Science.gov

Sample records for maximum wind velocity

  1. 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)

  2. A general optimization for maximum terminal velocity

    NASA Astrophysics Data System (ADS)

    Vulpetti, G.

    1982-09-01

    A numerical model is developed to determine the maximum velocity which can be attained by a rocket propulsion system. Particular attention is given to the ratio of active mass, that which can be converted to propulsive energy, to inert mass, which remains after the propulsive energy is expended. Calculations are based on the law of conservation of energy applied to a spaceship with chemical, laser-sail, interstellar ramjet, and annihilation engines. Limits on the exhaust velocity of the thrust system are neglected. Specific attention is given to relativistic calculations involving the annihilation reactions, noting that classical propulsion systems have critical mass values significantly lower than the propulsion required by extra-solar system flight. Numerical results are presented of critical values of propellant which produce an optimal jet speed, which is determined to be a constant.

  3. 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...

  4. 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...

  5. 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...

  6. 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... velocities. (a) For land planes and amphibians, the following applies: (1) A 90-degree cross component of wind velocity, demonstrated to be safe for takeoff and landing, must be established for dry runways...

  7. 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... velocities. (a) For land planes and amphibians, the following applies: (1) A 90-degree cross component of wind velocity, demonstrated to be safe for takeoff and landing, must be established for dry runways...

  8. 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

  9. Distribution of Maximum Velocities in Avalanches Near the Depinning Transition

    NASA Astrophysics Data System (ADS)

    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 vm in the mean field theory of the interface depinning transition. We derive the extreme value distribution P(vm|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, vm, scales as P(vm)˜vm-2 for large vm. 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.

  10. Spatiotemporal Dynamics of the Wind Velocity from Minisodar Measurement Data

    NASA Astrophysics Data System (ADS)

    Simakhin, V. A.; Cherepanov, O. S.; Shamanaeva, L. G.

    2016-04-01

    The spatiotemporal dynamics of the three wind velocity components in the atmospheric boundary layer is analyzed on the basis of Doppler minisodar measurements. The data were processed and analyzed with the help of robust nonparametric methods based on the weighted maximum likelihood method and classical methods. Distribution laws were obtained for each wind velocity component. There are outliers in the distribution functions; both right and left asymmetry of the distributions are observed. For the x- and ycomponents, the width of the distribution increases as the observation altitude is increased, but the maximum of the distribution function decreases, which is in agreement with the data available in the literature. For the zcomponents the width of the distribution remains practically constant, but the value of the maximum also decreases with altitude. Analysis of the hourly semidiurnal dynamics showed that all three components have maxima in the morning and evening hours. For the y- and z-components the maxima in the evening hours are more strongly expressed than in the morning hours. For the x- and y-components the horizontal wind shear is closely tracked in the evening hours. It is shown that adaptive estimates on the efficiency significantly exceed the classical parametric estimates and allow one to analyze the spatiotemporal dynamics of the wind velocity, and reveal jets and detect wind shears.

  11. 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.

  12. 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.

  13. Wind Velocity and Position Sensor-less Operation for PMSG Wind Generator

    NASA Astrophysics Data System (ADS)

    Senjyu, Tomonobu; Tamaki, Satoshi; Urasaki, Naomitsu; Uezato, Katsumi; Funabashi, Toshihisa; Fujita, Hideki

    Electric power generation using non-conventional sources is receiving considerable attention throughout the world. Wind energy is one of the available non-conventional energy sources. Electrical power generation using wind energy is possible in two ways, viz. constant speed operation and variable speed operation using power electronic converters. Variable speed power generation is attractive, because maximum electric power can be generated at all wind velocities. However, this system requires a rotor speed sensor, for vector control purpose, which increases the cost of the system. To alleviate the need of rotor speed sensor in vector control, we propose a new sensor-less control of PMSG (Permanent Magnet Synchronous Generator) based on the flux linkage. We can estimate the rotor position using the estimated flux linkage. We use a first-order lag compensator to obtain the flux linkage. Furthermore‚we estimate wind velocity and rotation speed using a observer. The effectiveness of the proposed method is demonstrated thorough simulation results.

  14. Design of a wind turbine-generator system considering the conformability to wind velocity fluctuations

    SciTech Connect

    Wakui, Tetsuya; Hashizume, Takumi; Outa, Eisuke

    1999-07-01

    The conformability of the rated power output of the wind turbine-generator system and of the wind turbine type to wind velocity fluctuations are investigated with a simulation model. The authors examine three types of wind turbines: the Darrieus-Savonius hybrid, the Darrieus proper and the Propeller. These systems are mainly operated at a constant tip speed ratio, which refers to a maximum power coefficient points. As a computed result of the net extracting power, the Darrieus turbine proper has little conformability to wind velocity fluctuations because of its output characteristics. As for the other turbines, large-scale systems do not always have an advantage over small-scale systems as the effect of its dynamic characteristics. Furthermore, it is confirmed that the net extracting power of the Propeller turbine, under wind direction fluctuation, is much reduced when compared with the hybrid wind turbine. Thus, the authors conclude that the appropriate rated power output of the system exists with relation to the wind turbine type for each wind condition.

  15. Maximum wind speeds and US hurricane losses

    NASA Astrophysics Data System (ADS)

    Murnane, R. J.; Elsner, J. B.

    2012-08-01

    There is academic, commercial, and public interest in estimating loss from hurricanes striking land and understanding how loss might change as a result of future variations in climate. Here we show that the relationship between wind speed and loss is exponential and that loss increases with wind speed at a rate of 5% per m s-1. The relationship is derived using quantile regression and a data set comprising wind speeds of hurricanes hitting the United States and normalized economic losses. We suggest that the “centercepts” for the different quantiles account for exposure-related factors such as population density, precipitation, and surface roughness, and that once these effects are accounted for, the increase in loss with wind speed is consistent across quantiles. An out-of-sample test of this relationship correctly predicts economic losses from Hurricane Irene in 2011. The exponential relationship suggests that increased wind speeds will produce significantly higher losses; however, increases in exposed property and population are expected to be a more important factor for near future losses.

  16. Wind velocity profiles measured by the smoke-trail method at Wallops Island, Virginia, 1965 - 1969

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    Thirty-nine detailed wind profiles measured by the smoke-trail method at the Wallops Island Test Range during the years 1965 through 1969 are presented as west-to-east and south-to-north velocity components at height intervals of 25 meters. The overall altitude range of the wind profile data varies from about 1 to 23 km. The wind measurements, which were made under a variety of conditions, include velocities in excess of the annual 99-percent highest wind value (the wind value which will not be exceeded 99 percent of the time) for the Wallops Island Test Range. The report also includes a listing of the wind soundings and their maximum velocities and direction of the maximum velocities measured at Wallops Island from 1959 through 1969. Results of smoke-trail enhancement experiments are also indicated.

  17. An approximate, maximum-terminal-velocity descent to a point

    NASA Astrophysics Data System (ADS)

    Eisler, G. Richard; Hull, David G.

    A neighboring extremal control problem is formulated for a hypersonic glider to execute a maximum-terminal-velocity descent to a stationary target in a vertical plane. The resulting two-part, feedback control scheme initially solves a nonlinear algebraic problem to generate a nominal trajectory to the target altitude. Secondly, quadrature about the nominal provides the lift perturbation necessary to achieve the target downrange. On-line feedback simulations are run for the proposed scheme and a form of proportional navigation and compared with an off-line parameter optimization method. The neighboring extremal terminal velocity compares very well with the parameter optimization solution and is far superior to proportional navigation. However, the update rate is degraded, though the proposed method can be executed in real time.

  18. Wind Velocity Measurements By Optical Scintillations Methods

    NASA Astrophysics Data System (ADS)

    Tsadka, S.; Shaft, S.; Azar, Z.; Tur, Moshe

    1990-01-01

    Scintillations-based optical techniques for the measurement of the atmospheric transverse average wind velocity are re-examined. Three different methods for the processing of the resultant time-lagged covariance function are compared to in-situ anemometer measurements. A correlation index of 0.89-0.95 is obtained between the optical and anemometer results and it tends to increasing with the measurement time constant. Some degradation in the accuracy of the optical methods is observed when the spacing between the detectors is either much smaller or much larger than the Fresnel zone [AL]1/2.

  19. 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.)

  20. Velocity shear generation of solar wind turbulence

    SciTech Connect

    Roberts, D.A.; Goldstein, M.L.; Ghosh, S.; Matthaeus, W.H.

    1992-11-01

    The authors use a two-dimensional, incompressible MHD spectral code to establish that shear-driven turbulence is a possible means for producing many observed properties of the evolution of the magnetic and velocity fluctuations in the solar wind and, in particular, the evolution of the cross helicity ({open_quotes}Alfvenicity{close_quotes}) at small scales. They find that large-scale shear can nonlinearly produce a cascade to smaller scale fluctuations even when the linear Kelvin-Helmholtz mode is stable and that a roughly power law inertial range is established by this process. While the fluctuations thus produced are not Alfvenic, they are nearly equipartitioned between magnetic and kinetic energy. The authors report simulations with Alfvenic fluctuations at high wave numbers, both with and without shear layers and find that it is the low cross helicity at low wave numbers that is critical to the cross helicity evolution, rather than the geometry of the flow or the dominance of kinetic energy at large scales. The fluctuations produced by shear effects are shown to evolve similarly but more slowly in the presence of a larger mean field and to be anisotropic with a preferred direction of spectral transfer perpendicular to the mean field. The evolution found is similar to that seen in some other simulations of HMD turbulence, and thus seems in many respects to be an instance of a more generic turbulent evolution rather than due to specific conditions in the solar wind. 75 refs., 18 figs.

  1. 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.

  2. Monitoring of wind pressure distribution at a supertall structure above maximum gradient wind level (presentation video)

    NASA Astrophysics Data System (ADS)

    Ni, Y. Q.; Wang, Y. W.; Song, S. D.

    2014-04-01

    While the field measurement of wind speed at buildings and towers has been made by numerous investigators, the direct measurement of wind pressure at high-rise structures was seldom reported. Up to now, the information regarding wind pressure distribution above the maximum gradient wind level (it is 450 m stipulated in the Chinese code) has never been experimentally obtained. This paper presents a field monitoring investigation on the measurement of wind pressure and its distribution at the Canton Tower of 600 m high above the maximum gradient wind level during the typhoon Kaitak.

  3. 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

  4. Estimating maximum global wind power availability and associated climatic consequences

    NASA Astrophysics Data System (ADS)

    Miller, Lee; Gans, Fabian; Kleidon, Axel

    2010-05-01

    Estimating maximum global wind power availability and associated climatic consequences Wind speed reflects the continuous generation of kinetic energy and its dissipation, primarily in the atmospheric boundary layer. When wind turbines extract kinetic wind energy, less kinetic energy remains in the atmosphere in the mean state. While this effect does not play a significant role for a single turbine, it becomes a critical factor for the estimation of large-scale wind power availability. This extraction of kinetic energy by turbines also competes with the natural processes of kinetic energy dissipation, thus setting fundamental limits on extractability that are not considered in previous large-scale studies [1,2,3]. Our simple momentum balance model using ECMWF climate data illustrates a fundamental limit to global wind power extractability and thereby electricity potential (93TW). This is independent of engineering advances in turbine design and wind farm layout. These results are supported by similar results using a global climate model of intermediate complexity. Varying the surface drag coefficient with different simulations allows us to directly relate changes in atmospheric and boundary layer dissipation with resulting climate indices and wind power potential. These new estimates of the maximum power generation by wind turbines are well above the currently installed capacity. Hence, present day installations are unlikely to have a global impact. However, when compared to the current human energy demand of 17TW combined with plans by the US and EU to drastically increase onshore and offshore wind turbine installations [4,5,6], understanding the climatic response and ultimate limitations of wind power as a large-scale renewable energy source is critical. [1] Archer, C., and M.Z. Jacobson, (2005) Evaluation of global wind power, J. Geophys. Res. 110:D12110. [2] Lu, X., M.B. McElroy, and J. Kiviluoma, (2009) Global potential for wind-generated electricity, Proc Natl Acad Sci, 106. [3] Liu, W.T., W. Tang, and X. Xie, (2008) Wind power distribution over the ocean, Geophys. Res. Lett., 35 L13808. [4] IPCC, (2008) IPCC scoping meeting on renewable energy sources - proceedings, Intergovernmental Panel on Climate Change [5] U.S. Department of Energy, (2008) 20% wind energy by 2030: increasing wind energy's contribution to U.S. electricity supply, U.S. Dept. of Energy - Energy Information Administration. [6] EEA, (2009) Europe's onshore and offshore wind energy potential, European Environment Agency, ISSN 1725-2237.

  5. 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).

  6. Statistical Analysis of Solar Wind Turbulence at Solar Maximum and Solar Minimum

    NASA Astrophysics Data System (ADS)

    Olson, D. K.; Coplan, M.; Ogilvie, K.; Holland, M.; Kulkarni, V.; Banerjee, A.

    2008-12-01

    We have applied statistical methods to a study of turbulence in the solar wind using data from the SWE experiment on NASA's WIND mission during solar minimum (1996 and 2006) and solar maximum (2001). We examined the probability distribution functions (PDFs) for solar wind velocity differences at lag times from 1 to 105 minutes. The statistical features of these PDFs reveal information regarding the cascade of momentum from large to small scale structures as well as intermittency within the solar wind. We have analyzed the velocity differences using three component velocity data, allowing us to determine turbulent anisotropies and examine the PDFs for velocity differences parallel and perpendicular to the local magnetic field. At small time differences, the PDFs of bulk velocity differences have the form of a double exponential function. For increasing time differences, there is a shift in the mean of the PDF to negative velocity difference with a noticeable asymmetry as seen previously by Burlaga et al. (J. Geophys. Res., 107, 1403, 2002). However, the shift and asymmetry are absent when examining velocities parallel to the magnetic field suggesting anisotropy in the turbulence is found in the component perpendicular to the magnetic field. The second statistical moment (variance) of the PDFs are found to have different behavior in time scales less and greater than about 103 minutes. These two regimes each follow a separate power law scaling with the time difference. The regimes appear to be related to the Kolmogorov 2/3 and 4/5 laws that define the power law scaling for inertial and Gaussian regimes. The third and fourth statistical moments (skew and kurtosis) also follow power laws. Comparison between solar minimum and solar maximum shows general similarity in the results. However, at solar maximum only a single regime exists for the kurtosis, while at solar minimum two regimes are present, similar to the regimes found for the variance.

  7. Wind velocity effects on sampling rate of NO2 badge.

    PubMed

    Lee, K; Yanagisawa, Y; Spengler, J D; Billick, I H

    1992-01-01

    The effects of wind velocity on a sampling rate of a nitrogen dioxide (NO2) diffusive badge were experimentally determined using a turntable. The use of a turntable permits the collection of the large amounts of data that are needed for statistically reliable results at several wind velocities in one experiment. The regression model for the wind effect determined by these experiments was closely correlated with data previously gathered from experiments using wind tunnels. Experiments at two different relative humidities, 35% and 60%, were performed and analyzed by a simple least square regression model. A multi-regression model containing two independent variables, wind velocity and relative humidity, also was developed. The multi-regression model was useful at relative humidity between 20% and 60% and wind velocity between 0 and 7 meter per second (m/sec). PMID:1515772

  8. 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.

  9. Influence of sand grain diameter and wind velocity on lift-off velocities of sand particles.

    PubMed

    Bo, Tian-Li; Zheng, Xiao-Jing; Duan, Shao-Zhen; Liang, Yi-Rui

    2013-05-01

    In this paper, the velocities of sand particles near the sand bed in the saltation cloud were measured in a wind tunnel through an improved experimental scheme of the Particle Image Velocimetry (PIV) system. The influences of the diameter of sand particles in the saltation cloud and wind velocity on the probability distribution function (PDF) of lift-off velocities of sand particles were investigated. Results demonstrate that for the sand particles saltating above the sand bed with the mean grain diameter (d m = 0.3 mm), smaller and larger ones have the same velocity distribution, and wind velocity has no obvious influence on the distribution shape of the lift-off velocities, i.e., the PDFs of the horizontal and vertical lift-off velocities both follow a lognormal distribution, but the diameter of sand particles in the saltation cloud and wind velocity have an influence on the parameters of the PDF of horizontal and vertical lift-off velocities. Eventually, we present formulas to describe the PDF of lift-off velocities of sand particles with regard to the influence of wind velocity and the diameter of sand particles in the saltation cloud above the sand bed with d m = 0.3 mm. PMID:23695368

  10. Vertical velocity in cirrus case obtained from wind profiler

    NASA Technical Reports Server (NTRS)

    Song, Ran; Cox, Stephen K.

    1993-01-01

    Cirrus clouds play an important role in the climate and general circulation because they significantly modulate the radiation properties of the atmosphere. However understanding the processes that govern their presence is made difficult by their high altitude, variable thickness, complex microphysical structure, and relatively little knowledge of the vertical motion field. In the FIRE 2 (First International Satellite Cloud Climatology Regional Experiment) experiment, a 404 MHz wind profiler was set up to provide continuous measurements of clear air wind field at Parsons, Kansas. Simultaneously, the NOAA wind profiler network supplied a wider spacial scale observation. On 26 Nov. 1991, the most significant cirrus cloud phenomena during the experiment with a jet streak at 250 Mb occurred. Analyses of the vertical wind velocity are made by utilizing different methods based on wind profiler data, among them the direct measurements from CSU wind profiler and NOAA network wind profilers, VAD (Velocity Azimuth Display) technique and the kinematic method.

  11. 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.

  12. 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.

  13. 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.

  14. High-velocity tails on the velocity distribution of solar wind ions

    SciTech Connect

    Ogilvie, K.W. ); Geiss, J. ); Gloeckler, G. ); Berdichevsky, D. ); Wilken, B. )

    1993-03-01

    Recent observations of the solar wind using the SWICS instrument on the Ulysses spacecraft have shown the presence of high-velocity [open quotes]tails[close quotes] on the velocity distribution of protons. Similar features have also been observed on the velocity distributions of helium and oxygen ions. Of the order of 1% of the solar wind density is involved in these tails, which are approximately exponential in shape and persist to V = V[sub B] + 10V[sub th] or beyond, where V[sub B] is the bulk velocity and V[sub th] the thermal velocity of the solar wind. This paper contains a preliminary description of the phenomenon. It is clear that it is ultimately connected with the passage of interplanetary shocks past the spacecraft and that particle acceleration at oblique shocks is involved. 21 refs., 6 figs., 2 tabs.

  15. An estimate of the maximum speed of the solar wind, 1938-1989

    NASA Technical Reports Server (NTRS)

    Cliver, E. W.; Feynman, J.; Garrett, H. B.

    1990-01-01

    In an effort to estimate the highest flow velocity that the solar wind has exhibited at earth during the past 50 years, geomagnetic storms that occurred from 1938 to 1989 were surveyed, and the storms that were preceded by a major proton flare were selected. For each identified flare-storm pair, the average speed ('transit speed') of the associated interplanetary shock from the interval between the flare onset and the sudden commencement of the geomagnetic storm was calculated. In each case, the maximum solar wind flow speed was inferred from an empirical relationship (derived for a sample of recent events) between the shock transit speed and the peak flow velocity of the associated transient stream, obtaining a distribution of maximum solar wind speeds, which presumably corresponds to a sample of the most energetic events of this 50-yr period. Results show no evidence for bulk flow velocities greater than the about 2000 km/sec value deduced by Zastenker et al. (1978) and Grunwaldt (1975) for the August 4, 1972 event.

  16. Detonation velocity of pure and mixed CHNO explosives at maximum nominal density.

    PubMed

    Keshavarz, Mohammad Hossein

    2007-03-22

    In this paper, a simple approach is introduced to predict detonation velocity of pure and mixed explosives at maximum nominal density. This technique may be applied to any pure or mixed explosives that contain elements of carbon, hydrogen, nitrogen and oxygen. The new method requires only elemental composition and some specific structural parameters. The introduced correlation can easily be applied for determining maximum expected detonation velocity of any new CHNO explosive without using its crystal density. Calculated detonation velocities by this procedure for both pure and composite explosive formulations show good agreement with respect to measured detonation velocity at maximum nominal density. PMID:16959409

  17. Double-hump H+ velocity distribution in the polar wind

    NASA Astrophysics Data System (ADS)

    Barakat, A. R.; Barghouthi, I. A.; Schunk, R. W.

    The polar wind is an ambipolar plasma outflow from the terrestrial ionosphere at high latitudes. As the ions drift upward along geomagnetic flux tubes, they move from collision-dominated (ion barosphere) to collisionless (ion exosphere) regions. A transition layer is embedded between these two regions where the ion characteristics change rapidly. A Monte Carlo simulation was used to study the steady-state flow of H+ ions through a background of O+ ions. The simulation domain covered the collision-dominated, transition, and collisionless regions. The model properly accounted for the divergence of magnetic field lines, the gravitational force, the electrostatic field, and H+-O+ collisions. The H+ velocity distribution, f(H+), was found to be very close to Maxwellian at low altitudes (deep in the barosphere). As the ions drifted to higher altitudes, f(H+) formed an upward tail. In the transition layer, the upward tail evolved into a second peak with a kidney bean shape, and hence, f(H+) developed a double-humped shape. The second peak grew with altitude and eventually became dominant as the ions reached the exosphere. This behavior is due to the interplay between the electrostatic force and the velocity-dependent Coulomb collisions. Moreover, the H+ heat flux, q(H+), was found to change rapidly with altitude in the transition layer from a positive maximum to a negative minimum. This remarkable feature of q(H+) is closely related to the coincident formation of the double-humped structure of f(H+). The double-hump distribution might destabilize the plasma or, at least, cause enhanced thermal fluctuations. The double-hump f(H+), and the associated wave turbulence, have several consequences with regard to our understanding of the polar wind and similar space physics problems. The plasma turbulence can significantly alter the behavior of the plasma in and above the transition region and, therefore, should be considered in future polar wind models. The wave turbulence can serve as a signature for the formation of the double-hump f(H+). Also, more sophisticated (than the existing bi-Maxwellian 16-moment) generalized transport equations might be needed to properly handle problems such as the one considered here.

  18. A proposed method for wind velocity measurement from space

    NASA Technical Reports Server (NTRS)

    Censor, D.; Levine, D. M.

    1980-01-01

    An investigation was made of the feasibility of making wind velocity measurements from space by monitoring the apparent change in the refractive index of the atmosphere induced by motion of the air. The physical principle is the same as that resulting in the phase changes measured in the Fizeau experiment. It is proposed that this phase change could be measured using a three cornered arrangement of satellite borne source and reflectors, around which two laser beams propagate in opposite directions. It is shown that even though the velocity of the satellites is much larger than the wind velocity, factors such as change in satellite position and Doppler shifts can be taken into account in a reasonable manner and the Fizeau phase measured. This phase measurement yields an average wind velocity along the ray path through the atmosphere. The method requires neither high accuracy for satellite position or velocity, nor precise knowledge of the refractive index or its gradient in the atmosphere. However, the method intrinsically yields wind velocity integrated along the ray path; hence to obtain higher spatial resolution, inversion techniques are required.

  19. Relationships between wind velocity and underwater irradiance in a shallow lake (Lake Okeechobee, Florida, USA)

    USGS Publications Warehouse

    Hanlon, C.G.; Miller, R.L.; McPherson, B.F.

    1998-01-01

    Relationships between wind velocity and the vertical light attenuation coefficient (K0) were determined at two locations in a large, shallow lake (Lake Okeechobee, Florida, USA). K0 was significantly correlated with antecedent wind conditions, which explained as much as 90 percent of the daily variation in K0. Sub-surface irradiance began to change within 60 to 90 minutes of the time when wind velocity exceeded or dropped below a threshold value. Maximum one hour changes in K0 were > 50 percent, however, 20 to 30 percent changes were more common. The magnitude of change in K0 varied spatially based on differences in sediment type. K0 never exceeded 2.8 at a location where bottom sediments were dominated by a mixture of coarse sand and shells. In comparison, K0 exceeded 9 during episodic wind events where the bottom sediment was comprised of fine grain mud. Underwater irradiance data can be used to determine threshold wind velocity and account for the influence sediment type has on K0. Once a threshold velocity has been established, the frequency, rate, and duration of expected change in underwater irradiance can be evaluated. This is critical information for scientists who are studying algal productivity or other light-related phenomena.Relationships between wind velocity and the vertical light attenuation coefficient (K0) were determined at two locations in a large, shallow lake (Lake Okeechobee, Florida, USA). K0 was significantly correlated with antecedent wind conditions, which explained as much as 90 percent of the daily variation in K0. Sub-surface irradiance began to change within 60 to 90 minutes of the time when wind velocity exceeded or dropped below a threshold value. Maximum one hour changes in K0 were >50 percent, however, 20 to 30 percent changes were more common. The magnitude of change in K0 varied spatially based on differences in sediment type. K0 never exceeded 2.8 at a location where bottom sediments were dominated by a mixture of coarse sand and shells. In comparison, K0 exceeded 9 during episodic wind events where the bottom sediment was comprised of fine grain mud. Underwater irradiance data can be used to determine threshold wind velocity and account for the influence sediment type has on K0. Once a threshold velocity has been established, the frequency, rate, and duration of expected change in underwater irradiance can be evaluated. This is critical information for scientists who are studying algal productivity or other light-related phenomena.

  20. On the long-tail solar wind electron velocity distribution

    NASA Technical Reports Server (NTRS)

    Shlesinger, Michael F.; Coplan, Michael A.

    1988-01-01

    The role of the log-normal distribution in the description of the high-energy tail of the electron velocity distribution in the solar wind plasma is examined. Specifically, it is shown that the core-halo solar wind distribution function can be understood in terms of a simple phenomenological model of general applicability in which the core has a Maxwellian or normal distribution and the halo a log-normal distribution. In the presence of structures in the interplanetary medium capable of interacting with the electrons, the model predicts a transition at the highest velocities to a secondary halo distribution.

  1. Terminal velocities of the winds from rapidly rotating OB stars

    NASA Technical Reports Server (NTRS)

    Friend, David B.

    1990-01-01

    This paper presents measurements of terminal velocities of OB stars which are rapid rotators, based on archival high-dispersion IUE spectra of the C IV resonance doublet. The terminal velocities of the most rapidly rotating stars appear to be systematically lower than those of the less rapidly rotating stars (at least for the cooler stars), although the number of very rapid rotators is only three. The modified line-radiation driven wind model of Friend and Abbott, which takes into account the finite size of the star as well as its rotation, predicts that the terminal velocity should drop with increasing rotational velocity. However, when a smaller but very homogeneous subset of the data is used (BO giants only), the correlation between terminal velocity and rotational velocity disappears.

  2. 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.

  3. 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.

  4. [Wind tunnel experiment on canopy structural parameters of isolated tree and wind velocity field characters nearby].

    PubMed

    Guan, D; Zhu, T

    2000-04-01

    The canopy structural parameters(porosity beta and permeability alpha) of isolated tree, and the wind velocity field character nearby were analyzed by wind tunnel experiment. The results show that alpha and beta fitted the function of alpha = beta 0.6, and the wind velocity nearby decreased in ellipsoid contour. The contour increased with increasing tree height and canopy width, and decreased with increasing permeability (or porosity). The isotach became the shape of ellipses or elliptic segments in horizontal and vertical plans. PMID:11767595

  5. Wind velocities on venus: vector determination by radio interferometry.

    PubMed

    Counselman, C C; Gourevitch, S A; King, R W; Pettengill, G H; Prinn, R G; Shapiro, I I; Miller, R B; Smith, J R; Ramos, R; Liebrecht, P

    1979-02-23

    To determine the wind directions and speeds on Venus, as each Pioneer probe fell to the surface we tracked its motion in three dimensions using a combination of Doppler and long-baseline radio interferometric methods. Preliminary results from this tracking, coupled with results from test observations of other spacecraft, enable us to estimate the uncertainties of our eventual determinations of the velocity vectors of the probes with respect to Venus. For altitudes below about 65 kilometers and with time-averaging over 100-second intervals, all three components of the velocity should have errors of the order of 0.3 meter per second or less. PMID:17833005

  6. Does the scatterometer see wind speed or friction velocity?

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    Studies of radar backscatter from the sea surface are referred either to the wind speed, U, or friction velocity, u(sub *). Bragg scattering theory suggests that these variations in backscatter are directly related to the height of the capillary-gravity waves modulated by the larger waves in tilt and by straining of the short wave field. The question then arises as to what characteristic of the wind field is most probably correlated with the wave number spectrum of the capillary-gravity waves. The justification for selecting U as the appropriate meteorological parameter to be associated with backscatter from L-band to Ku-band are reviewed. Both theoretical reasons and experimental evidence are used to demonstrate that the dominant parameter is U/C(lambda) where U is the wind speed at a height of about lambda/2 for waves having a phase speed of C(lambda).

  7. 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 β ~ 0.5 is favoured. Even if still incomplete, hydrodynamic simulations successfully reproduce several observational properties of Vela X-1.

  8. 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.

  9. Observations of Rapid Velocity Variations in the Slow Solar Wind

    NASA Astrophysics Data System (ADS)

    Hardwick, S. A.; Bisi, M. M.; Davies, J. A.; Breen, A. R.; Fallows, R. A.; Harrison, R. A.; Davis, C. J.

    2013-07-01

    The technique of interplanetary scintillation (IPS) is the observation of rapid fluctuations of the radio signal from an astronomical compact source as the signal passes through the ever-changing density of the solar wind. Cross-correlation of simultaneous observations of IPS from a single radio source, received at multiple sites of the European Incoherent SCATter (EISCAT) radio antenna network, is used to determine the velocity of the solar wind material passing over the lines of sight of the antennas. Calculated velocities reveal the slow solar wind to contain rapid velocity variations when viewed on a time-scale of several minutes. Solar TErrestrial RElations Observatory (STEREO) Heliospheric Imager (HI) observations of white-light intensity have been compared with EISCAT observations of IPS to identify common density structures that may relate to the rapid velocity variations in the slow solar wind. We have surveyed a one-year period, starting in April 2007, of the EISCAT IPS observing campaigns beginning shortly after the commencement of full science operations of the STEREO mission in a bid to identify common density structures in both EISCAT and STEREO HI datasets. We provide a detailed investigation and presentation of joint IPS/HI observations from two specific intervals on 23 April 2007 and 19 May 2007 for which the IPS P-Point (point of closest approach of the line of sight to the Sun) was between 72 and 87 solar radii out from the Sun's centre. During the 23 April interval, a meso-scale (of the order of 105 km or larger) transient structure was observed by HI-1A to pass over the IPS ray path near the P-Point; the observations of IPS showed a micro-scale structure (of the order of 102 km) within the meso-scale transient. Observations of IPS from the second interval, on 19 May, revealed similar micro-scale velocity changes, however, no transient structures were detected by the HIs during that period. We also pose some fundamental thoughts on the slow solar wind structure itself.

  10. Estimation of power in low velocity vertical axis wind turbine

    NASA Astrophysics Data System (ADS)

    Sampath, S. S.; Shetty, Sawan; Chithirai Pon Selvan, M.

    2015-06-01

    The present work involves in the construction of a vertical axis wind turbine and the determination of power. Various different types of turbine blades are considered and the optimum blade is selected. Mechanical components of the entire setup are built to obtain maximum rotation per minute. The mechanical energy is converted into the electrical energy by coupling coaxially between the shaft and the generator. This setup produces sufficient power for consumption of household purposes which is economic and easily available.

  11. Velocity diffusion of energetic electrons in the solar wind

    NASA Astrophysics Data System (ADS)

    Volokitin, A.; Krafft, C.

    2016-03-01

    Particle diffusion in velocity space is studied on the basis of 1D simulations of Langmuir turbulence generated by electron beams in solar wind plasmas. Using a large amount of particle trajectories calculated with a great accuracy and over long times and analyzing them with statistical algorithms, the diffusion coefficients of particles in wave packets are estimated, as well as their relation to the waves' intensities and spectra and their dependence on the average level of background plasma density fluctuations. Results are compared with analytical solutions provided by the quasilinear theory of weak turbulence.

  12. 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.

  13. 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.

  14. Measurements of wind velocity and pressure with a wave follower during Marsen

    NASA Technical Reports Server (NTRS)

    Hsiao, S. V.; Shemdim, O. H.

    1983-01-01

    Air pressure data are used in determining the rate of momentum transfer from wind to waves. On the basis of the wind velocity measurements, the wave-induced airflow and its coherence with waves are obtained for various wind velocities and phase speeds of the ocean waves. The pressure results suggest that momentum transfer to waves can be specified by a certain relation, which is given. The wind-velocity results suggest that the wave-induced airflow is much smaller than the mean wind speed. An empirical equation is proposed for the modulation of atmospheric transfer to short waves caused by the orbital velocity of long waves.

  15. Maximum group velocity in a one-dimensional model with a sinusoidally varying staggered potential

    NASA Astrophysics Data System (ADS)

    Nag, Tanay; Sen, Diptiman; Dutta, Amit

    2015-06-01

    We use Floquet theory to study the maximum value of the stroboscopic group velocity in a one-dimensional tight-binding model subjected to an on-site staggered potential varying sinusoidally in time. The results obtained by numerically diagonalizing the Floquet operator are analyzed using a variety of analytical schemes. In the low-frequency limit we use adiabatic theory, while in the high-frequency limit the Magnus expansion of the Floquet Hamiltonian turns out to be appropriate. When the magnitude of the staggered potential is much greater or much less than the hopping, we use degenerate Floquet perturbation theory; we find that dynamical localization occurs in the former case when the maximum group velocity vanishes. Finally, starting from an "engineered" initial state where the particles (taken to be hard-core bosons) are localized in one part of the chain, we demonstrate that the existence of a maximum stroboscopic group velocity manifests in a light-cone-like spreading of the particles in real space.

  16. 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.

  17. 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.

  18. Multifractal two-scale Cantor set model for slow solar wind turbulence in the outer heliosphere during solar maximum

    NASA Astrophysics Data System (ADS)

    Macek, W. M.; Wawrzaszek, A.

    2011-05-01

    To quantify solar wind turbulence, we consider a generalized two-scale weighted Cantor set with two different scales describing nonuniform distribution of the kinetic energy flux between cascading eddies of various sizes. We examine generalized dimensions and the corresponding multifractal singularity spectrum depending on one probability measure parameter and two rescaling parameters. In particular, we analyse time series of velocities of the slow speed streams of the solar wind measured in situ by Voyager 2 spacecraft in the outer heliosphere during solar maximum at various distances from the Sun: 10, 30, and 65 AU. This allows us to look at the evolution of multifractal intermittent scaling of the solar wind in the distant heliosphere. Namely, it appears that while the degree of multifractality for the solar wind during solar maximum is only weakly correlated with the heliospheric distance, but the multifractal spectrum could substantially be asymmetric in a very distant heliosphere beyond the planetary orbits. Therefore, one could expect that this scaling near the frontiers of the heliosphere should rather be asymmetric. It is worth noting that for the model with two different scaling parameters a better agreement with the solar wind data is obtained, especially for the negative index of the generalized dimensions. Therefore we argue that there is a need to use a two-scale cascade model. Hence we propose this model as a useful tool for analysis of intermittent turbulence in various environments and we hope that our general asymmetric multifractal model could shed more light on the nature of turbulence.

  19. Sensitivity of estuarine turbidity maximum to settling velocity, tidal mixing, and sediment supply

    USGS Publications Warehouse

    Warner, J.C.; Sherwood, C.R.; Geyer, W.R.

    2007-01-01

    Estuarine turbidity maximum, numerical modeling, settling velocity, stratification The spatial and temporal distribution of suspended material in an Estuarine Turbidity Maxima (ETM) is primarily controlled by particle settling velocity, tidal mixing, shear-stress thresholds for resuspension, and sediment supply. We vary these parameters in numerical experiments of an idealized two-dimensional (x-z) estuary to demonstrate their affects on the development and retention of particles in an ETM. Parameters varied are the settling velocity (0.01, 0.1, and 0.5 mm/s), tidal amplitude (0.4 m 12 hour tide and 0.3 to 0.6 m 14 day spring neap cycle), and sediment availability (spatial supply limited or unlimited; and temporal supply as a riverine pulse during spring vs. neap tide). Results identify that particles with a low settling velocity are advected out of the estuary and particles with a high settling velocity provide little material transport to an ETM. Particles with an intermediate settling velocity develop an ETM with the greatest amount of material retained. For an unlimited supply of sediment the ETM and limit of salt intrusion co-vary during the spring neap cycle. The ETM migrates landward of the salt intrusion during spring tides and seaward during neap tides. For limited sediment supply the ETM does not respond as an erodible pool of sediment that advects landward and seaward with the salt front. The ETM is maintained seaward of the salt intrusion and controlled by the locus of sediment convergence in the bed. For temporal variability of sediment supplied from a riverine pulse, the ETM traps more sediment if the pulse encounters the salt intrusion at neap tides than during spring tides. ?? 2007 Elsevier B.V. All rights reserved.

  20. 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.

  1. 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.

  2. 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.

  3. Maximum likelihood estimation of blood velocity using Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Chan, Aaron C.; Merkle, Conrad W.; Lam, Edmund Y.; Srinivasan, Vivek J.

    2014-03-01

    A recent trend in optical coherence tomography (OCT) hardware has been the move towards higher A-scan rates. However, the estimation of axial blood flow velocities is affected by the presence and type of noise, as well as the estimation method. Higher acquisition rates alone do not enable the accurate quantification of axial blood velocity. Moreover, decorrelation is an unavoidable feature of OCT signals when there is motion relative to the OCT beam. For in-vivo OCT measurements of blood flow, decorrelation noise affects Doppler frequency estimation by broadening the signal spectrum. Here we derive a maximum likelihood estimator (MLE) for Doppler frequency estimation that takes into account spectral broadening due to decorrelation. We compare this estimator with existing techniques. Both theory and experiment show that this estimator is effective, and outperforms the Kasai and additive white Gaussian noise (AWGN) ML estimators. We find that maximum likelihood estimation can be useful for estimating Doppler shifts for slow axial flow and near transverse flow. Due to the inherent linear relationship between decorrelation and Doppler shift of scatterers moving relative to an OCT beam, decorrelation itself may be a measure of flow speed.

  4. Phase diagrams on an unsignalized intersection for the cases of different maximum velocities of vehicles

    NASA Astrophysics Data System (ADS)

    Li, Qi-Lang; Wang, Bing-Hong; Liu, Mu-Ren

    2012-01-01

    Using the cellular automaton traffic flow model, we investigate an unsignalized intersection which consists of two perpendicular one-lane roads. Both the roads cross at a point and the intersecting roads are cyclic. Each vehicle may pass or occupy the intersection where all the vehicles on both roads are not allowed to turn. Different from Ishibashi and Fukui's studies in which the update is carried out for both roads in turn, the parallel update is proposed and its detailed rules are presented in our model. In this work, the cases of different maximum vehicle velocities on both roads are considered. Based on simulation results and the principle for constructing phase diagrams, phase diagrams are mapped out and their specific flow formulas for all the regions in the phase diagrams are obtained for various vehicle densities, which are seldom done in previous studies. One also finds that the topology of phase diagrams depends on the update rules of eastbound and northbound roads and their maximum velocities of vehicles.

  5. Loop Current variability due to wind stress and reduced sea level during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Mildner, T. C.; Eden, C.; Nuernberg, D.; Schoenfeld, J.

    2011-12-01

    One of the most prominent features of the circulation in the Gulf of Mexico is the Loop Current (LC). It is of special interest as it influences not only the climate in the Gulf of Mexico. Although causation is not well understood yet, dynamical relationships between LC retraction and extension, seasonal migrations of the Intertropical Convergence Zone (ITCZ) and the related wind stress curl over the subtropical North Atlantic, and changes in the thermohaline circulation are indicated by model simulations. A characteristic feature of the LC is the shedding of anticyclonic eddies. These eddies can have depth signatures of up to 1000 m and are of special interest as they supply heat and moisture into the western and northern Gulf. The eddies are generated aperiodically every 3 to 21 months, with an average shedding time of 9.5 months. Eddy shedding appears to be related to a suite of oceanographic forcing fields such as the Yucatan Channel throughflow, the Florida Current and North Brazil Current variability, as well as synoptic meteorological forcing variability. By combining state-of-the-art paleoceanographic and meso-scale eddy-resolving numerical modeling techniques, we examined the Loop Current dynamics and hydrographic changes in the Gulf going back in time up to ~21,000 years. To assess the impact of Last Glacial Maximum (LGM) wind stress and reduced sea level we have re-configured an existing hierarchy of models of the North Atlantic Ocean (FLAME) with a horizontal grid resolution of ca. 30 km (wind stress was taken from the PMIP-II database). The sea level was lowered compared to the CONTROL run by 110 m and 67 m. These sea level changes have been chosen according to the cold-deglacial periods Heinrich I and Younger Dryas. The result of our model simulations is a continuous increase in eddy shedding from the LGM to the Holocene. This increase is predominantly controlled by the continuous deglacial sea level rise. Changes in wind stress curl related to the southward displacement of the ITCZ tend to produce larger Yucatan and Florida Strait throughflow but do not play a dominant role in controlling the eddy shedding, and appear thus of minor importance for the regional climate in the Gulf of Mexico. Comparing our results to observations we found that mean sortable silt values from Florida Strait depict an increase in bottom current velocities during cold climatic periods and times of lowered sea level, too. This is in contrast to recent hydrographic estimates pointing to reduced transports through the Florida Straits.

