an extended existence in a gaseous protoplanetary nebula prior to their incorporation into their parent primitive bodies. In this paper we explore in some detail the velocities acquired by such particles in a turbulent nebula. We treat velocities in inertial space (relevant to diffusion), velocities relative to the gas and entrained microscopic dust (relevant to accretion of dust rims), and velocities relative to each other (relevant to collisions). We extend previous work by presenting explicit, closed-form solutions for the magnitude and size dependence of these velocities in this important particle size regime, and compare these expressions with new numerical calculations. The magnitude and size dependence of these velocities have immediate applications to chondrule and CAI rimming by fine dust, and to their diffusion in the nebula, which we explore separately.

  3. Wind motor applications for transportation

    SciTech Connect

    Lysenko, G.P.; Grigoriev, B.V.; Karpin, K.B.

    1996-12-31

    Motion equation for a vehicle equipped with a wind motor allows, taking into account the drag coefficients, to determine the optimal wind drag velocity in the wind motor`s plane, and hence, obtain all the necessary data for the wind wheel blades geometrical parameters definition. This optimal drag velocity significantly differs from the flow drag velocity which determines the maximum wind motor power. Solution of the motion equation with low drag coefficients indicates that the vehicle speed against the wind may be twice as the wind speed. One of possible transportation wind motor applications is its use on various ships. A ship with such a wind motor may be substantially easier to steer, and if certain devices are available, may proceed in autonomous control mode. Besides, it is capable of moving within narrow fairways. The cruise speed of a sailing boat and wind-motored ship were compared provided that the wind velocity direction changes along a harmonic law with regard to the motion direction. Mean dimensionless speed of the wind-motored ship appears to be by 20--25% higher than that of a sailing boat. There was analyzed a possibility of using the wind motors on planet rovers in Mars or Venus atmospheric conditions. A Mars rover power and motor system has been assessed for the power level of 3 kW.

  4. Differential Velocity between Solar Wind Protons and Alpha Particles in Pressure Balance Structures

    NASA Technical Reports Server (NTRS)

    Yamauchi, Yohei; Suess, Steven T.; Steinberg, John T.; Sakurai, Takashi

    2004-01-01

    Pressure balance structures (PBSs) are a common high-plasma beta feature in high-latitude, high-speed solar wind. They have been proposed as remnants of coronal plumes. If true, they should reflect the observation that plumes are rooted in unipolar magnetic flux concentrations in the photosphere and are heated as oppositely directed flux is advected into and reconnects with the flux concentration. A minimum variance analysis (MVA) of magnetic discontinuities in PBSs showed there is a larger proportion of tangential discontinuities than in the surrounding high-speed wind, supporting the hypothesis that plasmoids or extended current sheets are formed during reconnection at the base of plumes. To further evaluate the character of magnetic field discontinuities in PBSs, differential streaming between alpha particles and protons is analyzed here for the same sample of PBSs used in the MVA. Alpha particles in high-speed wind generally have a higher radial flow speed than protons. However, if the magnetic field is folded back on itself, as in a large-amplitude Alfven wave, alpha particles will locally have a radial flow speed less than protons. This characteristic is used here to distinguish between folded back magnetic fields (which would contain rotational discontinuities) and tangential discontinuities using Ulysses high-latitude, high-speed solar wind data. The analysis indicates that almost all reversals in the radial magnetic field in PBSs are folded back field lines. This is found to also be true outside PBSs, supporting existing results for typical high-speed, high-latitude wind. There remains a small number of cases that appear not to be folds in the magnetic field and which may be flux tubes with both ends rooted in the Sun. The distinct difference in MVA results inside and outside PBSs remains unexplained.

  5. Differential Velocity Between Solar Wind Protons and Alpha Particles in Pressure Balance Structures

    NASA Technical Reports Server (NTRS)

    Yamauchi, Y.; Suess, S. T.; Steinberg, J. T.; Sakurai, T.

    2003-01-01

    Pressure balance structures (PBSs) are a common high plasma beta feature in high latitude, high speed solar wind. They have been proposed as remnants of coronal plumes. If true, they should reflect the observation that plumes are rooted in unipolar magnetic flux concentrations in the photosphere and are heated as oppositely directed flux is advected into and reconnects with the flux concentration. A minimum variance analysis (MVA) of magnetic discontinuities in PBSs showed there is a larger proportion of tangential discontinuities than in the surrounding high speed wind, supporting the hypothesis that plasmoids or extended current sheets are formed during reconnection at the base of plumes. To further evaluate the character of magnetic field discontinuities in PBSs, differential streaming between alpha particles and protons is analyzed here for the same sample of PBSs used in the MVA. Alpha particles in high speed wind generally have a higher radial flow speed than protons. However, if the magnetic field is folded back on itself, as in a large amplitude Alfven wave, alpha particles will locally have a radial flow speed less than protons. This characteristic is used here to distinguish between folded back magnetic fields (which would contain rotational discontinuities) and tangential discontinuities using Ulysses high latitude, high speed solar wind data. The analysis indicates that almost all reversals in the radial magnetic field in PBSs are folded back field lines. This is found to also be true outside PBSs, supporting existing results for typical high speed, high latitude wind. There remains a small number of cases that appear not to be folds in the magnetic field and which may be flux tubes with both ends rooted in the Sun. The distinct difference in MVA results inside and outside PBSs remains unexplained.

  6. A comparison of mesh-adaptive LES with wind tunnel data for flow past buildings: Mean flows and velocity fluctuations

    NASA Astrophysics Data System (ADS)

    Aristodemou, Elsa; Bentham, Tom; Pain, Christopher; Colvile, Roy; Robins, Alan; ApSimon, Helen

    2009-12-01

    In this paper we address two important aspects of micro-scale urban airflow model evaluation: (a) the identification of key flow features as dictated by the physics of the problem and as captured by the simulations, and (b) the comparison of important model output parameters (mean flows and fluctuations) with experimental data. A series of mesh-adaptive large eddy simulations (LES) was carried out for the study of air flows within two intersecting street canyons with varying building configurations. The novelty of the approach lies in the combination of LES with mesh adaptivity, which allows a variable-filter length and the implementation of an anisotropic eddy-viscosity model. Both coarse and fine-mesh simulations were carried out, using single and parallel-processor systems respectively. The simulations showed clearly that the expected flow patterns such as the street canyon recirculation and the street-mouth vortices, as well as the exchange of air flow at the street intersections, can readily be captured by the mesh-adaptive LES. In addition, the detailed comparisons of mean flows and fluctuations of the resolved velocity field with the measured data showed that the simulation results agreed well with the patterns and trends of the wind tunnel measurements. In most cases the finer-mesh simulations improved considerably the accuracy of the mean flows, especially for the symmetrical configuration. The improvement in the predicted fluctuations was less obvious, with several detector locations underpredicting the measured values, although the overall comparison was also satisfactory. The typical errors for the mean flows for all three building configurations were less than 30%, whilst for the velocity fluctuations less that 40%. Both the simulated means flows and turbulence levels were generally more accurate in the streets parallel to the wind (streamwise direction) than in the streets normal to the wind.

  7. Measuring air-sea gas-exchange velocities in a large-scale annular wind-wave tank

    NASA Astrophysics Data System (ADS)

    Mesarchaki, E.; Kräuter, C.; Krall, K. E.; Bopp, M.; Helleis, F.; Williams, J.; Jähne, B.

    2015-01-01

    In this study we present gas-exchange measurements conducted in a large-scale wind-wave tank. Fourteen chemical species spanning a wide range of solubility (dimensionless solubility, ? = 0.4 to 5470) and diffusivity (Schmidt number in water, Scw = 594 to 1194) were examined under various turbulent (u10 = 0.73 to 13.2 m s-1) conditions. Additional experiments were performed under different surfactant modulated (two different concentration levels of Triton X-100) surface states. This paper details the complete methodology, experimental procedure and instrumentation used to derive the total transfer velocity for all examined tracers. The results presented here demonstrate the efficacy of the proposed method, and the derived gas-exchange velocities are shown to be comparable to previous investigations. The gas transfer behaviour is exemplified by contrasting two species at the two solubility extremes, namely nitrous oxide (N2O) and methanol (CH3OH). Interestingly, a strong transfer velocity reduction (up to a factor of 3) was observed for the relatively insoluble N2O under a surfactant covered water surface. In contrast, the surfactant effect for CH3OH, the high solubility tracer, was significantly weaker.

  8. Lidar measurement of wind velocity turbulence spectra encountered by a rotating turbine blade

    SciTech Connect

    Hardesty, R.M.; Korrell, J.A.; Hall, F.F. Jr.

    1982-01-01

    A homodyne CO/sub 2/ lidar system beam was conically scanned around a horizontal axis to measure the wind speed and turbulence characteristics encountered by a rotating turbine blade. Turbulence spectra obtained from the scanning lidar differed considerably from those calculated from fixed-point anemometer measurements, showing a redistribution of energy from lower to higher frequencies. The differences appeared more pronounced during periods when the atmosphere was stable.

  9. Forecasting the velocity of quasi-stationary solar wind and the intensity of geomagnetic disturbances produced by it

    NASA Astrophysics Data System (ADS)

    Eselevich, V. G.; Fainshtein, V. G.; Rudenko, G. V.; Eselevich, M. V.; Kashapova, L. K.

    2009-04-01

    A brief review is given of contemporary approaches to solving the problem of medium-term forecast of the velocity of quasi-stationary solar wind (SW) and of the intensity of geomagnetic disturbances caused by it. At the present time, two promising models of calculating the velocity of quasi-stationary SW at the Earth’s orbit are realized. One model is the semi-empirical model of Wang-Sheeley-Arge (WSA) which allows one to calculate the dependence V( t) of SW velocity at the Earth’s orbit using measured values of the photospheric magnetic field. This model is based on calculation of the local divergence f S of magnetic field lines. The second model is semi-empirical model by Eselevich-Fainshtein-Rudenko (EFR). It is based on calculation in a potential approximation of the area of foot points on the solar surface of open magnetic tubes (sources of fast quasistationary SW). The new Bd-technology is used in these calculations, allowing one to calculate instantaneous distributions of the magnetic field above the entire visible surface of the Sun. Using predicted V( t) profiles, one can in EFR model calculate also the intensity of geomagnetic disturbances caused by quasi-stationary SW. This intensity is expressed through the K p index. In this paper the EFR model is discussed in detail. Some examples of epignosis and real forecast of V( t) and K p ( t) are discussed. A comparison of the results of applying these two models for the SW velocity forecasting is presented.

  10. The Low Velocity Wind from the Circumstellar Matter Around the B9V Star sigma Herculis

    E-print Network

    C. H. Chen; M. Jura

    2002-09-04

    We have obtained FUSE spectra of sigma Her, a nearby binary system, with a main sequence primary, that has a Vega-like infrared excess. We observe absorption in the excited fine structure lines C II* at 1037 A, N II* at 1085 A, and N II** at 1086 A that are blueshifted by as much as ~30 km/sec with respect to the star. Since these features are considerably narrower than the stellar lines and broader than interstellar features, the C II and N II are circumstellar. We suggest that there is a radiatively driven wind, arising from the circumstellar matter, rather than accretion as occurs around beta Pic, because of sigma Her's high luminosity. Assuming that the gas is liberated by collisions between parent bodies at 20 AU, the approximate distance at which blackbody grains are in radiative equilibrium with the star and at which 3-body orbits become unstable, we infer dM/dt ~ 6 * 10^-12 M_{sun}/yr. This wind depletes the minimum mass of parent bodies in less than the estimated age of the system.

  11. An atlas of monthly mean distributions of SSMI surface wind speed, AVHRR/2 sea surface temperature, AMI surface wind velocity, TOPEX/POSEIDON sea surface height, and ECMWF surface wind velocity during 1993

    NASA Technical Reports Server (NTRS)

    Halpern, D.; Fu, L.; Knauss, W.; Pihos, G.; Brown, O.; Freilich, M.; Wentz, F.

    1995-01-01

    The following monthly mean global distributions for 1993 are presented with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States (U.S.) Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the Advanced Very High Resolution Radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) satellite; 10-m height wind speed and direction estimated from the Active Microwave Instrument (AMI) on the European Space Agency (ESA) European Remote Sensing (ERS-1) satellite; sea surface height estimated from the joint U.S.-France Topography Experiment (TOPEX)/POSEIDON spacecraft; and 10-m height wind speed and direction produced by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of annual mean, monthly mean, and sampling distributions are displayed.

  12. A Study of the Coronal Non-thermal Velocity in Polar Regions During the Rise from Solar Minimum to Solar Maximum in Cycle 24

    NASA Astrophysics Data System (ADS)

    Harra, L.; Baker, D.; Edwards, S. J.; Hara, H.; Howe, R.; van Driel-Gesztelyi, L.

    2015-11-01

    We explore the changes in coronal non-thermal velocity ( V nt) measurements at the poles from solar minimum to solar maximum using Hinode EUV Imaging Spectrometer data. We find that although the intensity in the corona at the poles does tend to increase with the cycle, there are no significant changes in the V nt values. The locations of enhanced V nt values measured do not always have a counterpart in intensity, and they are sometimes located in weak emission regions. Unipolar magnetic streams, created through diffusion of the following polarity of the decaying active regions, slowly progress towards the poles. These streams are expected to be related to magnetic nulls as locations that indicate an increased likelihood for magnetic reconnection to occur. Through global potential field source-surface modelling, we determine how the number of nulls varied during the cycle and find that those that lie at < 1.1 solar radii vary significantly. We search for a correlation between the variation of the magnetic nulls and the V nt values, as it may be expected that with an increasing number of nulls, the V nt values in the corona increase as well. There is no correlation with the V nt values, however. This indicates that the magnetic structures that create the enhanced V nt behaviour are small-scale features and hence not easily measurable at the poles. Because they do not change during the solar cycle, they are likely to be created by a local dynamo. The variation of the upper range of V nt is reduced, which highlights that strongly dynamic behaviour is reduced as the solar maximum approaches. This is likely to be due to the reduced area of the polar coronal hole, which allows fewer opportunities for reconnection to occur between open and closed magnetic fields.

  13. A Study of the Coronal Non-thermal Velocity in Polar Regions During the Rise from Solar Minimum to Solar Maximum in Cycle 24

    NASA Astrophysics Data System (ADS)

    Harra, L.; Baker, D.; Edwards, S. J.; Hara, H.; Howe, R.; van Driel-Gesztelyi, L.

    2015-01-01

    We explore the changes in coronal non-thermal velocity (V nt) measurements at the poles from solar minimum to solar maximum using Hinode EUV Imaging Spectrometer data. We find that although the intensity in the corona at the poles does tend to increase with the cycle, there are no significant changes in the V nt values. The locations of enhanced V nt values measured do not always have a counterpart in intensity, and they are sometimes located in weak emission regions. Unipolar magnetic streams, created through diffusion of the following polarity of the decaying active regions, slowly progress towards the poles. These streams are expected to be related to magnetic nulls as locations that indicate an increased likelihood for magnetic reconnection to occur. Through global potential field source-surface modelling, we determine how the number of nulls varied during the cycle and find that those that lie at < 1.1 solar radii vary significantly. We search for a correlation between the variation of the magnetic nulls and the V nt values, as it may be expected that with an increasing number of nulls, the V nt values in the corona increase as well. There is no correlation with the V nt values, however. This indicates that the magnetic structures that create the enhanced V nt behaviour are small-scale features and hence not easily measurable at the poles. Because they do not change during the solar cycle, they are likely to be created by a local dynamo. The variation of the upper range of V nt is reduced, which highlights that strongly dynamic behaviour is reduced as the solar maximum approaches. This is likely to be due to the reduced area of the polar coronal hole, which allows fewer opportunities for reconnection to occur between open and closed magnetic fields.

  14. Crustal seismicity and the earthquake catalog maximum moment magnitudes (Mcmax) in stable continental regions (SCRs): correlation with the seismic velocity of the lithosphere

    USGS Publications Warehouse

    Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun

    2012-01-01

    A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (?VS) relative to the Preliminary Reference Earth Model (PREM). We compare ?VS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by ?VS?3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with ?VS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

  15. Transducer Shadowing Explains Observed Underestimates in Vertical Wind Velocity from Non-orthogonal Sonic Anemometers

    NASA Astrophysics Data System (ADS)

    Frank, J. M.; Massman, W. J.; Swiatek, E.; Zimmerman, H.; Ewers, B. E.

    2014-12-01

    Sonic anemometry is fundamental to all eddy-covariance studies of surface energy and ecosystem carbon and water balance. While recent studies have shown that some anemometers underestimate vertical wind, we hypothesize that this is caused by the lack of transducer shadowing correction in non-orthogonal models. We tested this in an experiment comparing three sonic anemometer designs: orthogonal (O), non-orthogonal (NO), and quasi-orthogonal (QO); using four models: K-probe (O) and A-probe (NO) (Applied Technologies, Inc.) and CSAT3 (NO) and CSAT3V (QO) (Campbell Scientific, Inc.). For each of a 12-week experiment at the GLEES AmeriFlux site, five instruments from a pool of twelve (three of each model) were randomly selected and located around a control (CSAT3); mid-week all but the control were re-mounted horizontally. We used Bayesian analysis to test differences between models in half-hour standard deviations (?u, ?v, ?w, and ?T), turbulent kinetic energy (TKE), and the ratio between vertical/horizontal TKE (VHTKE). The K-probe experiences horizontal transducer shadowing which is effectively corrected using an established wind-tunnel derived algorithm. We constructed shadow correction algorithms for the NO/QO anemometers by applying the K-probe function to each non-orthogonal transducer pair (SC1) as well as a stronger correction of twice the magnitude (SC2). While the partitioning of VHTKE was higher in O than NO/QO anemometers, the application of SC1 explained 45-60% of this discrepancy while SC2 overcorrected it. During the horizontal manipulation changes in the NO/QO were moderate in ?u (4-8% decrease), very strong in ?v (9-11% decrease), and minimal in ?w (-3 to 4% change) while only ?u measurements changed (3% decrease) with the K-probe. These changes were predicted by both shadow correction algorithms, with SC2 better explaining the data. This confirms our hypothesis while eliminating others that attribute the underestimate to a systematic bias in the w-axis. All flux sites that employ these non-orthogonal sonic anemometers will underestimate vertical fluxes of mass and energy, but since 1) the correction is a function both of sensor geometry and local wind and 2) the true shadow correction function is unknown at this time, the actual underestimate is uncertain and will vary between sites.

  16. Remote sensing of wind velocity and strength of refractive turbulence using a two-spatial-filter receiver.

    PubMed

    Hanson, S G; Churnside, J H; Wilson, J J

    1994-09-01

    Wind velocity across an optical path and refractive turbulence strength can be measured by observing a light source through the atmosphere with a receiver that contains two spatial filters. The frequency of the detected signal gives the transverse velocity of the turbulent structure, whereas signal intensity is proportional to refractive turbulence strength. The size of turbulent eddies that produce signals is determined by the optical setup. The position along the detector's field of view at which the measurement is made depends on the separation of the filters, and profiles can be made by varying the separation and using a telescope. The system requires longer integration times than one which uses a spatial filter at each end of the optical path, but it has the advantage of being able to use a natural source such as the Sun or a planet. An analysis of the system is presented along with numerical simulations and results from a short-range (several meters) laboratory experiment. The analysis assumes a single layer of refractive turbulence. Scales of the refractive turbulence in the inertial subrange from 5 to 20 cm will be of primary interest for this method. PMID:20935989

  17. Full field flow visualization and computer-aided velocity measurements in a bank of cylinders in a wind tunnel

    NASA Technical Reports Server (NTRS)

    Braun, M. J.; Canacci, V. A.; Russell, L. M.

    1992-01-01

    The full field flow tracking (FFFT) method that is presented in this paper uses a laser-generated, mechanically strobed planar sheet of light, a low luminosity TV camera coupled with a long distance microscope, and a computer-controlled video recorder to study nonintrusively and qualitatively the flow structures in a bank of cylinders that are placed in a wind tunnel. This setup simulates an upscale version of the geometry of internal cooling passageways characteristic of small air-cooled radial turbines. The qualitative images supplied by the FFFT system are processed by means of a computer-integrated image quantification (CIIQ) method into quantitative information, trajectories and velocities, that describe the flow upstream of and within the bank of cylinders. The tracking method is Lagrangian in concept, and permits identification and tracking of the same particle, thus facilitating construction of time dependent trajectories and the calculation of true velocities and accelerations. The error analysis evaluates the accuracy with which the seed particles follow the flow and the errors incurred during the quantitative processing of the raw data derived from the FFFT/CIIQ method.

  18. Contributions of the secondary jet to the maximum tangential velocity and to the collection efficiency of the fixed guide vane type axial flow cyclone dust collector

    NASA Astrophysics Data System (ADS)

    Ogawa, Akira; Anzou, Hideki; Yamamoto, So; Shimagaki, Mituru

    2015-11-01

    In order to control the maximum tangential velocity V?m(m/s) of the turbulent rotational air flow and the collection efficiency ?c (%) using the fly ash of the mean diameter XR50=5.57 µm, two secondary jet nozzles were installed to the body of the axial flow cyclone dust collector with the body diameter D1=99mm. Then in order to estimate V?m (m/s), the conservation theory of the angular momentum flux with Ogawa combined vortex model was applied. The comparisons of the estimated results of V?m(m/s) with the measured results by the cylindrical Pitot-tube were shown in good agreement. And also the estimated collection efficiencies ?cth (%) basing upon the cut-size Xc (µm) which was calculated by using the estimated V? m(m/s) and also the particle size distribution R(Xp) were shown a little higher values than the experimental results due to the re-entrainment of the collected dust. The best method for adjustment of ?c (%) related to the contribution of the secondary jet flow is principally to apply the centrifugal effect ?c (1). Above stated results are described in detail.

  19. Investigations of the air flow velocity field structure above the wavy surface under severe wind conditions by particle image velosimetry technique.

    NASA Astrophysics Data System (ADS)

    Troitskaya, Yuliya; Kandaurov, Alexander; Sergeev, Daniil; Ermakova, Olga

    2013-04-01

    Preliminary experiments devoted to measuring characteristics of the air flow above the waved water surface for the wide range of wind speeds were performed with the application of modified Particle Image Velosimetry (PIV) technique. Experiments were carried out at the Wind - wave stratified flume of IAP RAS (length 10 °, cross section of air channel 0.4×0.4 m) for four different axial wind speeds: 8.7, 13.5, 19 and 24 m/s, corresponding to the equivalent 10-m wind speeds 15, 20, 30 40 m/s correspondingly. Intensive wave breaking with forming foam crest and droplets generations was occurred for two last wind conditions. The modified PIV-method based on the use of continuous-wave (CW) laser illumination of the airflow seeded by tiny particles and with highspeed video. Spherical 20 ?m polyamide particles with density 1.02 g/sm3 and inertial time 7•10-3 s were used for seeding airflow with special injecting device. Green (532 nm) CW laser with 4 Wt output power was used as a source for light sheet. High speed digital camera Videosprint was used for taking visualized air flow images with the frame rate 2000 Hz s and exposure time 10 ms Combination including iteration Canny method [1] for obtaining curvilinear surface from the images in the laser sheet view and contact measurements of surface elevation by wire wave gauge installed near the border of working area for the surface wave profile was used. Then velocity air flow field was retrieved by PIV images processing with adaptive cross-correlation method on the curvilinear grid following surface wave profile. The mean wind velocity profiles were retrieved by averaging over obtained ensembles of wind velocity field realizations and over a wave period even for the cases of intensive wave breaking and droplets generation. To verify the PIV method additional measurements of mean velocity profiles over were carried out by the contact method using the Pitot tube. In the area of overlap, wind velocity profiles measured by both method were in a good agreement. The application of PIV method enabled us measuring wind velocity profiles much closer to water surface than in the case of contact method. As a result there exists the logarithmic parts in velocity profiles, which yield turbulent momentum flux from the slope and also the equivalent 10-m wind speed and the surface drag coefficient. It was shown that similarly to [2] the surface drag coefficient tends to saturate at wind velocities exceeding 25 m/s. The decrease of the water surface drag coefficient with wind velocity increase was not observed. This work was supported by RFBR (project 11-05-12047-ofi-m, 13-05-00865-a, 12-05-33070 mol-a-ved, 12-05-31435 mol-a, 12-05-01064-a). References 1. Canny, J. A. Computational approach to edge detection/ J.A. Canny// IEEE Trans. Pattern Analysis and Machine Intelligence. - 1986. - V. 8(6). - P. 679-698.. 2. Troitskaya, Y. I., D. A. Sergeev, A. A. Kandaurov, G. A. Baidakov, M. A. Vdovin, and V. I. Kazakov Laboratory and theoretical modeling of air-sea momentum transfer under severe wind conditions J.Geophys. Res., 117, C00J21, doi:10.1029/2011JC007778.

  20. On the prediction of threshold friction velocity of wind erosion using soil reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Junran; Flagg, Cody; Okin, Gregory S.; Painter, Thomas H.; Dintwe, Kebonye; Belnap, Jayne

    2015-12-01

    Current approaches to estimate threshold friction velocity (TFV) of soil particle movement, including both experimental and empirical methods, suffer from various disadvantages, and they are particularly not effective to estimate TFVs at regional to global scales. Reflectance spectroscopy has been widely used to obtain TFV-related soil properties (e.g., moisture, texture, crust, etc.), however, no studies have attempted to directly relate soil TFV to their spectral reflectance. The objective of this study was to investigate the relationship between soil TFV and soil reflectance in the visible and near infrared (VIS-NIR, 350-2500 nm) spectral region, and to identify the best range of wavelengths or combinations of wavelengths to predict TFV. Threshold friction velocity of 31 soils, along with their reflectance spectra and texture were measured in the Mojave Desert, California and Moab, Utah. A correlation analysis between TFV and soil reflectance identified a number of isolated, narrow spectral domains that largely fell into two spectral regions, the VIS area (400-700 nm) and the short-wavelength infrared (SWIR) area (1100-2500 nm). A partial least squares regression analysis (PLSR) confirmed the significant bands that were identified by correlation analysis. The PLSR further identified the strong relationship between the first-difference transformation and TFV at several narrow regions around 1400, 1900, and 2200 nm. The use of PLSR allowed us to identify a total of 17 key wavelengths in the investigated spectrum range, which may be used as the optimal spectral settings for estimating TFV in the laboratory and field, or mapping of TFV using airborne/satellite sensors.

  1. On the prediction of threshold friction velocity of wind erosion using soil reflectance spectroscopy

    USGS Publications Warehouse

    Li, Junran; Flagg, Cody B.; Okin, Gregory S.; Painter, Thomas H.; Dintwe, Kebonye; Belnap, Jayne

    2015-01-01

    Current approaches to estimate threshold friction velocity (TFV) of soil particle movement, including both experimental and empirical methods, suffer from various disadvantages, and they are particularly not effective to estimate TFVs at regional to global scales. Reflectance spectroscopy has been widely used to obtain TFV-related soil properties (e.g., moisture, texture, crust, etc.), however, no studies have attempted to directly relate soil TFV to their spectral reflectance. The objective of this study was to investigate the relationship between soil TFV and soil reflectance in the visible and near infrared (VIS–NIR, 350–2500 nm) spectral region, and to identify the best range of wavelengths or combinations of wavelengths to predict TFV. Threshold friction velocity of 31 soils, along with their reflectance spectra and texture were measured in the Mojave Desert, California and Moab, Utah. A correlation analysis between TFV and soil reflectance identified a number of isolated, narrow spectral domains that largely fell into two spectral regions, the VIS area (400–700 nm) and the short-wavelength infrared (SWIR) area (1100–2500 nm). A partial least squares regression analysis (PLSR) confirmed the significant bands that were identified by correlation analysis. The PLSR further identified the strong relationship between the first-difference transformation and TFV at several narrow regions around 1400, 1900, and 2200 nm. The use of PLSR allowed us to identify a total of 17 key wavelengths in the investigated spectrum range, which may be used as the optimal spectral settings for estimating TFV in the laboratory and field, or mapping of TFV using airborne/satellite sensors.

  2. Traveling solar-wind bulk-velocity fluctuations and their effects on electron heating in the heliosphere

    NASA Astrophysics Data System (ADS)

    Fahr, Hans J.; Chashei, Igor V.; Verscharen, Daniel

    2014-11-01

    Ambient plasma electrons undergo strong heating in regions associated with compressive bulk-velocity jumps ?U that travel through the interplanetary solar wind. The heating is generated by their specific interactions with the jump-inherent electric fields. After this energy gain is thermalized by the shock passage through the operation of the Buneman instability, strong electron heating occurs that substantially influences the radial electron temperature profile. We previously studied the resulting electron temperature assuming that the amplitude of the traveling velocity jump remains constant with increasing solar distance. Now we aim at a more consistent view, describing the change in jump amplitude with distance that is caused by the heated electrons. We describe the reduction of the jump amplitude as a result of the energy expended by the traveling jump structure. We consider three effects: energy loss due to heating of electrons, energy loss due to work done against the pressure gradient of the pick-up ions, and an energy gain due to nonlinear jump steepening. Taking these effects into account, we show that the decrease in jump amplitude with solar distance is more pronounced when the initial jump amplitude is higher in the inner solar system. Independent of the initial jump amplitude, it eventually decreases with increasing distance to a value of about ?U/U ? 0.1 at the position of the heliospheric termination shock, where ?U is the jump amplitude, and U is the average solar-wind bulk velocity.The electron temperature, on the other hand, is strongly correlated with the initial jump amplitude and leads to electron temperatures between 6000 K and 20 000 K at distances beyond 50 AU. We compare our results with in situ measurements of the electron-core temperature from the Ulysses spacecraft in the plane of the ecliptic for 1.5 AU ? r ? 5 AU, where r is the distance from the Sun. Our results agree very well with these observations, which corroborates our extrapolated predictions beyond r = 5 AU.

  3. Ground and space based cloud-top wind velocities using CFHT/ESPaDOnS (Doppler velocimetry) and VEx/VIRTIS (cloud tracking) coordinated measurements

    NASA Astrophysics Data System (ADS)

    Machado, P.; Widemann, T.; Peralta, J.; Luz, D.

    2015-10-01

    We will present wind velocity results based in the measurements of the horizontal wind field at the cloud top level of the atmosphere of Venus, near 70 km altitude. Our aim is contribute to the characterisation of the zonal and meridional wind latitudinal profiles on hour and day-timescales. This will be done by tracking Doppler shift of solar and CO2 lines over the dayside hemisphere in coordination with ESA's Venus Express orbiter. Our observations measured winds at cloud tops at latitudes 60°S-60°N, while Vex/VIRTIS privileged southern latitudes poleward of 45°S. This coor- dination effort intended to provide a combined monitoring of short-term changes of wind amplitude and directions with extensive spatial coverage.

  4. Determination of the mass loss rate and the terminal velocity of stellar winds. I Genetic algorithm for automatic line profile fitting

    E-print Network

    Georgiev, L

    2005-01-01

    Terminal wind velocity and mass loss rate are the most fundamental parameters of stellar winds. Unfortunately, their determination calls for high resolution spectroscopy in a range of wavelengths spanning from the ultraviolet to the infrared. For weak and/or distant objects, this becomes unfeasible. Nevertheless, it is possible to obtain an accurate estimate of these parameters through a simplified study of the formation processes of resonant lines which show P Cyg profiles. In this case, the line profile is a complex function of 6 parameters, with the radiative transport treatment becoming relatively inexpensive. However, preforming a 6 dimensional parameter fit raises a number of problems if one seeks an objective and automatic procedure to yield the optimal values, from which wind velocities and mass loss rates can be estimated. Useing a Likelihood function to construct a well defined statistical estimator of the goodness of fit which corresponds to a given model, we turn to a genetic algorithm through whi...

  5. Simulation comparison of a decoupled longitudinal control system and a velocity vector control wheel steering system during landings in wind shear

    NASA Technical Reports Server (NTRS)

    Kimball, G., Jr.

    1980-01-01

    A simulator comparison of the velocity vector control wheel steering (VCWS) system and a decoupled longitudinal control system is presented. The piloting task was to use the electronic attitude direction indicator (EADI) to capture and maintain a 3 degree glide slope in the presence of wind shear and to complete the landing using the perspective runway included on the EADI. The decoupled control system used constant prefilter and feedback gains to provide steady state decoupling of flight path angle, pitch angle, and forward velocity. The decoupled control system improved the pilots' ability to control airspeed and flight path angle during the final stages of an approach made in severe wind shear. The system also improved their ability to complete safe landings. The pilots preferred the decoupled control system in severe winds and, on a pilot rating scale, rated the approach and landing task with the decoupled control system as much as 3 to 4 increments better than use of the VCWS system.

  6. Monte Carlo studies of ocean wind vector measurements by SCATT: Objective criteria and maximum likelihood estimates for removal of aliases, and effects of cell size on accuracy of vector winds

    NASA Technical Reports Server (NTRS)

    Pierson, W. J.

    1982-01-01

    The scatterometer on the National Oceanic Satellite System (NOSS) is studied by means of Monte Carlo techniques so as to determine the effect of two additional antennas for alias (or ambiguity) removal by means of an objective criteria technique and a normalized maximum likelihood estimator. Cells nominally 10 km by 10 km, 10 km by 50 km, and 50 km by 50 km are simulated for winds of 4, 8, 12 and 24 m/s and incidence angles of 29, 39, 47, and 53.5 deg for 15 deg changes in direction. The normalized maximum likelihood estimate (MLE) is correct a large part of the time, but the objective criterion technique is recommended as a reserve, and more quickly computed, procedure. Both methods for alias removal depend on the differences in the present model function at upwind and downwind. For 10 km by 10 km cells, it is found that the MLE method introduces a correlation between wind speed errors and aspect angle (wind direction) errors that can be as high as 0.8 or 0.9 and that the wind direction errors are unacceptably large, compared to those obtained for the SASS for similar assumptions.

  7. VELOCITY-SHEAR-INDUCED MODE COUPLING IN THE SOLAR ATMOSPHERE AND SOLAR WIND: IMPLICATIONS FOR PLASMA HEATING AND MHD TURBULENCE

    SciTech Connect

    Hollweg, Joseph V.; Chandran, Benjamin D. G.; Kaghashvili, Edisher Kh. E-mail: ekaghash@aer.com

    2013-06-01

    We analytically consider how velocity shear in the corona and solar wind can cause an initial Alfven wave to drive up other propagating signals. The process is similar to the familiar coupling into other modes induced by non-WKB refraction in an inhomogeneous plasma, except here the refraction is a consequence of velocity shear. We limit our discussion to a low-beta plasma, and ignore couplings into signals resembling the slow mode. If the initial Alfven wave is propagating nearly parallel to the background magnetic field, then the induced signals are mainly a forward-going (i.e., propagating in the same sense as the original Alfven wave) fast mode, and a driven signal propagating like a forward-going Alfven wave but polarized like the fast mode; both signals are compressive and subject to damping by the Landau resonance. For an initial Alfven wave propagating obliquely with respect to the magnetic field, the induced signals are mainly forward- and backward-going fast modes, and a driven signal propagating like a forward-going Alfven wave but polarized like the fast mode; these signals are all compressive and subject to damping by the Landau resonance. A backward-going Alfven wave, thought to be important in the development of MHD turbulence, is also produced, but it is very weak. However, we suggest that for oblique propagation of the initial Alfven wave the induced fast-polarized signal propagating like a forward-going Alfven wave may interact coherently with the initial Alfven wave and distort it at a strong-turbulence-like rate.

  8. Interpretation of the cross-correlation function of ACE and STEREO solar wind velocities using a global MHD Model

    NASA Astrophysics Data System (ADS)

    Riley, Pete; Luhmann, J.; Opitz, A.; Linker, J. A.; Mikic, Z.

    2010-11-01

    Measurements from the ACE and STEREO A and B spacecraft are allowing an unprecedented view of the structure of the three-dimensional heliosphere. One aspect of this is the degree to which the measurements at one spacecraft correlate with those at the other. We have computed the cross-correlation functions (CCFs) for all three combinations of ACE and STEREO A and B in situ observations of the bulk solar wind velocity as the spacecraft moved progressively farther away from one another. Our results confirm previous studies that the phase lag between the signals becomes linearly larger with time. However, we have identified two intervals where this appears to break down. During these "lulls," the CCF reveals a phase lag considerably less than that which would be predicted based only on the angular separation of the spacecraft. We modeled the entire STEREO time period using a global MHD model to investigate the cause for these "lulls." We find that a combination of time-dependent evolution of the streams as well as spatial inhomogeneities, due to the latitudinal separation of the spacecraft, are sufficient to explain them.

  9. Response of the radiation belt electron flux to the solar wind velocity: Parameterization by radial distance and energy

    NASA Astrophysics Data System (ADS)

    Vassiliadis, D.

    2008-11-01

    The solar wind velocity is the primary driver of the electron flux variability in Earth's radiation belts. The response of the logarithmic flux ("log-flux") to this driver has been determined at the geosynchronous orbit and at a fixed energy [Baker, D.N., McPherron, R.L., Cayton, T.E., Klebesadel, R.W., 1990. Linear prediction filter analysis of relativistic electron properties at 6.6 RE. Journal of Geophysical Research 95(A9), 15,133-15,140) and as a function of L shell and fixed energy [Vassiliadis, D., Klimas, A.J., Kanekal, S.G., Baker, D.N., Weigel, R.S., 2002. Long-term average, solar-cycle, and seasonal response of magnetospheric energetic electrons to the solar wind speed. Journal of Geophysical Research 107, doi:10.1029/2001JA000506). In this paper we generalize the response model as a function of particle energy (0.8-6.4 MeV) using POLAR HIST measurements. All three response peaks identified earlier figure prominently in the high-altitude POLAR measurements. The positive response around the geosynchronous orbit is peak P1 ([tau]=2±1 d; L=5.8±0.5; E=0.8-6.4 MeV), associated with high-speed, low-density streams and the ULF wave activity they produce. Deeper in the magnetosphere, the response is dominated by a positive peak P0 (0±1 d; 2.9±0.5RE; 0.8-1.1 MeV), of a shorter duration and producing lower-energy electrons. The P0 response occurs during the passage of geoeffective structures containing high IMF and high-density parts, such as ICMEs and other mass ejecta. Finally, the negative peak V1 (0±0.5 d; 5.7±0.5RE; 0.8-6.4 MeV) is associated with the "Dst effect" or the quasiadiabatic transport produced by ring-current intensifications. As energies increase, the P1 and V1 peaks appear at lower L, while the Dst effect becomes more pronounced in the region L<3. The P0 effectively disappears for E>1.6 MeV because of low statistics, although it is evident in individual events. The continuity of the response across radial and energy scales supports the earlier hypothesis that each of the three modes corresponds to a qualitatively different type of large-scale electron acceleration and transport.

  10. Comparison of wind velocity in thunderstorms determined from measurements by a ground-based Doppler radar and an F-106B airplane

    NASA Technical Reports Server (NTRS)

    Usry, J. W.; Dunham, R. E., Jr.; Lee, J. T.

    1985-01-01

    As a part of the NASA Storm Hazards Program, the wind velocity in several thunderstorms was measured by an F-106B instrumented airplane and a ground-based Doppler radar. The results of five airplane penetrations of two storms in 1980 and six penetrations of one storm in 1981 are given. Comparisons were made between the radial wind velocity components measured by the radar and the airplane. The correlation coefficients for the 1980 data and part of the 1981 data were 0.88 and 0.78, respectively. It is suggested that larger values for these coefficients may be obtained by improving the experimental technique and in particular by slaving the radar to track the airplane during such tests.

  11. EnKF OSSE Experiments Assessing the Impact of HIRAD Wind Speed and HIWRAP Radial Velocity Data on Analysis of Hurricane Karl (2010)

    NASA Technical Reports Server (NTRS)

    Albers, Cerese; Sippel, Jason A.; Braun, Scott A.; Miller, Timothy

    2012-01-01

    Previous studies (e.g., Zhang et al. 2009, Weng et al. 2011) have shown that radial velocity data from airborne and ground-based radars can be assimilated into ensemble Kalman filter (EnKF) systems to produce accurate analyses of tropical cyclone vortices, which can reduce forecast intensity error. Recently, wind speed data from SFMR technology has also been assimilated into the same types of systems and has been shown to improve the forecast intensity of mature tropical cyclones. Two instruments that measure these properties were present during the NASA Genesis and Rapid Intensification Processes (GRIP) field experiment in 2010 which sampled Hurricane Karl, and will next be co-located on the same aircraft for the subsequent NASA HS3 experiment. The High Altitude Wind and Rain Profiling Radar (HIWRAP) is a conically scanning Doppler radar mounted upon NASAs Global Hawk unmanned aerial vehicle, and the usefulness of its radial velocity data for assimilation has not been previously examined. Since the radar scans from above with a fairly large fixed elevation angle, it observes a large component of the vertical wind, which could degrade EnKF analyses compared to analyses with data taken from lesser elevation angles. The NASA Hurricane Imaging Radiometer (HIRAD) is a passive microwave radiometer similar to SFMR, and measures emissivity and retrieves hurricane surface wind speeds and rain rates over a much wider swath. Thus, this study examines the impact of assimilating simulated HIWRAP radial velocity data into an EnKF system, simulated HIRAD wind speed, and HIWRAP+HIRAD with the Weather Research and Forecasting (WRF) model and compares the results to no data assimilation and also to the Truth from which the data was simulated for both instruments.

  12. Solar Wind Halo Formation by the Scattering of the Strahl via Direct Cluster/PEACE Observations of the 3D Velocity Distribution Function

    NASA Technical Reports Server (NTRS)

    Figueroa-Vinas, Adolfo; Gurgiolo, Chris A.; Nieves-Chinchilla, Teresa; Goldstein, Melvyn L.

    2010-01-01

    It has been suggested by a number of authors that the solar wind electron halo can be formed by the scattering of the strahl. On frequent occasions we have observed in electron angular skymaps (Phi/Theta-plots) of the electron 3D velocity distribution functions) a bursty-filament of particles connecting the strahl to the solar wind core-halo. These are seen over a very limited energy range. When the magnetic field is well off the nominal solar wind flow direction such filaments are inconsistent with any local forces and are probably the result of strong scattering. Furthermore, observations indicates that the strahl component is frequently and significantly anisotropic (Tper/Tpal approx.2). This provides a possible free energy source for the excitation of whistler waves as a possible scattering mechanism. The empirical observational evidence between the halo and the strahl suggests that the strahl population may be, at least in part, the source of the halo component.

  13. Stellar Winds Geoffrey V. Bicknell Stellar Winds

    E-print Network

    Bicknell, Geoff

    Stellar Winds © Geoffrey V. Bicknell Stellar Winds vw Star #12;Astrophysical Gas Dynamics: Stellar Winds 2/66 1 Characteristics of stellar winds Solar wind Velocity at earth's orbit: (1) Density: (2: Stellar Winds 3/66 Mass flux (spherically symmetric wind): (5) Other stars Red giants: O&B type stars

  14. Simultaneous measurements of particle backscattering and extinction coefficients and wind velocity by lidar with a Mach-Zehnder interferometer: principle of operation and performance assessment.

    PubMed

    Bruneau, Didier; Pelon, Jacques

    2003-02-20

    The development of remote-sensing instruments that can be used to monitor several parameters at the same time is important for the study of complex processes such as those that control climate and environment. In this paper the performance of a new concept of lidar receiver that allows for the direct measurement of aerosol and cloud optical properties simultaneously with wind velocity is investigated. This receiver uses a Mach-Zehnder interferometer. Two different configurations, either with four photometric output channels or with fringe imaging on a multichannel detector, are studied. Analytical expressions of the statistical errors are given under the assumption of Gaussian signal spectra. It is shown that similar accuracies can be achieved for both configurations. Performance modeling of the retrieval of semitransparent cloud optical scattering properties and wind velocity was done at different operation wavelengths for a Nd:YAG laser source. Results for such a lidar system onboard an aircraft flying at an altitude of 12 km show that for semitransparent clouds the best results were obtained at 355 nm, with relative standard deviations of 0.5% and 5% for the backscatter and extinction coefficients, respectively, together with a velocity accuracy of 0.2 ms(-1). The accuracy of optical properties retrieved for boundary layer aerosols are comparable, whereas the velocity accuracy is decreased to 1 ms(-1). Finally, an extrapolation to a large 355-nm spaceborne lidar shows accuracies in the range from 2.5% to 5% for the backscatter coefficient and from 10% to 15% for the extinction coefficient together with a vertical wind speed accuracy of better than 0.5 ms(-1) for semitransparent clouds and boundary layer, with a vertical resolution of 500 m and a 100 shot averaging. PMID:12617228

  15. WIND VELOCITIES AND SAND FLUXES IN MESQUITE DUNE-LANDS IN THE NORTHERN CHIHUAHUAN DESERT: A COMPARISON BETWEEN FIELD MEASUREMENTS AND THE QUIC (QUICK URBAN AND INDUSTRIAL COMPLEX) MODEL

    EPA Science Inventory

    The poster shows comparisons of wind velocities and sand fluxes between field measurements and a computer model, called QUIC (Quick Urban & Industrial Complex). The comparisons were made for a small desert region in New Mexico.

