Science.gov

Sample records for 10-m wind speed

  1. An Examination of Residual Wind Fluctuations Observed at 10 m over Flat Terrain.

    NASA Astrophysics Data System (ADS)

    Leahey, D. M.; Hansen, M. C.; Schroeder, M. B.

    1996-01-01

    This study investigates the behavior of wind fluctuations observed at the 10-m level over a flat terrain site located some 100 km east of the Rocky Mountains. The purposes were to assess residual fluctuations in order to ascertain effects attributable to the nonhomogenous, nonstationary character of turbulence and to evaluate influences of gravity waves. Residual wind fluctuations were defined for purposes of this study as the differences between observed half-hourly average standard deviations of wind fluctuations (v, u, w) and those that are expected to occur in association with simultaneous wind speeds and static stabilities. These latter fluctuations were estimated from equations developed by Leahey, Hansen, and Schroeder (LHS).Results of the analyses showed, as expected, that residual distributions for nonwesterly wind conditions were nearly Gaussian. Standard deviations for residuals of horizontal fluctuations, attributable to the nonhomogenous, nonstationary nature of turbulence, were 0.165 and 0.210 m s1 for stable and unstable situations, respectively. For residuals associated with vertical fluctuations they were, respectively, 0.065 and 0.075 m s1.Residuals for horizontal and vertical wind fluctuations observed when winds were from the mountains showed a greater tendency for the positive bias associated with gravity waves. This tendency was most evident under unstable conditions when gravity wave influences on horizontal fluctuations were apparent about 25% of the time. These influences are explained as being associated with mountain lee waves occurring at the planetary boundary layer's capping inversion. They are evidenced at the 10-m level because atmospheric mixing processes occurring in thermally unstable atmospheric situations bring momentum generated from these waves downward to the ground.Nonstationary and nonhomogenous atmospheric turbulence effects result in wind fluctuations whose half-hourly average standard deviations differ from those

  2. Wind Speed Perception and Risk

    PubMed Central

    Agdas, Duzgun; Webster, Gregory D.; Masters, Forrest J.

    2012-01-01

    Background How accurately do people perceive extreme wind speeds and how does that perception affect the perceived risk? Prior research on human–wind interaction has focused on comfort levels in urban settings or knock-down thresholds. No systematic experimental research has attempted to assess people's ability to estimate extreme wind speeds and perceptions of their associated risks. Method We exposed 76 people to 10, 20, 30, 40, 50, and 60 mph (4.5, 8.9, 13.4, 17.9, 22.3, and 26.8 m/s) winds in randomized orders and asked them to estimate wind speed and the corresponding risk they felt. Results Multilevel modeling showed that people were accurate at lower wind speeds but overestimated wind speeds at higher levels. Wind speed perceptions mediated the direct relationship between actual wind speeds and perceptions of risk (i.e., the greater the perceived wind speed, the greater the perceived risk). The number of tropical cyclones people had experienced moderated the strength of the actual–perceived wind speed relationship; consequently, mediation was stronger for people who had experienced fewer storms. Conclusion These findings provide a clearer understanding of wind and risk perception, which can aid development of public policy solutions toward communicating the severity and risks associated with natural disasters. PMID:23226230

  3. Estimation of friction velocity from the wind-wave spectrum at extremely high wind speeds

    NASA Astrophysics Data System (ADS)

    Takagaki, N.; Komori, S.; Suzuki, N.

    2016-05-01

    The equilibrium range of wind-waves at normal and extremely high wind speeds was investigated experimentally using a high-speed wind-wave tank together with field measurements at normal wind speeds. Water level fluctuations at normal and extremely high wind speeds were measured with resistance-type wave gauges, and the wind-wave spectrum and significant phase velocity were calculated. The equilibrium range constant was estimated from the wind-wave spectrum and showed the strong relationship with inverse wave age at normal and extremely high wind speeds. Using the strong relation between the equilibrium range constant and inverse wave age, a new method for estimating the wind speed at 10-m height (U 10) and friction velocity (u*) was proposed. The results suggest that U 10 and u* can be estimated from wave measurements alone at extremely high wind speeds in oceans under tropical cyclones.

  4. Maxometers (peak wind speed anemometers)

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  5. Wind speed forecasting for wind energy applications

    NASA Astrophysics Data System (ADS)

    Liu, Hong

    With more wind energy being integrated into our grid systems, forecasting wind energy has become a necessity for all market participants. Recognizing the market demands, a physical approach to site-specific hub-height wind speed forecasting system has been developed. This system is driven by the outputs from the Canadian Global Environmental Multiscale (GEM) model. A simple interpolation approach benchmarks the forecasting accuracy inherited from GEM. Local, site specific winds are affected on a local scale by a variety of factors including representation of the land surface and local boundary-layer process over heterogeneous terrain which have been a continuing challenge in NWP models like GEM with typical horizontal resolution of order 15-km. In order to resolve these small scale effects, a wind energy industry standard model, WAsP, is coupled with GEM to improve the forecast. Coupling the WAsP model with GEM improves the overall forecasts, but remains unsatisfactory for forecasting winds with abrupt surface condition changes. Subsequently in this study, a new coupler that uses a 2-D RANS model of boundary-layer flow over surface condition changes with improved physics has been developed to further improve the forecasts when winds coming from a water surface to land experience abrupt changes in surface conditions. It has been demonstrated that using vertically averaged wind speeds to represent geostrophic winds for input into the micro-scale models could reduce forecast errors. The hub-height wind speed forecasts could be further improved using a linear MOS approach. The forecasting system has been evaluated, using a wind energy standard evaluation matrix, against data from an 80-m mast located near the north shore of Lake Erie. Coupling with GEM-LAM and a power conversion model using a theoretical power curve have also been investigated. For hub-height wind speeds GEM appears to perform better with a 15-Ian grid than the high resolution GEM-2.5Ian version at the

  6. ECMWF and SSMI Global Surface Wind Speeds

    NASA Technical Reports Server (NTRS)

    Halpern, David; Hollingsworth, Anthony; Wentz, Frank

    1993-01-01

    Monthly mean, 2.5 deg - x 2.5 deg-resolution, 10-m height wind speeds from the Special Sensor Microwave Imager (SSMI) instrument and the European Center for Medium-Range Weather Forecasts (ECMWF) forecast-analysis system are compared between 60 deg S and 60 deg N during 1988-1991. The SSMI data were uniformly processed while numerous changes were made to the ECMWF forecast-analysis system. The SSMI measurements, which were compared with moored-buoy wind observations, were considered to be a reference data set to evaluate the influence of the changes made to the ECMWF system upon the ECMWF surface wind speed over the ocean. A demonstrable yearly decrease of the difference between SSMI and ECMWF wind speeds occurred in the 10 deg S - 10 deg N region, including the 5 deg S - 5 deg N zone of the Pacific Ocean, where nearly all of the variations occurred in the 160 deg E - 160 deg W region. The apparent improvement of the ECMWF wind speed occurred at the same time as the yearly decrease of the equatorial Pacific SSMI wind speed, which was associated with the natural transition from La Nina to El Nino conditions. In the 10 deg S - 10 deg N tropical Atlantic, the ECMWF wind speed had a 4-year trend, which was not expected nor was it duplicated with the SSMI data. No yearly trend was found in the difference between SSMI and ECMWF surface wind speeds in middle latitudes of the northern and southern hemispheres. The magnitude of the differences between SSMI and ECMWF was 0.4 m s^(-1) or 100 percent larger in the northern than in the southern hemisphere extratropics. In two areas (Arabian Sea and North Atlantic Ocean) where ECMWF and SSMI wind speeds were compared to ship measurements, the ship data had much better agreement with the ECMWF analyses compared to SSMI data. In the 10 deg S - 10 deg N area the difference between monthly standard deviations of the daily wind speeds dropped significantly from 1988 to 1989, but remained constant at about 30 percent for the remaining

  7. High-speed Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Ackeret, J

    1936-01-01

    Wind tunnel construction and design is discussed especially in relation to subsonic and supersonic speeds. Reynolds Numbers and the theory of compressible flows are also taken into consideration in designing new tunnels.