  6. Thermal acclimation effects differ between voluntary, maximum, and critical swimming velocities in two cyprinid fishes.

    PubMed

    O'Steen, Shyril; Bennett, Albert F

    2003-01-01

    Temperature acclimation may be a critical component of the locomotor physiology and ecology of ectothermic animals, particularly those living in eurythermal environments. Several studies of fish report striking acclimation of biochemical and kinetic properties in isolated muscle. However, the relatively few studies of whole-animal performance report variable acclimation responses. We test the hypothesis that different types of whole-animal locomotion will respond differently to temperature acclimation, probably due to divergent physiological bases of locomotion. We studied two cyprinid fishes, tinfoil barbs (Puntius schwanenfeldii) and river barbels (Barbus barbus). Study fish were acclimated to either cold or warm temperatures for at least 6 wk and then assayed at four test temperatures for three types of swimming performance. We measured voluntary swimming velocity to estimate routine locomotor behavior, maximum fast start velocity to estimate anaerobic capacity, and critical swimming velocity to estimate primarily aerobic capacity. All three performance measures showed some acute thermal dependence, generally a positive correlation between swimming speed and test temperature. However, each performance measure responded quite differently to acclimation. Critical speeds acclimated strongly, maximum speeds not at all, and voluntary speeds uniquely in each species. Thus we conclude that long-term temperature exposure can have very different consequences for different types of locomotion, consistent with our hypothesis. The data also address previous hypotheses that predict that polyploid and eurythermal fish will have greater acclimation abilities than other fish, due to increased genetic flexibility and ecological selection, respectively. Our results conflict with these predictions. River barbels are eurythermal polyploids and tinfoil barbs stenothermal diploids, yet voluntary swimming acclimated strongly in tinfoil barbs and minimally in river barbels, and acclimation was otherwise comparable. PMID:13130428

  7. A Statistical Analysis of 50 Years of Daily Solar Wind Velocity Data

    NASA Astrophysics Data System (ADS)

    LI, K. J.; ZHANNG, J.; FENG, W.

    2016-05-01

    Daily mean value of solar wind velocity measured by various spacecraft near the Earth’s orbit from 1963 November 27 to 2013 December 31 given by OMNIWeb is utilized to investigate its characteristics through statistical analyses. The percent probability distribution of solar wind velocity can be described well by the Γ distribution function with the most probable velocity to be 373 {km} {{{s}}}-1. It is found that solar wind could be statistically classified into three groups: (1) the low-velocity wind, v\\lt 450 {km} {{{s}}}-1, which positively responds to, and in the cycle phase lags, the solar activity cycle; (2) the high-velocity wind, 450≤slant v\\lt 725 {km} {{{s}}}-1, which negatively responds to, and in the cycle phase leads, the solar activity cycle, but in a short timescale (one-rotation-period) lags the solar activity cycle; and (3) the extreme-high-velocity wind, v≥slant 725 {km} {{{s}}}-1, which positively responds to, and in cycle phase leads, the solar activity cycle. A period of about 27 days is determined for solar wind in the first two groups, so that solar wind in the groups is modulated by the solar rotation and related with solar long-life magnetic structures. Solar wind of extreme high velocity appears mainly at the descending phases of the solar cycles.

  8. 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 ...

  9. Generalized multidemensional propagation velocity equations for pool-boiling superconducting windings

    SciTech Connect

    Christensen, E.H.; O'Loughlin, J.M.

    1984-09-01

    Several finite difference, finite element detailed analyses of propagation velocities in up to three dimensions in pool-boiling windings have been conducted for different electromagnetic and cryogenic environments. Likewise, a few full scale simulated winding and magnet tests have measured propagation velocities. These velocity data have been correlated in terms of winding thermophysical parameters. This analysis expresses longitudinal and transverse propagation velocities in the form of power function regression equations for a wide variety of windings and electromagnetic and thermohydraulic environments. The generalized velocity equations are considered applicable to well-ventilated, monolithic conductor windings. These design equations are used piecewise in a gross finite difference mode as functions of field to predict the rate of normal zone growth during quench conditions. A further check of the validity of these predictions is available through total predicted quench durations correlated with actual quench durations of large magnets.

  10. 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.

  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 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.

  12. Analysis of the Velocity Distribution in Partially-Filled Circular Pipe Employing the Principle of Maximum Entropy.

    PubMed

    Jiang, Yulin; Li, Bin; Chen, Jie

    2016-01-01

    The flow velocity distribution in partially-filled circular pipe was investigated in this paper. The velocity profile is different from full-filled pipe flow, since the flow is driven by gravity, not by pressure. The research findings show that the position of maximum flow is below the water surface, and varies with the water depth. In the region of near tube wall, the fluid velocity is mainly influenced by the friction of the wall and the pipe bottom slope, and the variation of velocity is similar to full-filled pipe. But near the free water surface, the velocity distribution is mainly affected by the contractive tube wall and the secondary flow, and the variation of the velocity is relatively small. Literature retrieval results show relatively less research has been shown on the practical expression to describe the velocity distribution of partially-filled circular pipe. An expression of two-dimensional (2D) velocity distribution in partially-filled circular pipe flow was derived based on the principle of maximum entropy (POME). Different entropies were compared according to fluid knowledge, and non-extensive entropy was chosen. A new cumulative distribution function (CDF) of partially-filled circular pipe velocity in terms of flow depth was hypothesized. Combined with the CDF hypothesis, the 2D velocity distribution was derived, and the position of maximum velocity distribution was analyzed. The experimental results show that the estimated velocity values based on the principle of maximum Tsallis wavelet entropy are in good agreement with measured values. PMID:26986064

  13. Analysis of the Velocity Distribution in Partially-Filled Circular Pipe Employing the Principle of Maximum Entropy

    PubMed Central

    2016-01-01

    The flow velocity distribution in partially-filled circular pipe was investigated in this paper. The velocity profile is different from full-filled pipe flow, since the flow is driven by gravity, not by pressure. The research findings show that the position of maximum flow is below the water surface, and varies with the water depth. In the region of near tube wall, the fluid velocity is mainly influenced by the friction of the wall and the pipe bottom slope, and the variation of velocity is similar to full-filled pipe. But near the free water surface, the velocity distribution is mainly affected by the contractive tube wall and the secondary flow, and the variation of the velocity is relatively small. Literature retrieval results show relatively less research has been shown on the practical expression to describe the velocity distribution of partially-filled circular pipe. An expression of two-dimensional (2D) velocity distribution in partially-filled circular pipe flow was derived based on the principle of maximum entropy (POME). Different entropies were compared according to fluid knowledge, and non-extensive entropy was chosen. A new cumulative distribution function (CDF) of partially-filled circular pipe velocity in terms of flow depth was hypothesized. Combined with the CDF hypothesis, the 2D velocity distribution was derived, and the position of maximum velocity distribution was analyzed. The experimental results show that the estimated velocity values based on the principle of maximum Tsallis wavelet entropy are in good agreement with measured values. PMID:26986064

  14. Effects of forward velocity on noise for a J85 turbojet engine with multitube suppressor from wind tunnel and flight tests

    NASA Technical Reports Server (NTRS)

    Stone, J. R.; Miles, J. H.; Sargent, N. B.

    1976-01-01

    Flight and wind tunnel noise tests were conducted using a J85 turbojet engine as a part of comprehensive programs to obtain an understanding of forward velocity effects on jet exhaust noise. Nozzle configurations of primary interest were a 104-tube suppressor with and without an acoustically-treated shroud. The installed configuration of the engine was as similar as possible in the flight and wind tunnel tests. Exact simultaneous matching of engine speed, exhaust velocity, and exhaust temperature was not possible, and the wind tunnel maximum Mach number was approximately 0.27, while the flight Mach number was approximately 0.37. The nominal jet velocity range was 450 to 640 m/sec. For both experiments, background noise limited the jet velocity range for which significant data could be obtained. In the present tests the observed directivity and forward velocity effects for the suppressor are more similar to predicted trends for internally-generated noise than unsuppressed jet noise.

  15. Wind Observations of Anomalous Cosmic Rays from Solar Minimum to Maximum

    NASA Technical Reports Server (NTRS)

    Reames, D. V.; McDonald, F. B.

    2003-01-01

    We report the first observation near Earth of the time behavior of anomalous cosmic-ray N, O, and Ne ions through the period surrounding the maximum of the solar cycle. These observations were made by the Wind spacecraft during the 1995-2002 period spanning times from solar minimum through solar maximum. Comparison of anomalous and galactic cosmic rays provides a powerful tool for the study of the physics of solar modulation throughout the solar cycle.

  16. Passive acoustic measurements of wind velocity and sound speed in air.

    PubMed

    Godin, Oleg A; Irisov, Vladimir G; Charnotskii, Mikhail I

    2014-02-01

    Random acoustic fields generated by uncorrelated sources in moving media contain information about the propagation environment, including sound speed and flow velocity. This information can be recovered by noise interferometry. Here interferometric techniques are applied to road traffic noise. Acoustic travel times and their nonreciprocity are retrieved from two-point cross-correlation functions of noise. The feasibility of passive acoustic measurements of wind velocity using diffuse noise is experimentally demonstrated for the first time. The accuracy of the interferometric measurements of sound speed and wind velocity is confirmed by comparison with in situ measurements of wind, air temperature, and humidity. PMID:25234917

  17. Method for Determination of the Wind Velocity and Direction

    NASA Technical Reports Server (NTRS)

    Dahlin, Goesta Johan

    1988-01-01

    Accurate determination of the position of an artillery piece, for example, using sound measurement systems through measurement of the muzzle noise requires access to wind data that is representative of the portion of the air from where the sound wave is propagated up the microphone base of the system. The invention provides a system for determining such representative wind data.

  18. 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

  19. 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

  20. Dependence of velocity fluctuations on solar wind speeds: A simple analysis with IPS method

    NASA Technical Reports Server (NTRS)

    Misawa, H.; Kojima, M.

    1995-01-01

    A number of theoretical works have suggested that MHD plasma fluctuations in solar winds should play an important role particularly in the acceleration of high speed winds inside or near 0.1 AU from the sun. Since velocity fluctuations in solar winds are expected to be caused by the MHD plasma fluctuations, measurements of the velocity fluctuations give clues to reveal the acceleration process of solar winds. We made interplanetary scintillation (IPS) observations at the region out of 0.1 AU to investigate dependence of velocity fluctuations on flow speeds. For evaluating the velocity fluctuation of a flow, we selected the IPS data-set acquired at 2 separate antennas which located in the projected flow direction onto the baseline plane, and tried to compare skewness of the observed cross correlation function(CCF) with skewness of modeled CCFs in which velocity fluctuations were parametrized. The integration effect of IPS along a ray path was also taken into account in the estimation of modeled CCFs. Although this analysis method is significant to derive only parallel fluctuation components to the flow directions, preliminary analyses show following results: (1) High speed winds (Vsw greater than or equal to 500 km/s out of 0.3 AU) indicate enhancement of velocity fluctuations near 0.1 AU; and (2) Low speed winds (Vsw less than or equal to 400 Km/s out of 0.3 AU) indicate small velocity fluctuations at any distances.

  1. The stellar wind velocity function for red supergiants determined in eclipsing binaries

    NASA Technical Reports Server (NTRS)

    Ahmad, Imad A.; Stencel, Robert E.

    1988-01-01

    The potential for direct measurement of the acceleration of stellar winds from the supergiant component of Zeta Aurigae-type binary stars is discussed. The aberration angle of the interaction shock cone centered on the hot star provides a measure of the velocity of the cool star wind at the orbit of the secondary. This is confirmed by direct observations of stellar wind (P Cygni) line profile variations. This velocity is generally smaller than the final (terminal) velocity of the wind, deduced from the P Cygni line profiles. The contrast between these results and previously published supergiant wind models is discussed. The implication on the physics of energy source dissipation predicted in the theoretical models is considered.

  2. 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.

  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.

    1976-01-01

    Strong 10-micron line emission from (C-12)(O-16)2 in the upper atmosphere of Venus has been detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicated mean zonal wind velocities less than 10 m/s in the upper atmosphere near the equator. No evidence was found for the 100-m/s wind velocity implied by the apparent four-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. Solar wind velocity and temperature in the outer heliosphere

    NASA Technical Reports Server (NTRS)

    Gazis, P. R.; Barnes, A.; Mihalov, J. D.; Lazarus, A. J.

    1994-01-01

    At the end of 1992, the Pioneer 10, Pioneer 11, and Voyager 2 spacecraft were at heliocentric distances of 56.0, 37.3, and 39.0 AU and heliographic latitudes of 3.3 deg N, 17.4 deg N, and 8.6 deg S, respectively. Pioneer 11 and Voyager 2 are at similar celestial longitudes, while Pioneer 10 is on the opposite side of the Sun. All three spacecraft have working plasma analyzers, so intercomparison of data from these spacecraft provides important information about the global character of the solar wind in the outer heliosphere. The averaged solar wind speed continued to exhibit its well-known variation with solar cycle: Even at heliocentric distances greater than 50 AU, the average speed is highest during the declining phase of the solar cycle and lowest near solar minimum. There was a strong latitudinal gradient in solar wind speed between 3 deg and 17 deg N during the last solar minimum, but this gradient has since disappeared. The solar wind temperature declined with increasing heliocentric distance out to a heliocentric distance of at least 20 AU; this decline appeared to continue at larger heliocentric distances, but temperatures in the outer heliosphere were suprisingly high. While Pioneer 10 and Voyager 2 observed comparable solar wind temperatures, the temperature at Pioneer 11 was significantly higher, which suggests the existence of a large-scale variation of temperature with heliographic longitude. There was also some suggestion that solar wind temperatures were higher near solar minimum.

  6. 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...

  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. Quasi-decadal variations in total ozone content, wind velocity, temperature, and geopotential height over the Arosa station (Switzerland)

    NASA Astrophysics Data System (ADS)

    Visheratin, K. N.

    2016-01-01

    We present the results of the analysis of the phase relationships between the quasi-decadal variations (QDVs) (in the range from 8 to 13 years) in the total ozone content (TOC) at the Arosa station for 1932-2012 and a number of meteorological parameters: monthly mean values of temperature, meridional and zonal components of wind velocity, and geopotential heights for isobaric surfaces in the layer of 10-925 hPa over the Arosa station using the Fourier methods and composite and cross-wavelet analysis. It has been shown that the phase relationships of the QDVs in the TOC and meteorological parameters with an 11-year cycle of solar activity change in time and height; starting with cycle 24 of solar activity (2008-2010), the variations in the TOC and a number of meteorological parameters occur in almost counter phase with the variations in solar activity. The periods of the maximum growth rate of the temperature at isobaric surfaces 50-100 hPa nearly correspond to the TOC's maximum periods, and the periods of the maximum temperature correspond the periods of the decrease of the peak TOC rate. The highest correlation coefficients between the meridional wind velocity and temperature are observed at 50 hPa at positive and negative delays of ~27 months. The times of the maxima (minima) of the QDVs in the meridional wind velocity nearly correspond to the periods of the maximum amplification (attenuation) rate of the temperature of the QDVs. The QDVs in the geopotential heights of isobaric surfaces fall behind the variations in the TOC by an average of 1.5 years everywhere except in the lower troposphere. In general, the periods of variations in the TOC and meteorological parameters in the range of 8-13 years are smaller than the period of variations in the level of solar activity.

  9. 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.

  10. Influence of wind velocity on pollen concentration in urban canopy layer

    NASA Astrophysics Data System (ADS)

    Pospisil, J.; Jícha, M.

    2009-09-01

    POLLEN RELEASE Temperature is the basic parameter for prediction of the beginning of the pollen season and identification days with good potential for pollen release. Different approaches are used for determination of the start of the pollen season: i) the sum of daily pollen counts = x criterion (Arnold 2002), ii) the mean temperature method during pre-defined period (Sparks, 2000), iii) the temperature sum method (Jones 1992). Another parameters influencing pollen release are: day light length, morning temperature gradient, relative humidity. The mentioned parameters enable to create the "statistical” model for determination of timing of pollen potential release. But, the correct determination of pollen release timing is only the first step to correct prediction of pollen concentration in air. The above mentioned collection of parameters isn't complete for correct pollen production prediction without inclusion of the actual wind velocity. The wind velocity directly influences the pollen release rate from mother plant and subsequently transport of pollen grains. From this reason, influence of wind conditions has to be considered as exactly as possible in complex prediction models. WIND VELOCITY AND POLLEN CONCENTRATION Results of in-situ measurements were used for carried out analysis of the relation between wind velocity and pollen concentration in an urban canopy layer. The mean daily wind velocities and the mean daily pollen concentrations were used as the input data describing the pollen season 2005 in an inner part of the city of Brno (pop. 400 000). The mean daily pollen concentrations were matched to corresponding mean daily wind velocity and depicted in graphs. This procedure was done for all locally monitored aeroallergens, namely Alnus, Ambrosia, Betula, Artemis, Corylus, Fraxinus, Poaceae and Quercus. Only days with significant pollen concentration (above 10% of maximal pollen season concentration) were considered for detail analysis. Clear evidence of the wind threshold velocity of pollination appears in the carried out graphical expression of in-situ measurement. The threshold velocity of pollination is the lowest wind velocity with significant concentration of pollen grains in the air. Wind velocity increase above the wind threshold velocity of pollination causes another increase in pollen maximal concentration until reaching the highest concentration of the pollen season. This trend reflects increase in the total pollen release rate due to increase of the air velocity in deeper layers of vegetation and branch bundles. Another increase of wind velocity causes decrease of the maximal air pollen concentration due to "dilution” of the canopy layer by vast quantity of fresh air. The described "triangle" trend was confirmed for majority of considered species. The particularly determined values of the wind threshold velocity of pollination in urban area are: Alnus 0,66 m/s, Ambrosia 0,4 m/s, Betula 0,59 m/s, Artemis 0,62 m/s, Corylus 0,75 m/s, Fraxinus 0,5 m/s, Poaceae 0,45 m/s and Quercus 0,66 m/s. The wind velocities corresponding to the highest pollen concentration values are: Alnus 0,95 m/s, Ambrosia 1,01 m/s, Betula 1,1 m/s, Artemis 0,8 m/s, Corylus 0,95 m/s, Fraxinus 1,1 m/s, Poaceae 1,29 m/s and Quercus 0,96 m/s.

  11. On the relationships of gas transfer velocity with turbulent kinetic energy dissipation rate and wind waves

    NASA Astrophysics Data System (ADS)

    Zhao, D.

    2012-12-01

    The exchange of carbon dioxide across the air-sea interface is an important component of the atmospheric CO2 budget. Understanding how future changes in climate will affect oceanic uptake and releaser CO2 requires accurate estimation of air-sea CO2 flux. This flux is typically expressed as the product of gas transfer velocity, CO2 partial pressure difference in seawater and air, and the CO2 solubility. As the key parameter, gas transfer velocity has long been known to be controlled by the near-surface turbulence in water, which is affected by many factors, such as wind forcing, ocean waves, water-side convection and rainfall. Although the wind forcing is believed as the major factor dominating the near-surface turbulence, many studies have shown that the wind waves and their breaking would greatly enhance turbulence compared with the classical solid wall theory. Gas transfer velocity has been parameterized in terms of wind speed, turbulent kinetic energy dissipation rate, and wave parameters on the basis of observational data or theoretical analysis. However, great discrepancies, as large as one order, exist among these formulas. In this study, we will systematically analyze the differences of gas transfer velocity proposed so far, and try to find the reason that leads to their uncertainties. Finally, a new formula for gas transfer velocity will be given in terms of wind speed and wind wave parameter.

  12. Altitude profile of the polar wind velocity and its relationship to ionospheric conditions

    SciTech Connect

    Abe, T. ); Whalen, B.A.; Yau, A.W. ); Watanabe, S. ); Sagawa, E. ); Oyama, K.I. )

    1993-12-23

    The authors report recent results from the Akebono satellite. They present data on polar wind velocities, examined in conjunction with electron properties, as a function of altitude in the ionosphere. This data came from the Suprathermal ion Mass Spectrometer and the Thermal Electron energy Distribution instruments. The measurements show a vertical component to the polar wind, consistent with model results, when measured in terms of H[sup +] ions. There was a definite altitude dependence of the velocity of the hydrogen ions, and there was also a positive correlation of this velocity with the measured electron temperature.

  13. 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.

    2015-01-01

    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 the measurements of the Doppler lidar can extent the view of the cloud radar and the wind profiler, especially when observing clouds.

  14. 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.

  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 Qur, 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 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 (>4C) 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. Magnetic Cloud Field Intensities and Solar Wind Velocities

    NASA Technical Reports Server (NTRS)

    Gonzalez, Walter D.; Clau de Gonzalez, Alicia D.; Tsurutani, Bruce T.; Arballo, John K.

    1997-01-01

    For the sets of magnetic clouds studied in this work we have shown that there is a general relationship between their magnetic fields strength and velocities. With a clear tendency that the faster the speed of the cloud the higher the magnetic field.

  17. Hydrogen and helium velocities in the solar wind.

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Zwally, H. J.

    1972-01-01

    Examination of separately determined helium and hydrogen bulk speeds in the solar wind show these to be equal, both on time scales of 30 min and 3 min. Observations of two interplanetary shocks and 12 discontinuities show the changes in bulk speed across them to take place simultaneously for the two species. Observations made at times of high helium abundance following an interplanetary shock, and at times of observation of colliding streams in the plasma, confirm the conclusion that, if bulk speed differences between species occur, they do so very rarely.

  18. Dependence of velocity fluctuations on solar wind speeds from an IPS analysis method

    SciTech Connect

    Misawa, Hiroaki; Kojima, Masayoshi

    1996-07-20

    Interplanetary scintillation (IPS) observations were made with radio telescopes of the STE Lab. (327 MHz) and the EISCAT facilities (932 MHz) in 1993 and 1994 to investigate the dependence of the parallel component of velocity fluctuation ({delta}V{sub parallel}) on flow speeds. Preliminary analyses show the following results; 1) {delta}V{sub parallel} in high speed winds (V{sub IPS}> or approx. 500 km/s at distances beyond 0.3 AU) increases with approaching the sun, 2) Low speed winds (V{sub IPS} < or approx. 400 km/s at distances beyond 0.3AU) have a small {delta}V{sub parallel} at all distances. Here, V{sub IPS} is the solar wind velocity observed with the IPS method. Since the parallel fluctuation component is expected to be related to magnetoacoustic waves near the sun, the results infer that magnetoacoustic waves have some relation to the acceleration of high speed solar winds.

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

    NASA Astrophysics Data System (ADS)

    Mursula, Kalevi; Lukianova, Renata; Holappa, Lauri

    2015-04-01

    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, suggesting that typically only one strong activation leading to a coronal hole extension is responsible for the HSS maximum. We find that the most persistent HSS activity occurred in the declining phase of solar cycle 18. This suggests that cycle 19, which marks the sunspot maximum period of the GMM, was preceded by exceptionally strong polar fields during the previous sunspot minimum. This gives interesting support for the validity of solar dynamo theory during this dramatic period of solar magnetism.

  1. 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.

  2. Latitude dependence of solar wind velocity observed > or approx. =1 AU

    SciTech Connect

    Mitchell, D.G.; Roelof, E.C.; Wolfe, J.H.

    1981-01-01

    The large-scale solar wind velocity structure in the outer heliosphere has been systematically analyzed for Carrington rotations 1587-1541 (March 1972 to April 1976). Spacecraft data were taken from Imp 7/8 at earth, Pioneer 6, 8, and 9 near 1AU, and Pioneer 10 and 11 between 1.6 and 5 AU. Using the constant radial velocity solar wind approximation to map all of the velocity data to its high coronal emission heliolongitude, we examined the velocity structure observed at different spacecraft for latitudinal dependence and compared it with coronal structure in soft X rays and Ha absorption features. The constant radial velocity approximation usually remains self-consistent in decreasing or constant velocity solar wind out to 5 AU, enabling us to separate radial from latitudinal propagation effects. We found several examples of sharp nonmeridional stream boundaries in interplanetary space (approx.5/sup 0/ latitude in width), often directly associated with features in coronal X rays and Ha. In one structure there is evidence for significant (up to 40/sup 0/) nonradial flow of the plasma in the corona below the altitude of transition to super-Alfvenic flow.

  3. Latitude dependence of solar wind velocity observed at not less than 1 AU

    NASA Technical Reports Server (NTRS)

    Mitchell, D. G.; Roelof, E. C.; Wolfe, J. H.

    1981-01-01

    The large-scale solar wind velocity structure in the outer heliosphere has been systematically analyzed for Carrington rotations 1587-1541 (March 1972 to April 1976). Spacecraft data were taken from Imp 7/8 at earth, Pioneer 6, 8, and 9 near 1 AU, and Pioneer 10 and 11 between 1.6 and 5 AU. Using the constant radial velocity solar wind approximation to map all of the velocity data to its high coronal emission heliolongitude, the velocity structure observed at different spacecraft was examined for latitudinal dependence and compared with coronal structure in soft X-rays and H-alpha absorption features. The constant radial velocity approximation usually remains self-consistent in decreasing or constant velocity solar wind out to 5 AU, enabling us to separate radial from latitudinal propagation effects. Several examples of sharp nonmeridional stream boundaries in interplanetary space (about 5 deg latitude in width), often directly associated with features in coronal X-rays and H-alpha were found.

  4. Occurrence of High-speed Solar Wind Streams over the Grand Modern Maximum

    NASA Astrophysics Data System (ADS)

    Mursula, K.; Lukianova, R.; Holappa, L.

    2015-03-01

    In the declining phase of the solar cycle (SC), 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 (SW) streams (HSS) and related co-rotating interaction regions in the low-latitude heliosphere, and cause moderate, recurrent geomagnetic activity (GA) in the near-Earth space. Here, using a novel definition of GA at high (polar cap) latitudes and the longest record of magnetic observations at a polar cap station, we calculate the annually averaged SW speeds as proxies for the effective annual occurrence of HSS over the whole Grand Modern Maximum (GMM) from 1920s onward. We find that a period of high annual speeds (frequent occurrence of HSS) occurs in the declining phase of each of SCs 16-23. For most cycles the HSS activity clearly reaches a maximum in one year, suggesting that typically only one strong activation leading to a coronal hole extension is responsible for the HSS maximum. We find that the most persistent HSS activity occurred in the declining phase of SC 18. This suggests that cycle 19, which marks the sunspot maximum period of the GMM, was preceded by exceptionally strong polar fields during the previous sunspot minimum. This gives interesting support for the validity of solar dynamo theory during this dramatic period of solar magnetism.

  5. 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.

  6. Correlated studies at activity maximum: The Sun and the solar wind

    NASA Technical Reports Server (NTRS)

    Hudson, H. S.; Galvin, A. B.

    1997-01-01

    The breadth and power of the set of solar and heliospheric observatories presently in space is unprecedented. Their observations generally began at solar minimum or in the declining phase of the past maximum, but it is anticipated that most of the instruments will be able to observe the rise to the next maximum and that the events will happen then. The second orbit of Ulysses will be especially interesting and the Yokhoh orbital decay is not projected until 2002. New spacecraft, including TRACE, HESSI, and SOLAR-B, may also become available. The current remote sensing and in situ measurements are characterized by a much stronger understanding of how the solar and interplanetary phenomena match. The novel discoveries from the current data are reviewed, and speculations are expressed on how to take advantage of the future data, emphasizing the use of heliospheric observations to help probe the connectivity of the corona/solar wind interface region. It is suggested that there now exists a possibility of understanding the heliospheric structure empirically in new ways: by using particles as tracers of the field, and by correlating multi-point measurements of structures in the solar wind with solar images.

  7. 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.

  8. Reduction of Near-Inertial Energy by Ocean-Surface-Velocity-Dependent Wind Stress

    NASA Astrophysics Data System (ADS)

    Rath, Willi; Greatbatch, Richard; Zhai, Xiaoming

    2013-04-01

    This study aims at understanding the effect of including or neglecting the surface velocity of the ocean into the wind stress parameterization for the strength and distribution of near-inertial oscillations. Wind-generated near-inertial oscillations are an important source of energy for surface mixed layer deepening as well as for internal wave breaking and the associated diapycnal mixing at depth which, in turn, is thought to be important for driving the meridional overturning circulation. By using a realistic primitive equation model of the Southern Ocean at eddying resolution, we find that including ocean surface velocities into the wind stress leads to a large reduction of both wind power input into near-inertial oscillations (WPI) and near-inertial energy (NIE) in the surface mixed layer. The relative reduction of WPI can be as large as 30 percent and the relative reduction of NIE can be as large as 50 percent. Using both, the primitive equation model and a simple linear local slab-ocean model for illustration, we find that a large part of this reduction can be explained by the leading order modification to the wind stress if ocean surface velocities are included. We also find that the strength of the reduction is modulated by the inverse of the ocean surface mixed layer depth.

  9. Active removal of wind noise from outdoor microphones using local velocity measurements

    NASA Astrophysics Data System (ADS)

    Shust, Michael Ray

    1998-07-01

    Wind noise in outdoor microphone measurements can significantly degrade acoustic data. Since acoustic and wind spectra often overlap when low frequency acoustic sources are observed, wind noise is generally impossible to remove by band selective filtering. This research examines active removal of wind noise from an outdoor microphone. Measurements performed outdoors on a horizontally positioned microphone demonstrate that a major part of unscreened microphone wind noise is flow noise caused by interaction between the microphone and adjacent air flow. It is concluded that pressure fluctuations in the passing air volume are a second significant contributor. While wind noise contamination is most often treated with passive spherical foam windscreens, an active wind noise reduction system based upon local velocity measurements applied to a passively screened or unscreened microphone is proposed. A simple relationship, developed from the Bernoulli equation, is used to transform these wind velocity measurements into microphone wind pressure estimates. Extensive measurements of coherence between these anemometer derived pressure estimates and wind noise in screened and unscreened microphones are performed for a variety of anemometer positions. These measurements indicate the dominant source of wind noise in a passively screened microphone is local pressure fluctuations that are not correlated with pressure estimates based on local velocity fluctuations. This important observation indicates than an active system based upon velocity measurements is unlikely to quiet a microphone that has convential passive screening by a substantial amount and that an active system based upon velocity measurements applied to an unscreened microphone is unlikely to surpass the performance of a passively screened microphone. An outdoor active wind noise cancellation system is demonstrated for a horizontally positioned unscreened microphone. A signal space approach is used to determine the effectiveness of single and multiple anemometer channels in the system and it is shown that while additional quieting is obtained with additional anemometers the additional quieting achieved diminishes rapidly with new channels. The active system transfer functions are observed to possess significant stability of over periods of tens of minutes to hours. This stability apparently depends upon the stability of the wind environment. It is concluded that adaptive active quieting systems would require only infrequent updates in such an environment. System performance with a four channel anemometer system is observed to be similar to that using a small passive screen. Wind energy reduction performance of the active windscreen is shown to be between 10 and 13 dB for frequencies below 200Hz and this performance decreases smoothly to approximately 5 dB at 500 Hz. The active system has application when the presence or physical size of the passive windscreen is undesirable. Further, it is concluded that the concepts presented also provide an effective approach for studying the behavior of passive wind screens and outdoor microphone wind noise.

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

    NASA Astrophysics Data System (ADS)

    Küpper, Markus; Wurm, Gerhard

    2015-07-01

    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 subsurface overpressure which supports lift imposed by wind. The wind tunnel was run with Mojave Mars Simulant and air at 3, 6, and 9mbar, 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.

  11. Atlantic Tropical Cyclone Monitoring with AMSU-A: Estimation of Maximum Sustained Wind Speeds

    NASA Technical Reports Server (NTRS)

    Spencer, Roy; Braswell, William D.; Goodman, H. Michael (Technical Monitor)

    2001-01-01

    The first Advanced Microwave Sounding Unit temperature sounder (AMSU-A) was launched on the NOAA-15 satellite on 13 May 1998. The AMSU-A's higher spatial and radiometric resolutions provide more useful information on the strength of the middle and upper tropospheric warm cores associated with tropical cyclones than have previous microwave temperature sounders. The gradient wind relationship suggests that the temperature gradient near the core of tropical cyclones increases nonlinearly with wind speed. We recast the gradient wind equation to include AMSU-A derived variables. Stepwise regression is used to determine which of these variables is most closely related to maximum sustained winds (V(sub max)). The satellite variables investigated include the radially averaged gradients at two spatial resolutions of AMSU-A channels 1 through 10 T(sub b) data (delta(sub r)T(sub b)), the squares of these gradients, a channel 15 based scattering index (SI-89), and area averaged T(sub b). Calculations of Tb and delta(sub r)T(sub b) from mesoscale model simulations of Andrew reveal the effects of the AMSU spatial sampling on the cyclone warm core presentation. Stepwise regression of 66 AMSU-A terms against National Hurricane Center (NHC) V(sub max) estimates from the 1998 and 1999 Atlantic hurricane season confirms the existence of a nonlinear relationship between wind speed and radially averaged temperature gradients near the cyclone warm core. Of six regression terms, four are dominated by temperature information, and two are interpreted as correcting for hydrometeor contamination. Jackknifed regressions were performed to estimate the algorithm performance on independent data. For the 82 cases that had in situ measurements of V(sub max), the average error standard deviation was 4.7 m/s. For 108 cases without in situ wind data, the average error standard deviation was 7.5 m/s. Operational considerations, including the detection of weak cyclones and false alarm reduction are also discussed.

  12. Atlantic Tropical Cyclone Monitoring with AMSU-A: Estimation of Maximum Sustained Wind Speeds

    NASA Technical Reports Server (NTRS)

    Spencer, Roy W.; Braswell, William D.

    2001-01-01

    The first Advanced Microwave Sounding Unit temperature sounder (AMSU-A) was launched on the NOAA-15 satellite on 13 May 1998. The AMSU-A's higher spatial and radiometric resolutions provide more useful information on the strength of the middle- and upper-tropospheric warm cores associated with tropical cyclones than have previous microwave temperature sounders. The gradient wind relationship suggests that the temperature gradient near the core of tropical cyclones increases nonlinearly with wind speed. The gradient wind equation is recast to include AMSU-A-derived variables, Stepwise regression is used to determine which of these variables is most closely related to maximum sustained winds (V(sub max)). The satellite variables investigated include the radially averaged gradients at two spatial resolutions of AMSU-A channels 1-10 T(sub b) data (delta(sub r)T(sub B)), the squares of these gradients, a channel-15-based scattering index (SI(sub 89)), and area-averaged T(sub B). Calculations of T(sub B) and delta(sub r)T(sub B) from mesoscale model simulations of Andrew reveal the effects of the AMSU spatial sampling on the cyclone warm core presentation. Stepwise regression of 66 AMSU-A terms against National Hurricane Center V(sub max) estimates from the 1998 and 1999 Atlantic hurricane season confirms the existence of a nonlinear relationship between wind speed and radially averaged temperature gradients near the cyclone warm core. Of six regression terms, four are dominated by temperature information, and two are interpreted as correcting for hydrometeor contamination. Jackknifed regressions were performed to estimate the algorithm performance on independent data. For the 82 cases that had in situ measurements of V(sub max), the average error standard deviation was 4.7 m/s. For 108 cases without in situ wind data, the average error standard deviation was 7.5 m/s Operational considerations, including the detection of weak cyclones and false alarm reduction, are also discussed.

  13. A Survey of Velocity Distributions of Solar Wind Ions : ACE/SWICS observations

    NASA Astrophysics Data System (ADS)

    Berger, L.; Marsch, E.; Wimmer-Schweingruber, R. F.

    2014-12-01

    The state of solar wind ions is generally described by a small set of state variables. In detail these aretotal density (or flux), center of mass (or bulk) velocity, and temperature. These variables are obtainedfrom measured velocity distributions either by fitting a Maxwell-Boltzmann distribution or by calculatingthe zeroth, first, and second order moments of the distribution. Obviously the first approach requires athermalized distribution to yield meaningful results, while the second approach is universally valid.However, in both cases the shape of the distribution can not be reproduced by the derived parameters.From observations of solar wind protons and alpha particles it is known that the assumption of a thermalized distribution is not valid, at least for the majority of observations. For heavy solar wind ions most observationsare severely limited by statistics and do not even allow to distinguish whether the distribution is thermal or not.This often insufficient characterization of the solar wind VDF severely limits the information which can beobtained for more detailed studies, especially about microscopic kinetic physics and the associatedwave-particle interactions. These naturally yield deviations from Maxwell-Boltzmann distributions.To address this problem we have analyzed ten years worth of data from the Solar Wind Ion Composition Spectrometer (SWICS)and the Magnetometer (MAG) on the Advanced Composition Explorer (ACE). From our analysis we obtained reduced 1D velocity spectra in 12 minute cadence for some 40 solar wind ions, from protons and alpha particles up to iron.Using the magnetic field vector information we were able to study periods where the reduced 1D spectra representthe parallel and perpendicular shape of the velocity distributions. We present our results and discussthem in the aforementioned context.

  14. 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.

  15. LDA system for long-range cross-wind velocity measurements using pulsed laser radiation

    NASA Astrophysics Data System (ADS)

    Sommer, E.; Pfeifer, H. J.

    1986-07-01

    A mobile long-range LDA system, using frequency-doubled Nd:YAG lasers to deliver long-duration, nearly rectangular pulses with low electrical input, for the measurement of the atmospheric crosswind velocity is described. A microcomputer controls the correlator and contains new software to extract the wind velocity information from the LDA signals, taking into acount the particular shape of the signals and the occasionally poor SNR. Field measurements carried out over a distance of 100 m show that though the SNR is high enough under certain weather conditions to obtain accurate cross-wind velocity components, signals of good quality cannot be obtained either if the atmospheric optical scintillation is too high, or if the particle size distribution is biased towards particles with diameters of less than 5 microns.

  16. 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.

  17. 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.

  18. On the stability of the moments of the maximum entropy wind wave spectrum

    SciTech Connect

    Pena, H.G.

    1983-03-01

    The stability of some current wind wave parameters as a function of high-frequency cut-off and degrees of freedom of the spectrum has been numerically investigated when computed in terms of the moments of the wave energy spectrum. From the Pierson-Moskovitz wave spectrum type, a sea surface profile is simulated and its wave energy spectrum is estimated by the Maximum Entropy Method (MEM). As the degrees of freedom of the MEM spectral estimation are varied, the results show a much better stability of the wave parameters as compared to the classical periodogram and correlogram spectral approaches. The stability of wave parameters as a function of high-frequency cut-off has the same result as obtained by the classical techniques.

  19. Evidence for a maximum of sinking velocities of suspended particulate matter in a coastal transition zone

    NASA Astrophysics Data System (ADS)

    Maerz, Joeran; Hofmeister, Richard; van der Lee, Eefke M.; Gräwe, Ulf; Riethmüller, Rolf; Wirtz, Kai W.

    2016-02-01

    Marine coastal ecosystem functioning is crucially linked to the transport and fate of suspended particulate matter (SPM). Transport of SPM is, amongst others, controlled by sinking velocity ws. Since ws of cohesive SPM aggregates varies significantly with size and composition of mineral and organic origin, ws probably exhibits large spatial variability along gradients of turbulence, SPM concentration and SPM composition. In this study, we retrieved ws for the German Bight, North Sea, by combining measured vertical turbidity profiles with simulation results for turbulent eddy diffusivity. Analyzed with 5 respect to modeled prevailing energy dissipation rates &epsilon,, mean ws were significantly enhanced around log10(ɛ (m2s-3)) ≈ -5.5. This ɛ region is typically found at water depths of approximately 15 m to 20 m on a cross-shore transect. Across this zone, SPM concentration declines drastically towards the offshore and a change in particle composition occurs. This characterizes a transition zone with potentially enhanced vertical fluxes. Our findings contribute to the conceptual understanding of nutrient cycling in the coastal region which is as follows: Previous studies identified an estuarine circulation. Its residual landward-oriented bottom currents are likely loaded with SPM particularly within the transition zone. This retains and traps fine sediments and particulate-bound nutrients in coastal waters where organic components of SPM become re-mineralized. Residual surface currents transport dissolved nutrients towards the off-shore, where they are again consumed by phytoplankton. Algae excrete extracellular polymeric substances which are known to mediate mineral aggregation and thus sedimentation. This probably takes place particularly in the transition zone and completes the coastal nutrient cycle. The efficiency of the transition zone for retention is thus suggested as an important mechanism that underlies the often observed nutrient gradients towards the coast.