  16. The velocity and the density spectrum of the solar wind from simultaneous three-frequency IPS observations

    NASA Technical Reports Server (NTRS)

    Scott, S. L.; Rickett, B. J.; Armstrong, J. W.

    1983-01-01

    Density inhomogeneities in the solar wind cause fluctuations regarding the emission of small diameter radio sources. Such fluctuations are called interplanetary scintillation (IPS). IPS has been studied to obtain information on both the solar wind and on the radio sources. In the present investigation it is attempted to extract information about the solar wind from simultaneous IPS observations at three radio frequencies and a single antenna. Data were recorded at frequencies of 270 MHz, 340 MHz, and 470 MHz on a 91 m telescope. Five different radio sources were observed. The observations are compared with theoretical predictions for spectra, cross-spectra, and cross-correlations using weak scattering theory and various models for the wavenumber spectrum of density inhomogeneities in the solar wind. Good fits are obtained over the observed wavenumbers to a spectrum modeled as a power law.

  17. MACS, An Instrument and a Methodology for Simultaneous and Global Measurements of the Coronal Electron Temperature and the Solar Wind Velocity on the Solar Corona

    NASA Technical Reports Server (NTRS)

    Reginald, Nelson L.

    2000-01-01

    In Cram's theory for the formation of the K-coronal spectrum he observed the existence of temperature sensitive anti-nodes, which were separated by temperature insensitive nodes, at certain wave-lengths in the K-coronal spectrum. Cram also showed these properties were remarkably independent of altitude above the solar limb. In this thesis Cram's theory has been extended to incorporate the role of the solar wind in the formation of the K-corona, and we have identified both temperature and wind sensitive intensity ratios. The instrument, MACS, for Multi Aperture Coronal Spectrometer, a fiber optic based spectrograph, was designed for global and simultaneous measurements of the thermal electron temperature and the solar wind velocity in the solar corona. The first ever experiment of this nature was conducted in conjunction with the total solar eclipse of 11 August 1999 in Elazig, Turkey. Here twenty fiber optic tips were positioned in the focal plane of the telescope to observe simultaneously at many different latitudes and two different radial distances in the solar corona. The other ends were vertically stacked and placed at the primary focus of the spectrograph. By isolating the K-coronal spectrum from each fiber the temperature and the wind sensitive intensity ratios were calculated.

  18. A theory of local and global processes which affect solar wind electrons. 1: The origin of typical 1 AU velocity distribution functions: Steady state theory

    NASA Technical Reports Server (NTRS)

    Scudder, J. D.

    1978-01-01

    A detailed first principle kinetic theory for electrons which is neither a classical fluid treatment nor an exospheric calculation is presented. This theory illustrates the global and local properties of the solar wind expansion that shape the observed features of the electron distribution function, such as its bifurcation, its skewness and the differential temperatures of the thermal and suprathermal subpopulations. Coulomb collisions are substantial mediators of the interplanetary electron velocity distribution function and they place a zone for a bifurcation of the electron distribution function deep in the corona. The local cause and effect precept which permeates the physics of denser media is modified for electrons in the solar wind. The local form of transport laws and equations of state which apply to collision dominated plasmas are replaced with global relations that explicitly depend on the relative position of the observer to the boundaries of the system.

  19. Wind emission of OB supergiants and the influence of clumping

    E-print Network

    Michaela Kraus; Jiri Kubat; Jiri Krticka

    2007-08-06

    The influence of the wind to the total continuum of OB supergiants is discussed. For wind velocity distributions with \\beta > 1.0, the wind can have strong influence to the total continuum emission, even at optical wavelengths. Comparing the continuum emission of clumped and unclumped winds, especially for stars with high \\beta values, delivers flux differences of up to 30% with maximum in the near-IR. Continuum observations at these wavelengths are therefore an ideal tool to discriminate between clumped and unclumped winds of OB supergiants.

  20. a New Pattern Recognition Technique, with AN Example of Locating Fronts in Model Output and AN Example of Identifying Incorrect Velocities in Doppler Wind Profiler Data

    NASA Astrophysics Data System (ADS)

    Fine, Steven S.

    A statistical pattern recognition technique called Independent Rules with Empirical Weights (IREW) is described. IREW has several strengths, such as fast execution, small storage requirements, and incremental learning, that can make the technique useful for many meteorological pattern recognition problems. A weakness of IREW is that it may not recognize complex patterns as well as more sophisticated pattern recognition techniques do. IREW analyzes data by using a derivative of Bayes' rule to multiplicatively combine the influence of predictors. The weight assigned to each predictor is determined empirically from a training data set containing the data and verifications for multiple cases. IREW uses several methods to select useful subsets of a large set of predictors. The objective identification of surface fronts in Nested Grid Model forecasts is described to illustrate how IREW can be applied to a typical pattern recognition problem. The work consisted of identifying factors related to fronts and using some of those factors to make analyses. Given 27,000 predictors, IREW selected many that meteorologists associate with fronts. IREW's analyses were compared to subjective analyses for seven test cases. In this limited test, IREW performed similarly to meteorologists in terms of the number of grid points correctly classified as frontal or non-frontal. The identification of incorrect velocities in Doppler wind profiler data is also described. This work further illustrates IREW's usefulness and also illustrates the feasibility of correcting profiles in real time. IREW was able to correctly classify many of the velocities that a meteorologist considered to be incorrect, but for some cases IREW also classified as incorrect many velocities that the meteorologist considered to be correct. The results of a composite technique, which included IREW, for identifying and correcting incorrect velocities are also presented. The composite technique required two-tenths of a second of computation time on a microcomputer to analyze one profile, and the technique noticeably reduced the magnitude of errors in strongly contaminated profiles without greatly increasing the errors in most of the reliable profiles.

  1. X-ray high-resolution spectroscopy reveals feedback in a Seyfert galaxy from an ultra fast wind with complex ionization and velocity structure

    E-print Network

    Longinotti, Anna Lia; Guainazzi, Matteo; Giroletti, Marcello; Panessa, Francesca; Costantini, Elisa; Lleo, Maria Santos; Rodriguez-Pascual, Pedro

    2015-01-01

    Winds outflowing from Active Galactic Nuclei (AGNs) may carry significant amount of mass and energy out to their host galaxies. In this paper we report the detection of a sub-relativistic outflow observed in the Narrow Line Seyfert 1 Galaxy IRAS17020+4544 as a series of absorption lines corresponding to at least 5 absorption components with an unprecedented wide range of associated column densities and ionization levels and velocities in the range of 23,000-33,000 km/s, detected at X-ray high spectral resolution (E/Delta E ~1000) with the ESA's observatory XMM-Newton. The charge states of the material constituting the wind clearly indicate a range of low to moderate ionization states in the outflowing gas and column densities significantly lower than observed in highly ionized ultra fast outflows. We estimate that at least one of the outflow components may carry sufficient energy to substantially suppress star formation, and heat the gas in the host galaxy. IRAS17020+4544 provides therefore an interesting exa...

  2. X-Ray High-resolution Spectroscopy Reveals Feedback in a Seyfert Galaxy from an Ultra-fast Wind with Complex Ionization and Velocity Structure

    NASA Astrophysics Data System (ADS)

    Longinotti, A. L.; Krongold, Y.; Guainazzi, M.; Giroletti, M.; Panessa, F.; Costantini, E.; Santos-Lleo, M.; Rodriguez-Pascual, P.

    2015-11-01

    Winds outflowing from active galactic nuclei (AGNs) may carry significant amounts of mass and energy out to their host galaxies. In this paper we report the detection of a sub-relativistic outflow observed in the narrow line Seyfert 1 galaxy IRAS 17020+4544 as a series of absorption lines corresponding to at least five absorption components with an unprecedented wide range of associated column densities and ionization levels and velocities in the range of 23,000–33,000 km s?1, detected at X-ray high spectral resolution (E/?E ? 1000) with the ESA's observatory XMM-Newton. The charge states of the material constituting the wind clearly indicate a range of low to moderate ionization states in the outflowing gas and column densities that are significantly lower than observed in highly ionized ultra-fast outflows. We estimate that at least one of the outflow components may carry sufficient energy to substantially suppress star formation and heat the gas in the host galaxy. IRAS 17020+4544 therefore provides an interesting example of feedback by a moderately luminous AGN that is hosted in a spiral galaxy, a case barely envisaged in most evolution models, which often predict that feedback processes take place in massive elliptical galaxies hosting luminous quasars in a post-merger phase.

  3. Rotorwash wind sensor evaluation

    NASA Astrophysics Data System (ADS)

    Meyerhoff, Curtis L.; Lake, Robert E.; Gordge, Dennis N.

    1993-08-01

    This project's purpose was to assess and document the ability of the Qualimetrics, Inc. model 2132 wind sensor (a cup and vane type sensor) to measure a rotor wash flow field as compared to the TSI, Inc. model 204D ion beam deflection sensor. The tests concentrated on the sensor's ability to capture dynamic characteristics of a helicopter rotor wash flow field. The project was conducted from April to November 1992 and consisted of quantitative laboratory and field testing. The laboratory testing included 9.5 hours of wind tunnel test time, subjecting each sensor to three step input tests at velocities of 20 knots, 50 knots, and 80 knots. Field test data were collected during one hour of SH-60B helicopter hover time at heights of 15 and 25 feet above ground level at distances of 35 and 70 feet from the wind sensors. Aircraft gross weights ranged between 19,600 and 20,500 pounds. All field test data were obtained in ambient wind conditions of approximately 8 knots at 40 degrees relative to the aircraft nose, -40 feet pressure altitude in an ambient temperature of 85 F. Laboratory data analysis indicates the model 2132 cup and vane sensor's time constant values were significantly higher than those of the model 204D ion beam sensor and varied relative to wind tunnel velocity settings. This indicates the model 2132 sensor's ability to accurately capture oscillations in a dynamic flow field is significantly less than the model 204D sensor. The model 2132 sensor did detect periodic or pulsating velocity magnitudes, but failed to capture significant oscillations as compared to the model 204D sensor. Comparative analysis of all field test event data indicate the model 2132 sensor only detected frequencies below 1.5 Hz and only captured an average of 46 percent of the model 204D sensor's maximum amplitude pulse values that were below 1.5 Hz. The model 2132 sensor's inability to capture many of the maximum pulse amplitudes is evidence of the sensor's limited capability to capture velocity magnitude variations in a dynamic flow field. The model 2132 cup and vane sensor's average and minimum velocities for each test event were significantly higher than the model 204D ion beam sensor's values. This is additional evidence that the model 2132 sensor is slower to respond to rapid changes in a dynamic flow field. Compared to the TSI, Inc. model 204D ion beam sensor, the Qualimetrics, Inc. model 2132 cup and vane sensor failed to measure accurately a rotorwash flow field in terms of frequency, amplitude, frequency content, and velocity magnitude and thus is not recommended for helicopter rotorwash velocity data collection.

  4. A new model of relativistic equation of state in accretion and wind flows using 4-velocity distribution function

    NASA Astrophysics Data System (ADS)

    Basu, Prasad; Mondal, Soumen

    Following the original line of argument by Maxwell and Boltzmann (MB) we derive a 4-velocity distribution function for a relativistic ideal gas of massive particles. Most importantly, this distribution function can be factorized and perfectly reduces to non-relativistic MB speed distribution formula in low temperature (non relativistic) limit. Using this distribution function we express the pressure p, and kinetic energy density ? -?_0 as the functions of a parameter ? directly related to the kinetic energy density and hence to the temperature. We compute the adiabatic index ?={c_p}/{c_v} from the relativistic equation of state ? -?_0=(? -1)p as a function of the parameter ?. The value of ? exactly reduces to 5/3 and 4/3 in the non-relativistic and ultra-relativistic limit respectively. We also find the sound speed(a_s) satisfies a_s? {1}/{?{3}}.

  5. Microburst vertical wind estimation from horizontal wind measurements

    NASA Technical Reports Server (NTRS)

    Vicroy, Dan D.

    1994-01-01

    The vertical wind or downdraft component of a microburst-generated wind shear can significantly degrade airplane performance. Doppler radar and lidar are two sensor technologies being tested to provide flight crews with early warning of the presence of hazardous wind shear. An inherent limitation of Doppler-based sensors is the inability to measure velocities perpendicular to the line of sight, which results in an underestimate of the total wind shear hazard. One solution to the line-of-sight limitation is to use a vertical wind model to estimate the vertical component from the horizontal wind measurement. The objective of this study was to assess the ability of simple vertical wind models to improve the hazard prediction capability of an airborne Doppler sensor in a realistic microburst environment. Both simulation and flight test measurements were used to test the vertical wind models. The results indicate that in the altitude region of interest (at or below 300 m), the simple vertical wind models improved the hazard estimate. The radar simulation study showed that the magnitude of the performance improvement was altitude dependent. The altitude of maximum performance improvement occurred at about 300 m.

  6. The Impact of T-TREC-retrieved Wind and Radial Velocity Data Assimilation5 using EnKF and Effects of Assimilation Window on the Analysis and Prediction of6

    E-print Network

    Droegemeier, Kelvin K.

    the relative impact of assimilating T-TREC retrieved winds (VTREC)30 versus radial velocity (Vr) on the analysis and forecast of Typhoon Jangmi (2008) using31 an ensemble Kalman filter. The VTREC and Vr data and intensity than the assimilation of Vr data during the earlier assimilation36 windows but during the later

  7. Dry deposition velocities

    SciTech Connect

    Sehmel, G.A.

    1984-03-01

    Dry deposition velocities are very difficult to predict accurately. In this article, reported values of dry deposition velocities are summarized. This summary includes values from the literature on field measurements of gas and particle dry deposition velocities, and the uncertainties inherent in extrapolating field results to predict dry deposition velocities are discussed. A new method is described for predicting dry deposition velocity using a least-squares correlation of surface mass transfer resistances evaluated in wind tunnel experiments. 14 references, 4 figures, 1 table.

  8. Field evidence for the upwind velocity shift at the crest of low dunes

    E-print Network

    P. Claudin; G. F. S. Wiggs; B. Andreotti

    2013-02-11

    Wind topographically forced by hills and sand dunes accelerates on the upwind (stoss) slopes and reduces on the downwind (lee) slopes. This secondary wind regime, however, possesses a subtle effect, reported here for the first time from field measurements of near-surface wind velocity over a low dune: the wind velocity close to the surface reaches its maximum upwind of the crest. Our field-measured data show that this upwind phase shift of velocity with respect to topography is found to be in quantitative agreement with the prediction of hydrodynamical linear analysis for turbulent flows with first order closures. This effect, together with sand transport spatial relaxation, is at the origin of the mechanisms of dune initiation, instability and growth.

  9. Satellite-tracked cumulus velocities

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.; Pearl, E. W.; Shenk, W. E.

    1975-01-01

    Basic problems in the interpretation of satellite-tracked low-cloud velocities are reviewed. The METRACOM system of cloud velocity computation is outlined, and caution is urged in converting cloud velocities into wind velocities. The motion of various cumulus cells over Springfield, Mo., Barbados, and Tampa, Fla., is analyzed. It is shown that multiturret cells do not always move with the wind, that addition and deletion of turrets belonging to a specific cell may cause erratic motion in a tracer cell, and that cumulus turrets between 0.3 and 2 miles in size are the best targets for inferring the mean wind velocity within the subcloud layers. It is concluded that the accuracy of wind velocity estimates will be no better than 2 meters/sec unless the physical and dynamic characteristics of cumulus motion are further investigated.

  10. Wind loads on flat plate photovoltaic array fields. Phase III, final report

    SciTech Connect

    Miller, R.D.; Zimmerman, D.K.

    1981-04-01

    The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads.

  11. Wind regime and sand transport in China's Badain Jaran Desert

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengcai; Dong, Zhibao; Li, Chunxiao

    2015-06-01

    Wind controls the formation and development of aeolian dunes, therefore understanding the wind environment is necessary in aeolian dune research. In recent years, climate has changed in and around the Badain Jaran Desert, and the factors that control aeolian dune development have changed with it. In this paper, we analyzed characteristics of the desert's wind regime based on data from seven weather stations in and around the desert. The temporal and spatial variation in the wind regime's characteristics have different effects on dune formation and development. The annual mean wind velocity, maximum wind velocity, and the proportion of the time the wind exceeded the sand-entrainment threshold are largest at the northern margin of the desert, and these values decrease from north to south and from east to west. The dominant winds are from the northwest, northeast, and southwest. The drift potential (DP) in the desert decreases from north to south, and can be divided into three regions: high in the north, intermediate in the central region, and low in the south. The effects of climate change on the calculated DP will be complex; although DP increased with increasing mean wind velocity and temperature, there was little or no relationship with precipitation and relative humidity.

  12. Calculation of wind speeds required to damage or destroy buildings

    NASA Astrophysics Data System (ADS)

    Liu, Henry

    Determination of wind speeds required to damage or destroy a building is important not only for the improvement of building design and construction but also for the estimation of wind speeds in tornadoes and other damaging storms. For instance, since 1973 the U.S. National Weather Service has been using the well-known Fujita scale (F scale) to estimate the maximum wind speeds of tornadoes [Fujita, 1981]. The F scale classifies tornadoes into 13 numbers, F-0 through F-12. The wind speed (maximum gust speed) associated with each F number is given in Table 1. Note that F-6 through F-12 are for wind speeds between 319 mi/hr (mph) and the sonic velocity (approximately 760 mph; 1 mph = 1.6 km/kr). However, since no tornadoes have been classified to exceed F-5, the F-6 through F-12 categories have no practical meaning [Fujita, 1981].

  13. A Monte Carlo comparison of the recovery of winds near upwind and downwind from the SASS-1 model function by means of the sum of squares algorithm and a maximum likelihood estimator

    NASA Technical Reports Server (NTRS)

    Pierson, W. J., Jr.

    1984-01-01

    Backscatter measurements at upwind and crosswind are simulated for five incidence angles by means of the SASS-1 model function. The effects of communication noise and attitude errors are simulated by Monte Carlo methods, and the winds are recovered by both the Sum of Square (SOS) algorithm and a Maximum Likelihood Estimater (MLE). The SOS algorithm is shown to fail for light enough winds at all incidence angles and to fail to show areas of calm because backscatter estimates that were negative or that produced incorrect values of K sub p greater than one were discarded. The MLE performs well for all input backscatter estimates and returns calm when both are negative. The use of the SOS algorithm is shown to have introduced errors in the SASS-1 model function that, in part, cancel out the errors that result from using it, but that also cause disagreement with other data sources such as the AAFE circle flight data at light winds. Implications for future scatterometer systems are given.

  14. Microburst wind structure and evaluation of Doppler radar for airport wind shear detection

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Roberts, R. D.; Kessinger, C.; Mccarthy, J.

    1984-01-01

    The horizontal and vertical structure of airflow within microbursts has been determined using Doppler weather radar data from the Joint Airport Weather Studies (JAWS) Project. It is shown that the downdraft typically associated with microbursts is about 1 km wide and begins to spread horizontally at a height below 1 km. The median time from initial divergence at the surface to maximum differential wind velocity across the microburst is five minutes. The height of maximum differential velocity is about 75 m, and the median velocity differential is 22 m/s over an average distance of 3.1 km. The outflow of the air is asymmetric, averaging twice as strong along the maximum axis compared to the mininum axis. Some technical requirements for a radar system to detect microbursts and to provide aircraft with early warnings of the onset of windshear are identified.

  15. After the Wind Storm 

    E-print Network

    Unknown

    2011-09-05

    Accidents and hazards continue to plague the construction industry. One often overlooked hazard to workers is the potential for flying debris and materials during high winds. This research was designed to evaluate the wind velocity required...

  16. Wind power generating system

    SciTech Connect

    Schachle, Ch.; Schachle, E. C.; Schachle, J. R.; Schachle, P. J.

    1985-03-12

    Normally feathered propeller blades of a wind power generating system unfeather in response to the actuation of a power cylinder that responds to actuating signals. Once operational, the propellers generate power over a large range of wind velocities. A maximum power generation design point signals a feather response of the propellers so that once the design point is reached no increase in power results, but the system still generates power. At wind speeds below this maximum point, propeller speed and power output optimize to preset values. The propellers drive a positive displacement pump that in turn drives a positive displacement motor of the swash plate type. The displacement of the motor varies depending on the load on the system, with increasing displacement resulting in increasing propeller speeds, and the converse. In the event of dangerous but not clandestine problems developing in the system, a control circuit dumps hydraulic pressure from the unfeathering cylinder resulting in a predetermined, lower operating pressure produced by the pump. In the event that a problem of potentially cladestine consequence arises, the propeller unfeathering cylinder immediately unloads. Upon startup, a bypass around the motor is blocked, applying a pressure across the motor. The motor drives the generator until the generator reaches a predetermined speed whereupon the generator is placed in circuit with a utility grid and permitted to motor up to synchronous speed.

  17. PULSED ALFVEN WAVES IN THE SOLAR WIND

    SciTech Connect

    Gosling, J. T.; Tian, H.; Phan, T. D.

    2011-08-20

    Using 3 s plasma and magnetic field data from the Wind spacecraft located in the solar wind well upstream from Earth, we report observations of isolated, pulse-like Alfvenic disturbances in the solar wind. These isolated events are characterized by roughly plane-polarized rotations in the solar wind magnetic field and velocity vectors away from the directions of the underlying field and velocity and then back again. They pass over Wind on timescales ranging from seconds to several minutes. These isolated, pulsed Alfven waves are pervasive; we have identified 175 such events over the full range of solar wind speeds (320-550 km s{sup -1}) observed in a randomly chosen 10 day interval. The large majority of these events are propagating away from the Sun in the solar wind rest frame. Maximum field rotations in the interval studied ranged from 6 Degree-Sign to 109 Degree-Sign . Similar to most Alfvenic fluctuations in the solar wind at 1 AU, the observed changes in velocity are typically less than that predicted for pure Alfven waves (Alfvenicity ranged from 0.28 to 0.93). Most of the events are associated with small enhancements or depressions in magnetic field strength and small changes in proton number density and/or temperature. The pulse-like and roughly symmetric nature of the magnetic field and velocity rotations in these events suggests that these Alfvenic disturbances are not evolving when observed. They thus appear to be, and probably are, solitary waves. It is presently uncertain how these waves originate, although they may evolve out of Alfvenic turbulence.

  18. Aspects of the determination of winds by means of scatterometry and of the utilization of vector wind data for meteorological forecasts

    NASA Technical Reports Server (NTRS)

    Pierson, W. J., Jr.; Sylvester, W. B.; Donelan, M. A.

    1986-01-01

    The present paper provides a description of four aspects of scatterometer winds and their uses. The theory of wave generation by the wind is considered along with an analysis of the properties of superobservations, and studies of intermittent versus continuous data assimilation methods for numerical weather predictions which use remotely sensed data. A comparison of the sum of squares versus the maximum likelihood method for recovering the vector winds is also conducted. Questions regarding wind speed, friction velocity, or normal stress are discussed and synoptic scale fields from Seasat-SASS data are examined.

  19. Quantitative analysis of a wind energy conversion model

    NASA Astrophysics Data System (ADS)

    Zucker, Florian; Gräbner, Anna; Strunz, Andreas; Meyn, Jan-Peter

    2015-03-01

    A rotor of 12 cm diameter is attached to a precision electric motor, used as a generator, to make a model wind turbine. Output power of the generator is measured in a wind tunnel with up to 15 m s-1 air velocity. The maximum power is 3.4 W, the power conversion factor from kinetic to electric energy is cp = 0.15. The v3 power law is confirmed. The model illustrates several technically important features of industrial wind turbines quantitatively.

  20. Fuzzy Regulator Design for Wind Turbine Yaw Control

    PubMed Central

    Koulouras, Grigorios

    2014-01-01

    This paper proposes the development of an advanced fuzzy logic controller which aims to perform intelligent automatic control of the yaw movement of wind turbines. The specific fuzzy controller takes into account both the wind velocity and the acceptable yaw error correlation in order to achieve maximum performance efficacy. In this way, the proposed yaw control system is remarkably adaptive to the existing conditions. In this way, the wind turbine is enabled to retain its power output close to its nominal value and at the same time preserve its yaw system from pointless movement. Thorough simulation tests evaluate the proposed system effectiveness. PMID:24693237

  1. Fuzzy regulator design for wind turbine yaw control.

    PubMed

    Theodoropoulos, Stefanos; Kandris, Dionisis; Samarakou, Maria; Koulouras, Grigorios

    2014-01-01

    This paper proposes the development of an advanced fuzzy logic controller which aims to perform intelligent automatic control of the yaw movement of wind turbines. The specific fuzzy controller takes into account both the wind velocity and the acceptable yaw error correlation in order to achieve maximum performance efficacy. In this way, the proposed yaw control system is remarkably adaptive to the existing conditions. In this way, the wind turbine is enabled to retain its power output close to its nominal value and at the same time preserve its yaw system from pointless movement. Thorough simulation tests evaluate the proposed system effectiveness. PMID:24693237

  2. Maximum gravitational recoil.

    PubMed

    Campanelli, Manuela; Lousto, Carlos O; Zlochower, Yosef; Merritt, David

    2007-06-01

    Recent calculations of gravitational radiation recoil generated during black-hole binary mergers have reopened the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy. Here we report the first systematic study of gravitational recoil of equal-mass binaries with equal, but counteraligned, spins parallel to the orbital plane. Such an orientation of the spins is expected to maximize the recoil. We find that recoil velocity (which is perpendicular to the orbital plane) varies sinusoidally with the angle that the initial spin directions make with the initial linear momenta of each hole and scales up to a maximum of approximately 4000 km s-1 for maximally rotating holes. Our results show that the amplitude of the recoil velocity can depend sensitively on spin orientations of the black holes prior to merger. PMID:17677894

  3. Wind loads on flat plate photovoltaic array fields

    NASA Technical Reports Server (NTRS)

    Miller, R. D.; Zimmerman, D. K.

    1981-01-01

    The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads. The arrays located at the outer boundary of an array field have a protective influence on the interior arrays of the field. A significant decrease of the array wind loads were recorded in the wind tunnel test on array panels located behind a fence and/or interior to the array field compared to the arrays on the boundary and unprotected from the wind. The magnitude of this decrease was the same whether caused by a fence or upwind arrays.

  4. Maximum Jailbreak

    NASA Astrophysics Data System (ADS)

    Singleton, B.

    First formulated one hundred and fifty years ago by the heretical scholar Nikolai Federov, the doctrine of cosmism begins with an absolute refusal to treat the most basic factors conditioning life on Earth ­ gravity and death ­ as necessary constraints on action. As manifest through the intoxicated cheers of its early advocates that humans should storm the heavens and conquer death, cosmism's foundational gesture was to conceive of the earth as a trap. Its duty was therefore to understand the duty of philosophy, economics and design to be the creation of means to escape it. This could be regarded as a jailbreak at the maximum possible scale, a heist in which the human species could steal itself from the vault of the Earth. After several decades of relative disinterest new space ventures are inspiring scientific, technological and popular imaginations, this essay explores what kind of cosmism might be constructed today. In this paper cosmism's position as a means of escape is both reviewed and evaluated by reflecting on the potential of technology that actually can help us achieve its aims and also through the lens and state-ofthe-art philosophy of accelerationism, which seeks to outrun modern tropes by intensifying them.

  5. Wind speeds in two tornadic storms and a tornado, deduced from Doppler Spectra

    SciTech Connect

    Zrnic, D.; Istok, M.

    1980-12-01

    Doppler spectra of a tornado were collected with a radar having a large unambiguous velocity range, +- 91 m s/sup -1/. Thus for the first time a presentation of nonaliased spectra was possible, showing direct measurement of radial velocities. By fitting the tornado model spectrum to data, the radius of maximum winds and tornado center location are deduced. Tornado spectral signature is defined as a double peak, symmetric with respect to the mean wind spectrum. Histograms of maximum measured wind speeds (from spectrum skirts) for two tornadic storms are obtained, and the histograms of velocity difference (between the left and right spectrum skirt) suggest that smaller scale turbulence (<500 m) is principally responsible for spectrum broadness.

  6. Effects of atmospheric stability on the evolution of wind turbine wakes: Volumetric LiDAR scans

    NASA Astrophysics Data System (ADS)

    Valerio Iungo, Giacomo; Porté-Agel, Fernando

    2014-05-01

    Aerodynamic optimization of wind farm layout is a fundamental task to reduce wake effects on downstream wind turbines, thus to maximize wind power harvesting. However, downstream evolution and recovery of wind turbine wakes are strongly affected by the characteristics of the incoming atmospheric boundary layer (ABL) flow, like the vertical profiles of the mean wind velocity and the turbulence intensity, which are in turn affected by the ABL stability regime. Therefore, the characterization of the variability of wind turbine wakes under different ABL stability regimes becomes fundamental to better predict wind power harvesting and improve wind farm efficiency. To this aim, wind velocity measurements of the wake produced by a 2 MW Enercon E-70 wind turbine were performed with three scanning Doppler wind Light Detection and Ranging (LiDAR) instruments. One LiDAR was typically devoted to the characterization of the incoming wind, in particular wind velocity, shear and turbulence intensity at the height of the rotor disc. The other two LiDARs performed scans in order to characterize the wake velocity field produced by the tested wind turbine. The main challenge in performing field measurements of wind turbine wakes is represented by the varying wind conditions, and by the consequent adjustments of the turbine yaw angle needed to maximize power production. Consequently, taking into account possible variations of the relative position between LiDAR measurement volume and wake location, different LiDAR measurement procedures were carried out in order to perform 2-D and 3-D characterizations of the mean wake velocity field. However, larger measurement volumes and higher spatial resolution require longer sampling periods; thus, to investigate wake turbulence tests were also performed by staring the LiDAR laser beam over fixed directions and with the maximum sampling frequency. Furthermore, volumetric scans of the wind turbine wake were performed under different wind conditions via two simultaneous LiDARs. Through the evaluation of the minimum wake velocity deficit as a function of the downstream distance, it is shown that the stability regime of the ABL has a significant effect on the wake evolution; specifically the wake recovers faster under convective conditions. This result suggests that atmospheric inflow conditions, and particularly thermal stability, should be considered for improved wake models and predictions of wind power harvesting.

  7. Upstream proton cyclotron waves at Venus near solar maximum

    NASA Astrophysics Data System (ADS)

    Delva, M.; Bertucci, C.; Volwerk, M.; Lundin, R.; Mazelle, C.; Romanelli, N.

    2015-01-01

    magnetometer data of Venus Express are analyzed for the occurrence of waves at the proton cyclotron frequency in the spacecraft frame in the upstream region of Venus, for conditions of rising solar activity. The data of two Venus years up to the time of highest sunspot number so far (1 Mar 2011 to 31 May 2012) are studied to reveal the properties of the waves and the interplanetary magnetic field (IMF) conditions under which they are observed. In general, waves generated by newborn protons from exospheric hydrogen are observed under quasi- (anti)parallel conditions of the IMF and the solar wind velocity, as is expected from theoretical models. The present study near solar maximum finds significantly more waves than a previous study for solar minimum, with an asymmetry in the wave occurrence, i.e., mainly under antiparallel conditions. The plasma data from the Analyzer of Space Plasmas and Energetic Atoms instrument aboard Venus Express enable analysis of the background solar wind conditions. The prevalence of waves for IMF in direction toward the Sun is related to the stronger southward tilt of the heliospheric current sheet for the rising phase of Solar Cycle 24, i.e., the "bashful ballerina" is responsible for asymmetric background solar wind conditions. The increase of the number of wave occurrences may be explained by a significant increase in the relative density of planetary protons with respect to the solar wind background. An exceptionally low solar wind proton density is observed during the rising phase of Solar Cycle 24. At the same time, higher EUV increases the ionization in the Venus exosphere, resulting in higher supply of energy from a higher number of newborn protons to the wave. We conclude that in addition to quasi- (anti)parallel conditions of the IMF and the solar wind velocity direction, the higher relative density of Venus exospheric protons with respect to the background solar wind proton density is the key parameter for the higher number of observable proton cyclotron waves near solar maximum.

  8. Velocity and rolling-moment measurements in the wake of a swept-wing model in the 40 by 80 foot wind tunnel

    NASA Technical Reports Server (NTRS)

    Rossow, V. J.; Corsiglia, V. R.; Schwind, R. G.; Frick, J. K. D.; Lemmer, O. J.

    1975-01-01

    Measurements were made in the wake of a swept wing model to study the structure of lift generated vortex wakes shed by conventional span loadings and by several span loadings designed to reduce wake velocities. Variations in the span loading on the swept wing generator were obtained by deflecting seven flap segments on each side by amounts determined by vortex lattice theory to approximate the desired span loadings. The resulting wakes were probed with a three component, hot wire probe to measure velocity, and with a wing to measure the rolling moment that would be induced on a following aircraft. The experimental techniques are described herein, and the measured velocity and rolling moments are presented, along with some comparisons with the applicable theories.

  9. SAND DETACHMENT BY WIND-DRIVEN RAINDROPS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind movement and velocities can have profound effect on some aspects of the soil erosion process. In the case of wind-driven rain, differences in raindrop trajectory are expected: wind-driven raindrops achieve some degree of horizontal velocity, which increases their resultant impact velocity and s...

  10. Energy from the Wind

    ERIC Educational Resources Information Center

    Pelka, David G.; And Others

    1978-01-01

    The large-scale generation of electrical power by wind turbine fields is discussed. It is shown that the maximum power that can be extracted by a wind turbine is 16/27 of the power available in the wind. (BB)

  11. Characteristics of the disastrous wind-sand environment along railways in the Gobi area of Xinjiang, China

    NASA Astrophysics Data System (ADS)

    Cheng, Jian-jun; Jiang, Fu-qiang; Xue, Chun-xiao; Xin, Guo-wei; Li, Kai-chong; Yang, Yin-hai

    2015-02-01

    Based on detailed long-term data of wind regimes collected from typical ventilation sites along the railways in the Gobi area of Xinjiang, this study systematically analyzes the characteristics of the disastrous wind-sand environment along the railways by combining gradient sand sampling data collected by a wind-drift sand monitoring system and site survey data. Wind direction and speed rose diagrams revealed the prevailing wind direction in each wind area along the railways, and this is the wind direction from which the maximum frequency of sandstorms occurred. Drift potential characteristic parameters (RDP, RDD) and the direction variability (RDP/DP) showed that each wind area along the Gobi railway featured a long wind period, with strong power in a single wind direction. The special geological environment of the Gobi determines the wind-drift sand that features gravel of large grain size and unsaturation, which are different from the wind-drift sand in deserts. With increasing wind velocity, the density of the wind-drift sand increased steadily; however, at a certain critical value, the density surged. This study on the wind-sand environment of the Gobi has significance for railway safety. The critical value of wind velocity corresponded to an abrupt increase in the wind-drift sand density and should be taken into account during the planning process of railway safety passage, since this will lead to a decrease in frontal visual distance, and an associated decrease in safety. Additionally, the specific features of wind-drift sand activities, such as the abruptness and higher than usual sand height, should be considered during the process of designing sand-damage-control engineering measures.

  12. 33 CFR 156.320 - Maximum operating conditions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... of the following conditions exist: (1) The wind velocity is 56 km/hr (30 knots) or more; or (2) The... shall be drained when— (1) The wind velocity exceeds 82 km/hr (44 knots); or (2) Wave heights exceed...

  13. 33 CFR 156.320 - Maximum operating conditions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... of the following conditions exist: (1) The wind velocity is 56 km/hr (30 knots) or more; or (2) The... shall be drained when— (1) The wind velocity exceeds 82 km/hr (44 knots); or (2) Wave heights exceed...

  14. 33 CFR 156.320 - Maximum operating conditions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... of the following conditions exist: (1) The wind velocity is 56 km/hr (30 knots) or more; or (2) The... shall be drained when— (1) The wind velocity exceeds 82 km/hr (44 knots); or (2) Wave heights exceed...

  15. Wind tunnel simulation of a wind turbine wake in neutral, stable and unstable wind flow

    NASA Astrophysics Data System (ADS)

    Hancock, P. E.; Zhang, S.; Pascheke, F.; Hayden, P.

    2014-12-01

    Measurements of mean velocity, Reynolds stresses, temperature and heat flux have been made in the wake of a model wind turbine in the EnFlo meteorology wind tunnel, for three atmospheric boundary layer states: the base-line neutral case, stable and unstable. The full-to-model scale is approximately 300:1. Primary instrumentation is two-component LDA combine with cold-wire thermometry to measure heat flux. In terms of surface conditions, the stratified cases are weak, but there is a strong 'imposed' condition in the stable case. The measurements were made between 0.5D and 10D, where D is the turbine disk diameter. In the stable case the velocity deficit decreases more slowly; more quickly in the unstable case. Heights at which quantities are maximum or minimum are greater in the unstable case and smaller in the stable case. In the stable case the wake height is suppressed but the width is increased, while in the unstable case the height is increased and the width (at hub height) reaches a maximum and then decreases. The turbulence in the wake behaves in a complex way. Further work needs to be done, to cover stronger levels of surface condition, requiring more extensive measurements to properly capture the wake development.

  16. High-velocity blueshifted Fe II absorption in the dwarf star-forming galaxy PHL 293B: evidence for a wind driven supershell?

    NASA Astrophysics Data System (ADS)

    Terlevich, Roberto; Terlevich, Elena; Bosch, Guillermo; Díaz, Ángeles; Hägele, Guillermo; Cardaci, Mónica; Firpo, Verónica

    2014-12-01

    X-shooter and WHT-ISIS spectra of the star-forming galaxy PHL 293B also known as A2228-00 and SDSS J223036.79-000636.9 are presented in this paper. We find broad (FWHM = 1000 km s-1) and very broad (FWZI = 4000 km s-1) components in the Balmer lines, narrow absorption components in the Balmer series blueshifted by 800 km s-1, previously undetected Fe II multiplet (42) absorptions also blueshifted by 800 km s-1, IR Ca II triplet stellar absorptions consistent with [Fe/H] < -2.0 and no broad components or blueshifted absorptions in the He I lines. Based on historical records, we found no optical variability at the 5? level of 0.02 mag between 2005 and 2013 and no optical variability at the level of 0.1 mag for the past 24 yr. The lack of variability rules out transient phenomena like luminous blue variables or Type IIn supernovae as the origin of the blueshifted absorptions of H I and Fe II. The evidence points to either a young and dense expanding supershell or a stationary cooling wind, in both cases driven by the young cluster wind.

  17. Wind velocity measurement accuracy with highly stable 12 mJ/pulse high repetition rate CO2 laser master oscillator power amplifier

    NASA Technical Reports Server (NTRS)

    Bilbro, James W.; Johnson, Steven C.; Rothermel, Jeffry

    1987-01-01

    A coherent CO2 lidar operating in a master oscillator power amplifier configuration (MOPA) is described for both ground-based and airborne operation. Representative data taken from measurements against stationary targets in both the ground-based and airborne configurations are shown for the evaluation of the frequency stability of the system. Examples of data are also given which show the results of anomalous system operation. Overall results demonstrate that velocity measurements can be performed consistently to an accuracy of + or - 0.5 m/s and in some cases + or - 0.1 m/s.

  18. From Dust Devil to Sustainable Swirling Wind Energy

    NASA Astrophysics Data System (ADS)

    Zhang, Mingxu; Luo, Xilian; Li, Tianyu; Zhang, Liyuan; Meng, Xiangzhao; Kase, Kiwamu; Wada, Satoshi; Yu, Chuck Wah; Gu, Zhaolin

    2015-02-01

    Dust devils are common but meteorologically unique phenomena on Earth and on Mars. The phenomenon produces a vertical vortex motion in the atmosphere boundary layer and often occurs in hot desert regions, especially in the afternoons from late spring to early summer. Dust devils usually contain abundant wind energy, for example, a maximum swirling wind velocity of up to 25 m/s, with a 15 m/s maximum vertical velocity and 5 m/s maximum near-surface horizontal velocity can be formed. The occurrences of dust devils cannot be used for energy generation because these are generally random and short-lived. Here, a concept of sustained dust-devil-like whirlwind is proposed for the energy generation. A prototype of a circular shed with pre-rotation vanes has been devised to generate the whirlwind flow by heating the air inflow into the circular shed. The pre-rotation vanes can provide the air inflow with angular momentum. The results of numerical simulations and experiment illustrate a promising potential of the circular shed for generating swirling wind energy via the collection of low-temperature solar energy.

  19. From Dust Devil to Sustainable Swirling Wind Energy

    PubMed Central

    Zhang, Mingxu; Luo, Xilian; Li, Tianyu; Zhang, Liyuan; Meng, Xiangzhao; Kase, Kiwamu; Wada, Satoshi; Yu, Chuck Wah; Gu, Zhaolin

    2015-01-01

    Dust devils are common but meteorologically unique phenomena on Earth and on Mars. The phenomenon produces a vertical vortex motion in the atmosphere boundary layer and often occurs in hot desert regions, especially in the afternoons from late spring to early summer. Dust devils usually contain abundant wind energy, for example, a maximum swirling wind velocity of up to 25?m/s, with a 15?m/s maximum vertical velocity and 5?m/s maximum near-surface horizontal velocity can be formed. The occurrences of dust devils cannot be used for energy generation because these are generally random and short-lived. Here, a concept of sustained dust-devil-like whirlwind is proposed for the energy generation. A prototype of a circular shed with pre-rotation vanes has been devised to generate the whirlwind flow by heating the air inflow into the circular shed. The pre-rotation vanes can provide the air inflow with angular momentum. The results of numerical simulations and experiment illustrate a promising potential of the circular shed for generating swirling wind energy via the collection of low-temperature solar energy. PMID:25662574

  20. From dust devil to sustainable swirling wind energy.

    PubMed

    Zhang, Mingxu; Luo, Xilian; Li, Tianyu; Zhang, Liyuan; Meng, Xiangzhao; Kase, Kiwamu; Wada, Satoshi; Yu, Chuck Wah; Gu, Zhaolin

    2015-01-01

    Dust devils are common but meteorologically unique phenomena on Earth and on Mars. The phenomenon produces a vertical vortex motion in the atmosphere boundary layer and often occurs in hot desert regions, especially in the afternoons from late spring to early summer. Dust devils usually contain abundant wind energy, for example, a maximum swirling wind velocity of up to 25?m/s, with a 15?m/s maximum vertical velocity and 5?m/s maximum near-surface horizontal velocity can be formed. The occurrences of dust devils cannot be used for energy generation because these are generally random and short-lived. Here, a concept of sustained dust-devil-like whirlwind is proposed for the energy generation. A prototype of a circular shed with pre-rotation vanes has been devised to generate the whirlwind flow by heating the air inflow into the circular shed. The pre-rotation vanes can provide the air inflow with angular momentum. The results of numerical simulations and experiment illustrate a promising potential of the circular shed for generating swirling wind energy via the collection of low-temperature solar energy. PMID:25662574

  1. Terminal velocity of wind, mass loss, and absorption lines of the central star of the planetary nebula 75 + 35. 1 deg

    SciTech Connect

    Feibelman, W.A.; Bruhweiler, F.C. Catholic Univ. of America, Washington, DC )

    1989-12-01

    The high-galactic latitude planetary nebula 75 + 35.1 deg was observed in the high-dispersion mode of the International Ultraviolet Explorer (IUE) satellite in the wavelength range 1150-1950 A. The N V resonance doublet at 1240 A and O V subordinate line at 1371 A exhibit strong stellar P Cygni profiles with absorption extending to -2150 km/s and -1000 km/s, respectively. Application of the first moment method implies a mass-loss rate of M = (1-3) x 10 to the -8th solar mass/yr. The high ionization of the wind lines and the presence of strong Fe VI and Fe V lines in the stellar photosphere support that this object is quite hot. A Teff of 75,000 + or - 10,000 K was adopted, although Tc = 94,000 K was found previously from low-resolution IUE data. 18 refs.

  2. Terminal velocity of wind, mass loss, and absorption lines of the central star of the planetary nebula 75 + 35.1 deg

    NASA Technical Reports Server (NTRS)

    Feibelman, Walter A.; Bruhweiler, Frederick C.

    1989-01-01

    The high-galactic latitude planetary nebula 75 + 35.1 deg was observed in the high-dispersion mode of the International Ultraviolet Explorer (IUE) satellite in the wavelength range 1150-1950 A. The N V resonance doublet at 1240 A and O V subordinate line at 1371 A exhibit strong stellar P Cygni profiles with absorption extending to -2150 km/s and -1000 km/s, respectively. Application of the first moment method implies a mass-loss rate of M = (1-3) x 10 to the -8th solar mass/yr. The high ionization of the wind lines and the presence of strong Fe VI and Fe V lines in the stellar photosphere support that this object is quite hot. A Teff of 75,000 + or - 10,000 K was adopted, although Tc = 94,000 K was found previously from low-resolution IUE data.