  8. Numerical wind speed simulation model

    SciTech Connect

    Ramsdell, J.V.; Athey, G.F.; Ballinger, M.Y.

    1981-09-01

    A relatively simple stochastic model for simulating wind speed time series that can be used as an alternative to time series from representative locations is described in this report. The model incorporates systematic seasonal variation of the mean wind, its standard deviation, and the correlation speeds. It also incorporates systematic diurnal variation of the mean speed and standard deviation. To demonstrate the model capabilities, simulations were made using model parameters derived from data collected at the Hanford Meteorology Station, and results of analysis of simulated and actual data were compared.

  9. Unsafe at Any (Wind) Speed?.

    NASA Astrophysics Data System (ADS)

    Schmidlin, Thomas; Hammer, Barbara; King, Paul; Ono, Yuichi; Miller, L. Scott; Thumann, Gregory

    2002-12-01

    The goal of this research was to examine the relative safety and stability of stationary motor vehicles exposed to severe winds. The focus was on private passenger vehicles. 1) The behavior of two instrumented storm-chase vehicles that were exposed to severe winds, 2) the behavior of 291 vehicles exposed to a tornado, and 3) the wind speed required to upset a sedan and a minivan exposed to winds in a wind tunnel were studied. A wind as strong as 47 m s1 (105 mph) has been measured by a storm-chase pickup truck and 44 m s1 (98 mph) by a storm chase sedan. The vehicles were not adversely affected by the wind. Also studied were 291 vehicles parked outdoors at homes struck by tornadoes, and the behavior of the vehicles was compared to the F-scale damage to the house. At sites with F1 or F2 damage, 72% of the vehicles were not moved by the wind and 96% were not tipped over. At sites with F3 or F4 damage, 50% were not moved by the wind and 82% were not tipped over. Wind tunnel tests on a sedan and minivan showed they were most vulnerable to upset (lifting of one tire from the ground) with wind directions near 45° and 135°, as measured from the front. When modeled with 5° of suspension tilt to the side, the sedan was found to be upset at wind speeds of 51-67 m s1 (115-150 mph), and the minivan was upset at wind speeds of 58-80 m s1 (130-180 mph). Although an underground shelter or sturdy building offer the best protection from severe winds, it is found that a vehicle may be a relatively stable place and may be safer than a mobile home or the outdoors. These findings may warrant changes to public recommendations made during tornado warnings and other severe storm situations.

  10. Offshore wind speed and wind power characteristics for ten locations in Aegean and Ionian Seas

    NASA Astrophysics Data System (ADS)

    Bagiorgas, Haralambos S.; Mihalakakou, Giouli; Rehman, Shafiqur; Al-Hadhrami, Luai M.

    2012-08-01

    This paper utilizes wind speed data measured at 3 and 10 m above water surface level using buoys at 10 stations in Ionian and Aegean Seas to understand the behaviour of wind and thereafter energy yield at these stations using 5 MW rated power offshore wind turbine. With wind power densities of 971 and 693 W/m2 at 50 m above water surface level, Mykonos and Lesvos were found to be superb and outstanding windy sites with wind class of 7 and 6, respectively. Other locations like Athos, Santorini and Skyros with wind power density of more than 530 W/m2 and wind class of 5 were found to be the excellent sites. Around 15-16% higher winds were observed at 10 m compared to that at 3 m. Lower values of wind speed were found during summer months and higher during winter time in most of the cases reported in the present work. Slightly decreasing (~2% per year) linear trends were observed in annual mean wind speed at Lesvos and Santorini. These trends need to be verified with more data from buoys or from nearby onshore meteorological stations. At Athos and Mykonos, increasing linear trends were estimated. At all the stations the chosen wind turbine could produce energy for more than 70% of the time. The wind speed distribution was found to be well represented by Weibull parameters obtained using Maximum likelihood method compared to WAsP and Method of Moments.

  11. Dual-speed wind turbine generation

    SciTech Connect

    Muljadi, E.; Butterfield, C.P.; Handman, D.

    1996-10-01

    Induction generator has been used since the early development of utility-scale wind turbine generation. An induction generator is the generator of choice because of its ruggedness and low cost. With an induction generator, the operating speed of the wind turbine is limited to a narrow range (almost constant speed). Dual- speed operation can be accomplished by using an induction generator with two different sets of winding configurations or by using a dual output drive train to drive two induction generators with two different rated speeds. With single-speed operation, the wind turbine operates at different power coefficients (Cp) as the wind speed varies. Operation at maximum Cp can occur only at a single wind speed. However, if the wind speed.varies across a wider range, the operating Cp will vary significantly. Dual-speed operation has the advantage of enabling the wind turbine to operate at near maximum Cp over a wider range of wind speeds. Thus, annual energy production can be increased. The dual-speed mode may generate less energy than a variable-speed mode; nevertheless, it offers an alternative which captures more energy than single-speed operation. In this paper, dual-speed operation of a wind turbine is investigated. Annual energy production is compared between single-speed and dual-speed operation. One type of control algorithm for dual-speed operation is proposed. Some results from a dynamic simulation will be presented to show how the control algorithm works as the wind turbine is exposed to varying wind speeds.

  12. Wind speeds on extrasolar worlds

    NASA Astrophysics Data System (ADS)

    Allers, Katelyn; Biller, Beth; Vos, Johanna; Williams, Peter; Berger, Edo

    2016-08-01

    We propose for photometric monitoring observations of 2MASS J10475385+2124234 and WISE J112254.73+255021.5 using Spitzer/IRAC. 2MASS J1047+21 and WISE J1122+25 are late spectral type (T6.5 and T6) radio emitters and have measured radio periods of 1.77 hrs and 1.30 hrs, respectively. Our proposed observations will not only characterize the variability of the two coolest known radio emitters but also provide a unique opportunity to measure the first wind speeds for brown dwarfs. Spitzer is currently the only facility capable of the photometric stability, continuous observations and 4.5 micron sensitivity necessary for the success of our program.

  13. Deterministic prediction of surface wind speed variations

    NASA Astrophysics Data System (ADS)

    Drisya, G. V.; Kiplangat, D. C.; Asokan, K.; Satheesh Kumar, K.

    2014-11-01

    Accurate prediction of wind speed is an important aspect of various tasks related to wind energy management such as wind turbine predictive control and wind power scheduling. The most typical characteristic of wind speed data is its persistent temporal variations. Most of the techniques reported in the literature for prediction of wind speed and power are based on statistical methods or probabilistic distribution of wind speed data. In this paper we demonstrate that deterministic forecasting methods can make accurate short-term predictions of wind speed using past data, at locations where the wind dynamics exhibit chaotic behaviour. The predictions are remarkably accurate up to 1 h with a normalised RMSE (root mean square error) of less than 0.02 and reasonably accurate up to 3 h with an error of less than 0.06. Repeated application of these methods at 234 different geographical locations for predicting wind speeds at 30-day intervals for 3 years reveals that the accuracy of prediction is more or less the same across all locations and time periods. Comparison of the results with f-ARIMA model predictions shows that the deterministic models with suitable parameters are capable of returning improved prediction accuracy and capturing the dynamical variations of the actual time series more faithfully. These methods are simple and computationally efficient and require only records of past data for making short-term wind speed forecasts within practically tolerable margin of errors.