  20. Effects of three types of resisted sprint training devices on the kinematics of sprinting at maximum velocity.

    PubMed

    Alcaraz, Pedro E; Palao, José M; Elvira, José L L; Linthorne, Nicholas P

    2008-05-01

    Resisted sprint running is a common training method for improving sprint-specific strength. For maximum specificity of training, the athlete's movement patterns during the training exercise should closely resemble those used when performing the sport. The purpose of this study was to compare the kinematics of sprinting at maximum velocity to the kinematics of sprinting when using three of types of resisted sprint training devices (sled, parachute, and weight belt). Eleven men and 7 women participated in the study. Flying sprints greater than 30 m were recorded by video and digitized with the use of biomechanical analysis software. The test conditions were compared using a 2-way analysis of variance with a post-hoc Tukey test of honestly significant differences. We found that the 3 types of resisted sprint training devices are appropriate devices for training the maximum velocity phase in sprinting. These devices exerted a substantial overload on the athlete, as indicated by reductions in stride length and running velocity, but induced only minor changes in the athlete's running technique. When training with resisted sprint training devices, the coach should use a high resistance so that the athlete experiences a large training stimulus, but not so high that the device induces substantial changes in sprinting technique. We recommend using a video overlay system to visually compare the movement patterns of the athlete in unloaded sprinting to sprinting with the training device. In particular, the coach should look for changes in the athlete's forward lean and changes in the angles of the support leg during the ground contact phase of the stride. PMID:18438225

  1. Estimations of One Repetition Maximum and Isometric Peak Torque in Knee Extension Based on the Relationship Between Force and Velocity.

    PubMed

    Sugiura, Yoshito; Hatanaka, Yasuhiko; Arai, Tomoaki; Sakurai, Hiroaki; Kanada, Yoshikiyo

    2016-04-01

    Sugiura, Y, Hatanaka, Y, Arai, T, Sakurai, H, and Kanada, Y. Estimations of one repetition maximum and isometric peak torque in knee extension based on the relationship between force and velocity. J Strength Cond Res 30(4): 980-988, 2016-We aimed to investigate whether a linear regression formula based on the relationship between joint torque and angular velocity measured using a high-speed video camera and image measurement software is effective for estimating 1 repetition maximum (1RM) and isometric peak torque in knee extension. Subjects comprised 20 healthy men (mean ± SD; age, 27.4 ± 4.9 years; height, 170.3 ± 4.4 cm; and body weight, 66.1 ± 10.9 kg). The exercise load ranged from 40% to 150% 1RM. Peak angular velocity (PAV) and peak torque were used to estimate 1RM and isometric peak torque. To elucidate the relationship between force and velocity in knee extension, the relationship between the relative proportion of 1RM (% 1RM) and PAV was examined using simple regression analysis. The concordance rate between the estimated value and actual measurement of 1RM and isometric peak torque was examined using intraclass correlation coefficients (ICCs). Reliability of the regression line of PAV and % 1RM was 0.95. The concordance rate between the actual measurement and estimated value of 1RM resulted in an ICC(2,1) of 0.93 and that of isometric peak torque had an ICC(2,1) of 0.87 and 0.86 for 6 and 3 levels of load, respectively. Our method for estimating 1RM was effective for decreasing the measurement time and reducing patients' burden. Additionally, isometric peak torque can be estimated using 3 levels of load, as we obtained the same results as those reported previously. We plan to expand the range of subjects and examine the generalizability of our results. PMID:26382131

  2. 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.

  3. Wavelet profiling of wind velocity using intensity fluctuations of laser beam propagating in the atmosphere

    NASA Astrophysics Data System (ADS)

    Afanas'ev, A. L.; Banakh, V. A.; Rostov, A. P.

    2008-10-01

    A method for the remote determination of the crosswind velocity profile using a wavelet analysis of fluctuations in the intensity of transmitted laser radiation is proposed. Results of an experimental investigation are presented that show how turbulent flow inhomogeneities (intensity fluctuations) localized in separate parts of the path contribute to the total distortions of the intensity distribution in a beam propagating along the path. It is demonstrated that, by separating fluctuations on various scales in the beam intensity distribution and following the evolution of these fluctuations, it is possible to determine the arrangement of turbulent zones along the path of propagation of the laser beam and to evaluate the velocity of motion of the medium in these zones. Wavelet estimates of the wind velocity from fluctuations of the transmitted radiation intensity for a given point of the atmospheric path agree with the results of direct velocity measurements at this point.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

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

    PubMed

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

    2011-07-20

    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 (>1 mJ) 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 0.4 ms(-1). PMID:21772386

  10. One year variations in the near earth solar wind ion density and bulk flow velocity

    NASA Technical Reports Server (NTRS)

    Bolton, Scott J.

    1990-01-01

    One-year periodic variations in the near earth solar wind ion density and bulk flow velocity are reported. The variations show an inverse relationship between the ion velocity and density. The peak strength of the observed density variation ranges from 50-100 percent over the background. These variations imply either large scale mass loading inside the earth's orbit or intrinsic solar modulations. Analyses of both near earth and Pioneer Venus Orbiter spacecraft data provide a comparison at two different heliocentric distances. Several explanations for these variations are discussed.

  11. 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.

  12. 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.

  13. Spatiotemporal Dynamics of the Variance of the Wind Velocity from Mini-Sodar Measurements

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Statistical trends of the spatiotemporal dynamics of the variance of the three wind velocity components in the atmospheric boundary layer have been established from Doppler mini-sodar measurements. Over the course of a 5-day period of measurements in the autumn time frame from 12 to 16 September 2003, values of the variance of the x- and y-components of the wind velocity lay in the interval from 0.001 to 10 m2/s2, and for the z-component, from 0.001 to 1.2 m2/s2. They were observed to grow during the morning hours (around 11:00 local time) and in the evening (from 18:00 to 22:00 local time), which is explained by the onset of heating and subsequent cooling of the Earth's surface, which are accompanied by an increase in the motion of the air masses. Analysis of the obtained vertical profiles of the standard deviations of the three wind velocity components showed that growth of σ x and σ y with altitude is well described by a power-law dependence with its exponent varying from 0.22 to 1.3 as a function of the time of day while σ z varies according to a linear law. At night (from 00:00 to 5:00 local time) the variance of the z-component changes from 0.01 to 0.56 m2/s2, which is in good agreement with the data available in the literature. Fitting parameters are found and the error of the corresponding fits is estimated, which makes it possible to describe the diurnal dynamics of the wind velocity variance.

  14. 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.

  15. Tracing Slow Winds from T Tauri Stars via Low Velocity Forbidden Line Emission

    NASA Astrophysics Data System (ADS)

    Simon, Molly; Pascucci, Ilaria; Edwards, Suzan; Feng, Wanda; Rigliaco, Elisabetta; Gorti, Uma; Hollenbach, David J.; Tuttle Keane, James

    2016-06-01

    Protoplanetary disks are a natural result of star formation, and they provide the material from which planets form. The evolutional and eventual dispersal of protoplanetary disks play critical roles in determining the final architecture of planetary systems. Models of protoplanetary disk evolution suggest that viscous accretion of disk gas onto the central star and photoevaporation driven by high-energy photons from the central star are the main mechanisms that drive disk dispersal. Understanding when photoevaporation begins to dominate over viscous accretion is critically important for models of planet formation and planetary migration. Using Keck/HIRES (resolution of ~ 7 km/s) we analyze three low excitation forbidden lines ([O I] 6300 Å, [O I] 5577 Å, and [S II] 6731 Å) previously determined to trace winds (including photoevaporative winds). These winds can be separated into two components, a high velocity component (HVC) with blueshifts between ~30 – 150 km/s, and a low velocity component (LVC) with blueshifts on the order of ~5 km/s (Hartigan et al. 1995). We selected a sample of 32 pre-main sequence T Tauri stars in the Taurus-Auriga star-forming region (plus TW Hya) with disks that span a range of evolutionary stages. We focus on the origin of the LVC specifically, which we are able to separate into a broad component (BC) and a narrow component (NC) due to the high resolution of our optical spectra. We focus our analysis on the [O I] 6300 Å emission feature, which is detected in 30/33 of our targets. Interestingly, we find wind diagnostics consistent with photoevaporation for only 21% of our sample. We can, however, conclude that a specific component of the LVC is tracing a magnetohydrodynamic (MHD) wind rather than a photoevaporative wind. We will present the details behind these findings and the implications they have for planet formation more generally.

  16. 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

  17. 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.

  18. 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.

  19. Magnetohydrodynamic modification of the TEACH-T code and the prediction of the maximum azimuthal velocity in a conducting fluid

    NASA Astrophysics Data System (ADS)

    Willis, Michael Greene

    1989-12-01

    An extension of the 2-D turbulent fluid dynamics code, TEACH, is developed. This extension incorporates a third (azimuthal) velocity component, with azimuthal symmetry assumed. Also included is the ability to solve for an electrostatic potential field with given boundary conditions. This electrostatic potential yields an electric field which, when coupled with the included constant magnetic field, produces Lorentz forces. These are accounted for as body forces in the appropriate components of the Navier-Stokes' momentum equation. The extensions in the code are compared with analytic results where possible and are found to be highly accurate. Finally, a semi-empirical correlation is developed to predict the magnitude and position of the maximum value of the added velocity component give the magnetic field strength and the value of the potential difference between an assumed central electrode and grounded outer shell. The correlation is seen to give excellent results for a wide range of electrostatic potential boundary conditions and magnetic field strengths acting on the working fluid sodium.

  20. Solar wind acceleration obtained from kinetic models based on electron velocity distribution functions with suprathermal particles

    NASA Astrophysics Data System (ADS)

    Pierrard, V.; Pieters, M.; Lazar, M.; Voitenko, Y.; Lamy, H.; Echim, M.

    2014-12-01

    Astrophysical and space plasmas are commonly found to be out ofthermal equilibrium, i.e., the velocity distribution functions (VDF)of plasma particles cannot be described well enough by Maxwelliandistribution functions. The suprathermal populations are ubiquitousenhancing the high-energy tail of the distribution. A kinetic model has been developed to successfullydescribe such plasmas with tails decreasing as a power law of thevelocity. In the present work, we show that a natural heating ofsolar and stellar coronas automatically appears when an enhancedpopulation of suprathermal particles is present at low altitude inthe solar (or stellar) atmosphere. This is true not only forelectrons and protons, but also for the minor ions which exhibit atemperature increase proportional to their mass. Moreover,suprathermal electrons contribute to the acceleration of stellarwinds to high bulk velocities when Coulomb collisions are neglected.These results are illustrated by using a global model of the solarcorona and solar wind based on VDF with suprathermal tails for thedifferent particle species. The energetic particles are non-collisional (without Coulomb collisions) even when thermalparticles are submitted to collisions. In the presence of long-rangecorrelations supplied by the fields and plasma instabilities,turbulence can play a role in the generation of such suprathermaltails. Solar wind observations are used as boundary conditions to determine the VDF in the other regions of the heliosphere. Consequences of suprathermal particles are also illustratedfor other space plasmas like the plasmasphere and the polar wind ofthe Earth and other planets.

  1. Detection of a second high-velocity component in the highly ionized wind from PG 1211+143

    NASA Astrophysics Data System (ADS)

    Pounds, Ken; Lobban, Andrew; Reeves, James; Vaughan, Simon

    2016-04-01

    An extended XMM-Newton observation of the luminous narrow line Seyfert galaxy PG1211+143 in 2014 has revealed a more complex highly ionized, high-velocity outflow. The detection of previously unresolved spectral structure in Fe K absorption finds a second outflow velocity component of the highly ionized wind, with an outflow velocity of v ˜ 0.066 ± 0.003c, in addition to a still higher velocity outflow of v ˜ 0.129 ± 0.002c consistent with that first seen in 2001. We note that chaotic accretion, consisting of many prograde and retrograde events, offers an intriguing explanation of the dual velocity wind. In that context the persisting outflow velocities could relate to physically distinct orientations of the inner accretion flow, with prograde accretion yielding a higher launch velocity than retrograde accretion in a ratio close to that observed.

  2. An analysis of maximum vertical gusts recorded at NASA's 150-meter ground winds tower facility at Kennedy Space Center, Florida

    NASA Technical Reports Server (NTRS)

    Alexander, M. B.

    1977-01-01

    A statistical summary is presented of vertical wind speed data recorded at NASA's 150-Meter Ground Winds Tower Facility on Merritt Island, Kennedy Space Center, Florida. One year of continuous around-the-clock vertical wind speed measurements processed by the Automatic Data Acquisition System (ADAS) is 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. Intensity, frequency, time of occurrence, prevailing conditions, etc., of the daily maximum vertical gusts (i.e., updraft and downdraft) are determined. The results are compared with the vertical gusts associated with the daily maximum horizontal gust. The intent of this summarization of vertical wind speed data is to provide a general description of wind flow in the lower 150 meters of the atmosphere for the identification of hazards involved in wind shear encounters relative to ascent and descent of the Space Shuttle and conventional aircraft.

  3. Temporal Evolution of the Solar Wind Bulk Velocity at Solar Minimum by Correlating the STEREO A and B PLASTIC Measurements

    NASA Astrophysics Data System (ADS)

    Opitz, A.; Karrer, R.; Wurz, P.; Galvin, A. B.; Bochsler, P.; Blush, L. M.; Daoudi, H.; Ellis, L.; Farrugia, C. J.; Giammanco, C.; Kistler, L. M.; Klecker, B.; Kucharek, H.; Lee, M. A.; Möbius, E.; Popecki, M.; Sigrist, M.; Simunac, K.; Singer, K.; Thompson, B.; Wimmer-Schweingruber, R. F.

    2009-05-01

    The two STEREO spacecraft with nearly identical instrumentation were launched near solar activity minimum and they separate by about 45° per year, providing a unique tool to study the temporal evolution of the solar wind. We analyze the solar wind bulk velocity measured by the two PLASTIC plasma instruments onboard the two STEREO spacecraft. During the first half year of our measurements (March - August 2007) we find the typical alternating slow and fast solar wind stream pattern expected at solar minimum. To evaluate the temporal evolution of the solar wind bulk velocity we exclude the spatial variations and calculate the correlation between the solar wind bulk velocity measured by the two spacecraft. We account for the different spacecraft positions in radial distance and longitude by calculating the corresponding time lag. After adjusting for this time lag we compare the solar wind bulk velocity measurements at the two spacecraft and calculate the correlation between the two time-shifted datasets. We show how this correlation decreases as the time difference between two corresponding measurements increases. As a result, the characteristic temporal changes in the solar wind bulk velocity can be inferred. The obtained correlation is 0.95 for a time lag of 0.5 days and 0.85 for 2 days.

  4. 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.

  5. Comparative Flight and Full-Scale Wind-Tunnel Measurements of the Maximum Lift of an Airplane

    NASA Technical Reports Server (NTRS)

    Silverstein, Abe; Katzoff, S; Hootman, James A

    1938-01-01

    Determinations of the power-off maximum lift of a Fairchild 22 airplane were made in the NACA full-scale wind tunnel and in flight. The results from the two types of test were in satisfactory agreement. It was found that, when the airplane was rotated positively in pitch through the angle of stall at rates of the order of 0.1 degree per second, the maximum lift coefficient was considerably higher than that obtained in the standard tests, in which the forces are measured with the angles of attack fixed. Scale effect on the maximum lift coefficient was also investigated.

  6. Anorthite sputtering by H+ and Arq+ (q = 1-9) at solar wind velocities

    NASA Astrophysics Data System (ADS)

    Hijazi, H.; Bannister, M. E.; Meyer, H. M.; Rouleau, C. M.; Barghouty, A. F.; Rickman, D. L.; Meyer, F. W.

    2014-10-01

    We report sputtering measurements of anorthite-like material, taken to be representative of soils found in the lunar highlands, impacted by singly and multicharged ions representative of the solar wind. The ions investigated include protons, as well as singly and multicharged Ar ions (as proxies for the nonreactive heavy solar wind constituents), in the charge state range +1 to +9, at fixed solar wind-relevant impact velocities of 165 and 310 km/s (0.25 keV/amu and 0.5 keV/amu). A quartz microbalance approach (QCM) for determination of total sputtering yields was used. The goal of the measurements was to determine the sputtering contribution of the heavy, multicharged minority solar wind constituents in comparison to that due to the dominant H+ fraction. The QCM results show a yield increase of a factor of about 80 for Ar+ versus H+ sputtering and an enhancement by a factor of 1.67 between Ar9+ and Ar+, which is a clear indication of a potential sputtering effect.

  7. Time scales for formation and spreading of velocity shells of pickup ions in the solar wind

    NASA Technical Reports Server (NTRS)

    Gaffey, J. D., Jr.; Wu, C. S.; Winske, D.

    1988-01-01

    This paper discusses the process of assimilation (pickup) by the solar wind of newly ionized atoms and molecules. Generally, the pickup process is considered to evolve in three stages: (1) the initial interaction of newly created ions with the interplanetary magnetic field to form the ring-beam distribution; (2) pitch angle scattering of the ring beam to form a hollow shell; and (3) slower velocity diffusion to form a partially filled-in shell distribution. Using numerical simulations of turbulence such as would occur naturally in the solar wind and such as would be encountered near cometary bow shocks, the processes of shell formation and evolution are studied, and the results are used to estimate the time scales for shell formation and diffusion in several situations of recent observational interest, the interstellar He data obtained by AMPTE and cometary ion pickup distributions obtained by various spacecraft at comets Giacobini-Zinner and Halley.

  8. Cluster/PEACE Electrons Velocity Distribution Function: Modeling the Strahl in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Gurgiolo, C.; Viñas, A. F.; Nieves-Chinchilla, T.; Goldstein, M. L.

    2008-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Li, Junran; Okin, Gregory S.; Herrick, Jeffrey E.; Belnap, Jayne; Munson, Seth M.; Miller, Mark E.

    2010-05-01

    This study provides a fast and easy-to-apply method to estimate threshold friction velocity (TFV) of wind erosion in the field. Wind tunnel experiments and a variety of ground measurements including air gun, pocket penetrometer, torvane, and roughness chain were conducted in Moab, Utah and cross-validated in the Mojave Desert, California. Patterns between TFV and ground measurements were examined to identify the optimum method for estimating TFV. The results show that TFVs were best predicted using the air gun and penetrometer measurements in the Moab sites. This empirical method, however, systematically underestimated TFVs in the Mojave Desert sites. Further analysis showed that TFVs in the Mojave sites can be satisfactorily estimated with a correction for rock cover, which is presumably the main cause of the underestimation of TFVs. The proposed method may be also applied to estimate TFVs in environments where other non-erodible elements such as postharvest residuals are found.

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Lu, Jian; Leung, L. Ruby; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang

    2015-12-01

    Motivated by indications from paleo-evidence, this paper investigates the changes of the Southern Westerly Winds (SWW) and westerly-wind stress between the Last Glacial Maximum (LGM) and pre-industrial in the PMIP3/CMIP5 simulations, highlighting the role of Antarctic sea ice in modulating the wind effect on ocean. Particularly, a de-correlation occurs between the changes in SWW and westerly-wind stress, caused primarily by an equatorward expansion of winter Antarctic sea ice that undermines the efficacy of wind in generating stress over the liquid ocean. Such de-correlation may reflect the LGM condition in reality, in view of the fact that the model which simulates this condition has most fidelity in simulating modern SWW and Antarctic sea ice. Therein two models stand out for their agreements with paleo-evidence regarding the change of SWW and the westerly-wind stress. They simulate strengthened and poleward-migrated LGM SWW in the atmosphere, consistent with the indications from dust records. Whilst in the ocean, they well capture an equatorward-shifted pattern of the observed oceanic front shift, with most pronounced equatorward-shifted westerly wind stress during the LGM.

  13. Maximum tension and force-velocity properties of fatigued, single Xenopus muscle fibres studied by caffeine and high K+.

    PubMed Central

    Lännergren, J; Westerblad, H

    1989-01-01

    1. The importance of reduced maximum force-generating capacity in the development of skeletal muscle fatigue has been studied using potassium and caffeine contractures as tools. 2. Single, intact fibres isolated from the lumbrical and iliofibularis muscles of Xenopus were fatigued by repeated tetanic stimulations until they produced close to 40% of the original tetanic tension (P0). Using this stimulation scheme three major types of fibres can be distinguished: easily fatigued (type 1), fatigue resistant (type 2), and very fatigue-resistant (type 3) fibres (Westerblad & Lännergren, 1986). 3. When activated by 8-15 mM-caffeine-Ringer solutions fatigued fibres of all three types developed tensions similar to those of controls (81.0 +/- 6.6 vs. 83.9 +/- 4.2% of P0, respectively; means +/- S.D.). 4. Tension output also increased markedly when fatigued fibres were depolarized by 190 mM-K+ solution. The tension produced was in this case fibre type dependent: 71.4 +/- 6.6, 81.3 +/- 2.5 and 95.0 +/- 4.4% of P0 in fibre types 1, 2 and 3, respectively. 5. Force-velocity measurements were performed during caffeine contractures in fatigued iliofibularis fibres (types 1 and 2) to obtain more information about the functional state of cross-bridges. 6. In fatigued type 1 fibres the shortening velocity was reduced to about 25% of that in controls, while it was not significantly depressed in type 2 fibres. 7. It is concluded that cross-bridges of fatigued fibres can produce nearly full tension, but they may work at a much slower rate in this state. 8. Fibre types 1 and 2 mostly display a long-lasting, reversible state of severely depressed tension production during the recovery period, which has been named post-contractile depression, PCD (Westerblad & Lännergren, 1986). Fibres tested in this state generated full caffeine-activated tension and the shortening velocity was not significantly reduced. The tension output during K+ contractures was, however, markedly depressed (12.4 +/- 4.1% of P0). 9. In conclusion, cross-bridges are able to produce close to full tension during PCD as well as in the fatigued state if they are fully activated. The form of functional impairment seems, however, not to be the same in the two cases. PMID:2585298

  14. 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.

  15. 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.

  16. 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.

  17. 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.

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

    PubMed

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

    2014-04-01

    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

  19. 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 Śnieżnik 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.

  20. Vertical velocity variance in the mixed layer from radar wind profilers.

    SciTech Connect

    Eng, K.; Coulter, R. L.; Brutsaert, W.; Environmental Research; Cornell Univ.

    2003-11-01

    Vertical velocity variance data were derived from remotely sensed mixed layer turbulence measurements at the Atmospheric Boundary Layer Experiments (ABLE) facility in Butler County, Kansas. These measurements and associated data were provided by a collection of instruments that included two 915 MHz wind profilers, two radio acoustic sounding systems, and two eddy correlation devices. The data from these devices were available through the Atmospheric Boundary Layer Experiment (ABLE) database operated by Argonne National Laboratory. A signal processing procedure outlined by Angevine et al. was adapted and further built upon to derive vertical velocity variance, {omega}'{sup 2}, from 915 MHz wind profiler measurements in the mixed layer. The proposed procedure consisted of the application of a height-dependent signal-to-noise ratio (SNR) filter, removal of outliers plus and minus two standard deviations about the mean on the spectral width squared, and removal of the effects of beam broadening and vertical shearing of horizontal winds. The scatter associated with {omega}'{sup 2} was mainly affected by the choice of SNR filter cutoff values. Several different sets of cutoff values were considered, and the optimal one was selected which reduced the overall scatter on {omega}'{sup 2} and yet retained a sufficient number of data points to average. A similarity relationship of {omega}'{sup 2} versus height was established for the mixed layer on the basis of the available data. A strong link between the SNR and growth/decay phases of turbulence was identified. Thus, the mid to late afternoon hours, when strong surface heating occurred, were observed to produce the highest quality signals.

  1. The electron velocity distribution in the high-speed solar wind: Modeling the effects of protons

    NASA Astrophysics Data System (ADS)

    Lie-Svendsen, Øystein; Leer, Egil

    2000-01-01

    The evolution of the electron velocity distribution function (VDF) in high-speed solar wind streams is modeled taking the expanding geometry, the polarization electric field, and Coulomb collisions into account. The VDF we find at the orbit of Mercury is composed of an isotropic, collision-dominated core, a trapped, anisotropic population called ``halo'' in this study, and a narrow, high-energy ``strahl'' that escapes along the magnetic field. The distribution function is very similar to the electron VDF observed in the low-density, high-speed solar wind by Pilipp et al. [1987] and Phillips et al. [1989]. The main features of the VDF can be obtained by considering only electron self-collisions; the effect of proton collisions is to make the distribution function more isotropic. At low energies, collisions with protons dominate the angular scattering, but electron self-collisions alone are frequent enough to keep the core of the distribution function quite isotropic. The expanding geometry produces an anisotropic halo and a narrow strahl. The angular scattering by protons reduces the anisotropy of the trapped halo particles and broadens the lower-energy part of the strahl. Along the magnetic field the resulting electron velocity distribution is composed of a relatively cold core and a halo-strahl spectrum that is ``flatter'' than the coronal spectrum. The two-temperature electron distribution function often observed in the solar wind may therefore be produced by Coulomb collisions and should not be taken as a ``proof'' of a non-Maxwellian (two-temperature) distribution function in the corona.

  2. Vertical velocity variance in the mixed layer from radar wind profilers

    USGS Publications Warehouse

    Eng, K.; Coulter, R.L.; Brutsaert, W.

    2003-01-01

    Vertical velocity variance data were derived from remotely sensed mixed layer turbulence measurements at the Atmospheric Boundary Layer Experiments (ABLE) facility in Butler County, Kansas. These measurements and associated data were provided by a collection of instruments that included two 915 MHz wind profilers, two radio acoustic sounding systems, and two eddy correlation devices. The data from these devices were available through the Atmospheric Boundary Layer Experiment (ABLE) database operated by Argonne National Laboratory. A signal processing procedure outlined by Angevine et al. was adapted and further built upon to derive vertical velocity variance, w_pm???2, from 915 MHz wind profiler measurements in the mixed layer. The proposed procedure consisted of the application of a height-dependent signal-to-noise ratio (SNR) filter, removal of outliers plus and minus two standard deviations about the mean on the spectral width squared, and removal of the effects of beam broadening and vertical shearing of horizontal winds. The scatter associated with w_pm???2 was mainly affected by the choice of SNR filter cutoff values. Several different sets of cutoff values were considered, and the optimal one was selected which reduced the overall scatter on w_pm???2 and yet retained a sufficient number of data points to average. A similarity relationship of w_pm???2 versus height was established for the mixed layer on the basis of the available data. A strong link between the SNR and growth/decay phases of turbulence was identified. Thus, the mid to late afternoon hours, when strong surface heating occurred, were observed to produce the highest quality signals.

  3. 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.

  4. 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.

  5. 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.

  6. The Lick AGN Monitoring Project: Velocity-delay Maps from the Maximum-entropy Method for Arp 151

    NASA Astrophysics Data System (ADS)

    Bentz, Misty C.; Horne, Keith; Barth, Aaron J.; Bennert, Vardha Nicola; Canalizo, Gabriela; Filippenko, Alexei V.; Gates, Elinor L.; Malkan, Matthew A.; Minezaki, Takeo; Treu, Tommaso; Woo, Jong-Hak; Walsh, Jonelle L.

    2010-09-01

    We present velocity-delay maps for optical H I, He I, and He II recombination lines in Arp 151, recovered by fitting a reverberation model to spectrophotometric monitoring data using the maximum-entropy method. H I response is detected over the range 0-15 days, with the response confined within the virial envelope. The Balmer-line maps have similar morphologies but exhibit radial stratification, with progressively longer delays for Hγ to Hβ to Hα. The He I and He II response is confined within 1-2 days. There is a deficit of prompt response in the Balmer-line cores but strong prompt response in the red wings. Comparison with simple models identifies two classes that reproduce these features: free-falling gas and a half-illuminated disk with a hot spot at small radius on the receding lune. Symmetrically illuminated models with gas orbiting in an inclined disk or an isotropic distribution of randomly inclined circular orbits can reproduce the virial structure but not the observed asymmetry. Radial outflows are also largely ruled out by the observed asymmetry. A warped-disk geometry provides a physically plausible mechanism for the asymmetric illumination and hot spot features. Simple estimates show that a disk in the broad-line region of Arp 151 could be unstable to warping induced by radiation pressure. Our results demonstrate the potential power of detailed modeling combined with monitoring campaigns at higher cadence to characterize the gas kinematics and physical processes that give rise to the broad emission lines in active galactic nuclei.

  7. High-velocity Wind from IRS 1 in the NGC 2071IR

    NASA Astrophysics Data System (ADS)

    Trinidad, Miguel Angel

    2015-10-01

    We present the results of 1.3 and 3.6 cm radio continuum emission toward the NGC 2071IR star-forming region, carried out with the VLA in its A configuration. We detect continuum emission toward the infrared sources IRS 1 and IRS 3 at both wavelengths. In particular, IRS 1 breaks up into three continuum peaks (IRS 1E, 1C, and 1W), aligned in the east-west direction, being IRS 1 the central source. The morphology of the condensation IRS 1W is very interesting, which has an elongated structure and shows a significant curvature towards the north. We suggest that this morphology could be explained as the impact of a high-velocity wind or jetlike outflow from IRS 1 on a close companion or other obstruction, which also explains the strong water maser emission observed toward IRS 1W.

  8. Wind tunnel investigation of the effect of high relative velocities on the structural integrity of birds

    NASA Technical Reports Server (NTRS)

    Bresnahan, D. L.

    1972-01-01

    An experimental investigation was conducted in a supersonic wind tunnel to determine the effect a sudden high velocity headwind had on the physical deformation and structural breakup characteristics of birds. Several sizes of recently killed birds were dropped into the test section at free-stream Mach numbers ranging from 0.2 to 0.8 and photographed with high-speed motion-picture cameras. These conditions simulated flow conditions encountered when birds are ingested into the inlets of high speed aircraft, thereby constituting a safety hazard to the aircraft and its occupants. The investigation shows that, over the range of headwind conditions tested, the birds remained structurally intact and did not suffer any appreciable deformation or structural breakup.

  9. Intensity of the Fe XV emission line corona, the level of geomagnetic activity, and the velocity of the solar wind

    NASA Technical Reports Server (NTRS)

    Bell, B.; Noci, G.

    1976-01-01

    The method of superposed epochs is used to determine the average solar wind velocity and the Kp index following central meridian passage of coronal weak and bright features identified from OSO 7 isophotograms of the Fe XV (284 A) emission line. It is found that bright coronal regions possess magnetic fields of closed configuration, thus reducing particle escape, while coronal holes possess open magnetic field lines favorable to particle escape or enhanced outflow of the solar wind.

  10. 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

  11. 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.

  12. Velocity distributions of cometary protons picked up by the solar wind

    SciTech Connect

    Neugebauer, M.; Lazarus, A.J.; Balsiger, H.; Fuselier, S.A.; Neubauer, F.M.; Rosenbauer, H.

    1989-05-01

    Velocity space distributions of picked up cometary protons were measured by the ion mass spectrometer on the Giotto spacecraft upstream of the Halley bow shock. Large pitch angle anisotropies were observed at all distances >1.2 x 10/sup 6/ km from the comet. As expected, pitch angle diffusion was much more rapid than energy diffusion. When the field was quasi-parallel to the solar wind velocity vector, it was possible to discern the effect of pitch angles scattering by sunward propagating, field-aligned hydromagnetic waves, but there is evidence for other scattering modes as well. For quasi-perpendicular geometries, the pitch angle distribution was very asymmetric with phase space density peaks near pitch angles of 180/sup 0/. It is suggested that the asymmetric pitch angle distribution may be caused by global rather than local wave-particle interactions. Just outside the shock, the pitch angle distribution was nearly isotropic and the radius of the pickup shell increased significantly. copyright American Geophysical Union 1989

  13. The velocity distributions of cometary protons picked up by the solar wind

    NASA Technical Reports Server (NTRS)

    Neugebauer, M.; Lazarus, A. J.; Balsiger, H.; Fuselier, S. A.; Neubauer, F. M.

    1989-01-01

    Velocity space distributions of picked up cometary protons were measured by the ion mass spectrometer on the Giotto spacecraft upstream of the Halley bow shock. Large pitch angle anisotropies were observed at all distances greater than 1.2 x 10 to the 6th km from the comet. As expected, pitch angle diffusion was much more rapid than energy diffusion. When the field was quasi-parallel to the solar wind velocity vector, it was possible to discern the effect of pitch angle scattering by sunward propagating, field-aligned hydromagnetic waves, but there is evidence for other scattering modes as well. For quasi-perpendicular geometries, the pitch angle distribution was very asymmetric with phase space density peaks near pitch angles of 180 deg. It is suggested that the asymmetric pitch angle distribution may be caused by global rather than local wave-particle interactions. Just outside the shock, the pitch angle distribution was nearly isotropic and the radius of the pickup shell increased significantly.

  14. Calibration of the maximum carboxylation velocity (vcmax) for the Caatinga for use in dynamic global vegetation models (DGVMs)

    NASA Astrophysics Data System (ADS)

    Rezende, L. C.; Arenque, B.; von Randow, C.; Moura, M. S.; Aidar, S. D.; Buckeridge, M. S.; Menezes, R.; Souza, L. S.; Ometto, J. P.

    2013-12-01

    The Caatinga biome in the semi-arid region of northeastern Brazil is extremely important due to its biodiversity and endemism. This biome, which is under high anthropogenic influences, presents high levels of environmental degradation, land use being among the main causes of such degradation. The simulations of land cover and the vegetation dynamic under different climate scenarios are important features for prediction of environmental risks and determination of sustainable pathways for the planet in the future. Modeling of the vegetation can be performed by use of dynamic global vegetation models (DGVMs). The DGVMs simulate the surface processes (e.g. transfer of energy, water, CO2 and momentum); plant physiology (e.g. photosynthesis, stomatal conductance) phenology; gross and net primary productivity, respiration, plant species classified by functional traits; competition for light, water and nutrients, soil characteristics and processes (e.g. nutrients, heterotrophic respiration). Currently, most of the parameters used in DGVMs are static pre-defined values, and the lack of observational information to aid choosing the most adequate values for these parameters is particularly critical for the semi-arid regions in the world. Through historical meteorological data and measurements of carbon assimilation we aim to calibrate the maximum carboxylation velocity (Vcmax), for the native species Poincianella microphylla, abundant in the Caatinga region. The field data (collected at Lat: 90 2' S, Lon: 40019' W) displayed two contrasting meteorological conditions, with precipitations of 16 mm and 104 mm prior to the sampling campaigns (April 9-13, 2012 and February 4-8, 2013; respectively). Calibration (obtaining values of Vcmax more suitable for vegetation of Caatinga) has been performed through an algorithm of pattern recognition: Classification And Regression Tree (CART) and calculation of the vapor pressure deficit (VPD), which was used as attribute for discrimination of data. CART can be utilized for classification or regression, being used in the context of this work for non-linear regression. Our results show that CART algorithm correctly classified data according to the two contrasting periods (i.e. correctly distinguished assimilation data measured during drier or rainy periods), and suggest average Vcmax values of 14.2 μmol CO2 m-2 s-1 for the drier period and of 102.5 μmol CO2 m-2 s-1 for the rainy period. Comparing the values obtained in this work with values obtained through a traditional parameter optimization technique, it is possible to gauge pros and cons of such a combination of field measurements and machine learning technique.

  15. 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.

  16. Measurements of solar transition zone velocities and line broadening using the ultraviolet spectrometer and polarimeter on the Solar Maximum Mission

    NASA Technical Reports Server (NTRS)

    Simon, G.; Mein, P.; Vial, J. C.; Shine, R. A.; Woodgate, B. E.

    1982-01-01

    The UVSP instrument on SMM is able to observe solar regions at two wavelengths in the same line with a band-pass of 0.3 A. Intensity and Doppler velocity maps are derived. It is shown that the numerical values are sensitive to the adopted Doppler width and the range of velocities is limited to within 30 km/sec. A method called Double Dopplergram Determination (DDD) is described for deriving both the Doppler width and the velocity (up to 80 km/sec), and the main sources of uncertainties are discussed. To illustrate the method, a set of C IV 1548 A observations is analyzed according to this procedure. The mean C IV Doppler width measured (0.15 A) is comparable to previous determinations. A relation is found between bright regions and down-flows. Large Doppler widths correspond to strong velocity gradients.

  17. A dual velocity in the highly ionized wind of the luminous narrow line Seyfert galaxy PG 1211+143

    NASA Astrophysics Data System (ADS)

    Pounds, K. A.; Lobban, A.; Reeves, J. N.; Vaughan, S.

    2016-05-01

    An extended XMM-Newton observation of the luminous narrow line Seyfert galaxy PG 1211+143 in 2014 has revealed a complex high velocity outflow, with components distinguished in velocity, ionization and short-term variability. We report here the detection of previously unseen spectral structure in Fe K absorption, finding a second velocity component of the highly ionized wind, apparently co-moving with a low ionization flow detected in the soft X-ray spectrum. Comparison with the first observation in 2001 finds a similar outflow energy rate.

  18. 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...

  19. Effect of Solar-Wind Velocity, Magnetic Field and Density on Solar Energetic Particle Transport

    NASA Astrophysics Data System (ADS)

    Ng, C. K.

    2014-05-01

    In large gradual solar energetic particle (SEP) events, energetic protons greatly amplify ambient upstream Alfvn waves near coronal-mass-ejection (CME) driven shocks. The waves grow until they are swept downstream of the shock. The amplified waves scatter the particles and flatten the SEP intensity energy spectrum at low energy at 1 AU, causing the streaming limit phenomenon. Both the wave and SEP intensities maximize near the shock and fall steeply with distance upstream. The SEPs are focused by the longitudinal gradient of the magnetic field B. The wave growth rate increases with energetic proton streaming and varies as f/?(np), with f the energetic proton phase-space density and np the plasma proton number density. Thus, in addition to the SEP release rate at the shock, the environmental quantities: np(r), B(r), the solar-wind velocity Vsw(r), and the Alfvn speed VA(r) also influence SEP transport. At heliocentric distance r? 8r?, np as well as B deviate significantly from r-2, Vsw rises slowly from near zero on the photosphere, and VA peaks near 4 r?. We have generalized our SEP transport model to take account of realistic radial dependences of the above solar-wind properties down to 2 r? in addition to the usual processes of wave and particle transport and Alfvn wave growth. The model has been applied to STEREO A observation of the 2011 March 21 SEP event with the preliminary conclusion that wave-damping processes rather than the environmental quantities are more likely to raise the predicted proton intensity at < 5 MeV to the higher observed values.

  20. 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.

  1. 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.

  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. Real-time approaches to the estimation of local wind velocity for a fixed-wing unmanned air vehicle

    NASA Astrophysics Data System (ADS)

    Chan, W. L.; Lee, C. S.; Hsiao, F. B.

    2011-10-01

    Three real-time approaches to estimating local wind velocity for a fixed-wing unmanned air vehicle are presented in this study. All three methods work around the navigation equations with added wind components. The first approach calculates the local wind speed by substituting the ground speed and ascent rate data given by the Global Positioning System (GPS) into the navigation equations. The second and third approaches utilize the extended Kalman filter (EKF) and the unscented Kalman filter (UKF), respectively. The results show that, despite the nonlinearity of the navigation equations, the EKF performance is proven to be on a par with the UKF. A time-varying noise estimation method based on the Wiener filter is also discussed. Results are compared with the average wind speed measured on the ground. All three approaches are proven to be reliable with stated advantages and disadvantages.

  4. Simultaneous measurements of air-sea gas transfer velocity and near surface turbulence at low to moderate winds (Invited)

    NASA Astrophysics Data System (ADS)

    Wang, B.; Liao, Q.; Fillingham, J. H.; Bootsma, H. A.