  3. NAME: Date: = Total Velocity

    E-print Network

    Lega, Joceline

    NAME: Date: = Total Velocity = Vertical Velocity = Horizontal Velocity Instructions: Fire your horizontal velocity. My average rate is________________________ #12;To find the average vertical velocity the ground, given an initial vertical velocity v. My average vertical velocity

  4. Wind turbine

    DOEpatents

    Cheney, Jr., Marvin C. (Glastonbury, CT)

    1982-01-01

    A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

  5. AGN Obscuration Through Dusty Infrared Dominated Flows. 1; Radiation-Hydrodynamics Solution for the Wind

    NASA Technical Reports Server (NTRS)

    Dorodnitsyn, A.; Bisnovatyi-Kogan. G. S.; Kallman, T.

    2011-01-01

    We construct a radiation-hydrodynamics model for the obscuring toroidal structure in active galactic nuclei. In this model the obscuration is produced at parsec scale by a dense, dusty wind which is supported by infrared radiation pressure on dust grains. To find the distribution of radiation pressure, we numerically solve the 2D radiation transfer problem in a flux limited diffusion approximation. We iteratively couple the solution with calculations of stationary 1D models for the wind, and obtain the z-component of the velocity. Our results demonstrate that for AGN luminosities greater than 0.1 L(sub edd) external illumination can support a geometrically thick obscuration via outflows driven by infrared radiation pressure. The terminal velocity of marginally Compton-thin models (0.2 < tau(sub T) < 0.6), is comparable to or greater than the escape velocity. In Compton thick models the maximum value of the vertical component of the velocity is lower than the escape velocity, suggesting that a significant part of our torus is in the form of failed wind. The results demonstrate that obscuration via normal or failed infrared-driven winds is a viable option for the AGN torus problem and AGN unification models. Such winds can also provide an important channel for AGN feedback.

  6. Erosion by Wind: Modeling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Models of wind erosion are used to investigate fundamental processes and guide resource management. Many models are similar in that - temporal variables control soil wind erodibility; erosion begins when friction velocity exceeds a threshold; and transport capacity for saltation/creep is proportion...

  7. Near-lunar proton velocity distribution explained by electrostatic acceleration

    E-print Network

    Hutchinson, Ian H.

    The observation of parallel ion velocity in the near-lunar wake approximately equal to external solar wind velocity can be explained within uncertainties by an analytic electrostatic expansion model. The one-dimensional ...

  8. Influence of orographic and canopy conditions on friction velocities observed during frontal events using Doppler sodar observations

    SciTech Connect

    Kotroni, V.; Amory-Mazaudier, C. )

    1993-03-01

    Sodar friction velocities, obtained during frontal events traversing areas characterized by different orographic and canopy conditions (flat, bare ground, small hills and valleys with agricultural crops and trees, agricultural crops and forest on a flat ground, bare ground on the side of a mountain), are compared in order to identify the influence of topography on this parameter. For some case studies, sounding and sodar data are combined in order to provide a relation between the friction velocity and the low-level jet presence. For the cases analyzed in this paper, the following results are obtained: the frontal passage is associated with a decrease of the horizontal wind speed (about 50% in magnitude) in the surface layer, and an increase of the friction velocity before the frontal passage followed by a decrease just at the time of the frontal passage or with a little delay. Friction velocity is more intense in the cold side of the low-level jet and its maximum represents 2% of the low-level jet maximum magnitude. As it concerns the influence of the terrain conditions on friction velocity, mountain effects yield to more intense friction-velocity values and to a superposition of an oscillating behavior on the time variation of friction velocity, while forest effects induce a shift of the frontal signature on the time variation of friction velocity at higher height levels. 25 refs., 18 figs., 3 tabs.

  9. Velocity and velocity bounds in static spherically symmetric metrics

    E-print Network

    I. Arraut; D. Batic; M. Nowakowski

    2010-05-06

    We find simple expressions for velocity of massless particles in dependence of the distance $r$ in Schwarzschild coordinates. For massive particles these expressions put an upper bound for the velocity. Our results apply to static spherically symmetric metrics. We use these results to calculate the velocity for different cases: Schwarzschild, Schwarzschild-de Sitter and Reissner-Nordstr\\"om with and without the cosmological constant. We emphasize the differences between the behavior of the velocity in the different metrics and find that in cases with naked singularity there exists always a region where the massless particle moves with a velocity bigger than the velocity of light in vacuum. In the case of Reissner-Nordstr\\"om-de Sitter we completely characterize the radial velocity and the metric in an algebraic way. We contrast the case of classical naked singularities with naked singularities emerging from metric inspired by noncommutative geometry where the radial velocity never exceeds one. Furthermore, we solve the Einstein equations for a constant and polytropic density profile and calculate the radial velocity of a photon moving in spaces with interior metric. The polytropic case of radial velocity displays an unexpected variation bounded by a local minimum and maximum.

  10. The sun and heliosphere at solar maximum.

    PubMed

    Smith, E J; Marsden, R G; Balogh, A; Gloeckler, G; Geiss, J; McComas, D J; McKibben, R B; MacDowall, R J; Lanzerotti, L J; Krupp, N; Krueger, H; Landgraf, M

    2003-11-14

    Recent Ulysses observations from the Sun's equator to the poles reveal fundamental properties of the three-dimensional heliosphere at the maximum in solar activity. The heliospheric magnetic field originates from a magnetic dipole oriented nearly perpendicular to, instead of nearly parallel to, the Sun's rotation axis. Magnetic fields, solar wind, and energetic charged particles from low-latitude sources reach all latitudes, including the polar caps. The very fast high-latitude wind and polar coronal holes disappear and reappear together. Solar wind speed continues to be inversely correlated with coronal temperature. The cosmic ray flux is reduced symmetrically at all latitudes. PMID:14615526

  11. Impact of wind on the dynamics of explosive volcanic plumes inferred from analog experiments

    NASA Astrophysics Data System (ADS)

    Carazzo, G.; Girault, F.; Aubry, T. J.; Bouquerel, H.; Kaminski, E. C.

    2014-12-01

    Volcanic plumes produced by explosive eruptions commonly interact with atmospheric wind causing plume bending and a reduction of its maximum height. Strength of the wind field and intensity of the eruption control the behavior of the column in the atmosphere, which may form either a strong plume that is little affected by the presence of wind or a weak plume that is bent-over in the wind field. To better understand the transition between weak and strong plumes, we present a series of new laboratory reproducing a buoyant jet rising in a stratified environment with a uniform cross-flow. The experiments consist in injecting downward fresh water in a tank containing an aqueous NaCl solution with linear density stratification. The jet source is towed at a constant speed through the stationary fluid in order to produce a cross-flow. We show that depending on the environmental and source conditions, the buoyant jet may form either a strong, distorted, or weak plume. The transition from one dynamical regime to another is governed by the strength of the horizontal wind velocity compared to the vertical buoyant rise of the plume. A review of field data on historical eruptions confirms that the experimentally-determined transition curves capture the behavior of volcanic columns. We quantify the impact of wind on the maximum height reached by the column, and we propose a universal scaling relationship to link the mass discharge rate feeding an eruption to its observed maximum height in the presence of wind.

  12. Optimization of Wind Turbine Airfoils/Blades and Wind Farm Layouts

    NASA Astrophysics Data System (ADS)

    Chen, Xiaomin

    Shape optimization is widely used in the design of wind turbine blades. In this dissertation, a numerical optimization method called Genetic Algorithm (GA) is applied to address the shape optimization of wind turbine airfoils and blades. In recent years, the airfoil sections with blunt trailing edge (called flatback airfoils) have been proposed for the inboard regions of large wind-turbine blades because they provide several structural and aerodynamic performance advantages. The FX, DU and NACA 64 series airfoils are thick airfoils widely used for wind turbine blade application. They have several advantages in meeting the intrinsic requirements for wind turbines in terms of design point, off-design capabilities and structural properties. This research employ both single- and multi-objective genetic algorithms (SOGA and MOGA) for shape optimization of Flatback, FX, DU and NACA 64 series airfoils to achieve maximum lift and/or maximum lift to drag ratio. The commercially available software FLUENT is employed for calculation of the flow field using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a two-equation Shear Stress Transport (SST) turbulence model and a three equation k-kl-o turbulence model. The optimization methodology is validated by an optimization study of subsonic and transonic airfoils (NACA0012 and RAE 2822 airfoils). In this dissertation, we employ DU 91-W2-250, FX 66-S196-V1, NACA 64421, and Flat-back series of airfoils (FB-3500-0050, FB-3500-0875, and FB-3500-1750) and compare their performance with S809 airfoil used in NREL Phase II and III wind turbines; the lift and drag coefficient data for these airfoils sections are available. The output power of the turbine is calculated using these airfoil section blades for a given B and lambda and is compared with the original NREL Phase II and Phase III turbines using S809 airfoil section. It is shown that by a suitable choice of airfoil section of HAWT blade, the power generated by the turbine can be significantly increased. Parametric studies are also conducted by varying the turbine diameter. In addition, a simplified dynamic inflow model is integrated into the BEM theory. It is shown that the improved BEM theory has superior performance in capturing the instantaneous behavior of wind turbines due to the existence of wind turbine wake or temporal variations in wind velocity. The dissertation also considers the Wind Farm layout optimization problem using a genetic algorithm. Both the Horizontal --Axis Wind Turbines (HAWT) and Vertical-Axis Wind Turbines (VAWT) are considered. The goal of the optimization problem is to optimally position the turbines within the wind farm such that the wake effects are minimized and the power production is maximized. The reasonably accurate modeling of the turbine wake is critical in determination of the optimal layout of the turbines and the power generated. For HAWT, two wake models are considered; both are found to give similar answers. For VAWT, a very simple wake model is employed. Finally, some preliminary investigation of shape optimization of 3D wind turbine blades at low Reynolds numbers is conducted. The optimization employs a 3D straight untapered wind turbine blade with cross section of NACA 0012 airfoils as the geometry of baseline blade. The optimization objective is to achieve maximum Cl/Cd as well as maximum Cl. The multi-objective genetic algorithm is employed together with the commercially available software FLUENT for calculation of the flow field using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a one-equation Sparlart-Allmaras turbulence model. The results show excellent performance of the optimized wind turbine blade and indicate the feasibility of optimization on real wind turbine blades with more complex shapes in the future. (Abstract shortened by UMI.)

  13. CAT LIDAR wind shear studies

    NASA Technical Reports Server (NTRS)

    Goff, R. W.

    1978-01-01

    The studies considered the major meteorological factors producing wind shear, methods to define and classify wind shear in terms significant from an aircraft perturbation standpoint, the significance of sensor location and scan geometry on the detection and measurement of wind shear, and the tradeoffs involved in sensor performance such as range/velocity resolution, update frequency and data averaging interval.

  14. Sensitivities of eyewall replacement cycle to model physics, vortex structure, and background winds in numerical simulations of tropical cyclones

    NASA Astrophysics Data System (ADS)

    Zhu, Zhenduo; Zhu, Ping

    2015-01-01

    series of sensitivity experiments by the Weather Research and Forecasting (WRF) model is used to investigate the impact of model physics, vortex axisymmetric radial structure, and background wind on secondary eyewall formation (SEF) and eyewall replacement cycle (ERC) in three-dimensional full physics numerical simulations. It is found that the vertical turbulent mixing parameterization can substantially affect the concentric ring structure of tangential wind associated with SEF through a complicated interaction among eyewall and outer rainband heating, radial inflow in the boundary layer, surface layer processes, and shallow convection in the moat. Large snow terminal velocity can substantially change the vertical distribution of eyewall diabatic heating to result in a strong radial inflow in the boundary layer, and thus, favors the development of shallow convection in the moat allowing the outer rainband convection to move closer to the inner eyewall, which may leave little room both temporally and spatially for a full development of a secondary maximum of tangential wind. Small radius of maximum wind (RMW) of a vortex and small potential vorticity (PV) skirt outside the RMW tend to generate double-eyewall replacement and may lead to an ERC without a clean secondary concentric maximum of tangential wind. A sufficiently large background wind can smooth out an ERC that would otherwise occur without background wind for a vortex with a small or moderate PV skirt. However, background wind does not appear to have an impact on an ERC if the vortex has a sufficiently large PV skirt.

  15. On optimal velocity during cycling.

    PubMed

    Maro?ski, R

    1994-02-01

    This paper focuses on the solution of two problems related to cycling. One is to determine the velocity as a function of distance which minimizes the cyclist's energy expenditure in covering a given distance in a set time. The other is to determine the velocity as a function of the distance which minimizes time for fixed energy expenditure. To solve these problems, an equation of motion for the cyclist riding over arbitrary terrain is written using Newton's second law. This equation is used to evaluate either energy expenditure or time, and the minimization problems are solved using an optimal control formulation in conjunction with the method of Miele [Optimization Techniques with Applications to Aerospace Systems, pp. 69-98 (1962) Academic Press, New York]. Solutions to both optimal control problems are the same. The solutions are illustrated through two examples. In one example where the relative wind velocity is zero, the optimal cruising velocity is constant regardless of terrain. In the second, where the relative wind velocity fluctuates, the optimal cruising velocity varies. PMID:8132689

  16. Dynamic stall occurrence on a horizontal axis wind turbine blade

    SciTech Connect

    Shipley, D.E.; Miller, M.S.; Robinson, M.C.

    1995-07-01

    Surface pressure data from the National Renewable Energy Laboratory`s ``Combined Experiment`` were analyzed to provide a statistical representation of dynamic stall occurrence on a downwind horizontal axis wind turbine (HAWT). Over twenty thousand blade rotational cycles were each characterized at four span locations by the maximum leading edge suction pressure and by the azimuth, velocity, and yaw at which it occurred. Peak suction values at least twice that seen in static wind tunnel tests were taken to be indicative of dynamic stall. The occurrence of dynamic stall at all but the inboard station (30% span) shows good quantitative agreement with the theoretical limits on inflow velocity and yaw that should yield dynamic stall. Two hypotheses were developed to explain the discrepancy at 30% span. Estimates are also given for the frequency of dynamic stall occurrence on upwind turbines. Operational regimes were identified which minimize the occurrence of dynamic stall events.

  17. Dynamic stall occurrence on a horizontal axis wind turbine blade

    SciTech Connect

    Shipley, D.E.; Miller, M.S.; Robinson, M.C.

    1995-09-01

    Surface pressure data from the National Renewable Energy Laboratory`s ``Combined Experiment`` were analyzed to provide a statistical representation of dynamic stall occurrence on a downwind horizontal axis wind turbine (HAWT). Over twenty thousand blade rotational cycles were each characterized at four span locations by the maximum leading edge suction pressure and by the azimuth, velocity, and yaw at which it occurred. Peak suction values at least twice that seen in static wind tunnel tests were taken to be indicative of dynamic stall. The occurrence of dynamic stall at all but the inboard station (30% span) shows good quantitative agreement with the theoretical limits on inflow velocity and yaw that should yield dynamic stall. Two hypotheses were developed to explain the discrepancy at 30% span. Estimates are also given for the frequency of dynamic stall occurrence on upwind turbines. Operational regimes were identified which minimize the occurrence of dynamic stall events.

  18. Maxometers (peak wind speed anemometers)

    NASA Technical Reports Server (NTRS)

    Kaufman, J. W.; Camp, D. W.; Turner, R. E. (inventors)

    1973-01-01

    An instrument for measuring peak wind speeds under severe environmental conditions is described, comprising an elongated cylinder housed in an outer casing. The cylinder contains a piston attached to a longitudinally movable guided rod having a pressure disk mounted on one projecting end. Wind pressure against the pressure disk depresses the movable rod. When the wind reaches its maximum speed, the rod is locked by a ball clutch mechanism in the position of maximum inward movement. Thereafter maximum wind speed or pressure readings may be taken from calibrated indexing means.

  19. 33 CFR 156.320 - Maximum operating conditions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... wave height is 3 meters (10 feet) or more. (b) Cargo transfer operations shall cease and transfer hoses shall be drained when— (1) The wind velocity exceeds 82 km/hr (44 knots); or (2) Wave heights exceed...

  20. 33 CFR 156.320 - Maximum operating conditions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... wave height is 3 meters (10 feet) or more. (b) Cargo transfer operations shall cease and transfer hoses shall be drained when— (1) The wind velocity exceeds 82 km/hr (44 knots); or (2) Wave heights exceed...

  1. New Sensors For Flow Velocity And Acoustics

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.

    1991-01-01

    Paper describes two sensor-development programs at Fluid Mechanics Laboratory at NASA Ames Research Center. One program for digital image velocimetry (DIV) sensors, and other program, for advanced acoustic sensors for wind tunnels. DIV measures, in real time, instantaneous velocity fields of time-varying flow or of collection of objects moving with varying velocities. Advanced acoustic sensors for wind tunnels being developed to reduce effects of interference from wind noise, noise from interactions between flows and sensors, flow-induced vibrations of sensors, deflections of accoustic waves by boundary layers induced by sensors, and reflections from walls and sensor supports.

  2. Maximum Power Training and Plyometrics for Cross-Country Running.

    ERIC Educational Resources Information Center

    Ebben, William P.

    2001-01-01

    Provides a rationale for maximum power training and plyometrics as conditioning strategies for cross-country runners, examining: an evaluation of training methods (strength training and maximum power training and plyometrics); biomechanic and velocity specificity (role in preventing injury); and practical application of maximum power training and…

  3. Approximate maximum parsimony and ancestral maximum likelihood.

    PubMed

    Alon, Noga; Chor, Benny; Pardi, Fabio; Rapoport, Anat

    2010-01-01

    We explore the maximum parsimony (MP) and ancestral maximum likelihood (AML) criteria in phylogenetic tree reconstruction. Both problems are NP-hard, so we seek approximate solutions. We formulate the two problems as Steiner tree problems under appropriate distances. The gist of our approach is the succinct characterization of Steiner trees for a small number of leaves for the two distances. This enables the use of known Steiner tree approximation algorithms. The approach leads to a 16/9 approximation ratio for AML and asymptotically to a 1.55 approximation ratio for MP. PMID:20150680

  4. The H_2O(+) Velocity Field in Comet Hale-Bopp, Observations and MHD Models

    NASA Astrophysics Data System (ADS)

    Anderson, C. M.; Combi, M. R.; Gombosi, T.; Hansen, K. C.

    1998-09-01

    The 3.5-meter WIYN Telescope and its Multi-Object Spectrograph (MOS)obtained simultaneous spectra at many points in the coma of Comet Hale-Bopp between 1996 October and 1997 April. The "Hydra" fiber positioner was used to sample a ring pattern of points about the nucleus with a minimum spacing of 40 arc seconds and a maximum radius of 22.5 arc minutes. A integral field device called "Densepak" was also used to sample a 7 x 13 rectangular pattern of 91, 3 arc second fibers on 4 arc second centers. The bench spectrograph was used in the echelle mode with an interference filter to isolate a single order and covered the wavelength range from 6100 Angstroms to 6400 Angstroms with resolution of approximately 15,000. This spectral region contains the emission features of H_2O(+) . From these data we have extracted the radial velocity of the H_2O(+) . We find the acceleration in the anit-sun direction to be of the order of 20 cm sec(-) (2) . The measured velocity fields have been compared to full 3D MAUS-MHD models. The models suggest that the degree ofconfinement of the coma and the velocities attained in the anti-sun direction depend sensitively upon the velocity of the ambient solar wind. The observed velocity fields are consistent with the confinement of the near coma by a relatively slow solar wind while the speeds attained at distances of the order of a million kilometers in the anti-sun direction are more like those produced by a fast solar wind. The observations were obtained at a time when Hale-Bopp was at intermediate heliocentric latitudes where the solar wind speed is known to change rapidly from slow to fast modes. This situation is under further investigation.

  5. Maximum a Posteriori Maximum Entropy Signal Denoising

    NASA Astrophysics Data System (ADS)

    Seghouane, Abd-Krim; Knockaert, Luc

    2007-11-01

    When fitting wavelet based models, shrinkage of the empirical wavelet coefficients is an effective tool for signal denoising. Based on different approaches, different shrinkage functions have been proposed in the literature. The shrinkage functions derived using Bayesian estimation theory depend on the prior used on the wavelet coefficients. However, no simple and direct method exists for the choice of the prior. In this paper a new method based on maximum entropy considerations is proposed for the construction of the prior on the wavelet coefficients. The new shrinkage function is obtained by coupling this prior to maximum a posteriori arguments. A comparison with classical shrinkage functions is given in a simulation example of image denoising in order to illustrate the effectiveness of the proposed thresholding method.

  6. VARIABLE WINDS AND DUST FORMATION IN R CORONAE BOREALIS STARS

    SciTech Connect

    Clayton, Geoffrey C.; Zhang Wanshu; Geballe, T. R. E-mail: wzhan21@lsu.edu

    2013-08-01

    We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I {lambda}10830 lines of 12 R Coronae Borealis stars over short (1 month) and long (3 yr) timescales to look for variations linked to their dust-formation episodes. In almost all cases, the strengths and terminal velocities of the line vary significantly and are correlated with dust formation events. Strong absorption features with blue-shifted velocities {approx}400 km s{sup -1} appear during declines in visible brightness and persist for about 100 days after recovery to maximum brightness. Small residual winds of somewhat lower velocity are present outside of the decline and recovery periods. The correlations support models in which recently formed dust near the star is propelled outward at high speed by radiation pressure and drags the gas along with it.

  7. Interaction of katabatic wind and local surface mass balance at Scharffenbergbotnen Blue Ice Area, Antarctica

    NASA Astrophysics Data System (ADS)

    Zwinger, T.; Malm, T.; Schäfer, M.; Stenberg, R.; Moore, J. C.

    2015-04-01

    We model the wind causing the formation of a blue ice area in Scharffenbergbotnen valley, Antarctica, using the finite element code Elmer. The high resolution numerical simulations of the local wind flow from katabatic wind fronts show highly spatially variable wind impact patterns and good congruence between places of enhanced wind-impact and the blue ice area. The results were fortuitously confirmed by the destruction of a field camp located in a high wind speed area and its subsequent redistribution to low velocity areas. In addition we perform wind simulations on an altered glacier geometry that resembles the thicker ice cover at the Late Glacial Maximum (LGM). These simulations indicate that the pronounced spatial wind-impact patterns depend on present day geometry and did not occur during the LGM. This leads to the conclusion that the formation of the blue ice area that is situated more inside the valley of Scharffenbergbotnen started only after the lowering of the ice surface, later than the LGM. Experiments with smoothed surface topography suggest that detailed positions of the high wind regions and hence individual blue ice fields, may have varied as the ice sheet lowered. The experiments and the field observations are consistent with localized violent katabatic events, rather than synoptic scale storms, playing the dominant role in the formation and maintenance of this, and perhaps many blue ice areas.

  8. Application of a method for the automatic detection and Ground-Based Velocity Track Display (GBVTD) analysis of a tornado crossing the Hong Kong International Airport

    NASA Astrophysics Data System (ADS)

    Chan, P. W.; Wurman, J.; Shun, C. M.; Robinson, P.; Kosiba, K.

    2012-03-01

    A weak tornado with a maximum Doppler velocity shear of about 40 m s - 1 moved across the Hong Kong International Airport (HKIA) during the evening of 20 May 2002. The tornado caused damage equivalent to F0 on the Fujita Scale, based on a damage survey. The Doppler velocity data from the Hong Kong Terminal Doppler Weather Radar (TDWR) are studied using the Ground-Based Velocity Track Display (GBVTD) method of single Doppler analysis. The GBVTD analysis is able to clearly depict the development and decay of the tornado though it appears to underestimate its magnitude. In the pre-tornadic state, the wind field is characterized by inflow toward the center near the ground and upward motion near the center. When the tornado attains its maximum strength, an eye-like structure with a downdraft appears to form in the center. Several minutes later the tornado begins to decay and outflow dominates at low levels. Assuming cyclostrophic balance, the pressure drop 200 m from the center of the tornado at its maximum strength is calculated to be about 6 hPa. To estimate the maximum ground-relative wind speed of the tornado, the TDWR's Doppler velocities are adjusted for the ratio of the sample-volume size of the radar and the radius of the tornado, resulting in a peak wind speed of 28 m s - 1 , consistent with the readings from a nearby ground-based anemometers and the F0 damage observed. An automatic tornado detection algorithm based on Doppler velocity difference (delta-V) and temporal and spatial continuity is applied to this event. The locations and the core flow radii of the tornado as determined by the automatic method and by subjective analysis agree closely.

  9. Wind Speed Estimation and Wake model Re-calibration for Downregulated Offshore Wind Farms

    NASA Astrophysics Data System (ADS)

    Göçmen Bozkurt, Tuhfe; Giebel, Gregor; Kjølstad Poulsen, Niels; Réthoré, Pierre-Elouan; Mirzaei, Mahmood

    2014-05-01

    In recent years, the wind farm sizes have increased tremendously and with increasing installed capacity, the wind farms are requested to downregulate from their maximum possible power more frequently, especially in the offshore environment. Determination of the possible (or available) power is crucial not only because the reserve power has considerable market value but also for wind farm developers to be properly compensated for the loss during downregulation. While the available power calculation is straightforward for a single turbine, it gets rather complicated for the whole wind farm due to the change in the wake characteristics. In fact, the wake losses generated by the upstream turbine(s) decrease during downregulation and the downstream turbines therefore see more wind compared to the normal operation case. Currently, the Transmission System Operators (TSOs) have no real way to determine exactly the available power of a whole wind farm which is downregulated. Therefore, the PossPOW project aims to develop a verified and internationally accepted way to determine the possible power of a down-regulated offshore wind farm. The first phase of the project is to estimate the rotor effective wind speed. Since the nacelle anemometers are not readily available and are known to have reliability issues, the proposed method is to use power, pitch angle and rotational speed as inputs and combine it with a generic Cp model to estimate the wind speed. The performance of the model has been evaluated for both normal operation and downregulation periods using two different case studies: Horns Rev-I wind farm and NREL 5MW single turbine. During downregulation, the wake losses are not as severe and the velocity deficits at the downstream turbines are smaller as if also the wake is "downregulated". On the other hand, in order to calculate the available power, the wakes that would have been produced normally (if the turbines were not curtailed) are of importance, not the downregulated wake. For this reason, the proposed methodology is to use the clear wind without the wake (downregulated or not) as inputs to the wake model. Then a dynamic wake model can be directly applied to estimate the velocity deficit row by row inside the wind farm and calculate the possible power output on the wind farm scale. Most of the computationally affordable wake models have only been used to acquire long term, statistical information and verified using 10-min averaged data. However for smaller averaging bins or real-time modeling, the dynamics of the flow inside the wind farm such as wind direction variability and wake meandering is much more significant. Therefore GCLarsen wake model, which has been implemented in WindPro and shown to perform also well on offshore in Wake benchmark work package in EERA-DTOC, is re-calibrated and validated for single wake case in Horns Rev-I offshore wind farm.

  10. Observations of sunspot umbral velocity oscillations.

    NASA Technical Reports Server (NTRS)

    Bhatnagar, A.; Livingston, W. C.; Harvey, J. W.

    1972-01-01

    Review of sunspot umbral velocity measurements obtained free from any cross talk introduced by photospheric and penumbral scattered light by using lines formed only in the sunspot umbrae and showing no Zeeman effect. The maximum peak-to-peak amplitude of the umbral oscillatory velocity component is found to be of the order of 0.5 km per sec.

  11. Winds over saltcedar

    USGS Publications Warehouse

    Van Hylckama, T. E. A.

    1970-01-01

    An analysis of hourly wind speeds above and within a stand of saltcedar near Buckeye, Arizona, reveals that in 90% of all observed cases, the wind profiles above the stand can be represented by the simple logarithmic equation: uz = u* k 1n ( z z0) where uz is the velocity at height z. The roughness length (z0), (disregarding zero displacement), varies with a stability ratio similar to Richardson's number. The friction velocity, u*, depends on the wind speeds above the vegetation. Von Karman's constant, k, equals 0.41. Within the thickets there is considerable turbulence, and irregular wind inversions occur during daylight hours. The results are important for estimating water losses by evapotranspiration by either the energy-budget or the mass-transfer formulae. ?? 1970.

  12. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    NASA Technical Reports Server (NTRS)

    Simon-Miller, Amy A.; Choi, David; Rogers, John H.; Gierasch, Peter J.; Allison, Michael D.; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-01-01

    A detailed study of the chevron-shaped dark spots on the strong southern equatorial wind jet near 7.5 S planetographic latitude shows variations in velocity with longitude and time. The presence of the large anticyclonic South Equatorial Disturbance (SED) has a profound effect on the chevron velocity, causing slower velocities to its east and accelerations over distance from the disturbance. The chevrons move with velocities near the maximum wind jet velocity of approx 140 m/s, as deduced by the history of velocities at this latitude and the magnitude of the symmetric wind jet near 7 N latitude. Their repetitive nature is consistent with a gravity-inertia wave (n = 75 to 100) with phase speed up to 25 m/s, relative to the local flow, but the identity of this wave mode is not well constrained. However, for the first time, high spatial resolution movies from Cassini images show that the chevrons oscillate in latitude with a 6.7 +/- 0.7-day period. This oscillating motion has a wavelength of approx 20 and a speed of 101 +/- 3 m/s, following a pattern similar to that seen in the Rossby wave plumes of the North Equatorial Zone, and possibly reinforced by it. All dates show chevron latitude variability, but it is unclear if this larger wave is present during other epochs, as there are no other suitable time series movies that fully delineate it. In the presence of mUltiple wave modes, the difference in dominant cloud appearance between 7 deg N and 7.5 deg S is likely due to the presence of the Great Red Spot, either through changes in stratification and stability or by acting as a wave boundary.

  13. Maximum thrust mode evaluation

    NASA Technical Reports Server (NTRS)

    Orme, John S.; Nobbs, Steven G.

    1995-01-01

    Measured reductions in acceleration times which resulted from the application of the F-15 performance seeking control (PSC) maximum thrust mode during the dual-engine test phase is presented as a function of power setting and flight condition. Data were collected at altitudes of 30,000 and 45,000 feet at military and maximum afterburning power settings. The time savings for the supersonic acceleration is less than at subsonic Mach numbers because of the increased modeling and control complexity. In addition, the propulsion system was designed to be optimized at the mid supersonic Mach number range. Recall that even though the engine is at maximum afterburner, PSC does not trim the afterburner for the maximum thrust mode. Subsonically at military power, time to accelerate from Mach 0.6 to 0.95 was cut by between 6 and 8 percent with a single engine application of PSC, and over 14 percent when both engines were optimized. At maximum afterburner, the level of thrust increases were similar in magnitude to the military power results, but because of higher thrust levels at maximum afterburner and higher aircraft drag at supersonic Mach numbers the percentage thrust increase and time to accelerate was less than for the supersonic accelerations. Savings in time to accelerate supersonically at maximum afterburner ranged from 4 to 7 percent. In general, the maximum thrust mode has performed well, demonstrating significant thrust increases at military and maximum afterburner power. Increases of up to 15 percent at typical combat-type flight conditions were identified. Thrust increases of this magnitude could be useful in a combat situation.

  14. Observation of high-resolution wind fields and offshore wind turbine wakes using TerraSAR-X imagery

    NASA Astrophysics Data System (ADS)

    Gies, Tobias; Jacobsen, Sven; Lehner, Susanne; Pleskachevsky, Andrey

    2014-05-01

    1. Introduction Numerous large-scale offshore wind farms have been built in European waters and play an important role in providing renewable energy. Therefore, knowledge of behavior of wakes, induced by large wind turbines and their impact on wind power output is important. The spatial variation of offshore wind turbine wake is very complex, depending on wind speed, wind direction, ambient atmospheric turbulence and atmospheric stability. In this study we demonstrate the application of X-band TerraSAR-X (TS-X) data with high spatial resolution for studies on wind turbine wakes in the near and far field of the offshore wind farm Alpha Ventus, located in the North Sea. Two cases which different weather conditions and different wake pattern as observed in the TS-X image are presented. 2. Methods The space-borne synthetic aperture radar (SAR) is a unique sensor that provides two-dimensional information on the ocean surface. Due to their high resolution, daylight and weather independency and global coverage, SARs are particularly suitable for many ocean and coastal applications. SAR images reveal wind variations on small scales and thus represent a valuable means in detailed wind-field analysis. The general principle of imaging turbine wakes is that the reduced wind speed downstream of offshore wind farms modulates the sea surface roughness, which in turn changes the Normalized Radar Cross Section (NRCS, denoted by ?0) in the SAR image and makes the wake visible. In this study we present two cases at the offshore wind farm Alpha Ventus to investigate turbine-induced wakes and the retrieved sea surface wind field. Using the wind streaks, visible in the TS-X image and the shadow behind the offshore wind farm, induced by turbine wake, the sea surface wind direction is derived and subsequently the sea surface wind speed is calculated using the latest generation of wind field algorithm XMOD2. 3. Case study alpha ventus Alpha Ventus is located approximately 45 km from the coast of Borkum, Germany, and consists of twelve 5-Megawatt wind power turbines. The retrieved results are validated by comparing with QuikSCAT measurements, the results of the German Weather Service (DWD) atmospheric model and in-situ measurements of wind speed and wind direction, obtained from the research platform FiNO1, installed 400 m west of Alpha Ventus. 4. Conclusion In the presented case study we quantify the wake characteristics of wake length, wake width, maximum velocity de?cit, wake merging and wake meandering. We show that SAR has the capability to map the sea surface two-dimensionally in high spatial resolution which provides a unique opportunity to observe spatial characteristics of offshore wind turbine wakes. The SAR derived information can support offshore wind farming with respect to optimal siting and design and help to estimate their effects on the environment.

  15. The F2 wind tunnel at Fauga-Mauzac

    NASA Technical Reports Server (NTRS)

    Afchain, D.; Broussaud, P.; Frugier, M.; Rancarani, G.

    1984-01-01

    Details on the French subsonic wind-tunnel F2 that becomes operational on July 1983 are presented. Some of the requirements were: (1) installation of models on any wall of the facility, (2) good observation points due to transparent walls, (3) smooth flow, (4) a laser velocimeter, and (5) easy access and handling. The characteristics include a nonpressurized return circuit, dimensions of 5 x 1.4 x 1.8 m, maximum velocity of 100 m/s and a variable speed fan of 683 kW.

  16. A Wind-Tunnel Investigation of Wind-Turbine Wakes: Boundary-Layer Turbulence Effects

    NASA Astrophysics Data System (ADS)

    Chamorro, Leonardo P.; Porté-Agel, Fernando

    2009-07-01

    Wind-tunnel experiments were performed to study turbulence in the wake of a model wind turbine placed in a boundary layer developed over rough and smooth surfaces. Hot-wire anemometry was used to characterize the cross-sectional distribution of mean velocity, turbulence intensity and kinematic shear stress at different locations downwind of the turbine for both surface roughness cases. Special emphasis was placed on the spatial distribution of the velocity deficit and the turbulence intensity, which are important factors affecting turbine power generation and fatigue loads in wind energy parks. Non-axisymmetric behaviour of the wake is observed over both roughness types in response to the non-uniform incoming boundary-layer flow and the effect of the surface. Nonetheless, the velocity deficit with respect to the incoming velocity profile is nearly axisymmetric, except near the ground in the far wake where the wake interacts with the surface. It is found that the wind turbine induces a large enhancement of turbulence levels (positive added turbulence intensity) in the upper part of the wake. This is due to the effect of relatively large velocity fluctuations associated with helicoidal tip vortices near the wake edge, where the mean shear is strong. In the lower part of the wake, the mean shear and turbulence intensity are reduced with respect to the incoming flow. The non-axisymmetry of the turbulence intensity distribution of the wake is found to be stronger over the rough surface, where the incoming flow is less uniform at the turbine level. In the far wake the added turbulent intensity, its positive and negative contributions and its local maximum decay as a power law of downwind distance (with an exponent ranging from -0.3 to -0.5 for the rough surface, and with a wider variation for the smooth surface). Nevertheless, the effect of the turbine on the velocity defect and added turbulence intensity is not negligible even in the very far wake, at a distance of fifteen times the rotor diameter.

  17. Stationary Plasma Thruster Ion Velocity Distribution

    NASA Technical Reports Server (NTRS)

    Manzella, David H.

    1994-01-01

    A nonintrusive velocity diagnostic based on laser induced fluorescence of the 5d4F(5/2)-6p4D(5/2) singly ionized xenon transition was used to interrogate the exhaust of a 1.5 kW Stationary Plasma Thruster (SPT). A detailed map of plume velocity vectors was obtained using a simplified, cost-effective, nonintrusive, semiconductor laser based scheme. Circumferential velocities on the order of 250 m/s were measured which implied induced momentum torques of approximately 5 x 10(exp -2) N-cm. Axial and radial velocities were evaluated one mm downstream of the cathode at several locations across the width of the annular acceleration channel. Radial velocities varied linearly with radial distance. A maximum radial velocity of 7500 m/s was measured 8 mm from the center of the channel. Axial velocities as large as 16,500 m/s were measured.

  18. Exploration of Solar Wind Acceleration Region Using Interplanetary Scintillation of Water Vapor Maser Source and Quasars

    NASA Technical Reports Server (NTRS)

    Tokumaru, Munetoshi; Yamauchi, Yohei; Kondo, Tetsuro

    2001-01-01

    Single-station observations of interplanetary scintillation (IPS) at three microwave frequencies; 2 GHz, 8 GHz and 22 GHz have been carried out between 1989 and 1998 using a large (34 m farad) radio telescope at the Kashima Space Research Center of the Communications Research Laboratory. The aim of these observations is to explore the near-sun solar wind, which is the key region for the study of the solar wind acceleration mechanism. Strong quasars; 3C279 and 3C273B were used for Kashima IPS observations at 2 GHz and 8 GHz, and a water vapor maser source, IRC20431 was used for the IPS observations at 22 GHz. Solar wind velocities derived from Kashima IPS data suggest that the solar wind acceleration takes place at radial distances between 10 and 30 solar radii (R(sub s)) from the sun. Properties of the turbulence spectrum (e.g. anisotropy, spectral index, inner scale) inferred from Kashima data are found to change systematically in the solar wind acceleration region. While the solar wind in the maximum phase appears to be dominated by the slow wind, fast and rarefied winds associated with coronal holes are found to develop significantly at high latitudes as the solar activity declines. Nevertheless, Kashima data suggests that the location of the acceleration region is stable throughout the solar cycle.

  19. High-resolution optical spectroscopy of the R Coronae Borealis star V532 Ophiuchi at maximum light

    E-print Network

    Rao, N Kameswara; Woolf, Vincent M; Hema, B P

    2014-01-01

    High-resolution optical spectra of the R Coronae Borealis (RCB) star V532 Oph at light maximum are discussed. The absolute visual magnitude M_V of the star is found to be -4.9 \\pm 0.5. The elemental abundances suggest the star belongs to the majority class of RCB stars but is among the most O-poor of this class with mild enhancements of heavy elements Y, Zr, Ba and La. The C_2 Swan bands are weak in V532 Oph relative to R CrB. Other aspects of the high-resolution spectrum confirm that V532 Oph is representative of majority RCBs, i.e., the radial velocity is variable, circumstellar material is present and the photosphere feeds a high-velocity stellar wind.

  20. Understanding extreme winds in Iceland

    NASA Astrophysics Data System (ADS)

    Petersen, Gudrun Nina

    2015-04-01

    Iceland is a fairly windy country, due to it's location adjacent the North Atlantic storm track. The orography of the island is rugged, mountains are steep and fjords and valleys narrow, and this impacts local winds. Thus, mountain wind phenomena such as low level jets, gap winds, down-slope wind storms, mountain waves and wind wakes are common. To increase our knowledge of the behaviour of wind in Iceland an extreme value analysis was conducted based on observations from 61 automatic weather stations, applying the Peak Over Threshold technique on maximum daily wind speed and maximum daily wind gust at each site. The time series included at least 10 years of data and the threshold was chosen as the 0.9 quantile of maximum mean wind speed/maximum wind gust at each location. Among the results is the larger impact the local orography has on the extreme wind gusts compared to the mean wind. With extreme value models in place, a few significant weather events were selected from recent years and the observed wind speeds compared to the models in order to evaluate how extreme the events were and how large area they impacted. Actually, in most of these events the observed wind speed only turned out to be extreme at a few stations, emphasising the local effects. However, in an event from December 2007, when the observed maximum wind speed exceeded 23 m/s in most of western Iceland, the event was estimated as rare at a number of weather stations. Clearly this gives indication for further studying this particular weather event. An automatic system has been set up, running once an hour, comparing observed wind measurements to the extreme value models and producing maps of the return periods for all sites. This system gives us the possibility to, on a daily basis, evaluate the extremeness of each situation and simultaneously increase our knowledge of extreme wind behaviour in Iceland. This work is a foundation for studying changes in extreme winds in Iceland.

  1. Group velocity Roger Grimshaw

    E-print Network

    Group velocity Roger Grimshaw July 2, 2002 Abstract A short and largely traditional review, called the phase velocity, is dif- ferent from that of the group as a whole, this speed being called the group velocity. For water waves, the phase velocity is greater than the group velocity, except

  2. Stellar winds on the main-sequence. I. Wind model

    NASA Astrophysics Data System (ADS)

    Johnstone, C. P.; Güdel, M.; Lüftinger, T.; Toth, G.; Brott, I.

    2015-05-01

    Aims: We develop a method for estimating the properties of stellar winds for low-mass main-sequence stars between masses of 0.4 M? and 1.1 M? at a range of distances from the star. Methods: We use 1D thermal pressure driven hydrodynamic wind models run using the Versatile Advection Code. Using in situ measurements of the solar wind, we produce models for the slow and fast components of the solar wind. We consider two radically different methods for scaling the base temperature of the wind to other stars: in Model A, we assume that wind temperatures are fundamentally linked to coronal temperatures, and in Model B, we assume that the sound speed at the base of the wind is a fixed fraction of the escape velocity. In Paper II of this series, we use observationally constrained rotational evolution models to derive wind mass loss rates. Results: Our model for the solar wind provides an excellent description of the real solar wind far from the solar surface, but is unrealistic within the solar corona. We run a grid of 1200 wind models to derive relations for the wind properties as a function of stellar mass, radius, and wind temperature. Using these results, we explore how wind properties depend on stellar mass and rotation. Conclusions: Based on our two assumptions about the scaling of the wind temperature, we argue that there is still significant uncertainty in how these properties should be determined. Resolution of this uncertainty will probably require both the application of solar wind physics to other stars and detailed observational constraints on the properties of stellar winds. In the final section of this paper, we give step by step instructions for how to apply our results to calculate the stellar wind conditions far from the stellar surface.

  3. Application of Wind Fetch and Wave Models for Habitat Rehabilitation and Enhancement Projects

    USGS Publications Warehouse

    Rohweder, Jason J.; Rogala, James T.; Johnson, Barry L.; Anderson, Dennis; Clark, Steve; Chamberlin, Ferris; Runyon, Kip

    2008-01-01

    Models based upon coastal engineering equations have been developed to quantify wind fetch length and several physical wave characteristics including significant height, length, peak period, maximum orbital velocity, and shear stress. These models, developed using Environmental Systems Research Institute's ArcGIS 9.2 Geographic Information System platform, were used to quantify differences in proposed island construction designs for three Habitat Rehabilitation and Enhancement Projects (HREPs) in the U.S. Army Corps of Engineers St. Paul District (Capoli Slough and Harpers Slough) and St. Louis District (Swan Lake). Weighted wind fetch was calculated using land cover data supplied by the Long Term Resource Monitoring Program (LTRMP) for each island design scenario for all three HREPs. Figures and graphs were created to depict the results of this analysis. The difference in weighted wind fetch from existing conditions to each potential future island design was calculated for Capoli and Harpers Slough HREPs. A simplistic method for calculating sediment suspension probability was also applied to the HREPs in the St. Paul District. This analysis involved determining the percentage of days that maximum orbital wave velocity calculated over the growing seasons of 2002-2007 exceeded a threshold value taken from the literature where fine unconsolidated sediments may become suspended. This analysis also evaluated the difference in sediment suspension probability from existing conditions to the potential island designs. Bathymetric data used in the analysis were collected from the LTRMP and wind direction and magnitude data were collected from the National Oceanic and Atmospheric Administration, National Climatic Data Center.

  4. High-velocity flow in the central part of the highly evolved planetary nebula Abell 30

    NASA Astrophysics Data System (ADS)

    Yadoumaru, Yasushi; Tamura, Shin'ichi

    1994-02-01

    We obtained a high-dispersion (O III) lambda 5007 spectrum of the highly evolved planetary nebula, Abell 30 (PK 208 + 33 deg 1 = IRAS 08440 + 1803). We found a high-velocity component in the profile, whose expansion velocity is derived from its full width at half maximum, 166 km/sec, and from the full width at zero intensity, VFWZI approximately equals 450 km/sec, in addition to the two velocity components from the previously identified knots. Moreover, from the position of the broad component, we determined the systemic velocity as Vsys = 13 km/sec in the frame of the Local Standard of Rest. These narrow components are attributed to J2 and J3-H4 identified by Jacoby (1979) and Hazard et al. (1980). Because Abell 30 is famous as a hydrogen-deficient planetary nebula, we suggest that its central star, having already shed its hydrogen envelope to expose the helium core, is now shedding its helium envelope. Abell 30 is, therefore, considered to have experienced the secondary ejection phase. Moreover the evidence of the existence of the fast stellar wind suggests that there is a dramatic effect on the material around the central star. We briefly discuss the origin of such a high-velocity flow.

