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1

Extreme Wind Velocity Measurement System  

NASA Technical Reports Server (NTRS)

A wind velocity measurement system employs two different principles of physics to measure wind speed: (1) the aerodynamic force imparted to a low profile, rigidly mounted cylindrical rod, and (2) the vibrating frequency of the rod as vortices are shed from the rod's cylindrical surface. A set of strain gages is used as a common sensor for both measurements, and these provide force measurements imparted by the wind on the rod. The signals generated by the strain gages are fed to processing circuitry that calculates the wind speed and direction from the signals. The force measurement is proportional to the square of the wind speed. Since it is a vector quantity, it can also be used to derive wind direction. The vortex shedding frequency is a scalar quantity and is linearly proportional to wind speed. This frequency can be calculated by analyzing the force measurements generated by the strain gages over time. Both of the wind velocity calculations can be advantageously used by the processing circuitry to generate an accurate wind velocity reading.

Zysko, Jan A. (Inventor); Starr, Stanley O. (Inventor)

2002-01-01

2

Maximum Possible Transverse Velocity in Special Relativity.  

ERIC Educational Resources Information Center

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)

Medhekar, Sarang

1991-01-01

3

14 CFR 25.237 - Wind velocities.  

Code of Federal Regulations, 2013 CFR

...25.237 Wind velocities. (a) For land planes and amphibians, the following applies: (1) A 90-degree cross...accretion defined in appendix C. (b) For seaplanes and amphibians, the following applies: (1) A 90-degree...

2013-01-01

4

14 CFR 25.237 - Wind velocities.  

Code of Federal Regulations, 2011 CFR

...25.237 Wind velocities. (a) For land planes and amphibians, the following applies: (1) A 90-degree cross...accretion defined in appendix C. (b) For seaplanes and amphibians, the following applies: (1) A 90-degree...

2011-01-01

5

14 CFR 25.237 - Wind velocities.  

Code of Federal Regulations, 2010 CFR

...25.237 Wind velocities. (a) For land planes and amphibians, the following applies: (1) A 90-degree cross...accretion defined in appendix C. (b) For seaplanes and amphibians, the following applies: (1) A 90-degree...

2010-01-01

6

14 CFR 25.237 - Wind velocities.  

Code of Federal Regulations, 2012 CFR

...25.237 Wind velocities. (a) For land planes and amphibians, the following applies: (1) A 90-degree cross...accretion defined in appendix C. (b) For seaplanes and amphibians, the following applies: (1) A 90-degree...

2012-01-01

7

14 CFR 25.237 - Wind velocities.  

Code of Federal Regulations, 2014 CFR

...25.237 Wind velocities. (a) For land planes and amphibians, the following applies: (1) A 90-degree cross...accretion defined in appendix C. (b) For seaplanes and amphibians, the following applies: (1) A 90-degree...

2014-01-01

8

Maximum wind energy extraction strategies using power electronic converters  

Microsoft Academic Search

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

Quincy Qing Wang

2003-01-01

9

Effects of increasing tip velocity on wind turbine rotor design.  

SciTech Connect

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.

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

2014-05-01

10

Satellite-tracked cumulus velocities. [for determining wind velocity  

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

11

Constraining Maximum Disk Velocities of High-Mass Galaxies  

Microsoft Academic Search

We present high resolution H-alpha long-slit rotation curves for a sample of high-mass galaxies. These well-resolved long-slit data will serve to probe the interior shape of rotation curves and therefore put constraints on maximum-disk velocities. This is crucial for accurately modeling both the luminous and dark velocity components. Ultimately, this data will be combined with optical and near-IR photometry to

Matthew J. Zagursky; S. S. McGaugh

2007-01-01

12

Maximum power tracking control scheme for wind generator systems  

E-print Network

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

Mena, Hugo Eduardo

2009-05-15

13

Maximum power tracking control scheme for wind generator systems  

E-print Network

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

Mena Lopez, Hugo Eduardo

2008-10-10

14

Maximum tunneling velocities in symmetric double well potentials  

E-print Network

We consider coherent tunneling of one-dimensional model systems in non-cyclic or cyclic symmetric double well potentials. Generic potentials are constructed which allow for analytical estimates of the quantum dynamics in the non-relativistic deep tunneling regime, in terms of the tunneling distance, barrier height and mass (or moment of inertia). For cyclic systems, the results may be scaled to agree well with periodic potentials for which semi-analytical results in terms of Mathieu functions exist. Starting from a wavepacket which is initially localized in one of the potential wells, the subsequent periodic tunneling is associated with tunneling velocities. These velocities (or angular velocities) are evaluated as the ratio of the flux densities versus the probability densities. The maximum velocities are found under the top of the barrier where they scale as the square root of the ratio of barrier height and mass (or moment of inertia), independent of the tunneling distance. They are applied exemplarily to ...

Manz, Jörn; Schmidt, Burkhard; Yang, Yonggang

2014-01-01

15

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

E-print Network

Design of wind farm layout for maximum wind energy capture Andrew Kusiak*, Zhe Song Intelligent sources of alternative energy. The construction of wind farms is destined to grow in the U.S., possibly twenty-fold by the year 2030. To maximize the wind energy capture, this paper presents a model for wind

Kusiak, Andrew

16

Maximum tunneling velocities in symmetric double well potentials  

E-print Network

We consider coherent tunneling of one-dimensional model systems in non-cyclic or cyclic symmetric double well potentials. Generic potentials are constructed which allow for analytical estimates of the quantum dynamics in the non-relativistic deep tunneling regime, in terms of the tunneling distance, barrier height and mass (or moment of inertia). For cyclic systems, the results may be scaled to agree well with periodic potentials for which semi-analytical results in terms of Mathieu functions exist. Starting from a wavepacket which is initially localized in one of the potential wells, the subsequent periodic tunneling is associated with tunneling velocities. These velocities (or angular velocities) are evaluated as the ratio of the flux densities versus the probability densities. The maximum velocities are found under the top of the barrier where they scale as the square root of the ratio of barrier height and mass (or moment of inertia), independent of the tunneling distance. They are applied exemplarily to several prototypical molecular models of non-cyclic and cyclic tunneling, including ammonia inversion, Cope rearrangment of semibullvalene, torsions of molecular fragments, and rotational tunneling in strong laser fields. Typical maximum velocities and angular velocities are in the order of a few km/s and from 10 to 100 THz for our non-cyclic and cyclic systems, respectively, much faster than time-averaged velocities. Even for the more extreme case of an electron tunneling through a barrier of height of one Hartree, the velocity is only about one percent of the speed of light. Estimates of the corresponding time scales for passing through {the narrow domain just} below the potential barrier are in the domain from 2 to 40 fs, much shorter than the tunneling times.

Jörn Manz; Axel Schild; Burkhard Schmidt; Yonggang Yang

2014-04-23

17

Speed and Position Sensor-less Maximum Power Point Tracking Control for Wind Generation System with Squirrel Cage Induction Generator  

Microsoft Academic Search

Wind energy is a significant and powerful resource. It is safe, clean, and abundant. Variable speed power generation for a wind turbine is attractive, because maximum efficiency can be achieved at all wind velocities. However, this system requires a rotor speed sensor for vector control purposes, which increases the cost of the system. In this paper, a technique is proposed

Tomonobu Senjyu; Yasutaka Ochi; Endusa Muhando; Naomitsu Urasaki; Hideomi Sekine

2006-01-01

18

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

SciTech Connect

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.

Buttler, W.T.

1996-05-01

19

Maximum power extraction algorithm for a small wind turbine  

Microsoft Academic Search

Today, a characteristic of the operating regime of small wind turbines is that they do not obtain the maximum power efficiency. Taking into account that that the operability margin can, in general, be enhanced, this paper sets out to develop algorithms designed to extract the maximum power. First, an analysis is made of existing algorithms and as a result, a

I. Kortabarria; J. Andreu; I. Marti?nez de Alegri?a; E. Ibarra; E. Robles

2010-01-01

20

Developing and Testing Wind Velocity Retrieval Algorithms for Doppler Wind Lidar  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

21

Wind velocity effects on sampling rate of NO2 badge  

SciTech Connect

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).

Lee, K.; Yanagisawa, Y.; Spengler, J.D.; Billick, I.H. (Harvard School of Public Health, Department of Environmental Health, Boston, MA (United States))

1992-04-01

22

Dependence of Turbulent Velocities on Wind Speed and Stratification  

NASA Astrophysics Data System (ADS)

We examine the dependence of several turbulence quantities on the wind speed and stability using nocturnal data from the Shallow Cold Pool Experiment. The turbulent quantities (velocities) are defined in terms of the standard deviation of the horizontal and vertical velocity fluctuations, two different calculations of the friction velocity, and two turbulent velocities based on the heat flux. The dependence of the turbulent velocities on the wind speed shows a transition between the weak-wind regime of small slope and the stronger wind regime of larger slope, as found in previous studies. This transition occurs for all of the turbulent velocities examined and occurs for a wide range of averaging times. Although this study concentrates primarily on data over a flat surface above the valley, the transition also occurs at the other 18 stations that have non-zero local slopes up to about 10 %. At the same time, the relationship between the turbulence and the wind speed cannot be universal because of the influence of stratification and site-dependent non-stationarity in the weak-wind regime. The wind speed of the transition increases with increasing stratification at a rate that is an order of magnitude slower than that predicted by a constant transition bulk Richardson number. For the weakest winds, the impact of stratification is unexpectedly small.

Mahrt, L.; Sun, Jielun; Stauffer, David

2015-04-01

23

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

SciTech Connect

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.

Carlin, P.W.

1996-12-01

24

Estimation of the maximum velocity of convective Iwan Holleman  

E-print Network

contained by the downdraft is deflected by the surface and causes the wind gusts. The resulting (strong) wind gusts can cause considerable damage for an aircraft at low-altitude (Fujita and Wakimoto, 1983 and limited damage, whilst a macroburst can produce tornado-like damage. The microburst type has been

Stoffelen, Ad

25

Exploratory Meeting on Airborne Doppler Lidar Wind Velocity Measurements  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

26

[The study of maximum entropy method used in wind profiler].  

PubMed

In order to know the feasibility that the modern spectrum analysis ways are applied in wind profiler, the fast Fourier transform (FFT) and maximum entropy method (MEM) are contrasted by using simulation data and radar measurement data respectively. The result shows: (1) When the radar echo is strong, the effect of two methods are equivalent. But when the echo is weak, the MEM spectra are better than others. The MEM can powerfully remove the ground clutter contaminant. (2) The MEM spectra are smooth, so it can be used to reduce white noise influence also. (3) The iterative steps in MEM have some influence on the spectrum. The step calculated by final prediction error (FPE) rule is less. Using 15 steps in MEM can get a better result. The wind profiler radar echo is weak usually, so the conclusions of this paper can help improve the effect of spectrum analysis. PMID:22715790

Hu, Ming-bao; Zheng, Guo-guang; Zhang, Pei-chang

2012-04-01

27

Neural-network-based sensorless maximum wind energy capture with compensated power coefficient  

Microsoft Academic Search

This paper describes a small wind generation system where neural network principles are applied for wind speed estimation and robust control of maximum wind power extraction against potential drift of wind turbine power coefficient curve. The new control system will deliver maximum electric power to a customer with light weight, high efficiency, and high reliability without mechanical sensors. The concept

Hui Li; K. L. Shi; P. G. McLaren

2005-01-01

28

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

E-print Network

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

California at Berkeley, University of

29

An intelligent maximum power extraction algorithm for inverter-based variable speed wind turbine systems  

Microsoft Academic Search

This paper focuses on the development of maximum wind power extraction algorithms for inverter-based variable speed wind power generation systems. A review of existing maximum wind power extraction algorithms is presented in this paper, based on which an intelligent maximum power extraction algorithm is developed by the authors to improve the system performance and to facilitate the control implementation. As

Quincy Wang; Liuchen Chang

2004-01-01

30

A proposed method for wind velocity measurement from space  

NASA Technical Reports Server (NTRS)

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.

Censor, D.; Levine, D. M.

1980-01-01

31

Maximum velocity of self-propulsion for an active segment  

E-print Network

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

Recho, Pierre

2015-01-01

32

Maximum power extraction from a small wind turbine using 4-phase interleaved boost converter  

Microsoft Academic Search

This paper describes a 4-phase interleaved boost converter in a small wind turbine application. The boost converter is placed between the wind turbine and the load and is controlled to extract the maximum power from wind turbine. The boost converter duty ratio adjusted, based on the wind speed and rotor speed values, so that the wind turbine would be operated

Liqin Ni; D. J. Patterson; J. L. Hudgins

2009-01-01

33

Extremely long baseline interplanetary scintillation measurements of solar wind velocity  

NASA Astrophysics Data System (ADS)

We present results of observations of interplanetary scintillation (IPS) made using the telescopes of the MERLIN and EISCAT networks in which the beam separation approached 2000 km, much larger than in any previous IPS experiments. Significant correlation between the scintillation patterns was observed at time lags of up to 8 s and fast and slow streams of solar wind were very clearly resolved. One observation showed clear evidence of two discrete modes of fast solar wind, which we interpret as originating in the crown of the northern polar coronal hole and in an equatorward extension of the polar hole. We suggest that experiments of this type will provide a new and important source of information on the temporal and spatial variation of small-scale turbulence in the solar wind. The improved velocity resolution available from extremely long baseline measurements also provides new information on the development of the large-scale velocity structure of the solar wind in interplanetary space.

Breen, A. R.; Fallows, R. A.; Bisi, M. M.; Thomasson, P.; Jordan, C. A.; Wannberg, G.; Jones, R. A.

2006-08-01

34

High-Speed Vortex Wind Velocity Imaging by Acoustic Tomography  

Microsoft Academic Search

\\u000a A technique for monitoring strong vortex wind fields is highly desired due to the rapid development of global warming. Vortex\\u000a wind velocity imaging using an acoustic travel time tomography technique was developed to meet this need. The method can be\\u000a implemented with a small number of parallel facing pairs of acoustic transmitters\\/receivers from just a single illumination\\u000a view direction, so

H. Li; T. Ueki; K. Hayashi; A. Yamada

35

Terminal velocities of the winds from rapidly rotating OB stars  

SciTech Connect

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. 31 refs.

Friend, D.B. (Weber State College, Ogden, UT (USA))

1990-04-01

36

Terminal velocities of the winds from rapidly rotating OB stars  

NASA Technical Reports Server (NTRS)

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.

Friend, David B.

1990-01-01

37

Velocity dependence of heavy-ion stopping below the maximum  

NASA Astrophysics Data System (ADS)

In the slowing-down of heavy ions in materials, the standard description by Lindhard and Scharff assumes the electronic stopping cross section to be proportional to the projectile speed v up to close to a stopping maximum, which is related to the Thomas-Fermi speed vTF . It is well known that strict proportionality with v is rarely observed, but little is known about the systematics of observed deviations. In this study we try to identify factors that determine positive or negative curvature of stopping cross sections on the basis of experimental data and of binary stopping theory. We estimate the influence of shell structure of the target and of the equilibrium charge of the ion and comment the role of dynamic screening.

Sigmund, P.; Schinner, A.

2015-01-01

38

Measurement of turbulent wind velocities using a rotating boom apparatus  

SciTech Connect

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.

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

1984-04-01

39

Does the scatterometer see wind speed or friction velocity?  

Microsoft Academic Search

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

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

1984-01-01

40

Solar wind bulk velocity fluctuations acting as velocity space diffusion on comoving ions  

NASA Astrophysics Data System (ADS)

From most in-situ plasma observations made in the outer heliosphere it became evident that above the injection border of pick-up ions (?1 keV), an extended suprathermal ion tail is found which in most cases can be fitted by a power law with velocity power indices of (-6) ? ?v ? (-4). As has been shown by theory such energetic ion tails cannot be explained by Fermi-2 type velocity diffusion, since in the outer heliosphere both Alfvenic and magnetoacoustic turbulences become too weak. Here we come to a new solution of this unsolved problem by studying the action of solar wind bulk velocity fluctuations on ions co-moving with the wind. As we show the passage of such fluctuations results in energization of each individual ion and systematic evolution of the ion distribution function towards suprathermal tails. From the basic knowledge that we can obtain on this process we can calculate the velocity divergence of the ion phasespace flow and thus can derive a velocity diffusion operator. As we can show here this operator leads to a velocity diffusion coefficient proportional to the square of the ion velocity and, when employed in the phasespace transport equation, together with terms for convective changes, cooling processes and pick-up ion injection, interestingly enough, permits to find solutions for suprathermal power law tails with power indices of ?v ? -5 as very often observed.

Fahr, H.-J.; Chashei, I. V.; Siewert, M.

2012-01-01

41

Measuring solar wind velocity with spacecraft phase scintillations  

NASA Technical Reports Server (NTRS)

The measurement of spacecraft phase scintillations with a coherent dual-frequency radio system permits solar-wind velocity measurements based on multiple-station phase scintillations. Advantages of measuring solar-wind velocity on the basis of multiple-station phase scintillations are discussed with respect to amplitude scintillations. These advantages include the ability to carry out observations closer to the sun, a much wider range of possible baselines, a lower S/N ratio for long-baseline phase measurements, and a wider range of antenna sizes and receiver noise temperatures. NASA antennas particularly suitable for these measurements are identified, and observations with the coherent S/X radio system aboard various NASA spacecraft intended for deep-space missions are proposed.

Woo, R.

1977-01-01

42

Geomagnetic activity and wind velocity during the Maunder minimum  

Microsoft Academic Search

Following a given classification of geomag- netic activity, we obtained aa index values for the Maunder minimum (1645-1715). It is found that the recurrent and fluctuating activities were not appreciable and that the shock activity levels were very low. The aa index level was due almost entirely to the quiet days. Calculated average solar-wind velocities were 194.3 km s)1 from

B. Mendoza

1997-01-01

43

Does the scatterometer see wind speed or friction velocity?  

NASA Technical Reports Server (NTRS)

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).

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

1984-01-01

44

CFD wind tunnel test: Field velocity patterns of wind on a building with a refuge floor  

NASA Astrophysics Data System (ADS)

This paper reports a CFD wind tunnel study of wind patterns on a square-plan building with a refuge floor at its mid-height level. In this study, a technique of using calibrated power law equations of velocity and turbulent intensity applied as the boundary conditions in CFD wind tunnel test is being evaluated by the physical wind tunnel data obtained by the Principal Author with wind blowing perpendicularly on the building without a refuge floor. From the evaluated results, an optimised domain of flow required to produce qualitative agreement between the wind tunnel data and simulated results is proposed in this paper. Simulated results with the evaluated technique are validated by the wind tunnel data obtained by the Principal Author. The results contribute to an understanding of the fundamental behaviour of wind flow in a refuge floor when wind is blowing perpendicularly on the building. Moreover, the results reveal that the designed natural ventilation of a refuge floor may not perform desirably when the wind speed on the level is low. Under this situation, the refuge floor may become unsafe if smoke was dispersed in the leeward side of the building at a level immediately below the refuge floor.

Cheng, C. K.; Yuen, K. K.; Lam, K. M.; Lo, S. M.

2005-10-01

45

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

NASA Technical Reports Server (NTRS)

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

Rhyne, R. H.

1980-01-01

46

Observations of Rapid Velocity Variations in the Slow Solar Wind  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

47

Maximum Velocity of a Boulder Ejected From an Impact Crater Formed on a Regolith Covered Surface  

NASA Astrophysics Data System (ADS)

We investigate the effect of regolith depth on boulder ejection velocity. A "boulder" refers to an apparently intact rock or rock fragment lying on a planetary surface, regardless of emplacement mechanism. Boulders appear in planetary images as positive relief features --- bright, sun-facing pixels adjacent to dark, shadowed pixels. We studied 12 lunar craters in high resolution (1~m) photographs from Lunar Orbiter III and V. Local regolith depth was measured using the method of small crater morphology. Ejection velocities of boulders were calculated assuming a ballistic trajectory to the final boulder location. A plot of regolith depth/crater diameter vs. maximum boulder ejection velocity shows that craters formed in deeper regolith (with respect to crater size) eject boulders at lower velocities. When ejection velocity (EjV) is in m/s, and regolith depth (Dr) and crater diameter (Dc) are in meters, the data fit the relation Dr / Dc = 1053 × EjVmax-2.823. To explain the data, we turn to impact cratering theory. An ejected particle will follow a streamline from its place of origin to its ejection point (the Z-model), and then follow a ballistic trajectory. Material ejected along more shallow streamlines is ejected at greater velocities. If shallow regolith covers the surface, the most shallow (greatest velocity) streamlines will travel only through the regolith. Boulders, however, must be ejected from the bedrock below the regolith. Thus, the boulder ejected with the greatest velocity originates just below the regolith, along the most shallow streamline through the bedrock. If the regolith is deeper, the most shallow streamline through the bedrock will be deeper, and the maximum velocity of an ejected boulder will be lower. Hence, the regolith depth and maximum ejection velocity of a boulder are correlated: greater boulder ejection velocities correspond to thinner regolith. We observe this correlation in the data.

Bart, G. D.; Melosh, H. J.

2007-12-01

48

Mechanical sensorless maximum power tracking control for direct-drive PMSG wind turbines  

Microsoft Academic Search

Wind turbine generators (WTGs) are usually equipped with mechanical sensors to measure wind speed and rotor position for system control, monitoring, and protection. The use of mechanical sensors increases the cost and hardware complexity and reduces the reliability of the WTG systems. This paper proposes a mechanical sensorless maximum power tracking control for wind turbines directly driving permanent magnetic synchronous

Xu Yang; Xiang Gong; Wei Qiao

2010-01-01

49

A critical examination of the maximum velocity of shortening used in simulation models of human movement.  

PubMed

The maximum velocity of shortening of a muscle is an important parameter in musculoskeletal models. The most commonly used values are derived from animal studies; however, these values are well above the values that have been reported for human muscle. The purpose of this study was to examine the sensitivity of simulations of maximum vertical jumping performance to the parameters describing the force-velocity properties of muscle. Simulations performed with parameters derived from animal studies were similar to measured jump heights from previous experimental studies. While simulations performed with parameters derived from human muscle were much lower than previously measured jump heights. If current measurements of maximum shortening velocity in human muscle are correct, a compensating error must exist. Of the possible compensating errors that could produce this discrepancy, it was concluded that reduced muscle fibre excursion is the most likely candidate. PMID:20162474

Domire, Zachary J; Challis, John H

2010-12-01

50

Low-level nocturnal wind maximum over the Central Amazon Basin  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

51

Kinematical Structure of Wolf-Rayet Winds. I.Terminal Wind Velocity  

Microsoft Academic Search

New terminal wind velocities for 164 Wolf-Rayet stars (from the Galaxy and LMC) based on PCyg profiles of lambda1550 CIV resonance line were derived from the archive high and low resolution IUE spectra available form the INES database. The high resolution data on 59 WR stars (39 from the Galaxy and 20 from LMC) were used to calibrate the empirical

A. Niedzielski; W. Skorzynski

2002-01-01

52

Control of IPM Synchronous Generator for Maximum Wind Power Generation Considering Magnetic Saturation  

Microsoft Academic Search

Permanent-magnet synchronous generators (PMSGs) are commonly used for small variable-speed wind turbines to produce high-efficiency, high-reliability, and low-cost wind power generation. This paper proposes a novel control scheme for an interior PMSG (IPMSG) driven by a wind turbine, in which the d-axis and q-axis stator-current components are optimally controlled to achieve the maximum wind power generation and loss minimization of

Wei Qiao; Liyan Qu; Ronald G. Harley

2009-01-01

53

Errors in the estimation of wall shear stress by maximum Doppler velocity  

PubMed Central

Objective Wall shear stress (WSS) is an important parameter with links to vascular (dys)function. Difficult to measure directly, WSS is often inferred from maximum spectral Doppler velocity (Vmax) by assuming fully-developed flow, which is valid only if the vessel is long and straight. Motivated by evidence that even slight/local curvatures in the nominally straight common carotid artery (CCA) prevent flow from fully developing, we investigated the effects of velocity profile skewing on Vmax-derived WSS. Methods Velocity profiles, representing different degrees of skewing, were extracted from the CCA of image-based computational fluid dynamics (CFD) simulations carried out as part of the VALIDATE study. Maximum velocities were calculated from idealized sample volumes and used to estimate WSS via fully-developed (Poiseuille or Womersley) velocity profiles, for comparison with the actual (i.e. CFD-derived) WSS. Results For cycle-averaged WSS, mild velocity profile skewing caused ±25% errors by assuming Poiseuille or Womersley profiles, while severe skewing caused a median error of 30% (maximum 55%). Peak systolic WSS was underestimated by ~50% irrespective of skewing with Poiseuille; using a Womersley profile removed this bias, but ±30% errors remained. Errors were greatest in late systole, when skewing was most pronounced. Skewing also introduced large circumferential WSS variations: ±60%, and up to ±100%, of the circumferentially averaged value. Conclusion Vmax-derived WSS may be prone to substantial variable errors related to velocity profile skewing, and cannot detect possibly large circumferential WSS variations. Caution should be exercised when making assumptions about velocity profile shape to calculate WSS, even in vessels usually considered long and straight. PMID:23398945

Mynard, Jonathan P.; Wasserman, Bruce A.; Steinman, David A.