    2013-12-01

    Parameterization of air-sea gas transfer velocity was routinely made with wind speed. Near surface turbulent dissipation rate has been shown to have better correlation with the gas transfer velocity in a variety of aquatic environments (i.e., the small eddy model) while wind speed is low to moderate. Wind speed model may underestimate gas transfer velocity at low to moderate winds when the near surface turbulence is produced by other environmental forcing. We performed a series of field experiments to measure the CO2 transfer velocity, and the statistics of turbulence immediately below the air-water interface using a novel floating PIV and chamber system. The small eddy model was evaluated and the model coefficient was found to be a non-constant, and it varies with the local turbulent level (figure 1). Measure results also suggested an appropriate scaling of the vertical dissipation profile immediately below the interface under non-breaking conditions, which can be parameterized by the wind shear, wave height and wave age (figure 2). Figure 1. Relation between the coefficient of the small eddy model and dissipation rate. The data also include Chu & Jirka (2003) and Vachon et al. (2010). The solid regression line: α = 0.188log(ɛ)+1.158 Figure 2. Non-dimensional dissipation profiles. Symbols: measured data with the floating PIV. Solid line: regression of measured data with a -0.79 decaying rate. Dash line with -2 slope: Terray et al. (1996) relation. Dash line with two layer structure: Siddiqui & Loewen (2007) relation.

  5. Diode laser lidar wind velocity sensor using a liquid-crystal retarder for non-mechanical beam-steering.

    PubMed

    Rodrigo, Peter John; Iversen, Theis F Q; Hu, Qi; Pedersen, Christian

    2014-11-01

    We extend the functionality of a low-cost CW diode laser coherent lidar from radial wind speed (scalar) sensing to wind velocity (vector) measurements. Both speed and horizontal direction of the wind at ~80 m remote distance are derived from two successive radial speed estimates by alternately steering the lidar probe beam in two different lines-of-sight (LOS) with a 60° angular separation. Dual-LOS beam-steering is implemented optically with no moving parts by means of a controllable liquid-crystal retarder (LCR). The LCR switches the polarization between two orthogonal linear states of the lidar beam so it either transmits through or reflects off a polarization splitter. The room-temperature switching time between the two LOS is measured to be in the order of 100 μs in one switch direction but 16 ms in the opposite transition. Radial wind speed measurement (at 33 Hz rate) while the lidar beam is repeatedly steered from one LOS to the other every half a second is experimentally demonstrated - resulting in 1 Hz rate estimates of wind velocity magnitude and direction at better than 0.1 m/s and 1° resolution, respectively. PMID:25401817

  6. 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.

  7. Limits imposed by solenoid damage on the maximum velocity achieved by an electromagnetic coilgun: A computational study

    NASA Astrophysics Data System (ADS)

    Madhavan, S.; Sijoy, C. D.; Pahari, S.; Chaturvedi, S.

    2012-06-01

    CAD has set up an electromagnetic acceleration and impact facility for studies of material fracture and deformation at high strain rates. The target is to reach projectile velocities of 200-500 m/s. The mechanical strength of the solenoid coil and potting material is an important factor affecting coil survival during experiments. We have performed a computational study, using the materials and coil and circuit parameters typically used in experiments, and found the operating limits up to which the coil can survive without breaking.

  8. 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.

  9. The effect of wind velocity on transpiration in a mixed broadleaved deciduous forest

    NASA Astrophysics Data System (ADS)

    Kim, D.; Oren, R.; Oishi, A. C.; Hsieh, C.; Phillips, N. G.; Novick, K. A.; Stoy, P. C.

    2013-12-01

    Wind velocity (U) within and above forest canopies can alter the coupling between the vapor-saturated sub-stomatal airspace and the drier atmosphere aloft, thereby influencing transpiration rates. In practice, however, the actual increase in transpiration with increasing U depends on the aerodynamic resistance (RA) to vapor transfer compared to canopy resistance to water vapor flux out of leaves (RC, dominated by stomatal resistance, Rstom), and the rate at which RA decreases with increasing U. We investigated the effect of U on transpiration at the canopy scale using filtered meteorological data and sap flux measurements gathered from six diverse species of a mature broadleaved deciduous forest. Only under high light conditions, stand transpiration (EC) increased slightly (6.5%) with increasing U ranging from ~0.7 to ~4.7 m s-1. Under other conditions, sap flux density (Js) and EC responded weakly or did not change with U. RA, estimated from Monin-Obukhov similarity theory, decreased with increasing U, but this decline was offset by increasing RC, estimated from a rearranged Penman-Monteith equation, due to a concurrent increase in vapor pressure deficit (D). The increase of RC with D over the observed range of U was consistent with increased Rstom by ~40% based on hydraulic theory. Except for very rare half-hourly values, the proportion of RA to total resistance (RT) remained < 15% over the observed range of conditions. These results suggest that in similar forests and conditions, accounting for the effects of U-D relationship on Rstom would reduce the uncertainty of modeling canopy gas exchange more than accounting for the direct effect of U on RA.

  10. On the minimum variance direction of magnetic field fluctuations in the azimuthal velocity structure of the solar wind

    NASA Technical Reports Server (NTRS)

    Solodyna, C. V.; Belcher, J. W.

    1976-01-01

    The paper examines the properties of microscale magnetic field fluctuations for diverse classes of large-scale azimuthal velocity structures in the solar wind, with particular reference to the orientation of the wave normal vector for MHD waves in the interplanetary medium. It is shown that the direction of minimum variance does not exhibit any characteristic refraction pattern with respect to large-scale velocity structures in the solar wind. It is suggested that the direction of minimum variance is not indicative of the wave normal vector directions. The determination of the wave normal vector directions for the predominantly transverse MHD waves in the interplanetary medium is presently beyond the capability of single spacecraft observations.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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, Hiroshi; Wu, Wenjie

    2016-03-01

    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 study reviews the existing estimation methods for Rmax based on central pressure or maximum wind speed. These over- or underestimate Rmax because of substantial variations in the data, although an average radius can be estimated with moderate accuracy. As an alternative, we propose an Rmax estimation method based on the radius of the 50 kt wind (R50). Data obtained by a meteorological station network in the Japanese archipelago during the passage of strong typhoons, together with the JMA typhoon best track data for 1990-2013, enabled us to derive the following simple equation, Rmax = 0.23 R50. Application to a recent strong typhoon, the 2015 Typhoon Goni, confirms that the equation provides a good estimation of Rmax, particularly when the central pressure became considerably low. Although this new method substantially improves the estimation of Rmax compared to the existing models, estimation errors are unavoidable because of fundamental uncertainties regarding the typhoon's structure or insufficient number of available typhoon data. In fact, a numerical simulation for the 2013 Typhoon Haiyan as well as 2015 Typhoon Goni demonstrates 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 (e.g., Rmax = 0.15 R50-0.35 R50), independently of the model used, to minimize the risk of over- or underestimating storm surges. The proposed method is expected to increase the predictability of major storm surges and to contribute to disaster risk management, particularly in the western North Pacific, including countries such as Japan, China, Taiwan, the Philippines, and Vietnam.

  16. 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.

  17. 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.

  18. Influence of current velocity and wind speed on air-water gas exchange in a mangrove estuary

    NASA Astrophysics Data System (ADS)

    Ho, David T.; Coffineau, Nathalie; Hickman, Benjamin; Chow, Nicholas; Koffman, Tobias; Schlosser, Peter

    2016-04-01

    Knowledge of air-water gas transfer velocities and water residence times is necessary to study the fate of mangrove derived carbon exported into surrounding estuaries and ultimately to determine carbon balances in mangrove ecosystems. For the first time, the 3He/SF6 dual tracer technique, which has been proven to be a powerful tool to determine gas transfer velocities in the ocean, is applied to Shark River, an estuary situated in the largest contiguous mangrove forest in North America. The mean gas transfer velocity was 3.3 ± 0.2 cm h-1 during the experiment, with a water residence time of 16.5 ± 2.0 days. We propose a gas exchange parameterization that takes into account the major sources of turbulence in the estuary (i.e., bottom generated shear and wind stress).

  19. Imprints of a high velocity wind on the soft x-ray spectrum of PG1211+143

    NASA Astrophysics Data System (ADS)

    Pounds, K. A.; Lobban, A.; Reeves, J. N.; Vaughan, S.; Costa, M.

    2016-04-01

    An extended XMM-Newton observation of the luminous narrow line Seyfert galaxy PG1211+143 in 2014 has revealed a more complex high velocity wind, with components distinguished in velocity, ionization level, and column density. Here we report soft x-ray emission and absorption features from the ionized outflow, finding counterparts of both high velocity components, v˜0.129c and v˜0.066c, recently identified in the highly ionized Fe K absorption spectrum. The lower ionization of the co-moving soft x-ray absorbers imply a distribution of higher density clouds embedded in the main outflow, while much higher column densities for the same flow component in the hard x-ray spectra suggest differing sight lines to the continuum x-ray source.

  20. 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...

  1. Equilibrium points and zero velocity surfaces in the restricted four-body problem with solar wind drag

    NASA Astrophysics Data System (ADS)

    Kumari, Reena; Kushvah, Badam Singh

    2013-04-01

    We have analyzed the motion of an infinitesimal mass in the restricted four-body problem with solar wind drag. It is assumed that the forces which govern the motion are mutual gravitational attractions of the primaries, radiation pressure force and solar wind drag. We have derived the equations of motion and found the Jacobi integral, zero velocity surfaces, and particular solutions of the system. It is found that three collinear points are real when the radiation factor 0< β<0.1 whereas only one real point is obtained when 0.125< β<0.2. The stability property of the system is examined with the help of Poincaré surface of section (PSS) and Lyapunov characteristic exponents (LCEs). It is found that in presence of drag forces LCE is negative for a specific initial condition, hence the corresponding trajectory is regular whereas regular islands in the PSS are expanded.

  2. Development of pitch angle anisotropy and velocity diffusion of pickup ion shell distribution by solar wind turbulence

    NASA Technical Reports Server (NTRS)

    Yoon, Peter H.; Ziebell, L. F.

    1990-01-01

    The evolution of pitch angle anisotropy in initially isotropic spherical shell distribution of pickup ions subjected to a continuous influence of weak or moderate intrinsic solar wind turbulence is investigated using a physical model which assumes that the wave of the solar wind turbulence is propagating mainly in the direction parallel to the ambient magnetic field. It is shown that, because of the pitch angle dependence of the velocity diffusion process, a significant pitch angle anisotropy of pickup ion shell distribution develops in the early stage of the diffusion process. Although it is smeared out later on, the result can be of significant importance, especially if the pickup ion density is large, because the pitch angle anisotropy can excite collective instabilities and increase the wave level, thus accelerating the diffusion process.

  3. 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.

  4. 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

  5. Effect of Soil Crusting on the Threshold Friction Wind Velocity of Major Soils Across the Columbia Plateau

    NASA Astrophysics Data System (ADS)

    Vaddella, V. K.; Sharratt, B. S.

    2010-12-01

    Windblown dust emissions from agricultural soils in Columbia Plateau have resulted in exceedance of air quality standards set by the US Environmental Protection Agency (USEPA) and traffic fatalities caused by poor visibility. In addition to these effects, atmospheric dust contributes to global warming and the loss of topsoil depletes the soil of its fertility. Fine aerosols emitted during wind storms have aerodynamic diameters less than or equal to 2.5 and 10 microns, commonly known as PM2.5 and PM10. These aerosols are regulated as criteria pollutants under EPAs National Ambient Air Quality Standards. Several communities in the Columbia Plateau have been in non-attainment for these air pollutants. The objective of this study was to examine the effect of soil crusting on the threshold friction wind velocity of five major soil types commonly found across the Columbia Plateau. Soil crusts of varying thickness were created by altering rainfall intensity. Soil samples were collected from the top 3 cm of the soil profile from five different locations across the Plateau. The samples were screened through a 2 mm sieve to remove debris and non-erodible aggregates and were air dried at 30C. The samples were placed in shallow trays and were subjected to different intensities of rainfall using the Palouse Rainfall Simulator at typical intensities observed in Columbia Plateau. The trays were air dried to allow soil crust formation. The trays were then subjected to a range of wind velocities in a portable wind tunnel. The onset of saltation and suspension of windblown sediment was observed using a Sensit and aerosol samplers (DustTrak and E-samplers) installed at heights of 0.5 to 10 cm above the soil surface. The crust was observed to be the same thickness for every soil at any one particular rainfall intensity. The crust thickness increased with increase in rainfall intensity; hence, the threshold friction velocity increased with an increase in crust thickness. Variations in the threshold friction velocity were observed among the five different soil types. This information will better enable atmospheric scientists to predict dust storms in the Columbia Plateau.

  6. Wind-wave-induced velocity in ATI SAR ocean surface currents: First experimental evidence from an airborne campaign

    NASA Astrophysics Data System (ADS)

    Martin, Adrien C. H.; Gommenginger, Christine; Marquez, Jose; Doody, Sam; Navarro, Victor; Buck, Christopher

    2016-03-01

    Conventional and along-track interferometric (ATI) Synthetic Aperture Radar (SAR) senses the motion of the ocean surface by measuring the Doppler shift of reflected signals. Measurements are affected by a Wind-wave-induced Artifact Surface Velocity (WASV) which was modeled theoretically in past studies and has been estimated empirically only once before with Envisat ASAR by Mouche et al. (2012). An airborne campaign in the tidally dominated Irish Sea served to evaluate this effect and the current retrieval capabilities of a dual-beam SAR interferometer known as Wavemill. A comprehensive collection of Wavemill airborne data acquired in a star pattern over a well-instrumented validation site made it possible for the first time to estimate the magnitude of the WASV, and its dependence on azimuth and incidence angle from data alone. In light wind (5.5 m/s) and moderate current (0.7 m/s) conditions, the wind-wave-induced contribution to the measured ocean surface motion reaches up to 1.6 m/s upwind, with a well-defined second-order harmonic dependence on direction to the wind. The magnitude of the WASV is found to be larger at lower incidence angles. The airborne WASV results show excellent consistency with the empirical WASV estimated from Envisat ASAR. These results confirm that SAR and ATI surface velocity estimates are strongly affected by WASV and that the WASV can be well characterized with knowledge of the wind knowledge and of the geometry. These airborne results provide the first independent validation of Mouche et al. (2012) and confirm that the empirical model they propose provides the means to correct airborne and spaceborne SAR and ATI SAR data for WASV to obtain accurate ocean surface current measurements. After removing the WASV, the airborne Wavemill-retrieved currents show very good agreement against ADCP measurements with a root-mean-square error (RMSE) typically around 0.1 m/s in velocity and 10° in direction.

  7. 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.

  8. 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.

  9. 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.

  10. High velocity wind tunnels : their application to ballistics, aerodynamics, and aeronautics

    NASA Technical Reports Server (NTRS)

    Huguenard, E

    1925-01-01

    The object of this article is to set forth the particular properties of swiftly-moving air, how these affect the installation of a wind tunnel, the experimental results already obtained, the possible applications of such a tunnel, and what can be easily accomplished at the present time.

  11. 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.

  12. 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.

  13. Large-scale vertical motion calculations in the AVE IV Experiment. [of atmospheric wind velocity

    NASA Technical Reports Server (NTRS)

    Wilson, G. S.

    1976-01-01

    Using 3- and 6-h consecutive rawinsonde and surface data from NASA's AVE IV Experiment, synoptic-scale vertical motion calculations are made using an adiabatic technique and three variations of the kinematic technique. Both subjective and objective comparisons in space and time between the sign and magnitude of the computed vertical velocities and precipitation intensities are made. These comparisons are conducted to determine which method would consistently produce realistic magnitudes, patterns, and vertical profiles of vertical velocity essential to the diagnostic study of the relationship between severe convective storms and their environment in AVE IV. The kinematic method, adjusted to the adiabatic value at 100 mb, proved to produce the best overall vertical velocities.

  14. Development of Simultaneous Pressure and Velocity Measurements Using Multi-Luminophore Microspheres for Wind Tunnel Application

    NASA Astrophysics Data System (ADS)

    Pryor, Lillian; Cottingham, Trey; Tien, Wei-Hsin; Khalil, Gamal; Dabiri, Dana

    2014-11-01

    The development of pressure-sensitive microbeads allows for simultaneous measurement of pressure and velocity. These aerosolized microbeads are loaded with a pressure-sensitive dye coupled with a pressure-insensitive reference dye to provide pressure measurements. Their motions are tracked to provide velocity measurements. This research focuses on optimizing a dual-dye microsphere that responds on the order of microseconds. Intensities measured from the pressure-sensitive dye are normalized to those from the reference dye and then to a baseline condition intensity ratio. Light intensity from the microspheres is measured using EMCCD cameras and processed to back-calculate pressure. A PIV camera can be used to track the particles' velocities. Further results regarding technique development will be discussed.

  15. Solar wind proton velocity distributions - Comparison of the bi-Maxwellian based 16-moment expansion with observations

    NASA Technical Reports Server (NTRS)

    Demars, H. G.; Schunk, R. W.

    1990-01-01

    The purpose of this paper is to study the possible types of velocity distributions that can be obtained from the bi-Maxwellian based 16-moment expansion of the distribution function, assuming macroscopic parameter values characteristic of the range of solar wind conditions. While previous studies also took heat flow into account, the theoretical expansions for f and the definitions of the physical moments adopted in these studies were different from those used in this paper. The choice of the 16-moment expansion and corresponding moment definitions was motivated by the fact that this is the correct generalization of the widely-used Maxwellian-based 13-moment expansion to the case where the zeroth-order distribution is a bi-Maxwellian. It is found that most of the features characteristic of solar wind proton distributions can be reproduced with the 16-moment distribution, including the appearance of secondary peaks. It is also shown how each of the physically significant velocity moments affects the shape of the distribution function.

  16. Survey of the spectral properties of turbulence in the solar wind, the magnetospheres of Venus and Earth, at solar minimum and maximum

    NASA Astrophysics Data System (ADS)

    Echim, Marius M.

    2014-05-01

    In the framework of the European FP7 project STORM ("Solar system plasma Turbulence: Observations, inteRmittency and Multifractals") we analyze the properties of turbulence in various regions of the solar system, for the minimum and respectively maximum of the solar activity. The main scientific objective of STORM is to advance the understanding of the turbulent energy transfer, intermittency and multifractals in space plasmas. Specific analysis methods are applied on magnetic field and plasma data provided by Ulysses, Venus Express and Cluster, as well as other solar system missions (e.g. Giotto, Cassini). In this paper we provide an overview of the spectral properties of turbulence derived from Power Spectral Densities (PSD) computed in the solar wind (from Ulysses, Cluster, Venus Express) and at the interface of planetary magnetospheres with the solar wind (from Venus Express, Cluster). Ulysses provides data in the solar wind between 1992 and 2008, out of the ecliptic, at radial distances ranging between 1.3 and 5.4 AU. We selected only those Ulysses data that satisfy a consolidated set of selection criteria able to identify "pure" fast and slow wind. We analyzed Venus Express data close to the orbital apogee, in the solar wind, at 0.72 AU, and in the Venus magnetosheath. We investigated Cluster data in the solar wind (for time intervals not affected by planetary ions effects), the magnetosheath and few crossings of other key magnetospheric regions (cusp, plasma sheet). We organize our PSD results in three solar wind data bases (one for the solar maximum, 1999-2001, two for the solar minimum, 1997-1998 and respectively, 2007-2008), and two planetary databases (one for the solar maximum, 2000-2001, that includes PSD obtained in the terrestrial magnetosphere, and one for the solar minimum, 2007-2008, that includes PSD obtained in the terrestrial and Venus magnetospheres and magnetosheaths). In addition to investigating the properties of turbulence for the minimum and maximum of the solar cycle we also analyze the spectral similarities and differences between fast and slow wind turbulence. We emphasize the importance of our data survey and analysis in the context of understanding the solar wind turbulence, the exploitation of data bases and as a first step towards developing a (virtual) laboratory for studying solar system plasma turbulence. Research supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS - UEFISCDI, project number PN-II-ID-PCE-2012-4-0418.

  17. 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.

  18. A Method for the Instantaneous Determination of the Velocity and Direction of the Wind

    NASA Technical Reports Server (NTRS)

    Huguenard, E; Magnan, A; Planiol, A

    1924-01-01

    The laboratory instruments, which we often constructed with makeshift means, gave encouraging results and showed that they could satisfactorily meet the required conditions. By limiting ourselves to the employment of hot wires of 0.05 mm (0.002 in.) diameter, we obtained instruments which faithfully followed all the wind fluctuations of over 0.1 second and even much more rapid variations without any very great error.

  19. 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, α = 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.

  20. (abstract) Interplanetary Lyman-alpha Observations with the Galileo Ultraviolet Spectrometer: Solar Wind Latitude Variations and Multiple Scattering at Solar Maximum

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.; Prior, W. R.; Barth, C. A.; Hord, C. W.; Simmons, K. E.; Hall, D. T.; White, O. R.

    1993-01-01

    The Galileo Ultraviolet Spectrometer obtained a Lyman-alpha celestrial sphere map on 13,14 December 1990 near the first Earth encounter, with spacecraft near the interstellar wind downwind axis. The data show solar flux longitudinal and latitudinal asymmetries which are modeled with He 10830 Ssolar images. The difference between the observed brightness and a single scattering model is attributed to multiple scattering effects, which we also calculate. The data constrain the solar wind flux latitude variation at solar maximum. Other 1990-1992 Galileo Lyman-alpha data will be discussed.

  1. Development of Simultaneous Pressure and Velocity Measurements Using Multi-Luminophore Microspheres for Wind Tunnel Application

    NASA Astrophysics Data System (ADS)

    Pryor, Lillian

    The development of pressure-sensitive microbeads allows for simultaneous measurement of pressure and velocity. These aerosolized microbeads are loaded with a pressure-sensitive dye coupled with a pressure-insensitive reference dye to provide pressure measurements. Methods of fabricating these particles and the results from their response times, characterized using a shock tube facility, are presented and discussed. Imaging techniques of these particles are developed and are used for creating Stern-Volmer plots for each of the particle types developed by measuring the intensities of the pressure-sensitive dye normalized to those of the reference dye and then to a baseline condition intensity ratio. Light intensity from the microspheres is measured using EMCCD cameras and processed to back-calculate pressure. A PIV camera is used to measure light intensity from the reference dye and in the future will be used to track the particles velocities. Further results regarding technique development will be discussed.

  2. Comparative Solar Wind Properties at 9AU between the maximum and late declining phases of the Solar Cycle and possible implications for the magnetospheric dynamics of Saturn

    NASA Astrophysics Data System (ADS)

    Went, D. R.; Jackman, C. M.; Forsyth, R. J.; Dougherty, M. K.; Crary, F. J.

    2009-04-01

    We compare and contrast the general plasma and magnetic field properties of the solar wind upstream of Saturn (8.5-9.5 AU) at solar maximum (Pioneer-11 encounter) and the late-declining (Cassini approach) phase of the solar cycle. In both cases we find a highly structured solar wind dominated by co-rotating interaction regions (CIRs), merged interaction regions (MIRs) and Interplanetary Coronal Mass Ejections (ICMEs) that temporarily disrupt an otherwise clear two sector interplanetary magnetic field structure. Solar rotations generally contain two CIR compressions with embedded crossings of the heliospheric current sheet. There is no conclusive evidence for (persistent) departures from the Parker Spiral IMF model in this region of the heliosphere at either phase of the solar cycle, consistent with previous analyses (Thomas and Smith 1980, Jackman et al. 2008). However it is clear that average plasma properties vary significantly between the maximum and late declining phases of the cycle and there are a number of small but notable deviations. In particular, the average dynamic pressure of the solar wind varies by a factor of roughly two between solar maximum and solar minimum with potentially important consequences for the dynamics of Saturn's magnetosphere. These consequences should become apparent as Cassini enters its extended Equinox Mission which should encompass the rising phase and eventually maximum of Solar Cycle 24. They will be discussed and predictions will be made for future Cassini observations.

  3. Observations of thermospheric wind velocities and temperatures by the use of a Fabry-Perot Doppler imaging system at Syowa Station, Antarctica.

    PubMed

    Nakajima, H; Okano, S; Fukunishi, H; Ono, T

    1995-12-20

    A new optical instrument, the Fabry-Perot Doppler imaging system (FPDIS), has been developed for observations of two-dimensional distributions of thermospheric wind velocities and temperatures by the measurement of the Doppler shift and width of the aurora or of the airglow emission lines of atomic oxygen OI 557.7 nm and OI 630.0 nm over a wide field of view (165°). A technique for the derivation of Doppler temperatures and wind velocities was developed by use of a truncated Fourier series. Thermospheric wind velocities and temperatures have been obtained with unprecedented high temporal (1 min) and spatial (24 points for an all-sky image) resolutions. Errors in the derived wind velocities and temperatures are estimated to be less than 25 m/s and 100 K, respectively, for inner-fringe positions and 35 m/s and 170 K for outer-fringe positions, respectively. This system was applied to observations of thermospheric wind velocities and temperatures at Syowa Station (69.00° S, 39.58° E), Antarctica for the period of one austral winter in 1990. PMID:21068959

  4. Non-gyrotropic Velocity Distributions of Solar Wind Protons Observed by WIND/3DP --A Possible Evidence for Perpendicular Heating by Lower Hybrid Waves

    NASA Astrophysics Data System (ADS)

    He, J.; Tu, C.; Wang, L.; Marsch, E.; Yang, L.; Yao, S.

    2013-12-01

    The velocity distribution function (VDF) of fast solar wind protons usually shows following features: (1) an anisotropic bi-shell-like core with T_perp>T_para; (2) a minor beam component aligned mainly along the local background magnetic field vector. The anisotropic core is theoretically characterized as a heating result by Alfven-cyclotron waves, while the field-aligned beam is attributed to be accelerated probably by kinetic Alfven waves or ion-acoustic waves. Here, we report a third part of the distribution, 'non-gyrotropic patch', based on observations from the 3DP plasma instrument onboard WIND. With the non-gyrotropic patch sticking out from the normal core part, the VDF is no longer axis-symmetric around local background magnetic field. This extra non-gyrotropic part may be a result of unidirectional perpendicular heating by some kind of high-frequency quasi-perpendicular electrostatic wave, which has yet to be observationally identified. As a speculation, we study the modification of protons in the velocity phase space by lower hybrid waves. In our result of test-particle simulation, we find the protons can be perpendicularly heated along the wave propagation direction, and a non-gyrotropic patch is formed as a result of such heating. Moreover, although the perpendicular-heated protons then diffusively rotate around the magnetic field, the non-gyrotropic patch still remains more condensed as compared with the other part of the same shell. Therefore, the observed non-gyrotropic distribution is suggested to be a possible evidence of perpendicular heating by high-frequency quasi-perpendicular electrostatic waves, e.g., lower hybrid waves.

  5. Optical fiber-based laser remote sensor for airborne measurement of wind velocity and turbulence.

    PubMed

    Spuler, Scott M; Richter, Dirk; Spowart, Michael P; Rieken, Kathrin

    2011-02-20

    We discuss an optical fiber-based continuous-wave coherent laser system for measuring the wind speed in undisturbed air ahead of an aircraft. The operational principles of the instrument are described, and estimates of performance are presented. The instrument is demonstrated as a single line of sight, and data from the inaugural test flight of August 2010 is presented. The system was successfully operated under various atmospheric conditions, including cloud and clear air up to 12 km (40,300 ft). PMID:21343963

  6. 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.

  7. 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.

  8. 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 (σu, σv, σw, and σT), 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 σu (4-8% decrease), very strong in σv (9-11% decrease), and minimal in σw (-3 to 4% change) while only σu 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.

  9. A study of the geographic coverage properties of a satellite borne Doppler lidar wind velocity measuring system

    NASA Technical Reports Server (NTRS)

    Pate, T. H.

    1982-01-01

    Geographic coverage frequency and geographic shot density for a satellite borne Doppler lidar wind velocity measuring system are measured. The equations of motion of the light path on the ground were derived and a computer program devised to compute shot density and coverage frequency by latitude-longitude sections. The equations for the coverage boundaries were derived and a computer program developed to plot these boundaries, thus making it possible, after an application of a map coloring algorithm, to actually see the areas of multiple coverage. A theoretical cross-swath shot density function that gives close approximations in certain cases was also derived. This information should aid in the design of an efficient data-processing system for the Doppler lidar.

  10. Wind-velocity lidar measurements by use of a Mach-Zehnder interferometer, comparison with a Fabry-Perot interferometer.

    PubMed

    Bruneau, Didier; Garnier, Anne; Hertzog, Albert; Porteneuve, Jacques

    2004-01-01

    We present the first wind-velocity profiles obtained with a direct-detection Doppler lidar that uses a Mach-Zehnder interferometer (MZI) as spectral discriminator. The measurements were performed in the lower stratosphere, between 10 and 40 km in altitude, at the Observatoire de Haute Provence (OHP), France, during nighttime. They are in excellent agreement with those obtained simultaneously and independently with the already validated double Fabry-Perot interferometer (FPI) of the OHP Doppler lidar (mean difference lower than the combined standard deviation). A statistical analysis shows that the random error obtained with this experimental MZI is 1.94 times the Cramer-Rao lower bound and is approximately half of that given by the FPI (both operating in photometric mode). Nevertheless, the present MZI measurements are sensitive to the presence of atmospheric particles and need an additional correction, whereas the OHP FPI is designed to be insensitive to particulate scattering. PMID:14714660

  11. Estimation of the Solar Wind Velocity at 85 AU from Voyager-1/LECP Energetic Ion Angular Distributions

    NASA Astrophysics Data System (ADS)

    Roelof, E. C.; Decker, R. B.; Krimigis, S. M.

    2003-12-01

    Voyager-1 (V1) encountered a remarkable region of the heliosphere at 85 AU during the last half of 2002 (Krimigis, et al., this Conference). Because the plasma instrument on Voyager-1 is inoperative, we extract the solar wind velocity (V) by using its effect upon the intensity anisotropy measured by the Low Energy Charged Particle (LECP) instrument. The V1 LECP measurements indicated significant field-aligned anisotropies strong enough to invalidate the use of the linearized Compton-Getting transformation. Consequently, based on gyrotropic weak-scattering theory we assume an exponential distribution ˜ exp(α μ ) in pitch-cosine (μ ) that is convected with the solar wind. We transform it (non-linearly) into the spacecraft frame with a Galilean velocity transformation. We measure a power-law index for the energy spectrum k=1.5. We allow for weak coupling (backscatter) between hemispheres by setting the anisotropy parameter α =α + for the forward and α =α - for the backward hemisphere. The time-averaged LECP distributions consistently peak in spin sector 7 (the Sun splits sectors 1 and 8, the latter being blocked by a shield), so we assign the mean direction of the magnetic field to its center and normalize the intensities there. The normalized intensities in the remaining 6 sectors for each LECP channel are then fitted by a least-squares minimization that varies the remaining parameters (α +, α -, and V). Thus we extract the solar wind velocity from the LECP angular distributions. The best fits give V=0 over proton energies from 30 keV to 1 MeV, with energy-dependent uncertainties averaging ˜50 km/s. We cannot explain our observations using conventional diffusion-convection (strong-scattering) theory under the assumption that V1 did not leave the normal solar wind and magnetic field. The condition for diffusion-convection equilibrium with no radial streaming in the inertial frame implies a positive radial gradient with a source of particles beyond V1 in order to nullify the solar wind convection. Over the same time period, LECP observes a strong azimuthal anisotropy, which (if the average magnetic field is wound in a Parker sense), corresponds to gradient of increasing intensity as one moves inward along the field. This parallel streaming then implies a source of particles inside the radius of Voyager, but this is inconsistent with the positive radial gradient demanded by the radial transport equation. A quantitative analysis of the latter leads to a mean radial gradient ˜100%/AU with a comparable standard deviation. These are orders of magnitude bigger than gradients usually deduced for the outer heliosphere. We consider it unreasonable that such a configuration could endure there for half a year.

  12. Estimation of neutral wind velocity in the ionospheric heights by HF-Doppler technique

    NASA Technical Reports Server (NTRS)

    Kitamura, T.; Takefu, M.; Hiroshige, N.

    1985-01-01

    Three net stations located about 100 kilometers apart were set up around the station of the standard frequency and time signals (JJY) in central Japan and measurements of atmospheric gravity waves in the ionospheric heights (F-region, 200 to 400 km) were made by means of the HF-Doppler technique during the period of February 1983 to December 1983. The frequencies of the signals received are 5.0, 8.0 and 10.0 MHz, but only the 8.0 MHz signals are used for the present study, because no ambiguities due to the interference among other stations such as BPM, BSF, etc. exist by the use of 8.0 MHz. Two main results concerning the horizontal phase velocity of the atmospheric gravity waves with periods of 40 to 70 min may be summarized as follows: (1) the value of the phase velocity ranges from 50 m/s to 300 m/s; (2) the direction of the gravity wave propagation shows a definite seasonal variation. The prevailing direction of the gravity waves in winter is from north to south, which is consistent with the results obtained from other investigations. On the other hand, the two directions, from northeast to southwest and from southeast to northeast, dominate in summer.

  13. Pitch angle and velocity diffusions of newborn ions by turbulence in the solar wind

    NASA Technical Reports Server (NTRS)

    Ziebell, L. F.; Yoon, Peter H.

    1990-01-01

    The temporal evolution of the distribution function of newborn ions under the influence of intrinsic low-frequency solar wind turbulences is studied. In particular, an initial ring-beam distribution of newborn ions under the influence of hydromagnetic waves is considered. A simplified treatment of the resonance broadening effect is given, and its role in the pickup process is discussed. Two different configurations of wave polarization amd direction of propagation are considered. The conditions that lead either to the formation of anisotropic shells as a long-duration transient state or to rapid isotropization of the ion pitch angle distribution are discussed, as are the conditions which lead to significant acceleration of the ions.

  14. Tsallis Distribution Functions in the Solar Wind: Magnetic Field and Velocity Observations

    SciTech Connect

    Burlaga, Leonard F.; Vinas, Adolfo F.

    2007-12-06

    The distributions the fluctuations of magnetic field strengths B(t) observed on a scale of a year in the heliosphere between 1 AU and 90 AU are approximately lognormal. The PDFs of the corresponding increments of B(t) are Tsallis distributions on scales from 1 hr--128 days between 1 and 90 AU. A deterministic MHD model predicts these results. The model predicts that small chaotic structures merge to form large structures. There is a 'phase transition' near {approx}40 AU at which the there is a change from growth to decay. Between R{approx}40 and 85 AU the solar wind is in a quasi-equilibrium state described by a 'q-triplet'.

  15. Characteristics of electron velocity distribution functions in the solar wind derived from the Helios plasma experiment

    NASA Technical Reports Server (NTRS)

    Pilipp, W. G.; Muehlhaeuser, K.-H.; Miggenrieder, H.; Montgomery, M. D.; Rosenbauer, H.

    1987-01-01

    The details of the shapes of three typical electron distribution functions observed by the Helios 1 and 2 probes in the solar wind between 0.3 AU and 1 AU are analyzed and compared with theoretical predictions. These are (1) a distribution function with a narrow 'strahl' (narrow beam), which is extremely anisotropic and skewed with respect to the magnetic field direction at particle energies above 100 eV; (2) a distribution function with a broad 'strahl', less anisotropic and skewed; and (3) a nearly isotropic distribution function. For each distribution function, a sudden change in the slope was discerned, separating the 'core' at lower energies from the 'halo' at higher energies. The most obvious differences of the analyzed electron distribution functions were observed at energies above 50-100 eV. The possible origins for the observed features of the distribution functions are discussed.

  16. 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 (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS 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 δVS≥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 δVS>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.

  17. 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.

  18. 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.

  19. Calibration of the maximum carboxylation velocity (Vcmax) using data mining techniques and ecophysiological data from the Brazilian semiarid region, for use in Dynamic Global Vegetation Models.

    PubMed

    Rezende, L F C; Arenque-Musa, B C; Moura, M S B; Aidar, S T; Von Randow, C; Menezes, R S C; Ometto, J P B H

    2016-06-01

    The semiarid region of northeastern Brazil, the Caatinga, is extremely important due to its biodiversity and endemism. Measurements of plant physiology are crucial to the calibration of Dynamic Global Vegetation Models (DGVMs) that are currently used to simulate the responses of vegetation in face of global changes. In a field work realized in an area of preserved Caatinga forest located in Petrolina, Pernambuco, measurements of carbon assimilation (in response to light and CO2) were performed on 11 individuals of Poincianella microphylla, a native species that is abundant in this region. These data were used to calibrate the maximum carboxylation velocity (Vcmax) used in the INLAND model. The calibration techniques used were Multiple Linear Regression (MLR), and data mining techniques as the Classification And Regression Tree (CART) and K-MEANS. The results were compared to the UNCALIBRATED model. It was found that simulated Gross Primary Productivity (GPP) reached 72% of observed GPP when using the calibrated Vcmax values, whereas the UNCALIBRATED approach accounted for 42% of observed GPP. Thus, this work shows the benefits of calibrating DGVMs using field ecophysiological measurements, especially in areas where field data is scarce or non-existent, such as in the Caatinga. PMID:26959950

  20. 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 Vθm(m/s) of the turbulent rotational air flow and the collection efficiency ηc (%) 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 Vθm (m/s), the conservation theory of the angular momentum flux with Ogawa combined vortex model was applied. The comparisons of the estimated results of Vθm(m/s) with the measured results by the cylindrical Pitot-tube were shown in good agreement. And also the estimated collection efficiencies ηcth (%) basing upon the cut-size Xc (µm) which was calculated by using the estimated Vθ 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 ηc (%) related to the contribution of the secondary jet flow is principally to apply the centrifugal effect Φc (1). Above stated results are described in detail.

  1. 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.

  2. Time changes of solar activity, interplanetary magnetic field and solar wind velocity at the Earth's orbit in different spectral bands

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Tamara V.; Tsirulnik, Lev B.

    2008-02-01

    We present the results of our analysis of the spectra of the interplanetary magnetic field (IMF) and the solar wind velocity (V) calculated on the basis of measurements near the Earth's orbit for the period 1964-1997, and of the sunspot number W. The major aim is to search for similar features in various frequency bands, with an emphasis on the period of solar (sunspot) cycle and its harmonics, and on so-called "intermittent" oscillations at periods and . We also extract trends from the data to determine long-period changes of IMF and V. A method of non-linear spectral analysis, which we term "the method of global minimum" (MGM) is used. MGM allows self-consistent identification of trends from data and nonstationary sinusoids and estimation of statistical significance of spectral components. The IMF and W spectra both show the main solar cycle at . In addition, the spectrum of the IMF includes (at 99.8% confidence levels) harmonics of this cycle with periods of 151.3 and 136.5 d. We also detect nonstationary sinusoids at in the spectra of IMF and of V and describe their parameters. The detailed description of the 1.3-yr oscillations in the solar wind is of particular interest in that the oscillations are likely to be connected to variations in the rotation rate with the same period near the base of convection zone of the Sun discovered in SOHO data. The 1.3-yr oscillations are not present in the W spectra. Instead, we find oscillations at T=1.014 and 0.950 yr and suggest an explanation of their presence. Relation between the variations in the spectra of W and V is not as evident as between W and the IMF, however, it exists. In particular, harmonics of the 10.8-yr solar cycle (e.g., sinusoid at ) are present in the spectrum of V. Components in the spectra described by high-amplitude sinusoids with in the IMF spectrum and with in the V spectrum make contributions to the long-term trends in these parameters. The trend of V demonstrates a 55% increase in the solar wind velocity for the period 1964-1997. The IMF trend shows a 45% increase of the IMF magnitude for the same time interval; extrapolation of this temporal variation to the past leads to a doubling of the IMF value during the last 100 yr.

  3. Threshold wind velocity dynamics as a driver of aeolian sediment mass flux

    NASA Astrophysics Data System (ADS)

    Webb, Nicholas P.; Galloza, Magda S.; Zobeck, Ted M.; Herrick, Jeffrey E.

    2016-03-01

    Horizontal (saltation) mass flux is a key driver of aeolian dust emission. Estimates of the horizontal mass flux underpin assessments of the global dust budget and influence our understanding of the dust cycle and its interactions. Current equations for predicting horizontal mass flux are based on limited field data and are constrained to representing transport-limited equilibrium saltation, driven by the wind momentum flux in excess of an entrainment threshold. This can result in large overestimation of the sediment mass flux. Here we compare measurements of the soil entrainment threshold, horizontal mass flux, and their temporal variability for five undisturbed dryland soils to explore the role of threshold in controlling the magnitude of mass flux. Average and median entrainment threshold showed relatively small variability among sites and relatively small variability between seasons, despite significant differences in soil surface conditions. Physical and biological soil crusts had little effect on the threshold value, and threshold appeared to play a minor role in determining the magnitude of sediment transport. Our results suggest that horizontal mass flux was controlled more by the supply limitation and abrasion efficiency of saltators present as loose erodible material or originating from neighboring soil sources. The omission of sediment supply and explicit representation of saltation bombardment from horizontal flux equations is inconsistent with the process representation in dust emission schemes and contributes to uncertainty in model predictions. This uncertainty can be reduced by developing greater process fidelity in models to predict horizontal mass flux under both supply- and transport-limited conditions.