  5. Meaningful wind chill indicators derived from heat transfer principles

    NASA Astrophysics Data System (ADS)

    Brauner, Neima; Shacham, M.

    1995-03-01

    The wind chill index (WCI) and the more widely used wind chill equivalent temperature represent an attempt to combine several weather-related variables (temperature, wind velocity and solar radiation) into a single index which can indicate human comfort. Since its introduction in 1945, the WCI has been criticized mainly on the ground that the underlying model does not comply with modern heat transfer theory. In spite of that, the WCI, “calibrated” to human comfort, has proven to be successful in predicting discomfort and tolerance of man to the cold. Nevertheless, neither the WCI nor the wind chill equivalent temperature can be actually measured and, therefore, without the additional ‘calibration’ they are meaningless. In this study we have shown that the WCI represents the instantaneous rate of heat loss from bare skin at the moment of exposure to the cold, and as such, it correlates reasonably well with measurable variables that represent a feeling of cold. Two new wind chill indicators have been introduced: exposed skin temperature and maximum exposure time. These indicators yield more information than the WCI provides, are measurable, have physical meaning and are based on established heat transfer principles.

  6. Meaningful wind chill indicators derived from heat transfer principles.

    PubMed

    Brauner, N; Shacham, M

    1995-08-01

    The wind chill index (WCI) and the more widely used wind chill equivalent temperature represent an attempt to combine several weather-related variables (temperature, wind velocity and solar radiation) into a single index which can indicate human comfort. Since its introduction in 1945, the WCI has been criticized mainly on the ground that the underlying model does not comply with modern heat transfer theory. In spite of that, the WCI, "calibrated" to human comfort, has proven to be successful in predicting discomfort and tolerance of man to the cold. Nevertheless, neither the WCI nor the wind chill equivalent temperature can be actually measured and, therefore, without the additional 'calibration' they are meaningless. In this study we have shown that the WCI represents the instantaneous rate of heat loss from bare skin at the moment of exposure to the cold, and as such, it correlates reasonably well with measurable variables that represent a feeling of cold. Two new wind chill indicators have been introduced: exposed skin temperature and maximum exposure time. These indicators yield more information than the WCI provides, are measurable, have physical meaning and are based on established heat transfer principles. PMID:7558408

  7. Long term variability of B supergiant winds

    NASA Technical Reports Server (NTRS)

    Massa, Derck L.

    1995-01-01

    The object of this observing proposal was to sample wind variability in B supergiants on a daily basis over a period of several days in order to determine the time scale with which density variability occurs in their winds. Three stars were selected for this project: 69 Cyg (B0 Ib), HD 164402 (B0 Ib), and HD 47240 (B1 Ib). Three grey scale representations of the Si IV lambda lambda 1400 doublet in each star are attached. In these figures, time (in days) increases upward, and the wavelength (in terms of velocity relative to the rest wavelength of the violet component of the doublet) is the abscissa. The spectra are normalized by a minimum absorption (maximum flux) template, so that all changes appear as absorptions. As a result of these observations, we can now state with some certainty that typical B supergiants develop significant wind inhomogeneities with recurrence times of a few days, and that some of these events show signs of strong temporal coherence.

  8. Screening length and the direction of plasma winds

    E-print Network

    Makoto Natsuume; Takashi Okamura

    2007-08-19

    We study the screening length of a heavy quark-antiquark pair in strongly coupled gauge theory plasmas flowing at velocity v following a proposal by Liu, Rajagopal, and Wiedemann. We analyze the screening length as the direction of the plasma winds vary. To leading order in v, this angle-dependence can be studied analytically for many theories by extending our previous formalism. We show that the screening length is locally a minimum (maximum) when the pair is perpendicular (parallel) to the plasma winds, which has been observed for the N=4 plasma. Also, we compare AdS/CFT results with weak coupling ones, and we discuss the subleading dependence on v for the Dp-brane.

  9. Detection of Solar Wind Disturbances: Mexican Array Radio Telescope IPS Observations at 140 MHz

    NASA Astrophysics Data System (ADS)

    Romero-Hernandez, E.; Gonzalez-Esparza, J. A.; Aguilar-Rodriguez, E.; Ontiveros-Hernandez, V.; Villanueva-Hernandez, P.

    2015-09-01

    The interplanetary scintillation (IPS) technique is a remote-sensing method for monitoring solar-wind perturbations. The Mexican Array Radio Telescope (MEXART) is a single-station instrument operating at 140 MHz, fully dedicated to performing solar-wind studies employing the IPS technique. We report MEXART solar-wind measurements (scintillation indices and solar-wind velocities) using data obtained during the 2013 and 2014 campaigns. These solar-wind measurements were calculated employing a new methodology based on the wavelet transform (WT) function. We report the variation of the scintillation indices versus the heliocentric distance for two IPS sources (3C48 and 3C147). We found different average conditions of the solar-wind density fluctuations in 2013 and 2014. We used the fittings of the radial dependence of the scintillation index to calculate g-indices. Based on the g-index value, we identified 17 events that could be associated with strong compression regions in the solar wind. We present the first ICME identifications in our data. We associated 14 IPS events with preceding CME counterparts by employing white-light observations from the Large Angle and Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) spacecraft. We found that most of the IPS events, detected during the solar maximum of Cycle 24 were associated with complex CME events. For the IPS events associated with single CME counterparts, we found a deceleration tendency of the CMEs as they propagate in the interplanetary medium. These results show that the instrument detects solar-wind disturbances, and the WT methodology provides solar-wind information with good accuracy. The MEXART observations will complement solar-wind IPS studies using other frequencies, and the tracking of solar-wind disturbances by other stations located at different longitudes.

  10. An Investigation of a Mathematical Model for the Internal Velocity Profile of Conical Diffusers Applied to DAWTs.

    PubMed

    Barbosa, Disterfano L M; Vaz, Jerson R P; Figueiredo, Sávio W O; De Oliveira e Silva, Marcelo; Lins, Erb F; Mesquita, André L A

    2015-01-01

    The Diffuser Augmented Wind Turbines (DAWTs) have been widely studied, since the diffusers improve the power coefficient of the wind turbine, particularly of small systems. The diffuser is a device which has the function of causing an increase on the flow velocity through the wind rotor plane due to pressure drop downstream, therefore resulting in an increase of the rotor power coefficient. This technology aids the turbine to exceed the Betz limit, which states that the maximum kinetic energy extracted from the flow is 59.26%. Thus, the present study proposes a mathematical model describing the behavior of the internal velocity for three conical diffusers, taking into account the characteristics of flow around them. The proposed model is based on the Biot-Savart's Law, in which the vortex filament induces a velocity field at an arbitrary point on the axis of symmetry of the diffusers. The results are compared with experimental data obtained for the three diffusers, and present good agreement. PMID:25923169

  11. Kinetic and Potential Sputtering of Lunar Regolith: Contribution of Solar-Wind Heavy Ions

    NASA Technical Reports Server (NTRS)

    Meyer, F. W.; Harris, P. R.; Meyer, H. M., III; Hijiazi, H.; Barghouty, A. F.

    2013-01-01

    Sputtering of lunar regolith by protons as well as solar-wind heavy ions is considered. From preliminary measurements of H+, Ar+1, Ar+6 and Ar+9 ion sputtering of JSC-1A AGGL lunar regolith simulant at solar wind velocities, and TRIM simulations of kinetic sputtering yields, the relative contributions of kinetic and potential sputtering contributions are estimated. An 80-fold enhancement of oxygen sputtering by Ar+ over same-velocity H+, and an additional x2 increase for Ar+9 over same-velocity Ar+ was measured. This enhancement persisted to the maximum fluences investigated is approximately 1016/cm (exp2). Modeling studies including the enhanced oxygen ejection by potential sputtering due to the minority heavy ion multicharged ion solar wind component, and the kinetic sputtering contribution of all solar wind constituents, as determined from TRIM sputtering simulations, indicate an overall 35% reduction of near-surface oxygen abundance. XPS analyses of simulant samples exposed to singly and multicharged Ar ions show the characteristic signature of reduced (metallic) Fe, consistent with the preferential ejection of oxygen atoms that can occur in potential sputtering of some metal oxides.

  12. Wind Simulation

    Energy Science and Technology Software Center (ESTSC)

    2008-12-31

    The Software consists of a spreadsheet written in Microsoft Excel that provides an hourly simulation of a wind energy system, which includes a calculation of wind turbine output as a power-curve fit of wind speed.

  13. High-Velocity Features: a ubiquitous property of Type Ia SNe

    E-print Network

    Mazzali, P A; Altavilla, G; Blanc, G; Cappellaro, E; Elias-Rosa, N; Garavini, G; Goobar, A; Harutyunyan, A; Kotak, R; Leibundgut, B; Lundqvist, P; Mattila, S; Méndez, J; Nobili, S; Pain, R; Pastorello, A; Patat, F; Pignata, G; Podsiadlowski, P; Ruiz-Lapuente, P; Salvo, M; Schmidt, B P; Sollerman, J; Stanishev, V; Stehle, M; Tout, C; Turatto, M; Hillebrandt, W; Podsiadlowski, Ph.

    2005-01-01

    Evidence of high-velocity features such as those seen in the near-maximum spectra of some Type Ia Supernovae (eg SN 2000cx) has been searched for in the available SNIa spectra observed earlier than one week before B maximum. Recent observational efforts have doubled the number of SNeIa with very early spectra. Remarkably, all SNeIa with early data (7 in our RTN sample and 10 from other programmes) show signs of such features, to a greater or lesser degree, in CaII IR, and some also in SiII 6255A line. High-velocity features may be interpreted as abundance or density enhancements. Abundance enhancements would imply an outer region dominated by Si and Ca. Density enhancements may result from the sweeping up of circumstellar material by the highest velocity SN ejecta. In this scenario, the high incidence of HVFs suggests that a thick disc and/or a high-density companion wind surrounds the exploding white dwarf, as may be the case in Single Degenerate systems. Large-scale angular fluctuations in the radial densit...

  14. Streamwise evolution of statistical events and the triple correlation in a model wind turbine array

    NASA Astrophysics Data System (ADS)

    Viestenz, Kyle; Cal, Raúl Bayoán

    2013-11-01

    Hot-wire anemometry data, obtained from a wind tunnel experiment containing a 3 × 3 wind turbine array, are used to conditionally average the Reynolds stresses. Nine profiles at the centerline behind the array are analyzed to characterize the turbulent velocity statistics of the wake flow. Quadrant analysis yields statistical events occurring in the wake of the wind farm, where quadrants 2 and 4 produce ejections and sweeps, respectively. A balance between these quadrants is expressed via the ?So parameter, which attains a maximum value at the bottom tip and changes sign near the top tip of the rotor. These are then associated to the triple correlation term present in the turbulent kinetic energy equation of the fluctuations. The development of these various quantities is assessed in light of wake remediation, energy transport and possess significance in closure models. National Science Foundation: ECCS-1032647.

  15. Concepts of relative velocity

    E-print Network

    Zbigniew Oziewicz; William S. Page

    2011-03-30

    The central concept of the theory of relativity is the relativity of velocity. The velocity of a material body is not an intrinsic property of the body; it depends on a free choice of reference system. Relative velocity is thus reference-dependent, it is not an absolute concept. We stress that even zero-velocity must be relative. Every reference system possesses its own zero-velocity relative only to that particular reference system. Does the theory of relativity formulated in terms of relative velocities, with many zero-velocities, imply the Lorentz isometry group? We discuss the many relative spaces of Galileo and Poincare, as quotient spaces.

  16. Maximum windmill efficiency in finite time

    NASA Astrophysics Data System (ADS)

    Huleihil, Mahmoud

    2009-05-01

    The fraction of the kinetic energy of the wind impinging on the rotor-swept area that a wind turbine can convert to useful power has been shown by Betz in an idealized laminar-flow model to have an upper limit of 16/27 or 59% approximately [I. H. Shames, Mechanics of Fluids, 2nd ed. (McGraw-Hill, New York, 1982), pp. A26-A31]. This figure is known as Betz number. Other studies [A. Rauh and W. Seelret, Appl. Energy 17, 15 (1984)] suggested that this figure should be considered as a guideline. In this paper, a new model is introduced and its efficiency at maximum power output is derived. The derived value is shown to be a function of the Betz number B and given by the formula ?mp=1-?1-B . This value is 36.2%, which agrees well with those of actually operating wind turbines. As a guideline, the wind turbine efficiency can be considered to be within the range of the two numbers of merit, the Betz number and ?mp.

  17. Wind tunnel simulation of wind effects and associated displacement hazards on flat surface construction materials such as plywood 

    E-print Network

    Madeley, Jack T.

    1996-01-01

    Accidents and hazards continue to plague the construction industry. One often overlooked hazard to workers is the potential for flying debris and materials during high winds. This research was designed to evaluate the wind velocity required...

  18. A laboratory study of friction-velocity estimates from scatterometry - Low and high regimes

    NASA Technical Reports Server (NTRS)

    Bliven, L. F.; Giovanangeli, J.-P.; Wanninkhof, R. H.; Chapron, B.

    1993-01-01

    Measurements from scatterometers pointing at wind-waves in three large wave tanks are examined to study fetch effects and the correlation with wind friction velocity. Time-series measurements were made at 13, 35, and 95 m with a Ka-band scatterometer aimed upwind at 30 deg incidence angle and vertical polarization. Average normalized radar cross-section (sigma-0) values from all fetches follow a common trend for sigma-0 as a function of wind friction velocity, so the fetch dependence is negligible. An empirical power-law model yields a high correlation between sigma-0 and wind friction velocity, but, because systematic anomalies arise, we reexamine a turbulence approach that delineates low and high regimes with a transition at a wind friction velocity of approximately 25 cm/s. Using this criteria, the data are well represented by a two-section power-law relationship between sigma-0 and wind friction velocity.

  19. The Average Velocity in a Queue

    ERIC Educational Resources Information Center

    Frette, Vidar

    2009-01-01

    A number of cars drive along a narrow road that does not allow overtaking. Each driver has a certain maximum speed at which he or she will drive if alone on the road. As a result of slower cars ahead, many cars are forced to drive at speeds lower than their maximum ones. The average velocity in the queue offers a non-trivial example of a mean…

  20. Maximum Entropy Approximation

    NASA Astrophysics Data System (ADS)

    Sukumar, N.

    2005-11-01

    In this paper, the construction of scattered data approximants is studied using the principle of maximum entropy. For under-determined and ill-posed problems, Jaynes's principle of maximum information-theoretic entropy is a means for least-biased statistical inference when insufficient information is available. Consider a set of distinct nodes {xi}i=1n in Rd, and a point p with coordinate x that is located within the convex hull of the set {xi}. The convex approximation of a function u(x) is written as: uh(x) = ?i=1n ?i(x)ui, where {?i}i=1n ? 0 are known as shape functions, and uh must reproduce affine functions (d = 2): ?i=1n ?i = 1, ?i=1n ?ixi = x, ?i=1n ?iyi = y. We view the shape functions as a discrete probability distribution, and the linear constraints as the expectation of a linear function. For n > 3, the problem is under-determined. To obtain a unique solution, we compute ?i by maximizing the uncertainty H(?) = - ?i=1n ?i log ?i, subject to the above three constraints. In this approach, only the nodal coordinates are used, and neither the nodal connectivity nor any user-defined parameters are required to determine ?i—the defining characteristics of a mesh-free Galerkin approximant. Numerical results for {?i}i=1n are obtained using a convex minimization algorithm, and shape function plots are presented for different nodal configurations.

  1. WIND VARIABILITY IN BZ CAMELOPARDALIS

    SciTech Connect

    Honeycutt, R. K.; Kafka, S.; Robertson, J. W. E-mail: skafka@dtm.ciw.edu

    2013-02-01

    Sequences of spectra of the nova-like cataclysmic variable (CV) BZ Cam were acquired on nine nights in 2005-2006 in order to study the time development of episodes of wind activity known to occur frequently in this star. We confirm the results of Ringwald and Naylor that the P-Cygni absorption components of the lines mostly evolve from higher expansion velocity to lower velocity as an episode progresses. We also commonly find blueshifted emission components in the H{alpha} line profile, whose velocities and durations strongly suggest that they are also due to the wind. Curiously, Ringwald and Naylor reported common occurrences of redshifted H{alpha} emission components in their BZ Cam spectra. We have attributed these emission components in H{alpha} to occasions when gas concentrations in the bipolar wind (both front side and back side) become manifested as emission lines as they move beyond the disk's outer edge. We also suggest, based on changes in the P-Cygni profiles during an episode, that the progression from larger to smaller expansion velocities is due to the higher velocity portions of a wind concentration moving beyond the edge of the continuum light of the disk first, leaving a net redward shift of the remaining absorption profile. We derive a new orbital ephemeris for BZ Cam, using the radial velocity of the core of the He I {lambda}5876 line, finding P = 0.15353(4). Using this period, the wind episodes in BZ Cam are found to be concentrated near the inferior conjunction of the emission line source. This result helps confirm that the winds in nova-like CVs are often phase dependent, in spite of the puzzling implication that such winds lack axisymmetry. We argue that the radiation-driven wind in BZ Cam receives an initial boost by acting on gas that has been lifted above the disk by the interaction of the accretion stream with the disk, thereby imposing flickering timescales onto the wind events, as well as leading to an orbital modulation of the wind due to the non-axisymmetric nature of the stream/disk interaction. Simultaneous photometry and spectroscopy were acquired on three nights in order to test the possible connection between flickering continuum light and the strength of the front-side wind. We found strong agreement on one night, some agreement on another, and no agreement on the third. We suggest that some flickering events lead to only back-side winds which will not have associated P-Cygni profiles.

  2. university-logo Maximum likelihood

    E-print Network

    McCullagh, Peter

    university-logo Maximum likelihood Applications and examples REML and residual likelihood Peter McCullagh REML #12;university-logo Maximum likelihood Applications and examples JAN: Some personal remarks... IC #12;university-logo Maximum likelihood Applications and examples Outline 1 Maximum likelihood REML

  3. Sea surface velocities from visible and infrared multispectral atmospheric mapping sensor imagery

    NASA Technical Reports Server (NTRS)

    Pope, P. A.; Emery, W. J.; Radebaugh, M.

    1992-01-01

    High resolution (100 m), sequential Multispectral Atmospheric Mapping Sensor (MAMS) images were used in a study to calculate advective surface velocities using the Maximum Cross Correlation (MCC) technique. Radiance and brightness temperature gradient magnitude images were formed from visible (0.48 microns) and infrared (11.12 microns) image pairs, respectively, of Chandeleur Sound, which is a shallow body of water northeast of the Mississippi delta, at 145546 GMT and 170701 GMT on 30 Mar. 1989. The gradient magnitude images enhanced the surface water feature boundaries, and a lower cutoff on the gradient magnitudes calculated allowed the undesirable sunglare and backscatter gradients in the visible images, and the water vapor absorption gradients in the infrared images, to be reduced in strength. Requiring high (greater than 0.4) maximum cross correlation coefficients and spatial coherence of the vector field aided in the selection of an optimal template size of 10 x 10 pixels (first image) and search limit of 20 pixels (second image) to use in the MCC technique. Use of these optimum input parameters to the MCC algorithm, and high correlation and spatial coherence filtering of the resulting velocity field from the MCC calculation yielded a clustered velocity distribution over the visible and infrared gradient images. The velocity field calculated from the visible gradient image pair agreed well with a subjective analysis of the motion, but the velocity field from the infrared gradient image pair did not. This was attributed to the changing shapes of the gradient features, their nonuniqueness, and large displacements relative to the mean distance between them. These problems implied a lower repeat time for the imagery was needed in order to improve the velocity field derived from gradient imagery. Suggestions are given for optimizing the repeat time of sequential imagery when using the MCC method for motion studies. Applying the MCC method to the infrared brightness temperature imagery yielded a velocity field which did agree with the subjective analysis of the motion and that derived from the visible gradient imagery. Differences between the visible and infrared derived velocities were 14.9 cm/s in speed and 56.7 degrees in direction. Both of these velocity fields also agreed well with the motion expected from considerations of the ocean bottom topography and wind and tidal forcing in the study area during the 2.175 hour time interval.

  4. Maximum Entropy Fundamentals

    NASA Astrophysics Data System (ADS)

    Harremoeës, P.; Topsøe, F.

    2001-09-01

    In its modern formulation, the Maximum Entropy Principle was promoted by E.T. Jaynes, starting in the mid-fifties. The principle dictates that one should look for a distribution, consistent with available information, which maximizes the entropy. However, this principle focuses only on distributions and it appears advantageous to bring information theoretical thinking more prominently into play by also focusing on the "observer" and on coding. This view was brought forward by the second named author in the late seventies and is the view we will follow-up on here. It leads to the consideration of a certain game, the Code Length Game and, via standard game theoretical thinking, to a principle of Game Theoretical Equilibrium. This principle is more basic than the Maximum Entropy Principle in the sense that the search for one type of optimal strategies in the Code Length Game translates directly into the search for distributions with maximum entropy. In the present paper we offer a self-contained and comprehensive treatment of fundamentals of both principles mentioned, based on a study of the Code Length Game. Though new concepts and results are presented, the reading should be instructional and accessible to a rather wide audience, at least if certain mathematical details are left aside at a rst reading. The most frequently studied instance of entropy maximization pertains to the Mean Energy Model which involves a moment constraint related to a given function, here taken to represent "energy". This type of application is very well known from the literature with hundreds of applications pertaining to several different elds and will also here serve as important illustration of the theory. But our approach reaches further, especially regarding the study of continuity properties of the entropy function, and this leads to new results which allow a discussion of models with so-called entropy loss. These results have tempted us to speculate over the development of natural languages. In fact, we are able to relate our theoretical findings to the empirically found Zipf's law which involves statistical aspects of words in a language. The apparent irregularity inherent in models with entropy loss turns out to imply desirable stability properties of languages.

  5. Threshold friction velocity of soils within the Columbia Plateau

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind erosion only occurs when the friction velocity exceeds the threshold friction velocity (TFV) of the surface. The TFV of loessial soils commonly found across the Columbia Plateau region of the U.S. Pacific Northwest is virtually unknown even though these soils are highly erodible and a source of...

  6. Instrumentation in wind tunnels

    NASA Technical Reports Server (NTRS)

    Takashima, K.

    1986-01-01

    Requirements in designing instrumentation systems and measurements of various physical quantities in wind tunnels are surveyed. Emphasis is given to sensors used for measuring pressure, temperature, and angle, and the measurements of air turbulence and boundary layers. Instrumentation in wind tunnels require accuracy, fast response, diversity and operational simplicity. Measurements of force, pressure, attitude angle, free flow, pressure distribution, and temperature are illustrated by a table, and a block diagram. The LDV (laser Doppler velocimeter) method for measuring air turbulence and flow velocity and measurement of skin friction and flow fields using laser holograms are discussed. The future potential of these techniques is studied.

  7. A correlative study of simultaneously measured He(++) fluxes in the solar wind and in the magnetosphere utilizing Imp-1 and 1971-089A satellite data

    NASA Technical Reports Server (NTRS)

    Shelley, E. G.

    1975-01-01

    Simultaneously measured He(++) fluxes in the solar wind and in the magnetosphere were studied using data from the plasma spectrometer on the Imp I satellite and the energetic ion mass spectrometer on the low altitude polar orbiting satellite 1971-89A. A detailed comparison of the He(++) energy spectra measured simultaneously in the solar wind and in the low altitude dayside polar cusp on March 7, 1972 was made. The energy-per-unit-charge range of the energetic ion mass spectrometer on board the polar orbiting satellite was 700 eV to 12 keV. Within this range there was a clear maximum in the He(++) energy spectrum at approximately 1.5 keV/nucleon. There was not a clearly defined maximum in the H(+) spectrum, but the data were consistent with a peak between 0.7 and 1.0 keV/nucleon. Both spectra could be reasonably well fit with a convecting Maxwellian plus a high energy tail; however, the mean velocity for He(++) distribution was significantly greater than that for the H(+) distribution. The simultaneous solar wind measurements showed the mean velocities for both ion species to be approximately 600 km/sec. The discrepancies between the relative velocity distributions in the low altitude cusp and those in the solar wind are consistent with a potential difference of approximately 1.4 kV along their flow direction between the two points of observation.

  8. Introduction to maximum entropy

    SciTech Connect

    Sivia, D.S.

    1988-01-01

    The maximum entropy (MaxEnt) principle has been successfully used in image reconstruction in a wide variety of fields. We review the need for such methods in data analysis and show, by use of a very simple example, why MaxEnt is to be preferred over other regularizing functions. This leads to a more general interpretation of the MaxEnt method, and its use is illustrated with several different examples. Practical difficulties with non-linear problems still remain, this being highlighted by the notorious phase problem in crystallography. We conclude with an example from neutron scattering, using data from a filter difference spectrometer to contrast MaxEnt with a conventional deconvolution. 12 refs., 8 figs., 1 tab.

  9. Erosion: Wind

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind erosion refers to the detachment, transport and deposition of sediment by wind. It is a dynamic, physical process where loose, dry, bare soils are transported by strong winds. Wind erosion is a soil degrading process that affects over 500 million ha of land worldwide and creates between 500 an...

  10. High-velocity regions in planetary nebulae

    E-print Network

    Krzysztof Gesicki; Albert A. Zijlstra

    2002-11-02

    The internal velocity fields of planetary nebulae are studied with a resolution of 5 km s$^{-1}$. We analyze deep echelle spectra from three nebulae in the Bulge, the Sagittarius Dwarf and the SMC. No effects of metallicity is seen, except possibly a slower onset of the fast wind from the central star. Robust evidence is found for the existence of a high-velocity shock at the inner edges of the nebulae. Such a shock is predicted in hydrodynamical models but had not previously been observed. The shock gas is accelerated by the fast wind from the central star. A similar shock at the outer edges traces the expansion of the ionized shell into the ambient AGB wind. Evidence for localized regions of high velocity is also found from lines of intermediate excitation, for two of nebulae. We explore several possible interpretations: (1) an embedded shock at intermediate radii, as predicted by hydrodynamic models at the position of the outer edge of the swept-up inner shell; (2) deviations form spherical symmetry, where in some directions the intermediate-excitation lines extend into the region of the outer shock; (3) An intermediate swept-up shell, as seen in some Galactic planetary nebulae. The remaining nebula, with a [WC] star, shows strong turbulence. This may trace a superposition of many embedded shock-lets. We suggest a relation to the time-variable [WC] wind, giving a planetary nebula subjected to a multitude of sound waves.

  11. Processing: Ball Velocity (if and velocity) Peabody Charter 5th

    E-print Network

    Wood, Zoë J.

    Processing: Ball Velocity (if and velocity) Peabody Charter 5th grade a ball travelling in different directions. Our goal is learn about velocity the velocity in x and vy to represent the velocity in y. These variables should

  12. Role of velocity shears in turbulent dissipation

    NASA Astrophysics Data System (ADS)

    Parashar, T. N.; Ghosh, S.

    2013-12-01

    The discussion about what processes are important in solar wind plasma heating usually concentrates on wave particle interactions or on energization by low frequency structures like current sheets and reconnection sites. Less attention has been paid to the role of local velocity shears in plasma heating. We study this problem using Hall-FLR MHD and hybrid codes. We see that the velocity shear sites are related to hot spots and most of the dissipated energy comes from velocity shears. The ultimate energy deposition mechanism is electromagnetic interactions but these interactions are enhanced at the velocity shear sites making them an attractive candidate for sites of dissipation along with magnetic shear sites like the current sheets and reconnection sites.

  13. Investigations of high latitude wind shears in the lower thermosphere

    NASA Astrophysics Data System (ADS)

    Marshall, Timothy Richard

    The Atmospheric Response in Aurora (ARIA) rocket campaign of March 1992 represented an effort to measure the effect of the prolonged heating due to a diffuse aurora on the neutral atmosphere. A previous model had predicted strong zonal winds in the lower thermosphere as the result of the strong coupling between the ionosphere and neutral atmosphere. An instrumented payload was launched into the diffuse aurora to measure neutral and plasma compositions, and two chemical releases provided the neutral wind measurements. In addition to this data, ground-based magnetometers and satellite measurements of the interplanetary magnetic field (IMF), electric fields, particle precipitation, and ram drift were incorporated into the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure. The AMIE procedure provided patterns of the electrostatic potential, electric fields, conductivities, and Joule heating on a global scale. The results of this analysis show the activity the chemical release of March 3 occurred in the region of greatest Joule heating. The neutral wind profile show strong wind shear existing at 115 km altitude, approximately the same altitude of the maximum electron density measured by the instrumented payload. This feature had a magnitude of approximately 150 m/s and was in the direction of the auroral electric field (southwestward). These wind shears coexisting with maximum's in electron densities have been studied for many years from chemical releases done at midlatitudes. The explanation for the midlatitude wind shears however fails to explain the high latitude wind shears seen in the ARIA release due to the vertical nature of the magnetic field. At auroral latitudes the electron density does not build up like at lower latitudes. In order to investigate high latitude wind shears, 15 additional high latitude chemical release experiments, performed by Heppner during the 1970's, have been reanalyzed. A steady state solution called modified geostrophic adjustment is used in attempting to model these features. This model is simply a balance of the pressure gradient, Corolis and Lorentz forces. By incorporating the Time Dependent Ionospheric Model (TDIM) of Utah State, along with a model neutral atmosphere provided by MSIS90E, wind simulations were compared with sixteen chemical release experiments. Simulation results show the presence of wind shears around 120 km altitude whenever the electron density profile shows a maximum at approximately that height. The existence of this wind shear is shown to be dependent on the Hall conductivity, which can dominate the Pedersen conductivity at lower thermospheric heights. The magnitude of the wind shear produced in the steady-state solution is also observed to be dependent on the strength of the imposed electric field. Comparisons of these modeled velocities with the neutral wind profiles obtained from the Heppner chemical releases show varied results depending on the stability of the prevailing conditions, but results from the ARIA release compare quite well due to the prolonged heating due to the diffuse aurora.

  14. Wind fence enclosures for infrasonic wind noise reduction.

    PubMed

    Abbott, JohnPaul; Raspet, Richard; Webster, Jeremy

    2015-03-01

    A large porous wind fence enclosure has been built and tested to optimize wind noise reduction at infrasonic frequencies between 0.01 and 10?Hz to develop a technology that is simple and cost effective and improves upon the limitations of spatial filter arrays for detecting nuclear explosions, wind turbine infrasound, and other sources of infrasound. Wind noise is reduced by minimizing the sum of the wind noise generated by the turbulence and velocity gradients inside the fence and by the area-averaging the decorrelated pressure fluctuations generated at the surface of the fence. The effects of varying the enclosure porosity, top condition, bottom gap, height, and diameter and adding a secondary windscreen were investigated. The wind fence enclosure achieved best reductions when the surface porosity was between 40% and 55% and was supplemented by a secondary windscreen. The most effective wind fence enclosure tested in this study achieved wind noise reductions of 20-27?dB over the 2-4?Hz frequency band, a minimum of 5?dB noise reduction for frequencies from 0.1 to 20?Hz, constant 3-6?dB noise reduction for frequencies with turbulence wavelengths larger than the fence, and sufficient wind noise reduction at high wind speeds (3-6?m/s) to detect microbaroms. PMID:25786940

  15. Maximum likelihood estimation of turbulence spectrum parameters

    NASA Technical Reports Server (NTRS)

    Mark, W. D.

    1984-01-01

    Estimation of the integral scale and intensity of a generic turbulence record is treated as a statistical problem of parameter estimation. Properties of parameter estimators and the method of maximum likelihood are reviewed. Likelihood equations are derived for estimation of the integral scale and intensity applicable to a general class of turbulence spectra that includes the von Karman and Dryden transverse and longitudinal spectra as special cases. The method is extended to include the Bullen transverse and longitudinal spectra. Coefficients of variation are given for maximum likelihood estimates of the integral scale and intensity of the von Karman spectra. Application of the method is illustrated by estimating the integral scale and intensity of an atmospheric turbulence vertical velocity record assumed to be governed by the von Karman transverse spectrum.

  16. Generalized Maximum Entropy

    NASA Technical Reports Server (NTRS)

    Cheeseman, Peter; Stutz, John

    2005-01-01

    A long standing mystery in using Maximum Entropy (MaxEnt) is how to deal with constraints whose values are uncertain. This situation arises when constraint values are estimated from data, because of finite sample sizes. One approach to this problem, advocated by E.T. Jaynes [1], is to ignore this uncertainty, and treat the empirically observed values as exact. We refer to this as the classic MaxEnt approach. Classic MaxEnt gives point probabilities (subject to the given constraints), rather than probability densities. We develop an alternative approach that assumes that the uncertain constraint values are represented by a probability density {e.g: a Gaussian), and this uncertainty yields a MaxEnt posterior probability density. That is, the classic MaxEnt point probabilities are regarded as a multidimensional function of the given constraint values, and uncertainty on these values is transmitted through the MaxEnt function to give uncertainty over the MaXEnt probabilities. We illustrate this approach by explicitly calculating the generalized MaxEnt density for a simple but common case, then show how this can be extended numerically to the general case. This paper expands the generalized MaxEnt concept introduced in a previous paper [3].

  17. Solar Maximum Mission

    SciTech Connect

    Chipman, E.G.

    1981-03-15

    The Solar Maximum Mission spacecraft, launched on 1980 February 14, carries seven instruments for the study of solar flares and other aspects of solar activity. These instruments observe in spectral ranges from gamma-rays through the visible, using imaging, spectroscopy, and high-time-resolution light curves to study flares phenomena. In addition, one instrument incorporates an Active Cavity Radiometer for accurate measurement of the total solar radiant output. We review some of the most important current observational and theoretical questions of solar flare physics and indicate the ways in which the experiments on SMM will be able to attack these questions. The SMS observing program is described. The observing programs of the instruments for the study of flares are planned together, at a central location, to provide simultaneous observations of solar events by several instruments whenever possible. A Guest Investigator program has been initiated which allows broad use of these instruments by the scientific community and supports ground-based observations in conjunction with SMM observing programs.

  18. On the correlation between interplanetary nano dust particles and solar wind properties from STEREO/SWAVES

    NASA Astrophysics Data System (ADS)

    Issautier, K.; LE CHAT, G.; Meyer-Vernet, N.; Belheouane, S.; Zaslavsky, A.; Zouganelis, I.; Mann, I.; Maksimovic, M.

    2012-12-01

    Dust particles provide an important fraction of the matter composing the interplanetary medium, their mass density at 1 AU being comparable to the one of the solar wind. Among them, dusts of nanometer size-scale can be detected using radio and plasma waves instruments because they move at roughly the solar wind speed. The high velocity impact of a dust particle generates a small crater on the spacecraft: the dust particle and the crater material are vaporized. This produces a plasma cloud whose associated electrical charge induces an electric pulse measured with radio and plasma instruments. Since their first detection in the interplanetary medium (Meyer-Vernet et al. 2009), nanodusts have been routinely measured using STEREO/WAVES instrument (Zaslavsky et al. 2012) We present the nanodust properties during the 2007-2012 period on STEREO. Since the maximum size of the plasma cloud is larger for smaller local solar wind density, we expect to observe an anticorrelation between the detected voltage amplitude and the ambient solar wind density, as suggested recently by Le Chat et al. (2012). Moreover, the variations in solar wind speed and magnetic field are expected to affect the nano dust dynamics. Using STEREO/WAVES/Low Frequency Receiver (LFR) data, we study correlations of in situ solar wind properties and detection of nanodust impacts as well as some possible effects of Coronal Mass Ejections (CME) on nanodusts acceleration.

  19. Validation of a UHF spaced antenna wind profiler for high-resolution boundary layer observations

    SciTech Connect

    Cohn, S.A.; Holloway, C.L.; Oncley, S.P.; Doviak, R.J.; Lataitis, R.J.

    1997-05-01

    In this paper we apply a spaced antenna technique derived from the recent work of {ital Doviak} {ital et al.} and {ital Holloway} {ital et al.} to wind measurement with a small UHF boundary layer profiler. We discuss the implementation of the technique, averaging and quality control strategies, and some advantages and limitations of spaced antenna methods over conventional Doppler beam swinging wind profilers in the boundary layer. Such advantages include a relaxation of the assumption of a horizontally uniform wind field and the possibility of high temporal resolution wind profiles. In this regard we present velocity measurements derived from this UHF system with time resolution of about 30 s and compare these measurements with in situ sonic anemometer data taken on a 300-m tower. Finally, we present an example of a high-resolution time-height cross section of atmospheric winds. This example, collected in stratiform precipitation, shows the intriguing situation of a wind speed maximum (jet) which closely follows the height of the melting layer over several hours even as this height changes by several hundred meters.{copyright} 1997 American Geophysical Union

  20. Aalborg Universitet Control and Protection of Wind Power Plants with VSC-HVDC Connection

    E-print Network

    Chaudhary, Sanjay

    energy. The European Union expects to generate 230 GW wind power, in which the offshore wind power is expected to contribute 40 GW. Offshore wind power plants have better wind velocity profile leading and sustainable resource. All these have led to the development of offshore wind power plants. However, overall

  1. Winds from T Tauri stars. II - Balmer line profiles for inner disk winds

    NASA Technical Reports Server (NTRS)

    Calvet, Nuria; Hartmann, Lee; Hewett, Robert

    1992-01-01

    Results are presented of calculations of Balmer emission line profiles using escape probability methods for T Tauri wind models with nonspherically symmetric geometry. The wind is assumed to originate in the inner regions of an accretion disk surrounding the T Tauri star, and flows outward in a 'cone' geometry. Two types of wind models are considered, both with monotonically increasing expansion velocities as a function of radial distance. For flows with large turbulent velocities, such as the HF Alfven wave-driven wind models, the effect of cone geometry is to increase the blue wing emission, and to move the absorption reversal close to line center. Line profiles for a wind model rotating with the same angular velocity as the inner disk are also calculated. The Balmer lines of this model are significantly broader than observed in most objects, suggesting that the observed emission lines do not arise in a region rotating at Keplerian velocity.

  2. Wind height distribution influence on offshore wind farm feasibility study

    NASA Astrophysics Data System (ADS)

    Benassai, Guido; Della Morte, Renata; Matarazzo, Antonio; Cozzolino, Luca

    2015-04-01

    The economic feasibility of offshore wind power utilization depends on the favourable wind conditions offshore as compared to sites on land. The higher wind speeds have to compensate the additional cost of offshore developments. However, not only the mean wind speed is different, but the whole flow regime, as can be seen in the vertical wind speed profile. The commonly used models to describe this profile have been developed mainly for land sites, so they have to be verified on the basis of field data. Monin-Obukhov theory is often used for the description of the wind speed profile at a different height with respect to a measurement height. Starting from the former, , the profile is predicted using two parameters, Obukhov length and sea surface roughness. For situations with near-neutral and stable atmospheric stratification and long (>30km) fetch, the wind speed increase with height is larger than what is predicted from Monin-Obukhov theory. It is also found that this deviation occurs at wind speeds important for wind power utilization, mainly at 5-9 ms-1. In the present study the influence of these aspects on the potential site productivity of an offshore wind farm were investigated, namely the deviation from the theory of Monin-Obukhov due to atmospheric stability and the influence of the fetch length on the Charnock model. Both these physical effects were discussed and examined in view of a feasibility study of a site for offshore wind farm in Southern Italy. Available data consisted of time histories of wind speeds and directions collected by National Tidegauge Network (Rete Mareografica Nazionale) at the height of 10m a.s.l. in ports. The theory of Monin-Obukhov was used to extrapolate the data to the height of the wind blades, while the Charnock model was used to extend the wind speed on the sea surface from the friction velocity on the ground. The models described were used to perform calculations for a feasibility study of an offshore wind farm in Southern Italy. The potential site productivity was established on the basis of the wind speed distribution function for different heights (site specific) and the power law of the wind turbine considered, as a function of the wind speed at the nacelle height (machine specific). The results of the optimization study for different sites and different wind turbines were compared with the power estimates of Italian Wind Atlas, which provided useful insights for further study.

  3. Effects of wind direction and wind farm layout on turbine wakes and power losses in wind farms: An LES study

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Ting; Porté-Agel, Fernando

    2014-05-01

    A recently-developed large-eddy simulation (LES) framework is validated and used to investigate the effects of wind direction and wind farm layout on the turbine wakes and power losses in wind farms. The subgrid-scale (SGS) turbulent stress is parameterized using a tuning-free Lagrangian scale-dependent dynamic SGS model. The turbine-induced forces are computed using a dynamic actuator-disk model with rotation (ADM-R), which couples blade-element theory with a turbine-specific relation between the blade angular velocity and the shaft torque to compute simultaneously turbine angular velocity and power output. Here, we choose the Horns Rev offshore wind farm as a case study for model validation. A series of simulations are performed for a wide range of wind direction angles. Results from the simulations are in good agreement with observed power data from the Horns Rev wind farm, and show a strong impact of wind direction on the farm power production and the spatial distribution of turbine-wake characteristics (e.g., velocity deficit and turbulence intensity). This can be explained by the fact that changing the wind angle can be viewed as changing the wind farm layout relative to the incoming wind, while keeping the same wind turbine density. To further investigate the effect of wind farm layout on the flow and the power extracted by the farm, simulations of wind farms with different circular and elliptic layouts are performed to compare with the results of the Horns Rev wind farm simulations. The results show that the proposed layouts not only provide more stable power output with different wind directions, but also enhance the performance of the total farm power production.

  4. Paper waves in the wind

    E-print Network

    Jia, Pan; Claudin, Philippe

    2015-01-01

    A flexible sheet clamped at both ends and submitted to a permanent wind is unstable and propagates waves. Here, we experimentally study the selection of frequency and wavenumber as a function of the wind velocity. These quantities obey simple scaling laws, which are analytically derived from a linear stability analysis of the problem, and which also involve a gravity-induced velocity scale. This approach allows us to collapse data obtained with sheets whose flexible rigidity is varied by two orders of magnitude. This principle may be applied in the future for energy harvesting.

  5. Paper waves in the wind

    NASA Astrophysics Data System (ADS)

    Jia, Pan; Andreotti, Bruno; Claudin, Philippe

    2015-10-01

    A flexible sheet clamped at both ends and submitted to a permanent wind is unstable and propagates waves. Here, we experimentally study the selection of frequency and wavenumber as a function of the wind velocity. These quantities obey simple scaling laws, which are analytically derived from a linear stability analysis of the problem and which also involve a gravity-induced velocity scale. This approach allows us to collapse data obtained with sheets whose flexible rigidity is varied by two orders of magnitude. This principle may be applied in the future for energy harvesting.

  6. What is a Hurricane? Tropical system with maximum sustained

    E-print Network

    Meyers, Steven D.

    Hurricane 101 #12;What is a Hurricane? · Tropical system with maximum sustained surface wind of 74 mph or greater. A hurricane is the worst and the strongest of all tropical systems. · Also known as a tropical cyclone. #12;Hurricanes in Florida · 1851-2004 Florida's Hurricane Total: 110 Southwest Florida

  7. A Windmill's Theoretical Maximum Extraction of Power from the Wind.

    ERIC Educational Resources Information Center

    Inglis, David Rittenhouse

    1979-01-01

    Explains that the efficiency and the useful power available from a windmill turbine, of a laminar-flow model, will vary due to rotational kinetic energy of the downwind stream and turbulent mixing from outside the boundaries of the idealized stream. (GA)

  8. RAWS: The spaceborne radar wind sounder

    NASA Astrophysics Data System (ADS)

    Moore, Richard K.

    1991-09-01

    The concept of the Radar Wind Sounder (RAWS) is discussed. The goals of the RAWS is to estimate the following three qualities: the echo power, to determine rain rate and surface wind velocity; the mean Doppler frequency, to determine the wind velocity in hydrometers; and the spread of the Doppler frequency, to determine the turbulent spread of the wind velocity. Researchers made significant progress during the first year. The feasibility of the concept seems certain. Studies indicate that a reasonably sized system can measure in the presence of ice clouds and dense water clouds. No sensitivity problems exist in rainy environments. More research is needed on the application of the radar to the measurement of rain rates and winds at the sea surface.

  9. Stellar winds driven by Alfven waves

    NASA Technical Reports Server (NTRS)

    Belcher, J. W.; Olbert, S.

    1973-01-01

    Models of stellar winds were considered in which the dynamic expansion of a corona is driven by Alfven waves propagating outward along radial magnetic field lines. In the presence of Alfven waves, a coronal expansion can exist for a broad range of reference conditions which would, in the absence of waves, lead to static configurations. Wind models in which the acceleration mechanism is due to Alfven waves alone and exhibit lower mass fluxes and higher energies per particle are compared to wind models in which the acceleration is due to thermal processes. For example, winds driven by Alfven waves exhibit streaming velocities at infinity which may vary between the escape velocity at the coronal base and the geometrical mean of the escape velocity and the speed of light. Upper and lower limits were derived for the allowed energy fluxes and mass fluxes associated with these winds.