  14. Annual variations in sea surface wind speed around Japan observed by ASCAT

    NASA Astrophysics Data System (ADS)

    Takeyama, Y.; Shimada, S.; Ohsawa, T.; Kozai, K.; Kogaki, T.

    2015-12-01

    Sea surface wind speeds and these statistics can be applied for many marine industrial activities. For example, the averaged wind speed is crucial information for a site selection of an offshore wind farm. It has widely been recognized that a total amount of the offshore wind generation is strongly depended on the annual average wind speeds. A advanced scatterometer (ASCAT), which is a kind of scatterometer aboard METOP-A and B, has observed sea surface wind speeds at the height of 10 m above the sea surface approximately twice a day using active microwaves. The annual average wind speed can be calculated from the observed wind speed. For an actual use of the annual average wind speed, generalities and representativeness of the wind speed must be clarified. To investigate annual variations in sea surface wind speed around Japan (120°E to 165°E, 19°N to 49°N), the annual average wind speeds and these standard deviations are calculated from 5 years of ASCAT observations from 2010 through 2014. It is found that there are some sea areas where standard deviations are relatively higher than their surroundings. Annual average wind speed maps indicate that the high standard deviation is caused by strong winds from Eurasia in the winter of 2011 in part of North Pacific Ocean and Sea of Okhotsk. Additionally standard deviations for only winter are also higher than for summer in those sea areas. Therefore the strong wind speed in the winter of a particular year can easily affect to the annual average wind speed. Meanwhile off the coast of Niigata and Hokkaido, there are also higher standard deviation areas than their surroundings. Differences between monthly maximum wind speeds for the winter and minimum wind speeds for the summer in these areas are larger and the large differences seem to be a cause of the high standard deviations.

  15. Generalized extreme gust wind speeds distributions

    USGS Publications Warehouse

    Cheng, E.; Yeung, C.

    2002-01-01

    Since summer 1996, the US wind engineers are using the extreme gust (or 3-s gust) as the basic wind speed to quantify the destruction of extreme winds. In order to better understand these destructive wind forces, it is important to know the appropriate representations of these extreme gust wind speeds. Therefore, the purpose of this study is to determine the most suitable extreme value distributions for the annual extreme gust wind speeds recorded in large selected areas. To achieve this objective, we are using the generalized Pareto distribution as the diagnostic tool for determining the types of extreme gust wind speed distributions. The three-parameter generalized extreme value distribution function is, thus, reduced to either Type I Gumbel, Type II Frechet or Type III reverse Weibull distribution function for the annual extreme gust wind speeds recorded at a specific site.With the considerations of the quality and homogeneity of gust wind data collected at more than 750 weather stations throughout the United States, annual extreme gust wind speeds at selected 143 stations in the contiguous United States were used in the study. ?? 2002 Elsevier Science Ltd. All rights reserved.

  16. Evaluation of SEASAT SMMR wind speed measurements

    NASA Astrophysics Data System (ADS)

    Cardone, V.; Chester, T.; Lipes, R.

    1983-02-01

    The SEASAT scanning multichannel microwave radiometer (SMMR) is able to measure the wind speed at the ocean surface through the change in ocean surface microwave emissivity caused by the wind. In this paper we compare the SMMR-derived wind speeds to the wind speeds derived from an active microwave scatterometer also aboard the SEASAT, the SEASAT A scanning scatterometer (SASS), Four orbits that passed over the severe storm that damaged the Queen Elizabeth II are examined in detail. These orbits and five others were used to investigate effects which degrade the SMMR wind retrievals. When the data are filtered for such effects, we find that the SMMR winds agree with the SASS winds with a scatter (1σ) of less than 2 m/s about a bias of 1 to 2 m/s.

  17. Evaluation of Seasat SMMR wind speed measurements

    NASA Technical Reports Server (NTRS)

    Cardone, V.; Chester, T.; Lipes, R.

    1983-01-01

    The Seasat scanning multichannel microwave radiometer (SMMR) is able to measure the wind speed at the ocean surface through the change in ocean surface microwave emissivity caused by the wind. In this paper the SMMR-derived wind speeds are compared to the wind speeds derived from an active microwave scatterometer also aboard the Seasat, the Seasat A scanning scatterometer (SASS). Four orbits that passed over the severe storm that damaged the Queen Elizabeth II are examined in detail. These orbits and five others were used to investigate effects which degrade the SMMR wind retrievals. When the data are filtered for such effects, it is found that the SMMR winds agree with the SASS winds with a scatter (1 sigma) of less than 2 m/s about a bias of 1 to 2 m/s.

  18. Rain-aerosol relationships influenced by wind speed

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Russell, Lynn M.; Lou, Sijia; Liu, Ying; Singh, Balwinder; Ghan, Steven J.

    2016-03-01

    Aerosol optical depth (AOD) has been shown to correlate with precipitation rate (R) in recent studies. The R-AOD relationships over oceans are examined in this study using 150 year simulations with the Community Earth System Model. Through partial correlation analysis, with the influence of 10 m wind speed removed, R-AOD relationships exert a change from positive to negative over the midlatitude oceans, indicating that wind speed makes a large contribution to the relationships by changing the sea-salt emissions. A simulation with prescribed sea-salt emissions shows that wind speed leads to increasing R by +0.99 mm d-1 averaged globally, offsetting 64% of the wet scavenging-induced decrease between polluted and clean conditions, defined according to percentiles of AOD. These demonstrate that wind speed is one of the major drivers of R-AOD relationships. Relative humidity at 915 hPa can also result in the positive relationships; however, its role is smaller than that of wind speed.

  19. One- to two-month oscillations in SSMI surface wind speed in western tropical Pacific Ocean

    NASA Technical Reports Server (NTRS)

    Collins, Michael L.; Stanford, John L.; Halpern, David

    1994-01-01

    The 10-m wind speed over the ocean can be estimated from microwave brightness temperature measurements recorded by the Special Sensor Microwave Imager (SSMI) instrument mounted on a polar-orbiting spacecraft. Four-year (1988-1991) time series of average daily 1 deg x 1 deg SSMI wind speeds were analyzed at selected sites in the western tropical Pacific Ocean. One- to two-month period wind speed oscillations with amplitudes statistically significant at the 95% confidence level were observed near Kanton, Eniwetok, Guam, and Truk. This is the first report of such an oscillation in SSMI wind speeds.