2015-01-01

54

A new wideband spread target maximum likelihood estimator for blood velocity estimation. I. Theory  

Microsoft Academic Search

The derivation and theoretical evaluation of new wideband maximum-likelihood strategies for the estimation of blood velocity using acoustic signals are presented. A model for the received signal from blood scatterers, using a train of short wideband pulses, is described. Evaluation of the autocorrelation of the signal based on this model shows that the magnitude, periodicity, and phase of the autocorrelation

Katherine W. Ferrara; V. Ralph Algazi

1991-01-01

55

A new wideband spread target maximum likelihood estimator for blood velocity estimation. I. Theory.  

PubMed

The derivation and theoretical evaluation of new wideband maximum-likelihood strategies for the estimation of blood velocity using acoustic signals are presented. A model for the received signal from blood scatterers, using a train of short wideband pulses, is described. Evaluation of the autocorrelation of the signal based on this model shows that the magnitude, periodicity, and phase of the autocorrelation are affected by the mean scatterer velocity and the presence of a velocity spread target. New velocity estimators are then derived that exploit the effect of the scatterer velocity on both the signal delay and the shift in frequency. The wideband range spread estimator is derived using a statistical model of the target. Based on the point target assumption, a simpler wideband maximum-likelihood estimator is also obtained. These new estimation strategies are analyzed for their local and global performance. Evaluation of the Cramer-Rao bound shows that the bound on the estimator variance is reduced using these estimators, in comparison with narrowband strategies. In order to study global accuracy, the expected estimator output is evaluated, and it is determined that the width of the mainlobe is reduced. In addition, it is shown that the height of subsidiary velocity peaks is reduced through the use of these new estimators. PMID:18267551

Ferrara, K W; Algazi, V R

1991-01-01

56

Maximum power point tracking for variable speed grid connected small wind turbine  

Microsoft Academic Search

This paper presents a method for harmonic mitigation and maximum power point tracking (MPPT) for a variable speed-grid connected 20 kW wind turbine. The wind energy conversion systems consist of permanent magnet synchronous generator (PMSG) driven by variable-speed 20 kW wind turbine. The output of the PMSG is connected to a single switch three-phase boost rectifier to generate DC voltage

Mazen Abdel-Salam; Adel Ahmed; Mohamed Abdel-Sater

2010-01-01

57

Fuzzy logic control based maximum power tracking of a wind energy system  

Microsoft Academic Search

In this paper a utility interactive wind energy conversion system (WECS) with an asynchronous (AC–DC–AC) link is described. The control system has the objective of identifying and extracting the maximum power from the wind energy system and transferring this power to utility. A fuzzy logic control (FLC) technique has been implemented to design the tracking controller of the WECS. A

Amal Z. Mohamed; Mona N. Eskander; Fadia A. Ghali

2001-01-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

59

Pulsar Wind Nebulae, Space Velocities and Supernova Remnant  

NASA Technical Reports Server (NTRS)

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.

2005-01-01

60

Maximum likelihood angle and velocity estimation with space-time adaptive processing radar  

Microsoft Academic Search

Airborne surveillance radar performance can be improved with space-time adaptive processing (STAP) to cancel ground clutter and interference. This paper considers maximum likelihood (ML) angle and velocity estimation for airborne radar employing STAP. The ML estimator requires a two-dimensional optimization. A computationally efficient quasi-Newton approach is proposed, whereby a positive definite approximate Hessian is formed using only the secondary data

James Ward

1996-01-01

61

The maximum potential to generate wind power in the contiguous United States is more than three times  

E-print Network

The maximum potential to generate wind power in the contiguous United States is more than three, the installed U.S. wind power capacity is now about 35 GW. While most of the wind potential comes from the windy) study. The new analysis is based on the latest computer models and examines the wind potential at wind

62

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

63

Noise reduction in LOS wind velocity of Doppler lidar using discrete wavelet analysis  

Microsoft Academic Search

The line of sight (LOS) wind velocity can be determined from the incoherent Doppler lidar backscattering signals. Noise and interference in the measurement greatly degrade the inversion accuracy. In this paper, we apply the discrete wavelet denoising method by using biorthogonal wavelets and adopt a distancedependent thresholds algorithm to improve the accuracy of wind velocity measurement by incoherent Doppler lidar.

Songhua Wu; Zhishen Liu; Dapeng Sun

2003-01-01

64

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 ...

65

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

USGS Publications Warehouse

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.

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

2007-01-01

66

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

E-print Network

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

Groppi, Christopher

67

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

USGS Publications Warehouse

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.

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

1982-01-01

68

Design of a maximum power tracking system for wind-energy-conversion applications  

Microsoft Academic Search

A wind-generator (WG) maximum-power-point-tracking (MPPT) system is presented, consisting of a high-efficiency buck-type dc\\/dc converter and a microcontroller-based control unit running the MPPT function. The advantages of the proposed MPPT method are that no knowledge of the WG optimal power characteristic or measurement of the wind speed is required and the WG operates at a variable speed. Thus, the system

Eftichios Koutroulis; Kostas Kalaitzakis

2006-01-01

69

Gas transfer velocities measured at low wind speed over a lake  

USGS Publications Warehouse

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.

Crusius, J.; Wanninkhof, R.

2003-01-01

70

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)

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.

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

1976-01-01

71

Effects of a tip vane on velocity distribution around wind turbine blade  

Microsoft Academic Search

It is proved that a tip vane can improve the wind turbine's efficiency by the test and CFD. In this paper, the performance of horizontal axis wind turbine and horizontal axis wind turbine with a tip vane by CFD were simulated. After comparing the velocity distribution around wind turbine blade with the tip vane-V(8.8×8) and without the tip vane and

Jia Rui-Bo; Wang Jian-Wen

2010-01-01

72

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

E-print Network

Observatory July 6, 1995 Abstract MMA Memo 129 (Holdaway, et al. 1995) introduced the basic data reduction velocity aloft agree to 5­10%. Wind Velocity Aloft In MMA Memo 129 (Holdaway, et al. 1995), we showed one the observed range in ff. Figure 7 of MMA Memo 129 shows a time series of the velocity aloft and the surface

Groppi, Christopher

73

Wind Observations of Anomalous Cosmic Rays from Solar Minimum to Maximum  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

74

Sensorless Maximum Power Point Tracking of Wind by DFIG Using Rotor Position Phase Lock Loop (PLL)  

Microsoft Academic Search

This paper presents an invention, the rotor position phase lock loop (PLL), which enables maximum power point (MPPT) tracking of wind by doubly-fed induction generators without needing a tachometer, an absolute position encoder, or an anemometer. The rotor position PLL is parameter variation insensitive, requiring only an estimate of the magnetization inductance for it to operate. It is also insensitive

Baike Shen; Bakari Mwinyiwiwa; Yongzheng Zhang; Boon-Teck Ooi

2009-01-01

75

Design of Small Wind Turbine with Maximum Power Point Tracking Algorithm  

Microsoft Academic Search

This paper presents a complex design of Turbine with AC\\/DC converter containing Point Tracking Algorithm. The paper describes phenomenon and problems connected with designing particular parts for small wind turbine, such a generator addition, it shows short discussion between two different Maximum Power Point Tracking approaches experimental results.

M. Rolak; R. Kot; M. Malinowski; Z. Goryca; J. T. Szuster

2011-01-01

76

Maximum likelihood estimation of high frequency machine and transformer winding parameters  

Microsoft Academic Search

This paper presents a method to establish a multisection network model for study of high frequency transient behavior of transformer and machine windings. The parameters of the network model are estimated using maximum likelihood estimation technique. In order to verify the proposed estimation method, the parameters of a six-section network model are estimated.

A. Keyhani; H. Tsai; A. Abur

1990-01-01

77

Remote Sensing of Solar Wind Velocity Applying IPS Technique using MEXART  

NASA Astrophysics Data System (ADS)

Radio waves coming from compact cosmic radio sources are scattered by electron density fluctuations in the solar wind plasma, producing a diffraction pattern at Earth which moves along with the solar wind. This phenomenon results into flux density fluctuations observed by a radio telescope and it is known as Interplanetary Scintillation (IPS). By employing IPS observations, it is possible to track solar wind velocities in the inner heliosphere. The Mexican Array Radio Telescope (MEXART) is an new instrument devoted to IPS observations at 140 MHz. We present preliminar estimates of solar wind velocities by using IPS observations of the MEXART.

Mejia-Ambriz, J. C.; Gonzalez-Esparza, A.; Romero Hernandez, E.

2012-12-01

78

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

NASA Technical Reports Server (NTRS)

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.

Misawa, H.; Kojima, M.

1995-01-01

79

AMSU-A Tropical Cyclone Maximum Sustained Winds and Web Site  

NASA Technical Reports Server (NTRS)

The Advanced Microwave Sounding Unit (AMSU)-A instruments on the NOAA-15 and NOAA-16 satellites provide information on the warm cores of tropical cyclones from oxygen channel brightness temperature (Tb) measurements near 55 GHz. With appropriate assumptions, cyclone-scale Tb gradients can be directly related to middle-to-lower tropospheric height gradients. We have developed a method for diagnosis of maximum sustained winds (Vmax) from radially averaged Tb gradients in several of the AMSU channels. Calibration of the method with recon-based (or other in situ) winds results in better agreement than with Dvorak wind estimates. Gradient wind theory shows that the warm core Tb gradient signal increases non-linearly with wind speed, making microwave temperature sounders useful for diagnosing high wind speeds, but at the expense of a minimum useful detection limit of about 40 knots. It is found that accurate wind diagnoses depend upon (1) accounting for hydrometeor effects in the AMSU channels, and (2) maximizing signal-to-noise, since the 50 km resolution data cannot fully resolve the temperature gradients in the Vmax region, typically 10-20 km in scale. AMSU imagery and max diagnoses from specific hurricanes will be shown, including independent tests from the 2000 hurricane season.

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

2001-01-01

80

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

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

81

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...

82

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...

83

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

84

Thermal iron ions in high speed solar wind streams. II - Temperatures and bulk velocities  

NASA Technical Reports Server (NTRS)

Mitchel and Roelof (1980) reported the detection of iron in high speed solar wind flows using the small, but finite sensitivity of solid state detectors to Fe ions in the low energy (50-200 keV protons) L1 channel of the NOAA/JHU energetic particle experiment (EPE). In the current investigation, the EPE response is modeled to a convected Maxwellian to obtain the thermal velocity, flow angle, and bulk velocity of the iron distribution. It is assumed that the iron bulk flow velocity can be represented as a vector sum of the hydrogen bulk velocity and an interplanetary magnetic field (IMF) aligned velocity increment. It is found that the velocity increment is smaller than the local Alfven speed in magnitude, and that the iron thermal velocity is comparable with or greater than the proton thermal velocity, with the 'thermal' velocity defined as the square root of 2kT/m.

Mitchell, D. G.; Roelof, E. C.; Feldman, W. C.; Bame, S. J.; Williams, D. J.

1981-01-01

85

Maximum shortening velocity of lymphatic muscle approaches that of striated muscle  

PubMed Central

Lymphatic muscle (LM) is widely considered to be a type of vascular smooth muscle, even though LM cells uniquely express contractile proteins from both smooth muscle and cardiac muscle. We tested the hypothesis that LM exhibits an unloaded maximum shortening velocity (Vmax) intermediate between that of smooth muscle and cardiac muscle. Single lymphatic vessels were dissected from the rat mesentery, mounted in a servo-controlled wire myograph, and subjected to isotonic quick release protocols during spontaneous or agonist-evoked contractions. After maximal activation, isotonic quick releases were performed at both the peak and plateau phases of contraction. Vmax was 0.48 ± 0.04 lengths (L)/s at the peak: 2.3 times higher than that of mesenteric arteries and 11.4 times higher than mesenteric veins. In cannulated, pressurized lymphatic vessels, shortening velocity was determined from the maximal rate of constriction [rate of change in internal diameter (?dD/dt)] during spontaneous contractions at optimal preload and minimal afterload; peak ?dD/dt exceeded that obtained during any of the isotonic quick release protocols (2.14 ± 0.30 L/s). Peak ?dD/dt declined with pressure elevation or activation using substance P. Thus, isotonic methods yielded Vmax values for LM in the mid to high end (0.48 L/s) of those the recorded for phasic smooth muscle (0.05–0.5 L/s), whereas isobaric measurements yielded values (>2.0 L/s) that overlapped the midrange of values for cardiac muscle (0.6–3.3 L/s). Our results challenge the dogma that LM is classical vascular smooth muscle, and its unusually high Vmax is consistent with the expression of cardiac muscle contractile proteins in the lymphatic vessel wall. PMID:23997104

Zhang, Rongzhen; Taucer, Anne I.; Gashev, Anatoliy A.; Muthuchamy, Mariappan; Zawieja, David C.

2013-01-01

86

Biomarkers affected by impact velocity and maximum strain of cartilage during injury.  

PubMed

Osteoarthritis is one of the most common, debilitating, musculoskeletal diseases; 12% associated with traumatic injury resulting in post-traumatic osteoarthritis (PTOA). Our objective was to develop a single impact model with cartilage "injury level" defined in terms of controlled combinations of strain rate to a maximum strain (both independent of cartilage load resistance) to study their sensitivity to articular cartilage cell viability and potential PTOA biomarkers. A servo-hydraulic test machine was used to measure canine humeral head cartilage explant thickness under repeatable pressure, then subject it (except sham and controls) to a single impact having controlled constant velocity V=1 or 100mm/s (strain rate 1.82 or 182/s) to maximum strain ?=10%, 30%, or 50%. Thereafter, explants were cultured in media for twelve days, with media changed at day 1, 2, 3, 6, 9, 12. Explant thickness was measured at day 0 (pre-injury), 6 and 12 (post-injury). Cell viability, and tissue collagen and glycosaminoglycan (GAG) were analyzed immediately post-injury and day 12. Culture media were tested for biomarkers: GAG, collagen II, chondroitin sulfate-846, nitric oxide, and prostaglandin E2 (PGE2). Detrimental effects on cell viability, and release of GAG and PGE2 to the media were primarily strain-dependent, (PGE2 being more prolonged and sensitive at lower strains). The cartilage injury model appears to be useful (possibly superior) for investigating the relationship between impact severity of injury and the onset of PTOA, specifically for discovery of biomarkers to evaluate the risk of developing clinical PTOA, and to compare effective treatments for arthritis prevention. PMID:25005436

Waters, Nicole Poythress; Stoker, Aaron M; Carson, William L; Pfeiffer, Ferris M; Cook, James L

2014-09-22

87

Do Inner Planets Modulate the Solar Wind Velocity at 1 AU from the Sun?  

NASA Astrophysics Data System (ADS)

Quite recently, it has been suggested that the interaction of the solar wind with Mercury results in the variation in the solar wind velocity in the Earth's neighborhood during inferior conjunctions with Mercury. This suggestion has important implications both on the plasma physics of the interplanetary space and on the space weather forecast. In this study we have attempted to answer a question of whether the claim is properly tested. We confirm that there are indeed ups and downs in the profile of the solar wind velocity measured at the distance of 1 AU from the Sun. However, the characteristic attribute of the variation in the solar wind velocity during the inferior conjunctions with Mercury is found to be insensitive to the phase of the solar cycles, contrary to an earlier suggestion. We have found that the cases of the superior conjunctions with Mercury and of even randomly chosen data sets rather result in similar features. Cases of Venus are also examined, where it is found that the ups and downs with a period of ~ 10 to 15 days can be also seen. We conclude, therefore, that those variations in the solar wind velocity turn out to be a part of random fluctuations and have nothing to do with the relative position of inner planets. At least, one should conclude that the solar wind velocity is not a proper observable modulated by inner planets at the distance of 1 AU from the Sun in the Earth's neighborhood during inferior conjunctions.

Kim, Jung-Hee; Chang, Heon-Young

2014-03-01

88

The influence of velocity variability on the determination of wind profiles  

NASA Technical Reports Server (NTRS)

High sensitivity radars allow the determination of velocity estimates at time resolutions down to one minute or better. Because of the variability introduced to the mean wind due to turbulence and waves, the high resolution profiles may not be too useful for forecasting applications, although they yield the most realistic estimate of the instantaneous wind profile. Profiles of wind speed and direction, vertical velocity and echo power, which were deduced in real-time on 23 August 1981 with the spaced antenna drift mode of the SOUSY-VHF-Radar are shown. Whereas these profiles were measured within 1 minute, the operating routine allowed the selection of variable (longer) measuring periods, and one has to search for the optimum duration of the data averaging period. A high time resolution wind vector diagram is given which gives an idea of the temporal variability. The data were obtained with the spaced antenna technique, which allows a good estimate of the horizontal wind without having to correct for the vertical velocity component. The wind vectors specifically indicate a quasi-periodic variation in direction. This is assumed to be due to gravity waves since the vertical velocity also shows periodical variations with the same period. The consistency of these spaced-antenna VHF radar results along with the radiosonde data convinced researchers that the method is quite suitable for wind profiling applications.

Rottger, J.

1986-01-01

89

Density, Velocity and Ionization Structure in Accretion-Disc Winds  

NASA Technical Reports Server (NTRS)

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.

Sonneborn, George (Technical Monitor); Long, Knox

2004-01-01

90

Radial gradient of solar wind velocity from 1 to 5 AU  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

91

Extremely long baseline interplanetary scintillation measurements of solar wind velocity  

Microsoft Academic Search

We present results of observations of interplanetary scintillation (IPS) made using the telescopes of the MERLIN and EISCAT networks in which the beam separation approached 2000 km, much larger than in any previous IPS experiments. Significant correlation between the scintillation patterns was observed at time lags of up to 8 s and fast and slow streams of solar wind were

A. R. Breen; R. A. Fallows; M. M. Bisi; P. Thomasson; C. A. Jordan; G. Wannberg; R. A. Jones

2006-01-01

92

A large time scale wind velocity simulation method  

Microsoft Academic Search

The wind speed has strong stochastic characteristics, and can be divided into long-term component and turbulence component. In short time scale simulation, the long-term component can be considered as constant. But in long time scale simulation, the slow fluctuating characteristics simulated by using Van der Hoven spectrum model presented in this paper must be included. The turbulence component is obtained

Liu Yanjie; Wang Jun

2010-01-01

93

Aeolian dust deposition on photovoltaic solar cells: the effects of wind velocity and airborne dust concentration on cell performance  

Microsoft Academic Search

Wind tunnel experiments were conducted to investigate the effect of wind velocity and airborne dust concentration on the drop of photovoltaic (PV) cell performance caused by dust accumulation on such cells. Performance drop was investigated at four wind velocities and four dust concentrations. I–V characteristics were determined for various intensities of cell pollution. The evolutions of the short circuit current,

Dirk Goossens; Emmanuel Van Kerschaever

1999-01-01

94

Comparison of vertical velocities analyzed by a numerical model and measured by a VHF wind profiler  

NASA Technical Reports Server (NTRS)

The use of wind profilers for measuring vertical velocities in the troposphere and lower stratosphere is potentially of great interest for verification of forecasts, diagnosis of mesoscale circulations, and studies of wave motions. The studies of profiler vertical velocities to date have shown that the observed patterns of ascent and subsidence are reasonable when compared to the synoptic conditions. However, difficulties arise when a direct verification of the profiler vertical winds is sought. Since no other technique can measure the vertical velocities over the same height range and with the same claimed accuracy as the profilers, direct comparisons are impossible. The only alternative is to compare the measurements to analyzed vertical velocity fields. Here, researchers compare vertical measurements made with the SOUSY VHF radar over a period of 11 days at the beginning of November 1981 to the analyzed vertical velocities produced by the European Center for Medium-range Weather Forecasting (ECMWF) model for grid points near the radar site.

Larsen, M. F.; Rottger, J.; Dennis, T. S.

1986-01-01

95

Low-velocity variability in the stellar wind of HD 152408 (O8: Iafpe)  

NASA Technical Reports Server (NTRS)

We describe high-quality, spectroscopic time series observations of variability at low velocities in the stellar wind of the extreme O-supergiant HD 152408. These observations were obtained during a monitoring campaign coordinated between Australia and Chile in 1992 July. Systematic variability on hourly time scales is particularly apparent in the He I lambda 5876 P Cygni profile, which diagnoses the deeper, denser region of the wind. These changes indicate the presence of evolving wind structure, which takes the form of blueward-migrating, discrete optical depth enhancements. Four distinct features are identified over approximately 5 days, spanning a velocity range of about -50 km/s at formation to about -500 km/s (i.e., greater than or approximately equal to 0.5 of the terminal velocity) at the blue edge of the He I absorption trough. Sympathetic variations are also apparent in the Balmer emission lines of HD 152408. The characteristics of these features, including their widths, column densities, and accelerations, suggest similarities to discrete absorption components commonly seen at larger velocities in UV P Cygni profiles of other O-type stars. These optical results demonstrate that frequent, systematic wind variability is present down to very large depths, and provide constraints on the stability of the low-velocity regime of hot-star winds.

Prinja, Raman K.; Fullerton, A. W.

1994-01-01

96

High velocity molecular emission in Orion: A case for stellar winds  

SciTech Connect

We report sensitive observations of a variety of molecules in the high velocity source (''plateau'') of the Orion molecular cloud. We also report a search for high velocity emission in other molecular clouds. On the basis of these data and data in the literature, we propose that the high velocity source consists of clumps of dense molecular gas which are being accelerated by the high velocity stellar wind of a pre--main-sequence star. The H/sub 2/, some of the H/sub 2/O maser, and the Herbig-Haro--type emissions are attributed to shocks associated with the breakup of the protostellar cocoon.

Kuiper, T.B.H.; Zuckerman, B.; Kuiper, E.N.R.

1981-12-01

97

High velocity molecular emission in Orion - A case for stellar winds  

NASA Technical Reports Server (NTRS)

On the basis of data from the literature and observations of both a variety of molecules in the high-velocity source of the Orion molecular cloud and high-velocity emissions in other molecular clouds, it is proposed that the high-velocity source consists of clumps of dense molecular gas which are accelerated by the high-velocity stellar wind of a pre-main sequence star. Some of the H2O maser emissions, and the H2 and Herbig-Haro-type emissions, are attributed to shocks associated with the breakup of the protostellar cocoon.

Kuiper, T. B. H.; Zuckerman, B.; Rodriguez Kuiper, E. N.