  4. 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 ΔU 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 ΔU/U ≃ 0.1 at the position of the heliospheric termination shock, where ΔU 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.

  5. Vortical Structures in the Near-tail Boundary Layer Under Collinear Magnetic and Velocity Fields in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Gratton, F. T.; Gnavi, G.; Torbert, R. B.

    2011-12-01

    A data example is presented of rolled - up vortical structures in the near-equatorial plasma sheet-boundary layer tailward of the terminator (X = -12 RE) under an almost radially-directed IMF vector. The observations were made by the Wind spacecraft moving across the region. The rolling up is inferred from the presence of tenuous-hot plasma being accelerated to speeds higher than that in the adjoining magnetosheath. The low-density plasma phase alternates quasi-periodically with dense-cold matter, that moves sunward with significant velocities with respect to the average tailward speed. These features form a good criterion to decide the presence of whirling plasma in the BL using records of one spacecraft alone. A repetitive sequence of about 15 vortices are observed over the entire 1.5 hour-long crossing. A blob of cold, dense plasma sheet was entrained in each vortex, an instance of CDPS. On the opposite side of noon tailward of the terminator spacecraft Polar was crossing the equatorial current sheet. It recorded several instances of compressive magnetic field oscillations of period ~4.1 min, similar to the periodicity of the dynamic pressure changes occasioned by the vortices. Inquiring into the generation mechanism of the vortical structures, we analyze the plasma sheet using compressible MHD Kelvin - Helmholtz stability theory, using continuous profiles for the physical quantities. We input parameters resulting from the exact theory of magnetosheath flow under aligned solar wind field and flow vectors (Spreiter and Rizzi, 1974) near the terminator, and derived from Wind data at the spacecraf's locale. Theory shows that the configuration is indeed KH unstable, all the way from near Earth to the Wind position. Therefore, the analysis of BL data proves the presence of vortical motions with plasma mixing, and theory suggests a KH origin of the structures, under an almost radial IMF and supersonic magnetosheath flow. Here we depart substantially from previous studies which showed vortices to occur under a strongly northward (or, more rarely, southward) IMF orientation.

  6. Effects of forward velocity on noise for a J85 turbojet engine with multitube suppressor from wind tunnel and flight tests

    NASA Technical Reports Server (NTRS)

    Stone, J. R.; Miles, J. H.; Sargent, N. B.

    1976-01-01

    Flight tests and wind tunnel noise tests using a J85 engine with some representative jet exhaust noise suppressors are reported. Capabilities and limitations of the two types of experimental methods are evaluated with emphasis on investigation of forward velocity effects. The suppressor arrangement was a 104-elliptical-tube nozzle configuration, with or without an acoustically lined shroud. The suppressor noise levels are found not reduced as much by forward velocity as expected for unsuppressed jets. The directivity and forward velocity effects appear more similar to predicted trends for internally generated noise than for unsuppressed jet noise.

  7. 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.

  8. Estimation of the path-averaged wind velocity by cross-correlation of the received power and the shift of laser beam centroid

    NASA Astrophysics Data System (ADS)

    Marakasov, Dmitri A.; Tsvyk, Ruvim S.

    2015-11-01

    We consider the problem of estimation of the average wind speed on atmospheric path from measurements of time series of average power of the laser radiation detected through the receiving aperture and the position of the centroid of the image of the laser beam. It is shown that the mutual correlation function of these series has a maximum, whose position characterizes the average speed of the cross wind on the path. The dependence of the coordinates and magnitude of the maximum of the correlation function from the size of the receiving aperture and the distribution of turbulence along the atmospheric path.

  9. 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.

  10. RETRACTED: The influence of sand diameter and wind velocity on sand particle lift-off and incident angles in the windblown sand flux

    NASA Astrophysics Data System (ADS)

    Bo, Tian-Li; Zheng, Xiao-Jing; Duan, Shao-Zhen; Liang, Yi-Rui

    2013-05-01

    This article has been retracted: please see Elsevier Policy on Article Withdrawal. This article has been retracted at the request of the Editors-in-Chief. This article also contains significant similarity with parts of text, written by the same author(s), that have appeared in Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, The influence of wind velocity and sand grain diameter on the falling velocities of sand particles, Powder Technology, Volume 241, June 2013, Pages 158-165. Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, Analysis of sand particles' lift-off and incident velocities in wind-blown sand flux, Acta Mechanica Sinica, April 2013, Volume 29, Issue 2, pp 158-165. Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, Influence of sand grain diameter and wind velocity on lift-off velocities of sand particles, The European Physical Journal E, May 2013, 36:50. Tian-Li Bo, Shao-Zhen Duan, Xiao-Jing Zheng, Yi-Rui Liang, The influence of sand bed temperature on lift-off and falling parameters in windblown sand flux, Geomorphology, Volume 204, 1 January 2014, Pages 477-484. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

  11. Wind-tunnel and Flight Investigations of the Use of Leading-Edge Area Suction for the Purpose of Increasing the Maximum Lift Coefficient of a 35 Degree Swept-Wing Airplane

    NASA Technical Reports Server (NTRS)

    Holzhauser, Curt A; Bray, Richard S

    1956-01-01

    An investigation was undertaken to determine the increase in maximum lift coefficient that could be obtained by applying area suction near the leading edge of a wing. This investigation was performed first with a 35 degree swept-wing model in the wind tunnel, and then with an operational 35 degree swept-wing airplane which was modified in accord with the wind-tunnel results. The wind-tunnel and flight tests indicated that the maximum lift coefficient was increased more than 50 percent by the use of area suction. Good agreement was obtained in the comparison of the wind-tunnel results with those measured in flight.

  12. 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.

  13. The effect of the time interval used to calculate mean wind velocity on the calculated drift potential, relative drift potential, and resultant drift direction for sands from three deserts in northern China

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengcai; Dong, Zhibao; Zhao, Aiguo

    2016-01-01

    Wind is the power behind many erosion processes and is responsible for many of the characteristics of arid zone geomorphology. Wind velocity is a key factor in determining the potential sand transport, but the nature of the wind velocity data can strongly affect assessments of the risk of blowing sand. In this study, we obtained real-time wind velocity data in a region of the Tengger Desert with shifting sands, in the Badain Jaran Desert, and in the Madoi desertification land, with the data obtained at 1-min intervals, and used the data to determine the influence of how the wind velocity was calculated (mean versus mid-point values and the averaging time used to calculate these values) on sand drift potential. In the three regions, for both the mean and the mid-point wind velocities, the estimated drift potential decreased with increasing averaging time. The relationships between velocities calculated using the different averaging time intervals and the value calculated using a 1-min interval could be expressed as linear functions. The drift potential calculated using the mid-point wind velocity was larger than that calculated using the mean wind velocity.

  14. Solar-wind velocity measurements from near-Sun comets C/2011 W3 (Lovejoy), C/2011 L4 (Pan-STARRS), and C/2012 S1 (ISON)

    NASA Astrophysics Data System (ADS)

    Ramanjooloo, Y.; Jones, G. H.; Coates, A.; Owens, M. J.; Battams, K.

    2014-07-01

    Since the mid-20th century, comets' plasma (type I) tails have been studied as natural probes of the solar wind [1]. Comets have induced magnetotails, formed through the draping of the heliospheric magnetic field by the velocity shear in the mass-loaded solar wind. These can be easily observed remotely as the comets' plasma tails, which generally point away from the Sun. Local solar-wind conditions directly influence the morphology and dynamics of a comet's plasma tail. During ideal observing geometries, the orientation and structure of the plasma tail can reveal large-scale and small-scale variations in the local solar-wind structure. These variations can be manifested as tail condensations, kinks, and disconnection events. Over 50 % of observed catalogued comets are sungrazing comets [2], fragments of three different parent comets. Since 2011, two bright new comets, C/2011 W3 [3] (from hereon comet Lovejoy) and C/2012 S1 [4] (hereon comet ISON) have experienced extreme solar-wind conditions and insolation of their nucleus during their perihelion passages, approaching to within 8.3×10^5 km (1.19 solar radii) and 1.9×10^6 km (2.79 solar radii) of the solar centre. They each displayed a prominent plasma tail, proving to be exceptions amongst the observed group of sungrazing comets. These bright sungrazers provide unprecedented access to study the solar wind in the heretofore unprobed innermost region of the solar corona. The closest spacecraft in-situ sampling of the solar wind by the Helios probes reached 0.29 au. For this study, we define a sungrazing comet as one with its perihelion within the solar Roche limit (3.70 solar radii). We also extend this study to include C/2011 L4 [5] (comet Pan-STARRS), a comet with a much further perihelion distance of 0.302 au. The technique employed in this study was first established by analysing geocentric amateur observations of comets C/2001 Q4 (NEAT) and C/2004 Q2 (Machholz) [7]. These amateur images, obtained with modern equipment and sensors, rival and sometimes arguably exceed the quality of professional images obtained only 2--3 decades ago. Multiple solar-wind velocity estimates were derived from each image and the results compared to observed and modelled near-Earth solar-wind data. Our unique analysis technique [Ramanjooloo et al., in preparation] allows us to determine the latitudinal variations of the solar wind, heliospheric current-sheet sector boundaries and the boundaries of transient features as a comet with an observable plasma tail probes the inner heliosphere. We present solar-wind velocity measurements derived from multiple observing locations of comets Lovejoy from the 14th -- 19th December 2011, comet Pan-STARRS during 11th -- 16th March 2013 and comet ISON from 12th -- 29th November 2013. Observations were gathered from multiple resources, from the SECCHI heliospheric imagers aboard STEREO A and B [8], the LASCO coronagraphs aboard SOHO [9], as well as ground-based amateur and professional observations coordinated by the CIOC. Overlapping observation sessions from the three spacecraft and ground-based efforts provided the perfect opportunity to use these comets as a diagnostic tool to understand solar-wind variability close to the Sun. We plan to compare our observations to results of suitable simulations [10] of plasma conditions in the corona and inner heliosphere during each of the comets' perihelion passage. The correlation of the solar-wind velocity distribution from different observing locations can provide clues towards the morphology and orientation of the plasma tail. We also attempt to determine the difficult-to-determine non-radial components of the measured solar-wind velocities.

  15. 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.

  16. 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.

  17. Seismic velocity structure of the slab and continental plate in the region of the 1960 Valdivia (Chile) slip maximum — Insights into fluid release and plate coupling

    NASA Astrophysics Data System (ADS)

    Dzierma, Yvonne; Rabbel, Wolfgang; Thorwart, Martin; Koulakov, Ivan; Wehrmann, Heidi; Hoernle, Kaj; Comte, Diana

    2012-05-01

    The south-central Chilean subduction zone has witnessed some of the largest earthquakes in history, making this region particularly important for understanding plate coupling. Here we present the results of a local earthquake tomography study from a temporary local seismic network in the Villarrica region between 39 and 40°S, where the largest coseismic displacement of the 1960 Valdivia earthquake occurred. A low-velocity anomaly and high Vp/Vs values occur under the coastal region, indicating mantle serpentinisation and/or underthrusting of forearc material. Further east, a high-velocity anomaly is observed, interpreted as "normal" high-velocity mantle. Under the active volcanic arc a low-velocity anomaly together with high Vp/Vs ratios (1.8 and higher) likely images fluid ascent beneath the volcanoes. Close to the subducting Valdivia Fracture Zone, the coastal low-velocity anomaly extends further inland, where it interrupts and shifts the high-velocity anomalies associated with "normal" fast mantle velocities. This may indicate enhanced fluid presence along this part of the margin, probably caused by a stronger hydration of the incoming plate along the Valdivia Fracture Zone. This is consistent with geochemical fluid proxies (U/Th, Pb/Ce, Ba/Nb) in young volcanic rocks displaying peak values along the volcanic front at Llaima and Villarrica Volcanoes, and with recent GPS measurements, which suggested a local reduction in plate coupling in this region. The shift in the high-velocity anomaly underlying the central part may be caused by a north to south decrease in plate age and hydration across the Valdivia Fracture Zone, and may explain why a Central Valley is absent in this segment of the margin. The low La/Yb ratios in the volcanic rocks from Villarrica and Llaima suggest that the high slab-derived fluid flux causes elevated degrees of melting beneath these volcanoes, providing an explanation as to why these are amongst the most active volcanoes in South America.

  18. 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.

  19. Inverse maximum gross bedform-normal transport 1: How to determine a dune-constructing wind regime using only imagery

    NASA Astrophysics Data System (ADS)

    Fenton, Lori K.; Michaels, Timothy I.; Beyer, Ross A.

    2014-02-01

    It has been a goal of aeolian science to use bedforms as indicators of local and regional sediment transport and atmospheric circulation, but even with the application of the rule of maximum gross-bedform normal transport (MGBNT), the underdetermined nature of the problem has precluded its application in all but the most simple cases. We present a method to apply the rule of MGBNT and its inverse (IMGBNT) from analysis of aeolian dune crestlines derived from aerial imagery. Although the solutions to IMGBNT analysis are non-unique, the possible transport vectors influencing bedform morphology can often be constrained by making inferences regarding bedform type (e.g., transverse, oblique, or longitudinal), resultant drift direction, and the ratio of transport vector magnitudes. The technique is demonstrated on the Great Sand Dunes, located in Colorado, USA. This dune field has a wide array of dune morphologies; eight crestline sets were identified and mapped. IMGBNT analysis and the subsequent constraint of possible solutions suggests that transport vectors from the southeast and southwest, with a SE:SW transport ratio of ˜1:2, produce oblique north-south oriented dunes that dominate the main dune field. These results compare favorably with MGBNT analysis of meteorologic measurements from three stations located adjacent to the Great Sand Dunes, which predict dune types and orientations similar to those observed in their vicinity.

  20. Coronal holes as sources of solar wind

    NASA Technical Reports Server (NTRS)

    Nolte, J. T.; Krieger, A. S.; Timothy, A. F.; Gold, R. E.; Roelof, E. C.; Vaiana, G.; Lazarus, A. J.; Sullivan, J. D.; Mcintosh, P. S.

    1976-01-01

    We investigate the association of high-speed solar wind with coronal holes during the Skylab mission by: (1) direct comparison of solar wind and coronal X-ray data; (2) comparison of near-equatorial coronal hole area with maximum solar wind velocity in the associated streams; and (3) examination of the correlation between solar and interplanetary magnetic polarities. We find that all large near-equatorial coronal holes seen during the Skylab period were associated with high-velocity solar wind streams observed at 1 AU.

  1. Results from 1984 airborne Doppler lidar wind measurement program. Flight 6: Analysis of line-of-sight elevation angle errors and apparent Doppler velocities

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry

    1987-01-01

    During the summer of 1984 the Marshall Space Flight Center's Airborne Doppler Lidar System (ADLS) made a series of wind measurements in the California Central Valley. This study quantifies the lidar beam angle errors and velocity errors through analysis of ground return signals. Line-of-sight elevation (LOSE) angle errors are under 1 deg. Apparent Doppler ground velocities, as large as 2m/s, are considerably less than in a previous flight experiment in 1981. No evidence was found of a Schuler resonance phenomenon common to inertial navigation systems (INS), however the aperiodic nature of the apparent velocities implies an error in the INS-derived ground speeds. Certain features and subtleties in the ground returns are explained in terms of atmospheric structure and characteristics of the ADLS hardware and software. Finally, least squares and low-pass filtering techniques are suggested for eliminating errors during post-processing.

  2. Orientation cues for high-flying nocturnal insect migrants: do turbulence-induced temperature and velocity fluctuations indicate the mean wind flow?

    PubMed

    Reynolds, Andy M; Reynolds, Don R; Smith, Alan D; Chapman, Jason W

    2010-01-01

    Migratory insects flying at high altitude at night often show a degree of common alignment, sometimes with quite small angular dispersions around the mean. The observed orientation directions are often close to the downwind direction and this would seemingly be adaptive in that large insects could add their self-propelled speed to the wind speed, thus maximising their displacement in a given time. There are increasing indications that high-altitude orientation may be maintained by some intrinsic property of the wind rather than by visual perception of relative ground movement. Therefore, we first examined whether migrating insects could deduce the mean wind direction from the turbulent fluctuations in temperature. Within the atmospheric boundary-layer, temperature records show characteristic ramp-cliff structures, and insects flying downwind would move through these ramps whilst those flying crosswind would not. However, analysis of vertical-looking radar data on the common orientations of nocturnally migrating insects in the UK produced no evidence that the migrants actually use temperature ramps as orientation cues. This suggests that insects rely on turbulent velocity and acceleration cues, and refocuses attention on how these can be detected, especially as small-scale turbulence is usually held to be directionally invariant (isotropic). In the second part of the paper we present a theoretical analysis and simulations showing that velocity fluctuations and accelerations felt by an insect are predicted to be anisotropic even when the small-scale turbulence (measured at a fixed point or along the trajectory of a fluid-particle) is isotropic. Our results thus provide further evidence that insects do indeed use turbulent velocity and acceleration cues as indicators of the mean wind direction. PMID:21209956

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

    NASA Astrophysics Data System (ADS)

    Bruneau, Didier; Pelon, Jacques

    2003-02-01

    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.

  4. 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.

  5. 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.

  6. Some features of the radial-velocity variations of lines of different intensity in the spectrum of HD 93521. Variability of the stellar wind

    NASA Astrophysics Data System (ADS)

    Rzaev, A. Kh.

    2007-12-01

    CCD spectra taken with the PFES echelle spectrograph of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences are used to perform a detailed study of the variability of the profiles of Hell, H β, and H α lines in the spectrum of HD 93521. The pattern and nature of the variability of the Hell lines are similar to those of weak HeI lines and are due to nonradial pulsations. The period and amplitude of the radial-velocity variations are the same for the blue and red halves of the absorption profile but their phases are opposite. The behavior of the variations of H β and H α hydrogen lines relative to their mean profiles is the same as that of strong HeI line and is due to nonradial pulsations. The period and phase of the radial-velocity oscillations are the same for the blue and red halves of the absorption profile but their amplitude are different. The behavior of the radial-velocity variations of the absorption and emission components of the H α line indicates that the latter also are caused by nonradial pulsations. All this is indicative of the complex structure of the stellar wind in the region of its origin. The behavior of variability and wind kinematics differ in different directions and for different regions of the atmosphere and/or envelope.

  7. Scatterometer azimuthal response and wind wave directionality

    NASA Technical Reports Server (NTRS)

    Giovanangeli, J. P.; Le Calve, O.; Bliven, L.

    1989-01-01

    Azimuthal response of a scatterometer to radiation scattered by the sea surface was studied in a wind-wave tank. The variation of the normalized radar cross section with the azimuth angle is fitted by a three-term series. Results show that the upwind-downwind asymmetry decreases as the wind speed increases. The crosswind modulation depends on the wind velocity. The results show that the evolution of the long-wind-crosswind ratio evolves with wind speed in a manner similar to the evolution of the isotropy of short capillary-gravity waves. The maximum of the isotropy of the short wind waves is obtained for wind velocities close to 4 m/s. For the same value of the velocity, the variations of radar response between long-wind and crosswind directions is minimum. For lower or higher values of wind velocities the directional accuracy of the radar increases, since the wind-wave field tends to align in the wind direction.

  8. 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.

  9. MACS, An Instrument, and a Methodology for Simulations 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.; Fisher, Richard R. (Technical Monitor)

    2000-01-01

    The determination of the radial and latitudinal temperature and wind profiles of the solar corona is of great importance in understanding the coronal heating mechanism and the dynamics of coronal expansion. Cram presented the theory for the formation of the K-coronal spectrum and identified two important observations. He observed the existence of temperature sensitive anti-nodes at certain wavelengths in the theoretical K-coronal spectra. The anti-nodes are separated by temperature-insensitive nodes. Remarkably, Cram showed that the wavelengths of the nodes and anti-nodes are almost independent of altitude above the solar limb. Because of these features, Cram suggested that the intensity ratios at two anti-nodes could be used as a diagnostic of the electron temperature in the K-corona. Based on this temperature diagnostic technique prescribed by Cram a slit-based spectroscopic study was performed by Ichimoto et al. on the solar corona in conjunction with the total solar eclipse of 3 Nov 1994 in Putre, Chile to determine the temperature profile of the solar corona. 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 measurement 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 Aug 1999 in Elazig, Turkey. In this instrument one end of each of twenty fiber optic tips were positioned in the focal plane of the telescope in such a way that we could observe conditions simultaneously at many different latitudes and two different radial distances in the solar corona. The other ends of the fibers were vertically aligned and placed at the primary focus of the collimating lens of the spectrograph to obtain simultaneous and global spectra on the solar corona. By isolating the K-coronal spectrum from the spectrum recorded by each fiber the temperature and the wind sensitive intensity ratios were calculated to obtain simultaneous and global measurements of the thermal electron temperature and the solar wind velocity. We were successful in obtaining reliable estimates of the coronal temperature at many positions in the corona. This is the first time that simultaneous measurements of coronal temperatures have been obtained at so many points. However due to instrumental scattering encountered during observations, reliable estimates of the wind velocity turned out to be impossible to obtain. Although remedial measures were taken prior to observation, this task proved to be difficult owing to the inability to replicate the conditions expected during an eclipse in the laboratory. The full extent of the instrumental scattering was apparent only when we analyzed the observational sequence. Nevertheless the experience obtained from this very first attempt to simultaneously and globally measure both the wind velocity and the temperature on the solar corona have provided valuable information to conduct any future observations successfully.

  10. 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.

  11. Linear dependence of the postsunset equatorial anomaly electron density on solar flux and its relation to the maximum prereversal E × B drift velocity through its dependence on solar flux

    NASA Astrophysics Data System (ADS)

    Whalen, James A.

    2004-07-01

    The postsunset equatorial ionization anomaly, with maximum F layer electron density, Nemax, occurring near 2100 LT, has been found during solar maximum to be a linear function of the maximum prereversal E × B drift velocity (E × B drift). In order to examine this relation at all levels of solar flux, Nemax is measured during 13 years of an entire solar cycle by eight ionospheric sounders located in the anomaly in both north and south dip latitudes and in eastern Asia, the Pacific, and South America. At each location the monthly median Nemax increases linearly with the monthly average solar flux, Sa, over the range from 70 to 285 sfu. The linear function varies markedly with location and by month at each location. The relation to E × B drift, which is also a linear function of Sa, is determined using measurements of Nemax versus Sa measured at Bogota in the anomaly plotted as a function of E × B versus Sa measured at Jicamarca at the dip equator. The result is that Nemax is a linear function of E × B, which is in agreement with that found previously during solar maximum. Accordingly, the Nemax versus E × B relation is independent of Sa. The fact that Nemax is linear in Sa at each site implies Nemax is linear in E × B at each but with a functional dependence that varies with latitude and longitude.

  12. Evolution of The Proton Velocity Distribution due to Stochastic Heating in the Near-Sun Solar Wind

    NASA Astrophysics Data System (ADS)

    Klein, Kristopher G.; Chandran, Benjamin D. G.

    2016-03-01

    We investigate how the proton distribution function evolves when the protons undergo stochastic heating by strong, low-frequency, Alfvén-wave turbulence under the assumption that β is small. We apply our analysis to protons undergoing stochastic heating in the supersonic fast solar wind and obtain proton distributions at heliocentric distances ranging from 4 to 30 solar radii. We find that the proton distribution develops non-Gaussian structure with a flat core and steep tail. For r\\gt 5 {R}{{S}}, the proton distribution is well approximated by a modified Moyal distribution. Comparisons with future measurements from Solar Probe Plus could be used to test whether stochastic heating is occurring in the solar-wind acceleration region.

  13. Wind velocity, water vapor, and temperature measurements from space using 2 um Tm:Ho;YAG laser

    NASA Astrophysics Data System (ADS)

    Ghibaudo, Jean-Bernard; Krawczyk, Rodolphe; Armandillo, Errico; Faucheux, Marc A.; Benedetti-Michelangeli, G.; Hettlage, E.; Flamant, Pierre H.; Pelon, Jacques R.; Fantoni, Roberta; Salvetti, G.; Fiocco, G.; Luthy, Willy

    1994-09-01

    In meteorological and climatological fields, the scientific community will increasingly need global measurements of key atmospheric parameters with high spatial resolution (horizontal as well as vertical): the spaceborne lidars are the most suitable instruments for those missions. While backscatter lidar (ATLID, currently studied as ESA) is presently first candidate for space deployment, the next generation of lidars will be DIAL and Doppler wind lidars, presenting a higher level of complexity, mainly due to the large power and complex signal processing required. The present considered wind lidars are based on CO(subscript 2) lasers, whose space compliance still needs confirmation, while alexandrite lasers are considered for water vapor and temperature measurements, but they need flashlamp pumping which poses a lot of several thermal constraints and lifetime problems: on the other side, the recent developments achieved in solid-state technology allow to envisage diode pumping as most promising possibility for both previous applications.

  14. Empirical relation between induced velocity, thrust, and rate of descent of a helicopter rotor as determined by wind-tunnel tests on four model rotors

    NASA Technical Reports Server (NTRS)

    Castles, Walter, Jr.; Gray, Robin B.

    1951-01-01

    The empirical relation between the induced velocity, thrust, and rate of vertical descent of a helicopter rotor was calculated from wind tunnel force tests on four model rotors by the application of blade-element theory to the measured values of the thrust, torque, blade angle, and equivalent free-stream rate of descent. The model tests covered the useful range of C(sub t)/sigma(sub e) (where C(sub t) is the thrust coefficient and sigma(sub e) is the effective solidity) and the range of vertical descent from hovering to descent velocities slightly greater than those for autorotation. The three bladed models, each of which had an effective solidity of 0.05 and NACA 0015 blade airfoil sections, were as follows: (1) constant-chord, untwisted blades of 3-ft radius; (2) untwisted blades of 3-ft radius having a 3/1 taper; (3) constant-chord blades of 3-ft radius having a linear twist of 12 degrees (washout) from axis of rotation to tip; and (4) constant-chord, untwisted blades of 2-ft radius. Because of the incorporation of a correction for blade dynamic twist and the use of a method of measuring the approximate equivalent free-stream velocity, it is believed that the data obtained from this program are more applicable to free-flight calculations than the data from previous model tests.

  15. Empirical Relation Between Induced Velocity, Thrust, and Rate of Descent of a Helicopter Rotor as Determined by Wind-tunnel Tests on Four Model Rotors

    NASA Technical Reports Server (NTRS)

    Castles, Walter, Jr; Gray, Robin B

    1951-01-01

    The empirical relation between the induced velocity, thrust, and rate of vertical descent of a helicopter rotor was calculated from wind tunnel force tests on four model rotors by the application of blade-element theory to the measured values of the thrust, torque, blade angle, and equivalent free-stream rate of descent. The model tests covered the useful range of C(sub t)/sigma(sub e) (where C(sub t) is the thrust coefficient and sigma(sub e) is the effective solidity) and the range of vertical descent from hovering to descent velocities slightly greater than those for autorotation. The three bladed models, each of which had an effective solidity of 0.05 and NACA 0015 blade airfoil sections, were as follows: (1) constant-chord, untwisted blades of 3-ft radius; (2) untwisted blades of 3-ft radius having a 3/1 taper; (3) constant-chord blades of 3-ft radius having a linear twist of 12 degrees (washout) from axis of rotation to tip; and (4) constant-chord, untwisted blades of 2-ft radius. Because of the incorporation of a correction for blade dynamic twist and the use of a method of measuring the approximate equivalent free-stream velocity, it is believed that the data obtained from this program are more applicable to free-flight calculations than the data from previous model tests.

  16. Forward velocity effects on fan noise and the suppression characteristics of advanced inlets as measured in the NASA Ames 40 by 80 foot wind tunnel: Acoustic data report

    NASA Technical Reports Server (NTRS)

    Moore, M. T.

    1981-01-01

    Forward velocity effects on the forward radiated fan noise and on the suppression characteristics of three advanced inlets relative to a baseline cylindrical inlet were measured in a wind tunnel. A modified JT15D turbofan engine in a quiet nacelle was the source of fan noise; the advanced inlets were a CTOL hybrid inlet, an STOL hybrid inlet, and a treated deflector inlet. Also measured were the static to flight effects on the baseline inlet noise and the effects on the fan noise of canting the baseline inlet 4 deg downward to simulate typical wing mounted turbofan engines. The 1/3 octave band noise data from these tests are given along with selected plots of 1/3 octave band spectra and directivity and full scale PNL directivities. The test facilities and data reduction techniques used are also described.

  17. Non-gyrotropic proton and alpha-particle velocity distributions in the solar wind: TAUS observations and stability analysis

    NASA Technical Reports Server (NTRS)

    Astudillo, H. F.; Marsch, E.; Livi, S.; Rosenbauer, H.

    1995-01-01

    Ion velocity distribution functions have been measured with high time resolution by the TAUS plasma instrument on the PHOBOS mission to Mars in 1989. The unambiguous separation of protons and alpha-particles by TAUS enabled us to study the nonthermal features of their distributions separately and to analyze the stability of the distributions against excitation of waves in the cyclotron-frequency domain. Typical nonthermal features include temperature anisotropies, with T(sub perpendicular) larger than T(sub parallel), and ion beam populations drifting along the local magnetic field direction. Also, distinctly non-gyrotropic alpha-particle velocity distributions were sometimes found. Non-gyrotropy strongly changes the wave dispersion and gives rise to new growing modes, related to the coupling of the standard wave modes existing in gyrotropic plasma. It is found that for the measured non-gyrotropic ion distributions the right-hand polarized wave can also be excited by a temperature anistropy instead of the usual beam drift.

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

    NASA Astrophysics Data System (ADS)

    Vinas, A. F.; Gurgiolo, C. A.; Nieves-Chinchilla, T.; Wendel, D. E.; Goldstein, M. L.; Fazakerley, A. N.

    2010-12-01

    The current hypothesis of the formation of the solar wind halo electrons is that they are produced from scattering of the strahl. This hypothesis is strengthened by direct observations of the strahl electrons being scattered into the halo in an isolated event. 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 limited energy range. The observation implies that the formation of the halo is not a continuous process but occurs in bursts in regions where conditions for wave growth providing the scattering are optimum. Sometimes, observations indicates that the strahl component is anisotropic (Tper/Tpal ~ 2). This provides a possible free energy source for the excitation of whistler waves as a possible scattering mechanism, however this condition is not always observed. 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.

  19. Non-axisymmetric wind-accretion simulations. I. Velocity gradients of 3% and 20% over one accretion radius.

    NASA Astrophysics Data System (ADS)

    Ruffert, M.

    1997-02-01

    We investigate the hydrodynamics of a variant of classical Bondi-Hoyle-Lyttleton accretion: a totally absorbing sphere moves at various Mach numbers (3 and 10) relative to a medium, which is taken to be an ideal gas having a velocity gradient (of 3% or 20% over one accretion radius) perpendicular to the relative motion. We examine the influence of the Mach number of the flow and the strength of the gradient upon the physical behaviour of the flow and the accretion rates of the angular momentum in particular. The hydrodynamics is modeled by the "Piecewise Parabolic Method" (PPM). The resolution in the vicinity of the accretor is increased by multiply nesting several grids around the sphere. Similarly to the 3D models without gradients published previously, models exhibit non-stationary flow patterns, although the Mach cone remains fairly stable. The accretion rates of mass, linear and angular momenta do not fluctuate as strongly as published previously for 2D models, but similarly to the 2D models, transient disks form around the accretor that alternate their direction of rotation with time. The average specific angular momentum accreted is roughly between 7% and 70% of the total angular momentum available in the accretion cylinder and is always smaller than the value of a vortex with Kepler velocity around the surface of the accretor. The fluctuations of the mass accretion rate in the models with small gradients (2%) are similar to the values of the models without gradients, while the models with large gradients (20%) exhibit larger fluctuations. The mass accretion rate is maximal when the specific angular momentum is zero, while the specific entropy tends to be smaller when the disks are prograde.

  20. Forward velocity effects on fan noise and the suppression characteristics of advanced inlets as measured in the NASA-Ames 40 by 80 foot wind tunnel

    NASA Technical Reports Server (NTRS)

    Moore, M. T.

    1980-01-01

    Forward velocity effects on the forward radiated fan noise and on the suppression characteristics of three advanced inlets relative to a baseline cylindrical inlet were measured in the NASA Ames Research Center 40 x 80 foot Wind Tunnel. A modified JT15D turbofan engine in a quiet nacelle was the source of fan noise; the advanced inlets were a Conventional Takeoff/Landing (CTOL) hybrid inlet, a Short Takeoff/Landing (STOL) hybrid inlet, and a treated deflector inlet. Also measured were the static to flight effects on the fan noise of canting the baseline inlet 4 deg downward to simulate typical wing mounted turbofan engines. The CTOL hybrid inlet suppressed the high tip speed fan noise as much as 18 PNdB on a 61 m (200 ft) sideline scaled to a CF6 size engine while the STOL hybrid inlet suppressed the low tip speed fan noise as much as 13 PNdB on a 61 m (200 ft) sideline scaled to a OCSEE size engine. The deflector inlet suppressed the high tip speed fan noise as much as 13 PNdB at 61 m (200 ft) overhead scaled to a CF6 size engine. No significant changes in fan noise suppression for the CTOL and STOL hybrid inlets occurred for forward velocity changes above 21 m/s (68 ft/s) or for angle of attack changes up to 15 deg. However, changes in both forward velocity and angle of attack changed the deflector inlet noise unpredictably due to the asymmetry of the inlet flow field into the fan.

  1. VisibleWind: wind profile measurements at low altitude

    NASA Astrophysics Data System (ADS)

    Wilkerson, Tom; Bradford, Bill; Marchant, Alan; Apedaile, Tom; Wright, Cordell

    2009-09-01

    VisibleWindTM is developing an inexpensive rapid response system, for accurately characterizing wind shear and small scale wind phenomena in the boundary layer and for prospecting suitable locations for wind power turbines. The ValidWind system can also collect reliable "ground truth" for other remote wind sensors. The system employs small (0.25 m dia.) lightweight balloons and a tracker consisting of an Impulse 200 XL laser rangefinder coupled to a PC for automated data recording. Experiments on balloon trajectories demonstrate that the laser detection of range (+/- 0.5 m), together with measured azimuth and altitude, is an inexpensive, convenient, and capable alternative to other wind tracking methods. The maximum detection range has been increased to 2200 meters using micro-corner-cube retroreflector tape on balloons. Low power LEDs enable nighttime tracking. To avoid large balloon gyrations about the mean trajectory, we use balloons having low ascent rates and subcritical Reynolds numbers. Trajectory points are typically recorded every 4 - 7 seconds. Atmospheric features observed under conditions of inversions or "light and variable winds" include abrupt onsets of shear at altitudes of 100-250 m, velocity changes of order 1-3 m/s within layers of 10-20 m thickness, and veering of the wind direction by 180 degrees or more as altitude increases from 300 to 500 m. We have previously reported comparisons of balloon-based wind profiles with the output of a co-located sodar. Even with the Impulse rangefinder, our system still requires a "man in the loop" to track the balloon. A future system enhancement will automate balloon tracking, so that laser returns are obtained automatically at 1 Hz. While balloon measurements of large-scale, high altitude wind profiles are well known, this novel measurement system provides high-resolution, real-time characterization of the fluctuating local wind fields at the bottom of the boundary layer where wind power turbines and other remote wind sensors must operate.

  2. 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.

  3. Dynamics of the turbidity maximum in the Fly River estuary, Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Wolanski, Eric; King, Brian; Galloway, Duncan

    Field studies in the Fly River estuary, Papua New Guinea, show that the turbidity maximum exists only at spring tides. The wind is important in wave-driven fluidization of the bed. The erosion rate varies with the sixth power of the water velocity. The suspended sediment settling velocity varies nonlinearly with the concentration. At least three-quarters of the river sediment inflow appears to be trapped in the estuary. A numerical hydrodynamics-sediment transport model is able to reproduce a number of the key features of the turbidity maximu, and suggests that the turbidity maximum is due to the simultaneous influence of the baroclinic circulation and the tidal pumping.

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

    NASA Technical Reports Server (NTRS)

    Kelley, Mark W; Tolhurst, William H JR

    1955-01-01

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

  5. 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.

  6. Wind machine

    SciTech Connect

    Gaston, E. E.

    1985-01-15

    To generate power from wind economically, a feathering vane is pivotally mounted perpendicular to a tail vane and shifts the orientation of a sprocket assembly controlled by the tail vane in response to wind velocity. The sprocket assembly changes the orientation of blades which orbit about and rotate the main power shaft so that, as wind velocity changes, the blade orientations are shifted in a compensating direction under the control of the tail vane. A lever shifts the position of the blades to positions that balance wind power and brake the rotation for maintenance purposes. The speed-control mechanism includes a damper to avoid being excessively affected by wind gusts. The main shaft is connected through a speed increaser which has less mass at the high-speed end than the low-speed end to an induction generator when used for cogeneration, the field of the induction generator being excited by the cogeneration frequency.

  7. The Relevance of Surface Roughness Data Qualities in Diagnostic Modeling of Wind Velocity in Complex Terrain: A Case Study from the Śnieżnik Massif (SW Poland)

    NASA Astrophysics Data System (ADS)

    Jancewicz, Kacper; Szymanowski, Mariusz

    2016-04-01

    Numerical modeling of wind velocity above complex terrain has become a subject of numerous contemporary studies. Regardless of the methodical approach (dynamic or diagnostic), it can be observed that information about surface roughness is indispensable to achieve realistic results. In this context, the current state of GIS and remote sensing development allows access to a number of datasets providing information about various properties of land coverage in a broad spectrum of spatial resolution. Hence, the quality of roughness information may vary depending on the properties of primary land coverage data. As a consequence, the results of the wind velocity modeling are affected by the accuracy and spatial resolution of roughness data. This paper describes further attempts to model wind velocity using the following sources of roughness information: LiDAR data (Digital Surface Model and Digital Terrain Model), database of topographical objects (BDOT10k) and both raster and vector versions of Corine Land Cover 2006 (CLC). The modeling was conducted in WindStation 4.0.2 software which is based on the computational fluid dynamics (CFD) diagnostic solver Canyon. Presented experiment concerns three episodes of relatively strong and constant synoptic forcing: 26 November 2011, 25 May 2012 and 26 May 2012. The modeling was performed in the spatial resolution of 50 and 100 m. Input anemological data were collected during field measurements while the atmosphere boundary layer parameters were derived from the meteorological stations closest to the study area. The model's performance was verified using leave-one-out cross-validation and calculation of error indices such as bias error, root mean square error and index of wind speed. Thus, it was possible to compare results of using roughness datasets of different type and resolution. The study demonstrates that the use of LiDAR-based roughness data may result in an improvement of the model's performance in 100 and 50 m resolution, comparing to CLC and BDOT10k. Furthermore, a slight improvement of these results can be accomplished if the LiDAR-based roughness calculation process includes the variable of prevailing wind direction. Qualities of both CLC and BDOT10k raw datasets (imposed land coverage classes, necessity of the roughness classes assignment) induce relatively high values of the modeled velocity error indices. Hence, these and other similar datasets need to be carefully analyzed (e.g. compared with aerial or satellite imagery) before they are used in the process of roughness length parameterization.

  8. 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.

  9. 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.

  10. Laboratory investigation of wind wave breaking modulation in the inhomogeneous current field

    NASA Astrophysics Data System (ADS)

    Bakhanov, Victor; Bogatov, Nikolai; Ermoshkin, Alexei; Kemarskaya, Olga

    2015-10-01

    A experimental laboratory study of the effect of a horizontally inhomogeneous current on breaking statistics of wind waves was carried out. Were creating a current having the same direction as wind waves with positive and negative gradients and a current of the counter direction with a negative gradient. The wind speed varied from 10.4 to 20.1 m/s based on a standard height of 10 m. The maximum current velocity near the surface was 27 cm/s. The maximum current gradient was equal to 0.09 1/s. The codirected current reduces the wind wave amplitude for all wind speeds, while the frequency of the spectral density maximum of wind waves remains the same. The frequency of the recorded by radar wind-wave breaking also decreases for positive, negative, and zero gradients. In the case of counter directions, for light winds in the presence of a current the wind wave amplitude reduces, the wind wave spectrum displaces in the direction of lower frequencies. At higher wind speeds, there were neither differences in the surface wave spectra in the presence and absence of a current, however, an increase in the frequency of the recorded by radar wind-wave breaking is observed. These laboratory investigations are carried out in the interests of the remote diagnostics methods development of inhomogeneous currents at higher wind speeds.