  20. ECMWF and SSM/I global surface wind speeds

    NASA Technical Reports Server (NTRS)

    Halpern, David; Hollingsworth, Anthony; Wentz, Frank

    1994-01-01

    Monthly mean 2.5 deg x 2.5 deg resolution 10-m height wind speeds from the Special Sensor Microwave/Imager (SSM/I) instrument and the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast-analysis system are compared between 60 deg S and 60 deg N during 1988-91. The SSM/I data were uniformly processed while numerous changes were made to the ECMWF forecast-analysis system. The SSM/I measurements, which were compared with moored-buoy wind observations, were used as a reference dataset to evaluate the influence of the changes made to the ECMWF system upon the ECMWF surface wind speed over the ocean. A demonstrable yearly decrease of the difference between SSM/I and ECMWF wind speeds occurred in the 10 deg S-10 deg N region, including the 5 deg S-5 deg N zone of the Pacific Ocean, where nearly all of the variations occurred in the 160 deg E-160 deg W region. The apparent improvement of the ECMWF wind speed occurred at the same time as the yearly decrease of the equatorial Pacific SSM/I wind speed, which was associated with the natural transition from La Nina to El Nino conditions. In the 10 deg S-10 deg N tropical Atlantic, the ECMWF wind speed had a 4-yr trend, which was not expected nor was it duplicated with the SSM/I data. No yearly trend was found in the difference between SSM/I and ECMWF surface wind speeds in middle latitudes of the Northern and Southern Hemispheres. The magnitude of the differences between SSM/I and ECMWF was 0.4 m/s or 100% larger in the Northern than in the Southern Hemisphere extratropics. In two areas (Arabian Sea and North Atlantic Ocean) where ECMWF and SSM/I wind speeds were compared to ship measurements, the ship data had much better agreement with the ECMWF analyses compared to SSM/I data. In the 10 deg S-10 deg N area the difference between monthly standard deviations of the daily wind speeds dropped significantly from 1988 to 1989 but remained constant at about 30% for the remaining years.

  1. LIDAR Wind Speed Measurements of Evolving Wind Fields

    SciTech Connect

    Simley, E.; Pao, L. Y.

    2012-07-01

    Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. Past studies have assumed Taylor's frozen turbulence hypothesis, which implies that turbulence remains unchanged as it advects downwind at the mean wind speed. With Taylor's hypothesis applied, the only source of wind speed measurement error is distortion caused by the LIDAR. This study introduces wind evolution, characterized by the longitudinal coherence of the wind, to LIDAR measurement simulations to create a more realistic measurement model. A simple model of wind evolution is applied to a frozen wind field used in previous studies to investigate the effects of varying the intensity of wind evolution. LIDAR measurements are also evaluated with a large eddy simulation of a stable boundary layer provided by the National Center for Atmospheric Research. Simulation results show the combined effects of LIDAR errors and wind evolution for realistic turbine-mounted LIDAR measurement scenarios.

  2. Characterization of Wind Meandering in Low-Wind-Speed Conditions

    NASA Astrophysics Data System (ADS)

    Mortarini, Luca; Stefanello, Michel; Degrazia, Gervasio; Roberti, Debora; Trini Castelli, Silvia; Anfossi, Domenico

    2016-06-01

    Investigation of low-wind cases observed during the Urban Turbulent Project campaign (Torino, Italy) and at the Santa Maria meteorological station (Santa Maria, Brazil) provides insight into the wind-meandering phenomenon, i.e. large, non-turbulent oscillations of horizontal wind speed and temperature. Meandering and non-meandering cases are identified through analysis of the Eulerian autocorrelation functions of the horizontal wind-velocity components and temperature. When all three autocorrelation functions oscillate, meandering is present. As with weak turbulence, meandering shows no dependence on stability but is influenced by presence of buildings and depends on wind speed. We show that, while the standard deviation of the horizontal velocity is always large in low-wind conditions, the standard deviation of the vertical velocity shows very different behaviour in meandering and non-meandering conditions. In particular, the value of the ratio of the standard deviations of the vertical and horizontal velocities typifies the meandering condition.

  3. Maximum wind speeds and US hurricane losses

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  4. An Altimeter Wind Speed Model Using Both Radar Backscatter and Significant Wave Height

    NASA Technical Reports Server (NTRS)

    Vandemark, D.; Gourrion, J.; Bailey, S.; Chapron, B.; Zukor, Dorothy (Technical Monitor)

    2000-01-01

    The development and validation of a new altimeter wind speed model will be presented. This algorithm provides a direct mapping of TOPEX-measured backscatter and significant wave height to 10 m wind speed. A large scatterometer/altimeter crossover data set was assembled to develop the routine and several large ancillary data sets have been assembled for validation purposes. Validation results suggest that this two input routine provides marginal, yet measurable improvements over the standard single-parameter MCW algorithm.

  5. LIDAR wind speed measurements at a Taiwan onshore wind park

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Ting; Lin, Ta-Hui; Hsuan, Chung-Yao; Li, Yu-Cheng; Yang, Ya-Fei; Tai, Tzy-Hwan; Huang, Chien-Cheng

    2016-04-01

    Measurements of wind speed and wind direction were carried out using a Leosphere Windcube LIDAR system at a Taiwan onshore wind park. The Lidar shot a total of five laser beams to the atmosphere to collect the light-of-sight (LOS) velocity. Four beams were sent successively in four cardinal directions along a 28° scanning cone angle, followed by a fifth, vertical beam. An unchangeable sampling rate of approximately 1.2 Hz was set in the LIDAR system to collect the LOS velocity. The supervisory control and data acquisition (SCADA) data from two GE 1.5 MW wind turbines near the LIDAR deployment site were acquired for the whole measuring period from February 4 to February 16 of 2015. The SCADA data include the blade angular velocity, the wind velocity measured at hub height from an anemometer mounted on the nacelle, the wind turbine yaw angle, and power production; each parameter was recorded as averages over 1-min periods. The data analysis involving the LIDAR measurements and the SCADA data were performed to obtain the turbulent flow statistics. The results show that the turbine power production has significant dependence to the wind speed, wind direction, turbulence intensity and wind shear.

  6. LIDAR Wind Speed Measurements of Evolving Wind Fields

    SciTech Connect

    Simley, E.; Pao, L. Y.; Kelley, N.; Jonkman, B.; Frehlich, R.

    2012-01-01

    Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems that are designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. Past studies have assumed the validity of physicist G.I. Taylor's 1938 frozen turbulence hypothesis, which implies that turbulence remains unchanged as it advects downwind at the mean wind speed. With Taylor's hypothesis applied, the only source of wind speed measurement error is distortion caused by the LIDAR. This study introduces wind evolution, characterized by the longitudinal coherence of the wind, to LIDAR measurement simulations using the National Renewable Energy Laboratory's (NREL's) 5-megawatt turbine model to create a more realistic measurement model. A simple model of wind evolution was applied to a frozen wind field that was used in previous studies to investigate the effects of varying the intensity of wind evolution. LIDAR measurements were also evaluated using a large eddy simulation (LES) of a stable boundary layer that was provided by the National Center for Atmospheric Research. The LIDAR measurement scenario investigated consists of a hub-mounted LIDAR that scans a circle of points upwind of the turbine in order to estimate the wind speed component in the mean wind direction. Different combinations of the preview distance that is located upwind of the rotor and the radius of the scan circle were analyzed. It was found that the dominant source of measurement error for short preview distances is the detection of transverse and vertical wind speeds from the line-of-sight LIDAR measurement. It was discovered in previous studies that, in the absence of wind evolution, the dominant source of error for large preview distances

  7. Wind Speed Measurement by Paper Anemometer

    ERIC Educational Resources Information Center

    Zhong, Juhua; Cheng, Zhongqi; Guan, Wenchuan

    2011-01-01

    A simple wind speed measurement device, a paper anemometer, is fabricated based on the theory of standing waves. In providing the working profile of the paper anemometer, an experimental device is established, which consists of an anemometer sensor, a sound sensor, a microphone, paper strips, a paper cup, and sonic acquisition software. It shows…

  8. Dynamic simulation of dual-speed wind turbine generation

    SciTech Connect

    Muljadi, E.; Butterfield, C.P.