1981-01-01

98

FIS/ANFIS Based Optimal Control for Maximum Power Extraction in Variable-speed Wind Energy Conversion System  

NASA Astrophysics Data System (ADS)

An optimal control for maximizing extraction of power in variable-speed wind energy conversion system is presented. Intelligent gradient detection by fuzzy inference system (FIS) in maximum power point tracking control is proposed to achieve power curve operating near optimal point. Speed rotor reference can be adjusted by maximum power point tracking fuzzy controller (MPPTFC) such that the turbine operates around maximum power. Power curve model can be modelled by using adaptive neuro fuzzy inference system (ANFIS). It is required to simply well estimate just a few number of maximum power points corresponding to optimum generator rotor speed under varying wind speed, implying its training can be done with less effort. Using the trained fuzzy model, some estimated maximum power points as well as their corresponding generator rotor speed and wind speed are determined, from which a linear wind speed feedback controller (LWSFC) capable of producing optimum generator speed can be obtained. Applied to a squirrel-cage induction generator based wind energy conversion system, MPPTFC and LWSFC could maximize extraction of the wind energy, verified by a power coefficient stay at its maximum almost all the time and an actual power line close to a maximum power efficiency line reference.

Nadhir, Ahmad; Naba, Agus; Hiyama, Takashi

99

High temporal resolution velocity estimates from the NASA 50 MHz wind profiler  

NASA Technical Reports Server (NTRS)

A three-point medium filter for wind profiling radar has been found which, when applied to successive spectral data, effectively eliminates most spurious echoes from the data while improving SNRs. When combined with velocity calculations using a first guess, the result is a robust system that can extract high-quality wind profiles at three-minute intervals. The velocity computation methodology is described and its performance is illustrated using two sample data sets taken during very different synoptic regimes. Operational considerations are discussed.

Wilfong, Timothy L.; Creasey, Robert L.; Smith, Steve A.

1992-01-01

100

IPS observations of the solar wind velocity and the acceleration mechanism  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

101

Vertical wind velocities from superpressure balloons - A case study using Eole data  

NASA Technical Reports Server (NTRS)

A method for determining vertical wind velocities using the pressure- and temperature-change data from superpressure (constant-density) balloons was proposed in an earlier paper (1975). In this paper, we present a case study using actual balloon data to test the method. Data from the Eole balloon experiment were used to estimate the sign of vertical wind velocities, as well as the horizontal velocity field, near 200 mb over Australia. The resulting patterns of vertical velocity compare favorably with satellite pictures and with current models of flow near jet-stream maxima. Additionally, this study provides evidence that areas of vertical motion in the troposphere extend upward into the lower stratosphere without changing sign.

Banta, R. M.

1976-01-01

102

Effect of Wind Velocity on Flame Spread in Microgravity  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

103

A wind tunnel study of air flow in waving wheat: Two-point velocity statistics  

Microsoft Academic Search

Two-point, space-time correlations of streamwise and vertical velocity were obtained from a wind tunnel simulation of an atmospheric surface layer with an underlying model wheat canopy constructed of flexible nylon stalks. Velocity data extend from 1\\/6 canopy height to several canopy heights, with in excess of 2000 three-dimensional vector separations of the two x-wire probes. Isocorrelation contours over anx, z

R. H. Shaw; Y. Brunet; J. J. Finnigan; M. R. Raupach

1995-01-01

104

A wind tunnel study of air flow in waving wheat: Two-point velocity statistics  

Microsoft Academic Search

Two-point, space-time correlations of streamwise and vertical velocity were obtained from a wind tunnel simulation of an atmospheric surface layer with an underlying model wheat canopy constructed of flexible nylon stalks. Velocity data extend from 1\\/6 canopy height to several canopy heights, with in excess of 2000 three-dimensional vector separations of the two x-wire probes. Isocorrelation contours over an x,

R. H. Shaw; Y. Brunet; J. J. Finnigan; M. R. Raupach

1995-01-01

105

Climatological mean and interannual variance of United States surface wind speed, direction and velocity  

Microsoft Academic Search

Means and variances of monthly mean wind speed, direction and velocity (the mean resultant vector) are derived for the period 1961-1990 at 216 stations in the coterminous United States. Direction and velocity means and variances are calculated using a complex-arithmetic extension of the equations for scalar mean and variance. Variance is derived from the 30-year time series of monthly means.

Katherine Klink

1999-01-01

106

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

NASA Astrophysics Data System (ADS)

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.

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

2015-03-01

107

The winds of O-stars. II - The terminal velocities of stellar winds of O-type stars  

NASA Technical Reports Server (NTRS)

The SEI method (Lamers et al., 1987) is used to obtain P Cygni profiles of the UV resonance lines of C IV, N V, and S IV and of the subordinate UV lines of N IV and C III observed in the spectra of 27 O-type stars. Theoretical profiles which include the turbulence effects agree well with the observations, and they can account for the deep absorption troughs, the shape of the violet absorption wings, and the wavelength of the emission peak. The resulting terminal velocities of the stellar winds are found to be systematically lower by about 400 km/s than previous estimates obtained using the Sobolev approximation (Castor and Lamers, 1979), suggesting that the narrow absorption components, observed in the UV resonance lines of O and B stars, reach the terminal velocity of the winds.

Groenewegen, M. A. T.; Lamers, H. J. G. L. M.; Pauldrach, A. W. A.

1989-01-01

108

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

E-print Network

Estimating attitude and wind velocity using biomimetic sensors on a microrobotic bee Sawyer B The Harvard RoboBee is a sub-100 mg micro-aerial ve- hicle (MAV), the first insect-sized robot able to take not demonstrated their operation on insect-scale robots. In this work we consider The authors are with the School

Fuller, Sawyer Buckminster

109

Nearfield acoustic holography in wind tunnel by means of velocity LDV measurements  

E-print Network

Nearfield acoustic holography in wind tunnel by means of velocity LDV measurements H. Parisot helene.parisot dupuis@onera.fr Proceedings of the Acoustics 2012 Nantes Conference 23-27 April 2012, a new method based on Nearfield Acoustic Hologra- phy using a convective spectral pressure

Boyer, Edmond

110

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

111

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

NASA Astrophysics Data System (ADS)

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.

Ning, A.; Dykes, K.

2014-06-01

112

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

Microsoft Academic Search

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,

Simpkins

1996-01-01

113

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

114

Dynamic aeroelastic stability of vertical-axis wind turbines under constant wind velocity  

NASA Astrophysics Data System (ADS)

The flutter problem associated with the blades of a class of vertical-axis wind turbines called Darrieus is studied in detail. The spinning blade is supposed to be initially curved in a particular shape characterized by a state of pure tension at the blade cross section. From this equilibrium position a three-dimensional linear perturbation pattern is superimposed to determine the dynamic aeroelastic stability of the blade in the presence of free wind speed by means of the Floquet-Lyapunov theory for periodic systems.

Nitzsche, Fred

1994-05-01

115

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

E-print Network

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...

Mursula, Kalevi; Holappa, Lauri

2015-01-01

116

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

E-print Network

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

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

2015-01-01

117

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

NASA Technical Reports Server (NTRS)

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.

Roberts, D. Aaron

2010-01-01

118

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

NASA Astrophysics Data System (ADS)

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.

Kieu, Chanh Q.

2012-01-01

119

CO2 lidar for measurements of trace gases and wind velocities  

NASA Technical Reports Server (NTRS)

CO2 lidar systems technology and signal processing requirements relevant to measurement needs and sensitivity are discussed. Doppler processing is similar to microwave radar, with signal reception controlled by a computer capable of both direct and heterodyne operations. Trace gas concentrations have been obtained with the NASA DIAL system, and trace gas transport has been determined with Doppler lidar measurements for wind velocity and turbulence. High vertical resolution measurement of trace gases, wind velocity, and turbulence are most important in the planetary boundary layer and in regions between the PBL and the lower stratosphere. Shear measurements are critical for airport operational safety. A sensitivity analysis for heterodyne detection with the DIAL system and for short pulses using a Doppler lidar system is presented. The development of transient injection locking techniques, as well as frequency stability by reducing chirp and catalytic control of closed cycle CO2 laser chemistry, is described.

Hess, R. V.

1982-01-01

120

Equations and approximations involved in computing vertical wind velocities from superpressure balloon data  

NASA Technical Reports Server (NTRS)

Superpressure, or constant-level, balloons have long been used to obtain horizontal wind velocities in the atmosphere. This paper presents equations which can be used to evaluate omega, the vertical wind component in pressure coordinates, from on-board pressure and temperature sensors. These equations take into account the short-term displacements of a balloon from its equilibrium density level, and thus they do not assume that the balloon precisely maintains constant density. The longer-term and larger-amplitude diurnal oscillations in balloon level, and also an approximation used in deriving the vertical velocity equations, are both discussed in some detail. These equations can be used to obtain quantitative estimates of omega if reasonable estimates of the ambient lapse rate could be obtained.

Banta, R. M.

1976-01-01

121

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

NASA Technical Reports Server (NTRS)

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.

Intriligator, D. S.

1974-01-01

122

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

123

The development of a low velocity wind tunnel with instrumentation for boundary layer investigations  

E-print Network

fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY May 1958 Major Subject: Mechanical Engineering THE DEVELOPMENT OF A LOW VELOCITY WIND TUNNEL WITH INSTRUMENTATION FOR BOUNDARY LAYER INVESTIGATIONS A Dissertation By John Robert.... The writer is also appreciative of the assistance given by Dr. J. D. Lindsay, Graduate School Representative, and Dr. C. M. Simmang, Head of the Department of Mechanical Engineering, The writer wishes to express much gratitude to Warren Rice, principal...

Massey, John Robert

1958-01-01

124

Maximum capacity model of grid-connected multi-wind farms considering static security constraints in electrical grids  

NASA Astrophysics Data System (ADS)

An increasing interest in wind energy and the advance of related technologies have increased the connection of wind power generation into electrical grids. This paper proposes an optimization model for determining the maximum capacity of wind farms in a power system. In this model, generator power output limits, voltage limits and thermal limits of branches in the grid system were considered in order to limit the steady-state security influence of wind generators on the power system. The optimization model was solved by a nonlinear primal-dual interior-point method. An IEEE-30 bus system with two wind farms was tested through simulation studies, plus an analysis conducted to verify the effectiveness of the proposed model. The results indicated that the model is efficient and reasonable.

Zhou, W.; Qiu, G. Y.; Oodo, S. O.; He, H.

2013-03-01

125

Low-latitude thermospheric neutral winds determined from AE-E measurements of the 6300-A nightglow at solar maximum  

NASA Astrophysics Data System (ADS)

Atmosphere Explorer E (AE-E) measurements of the O(1D) 6300-A emission in the nighttime equatorial thermosphere are used to infer the height of the F2 layer peak as a function of latitude and local time. The investigation is conducted both for northern hemisphere winter solstice and for spring equinox, under solar maximum conditions. The layer heights are used to derive magnetic meridional components of the transequatorial neutral wind, in conjunction with the MSIS-86 model and previous Jicamarca incoherent scatter measurements of the zonal electric field. The AE-E wind estimates indicate a predominant summer to winter flow for the winter solstice case. Comparisons are made with the empirical horizontal wind model HWM87 and with winds generated by the thermospheric general circulation model. The model predictions and experimental results are generally in good agreement, confirming the applicability of visible airglow data to studies of the global neutral wind pattern.

Burrage, M. D.; Abreu, V. J.; Fesen, C. G.

1990-07-01

126

Low-latitude thermospheric neutral winds determined from AE-E measurements of the 6300-A nightglow at solar maximum  

NASA Technical Reports Server (NTRS)

Atmosphere Explorer E (AE-E) measurements of the O(1D) 6300-A emission in the nighttime equatorial thermosphere are used to infer the height of the F2 layer peak as a function of latitude and local time. The investigation is conducted both for northern hemisphere winter solstice and for spring equinox, under solar maximum conditions. The layer heights are used to derive magnetic meridional components of the transequatorial neutral wind, in conjunction with the MSIS-86 model and previous Jicamarca incoherent scatter measurements of the zonal electric field. The AE-E wind estimates indicate a predominant summer to winter flow for the winter solstice case. Comparisons are made with the empirical horizontal wind model HWM87 and with winds generated by the thermospheric general circulation model. The model predictions and experimental results are generally in good agreement, confirming the applicability of visible airglow data to studies of the global neutral wind pattern.

Burrage, M. D.; Abreu, V. J.; Fesen, C. G.

1990-01-01

127

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

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

128

Uncertainties in wind speed dependent CO2 transfer velocities due to airflow distortion at anemometer sites on ships  

Microsoft Academic Search

Data from research vessels and merchant ships are used to estimate ocean CO2 uptake via parameterizations of the gas transfer velocity (k) and measurements of the difference between the concentration of CO2 in the ocean (pCO2sw) and atmosphere (pCO2atm) and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be in error due to air flow

F. Griessbaum; B. I. Moat; Y. Narita; M. J. Yelland; O. Klemm; M. Uematsu

2009-01-01

129

Uncertainties in wind speed dependent CO 2 transfer velocities due to airflow distortion at anemometer sites on ships  

Microsoft Academic Search

Data from platforms, research vessels and mer- chant ships are used to estimate ocean CO2 uptake via param- eterisations of the gas transfer velocity (k) and measurements of the difference between the partial pressures of CO2 in the ocean (pCO2 sw) and atmosphere (pCO2 atm) and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be

F. Griessbaum; B. I. Moat; Y. Narita; M. J. Yelland; O. Klemm; M. Uematsu

2010-01-01

130

Uncertainties in wind speed dependent CO2 transfer velocities due to airflow distortion at anemometer sites on ships  

Microsoft Academic Search

Data from platforms, research vessels and merchant ships are used to estimate ocean CO2 uptake via parameterisations of the gas transfer velocity (k) and measurements of the difference between the partial pressures of CO2 in the ocean (pCO2 sw) and atmosphere (pCO2 atm) and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be in error

F. Griessbaum; B. I. Moat; Y. Narita; M. J. Yelland; O. Klemm; M. Uematsu

2010-01-01

131

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

132

Responses of giant interneurons of the cockroach Periplaneta americana to wind puffs of different directions and velocities  

Microsoft Academic Search

1.Controlled wind puffs of different directions and velocities were delivered to the cerci of cockroaches (Periplaneta americana), while the responses of individually identifiable giant interneurons (GI's) were recorded intracellularly.2.All fourteen histologically identified GI's (seven bilateral pairs) respond with a burst of action potentials to wind from some or all directions. The directional sensitivity of a given GI is consistent from

Joanne Westin; Jonathan J. Langberg; Jeffrey M. Camhi

1977-01-01

133

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

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

134

Dependence of the Occurrence of Low Latitude Pc3 Geomagnetic Pulsations on Solar Wind Velocity  

NASA Astrophysics Data System (ADS)

Energy for the Earth's magnetospheric processes is provided by solar wind. Pc3 Geomagnetic pulsations are quasi-sinusoidal variations in the Earth's Magnetic field in the period range 10-45 seconds. The magnitude of these pulsations ranges from fraction of a nT(nano Tesla) to several nT. These pulsations can be observed in a number of ways. However the application of ground based manetometer arrays has proven to be one of the most successful methods of studying the spatial structure of hydromagnetic waves in the Earth's magnetosphere. With few exceptions, the Pc3 studies undertaken in the past have been confined to middle and high latitudes. The spatial and temporal variations observed in Pc3 occurrence are of vital importance because they provide evidence which can be directly related to wave generation mechanisms both inside and external to the magnetosphere. At low latitudes (L < 3) wave energy predominates in the Pc3 band and the spatial characteristics of these pulsations have received little attention in the past. An array of four low latitude induction coil magnetometers was established in south-east Australia over a longitudinal range of 17 degrees at L=1.8 to 2.7 for carrying out the study of the effect of the solar wind velocity on these pulsations. Digital dynamic spectra showing Pc3 pulsation activity over a period of about six months have been used to evaluate Pc3 pulsation occurrence. Pc3 occurrence probability at low latitudes has been found to be dominant for the solar wind velocity in the range 400-700 Km/sec. The results suggest that solar wind controls Pc3 occurrence through a mechanism in which Pc3 wave energy is convected through the magnetosheath and coupled to the standing oscillations of magnetospheric field lines.

Ansari, I. A.

2005-05-01

135

Determination of the solar wind velocity on the basis of observations of the plasma tail of Comet 1976 VI  

Microsoft Academic Search

The position angles of axes of the plasma tail of Comet West 1976 VI relative to the radius vector of the comet were determined from 17 photographic plates of the comet obtained from March 5 to 30, 1976. The solar wind velocity was determined on the basis of these position angles. The velocity at heliographic latitudes of 33-43 deg was

Kh. I. Ibadinov; M. Kh. Rasulova; E. Pittich

1987-01-01

136

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

NASA Astrophysics Data System (ADS)

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.

Karkar, S.; Paillard, D.

2015-03-01

137

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

NASA Technical Reports Server (NTRS)

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.

Smith, M. A. H.

1978-01-01

138

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

PubMed

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

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

2014-04-01

139

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

NASA Technical Reports Server (NTRS)

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.

Marsch, E.

1995-01-01

140

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

NASA Astrophysics Data System (ADS)

In this study we present gas exchange measurements conducted in a large scale wind-wave tank. Fourteen chemical species spanning a wide range of solubility (dimensionless solubility, ? = 0.4 to 5470) and diffusivity (Schmidt number in water, Scw = 594 to 1194) were examined under various turbulent (u10 = 0.8 to 15 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 three) was observed for N2O under a surfactant covered water surface. In contrast, the surfactant affected CH3OH, the high solubility tracer only weakly.

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

2014-06-01

141

Spectral Types and Wind Velocities for Massive Stars in R136  

NASA Astrophysics Data System (ADS)

We analyze spatially resolved, long-slit ultraviolet (UV) and optical stellar spectra of the compact starburst cluster R136 at the core of 30 Doradus. R136 is young and massive, making it an ideal place to study the upper end of the initial mass function. These spectra, taken with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, cover over 100 stars in the inner 4 arcseconds (1 parsec) of R136, a region which cannot be resolved with ground-based spectroscopy. In this poster we present both the UV and optical of over 20 of the brightest stars in R136, extracted with MULTISPEC, a tool written specifically for multiple objects in crowded fields. For each star we present an optical spectral type and a terminal wind velocity derived from the UV data

Bostroem, K. A.; Maíz Apellániz, J.; Caballero-Nieves, S. M.; Walborn, N. R.; Crowther, P. A.

2014-01-01

142

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

SciTech Connect

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.

Simpkins, A.A.

1996-09-01

143

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

PubMed Central

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

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

2014-01-01

144

Investigation on the impact of the environment wind velocity on the indirect air-cooling tower performance  

NASA Astrophysics Data System (ADS)

The wind velocity plays a crucial role in the operation characteristic of indirect cooling tower. In this paper a 2×330MW vertical arrangement indirect air-cooled system was taken as research object, and numerical simulation method was used to analyze the relative influence of the wind speed, ranging from 4m/s to 18m/s, on the outlet water temperature of cooling tower, the outlet air temperature of radiator, the facing wind speed of the fan segment and on the outlet air speed of the cooling tower. The result shows that the impact of the natural wind speed on the cooling tower efficiency varies greatly and this impact increases as the wind speed increases.

Qin, Yongbo; Gu, Hongfang; Wang, Haijun; Chen, Guoyong

2013-07-01

145

Storm-Time Ion Velocity Distributions in the Generalized Polar Wind  

NASA Astrophysics Data System (ADS)

At high latitudes the plasma escapes along geomagnetic field lines from the high pressure ionosphere into the low pressure magnetosphere. As the plasma flows upwards, it goes through transitions from collision-dominated to collisionless conditions, from subsonic to supersonic flows, and form O+-dominated to H+-dominated compositions. Meanwhile, the plasma E×B drifts across the cusp, the polar cap, the auroral oval, and the subauroral regions, where it is exposed to different intensities of physical factors, e.g. wave-particle interactions, magnetospheric particle precipitation, and centrifugal acceleration. Moreover, during geomagnetic activity these effects vary significantly with time. We used a 3-D generalized polar wind (GPW) model in order to simulate the plasma behavior during a geomagnetic storm. The northern polar region was modeled with 1000 convecting trajectories and about one billion simulation particles. Special attention was given to investigating the interplay between the different mechanisms regarding their influence on the velocity distributions of the O+ and H+ ions at different altitudes, latitudes and storm phases. We present the evolution of the ion velocity distributions and how they depend on space and time. The results will be compared with previous results from simpler models.

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

2009-12-01

146

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

NASA Technical Reports Server (NTRS)

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

Hauser, Cavour H; Plohr, Henry W

1951-01-01

147

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

NASA Astrophysics Data System (ADS)

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

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

2003-05-01

148

14 CFR Appendix J to Part 36 - Alternative Noise Certification Procedure for Helicopters Under Subpart H Having a Maximum...  

Code of Federal Regulations, 2010 CFR

...humidity of 70 percent; and (4) Zero wind. (b) Reference test site. ...using the minimum specification engine power corresponding to maximum continuous...band centered at 8 kiloHertz. (3) Wind velocity that does not exceed 10...

2010-01-01

149

14 CFR Appendix J to Part 36 - Alternative Noise Certification Procedure for Helicopters Under Subpart H Having a Maximum...  

Code of Federal Regulations, 2011 CFR

...humidity of 70 percent; and (4) Zero wind. (b) Reference test site. ...using the minimum specification engine power corresponding to maximum continuous...band centered at 8 kiloHertz. (3) Wind velocity that does not exceed 10...

2011-01-01

150

14 CFR Appendix J to Part 36 - Alternative Noise Certification Procedure for Helicopters Under Subpart H Having a Maximum...  

Code of Federal Regulations, 2014 CFR

...humidity of 70 percent; and (4) Zero wind. (b) Reference test site. ...using the minimum specification engine power corresponding to maximum continuous...band centered at 8 kiloHertz. (3) Wind velocity that does not exceed 10...

2014-01-01

151

14 CFR Appendix J to Part 36 - Alternative Noise Certification Procedure for Helicopters Under Subpart H Having a Maximum...  

Code of Federal Regulations, 2013 CFR

...humidity of 70 percent; and (4) Zero wind. (b) Reference test site. ...using the minimum specification engine power corresponding to maximum continuous...band centered at 8 kiloHertz. (3) Wind velocity that does not exceed 10...

2013-01-01

152

14 CFR Appendix J to Part 36 - Alternative Noise Certification Procedure for Helicopters Under Subpart H Having a Maximum...  

Code of Federal Regulations, 2012 CFR

...humidity of 70 percent; and (4) Zero wind. (b) Reference test site. ...using the minimum specification engine power corresponding to maximum continuous...band centered at 8 kiloHertz. (3) Wind velocity that does not exceed 10...

2012-01-01

153

Measurement of wind velocity on the surface of Venus during operation of the Venera 9 and Venera 10 space probes  

Microsoft Academic Search

The paper reports on the first measurements of the wind velocity on the surface of Venus recorded during final phase of descent of Venera 9 and 10 and while on the surface. The cup anemometer system and some tests on earth for determining best placement of the equipment in order to eliminate any effect of the spacecraft are described. Venera-9

V. S. Avduevskii; S. L. Vishnevetskii; I. A. Golov; Iu. Ia. Karpeiskii; A. D. Lavrov; V. Ia. Likhushin; M. Ia. Marov; D. A. Melnikov; N. I. Pomogin; N. N. Pronina

1976-01-01

154

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...

155

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

SciTech Connect

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.

Fichtl, G.H.

1983-09-01

156

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

NASA Technical Reports Server (NTRS)

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.

Roberts, D. Aaron

2011-01-01

157

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

NASA Astrophysics Data System (ADS)

In large gradual solar energetic particle (SEP) events, energetic protons greatly amplify ambient upstream Alfvén 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 Alfvén 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 Alfvén 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.