  10. Rapidly rotating winds of hot stars

    NASA Astrophysics Data System (ADS)

    Ceniga, M.; Kubát, J.

    The CAK theory is used for a description of a line driven wind of hot stars. We have developed a code using the Newton-Raphson method to obtain a solution of a 1D isothermal line driven wind with rotation. Our calculations confirmed that there exists a "break" value of stellar rotation velocity, for which the wind solution switches to a new one, which yields much denser and slower wind than in the non-rotating case. For this new solution we found a new critical point, which is located far from the stellar photosphere. Close to the star the outflow is 100 times denser at the equator than at the pole. The wind velocity profile is shallower and reaches a terminal velocity of only several hundred km s-1.

  11. RAWS: The spaceborne radar wind sounder

    NASA Technical Reports Server (NTRS)

    Moore, Richard K.

    1991-01-01

    The concept of the Radar Wind Sounder (RAWS) is discussed. The goals of the RAWS is to estimate the following three qualities: the echo power, to determine rain rate and surface wind velocity; the mean Doppler frequency, to determine the wind velocity in hydrometers; and the spread of the Doppler frequency, to determine the turbulent spread of the wind velocity. Researchers made significant progress during the first year. The feasibility of the concept seems certain. Studies indicate that a reasonably sized system can measure in the presence of ice clouds and dense water clouds. No sensitivity problems exist in rainy environments. More research is needed on the application of the radar to the measurement of rain rates and winds at the sea surface.

  12. Impacts of winds on volcanic plumes - Do crossflows challenge the Morton, Turner and Taylor entrainment assumptions?

    NASA Astrophysics Data System (ADS)

    Aubry, T. J.; Jellinek, M.; Carazzo, G.

    2014-12-01

    Volcanic plumes rising into Earth's atmosphere are influenced strongly by tropospheric and stratospheric winds. In the absence of wind effects, Morton, Taylor and Turner (MTT, 1956) used a similarity theory to show that the maximum height for these flows is governed mostly by the atmospheric stratification and the buoyancy flux at the vent. Crucially, in developing this theory MTT introduced the "entrainment hypothesis" in which the rate of entrainment of atmospheric air by the large eddies forming at the edge of the plume is proportional to some bulk velocity. In the presence of wind a key question is whether the additional stirring deforms eddies sufficiently to alter their mixing properties. In particular, under what conditions will wind effects enhance or reduce entrainment? Can these effects be captured in a modified form of the MTT similarity theory or is a new theory required? We use an extensive set of experiments on wind-forced turbulent plumes in order to overcome the restricted dynamical conditions explored in previous experimental studies. We introduce a new regime parameter allowing to quantitatively separate three distinct plume regimes. Remarkably, we show that for reasonable conditions on Earth, the major effects of wind can still be captured by a modified scaling law derived from the self-similar theory of MTT, with an entrainment rate including the contributions of wind. However, analysis of the turbulence motions in our experiments shows that even weak winds introduce large asymmetries in the structure of entraining eddies. Our successful application of a mean entrainment rate at the plume edge and a modified MTT similarity theory is, thus, surprising. Does this apparent contradiction simply reveal the way turbulent instabilities driven by wind manifest themselves?

  13. Observed drag coefficients in high winds in the near offshore of the South China Sea

    DOE PAGESBeta

    Bi, Xueyan; Liu, Yangan; Gao, Zhiqiu; Liu, Feng; Song, Qingtao; Huang, Jian; Huang, Huijun; Mao, Weikang; Liu, Chunxia

    2015-07-14

    This paper investigates the relationships between friction velocity, 10 m drag coefficient, and 10 m wind speed using data collected at two offshore observation towers (one over the sea and the other on an island) from seven typhoon episodes in the South China Sea from 2008 to 2014. The two towers were placed in areas with different water depths along a shore-normal line. The depth of water at the tower over the sea averages about 15 m, and the depth of water near the island is about 10 m. The observed maximum 10 min average wind speed at a heightmore »of 10 m is about 32 m s?¹. Momentum fluxes derived from three methods (eddy covariance, inertial dissipation, and flux profile) are compared. The momentum fluxes derived from the flux profile method are larger (smaller) over the sea (on the island) than those from the other two methods. The relationship between the 10 m drag coefficient and the 10 m wind speed is examined by use of the data obtained by the eddy covariance method. The drag coefficient first decreases with increasing 10 m wind speed when the wind speeds are 5–10 m s?¹, then increases and reaches a peak value of 0.002 around a wind speed of 18 m s?¹. The drag coefficient decreases with increasing 10 m wind speed when 10 m wind speeds are 18–27 m s?¹. A comparison of the measurements from the two towers shows that the 10 m drag coefficient from the tower in 10 m water depth is about 40% larger than that from the tower in 15 m water depth when the 10 m wind speed is less than 10 m s?¹. Above this, the difference in the 10 m drag coefficients of the two towers disappears.« less

  14. Observed drag coefficients in high winds in the near offshore of the South China Sea

    SciTech Connect

    Bi, Xueyan; Liu, Yangan; Gao, Zhiqiu; Liu, Feng; Song, Qingtao; Huang, Jian; Huang, Huijun; Mao, Weikang; Liu, Chunxia

    2015-07-14

    This paper investigates the relationships between friction velocity, 10 m drag coefficient, and 10 m wind speed using data collected at two offshore observation towers (one over the sea and the other on an island) from seven typhoon episodes in the South China Sea from 2008 to 2014. The two towers were placed in areas with different water depths along a shore-normal line. The depth of water at the tower over the sea averages about 15 m, and the depth of water near the island is about 10 m. The observed maximum 10 min average wind speed at a height of 10 m is about 32 m s?¹. Momentum fluxes derived from three methods (eddy covariance, inertial dissipation, and flux profile) are compared. The momentum fluxes derived from the flux profile method are larger (smaller) over the sea (on the island) than those from the other two methods. The relationship between the 10 m drag coefficient and the 10 m wind speed is examined by use of the data obtained by the eddy covariance method. The drag coefficient first decreases with increasing 10 m wind speed when the wind speeds are 5–10 m s?¹, then increases and reaches a peak value of 0.002 around a wind speed of 18 m s?¹. The drag coefficient decreases with increasing 10 m wind speed when 10 m wind speeds are 18–27 m s?¹. A comparison of the measurements from the two towers shows that the 10 m drag coefficient from the tower in 10 m water depth is about 40% larger than that from the tower in 15 m water depth when the 10 m wind speed is less than 10 m s?¹. Above this, the difference in the 10 m drag coefficients of the two towers disappears.

  15. Spall velocity measurements from laboratory impact craters

    NASA Technical Reports Server (NTRS)

    Polanskey, Carol A.; Ahrens, Thomas J.

    1986-01-01

    Spall velocities were measured for a series of impacts into San Marcos gabbro. Impact velocities ranged from 1 to 6.5 km/sec. Projectiles varied in material and size with a maximum mass of 4g for a lead bullet to a minimum of 0.04 g for an aluminum sphere. The spall velocities were calculated both from measurements taken from films of the events and from estimates based on range measurements of the spall fragments. The maximum spall velocity observed was 27 m/sec, or 0.5 percent of the impact velocity. The measured spall velocities were within the range predicted by the Melosh (1984) spallation model for the given experimental parameters. The compatability between the Melosh model for large planetary impacts and the results of these small scale experiments is considered in detail. The targets were also bisected to observe the internal fractures. A series of fractures were observed whose location coincided with the boundary of the theoretical near surface zone predicted by Melosh. Above this boundary the target material should receive reduced levels of compressive stress as compared to the more highly shocked region below.

  16. The Local Velocity Field

    E-print Network

    Karen L. Masters

    2008-03-27

    We only see a small fraction of the matter in the universe, but the rest gives itself away by the impact of its gravity. The distortions from pure Hubble flow (or peculiar velocities) that this matter creates have the potential to be a powerful cosmological tool, but are also a nuisance for extragalactic astronomers who wish to use redshifts to estimate distances to local galaxies. We provide a quick overview of work on the local peculiar velocity field, discussing both simple spherical infall models, non-parametric modeling using redshifts surveys, and full velocity and density field reconstruction from peculiar velocities. We discuss results from a multiattractor model fit to data from the SFI++ sample of peculiar velocities - the best peculiar velocity data currently available. We also talk about the future of samples for the study of the local velocity field, especially the 2MASS Tully-Fisher (2MTF) survey.

  17. Mesosphere and lower thermosphere neutral winds observations using rocket-released chemical trails at Poker Flat, Alaska

    NASA Astrophysics Data System (ADS)

    Zhan, Tianyu

    Sounding rocket campaigns ARIA I through ARIA IV, CODA 2, HEX 1, JOULE 1 and JOULE 2 all carried out at Poker Flat Research Range at Alaska, covering the geomagnetic condition from quiet to highly disturbed. Trimethyl aluminum (TMA) were released during the rocket flights to study the mesosphere and lower thermosphere neutral wind at high-latitude region. The results of horizontal neutral wind profiles are presented. The comparison shows that under disturbed condition the wind velocity is stronger and the jet feature at the bottom side of wind maximum with unstable wind shear is lifted to a higher altitude. Under the quiet condition, the dominance forcing acting on the neutral atmosphere is the upward propagating tides below 120 km and the Lorentz force and viscosity in the region above 120 km. While under the disturbed condition, the tidal force is disrupted by Hall drag in the region of 105--125 km and the wind profile is a result of complex interplay of tidal force, Lorentz force and Joule heating. Modeling works have also been presented. The comparisons are poor for the global general circulation models and are better for localized non-hydrostatic models. It is also concluded that a detailed high-resolution time-history of auroral forcing and the upward propagating tidal forcing are both important for theoretical model to predict the small scale features of the horizontal neutral wind in the auroral E region and lower F region.

  18. Solar wind electron measurements from the Wind spacecraft

    NASA Astrophysics Data System (ADS)

    Bale, S. D.

    2014-12-01

    The Wind spacecraft has been on orbit for 20 years and produced a wealth solar wind science. In this talk, I will describe results from the Three Dimensional Plasma (3DP) instrument on Wind. In particular, we will use measurements of 1 AU electron distribution functions to show that the thermal electron bulk speed lags the proton speed and that this velocity difference is controlled by Coulomb collisions. By integrating the equation of dynamical friction back into the inner heliosphere, we infer that the plasma environment of the corona (within 20 Rs) is higher kinetic.

  19. Measuring Venus’ winds using the Absolute Astronomical Accelerometer: Solid super-rotation model of Venus’ clouds

    NASA Astrophysics Data System (ADS)

    Gabsi, Younes; Bertaux, Jean Loup; Hauchecorne, Alain; Schmitt, Jérôme; Guibert, Stéphane

    2008-10-01

    We present a new method of measuring the Venus winds by Doppler velocimetry on the full visible spectrum of solar light scattered by the clouds. In January 2003, we carried out observations to measure the winds of Venus, using the EMILIE high-resolution, cross-dispersed spectrograph and its associated calibrating instrument the Absolute Astronomical Accelerometer (AAA), at Observatoire de Haute-Provence, France. The motivation of this type of measurements is that it measures the actual velocity of cloud particles, while the other method (track of cloud features) may be sensitive to the deformation of the clouds. During observations, Venus was near maximum western elongation, at a phase angle near 90°. The EMILIE-AAA system allows us to measure accurately the Doppler shift induced in the reflected solar spectrum by the radial component of the motion of the clouds of Venus. We present the measurements and compare them with a forward simulation of a solid super-rotation of the atmosphere of Venus. Taking into account the Doppler shift relative to the Sun and that relative to the Earth, the theoretical total Doppler shift induced in the solar spectra is easily computed as a function of the velocity of the reflecting target. A first forward simulation is computed, with a wind model considering a purely horizontal and zonal wind. The magnitude of the wind is assumed to depend on cos(latitude), as for a solid-body rotation. The comparison with the measurements at various points on the illuminated semi-disc allowed us to determine an equatorial velocity of 66, 75, 91 and 85 m/s on 4 consecutive mornings, consistent with previous ultraviolet cloud tracking wind measurements, showing that wave propagation is not a major factor in the apparent motion of the cloud marks. Further, we discuss the effect of the finite angular size of the Sun and its rapid equatorial rotation (that we call the Young effect). It mainly affects measurements taken near the terminator, where the largest discrepancies are found. These discrepancies are alleviated when the Young effect is taken into account in the model but then the retrieved Venus equatorial velocity is reduced to only 48±3 m/s. This is well below classical ultraviolet markings velocities, but the altitude at which the visible photons are scattered (66 km) that we use is 5 km below the UV markings, confirming the vertical gradient of the horizontal winds shown by previous in-situ measurements.

  20. Calculations of the cosmic ray modulation in interplanetary space taking into account the possible dependence of the transport travel for the scattering of the particles and of the velocity of the solar winds on the angles they make with the helioequator plane: The case of isotropic diffusion

    NASA Technical Reports Server (NTRS)

    Dorman, L. I.; Kobilinski, Z.

    1975-01-01

    The modulation of galactic cosmic rays is studied by the magnetic heterogeneities stream on the assumption that the diffusion coefficient is reduced whereas the solar wind velocity is increased with the growth of the angle between the sun's rotation axis and the direction of solar plasma motion. The stationary plane problem of isotropic diffusion is solved as it applies to two cases: (1) with due account of particle retardation by the antiphermium mechanism; and (2) without an account of the above mechanism. This problem is solved by the grid method in the polar coordinate system. The results of the calculations are followed by a discussion of the method of solution and of the errors.

  1. A threshold for wind-wave growth

    NASA Astrophysics Data System (ADS)

    Donelan, Mark A.; Plant, William J.

    2009-07-01

    Measurements in a closed, recirculating wind-wave tank using variable wind speeds showed that wind waves in the gravity-capillary range exhibit a threshold in their growth. Surface wave height variance spectral densities in the wave number domain were measured for gravity-capillary waves using both radar backscatter and a wavelet transform technique applied to a laser probe. The measurements showed that when the wind speed was slowly ramped up, a threshold wind speed or friction velocity was required to produce waves. Turning the wind on suddenly showed that the wind stress did not grow as rapidly as the wind since the surface waves supporting the stress grew relatively slowly. Changing water temperature or current in the water caused a pronounced change in the wind speed threshold but not in the friction velocity threshold. Changes in fetch of as much as a factor of 2 had no discernible effect on the thresholds. The results imply that wind speed, being a condition imposed on the air-water interface, causes wave growth, while friction velocity, being a result of air-water interactions, is closely related to surface roughness, hence radar cross section, and changes during wave growth.

  2. Reliability analysis for wind turbines with incomplete failure data collected from after the date of initial installation

    E-print Network

    McCalley, James D.

    Reliability analysis for wind turbines with incomplete failure data collected from after the date model Maximum likelihood Least squares Wind turbines a b s t r a c t Reliability has an impact on wind analysis. In wind energy industry, wind farm operators have greater interest in recording wind turbine

  3. Electronic excitation and charge transfer processes in collisions of H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} ions with carbon monoxide at typical solar-wind velocities

    SciTech Connect

    Werbowy, S.; Pranszke, B.

    2014-01-10

    Luminescence in the 200-580 nm spectral region was observed in the collisions of H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} with CO in the 50-1000 eV projectile energy range. Using computer simulations, we have identified emission of the following products in the observed spectra: the CO{sup +}(A-X) comet-tail system, CO{sup +}(B-X) first negative system, CO{sup +}(B-A) Baldet-Johnson system, and CO(b-a) third positive system. Also, an emission from atomic hydrogen (H{sub ?} line at 486nm) has been observed. From the analysis of the experimental spectra, we have determined the absolute emission cross-sections for the formation of the observed products. Computer simulations gave the excited-product population distributions over vibrational and rotational energy levels. The vibrational level distribution from the CO{sup +}(A-X) comet-tail system is compared with the data for CO excited by 100 eV electrons and extreme ultraviolet radiation (XUV) photons. We have used these data to analyze the excitation conditions in the comet Humason (1961e). From the vibrational population distributions observed in the comet, we found that this distribution can be reproduced if electrons produce 25%, protons 70%, and XUV photons produce 5% of the emitting molecules. We find that the ratio of the CO{sup +}(B-X) emission to the sum of two main emissions (CO{sup +}(A-X)+CO{sup +}(B-X)) is velocity dependent and does not depend on the projectile ion type. For small velocities (below 100 km s{sup –1}) the ratio is about 5%, while for higher velocities it increases to 30%. For these data, we have found an empirical formula that satisfactorily describes the experimental data: R = R {sub max}(1 – v {sub th}/v), (where R {sub max} = 33%, v {sub th} = 87 km s{sup –1}). This could be used to infer the velocity of ions producing the observed emission of CO{sup +} products.

  4. Wind Turbine

    USGS Multimedia Gallery

    The species of bats that are most susceptible to wind turbines all roost in trees throughout the year, leading some scientists to speculate that they may be visually mistaking wind turbines for trees in which to roost....

  5. Airfoils for wind turbine

    DOEpatents

    Tangler, James L. (Boulder, CO); Somers, Dan M. (State College, PA)

    1996-01-01

    Airfoils for the blade of a wind turbine wherein each airfoil is characterized by a thickness in a range from 16%-24% and a maximum lift coefficient designed to be largely insensitive to roughness effects. The airfoils include a family of airfoils for a blade 15 to 25 meters in length, a family of airfoils for a blade 1 to 5 meters in length, and a family of airfoils for a blade 5 to 10 meters in length.

  6. Airfoils for wind turbine

    DOEpatents

    Tangler, J.L.; Somers, D.M.

    1996-10-08

    Airfoils are disclosed for the blade of a wind turbine wherein each airfoil is characterized by a thickness in a range from 16%-24% and a maximum lift coefficient designed to be largely insensitive to roughness effects. The airfoils include a family of airfoils for a blade 15 to 25 meters in length, a family of airfoils for a blade 1 to 5 meters in length, and a family of airfoils for a blade 5 to 10 meters in length. 10 figs.

  7. Tiber winding pack design

    SciTech Connect

    Miller, J.R.

    1985-08-19

    A preliminary winding pack design was performed with the goal of showing feasibility of producing 10-T maximum field with a pack current density of 40 A.mm/sup -2/ while accepting 2.7 kW per coil nuclear heating. A cable-in-conduit conductor design (CIC), reported at the 6th Topical Meeting on the Technology of Fusion Energy, was based on several key issues.

  8. Video Measurement of the Muzzle Velocity of a Potato Gun

    ERIC Educational Resources Information Center

    Jasperson, Christopher; Pollman, Anthony

    2011-01-01

    Using first principles, a theoretical equation for the maximum and actual muzzle velocities for a pneumatic cannon was recently derived. For a fixed barrel length, this equation suggests that the muzzle velocity can be enhanced by maximizing the product of the initial pressure and the volume of the propellant gas and decreasing the projectile…

  9. Three-Dimensional Venturi Sensor for Measuring Extreme Winds

    NASA Technical Reports Server (NTRS)

    Zysko, Jan A.; Perotti, Jose M.; Amis, Christopher; Randazzo, John; Blalock, Norman; Eckhoff, Anthony

    2003-01-01

    A three-dimensional (3D) Venturi sensor is being developed as a compact, rugged means of measuring wind vectors having magnitudes of as much as 300 mph (134 m/s). This sensor also incorporates auxiliary sensors for measuring temperature from -40 to +120 F (-40 to +49 C), relative humidity from 0 to 100 percent, and atmospheric pressure from 846 to 1,084 millibar (85 to 108 kPa). Conventional cup-and-vane anemometers are highly susceptible to damage by both high wind forces and debris, due to their moving parts and large profiles. In addition, they exhibit slow recovery times contributing to an inaccurately high average-speed reading. Ultrasonic and hot-wire anemometers overcome some of the disadvantages of the cup and-vane anemometers, but they have other disadvantageous features, including limited dynamic range and susceptibility to errors caused by external acoustic noise and rain. In contrast, the novel 3D Venturi sensor is less vulnerable to wind damage because of its smaller profile and ruggedness. Since the sensor has no moving parts, it provides increased reliability and lower maintenance costs. It has faster response and recovery times to changing wind conditions than traditional systems. In addition, it offers wide dynamic range and is expected to be relatively insensitive to rain and acoustic energy. The Venturi effect in this sensor is achieved by the mirrored double-inflection curve, which is then rotated 360 to create the desired detection surfaces. The curve is optimized to provide a good balance of pressure difference between sensor ports and overall maximum fluid velocity while in the shape. Four posts are used to separate the two shapes, and their size and location were chosen to minimize effects on the pressure measurements. The 3D Venturi sensor has smart software algorithms to map the wind pressure exerted on the surfaces of the design. Using Bernoulli's equation, the speed of the wind is calculated from the differences among the pressure readings at the various ports. The direction of the wind is calculated from the spatial distribution and magnitude of the pressure readings. All of the pressure port sizes and locations have been optimized to minimize measurement errors and to reside in areas demonstrating a stable pressure reading proportional to the velocity range.

  10. The Local Velocity Anomaly

    E-print Network

    R. Brent Tully

    2007-08-17

    There is a velocity discontinuity at about 7 Mpc between the galaxies of the Local Sheet that are moving together with low internal velocity dispersion and the adjacent structures. The Local Sheet bounds the Local Void. The Local Sheet is determined to have a peculiar velocity of 260 km/s away from the center of the void. In order for this large velocity to be generated by an absence of gravity, the Local Void must be at least 45 Mpc in diameter and be very empty.

  11. Solar wind

    NASA Astrophysics Data System (ADS)

    Marsch, E.; Axford, W. I.; McKenzie, J. F.

    There are three major types of solar wind - the steady fast wind, the unsteady slow wind, and the variable transient wind. The fast streams are the normal modes of the solar wind. Their basic properties can be reproduced by multi-fluid models involving waves. After briefly reviewing the history of the subject and describing some of the modern theories of the fast wind, the boundary conditions and in-situ constraints are discussed which are imposed on the models, in particular by Ulysses at high latitudes. Some of the results are then presented from SOHO observations that have brought a wealth of new information on the state of the wind in the inner corona as well as the plasma source conditions prevailing in the transition region and solar chromosphere. Finally, problem areas are identified and future research perspectives are outlined.

  12. Utility scale application of wind turbines

    NASA Astrophysics Data System (ADS)

    Belt, R. M.

    The development of wind turbines for utility interconnection, problems inherent in utility scale application of wind-derived power, and specific features of interconnection with the Hawaiian electric system are discussed. Modern wind turbine generators are being developed to withstand sudden wind gusts, maintain generation stability, and tolerate external electrical faults. Utility integration of wind power is constrained by necessities of using optimized generator mixes. The total proportion of wind derived power that a grid may tolerate is as yet unknown, and is dependent on the generator control system response rates, noting that conventional ramping rates are in the range 1-5%. Control rates are bounded by maximum and minimum generation rates on spinning generators. Methods of determining on-site wind patterns using anemometry and electronically stored data are reviewed. Studies to determine the effects of frequent fluctuations on consumer equipment, and to adequately model the introduction of integrated wind farm-grid systems are indicated.

  13. Flatback airfoil wind tunnel experiment.

    SciTech Connect

    Mayda, Edward A.; van Dam, C.P.; Chao, David D.; Berg, Dale E.

    2008-04-01

    A computational fluid dynamics study of thick wind turbine section shapes in the test section of the UC Davis wind tunnel at a chord Reynolds number of one million is presented. The goals of this study are to validate standard wind tunnel wall corrections for high solid blockage conditions and to reaffirm the favorable effect of a blunt trailing edge or flatback on the performance characteristics of a representative thick airfoil shape prior to building the wind tunnel models and conducting the experiment. The numerical simulations prove the standard wind tunnel corrections to be largely valid for the proposed test of 40% maximum thickness to chord ratio airfoils at a solid blockage ratio of 10%. Comparison of the computed lift characteristics of a sharp trailing edge baseline airfoil and derived flatback airfoils reaffirms the earlier observed trend of reduced sensitivity to surface contamination with increasing trailing edge thickness.

  14. Terrestrial exospheric hydrogen density distributions under solar minimum and solar maximum conditions observed by the TWINS stereo mission

    NASA Astrophysics Data System (ADS)

    Zoennchen, J. H.; Nass, U.; Fahr, H. J.

    2015-03-01

    Circumterrestrial Lyman-? column brightness observations above 3 Earth radii (Re) have been used to derive separate 3-D neutral hydrogen density models of the Earth's exosphere for solar minimum (2008, 2010) and near-solar-maximum (2012) conditions. The data used were measured by Lyman-? detectors (LAD1/2) onboard each of the TWINS satellites from very different orbital positions with respect to the exosphere. Exospheric H atoms resonantly scatter the near-line-center solar Lyman-? flux at 121.6 nm. Assuming optically thin conditions above 3Re along a line of sight (LOS), the scattered LOS-column intensity is proportional to the LOS H-column density. We found significant differences in the density distribution of the terrestrial exosphere under different solar conditions. Under solar maximum conditions we found higher H densities and a larger spatial extension compared to solar minimum. After a continuous, 2-month decrease in (27 day averaged) solar activity, significantly lower densities were found. Differences in shape and orientation of the exosphere under different solar conditions exist. Above 3 Re, independent of solar activity, increased H densities appear on the Earth's nightside shifted towards dawn. With increasing distance (as measured at 8Re) this feature is shifted westward/duskward by between -4 and -5° with respect to midnight. Thus, at larger geocentric distance the exosphere seems to be aligned with the aberrated Earth-solar-wind line, defined by the solar wind velocity and the orbital velocity of the Earth. The results presented in this paper are valid for geocentric distances between 3 and 8Re.

  15. Gravity wave and elevated localized ozone maximum

    SciTech Connect

    Bian, X.; Berkowitz, C.M.; Zhong, S.S.

    1996-12-31

    During the 1992 field study of Northern Atlantic Regional Experiment, relatively localized O{sub 3} maximum were observed by aircraft flight along a horizontal sampling path between Nantucket and Halifax on several occasions. While sampling at a constant altitude between 1500 and 2000 m, the aircraft encountered a plume having O{sub 3} mixing ratio twice as much as the values that had been measured prior to entering the plume. Concurrent with this increase in O{sub 3} mixing ratio was a pronounced drop in the dew point. This feature occurred over a horizontal distance of approximately 200 km. Prior to descending to a lower elevation, a second O{sub 3} maximum/dew point minimum appeared to be encountered. Several hypotheses concerning the origin of this localized O{sub 3} maximum along a horizontal path are rejected, and the periodic nature of the phenomena suggests that they could be explained by propagating internal gravity wave at the top of the boundary layer. Observational support of this hypothesis are soundings from surrounding stations that had temperature profiles resemble those that are typical for gravity wave occurrence. A simple numerical model is used to simulate the variations of ozone concentration, temperature, and dew point caused by perturbation horizontal and vertical wind fields associated with traveling internal gravity waves and to illustrate how the localized O{sub 3} maximum are formed from downward displacement of air parcels from the free troposphere by these waves. The observed ozone oscillation corresponds reasonable well in amplitude and phase with the simple model prediction.

  16. A new analytical model for wind farm power prediction

    NASA Astrophysics Data System (ADS)

    Niayifar, Amin; Porte-Agel, Fernando

    2015-04-01

    In this study, a new analytical approach is presented and validated to predict wind farm power production. The new model assumes a Gaussian distribution for the velocity deficit in the wake which has been recently proposed by Bastankhah and Porté-Agel (2014). To estimate the velocity deficit in the wake, this model needs the local wake growth rate parameter which is calculated based on the local turbulence intensity in the wind farm. The interaction of the wakes is modeled by use of the velocity deficit superposition principle. Finally, the power curve is used to estimate the power production from the wind turbines. The wind farm model is compared to large-eddy simulation (LES) data of Horns Rev wind farm for a wide range of wind directions. Reasonable agreement between the proposed analytical model and LES data is obtained. This prediction is substantially better than the one obtained with common wind farm softwares such as WAsP.

  17. Constraints on Deep-seated Zonal Winds Inside Jupiter and Saturn

    E-print Network

    Junjun Liu; Peter Goldreich; David Stevenson

    2007-11-25

    The atmospheres of Jupiter and Saturn exhibit strong and stable zonal winds. How deep the winds penetrate unabated into each planet is unknown. Our investigation favors shallow winds. It consists of two parts. The first part makes use of an Ohmic constraint; Ohmic dissipation associated with the planet's magnetic field cannot exceed the planet's net luminosity. Application to Jupiter (J) and Saturn (S) shows that the observed zonal winds cannot penetrate below a depth at which the electrical conductivity is about six orders of magnitude smaller than its value at the molecular-metallic transition. Measured values of the electrical conductivity of molecular hydrogen yield radii of maximum penetration of 0.96R_J and 0.86R_S, with uncertainties of a few percent of R. At these radii, the magnetic Reynolds number based on the zonal wind velocity and the scale height of the magnetic diffusivity is of order unity. These limits are insensitive to difficulties in modeling turbulent convection. They permit complete penetration along cylinders of the equatorial jets observed in the atmospheres of Jupiter and Saturn. The second part investigates how deep the observed zonal winds actually do penetrate. Truncation of the winds in the planet's convective envelope would involve breaking the Taylor-Proudman constraint on cylindrical flow. This would require a suitable nonpotential acceleration which none of the obvious candidates appears able to provide. Accelerations arising from entropy gradients, magnetic stresses, and Reynolds stresses appear to be much too weak. These considerations suggest that strong zonal winds are confined to shallow, stably stratified layers, with equatorial jets being the possible exception.

  18. Towers for Offshore Wind Turbines

    NASA Astrophysics Data System (ADS)

    Kurian, V. J.; Narayanan, S. P.; Ganapathy, C.

    2010-06-01

    Increasing energy demand coupled with pollution free production of energy has found a viable solution in wind energy. Land based windmills have been utilized for power generation for more than two thousand years. In modern times wind generated power has become popular in many countries. Offshore wind turbines are being used in a number of countries to tap the energy from wind over the oceans and convert to electric energy. The advantages of offshore wind turbines as compared to land are that offshore winds flow at higher speed than onshore winds and the more available space. In some land based settings, for better efficiency, turbines are separated as much as 10 rotor diameters from each other. In offshore applications where only two wind directions are likely to predominate, the distances between the turbines arranged in a line can be shortened to as little as two or four rotor diameters. Today, more than a dozen offshore European wind facilities with turbine ratings of 450 kw to 3.6 MW exist offshore in very shallow waters of 5 to 12 m. Compared to onshore wind turbines, offshore wind turbines are bigger and the tower height in offshore are in the range of 60 to 80 m. The water depths in oceans where offshore turbines can be located are within 30 m. However as the distance from land increases, the costs of building and maintaining the turbines and transmitting the power back to shore also increase sharply. The objective of this paper is to review the parameters of design for the maximum efficiency of offshore wind turbines and to develop types offshore towers to support the wind turbines. The methodology of design of offshore towers to support the wind turbine would be given and the environmental loads for the design of the towers would be calculated for specific cases. The marine corrosion on the towers and the methods to control the corrosion also would be briefly presented. As the wind speeds tend to increase with distance from the shore, turbines build father offshore will be able to capture more wind energy. Currently two types of towers are considered. Cylindrical tubular structures and truss type structures. But truss type structures have less weight and flexibility in design. The construction of the offshore towers to harness the wind energy is also presented. The results will include the calculation of wind and wave forces on the tower and the design details for the tower.

  19. DEPOSITION VELOCITY ESTIMATION WITH THE GENII V2 SOFTWARE

    SciTech Connect

    Hutchins, H.

    2012-04-23

    In 2010, the Department of Energy (DOE) Chief of Nuclear Safety and Office of Health, Safety and Security (HSS), with the support of industry experts in atmospheric sciences and accident dose consequences analysis, performed detailed analyses of the basis for the dry deposition velocity (DV) values used in the MACCS2 computer code. As a result of these analyses, DOE concluded that the historically used default DV values of 1 centimeter/second (cm/s) for unfiltered/unmitigated releases and 0.1 cm/s for filtered/mitigated releases may not be reasonably conservative for all DOE sites and accident scenarios. HSS recently issued Safety Bulletin 2011-02, Accident Analysis Parameter Update, recommending the use of the newly developed default DV, 0.1 cm/s for an unmitigated/unfiltered release. Alternatively site specific DV values can be developed using GENII version 2 (GENII v2) computer code. Key input parameters for calculating DV values include surface roughness, maximum wind speed for calm, particle size, particle density and meteorological data (wind speed and stability class). This paper will include reasonably conservative inputs, and a truncated parametric study. In lieu of the highly-conservative recommended DV value (0.1cm/s) for unmitigated/unfiltered release, GENII v2 has been used to justify estimated 95th percentile DV values. Also presented here are atmospheric dilution factors ({chi}/Q values) calculated with the MACCS2 code using the DV values form GENII v2, {chi}/Q values calculated directly with GENII v2, and a discussion of these results compare with one another. This paper will give an overview of the process of calculating DV with GENII v2 including a discussion of the sensitivity of input parameters.

  20. Group Velocity Measurement Distance Travelled

    E-print Network

    Gerstoft, Peter

    Group Velocity Measurement Distance Travelled Time It TookGroup Velocity (8.3) #12;Group Velocity Measurement Distance Travelled Time It TookGroup Velocity (8.3) earthquake station distance Earthquake timet d #12;Group Velocity Measurement Distance Travelled Time It TookGroup Velocity (8.3) earthquake station

  1. Transition from Zonal Wind to Subsolar-to-Antisolar Flow on Venus

    NASA Astrophysics Data System (ADS)

    Kostiuk, Theodor; Livengood, T. A.; Hewagama, T.; Fast, K.; Annen, J.

    2012-10-01

    We observed Venus on 19-23 Aug 2010 (UT) to investigate equatorial wind velocities from above the cloud tops through the lower thermosphere. Measurements were made from the NASA Infrared Telescope Facility using the NASA Goddard Space Flight Center Heterodyne Instrument for Planetary Winds and Composition. High-resolution spectra were acquired on a CO2 pressure-broadened absorption feature that probes the lower mesosphere ( 70 km altitude) with a non-LTE core emission of the same transition that probes the lower thermosphere ( 110 km). The resolving power of ?/? ?=2.5107 determines line-of-sight velocity from Doppler shifts to high precision. The altitude differential between the features enables investigating the transition from zonal wind flow near the cloud tops to subsolar-to-antisolar flow in the thermosphere. The fully-resolved carbon dioxide transition was measured near 952.8808 cm-1 (10.494 µm) rest frequency at the equator with 1 arcsec field-of-view on Venus (24 arcsec diameter) distributed about the central meridian and across the terminator at ±15° intervals in longitude. The non-LTE emission is solar-pumped and appears only on the daylight side, probing subsolar-to-antisolar wind velocity vector flowing radially from the subsolar point through the terminator, which was near the central meridian in these observations and had zero line-of-sight wind projection at the terminator. The velocity of the zonal flow is approximately uniform, with maximum line-of-sight projection at the limb, and can be measured by the frequency of the absorption line on both the daylight and dark side. Variations in Doppler shift between the observable features and the differing angular dependence of the contributing wind phenomena thus provide independent mechanisms to distinguish the dynamical processes at the altitude of each observed spectral feature. Winds up to >100 m/s were determined in previous investigations with uncertainties of order 10 m/s or less. This work was supported by the NASA Planetary Astronomy Program.

  2. Forecastability as a Design Criterion in Wind Resource Assessment: Preprint

    SciTech Connect

    Zhang, J.; Hodge, B. M.

    2014-04-01

    This paper proposes a methodology to include the wind power forecasting ability, or 'forecastability,' of a site as a design criterion in wind resource assessment and wind power plant design stages. The Unrestricted Wind Farm Layout Optimization (UWFLO) methodology is adopted to maximize the capacity factor of a wind power plant. The 1-hour-ahead persistence wind power forecasting method is used to characterize the forecastability of a potential wind power plant, thereby partially quantifying the integration cost. A trade-off between the maximum capacity factor and the forecastability is investigated.

  3. Radial velocity moments of dark matter haloes

    E-print Network

    Radoslaw Wojtak; Ewa L. Lokas; Stefan Gottloeber; Gary A. Mamon

    2005-04-19

    Using cosmological N-body simulations we study the radial velocity distribution in dark matter haloes focusing on the lowest-order even moments, dispersion and kurtosis. We determine the properties of ten massive haloes in the simulation box approximating their density distribution by the NFW formula characterized by the virial mass and concentration. We also calculate the velocity anisotropy parameter of the haloes and find it mildly radial and increasing with distance from the halo centre. The radial velocity dispersion of the haloes shows a characteristic profile with a maximum, while the radial kurtosis profile decreases with distance starting from a value close to Gaussian near the centre. We therefore confirm that dark matter haloes possess intrinsically non-Gaussian, flat-topped velocity distributions. We find that the radial velocity moments of the simulated haloes are quite well reproduced by the solutions of the Jeans equations obtained for the halo parameters with the anisotropy measured in the simulations. We also study the radial velocity moments for a composite cluster made of ten haloes out to ten virial radii. In this region the velocity dispersion decreases systematically to reach the value of the background, while kurtosis increases from below to above the Gaussian value of 3 signifying a transition from a flat-topped to a strongly peaked velocity distribution with respect to the Gaussian, which can be interpreted as the dominance of ordered flow with a small dispersion. We illustrate the transition by showing explicitly the velocity distribution of the composite cluster in a few radial bins.

  4. Wind Resource Assessment in Complex Terrain with a High-Resolution Numerical Weather Prediction Model

    NASA Astrophysics Data System (ADS)

    Gruber, Karin; Serafin, Stefano; Grubiši?, Vanda; Dorninger, Manfred; Zauner, Rudolf; Fink, Martin

    2014-05-01

    A crucial step in planning new wind farms is the estimation of the amount of wind energy that can be harvested in possible target sites. Wind resource assessment traditionally entails deployment of masts equipped for wind speed measurements at several heights for a reasonably long period of time. Simplified linear models of atmospheric flow are then used for a spatial extrapolation of point measurements to a wide area. While linear models have been successfully applied in the wind resource assessment in plains and offshore, their reliability in complex terrain is generally poor. This represents a major limitation to wind resource assessment in Austria, where high-altitude locations are being considered for new plant sites, given the higher frequency of sustained winds at such sites. The limitations of linear models stem from two key assumptions in their formulation, the neutral stratification and attached boundary-layer flow, both of which often break down in complex terrain. Consequently, an accurate modeling of near-surface flow over mountains requires the adoption of a NWP model with high horizontal and vertical resolution. This study explores the wind potential of a site in Styria in the North-Eastern Alps. The WRF model is used for simulations with a maximum horizontal resolution of 800 m. Three nested computational domains are defined, with the innermost one encompassing a stretch of the relatively broad Enns Valley, flanked by the main crest of the Alps in the south and the Nördliche Kalkalpen of similar height in the north. In addition to the simulation results, we use data from fourteen 10-m wind measurement sites (of which 7 are located within valleys and 5 near mountain tops) and from 2 masts with anemometers at several heights (at hillside locations) in an area of 1600 km2 around the target site. The potential for wind energy production is assessed using the mean wind speed and turbulence intensity at hub height. The capacity factor is also evaluated, considering the frequency of wind speed between cut-in and cut-out speed and of winds with a low vertical velocity component only. Wind turbines do not turn on at wind speeds below cut-in speed. Wind turbines are taken off from the generator in the case of wind speeds higher than cut-out speed and inclination angles of the wind vector greater than 8o. All of these parameters were computed at each model grid point in the innermost domain in order to map their spatial variability. The results show that in complex terrain the annual mean wind speed at hub height is not sufficient to predict the capacity factor of a turbine; vertical wind speed and the frequency of horizontal wind speed out of the range of cut-in and cut-out speed contribute substantially to a reduction of the energy harvest and locally high turbulence may considerably raise the building costs.

  5. Tachoastrometry: astrometry with radial velocities

    NASA Astrophysics Data System (ADS)

    Pasquini, L.; Cortés, C.; Lombardi, M.; Monaco, L.; Leão, I. C.; Delabre, B.

    2015-02-01

    Context. Spectra of composite systems (e.g., spectroscopic binaries) contain spatial information that can be retrieved by measuring the radial velocities (i.e., Doppler shifts) of the components in four observations with the slit rotated by 90 degrees in the sky. Aims: We aim at developing a framework to describe the method and to test its capabilities in a real case. Methods: By using basic concepts of slit spectroscopy we show that the geometry of composite systems can be reliably retrieved by measuring only radial velocity differences taken with different slit angles. The spatial resolution is determined by the precision with which differential radial velocities can be measured. Results: We use the UVES spectrograph at the VLT to observe the known spectroscopic binary star HD 188088 (HIP 97944), which has a maximum expected separation of 23 milli-arcseconds. We measure an astrometric signal in radial velocity of 276 m s-1 , which corresponds to a separation between the two components at the time of the observations of 18 ± 2 milli-arcseconds. The stars were aligned east-west. We describe a simple optical device to simultaneously record pairs of spectra rotated by 180 degrees, thus reducing systematic effects. We compute and provide the function expressing the shift of the centroid of a seeing-limited image in the presence of a narrow slit. Conclusions: The proposed technique is simple to use and our test shows that it is amenable for deriving astrometry with milli-arcsecond accuracy or better, beyond the diffraction limit of the telescope. The technique can be further improved by using simple devices to simultaneously record the spectra with 180 degrees angles. This device together with an optimized data analysis will further reduce the measurement errors. With tachoastrometry, radial velocities and astrometric positions can be measured simultaneously for many double line system binaries in an easy way. The method is not limited to binary stars, but can be applied to any astrophysical configuration in which spectral lines are generated by separate (non-rotational symmetric) regions.

  6. Pulsar space velocities

    SciTech Connect

    Tutukov, A.V.; Chugai, N.N.; Yungel'son, L.R.

    1984-07-01

    Allowing for selection effects, about half of all radio pulsars have low space velocities (v<50 km/sec). A theoretical spectrum is derived for the space velocities of the neutron stars resulting from evolution in massive close binaries. The observed pulsar velocity spectrum and the rarity of pulsars in wide binaries imply that either (a) the supernova explosion gives the resultant neutron star a kick ..delta..vroughly-equal30--100 km/sec or (b) radio pulsars can develop only in close binary systems.

  7. Development of a Wind Turbine Test Rig and Rotor for Trailing Edge Flap Investigation: Static Flap Angles Case

    NASA Astrophysics Data System (ADS)

    Abdelrahman, Ahmed; Johnson, David A.

    2014-06-01

    One of the strategies used to improve performance and increase the life-span of wind turbines is active flow control. It involves the modification of the aerodynamic characteristics of a wind turbine blade by means of moveable aerodynamic control surfaces. Trailing edge flaps are relatively small moveable control surfaces placed at the trailing edge of a blade's airfoil that modify the lift of a blade or airfoil section. An instrumented wind turbine test rig and rotor were specifically developed to enable a wide-range of experiments to investigate the potential of trailing edge flaps as an active control technique. A modular blade based on the S833 airfoil was designed to allow accurate instrumentation and customizable settings. The blade is 1.7 meters long, had a constant 178mm chord and a 6° pitch. The modular aerodynamic parts were 3D printed using plastic PC-ABS material. The blade design point was within the range of wind velocities in the available large test facility. The wind facility is a large open jet wind tunnel with a maximum velocity of 11m/s in the test area. The capability of the developed system was demonstrated through an initial study of the effect of stationary trailing edge flaps on blade load and performance. The investigation focused on measuring the changes in flapwise bending moment and power production for different trailing edge flap spanwise locations and deflection angles. The relationship between the load reduction and deflection angle was linear as expected from theory and the highest reduction was caused by the flap furthest from the rotor center. Overall, the experimental setup proved to be effective in measuring small changes in flapwise bending moment within the wind turbine blade and will provide insight when (active) flap control is targeted.

  8. Sensitivity of Southern Ocean circulation to wind stress changes: Role of relative wind stress

    NASA Astrophysics Data System (ADS)

    Munday, D. R.; Zhai, X.

    2015-11-01

    The influence of different wind stress bulk formulae on the response of the Southern Ocean circulation to wind stress changes is investigated using an idealised channel model. Surface/mixed layer properties are found to be sensitive to the use of the relative wind stress formulation, where the wind stress depends on the difference between the ocean and atmosphere velocities. Previous work has highlighted the surface eddy damping effect of this formulation, which we find leads to increased circumpolar transport. Nevertheless the transport due to thermal wind shear does lose sensitivity to wind stress changes at sufficiently high wind stress. In contrast, the sensitivity of the meridional overturning circulation is broadly the same regardless of the bulk formula used due to the adiabatic nature of the relative wind stress damping. This is a consequence of the steepening of isopycnals offsetting the reduction in eddy diffusivity in their contribution to the eddy bolus overturning, as predicted using a residual mean framework.