  11. 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].

  12. 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.

  13. 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.

  14. Acoustic particle velocity horns.

    PubMed

    Donskoy, Dimitri M; Cray, Benjamin A

    2012-05-01

    The paper considers receiving acoustic horns designed for particle velocity amplification and suitable for use in vector sensing applications. Unlike conventional horns, designed for acoustic pressure amplification, acoustic velocity horns (AVHs) deliver significant velocity amplification even when the overall size of the horn is much less than an acoustic wavelength. An AVH requires an open-ended configuration, as compared to pressure horns which are terminated at the throat. The appropriate formulation, based on Webster's one-dimensional horn equation, is derived and analyzed for single conical and exponential horns as well as for double-horn configurations. Predicted horn amplification factors (ratio of mouth-to-throat radii) were verified using numerical modeling. It is shown that three independent geometrical parameters principally control a horn's performance: length l, throat radius R(1), and flare rate. Below a predicted resonance region, velocity amplification is practically independent of frequency. Acoustic velocity horns are naturally directional, providing maximum velocity amplification along the boresight. PMID:22559364

  15. 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.

  16. Power augmentation of a horizontal axis wind turbine using a Mie type tip vane: Velocity distribution around the tip of a HAWT blade with and without a Mie type tip vane

    SciTech Connect

    Shimizu, Y.; Imamura, H.; Matsumura, S.; Maeda, T.; Bussel, G.J.W. van

    1995-11-01

    Power augmentation and velocity measurements in the wake of a HAWT blade with Mie type tip vane (a tip device on the main blade) are presented. The maximum C{sub p} with a Mie type tip vane is found to be 15% larger than that without the Mie type tip vane. Power augmentation caused by the Mie type tip vane is mainly due to the reduction of tip vortex and the diffusing effect by the Mie type tip vane. The effects of a Mie type tip vane are quantitatively verified by the velocity distributions around the tip of the main blade. The velocity distribution was measured by three-dimensional hot wire probes, which measured the axial, radial, and tangential velocity components. The circulation distributions along the main blade with a Mie type tip vane and without a Mie type tip vane were obtained from the measured velocity distributions. A strong reduction of bound vorticity is found for the main blade tip without the Mie type tip vane, whereas the bound vorticity persists on the main blade tip with the Mie type tip vane.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. Numerical simulations of flow fields through conventionally controlled wind turbines & wind farms

    NASA Astrophysics Data System (ADS)

    Emre Yilmaz, Ali; Meyers, Johan

    2014-06-01

    In the current study, an Actuator-Line Model (ALM) is implemented in our in-house pseudo-spectral LES solver SP-WIND, including a turbine controller. Below rated wind speed, turbines are controlled by a standard-torque-controller aiming at maximum power extraction from the wind. Above rated wind speed, the extracted power is limited by a blade pitch controller which is based on a proportional-integral type control algorithm. This model is used to perform a series of single turbine and wind farm simulations using the NREL 5MW turbine. First of all, we focus on below-rated wind speed, and investigate the effect of the farm layout on the controller calibration curves. These calibration curves are expressed in terms of nondimensional torque and rotational speed, using the mean turbine-disk velocity as reference. We show that this normalization leads to calibration curves that are independent of wind speed, but the calibration curves do depend on the farm layout, in particular for tightly spaced farms. Compared to turbines in a lone-standing set-up, turbines in a farm experience a different wind distribution over the rotor due to the farm boundary-layer interaction. We demonstrate this for fully developed wind-farm boundary layers with aligned turbine arrangements at different spacings (5D, 7D, 9D). Further we also compare calibration curves obtained from full farm simulations with calibration curves that can be obtained at a much lower cost using a minimal flow unit.

  3. 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.

  4. Wind tunnel measurements of the power output variability and unsteady loading in a micro wind farm model

    NASA Astrophysics Data System (ADS)

    Bossuyt, Juliaan; Howland, Michael; Meneveau, Charles; Meyers, Johan

    2015-11-01

    To optimize wind farm layouts for a maximum power output and wind turbine lifetime, mean power output measurements in wind tunnel studies are not sufficient. Instead, detailed temporal information about the power output and unsteady loading from every single wind turbine in the wind farm is needed. A very small porous disc model with a realistic thrust coefficient of 0.75 - 0.85, was designed. The model is instrumented with a strain gage, allowing measurements of the thrust force, incoming velocity and power output with a frequency response up to the natural frequency of the model. This is shown by reproducing the -5/3 spectrum from the incoming flow. Thanks to its small size and compact instrumentation, the model allows wind tunnel studies of large wind turbine arrays with detailed temporal information from every wind turbine. Translating to field conditions with a length-scale ratio of 1:3,000 the frequencies studied from the data reach from 10-4 Hz up to about 6 .10-2 Hz. The model's capabilities are demonstrated with a large wind farm measurement consisting of close to 100 instrumented models. A high correlation is found between the power outputs of stream wise aligned wind turbines, which is in good agreement with results from prior LES simulations. Work supported by ERC (ActiveWindFarms, grant no. 306471) and by NSF (grants CBET-113380 and IIA-1243482, the WINDINSPIRE project).

  5. 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 5σ 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.

  6. 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.

  7. 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)

  8. 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.

  9. 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.

  10. Efficient Low-Speed Flight in a Wind Field

    NASA Technical Reports Server (NTRS)

    Feldman, Michael A.

    1996-01-01

    A new software tool was needed for flight planning of a high altitude, low speed unmanned aerial vehicle which would be flying in winds close to the actual airspeed of the vehicle. An energy modeled NLP (non-linear programming) formulation was used to obtain results for a variety of missions and wind profiles. The energy constraint derived included terms due to the wind field and the performance index was a weighted combination of the amount of fuel used and the final time. With no emphasis on time and with no winds the vehicle was found to fly at maximum lift to drag velocity, V(sub md). When flying in tail winds the velocity was less than V(sub md), while flying in head winds the velocity was higher than V(sub md). A family of solutions was found with varying times of flight and varying fuel amounts consumed which will aid the operator in choosing a flight plan depending on a desired landing time. At certain parts of the flight, the turning terms in the energy constraint equation were found to be significant. An analysis of a simpler vertical plane cruise optimal control problem was used to explain some of the characteristics of the vertical plane NLP results.

  11. 49 CFR 193.2067 - Wind forces.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... velocity of not less than 150 miles per hour, unless the Administrator finds a lower velocity is justified by adequate supportive data; or (ii) The most critical combination of wind velocity and...

  12. 49 CFR 193.2067 - Wind forces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... velocity of not less than 150 miles per hour, unless the Administrator finds a lower velocity is justified by adequate supportive data; or (ii) The most critical combination of wind velocity and...

  13. 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.

  14. 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.

  15. Wind turbine

    DOEpatents

    Cheney, Jr., Marvin C.

    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.

  16. VisibleWind: a rapid-response system for high-resolution wind profiling

    NASA Astrophysics Data System (ADS)

    Wilkerson, Tom; Bradford, Bill; Marchant, Alan; Wright, Cordell; Apedaile, Tom; Fowles, Eve; Howard, Allen; Naini, Tom

    2009-08-01

    The VisibleWindTM initiative has sponsored the development and demonstration of a simple balloon tracking system for low altitude wind profile measurements using laser rangefinders, a surveying station, and small (0.25 m diameter) lightweight balloons. Experiments on balloon trajectories demonstrate that laser range detection (+/- 0.5 m) combined with azimuth and elevation measurements is a simple, accurate, and inexpensive alternative to other wind profiling methods. The maximum detection range has been increased to 2200 m using retroreflector tape on the balloons. Nighttime tracking is facilitated by low power LEDs. Small balloons with low ascent rates and Reynolds numbers are preferred to avoid the large trajectory fluctuations previously observed with large balloons. Under conditions of "light and variable winds", the wind profile features observed by VisibleWindTM include the frequent onset of shear at altitudes 100 -200 m, 1-3 m/s velocity transitions across atmospheric layers only 10 -20 m thick, and rotation of wind direction exceeding 180 degrees in the altitude range 300 - 500 m. Wind speed and direction results are compared with simultaneous sodar measurements. The profiling resolution is greatly improved using a laser rangefinder, Impulse XL-200, with automatic coordinate and time recording; however, balloon tracking is still man-in-the-loop. Planned improvements include automation of the tracking system itself, so trajectory points are collected automatically at 1 Hz or faster. This ValidWindTM system is a precise and adaptable means for characterizing highly variable wind fields for wind energy, micrometeorology, and air quality studies.

  17. 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

  18. 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

  19. 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...

  20. The sun and heliosphere at solar maximum

    NASA Technical Reports Server (NTRS)

    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.

    2003-01-01

    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'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.

  1. 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

  2. Wind-Turbine Wakes in a Convective Boundary Layer: A Wind-Tunnel Study

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Markfort, Corey D.; Porté-Agel, Fernando

    2013-02-01

    Thermal stability changes the properties of the turbulent atmospheric boundary layer, and in turn affects the behaviour of wind-turbine wakes. To better understand the effects of thermal stability on the wind-turbine wake structure, wind-tunnel experiments were carried out with a simulated convective boundary layer (CBL) and a neutral boundary layer. The CBL was generated by cooling the airflow to 12-15 °C and heating up the test section floor to 73-75 °C. The freestream wind speed was set at about 2.5 m s-1, resulting in a bulk Richardson number of -0.13. The wake of a horizontal-axis 3-blade wind-turbine model, whose height was within the lowest one third of the boundary layer, was studied using stereoscopic particle image velocimetry (S-PIV) and triple-wire (x-wire/cold-wire) anemometry. Data acquired with the S-PIV were analyzed to characterize the highly three-dimensional turbulent flow in the near wake (0.2-3.2 rotor diameters) as well as to visualize the shedding of tip vortices. Profiles of the mean flow, turbulence intensity, and turbulent momentum and heat fluxes were measured with the triple-wire anemometer at downwind locations from 2-20 rotor diameters in the centre plane of the wake. In comparison with the wake of the same wind turbine in a neutral boundary layer, a smaller velocity deficit (about 15 % at the wake centre) is observed in the CBL, where an enhanced radial momentum transport leads to a more rapid momentum recovery, particularly in the lower part of the wake. The velocity deficit at the wake centre decays following a power law regardless of the thermal stability. While the peak turbulence intensity (and the maximum added turbulence) occurs at the top-tip height at a downwind distance of about three rotor diameters in both cases, the magnitude is about 20 % higher in the CBL than in the neutral boundary layer. Correspondingly, the turbulent heat flux is also enhanced by approximately 25 % in the lower part of the wake, compared to that in the undisturbed CBL inflow. This study represents the first controlled wind-tunnel experiment to study the effects of the CBL on wind-turbine wakes. The results on decreased velocity deficit and increased turbulence in wind-turbine wakes associated with atmospheric thermal stability are important to be taken into account in the design of wind farms, in order to reduce the impact of wakes on power output and fatigue loads on downwind wind turbines.

  3. The impact of T-TREC-retrieved wind and radial velocity data assimilation using EnKF and effects of assimilation window on the analysis and prediction of Typhoon Jangmi (2008)

    NASA Astrophysics Data System (ADS)

    Wang, Mingjun; Xue, Ming; Zhao, Kun

    2016-01-01

    This study examines the relative impact of assimilating T-TREC-retrieved winds (VTREC) versus radial velocity (Vr) on the analysis and forecast of Typhoon Jangmi (2008) using an ensemble Kalman filter (EnKF). The VTREC and Vr data at 30 min intervals are assimilated into the ARPS model at 3 km grid spacing over four different assimilation windows that cover, respectively, 0000-0200, 0200-0400, 0400-0600, and 0000-0600 UTC, 28 September 2008. The assimilation of VTREC data produces better analyses of the typhoon structure and intensity than the assimilation of Vr data during the earlier assimilation windows, but during the later assimilation windows when the coverage of Vr data on the typhoon from four Doppler radars is much improved, the assimilation of Vr outperforms VTREC data. The combination of VTREC and Vr data, either by assimilating both VTREC and Vr data in all cycles or by assimilating VTREC in the first cycle and Vr in the remaining cycles (labeled VTFVR), further improves the analyses of the typhoon structure and intensity compared to assimilating VTREC or Vr data alone. Quantitative verifications of 24 h forecasts of the typhoon show that the VTFVR assimilation experiments produces forecasts that best match the best track data and also have the highest precipitation prediction skills. The track forecast errors in experiment that assimilate VTREC data through the later cycles are the largest. The behaviors are discussed based on the coverage, information content, and accuracy of the various forms of data.

  4. WIND-DRIVEN RAINSPLASH EROSION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In wind-driven rains, variations in raindrop trajectory and frequency are highly expected due to the changes in the angle of raindrop incidence. This paper presents experimental data obtained on the effects of horizontal wind velocity on physical raindrop impact and rainsplash detachment. In a wind ...

  5. 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.

  6. Wind profiler signal detection improvements

    NASA Technical Reports Server (NTRS)

    Hart, G. F.; Divis, Dale H.

    1992-01-01

    Research is described on potential improvements to the software used with the NASA 49.25 MHz wind profiler located at Kennedy Space Center. In particular, the analysis and results are provided of a study to (1) identify preferred mathematical techniques for the detection of atmospheric signals that provide wind velocities which are obscured by natural and man-made sources, and (2) to analyze one or more preferred techniques to demonstrate proof of the capability to improve the detection of wind velocities.

  7. 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.

  8. Analysis of Change in the Wind Speed Ratio according to Apartment Layout and Solutions

    PubMed Central

    Hyung, Won-gil; Kim, Young-Moon; You, Ki-Pyo

    2014-01-01

    Apartment complexes in various forms are built in downtown areas. The arrangement of an apartment complex has great influence on the wind flow inside it. There are issues of residents' walking due to gust occurrence within apartment complexes, problems with pollutant emission due to airflow congestion, and heat island and cool island phenomena in apartment complexes. Currently, the forms of internal arrangements of apartment complexes are divided into the flat type and the tower type. In the present study, a wind tunnel experiment and computational fluid dynamics (CFD) simulation were performed with respect to internal wind flows in different apartment arrangement forms. Findings of the wind tunnel experiment showed that the internal form and arrangement of an apartment complex had significant influence on its internal airflow. The wind velocity of the buildings increased by 80% at maximum due to the proximity effects between the buildings. The CFD simulation for relaxing such wind flows indicated that the wind velocity reduced by 40% or more at maximum when the paths between the lateral sides of the buildings were extended. PMID:24688430

  9. Wind tunnel study on wind and turbulence intensity profiles in wind turbine wake

    NASA Astrophysics Data System (ADS)

    Maeda, Takao; Kamada, Yasunari; Murata, Junsuke; Yonekura, Sayaka; Ito, Takafumi; Okawa, Atsushi; Kogaki, Tetsuya

    2011-06-01

    In recent years, there has been a rapid development of the wind farms in Japan. It becomes very important to investigate the wind turbine arrangement in wind farm, in order that the wake of one wind turbine does not to interfere with the flow in other wind turbines. In such a case, in order to achieve the highest possible efficiency from the wind, and to install as many as possible wind turbines within a limited area, it becomes a necessity to study the mutual interference of the wake developed by wind turbines. However, there is no report related to the effect of the turbulence intensity of the external flow on the wake behind a wind turbine generated in the wind tunnel. In this paper, the measurement results of the averaged wind profile and turbulence intensity profile in the wake in the wind tunnel are shown when the turbulence intensity of the external wind was changed. The wind tunnel experiment is performed with 500mm-diameter two-bladed horizontal axis wind turbine and the wind velocity in wake is measured by an I-type hot wire probe. As a result, it is clarified that high turbulence intensities enable to the entrainment of the main flow and the wake and to recover quickly the velocity in the wake.

  10. 33 CFR 156.320 - Maximum operating conditions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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...

  11. 33 CFR 156.320 - Maximum operating conditions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 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...

  12. 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...

  13. 33 CFR 156.320 - Maximum operating conditions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 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...

  14. 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...

  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. Solar wind eddies and the heliospheric current sheet

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Mccomas, D. J.; Bame, S. J.; Goldstein, B. E.

    1995-01-01

    Ulysses has collected data between 1 and 5 AU during, and just following solar maximum, when the heliospheric current sheet (HCS) can be thought of as reaching its maximum tilt and being subject to the maximum amount of turbulence in the solar wind. The Ulysses solar wind plasma instrument measures the vector velocity and can be used to estimate the flow speed and direction in turbulent 'eddies' in the solar wind that are a fraction of an astronomical unit in size and last (have either a turnover or dynamical interaction time of) several hours to more than a day. Here, in a simple exercise, these solar wind eddies at the HCS are characterized using Ulysses data. This character is then used to define a model flow field with eddies that is imposed on an ideal HCS to estimate how the HCS will be deformed by the flow. This model inherently results in the complexity of the HCS increasing with heliocentric distance, but the result is a measure of the degree to which the observed change in complexity is a measure of the importance of solar wind flows in deforming the HCS. By comparison with randomly selected intervals not located on the HCS, it appears that eddies on the HCS are similar to those elsewhere at this time during the solar cycle, as is the resultant deformation of the interplanetary magnetic field (IMF). The IMF deformation is analogous to what is often termed the 'random walk' of interplanetary magnetic field lines.

  17. 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.)

  18. Dust-driven winds of AGB stars: The critical interplay of atmospheric shocks and luminosity variations

    NASA Astrophysics Data System (ADS)

    Liljegren, S.; Höfner, S.; Nowotny, W.; Eriksson, K.

    2016-04-01

    Context. Winds of AGB stars are thought to be driven by a combination of pulsation-induced shock waves and radiation pressure on dust. In dynamic atmosphere and wind models, the stellar pulsation is often simulated by prescribing a simple sinusoidal variation in velocity and luminosity at the inner boundary of the model atmosphere. Aims: We experiment with different forms of the luminosity variation in order to assess the effects on the wind velocity and mass-loss rate, when progressing from the simple sinusoidal recipe towards more realistic descriptions. This will also give an indication of how robust the wind properties derived from the dynamic atmosphere models are. Methods: Using state-of-the-art dynamical models of C-rich AGB stars, a range of different asymmetric shapes of the luminosity variation and a range of phase shifts of the luminosity variation relative to the radial variation are tested. These tests are performed on two stellar atmosphere models. The first model has dust condensation and, as a consequence, a stellar wind is triggered, while the second model lacks both dust and wind. Results: The first model with dust and stellar wind is very sensitive to moderate changes in the luminosity variation. There is a complex relationship between the luminosity minimum, and dust condensation: changing the phase corresponding to minimum luminosity can either increase or decrease mass-loss rate and wind velocity. The luminosity maximum dominates the radiative pressure on the dust, which in turn, is important for driving the wind. An earlier occurrence of the maximum, with respect to the propagation of the pulsation-induced shock wave, then increases the wind velocity, while a later occurrence leads to a decrease. These effects of changed luminosity variation are coupled with the dust formation. In contrast there is very little change to the structure of the model without dust. Conclusions: Changing the luminosity variation, both by introducing a phase shift and by modifying the shape, influences wind velocity and the mass-loss rate. To improve wind models it would probably be desirable to extract boundary conditions from 3D dynamical interior models or stellar pulsation models.

  19. 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.

  20. Wind Measurements from Arc Scans with Doppler Wind Lidar

    SciTech Connect

    Wang, H.; Barthelmie, R. J.; Clifton, Andy; Pryor, S. C.

    2015-11-25

    When defining optimal scanning geometries for scanning lidars for wind energy applications, we found that it is still an active field of research. Our paper evaluates uncertainties associated with arc scan geometries and presents recommendations regarding optimal configurations in the atmospheric boundary layer. The analysis is based on arc scan data from a Doppler wind lidar with one elevation angle and seven azimuth angles spanning 30° and focuses on an estimation of 10-min mean wind speed and direction. When flow is horizontally uniform, this approach can provide accurate wind measurements required for wind resource assessments in part because of its high resampling rate. Retrieved wind velocities at a single range gate exhibit good correlation to data from a sonic anemometer on a nearby meteorological tower, and vertical profiles of horizontal wind speed, though derived from range gates located on a conical surface, match those measured by mast-mounted cup anemometers. Uncertainties in the retrieved wind velocity are related to high turbulent wind fluctuation and an inhomogeneous horizontal wind field. Moreover, the radial velocity variance is found to be a robust measure of the uncertainty of the retrieved wind speed because of its relationship to turbulence properties. It is further shown that the standard error of wind speed estimates can be minimized by increasing the azimuthal range beyond 30° and using five to seven azimuth angles.

  1. Wind Measurements from Arc Scans with Doppler Wind Lidar

    DOE PAGESBeta

    Wang, H.; Barthelmie, R. J.; Clifton, Andy; Pryor, S. C.

    2015-11-25

    When defining optimal scanning geometries for scanning lidars for wind energy applications, we found that it is still an active field of research. Our paper evaluates uncertainties associated with arc scan geometries and presents recommendations regarding optimal configurations in the atmospheric boundary layer. The analysis is based on arc scan data from a Doppler wind lidar with one elevation angle and seven azimuth angles spanning 30° and focuses on an estimation of 10-min mean wind speed and direction. When flow is horizontally uniform, this approach can provide accurate wind measurements required for wind resource assessments in part because of itsmore » high resampling rate. Retrieved wind velocities at a single range gate exhibit good correlation to data from a sonic anemometer on a nearby meteorological tower, and vertical profiles of horizontal wind speed, though derived from range gates located on a conical surface, match those measured by mast-mounted cup anemometers. Uncertainties in the retrieved wind velocity are related to high turbulent wind fluctuation and an inhomogeneous horizontal wind field. Moreover, the radial velocity variance is found to be a robust measure of the uncertainty of the retrieved wind speed because of its relationship to turbulence properties. It is further shown that the standard error of wind speed estimates can be minimized by increasing the azimuthal range beyond 30° and using five to seven azimuth angles.« less

  2. Estimation of mesoscale thermospheric wind structure using a network of interferometers

    NASA Astrophysics Data System (ADS)

    Harding, Brian J.; Makela, Jonathan J.; Meriwether, John W.

    2015-05-01

    We introduce a technique for estimating the regional thermospheric wind field from measurements made by a network of interferometers. Unlike previous work, this technique does not make assumptions about the functional form of the wind field and instead uses inverse theory to find the smoothest wind field that agrees with the measurements. This technique is general and applies to any network making radial velocity measurements. We show reconstructions of the thermospheric wind field over the eastern United States and over eastern Brazil, using data from two distinct networks of Fabry-Perot interferometers measuring the Doppler shift of the 630.0 nm airglow emission. In Brazil, we find direct evidence of a convergent wind field during the period of rapid thermospheric temperature increase associated with the equatorial midnight temperature maximum.

  3. Maximum power tracking

    SciTech Connect

    O'Sullivan, G.

    1983-03-01

    By definition, a maximum power tracking device causes the photovoltaic array to operate on the locus of maximum power points within a specified accuracy. There are limitations to the application of maximum power tracking. A prerequisite is that the load be capable of absorbing all of the power availble at all times. Battery chargers, electrical heaters, water pumps, and most significantly, returning power to the utility grid, are prime examples of applications that are adaptable to maximum power tracking. Maximum power tracking is available to either dc or ac loads. An inverter equipped with a means of changing input voltage by controlling its input impedance can deliver maximum power to ac loads. The inverter can be fixed or variable frequency and fixed or variable voltage, but must be compatible with the ac load. The discussion includes applications, techniques, and cost factors.

  4. 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.

  5. Pickup Ion Velocity Distributions at Titan: Effects of Spatial Gradients

    NASA Astrophysics Data System (ADS)

    Hartle, R. E.; Sittler, E. C.

    2004-05-01

    The principle source of pickup ions at Titan is its neutral exosphere, extending well above the ionopause into the magnetosphere of Saturn or the solar wind, depending on the moon's orbital position. Thermal and nonthermal processes in the thermosphere generate the distribution of neutral atoms and molecules in the exosphere. The combination of these processes and the range of mass numbers, 1 to over 28, contribute to an exospheric source structure that produces pickup ions with gyroradii that are much larger or smaller than the corresponding scale heights of their neutral sources. The resulting phase space distributions are dependent on the spatial structure of the exosphere as well as that of the magnetic field and background plasma. When the pickup ion gyroradius is less than the source gas scale height, the pickup ion velocity distribution is characterized by a sharp cutoff near the maximum speed, which is twice that of the ambient plasma times the sine of the angle between the magnetic field and the flow velocity. This was the case for pickup H+ ions identified during the Voyager 1 flyby (1). In contrast, as the gyroradius becomes much larger than the scale height, the peak of the velocity distribution in the source region recedes from the maximum speed. In addition, the amplitude of the distribution near the maximum speed decreases. These more beam like distributions of heavy ions were not observed from Voyager 1, but should be observable by more sensitive instruments on future spacecraft, including Cassini. The finite gyroradius effects in the pickup ion velocity distributions are studied by including in the analysis the possible range of spatial structures in the neutral exosphere and background plasma. (1) Hartle, R. E., E. C. Sittler, Jr., K. W. Ogilvie, J. D. Scudder, A. J. Lazarus and S. K. Atrea, Titan's Ion Exosphere Observed from Voyager 1, J. Geophys. Res., 87, 1383-1394, 1982.

  6. Maxometers (peak wind speed anemometers)

    NASA Technical Reports Server (NTRS)

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

    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.

  7. 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.

  8. Constructibility limits of multiflow wind turbines with pivots

    NASA Astrophysics Data System (ADS)

    Maurer, Joerg

    If windmill wings are rigidly fixed to the hub, strong torques due to the windforce appear. The wing is bent by a conic angle, that requires much lighter wings. Tests in laboratory prove that for a rotor diameter of 3.5 to 7 m, it is possible to use wings of a five or three times lower weight. In this study, the feasibility of suitable wings for the higher than 15 m real diameters is discussed from a theoretical and economic point of a view. The maximum strength on the rotors appear on stopping and braking with extreme wind velocity. Wing mass increases very quickly with the rotor diameter. The first eigenfrequency increases almost linearly with the turn number. Higher eigen frequencies are very rarely dependent on turn number. With very high wind velocities, negative air force damping brings about oscillations where amplitudes does not depend on wing size.

  9. 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.

  10. Wind Tunnel Analysis of the Detachment Bubble on Bolund Island

    NASA Astrophysics Data System (ADS)

    Yeow, T. S.; Cuerva, A.; Conan, B.; J, Pérez-Álvarez

    2014-12-01

    The flow topology on two scaled models (1:230 and 1:115) of the Bolund Island is analysed in two wind tunnels, focusing on the characteristics of the detachment pattern when the wind blows from 270° wind direction and the atmospheric condition is neutral. Since the experiments are designed as the simplest possible reference cases, no additional roughness is added neither to the models surface nor to the wind tunnel floor. Pressure measurements on the surface of the 1:230 scale model are used to estimate the horizontal extension of the intermittent recirculation region, by applying the diagnostic means based in exploring the pressure statistics, proposed in the literature for characterising bubbles on canonical obstacles. The analysis is done for a range of Reynolds numbers based on the mean undisturbed wind speed, U∞ and the maximum height of the island, h[5.1×104,8.5×104]. An isoheight mapping of the velocity field is obtained using 3D hotwire (3D HW). The velocity field in a vertical plane is determined using 3D HW and 2D particle image velocimetry (PIV) on the 1:115 scale model in order to reproduce and complete already existing results in the literature.

  11. 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…

  12. A field experiment on dust emission by wind erosion in the Taklimakan Desert

    NASA Astrophysics Data System (ADS)

    Yang, Xinghua; He, Qing; Ali, Mamtimin; Huo, Wen; Liu, Xinchun; Strake, Miriam

    2012-04-01

    Dust emission by wind erosion in surface is a serious problem in many arid regions around the world, and it is harmful to the ecological environment, human health, and social economy. To monitor the characteristics of saltation activity and to calculate the threshold wind velocity and sediment discharge under field conditions have significance on the research of dust emission by wind erosion. Therefore, a field experiment was conducted over the flat sand in the hinterland of the Taklimakan Desert. One sampling system was installed on the flat sand surface at Tazhong, consisting of a meteorological tower with a height of 2 m, a piezoelectric saltation sensor (Sensit), and a Big Spring Number Eight (BSNE) sampler station. Occurrence of saltation activity was recorded every second using the Sensit. Each BSNE station consisted of five BSNE samplers with the lowest sampler at 0.05 m and the highest sampler at 1.0 m above the soil surface. Sediment was collected from the samplers every 24 h. It is found that saltation activity was detected for only 21.5% of the hours measured, and the longest period of saltation activity occurring continuously was not longer than 5 min under the field conditions. The threshold wind velocity was variable, its minimum value was 4.9 m s-1, the maximum value was 9.2 m s-1, and the average value was 7.0 m s-1. The threshold wind velocity presented a positive linear increase during the measurement period. The observation site had a sediment discharge of 82.1 kg m-1 over a period of 24 h. Based on hourly saltation counts, hourly sediment discharge was estimated. Overall, there was no obvious linear or other functional relationship between the hourly sediment discharge and wind velocity. The results show that the changes of sediment discharge do not quite depend on wind velocity.

  13. Solar wind travel time

    NASA Astrophysics Data System (ADS)

    Russell, C. T.

    A useful rule of thumb in solar terrestrial studies is that the solar wind travels 4 Earth radii (RE) per minute. Long-term studies of solar wind velocity [e.g., Luhmann et al., 1993; 1994] show that the median velocity is about 420 km/s, corresponding to 3.96 RE min-1. The quartiles are about 370 km/s and 495 km/s, corresponding to 3.48 Re min-1 and 4.66 Re min-1 respectively. This number helps estimate the delays expected when observing a discontinuity at a solar wind monitor; one example is ISEE-3 when it was at the forward libration point (about 60 min). It is also helpful for estimating how much time passes before the dayside magnetosphere is compressed as denser solar wind flows by (about 2.5 min).

  14. 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.

  15. Boundary Layer Wind Profile measurements for Emission Assessments

    NASA Astrophysics Data System (ADS)

    Prasad, Narasimha

    2010-05-01

    There is an ongoing effort to permanently equip NASA Langley Research Center (LaRC), Hampton, Virginia, USA as a super site for continuously monitoring weather and air quality in the atmospheric boundary layer. As a part of this effort, air quality campaign was carried out from August 1 to August 31, 2009 here at NASA LaRC. Various instruments for carrying out chemistry and physics measurements of the atmosphere as well as ground based in-situ experiments were assembled at this site. This suite of field instruments included atmospheric chemistry profiles using UV spectrometer, water vapor and temperature profiles using an IR Fourier Transform spectrometer, and wind lidar. The wind lidar was used to gather boundary layer wind velocity profiles. In this paper, wind field evolution measurements made using the Leosphere's WLS 70 windcubeTM lidar will be presented. The WindcubeTM is an active, compact, remote sensor that uses a pulsed laser source operating at 1.54 microns. The system operates based on heterodyne lidar techniques to measure Doppler shift of laser radiation backscattered by particles in the air. The output of lidar system provides minimum and maximum, direction, and standard deviation of horizontal and vertical wind speeds as well as SNR values. Wind profile measurements were made from August 10 to September 14, 2009. Wind speed and direction were gathered and analyzed. Boundary layer height up to 2 km with height resolution of 50 m has been obtained. The wind field evolution measurements includes strong wind veer and large updrafts. Plans are underway to expand this site with advanced wind lidar for air quality experiments.

  16. Performance of a 2-micrometer coherent Doppler lidar for wind measurements

    NASA Technical Reports Server (NTRS)

    Frehlich, Rod; Hannon, Stephen M.; Henderson, Sammy W.

    1994-01-01

    Measurements of boundary layer winds are presented using a 2-micrometer coherent Doppler lidar and the optimal performance of the maximum likelihood estimator. The systematic error for single-shot estimates was estimated as 3.6 cm/s using measurements from a stationary hard target. The estimation error for measurements of the radial component of the wind field was determined, as well as the fraction of the estimates that are randomly distributed over the velocity search space, when the signal power is low and speckle fading is important. The results from actual data are compared with the results from ideal simulations. The first direct estimation of the spatial structure function of the radial wind field and of the energy dissipation rate is presented for both horizontal and vertical directions of propagation. The rms estimation error of the velocity estimates is found to be within 30% of ideal performance based on simulation.

  17. A Theoretical Analysis of the Wind Power Generation System Using a Simulated Windmill

    NASA Astrophysics Data System (ADS)

    Amei, Kenji; Iida, Tadashi; Ohji, Takahisa; Sakui, Masaaki

    The new constitution method of the wind power generation simulator considering output characteristics of the windmill is proposed. The rotational speed of the windmill changes by not only wind velocity but also condition of the load connected with the generator. Therefore, the technique which fed back the torque of the generator was verified for the estimation of the rotational speed in addition to wind velocity and characteristics of the windmill. Characteristics of the operation of the simulator resembled actual windmill, and the validity of the simulator was approximately confirmed. In addition, derivation technique of the maximum power point proposed in advance was applied to this equipment, and the operating characteristic was verified by the experiment.

  18. Evaluation of wind electric energy based on martian wind measurements

    NASA Astrophysics Data System (ADS)

    Nishikawa, Y.; Kurita, K.

    2012-12-01

    Since Mars is characterized by strong surface wind, electric power generation by the wind activity has been proposed as a possible power source for martian base station as well as that for exploration module (George James et al., 1999, Vimal Kumar et al., 2010). George and Vimal estimated total power as 19kW and 500W, which they conclude is sufficient value as a power source of small exploration module. These values seem comparable to that used in MER( 900Wh per day ). But their estimate largely depends on the model of wind velocity and reevaluation is necessary based on plausible wind model as well as more realistic assumptions about power generation. This study evaluates plausible range of available power by using surface wind model estimated by Viking Lander measurements. Meteorological package of Viking Lander measured wind velocity and its direction at 1.6m hight at every 60 min. for 200 sols. We estimate wind statistics by using Weibull distribution function and elevation offset. We calculate the wind energy by wind turbines as the integrated value of power produced in a Martian day, and compare with solar panel and nuclear battery under various conditions (Mars ground roughness, blade length, shape of wind turbine and rotor height from the ground). As a result of the calculations, we obtain reasonable amount of wind electricity (1000 Wh per day ), which can be used if we select proper locations and suitable wind turbine.

  19. 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.

  20. An examination of wake effects and power production for a group of large wind turbines

    SciTech Connect

    Elliott, D.L.; Buck, J.W.; Barnard, J.C.

    1988-04-01

    Data from a group of three MOD-2 wind turbines and two meteorological towers at Goodnoe Hills were analyzed to evaluate turbine power output and wake effects (losses in power production due to operation of upwind turbines), and atmospheric factors influencing them. The influences of variations in the ambient wind speed, wind direction, and turbulence intensity were the primary factors evaluated. Meteorological and turbine data collected at the Goodnoe Hills site from April 1 to October 17, 1985, were examined to select the data sets for these analyses. Wind data from the two meteorological towers were evaluated to estimate the effect of a wake from an upwind turbine on the wind flow measured at the downwind tower. Maximum velocity deficits were about 25% and 12% at downwind distances of 5.8 and 8.3 rotor diameters (D), respectively. However, the maximum deficits at 5.8 D were about 14/degree/ off the centerline orientation between the turbine and the tower, indicating significant wake curvature. Velocity deficits were found to depend on the ambient wind speed, ranging from 27% at lower speeds (15 to 25 mph) to 20% at higher speeds (30 to 35 mph). Turbulence intensity increases dramatically in the wake by factors of about 2.3 and 1.5 over ambient conditions at 5.8 D and 8.3 D, respectively. An analysis of the ambient (non-wake) power production for all three turbines showed that the MOD-2 power output depends, not only on wind speed, but also on the turbulence intensity. At wind speeds below rated, there was a dramatic difference in turbine power output between low and high turbulence intensities for the same wind speed. One of the turbines had vortex generators on the blades. This turbine produced from 10% to 13% more power than the other two turbines when speeds were from 24 to 31 mph. 11 refs., 21 figs., 2 tabs.

  1. THREE-DIMENSIONAL NUMERICAL SIMULATIONS OF MAGNETIZED WINDS OF SOLAR-LIKE STARS

    SciTech Connect

    Vidotto, A. A.; Jatenco-Pereira, V.; Opher, M.; Gombosi, T. I.

    2009-07-01

    By means of self-consistent three-dimensional magnetohydrodynamics (MHD) numerical simulations, we analyze magnetized solar-like stellar winds and their dependence on the plasma-{beta} parameter (the ratio between thermal and magnetic energy densities). This is the first study to perform such analysis solving the fully ideal three-dimensional MHD equations. We adopt in our simulations a heating parameter described by {gamma}, which is responsible for the thermal acceleration of the wind. We analyze winds with polar magnetic field intensities ranging from 1 to 20 G. We show that the wind structure presents characteristics that are similar to the solar coronal wind. The steady-state magnetic field topology for all cases is similar, presenting a configuration of helmet streamer-type, with zones of closed field lines and open field lines coexisting. Higher magnetic field intensities lead to faster and hotter winds. For the maximum magnetic intensity simulated of 20 G and solar coronal base density, the wind velocity reaches values of {approx}1000 km s{sup -1} at r {approx} 20r {sub 0} and a maximum temperature of {approx}6 x 10{sup 6} K at r {approx} 6r {sub 0}. The increase of the field intensity generates a larger 'dead zone' in the wind, i.e., the closed loops that inhibit matter to escape from latitudes lower than {approx}45 deg. extend farther away from the star. The Lorentz force leads naturally to a latitude-dependent wind. We show that by increasing the density and maintaining B {sub 0} = 20 G the system recover back to slower and cooler winds. For a fixed {gamma}, we show that the key parameter in determining the wind velocity profile is the {beta}-parameter at the coronal base. Therefore, there is a group of magnetized flows that would present the same terminal velocity despite its thermal and magnetic energy densities, as long as the plasma-{beta} parameter is the same. This degeneracy, however, can be removed if we compare other physical parameters of the wind, such as the mass-loss rate. We analyze the influence of {gamma} in our results and we show that it is also important in determining the wind structure.

  2. Energy transfer in the solar wind magnetosphere: Long-term fluctuations and intermittency

    NASA Astrophysics Data System (ADS)

    Echim, M. M.; Lamy, H.

    In this paper, we investigate the transfer of energy from the solar wind to the terrestrial magnetosphere. We make a selected brief review of the links between long-term fluctuations of the solar wind variables (velocity, magnetic field) and several multiscale magnetospheric processes. We emphasize those aspects that describe the non-linear magnetospheric response to solar wind changes. The variations of the flux of relativistic electrons with solar wind velocity over a solar cycle are discussed. Experimental evaluation of the substorm energy budget at solar maximum and minimum is also reviewed. The paper provides also a brief review on the intermittent fluctuations observed in the solar wind and the magnetosphere. The solar wind intermittency may be viewed as the hallmark of a turbulent process that sometimes departs from the traditional fluid or MHD turbulence. Recent analysis of geomagnetic indices and their correlation with the solar wind show that large amplitude, intermittent fluctuations have probabilities larger than for a Gaussian distribution, at smaller temporal scales. In the magnetosphere, particularly in the plasma sheet and the cusp the magnetic field fluctuations also show signs of intermittency that could be associated to a multifractal structure of the energy transfer. The dynamical aspects reviewed in this paper contribute to a picture of the magnetosphere as a non-linear system, driven out of equilibrium and responding to solar forcing on a broad range of spatio-temporal scales.