Ng, C. K.

2014-05-01

158

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

Microsoft Academic Search

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

Michael Ray Shust

1998-01-01

159

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

PubMed

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 ?s 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

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

2014-11-01

160

Wind speed and velocity at three Estonian coastal stations 1969–1992  

Microsoft Academic Search

Wind climate, based on monthly average values of wind parameters during a 24-year period, is analysed for three data sets - two from surface recordings at meteorological stations and one from aerological measurements at 850 hPa level. Several statistically significant trends in wind properties have been detected in January, March, May and November. It is shown that the average air

Sirje Keevallik

2008-01-01

161

An Analysis of a Turbo-Fan Used to Improve the Velocity Distribution in a Low Speed Wind-Tunnel  

E-print Network

J ? U dr d(nit) VF + P -e 27f dr & r d. 0 -ff Where: R U e = ? ? J J U c 0 dr d(&t). b J' 2Tr 2 a D o -n' Therefore the pressure drop, due to viscosity, across the device will be calculated for the case where the disturbance velocities are zero...AN ANALYSIS OF A TURBO-FAN USED TO IMPROVE THE VELOCITY DISTRIBUTION IN A LOW SPEED WIND-TUNNEL A Thesis OTIS DEAN WELLS Submitted to the Graduate School of the Agricultural arid Mechanical College of Texas in partial fulfillment...

Wells, Otis Dean

1960-01-01

162

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

163

Vibratory hub load data reduction and analysis from the reverse velocity rotor wind tunnel test, phase 2B  

NASA Technical Reports Server (NTRS)

The vibratory hub loads data analysis from the reverse velocity rotor wind tunnel test is reported. Vibratory loads were obtained from the rotating hub balance and also by synthesis of generalized coordinates from the blade flap bending moments. Load trends were defined as a function of speed, rotor thrust and 2 per rev cyclic from each of the data methods. These trends were compared to determine the degree of agreement between each method and provide substantiation for the generalized coordinate approach.

Taylor, R. B.

1976-01-01

164

Theoretical relationship between maximum value of the post-sunset drift velocity and peak-to-valley ratio of anomaly TEC  

Microsoft Academic Search

Theoretical study of electron density distribution in the nighttime equatorial ionosphere shows that linear relationships with statistically significant correlation coefficients exist between the maximum value of the post-sunset plasma drift velocity and the peak-to-valley ratio of anomaly TEC. The study is based on the low-latitude density model of Air Force Research Laboratory (AFRL) and the obtained relationships are valid for

B. Basu; J. M. Retterer; O. de La Beaujardière; C. E. Valladares; E. Kudeki

2004-01-01

165

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

PubMed

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

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

2008-01-15

166

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

E-print Network

compresses as it drifts in the focusing section. The beam current can increase by more than a factor of 100 that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may

Kaganovich, Igor

167

Seed terminal velocity, wind turbulence, and demography drive the spread of an invasive tree in an analytical model.  

PubMed

Little is known about the relative importance of mechanistic drivers of plant spread, particularly when long-distance dispersal (LDD) events occur. Most methods to date approach LDD phenomenologically, and all mechanistic models, with one exception, have been implemented through simulation. Furthermore, the few recent mechanistically derived spread models have examined the relative role of different dispersal parameters using simulations, and a formal analytical approach has not yet been implemented. Here we incorporate an analytical mechanistic wind dispersal model (WALD) into a demographic matrix model within an analytical integrodifference equation spread model. We carry out analytical perturbation analysis on the combined model to determine the relative effects of dispersal and demographic traits and wind statistics on the spread of an invasive tree. Models are parameterized using data collected in situ and tested using independent data on historical spread. Predicted spread rates and direction match well the two historical phases of observed spread. Seed terminal velocity has the greatest potential influence on spread rate, and three wind properties (turbulence coefficient, mean horizontal wind speed, and standard deviation of vertical wind speed) are also important. Fecundity has marginal importance for spread rate, but juvenile survival and establishment are consistently important. This coupled empirical/theoretical framework enables prediction of plant spread rate and direction using fundamental dispersal and demographic parameters and identifies the traits and environmental conditions that facilitate spread. The development of an analytical perturbation analysis for a mechanistic spread model will enable multispecies comparative studies to be easily implemented in the future. PMID:22624318

Caplat, Paul; Nathan, Ran; Buckley, Yvonne M

2012-02-01

168

Spectral Analysis of the U Component of Wind Velocity at Three Meters  

Microsoft Academic Search

A broad-band spectral analysis has been carried out for 54 ten-minute observations of the u component of wind speed at a height three meters. The observations were made with mean wind speeds ranging from 2 to 9 m per sec and under all solar heating conditions. The data were taken on a flat grassland in Nebraska. The method of analysis

Robert P. Ely Jr.

1958-01-01

169

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...

170

THE WET BONDING FORCES IN SOILS AND THEIR EFFECT ON THRESHOLD FRICTION VELOCITY OF WIND EROSION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Wind erosion is a widespread process in the arid and semi arid regions of the world with implications on regional climate and desertification. The erosion process occurs when the wind speed exceeds a certain threshold value, which depends on a number of factors including surface soil moisture. Arid ...

171

Numerical simulation of stably stratified turbulent flows over an urban surface: Spectra and scales and parameterization of temperature and wind-velocity profiles  

NASA Astrophysics Data System (ADS)

Stably stratified turbulent flows over surfaces with explicit roughness elements have been calculated using an LES model. The results of calculations for different height distributions of external dynamic forcing are compared and discussed. The spatial spectra and cospectra of turbulent wind-velocity fluctuations have been calculated and different methods of normalizing them have been studied. A parameterization allowing mean wind-velocity and temperature profiles to be approximated has been proposed for turbulence scale.

Glazunov, A. V.

2014-07-01

172

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

SciTech Connect

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.

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

2012-06-21

173

Comparison of microburst-wind loads on low-rise structures of various geometric shapes  

E-print Network

on the ground resulting in a divergent outburst wind with the radial extent being less than 4.0 km (Fujita, 1985). This damaging outburst wind can sometimes reach up to 168 mph (NOAA Website, 2010) with the maximum velocity

Hu, Hui

174

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

NASA Astrophysics Data System (ADS)

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

Suzuki, H.; Hasegawa, Y.

2015-02-01

175

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

Microsoft Academic Search

A kinetic theory for the velocity distribution of solar wind electrons which illustrates the global and local properties of the solar wind expansion is proposed. By means of the Boltzmann equation with the Krook collision operator accounting for Coulomb collisions, it is found that Coulomb collisions determine the population and shape of the electron distribution function in both the thermal

J. D. Scudder; Stanislaw Olbert

1979-01-01

176

Plasma velocities in the Heliosheath and the influence of the interstellar wind  

E-print Network

A new coordinate system (Interstellar Heliospheric Coordinates, or IHC) is introduced to enable the detailed study of the influence of the interstellar wind on the heliosheath. Recent, in situ measurements of plasma ...

Chronopoulos, Chris

2009-01-01

177

Vector Wind Velocity, Speed, and Mode Summaries for the Southeastern U. S.  

SciTech Connect

This report presents wind speed and direction summaries for a wide area of the Southeastern United States (including EPA Region 4) and portions of the Ohio and Mississippi River Valleys in a monthly time series format that is further broken down for eight hours of the day (01:00, 04:00, 07:00, 10:00, 13:00, 16:00, 19:00, 22:00 EST). The data used for these summaries were obtained from the International Station MeteorologicalClimate Summary (FCCA, 1996), a publicly available source of tabular data from weather stations around the world distributed through the National Climatic Data Center. The advantage of examining the data in the form presented in this report is that it is far easier to examine and understand regional and diurnal weather patterns than would be possible with the tabular data in its original format. The winds presented here can be viewed online in any of three formats through an Internet link. The first format is the traditional wind rose as used in our earlier reports f or 13 stations in the Southeast, c.f., Weber, Buckley, and Parker 2002 and Weber, Buckley, and Kurzeja 2003. The second format is the mode, or most frequent wind direction sector from the wind rose plots (i.e., the longest ''petal'' from the individual station roses). Finally, the third format depicted is the average wind vector. The average wind vector was determined by extracting the wind speed and direction for each of the 16 sectors from a station's wind record and then summing components of these vectors for the month and time of observation. Each station was then plotted on a sequence of maps for the Southeastern U.S. using ArcView software. These maps form a time series in 3-hour increments showing changes in vector wind speed and direction for each month of the year. The complete set of color figures are too numerous to be included in this report, but may be accessed by contacting one of the authors.

WEBER, ALLENH.

2004-08-18

178

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

PubMed

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

Faganello, M; Califano, F; Pegoraro, F

2008-01-11

179

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

SciTech Connect

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.

Faganello, M.; Califano, F.; Pegoraro, F. [Physics Department, University of Pisa, Pisa (Italy)

2008-01-11

180

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

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

181

A New Atmospheric Neutral Analyzer Instrument for Thermospheric Composition, Density and Wind Velocity Measurements on the ISWEAT Micro-Satellite  

NASA Astrophysics Data System (ADS)

We present the concept of a new atmospheric neutral analyzer (ANA) instrument and its unique capability to measure thermospheric composition, density and wind velocity, and the proposed Ionospheric Space Weather Effects in the Auroral Thermosphere (ISWEAT) micro-satellite. Using the 'Quicksat' micro-satellite bus, the ISWEAT will carry ANA as well as a dual-frequency GPS receiver (DGR) and a fluxgate magnetometer (FMG) to study the effects of magnetic storms and substorms on the thermosphere. ANA will combine the techniques of radio-frequency ion mass spectrometry and CCD-based low-energy ion velocity imaging, respectively, to measure mass- resolved 2-dimensional velocity distribution functions of atmospheric neutral species, including their 'non-thermal' components ('high-energy tails'). The DGR will measure the satellite position and velocity to cm and cm/s precision, respectively, as well as the large-scale ionospheric total electron contents (TEC), while FMG will measure magnetic field perturbations due to field-aligned current structures. The primary objective of ISWEAT is to use these measurements to study the effects of thermospheric expansion and associated ionospheric changes on 'anomalous' satellite drags at auroral latitudes during magnetic storms and substorms. Results of our mission concept study will be presented.

Yau, A. W.; Langley, R. B.; Noel, J.; Wallis, D. D.; Harrison, P.; Lunscher, W.

2008-12-01

182

Terminal Velocities of Wolf-Rayet Winds from Infrared Hei Lines  

Microsoft Academic Search

We have observed 1- and 2- im spectra covering the He i 2s-2p triplet and singlet lines in a sample of Wolf-Rayet stars. Most of the He ilines have P Cygni profiles, which are fitted using the SEI (Sobolev with exact integration) method to derive terminal velocities. From our observations of 41 stars, the He i velocities are only about

P. R. J. Eenens; P. M. Williams

1994-01-01

183

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

184

Threshold wind velocity for particle entrainment at sub-atmospheric pressures as on the planet Mars  

Microsoft Academic Search

Low pressure wind tunnel data on particle entrainment were compared with predictions of two entrainment models in an attempt to improve the predictive capability for conditions near the Martian surface, where atmospheric pressure is 100-200 times lower than on earth. Fletcher's (1976) correlation model concerned the erosion of granular materials by atmospheric flows. Phillip's (1980) force balance model defined a

M. Phillips

1984-01-01

185

Nanogenerator as an active sensor for vortex capture and ambient wind-velocity detection  

E-print Network

maintainability, high system cost and risk of environment pollution, are important issues.1­3 Thus, a battery and mechanical (wind, water flow, vibration, friction and body movement) energies are common in the ambient is a potential solution for the independent, sustainable and wireless operation of self-powered wireless sensor

Wang, Zhong L.

186

Maximum Power Extraction from a Small Wind Turbine Emulator using a DC - DC Converter Controlled by a Microcontroller  

Microsoft Academic Search

An isolated small wind turbine emulator based on a separately excited DC motor is developed to emulate and evaluate the performance of a small wind turbine using different control strategies. The test rig consists of a 3HP separately excited DC motor coupled to a synchronous generator. A dump load is connected to the generator through a buck-boost converter controlled by

M. T. Iqbal; J. E. Quaicoe

2006-01-01

187

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

188

On the relationship of the 27-day variations of the solar wind velocity and galactic cosmic ray intensity in minimum epoch of solar activity  

E-print Network

We study the relationship of the 27-day variation of the galactic cosmic ray intensity with similar changes of the solar wind velocity and the interplanetary magnetic field based on the experimental data for the Bartels rotation period 2379 of 23 November 2007-19 December 2007. We develop a three dimensional (3-D) model of the 27-day variation of galactic cosmic ray intensity based on the heliolongitudinally dependent solar wind velocity. A consistent, divergence-free interplanetary magnetic field is derived by solving Maxwells equations with a heliolongitudinally dependent 27-day variation of the solar wind velocity reproducing in situ observations. We consider two types of 3-D models of the 27-day variation of galactic cosmic ray intensity - (1) with a plane heliospheric neutral sheet, and (2)- with the sector structure of the interplanetary magnetic field. The theoretical calculation shows that the sector structure does not influence significantly on the 27-day variation of galactic cosmic ray intensity as...

Alania, M V; Wawrzynczak, A

2015-01-01

189

Mitigation of Low-velocity, Wind-induced Vibration of an Architectural Spire  

Microsoft Academic Search

\\u000a This paper presents the results of analytical and experimental studies conducted on an architectural spire, which experienced\\u000a wind-induced vibrations shortly after its construction. The circular spire is attached to the corner of a 30-story building\\u000a along the upper ten stories then cantilevers up for 21.44 m (70.33 ft) with a pipe cross-section of 0.508 m (20 in)-diameter\\u000a for the first

Omer F. Tigli; Luca Caracoglia

190

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

PubMed

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

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

2011-02-20

191

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)

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.

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

1995-01-01

192

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

E-print Network

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

C. H. Chen; M. Jura

2002-09-04

193

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

194

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

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

195

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

196

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

197

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

198

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)

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.

Holzhauser, Curt A; Bray, Richard S

1956-01-01

199

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)

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.

Pierson, W. J.

1982-01-01

200

The effect of the wind speed velocity on the stack pressure in medium-rise buildings in cold region of China  

Microsoft Academic Search

This paper presents the numerical simulation results of the stack effect in medium-rise buildings in Harbin, a typical city in the severe cold region of China. The simulation was carried out using the multizone ventilation model COMIS. The effect of the wind speed velocity and the temperature of the stairwell on the pressure difference curves shape have been investigated. The

Maatouk Khoukhi; Hiroshi Yoshino; Jing Liu

2007-01-01

201

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

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

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

2012-01-01

202

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)

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.

Kimball, G., Jr.

1980-01-01

203

Comparing solar wind velocity measurements derived from Sun-grazing Comet Lovejoy (C/2011 W3) as observed from multiple locations  

NASA Astrophysics Data System (ADS)

Comets' plasma (type I) tails have been studied as natural probes of the solar wind since the mid-20th century. Local solar wind conditions directly control 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. The technique employed in this study was established by analysing geocentric amateur observations of comets C/2001 Q4 (NEAT) and C/2004 Q2 (Machholz). These amateur images, obtained with modern equipment and sensors, are arguably better in quality than 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 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 comet Lovejoy (C/2011 W3) from the 14th - 19th December 2011 using recent images from the SECCHI and LASCO heliospheric imagers and coronagraphs aboard STEREO A and B, and SOHO. Comet Lovejoy was a very bright sungrazer, which plunged into the solar corona and largely survived its perihelion (1.19 solar radii) on 16th December at 00:17 UT. Lovejoy, an exception amongst sungrazers, displayed a prominent plasma tail pre-perihelion and post-perihelion, as it probed the solar atmosphere. Overlapping observation sessions from the three spacecraft provided the perfect opportunity to use comet Lovejoy as a diagnostic tool to understand solar wind variability close to the Sun. We plan to compare our observations to results of suitable simulations of plasma conditions in the corona and inner heliosphere during the time of Lovejoy's 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 non-radial contributions to the measured solar wind velocities via this study.

Ramanjooloo, Yudish; Jones, Geraint H.; Coates, Andrew J.; Owens, Mathew J.; Battams, Karl

2013-04-01

204

The record of temperature, wind velocity and air humidity in the ? D and ? 18O of water inclusions in synthetic and Messinian halites  

NASA Astrophysics Data System (ADS)

Deuterium and oxygen isotope fractionations between liquid and vapor water were experimentally-determined during evaporation of a NaCl solution (35 g L -1) as a function of water temperature and wind velocity. In the case of a null wind velocity, slopes of ? D-? 18O trajectories of residual waters hyperbolically decrease with increasing water temperatures in the range 23-47 °C. For wind velocities ranging from 0.8 to 2.2 m s -1, slopes of the ? D-? 18O trajectories linearly increase with increasing wind velocity at a given water temperature. These experimental results can be modeled by using Rayleigh distillation equations taking into account wind-related kinetics effects. Deuterium and oxygen isotope compositions of water inclusions trapped by the precipitated halite crystals were determined by micro-equilibration techniques. These isotopic compositions accurately reflect those of the surrounding residual waters during halite growth. Isotopic compositions of water inclusions in twenty natural halites from the Messinian Realmonte mine in Sicily suggest precipitation temperatures of 34-4+10°C that match the homogenization temperatures obtained by microthermometry (median = 34 ± 5 °C). The similarity between the measured and experimental slopes of the ? D-? 18O evaporation trajectories suggests that the effect of wind was negligible during the genesis of these halite deposits. Hydrogen and oxygen isotope compositions of water inclusions from Realmonte halite also define a linear trend whose extrapolation until intersection with the Mediterranean Meteoric Water Line allows the characterization of the water source with ? D and ? 18O values of -70 ± 10‰ and -11.5 ± 1.5‰, respectively. These results reveal that the huge amounts of salts deposited in Sicily result from the evaporation of seawater mixed with a dominant fraction (?50%) of meteoric waters most likely deriving from alpine fluvial discharge.

Rigaudier, Thomas; Lécuyer, Christophe; Gardien, Véronique; Suc, Jean-Pierre; Martineau, François

2011-08-01

205

Sedimentation modified by wind induced resuspension in a shallow tropical lagoon (Cote d'Ivoire)  

Microsoft Academic Search

In shallow environments, under certain conditions of fetch, wind velocity, bathymetry and bottom characteristics, resuspension\\u000a can be generated by wind induced waves. In the tropical Ebri lagoon, austral trade winds are dominant almost all year long,\\u000a and their velocity shows a marked diel pattern with maximum speed between noon and midnight. Only austral trade winds with\\u000a a speed >3 m

Robert Arfi; Daniel Guiral; Marc Bouvy

1994-01-01

206

Wind  

NSDL National Science Digital Library

What part does the wind play in satisfying energy demands? This informational piece, part of a series about the future of energy, introduces students to wind as an energy source. Here students read about the history, uses, and efficiency of wind power. Information is also provided about benefits, limitations, and geographical considerations of wind power in the United States. Thought-provoking questions afford students chances to reflect on what they've read about the uses of wind power. Supplemental articles and information are available from a sidebar. Three energy-related web links are also provided. Copyright 2005 Eisenhower National Clearinghouse

Iowa Public Television. Explore More Project

2004-01-01

207

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)

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.

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

2014-07-01

208

Coronal holes as sources of solar wind  

Microsoft Academic Search

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

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

1976-01-01

209

Some preliminary results on the performance of a small vertical-axis cylindrical wind turbine  

Microsoft Academic Search

The performance of a newly developed small vertical-axis wind turbine with two sail blades is described. The model design is explained, and the effect of wind velocity and various blade angle settings on the power coefficient is studied. Maximum power coefficients for various conditions are plotted. Although the maximum efficiency of the model is only about 7%, it is suggested

G. Ahmadi

1978-01-01

210

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)

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.

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

2012-01-01

211

Impacts of wind velocity on sand and dust deposition during dust storm as inferred from a series of observations in the northeastern Qinghai–Tibetan Plateau, China  

Microsoft Academic Search

The monthly sand and dust deposition flux and modern dust storms were monitored in the northern Qaidam Basin of the Qinghai–Tibetan Plateau. The monthly sand and dust flux varied between 0.57 and 18.12 mg cm?2 month?1 from June 2003 to April 2005, and was well correlated with the monthly extreme wind velocity (Vextr) (r2=0.60, n=23). Sand and dust was mainly deposited

Mingrui Qiang; Fahu Chen; Aifeng Zhou; Shun Xiao; Jiawu Zhang; Zhenting Wang

2007-01-01

212

A novel control of a small wind turbine driven generator based on neural networks  

Microsoft Academic Search

This paper presents a novel control strategy of turbine directly driven permanent magnet synchronous generator (PMSG) for a small wind generation system. Compared to the traditional techniques, this new method has following advantages: 1) the proposed neural networks provides a fast and accurate estimation of actual wind velocity without anemometer; 2) the maximum mechanical power of small wind turbine can

K. L. Shi; H. Li

2004-01-01

213

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)

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.

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

2010-01-01

214

Modeling and experimental study of the 27-day variation of galactic cosmic-ray intensity for a solar-wind velocity depending on heliolongitude  

E-print Network

We develop a three dimensional (3-D) model of the 27-day variation of galactic cosmic ray (GCR) intensity with a spatial variation of the solar wind velocity. A consistent, divergence-free interplanetary magnetic field is derived by solving the corresponding Maxwell equations with a variable solar wind speed, which reproduces in situ observed experimental data for the time interval to be analyzed (24 August 2007-28 February 2008). We perform model calculations for the GCR intensity using the variable solar wind and the corresponding magnetic field. Results are compatible with experimental data; the correlation coefficient between our model predictions and observed 27-day GCR variation is 0.80 0.05.

Alania, M V; Wawrzynczak, A

2015-01-01

215

Orientation Cues for High-Flying Nocturnal Insect Migrants: Do Turbulence-Induced Temperature and Velocity Fluctuations Indicate the Mean Wind Flow?  

PubMed Central

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

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

2010-01-01

216

ON THE EFFECT OF MOISTURE BONDING FORCES IN AIR-DRY SOILS ON THRESHOLD FRICTION VELOCITY OF WIND EROSION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Wind erosion is a dominant geomorphological process in arid and semi-arid regions with major impacts on regional climate and desertification. The erosion process occurs when the wind speed exceeds a certain threshold value, which depends on a number of factors including surface soil moisture. The un...

217

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. ...

218

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

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

219

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)

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.

Reginald, Nelson L.

2000-01-01

220

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)

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.

Scudder, J. D.

1978-01-01

221

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

NASA Technical Reports Server (NTRS)

A kinetic theory for the velocity distribution of solar wind electrons which illustrates the global and local properties of the solar wind expansion is proposed. By means of the Boltzmann equation with the Krook collision operator accounting for Coulomb collisions, it is found that Coulomb collisions determine the population and shape of the electron distribution function in both the thermal and suprathermal energy regimes. For suprathermal electrons, the cumulative effects of Coulomb interactions are shown to take place on the scale of the heliosphere itself, whereas the Coulomb interactions of thermal electrons occur on a local scale near the point of observation (1 AU). The bifurcation of the electron distribution between thermal and suprathermal electrons is localized to the deep solar corona (1 to 10 solar radii).

Scudder, J. D.; Olbert, S.