  9. Application of Wind Fetch and Wave Models for Habitat Rehabilitation and Enhancement Projects

    USGS Publications Warehouse

    Rohweder, Jason J.; Rogala, James T.; Johnson, Barry L.; Anderson, Dennis; Clark, Steve; Chamberlin, Ferris

    2012-01-01

    Models based upon coastal engineering equations have been developed to quantify wind fetch length and several physical wave characteristics including significant height, length, peak period, maximum orbital velocity, and shear stress. These models were used to quantify differences in proposed island construction designs for three Habitat Rehabilitation and Enhancement Projects (HREPs) in the U.S. Army Corps of Engineers St. Paul District (Capoli Slough and Harpers Slough) and St. Louis District (Swan Lake). Weighted wind fetch was calculated using land cover data supplied by the Long Term Resource Monitoring Program (LTRMP) for each island design scenario for all three HREPs. Figures and graphs were created to depict the results of this analysis. The difference in weighted wind fetch from existing conditions to each potential future island design was calculated for Capoli and Harpers Slough HREPs. A simplistic method for calculating sediment suspension probability was also applied to the HREPs in the St. Paul District. This analysis involved determining the percentage of days that maximum orbital wave velocity calculated over the growing seasons of 2002–2007 exceeded a threshold value taken from the literature where fine unconsolidated sediments may become suspended. This analysis also evaluated the difference in sediment suspension probability from existing conditions to the potential island designs. Bathymetric data used in the analysis were collected from the LTRMP and wind direction and magnitude data were collected from the National Oceanic and Atmospheric Administration, National Climatic Data Center. These models are scheduled to be updated to operate using the most current Environmental Systems Research Institute ArcGIS Geographic Information System platform, and have several improvements implemented to wave calculations, data processing, and functions of the toolbox.

  10. Erratum: ``An Extensive Collection of Stellar Wind X-Ray Source Region Emission Line Parameters, Temperatures, Velocities, and Their Radial Distributions as Obtained from Chandra Observations of 17 OB Stars'' (ApJ, 668, 456 [2007])

    NASA Astrophysics Data System (ADS)

    Waldron, W. L.; Cassinelli, J. P.

    2008-06-01

    The major objective of the paper was to provide a detailed tabulation of the observed HETGS X-ray emission-line flux ratios. We presented the MEG and HEG He-like f/i line ratios, the H-like to He-like (H/He) line ratios, and the He-like G-ratios. The stellar wind spatial locations of the X-ray sources were derived from the f/i ratios, and their associated X-ray temperatures were obtained from the H/He ratios (THHe). This information was used to verify the correlations between Rfir and R?=1 (Fig. 6) and THHe and Rfir (Fig. 8). However, we have realized that some of our tabulated uncertainties for these line ratios were underestimated, primarily for those lines with low-S/N data. Hence, the primary purpose of this erratum is to provide a tabulation of the corrected line ratios and their uncertainties. The details of our line fitting procedure are discussed in § 3.3. All uncertainties were determined using standard ?2 statistics (e.g., P. R. Bevington, 1969, Data Reduction and Error Analysis for the Physical Sciences [New York: McGraw-Hill]). First, we would like to clarify a statement in § 3.3 (second paragraph), which states that all parameter uncertainties were determined from 90% confidence regions, but in actuality all uncertainties were established using 68% confidence regions. With regards to the main point of this erratum, we found that our algorithm for determining the ?2 covariance matrix which is used to determine the uncertainties of the fitting parameters had an indexing error in the coding logic which produced errors in some of the off-diagonal terms. From our detailed examination of the code, we found that certain cases were especially vulnerable to this coding error, in particular, those cases where the ?2 normalization ranges were large (i.e., low-S/N data). This code correction has also produced changes in some of the line ratios and their derived quantities (e.g., Rfir and THHe). The algorithm has been corrected and the affected Tables (Tables 3, 4, 5, 6, and 7) have been updated and are given in corrected form in this erratum. We also corrected a few entries that were originally tabulated incorrectly, and some data were removed, as they did not satisfy our S/N criterion, i.e., the HEG S XV f/i data for ? Ori, the MEG S XV f/i data for ? Oph, and the HEG Mg XI and Si XIII f/i data for Cyg OB2 No. 9. As discussed in § 3.1, we stated that if a reasonable flux had been established, these results would be used only for estimating line ratios that provide interesting limits. However, the meaning of a ``reasonable`` flux limit was unclear; the criterion used is that the observed total net counts from all three He-like fir lines must have a S/N>=3. We also need to clarify the significance of blank entries in our tables. The blanks just indicate that the given line ratio has either an unphysical result that produces an anomalously large uncertainty, or did not satisfy our He-like S/N>=3 criterion. An example of an unphysical result is when the fitting procedure predicts an He-like i-line flux that is too small. This occurs primarily in low-S/N high-energy He-like fir lines, where the effects of line overlap can lead to a poor determination of the i-line. In addition, we would like to clarify why the relative uncertainties in Rfir are typically smaller than the corresponding f/i relative uncertainties. As shown in equation (2) of the paper, for ?/?C>1 and ne<wind except when extremely close to the star), the f/i ratio is inversely proportional to the dilution factor, W(r), which changes rapidly for small changes in radius. Hence, dramatic changes in the f/i ratio can occur for only small changes in radius, which explains the differences seen in the relative uncertainties. Another key point that was not mentioned in the original paper is that there is a lower limit on the f/i ratio for the case where ne<

  11. Re-entrainment around a low-rise industrial building: 2D versus 3D wind tunnel study

    NASA Astrophysics Data System (ADS)

    Law, Adrian W. K.; Choi, Edmund C. C.; Britter, Rex E.

    We investigate the re-entrainment of pollutants around a low-rise industrial building under opposing cross winds through experimental means in a wind tunnel. Two scaled models of an industrial building for electrowinning metal extraction were tested. The first model was a two-dimensional simplified segment of the building with a scale ratio of 1:40, while the second was a 1:100 three-dimensional model of the full building. Particle image velocimetry was adopted to provide the planar velocity measurements that illustrated the flow distribution around the building. Flame ionization detection with propane tracer gas was used to measure the concentration distribution. The results of the 2D model show that the exhaust plume interacted with the opposing wind in two different stages, namely ground attachment and bent-over. The ground attachment stage occurred under low wind speeds, whereby the exhaust plume exhibited Coanda attachment with the ground surface before being lifted off by the cross wind and circulated to the leeward wake cavity. Upon further increase in the wind speed, the bent-over stage occurred with the exhaust plume being detached from the ground and deflected upward over the roof, before entrained by the wake. The re-entrainment ratio decreased with the increase in wind speed within the range of wind speeds tested, indicating that the range did not include the critical wind speed. Results from the 3D model painted a somewhat different picture and pointed to the significance of the end conditions. The maximum re-entrainment always occurred near the two ends of the building, where the pollutants mostly flowed around the ends rather than over the roof. The re-entrainment ratio was consistently higher at the two ends compared to the central sections. Finally, a building re-entrainment index, ( KR) ?, is proposed to characterize the re-entrainment performance of a specific building geometry.

  12. Predicting Vertical Jump Height from Bar Velocity

    PubMed Central

    García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

    2015-01-01

    The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s-2). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r2 = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r2 = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key points Vertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer. The relationship between the point at which bar acceleration is less than -9.81 m·s-2 and the real take-off is affected by the velocity of movement. Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance. PMID:25983572

  13. Predicting vertical jump height from bar velocity.

    PubMed

    García-Ramos, Amador; Štirn, Igor; Padial, Paulino; Argüelles-Cienfuegos, Javier; De la Fuente, Blanca; Strojnik, Vojko; Feriche, Belén

    2015-06-01

    The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s(-2)). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r(2) = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r(2) = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key pointsVertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer.The relationship between the point at which bar acceleration is less than -9.81 m·s(-2) and the real take-off is affected by the velocity of movement.Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance. PMID:25983572

  14. Oscillations of neutrino velocity

    E-print Network

    Branislav Sazdovi?; Milovan Vasili?

    2012-10-12

    In this paper, we consider the problem of quantum measurement of neutrino velocity. We show, that the well known neutrino flavor oscillations are always accompanied by the oscillations of neutrino velocity. In particular, the velocity of a freely moving neutrino is demonstrated to periodically exceed the speed of light. Unfortunately, the superluminal effect turns out to be too small to be experimentally detected. It is also shown that neutrino velocity significantly depends on the energy, size and shape of the neutrino wave packet. Owing to the big experimental error of the recent experiments, these dependences remained unnoticeable. Finally, we have shown that the recent claims that superluminal neutrinos should loose energy during their flight is not true. Instead, our formula suggests the approximate conservation of energy along neutrino trajectory. All these results have been obtained without violation of special theory of relativity.

  15. High Velocity Gas Gun

    NASA Technical Reports Server (NTRS)

    1988-01-01

    A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

  16. Summary of forward velocity effects on fan noise

    NASA Technical Reports Server (NTRS)

    Feiler, C. E.; Groeneweg, J. F.

    1977-01-01

    Available experimental data comparing the in-flight and static behavior of fan noise are reviewed. These results are then compared with recent data obtained for a fan stage tested with forward velocity in a low speed wind tunnel. Tentative conclusions are presented about the significance and nature of the changes in noise observed when a forward velocity is imposed. Finally, the implications of the emerging picture of in-flight fan source noise for suppressor design are discussed.

  17. Combustion velocities and propagation mechanisms of metastable interstitial composites

    NASA Astrophysics Data System (ADS)

    Bockmon, B. S.; Pantoya, M. L.; Son, S. F.; Asay, B. W.; Mang, J. T.

    2005-09-01

    Combustion velocities were experimentally determined for nanocomposite thermite powders composed of aluminum (Al) fuel and molybdenum trioxide (MoO3) oxidizer under well-confined conditions. Pressures were also measured to provide detailed information about the reaction mechanism. Samples of three different fuel particle sizes (44, 80, and 121 nm) were analyzed to determine the influence of particle size on combustion velocity. Bulk powder density was varied from approximately 5% to 10% of the theoretical maximum density (TMD). The combustion velocities ranged from approximately 600 to 1000 m/s. Results indicate that combustion velocities increase with decreasing particle size. Pressure measurements indicate that strong convective mechanisms are integral in flame propagation.

  18. Kick Velocity Induced by Magnetic Dipole and Quadrupole Radiation

    NASA Astrophysics Data System (ADS)

    Kojima, Yasufumi; Kato, Yugo E.

    2011-02-01

    We examine the recoil velocity induced by the superposition of magnetic dipole and quadrupole radiation from a pulsar/magnetar born with rapid rotation. The resultant velocity depends on not the magnitude, but rather the ratio of the two moments and their geometrical configuration. The model does not necessarily lead to high spatial velocity for a magnetar with a strong magnetic field, which is consistent with the recent observational upper bound. The maximum velocity predicted with this model is slightly smaller than that of observed fast-moving pulsars.

  19. Vertical wind turbine

    SciTech Connect

    Danson, D.P.

    1988-08-16

    This patent describes a wind driven turbine of the vertical axis type comprising: (a) a support base; (b) a generally vertical column rotatably mounted to the support base; (c) upper and lower support means respectively mounted on the column for rotation therewith; wind driven blades connected between the upper and lower support means for rotation about the column and each blade being individually rotatable about a blade axis extending longitudinally through the blade to vary a blade angle of attach thereof relative to wind velocity during rotation about the column; and (e) control means for variably adjusting angles of attack of each blade to incident wind, the control means including a connecting rod means having drive means for rotating each blade about the associated blade axis in response to radial movement of the connecting rod means and control shaft pivotally mounted within the column and having a first shaft portion connected to the connecting rod means and a second shaft portion radially offset from the first shaft portion and pivotally connected to radially displace the first portion and thereby the connecting rod means to vary the blade angles of attack during rotation about the column.

  20. Highly Alfvenic Slow Solar Wind

    NASA Technical Reports Server (NTRS)

    Roberts, D. Aaron

    2010-01-01

    It is commonly thought that fast solar wind tends to be highly Alfvenic, with strong correlations between velocity and magnetic fluctuations, but examples have been known for over 20 years in which slow wind is both Alfvenic and has many other properties more typically expected of fast solar wind. This paper will present a search for examples of such flows from more recent data, and will begin to characterize the general characteristics of them. A very preliminary search suggests that such intervals are more common in the rising phase of the solar cycle. These intervals are important for providing constraints on models of solar wind acceleration, and in particular the role waves might or might not play in that process.

  1. Maximum Entropy Production and the

    E-print Network

    Zeng, Ning

    : You can't break even. (Carnot 1824, Clausius 1850) #12;Thermodynamics 101 (Prigogine 1962) #12;Maximum representation of dynamical constraints (energy, water, carbon etc.) Type I: MEP through parameter optimization

  2. The appearance of highly relativistic, spherically symmetric stellar winds

    NASA Technical Reports Server (NTRS)

    Abramowicz, Marek A.; Novikov, Igor D.; Paczynski, Bohdan

    1991-01-01

    A nonluminous, steady state, spherically symmetric, relativistic wind, with the opacity dominated by electron scattering appears against a bright background as a dark circle with the radius rd. A luminous wind would appear as a bright spot with a radius rl = rd/2 pi gamma exp 3, where gamma is the Lorentz factor of the wind. The bright wind photosphere is convex for v equal to or less than 2c/3, and appears concave for higher outflow velocities.

  3. WIND TOMOGRAPHY IN BINARY SYSTEMS O.Knill, R.Dgani and M.Vogel

    E-print Network

    Knill, Oliver

    WIND TOMOGRAPHY IN BINARY SYSTEMS O.Knill, R.Dgani and M.Vogel ETH-Zurich, CH-8092, Switzerland method is particularly suitable for determining the velocity laws of stellar winds. 1. WIND TOMOGRAPHY AND ABEL'S INTEGRAL Binary systems in which a compact, point-like radiation source shines through the wind

  4. Efficiency at maximum power of motor traffic on networks

    NASA Astrophysics Data System (ADS)

    Golubeva, N.; Imparato, A.

    2014-06-01

    We study motor traffic on Bethe networks subject to hard-core exclusion for both tightly coupled one-state machines and loosely coupled two-state machines that perform work against a constant load. In both cases we find an interaction-induced enhancement of the efficiency at maximum power (EMP) as compared to noninteracting motors. The EMP enhancement occurs for a wide range of network and single-motor parameters and is due to a change in the characteristic load-velocity relation caused by phase transitions in the system. Using a quantitative measure of the trade-off between the EMP enhancement and the corresponding loss in the maximum output power we identify parameter regimes where motor traffic systems operate efficiently at maximum power without a significant decrease in the maximum power output due to jamming effects.

  5. Wind-driven circulation in Titan's seas

    NASA Astrophysics Data System (ADS)

    Tokano, Tetsuya; Lorenz, Ralph D.

    2015-01-01

    Circulation in Titan's seas forced by wind is simulated by an ocean circulation model using surface wind data predicted by a global circulation model. Wind-driven circulation is insignificant throughout much of the annual cycle but becomes significant from late spring to late summer, when the wind stress becomes strong. The large-scale circulation in summer is predominantly southward near the sea surface and northward near the sea bottom. The sea surface current can get as fast as 5 cms-1 in some areas. Titan's rotation affects the vertical structure of sea currents in the form of an Ekman spiral if the wind is strong. The maximum wind setup at the shores is of the same order of magnitude as the tidal range. Wind stirring may reduce thermal stratification in summer but may be unable to destroy stratification of methane-rich liquids on top of ethane-rich liquids that can result from imbalances between evaporation and precipitation.

  6. Scale Effect on Clark Y Airfoil Characteristics from NACA Full-Scale Wind-Tunnel Tests

    NASA Technical Reports Server (NTRS)

    Silverstein, Abe

    1935-01-01

    This report presents the results of wind tunnel tests conducted to determine the aerodynamic characteristics of the Clark Y airfoil over a large range of Reynolds numbers. Three airfoils of aspect ratio 6 and with 4, 6, and 8 foot chords were tested at velocities between 25 and 118 miles per hour, and the characteristics were obtained for Reynolds numbers (based on the airfoil chord) in the range between 1,000,000 and 9,000,000 at the low angles of attack, and between 1,000,000 and 6,000,000 at maximum lift. With increasing Reynolds number the airfoil characteristics are affected in the following manner: the drag at zero lift decreases, the maximum lift increases, the slope of the lift curve increases, the angle of zero lift occurs at smaller negative angles, and the pitching moment at zero lift does not change appreciably.

  7. Wind Tunnel 

    E-print Network

    Unknown

    2011-08-17

    Simulation of Cooling Effect of Wind Tower on Passively Ventilated Building John Seryak Kelly Kissock Project Engineer Associate Professor Department of Mechanical and Aerospace Engineering University of Dayton... Dayton, Ohio ABSTRACT Traditional buildings are cooled and ventilated by mechanically induced drafts. Natural ventilation aspires to cool and ventilate a building by natural means, such as cross ventilation or wind towers, without mechanical...

  8. Meteorology (Wind)

    Atmospheric Science Data Center

    2014-09-25

    ... is in each range (0-2, 3-6, 7-10, 11-14, 15-18, 19-25 m/s).   Wind Speed at 50 m at 3-hourly intervals (m/s)   ... be adjusted to heights from 10 to 300 meters using the Gipe power law. Wind speeds may be adjusted for different terrain by selecting from ...

  9. STATIONARITY IN SOLAR WIND FLOWS

    SciTech Connect

    Perri, S.; Balogh, A. E-mail: a.balogh@imperial.ac.u

    2010-05-01

    By using single-point measurements in space physics it is possible to study a phenomenon only as a function of time. This means that we cannot have direct access to information about spatial variations of a measured quantity. However, the investigation of the properties of turbulence and of related phenomena in the solar wind widely makes use of an approximation frequently adopted in hydrodynamics under certain conditions, the so-called Taylor hypothesis; indeed, the solar wind flow has a bulk velocity along the radial direction which is much higher than the velocity of a single turbulent eddy embedded in the main flow. This implies that the time of evolution of the turbulent features is longer than the transit time of the flow through the spacecraft position, so that the turbulent field can be considered frozen into the solar wind flow. This assumption allows one to easily associate time variations with spatial variations and stationarity to homogeneity. We have investigated, applying criteria for weak stationarity to Ulysses magnetic field data in different solar wind regimes, at which timescale and under which conditions the hypothesis of stationarity, and then of homogeneity, of turbulence in the solar wind is well justified. We extend the conclusions of previous studies by Matthaeus and Goldstein to different parameter ranges in the solar wind. We conclude that the stationarity assumption in the inertial range of turbulence on timescales of 10 minutes to 1 day is reasonably satisfied in fast and uniform solar wind flows, but that in mixed, interacting fast, and slow solar wind streams the assumption is frequently only marginally valid.

  10. Wind energy.

    PubMed

    Leithead, W E

    2007-04-15

    From its rebirth in the early 1980s, the rate of development of wind energy has been dramatic. Today, other than hydropower, it is the most important of the renewable sources of power. The UK Government and the EU Commission have adopted targets for renewable energy generation of 10 and 12% of consumption, respectively. Much of this, by necessity, must be met by wind energy. The US Department of Energy has set a goal of 6% of electricity supply from wind energy by 2020. For this potential to be fully realized, several aspects, related to public acceptance, and technical issues, related to the expected increase in penetration on the electricity network and the current drive towards larger wind turbines, need to be resolved. Nevertheless, these challenges will be met and wind energy will, very likely, become increasingly important over the next two decades. An overview of the technology is presented. PMID:17272245

  11. Short wind waves on the ocean: Long-wave and wind-speed dependences

    NASA Astrophysics Data System (ADS)

    Plant, William J.

    2015-09-01

    This second paper of our set on short wind waves on the ocean utilizes the wavenumber-frequency spectrum of short wave heights, F(k,f), derived in our previous paper to investigate kinematic effects on the dependence of the frequency spectrum, F(f), and the wavenumber spectrum, F(k), on long-wave height. We show that the model predicts that neither F(f) nor F(k) are exactly power law functions of their independent variables and that F(f) varies with significant wave height much more than F(k) does. After calibrating the model against wave gauges, we also investigate the dependence of mean-square-slopes (mss), mean-square heights (msh) and root-mean-square orbital velocities (rmsv) of short ocean waves on wind speed and maximum frequency or wavenumber. We use data from the wire wave gauges on University of Miami's Air-Sea Interaction Spar (ASIS) buoy for calibration purposes. Frequency spectra from the wave gauges begin to be affected by noise at about 2.5 Hz. Therefore, above 1 Hz, we utilize F(f) from the modeled F(k,f) to extend the frequency dependence up to 180 Hz. We set modeled spectral densities by matching measured spectra at 1 Hz. Using the calibrated F(f,k), we are able to estimate the average value of the total mss, for long and short waves, and its upwind and crosswind components up to 180 Hz for a variety of wind speeds. The average mss values are in good agreement with the measurements of Cox and Munk [1954], although the upwind and crosswind components agree less well.

  12. Maximum height and minimum time vertical jumping.

    PubMed

    Domire, Zachary J; Challis, John H

    2015-08-20

    The performance criterion in maximum vertical jumping has typically been assumed to simply raise the center of mass as high as possible. In many sporting activities minimizing movement time during the jump is likely also critical to successful performance. The purpose of this study was to examine maximum height jumps performed while minimizing jump time. A direct dynamics model was used to examine squat jump performance, with dual performance criteria: maximize jump height and minimize jump time. The muscle model had activation dynamics, force-length, force-velocity properties, and a series of elastic component representing the tendon. The simulations were run in two modes. In Mode 1 the model was placed in a fixed initial position. In Mode 2 the simulation model selected the initial squat configuration as well as the sequence of muscle activations. The inclusion of time as a factor in Mode 1 simulations resulted in a small decrease in jump height and moderate time savings. The improvement in time was mostly accomplished by taking off from a less extended position. In Mode 2 simulations, more substantial time savings could be achieved by beginning the jump in a more upright posture. However, when time was weighted more heavily in these simulations, there was a more substantial reduction in jump height. Future work is needed to examine the implications for countermovement jumping and to examine the possibility of minimizing movement time as part of the control scheme even when the task is to jump maximally. PMID:25964210

  13. Viscous Forces in Velocity Boundary Layers around Planetary Ionospheres.

    PubMed

    Pérez-De-Tejada

    1999-11-01

    A discussion is presented to examine the role of viscous forces in the transport of solar wind momentum to the ionospheric plasma of weakly magnetized planets (Venus and Mars). Observational data are used to make a comparison of the Reynolds and Maxwell stresses that are operative in the interaction of the solar wind with local plasma (planetary ionospheres). Measurements show the presence of a velocity boundary layer formed around the flanks of the ionosphere where the shocked solar wind has reached super-Alfvénic speeds. It is found that the Reynolds stresses in the solar wind at that region can be larger than the Maxwell stresses and thus are necessary in the local acceleration of the ionospheric plasma. From an order-of-magnitude calculation of the Reynolds stresses, it is possible to derive values of the kinematic viscosity and the Reynolds number that are suitable to the gyrotropic motion of the solar wind particles across the boundary layer. The value of the kinematic viscosity is comparable to those inferred from studies of the transport of solar wind momentum to the earth's magnetosphere and thus suggest a common property of the solar wind around planetary obstacles. Similar conditions could also be applicable to velocity boundary layers formed in other plasma interaction problems in astrophysics. PMID:10511515

  14. Impact and explosion crater ejecta, fragment size, and velocity

    NASA Technical Reports Server (NTRS)

    Okeefe, J. D.; Ahrens, T. J.

    1983-01-01

    A model was developed for the mass distribution of fragments that are ejected at a given velocity for impact and explosion craters. The model is semi-empirical in nature and is derived from (1) numerical calculations of cratering and the resultant mass versus ejection velocity, (2) observed ejecta blanket particle size distributions, (3) an empirical relationship between maximum ejecta fragment size and crater diameter and an assumption on the functional form for the distribution of fragements ejected at a given velocity. This model implies that for planetary impacts into competent rock, the distribution of fragments ejected at a given velocity are nearly monodisperse, e.g., 20% of the mass of the ejecta at a given velocity contain fragments having a mass less than 0.1 times a mass of the largest fragment moving at that velocity. Using this model, the largest fragment that can be ejected from asteroids, the moon, Mars, and Earth is calculated as a function of crater diameter. In addition, the internal energy of ejecta versus ejecta velocity is found. The internal energy of fragments having velocities exceeding the escape velocity of the moon will exceed the energy required for incipient melting for solid silicates and thus, constrains the maximum ejected solid fragment size.

  15. Effects of Airfoil Thickness and Maximum Lift Coefficient on Roughness Sensitivity: 1997--1998

    SciTech Connect

    Somers, D. M.

    2005-01-01

    A matrix of airfoils has been developed to determine the effects of airfoil thickness and the maximum lift to leading-edge roughness. The matrix consists of three natural-laminar-flow airfoils, the S901, S902, and S903, for wind turbine applications. The airfoils have been designed and analyzed theoretically and verified experimentally in the Pennsylvania State University low-speed, low-turbulence wind tunnel. The effect of roughness on the maximum life increases with increasing airfoil thickness and decreases slightly with increasing maximum lift. Comparisons of the theoretical and experimental results generally show good agreement.

  16. Velocity Based Modulus Calculations

    NASA Astrophysics Data System (ADS)

    Dickson, W. C.

    2007-12-01

    A new set of equations are derived for the modulus of elasticity E and the bulk modulus K which are dependent only upon the seismic wave propagation velocities Vp, Vs and the density ?. The three elastic moduli, E (Young's modulus), the shear modulus ? (Lamé's second parameter) and the bulk modulus K are found to be simple functions of the density and wave propagation velocities within the material. The shear and elastic moduli are found to equal the density of the material multiplied by the square of their respective wave propagation-velocities. The bulk modulus may be calculated from the elastic modulus using Poisson's ratio. These equations and resultant values are consistent with published literature and values in both magnitude and dimension (N/m2) and are applicable to the solid, liquid and gaseous phases. A 3D modulus of elasticity model for the Parkfield segment of the San Andreas Fault is presented using data from the wavespeed model of Thurber et al. [2006]. A sharp modulus gradient is observed across the fault at seismic depths, confirming that "variation in material properties play a key role in fault segmentation and deformation style" [Eberhart-Phillips et al., 1993] [EPM93]. The three elastic moduli E, ? and K may now be calculated directly from seismic pressure and shear wave propagation velocities. These velocities may be determined using conventional seismic reflection, refraction or transmission data and techniques. These velocities may be used in turn to estimate the density. This allows velocity based modulus calculations to be used as a tool for geophysical analysis, modeling, engineering and prospecting.

  17. Variations of Strahl Properties with Fast and Slow Solar Wind

    NASA Technical Reports Server (NTRS)

    Figueroa-Vinas, Adolfo; Goldstein, Melvyn L.; Gurgiolo, Chris

    2008-01-01

    The interplanetary solar wind electron velocity distribution function generally shows three different populations. Two of the components, the core and halo, have been the most intensively analyzed and modeled populations using different theoretical models. The third component, the strahl, is usually seen at higher energies, is confined in pitch-angle, is highly field-aligned and skew. This population has been more difficult to identify and to model in the solar wind. In this work we make use of the high angular, energy and time resolution and three-dimensional data of the Cluster/PEACE electron spectrometer to identify and analyze this component in the ambient solar wind during high and slow speed solar wind. The moment density and fluid velocity have been computed by a semi-numerical integration method. The variations of solar wind density and drift velocity with the general build solar wind speed could provide some insight into the source, origin, and evolution of the strahl.

  18. Nature and Variability of Coronal Streamers and their Relationship to the Slow Speed Wind

    NASA Technical Reports Server (NTRS)

    Strachan, Leonard

    2005-01-01

    NASA Grant NAG5-12781 is a study on the "Nature and Variability of Coronal Streamers and their Relationship to the Slow Speed Wind." The two main goals of this study are to identify: 1) Where in the streamer structure does the solar wind originate, and 2) What coronal conditions are responsible for the variability of the slow speed wind. To answer the first question, we examined the mostly closed magnetic field regions in streamer cores to search for evidence of outflow. Preliminary results from the OVI Doppler dimming ratios indicates that most of the flow originates from the edges of coronal streamers but this idea should be confirmed by a comparison of the coronal plasma properties with in situ solar wind data. To answer the second question, the work performed thus far suggests that solar minimum streamers have larger perpendicular velocity distributions than do solar maximum streamers. If it can be shown that solar minimum streamers also produce higher solar wind speeds then this would suggest that streamers and coronal holes have similar solar wind acceleration mechanisms. The key to both questions lie in the analysis of the in situ solar wind data sets. This work was not able to be completed during the period of performance and therefore the grant was formally extended for an additional year at no cost to NASA. We hope to have final results and a publication by the end of the calendar year 2004. The SAO personnel involved in the research are Leonard Strachan (PI), Mari Paz Miralles, Alexander Panasyuk, and a Southern University student Michael Baham.

  19. The Winds of B Supergiants

    NASA Technical Reports Server (NTRS)

    Massa, D.; Oliversen, R. (Technical Monitor)

    2002-01-01

    We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analyzed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include 'normal' stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasises the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters, but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures, and highlight the challenges that these phenomena present to theoretical studies of time-dependent outflows in massive stars. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (M (dot) q(sub i)) is a factor of approximately 1.5, when integrated between 0.2 and 0.9 v infinity; it can however be several times larger over localized velocity regions. At a given effective temperature the mean relative ion ratios can differ by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in terms of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.

  20. The Winds of B Supergiants

    NASA Technical Reports Server (NTRS)

    Massa, Derck; West, D. (Technical Monitor)

    2002-01-01

    We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analyzed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include 'normal' stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasizes the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures, and highlight the challenges that these phenomena present to theoretical studies of time-dependent outflows in massive stars. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (M qi) is a factor of approximately 1.5, when integrated between 0.2 and 0.9 v infinity; it it can however be several times larger over localized velocity regions. At a given effective temperature the mean relative ion ratios can differ by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in turns of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.

  1. Relativistic Radiation Hydrodynamical Accretion Disk Winds

    E-print Network

    Jun Fukue; Chizuru Akizuki

    2007-11-09

    Accretion disk winds browing off perpendicular to a luminous disk are examined in the framework of fully special relativistic radiation hydrodynamics. The wind is assumed to be steady, vertical, and isothermal. %and the gravitational fields is approximated by a pseudo-Newtonian potential. Using a velocity-dependent variable Eddington factor, we can solve the rigorous equations of relativistic radiative hydrodynamics, and can obtain radiatively driven winds accelerated up to the {\\it relativistic} speed. For less luminous cases, disk winds are transonic types passing through saddle type critical points, and the final speed of winds increases as the disk flux and/or the isothermal sound speed increase. For luminous cases, on the other hand, disk winds are always supersonic, since critical points disappear due to the characteristic nature of the disk gravitational fields. The boundary between the transonic and supersonic types is located at around $\\hat{F}_{\\rm c} \\sim 0.1 (\\epsilon+p)/(\\rho c^2)/\\gamma_{\\rm c}$, where $\\hat{F}_{\\rm c}$ is the radiative flux at the critical point normalized by the local Eddington luminosity, $(\\epsilon+p)/(\\rho c^2)$ is the enthalpy of the gas divided by the rest mass energy, and $\\gamma_{\\rm c}$ is the Lorentz factor of the wind velocity at the critical point. In the transonic winds, the final speed becomes 0.4--0.8$c$ for typical parameters, while it can reach $\\sim c$ in the supersonic winds.

  2. Streamwise Evolution of Statistical Events in a Model Wind-Turbine Array

    NASA Astrophysics Data System (ADS)

    Viestenz, Kyle; Cal, Raúl Bayoán

    2015-09-01

    Hot-wire anemometry data, obtained from a wind-tunnel experiment containing a 3 × 3 model wind-turbine array, are used to conditionally average the Reynolds stresses. Nine profiles at the centreline behind the array are analyzed to characterize the turbulent velocity statistics of the wake flow. Quadrant analysis yields statistical events occurring in the wake of the wind farm where quadrants 2 and 4 produce ejections and sweeps, respectively. The scaled difference between these two events is expressed via the ? R0 parameter and is based on the ? S0 quantity as introduced by M. R. Raupach (J Fluid Mech 108:363-382, 1981). ? R0 attains a maximum value at hub height and changes sign near the top of the rotor. The ratio of quadrant events of upward momentum flux to those of the downward flux, known as the exuberance, is examined and reveals the effect of root vortices persisting to eight rotor diameters downstream. These events are then associated with the triple correlation term present in the turbulent kinetic energy equation of the fluctuations where it is found that ejections play the dual role of entraining mean kinetic energy while convecting turbulent kinetic energy out of the turbine canopy. The development of these various quantities possesses significance in closure models, and is assessed in light of wake remediation, energy transport and power fluctuations, where it is found that the maximum fluctuation is about 30% of the mean power produced.

  3. Ocean's response to Hurricane Frances and its implications for drag coefficient parameterization at high wind speeds

    NASA Astrophysics Data System (ADS)

    Zedler, S. E.; Niiler, P. P.; Stammer, D.; Terrill, E.; Morzel, J.

    2009-04-01

    The drag coefficient parameterization of wind stress is investigated for tropical storm conditions using model sensitivity studies. The Massachusetts Institute of Technology (MIT) Ocean General Circulation Model was run in a regional setting with realistic stratification and forcing fields representing Hurricane Frances, which in early September 2004 passed east of the Caribbean Leeward Island chain. The model was forced with a NOAA-HWIND wind speed product after converting it to wind stress using four different drag coefficient parameterizations. Respective model results were tested against in situ measurements of temperature profiles and velocity, available from an array of 22 surface drifters and 12 subsurface floats. Changing the drag coefficient parameterization from one that saturated at a value of 2.3 × 10-3 to a constant drag coefficient of 1.2 × 10-3 reduced the standard deviation difference between the simulated minus the measured sea surface temperature change from 0.8°C to 0.3°C. Additionally, the standard deviation in the difference between simulated minus measured high pass filtered 15-m current speed reduced from 15 cm/s to 5 cm/s. The maximum difference in sea surface temperature response when two different turbulent mixing parameterizations were implemented was 0.3°C, i.e., only 11% of the maximum change of sea surface temperature caused by the storm.

  4. Sandia Wind Turbine Loads Database

    DOE Data Explorer

    The Sandia Wind Turbine Loads Database is divided into six files, each corresponding to approximately 16 years of simulation. The files are text files with data in columnar format. The 424MB zipped file containing six data files can be downloaded by the public. The files simulate 10-minute maximum loads for the NREL 5MW wind turbine. The details of the loads simulations can be found in the paper: “Decades of Wind Turbine Loads Simulations”, M. Barone, J. Paquette, B. Resor, and L. Manuel, AIAA2012-1288 (3.69MB PDF). Note that the site-average wind speed is 10 m/s (class I-B), not the 8.5 m/s reported in the paper.

  5. Amplitude modulation of wind turbine noise

    E-print Network

    Makarewicz, Rufin

    2013-01-01

    Due to swish and thump amplitude modulation, the noise of wind turbines cause more annoyance than other environmental noise of the same average level. The wind shear accounts for the thump modulation (van den Berg effect). Making use of the wind speed measurements at the hub height, as well as at the top and the bottom of the rotor disc (Fig.1), the non-standard wind profile is applied. It causes variations in the A-weighted sound pressure level, LpA. The difference between the maximum and minimum of LpA characterizes thump modulation (Fig.2).

  6. Near-lunar proton velocity distribution explained by electrostatic acceleration

    E-print Network

    Hutchinson, I H

    2013-01-01

    The observation of parallel ion velocity in the near-lunar wake approximately equal to external solar wind velocity \\emph{can} be explained within uncertainties by an analytic electrostatic expansion model. The one-dimensional model frequently used is inadequate because it does not account for the moon's spherical shape. However, application of a more recent generalization to three-dimensions of the solution along characteristics predicts higher velocities, and is probably sufficient to account for the SARA observations on the Chandrayaan-1 space-craft.

  7. Measurement and characterization of the wave-induced components of winds over waves

    NASA Astrophysics Data System (ADS)

    Grare, L.; Lenain, L.; Melville, W. K.

    2012-12-01

    Current wind-wave numerical models are largely based on a statistical description of the surface waves and the marine atmospheric boundary layer (MABL) and do not resolve the phase of the waves nor the modulation of the wind by the waves. However, the new generation of LES models provides wave-resolved dynamics, kinematics and the associated wave-coherent air-flow. Thus, it is important to provide experimental descriptions of the wave field and the structure of the MABL to test the validity of the numerical simulations. We present an analysis of coherent measurements of winds and waves from data collected during the ONR HiReS program from R/P FLIP off the coast of northern California in June 2010. A suite of wind and wave measuring systems were deployed allowing the resolution of the modulation of the MABL by the waves. Spectral analysis of the data gave the wave-induced components of the wind velocity for various wind and wave conditions over a large range of frequencies. The power spectral density, phase shift and transfer functions (relative to the waves) of these wave-induced components are computed and bin-averaged over normalized wave age c/U, or c/u*, and over the normalized height kz, where c and k are the phase speed and wavenumber, U is the mean wind speed, u* is the friction velocity in the air, and z is the height above the mean surface. Results are consistent with the critical layer theory of Miles (1957, 1959) for wave ages c/U up to 2 but show a different pattern for larger wave ages. Measurements of the phase shift between vertical and along-wave components of the wind with the waves show a jump at the critical height zc defined as U(zc)=c. The distribution of the coherent structures associated with the waves as function of the wave-age c/U shows a bi-modal distribution centered at c/U=1, or c/u*=20-30. This result is a consequence of the drop-off of the amplitude of the wave-induced velocity at the critical height. The normalized vertical profiles of the along wave and vertical wave-induced components of the wind do not follow an expected exponential trend. Indeed, for fast waves (c/U > 2), these wave-induced fluctuations reach a maximum around kz=1. Furthermore, these fast ("old") waves produce a positive vertical wave-induced momentum flux. These results are in agreement with the numerical study of Sullivan et al. (2008), for old waves or swell, that showed a coherent pattern of accelerated wind speed (with a maximum close to kz=1) over the troughs associated with decelerated wind speed over the crests.

  8. Stellar Winds

    NASA Astrophysics Data System (ADS)

    Owocki, Stan

    A "stellar wind" is the continuous, supersonic outflow of matter from the surface layers of a star. Our sun has a solar wind, driven by the gas-pressure expansion of the hot (T > 106 K) solar corona. It can be studied through direct in situ measurement by interplanetary spacecraft; but analogous coronal winds in more distant solar-type stars are so tenuous and transparent that that they are difficult to detect directly. Many more luminous stars have winds that are dense enough to be opaque at certain wavelengths of the star's radiation, making it possible to study their wind outflows remotely through careful interpretation of the observed stellar spectra. Red giant stars show slow, dense winds that may be driven by the pressure from magnetohydrodyanmic waves. As stars with initial mass up to 8 M ? evolve toward the Asymptotic Giant Branch (AGB), a combination of stellar pulsations and radiative scattering off dust can culminate in "superwinds" that strip away the entire stellar envelope, leaving behind a hot white dwarf stellar core with less than the Chandrasekhar mass of ˜ ?? 1. 4M ?. The winds of hot, luminous, massive stars are driven by line-scattering of stellar radiation, but such massive stars can also exhibit superwind episodes, either as Red Supergiants or Luminous Blue Variable stars. The combined wind and superwind mass loss can strip the star's hydrogen envelope, leaving behind a Wolf-Rayet star composed of the products of earlier nuclear burning via the CNO cycle. In addition to such direct effects on a star's own evolution, stellar winds can be a substantial source of mass, momentum, and energy to the interstellar medium, blowing open large cavities or "bubbles" in this ISM, seeding it with nuclear processed material, and even helping trigger the formation of new stars, and influencing their eventual fate as white dwarves or core-collapse supernovae. This chapter reviews the properties of such stellar winds, with an emphasis on the various dynamical driving processes and what they imply for key wind parameters like the wind flow speed and mass loss rate.

  9. Winds and Accretion in Young Stars

    E-print Network

    Suzan Edwards

    2008-09-21

    Establishing the origin of accretion powered winds from forming stars is critical for understanding angular momentum evolution in the star-disk interaction region. Here, the high velocity component of accretion powered winds is launched and accreting stars are spun down, in defiance of the expected spin-up during magnetospheric accretion. T Tauri stars in the final stage of disk accretion offer a unique opportunity to study the connection between accretion and winds and their relation to stellar spindown. Although spectroscopic indicators of high velocity T Tauri winds have been known for decades, the line of He I 10830 offers a promising new diagnostic to probe the magnetically controlled star-disk interaction and wind-launching region. The high opacity and resonance scattering properties of this line offer a powerful probe of the geometry of both the funnel flow and the inner wind that, together with other atomic and molecular spectral lines covering a wide range of excitation and ionization states, suggests that the magnetic interaction between the star and disk, and the subsequent launching of the inner high velocity wind, is sensitive to the disk accretion rate.

  10. Wind Tunnel, Field and Numerical Investigations of Plume Downwash and Dispersion at AN Arctic Industrial Site

    NASA Astrophysics Data System (ADS)

    Guenther, Alex Brian

    This study was designed to investigate the influence of the arctic atmospheric boundary layer and the complex flow pattern generated by building clusters on dispersion from a buoyant source. This was accomplished by analyzing data from wind tunnel, field, and numerical dispersion experiments for flow around a specific Prudhoe Bay, Alaska oil-gathering center. The results were used to describe plume downwash and the arctic boundary layer and to evaluate current Gaussian plume downwash techniques. Field observations indicate that the winter-time tundra surface has a very small (0.3 mm) surface roughness. A persistent temperature inversion was observed near the cold tundra surface and was attributed to the limited solar insolation and a relatively warm maritime-influenced air mass. Observations of turbulence and surface layer structure at heights above 15 m are similar to measurements made at lower latitudes. Field tracer measurements indicate that plume downwash and dispersion dominates the distribution of ground-level concentrations near the buoyant, short stack sources typical of arctic industrial facilities. An order of magnitude increase in maximum concentration occurs as wind speed increases from 5 to 8 m s^ {-1} and another order of magnitude increase occurs as wind speed increases to 16 m s ^{-1}. Maximum ground-level concentration occurs near the buildings and varies by a factor of 6 with changes in wind direction. Concentrations estimated by Gaussian plume models ranged from a factor of 6 lower than field observations to a factor of 8 higher. A three-dimensional, two-equation (k - epsilon) turbulence closure numerical model was capable of simulating the mean streamline bending, turbulence enhancement, and velocity defects observed in the recirculation cavity and building wake downwind of buildings. This technique provides a potential alternative to the wind tunnel and field studies which are currently the only means of estimating accurately ground-level concentrations near arctic industrial facilities.

  11. MSE velocity survey

    NASA Astrophysics Data System (ADS)

    Schimd, C.; Courtois, H.; Koda, J.

    2015-12-01

    A huge velocity survey based on the Maunakea Spectroscopic Explorer facility (MSE) is proposed, aiming at investigating the structure and dynamics of the cosmic web over 3? steradians up to ˜1 Gpc and at unprecedented spatial resolution, its relationship with the galaxy formation process, and the bias between galaxies and dark matter during the last three billions years. The cross-correlation of velocity and density fields will further allow the probe any deviation from General Relativity by measuring the the linear-growth rate of cosmic structures at precision competitive with high-redshift spectroscopic redshift surveys.

  12. Velocity pump reaction turbine

    DOEpatents

    House, Palmer A. (Walnut Creek, CA)

    1984-01-01

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  13. Velocity pump reaction turbine

    DOEpatents

    House, Palmer A. (Walnut Creek, CA)

    1982-01-01

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  14. Maximum attainable ion energy in the radiation pressure acceleration regime

    NASA Astrophysics Data System (ADS)

    Bulanov, Stepan; Esarey, Eric; Schroeder, Carl; Bulanov, Sergey; Esirkepov, Timur; Kando, Masaki; Pegoraro, Francesco; Leemans, Wim

    2014-10-01

    Radiation Pressure Acceleration is a highly efficient mechanism of laser driven ion acceleration, with the laser energy almost totally transferrable to the ions in the relativistic regime. There is a fundamental limit on the maximum attainable ion energy, which is determined by the group velocity of the laser. In the case of a tightly focused laser pulses, which are utilized to get the highest intensity, another factor limiting the maximum ion energy comes into play, the transverse expansion of the target. It makes the target transparent for radiation, thus reducing the effectiveness of acceleration. Utilization of an external guiding structure for the accelerating laser pulse may provide a way of compensating for the group velocity and transverse expansion effects. We acknowledge support from the NSF under Grant No. PHY-0935197 and the Office of Science of the US DOE under Contract No. DE-AC02-05CH11231 and No. DE-FG02-12ER41798.

  15. High Velocity Absorption during Eta Car B's Periastron Passage

    NASA Technical Reports Server (NTRS)

    Nielsen, Krister E.; Groh, J. H.; Hillier, J.; Gull, Theodore R.; Owocki, S. P.; Okazaki, A. T.; Damineli, A.; Teodoro, M.; Weigelt, G.; Hartman, H.