    1996-10-01

    Induction generators have been used since the early development of utility-scale wind turbine generation. An induction generator is the generator of choice because of its ruggedness, and low cost. With an induction generator, the operating speed of the wind turbine is limited to a narrow range (almost constant speed). Dual- speed operation can be accomplished by using an induction generator with two different sets of winding configurations or by using two induction generators with two different rated speeds. With single- speed operation, the wind turbine operates at different power coefficients (Cp) as the wind speed varies. The operation at maximum Cp can occur only at a single wind speed. However, if the wind speed varies across a wider range, the operating Cp will vary significantly. Dual-speed operation has the advantage of enabling the wind turbine to operate at near maximum Cp over a wider range of wind-speeds. Thus, annual energy production can be increased. The dual-speed mode may generate less energy than a variable-speed mode; nevertheless, it offers an alternative to capture more energy than single-speed operation. In this paper, dual-speed operation of a wind turbine will be investigated. One type of control algorithm for dual- speed operation is proposed. Results from a dynamic simulation will be presented to show how the control algorithm works and how power, current and torque of the system vary as the wind turbine is exposed to varying wind speeds.

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

    USGS Publications Warehouse

    Crusius, J.; Wanninkhof, R.

    2003-01-01

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

  10. How Phoenix Measures Wind Speed and Direction

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for animation

    This animation shows how NASA's Phoenix Mars Lander can measure wind speed and direction by imaging the Telltale with the Stereo Surface Imager (SSI).

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  11. Decadal predictability of regional scale wind speed and wind energy potentials over Central Europe

    NASA Astrophysics Data System (ADS)

    Moemken, Julia; Reyers, Mark; Buldmann, Benjamin; Pinto, Joaquim G.

    2016-04-01

    Regional climate predictions on timescales from one year to one decade are gaining importance since this time frame falls within the planning horizon of politics, economy, and society. In this context, decadal predictions are of particular interest for the development of renewable energies such as wind energy. The present study examines the decadal predictability of regional scale wind speed and wind energy potentials in the framework of the MiKlip consortium ("Mittelfristige Klimaprognosen"; www.fona-miklip.de). This consortium aims to develop a model system based on the Max-Planck-Institute Earth System Model (MPI-ESM) that can provide skilful decadal predictions on regional and global scales. Three generations of the decadal prediction system, which differ primarily in their ocean initialisation, are analysed here. Ensembles of uninitialised historical and yearly initialised hindcast experiments are used to assess different skill scores for 10m wind speeds and wind energy output (Eout) over Central Europe, with special focus given to Germany. With this aim, a statistical-dynamical downscaling (SDD) approach is used for the regionalisation of the global datasets. Its added value is evaluated by comparison of skill scores for MPI-ESM large-scale wind speeds and SDD simulated regional wind speeds. All three MPI-ESM ensemble generations show some forecast skill for annual mean wind speed and Eout over Central Europe on yearly and multi-yearly time scales. The forecast skill is mostly limited to the first years after initialisation. Differences between the three ensemble generations are generally small. The regionalisation preserves and sometimes increases the forecast skill of the global runs but results depend on lead time and ensemble generation. Moreover, regionalisation often improves the ensemble spread. Seasonal Eout skills are generally lower than for annual means. Skill scores are lowest during summer, and persist longest in autumn. A large-scale westerly

  12. Effect of wind speed and relative humidity on atmospheric dust concentrations in semi-arid climates.

    PubMed

    Csavina, Janae; Field, Jason; Félix, Omar; Corral-Avitia, Alba Y; Sáez, A Eduardo; Betterton, Eric A

    2014-07-15

    Atmospheric particulate have deleterious impacts on human health. Predicting dust and aerosol emission and transport would be helpful to reduce harmful impacts but, despite numerous studies, prediction of dust events and contaminant transport in dust remains challenging. In this work, we show that relative humidity and wind speed are both determinants in atmospheric dust concentration. Observations of atmospheric dust concentrations in Green Valley, AZ, USA, and Juárez, Chihuahua, México, show that PM10 concentrations are not directly correlated with wind speed or relative humidity separately. However, selecting the data for high wind speeds (>4m/s at 10 m elevation), a definite trend is observed between dust concentration and relative humidity: dust concentration increases with relative humidity, reaching a maximum around 25% and it subsequently decreases with relative humidity. Models for dust storm forecasting may be improved by utilizing atmospheric humidity and wind speed as main drivers for dust generation and transport. PMID:24769193

  13. Effect of Wind Speed and Relative Humidity on Atmospheric Dust Concentrations in Semi-Arid Climates

    PubMed Central

    Csavina, Janae; Field, Jason; Félix, Omar; Corral-Avitia, Alba Y.; Sáez, A. Eduardo; Betterton, Eric A.

    2014-01-01

    Atmospheric particulate have deleterious impacts on human health. Predicting dust and aerosol emission and transport would be helpful to reduce harmful impacts but, despite numerous studies, prediction of dust events and contaminant transport in dust remains challenging. In this work, we show that relative humidity and wind speed are both determinants in atmospheric dust concentration. Observations of atmospheric dust concentrations in Green Valley, AZ, USA, and Juárez, Chihuahua, México, show that PM10 concentrations are not directly correlated with wind speed or relative humidity separately. However, selecting the data for high wind speeds (> 4 m/s at 10 m elevation), a definite trend is observed between dust concentration and relative humidity: dust concentration increases with relative humidity, reaching a maximum around 25% and it subsequently decreases with relative humidity. Models for dust storm forecasting may be improved by utilizing atmospheric humidity and wind speed as main drivers for dust generation and transport. PMID:24769193

  14. On the problem of measuring interannual wind speed variations using SSMI data

    NASA Technical Reports Server (NTRS)

    Halpern, David; Wentz, Frank

    1994-01-01

    The first Special Sensor Microwave Imager (SSMI) was launched on the Defense Meteorological Satellite Program (DMSP) F8 spacecraft in July 1987, and wind speed was no longer retrieved after December 1991. A second SSMI was launched on DMSP F10 in December 1990. Interpretation of the 1987-1993 (or longer) SSMI wind speed time series is dependent upon the space and time characteristics of the differences between F8 and F10 SSMI measurements. The 10 deg-zonal averaged monthly mean F8-F10 wind speed difference was negative (positive) for wind speeds less (greater) than 7.9 m/s, reaching -0.43 (0.32) m/s at 5(10) m/s. Between 60 deg S and 60 deg N the 10 deg-zonal averaged monthly mean F8-F10 wind speed bias was greater than +/- 0.5 m/s on several occasions. From 60 deg S - 60 deg N the 1991 average value of the monthly mean root-mean-square difference between daily F8 and F10 wind speeds in 10 deg-longitudinal bands was 2.0 m/s.In the 60 deg S - 60 deg N region, about 50% of the daily F8 and F10 wind speed differences was caused by measurement non-simultaneity and about 50% of the difference was attributed to other factors, such as instrument noise and the different azimuthal orientations of each SSMI.

  15. Wind speed forecasting in the central California wind resource area

    SciTech Connect

    McCarthy, E.F.

    1997-12-31

    A wind speed forecasting program was implemented in the summer seasons of 1985 - 87 in the Central California Wind Resource Area (WRA). The forecasting program is designed to use either meteorological observations from the WRA and local upper air observations or upper air observations alone to predict the daily average windspeed at two locations. Forecasts are made each morning at 6 AM and are valid for a 24 hour period. Ease of use is a hallmark of the program as the daily forecast can be made using data entered into a programmable HP calculator. The forecasting program was the first step in a process to examine whether the electrical energy output of an entire wind power generation facility or defined subsections of the same facility could be predicted up to 24 hours in advance. Analysis of the results of the summer season program using standard forecast verification techniques show the program has skill over persistence and climatology.