1979-01-01

222

The Nature of Magnetohydrodynamic Fluctuations in the Solar Wind as Determined from Four-Point Measurements of Magnetic Field and (Electron) Plasma Velocity on Cluster  

NASA Astrophysics Data System (ADS)

One of the goals of the Cluster mission is to use large spacecraft separations (? 10,000 km) to examine the three-dimensional structure of magnetohydrodynamic turbulence in the solar wind. Pioneering work using the magnetometer data has been done in recent years. Analyses have included use of k-filtering or wave telescope, and correlation techniques (e.g., see, Glassmeier et al., 2001; Sahraoui et al., 2003; Matthaeus et al., 2005). The plasma properties of these fluctuations have not been examined due primarily to the lack of four-point measurements of the plasma velocity. We have examined the possibility of using velocity moments computed from high-resolution three-dimensional distribution functions obtained during burst mode from the PEACE experiment on all four Cluster spacecraft. Preliminary analysis suggests that for fluctuations with periods below about 10 sec, spectra of Elsässer variables have spectral indices close to the Kolmogorov value of -5/3 seen in fluid turbulence and known to be characteristic of solar wind turbulence when proton velocities are used. The spectra using PEACE data compare well with spectra for the same time intervals computed using proton velocity moments from the CIS experiment on C1. For some intervals, the PEACE spectra show the presence of highly compressible waves in the Earth's foreshock with periods of ? 30 sec. We will report on progress using multi-spacecraft techniques (e.g., the wave telescope) to identify the wave modes present at times when the spacecraft are in the solar wind at separations as large as 10,000 km. Glassmeier, K. H. et al. (2001), Cluster as a wave telescope--first results from the fluxgate magnetometer, Ann. Geophys., 19, 1439-1447. Sahraoui, F. et al. (2003), Ulf wave identification in the magnetosheath: K-filtering technique applied to Cluster II data, J. Geophys. Res., 108, 1335. Matthaeus, W. H. et al. (2005), Spatial correlation of solar-wind turbulence from two-point measurements, Phys. Rev. Lett., 95.

Goldstein, M. L.; Fazakerley, A.; Narita, Y.; Parks, G.; Roberts, D. A.; Glassmeier, K.; Le, G.

2006-12-01

223

Growing Neural Gas (GNG) based Maximum Power Point Tracking for high performance VOC-FOC based wind generator system with an induction machine  

Microsoft Academic Search

This paper presents a MPPT technique for high performance wind generator with induction machine based on the Growing Neural Gas (GNG) network. Here a GNG network has been trained off-line to learn the turbine characteristic surface torque versus wind speed and machine speed, and implemented on-line so to perform the inversion of this function obtaining the wind free speed on

Maurizio Cirrincione; Marcello Pucci; Gianpaolo Vitale

2009-01-01

224

Transverse velocity measurement  

NASA Technical Reports Server (NTRS)

Carbon dioxide (CO2) laser Doppler lidar systems are employed in the remote measurement of wind velocities. The cross velocity component is measured utilizing an appropriate detector array configuration. This allows determination of the three dimensional characteristics of the wind with conventional Doppler lidar systems.

1982-01-01

225

Winds  

NSDL National Science Digital Library

In this problem-based learning (PBL) scenario, students prepare a presentation for investors showing how their fishing company has a significant advantage because it locates upwelling zones and fishing areas using TRMM (Tropical Rainfall Measuring Mission) and other satellite data. Prior to launching the PBL, students learn about wind: the topics of air pressure, coriolis effect, upwelling and the role of differential heating on the atmosphere are explored in classroom demonstrations. Materials required include a beaker, coffee grounds, drinking straw, balloon, flashlight, and turntable. The resource includes teacher background information, glossary, assessment rubric, and an appendix introducing problem-based learning.

2012-08-03

226

Wind emission of OB supergiants and the influence of clumping  

E-print Network

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

Michaela Kraus; Jiri Kubat; Jiri Krticka

2007-08-06

227

Application of US upper wind data in one design of tethered wind energy systems  

SciTech Connect

The upper atmospheric wind resource for the continental United States, Hawaii, and Alaska is assessed. The raw data were obtained from the National Center for Atmospheric Research, Boulder, Colo. The probability distributions of velocity are presented for 54 sites, and detailed calm wind analyses have been undertaken for five of these locations. On the average, the wind lulls about one day per week for a period in excess of about 30 hours. It is shown that the average power density of this wind resource can be as high as 16 kW/m/sup 2/ at northeastern US sites. This power density is at a maximum around the 300-mb pressure level.

O'Doherty, R.J.; Roberts, B.W.

1982-02-01

228

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)

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.

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

1951-01-01

229

Three-dimensional elastic lidar winds  

SciTech Connect

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 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.

Buttler, W.T.

1996-07-01

230

First simultaneous measurement of vertical air velocity, particle fall velocity, and hydrometeor sphericity in stratiform precipitation: Results from 47 MHz wind-profiling radar and 532 nm polarization lidar observations  

NASA Astrophysics Data System (ADS)

Results from simultaneous measurements of vertical air velocity (W), particle fall velocity, and hydrometeor sphericity in stratiform precipitation are reported for the first time. Cases of stratiform precipitation on 8 (case A) and 16 December 2008 (case B) observed at Sumatra, Indonesia (0.2°S, 100.32°E), are described. A 47 MHz wind-profiling radar measuredWand reflectivity-weighted particle fall velocity relative to the air (VZ) simultaneously. Upward W above ˜6.0 km altitude in case B (>0.2 m s-1) was greater than in case A (<0.1 m s-1). VZ at 300 m above the 0°C altitude in case B (1.8 m s-1) was greater than in case A (1.3 m s-1). The thickness of melting layer (ML) in case B (900 m) was greater than in case A (300 m). Because the large-sized aggregates contribute to produce greaterVZ and thicker ML, it is likely that entangled growth of dendritic crystals under the presence of significant upward Wand enhanced aggregation occurrence by the well-developed dendritic crystals produced the large-sized aggregates. Lidar measured an increase of linear depolarization ratio (?) and lidar dark band in the ML. Volume ? of raindrops was 0.08-0.10 in case B and close to zero in case A. Stronger multiple scattering in case B is likely a cause that produced the greater ?. In case B, a dip of ? was measured at the bottom of ML. The decrease of hydrometeor nonsphericity at the final stage of melting explains the dip.

Mega, Tomoaki; Yamamoto, Masayuki K.; Abo, Makoto; Shibata, Yasukuni; Hashiguchi, Hiroyuki; Nishi, Noriyuki; Shimomai, Toyoshi; Shibagaki, Yoshiaki; Yamamoto, Mamoru; Yamanaka, Manabu D.; Fukao, Shoichiro; Manik, Timbul

2012-01-01

231

VisibleWind: wind profile measurements at low altitude  

NASA Astrophysics Data System (ADS)

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.

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

2009-09-01

232

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)

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.

Moore, M. T.

1981-01-01

233

Microburst vertical wind estimation from horizontal wind measurements  

NASA Technical Reports Server (NTRS)

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.

Vicroy, Dan D.

1994-01-01

234

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

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

235

Wind Engineering  

NASA Technical Reports Server (NTRS)

Dr. Jack Cermak, Director of Fluid Dynamics and Diffusion Laboratory, developed the first wind tunnel to simulate the changing temperatures, directions and velocities of natural winds. In this work, Cermak benefited from NASA technology related to what is known as the atmospheric boundary layer (ABL).

1983-01-01

236

Predicting species' maximum dispersal distances from simple plant traits.  

PubMed

Many studies have shown plant species' dispersal distances to be strongly related to life-history traits, but how well different traits can predict dispersal distances is not yet known. We used cross-validation techniques and a global data set (576 plant species) to measure the predictive power of simple plant traits to estimate species' maximum dispersal distances. Including dispersal syndrome (wind, animal, ant, ballistic, and no special syndrome), growth form (tree, shrub, herb), seed mass, seed release height, and terminal velocity in different combinations as explanatory variables we constructed models to explain variation in measured maximum dispersal distances and evaluated their power to predict maximum dispersal distances. Predictions are more accurate, but also limited to a particular set of species, if data on more specific traits, such as terminal velocity, are available. The best model (R2 = 0.60) included dispersal syndrome, growth form, and terminal velocity as fixed effects. Reasonable predictions of maximum dispersal distance (R2 = 0.53) are also possible when using only the simplest and most commonly measured traits; dispersal syndrome and growth form together with species taxonomy data. We provide a function (dispeRsal) to be run in the software package R. This enables researchers to estimate maximum dispersal distances with confidence intervals for plant species using measured traits as predictors. Easily obtainable trait data, such as dispersal syndrome (inferred from seed morphology) and growth form, enable predictions to be made for a large number of species. PMID:24669743

Tamme, Riin; Götzenberger, Lars; Zobel, Martin; Bullock, James M; Hooftman, Danny A P; Kaasik, Ants; Pärtel, Meelis

2014-02-01

237

Generation of temperature anisotropy for alpha particle velocity distributions in solar wind at 0.3 AU: Vlasov simulations and Helios observations  

NASA Astrophysics Data System (ADS)

Solar wind "in situ" measurements from the Helios spacecraft in regions of the Heliosphere close to the Sun (˜0.3 AU), at which typical values of the proton plasma beta are observed to be lower than unity, show that the alpha particle distribution functions depart from the equilibrium Maxwellian configuration, displaying significant elongations in the direction perpendicular to the background magnetic field. In the present work, we made use of multi-ion hybrid Vlasov-Maxwell simulations to provide theoretical support and interpretation to the empirical evidences above. Our numerical results show that, at variance with the case of ?p?1 discussed in Perrone et al. (2011), for ?p=0.1 the turbulent cascade in the direction parallel to the ambient magnetic field is not efficient in transferring energy toward scales shorter than the proton inertial length. Moreover, our numerical analysis provides new insights for the theoretical interpretation of the empirical evidences obtained from the Helios spacecraft, concerning the generation of temperature anisotropy in the particle velocity distributions.

Perrone, D.; Bourouaine, S.; Valentini, F.; Marsch, E.; Veltri, P.

2014-04-01

238

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

E-print Network

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

Claudin, P; Andreotti, B

2012-01-01

239

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

E-print Network

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

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

2013-02-11

240

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

SciTech Connect

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.

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

1981-04-01

241

Relative Velocity and Vectors  

NSDL National Science Digital Library

This activity is designed to enhance student comprehension of air and wind velocity, through the use of real time flight data. Students will read about relative velocity, complete a work sheet on vectors, and then gather and analyze real world data. All of the materials, including links to sites for data collection, are provided in this learning object. After completing the activity, students will be able to define relative velocity, add and subtract vectors, and determine aircraft speed using raw data.

Weaver, David

242

Severe Convective Wind Environments  

Microsoft Academic Search

Nontornadic thunderstorm winds from long-lived, widespread convective windstorms can have a tremen- dous impact on human lives and property. To examine environments that support damaging wind producing convection, sounding parameters from Rapid Update Cycle model analyses (at 3-hourly intervals) from 2003 were compared with 7055 reports of damaging winds and 377 081 occurrences of lightning. Ground- relative wind velocity was

Evan L. Kuchera; Matthew D. Parker

2006-01-01

243

Calculation of wind speeds required to damage or destroy buildings  

NASA Astrophysics Data System (ADS)

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].

Liu, Henry

244

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)

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.

Pierson, W. J., Jr.

1984-01-01

245

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)

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

Kelley, Mark W; Tolhurst, William H JR

1955-01-01

246

Wind tunnel investigation on wind turbine wakes and wind farms  

NASA Astrophysics Data System (ADS)

The interaction between atmospheric boundary layer and wind farms leads to flow modifications, which need to be deeply characterized in order to relate them to wind farm performance. The wake flow produced from a wind farm is the result of a strong interaction between multiple turbine wakes, so that the wind farm configuration turns out to be one of the dominant features to enhance power production. For the present work a wind tunnel investigation was carried out with hot-wire anemometry and velocity measurements performed with multi-hole pressure probes. The tested wind farms consist of miniature three-bladed wind turbine models. Preliminarily, the wake flow generated from a single wind turbine is surveyed, which is characterized by a strong velocity defect lying in proximity of the wind turbine hub height. The wake gradually recovers by moving downstream; the characteristics of the incoming boundary layer and wind turbulence intensity can strongly affect the wake recovery, and thus performance of following wind turbines. An increased turbulence level is typically detected downstream of each wind turbine for heights comparable to the wind turbine blade top-tip. These wake flow fluctuations produce increased fatigue loads on the following wind turbines within a wind farm, which could represent a significant hazard for real wind turbines. Dynamics of vorticity structures present in wind turbine wakes are also investigated; particular attention is paid to the downstream evolution of the tip helicoidal vortices and to oscillations of the hub vortex. The effect of wind farm layout on power production is deeply investigated. Particular emphasis is placed on studying how the flow adjusts as it moves inside the wind farm and can affect the power production. Aligned and staggered wind farm configurations are analysed, also with varying separation distances in the streamwise and spanwise directions. The present experimental results are being used to test and guide the development of improved parameterizations of wind turbines in high-resolution numerical models, such as large-eddy simulations (LES).

Iungo, G. V.; Coëffé, J.; Porté-Agel, F.

2012-04-01

247

Fuzzy regulator design for wind turbine yaw control.  

PubMed

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

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

2014-01-01

248

Quantitative analysis of a wind energy conversion model  

NASA Astrophysics Data System (ADS)

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.

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

2015-03-01

249

Fuzzy Regulator Design for Wind Turbine Yaw Control  

PubMed Central

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

Koulouras, Grigorios

2014-01-01

250

Physical Conditions and Velocity Structures in the Red Giant Winds in the Binaries CI CYG and EG and -- Repeat for HOPR#67  

Microsoft Academic Search

This proposal represents a two pronged attack aimed at understanding the detailed chracteristics of red giant winds in binary star systems. Red giant winds can provide the most massive, sustained form of mass transfer in binaries. The symbiotic and related stars, which contain red giant and hot companion stars, permit line of sight studies through a range of red giant

Kenneth Carpenter

1991-01-01

251

Helium, hydrogen, and oxygen velocities observed on isee-3  

Microsoft Academic Search

The velocities of hydrogen, helium, and oxygen ions over a full range of solar wind conditions were recorded by the ion composition instrument and Los Alamos National Laboratory plasma instrument aboard the International Sun Earth Explorer. Interspecie velocity differences were observed frequently. For solar wind velocities between 300 and 400 km s(-1) the helium velocity exceeded the hydrogen velocity by

K. W. Ogilvie; M. A. Coplan; R. D. Zwickl

1982-01-01

252

Maximum Likelihood  

NSDL National Science Digital Library

This material introduces the basic theory of maximum likelihood estimation by discussing the likelihood function, the log likelihood function, and maximizing these functions using calculus. Several exercises ask students to derive certain estimators, while others have students compare the behavior of those estimators with other possibilities through the use of various JAVA applets. The applets use the same control features: the sliders set the parameter values, the Â?Stop #Â? drop down menu sets the number of samples taken, the Â?Update #Â? drop down menu sets how often the graph and tables update during the experiment, the single arrow takes one sample, the double arrow runs the full experiment, the square stops the experiment, and the back arrow resets the applet. This page is one lesson from the Virtual Laboratories in Statistics.

Siegrist, Kyle

253

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

NASA Astrophysics Data System (ADS)

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.

Emre Yilmaz, Ali; Meyers, Johan

2014-06-01

254

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

NASA Astrophysics Data System (ADS)

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.

Valerio Iungo, Giacomo; Porté-Agel, Fernando

2014-05-01

255

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

SciTech Connect

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

Zrnic, D.; Istok, M.

1980-12-01

256

Upstream proton cyclotron waves at Venus near solar maximum  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

257

Design criteria for small wind turbines. Part 2: Wind characterizing  

Microsoft Academic Search

A calculation model to determine turbulent wind velocity and Wind Direction Fluctuations (WDFs) on a rotating wind turbine rotor was developed to draw up simply applicable and rotor type differentiated design criteria. Using statistical methods, fatiguing and extreme wind gusts as well as turbulent WDFs were constructed and determined as dependent upon criteria chosen (exceed chances). Interstationary (mesoscale) WDFs expected

G. L. H. Beugeling; P. E. J. Vermeulen

1985-01-01

258

Energy from the Wind  

ERIC Educational Resources Information Center

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)

Pelka, David G.; And Others

1978-01-01

259

Wind Shear Distributions Related  

E-print Network

for Translational Dynamics! Earth-relative velocity in earth-fixed polar coordinates:! v E = [V E g x] T! Earth-relative velocity in aircraft-fixed polar coordinates (zero wind):! v E = [V E b E a E] T! Body-frame air-mass-relative velocity:

Robert Stengel; Wind Rotors; Wake Vortices; Wake Vortices

260

Orientation Cues for High-Flying Nocturnal Insect Migrants: Do Turbulence-Induced Temperature and Velocity Fluctuations Indicate the Mean Wind Flow?  

Microsoft Academic Search

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

Andy M. Reynolds; Don R. Reynolds; Alan D. Smith; Jason W. Chapman; Alexander Borst

2010-01-01

261

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  

Microsoft Academic Search

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.

J. D. Scudder

1978-01-01

262

Describing Velocity  

NSDL National Science Digital Library

Learn to connect position-time and velocity-time graphs. Explore velocity using an animated car icon connected to either a position-time or a velocity-time graph, or both. Then investigate other motion graphs. Describing Velocity is the fourth of five SmartGraphs activities designed for a typical physical science unit of study on the motion of objects.

The Concord Consortium

2012-02-07

263

Efficient Low-Speed Flight in a Wind Field  

NASA Technical Reports Server (NTRS)

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.

Feldman, Michael A.

1996-01-01

264

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

265

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

266

Measurement procedures for characterization of wind turbine wakes with scanning Doppler wind LiDARs  

NASA Astrophysics Data System (ADS)

The wake flow produced from an Enercon E-70 wind turbine is investigated through three scanning Doppler wind LiDARs. One LiDAR is deployed upwind to characterize the incoming wind, while the other two LiDARs are located downstream to carry out wake measurements. The main challenge in performing 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 the LiDAR measurement volume and wake location, different measuring techniques 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. The characterization of the wake recovery along the downwind direction is performed. Moreover, wake turbulence peaks are detected at turbine top-tip height, which can represent increased fatigue loads for downstream wind turbines within a wind farm.

Iungo, G. V.; Porté-Agel, F.

2013-05-01

267

Wind turbine  

DOEpatents

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.

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

1982-01-01

268

From dust devil to sustainable swirling wind energy.  

PubMed

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

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

2015-01-01

269

From Dust Devil to Sustainable Swirling Wind Energy  

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

270

From Dust Devil to Sustainable Swirling Wind Energy  

PubMed Central

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

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

2015-01-01

271

The characteristics of near-surface velocity during the upwelling season on the northern Portugal shelf  

NASA Astrophysics Data System (ADS)

Observations made on the northern Portugal mid-shelf between May 13 and June 15, 2002 were used to characterise the near-surface velocity during one upwelling season. It was found that in the surface mixed layer, the ‘tidal current’ was diurnal, but the tidal elevation was semi-diurnal. Both the residual current and the major axes of all tidal constituents were nearly perpendicular to the isobaths and the tidal current ellipses rotated clockwise; the major axis of the major tidal ellipse was about 3 cm s-1. The extremely strong diurnal current in the surface layer was probably due to diurnal heating, cooling, and wind mixing that induced diurnal oscillations, including the diurnal oscillation of wind stress. The near-inertial spectral peaks occurred with periods ranging from 1047 min to 1170 min, the longest periods being observed in deeper layers, and the shortest in the surface layer. Weak inertial events appeared during strong upwelling events, while strong inertial events appeared during downwelling or weak subinertial events. The near-inertial currents were out of phase between 5 m and 35 m layers for almost the entire measurement period, but such relationship was very weak during periods of irregular weak wind. Strong persistent southerly wind blew from May 12 to 17 and forced a significant water transport onshore and established a strong barotropic poleward jet with a surface speed exceeding 20 cm s-1. The subinertial current was related to wind variation, especially in the middle layers of 15 m and 35 m, the maximum correlation between alongshore current and alongshore wind was about 0.5 at the 5 m layer and 0.8 at the 35 m layer. The strongest correlation was found at a time lag of 20h in the upper layer and of 30h in the deeper layer. The wind-driven surface velocity obtained from the PWP model had maximum amplitude of about 7 cm s-1, corresponding to a wind stress at 0.1 Pa, and the horizontal velocity shear due to thermal wind balance had the order of 3 cm s-1. So the local wind and thermal wind would only explain a part of the strong surface velocity variations.

Zuo, Juncheng; Du, Ling; Peliz, Alvaro; Miguel Santos, A.; Yu, Yifa

2007-07-01

272

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)

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

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

2014-12-01

273

An entropy-based surface velocity method for estuarine discharge measurement  

NASA Astrophysics Data System (ADS)

An entropy-based method is developed to estimate estuarine river discharge from surface velocity measurements. A two-dimensional velocity profile based on the principle of maximum entropy is employed to express the mean velocity as a function of average surface velocity. The entropy-based flow profile is parameterized by the location of maximum velocity in the channel and the shape of the velocity distribution. The entropy parameters are quantified over the tidal cycle to account for the unsteady nature of estuarine flow. The method was tested using experiments conducted at the Danshui River, the largest estuarine system in Taiwan. Surface velocities were measured using an Automated River-Estuary Discharge Imaging System (AREDIS), and full-channel velocity profiles were measured with a moving-boat ADP survey. Entropy parameters were calibrated over the tidal cycle and linearly correlated with the average surface velocity to facilitate estimation from AREDIS measurements. The discharge calculated from average surface velocity and entropy relationships exhibits a 7.7% relative error compared to the ADP velocity profiles. The error nearly doubles when the mean values for entropy parameters are used instead of the variable parameters, indicating the importance of accounting for the unsteady nature of estuarine flows. Furthermore, the effects of measurement coverage area, types of entropy distribution, and wind-induced drift current on the surface velocity-based discharge measurement are evaluated and discussed. Overall, surface velocity measurements in conjunction with the entropy profiles well represent the flow in a complex estuarine environment to provide a reliable estimate of discharge.

Bechle, Adam J.; Wu, Chin H.

2014-07-01

274

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

275

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

SciTech Connect

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.

Feibelman, W.A.; Bruhweiler, F.C. (NASA, Goddard Space Flight Center, Greenbelt, MD (USA) Catholic Univ. of America, Washington, DC (USA))

1989-12-01

276

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)

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.

Feibelman, Walter A.; Bruhweiler, Frederick C.

1989-01-01

277

The effects of solar wind velocity distributions on the refilling of the lunar wake: ARTEMIS observations and comparisons to one-dimensional theory  

NASA Astrophysics Data System (ADS)

The lunar plasma wake refills from all directions, with processes operating both parallel and perpendicular to the magnetic field. The resulting wake structure depends sensitively on the properties of the flowing plasma, including the form of the ion and electron velocity distributions. In this manuscript, we discuss theoretical approximations for the refilling of the lunar wake along the magnetic field. While an often-used treatment for the parallel refilling assumes cold ions, one can derive solutions for arbitrary ion velocity distributions. Similarly, though the most tractable theory utilizes Maxwellian electrons, one can derive solutions for other types of distributions. We discuss the theoretical framework for various one-dimensional solutions, spanning the full range from cold-ion theories to gas-dynamic solutions, and utilizing both Maxwellian and kappa electron distributions. We compare these solutions to ARTEMIS observations of the lunar wake, for time periods with appropriate plasma parameters. We also present cases that reveal the inherent limitations of one-dimensional approximations, including those related to electron anisotropies and those related to perpendicular processes associated with both fluid flow and ion gyro-motion.

Halekas, J. S.; Poppe, A. R.; McFadden, J. P.

2014-07-01

278

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

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

279

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

PubMed Central

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

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

2014-01-01

280

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

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

281

Solar wind eddies and the heliospheric current sheet  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

282

Discontinuities in the solar wind  

Microsoft Academic Search

The nonuniform emission of the solar wind from the sun means that conditions are established which favor the development of discontinuities in the plasma parameters. Since the solar wind is in rapid proper motion with respect to the sun and the earth, examination of these discontinuities requires that the wind velocity be transformed away. Then it is found that they

D. S. Colburn; C. P. Sonett

1966-01-01

283

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 ...

284

CAT LIDAR wind shear studies  

NASA Technical Reports Server (NTRS)

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.