    2010-01-01

    Eta Car is one of the most luminous massive stars in the Galaxy, with repeated eruptions with a 5.5 year periodicity. These events are caused by the periastron passage of a massive companion in an eccentric orbit. We report the VLT/CRIRES detection of a strong high-velocity, (<1900 km/s) , broad absorption wing in He I at 10833 A during the 2009.0 periastron passage. Previous observations during the 2003.5 event have shown evidence of such high-velocity absorption in the He I 10833 transition, allowing us to conclude that the high-velocity gas is crossing the line-of-sight toward Eta Car over a time period of approximately 2 months. Our analysis of HST/STlS archival data with observations of high velocity absorption in the ultraviolet Si IV and C IV resonance lines, confirm the presence of a high-velocity material during the spectroscopic low state. The observations provide direct detection of high-velocity material flowing from the wind-wind collision zone around the binary system, and we discuss the implications of the presence of high-velocity gas in Eta Car during periastron

  16. Impact Wind Farms on the Marine Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Volker, P.; Capps, S. B.; Huang, H. J.; Sun, F.; Badger, J.; Hahmann, A.

    2012-12-01

    We introduce a new, validated wind farm parametrization (Explicit Wake Parametrization, EWP) which is based on the assumption that the downstream propagation of a single turbine wake can be described by a turbulent diffusion process. Thus, the downstream velocity deficit distribution can be described explicitly. Additionally, it allows us to take into account turbine interactions, making it possible to determine the unresolved turbine hub height velocities. Both the EWP wind farm parametrization and the wind farm scheme available in the Weather Research & Forecasting Model (WRF) have been validated against in situ measurements from Horns Rev I (A large offshore wind farm consisting of 80 2MW turbines situated near the west coast of Denmark). The main quantities of interest are the thrust applied to the flow, a consequence of the energy extracted by the wind turbines which determines mainly the wind farm wake extension (around 50 km for Horns Rev I) and the vertical velocity deficit distribution. Results show that the thrust in the WRF-WF scheme is overestimated inside the wind farm. We noticed that the velocity deficit propagates from the first turbine-containing-grid-cell up to the boundary layer top, which is in contrast to the theoretical expected expansion (confirmed by turbulence resolving models and wind tunnel results). The vertical expansion of the velocity deficit is a consequence of the additional turbulence source term in the WRF-WF scheme. The EWP scheme estimates the total amount of thrust correctly and is also able to follow the reduced thrust downstream since it considers the turbine interaction. From the good agreement with the far wake measurement, we can conclude that the formulation of the sub grid scale vertical extension of the velocity deficit must be correct. We will present results from WRF simulations in which we analyze the atmospheric response within the wake of wind farms resulting from the energy extraction of wind turbines. We place hypotetical wind farms in offshore areas with good wind resources near California. The wind farm sizes are choosen to be comparable to present ones errected in the European North Sea. Of particular interest is the influence of wind farms on the persistent stratocumulus clouds of the California coastal region, the thermal stratification of the boundary layer and wind stress changes due to reduced wind speeds near the surface. Although no wind farms are presently constructed along the Californian coast, fast and steady wind speeds makes it an attractive region for future offshore wind farms, especially if the first floating turbines near the coast of Norway are proven to be a success.

  17. 14 CFR 151.79 - Runway paving: Second runway; wind conditions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Runway paving: Second runway; wind...: Second runway; wind conditions. (a) All airports. Paving a second runway on the basis of wind conditions... second runway is oriented with the existing paved runway to achieve the maximum wind coverage, with...

  18. 14 CFR 151.79 - Runway paving: Second runway; wind conditions.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Runway paving: Second runway; wind...: Second runway; wind conditions. (a) All airports. Paving a second runway on the basis of wind conditions... second runway is oriented with the existing paved runway to achieve the maximum wind coverage, with...

  19. 14 CFR 151.79 - Runway paving: Second runway; wind conditions.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Runway paving: Second runway; wind...: Second runway; wind conditions. (a) All airports. Paving a second runway on the basis of wind conditions... second runway is oriented with the existing paved runway to achieve the maximum wind coverage, with...

  20. 14 CFR 151.79 - Runway paving: Second runway; wind conditions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Runway paving: Second runway; wind...: Second runway; wind conditions. (a) All airports. Paving a second runway on the basis of wind conditions... second runway is oriented with the existing paved runway to achieve the maximum wind coverage, with...

  1. The Solar Wind in the Outer Heliosphere at Solar John D. Richardson and Chi Wang

    E-print Network

    Richardson, John

    (400 km/s) solar wind is con ned to a thin strip of half-width 10-20 near the heliographic equator wind speed, with the energy for this accel- eration coming from a slowdown of the solar windThe Solar Wind in the Outer Heliosphere at Solar Maximum John D. Richardson and Chi Wang Center

  2. RESEARCH ARTICLE Characterization of the wind loads and flow fields around

    E-print Network

    Hu, Hui

    on the Fujita Scale, i.e., they involve wind speeds less than 160 mph (Bluestein and Golden 1993; Womble et al and swirl- ing, turbulent tornado-like winds. The experimental work was conducted by using a large-scale wind speeds on earth, i.e., with the maximum wind speed up to 400 mph (Grazulis 1993). Large-scale

  3. Hardware-in-the-Loop Simulations and Control Design for a Small Vertical Axis Wind Turbine

    E-print Network

    Yanikoglu, Berrin

    Hardware-in-the-Loop Simulations and Control Design for a Small Vertical Axis Wind Turbine Ugur a maximum power point tracking (MPPT) algorithm for small vertical axis wind turbines (VAWTs). Wind torque tracking; vertical axis wind turbine, inertia emulation; disturbance torque compensation I. INTRODUCTION

  4. Wind tunnel interference factors for high-lift wings in closed wind tunnels. Ph.D. Thesis - Princeton Univ.

    NASA Technical Reports Server (NTRS)

    Joppa, R. G.

    1973-01-01

    A problem associated with the wind tunnel testing of very slow flying aircraft is the correction of observed pitching moments to free air conditions. The most significant effects of such corrections are to be found at moderate downwash angles typical of the landing approach. The wind tunnel walls induce interference velocities at the tail different from those induced at the wing, and these induced velocities also alter the trajectory of the trailing vortex system. The relocated vortex system induces different velocities at the tail from those experienced in free air. The effect of the relocated vortex and the walls is to cause important changes in the measured pitching moments in the wind tunnel.

  5. Relationship between gas exchange, wind speed, and radar backscatter in a large wind-wave tank

    NASA Technical Reports Server (NTRS)

    Wanninkhof, Richard H.; Bliven, L. F.

    1991-01-01

    The relationships between the gas exchange, wind speed, friction velocity, and radar backscatter from the water surface was investigated using data obtained in a large water tank in the Delft (Netherlands) wind-wave tunnel, filled with water supersaturated with SF6, N2O, and CH4. Results indicate that the gas-transfer velocities of these substances were related to the wind speed with a power law dependence. Microwave backscatter from water surface was found to be related to gas transfer velocities by a relationship in the form k(gas) = a 10 exp (b A0), where k is the gas transfer velocity for the particular gas, the values of a and b are obtained from a least squares fit of the average backscatter cross section and gas transfer at 80 m, and A0 is the directional (azimuthal) averaged return.

  6. 78 FR 29364 - Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-20

    ...-005, QF07-257-004] Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4, LLC, Exelon Wind 5, LLC, Exelon Wind 6, LLC, Exelon Wind 7, LLC, Exelon Wind 8, LLC, Exelon Wind 9, LLC, Exelon Wind 10, LLC, Exelon Wind 11, LLC, High Plains Wind Power, LLC v. Xcel...

  7. Cost of wind energy: comparing distant wind resources to local resources in the midwestern United States.

    PubMed

    Hoppock, David C; Patiño-Echeverri, Dalia

    2010-11-15

    The best wind sites in the United States are often located far from electricity demand centers and lack transmission access. Local sites that have lower quality wind resources but do not require as much power transmission capacity are an alternative to distant wind resources. In this paper, we explore the trade-offs between developing new wind generation at local sites and installing wind farms at remote sites. We first examine the general relationship between the high capital costs required for local wind development and the relatively lower capital costs required to install a wind farm capable of generating the same electrical output at a remote site,with the results representing the maximum amount an investor should be willing to pay for transmission access. We suggest that this analysis can be used as a first step in comparing potential wind resources to meet a state renewable portfolio standard (RPS). To illustrate, we compare the cost of local wind (?50 km from the load) to the cost of distant wind requiring new transmission (?550-750 km from the load) to meet the Illinois RPS. We find that local, lower capacity factor wind sites are the lowest cost option for meeting the Illinois RPS if new long distance transmission is required to access distant, higher capacity factor wind resources. If higher capacity wind sites can be connected to the existing grid at minimal cost, in many cases they will have lower costs. PMID:20931984

  8. Shelf response to intense offshore wind

    NASA Astrophysics Data System (ADS)

    Grifoll, Manel; Aretxabaleta, Alfredo L.; Espino, Manuel

    2015-09-01

    Cross and along-shelf winds drive cross-shelf transport that promotes the exchange of tracers and nutrients to the open sea. The shelf response to cross-shelf winds is studied in the north shelf of the Ebro Delta (Mediterranean Sea), where those winds are prevalent and intense. Offshore winds in the region exhibit strong intensities (wind stress larger than 0.8 Pa) during winter and fall. The monthly average flow observed in a 1 year current meter record at 43.5 m was polarized following the isobaths with the along-shelf variability being larger than the cross-shelf. Prevalent southwestward along-shelf flow was induced by the three-dimensional regional response to cross-shelf winds and the coastal constraint. Seaward near-surface velocities occurred predominantly during offshore wind events. During intense wind periods, the surface cross-shelf water transport exceeded the net along-shelf transport. During typically stratified seasons, the intense cross-shelf winds resulted in a well-defined two-layer flow and were more effective at driving offshore transport than during unstratified conditions. While transfer coefficients between wind and currents were generally around 1%, higher cross-shelf transfer coefficients were observed in the near-inertial band. The regional extent of the resulting surface cold water during energetic cross-shelf winds events was concentrated around the region of the wind jet. Cross-shelf transport due to along-shelf winds was only effective during northeast wind events. During along-shelf wind conditions, the transport was estimated to be between 10 and 50% of the theoretical Ekman transport.

  9. Filament winding

    NASA Astrophysics Data System (ADS)

    Shibley, A. M.

    The major aspects of filament winding are discussed, emphasizing basic reinforcement and matrix materials, winding procedures, process controls, and cured composite properties. Fiberglass (E-glass and S-glass strengths are 500,000 and 665,000 psi respectively) and polyester resins are the principal reinforcement constituent materials. Graphite and aramid reinforcements are being used more frequently, primarily for the more critical pressure vessels. Matrix systems are most commonly based on epoxy as it has superior mechanical properties, fatigue behavior, and heat resistance as compard with polyesters. A fiberglass overwrap of PVC pipe is an anticipated development in on-site winding and combination winding, and the compression molding of filament wound lay-ups will be investigated. The fabrication of weight-sensitive structural components may be achieved by using such moldings.

  10. Approach to forecasting daily maximum ozone levels in St. Louis

    NASA Technical Reports Server (NTRS)

    Prior, E. J.; Schiess, J. R.; Mcdougal, D. S.

    1981-01-01

    Measurements taken in 1976 from the St. Louis Regional Air Pollution Study (RAPS) data base, conducted by EPA, were analyzed to determine an optimum set of air-quality and meteorological variables for predicting maximum ozone levels for each day in 1976. A 'leaps and bounds' regression analysis was used to identify the best subset of variables. Three particular variables, the 9 a.m. ozone level, the forecasted maximum temperature, and the 6-9 a.m. averaged wind speed, have useful forecasting utility. The trajectory history of air masses entering St. Louis was studied, and it was concluded that transport-related variables contribute to the appearance of very high ozone levels. The final empirical forecast model predicts the daily maximum ozone over 341 days with a standard deviation of 11 ppb, which approaches the estimated error.

  11. Acoustic remote sensing of the ABL wind structure in Moscow city

    NASA Astrophysics Data System (ADS)

    Akhiyarova, Ksenia; Lokoshchenko, Mikhail

    2014-05-01

    The dynamics of wind velocity V in the atmospheric boundary layer (ABL) above Moscow city have been analyzed by long-term data of sodar measurements. The Doppler 'MODOS' sodar of METEK firm (Germany) production operates at Moscow University since 2004. Besides, data of two cup anemometers on 7 and 15 m heights inside 'dead zone' of the sodar have been added to analysis. The methodical questions of comparison between in situ and sodar data about V are discussed in details. The profile of wind velocity V in the air layer from 7 to 500 m has been received and analyzed in average of eight last years from 2004 to 2012. In average it is close to logarithmical law up to 60 m so that this value seems to be equal to the surface air layer height. It should be noted that sodar due to its high spatial resolution (20 m) allows studying the ABL fine-structure. Among others, the daily course of V has been investigated in details at different heights. It demonstrates clear daily maximum and nocturnal minimum at any height below 80 m and, vice versa, nocturnal maximum and daily minimum above 140 m everywhere. The air layer from 80 to 140 m represents intermediate zone of smoothed daily course of V. In general this zone corresponds to cross-over height (ideal level where the daily course of wind velocity is absent) but it is noted by important additional feature - minimum in the morning which is statistically significant. Besides, with using of the sodar data it's possible to study mostly interesting weather phenomena such as thunderstorm. Total sampling of this weather event was equal to 137 cases in Moscow from 2004 to 2012. Averaged values both of V, and of its vertical component W have been analyzed during these thunderstorms. As it was shown both V, and W values are increased at the moment of this phenomenon starting. The wind velocity at this moment is in average nearly on 1 m/s higher than three hours before thunderstorm and this increase is statistically significant with 0.95 confidence probability. This work was partially supported by the Russian Basic Research Foundation (project No.14-05-00594).

  12. Acoustic Doppler Velocity Meter

    USGS Multimedia Gallery

    An acoustic Doppler velocity meter mounted on a track for instream deployment. The USGS deployed devices similar to this on at three monitoring sites on northern Idaho's Kootenai River to estimate sediment concentrations in the spawning habitat of the endangered Kootenai River white sturgeon. Sedime...

  13. Critical velocities of ultracentrifuges

    NASA Technical Reports Server (NTRS)

    Sokolov, V I

    1951-01-01

    The Euler equations for the rotation of a solid body are applied to the problem of the motion of ultracentrifuges. Particular attention is paid to the problem of the passage of an ultracentrifuge rotor through the critical velocity. The factors that affect the passage of rotors through the critical point are stressed.

  14. Modeling Terminal Velocity

    ERIC Educational Resources Information Center

    Brand, Neal; Quintanilla, John A.

    2013-01-01

    Using a simultaneously falling softball as a stopwatch, the terminal velocity of a whiffle ball can be obtained to surprisingly high accuracy with only common household equipment. This classroom activity engages students in an apparently daunting task that nevertheless is tractable, using a simple model and mathematical techniques at their…

  15. Performance evaluation of coherent 2-?m differential absorption and wind lidar for wind measurement

    NASA Astrophysics Data System (ADS)

    Iwai, H.; Ishii, S.; Oda, R.; Mizutani, K.; Murayama, Y.

    2012-11-01

    A coherent 2-?m differential absorption and wind lidar (Co2DiaWiL) has been built with a high power Q-switched Tm,Hm:YLF laser to measure CO2 concentration and radial wind velocity. Our experiment was conducted to test the ability of the Co2DiaWiL to make wind measurement in the atmospheric boundary layer and lower free troposphere. The bias in the velocity measurement was estimated as -0.0069 m/s using measurements from a stationary hard target. The magnitude of the random error of radial velocity measurements was determined from data in the vertical pointing mode and the Co2DiaWiL achieved a velocity precision of 0.12 m/s. The radial velocity measurements to ranges up to 20-25 km by the horizontally fixed beam mode for average times of 1 min have been demonstrated with the high laser output power. The Co2DiaWiL-measured radial velocities were directly compared with the wind speeds measured by a closelylocated sonic anemometer. The correlation coefficient was as large as 0.99 for comparison of radial velocities averaged for 1 min from the Co2DiaWiL and sonic anemometer.

  16. Velocity measurements by laser resonance fluorescence. [single atom diffusional motion

    NASA Technical Reports Server (NTRS)

    She, C. Y.; Fairbank, W. M., Jr.

    1980-01-01

    The photonburst correlation method was used to detect single atoms in a buffer gas. Real time flow velocity measurements with laser induced resonance fluorescence from single or multiple atoms was demonstrated and this method was investigated as a tool for wind tunnel flow measurement. Investigations show that single atoms and their real time diffusional motion on a buffer gas can be measured by resonance fluorescence. By averaging over many atoms, flow velocities up to 88 m/s were measured in a time of 0.5 sec. It is expected that higher flow speeds can be measured and that the measurement time can be reduced by a factor of 10 or more by careful experimental design. The method is clearly not ready for incorporation in high speed wind tunnels because it is not yet known whether the stray light level will be higher or lower, and it is not known what detection efficiency can be obtained in a wind tunnel situation.

  17. Calibration of 3-D wind measurements on a single engine research aircraft

    NASA Astrophysics Data System (ADS)

    Mallaun, C.; Giez, A.; Baumann, R.

    2015-02-01

    An innovative calibration method for the wind speed measurement using a boom mounted Rosemount model 858 AJ air velocity probe is introduced. The method is demonstrated for a sensor system installed on a medium size research aircraft which is used for measurements in the atmospheric boundary layer. The method encounters a series of coordinated flight manoeuvres to directly estimate the aerodynamic influences on the probe and to calculate the measurement uncertainties. The introduction of a differential Global Positioning System (DGPS) combined with a high accuracy Inertial Reference System (IRS) has brought major advances to airborne measurement techniques. The exact determination of geometrical height allows the use of the pressure signal as an independent parameter. Furthermore, the exact height information and the stepwise calibration process lead to maximum accuracy. The results show a measurement uncertainty for the aerodynamic influence of the dynamic and static pressures of 0.1 hPa. The applied parametrisation does not require any height dependencies or time shifts. After extensive flight tests a correction for the flow angles (attack and sideslip angles) was found, which is necessary for a successful wind calculation. A new method is demonstrated to correct for the aerodynamic influence on the sideslip angle. For the 3-D wind vector (with 100 Hz resolution) a novel error propagation scheme is tested, which determines the measurement uncertainties to be 0.3 m s-1 for the horizontal and 0.2 m s-1 for the vertical wind components.

  18. Calibration of 3-D wind measurements on a single-engine research aircraft

    NASA Astrophysics Data System (ADS)

    Mallaun, C.; Giez, A.; Baumann, R.

    2015-08-01

    An innovative calibration method for the wind speed measurement using a boom-mounted Rosemount model 858 AJ air velocity probe is introduced. The method is demonstrated for a sensor system installed on a medium-size research aircraft which is used for measurements in the atmospheric boundary layer. The method encounters a series of coordinated flight manoeuvres to directly estimate the aerodynamic influences on the probe and to calculate the measurement uncertainties. The introduction of a differential Global Positioning System (DGPS) combined with a high-accuracy inertial reference system (IRS) has brought major advances to airborne measurement techniques. The exact determination of geometrical height allows the use of the pressure signal as an independent parameter. Furthermore, the exact height information and the stepwise calibration process lead to maximum accuracy. The results show a measurement uncertainty for the aerodynamic influence of the dynamic and static pressures of 0.1 hPa. The applied parametrisation does not require any height dependencies or time shifts. After extensive flight tests a correction for the flow angles (attack and sideslip angles) was found, which is necessary for a successful wind calculation. A new method is demonstrated to correct for the aerodynamic influence on the sideslip angle. For the three-dimensional (3-D) wind vector (with 100 Hz resolution) a novel error propagation scheme is tested, which determines the measurement uncertainties to be 0.3 m s-1 for the horizontal and 0.2 m s-1 for the vertical wind components.

  19. An anemometer for measuring velocities on the .25 to 4.25 M/sec range

    NASA Technical Reports Server (NTRS)

    Carpini, T. D.

    1978-01-01

    A vane type anemometer was developed as a secondary standard for the on site calibration of wind velocity sensors. The instrument outputs an electrical pulse for each interruption of a light source by an eight vane fan. The pulse rate is proportional to the fan's angular speed and linearly related to wind velocity over the range 0.25 to 4.27 m/sec.

  20. The Maximum Density of Water.

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    1985-01-01

    Discusses a series of experiments performed by Thomas Hope in 1805 which show the temperature at which water has its maximum density. Early data cast into a modern form as well as guidelines and recent data collected from the author provide background for duplicating Hope's experiments in the classroom. (JN)

  1. DECOMPOSITION USING MAXIMUM AUTOCORRELATION FACTORS

    E-print Network

    the maximum autocorrelation factor (MAF) transform was proposed for multivariate imagery in [18 with variable ordering. This corresponds to a Q-mode analysis of the data matrix. We denote this methods Q-MAF decomposition. It turns out that in many situations the new variables resulting from the MAF and the Q-MAF

  2. Effects of incoming wind condition and wind turbine aerodynamics on the hub vortex instability

    NASA Astrophysics Data System (ADS)

    Ashton, R.; Viola, F.; Gallaire, F.; Iungo, G. V.

    2015-06-01

    Dynamics and instabilities occurring in the near-wake of wind turbines have a crucial role for the wake downstream evolution, and for the onset of far-wake instabilities. Furthermore, wake dynamics significantly affect the intra-wind farm wake flow, wake interactions and potential power losses. Therefore, the physical understanding and predictability of wind turbine wake instabilities become a nodal point for prediction of wind power harvesting and optimization of wind farm layout. This study is focused on the prediction of the hub vortex instability encountered within wind turbine wakes under different operational conditions of the wind turbine. Linear stability analysis of the wake flow is performed by means of a novel approach that enables to take effects of turbulence on wake instabilities into account. Stability analysis is performed by using as base flow the time-averaged wake velocity field at a specific downstream location. The latter is modeled through Carton-McWilliams velocity profiles by mimicking the presence of the hub vortex and helicoidal tip vortices, and matching the wind turbine thrust coefficient predicted through the actuator disc model. The results show that hub vortex instability is promoted by increasing the turbine thrust coefficient. Indeed, a larger aerodynamic load produces an enhanced wake velocity deficit and axial shear, which are considered the main sources for the wake instability. Nonetheless, wake swirl also promotes hub vortex instability, and it can also affect the azimuthal wavenumber of the most unstable mode.

  3. Simulated synchrotron emission from Pulsar Wind Nebulae

    E-print Network

    Luca Del Zanna; Delia Volpi; Elena Amato; Niccolo' Bucciantini

    2006-03-03

    A complete set of diagnostic tools aimed at producing synthetic synchrotron emissivity, polarization, and spectral index maps from relativistic MHD simulations is presented. As a first application we consider here the case of the emission from Pulsar Wind Nebulae (PWNe). The proposed method is based on the addition, on top of the basic set of MHD equations, of an extra equation describing the evolution of the maximum energy of the emitting particles. This equation takes into account adiabatic and synchrotron losses along streamlines for the distribution of emitting particles and its formulation is such that it is easily implemented in any numerical scheme for relativistic MHD. Application to the axisymmetric simulations of PWNe, analogous to those described by Del Zanna et al. (2004, A&A, 421, 1063), allows direct comparison between the numerical results and observations of the inner structure of the Crab Nebula, and similar objects, in the optical and X-ray bands. We are able to match most of the observed features typical of PWNe, like the equatorial torus and the polar jets, with velocities in the correct range, as well as finer emission details, like arcs, rings and the bright knot, that turn out to arise mainly from Doppler boosting effects. Spectral properties appear to be well reproduced too: detailed spectral index maps are produced for the first time and show softening towards the PWN outer borders, whereas spectral breaks appear in integrated spectra. The emission details are found to strongly depend on both the average wind magnetization (here approximately 2%), and on the magnetic field shape.

  4. Airfoils for wind turbine

    DOEpatents

    Tangler, James L. (Boulder, CO); Somers, Dan M. (State College, PA)

    2000-01-01

    Airfoils for the tip and mid-span regions of a wind turbine blade have upper surface and lower surface shapes and contours between a leading edge and a trailing edge that minimize roughness effects of the airfoil and provide maximum lift coefficients that are largely insensitive to roughness effects. The airfoil in one embodiment is shaped and contoured to have a thickness in a range of about fourteen to seventeen percent, a Reynolds number in a range of about 1,500,000 to 2,000,000, and a maximum lift coefficient in a range of about 1.4 to 1.5. In another embodiment, the airfoil is shaped and contoured to have a thickness in a range of about fourteen percent to sixteen percent, a Reynolds number in a range of about 1,500,000 to 3,000,000, and a maximum lift coefficient in a range of about 0.7 to 1.5. Another embodiment of the airfoil is shaped and contoured to have a Reynolds in a range of about 1,500,000 to 4,000,000, and a maximum lift coefficient in a range of about 1.0 to 1.5.

  5. Magnetofluid Turbulence in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Goldstein, Melvyn L.

    2008-01-01

    The solar wind shows striking characteristics that suggest that it is a turbulent magnetofluid, but the picture is not altogether simple. From the earliest observations, a strong correlation between magnetic fluctuations and plasma velocity fluctuations was noted. The high corrections suggest that the fluctuations are Alfven waves. In addition, the power spectrum of the magnetic fluctuation showed evidence of an inertial range that resembled that seen in fully-developed fluid turbulence. Alfven waves, however, are exact solutions of the equations of incompressible magnetohydrodynamics. Thus, there was a puzzle: how can a magnetofluid consisting of Alfven waves be turbulent? The answer lay in the role of velocity shears in the solar wind that could drive turbulent evolution. Puzzles remain: for example, the power spectrum of the velocity fluctuations is less steep than the slope of the magnetic fluctuations, nor do we understand even now why the solar wind appears to be nearly incompressible with a -5/3 power-spectral index.

  6. On the application of the Principal Component Analysis for an efficient climate downscaling of surface wind fields

    NASA Astrophysics Data System (ADS)

    Chavez, Roberto; Lozano, Sergio; Correia, Pedro; Sanz-Rodrigo, Javier; Probst, Oliver

    2013-04-01

    With the purpose of efficiently and reliably generating long-term wind resource maps for the wind energy industry, the application and verification of a statistical methodology for the climate downscaling of wind fields at surface level is presented in this work. This procedure is based on the combination of the Monte Carlo and the Principal Component Analysis (PCA) statistical methods. Firstly the Monte Carlo method is used to create a huge number of daily-based annual time series, so called climate representative years, by the stratified sampling of a 33-year-long time series corresponding to the available period of the NCAR/NCEP global reanalysis data set (R-2). Secondly the representative years are evaluated such that the best set is chosen according to its capability to recreate the Sea Level Pressure (SLP) temporal and spatial fields from the R-2 data set. The measure of this correspondence is based on the Euclidean distance between the Empirical Orthogonal Functions (EOF) spaces generated by the PCA (Principal Component Analysis) decomposition of the SLP fields from both the long-term and the representative year data sets. The methodology was verified by comparing the selected 365-days period against a 9-year period of wind fields generated by dynamical downscaling the Global Forecast System data with the mesoscale model SKIRON for the Iberian Peninsula. These results showed that, compared to the traditional method of dynamical downscaling any random 365-days period, the error in the average wind velocity by the PCA's representative year was reduced by almost 30%. Moreover the Mean Absolute Errors (MAE) in the monthly and daily wind profiles were also reduced by almost 25% along all SKIRON grid points. These results showed also that the methodology presented maximum error values in the wind speed mean of 0.8 m/s and maximum MAE in the monthly curves of 0.7 m/s. Besides the bulk numbers, this work shows the spatial distribution of the errors across the Iberian domain and additional wind statistics such as the velocity and directional frequency. Additional repetitions were performed to prove the reliability and robustness of this kind-of statistical-dynamical downscaling method.

  7. Wind energy, a feasibility investigation for wind mills in agriculture

    NASA Astrophysics Data System (ADS)

    Koops, J.

    1982-01-01

    The investment possibilities of windpowered generators on dairy-farms in the northern Netherlands are investigated. Data concerning the energy consumption of four farms are statistically correlated with wind velocity distribution data and the characteristics of a 10 kWh windmill. Using the buying and selling energy prices of the local power stations and the investment costs, the feasibility is estimated. Unless special energy storage provisions are made, the investment will not pay within 10 years.

  8. Airborne lidar wind detection at 2 ?m

    NASA Astrophysics Data System (ADS)

    Targ, Russell; Hawley, James G.; Steakley, Bruce C.; Ames, Lawrence L.; Robinson, Paul A.

    1995-06-01

    NASA and the FAA have expressed interest in laser radar's capabilities to detect wind profiles at altitude. A number of programs have been addressing the technical feasibility and utility of laser radar atmospheric backscatter data to determine wind profiles and wind hazards for aircraft guidance and navigation. In addition, the U.S. Air Force is investigating the use of airborne lidar to achieve precision air drop capability, and to increase the accuracy of the AC- 130 gunship and the B-52 bomber by measuring the wind field from the aircraft to the ground. There are emerging capabilities of airborne laser radar to measure wind velocities and detect turbulence and other atmospheric disturbances out in front of an aircraft in real time. The measurement of these parameters can significantly increase fuel efficiency, flight safety, airframe lifetime, and terminal area capacity for new and existing aircraft. This is achieved through wind velocity detection, turbulence avoidance, active control utilization to alleviate gust loading, and detection of wingtip wake vortices produced by landing aircraft. This paper presents the first flight test results of an all solid-state 2-micrometers laser radar system measuring the wind field profile 1 to 2 km in front of an aircraft in real time. We find 0.7-m/s wind measurement accuracy for the system which is configured in a rugged, light weight, high- performance ARINC package.

  9. Radiation-driven winds of hot stars. V - Wind models for central stars of planetary nebulae

    NASA Technical Reports Server (NTRS)

    Pauldrach, A.; Puls, J.; Kudritzki, R. P.; Mendez, R. H.; Heap, S. R.

    1988-01-01

    Wind models using the recent improvements of radiation driven wind theory by Pauldrach et al. (1986) and Pauldrach (1987) are presented for central stars of planetary nebulae. The models are computed along evolutionary tracks evolving with different stellar mass from the Asymptotic Giant Branch. We show that the calculated terminal wind velocities are in agreement with the observations and allow in principle an independent determination of stellar masses and radii. The computed mass-loss rates are in qualitative agreement with the occurrence of spectroscopic stellar wind features as a function of stellar effective temperature and gravity.

  10. Doppler lidar atmospheric wind measurements

    NASA Technical Reports Server (NTRS)

    Bilbro, J. W.; Vaughan, W. W.

    1978-01-01

    A brief overview is provided of the coherent Doppler lidar work at the Marshall Space Flight Center, taking into account the status and planned development of the system to be used for severe storms research. The considered system is a CW Doppler lidar operating at a wavelength of 10.6 micrometers. This lidar uses a 20 watt carbon dioxide laser. It has a range which is continuously variable from 60 m to approximately 600 m. Range variation is achieved through changing the focus of a 30 cm f/2 Cassegrainian telescope. Successful measurements with the CW lidar have included two and three dimensional wind profiles, wing tip vortex tracks and profiles, dust devil tracks and profiles, and transverse as well as line-of-sight wind velocities. The pulsed lidar in recent ground tests has succeeded in measuring clear air returns to a range of 13 km and has provided substantial information on velocities associated with the gust fronts of thunderstorms.

  11. Pulsed laser Doppler measurements of wind shear

    NASA Technical Reports Server (NTRS)

    Dimarzio, C.; Harris, C.; Bilbro, J. W.; Weaver, E. A.; Burnham, D. C.; Hallock, J. N.

    1979-01-01

    There is a need for a sensor at the airport that can remotely detect, identify, and track wind shears near the airport in order to assure aircraft safety. To determine the viability of a laser wind-shear system, the NASA pulsed coherent Doppler CO2 lidar (Jelalian et al., 1972) was installed in a semitrailer van with a rooftop-mounted hemispherical scanner and was used to monitor thunderstorm gust fronts. Wind shears associated with the gust fronts at the Kennedy Space Center (KSC) between 5 July and 4 August 1978 were measured and tracked. The most significant data collected at KSC are discussed. The wind shears were clearly visible in both real-time velocity vs. azimuth plots and in postprocessing displays of velocities vs. position. The results indicate that a lidar system cannot be used effectively when moderate precipitation exists between the sensor and the region of interest.

  12. Coalescing Wind Turbine Wakes

    NASA Astrophysics Data System (ADS)

    Lee, S.; Churchfield, M.; Sirnivas, S.; Moriarty, P.; Nielsen, F. G.; Skaare, B.; Byklum, E.

    2015-06-01

    A team of researchers from the National Renewable Energy Laboratory and Statoil used large-eddy simulations to numerically investigate the merging wakes from upstream offshore wind turbines. Merging wakes are typical phenomena in wind farm flows in which neighboring turbine wakes consolidate to form complex flow patterns that are as yet not well understood. In the present study, three 6-MW turbines in a row were subjected to a neutrally stable atmospheric boundary layer flow. As a result, the wake from the farthest upstream turbine conjoined the downstream wake, which significantly altered the subsequent velocity deficit structures, turbulence intensity, and the global meandering behavior. The complexity increased even more when the combined wakes from the two upstream turbines mixed with the wake generated by the last turbine, thereby forming a “triplet” structure. Although the influence of the wake generated by the first turbine decayed with downstream distance, the mutated wakes from the second turbine continued to influence the downstream wake. Two mirror-image angles of wind directions that yielded partial wakes impinging on the downstream turbines yielded asymmetric wake profiles that could be attributed to the changing flow directions in the rotor plane induced by the Coriolis force. The turbine wakes persisted for extended distances in the present study, which is a result of low aerodynamic surface roughness typically found in offshore conditions.

  13. Coastal Ohio Wind Project

    SciTech Connect

    Gorsevski, Peter; Afjeh, Abdollah; Jamali, Mohsin; Bingman, Verner

    2014-04-04

    The Coastal Ohio Wind Project intends to address problems that impede deployment of wind turbines in the coastal and offshore regions of Northern Ohio. The project evaluates different wind turbine designs and the potential impact of offshore turbines on migratory and resident birds by developing multidisciplinary research, which involves wildlife biology, electrical and mechanical engineering, and geospatial science. Firstly, the project conducts cost and performance studies of two- and three-blade wind turbines using a turbine design suited for the Great Lakes. The numerical studies comprised an analysis and evaluation of the annual energy production of two- and three-blade wind turbines to determine the levelized cost of energy. This task also involved wind tunnel studies of model wind turbines to quantify the wake flow field of upwind and downwind wind turbine-tower arrangements. The experimental work included a study of a scaled model of an offshore wind turbine platform in a water tunnel. The levelized cost of energy work consisted of the development and application of a cost model to predict the cost of energy produced by a wind turbine system placed offshore. The analysis found that a floating two-blade wind turbine presents the most cost effective alternative for the Great Lakes. The load effects studies showed that the two-blade wind turbine model experiences less torque under all IEC Standard design load cases considered. Other load effects did not show this trend and depending on the design load cases, the two-bladed wind turbine showed higher or lower load effects. The experimental studies of the wake were conducted using smoke flow visualization and hot wire anemometry. Flow visualization studies showed that in the downwind turbine configuration the wake flow was insensitive to the presence of the blade and was very similar to that of the tower alone. On the other hand, in the upwind turbine configuration, increasing the rotor blade angle of attack reduced the wake size and enhanced the vortices in the flow downstream of the turbine-tower compared with the tower alone case. Mean and rms velocity distributions from hot wire anemometer data confirmed that in a downwind configuration, the wake of the tower dominates the flow, thus the flow fields of a tower alone and tower-turbine combinations are nearly the same. For the upwind configuration, the mean velocity shows a narrowing of the wake compared with the tower alone case. The downwind configuration wake persisted longer than that of an upwind configuration; however, it was not possible to quantify this difference because of the size limitation of the wind tunnel downstream of the test section. The water tunnel studies demonstrated that the scale model studies could be used to adequately produce accurate motions to model the motions of a wind turbine platform subject to large waves. It was found that the important factors that affect the platform is whether the platform is submerged or surface piercing. In the former, the loads on the platform will be relatively reduced whereas in the latter case, the structure pierces the wave free surface and gains stiffness and stability. The other important element that affects the movement of the platform is depth of the sea in which the wind turbine will be installed. Furthermore, the wildlife biology component evaluated migratory patterns by different monitoring systems consisting of marine radar, thermal IR camera and acoustic recorders. The types of radar used in the project are weather surveillance radar and marine radar. The weather surveillance radar (1988 Doppler), also known as Next Generation Radar (NEXRAD), provides a network of weather stations in the US. Data generated from this network were used to understand general migratory patterns, migratory stopover habitats, and other patterns caused by the effects of weather conditions. At a local scale our marine radar was used to complement the datasets from NEXRAD and to collect additional monitoring parameters such as passage rates, flight paths, flight directi

  14. An experimental investigation on wind turbine aeromechanics and wake interferences among multiple wind turbines

    NASA Astrophysics Data System (ADS)

    Ozbay, Ahmet

    A comprehensive experimental study was conducted to investigate wind turbine aeromechanics and wake interferences among multiple wind turbines sited in onshore and offshore wind farms. The experiments were carried out in a large-scale Aerodynamic/Atmospheric Boundary Layer (AABL) Wind Tunnel available at Iowa State University. An array of scaled three-blade Horizontal Axial Wind Turbine (HAWT) models were placed in atmospheric boundary layer winds with different mean and turbulence characteristics to simulate the situations in onshore and offshore wind farms. The effects of the important design parameters for wind farm layout optimization, which include the mean and turbulence characteristics of the oncoming surface winds, the yaw angles of the turbines with respect to the oncoming surface winds, the array spacing and layout pattern, and the terrain topology of wind farms on the turbine performances (i.e., both power output and dynamic wind loadings) and the wake interferences among multiple wind turbines, were assessed in detail. The aeromechanic performance and near wake characteristics of a novel dual-rotor wind turbine (DRWT) design with co-rotating or counter-rotating configuration were also investigated, in comparison to a conventional single rotor wind turbine (SRWT). During the experiments, in addition to measuring dynamic wind loads (both forces and moments) and the power outputs of the scaled turbine models, a high-resolution Particle Image Velocity (PIV) system was used to conduct detailed flow field measurements (i.e., both free-run and phase-locked flow fields measurements) to reveal the transient behavior of the unsteady wake vortices and turbulent flow structures behind wind turbines and to quantify the characteristics of the wake interferences among the wind turbines sited in non-homogenous surface winds. A miniature cobra anemometer was also used to provide high-temporal-resolution data at points of interest to supplement the full field PIV measurement results. The detailed flow field measurements are correlated with the dynamic wind loads and power output measurements to elucidate underlying physics in order to gain further insight into the characteristics of the power generation performance, dynamic wind loads and wake interferences of the wind turbines for higher total power yield and better durability of the wind turbines sited in atmospheric boundary layer (ABL) winds.

  15. Laser Doppler measurements of blood velocity in human retinal vessels.

    PubMed

    Feke, G T; Riva, C E

    1978-04-01

    We have measured Doppler shift frequency spectra (DSFS) of laser light scattered from red blood cells (RBC's) flowing through individual human retinal vessels. Each spectrum exhibits a cutoff frequency which is directly related to the maximum RBC velocity at the measurement site. Meaningful DSFS can be measured in times as short as 0.1 s. DSFS obtained from suspensions of polystyrene spheres and RBC's flowing through glass capillary tubes are used to illustrate the basic principles of the technique and to aid in the interpretation of the in vivo measurements. Our measurements show that maximum RBC velocities in retinal arteries vary markedly during each cardiac cycle. PMID:671138

  16. Integrated roof wind energy system

    NASA Astrophysics Data System (ADS)

    Suma, A. B.; Ferraro, R. M.; Dano, B.; Moonen, S. P. G.

    2012-10-01

    Wind is an attractive renewable source of energy. Recent innovations in research and design have reduced to a few alternatives with limited impact on residential construction. Cost effective solutions have been found at larger scale, but storage and delivery of energy to the actual location it is used, remain a critical issue. The Integrated Roof Wind Energy System is designed to overcome the current issues of urban and larger scale renewable energy system. The system is built up by an axial array of skewed shaped funnels that make use of the Venturi Effect to accelerate the wind flow. This inventive use of shape and geometry leads to a converging air capturing inlet to create high wind mass flow and velocity toward a vertical-axis wind turbine in the top of the roof for generation of a relatively high amount of energy. The methods used in this overview of studies include an array of tools from analytical modelling, PIV wind tunnel testing, and CFD simulation studies. The results define the main design parameters for an efficient system, and show the potential for the generation of high amounts of renewable energy with a novel and effective system suited for the built environment.

  17. Limitations to maximum running speed on flat curves.

    PubMed

    Chang, Young-Hui; Kram, Rodger

    2007-03-01

    Why is maximal running speed reduced on curved paths? The leading explanation proposes that an increase in lateral ground reaction force necessitates a decrease in peak vertical ground reaction force, assuming that maximum leg extension force is the limiting factor. Yet, no studies have directly measured these forces or tested this critical assumption. We measured maximum sprint velocities and ground reaction forces for five male humans sprinting along a straight track and compared them to sprints along circular tracks of 1, 2, 3, 4 and 6 m radii. Circular track sprint trials were performed either with or without a tether that applied centripetal force to the center of mass. Sprinters generated significantly smaller peak resultant ground reaction forces during normal curve sprinting compared to straight sprinting. This provides direct evidence against the idea that maximum leg extension force is always achieved and is the limiting factor. Use of the tether increased sprint speed, but not to expected values. During curve sprinting, the inside leg consistently generated smaller peak forces compared to the outside leg. Several competing biomechanical constraints placed on the stance leg during curve sprinting likely make the inside leg particularly ineffective at generating the ground reaction forces necessary to attain maximum velocities comparable to straight path sprinting. The ability of quadrupeds to redistribute function across multiple stance legs and decouple these multiple constraints may provide a distinct advantage for turning performance. PMID:17337710

  18. Seasonal variation in concentration, size, and settling velocity of muddy marine flocs in the benthic boundary layer

    NASA Astrophysics Data System (ADS)

    Fettweis, Michael; Baeye, Matthias

    2015-08-01

    Suspended Particulate Matter (SPM) concentration profiles of the lowest 2 m of the water column and particle size distribution at 2 m above the bed were measured in a coastal turbidity maximum area (southern North Sea) during more than 700 days between 2006 and 2013. The long-term data series of SPM concentration, floc size, and settling velocity have been ensemble averaged according to tidal range, alongshore residual flow direction, and season, in order to investigate the seasonal SPM dynamics and its relation with physical and biological processes. The data show that the SPM is more concentrated in the near-bed layer in summer, whereas in winter, the SPM is better mixed throughout the water column. The decrease of the SPM concentration in the water column during summer is compensated by a higher near-bed concentration indicating that a significant part of the SPM remains in the area during summer rather than being advected out of it. The opposite seasonality between near-bed layer and water column has to our knowledge not yet been presented in literature. Physical effects such as wave heights, wind climate, or storms have a weak correlation with the observed seasonality. The argument to favor microbial activity as main driver of the seasonality lies in the observed variations in floc size and settling velocity. On average, the flocs are larger and thus settling velocities higher in summer than winter.

  19. Study of mean- and turbulent-velocity fields in a large-scale turbine-vane passage

    NASA Technical Reports Server (NTRS)

    Bailey, D. A.

    1979-01-01

    Laser-Doppler velocimetry, and to a lesser extent hot-wire anemometry, were employed to measure three components of the mean velocity and the six turbulent stresses at four planes within the turbine inlet-guide-vane passage. One variation in the turbulent inlet boundary layer thickness and one variation in the blade aspect ratio (span/axial chord) were studied. A longitudinal vortex (passage vortex) was clearly identified in the exit plane of the passage for the three test cases. The maximum turbulence intensities within the longitudinal vortex were found to be on the order of 2 to 4 percent, with large regions appearing nonturbulent. Because a turbulent wall boundary layer was the source of vorticity that produced the passage vortex, these low turbulence levels were not anticipated. For the three test cases studied, the lateral velocity field extended significantly beyond the region of the longitudinal velocity defect. Changing the inlet boundary layer thickness produced a difference in the location, the strength, and the extent of the passage vortex. Changing the aspect ratio of the blade passage had a measurable but less significant effect. The experiment was performed in a 210 mm pitch, 272 mm axial chord model in low speed wind tunnel at an inlet Mach number of 0.07.

  20. Wind and IMP 8 Solar Wind, Magnetosheath and Shock Data

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The purpose of this project was to provide the community access to magnetosheath data near Earth. We provided 27 years of IMP 8 magnetosheath proton velocities, densities, and temperatures with our best (usually 1-min.) time resolution. IMP 8 crosses the magnetosheath twice each 125 day orbit, and we provided magnetosheath data for the roughly 27 years of data for which magnetometer data are also available (which are needed to reliably pick boundaries). We provided this 27 years of IMP 8 magnetosheath data to the NSSDC; this data is now integrated with the IMP 8 solar wind data with flags indicating whether each data point is in the solar wind, magnetosheath, or at the boundary between the two regions. The plasma speed, density, and temperature are provided for each magnetosheath point. These data are also available on the MIT web site ftp://space .mit.edu/pub/plasma/imp/www/imp.html. We provide ASCII time-ordered rows of data giving the observation time, the spacecraft position in GSE, the velocity is GSE, the density and temperature for protons. We also have analyzed and archived on our web site the Wind magnetosheath plasma parameters. These consist of ascii files of the proton and alpha densities, speeds, and thermal speeds. These data are available at ftp://space.mit.edu/pub/plasma/wind/sheath These are the two products promised in the work statement and they have been completed in full.