  16. Speed tolerant alternator system for wind or hydraulic power generation

    SciTech Connect

    Jallen, G.A.

    1984-07-24

    A wind electric generator employs a freewheeling clutch and an induction generator having several synchronous speeds. By selecting the synchronous speed as a function of the ambient wind speed, the generator can be made to operate more efficiently and without overloading. The freewheeling clutch which connects the generator to the wind turbine prevents the generator from acting as a motor when connected to a power grid, and wasting energy in turning the wind turbine.

  17. Model estimates hurricane wind speed probabilities

    NASA Astrophysics Data System (ADS)

    Mumane, Richard J.; Barton, Chris; Collins, Eric; Donnelly, Jeffrey; Eisner, James; Emanuel, Kerry; Ginis, Isaac; Howard, Susan; Landsea, Chris; Liu, Kam-biu; Malmquist, David; McKay, Megan; Michaels, Anthony; Nelson, Norm; O Brien, James; Scott, David; Webb, Thompson, III

    In the United States, intense hurricanes (category 3, 4, and 5 on the Saffir/Simpson scale) with winds greater than 50 m s -1 have caused more damage than any other natural disaster [Pielke and Pielke, 1997]. Accurate estimates of wind speed exceedance probabilities (WSEP) due to intense hurricanes are therefore of great interest to (re)insurers, emergency planners, government officials, and populations in vulnerable coastal areas.The historical record of U.S. hurricane landfall is relatively complete only from about 1900, and most model estimates of WSEP are derived from this record. During the 1899-1998 period, only two category-5 and 16 category-4 hurricanes made landfall in the United States. The historical record therefore provides only a limited sample of the most intense hurricanes.

  18. Further development of an improved altimeter wind speed algorithm

    NASA Technical Reports Server (NTRS)

    Chelton, Dudley B.; Wentz, Frank J.

    1986-01-01

    A previous altimeter wind speed retrieval algorithm was developed on the basis of wind speeds in the limited range from about 4 to 14 m/s. In this paper, a new approach which gives a wind speed model function applicable over the range 0 to 21 m/s is used. The method is based on comparing 50 km along-track averages of the altimeter normalized radar cross section measurements with neighboring off-nadir scatterometer wind speed measurements. The scatterometer winds are constructed from 100 km binned measurements of radar cross section and are located approximately 200 km from the satellite subtrack. The new model function agrees very well with earlier versions up to wind speeds of 14 m/s, but differs significantly at higher wind speeds. The relevance of these results to the Geosat altimeter launched in March 1985 is discussed.

  19. What Determines the Solar Wind Speed ?

    NASA Astrophysics Data System (ADS)

    Suzuki, T. K.; Fujiki, K.; Kojima, M.; Tokumaru, M.; Hirano, M.; Baba, D.; Yamasita, M.; Hakamada, K.

    2005-05-01

    Recent observations by Interplanetary Scintillation measurements by Nagoya-STEL group (Hirano et al.2003; Kojima et al.2004) show that solar wind speed is well-correlated with B/f, where B is radial magnetic field strength at the solar surface and f is a super-radial expansion factor of open flux tubes. We show that this correlation is nicely explained by dissipation of Alfven waves no matter what types of the wave dissipation processes operate. B determines the input energy flux of Alfven waves and f controls adiabatic loss of the wave energy, so that B/f is an important control parameter which determines the solar wind speed. (reference ) [1] Hirano, M., Kojima, M., Tokumaru, M., Fujiki, K., Ohmi, T., Yamashita, M, Hakamada, K., and Hayashi, K. 2003,, Eos Trans. AGU, 84(46), Fall Meet. Suppl., Abstract SH21B-0164 [2] Kojima, M., K. Fujiki, M. Hirano, M. Tokumaru, T. Ohmi, and K. Hakamada, 2004, "The Sun and the heliosphere as an Integrated System", Giannina Poletto and Steven T. Suess, Eds. Kluwer Academic Publishers, in press

  20. Nonparametric analysis of high wind speed data

    NASA Astrophysics Data System (ADS)

    Francisco-Fernández, Mario; Quintela-del-Río, Alejandro

    2013-01-01

    In this paper, nonparametric curve estimation methods are applied to analyze time series of wind speeds, focusing on the extreme events exceeding a chosen threshold. Classical parametric statistical approaches in this context consist in fitting a generalized Pareto distribution (GPD) to the tail of the empirical cumulative distribution, using maximum likelihood or the method of the moments to estimate the parameters of this distribution. Additionally, confidence intervals are usually computed to assess the uncertainty of the estimates. Nonparametric methods to estimate directly some quantities of interest, such as the probability of exceedance, the quantiles or return levels, or the return periods, are proposed. Moreover, bootstrap techniques are used to develop pointwise and simultaneous confidence intervals for these functions. The proposed models are applied to wind speed data in the Gulf Coast of US, comparing the results with those using the GPD approach, by means of a split-sample test. Results show that nonparametric methods are competitive with respect to the standard GPD approximations. The study is completed generating synthetic data sets and comparing the behavior of the parametric and the nonparametric estimates in this framework.

  1. Effects of rainfall on scatterometer derived wind speeds

    NASA Technical Reports Server (NTRS)

    Bliven, L. F.; Norcross, G.

    1988-01-01

    Rainfall modification of scatterometer response from the sea surface was simulated in wind-wave tank experiments. Data show that for a given wind speed, radar cross section increases as rainfall rate increases, but this effect decreases as wind speed increases. An empirical model accounts for these observations.

  2. Laser velocimetry in the low-speed wind tunnels at Ames Research Center

    NASA Technical Reports Server (NTRS)

    Orloff, K. L.; Snyder, P. K.; Reinath, M. S.

    1984-01-01

    The historical development of laser velocimetry and its application to low-speed (less than 100 m/sec) aerodynamic flows in the subsonic wind tunnels at Ames Research Center is reviewed. A fully three dimensional velocimeter for the Ames 7- by 10-Foot Wind Tunnel is described, and its capabilities are presented through sample data from a recent experiment. Finally, a long-range (2.6 to 10 m) velocimeter that is designed to be installed within the test section of the Ames 40- by 80-Foot Wind Tunnel is described and sample data are presented.

  3. Spatial and Temporal Patterns of Global Onshore Wind Speed Distribution

    SciTech Connect

    Zhou, Yuyu; Smith, Steven J.

    2013-09-09

    Wind power, a renewable energy source, can play an important role in electrical energy generation. Information regarding wind energy potential is important both for energy related modeling and for decision-making in the policy community. While wind speed datasets with high spatial and temporal resolution are often ultimately used for detailed planning, simpler assumptions are often used in analysis work. An accurate representation of the wind speed frequency distribution is needed in order to properly characterize wind energy potential. Using a power density method, this study estimated global variation in wind parameters as fitted to a Weibull density function using NCEP/CFSR reanalysis data. The estimated Weibull distribution performs well in fitting the time series wind speed data at the global level according to R2, root mean square error, and power density error. The spatial, decadal, and seasonal patterns of wind speed distribution were then evaluated. We also analyzed the potential error in wind power estimation when a commonly assumed Rayleigh distribution (Weibull k = 2) is used. We find that the assumption of the same Weibull parameter across large regions can result in substantial errors. While large-scale wind speed data is often presented in the form of average wind speeds, these results highlight the need to also provide information on the wind speed distribution.