Goff, R. W.

1978-01-01

285

Ion wind drag reduction  

NASA Technical Reports Server (NTRS)

In order to study the effect of ion wind on viscous drag, the equations of electrogasdynamics are solved numerically assuming the flow is incompressible, the electric field is steady and that the fluid velocity is negligible compared to ion drift velocity. The results obtained to date in a continuing theoretical and experimental research program are presented.

Malik, M. R.; Weinstein, L. M.; Hussaini, M. Y.

1983-01-01

286

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

Microsoft Academic Search

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

Leiming Zhang; Jeffrey R Brook

2001-01-01

287

Optimization of Wind Turbine Airfoils/Blades and Wind Farm Layouts  

NASA Astrophysics Data System (ADS)

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.)

Chen, Xiaomin

288

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

NASA Astrophysics Data System (ADS)

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.

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

2011-06-01

289

Airborne microwave radar measurements of surface velocity in a tidally-driven inlet  

NASA Astrophysics Data System (ADS)

A miniaturized dual-beam along-track interferometric (ATI) synthetic aperture radar (SAR), capable of measuring two components of surface velocity at high resolution, was operated during the 2012 Rivers and Inlets Experiment (RIVET) at the New River Inlet in North Carolina. The inlet is predominantly tidally-driven, with little upstream river discharge. Surface velocities in the inlet and nearshore region were measured during ebb and flood tides during a variety of wind and offshore wave conditions. The radar-derived surface velocities range from around ±2~m~s1 during times of maximum flow. We compare these radar-derived surface velocities with surface velocities measured with drifters. The accuracy of the radar-derived velocities is investigated, especially in areas of large velocity gradients where along-track interferometric SAR can show significant differences with surface velocity. The goal of this research is to characterize errors in along-track interferometric SAR velocity so that ATI SAR measurements can be coupled with data assimilative modeling with the goal of developing the capability to adequately constrain nearshore models using remote sensing measurements.

Farquharson, G.; Thomson, J. M.

2012-12-01

290

Wind Speed Estimation Based Sensorless Output Maximization Control for a Wind Turbine Driving a DFIG  

Microsoft Academic Search

This paper proposes a wind speed estimation based sensorless maximum wind power tracking control for variable-speed wind turbine generators (WTGs). A specific design of the proposed control algorithm for a wind turbine equipped with a doubly fed induction generator (DFIG) is presented. The aerodynamic characteristics of the wind turbine are approximated by a Gaussian radial basis function network based nonlinear

Wei Qiao; Wei Zhou; JosÉ M. Aller; Ronald G. Harley

2008-01-01

291

Maxometers (peak wind speed anemometers)  

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

292

The sun and heliosphere at solar maximum  

NASA Technical Reports Server (NTRS)

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.

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

293

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

NASA Astrophysics Data System (ADS)

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.

Zhu, Zhenduo; Zhu, Ping

2015-01-01

294

Velocity diagrams  

NASA Technical Reports Server (NTRS)

The selection and design of velocity diagrams for axial flow turbines are considered. Application is treated in two parts which includes: (1) mean-section diagrams, and (2) radial variation of diagrams. In the first part, the velocity diagrams occurring at the mean section are assumed to represent the average conditions encountered by the turbine. The different types of diagrams, their relation to stage efficiency, and their selection when staging is required are discussed. In the second part, it is shown that in certain cases the mean-section diagrams may or may not represent the average flow conditions for the entire blade span. In the case of relatively low hub- to tip-radius ratios, substantial variations in the velocity diagrams are encountered. The radial variations in flow conditions and their effect on the velocity diagrams are considered.

Whitney, W. J.; Stewart, W. L.

1972-01-01

295

SeaWinds ALGORITHM THEORETICAL BASIS DOCUMENT  

Microsoft Academic Search

Knowledge of wind velocity over the ocean is of critical importance for understanding and predicting many oceanographic, meteorological, and climate phenomena. Wind stress is the single largest source of momentum to the upper ocean, and winds drive oceanic motions on scales ranging from surface waves to basin-wide current systems. Winds over the oceans regulate the crucial coupling between the air

M. H. Freilich

296

Interferometric phase velocity measurements  

NASA Technical Reports Server (NTRS)

Phase velocities of plasma waves near the lower hybrid frequency were measured with an interferometer composed of two spatially separated electron-density probes. The plasma waves were produced in the F-region ionosphere by an argon ion beam. By calculating the normalized cross spectrum of the plasma waves a coherency of .98 was estimated along with a maximum phase difference of pi/3 radians between the two probes. This implies that the wavelength was 6 meters compared to an O(+) gyroradius of 3.8 meters, and that the phase velocity was 45 km/sec compared to an ion-beam velocity of 12.4 km/sec. These numbers compare favorably with recent predictions of a nonresonant mode produced by a dense ion beam.

Kintner, P. M.; Labelle, J.; Kelley, M. C.; Cahill, L. J., Jr.; Moore, T.; Arnoldy, R.

1984-01-01

297

A Simple Method to Predict Threshold Shear Velocity in the Field  

Microsoft Academic Search

A very important parameter in predicting wind erosion is the threshold shear velocity, which is the minimal shear velocity required to initiate deflation of soil particles. Modeling and wind tunnel are primary methods in predicting threshold shear velocity. However, most models have limited applications in the presence of roughness elements, and running a wind tunnel in the field is labor-intensive

J. Li; G. S. Okin; J. E. Herrick; M. E. Miller; S. M. Munson; J. Belnap

2009-01-01

298

Magnetically driven jets and winds: Exact solutions  

NASA Technical Reports Server (NTRS)

We present a general class of self-similar solutions of the full set of MHD equations that include matter flow, electromagnetic fields, pressure, and gravity. The solutions represent axisymmetric, time-independent, nonrelativistic, ideal, magnetohydrodynamic, collimated outflows (jet and winds) from magnetized accretion disks around compact objects. The magnetic field extracts angular momentum from the disk, accelerates the outflows perpedicular to the disk, and provides collimation at large distances. The terminal outflow velocities are of the order of or greater than the rotational velocity of the disk at the base of the flow. When a nonzero electric current flows along the jet, the outflow radius oscillates with axial distance, whereas when the total electric current is zero (with the return current flowing across the jet's cross section), the outflow radius increase to a maximum and then decreases. The method can also be applied to relativistic outflows.

Contopoulos, J.; Lovelace, R. V. E.

1994-01-01

299

Wind Tunnel Analysis of the Detachment Bubble on Bolund Island  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

300

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

301

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

SciTech Connect

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.

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

1988-04-01

302

Pickup Ion Velocity Distributions at Titan: Effects of Spatial Gradients  

NASA Technical Reports Server (NTRS)

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(sup +) ions identified during the Voyager 1 flyby. 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. Iri 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.

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

2004-01-01

303

Winds over saltcedar  

USGS Publications Warehouse

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.

Van Hylckama, T. E. A.

1970-01-01

304

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

305

Helium, hydrogen, and oxygen velocities observed on ISEE-3  

NASA Technical Reports Server (NTRS)

The velocities of hydrogen, helium, and oxygen ions over a full range of solar wind conditions were recorded by the ion composition instrument and Los Alamos National Laboratory plasma instrument aboard the International Sun Earth Explorer. Interspecie velocity differences were observed frequently. For solar wind velocities between 300 and 400 km s(-1) the helium velocity exceeded the hydrogen velocity by 5 km s(-1) the average difference was 14 km s(-1), however no evidence was found for a nonzero average velocity difference between helium and oxygen ions even at the higher velocities. Velocity differences were examined in a number of streams and across a number of interplanetary shocks. Generally helium hydrogen velocity differences are bounded by the Alfven speed. Velocity differences show abrupt changes across interplanetary discontinuities, presumably tangential. The electrostatic potential change across a shock produces differences between the velocities of ions having different charges.

Ogilvie, K. W.; Coplan, M. A.; Zwicki, R. D.

1982-01-01

306

Variable Winds and Dust Formation in R Coronae Borealis Stars  

NASA Astrophysics Data System (ADS)

We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I ?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 ~400 km s-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.

Clayton, Geoffrey C.; Geballe, T. R.; Zhang, Wanshu

2013-08-01

307

VARIABLE WINDS AND DUST FORMATION IN R CORONAE BOREALIS STARS  

SciTech Connect

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.

Clayton, Geoffrey C.; Zhang Wanshu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Geballe, T. R., E-mail: gclayton@fenway.phys.lsu.edu, E-mail: wzhan21@lsu.edu, E-mail: tgeballe@gemini.edu [Gemini Observatory, 670 N. A'ohoku Place, Hilo, HI 96720 (United States)

2013-08-01

308

Modern estimation of the parameters of the Weibull wind speed distribution for wind energy analysis  

Microsoft Academic Search

Three methods for calculating the parameters of the Weibull wind speed distribution for wind energy analysis are presented: the maximum likelihood method, the proposed modified maximum likelihood method, and the commonly used graphical method. The application of each method is demonstrated using a sample wind speed data set, and a comparison of the accuracy of each method is also performed.

J. V. Seguro; T. W. Lambert

2000-01-01

309

On the Effect of Offshore Wind Parks on Ocean Dynamics  

NASA Astrophysics Data System (ADS)

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.

Ludewig, E.; Pohlmann, T.

2012-12-01

310

Noise measurements around the Nibe (Denmark) wind turbines and the Windane 31 wind turbine  

Microsoft Academic Search

Noise around the two 640 kW wind turbines, and a 300 kW wind turbine at various distances and wind velocities was measured. The results are stated partly as the energy equivalent, A-weighted sound pressure level as a function of the wind velocity, partly as frequency analyses based on tape recordings of the A-weighted sound pressure level. A subjective evaluation of

J. Kristensen

1984-01-01

311

Harnessing Wind  

NSDL National Science Digital Library

Students are introduced to the ways that engineers study and harness the wind. They learn about the different kinds of winds and how to measure wind direction. In addition, they learn how air pressure creates winds and how engineers design and test wind turbines to harness renewable wind energy.

2014-09-18

312

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

313

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

314

Maximum modular graphs  

NASA Astrophysics Data System (ADS)

Modularity has been explored as an important quantitative metric for community and cluster detection in networks. Finding the maximum modularity of a given graph has been proven to be NP-complete and therefore, several heuristic algorithms have been proposed. We investigate the problem of finding the maximum modularity of classes of graphs that have the same number of links and/or nodes and determine analytical upper bounds. Moreover, from the set of all connected graphs with a fixed number of links and/or number of nodes, we construct graphs that can attain maximum modularity, named maximum modular graphs. The maximum modularity is shown to depend on the residue obtained when the number of links is divided by the number of communities. Two applications in transportation networks and data-centers design that can benefit of maximum modular partitioning are proposed.

Trajanovski, S.; Wang, H.; Van Mieghem, P.

2012-07-01

315

Water Velocity and Suspended Solids Measurements by In-situ Instruments in Upper Klamath Lake, Oregon  

USGS Publications Warehouse

The U. S. Geological Survey conducted hydrodynamic measurements in Upper Klamath Lake during four summer seasons (approximately mid-June to mid-September) during 2003 to 2006. Measurements included water current profiles made by acoustic Doppler current profilers at a number of fixed locations in the lake during all four years as well as from a moving boat during 2005 and 2006. Measurements of size distribution of suspended material were made at four locations in the lake during 2004-2006. Raw (unfiltered) data are presented as time series of measurements. In addition, water-velocity data have been filtered to remove wind-induced variations with periods less than thirty hours from the measurements. Bar graphs of horizontal and vertical water speed and acoustic backscatter have been generated to discern diurnal variations, especially as they relate to wind patterns over the lake. Mean speeds of the horizontal currents in the lake range between about 3.5 to 15 cm/s with the higher speeds at the deep locations in the trench on the west side of the lake. Current directions generally conform to the lake's bathymetry contours and the water circulation pattern is usually in a clockwise direction around the lake as established by the prevailing north to northwesterly surface winds in the region. Diurnal patterns in horizontal currents probably relate to diurnal wind patterns with minimum wind speeds near noon and maximum wind speeds near 2100. Diurnal variations in vertical velocities do not appear to be related to wind patterns; they do appear to be related to expected patterns of vertical migration of Aphanizomenon flos aquae, (AFA) the predominant species of blue-green algae in the lake. Similarly, diurnal variations in acoustic backscatter, especially near the lake's surface, are probably related to the vertical migration of AFA.

Gartner, Jeffrey W.; Wellman, Roy E.; Wood, Tamara M.; Cheng, Ralph T.

2007-01-01

316

Hanford Site peak gust wind speeds  

SciTech Connect

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.

Ramsdell, J.V.

1998-09-29

317

Unsteady Sand Saltation in Periodic Wind Variations  

NASA Astrophysics Data System (ADS)

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.

Wang, P.; Zheng, X. J.

2011-09-01

318

New Measurements of the Winds of Uranus  

Microsoft Academic Search

Hubble Space Telescope imaging of Uranus in 1994, 1997, 1998, and 2000 revealed 13 cloud features, allowing the first measurements of wind velocities at northern latitudes not accessible to the Voyager cameras and new measurements of southern-latitude wind velocities determined during the 1986 Voyager encounter. Images acquired with the Keck 10-meter telescope adaptive optics system in June 2000 also showed

H. B. Hammel; K. Rages; G. W. Lockwood; E. Karkoschka; I. de Pater

2001-01-01

319

Coupling a Neural Network-Based forward Model and a Bayesian Inversion Approach to Retrieve Wind Field from Spaceborne Polarimetric Radiometers  

PubMed Central

A simulation study to assess the potentiality of sea surface wind vector estimation based on the approximation of the forward model through Neural Networks and on the Bayesian theory of parameter estimation is presented. A polarimetric microwave radiometer has been considered and its observations have been simulated by means of the two scale model. To perform the simulations, the atmospheric and surface parameters have been derived from ECMWF analysis fields. To retrieve wind speed, Minimum Variance (MV) and Maximum Posterior Probability (MAP) criteria have been used while, for wind direction, a Maximum Likelihood (ML) criterion has been exploited. To minimize the cost function of MAP and ML, conventional Gradient Descent method, as well as Simulated Annealing optimization technique, have been employed. Results have shown that the standard deviation of the wind speed retrieval error is approximately 1.1 m/s for the best estimator. As for the wind direction, the standard deviation of the estimation error is less than 13° for wind speeds larger than 6 m/s. For lower wind velocities, the wind direction signal is too weak to ensure reliable retrievals. A method to deal with the non-uniqueness of the wind direction solution has been also developed. A test on a case study has yielded encouraging results.

Pulvirenti, Luca; Pierdicca, Nazzareno; Marzano, Frank S.

2008-01-01

320

Wind pressure distribution on shell structures  

E-print Network

. Hall for his aid in the testing of models; to Joseph Gray for his aid in setting up the models in the wind tunnel; to Matthew Nowak for his continuous aid in conducting the research; and to the many undergraduate students who assisted in construction... in Years X 10 4. Relationship Between Gust Factor and Five-Minute Wind Velocity . . 13 5. Relationship Between Five-Minute Wind Velocity Height and Velocity Pressure . . 15 6. Longitudinal Section Through Wind Tunnel Test Section. . . 7 . Control...

Yancey, Kenneth Earl, Jr

1963-01-01

321

The F2 wind tunnel at Fauga-Mauzac  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

322

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)

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.

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

2012-03-01

323

Estimation of Velocity Distribution and Suspended Sediment Discharge in Open Channels Using Entropy  

E-print Network

at Rosciano (Italy), (b) Velocity distribution at Santa Lucia (Italy), (c) Velocity distribution of Run A2-1 (Iran), and (d) Velocity distribution of Run B9-1 (Iran)??????????????????????? 68 Figure 5.8 Estimate of 1D velocity distribution????????????? 73... Figure 5.9 Location of maximum velocity??????????????? 75 Figure 5.10 Simulated depths of maximum velocity???????????... 77 Figure 5.11 Comparison of estimated and observed mean velocities. (a) Ponte Felcino River (Italy), (b) Santa Lucia River (Italy...

Cui, Huijuan

2011-08-08

324

1D wind model: sinusoidal piston  

E-print Network

1D wind model: sinusoidal piston For comparison, we also show a wind model with a sinusoidally moving piston and a corre­ sponding velocity amplitude of 5 km/s. This amplitude is comparable to the non­sinusoidal wind model (but with smaller temporal vari­ ations). A sinusoidal model with a piston

Freytag, Bernd

325

Stability Simulation of Wind Turbine Systems  

Microsoft Academic Search

A simulation and digital computer modeling effort is described in which a wind turbine-generator system is adapted for stability evaluation using a large scale transient stability computer program. Component models of the MOD-2 wind generator system are described and their digital model equations are provided. A versatile wind velocity model is described, which provides the capability of simulating a wide

P. M. Anderson; Anjan Bose

1983-01-01

326

Update on 1 Ori C: the Magnetically Confined Wind Shock model does a pretty good job  

E-print Network

Update on 1 Ori C: the Magnetically Confined Wind Shock model does a pretty good job David Cohen. fall-back/downflow) specific kinetic energy: shock velocity (pre-shock wind velocity) from ud-Doula et

Cohen, David

327

The Solar Wind  

NASA Technical Reports Server (NTRS)

The first evidence of the solar wind was provided through observations of comet tail deflections by L. Biermann in 1951. A cometary ion tail is oriented along the difference between the cometary and solar wind velocities, whereas the dust tail is in the antisunward direction; the ion tail directions demonstrated the existence of an outflow of ionized gas from the Sun (the solar wind) and allowed estimates of solar wind speed. Spacecraft observations have now established that at 1 AU the solar wind has a typical ion number density of about 7 /cc and is composed by number of about 95% protons and 5% Helium, with other minor ions also present. The solar wind as observed at 1 AU in the ecliptic has speeds typically in the range 300-700 km/ s. At such speeds ions travel from the Sun to 1 AU in from 2.5 to 6 days. The impact of the solar wind on planets with magnetic fields (Earth, Jupiter, Saturn, Uranus, Neptune) causes phenomena such as magnetospheres, aurorae, and geomagnetic storms, whereas at objects lacking magnetospheres (Mars, Venus, comets), atmospheric neutrals undergo charge exchange and are picked up by the solar wind flow. The solar wind also shields the Earth from low energy cosmic rays, and is responsible for the existence of the anomalous component of the cosmic rays a low energy component that is created locally rather than in the galaxy. Presented here is a brief introduction to the solar wind and a description of some current topics of research. Solar wind properties vary a great deal due to the changing magnetic structure on the Sun.

Goldstein, B. E.

1998-01-01

328

Velocity determination from velocity spectra  

E-print Network

' 1300C 14 00 I SUOX 5DQ SOQ ((CP I UI. O HEI/g ng Q T I m E. ITI 5 I'0 I'K )) tQ~P Tl fflE ITS ()l) ) -" SOD (& (U) 0GU 9 5 3 00 ~SP 3500 B ODD Sooof I ODQC flooo 12CD f 3000 1400$ I SRlG Q Figure 15. Ve1ocity spectra...; interval velocity, ft/sec h; thickness, ft d; depth from sea level, ft layer no. 12. 5 20. 5 location (89 no, ) 28. 5 39 43 52 V 1 h d V 2 h d V V 4 h d V 5 h d V 6 h d V 7 h d 6, 400 1, 312 1 &312 8, 549 898 2, 210 11, 311...

Yang, Sung Jin

1973-01-01

329

The Last Glacial Maximum  

Microsoft Academic Search

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

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

2009-01-01

330

Fast solar wind monitoring available: BMSW in operation  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

331

Fast solar wind monitoring available: BMSW in operation  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

332

Observations of sunspot umbral velocity oscillations.  

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

333

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

USGS Publications Warehouse

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.

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

2008-01-01

334

Screening length and the direction of plasma winds  

E-print Network

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

Makoto Natsuume; Takashi Okamura

2007-08-19

335

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

NASA Astrophysics Data System (ADS)

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.

Galal, Ahmed Mohamed; Kanemoto, Toshiaki

336

A new wind turbine generation system based on matrix converter  

Microsoft Academic Search

At a given wind velocity, the mechanical power available from a wind turbine is a function of its shaft speed. To maximize the power captured from the wind, the shaft speed has to be controlled. In low-cost wind energy conversion systems, the turbine shaft speed is not regulated and a squirrel-cage induction generator is used to convert the turbine mechanical

S. M. Barakati; M. Kazerani; X. Chen

2005-01-01

337

High-Resolution Optical Spectroscopy of the R Coronae Borealis Star V532 Ophiuchi at Maximum Light  

NASA Astrophysics Data System (ADS)

High-resolution optical spectra of the R Coronae Borealis (RCB) star V532 Oph at light maximum are discussed. The absolute visual magnitude MV of the star is found to be -4.9 ± 0.5. The elemental abundances suggest the star belongs to the majority class of RCB stars but is among the most O-poor of this class with mild enhancements of heavy elements Y, Zr, Ba, and La. The C2 Swan bands are weak in V532 Oph relative to R CrB. Other aspects of the high-resolution spectrum confirm that V532 Oph is representative of majority RCBs, i.e., the radial velocity is variable, circumstellar material is present, and the photosphere feeds a high-velocity stellar wind.

Kameswara Rao, N.; Lambert, David L.; Woolf, Vincent M.; Hema, B. P.

2014-10-01

338

On the formation of a fast thermospheric zonal wind at the magnetic dip equator  

NASA Astrophysics Data System (ADS)

Simulations with the NCAR Thermosphere - Ionosphere - Electrodynamics General Circulation Model (TIE-GCM) have been carried out to understand the cause of strong thermospheric zonal wind at the magnetic dip equator. The simulations show that the zonal winds blow strongly at the magnetic dip equator instead of at the geographic equator due to the latitude structure of ion drag. The fast winds at the dip equator are seen throughout the altitude between 280 km and 600 km, and the wind above 400 km is mainly accelerated via viscosity. A test simulation without viscosity verifies that the extension of the fast equatorial wind to heights above 400 km is maintained by viscous coupling with the winds at lower altitudes, in spite of there being an ion-drag maximum instead of relative minimum at the dip equator at high altitudes. Basically, viscosity is not so large compared to the pressure gradient and ion drag, but dynamics causes the pressure gradient and ion drag approximately to balance, and viscosity becomes important. The simulation results are consistent with the observations by the DE-2 and CHAMP satellites. Therefore we suggest that the zonal wind velocity in the low latitude region is controlled by ion drag and viscosity.

Kondo, T.; Richmond, A. D.; Liu, H.; Lei, J.; Watanabe, S.

2011-05-01

339

Wind and turbine characteristics needed for integration of wind turbine arrays into a utility system  

NASA Technical Reports Server (NTRS)

Wind data and wind turbine generator (WTG) performance characteristics are often available in a form inconvenient for use by utility planners and engineers. The steps used by utility planners are summarized and the type of wind and WTG data needed for integration of WTG arrays suggested. These included long term yearly velocity averages for preliminary site feasibility, hourly velocities on a 'wind season' basis for more detailed economic analysis and for reliability studies, worst-case velocity profiles for gusts, and various minute-to-hourly velocity profiles for estimating the effect of longer-term wind fluctuations on utility operations. wind turbine data needed includes electrical properties of the generator, startup and shutdown characteristics, protection characteristics, pitch control response and control strategy, and electro-mechanical model for stability analysis.

Park, G. L.

1982-01-01

340

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

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

341

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

NASA Technical Reports Server (NTRS)

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.