  1. Strong correlation between the drag coefficient and the shape of the wind sea spectrum over a broad range of wind speeds

    NASA Astrophysics Data System (ADS)

    Takagaki, Naohisa; Komori, Satoru; Suzuki, Naoya; Iwano, Koji; Kuramoto, Takenori; Shimada, Satoshi; Kurose, Ryoichi; Takahashi, Keiko

    2012-12-01

    Momentum transfer across the wind-driven breaking air-water interface under strong wind conditions was experimentally investigated using a high-speed wind-wave tank together with field measurements at normal wind speeds. An eddy correlation method was utilized to measure roughness length and drag coefficient from wind velocity components measured by laser Doppler and phase Doppler anemometers. As a result, a new model for the roughness length and drag coefficient was proposed for predicting momentum transfer across the sea surface under both normal and strong wind conditions using the universal relationship between energy and significant frequency of wind waves normalized by the roughness length. The model shows that the roughness length and drag coefficient are uniquely determined at all wind speeds by energy and significant frequency of wind waves, and they can be given against U10 only from the measurements of the wave parameters and one-point mean air velocity in the logarithmic law region.

  2. Fracture ventilation by surface winds

    NASA Astrophysics Data System (ADS)

    Nachshon, U.; Dragila, M. I.; Weisbrod, N.

    2011-12-01

    Gas exchange between the Earth subsurface and the atmosphere is an important mechanism, affecting hydrological, agricultural and environmental processes. From a hydrological aspect, water vapor transport is the most important process related to Earth-atmosphere gas exchange. In respect to agriculture, gas transport in the upper soil profile is important for soil aeration. From an environmental aspect, emission of volatile radionuclides, such as 3H, 14C and Rd from radioactive waste disposal facilities; volatile organic components from industrial sources and Rn from natural sources, all found in the upper vadose zone, can greatly affect public health when emissions occur in populated areas. Thus, it is vital to better understand gas exchange processes between the Earth's upper crust and atmosphere. Four major mechanisms are known to transfer gases between ground surface and atmosphere: (1) Diffusion; (2) Pressure gradients between ground pores and atmosphere due to changes in barometric pressure; (3) Density-driven gas flow in respond to thermal gradients in the ground; and (4) Winds above the ground surface. Herein, the wind ventilation mechanism is studied. Whereas the wind's impact on ground ventilation was explored in several studies, the physical mechanisms governing this process were hardly quantified or characterized. In this work the physical properties of fracture ventilation due to wind blowing along land surface were explored and quantified. Both field measurements and Hele-Shaw experiments under controlled conditions in the laboratory were used to study this process. It was found that winds in the range of 0.3 m/s result in fracture ventilation down to a depth of 0.2 m. As wind velocity increases, the depth of the ventilation inside the fracture increases respectively, in a linear manner. In addition, the fracture aperture also affects the depth of ventilation, which grows as fracture aperture increases. For the maximal examined aperture of 2 cm and wind velocity of 1.25 m/s, fracture ventilation was deeper than 0.45 m. This study sheds new light on fracture ventilation, showing that moderate winds may increase evaporation and gas exchange between fractured media and the atmosphere. Even though wind impact is limited to the top 0.5 m below the ground surface, it is an important process as most of the biological activities, as well as important hydrological processes occur in this region. Wind effect should be considered when modeling mass and energy balances between the Earth upper crust and atmosphere.

  3. Flight penetration of wind shear: Control strategies

    NASA Technical Reports Server (NTRS)

    Joshi, Amit S.

    1988-01-01

    Wind shear is a dangerous condition where there is a sharp change in the direction and magnitude of the wind velocity over a short distance or time. This condition is especially dangerous to aircraft during landing and takeoff and can cause a sudden loss of lift and thereby height at a critical time. A numerical simulation showed the effective performance of the Linear Quadratic Regulator and the Nonlinear Inverse Dynamics controllers. The major conclusions are listed and discussed.

  4. Magnetic energy flow in the solar wind.

    NASA Technical Reports Server (NTRS)

    Modisette, J. L.

    1972-01-01

    Discussion of the effect of rotation (tangential flow) of the solar wind on the conclusions of Whang (1971) suggesting an increase in the solar wind velocity due to the conversion of magnetic energy to kinetic energy. It is shown that the effect of the rotation of the sun on the magnetic energy flow results in most of the magnetic energy being transported by magnetic shear stress near the sun.

  5. The distribution of solar wind speeds during solar minimum: Calibration for numerical solar wind modeling constraints on the source of the slow solar wind

    NASA Astrophysics Data System (ADS)

    McGregor, S. L.; Hughes, W. J.; Arge, C. N.; Owens, M. J.; Odstrcil, D.

    2011-03-01

    It took the solar polar passage of Ulysses in the early 1990s to establish the global structure of the solar wind speed during solar minimum. However, it remains unclear if the solar wind is composed of two distinct populations of solar wind from different sources (e.g., closed loops which open up to produce the slow solar wind) or if the fast and slow solar wind rely on the superradial expansion of the magnetic field to account for the observed solar wind speed variation. We investigate the solar wind in the inner corona using the Wang-Sheeley-Arge (WSA) coronal model incorporating a new empirical magnetic topology-velocity relationship calibrated for use at 0.1 AU. In this study the empirical solar wind speed relationship was determined by using Helios perihelion observations, along with results from Riley et al. (2003) and Schwadron et al. (2005) as constraints. The new relationship was tested by using it to drive the ENLIL 3-D MHD solar wind model and obtain solar wind parameters at Earth (1.0 AU) and Ulysses (1.4 AU). The improvements in speed, its variability, and the occurrence of high-speed enhancements provide confidence that the new velocity relationship better determines the solar wind speed in the outer corona (0.1 AU). An analysis of this improved velocity field within the WSA model suggests the existence of two distinct mechanisms of the solar wind generation, one for fast and one for slow solar wind, implying that a combination of present theories may be necessary to explain solar wind observations.

  6. SMES for wind energy systems

    NASA Astrophysics Data System (ADS)

    Paul Antony, Anish

    Renewable energy sources are ubiquitous, wind energy in particular is one of the fastest growing forms of renewable energy, yet the stochastic nature of wind creates fluctuations that threaten the stability of the electrical grid. In addition to stability with increased wind energy, the need for additional load following capability is a major concern hindering increased wind energy penetration. Improvements in power electronics are required to increase wind energy penetration, but these improvements are hindered by a number of limitations. Changes in physical weather conditions, insufficient capacity of the transmission line and inaccurate wind forecasting greatly stymie their effect and ultimately lead to equipment damage. With this background, the overall goal of this research effort is to pitch a case for superconducting magnetic energy storage (SMES) by (1) optimally designing the SMES to be coupled with wind turbines thus reducing wind integration challenges and (2) to help influence decision makers in either increasing superconducting wire length/fill factor or improving superconducting splice technology thereby increasing the storage capacity of the SMES. Chapter 1 outlines the scope of this thesis by answering the following questions (1) why focus on wind energy? (2) What are the problems associated with increasing wind energy on the electric grid? (3) What are the current solutions related to wind integration challenges and (4) why SMES? Chapter 2, presents a detailed report on the study performed on categorizing the challenges associated with integrating wind energy into the electric grid. The conditions under which wind energy affected the electric grid are identified both in terms of voltage stability and excess wind generation. Chapter 3, details a comprehensive literature review on the different superconducting wires. A technology assessment of the five selected superconductors: [Niobium Titanium (NbTi), Niobium Tin (Nb3Sn), Bismuth strontium calcium copper oxide (BSCCO), Yttrium barium copper oxide (YBCO) and Magnesium diboride (MgB 2)] is carried out. The assessed attributes include superconducting transition temperature (Tc), critical current density (Jc ), the irreversibility field (H*) and the superconducting critical field (Hc). Chapter 4 presents the design of a solenoid shaped 1MJ MgB2 SMES. This SMES is used to mitigate the problem of momentary interruptions on a wind turbine. The total length of superconducting wire required for a 1MJ solenoid is calculated to be 21km. The maximum wire lengths currently available are 6km thus we hypothesize that either wire lengths have to be increased or work has to be done on MgB2 superconducting splice technology for multifilament wire. Another design consisting of 8 solenoids storing 120 kJ each is presented. The stress analysis on the proposed coil is performed using finite element analysis exhibiting the safety of the proposed design. Chapter 5 presents the design of a toroid shaped 20MJ MgB2 SMES. This is used to mitigate the problem of sustained interruptions on a wind turbine. The toroid coil is chosen since the magnetic field could be completely contained within the coil, thus reducing stray magnetic fields. A combination of genetic algorithm and nonlinear programming is used in determining the design. In Chapter 6, the different methods of operation of the SMES are examined. The Voltage Source Convertor (VSC) based SMES topology was chosen based on its ease of switching. The VSC switching strategy is based on a sinusoidal pulse width modulation technique. EMTDC/PSCAD software was used to demonstrate the efficacy of the VSC based SMES coupled to a wind turbine. The wind generator was modeled as an induction machine feeding into a load. The simulation results established that SMES connected to wind turbines improved output quality. Although the efficacy of SMES for wind energy has been stated previously in other work, this chapter specifically demonstrates through simulation results the utility of SMES in voltage sag mitigation for momentary interruptions

  7. Pulsar Wind Nebulae, Space Velocities and Supernova Remnant Associations

    NASA Technical Reports Server (NTRS)

    2002-01-01

    I am pleased to be able to report significant progress in my research relevant to my LTSA grant. This progress I believe is demonstrated by a long list of publications in 2002, as detailed below. I summarize the research results my collaborators and I obtained in 2002. First, my group announced the major discovery of soft-gamma-repeater-like X-ray bursts from the anomalous X-ray pulsars lE-1048.1$-$5937 and lE-2259+586, using the Rossi X-ray Timing Explorer. This result provides an elegant and long-sought-after confirmation that this class of objects and the soft gamma repeaters share a common nature, namely that they are magnetars. Magnetars are a novel manifestation of young neutron stars, quite different from conventional Crab-like radio pulsars. This discovery was made as part of our regular monitoring program, among the goals of which was to detect such outbursts.

  8. Observations of drainage winds on a simple slope

    SciTech Connect

    Doran, J.C.; Horst, T.W.

    1982-11-01

    Katabatic winds observed over a simple slope showed progressive deepening and strengthening with increased downslope distance. The maximum in the downslope wind component increases, and the height of the maximum rises as the flow develops. A measure of the flow depths obtained from the temperature profiles at the Rattlesnake Mountain site near Richland, Washington and the Cobb Mountain site in northern California shows that these depths are insensitive to the details of the ambient conditions, provided the drainage flows are well established. Depths of the katabatically driven winds appeared to be more sensitive to ambient wind directions.

  9. UPDATED ANALYSIS OF THE UPWIND INTERPLANETARY HYDROGEN VELOCITY AS OBSERVED BY THE HUBBLE SPACE TELESCOPE DURING SOLAR CYCLE 23

    SciTech Connect

    Vincent, Frederic E.; Ben-Jaffel, Lotfi; Harris, Walter M.

    2011-09-10

    The interplanetary hydrogen (IPH), a population of neutrals that fill the space between planets inside the heliosphere, carries the signature of the interstellar medium (ISM) and the heliospheric interface. As the incoming ISM-ionized component deflects at the heliopause, charge exchange reactions decelerate the bulk motion of the neutrals that penetrate the heliosphere. Inside the heliosphere, the IPH bulk velocity is further affected by solar gravity, radiation pressure, and ionization processes, with the latter two processes dependent on solar activity. Solar cycle 23 provided the first partial temporal map of the IPH velocity, including measurements from the Hubble Space Telescope (HST) spectrometers (Goddard High Resolution Spectrograph (GHRS) and Space Telescope Imaging Spectrograph (STIS)) and the Solar and Heliospheric Observatory/Solar Wind ANisotropies (SWAN) instrument. We present an updated analysis of IPH velocity measurements from GHRS and STIS and compare these results with those of SWAN and two different time-dependent models. Our reanalysis of STIS data reveals a significant change in IPH velocity relative to earlier reports, because of the contamination by geocoronal oxygen that was not accounted for. While current models of the heliospheric interface predict the observed IPH velocity for solar maximum, they are not consistent with data covering solar minimum. With updates to the HST data points, we now find that all data can be fit by the existing models to within 1{sigma}, with the exception of SWAN observations taken at solar minimum (1997/1998). We conclude that the current data lack the temporal coverage and/or precision necessary to determine the detailed characteristics of the solar cycle dependence. Hence, new observations are merited.

  10. Simulation of Variable Speed Wind Generation System Using Boost Converter of Permanent Magnet Synchronous Generator

    NASA Astrophysics Data System (ADS)

    Ohyama, Kazuhiro; Sakamoto, Tsuyoshi; Arinaga, Shinji; Yamashita, Yukio

    This paper proposes variable-speed wind generation system using the boost converter. The proposed system has three speed control modes for the wind velocity. The control mode of low wind velocity regulates the armature current of the generator with the boost converter to control the speed of wind turbine. The control mode of middle wind velocity regulates the DC link voltage with the vector controlled inverter to control the speed of wind turbine. The control mode of high wind velocity regulates the pitch angle of the wind turbine with the pitch angle control system to control the speed of wind turbine. The hybrid of three control modes extends the variable-speed range. The proposed system simplifies the maintenance and improves the reliability and reduces the cost in compare with the variable-speed wind generation system using PWM converter. This paper describes the control strategy and modeling for simulation using Matlab Simulink of the proposed system. Also this paper describes the control strategy and modeling of variable-speed wind generation system using PWM converter. The steady state and transient responses for wind velocity changes are simulated using the Matlab Simulink. This paper verifies the fundamental performance of the system using boost converter by discussing the simulation results of the both systems.

  11. Comparison of the impact of wind waves and fast ferries wash in the Tallinn Bay, Gulf of Finland

    NASA Astrophysics Data System (ADS)

    Soomere, T.; Rannat, K.

    2003-04-01

    The area between the Estonian and Finnish capitals, Tallinn and Helsinki, apparently has the heaviest fast ferry traffic among the open sea areas of the Baltic Sea. Nearly 70 crossings of the gulf take place daily during the high season. It is generally believed that ship wash is negligible in the open sea areas where natural waves are frequently much higher than the wash. This assumption is indeed true for coasts exposed to high tidal waves or open to dominating wind directions. However, the Tallinn Bay has a relatively mild local wave regime owing to a specific combination of its shape and the local wind regime. The tidal currents are negligible, and wind waves and local currents are responsible for near-bottom velocities in the area in question. These velocities mostly are moderate and only in extreme cases exceed 20 cm/s at the depths of 10-20. Several coastal regions are particularly favourably sheltered from high waves and may be vulnerable with respect to the abrupt increase of the anthropogenic wave activity. Comparison of local wind wave climate with direct ship wave measurements shows that in the coastal zone of the bay the mean energy of ship waves is 7-10% from the bulk wave energy and wave-induced energy flux as high as 40% from the bulk energy flux. The annual maximum of significant wind wave heights is frequently <1.5 m whereas wave periods do not exceed 5-6 s. The wave climate has significant annual variation, with relatively calm spring and summer season. The periods of the highest components of ship wash generally exceed these of wind waves and frequently are as long as 10-15 s. The ship wave heights frequently are about 1 m and cause unusually high near-bottom velocities at the depths of 5-20 m. This means that the wake of fast ferries is a new forcing component of vital impact on the local ecosystem. It may cause considerable intensification of beach processes and have significant influence on the aquatic wildlife. In particular, this wave component apparently dominates during the relatively calm high navigation season (April-September) when the biological productivity is at its seasonal maximum. In addition to the direct effect upon fish and benthic plants it may cause considerable intensification of beach processes. The reduced water transparency, besides the effects of direct mechanical disturbances, may have a suppressing feedback to the bottom vegetation. Another potential mechanical effect of ship waves is the enhancement of vertical mixing along the ship lane that may intensify the eutrophication effects due to the transport of nutrients into the euphotic layer.

  12. Maximum likelihood estimation for cooperative sequential adsorption

    E-print Network

    Scheichl, Robert

    Maximum likelihood estimation for cooperative sequential adsorption Mathew D. Penrose and Vadim;Maximum likelihood estimation for cooperative sequential adsorption M.D. Penrose, Department of the region. Keywords: cooperative sequential adsorption, space-time point pro- cess, maximum likelihood

  13. Solar Maximum Mission Experiment - Ultraviolet Spectroscopy and Polarimetry on the Solar Maximum Mission

    NASA Technical Reports Server (NTRS)

    Tandberg-Hanssen, E.; Cheng, C. C.; Woodgate, B. E.; Brandt, J. C.; Chapman, R. D.; Athay, R. G.; Beckers, J. M.; Bruner, E. C.; Gurman, J. B.; Hyder, C. L.

    1981-01-01

    The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacecraft is described. It is pointed out that the instrument, which operates in the wavelength range 1150-3600 A, has a spatial resolution of 2-3 arcsec and a spectral resolution of 0.02 A FWHM in second order. A Gregorian telescope, with a focal length of 1.8 m, feeds a 1 m Ebert-Fastie spectrometer. A polarimeter comprising rotating Mg F2 waveplates can be inserted behind the spectrometer entrance slit; it permits all four Stokes parameters to be determined. Among the observing modes are rasters, spectral scans, velocity measurements, and polarimetry. Examples of initial observations made since launch are presented.

  14. Analysis and Forecasting of Winds and Waves at Floating Type Wind Turbine Demonstration Site

    NASA Astrophysics Data System (ADS)

    Mase, Hajime; Yasuda, Tomohiro; Mori, Nobuhito; Tom, Tracey; Ikemoto, Ai; Utsunomiya, Tomoaki

    2013-04-01

    1. Introduction The floating type wind turbine demonstration project is being performed in Japan, and a 1:2 scale model was installed off the Kabashima Island in Nagasaki Prefecture on June 11th, 2012. As for the design, external forces such as wind and wave on the floating type wind turbine demonstration site were evaluated using various kinds of re-analysis and prediction data including NCEP wind data, JMA meteorological GPV data and NEDO data. Considerations for the design were given for wave characteristics of maximum and mean wave height, crest height, 2D height-period distribution, and wave energy spectrum. Tides, currents and winds were also evaluated. In addition the extreme wind speed was estimated including typhoon effects considering grid resolution dependence gust factor. A wind and wave prediction system was developed and its validity was examined by statistically comparing predicted values with measured data at the demonstration site. The present information system gives information for various user selected areas and lead times with both visual animations and time series graphs. 2. Design wave and wind The site is located off the Kabashima Island in Nagasaki Prefecture, Japan. Design forces were determined from extreme wind and wave statistics and an empirical method. The results are: 50 years return period wave and wind: Hs = 7.73 m, Ts = 14.0 s, U = 53.1 m/s 100 years return period wave and wind: Hs = 8.20 m, Ts = 14.3 m, U = 57.0 m/s Other characteristics were also determined, such as the maximum wave height, crest height, 2D height-period distribution and wave energy spectrum, tide, current and maximum wind. 3. Wind and wave prediction system The system composed of NCEP GFS (Global Forecasting System) meteorological data, down-scaling wind field by WRF (Weather Research Forecasting), JMA HAGPV (Hourly Analyzed Grid Point Value) 10m wind data, and wind-wave forecast data by SWAN (Simulating Waves Nearshore). The flowchart shown in Fig. 1 displays the information and process flow of wind and wave data, where a new web information site has been developed. 4. Verification of predictions Satisfactorily good agreement between prediction and observation has been found when evaluating the indices of correlation coefficient, root mean square error, and Brier score. The prediction system is shown to be useful for obtaining vital offshore wind and wave information.

  15. Wind Generators

    NASA Technical Reports Server (NTRS)

    1989-01-01

    When Enerpro, Inc. president, Frank J. Bourbeau, attempted to file a patent on a system for synchronizing a wind generator to the electric utility grid, he discovered Marshall Space Flight Center's Frank Nola's power factor controller. Bourbeau advanced the technology and received a NASA license and a patent for his Auto Synchronous Controller (ASC). The ASC reduces generator "inrush current," which occurs when large generators are abruptly brought on line. It controls voltage so the generator is smoothly connected to the utility grid when it reaches its synchronous speed, protecting the components from inrush current damage. Generator efficiency is also increased in light winds by applying lower than rated voltage. Wind energy is utilized to drive turbines to generate electricity for utility companies.

  16. An inconsistency in the standard maximum likelihood estimation of bulk flows

    SciTech Connect

    Nusser, Adi

    2014-11-01

    Maximum likelihood estimation of the bulk flow from radial peculiar motions of galaxies generally assumes a constant velocity field inside the survey volume. This assumption is inconsistent with the definition of bulk flow as the average of the peculiar velocity field over the relevant volume. This follows from a straightforward mathematical relation between the bulk flow of a sphere and the velocity potential on its surface. This inconsistency also exists for ideal data with exact radial velocities and full spatial coverage. Based on the same relation, we propose a simple modification to correct for this inconsistency.

  17. Friction velocity and aerodynamic roughness of conventional and undercutter tillage within the Columbia Plateau, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Friction velocity and aerodynamic roughness are characteristics of the soil-plant-atmosphere interface which affect wind erosion. Although exchange of momentum at the interface can be altered by land management practices, no attempts have been made to quantify the effect of tillage on friction veloc...

  18. Threshold friction velocity of crusted windblown soils in the Columbia Plateau

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind erosion processes are governed by soil physical properties and surface characteristics. Erosion is initiated when the friction velocity exceeds the threshold friction velocity (u*t) of soils. Although u*t is influenced by soil physical properties such as wetness and crusting, there is little in...

  19. Threshold friction velocity influenced by wetness of soils within the Columbia Plateau

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Windblown dust impacts air quality in the Columbia Plateau of the U.S. Pacific Northwest. Wind erosion of agricultural lands, which is the predominate source of windblown dust in the region, occurs when the friction velocity exceeds the threshold friction velocity (TFV) of the surface. Soil moisture...

  20. Blood velocity estimation using compressive sensing.

    PubMed

    Richy, Julien; Friboulet, Denis; Bernard, Adeline; Bernard, Olivier; Liebgott, Herve

    2013-11-01

    Duplex ultrasonography is a mode of medical ultrasonography that allows one to visualize, at the same time, the inner structure of the body (B-mode) and the blood flow at a particular point in the body (Doppler mode). This mode requires a strategy for alternating B-mode and flow emissions. Traditional strategies either halve the maximum measurable velocity or introduce gaps in the flow data. The objective of this article is to propose a completely original method based on compressive sensing for reconstructing the Doppler signal segment by segment. Our approach is based on randomly alternating B-mode and flow emissions. The influence of the different parameters on the reconstruction quality is studied in detail. The technique is evaluated and its feasability is validated in simulation and from experimental in vivo data. It is also compared to the only method from the literature, proposed by Jensen, that reconstructs blood velocity estimates from sparse data sets. PMID:23782797

  1. VLF wave activity in the solar wind and the photoelectron effect in electric field measurements: Ulysses observations

    E-print Network

    California at Berkeley, University of

    VLF wave activity in the solar wind and the photoelectron effect in electric field measurements periods for slow and intermediate speed solar wind. The maximum intensities of the electromagnetic waves for the waves' excitation are similar for the slow and intermediate solar wind in both solar maximum and minimum

  2. Interplanetary stream magnetism: Kinematic effects. [solar magnetic fields and wind

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Barouch, E.

    1974-01-01

    The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.

  3. Wind tunnel investigation of a 14 foot vertical axis windmill

    NASA Technical Reports Server (NTRS)

    Muraca, R. J.; Guillotte, R. J.

    1976-01-01

    A full scale wind tunnel investigation was made to determine the performance characteristics of a 14 ft diameter vertical axis windmill. The parameters measured were wind velocity, shaft torque, shaft rotation rate, along with the drag and yawing moment. A velocity survey of the flow field downstream of the windmill was also made. The results of these tests along with some analytically predicted data are presented in the form of generalized data as a function of tip speed ratio.

  4. Effects of incoming surface wind conditions on the wake characteristics and dynamic wind loads acting on a wind turbine model

    NASA Astrophysics Data System (ADS)

    Tian, Wei; Ozbay, Ahmet; Hu, Hui

    2014-12-01

    An experimental investigation was conducted to examine the effects of incoming surface wind conditions on the wake characteristics and dynamic wind loads acting on a wind turbine model. The experimental study was performed in a large-scale wind tunnel with a scaled three-blade Horizontal Axial Wind Turbine model placed in two different types of Atmospheric Boundary Layer (ABL) winds with distinct mean and turbulence characteristics. In addition to measuring dynamic wind loads acting on the model turbine by using a force-moment sensor, a high-resolution Particle Image Velocimetry system was used to achieve detailed flow field measurements to characterize the turbulent wake flows behind the model turbine. The measurement results reveal clearly that the discrepancies in the incoming surface winds would affect the wake characteristics and dynamic wind loads acting on the model turbine dramatically. The dynamic wind loads acting on the model turbine were found to fluctuate much more significantly, thereby, much larger fatigue loads, for the case with the wind turbine model sited in the incoming ABL wind with higher turbulence intensity levels. The turbulent kinetic energy and Reynolds stress levels in the wake behind the model turbine were also found to be significantly higher for the high turbulence inflow case, in comparison to those of the low turbulence inflow case. The flow characteristics in the turbine wake were found to be dominated by the formation, shedding, and breakdown of various unsteady wake vortices. In comparison with the case with relatively low turbulence intensities in the incoming ABL wind, much more turbulent and randomly shedding, faster dissipation, and earlier breakdown of the wake vortices were observed for the high turbulence inflow case, which would promote the vertical transport of kinetic energy by entraining more high-speed airflow from above to re-charge the wake flow and result in a much faster recovery of the velocity deficits in the turbine wake.

  5. Self-similarity and turbulence characteristics of wind turbine wakes via large-eddy simulation (Invited)

    NASA Astrophysics Data System (ADS)

    Xie, S.; Archer, C. L.

    2013-12-01

    In this study, a new large-eddy simulation code, the Wind Turbine and Turbulence Simulator (WiTTS), is developed to study the wake generated from a single wind turbine in the neutral ABL. The WiTTS formulation is based on a scale-dependent Lagrangian dynamical model of the sub-grid shear stress and uses actuator lines to simulate the effects of the rotating blades. WiTTS is first tested against wind tunnel experiments and then used to study the commonly-used assumptions of self-similarity and axis-symmetry of the wake under neutral conditions for a variety of wind speeds and turbine properties. The mean velocity deficit shows good self-similarity properties following a normal distribution in the horizontal plane at the hub-height level. Self-similarity is a less valid approximation in the vertical near the ground, due to strong wind shear and ground effects. The mean velocity deficit is strongly dependent on the thrust coefficient or induction factor. A new relationship is proposed to model the mean velocity deficit along the centerline at the hub-height level to fit the LES results piecewise throughout the wake. A logarithmic function is used in the near and intermediate wake regions whereas a power function is used in the far-wake. These two functions provide a better fit to both simulated and observed wind velocity deficits than other functions previously used in wake models such as WAsP. The wind shear and impact with the ground cause an anisotropy in the expansion of the wake such that the wake grows faster horizontally than vertically. The wake deforms upon impact with the ground and spreads laterally. WiTTS is also used to study the turbulence characteristics in the wake. Aligning with the mean wind direction, the streamwise component of turbulence intensity is the dominant among the three components and thus it is further studied. The highest turbulence intensity occurs near the top-tip level. The added turbulence intensity increases fast in the near-wake and reaches its maximum at about x/D ~ 5, then it gradually decreases further downstream. In the far-wake, the added turbulence intensity is primarily dependent on the induction factor and the ambient turbulence: it increases with the induction factor and ambient turbulence and it decays exponentially downstream. An analysis of the added TKE budget shows that production by shear and advection by the mean flow dominate throughout the wake, whereas dissipation and turbulent transport are less important. In the near-wake, TKE is entrained from the upper regions of the annular shear layer into the center of the wake. The nacelle causes a significant increase of production, advection, and dissipation in the near-wake. Wind shear and momentum fluxes are reduced in the lower part of the wake, thus TKE production is reduced at the bottom-tip level. In summary, we find that the WiTTS model, although applied to a simplified case of neutral stability with a single wind turbine, was able to offer new insights into wake properties, including non-symmetric wake growth and reduced vertical mixing near the ground.

  6. Wind or Antiwinds

    NASA Astrophysics Data System (ADS)

    Ayres, Thomas R.

    1984-07-01

    One of the surprising discoveries by IUE is that of redshifted emission lines of Si IV and C IV in the farultraviolet spectra of several late-type giants and supergiants. In the solar atmosphere, redshifts of high excitation emissions frequently are observed over magnetic active regions, and are thought to be associated with downflows of 10^5 K plasma in magnetic filaments. Nevertheless, the giants and supergiants that exhibit redshifted Si IV and C IV emissions differ substantially from dwarf stars like the Sun in terms of their fundamental stellar properties. It is possible, therefore, that the redshifts of the giants and supergiants have an entirely different origin than suggested by the solar analogy. For example, the appearance of a redshifted emission profile could result from an expanding, optically thick wind owing to the "P-Cygni" mechanism. We propose to continue, in the 7th year of IUE, the exploration of redshifts of high excitation emissions by addressing the question of whether the phenomenon in the supergiants is produced by an outflow of optically thick plasma (a "wind") or by a downflow of material (an "antiwind"). The test requires observations, using a precise radial velocity technique, of the intersystem lines of Si III (1892) and C III (1909) in the spectrum of the most luminous star, beta Draconis (G2 Ib-II), for which redshifts have been detected previously. In particular, the intersystem lines are optically thin, and therefore cannot exhibit a P-Cygni effect, whereas the Si IV and C IV doublets might be optically thick and therefore susceptible to the P-Cygni phenomenon. Furthermore, owing to different sensitivities to density, the C III] emission will be more heavily weighted towards a low-density, extended wind, while the Si III] emission will tend to be formed in the higher density structures from which the permitted lines of Si IV and C IV arise. Accordingly, the absolute velocity of Si III] 1892, and the difference in the velocities of 1892 and C III] 1909, can be used to test the wind and antiwind hypotheses. The highest precision in the measurement of the velocity differences can be achieved by taking a minimum of four separate spectra of the 1900A region of Beta Dra. The optimum exposures of the 1900 A region of Beta Ori are 7 hours, but the precise measurement of radial velocities requires that the satellite be thermally stable prior to the observations. The necessary stability can be attained, and maintained, only by coordinating US2, Vilspa, and US1 shifts on consecutive days. An important practical byproduct of the requirement for thermal stability is the opportunity to take Intensity Transfer Function calibrations in the LWR or LWP cameras during the long SWP exposures.

  7. Chemical Reaction Fronts in Ordered and Disordered Cellular Flows with Opposing Winds M. E. Schwartz* and T. H. Solomon

    E-print Network

    Solomon, Tom

    Chemical Reaction Fronts in Ordered and Disordered Cellular Flows with Opposing Winds M. E of chemical fronts in ordered and disordered vortex flows with imposed uniform winds. Fronts in a chain simply propagates at its reaction-diffusion (no flow) velocity minus the wind speed. If the same wind

  8. The Eect of the Tilt of the HCS on the Solar Wind Speed in the Outer Heliosphere

    E-print Network

    Richardson, John

    1 The Eect of the Tilt of the HCS on the Solar Wind Speed in the Outer Heliosphere J. D. Richardson: THE HCS TILT AND THE SOLAR WIND SPEED #12;2 Abstract. The ow of solar wind from the Sun is bimodal. High with the HCS tilt controls the solar wind velocities in the outer heliosphere near solar minimum when the Sun

  9. Measuring the equatorial plasma bubble drift velocities over Morroco

    NASA Astrophysics Data System (ADS)

    Lagheryeb, Amine; Benkhaldoun, Zouhair; Makela, Jonathan J.; Harding, Brian; Kaab, Mohamed; Lazrek, Mohamed; Fisher, Daniel J.; Duly, Timothy M.; Bounhir, Aziza; Daassou, Ahmed

    2015-08-01

    In this work, we present a method to measure the drift velocities of equatorial plasma bubbles (EPBs) in the low latitude ionosphere. To calculate the EPB drift velocity, we use 630.0-nm airglow images collected by the Portable Ionospheric Camera and Small Scale Observatory (PICASSO) system deployed at the Oukkaimden observatory in Morocco. To extract the drift velocity, the individual images were processed by first spatially registering the images using the star field. After this, the stars were removed from the images using a point suppression methodology, the images were projected into geographic coordinates assuming an airglow emission altitude of 250 km. Once the images were projected into geographic coordinates, the intensities of the airglow along a line of constant geomagnetic latitude (31°) are used to detect the presence of an EPB, which shows up as a depletion in airglow intensity. To calculate the EPB drift velocity, we divide the spatial lag between depletions found in two images (found by the application of correlation analysis) by the time difference between these two images. With multiple images, we will have several velocity values and consequently we can draw the EPB drift velocity curve. Future analysis will compare the estimates of the plasma drift velocity with the thermospheric neutral wind velocity estimated by a collocated Fabry-Perot interferometer (FPI) at the observatory.

  10. Wind energy systems

    NASA Technical Reports Server (NTRS)

    Stewart, H. J.

    1978-01-01

    A discussion on wind energy systems involved with the DOE wind energy program is presented. Some of the problems associated with wind energy systems are discussed. The cost, efficiency, and structural design of wind energy systems are analyzed.

  11. Maximum life spur gear design

    NASA Technical Reports Server (NTRS)

    Savage, M.; Mackulin, M. J.; Coe, H. H.; Coy, J. J.

    1991-01-01

    Optimization procedures allow one to design a spur gear reduction for maximum life and other end use criteria. A modified feasible directions search algorithm permits a wide variety of inequality constraints and exact design requirements to be met with low sensitivity to initial guess values. The optimization algorithm is described, and the models for gear life and performance are presented. The algorithm is compact and has been programmed for execution on a desk top computer. Two examples are presented to illustrate the method and its application.

  12. Pontryagin Maximum Principle - a generalization

    E-print Network

    Grabowski, Janusz

    2009-01-01

    The fundamental theorem of the theory of optimal control, the Pontryagin Maximum Principle (PMP), is extended to the setting of almost Lie (AL) algebroids - geometrical objects generalizing Lie algebroids. This formulation of the PMP may be viewed as a scheme comprising reductions of optimal control problems, like the Euler-Poincar'e equations arise as reductions of the Euler-Lagrange equations for the rigid body. The framework is based on a very general concept of homotopy of admissible paths and geometry of AL algebroids and goes back to some ideas of the Lagrangian and Hamiltonian formalisms in this general setting.

  13. Acoustic velocity meter systems

    USGS Publications Warehouse

    Laenen, Antonius

    1985-01-01

    Acoustic velocity meter (AVM) systems operate on the principles that the point-to-point upstream traveltime of an acoustic pulse is longer than the downstream traveltime and that this difference in traveltime can be accurately measured by electronic devices. An AVM system is capable of recording water velocity (and discharge) under a wide range of conditions, but some constraints apply: 1. Accuracy is reduced and performance is degraded if the acoustic path is not a continuous straight line. The path can be bent by reflection if it is too close to a stream boundary or by refraction if it passes through density gradients resulting from variations in either water temperature or salinity. For paths of less than 100 m, a temperature gradient of 0.1' per meter causes signal bending less than 0.6 meter at midchannel, and satisfactory velocity results can be obtained. Reflection from stream boundaries can cause signal cancellation if boundaries are too close to signal path. 2. Signal strength is attenuated by particles or bubbles that absorb, spread, or scatter sound. The concentration of particles or bubbles that can be tolerated is a function of the path length and frequency of the acoustic signal. 3. Changes in streamline orientation can affect system accuracy if the variability is random. 4. Errors relating to signal resolution are much larger for a single threshold detection scheme than for multiple threshold schemes. This report provides methods for computing the effect of various conditions on the accuracy of a record obtained from an AVM. The equipment must be adapted to the site. Field reconnaissance and preinstallation analysis to detect possible problems are critical for proper installation and operation of an AVM system.

  14. Evaluation of Multimode Coupled Bridge Response and Equivalent Static Wind Loading

    E-print Network

    Kareem, Ahsan

    is discussed with applications to bridge design. KEYWORDS: Flutter; Buffeting; Aeoelasticity; Aerodynamics-supported bridges leads to a concomitant decrease in their natural frequencies. Consequently, the reduced design wind velocity, which is defined as the ratio of design wind velocity to the bridge frequency and deck

  15. Wind erosion from a sagebrush steppe burned by wildfire: Measurements of PM10 and total horizontal sediment flux

    NASA Astrophysics Data System (ADS)

    Wagenbrenner, Natalie S.; Germino, Matthew J.; Lamb, Brian K.; Robichaud, Peter R.; Foltz, Randy B.

    2013-09-01

    Wind erosion and aeolian transport processes are under studied compared to rainfall-induced erosion and sediment transport on burned landscapes. Post-fire wind erosion studies have predominantly focused on near-surface sediment transport and associated impacts such as on-site soil loss and site fertility. Downwind impacts, including air quality degradation and deposition of dust or contaminants, are also likely post-fire effects; however, quantitative field measurements of post-fire dust emissions are needed for assessment of these downwind risks. A wind erosion monitoring system was installed immediately following a desert sagebrush and grass wildfire in southeastern Idaho, USA to measure wind erosion from the burned landscape. This paper presents measurements of horizontal sediment flux and PM10 vertical flux from the burned area. We determined threshold wind speeds and corresponding threshold friction velocities to be 6.0 and 0.20 m s-1, respectively, for the 4 months immediately following the fire and 10 and 0.55 m s-1 for the following spring months. Several major wind erosion events were measured in the months following the July 2010 Jefferson Fire. The largest wind erosion event occurred in early September 2010 and produced 1495 kg m-1 of horizontal sediment transport within the first 2 m above the soil surface, had a maximum PM10 vertical flux of 100 mg m-2 s-1, and generated a large dust plume that was visible in satellite imagery. The peak PM10 concentration measured on-site at a height of 2 m in the downwind portion of the burned area was 690 mg m-3. Our results indicate that wildfire can convert a relatively stable landscape into one that is a major dust source.

  16. Wind-enhanced resuspension in the shallow waters of South San Francisco Bay: Mechanisms and potential implications for cohesive sediment transport

    USGS Publications Warehouse

    Brand, Andreas; Lacy, Jessica R.; Hsu, Kevin; Hoover, Daniel; Gladding, Steve; Stacey, Mark T.

    2010-01-01

    We investigated the driving forces of sediment dynamics at the shoals in South San Francisco Bay. Two stations were deployed along a line perpendicular to a 14 m deep channel, 1000 and 2000 m from the middle of the channel. Station depths were 2.59 and 2.19 m below mean lower low water, respectively. We used acoustic Doppler velocimeters for the simultaneous determination of current velocities, turbulence, sediment concentration and fluxes. Maximum current shear velocities were 0.015 m s?1 at the station further from the channel (closer to the shore) and 0.02 m s?1 at the station closer to the channel. Peak wave-induced shear velocities exceeded 0.015 m s?1 at both stations. Maximum sediment concentrations were around 30 g m?3 during calm periods (root mean square wave height ?3 and sediment fluxes were 5 times higher than in calm conditions (0.02 g m?2 s?1 versus >0.10 g m?2 s?1) at the station further from the channel 0.36 m above the bed. Closer to the channel, sediment concentrations and vertical fluxes due to wind wave resuspension were persistently lower (maximum concentrations around 50 g m?3 and maximum fluxes around 0.04 g m?2 s?1). Most resuspension events occurred during flood tides that followed wave events during low water. Although wave motions are able to resuspend sediment into the wave boundary layer at low tide, the observed large increases in sediment fluxes are due to the nonlinear interaction of wind waves and the tidal currents.

  17. Composite wind turbine blades

    NASA Astrophysics Data System (ADS)

    Ong, Cheng-Huat

    Researchers in wind energy industry are constantly moving forward to develop higher efficiency wind turbine. One major component for wind turbine design is to have cost effective wind turbine blades. In addition to correct aerodynamic shape and blade geometry, blade performance can be enhanced further through aero-elastic tailoring design and material selections. An analytical tool for blade design has been improved and validated. This analytical tool is utilized to resolve issues related to elastic tailoring design. The investigation looks into two major issues related to the design and fabrication of a bend-twist-coupled blade. Various design parameters for a blade such as materials, laminate lay-up, skin thickness, ply orientation, internal spar, etc. have been examined for designing a bend-twist-coupled blade. The parametric study indicates that the critical design parameters are the ply material, the ply orientation, and the volume fraction ratio between the anisotropic layers and orthotropic layers. To produce a blade having the bend-twist coupling characteristics, the fiber lay-ups at the top and bottom skins of the blade must have a "mirror" lay-up in relation to the middle plane of the blade. Such lay-up causes fiber discontinuation at the seam. The joint design at the seam is one major consideration in fabricating a truly anisotropic blade. A new joint design was proposed and tensile failure tests were carried out for both the old and new joint designs. The tests investigated the effects of different types of joint designs, the laminate lay-up at the joints, and the stacking sequence of the joint retention strength. A major component of a wind turbine blade, D-spar, was designed to maximum coupling. Two D-spars were then fabricated using the new joint design; one of them was subjected to both static and modal testings. Traditionally, wind turbine blades are made of low cost glass material; however, carbon fibers are proposed as alternative material. Our study indicates that carbon fibers are more efficient than glass fibers not only in blade structural performance, but also in relative cost comparison.

  18. Dynamic impact of the vertical shear of gradient wind on the tropical cyclone boundary layer wind field

    NASA Astrophysics Data System (ADS)

    Cai, Ninghao; Xu, Xin; Song, Lili; Bai, Lina; Ming, Jie; Wang, Yuan

    2014-02-01

    This work studies the impact of the vertical shear of gradient wind (VSGW) in the free atmosphere on the tropical cyclone boundary layer (TCBL). A new TCBL model is established, which relies on fiveforce balance including the pressure gradient force, Coriolis force, centrifugal force, turbulent friction, and inertial deviation force. This model is then employed to idealize tropical cyclones (TCs) produced by DeMaria's model, under different VSGW conditions (non-VSGW, positive VSGW, negative VSGW, and VSGW increase/decrease along the radial direction). The results show that the free-atmosphere VSGW is particularly important to the intensity of TC. For negative VSGW, the total horizontal velocity in the TCBL is somewhat suppressed. However, with the maximum radial inflow displaced upward and outward, the radial velocity notably intensifies. Consequently, the convergence is enhanced throughout the TCBL, giving rise to a stronger vertical pumping at the TCBL top. In contrast, for positive VSGW, the radial inflow is significantly suppressed, even with divergent outflow in the middle-upper TCBL. For varying VSGW along the radial direction, the results indicate that the sign and value of VSGW is more important than its radial distribution, and the negative VSGW induces stronger convergence and Ekman pumping in the TCBL, which favors the formation and intensification of TC.

  19. Radial Velocity Eclipse Mapping of Exoplanets

    NASA Astrophysics Data System (ADS)

    Nikolov, Nikolay; Sainsbury-Martinez, Felix

    2015-07-01

    Planetary rotation rates and obliquities provide information regarding the history of planet formation, but have not yet been measured for evolved extrasolar planets. Here we investigate the theoretical and observational perspective of the Rossiter-McLaughlin effect during secondary eclipse (RMse) ingress and egress for transiting exoplanets. Near secondary eclipse, when the planet passes behind the parent star, the star sequentially obscures light from the approaching and receding parts of the rotating planetary surface. The temporal block of light emerging from the approaching (blueshifted) or receding (redshifted) parts of the planet causes a temporal distortion in the planet’s spectral line profiles resulting in an anomaly in the planet’s radial velocity curve. We demonstrate that the shape and the ratio of the ingress-to-egress radial velocity amplitudes depends on the planetary rotational rate, axial tilt, and impact factor (i.e., sky-projected planet spin-orbital alignment). In addition, line asymmetries originating from different layers in the atmosphere of the planet could provide information regarding zonal atmospheric winds and constraints on the hot spot shape for giant irradiated exoplanets. The effect is expected to be most-pronounced at near-infrared wavelengths, where the planet-to-star contrasts are large. We create synthetic near-infrared, high-dispersion spectroscopic data and demonstrate how the sky-projected spin axis orientation and equatorial velocity of the planet can be estimated. We conclude that the RMse effect could be a powerful method to measure exoplanet spins.

  20. Jet engine powers large, high-temperature wind tunnel

    NASA Technical Reports Server (NTRS)

    Benham, T. F.; Mulliken, S. R.

    1967-01-01

    Wind tunnel for large component testing uses a jet engine with afterburner to provide high temperatures /1200 degrees to 2000 degrees F/ and controlled high velocity gas. This economical wind tunnel can accommodate parts ten feet by ten feet or larger, and is a useful technique for qualitative information.