  4. SIMULATION OF WIND SPEED AND DIRECTION FROM LIMITED DATA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Wind Erosion Prediction System (WEPS) requires hourly wind data but these are not always available. Therefore, a procedure was developed to stochastically generate wind speed and direction from temporally limited wind data. For three locations. two statistical datasets were created to be used ...

  5. Effectiveness of Changing Wind Turbine Cut-in Speed to Reduce Bat Fatalities at Wind Facilities

    SciTech Connect

    Huso, Manuela M. P.; Hayes, John P.

    2009-04-01

    This report details an experiment on the effectiveness of changing wind turbine cut-in speed on reducing bat fatality from wind turbines at the Casselman Wind Project in Somerset County, Pennsylvania.

  6. Wind speed statistics for Goldstone, California, anemometer sites

    NASA Technical Reports Server (NTRS)

    Berg, M.; Levy, R.; Mcginness, H.; Strain, D.

    1981-01-01

    An exploratory wind survey at an antenna complex was summarized statistically for application to future windmill designs. Data were collected at six locations from a total of 10 anemometers. Statistics include means, standard deviations, cubes, pattern factors, correlation coefficients, and exponents for power law profile of wind speed. Curves presented include: mean monthly wind speeds, moving averages, and diurnal variation patterns. It is concluded that three of the locations have sufficiently strong winds to justify consideration for windmill sites.

  7. Relationship between wind speed and gas exchange over the ocean

    NASA Technical Reports Server (NTRS)

    Wanninkhof, Rik

    1992-01-01

    A quadratic dependence of gas exchange on wind speed is employed to analyze the relationship between gas transfer and wind speed with particular emphasizing variable and/or low wind speeds. The quadratic dependence is fit through gas-transfer velocities over the ocean determined by methods based on the natural C-14 disequilibrium and the bomb C-14 inventory. The variation in the CO2 levels is related to these mechanisms, but the results show that other causes play significant roles. A weaker dependence of gas transfer on wind is suggested for steady winds, and long-term averaged winds demonstrate a stronger dependence in the present model. The chemical enhancement of CO2 exchange is also shown to play a role by increasing CO2 fluxes at low wind speeds.

  8. Application-dependent Probability Distributions for Offshore Wind Speeds

    NASA Astrophysics Data System (ADS)

    Morgan, E. C.; Lackner, M.; Vogel, R. M.; Baise, L. G.

    2010-12-01

    The higher wind speeds of the offshore environment make it an attractive setting for future wind farms. With sparser field measurements, the theoretical probability distribution of short-term wind speeds becomes more important in estimating values such as average power output and fatigue load. While previous studies typically compare the accuracy of probability distributions using R2, we show that validation based on this metric is not consistent with validation based on engineering parameters of interest, namely turbine power output and extreme wind speed. Thus, in order to make the most accurate estimates possible, the probability distribution that an engineer picks to characterize wind speeds should depend on the design parameter of interest. We introduce the Kappa and Wakeby probability distribution functions to wind speed modeling, and show that these two distributions, along with the Biweibull distribution, fit wind speed samples better than the more widely accepted Weibull and Rayleigh distributions based on R2. Additionally, out of the 14 probability distributions we examine, the Kappa and Wakeby give the most accurate and least biased estimates of turbine power output. The fact that the 2-parameter Lognormal distribution estimates extreme wind speeds (i.e. fits the upper tail of wind speed distributions) with least error indicates that not one single distribution performs satisfactorily for all applications. Our use of a large dataset composed of 178 buoys (totaling ~72 million 10-minute wind speed observations) makes these findings highly significant, both in terms of large sample size and broad geographical distribution across various wind regimes. Boxplots of R2 from the fit of each of the 14 distributions to the 178 boy wind speed samples. Distributions are ranked from left to right by ascending median R2, with the Biweibull having the closest median to 1.

  9. Investigation of Wind Speed Persistence Over Marmara Region

    NASA Astrophysics Data System (ADS)

    Özgür, Evren; Koçak, Kasım

    2016-04-01

    Persistence is a measure of continuity of a variable over a period of time at any location. This definition implies that wind speed persistence means a positive serial correlation in a time series. In literature, there are numerous methods for measuring wind speed persistence. In this study, wind speed persistence were obtained for 19 stations located in Marmara Region by using two different methods. Daily wind speed data, taken from Turkish State Meteorological Service, were used in the study. The observation period was taken to be 1965-2014 for all stations. The methods used in the study are directional statistical method and wind speed duration curves approach. In directional statistical method, individual dates of winds are defined as directional variables; then, directional mean and variance are calculated. Wind dates are being converted to angular values and these days are being considered as a unit vector which has direction θ. In polar coordinate, the measures of directional mean and variance have been expressed as a vector with direction θmean and magnitude r. The r value can be considered as a measure of persistence. The wind speed duration curve is simply the cumulative distribution function of the wind speed in a certain period of time. In other words, it is the graphical representation of wind speed and percentage of exceedence time for a predefined threshold wind speed value in the same graphic. As a threshold wind speed, lower quartile (q0.25) value of ranked wind speed data were selected. In application, total time period was divided into five subperiods and changes of persistence in wind speeds as far as subperiods were presented. Persistence can be used in different kinds of study areas such as control of forest fires, dispersion of air pollutants, calculation of wind energy potential, ventilation of a city, etc. The results of this analysis showed that the proposed methods can be used as an alternative approach to determine whether a given time

  10. Observed Trends in Wind Speed over the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Hande, L. B.; Siems, S. T.; Manton, M. J.

    2012-06-01

    Most studies of trends in regional climate focus on temperature, however for maritime environments in particular, changes in the wind are equally important. An analysis of trends in the wind over Macquarie Island is performed with a radio-sonde database spanning nearly four decades. The results indicate that the surface wind speed is increasing, with the trend for the upper levels being less well defined. The surface wind is highly correlated with the upper level winds, and the wind at all levels are moderately correlated with the Southern Annular Mode. ECMWF ERA-Interim reanalysis data shows significant trends in wind speed over several levels, however slightly smaller than trends in the soundings over a similar time period. The correlations in ERA-Interim are similar to those in the soundings. A clustering analysis of the wind reveals four distinct regimes, with a trend towards a regime characterised by strong north westerly winds.

  11. Modulation of the Wind Speed Response of Marine Stratocumulus Clouds

    NASA Astrophysics Data System (ADS)

    Kazil, J.; Feingold, G.

    2014-12-01

    We explore a possible feedback mechanism of marine boundary layer clouds in response to expected 21st century changes in large scale wind speed. The mechanism proceeds via the effect of wind speed on the surface fluxes of sensible and latent heat, horizontal momentum (shear), and sea spray aerosol, and associated changes to cloud properties. An increase in wind speed produces, e.g., a higher latent heat flux from the surface, which causes stronger entrainment of free tropospheric air, and an adjustment in cloud properties. We have investigated how free tropospheric humidity and the evolution of the boundary layer modify the response of marine stratocumulus clouds to changes in wind speed. Results of cloud-system-resolving simulations are presented. The response of cloud properties and of radiative forcing to changes in surface wind speed is quantified under different free tropospheric conditions (dry vs. moist) and different boundary layer states (growing vs. steady state).