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

2013-01-01

342

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

343

A modification of the method of Carey and Sparks (1986) to estimate eruption column height from maximum clast dispersal  

NASA Astrophysics Data System (ADS)

The method of Carey and Sparks (1986) has been widely applied to estimate the hight of eruptive columns from the dispersal of the maximum clast size. These authors presented curves of maximum downwind range versus crosswind range for different clast diameters and wind speeds obtained from the numerical solution of a column model developed by Sparks(1986). An improved model of eruptive column was later developed by Woods (1988). In this work we present the results of the simulation of clast dispersal following the procedure of Carey and Sparks (1986) and the eruption column of Woods (1988). The numerical calculations were carried out with a code that computes the height of the column and the vertical velocity, the density and the radius along the column. The code determines then the support envelopes for a given clast size and their fall, after leaving the column, are computed from the equations of motion with viscous friction. For the same downwind and crosswind ranges, this method yields column heights about 10% smaller than the method of Carey and Sparks and about 20% higher wind velocities. The height of the crater above sea level plays also a small role in the results. We present comparisons for the 1982 eruption columns from El Chichon volcano. References Carey S and RSJ Sparks (1986) Bull. Volcanol. 48: 109-125 Sparks RSJ (1986) Bull. Volcanol. 48: 3-15 Woods AW (1988) Bull. Volcanol. 50: 169-193

Espindola, J.

2010-12-01

344

Wind noise under a pine tree canopy.  

PubMed

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

Raspet, Richard; Webster, Jeremy

2015-02-01

345

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

NASA Technical Reports Server (NTRS)

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

Withbroe, G. L.; Kohl, J. L.; Weiser, H.; Munro, R. H.

1985-01-01

346

Heating by wind  

NASA Astrophysics Data System (ADS)

The economical design of a wind power plant combined with a heat accumulator is discussed. A gliding-museum to be built on the Wasserkuppe in the Rhoen mountain is used as an example to investigate which wind power plant and storage alternative can be considered based on meteorological basic data and the heat demand required. A system optimization regarding technical and economical points is used to study the wind power plant and to indicate the best accumulator. The maximum storage time established by an economic optimization is one to two days. In this regard no difference is made between sun energy and wind energy, and the storage size can span the day/night cycle.

Auer, F.

1982-01-01

347

Wild Wind  

NSDL National Science Digital Library

Students learn the difference between global, prevailing and local winds. They make wind vanes out of paper, straws and soda bottles and use them to measure wind direction over time. They analyze their data to draw conclusions about the local prevailing winds.

2014-09-18

348

Meteorology (Wind)  

Atmospheric Science Data Center

Wind speed at 50 m (m/s) The average and percent difference minimum and ... are given.   Percent of time for ranges of wind speed at 50 m (percent) Percentage [frequency] of time that wind ... 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 ...

2014-09-25

349

WIND VARIABILITY IN BZ CAMELOPARDALIS  

SciTech Connect

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.

Honeycutt, R. K. [Astronomy Department, Indiana University, Swain Hall West, Bloomington, IN 47405 (United States); Kafka, S. [Department of Terrestrial Magnetism, Carnegie Institute of Washington, 5241 Broad Branch Road NW, Washington, DC 2001 (United States); Robertson, J. W., E-mail: honey@astro.indiana.edu, E-mail: skafka@dtm.ciw.edu, E-mail: jrobertson@atu.edu [Department of Physical Sciences, Arkansas Tech University, 1701 North Boulder Avenue, Russellville, AR 72801-2222 (United States)

2013-02-01

350

Maximum Entropy Image Reconstruction  

Microsoft Academic Search

Two-dimensional digital image reconstruction is an important imaging process in many of the physical sciences. If the data are insufficient to specify a unique reconstruction, an additional criterion must be introduced, either implicitly or explicitly before the best estimate can be computed. Here we use a principle of maximum entropy, which has proven useful in other contexts, to design a

Stephen J. Wernecke; Larry R. D'addario

1977-01-01

351

Maximum Power Point  

NSDL National Science Digital Library

Students learn how to find the maximum power point (MPP) of a photovoltaic (PV) panel in order to optimize its efficiency at creating solar power. They also learn about real-world applications and technologies that use this technique, as well as Ohm's law and the power equation, which govern a PV panel's ability to produce power.

2014-09-18

352

Benchmarking for maximum value.  

PubMed

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

Baldwin, Ed

2009-03-01

353

Maximum likelihood pitch estimation  

Microsoft Academic Search

A method for estimating the pitch period of voiced speech sounds is developed based on a maximum likelihood (ML) formulation. It is capable of resolution finer than one sampling period and is shown to perform better in the presence of noise than the cepstrum method.

J. Wise; J. Caprio; T. Parks

1976-01-01

354

Winding for the wind  

NASA Technical Reports Server (NTRS)

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.

Weingart, O.

1981-01-01

355

Winding for the wind  

NASA Astrophysics Data System (ADS)

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.

Weingart, O.

356

Stationary Plasma Thruster Ion Velocity Distribution  

NASA Technical Reports Server (NTRS)

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

Manzella, David H.

1994-01-01

357

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

NASA Astrophysics Data System (ADS)

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.

Fischer, A.; Madsen, H. A.

2014-12-01

358

Automated Analysis of Doppler Ultrasound Velocity Flow Diagrams  

Microsoft Academic Search

A highly automated method for the identification and quantization of maximum blood velocity curves from Doppler ultrasound flow diagrams is presented. The method uses an image processing scheme to analyze video-recorded image sequences of flow diagrams. The sequences are acquired, a sequence of images relating to chronological cardiac cycles is extracted, and a maximum blood velocity envelope is determined and

Juerg Tschirren; Ronald M. Lauer; Milan Sonka

2001-01-01

359

Maximum Confidence Quantum Measurements  

E-print Network

We consider the problem of discriminating between states of a specified set with maximum confidence. For a set of linearly independent states unambiguous discrimination is possible if we allow for the possibility of an inconclusive result. For linearly dependent sets an analogous measurement is one which allows us to be as confident as possible that when a given state is identified on the basis of the measurement result, it is indeed the correct state.

Sarah Croke; Erika Andersson; Stephen M. Barnett; Claire R. Gilson; John Jeffers

2006-04-05

360

Stellar Winds on the Main-Sequence I: Wind Model  

E-print Network

Aims: We develop a method for estimating the properties of stellar winds for low-mass main-sequence stars between masses of 0.4 and 1.1 solar masses at a range of distances from the star. Methods: We use 1D thermal pressure driven hydrodynamic wind models run using the Versatile Advection Code. Using in situ measurements of the solar wind, we produce models for the slow and fast components of the solar wind. We consider two radically different methods for scaling the base temperature of the wind to other stars: in Model A, we assume that wind temperatures are fundamentally linked to coronal temperatures, and in Model B, we assume that the sound speed at the base of the wind is a fixed fraction of the escape velocity. In Paper II of this series, we use observationally constrained rotational evolution models to derive wind mass loss rates. Results: Our model for the solar wind provides an excellent description of the real solar wind far from the solar surface, but is unrealistic within the solar corona. We run ...

Johnstone, C P; Lüftinger, T; Toth, G; Brott, I

2015-01-01

361

Wind fence enclosures for infrasonic wind noise reduction.  

PubMed

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

Abbott, JohnPaul; Raspet, Richard; Webster, Jeremy

2015-03-01

362

Solar wind composition  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

363

Ulysses Mission-Long Study of Radial Heliospheric Magnetic Fields in Solar Wind Rarefaction Regions  

NASA Astrophysics Data System (ADS)

We examine the distribution of directions of the heliospheric magnetic field (HMF) measured by the Ulysses spacecraft during its two and a half high-latitude orbits over the poles of the Sun (from 1992 to the end of 2007). We are looking in particular for the nearly radial field orientations that were first reported by Jones et al. [1998] and analyzed in greater detail by several subsequent authors. As they all noted, such radial fields are commonly observed in the mid-latitude region (~10°-40°), when the observed solar wind velocity shears from the high-latitude fast solar wind toward the low-latitude slow solar wind (i.e. in rarefaction regions where the solar wind velocity decreases monotonically over several days). In contrast to ICMEs where the HMF may be enhanced, the rarefaction regions with radial magnetic fields tend to have extremely low values of the HMF. Within these rarefaction regions, there are "dwells" in the coronal source longitude of the measured solar wind [Nolte and Roelof, 1973] in which the time dependence of the solar wind velocity is given to very good approximation by V(t)=r/(t-t0), where r is the radius of the spacecraft. We have therefore compiled distributions within the dwells of the parameter |Br/B| which is the cosine of the cone angle of the field from the radial direction. We study the mid-latitude transits that occurred during different phases of solar activity: 1992 (decline), 1996 (rise), 2002 (maximum), and 2005 (minimum). During three out of these four periods, the distributions of the HMF tended to be rather uniform in all HMF directions (0<|Br/B|<1), but during 2002, when the dwells were more frequent and of shorter duration, the distributions tended more strongly toward |Br/B|~1. Such distributions were observed up to very high latitudes (65°N). We discuss these observations in terms of the large-scale topology of the HMF as described by an analytic function that includes as special cases both a temporal variation in the coronal solar wind velocity [Gosling and Skoug, 2002] and a longitudinal velocity gradient at the eastern edge of a solar wind source region [Schwadron and McComas, 2005].

Lario, D.; Roelof, E. C.

2008-05-01

364

Question of the Day: Flow of Winds and Moisture  

NSDL National Science Digital Library

This activity addresses the flow of surface winds and moisture. On the figure below, draw a)direction of air flow (winds), b) locations with highest evaporation from the sea surface, and zone(s) of maximum ...

365

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

NASA Astrophysics Data System (ADS)

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

Wu, Yu-Ting; Porté-Agel, Fernando

2014-05-01

366

Solar Wind Electrons  

Microsoft Academic Search

Average characteristics of solar wind electron velocity distributions as well as the range and nature of their variations are presented. The measured distributions are generally symmetric about the heat flux direction and are adequately parameterized by the superposition of a nearly bi-Maxwellian function which characterizes the low-energy electrons and a bi-Maxwellian function which characterizes a distinct, ubiquitous component of higher-energy

W. C. Feldman; J. R. Asbridge; S. J. Bame; M. D. Montgomery; S. P. Gary

1975-01-01

367

The Solar Wind in the Outer Heliosphere at Solar John D. Richardson and Chi Wang  

E-print Network

The Solar Wind in the Outer Heliosphere at Solar Maximum John D. Richardson and Chi Wang Center solar wind observations in the outer heliosphere, concentrating on the recent data near solar maximum-absence of a latitudinal speed gradient at solar maximum allows us to measure the speed decrease of the solar wind and nd

Richardson, John

368

A wind energy analysis of Grenada: an estimation using the ‘Weibull’ density function  

Microsoft Academic Search

The Weibull density function has been used to estimate the wind energy potential in Grenada, West Indies. Based on historic recordings of mean hourly wind velocity this analysis shows the importance to incorporate the variation in wind energy potential during diurnal cycles. Wind energy assessments that are based on Weibull distribution using average daily\\/seasonal wind speeds fail to acknowledge that

D Weisser

2003-01-01

369

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

NASA Technical Reports Server (NTRS)

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

Shelley, E. G.

1975-01-01

370

Wind Turbine  

USGS Multimedia Gallery

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

371

Wind Energy  

NSDL National Science Digital Library

Students learn about wind energy by making a pinwheel to model a wind turbine. Just like engineers, they decide where and how their turbine works best by testing it in different areas of the playground.

2014-09-18

372

X-ray observations of massive colliding wind binaries  

Microsoft Academic Search

Massive stars in binary systems can generate X-ray emission in the region between the two stars where stellar winds collide. Colliding wind X-ray emission acts as an in-situ probe of important wind parameters like mass-loss rates, chemical abundances, wind velocities, and possibly magnetic field strengths. Variations in observed colliding-wind X-ray emission can be produced by the changing line-of-sight to the

Michael F. Corcoran

2003-01-01

373

The last glacial maximum  

USGS Publications Warehouse

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.

Clark, P.U.; Dyke, A.S.; Shakun, J.D.; Carlson, A.E.; Clark, J.; Wohlfarth, B.; Mitrovica, J.X.; Hostetler, S.W.; McCabe, A.M.

2009-01-01

374

The Last Glacial Maximum.  

PubMed

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

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

375

RAWS: The spaceborne radar wind sounder  

NASA Technical Reports Server (NTRS)

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.

Moore, Richard K.

1991-01-01

376

Stellar winds driven by Alfven waves  

NASA Technical Reports Server (NTRS)

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.

Belcher, J. W.; Olbert, S.

1973-01-01

377

Toasty Wind  

NSDL National Science Digital Library

In this quick activity, learners use a toaster to investigate the source for the Earth's wind. Learners hold a pinwheel above a toaster to discover that rising heat causes wind. Use this activity to introduce learners to the process of convection as a source for wind. This resource also explains how convection causes thunderstorms and lists important thunderstorm safety tips.

National Weather Service

2012-07-24

378

Wind Whispers  

NSDL National Science Digital Library

The Advanced Technology Environmental and Energy Center (ATEEC) provides this presentation on the career and technical aspects of wind energy. In addition to discussing careers in wind, the presentation covers the siting of wind turbines and some electricity basics. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.

379

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

SciTech Connect

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.

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

1987-09-01

380

Maximum range three-dimensional lifting planetary entry  

NASA Technical Reports Server (NTRS)

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.

Dickmanns, E. D.

1972-01-01

381

Airfoils for wind turbine  

DOEpatents

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.

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

1996-10-08

382

Airfoils for wind turbine  

DOEpatents

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.

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

1996-01-01

383

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

ERIC Educational Resources Information Center

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)

Inglis, David Rittenhouse

1979-01-01

384

Saltation transport rate in unsteady wind variations.  

PubMed

Wind flow in the atmospheric boundary layer is usually turbulent. The gusty wind significantly influences the saltation transport which is treated as equilibrium saltation. This study performs one-dimension numerical simulations of unsteady sand saltation to discuss the effects of parameters of periodical wind variations on saltation response and sand transport rate prediction. The results show that unsteady transport rates are larger than steady rates of equivalent mean wind velocity. The ratio of unsteady/steady transport rates increases with the increase of amplitude and frequency. For the average wind velocities much larger than the threshold value, the errors of transport rates predicted by unsteady and steady model are about 10%, while for a wind velocity slightly larger than saltation threshold, the errors will be more than 200%. The sand transport rates are not zero even though the average wind velocity equals (is even smaller than) the threshold value, whereas Q must be zero in the steady model. Finally, an unsteady transport rate prediction formula is proposed which takes mean velocity, fluctuating intensity and period as independent variables. PMID:24853633

Wang, Ping; Zheng, Xiaojing

2014-05-01

385

Study of quench propagation velocity in superconducting magnets for UNK  

Microsoft Academic Search

Two superconducting magnet models, warm-iron and cold-iron designs are studied within the frames of work on UNK. The present note describes the method and results on measuring quench propagation velocity in the superconducting cables with a transport current in external field under the cooling conditions typical for those of the magnet winding. The results on measuring quench propagation velocities in

I. V. Bogdanov; P. A. Shcherbakov; V. P. Snitko; N. P. Tkachenko; L. M. Vasiliev; M. G. Vybornov; A. V. Zlobin

1989-01-01

386

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...

387

Diffuse Interstellar Medium Basics, velocity widths  

E-print Network

describes a Gaussian profile, normally defined as: where vr = radial velocity, = velocity dispersion · Thus: · Note the full-width at half-maximum for a Gaussian is: 21 2- (v )1 2 (v ) r rP e ! "! = b 2= ! FWHM 2 at T = 50°K? · FWHM 1 km/sec - But what is observed? ·emission profiles are not Gaussian, much broader than

Crenshaw, Michael

388

Concepts for Wind Turbine Sound Mitigation Page 1 of 16 AWEA Windpower 2013  

E-print Network

methodology is presented to optimize wind turbine operation in order to meet target noise levels with maximum Wind turbine noise represents one of the obstacles to a more widespread use of wind energy today be used to produce quieter wind farms. Wind Turbine Noise Source Noise Characteristics The two main

McCalley, James D.

389

Stellar wind erosion of protoplanetary discs  

NASA Astrophysics Data System (ADS)

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.

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

2015-04-01

390

Control policies for wind-energy conversion systems  

Microsoft Academic Search

Wind energy is usually converted into electrical energy through a wind rotor driving a generator. It is well known that maximum conversion efficiency occurs when the wind rotor is loaded in such a way that its rotational speed is allowed to fluctuate in sympathy with wind-speed variations. In the paper, the wind-rotor\\/generator dynamics are investigated for a number of control

I. K. Buehring; L. L. Freris

1981-01-01

391

Radial Heliospheric Magnetic Fields in Solar Wind Rarefaction Regions: Ulysses Observations  

NASA Astrophysics Data System (ADS)

We examine the distribution of directions of the heliospheric magnetic field (HMF) measured by the Ulysses spacecraft during its mid-latitude transits of the heliosphere when it observed solar wind shears from the incursions of high-latitude fast solar wind toward the low-latitude slow solar wind. We look for nearly radial field orientations commonly observed in rarefaction regions (i.e. where the solar wind velocity decreases monotonically over several days). In contrast to CMEs where the HMF tends to be enhanced, the rarefaction regions with nearly radial magnetic fields tend to have extremely low magnetic field magnitude values. Within these rarefaction regions, there are ``dwells'' in the coronal source longitude of the measured solar wind in which the time dependence of the solar wind velocity is given to a very good approximation by V(t) = R/(t-t0), where R is the heliocentric radial distance of the spacecraft. We have therefore compiled distributions within the dwells of the parameter |Br|/B which is the cosine of the cone angle of the field from the radial direction. We study the mid-latitude transits that occurred during different phases of solar activity: 1992-1993 (decline), 1996-1997 (minimum), 2001-2002 (maximum), and 2005-2006 (decline). During three out of these four periods, the distributions of the HMF tended to be rather uniform in all HMF directions (0<|Br|/B<1), but during 2001-2002, when the dwells were more frequent, the distributions tended more strongly toward |Br|/B = 1. Such distributions were observed up to very high latitudes (65° N). We discuss these observations in the context of the models proposed to explain the underwinding of the Parker spiral in terms of both a temporal variation in the coronal solar wind velocity and/or a longitudinal velocity gradient at the eastern edge of the solar wind source region. Only the latter can explain 26-day recurrent periods of radial magnetic field.

Lario, D.; Roelof, E. C.

2010-03-01

392

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

393

Running title: Maximum discrimination HMMs Maximum Discrimination Hidden Markov Models  

E-print Network

Running title: Maximum discrimination HMMs Maximum Discrimination Hidden Markov Models of Sequence for building hidden Markov models (HMMs) of protein or nucleic acid primary sequence consensus. The method. Keywords: hidden Markov model, database searching, sequence consensus, sequence weighting #12; Introduction

Eddy, Sean

394

Generalized Maximum Entropy  

NASA Technical Reports Server (NTRS)

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].

Cheeseman, Peter; Stutz, John

2005-01-01

395

The Average Velocity in a Queue  

ERIC Educational Resources Information Center

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…

Frette, Vidar

2009-01-01

396

Estimates of solar wind heating inside 0.3 AU  

NASA Technical Reports Server (NTRS)

Helios 1 proton temperature data have been normalized in order to determine a base temperature-velocity curve at 0.3 AU and to provide quantitative estimates on the close-in heating at different solar wind velocities. The results suggest that the slope of the solar wind temperature gradients for high-speed streams inside 0.3 AU is about half of that found beyond it. The very-low-speed wind is shown to expand adiabatically all the way out. It is also found that intermediate speed winds have enhanced heating rates in proportion to their velocities.

Freeman, John W.

1988-01-01

397

Flatback airfoil wind tunnel experiment.  

SciTech Connect

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.

Mayda, Edward A. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Chao, David D. (University of California, Davis, CA); Berg, Dale E.

2008-04-01

398

Three-Dimensional Venturi Sensor for Measuring Extreme Winds  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

399

Towers for Offshore Wind Turbines  

NASA Astrophysics Data System (ADS)

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.

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

2010-06-01

400

What is a Hurricane? Tropical system with maximum sustained  

E-print Network

· Abnormal rise in sea level accompanying a hurricane. #12;Storm Surge Flooding-Katrina #12;HurricaneHurricane 101 #12;What is a Hurricane? · Tropical system with maximum sustained surface wind of 74 mph or greater. A hurricane is the worst and the strongest of all tropical systems. · Also known

Meyers, Steven D.

401

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)

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.

Dorman, L. I.; Kobilinski, Z.

1975-01-01

402

Combined power generation with wind and ocean waves  

Microsoft Academic Search

It is often advantageous to generate power with combinations of wind and ocean waves. In fact ocean waves, their generation, propagation, dissipation are directly related to wind velocity and its duration oven the sea. In this paper an attempt has been made to demonstrate statistically to present some advantages with combined wind and ocean wave power generation. Even though many

V. N. M. R. Lakkoju

1996-01-01

403

A short physical note on a new wind power formulation  

Microsoft Academic Search

Classical wind energy formulation is based on the kinetic energy definition whereby the mass is considered as a constant. Consequently, the wind energy is obtained as directly related to half (1\\/2) of the specific mass multiplied by the cube of wind velocity. The new approach in this note is based first on the basic definition of force and then energy

Zekai ?en

2003-01-01

404

Wind Generator  

NSDL National Science Digital Library

Windmills have been used for hundreds of years to collect energy from the wind in order to pump water, grind grain, and more recently generate electricity. There are many possible designs for the blades of a wind generator and engineers are always trying new ones. Design and test your own wind generator, then try to improve it by running a small electric motor connected to a voltage sensor.

The Concord Consortium

2012-05-21

405

Constraints on Deep-seated Zonal Winds Inside Jupiter and Saturn  

E-print Network

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

Junjun Liu; Peter Goldreich; David Stevenson

2007-11-25

406

Forecastability as a Design Criterion in Wind Resource Assessment: Preprint  

SciTech Connect

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

Zhang, J.; Hodge, B. M.

2014-04-01

407

A variable speed wind turbine power control  

Microsoft Academic Search

To optimize the power in a wind turbine, the speed of the turbine should be able to vary with the wind speed. A simple control scheme is proposed that will allow an induction motor to run a turbine at its maximum power coefficient. The control uses a standard V\\/Hz converter and controls the frequency to achieve the desired power at

Andrew Miller; Edward Muljadi; Donald S. Zinger

1997-01-01

408

Optimal control for a wind system considering the time evolution of the wind speed and the variation of the kinetic energy  

Microsoft Academic Search

xThis paper proposes an original method of determining the maximum power function of a wind turbine at variable wind speeds. In this paper we determine the speed at which the system must work in order to obtain a maximum amount of electricity in a time interval of hours and days. For this purpose, we measure the wind speed and knowing

M. Babescu; C. Sorandaru; M. Greconici; M. Svoboda; S. Musuroi

2011-01-01

409

Last Glacial Maximum  

NSDL National Science Digital Library

Short lecture on CLIMAP project (see PowerPoint) 20 minutes Powerpoint (PowerPoint 444kB Nov7 10) Group activity - Reading for CLIMAP study assumptions, 20 minutes to read, 20 minutes for discussion Student Handout (Microsoft Word 50kB Nov7 10) Students break into groups (4 per group is good division of work) with 2 students per paper. Split the assumptions between students. Each group skims the CLIMAP papers for the assumptions (modern and/or LGM) used in the CLIMAP model-based reconstruction of the LGM. In the groups, students compare the assumptions between papers. Resources: CLIMAP (1976), The surface of the ice-age earth, Science, 191(4232), 1131-1137 and CLIMAP (1984), The last interglacial ocean, Quaternary Research, 21(2), 123. Class Discussion - Summarize assumptions used in CLIMAP studies. Group activity Exploring CLIMAP LGM Reconstructions, 40 minutes for model data, 20 minutes for discussion (Could be modified with as a "jigsaw" activity with a larger class). Learn more about the jigsaw teaching method. Students work on this activity in pairs; one person will create LGM maps, the other modern. Students should sit together with their computer monitors close together to compare. The students will use the IRI/LDEO Climate Data Library to access the CLIMAP reconstruction and produce maps using the tools available on this web site. In a web browser, go to http://iridl.ldeo.columbia.edu/SOURCES/.CLIMAP/ This is the main page for the CLIMAP Model output for the LGM 18,000 BP. In the middle of the page is the label "Datasets and variables" with two data sets below http://iridl.ldeo.columbia.edu/SOURCES/.CLIMAP/.LGM/ and http://iridl.ldeo.columbia.edu/SOURCES/.CLIMAP/.MOD/. Each student clicks on the link they are assigned to. There are several data sets listed for each period and the students will examine each data set and compare the LGM and Modern. As a class, go through each data set allowing pairs to compare the maps then summarize the results as a class. The worksheet has a table for the students and the PowerPoint has table for summarizing. Class Discussion - Summarize differences between modern and LGM in the CLIMAP model output. Discuss how the assumptions of the CLIMAP model studies may have influenced the results. Extra activities The students can explore the data further using the data selection and filters in the IRI/LDEO Climate Data Library. For the two SST data sets, click on "Data Selection" and narrow the data to the just the tropics (23.5º N-S). Click on "Filters" then select XY next to "Average over." The next window gives you the average over the tropics close to the top of the page. In the next class, the students repeat the Readings exercise by reading the COHMAP and MARGO papers to see how the scientific knowledge has progressed since the original CLIMAP studies. COHMAP Members, (1988), Climatic Changes of the Last 18,000 Years: Observations and Model Simulations, Science, 241(4869), 1043-1052. MARGO (2009), Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum, Nature Geoscience, 2(2), 127-132.