  3. The dynamics of buoyant jets in a linearly stratified ambient cross-flow: Implications for the interaction between volcanic plumes and wind

    NASA Astrophysics Data System (ADS)

    Carazzo, Guillaume; Girault, Frédéric; Aubry, Thomas; Bouquerel, Hélène; Kaminski, Édouard

    2014-05-01

    Volcanic plumes produced by explosive eruptions commonly interact with atmospheric wind causing plume bending and a reduction of its maximum rise height. It is well known that the maximum height reached by a buoyant plume rising in a cross-flow with uniform velocity is controlled by the plume buoyancy flux at the source, the strength of the initial environmental density stratification, the wind velocity and the efficiency of turbulent entrainment. Although numerous studies have been carried out to understand the effects of variations of environmental and source conditions on the plume maximum height, turbulent entrainment has not been taken into account with the same level of detailed analysis. Here, we present new laboratory experiments aimed at better understanding the contribution of the turbulent entrainment to determining the plume maximum height. 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. According to the range of source and environmental conditions, the buoyant jet is distorted or bent-over and its maximum rise height is reduced up to a factor of 2 when wind speed is high. We quantify the efficiency of turbulent entrainment due to wind in our experiments and we show that the dynamical regime strongly depends on the ratio of the horizontal wind speed and the vertical plume velocity, and on the Richardson number defined at the source. Our results provide a robust framework to characterize the entrainment coefficient due to wind in a 1D model of turbulent jet rising in a linearly stratified ambient cross-flow, and hence can be used for the assessment of the impact of atmospheric winds on the dynamics of explosive volcanic plumes.

  4. 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.

  5. 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.

  6. Calculated wind noise for an infrasonic wind noise enclosure.

    PubMed

    Abbott, JohnPaul; Raspet, Richard

    2015-07-01

    A simple calculation of the wind noise measured at the center of a large porous wind fence enclosure is developed. The calculation provides a good model of the measured wind noise, with a good agreement within ±5 dB, and is derived by combining the wind noise contributions from (a) the turbulence-turbulence and turbulence-shear interactions inside the enclosure, (b) the turbulence interactions on the surface of the enclosure, and (c) the turbulence-shear interactions outside of the enclosure. Each wind noise contribution is calculated from the appropriate measured turbulence spectra, velocity profiles, correlation lengths, and the mean velocity at the center, surface, and outside of the enclosure. The model is verified by comparisons of the measured wind noise to the calculated estimates of the differing noise contributions and their sum. PMID:26233033

  7. Wind turbine wake characterization using long-range Doppler lidar

    NASA Astrophysics Data System (ADS)

    Aitken, M.; Lundquist, J. K.; Hestmark, K.; Banta, R. M.; Pichugina, Y.; Brewer, A.

    2012-12-01

    Wind turbines extract energy from the freestream flow, resulting in a waked region behind the rotor which is characterized by reduced wind speed and increased turbulence. The velocity deficit in the wake diminishes with distance, as faster-moving air outside is gradually entrained. In a concentrated group of turbines, then, downwind machines experience very different inflow conditions compared to those in the front row. As utility-scale turbines rarely exist in isolation, detailed knowledge of the mean flow and turbulence structure inside wakes is needed to correctly model both power production and turbine loading at modern wind farms. To this end, the Turbine Wake and Inflow Characterization Study (TWICS) was conducted in the spring of 2011 to determine the reduction in wind speeds downstream from a multi-MW turbine located at the National Renewable Energy Laboratory's National Wind Technology Center (NWTC) near Boulder, Colorado. Full-scale measurements of wake dynamics are hardly practical or even possible with conventional sensors, such as cup anemometers mounted on meteorological (met) masts. Accordingly, the High Resolution Doppler Lidar (HRDL) developed by the National Oceanic and Atmospheric Administration's Earth System Research Laboratory was employed to investigate the formation and propagation of wakes under varying levels of ambient wind speed, shear, atmospheric stability, and turbulence. HRDL remotely senses line-of-sight wind velocities and has been used in several previous studies of boundary layer aerodynamics. With a fully steerable beam and a maximum range up to about 5 km, depending on atmospheric conditions, HRDL performed a comprehensive survey of the wind flow in front of and behind the turbine to study the shape, meandering, and attenuation of wakes. Due in large part to limited experimental data availability, wind farm wake modeling is still subject to an unacceptable amount of uncertainty, particularly in complex terrain. Here, analytical techniques are developed to distinguish wakes from the background variability, and moreover, wakes are then classified by width, height, length, and velocity deficit based on atmospheric stability and inflow conditions. By integrating these advanced observational capabilities with innovative approaches to atmospheric modeling, this work will help to improve simulation tools used to quantify power loss and fatigue loading due to wake effects, thereby aiding the optimization of wind farm layouts.

  8. On the Effect of Offshore Wind Parks on Ocean Dynamics

    NASA Astrophysics Data System (ADS)

    Ludewig, E.; Pohlmann, T.

    2012-12-01

    Nowadays renewable energy resources play a key role in the energy supply discussion and especially an increasingly interest in wind energy induces intensified installations of wind parks. At this offshore wind energy gains in popularity in the course of higher and more consistent energy availability than over land. For example Germany's government adopted a national interurban offshore wind energy program comprising the construction of hundreds of wind turbines within Germany's Exclusive Economic Zone to ensure up to 50% of Germany's renewable energy supply. The large number of installation in coastal regions asks for analyzing the impact of offshore wind parks (OWPs) on the atmosphere and the ocean. As known from literature such wind parks excite also-called wake-effect and such an influence on the wind field in turn affects ocean circulation. To cover OWP's impact on ocean dynamics we evaluate model simulations using the Hamburg Shelf-Ocean-Model (HAMSOM). All simulations were driven with a wind forcing produced by the Mesoscale Atmosphere Model of the Hamburg University (METRAS) which has implemented wind turbines. Wind forcing data were generated in collaboration with and by courtesy of the Meteorological Institute of the University of Hamburg, Department Technical Meteorology, Numeric Modeling-METRAS. To evaluate dynamical changes forced by the OWP's wind wake-effect we did a sensitivity study with a theoretical setup of a virtual ocean of 60m depth with a flat bottom and a temperature and salinity stratification according to common North Sea's conditions. Here our results show that already a small OWP of 12 wind turbines, placed in an area of 4 km^2, lead to a complex change in ocean dynamics. Due to the wake-effect zones of upwelling and downwelling are formed within a minute after turning-on wind turbines. The evolving vertical cells have a size of around 15x15 kilometers with a vertical velocity in order of 10^-2 mm/sec influencing the dynamic of an area being hundred times bigger than the wind park itself. The emerged vertical structure is generated due to a newly created geostrophic balance resulting in a redistribution of the ocean mass field. A number of additional upwelling and downwelling cells around the wind park support an intensified vertical dispersion through all layers and incline the thermocline which also influences the lower levels. The disturbances of mass show a dipole structure across the main wind direction with a maximum change in thermocline depth of some meters close to the OWP. Diffusion, mostly driven by direct wind induced surface shear is also modified by the wind turbines and supports a further modification of the vertical patterns. Considering that wind turbines operate only in a special window of wind speed, i.e. wind turbines will stop in case of too weak or too strong wind speeds as well as in case of technical issues, the averaged dimension and intensity of occurring vertical cells depend on the number of rotors and expected wind speeds. Finally we will focus on scenario runs for the North Sea under fully realistic conditions to estimate possible changes in ocean dynamics due to OWPs in future and these results will be further used for process analyzes of the ecosystem. If we assume a continuous operation of North Sea's OWPs in future we expect a fundamental constant change in ocean dynamics and moreover in the ecosystem in its vicinity.

  9. 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.

  10. Longitudinal variation and waves in Jupiter's south equatorial wind jet

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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 increasing with distance from the disturbance. The chevrons move with velocities near the maximum wind jet velocity of ˜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 = 75-100) 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 ˜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°N and 7.5°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.

  11. 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.

  12. Benchmarking for maximum value.

    PubMed

    Baldwin, Ed

    2009-03-01

    Speaking at the most recent Healthcare Estates conference, Ed Baldwin, of international built asset consultancy EC Harris LLP, examined the role of benchmarking and market-testing--two of the key methods used to evaluate the quality and cost-effectiveness of hard and soft FM services provided under PFI healthcare schemes to ensure they are offering maximum value for money. PMID:19344004

  13. Maximum Likelihood Additivity Analysis.

    ERIC Educational Resources Information Center

    Takane, Yoshio

    1982-01-01

    A maximum likelihood estimation procedure was developed to fit weighted and unweighted additive models of conjoint data obtained by categorical rating, paired comparisons or directional ranking methods. Practical uses of the procedure are presented to demonstrate various advantages of the procedure as a statistical method. (Author/JKS)

  14. Maximum Likelihood Additivity Analysis.

    ERIC Educational Resources Information Center

    Takane, Yoshio

    A maximum likelihood estimation procedure is developed for the simple and the weighted additive models. The data are assumed to be taken by either one of the following methods: (1) categorical ratings--the subject is asked to rate a set of stimuli with respect to an attribute of the stimuli on rating scales with a relatively few observation…

  15. 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 σ0) 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.

  16. Unsteady Sand Saltation in Periodic Wind Variations

    NASA Astrophysics Data System (ADS)

    Wang, P.; Zheng, X. J.

    2011-09-01

    Numerical simulations of one dimensional unsteady sand saltation show that the transport rate's response depends on the amplitude and frequency and waveform of wind variations. Calculations show that the unsteady transport rates Qm in sequences of periodic velocity variations are larger than the steady transport rates Qs of the same mean wind velocity if the average wind velocity is much larger than the threshold velocity. When the frequency of wind fluctuating falls into the range of 0.05-10 Hz, Qm increases as gusty wind frequency increases. Comparisons of transport rate in sequences of square wave and triangular wave with sinusoidal wind variations show that, at the same amplitude, square wave wind variations lead to the largest transport rate and triangular wave wind variations lead to the smallest. The error caused by the threshold wind velocity is in the direction opposite to that caused by amplitude and frequency. It might therefore, cancel the amplification and thus cause the transport rate to be overestimated if the fraction of time, where the wind velocity is below the threshold value, is larger than zero.

  17. Mass loading in velocity shears

    SciTech Connect

    Perez-de-Tejada, H.; Durand-Manterola, H.

    1996-02-01

    An analysis is presented on the motion of contaminant ions picked up by the solar wind within velocity shears. An expression is obtained for the ion density in terms of the flow speed across the velocity shear. It is argued that enhanced densities occur in the region where the flow speed is small and that local values may become significantly larger than the ion density outside the velocity shear. A comparison is made with measurements obtained across the plasma wake of comet Giacobini{endash}Zinner with the International Cometary Explorer (ICE) spacecraft. Within the velocity shear of that comet{close_quote}s ionosheath the cometary ion density becomes large and reaches values that are different from those expected when the ion population depends only on the ionization of a uniform outflow of neutral particles from the cometary nucleus. The enhanced plasma density expected within the velocity shear is compatible with the shape of the density profile of contaminant ions detected in that region. {copyright} {ital 1996 American Institute of Physics.}

  18. Velocity measurement of the interplanetary hydrogen

    NASA Astrophysics Data System (ADS)

    Vincent, Frederic

    2011-10-01

    We are proposing to use HST/STIS over a single orbit to make Lyman-alpha observations of the interplanetary hydrogen during the March-April period of this year {2012}. This special request is driven by a recent reanalysis of HST data {Vincent et al. 2011, published after the last call for proposals}.The heliospheric interface results from the interaction of the solar wind and the interstellar medium {ISM}. Within the heliosphere, the interplanetary hydrogen {IPH} flows at an average speed of about 23 km/sec, carrying the signature of the ISM and the heliospheric interface. The IPH has been observed for decades through the backscattering of solar Lyman-alpha photons and solar cycle 23 provided the first partial temporal map of the IPH velocity. It is now well established that the IPH velocity depends on solar activity. Moreover some analyses suggested that it may be also affected by the obliquity of the interstellar magnetic field, yielding a change of 1-2 km/sec.However a combination of the uncertainty of some measurements {e.g. GHRS} and the clustering of others near points on the cycle make it difficult to identify an unambiguous trend. Only one limited set is able to show a cycle dependence, but these represent an annual average and do not match the existing models. The best approach to address these issues is a new set of yearly spectroscopic measurements for at least a half solar cycle. Since we are currently just leaving a solar maximum, it is essential to start immediately in order to have an adequate baseline for temporal measurements.

  19. 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.

  20. Hanford Site peak gust wind speeds

    SciTech Connect

    Ramsdell, J.V.

    1998-09-29

    Peak gust wind data collected at the Hanford Site since 1945 are analyzed to estimate maximum wind speeds for use in structural design. The results are compared with design wind speeds proposed for the Hanford Site. These comparisons indicate that design wind speeds contained in a January 1998 advisory changing DOE-STD-1020-94 are excessive for the Hanford Site and that the design wind speeds in effect prior to the changes are still appropriate for the Hanford Site.

  1. Wind-speed measurements with a scanning elastic-backscatter lidar

    SciTech Connect

    Buttler, W.T.; Eichinger, W.E.

    1994-01-01

    During the 1992 Summer Olympics, the Los Alamos National Laboratory (LANL) lidar team participated in the Barcelona Air Quality Initiative (BAQI). One of the main objectives of this experiment was the remote measurement of wind speeds around the city to verify wind speeds and directions predicted by the Nonhydrostatic Mesoscale Model (MEMO). Remote determination of wind velocities in the mixing layer is important for the verification and determination of critical input parameters of urban-pollution transport models. Most present elastic-backscatter-lidar wind-speed-measurement methods rely on data acquired over time periods between 5 to 10 minutes (Matsui, 1990) and 30 minutes to 1 hour (Schols, et al. 1992). Lidar can measure the spatial properties of the wind field over large volumes of space. This capability is an improvement over present methods, which rely on instruments attached to balloons that measure only those winds along the path the balloon travels. The material that follows describes the principles implicit in the measurement of winds with an elastic-backscatter lidar, as well as the maximum cross-correlation algorithm used to extract wind speeds from lidar data acquired during the Summer Olympics at Barcelona, Spain, in July 1992.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. An improved instantaneous laser Doppler velocity system

    NASA Astrophysics Data System (ADS)

    Desio, Charles V.; Olcmen, Semih; Schinetsky, Philip

    2016-02-01

    In this paper, improvements made on a single velocity component instantaneous laser Doppler velocimetry (ILDV) system are detailed. The ILDV system developed in this research effort is capable of measuring a single velocity component at a rate as high as two megahertz. The current system accounts for the effects of the laser intensity variation on the measured velocity and eliminates the use of a Pockels cell used in previous ILDV systems. The system developed in the current effort was tested using compressible, subsonic jet flows. The ILDV system developed would be most beneficial where a high data capture rate is needed such as in shock tubes, and high-speed wind tunnels.

  7. The Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Clark, Peter U.; Dyke, Arthur S.; Shakun, Jeremy D.; Carlson, Anders E.; Clark, Jorie; Wohlfarth, Barbara; Mitrovica, Jerry X.; Hostetler, Steven W.; McCabe, A. Marshall

    2009-08-01

    We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ~14.5 ka.

  8. The Last Glacial Maximum.

    PubMed

    Clark, Peter U; Dyke, Arthur S; Shakun, Jeremy D; Carlson, Anders E; Clark, Jorie; Wohlfarth, Barbara; Mitrovica, Jerry X; Hostetler, Steven W; McCabe, A Marshall

    2009-08-01

    We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level approximately 14.5 ka. PMID:19661421

  9. Development of a wind gust model to estimate gust speeds and their return periods

    NASA Astrophysics Data System (ADS)

    Seregina, Larisa; Haas, Rabea; Born, Kai; Pinto, Joaquim G.

    2014-05-01

    Spatially dense observations of gust speeds are necessary for various applications, but their availability is limited in space and time. This work presents an approach to help to overcome this problem. The main objective is the generation of synthetic wind gust velocities. With this aim, theoretical wind and gust distributions are estimated from ten years of hourly observations collected at 123 synoptic weather stations provided by the German Weather Service. In a first step, an exposure correction is applied on measurements of the mean wind velocity to reduce the influence of local urban and topographic effects. In a second step, a transfer function is built between distribution parameters of wind and gust velocities. The aim of this step is to estimate the parameters of gusts at stations where only wind speed data is available. These parameters can be used in a third step to generate synthetic gusts, which can improve the accuracy of return periods at test sites with a lack of observations. The second objective is to determine return periods much longer than the nominal length of the original time series by considering extreme value statistics. Estimates for both local maximum return periods and average return periods for single historical events are provided. The comparison of maximum and average return periods shows that even storms with short average return periods may lead to local wind gusts with return periods of several decades. Despite uncertainties caused by the short length of the observational records, the method leads to consistent results, enabling a wide range of possible applications.

  10. Wide velocity measurements by optical scintillations methods

    NASA Astrophysics Data System (ADS)

    Tsadka, S.; Shaft, S.; Azar, Z.; Tur, Moshe

    1989-07-01

    Scintillations-based optical techniques for the measurement of the atmospheric transverse average wind velocity are reexamined. Three different methods for the processing of the resultant time-lagged covariance function are compared to in situ anemometer measurements. A correlation index of 0.89-0.95 is obtained between the optical and anemometer results. It tends to increase with the measurement time constant.

  11. The effect of subgrid velocity scale on site-specific/subgrid area and grid-averaged dry deposition velocities

    NASA Astrophysics Data System (ADS)

    Zhang, Leiming; Brook, Jeffrey R.

    A method for deriving the site-specific and subgrid area wind speed and friction velocity from regional model output and detailed land type information is developed. The "subgrid velocity scale" is introduced to account for generation of turbulent fluxes by subgrid motions. The grid vector averaged wind speed is adjusted by adding the subgrid velocity scale. This is to account for the fact that the spatial average of the local wind speed is usually larger than the absolute value of the vector averaged velocity ( | limitV?| ), especially when there are different land or surface types within the spatial averaging area and when limitV? is small. The assumption of uu*=constant is then applied within a model grid area to obtain wind speed and friction velocity for specific sites and subgrid areas. Using this method, the site-specific and subgrid area wind speed and friction velocity can be estimated from grid-averaged model output. In addition, more realistic air pollutant dry deposition velocities for specific locations and subgrid areas can be calculated. Grid-averaged deposition velocity values calculated using this approach tend to be about 30% different (either larger or smaller) for HNO 3 and sulphate and about 10% different for SO 2 and O 3 compared to values calculated by assuming a constant wind speed over the whole model grid area. These differences are found to be even larger at specific sites or over some subgrid areas. This method can be applied to determine a more realistic wind speed, friction velocity and pollutant dry deposition velocity at specific locations using gridded meteorological data.

  12. Low and high velocity clouds produced by young stellar clusters

    NASA Astrophysics Data System (ADS)

    Rodrguez-Gonzlez, A.; Raga, A. C.; Cant, J.

    2009-07-01

    Context: Intermediate and high velocity HI clouds rain onto the plane of our Galaxy. They are observed at heights of between 500 and 1500 pc, falling onto the Galactic plane at velocities from 50 to 140 km s-1. Aims: To explain the origin of these clouds, we present a galactic fountain model, driven by the wind from a super stellar cluster (SSC). Methods: We solve the equations for a steady, radiative de Laval nozzle flow. We consider two effects not considered previously in astrophysical nozzle flow models: cooling functions for different metallicities, and the direct action of the galactic gravitational field on the gas flowing along the nozzle. Results: For an adiabatic nozzle flow, the gravity acting directly on the gas within the nozzle stalls the nozzle flow for initial wind velocities lower than the escape velocity from the Galaxy. For the same wind velocity, a radiative nozzle flow stalls at lower altitudes above the galactic plane. We find that SSC winds with velocities of vw = 500-800 km s-1 produce nozzles stall at heights of xm = 1-15 kpc. The stalled nozzle flow then rains back onto the galactic plane at velocities in the range observed in intermediate and high velocity HI clouds. Conclusions: We study a nozzle flow driven by a wind from a SSC close to the Galactic centre. We find that for velocities within the range expected for a SSC wind, we can produce nozzle flows that stall above the galactic plane. These stalled flows produce cool, infalling clouds with velocities similar to those of intermediate and high velocity HI clouds.

  13. 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 ηmp=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 ηmp.

  14. 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.

  15. Fast solar wind monitoring available: BMSW in operation

    NASA Astrophysics Data System (ADS)

    afrnkov, J.; N?me?ek, Z.; P?ech, L.; Zastenker, G.

    2013-06-01

    The Spektr-R spacecraft was launched on a Zenit-3F rocket into an orbit with a perigee of 10.000 kilometers and apogee of 390.000 km on July 18, 2011. The spacecraft operational lifetime would exceed five years. The main task of the mission is investigations of distant sources of electromagnetic emissions but, as a supporting measurement, the spacecraft carries a complex of instruments for solar wind monitoring because it will spend there ~ 8 days out of the 9-day orbit. The main task of the solar wind monitor (BMSW) is to provide fast measurements of the solar wind density, velocity, and temperature with a maximum time resolution of 31 ms. Such time resolution was obtained using simultaneous measurements of several Faraday cups oriented permanently nearly in the solar wind direction. In this paper, we describe briefly basic principles of the BMSWoperation, and show a few examples its observations. We present frequency spectra of the solar wind turbulence at the kinetic scale and an example of high-frequency waves associated with an IP shock.

  16. 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

  17. 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.

  18. 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.

  19. Field Tests of Wind Turbine Unit with Tandem Wind Rotors and Double Rotational Armatures

    NASA Astrophysics Data System (ADS)

    Galal, Ahmed Mohamed; Kanemoto, Toshiaki

    This paper discusses the field tests of the wind turbine unit, in which the front and the rear wind rotors drive the inner and the outer armatures of the synchronous generator. The wind rotors were designed conveniently by the traditional procedure for the single wind rotor, where the diameters of the front and the rear wind rotors are 2 m and 1.33 m. The tests were done on a pick-up type truck driven straightly at constant speed. The rotational torque of the unit is directly proportional to the induced electric current irrespective of the rotational speeds of the wind rotors, while the induced voltage is proportional to the relative rotational speed. The performance of the unit is significantly affected not only by the wind velocity, but also by the blade setting angles of both wind rotors and the applied load especially at lower wind velocity.

  20. Wind-driven coastal upwelling and westward circulation in the Yucatan shelf

    NASA Astrophysics Data System (ADS)

    Ruiz-Castillo, Eugenio; Gomez-Valdes, Jose; Sheinbaum, Julio; Rioja-Nieto, Rodolfo

    2016-04-01

    The wind-driven circulation and wind-induced coastal upwelling in a large shelf sea with a zonally oriented coast are examined. The Yucatan shelf is located to the north of the Yucatan peninsula in the eastern Gulf of Mexico. This area is a tropical shallow body of water with a smooth sloping bottom and is one of the largest shelves in the world. This study describes the wind-driven circulation and wind-induced coastal upwelling in the Yucatan shelf, which is forced by easterly winds throughout the year. Data obtained from hydrographic surveys, acoustic current profilers and environmental satellites are used in the analysis. Hydrographic data was analyzed and geostrophic currents were calculated in each survey. In addition an analytical model was applied to reproduce the currents. The results of a general circulation model were used with an empirical orthogonal function analysis to study the variability of the currents. The study area is divided in two regions: from the 40 m to the 200 m isobaths (outer shelf) and from the coast to the 40 m isobath (inner shelf). At the outer shelf, observations revealed upwelling events throughout the year, and a westward current with velocities of approximately 0.2 m s-1 was calculated from the numerical model output and hydrographic data. In addition, the theory developed by Pedlosky (2007) for a stratified fluid along a sloping bottom adequately explains the current's primary characteristics. The momentum of the current comes from the wind, and the stratification is an important factor in its dynamics. At the inner shelf, observations and numerical model output show a wind-driven westward current with maximum velocities of 0.20 m s-1. The momentum balance in this region is between local acceleration and friction. A cold-water band is developed during the period of maximum upwelling.

  1. Altimeter Estimation of Sea Surface Wind Stress for Light to Moderate Winds

    NASA Technical Reports Server (NTRS)

    Vandemark, Douglas; Edson, James B.; Chapron, Bertrand

    1997-01-01

    Aircraft altimeter and in situ measurements are used to examine relationships between altimeter backscatter and the magnitude of near-surface wind and friction velocities. Comparison of altimeter radar cross section with wind speed is made through the modified Chelton-Wentz algorithm. Improved agreement is found after correcting 10-m winds for both surface current and atmospheric stability. An altimeter friction velocity algorithm is derived based on the wind speed model and an open-ocean drag coefficient. Close agreement between altimeter- and in situ-derived friction velocities is found. For this dataset, quality of the altimeter inversion to surface friction velocity is comparable to that for adjusted winds and clearly better than the inversion to true 10-m wind speed.

  2. Investigation of the maximum load alleviation potential using trailing edge flaps controlled by inflow data

    NASA Astrophysics Data System (ADS)

    Fischer, A.; Madsen, H. A.

    2014-12-01

    The maximum fatigue load reduction potential when using trailing edge flaps on mega-watt wind turbines was explored. For this purpose an ideal feed forward control algorithm using the relative velocity and angle of attack at the blade to control the loads was implemented. The algorithm was applied to time series from computations with the aeroelastic code HAWC2 and to measured time series. The fatigue loads could be reduced by 36% in the computations if the inflow sensor was at the same position as the blade load. The decrease of the load reduction potential when the sensor was at a distance from the blade load location was investigated. When the algorithm was applied to measured time series a load reduction of 23% was achieved which is still promissing, but significantly lower than the value achieved in computations.

  3. 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.

  4. 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...

  5. Wind noise under a pine tree canopy.

    PubMed

    Raspet, Richard; Webster, Jeremy

    2015-02-01

    It is well known that infrasonic wind noise levels are lower for arrays placed in forests and under vegetation than for those in open areas. In this research, the wind noise levels, turbulence spectra, and wind velocity profiles are measured in a pine forest. A prediction of the wind noise spectra from the measured meteorological parameters is developed based on recent research on wind noise above a flat plane. The resulting wind noise spectrum is the sum of the low frequency wind noise generated by the turbulence-shear interaction near and above the tops of the trees and higher frequency wind noise generated by the turbulence-turbulence interaction near the ground within the tree layer. The convection velocity of the low frequency wind noise corresponds to the wind speed above the trees while the measurements showed that the wind noise generated by the turbulence-turbulence interaction is near stationary and is generated by the slow moving turbulence adjacent to the ground. Comparison of the predicted wind noise spectrum with the measured wind noise spectrum shows good agreement for four measurement sets. The prediction can be applied to meteorological estimates to predict the wind noise under other pine forests. PMID:25698000

  6. 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.

  7. 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].

  8. Semiannual variation of the geomagnetic activity and solar wind parameters

    NASA Astrophysics Data System (ADS)

    Orlando, M.; Moreno, G.; Parisi, M.; Storini, M.

    1993-10-01

    The semiannual variation of the geomagnetic activity is investigated in connection with a large set of solar wind and interplanetary magnetic field data (4494 daily averages from 1965 to 1987). Our analysis confirms that the geomagnetic activity (described by the aa index), is mainly modulated by the southward component of the magnetic field (BS), as suggested by Russell and McPherron. On the other hand, it is also found that the solar wind velocity (V) has a relevant role in this phenomenon. In fact, the amplitude of the aa modulation is best correlated with the function BSV2. We also explore the linkage between the annual trend of aa and the sunspot activity (1868-1989), showing that the modulation of the geomagnetic activity follows a more regular pattern during the descending phase of the solar cycle than during the rising and maximum parts.

  9. Winding for the wind

    NASA Astrophysics Data System (ADS)

    Weingart, O.

    The mechanical properties and construction of epoxy-impregnated fiber-glass blades for wind turbines are discussed, along with descriptions of blades for the Mod 0A and Mod 5A WECS and design goals for a 4 kW WECS. Multicell structure combined with transverse filament tape winding reduces labor and material costs, while placing a high percentage of 0 deg fibers spanwise in the blades yields improved strength and elastic properties. The longitudinal, transverse, and shear modulus are shown to resist stresses exceeding the 50 lb/sq ft requirements, with constant stress resistance expected until fatigue failure is approached. Regression analysis indicates a fatigue life of 400 million operating cycles. The small WECS under prototype development features composite blades, nacelle, and tower. Rated at 5.7 kW in a 15 mph wind, the machine operates over a speed range of 9-53.9 mph and is expected to produce 16,200 kWh annually in a 10 mph average wind measured at 30 ft.

  10. Winding for the wind

    NASA Technical Reports Server (NTRS)

    Weingart, O.

    1981-01-01

    The mechanical properties and construction of epoxy-impregnated fiber-glass blades for wind turbines are discussed, along with descriptions of blades for the Mod 0A and Mod 5A WECS and design goals for a 4 kW WECS. Multicell structure combined with transverse filament tape winding reduces labor and material costs, while placing a high percentage of 0 deg fibers spanwise in the blades yields improved strength and elastic properties. The longitudinal, transverse, and shear modulus are shown to resist stresses exceeding the 50 lb/sq ft requirements, with constant stress resistance expected until fatigue failure is approached. Regression analysis indicates a fatigue life of 400 million operating cycles. The small WECS under prototype development features composite blades, nacelle, and tower. Rated at 5.7 kW in a 15 mph wind, the machine operates over a speed range of 9-53.9 mph and is expected to produce 16,200 kWh annually in a 10 mph average wind measured at 30 ft.

  11. 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.

  12. Optimum windings for linear induction machines.

    NASA Technical Reports Server (NTRS)

    Elliott, D. G.

    1973-01-01

    The matrix method of calculating linear induction machine performance as a function of winding current distribution was extended to determine the winding current distribution for maximum efficiency. Application of the method to typical magnetohydrodynamic generator geometries showed that electrical efficiencies of 0.5 to 0.6 are possible with fractional wavelength windings and without insulating vanes in the flow.

  13. 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

  14. 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.

  15. 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.

  16. The structure of moderately strong winds at a mid-Atlantic coastal site /below 75m/

    NASA Technical Reports Server (NTRS)

    Tieleman, H. W.; Mullins, S. E.

    1980-01-01

    Velocity and temperature measurements were obtained from an instrumented 76-meter meteorological tower located near the Atlantic Ocean at Wallops Island, Virginia. The instrumentation consists of a slow-response cup-vane and resistance temperature system and a hot-film, thermocouple system for turbulence measurements. Results are presented for moderately strong winds from westerly directions (category I) and for on-shore winds from southerly directions (category II). Results from category I winds indicate the presence of low-frequency velocity fluctuations affecting all turbulence parameters similar to the observations made in Kansas and Minnesota. Winds of category II experience a change in surface roughness and surface temperature as they cross the coast line, resulting in the development of an internal boundary layer. The stable ocean air above the IBL shows extremely low turbulence levels (less than 3%). Because of the lack of turbulent mixing with adjacent layers, Coriolis effects are important and profiles with a maximum velocity at heights between 60-200 m exist.

  17. 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.

  18. 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)

  19. Multi-spacecraft observations of heliographic latitude-longitude structure in the solar wind

    NASA Technical Reports Server (NTRS)

    Rhodes, E. J., Jr.; Smith, E. J.

    1981-01-01

    The heliographic latitude-longitude structure of high speed solar winds observed prior to the maximum of sunspot cycle 20 is investigated by multi-spacecraft comparisons. It is shown that differences in solar wind structures are due to two different kinds of spatial structures. One structure is found to be consistent with the simultaneous existence of a single, broad stream at latitudes above 7 deg N and a series of narrow streams at lower latitudes, while the other is consistent with the existence of a latitudinally sloping stream boundary near the solar equator. For latitude separations less than 3.5 deg, cross-correlations of Explorer-Mariner velocities show only previously reported systematic increases in velocity with latitude, and for latitude separations from 3.5 to 6.2 deg, differences in high speed streams shift in longitude and/or amplitude are also identified on a timescale of one solar rotation.

  20. Impact of wind on ambient noise recorded by seismic array in northern Poland

    NASA Astrophysics Data System (ADS)

    Lepore, Simone; Markowicz, Krzysztof; Grad, Marek

    2016-03-01

    Seismic interferometry and beam-forming techniques were applied to the ambient noise recorded during January 2014 at the "13 BB star" array composed of thirteen seismic stations located in northern Poland. The circular and symmetric geometry of the array allowed the evaluation of the azimuths of noise sources and the velocities of recovered surface waves with a good reliability. After having pre-processed the raw records of the ambient noise in time- and frequency-domain, we studied the associated power spectral density to identify the frequency bands suitable for the recovery of the surface waves. Then the crosscorrelation was performed between all the station pairs of the array to retrieve the Green's function, from which the velocity range of the surface waves can be determined. Making use of that analysis, the direction of the noise wavefield was linked to the maximum amplitude of the beam-power, estimated by the mixing in the frequency-domain of all the corresponding noise records. The results were related day by day to the mean wind velocity around Europe at 10 m above ground level obtained from global surveys carried out during the same month. Significant correlation between the direction of maximum beam-power associated to the ambient noise recorded at "13 BB star" and the average wind velocity was found.

  1. Impact of wind on ambient noise recorded by seismic array in northern Poland

    NASA Astrophysics Data System (ADS)

    Lepore, Simone; Markowicz, Krzysztof; Grad, Marek

    2016-06-01

    Seismic interferometry and beam-forming techniques were applied to the ambient noise recorded during January 2014 at the `13 BB star' array composed of thirteen seismic stations located in northern Poland. The circular and symmetric geometry of the array allowed the evaluation of the azimuths of noise sources and the velocities of recovered surface waves with a good reliability. After having pre-processed the raw records of the ambient noise in time- and frequency-domain, we studied the associated power spectral density to identify the frequency bands suitable for the recovery of the surface waves. Then the cross-correlation was performed between all the station pairs of the array to retrieve the Green's function, from which the velocity range of the surface waves can be determined. Making use of that analysis, the direction of the noise wavefield was linked to the maximum amplitude of the beam-power, estimated by the mixing in the frequency-domain of all the corresponding noise records. The results were related day by day to the mean wind velocity around Europe at 10 m above ground level obtained from global surveys carried out during the same month. Significant correlation between the direction of maximum beam-power associated to the ambient noise recorded at `13 BB star' and the average wind velocity was found.

  2. Wind tunnel simulations of wind turbine wake interactions in neutral and stratified wind flow.

    NASA Astrophysics Data System (ADS)

    Hancock, P. E.; Pascheke, F.

    2010-09-01

    A second programme of work is about to commence as part of a further four years of funding for the UK-EPSRC SUPERGEN-Wind large-wind-farm consortium. The first part of the initial programme at Surrey was to establish and set up appropriate techniques for both on- and off-shore boundary layers (though with an emphasis on the latter) at a suitable scale, and to build suitable rotating model wind turbines. The EnFlo wind tunnel, a UK-NCAS special facility, is capable of creating scaled neutral, stable and unstable boundary layers in its 20m long working section. The model turbines are 1/300-scale of 5MW-size, speed controlled with phase-lock measurement capability, and the blade design takes into account low Reynolds-number effects. Velocity measurements are primarily made using two-component LDA, combined with a ‘cold-wire' probe in order to measure the local turbulent heat flux. Simulation of off-shore wakes is particularly constrained because i) at wind tunnel scale the inherently low surface roughness can be below that for fully rough conditions, ii) the power required to stratify the flow varies as the square of the flow speed, and could easily be impractically large, iii) low blade Reynolds number. The boundary layer simulations, set up to give near-equilibrium conditions in terms of streamwise development, and the model turbines have been designed against these constraints, but not all constraints can be always met simultaneously in practice. Most measurements so far have been made behind just one or two turbines in neutral off- and on-shore boundary layers, at stations up to 12 disk diameters downstream. These show how, for example, the wake of a turbine affects the development of the wake of a downwind turbine that is laterally off-set by say half or one diameter, and how the unaffected part from the first turbine merges with the affected wake of the second. As expected a lower level of atmospheric turbulence causes the wakes to develop and fill-in more slowly compared with the on-shore case. A turbine can also suppress the level of atmospheric turbulence below hub height. In neutral flow, the wakes grow in width and height. However, even in mild stable stratification the vertical development of the wake deficit can be completely inhibited; at least some reduction would be expected arising from the stabilizing influence on vertical fluctuations. The width in contrast develops at about the same rate. As anticipated, the wake development is slower still in the stable case because of the lower level ambient turbulence. The maximum deficit is at a lower height than it is for neutral flow. Various aspects of the turbulence in the wake have been investigated. Second-phase work will examine a larger number of wake-turbine and wake-wake interactions, make a more detailed study of how turbines alter the atmospheric turbulence, and examine more cases of stratification. Work is also in hand related to turbines in or near forested regions, and it is expected that aspects of the physics will have links with the effect a large wind farm will have on the ABL and on the wind resource for a downwind farm. The work will produce a series of test cases to assist in the development of better wake and wind resource prediction models as well as a better understanding of wake physics.

  3. 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...

  4. Wind information display system user's manual

    NASA Technical Reports Server (NTRS)

    Roe, J.; Smith, G.

    1977-01-01

    The Wind Information Display System (WINDS) provides flexible control through system-user interaction for collecting wind shear data, processing this data in real time, displaying the processed data, storing raw data on magnetic tapes, and post-processing raw data. The data are received from two asynchronous laser Doppler velocimeters (LDV's) and include position, velocity and intensity information. The raw data is written onto magnetic tape for permanent storage and is also processed in real time to depict wind velocities in a given spacial region.

  5. Reattachment Zone Characterisation Under Offshore Winds With Flow Separation On The Lee Side Of Coastal Dunes

    NASA Astrophysics Data System (ADS)

    Delgado-Fernandez, I.; Jackson, D.; Cooper, J. A.; Baas, A. C.; Lynch, K.; Beyers, M.

    2010-12-01

    Airflow separation, lee-side eddies and secondary flows play an essential role on the formation and maintenance of sand dunes. Downstream from dune crests the flow surface layer detaches from the ground and generates an area characterised by turbulent eddies in the dune lee slope (the wake). At some distance downstream from the dune crest, flow separates into a reversed component directed toward the dune toe and an offshore “re-attached” component. This reattachment zone (RZ) has been documented in fluvial and desert environments, wind tunnel experiments and numerical simulations, but not yet characterised in coastal dunes. This study examines the extent and temporal evolution of the RZ and its implications for beach-dune interaction at Magilligan, Northern Ireland. Wind parameters were measured over a profile extending from an 11 m height dune crest towards the beach, covering a total distance of 65 m cross-shore. Data was collected using an array of nine ultrasonic anemometers (UAs) deployed in April-May 2010, as part of a larger experiment to capture airflow data under a range of incident wind velocities and offshore directions. UAs were located along the profile (5 m tower spacing) over the beach, which allowed a detailed examination of the RZ with empirical data. Numerical modelling using Computational Fluid Dynamics (CFD) software was also conducted with input data from anemometer field measurements, running over a surface mesh generated from LiDAR and DGPS surveys. Results demonstrate that there is a wind threshold of approximately 5-6 ms-1 under which no flow separation exists with offshore winds. As wind speed increases over the threshold, a flow reversal area is quickly formed, with the maximum extent of the RZ at approximately 3.5 dune heights (h). The maximum extent of the RZ increases up to 4.5h with stronger wind speeds of 8-10 ms-1 and remains relatively constant as wind speed further increases. This suggests that the spatial extent of the RZ is independent of incident wind speed and is located between 4-5h. The magnitude of the maximum extent of the RZ is similar to that simulated using CFD and is consistent with previous studies conducted in desert dunes and wind tunnel simulations for offshore winds blowing over tall and sharp-crested dunes. Ongoing analyses are being conducted to evaluate the effect of changing wind direction, dune height and shape.

  6. On the theory of the horizontal-axis wind turbine

    NASA Astrophysics Data System (ADS)

    de Vries, O.

    The fluid mechanical theory of horizontal axis wind turbines (HAWT) in homogeneous, steady flows is presented. HAWT aerodynamic performance is governed by rotor torque and drag, the angular velocity, and power output, with governing equations for momentum, mass, and energy. The lift force and profile drag acting on the airfoil blades depend on the flow velocity, the chord length, the angle of attack, and the lift and drag coefficients. Single streamtube and multiple-stream tube and angular momentum analyses are employed to quantify the maximum wind turbine performance. Optimization studies for HAWT blades have indicated that a considerable amount of blade twist and taper enhances HAWT performance. Blade-element and vortex theory combined with panel methods are used to study optimum blade shapes. Techniques for assuring that wind tunnel studies of scale models are valid for full scale machines are defined. Sample runs have shown the accuracy of the blade element theory and the inaccuracies of two-dimensional analyses when stall is reached. The acquisition of more aerodynamic data on HAWT performance is indicated.

  7. Two dimensional velocity distribution in open channels using Renyi entropy

    NASA Astrophysics Data System (ADS)

    Kumbhakar, Manotosh; Ghoshal, Koeli

    2016-05-01

    In this study, the entropy concept is employed for describing the two-dimensional velocity distribution in an open channel. Using the principle of maximum entropy, the velocity distribution is derived by maximizing the Renyi entropy by assuming dimensionless velocity as a random variable. The derived velocity equation is capable of describing the variation of velocity along both the vertical and transverse directions with maximum velocity occurring on or below the water surface. The developed model of velocity distribution is tested with field and laboratory observations and is also compared with existing entropy-based velocity distributions. The present model has shown good agreement with the observed data and its prediction accuracy is comparable with the other existing models.

  8. Wind profile perturbation analysis for STS

    NASA Technical Reports Server (NTRS)

    Adelfang, S. I.; Smith, O. E.; Whitehead, D. S.

    1991-01-01

    Two case studies of the relationship between STS ascent structural loads and wind profile characteristics are described. In the first case study, a wind profile with relatively weak winds is used to demonstrate the importance of launch vehicle velocity relative to the air and its effect on loads. In the second study, a pair of wind profiles is used to show how the determination of load exceedances is strongly influenced by the wind load persistence allowances for the baseline and two day-of-launch (DOL) steering commands called I-LOADs. Characteristics of the wind profiles and associated trajectory variable and wind-sensitive load indicators are examined. Energy spectra of in-plane and out-of-plane wind component and a load indicator are presented. An analysis of load indicator sensitivity to wind perturbation energy in the 1600-6400 m wavelength band for baseline and DOL I-LOAD is described.

  9. 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

  10. Solar wind composition

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Coplan, M. A.

    1995-01-01

    Advances in instrumentation have resulted in the determination of the average abundances of He, C, N, O, Ne, Mg, Si, S, and Fe in the solar wind to approximately 10%. Comparisons with solar energetic particle (SEP) abundances and galactic cosmic ray abundances have revealed many similarities, especially when compared with solar photospheric abundances. It is now well established that fractionation in the corona results in an overabundance (with respect to the photosphere) of elements with first ionization potentials less than 10 eV. These observations have in turn led to the development of fractionation models that are reasonably successful in reproducing the first ionization (FIP) effect. Under some circumstances it has been possible to relate solar wind observations to particular source regions in the corona. The magnetic topologies of the source regions appear to have a strong influence on the fractionation of elements. Comparisons with spectroscopic data are particularly useful in classifying the different topologies. Ions produced from interstellar neutral atoms are also found in the solar wind. These ions are picked up by the solar wind after ionization by solar radiation or charge exchange and can be identified by their velocity in the solar wind. The pick-up ions provide most of the pressure in the interplanetary medium at large distances. Interstellar abundances can be derived from the observed fluxes of solar wind pick-up ions.

  11. 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 ΔSo 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    Hutchinson, I. H.

    2013-05-01

    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 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 spacecraft.

  14. Maximum range three-dimensional lifting planetary entry

    NASA Technical Reports Server (NTRS)

    Dickmanns, E. D.

    1972-01-01

    Variational equations for maximum range three-dimensional quasisteady glide are given. Nonlinear oscillatory maximum range trajectories obtained with a refined gradient program are approximated by a superposition of quasisteady glide and linearized perturbation equation results. A basic control law is found which is closely followed for maximum cross-range trajectories. The effect of a reradiative heating constraint involving velocity, altitude and angle of attack on a maximum cross-range trajectory for a space shuttle orbiter-type vehicle reentering the earth's atmosphere is investigated numerically.

  15. 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 β} 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.

  16. 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

  17. 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…

  18. Note on one-fluid modeling of low-frequency Alfvénic fluctuations in a solar wind plasma with multi-ion components

    NASA Astrophysics Data System (ADS)

    Nariyuki, Y.; Umeda, T.; Suzuki, T. K.; Hada, T.

    2015-12-01

    A simple point of view that non-zero Alfvén ratio (residual energy) appears as a consequence of one-fluid modeling of uni-directional Alfvén waves in a solar wind plasma is presented. Since relative speeds among ions are incorporated into the one-fluid model as a pressure anisotropy, the Alfvén ratio can be finite due to the decrease in the phase velocity. It is shown that a proton beam component typically found in the solar wind plasma can contribute to generating non-zero Alfvén ratio observed in the solar wind plasma. Local equilibrium velocity distribution functions of each ion component are also discussed by using maximum entropy principle.

  19. Note on one-fluid modeling of low-frequency Alfvénic fluctuations in a solar wind plasma with multi-ion components

    SciTech Connect

    Nariyuki, Y.; Umeda, T.; Suzuki, T. K.; Hada, T.

    2015-12-15

    A simple point of view that non-zero Alfvén ratio (residual energy) appears as a consequence of one-fluid modeling of uni-directional Alfvén waves in a solar wind plasma is presented. Since relative speeds among ions are incorporated into the one-fluid model as a pressure anisotropy, the Alfvén ratio can be finite due to the decrease in the phase velocity. It is shown that a proton beam component typically found in the solar wind plasma can contribute to generating non-zero Alfvén ratio observed in the solar wind plasma. Local equilibrium velocity distribution functions of each ion component are also discussed by using maximum entropy principle.

  20. Wind abrasion on Mars

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    1991-01-01

    Aeolian activity was predicted for Mars from earth based observations of changing surface patterns that were interpreted as dust storms. Mariner 9 images showed conclusive evidence for aeolian processes in the form of active dust storms and various aeolian landforms including dunes and yardangs. Windspeeds to initiate particle movement are an order of magnitude higher on Mars than on Earth because of the low atmospheric density on Mars. In order to determine rates of abrasion by wind blown particles, knowledge of three factors is required: (1) particle parameters such as numbers and velocities of windblown grains as functions of windspeeds at various heights above the surface; (2) the susceptibility to abrasion of various rocks and minerals; and (3) wind frequencies and speeds. For estimates appropriate to Mars, data for the first two parameters can be determined through lab and wind tunnel tests; data for the last two factors are available directly from the Viking Lander meteorology experiments for the two landing sites.

  1. The Local Velocity Field

    NASA Astrophysics Data System (ADS)

    Masters, Karen

    2008-08-01

    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.

  2. Wind Turbine

    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....

  3. 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.

  4. 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.

  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. Optimum propeller wind turbines

    SciTech Connect

    Sanderson, R.J.; Archer, R.D.

    1983-11-01

    The Prandtl-Betz-Theodorsen theory of heavily loaded airscrews has been adapted to the design of propeller windmills which are to be optimized for maximum power coefficient. It is shown that the simpler, light-loading, constant-area wake assumption can generate significantly different ''optimum'' performance and geometry, and that it is therefore not appropriate to the design of propeller wind turbines when operating in their normal range of high-tip-speed-to-wind-speed ratio. Design curves for optimum power coefficient are presented and an example of the design of a typical two-blade optimum rotor is given.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. The causes of geomagnetic storms during solar maximum

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce T.; Gonzalez, Walter D.

    1994-01-01

    One of the oldest mysteries in geomagnetism is the linkage between solar and geomagnetic activity. In investigating the causes of geomagnetic storms occurring during solar maximum, the following topics are discussed: solar phenomena; types of solar wind; magnetic reconnection and magnetic storms; an interplanetary example; and future space physics missions.

  13. Evidence for mass loss at moderate to high velocity in Be stars

    NASA Technical Reports Server (NTRS)

    Snow, T. P., Jr.; Marlborough, J. M.

    1976-01-01

    Ultraviolet spectra of intermediate resolution have been obtained with Copernicus for 12 objects classified as Be or shell stars and for 19 additional early B dwarfs. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si IV doublet at 1400 A, indicating the presence in some cases of outflowing material with maximum velocities of nearly 1000 km/s. Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5; the only objects later than B0.5 which show this effect are Be or shell stars. Among the stars considered, there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the ultraviolet flux from B1-B2 dwarfs is sufficient to drive high-velocity stellar winds only if rotational effects reduce the effective gravity near the equator. The mass-loss rate for one of the most active Be stars, 59 Cyg, is crudely estimated to be one billionth or one ten-billionth of a solar mass per year. The data suggest that the extended atmospheres associated with Be-star phenomena may be formed by mass ejection.

  14. Using a new characterization of turbulent wind for accurate correlation of wind turbine response with wind speed

    NASA Astrophysics Data System (ADS)

    Connell, J. R.; George, R. L.

    1987-09-01

    The turbulence encountered by a point on a rotating wind turbine blade has characteristics that in some important respects are different from those measured by a stationary anemometer. The conventional one-peaked continuous spectrum becomes, broadly, a two-peaked spectrum that in addition contains a set of narrow-band spikes of turbulence energy, one centered on the frequency of rotor rotation and the others centered on multiples of that frequency. The rotational sampling effect on wind spectra is quantified using measurements of wind velocity by anemometers on stationary crosswind circular arrays. Characteristics of fluctuating wind are compared to measured fluctuations of bending moments of the rotor blades and power output fluctuations of a horizontal-axis wind turbine at the same site. The wind characteristics and the correlations between wind fluctuations and wind turbine fluctuations provide a basis for improving turbine design, siting, and control.

  15. Using a new characterization of turbulent wind for accurate correlation of wind turbine response with wind speed

    SciTech Connect

    Connell, J.R.; George, R.L.

    1987-09-01

    The turbulence encountered by a point on a rotating wind turbine blade has characteristics that in some important respects are different from those measured by a stationary anemometer. The conventional one-peaked continuous spectrum becomes, broadly, a two-peaked spectrum that in addition contains a set of narrow-band spikes of turbulence energy, one centered on the frequency of rotor rotation and the others centered on multiples of that frequency. The rotational sampling effect on wind spectra is quantified using measurements of wind velocity by anemometers on stationary crosswind circular arrays. Characteristics of fluctuating wind are compared to measured fluctuations of bending moments of the rotor blades and power output fluctuations of a horizontal-axis wind turbine at the same site. The wind characteristics and the correlations between wind fluctuations and wind turbine fluctuations provide a basis for improving turbine design, siting, and control. 6 refs., 11 figs., 1 tab.

  16. VELOCITY INDICATOR FOR EXTRUSION PRESS

    DOEpatents

    Digney, F.J. Jr.; Bevilacqua, F.

    1959-04-01

    An indicator is presented for measuring the lowspeed velocity of an object in one direction where the object returns in the opposite direction at a high speed. The indicator comprises a drum having its axis of rotation transverse to the linear movement of the object and a tape wound upon the drum with its free end extending therefrom and adapted to be connected to the object. A constant torque is applied to the drum in a direction to wind the tape on the drum. The speed of the tape in the unwinding direction is indicated on a tachometer which is coupled through a shaft and clutch means to the drum only when the tape is unwinding.

  17. Kinematics and aerodynamics of the velocity vector roll

    NASA Technical Reports Server (NTRS)

    Durham, Wayne C.; Lutze, Frederick H.; Mason, W.

    1993-01-01

    The velocity vector roll is an angular rotation of an aircraft about its instantaneous velocity vector, constrained to be performed at constant angle-of-attack (AOA), no sideslip, and constant velocity. Consideration of the aerodynamic force equations leads to requirements for body-axis yawing and pitching rotations that satisfy these constraints. Here, the body axis rotations, and the constraints, are used in the moment equations to determine the aerodynamic moments required to perform the velocity vector roll. For representative tactical aircraft, the conditions for maximum pitching moment are a function of orientation, occurring at about 90 deg of bank in a level trajectory. Maximum required pitching moment occurs at peak roll rate, and is achieved at AOA above 45 deg. The conditions for maximum rolling moment depend on the value of the roll mode time constant. For a small time constant (fast response) the maximum rolling moment occurs at maximum roll acceleration and zero AOA, largely independent of aircraft orientation; for a large time constant, maximum required rolling moment occurs at maximum roll rate, at maximum AOA, and at 180 deg of bank in level flight. Maximum yawing moment occurs at maximum roll acceleration, maximum AOA, and is largely independent of airplane orientation.

  18. Initial drop size and velocity distributions for airblast coaxial atomizers

    NASA Technical Reports Server (NTRS)

    Eroglu, H.; Chigier, N.

    1991-01-01

    Phase Doppler measurements were used to determine initial drop size and velocity distributions after a complete disintegration of coaxial liquid jets. The Sauter mean diameter (SMD) distribution was found to be strongly affected by the structure and behavior of the preceding liquid intact jet. The axial measurement stations were determined from the photographs of the coaxial liquid jet at very short distances (1-2 mm) downstream of the observed break-up locations. Minimum droplet mean velocities were found at the center, and maximum velocities were near the spray boundary. Size-velocity correlations show that the velocity of larger drops did not change with drop size. Drop rms velocity distributions have double peaks whose radial positions coincide with the maximum mean velocity gradients.

  19. Principal wind turbines for a conditional portfolio approach to wind farms

    NASA Astrophysics Data System (ADS)

    Lopes, Vitor V.; Scholz, Teresa; Raischel, Frank; Lind, Pedro G.

    2014-06-01

    We introduce a measure for estimating the best risk-return relation of power production in wind farms within a given time-lag, conditioned to the velocity field. The velocity field is represented by a scalar that weighs the influence of the velocity at each wind turbine at present and previous time-steps for the present "state" of the wind field. The scalar measure introduced is a linear combination of the few turbines, that most influence the overall power production. This quantity is then used as the condition for computing a conditional expected return and corresponding risk associated to the future total power output.

  20. "SPURS" in the North Atlantic Salinity Maximum

    NASA Astrophysics Data System (ADS)

    Schmitt, Raymond

    2014-05-01

    The North Atlantic Salinity Maximum is the world's saltiest open ocean salinity maximum and was the focus of the recent Salinity Processes Upper-ocean Regional Study (SPURS) program. SPURS was a joint venture between US, French, Irish, and Spanish investigators. Three US and two EU cruises were involved from August, 1012 - October, 2013 as well as surface moorings, glider, drifter and float deployments. Shipboard operations included underway meteorological and oceanic data, hydrographic surveys and turbulence profiling. The goal is to improve our understanding of how the salinity maximum is maintained and how it may be changing. It is formed by an excess of evaporation over precipitation and the wind-driven convergence of the subtropical gyre. Such salty areas are getting saltier with global warming (a record high SSS was observed in SPURS) and it is imperative to determine the relative roles of surface water fluxes and oceanic processes in such trends. The combination of accurate surface flux estimates with new assessments of vertical and horizontal mixing in the ocean will help elucidate the utility of ocean salinity in quantifying the changing global water cycle.

  1. Angular velocity discrimination

    NASA Technical Reports Server (NTRS)

    Kaiser, Mary K.

    1990-01-01

    Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.

  2. 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.

  3. Hot relativistic winds and the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Fujimura, F. S.; Kennel, C. F.

    1981-01-01

    Efforts to formulate a self-consistent model of pulsar magnetospheres which links the particle source near the pulsar to the outflowing relativistic wind and couples the wind to the surrounding nebula are reviewed. The use of a relativistic MHD wind is recommended to account for global photon emission and the invisibility of the method of plasma transport. Consideration of a magnetic monopole relativistic wind due to an axially symmetric aligned rotator is combined with calculations of the initial velocity of the wind to show that the flow velocity in such a model will never exceed Mach 1. Extending the solution to the case of a hot relativistic wind at supersonic speeds is noted to yield results consistent with observations of the Crab Nebula

  4. Stellar wind erosion of protoplanetary discs

    NASA Astrophysics Data System (ADS)

    Schnepf, N. R.; Lovelace, R. V. E.; Romanova, M. M.; Airapetian, V. S.

    2015-04-01

    An analytic model is developed for the erosion of protoplanetary gas discs by high-velocity magnetized stellar winds. The winds are centrifugally driven from the surface of rapidly rotating, strongly magnetized young stars. The presence of the magnetic field in the wind leads to Reynolds numbers sufficiently large to cause a strongly turbulent wind/disc boundary layer which entrains and carries away the disc gas. The model uses the conservation of mass and momentum in the turbulent boundary layer. The time-scale for significant erosion depends on the disc accretion speed, disc accretion rate, the wind mass-loss rate, and the wind velocity. The time-scale is estimated to be ˜2 × 106 yr. The analytic model assumes a steady stellar wind with mass- loss rate dot {M}}_w ˜ 10^{-10} M_{⊙} yr-1 and velocity vw ˜ 103 km s-1. A significant contribution to the disc erosion can come from frequent powerful coronal mass ejections (CMEs) where the average mass-loss rate in CMEs, dot{M}_CME, and velocities, vCME, have values comparable to those for the steady wind.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  7. 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

  8. 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.

  9. Wind profiles for Space Shuttle loads analysis

    NASA Technical Reports Server (NTRS)

    Adelfang, S. I.

    1978-01-01

    The small scale wind velocity perturbations in vertical wind profiles at Cape Kennedy, Florida were analyzed in order to derive information for simulations of space shuttle ascent through the perturbed atmosphere. The available statistical data does not permit specification of various aspects of idealized singularities and wavelike perturbations with a reasonable degree of confidence. The information developed as a result of the analysis described in Section 3 of this report is suitable for the further development of idealized models. The term perturbation is used instead of the more common term, gust. According to the conventional approach, a gust profile is calculated by applying a high pass digital filter to a Jimsphere profile; all the speeds in the filtered profile are defined as gusts. The high pass filtered profile is defined as a residual profile and the maximum residual in the vicinity of a specified reference height is defined as the gust. Gusts defined in this manner represent the perturbation peaks. A detailed discussion of the calculation of residual profiles and gusts is given. The meteorological coordinate system, the data sample, and Jimsphere profiles are also described. Recommendations and conclusions are presented.

  10. Airfoils for wind turbine

    DOEpatents

    Tangler, James L.; Somers, Dan M.

    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.

  11. 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.

  12. An iterative algorithm for objective wind field analysis

    NASA Technical Reports Server (NTRS)

    Liu, C. Y.; Goodin, W. R.

    1976-01-01

    Three different algorithms for objective wind field analysis were tested on the same set of initial conditions: Dickerson-Sasaki's 'strong constraint' algorithm, a fixed-vorticity algorithm, and a newly proposed fixed-station-velocity algorithm. The three methods are compared with respect to the degree of minimization of wind divergence and the accuracy of wind data at a measured station. The first two techniques, though they reduce wind divergence, produce wind vectors substantially different from the observed values. The proposed iterative scheme is similar to Endlich's (1967) procedure for treating a macroscale wind field, and minimizes divergence while retaining the observed wind vectors.

  13. The Earth's bow shock velocity distribution function

    NASA Astrophysics Data System (ADS)

    Meziane, K.; Hamza, A. M.; Maksimovic, M.; Alrefay, T. Y.

    2015-02-01

    It is well established that interplanetary disturbances cause the Earth's bow shock to move sunward or earthward. Since the launch of the Cluster mission, precise determination of the shock velocity was carried out allowing for the possibility to perform sophisticated investigations about the shock dynamics. The shock normal and velocity are determined for 381 Earth's bow shock crossings using data from the Spatio Temporal Analysis of Field Fluctuations - Spectrum Analyzer experiment on board the Cluster spacecraft. We have found that the observed radial shock velocity is well fitted by a Maxwellian for speeds less than 80 km s-1. The Maxwellian fit provides a standard deviation σVobs=24 km s-1. Assuming that the shock motion is exclusively controlled by the time rate of change of solar wind ram pressure, a probability density for the shock velocity near the nose region is constructed using the basic elements of probability theory. The obtained results are in a very good agreement with the observations when typical conditions of the solar wind are considered. The present study indicates that the ram pressure is a predominant parameter in shock dynamics and the relevance of the Mach number is not a determinant.

  14. Gunshot residue particle velocity and deceleration.

    PubMed

    De Forest, Peter R; Martir, Kirby; Pizzola, Peter A

    2004-11-01

    The velocity of over 800 gunshot residue particles from eight different sources was determined using high speed stroboscopic photography (spark gap light source). These particles were found to have an average velocity of 500 to 600 ft per second. Many particles acquired considerably higher velocities. Thus, the particles have sufficient energy to embed themselves within certain nearby targets like skin or fabric. The relatively high velocity that the particles acquire explain the formation of stippling on skin in close proximity to a muzzle discharge. These findings also indicate little influence of air currents on particle behavior near the muzzle. The deceleration of less than 100 particles during a 100-microsecond interval was also calculated. The particles experienced rapid rates of deceleration which would explain why few particles are found in test firings beyond 3 ft from the muzzle of a discharged firearm. Because of their relatively high velocity, normal wind velocity would not be expected to significantly influence their motion near the muzzle. PMID:15568695

  15. Laser-Doppler measurement of crosswind velocity.

    PubMed

    Durst, F; Howe, B M; Richter, G

    1982-07-15

    There is a need for the remote sensing of local wind velocities over distances of hundreds of meters, and laser-Doppler anemometry (LDA) has been suggested as a suitable measuring technique. In this paper the major features of an LDA system optimized for crosswind velocity measurements are presented. Computer programs based on Mie scattering theory are used to predict the performance of such systems and to extend the experimentally verified information to larger distances. A complete system for the measurement of the crosswind velocity component is described, and measurements up to 106 m verifying its performance and corresponding predictions are presented and discussed. Suggestions for further studies and developments are given. PMID:20396080

  16. Solar Wind

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Tsurutani, B. T.

    2000-01-01

    The sun is losing mass in form of the solar wind, which has affected its evolution from its birth and will continue to do so until its death. This is not unusual in that nearly all stars are losing mass through stellar winds throughout a major portion of their lives. As far as the Earth is concerned, the solar wind blows against the Earth's magnetosphere, causes aurora and geomagnetic storms, and can affect the Earth's climate.

  17. Preliminary Investigations of Wind Potential at Marietta College

    NASA Astrophysics Data System (ADS)

    Vance, William; Kuhl, Dennis

    2012-04-01

    Marietta College received a grant to build a wind turbine on campus for educational purposes, as a demonstration of alternative energy production, and to promote new energy systems minors. We report on an investigation of the potential wind energy profile on Marietta College's campus and preliminary wind tunnel studies of variations in shroud design for a shrouded horizontal axis wind turbine. Anemometers were placed in three locations on the campus and wind velocity data was logged for several months. The data provides average wind speeds as well as prevailing wind directions. A wind tunnel was constructed to test shrouded wind turbines. A shrouded wind turbine with a diffuser and flange can maximize the wind speed through a turbine, thus maximizing its power output. This paper sets the stage for future projects to further develop the turbine models' geometry that will maximize power output.

  18. Studying Wake Deflection of Wind Turbines in Yaw using Drag Disk Experiments and Actuator Disk Modeling in LES

    NASA Astrophysics Data System (ADS)

    Howland, Michael; Bossuyt, Juliaan; Meyers, Johan; Meneveau, Charles

    2015-11-01

    Recently, there has been a push towards the optimization in the power output of entire large wind farms through the control of individual turbines, as opposed to operating each turbine in a maximum power point tracking manner. In this vane, the wake deflection by wind turbines in yawed conditions has generated considerable interest in recent years. In order to effectively study the wake deflection according to classical actuator disk momentum theory, a 3D printed drag disk model with a coefficient of thrust of approximately 0.75 - 0.85 and a diameter of 3 cm is used, studied under uniform inflow in a wind tunnel with test section of 1 m by 1.3 m, operating with a negligible inlet turbulence level at an inflow velocity of 10 m/s. Mean velocity profile measurements are performed using Pitot probes. Different yaw angles are considered, including 10, 20, and 30 degrees. We confirm earlier results that (e.g.) a 30 degree yaw angle deflects the center of the wake around 1/2 of a rotor diameter when it impinges on a downstream turbine. Detailed comparisons between the experiments and Large Eddy Simulations using actuator disk model for the wind turbines are carried out in order to help validate the CFD model. Work supported by NSF (grants CBET-113380 and IIA-1243482, the WINDINSPIRE project) and by ERC (ActiveWindFarms, grant no. 306471).

  19. Dynamics of the turbidity maximum in King Sound, tropical Western Australia

    NASA Astrophysics Data System (ADS)

    Wolanski, E.; Spagnol, S.

    2003-04-01

    King Sound is a 100-km-long embayment located in tropical northwestern Australia with a spring tidal range of 11 m. This is the second largest tide in the world after the Bay of Fundy in Canada. Intertidal areas cover about 800 km 2. The upper reaches of the sound are turbid with fine suspended sediment concentration reaching 3 kg m -3. Field studies of the dynamics of water and fine sediment were carried out in the dry seasons of 1997 and 1998. The tide was a propagating wave, shoaling and dissipating by friction as it entered the sound. This mode of propagation generated an asymmetric tidal current with a stronger current at flood than at ebb. An evaporation-driven salinity maximum zone was found in the upper reaches of the sound, and this was also where the turbidity maximum occurred. Tidal pumping by the tidal asymmetry and, possibly, the biological filter formed by muddy marine snow, trapped the fine sediment in the upper regions of King Sound. Wind-driven waves contributed significantly to entrainment of bottom fine sediment, possibly through wave pumping of the sediment and not wave-induced orbital velocities. Field data suggest that erosion of bottom fine sediment was proportional to the sixth power of the tidal current and the third power of the wave height.

  20. How to hit home runs: Optimum baseball bat swing parameters for maximum range trajectories

    NASA Astrophysics Data System (ADS)

    Sawicki, Gregory S.; Hubbard, Mont; Stronge, William J.

    2003-11-01

    Improved models for the pitch, batting, and post-impact flight phases of a baseball are used in an optimal control context to find bat swing parameters that produce maximum range. The improved batted flight model incorporates experimental lift and drag profiles (including the drag crisis). An improved model for bat-ball impact includes the dependence of the coefficient of restitution on the approach relative velocity and the dependence of the incoming pitched ball angle on speed. The undercut distance and bat swing angle are chosen to maximize the range of the batted ball. The sensitivity of the maximum range is calculated for all model parameters including bat and ball speed, bat and ball spin, and wind speed. Post-impact conditions are found to be independent of the ball-bat coefficient of friction. The lift is enhanced by backspin produced by undercutting the ball during batting. An optimally hit curve ball will travel farther than an optimally hit fastball or knuckleball due to increased lift during flight.

  1. 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.

  2. 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.

  3. 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.

  4. 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 directions, and flight altitudes of nocturnal migrating species. Our work focused on the design and development of custom built marine radar that used t-bar and parabolic dish antennas. The marine radar used in the project was Furuno (XANK250) which was coupled with a XIR3000B digitizing card from Russell Technologies for collection of the radar data. The radar data was processed by open source radR processing software using different computational techniques and methods. Additional data from thermal IR imaging cameras were collected to detect heat emitted from objects and provide information on movements of birds and bats, data which we used for different animal flight behavior analysis. Lastly, the data from the acoustic recorders were used to provide the number of bird calls for assessing patterns and peak passage rates during migration. The development of the geospatial database included collection of different data sources that are used to support offshore wind turbine development. Many different data sets were collected and organized using initial version of web-based repository software tools that can accommodate distribution of rectified pertinent data sets such as the lake depth, lake bottom engineering parameters, extent of ice, navigation pathways, wind speed, important bird habitats, fish efforts and other layers that are relevant for supporting robust offshore wind turbine developments. Additional geospatial products developed during the project included few different prototypes for offshore wind farm suitability which can involve different stakeholders and participants for solving complex planning problems and building consensus. Some of the prototypes include spatial decision support system (SDSS) for collaborative decision making, a web-based Participatory Geographic Information System (PGIS) framework for evaluating importance of different decision alternatives using different evaluation criteria, and an Android application for collection of field data using mobile and tablet devices . In summary, the simulations of two- and three-blade wind turbines suggested that two-bladed machines could produce comparable annual energy as the three-blade wind turbines but have a lighter tower top weight, which leads to lower cost of energy. In addition, the two-blade rotor configuration potentially costs 20% less than a three blade configuration that produces the same power at the same site. The cost model analysis predicted a potential cost savings of approximately 15% for offshore two-blade wind turbines. The foundation design for a wind turbine in Lake Erie is likely to be driven by ice loads based on the currently available ice data and ice mechanics models. Hence, for Lake Eire, the cost savings will be somewhat smaller than the other lakes in the Great Lakes. Considering the size of cranes and vessels currently available in the Great Lakes, the cost optimal wind turbine size should be 3 MW, not larger. The surveillance data from different monitoring systems suggested that bird and bat passage rates per hour were comparable during heavy migrations in both spring and fall seasons while passage rates were significantly correlated to wind directions and wind speeds. The altitude of migration was higher during heavy migrations and higher over water relative to over land. Notable portions of migration on some spring nights occurred parallel the shoreline, often moving perpendicular to southern winds. The birds approaching the Western basin have a higher propensity to cross than birds approaching the Central basin of Lake Erie and as such offshore turbine development might be a better option further east towards Cleveland than in the Western basin. The high stopover density was more strongly associated with migration volume the following night rather than the preceding night. The processed mean scalar wind speeds with temporal resolutions as fine as 10-minute intervals near turbine height showed that August is the month with the weakest winds while December is the month, which typically has the strongest winds. The ice data suggests that shallow western basin of Lake Erie has higher ice cover duration many times exceeding 90 days during some winters.

  5. 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.

  6. Wind measurements by electromagnetic probes

    NASA Technical Reports Server (NTRS)

    Susko, Michael

    1988-01-01

    The emerging technology of electromagnetic probing of the atmosphere to measure winds used in a space vehicle ascent winds load calculations is presented. The frequency range, altitude, and resolution for the following probes are presented: lidars, microwave radars, and clear-air Doppler radars (popularly known as wind profilers). The electromagnetic probing of the atmosphere by clear-air radars and lasers is the new technology to supplement balloon-borne wind sensors used to determine ascent wind loads of space vehicles. The electromagnetic probes measure the wind velocity using the Doppler effect. This is the radar technology used in MSFC's Radar Wind Profiler, and is similar to the technology used in conventional Doppler systems except that the frequency is generally lower, antenna is bigger, and dwell time much longer. Designed for unattended and automated instrumentation in providing measurements of the wind in the troposphere, the profiler employs Doppler radar technology and is currently being put in operation at NASA Kennedy Space Center, Florida.

  7. Wind-induced ground motion

    NASA Astrophysics Data System (ADS)

    Naderyan, Vahid; Hickey, Craig J.; Raspet, Richard

    2016-02-01

    Wind noise is a problem in seismic surveys and can mask the seismic signals at low frequency. This research investigates ground motions caused by wind pressure and shear stress perturbations on the ground surface. A prediction of the ground displacement spectra using the measured ground properties and predicted pressure and shear stress at the ground surface is developed. Field measurements are conducted at a site having a flat terrain and low ambient seismic noise. Triaxial geophones are deployed at different depths to study the wind-induced ground vibrations as a function of depth and wind velocity. Comparison of the predicted to the measured wind-induced ground displacement spectra shows good agreement for the vertical component but significant underprediction for the horizontal components. To validate the theoretical model, a test experiment is designed to exert controlled normal pressure and shear stress on the ground using a vertical and a horizontal mass-spring apparatus. This experiment verifies the linear elastic rheology and the quasi-static displacements assumptions of the model. The results indicate that the existing surface shear stress models significantly underestimate the wind shear stress at the ground surface and the amplitude of the fluctuation shear stress must be of the same order of magnitude as the normal pressure. Measurement results show that mounting the geophones flush with the ground provides a significant reduction in wind noise on all three components of the geophone. Further reduction in wind noise with depth of burial is small for depths up to 40 cm.

  8. Chart aids velocity conversion

    SciTech Connect

    Ganapathy, V.

    1983-02-28

    This paper presents a method of converting between ''gas mass velocity'' (used in the design of heating surfaces of boilers, fired heaters, and the convective sections of waste heat recovery equipment) and ''linear velocity'' (which gives a good idea of fouling, erosion, and gas pressure drop characteristics). It points out that estimation of the flue gas density makes conversion difficult. Equations are presented which take into account the molecular weight and density of common flue gases and hence no computation of density is needed. An example is presented which demonstrates how the featured velocity conversion chart is used.

  9. The Dornier Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Schlichting, H

    1938-01-01

    After completion of the required calibrations, the Dornier open-throat tunnel is now in operation. With an elliptic test section of 3 by 4 m (9.84 by 3.12 ft.), its length is 7 m (22.97 ft.), its maximum horsepower 800, and its maximum air speed 60 m/s (134.2 mph). As to local uniformity of velocity, static pressure as well as jet direction, and turbulence factor, this tunnel is on par with those of the good German and foreign research labs.

  10. Design, fabrication, and characterization of an anechoic wind tunnel facility

    NASA Astrophysics Data System (ADS)

    Mathew, Jose

    The design, fabrication, and characterization of an anechoic wind tunnel facility at the University of Florida are presented. The objective of this research is to develop and rigorously characterize an anechoic wind tunnel suitable for detailed aerodynamic and aeroacoustic research. A complete tunnel design methodology is developed to optimize the design of the individual components of the wind tunnel circuit, and modern analysis tools, such as computational fluid dynamics and structural finite element analyses, are used to validate the design. The wind tunnel design is an "L-shaped"open circuit with an open jet test section driven by a 300 HP centrifugal fan. Airflow enters the wind tunnel through a settling duct with a honeycomb section and a set of four screens. An optimized, minimum length (3.05 m) 8:1 contraction accelerates the flow into a rectangular test section that measures 0.74 m by 1.12 m by 1.83 m. Mach number similarity dictates the maximum velocity attainable in the test section to be 76 m/s; thus the maximum Reynolds number based on chord (chord=2/3 span) attainable is in the 3-4 million range. The flow leaving the test section enters an acoustically treated and 2D diffuser that simultaneously provides static pressure recovery and attenuates fan noise. The flow then turns a 90° corner with turning vanes and enters a second diffuser. The flow leaving the second diffuser enters the fan through a transition section. The wind tunnel was characterized rigorously at speeds up to 43 m/s to ensure the quality of the future aerodynamic and aeroacoustic measurements. The overall SPL from 100 Hz--20 kHz ranges from 54.8 dB at 18 m/s to 75.7 dB at 43 m/s. The freestream turbulence level has a value of 0.035%, and the flow non uniformity in the test section was found to be < 0.7% for a test section speed of 17 m/s. The outcome of this work is an anechoic wind tunnel with excellent flow quality, low background noise, and the largest Reynolds number capability among university-scale anechoic facilities in the US.

  11. Maximum leg force and power output during short-term dynamic exercise.

    PubMed

    Sargeant, A J; Hoinville, E; Young, A

    1981-11-01

    Force exerted and power generated were measured during short-term exercise performed on a bicycle ergometer that had been modified by the addition of an electric motor driving the cranks at a chosen constant velocity. Five subjects made a series of 20-s maximum efforts at different crank velocities (range 23--171 rev/min). The forces exerted were continuously monitored with strain gauges bonded to the cranks. Peak force was exerted at approximately 90 degrees past top dead center in each revolution. During the 20-s effort peak force declined from the maximum level (PFmax) attained near the start of exercise, the rate of decline being velocity dependent. PFmax was found to be inversely and linearly related to crank velocity and when standardized for upper leg muscle (plus bone) volume (ULV) was given by PFmax (kgf/l ULV) = 27.51--0.125 crank velocity (rev/min). Integration of the force records with pedal velocity enabled power output to be calculated. Maximum power output was a parabolic function of crank velocity, the apex of the relationship indicating that the velocity for greatest power output was 110 rev/min. At this velocity our subjects achieved a maximum mean power output, averaged over a complete revolution, of 840 +/- 153 W (85 +/- 5 W/l ULV). This was compared with the calculated value for maximum mechanical power output from aerobic sources, which was 272 +/- 49 W (30 +/- 1 W/l ULV). PMID:7298457

  12. Modeling and controller design of a wind energy conversion system including a matrix converter

    NASA Astrophysics Data System (ADS)

    Barakati, S. Masoud

    In this thesis, a grid-connected wind-energy converter system including a matrix converter is proposed. The matrix converter, as a power electronic converter, is used to interface the induction generator with the grid and control the wind turbine shaft speed. At a given wind velocity, the mechanical power available from a wind turbine is a function of its shaft speed. Through the matrix converter, the terminal voltage and frequency of the induction generator is controlled, based on a constant V/f strategy, to adjust the turbine shaft speed and accordingly, control the active power injected into the grid to track maximum power for all wind velocities. The power factor at the interface with the grid is also controlled by the matrix converter to either ensure purely active power injection into the grid for optimal utilization of the installed wind turbine capacity or assist in regulation of voltage at the point of connection. Furthermore, the reactive power requirements of the induction generator are satisfied by the matrix converter to avoid use of self-excitation capacitors. The thesis addresses two dynamic models: a comprehensive dynamic model for a matrix converter and an overall dynamical model for the proposed wind turbine system. The developed matrix converter dynamic model is valid for both steady-state and transient analyses, and includes all required functions, i.e., control of the output voltage, output frequency, and input displacement power factor. The model is in the qdo reference frame for the matrix converter input and output voltage and current fundamental components. The validity of this model is confirmed by comparing the results obtained from the developed model and a simplified fundamental-frequency equivalent circuit-based model. In developing the overall dynamic model of the proposed wind turbine system, individual models of the mechanical aerodynamic conversion, drive train, matrix converter, and squirrel-cage induction generator are developed and combined to enable steady-state and transient simulations of the overall system. In addition, the constraint constant V/f strategy is included in the final dynamic model. The model is intended to be useful for controller design purposes. The dynamic behavior of the model is investigated by simulating the response of the overall model to step changes in selected input variables. Moreover, a linearized model of the system is developed at a typical operating point, and stability, controllability, and observability of the system are investigated. Two control design methods are adopted for the design of the closed-loop controller: a state-feedback controller and an output feedback controller. The state-feedback controller is designed based on the Linear Quadratic method. An observer block is used to estimate the states in the state-feedback controller. Two other controllers based on transfer-function techniques and output feedback are developed for the wind turbine system. Finally, a maximum power point tracking method, referred to as mechanical speed-sensorless power signal feedback, is developed for the wind turbine system under study to control the matrix converter control variables in order to capture the maximum wind energy without measuring the wind velocity or the turbine shaft speed.

  13. Software Development for an Airborne Wind LIDAR

    NASA Astrophysics Data System (ADS)

    Zhu, Jishan; Li, Zhigang; Chen, Zhen; Liu, Zhishen

    2014-11-01

    Currently, Wind lidar offers an important way to obtain clear air wind field [1]. The principle of the wind lidar is based on the Doppler frequency shift in the air of the laser. The received signal of the lidar is scattered by the air molecular and particles [2]. They are Rayleigh scattering and Mie scattering. Coherent detection technique is an effective method to get the Doppler shift from the scattering in the air. From the Doppler shift we can get the radial wind speed. Generally, the horizontal wind field is that people concerned about. Based on the radial wind speed of more than 3 directions, we can use the VAD technique to retrieve the horizontal wind field. For an airborne lidar, some corrections such as the air plane posture, the air plane velocity must be performed. We developed a set of software for an airborne wind lidar using the MFC visual C++ Programming technology. Functions of the software are raw data decoding, radial wind speed inversion, horizontal wind field retrieve by VAD technique, air plane posture correction, air plane velocity correction, and so on. It also has functions for data display and saves. The results can be saved as picture or numerical values.

  14. 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 ...

  15. Nerve conduction velocity

    MedlinePlus

    Nerve conduction velocity (NCV) is a test to see how fast electrical signals move through a nerve. ... normal body temperature. Being too cold slows nerve conduction. Tell your doctor if you have a cardiac ...

  16. 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.

  17. Velocity of Sound

    ERIC Educational Resources Information Center

    Gillespie, A.

    1975-01-01

    Describes a method for the determination of the velocity of sound using a dual oscilloscope on which is displayed the sinusoidal input into a loudspeaker and the signal picked up by a microphone. (GS)

  18. 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…

  19. 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

  20. Principles of maximum entropy and maximum caliber in statistical physics

    NASA Astrophysics Data System (ADS)

    Pressé, Steve; Ghosh, Kingshuk; Lee, Julian; Dill, Ken A.

    2013-07-01

    The variational principles called maximum entropy (MaxEnt) and maximum caliber (MaxCal) are reviewed. MaxEnt originated in the statistical physics of Boltzmann and Gibbs, as a theoretical tool for predicting the equilibrium states of thermal systems. Later, entropy maximization was also applied to matters of information, signal transmission, and image reconstruction. Recently, since the work of Shore and Johnson, MaxEnt has been regarded as a principle that is broader than either physics or information alone. MaxEnt is a procedure that ensures that inferences drawn from stochastic data satisfy basic self-consistency requirements. The different historical justifications for the entropy S=-∑ipilog⁡pi and its corresponding variational principles are reviewed. As an illustration of the broadening purview of maximum entropy principles, maximum caliber, which is path entropy maximization applied to the trajectories of dynamical systems, is also reviewed. Examples are given in which maximum caliber is used to interpret dynamical fluctuations in biology and on the nanoscale, in single-molecule and few-particle systems such as molecular motors, chemical reactions, biological feedback circuits, and diffusion in microfluidics devices.