Kristine DeLong

410

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

NASA Astrophysics Data System (ADS)

A crucial step in planning new wind farms is the estimation of the amount of wind energy that can be harvested in possible target sites. Wind resource assessment traditionally entails deployment of masts equipped for wind speed measurements at several heights for a reasonably long period of time. Simplified linear models of atmospheric flow are then used for a spatial extrapolation of point measurements to a wide area. While linear models have been successfully applied in the wind resource assessment in plains and offshore, their reliability in complex terrain is generally poor. This represents a major limitation to wind resource assessment in Austria, where high-altitude locations are being considered for new plant sites, given the higher frequency of sustained winds at such sites. The limitations of linear models stem from two key assumptions in their formulation, the neutral stratification and attached boundary-layer flow, both of which often break down in complex terrain. Consequently, an accurate modeling of near-surface flow over mountains requires the adoption of a NWP model with high horizontal and vertical resolution. This study explores the wind potential of a site in Styria in the North-Eastern Alps. The WRF model is used for simulations with a maximum horizontal resolution of 800 m. Three nested computational domains are defined, with the innermost one encompassing a stretch of the relatively broad Enns Valley, flanked by the main crest of the Alps in the south and the Nördliche Kalkalpen of similar height in the north. In addition to the simulation results, we use data from fourteen 10-m wind measurement sites (of which 7 are located within valleys and 5 near mountain tops) and from 2 masts with anemometers at several heights (at hillside locations) in an area of 1600 km2 around the target site. The potential for wind energy production is assessed using the mean wind speed and turbulence intensity at hub height. The capacity factor is also evaluated, considering the frequency of wind speed between cut-in and cut-out speed and of winds with a low vertical velocity component only. Wind turbines do not turn on at wind speeds below cut-in speed. Wind turbines are taken off from the generator in the case of wind speeds higher than cut-out speed and inclination angles of the wind vector greater than 8o. All of these parameters were computed at each model grid point in the innermost domain in order to map their spatial variability. The results show that in complex terrain the annual mean wind speed at hub height is not sufficient to predict the capacity factor of a turbine; vertical wind speed and the frequency of horizontal wind speed out of the range of cut-in and cut-out speed contribute substantially to a reduction of the energy harvest and locally high turbulence may considerably raise the building costs.

Gruber, Karin; Serafin, Stefano; Grubiši?, Vanda; Dorninger, Manfred; Zauner, Rudolf; Fink, Martin

2014-05-01

411

MODELING IRON ABUNDANCE ENHANCEMENTS IN THE SLOW SOLAR WIND  

SciTech Connect

We have studied the behavior of Fe ions in the slow solar wind, using a fluid model extending from the chromosphere to 1 AU. Emphasis is on elemental 'pileup' in the corona, i.e., a region where the Fe density increases and has a local maximum. We study the behavior of individual Fe ions relative to each other in the pileup region, where Fe{sup +10} and Fe{sup +12} have been used as examples. We find that elemental pileups can occur for a variety of densities and temperatures in the corona. We also calculate the ion fractions and obtain estimates for the freezing-in distance of Fe in the slow solar wind. We find that the freezing-in distance for iron is high, between 3 and 11 R{sub sun}, and that a high outflow velocity, of order 50-100 km s{sup -1}, in the region above the temperature maximum is needed to obtain ion fractions for Fe{sup +10} and Fe{sup +12} that are consistent with observations.

Byhring, H. S.; Esser, R. [Department of Physics and Technology, University of Tromsoe, NO-9037 Tromsoe (Norway); Cranmer, S. R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lie-Svendsen, Oe. [Norwegian Defense Research Establishment, P.O. Box 25, NO-2027 Kjeller (Norway); Habbal, S. R., E-mail: hanne-sigrun.byhring@uit.no [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

2011-05-10

412

"SPURS" in the North Atlantic Salinity Maximum  

NASA Astrophysics Data System (ADS)

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.

Schmitt, Raymond

2014-05-01

413

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

NASA Astrophysics Data System (ADS)

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.

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

2003-11-01

414

Wind energy.  

PubMed

From its rebirth in the early 1980s, the rate of development of wind energy has been dramatic. Today, other than hydropower, it is the most important of the renewable sources of power. The UK Government and the EU Commission have adopted targets for renewable energy generation of 10 and 12% of consumption, respectively. Much of this, by necessity, must be met by wind energy. The US Department of Energy has set a goal of 6% of electricity supply from wind energy by 2020. For this potential to be fully realized, several aspects, related to public acceptance, and technical issues, related to the expected increase in penetration on the electricity network and the current drive towards larger wind turbines, need to be resolved. Nevertheless, these challenges will be met and wind energy will, very likely, become increasingly important over the next two decades. An overview of the technology is presented. PMID:17272245

Leithead, W E

2007-04-15

415

Highly Alfvenic Slow Solar Wind  

NASA Technical Reports Server (NTRS)

It is commonly thought that fast solar wind tends to be highly Alfvenic, with strong correlations between velocity and magnetic fluctuations, but examples have been known for over 20 years in which slow wind is both Alfvenic and has many other properties more typically expected of fast solar wind. This paper will present a search for examples of such flows from more recent data, and will begin to characterize the general characteristics of them. A very preliminary search suggests that such intervals are more common in the rising phase of the solar cycle. These intervals are important for providing constraints on models of solar wind acceleration, and in particular the role waves might or might not play in that process.

Roberts, D. Aaron

2010-01-01

416

Dust particle velocity measurement  

NASA Technical Reports Server (NTRS)

A laser Doppler velocimeter was used to measure the velocity distributions for particles entering a vacuum chamber from the atmosphere through calibrated leaks. The relative number of particles per velocity interval was obtained for particulates of three size distributions and two densities passing through six different leak geometries. The velocity range 15 to 320 meters per second was investigated. Peak particle velocities were found to occur in the 15 to 150 meters per second range depending upon type of particle and leak geometry. A small fraction of the particles were found to have velocities in the 150 to 320 meters per second range.

Thielman, L. O.

1976-01-01

417

Assessment of fatigue life for small composite wind turbine blades  

Microsoft Academic Search

The present design and assessment of fatigue life for the small composite wind turbine blades (SCWTBs) can be certified by IEC 61400-2 “Wind Turbines - Part2: Design requirements of small wind turbines”. The paper will establish an analytical method on the fatigue life analysis of SCWTBs. Using the Microsoft Office EXCEL to calculate the maximum stress, minimum stress and stress

Jia-Hroung Wu

2010-01-01

418

Power reserve in interconnected systems with high wind power production  

Microsoft Academic Search

A capacity of installed wind power of 40 GW in Europe, control areas with a wind power production exceeding the maximum load-these are serious plans that may come true in several years. Due to the high fluctuations and the limited predictability of wind power, this development will cause a severe change in the demands on the power reserve. Therefore, this

Gundolf Dany

2001-01-01

419

Wind-driven circulation in Titan's seas  

NASA Astrophysics Data System (ADS)

Circulation in Titan's seas forced by wind is simulated by an ocean circulation model using surface wind data predicted by a global circulation model. Wind-driven circulation is insignificant throughout much of the annual cycle but becomes significant from late spring to late summer, when the wind stress becomes strong. The large-scale circulation in summer is predominantly southward near the sea surface and northward near the sea bottom. The sea surface current can get as fast as 5 cms-1 in some areas. Titan's rotation affects the vertical structure of sea currents in the form of an Ekman spiral if the wind is strong. The maximum wind setup at the shores is of the same order of magnitude as the tidal range. Wind stirring may reduce thermal stratification in summer but may be unable to destroy stratification of methane-rich liquids on top of ethane-rich liquids that can result from imbalances between evaporation and precipitation.

Tokano, Tetsuya; Lorenz, Ralph D.

2015-01-01

420

Spall velocity measurements from laboratory impact craters  

NASA Technical Reports Server (NTRS)

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.

Polanskey, Carol A.; Ahrens, Thomas J.

1986-01-01

421

Wind speed and direction shears with associated vertical motion during strong surface winds  

NASA Technical Reports Server (NTRS)

Strong surface winds recorded at the NASA 150-Meter Ground Winds Tower facility at Kennedy Space Center, Florida, are analyzed to present occurrences representative of wind shear and vertical motion known to be hazardous to the ascent and descent of conventional aircraft and the Space Shuttle. Graphical (percentage frequency distributions) and mathematical (maximum, mean, standard deviation) descriptions of wind speed and direction shears and associated updrafts and downdrafts are included as functions of six vertical layers and one horizontal distance for twenty 5-second intervals of parameters sampled simultaneously at the rate of ten per second during a period of high surface winds.

Alexander, M. B.; Camp, D. W.

1984-01-01

422

Tropospheric Wind Measurements from Space: The SPARCLE Mission and Beyond  

NASA Technical Reports Server (NTRS)

For over 20 years researchers have been investigating the feasibility of profiling tropospheric vector wind velocity from space with a pulsed Doppler lidar. Efforts have included theoretical development, system and mission studies, technology development, and ground-based and airborne measurements. Now NASA plans to take the next logical step towards enabling operational global tropospheric wind profiles by demonstrating horizontal wind measurements from the Space Shuttle in early 2001 using a coherent Doppler wind lidar system.

Kavaya, Michael J.; Emmitt, G. David

1998-01-01

423

Modeled dependence of wind and waves on ocean temperature in tropical cyclones  

NASA Astrophysics Data System (ADS)

A coupled ocean-atmosphere-wave model is used to investigate the sensitivity of surface wind speed and significant wave height to ocean temperature for idealized tropical cyclones (TCs). More intense and larger TCs, with higher waves, form when ocean temperature is increased. The maximum significant wave height increases more than the maximum wind speed for TCs up to hurricane force wind. However, above hurricane force wind the change in maximum wind speed is similar or greater than the change in maximum significant wave height. This can be explained by the wind drag coefficient decreasing as wind speed exceeds hurricane force wind, so that the growth of waves is dampened. The areal footprint of wave height grows considerably more than the maximum as ocean temperature is increased. This suggests a large increase in the surface area of damaging waves generated by TCs may be the dominant impact of a future warmer ocean.

Phibbs, Samuel; Toumi, Ralf

2014-10-01

424

Neutral winds derived from IRI parameters and from the HWM87 wind model for the SUNDIAL campaign of September, 1986  

Microsoft Academic Search

Meridional neutral winds derived from the height of the maximum ionization of the F2-layer are compared with values from results of the HWM87 empirical neutral wind model. The time period considered in this study is the SUNDIAL-2 campaign, September 21 through October 5, 1986. Winds have been derived from measurements by a global network of ionosondes, as well as from

K. L. Miller; A. E. Hedin; P. J. Wilkinson; D. G. Torr; P. G. Richards

1990-01-01

425

Neutral winds derived from IRI parameters and from the HWM87 wind model for the sundial campaign of September, 1986  

Microsoft Academic Search

Meridional neutral winds derived from the height of the maximum ionization of the F2 layer are compared with values from results of the HWM87 empirical neutral wind model. The time period considered is the SUNDIAL-2 campaign, 21 Sept. through 5 Oct. 1986. Winds were derived from measurements by a global network of ionosondes, as well as from similar quantities generated

K. L. Miller; A. E. Hedin; P. J. Wilkinson; D. G. Torr; P. G. Richards

1990-01-01

426

Wind Energy Leasing Handbook  

E-print Network

Wind Energy Leasing Handbook Wind Energy Leasing Handbook E-1033 Oklahoma Cooperative Extension?..................................................................................................................... 31 What do wind developers consider in locating wind energy projects?............................................................................................ 37 How do companies and individuals invest in wind energy projects?....................................................................

Balasundaram, Balabhaskar "Baski"

427

Stochastic unit commitment of wind farms based on mixed-integer linear formulation  

Microsoft Academic Search

Due to uncertainty of wind velocity, wind power generators don't have deterministic output power. Utilizing wind power generation and thermal power plants together create new concerns for operation engineers of power systems. In this paper, a model is presented to implement the uncertainty of load and generated wind power which can be utilized in power system operation planning. Stochastic behavior

Sh. Mostafa Esmaeeli; A. Kazemi

2012-01-01

428

Sliding mode control of wind energy systems with DOIG-power efficiency and torsional dynamics optimization  

Microsoft Academic Search

Wind turbines with double output induction generators can operate at variable speed permitting conversion efficiency maximization over a wide range of wind velocities. However, random wind fluctuations, wind shear and tower shadow, may excite the oscillation mode of the mechanical system, producing large torque ripple. Consequently, damage to drive train components and power quality problems may occur. In this paper,

H. De Battista; P. F. Puleston; R. J. Mantz; C. F. Christiansen

2000-01-01

429

WIND TOMOGRAPHY IN BINARY SYSTEMS O.Knill, R.Dgani and M.Vogel  

E-print Network

WIND TOMOGRAPHY IN BINARY SYSTEMS O.Knill, R.Dgani and M.Vogel ETH-Zurich, CH-8092, Switzerland method is particularly suitable for determining the velocity laws of stellar winds. 1. WIND TOMOGRAPHY AND ABEL'S INTEGRAL Binary systems in which a compact, point-like radiation source shines through the wind

Knill, Oliver

430

Prediction of geomagnetic storms from solar wind data using Elman recurrent neural networks  

Microsoft Academic Search

In order to accurately predict geomagnetic storms, we exploit Elman recurrent neural networks to predict the Dst index one hour in advance only from solar wind data. The input parameters are the interplanetary magnetic field z-component Bz (GSM), the solar wind plasma number density n and the solar wind velocity V. The solar wind data and the geomagnetic index Dst

Jian-Guo Wu; Henrik Lundstedt

1996-01-01

431

Global Winds  

NSDL National Science Digital Library

On this worksheet, students examine a diagram of global winds and learn the position of the prevailing westerlies, the polar easterlies, the trade winds, the horse latitudes and the doldrums, and that together, the uneven heating of the planet by the Sun and the Coriolis Effect are responsible for the global wind belts. The resource is part of the teacher's guide accompanying the video, NASA Why Files: The Case of the Mysterious Red Light. Lesson objectives supported by the video, additional resources, teaching tips and an answer sheet are included in the teacher's guide.

2012-08-03

432

Stellar Winds  

NASA Astrophysics Data System (ADS)

A "stellar wind" is the continuous, supersonic outflow of matter from the surface layers of a star. Our sun has a solar wind, driven by the gas-pressure expansion of the hot (T > 106 K) solar corona. It can be studied through direct in situ measurement by interplanetary spacecraft; but analogous coronal winds in more distant solar-type stars are so tenuous and transparent that that they are difficult to detect directly. Many more luminous stars have winds that are dense enough to be opaque at certain wavelengths of the star's radiation, making it possible to study their wind outflows remotely through careful interpretation of the observed stellar spectra. Red giant stars show slow, dense winds that may be driven by the pressure from magnetohydrodyanmic waves. As stars with initial mass up to 8 M ? evolve toward the Asymptotic Giant Branch (AGB), a combination of stellar pulsations and radiative scattering off dust can culminate in "superwinds" that strip away the entire stellar envelope, leaving behind a hot white dwarf stellar core with less than the Chandrasekhar mass of ˜ ?? 1. 4M ?. The winds of hot, luminous, massive stars are driven by line-scattering of stellar radiation, but such massive stars can also exhibit superwind episodes, either as Red Supergiants or Luminous Blue Variable stars. The combined wind and superwind mass loss can strip the star's hydrogen envelope, leaving behind a Wolf-Rayet star composed of the products of earlier nuclear burning via the CNO cycle. In addition to such direct effects on a star's own evolution, stellar winds can be a substantial source of mass, momentum, and energy to the interstellar medium, blowing open large cavities or "bubbles" in this ISM, seeding it with nuclear processed material, and even helping trigger the formation of new stars, and influencing their eventual fate as white dwarves or core-collapse supernovae. This chapter reviews the properties of such stellar winds, with an emphasis on the various dynamical driving processes and what they imply for key wind parameters like the wind flow speed and mass loss rate.

Owocki, Stan

433

Wind Tunnel  

NSDL National Science Digital Library

Scientists use enormous wind tunnels to test the design of planes, helicopters, even the Space Shuttle. In this simulation activity, learners create a miniature wind tunnel test by blowing air with a fan or blow dryer through a large tube, then flying paper airplanes, helicopters and other folded paper models in the "wind." Unless the source of the air is a fan that stands on its own, for example, more than one person will be needed to do the activity.This activity can be combined with the Helicopter Twirl, Parachute Drop and Boomerang activities, also found on the Lawrence Hall of Science Kids Site.

Lawrence Hall of Science

2009-01-01

434

Quadraphonic Wind  

NSDL National Science Digital Library

In this activity, learners discover how the extent of various wind speeds changes in each of the four quadrants around a hurricane. Learners use data from the 'present' location of Hurricane Bill (2009) to plot the distance of various wind speeds that extend from the center of the storm. This resource includes brief background information about hurricanes and forecasting as well as an explanation of the Hurricane Bill data used in this activity and how small increases in wind speed can cause increased potential for damage.

National Weather Service

2012-12-18

435

Wind loading on solar collectors  

NASA Astrophysics Data System (ADS)

The present design methodology for the determination of wind loading on the various solar collectors were reviewed and assessed. The total force coefficients of flat plates of aspect ratios 1.0 and 3.0, respectively, at various angles of attack obtained by using the guidelines of the ANSI A58.1-1982, were compared with those obtained by using the methodology of the ASCE Task Committee, 1961, and the experimental results of the full-scale test of heliostats by Peglow. The turbulent energy spectra, currently employed in the building code, are compared with those of Kaimal et al., Lumley, and Ponofsky for wind velocities of 20.0 m/s and 40.24 m/s at an elevation of 9.15 m. The longitudinal spectra of the building code overestimates the Kaimal spectra in the frequency range of 0.007 Hz to 0.08 Hz and underestimates beyond the frequency of 0.08 Hz. The peak angles of attack, on the heliostat, stowed in horizontal position, due to turbulent vertical and lateral components of wind velocity, were estimated by using Daniel's methodology for three wind velocities and compared with the value suggested by the code. The experimental results of a simple test in the laboratory indicate the feasibility of decreasing the drag forces of the flat plate by reducing the solidity ratio.

Bhaduri, S.; Murphy, L. M.

1985-06-01

436

Wind loading on solar collectors  

SciTech Connect

The present design methodology for the determination of wind loading on the various solar collectors has been reviewed and assessed. The total force coefficients of flat plates of aspect ratios 1.0 and 3.0, respectively, at various angles of attack obtained by using the guidelines of the ANSI A58.1-1982, have been compared with those obtained by using the methodology of the ASCE Task Committee, 1961, and the experimental results of the full-scale test of heliostats by Peglow. The turbulent energy spectra, currently employed in the building code, are compared with those of Kaimal et al., Lumley, and Ponofsky for wind velocities of 20.0 m/s and 40.24 m/s at an elevation of 9.15 m. The longitudinal spectra of the building code overestimates the Kaimal spectra in the frequency range of 0.007 Hz to 0.08 Hz and underestimates beyond the frequency of 0.08 Hz. The peak angles of attack, on the heliostat, stowed in horizontal position, due to turbulent vertical and lateral components of wind velocity, have been estimated by using Daniel's methodology for three wind velocities and compared with the value suggested by the code. The experimental results of a simple test in the laboratory indicate the feasibility of decreasing the drag forces of the flat plate by reducing the solidity ratio.

Bhaduri, S.; Murphy, L.M.

1985-06-01

437

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

USGS Publications Warehouse

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

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

2012-01-01

438

The Winds of B Supergiants  

NASA Technical Reports Server (NTRS)

We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analyzed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include 'normal' stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasizes the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures, and highlight the challenges that these phenomena present to theoretical studies of time-dependent outflows in massive stars. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (M qi) is a factor of approximately 1.5, when integrated between 0.2 and 0.9 v infinity; it it can however be several times larger over localized velocity regions. At a given effective temperature the mean relative ion ratios can differ by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in turns of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.

Massa, Derck; West, D. (Technical Monitor)

2002-01-01

439

The Winds of B Supergiants  

NASA Technical Reports Server (NTRS)

We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analyzed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include 'normal' stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasises the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters, but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures, and highlight the challenges that these phenomena present to theoretical studies of time-dependent outflows in massive stars. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (M (dot) q(sub i)) is a factor of approximately 1.5, when integrated between 0.2 and 0.9 v infinity; it can however be several times larger over localized velocity regions. At a given effective temperature the mean relative ion ratios can differ by a factor of 5. The general excess in predicted (forward-scattered) emission in the low velocity regime is discussed in terms of structured outflows. Mean ion fractions are estimated over the B0 to B1 spectral classes, and trends in the ionic ratios as a function of wind velocity are described. The low values obtained for the ion fractions of UV resonance lines may reflect the role of clumping in the wind.

Massa, D.; Oliversen, R. (Technical Monitor)

2002-01-01

440

Relativistic Radiation Hydrodynamical Accretion Disk Winds  

E-print Network

Accretion disk winds browing off perpendicular to a luminous disk are examined in the framework of fully special relativistic radiation hydrodynamics. The wind is assumed to be steady, vertical, and isothermal. %and the gravitational fields is approximated by a pseudo-Newtonian potential. Using a velocity-dependent variable Eddington factor, we can solve the rigorous equations of relativistic radiative hydrodynamics, and can obtain radiatively driven winds accelerated up to the {\\it relativistic} speed. For less luminous cases, disk winds are transonic types passing through saddle type critical points, and the final speed of winds increases as the disk flux and/or the isothermal sound speed increase. For luminous cases, on the other hand, disk winds are always supersonic, since critical points disappear due to the characteristic nature of the disk gravitational fields. The boundary between the transonic and supersonic types is located at around $\\hat{F}_{\\rm c} \\sim 0.1 (\\epsilon+p)/(\\rho c^2)/\\gamma_{\\rm c}$, where $\\hat{F}_{\\rm c}$ is the radiative flux at the critical point normalized by the local Eddington luminosity, $(\\epsilon+p)/(\\rho c^2)$ is the enthalpy of the gas divided by the rest mass energy, and $\\gamma_{\\rm c}$ is the Lorentz factor of the wind velocity at the critical point. In the transonic winds, the final speed becomes 0.4--0.8$c$ for typical parameters, while it can reach $\\sim c$ in the supersonic winds.

Jun Fukue; Chizuru Akizuki

2007-11-09

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