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  13. Reducing the uncertainty in wind speed estimations near the coast

    NASA Astrophysics Data System (ADS)

    Floors, Rogier; Hahmann, Andrea N.; Karagali, Ioanna; Vasiljevic, Nikola; Lea, Guillaume; Simon, Elliot; Courtney, Michael; Ahsbahs, Tobias; Bay Hasager, Charlotte; Badger, Merete; Peña, Alfredo

    2016-04-01

    Many countries plan to meet renewable energy targets by installing near-shore wind farms, because of the high offshore wind speeds and good grid connectivity. Because of the strong relation between mean wind speed and the annual energy production, there is an interest in reducing uncertainty of the estimation of the wind speed in these coastal areas. The RUNE project aims to provide recommendations on the use of lidar systems and mesoscale models results to find the most effective (cost vs. accuracy) solution of estimating near-shore wind resources. Here we show some first results of the RUNE measuring campaign at the west coast of Jutland that started in December 2015. In this campaign, a long-range WindScanner system (a multi-lidar instrumentation) was used simultaneously with measurements from several vertical profiling lidars, a meteorological mast and an offshore buoy. These measurements result in a detailed picture of the flow in a transect across the coastline from approximately 5 km offshore up to 3 km inland. The wind speed obtained from a lidar in a sector-scanning mode and from two time-synchronized lidars that were separated horizontally but focused in the same point, will be compared. Furthermore it will be shown how the resulting horizontal wind speed transects compare with the wind speed measurements from the vertical profiling lidars and the meteorological mast. The behaviour of the coastal gradient in wind speed in this area is discussed. Satellite data for the wind over the RUNE measurement area were also collected. Synthetic Aperture Radar (SAR) winds from Sentinel-1 and TerraSAR-X were retrieved at different spatial resolutions. Advanced Scatterometer (ASCAT) swath winds were obtained from both METOP-A and B platforms. These were used for direct comparisons with the lidar in sector scanning mode.

  14. Transient response of sap flow to wind speed.

    PubMed

    Chu, Chia R; Hsieh, Cheng-I; Wu, Shen-Yuang; Phillips, Nathan G

    2009-01-01

    Transient responses of sap flow to step changes in wind speed were experimentally investigated in a wind tunnel. A Granier-type sap flow sensor was calibrated and tested in a cylindrical tube for analysis of its transient time response. Then the sensor was used to measure the transient response of a well-watered Pachira macrocarpa plant to wind speed variations. The transient response of sap flow was described using the resistance-capacitance model. The steady sap flow rate increased as the wind speed increased at low wind speeds. Once the wind speed exceeded 8.0 m s(-1), the steady sap flow rate did not increase further. The transpiration rate, measured gravimetrically, showed a similar trend. The response of nocturnal sap flow to wind speed variation was also measured and compared with the results in the daytime. Under the same wind speed, the steady sap flow rate was smaller than that in the daytime, indicating differences between diurnal and nocturnal hydraulic function, and incomplete stomatal closure at night. In addition, it was found that the temporal response of the Granier sensor is fast enough to resolve the transient behaviour of water flux in plant tissue. PMID:19022910

  15. The Poisson Gamma distribution for wind speed data

    NASA Astrophysics Data System (ADS)

    Ćakmakyapan, Selen; Özel, Gamze

    2016-04-01

    The wind energy is one of the most significant alternative clean energy source and rapidly developing renewable energy sources in the world. For the evaluation of wind energy potential, probability density functions (pdfs) are usually used to model wind speed distributions. The selection of the appropriate pdf reduces the wind power estimation error and also allow to achieve characteristics. In the literature, different pdfs used to model wind speed data for wind energy applications. In this study, we propose a new probability distribution to model the wind speed data. Firstly, we defined the new probability distribution named Poisson-Gamma (PG) distribution and we analyzed a wind speed data sets which are about five pressure degree for the station. We obtained the data sets from Turkish State Meteorological Service. Then, we modelled the data sets with Exponential, Weibull, Lomax, 3 parameters Burr, Gumbel, Gamma, Rayleigh which are used to model wind speed data, and PG distributions. Finally, we compared the distribution, to select the best fitted model and demonstrated that PG distribution modeled the data sets better.

  16. Towards a new tool of wind speed and wind direction verification

    NASA Astrophysics Data System (ADS)

    Dorninger, Manfred

    2016-04-01

    During MesoVICT the verification of 2D-surface wind fields will receive special attention. Vector fields like wind are more complex to verify than scalar quantities. It is common approach to verify the single scalar components with traditional verification measures. This makes an overall and easy to understand interpretation of wind speed and direction verification difficult. Alternatively only wind speed is verified, which is useful for evaluating wind storms or estimating wind power. Wind direction is rarely verified. Although it is an important quantity for e.g. the correct frontal position, in the case of forest fires or during landing procedures of airplanes. In this presentation a new and simple verification procedure is introduced dealing with wind speed and direction. It is a grid-point based scheme but can be applied for spatial, for temporal as well as for ensemble forecast evaluations. In a first step differences of forecasts and observations of wind speed and direction are calculated and are filled in a specific scatter plot in a polar coordinate system. The different quadrants of the scatter plot can be interpreted in the following way (quadrants are counted anti-clockwise): I) Forecasted wind direction is rotated too anti-clockwise (directed towards the cyclone center), wind speed too high II) Forecasted wind direction is rotated too anti-clockwise, wind speed too low III) Forecasted wind direction is rotated too clockwise, wind speed too low IV) Forecasted wind direction is rotated too clockwise, wind speed too high To reduce the information of the point cloud the centre of gravity is determined and radii containing 10%, 25%, .. are defined which represent another verification measure. Several examples and possibilities of a statistical evaluation of these difference scatter plots will be presented during the conference.

  17. 622 Mbps High-speed satellite communication system for WINDS

    NASA Astrophysics Data System (ADS)

    Ogawa, Yasuo; Hashimoto, Yukio; Yoshimura, Naoko; Suzuki, Ryutaro; Gedney, Richard T.; Dollard, Mike

    2006-07-01

    WINDS is the experimental communications satellite currently under joint development by Japanese Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT). The high-speed satellite communication system is very effective for quick deployment of high-speed networks economically. The WINDS will realize ultra high-speed networking and demonstrate operability of satellite communication systems in high-speed internet. NICT is now developing high-speed satellite communication system for WINDS. High-speed TDMA burst modem with high performance TPC error correction is underdevelopment. Up to the DAC on the transmitter and from the ADC on the receiver, all modem functions are performed in the digital processing technology. Burst modem has been designed for a user data rate up to 1244 Mbps. NICT is developing the digital terminal as a user interface and a network controller for this earth station. High compatibility with the Internet will be provided.

  18. A nonlinear dynamics approach for incorporating wind-speed patterns into wind-power project evaluation.

    PubMed

    Huffaker, Ray; Bittelli, Marco

    2015-01-01

    Wind-energy production may be expanded beyond regions with high-average wind speeds (such as the Midwest U.S.A.) to sites with lower-average speeds (such as the Southeast U.S.A.) by locating favorable regional matches between natural wind-speed and energy-demand patterns. A critical component of wind-power evaluation is to incorporate wind-speed dynamics reflecting documented diurnal and seasonal behavioral patterns. Conventional probabilistic approaches remove patterns from wind-speed data. These patterns must be restored synthetically before they can be matched with energy-demand patterns. How to accurately restore wind-speed patterns is a vexing problem spurring an expanding line of papers. We propose a paradigm shift in wind power evaluation that employs signal-detection and nonlinear-dynamics techniques to empirically diagnose whether synthetic pattern restoration can be avoided altogether. If the complex behavior of observed wind-speed records is due to nonlinear, low-dimensional, and deterministic system dynamics, then nonlinear dynamics techniques can reconstruct wind-speed dynamics from observed wind-speed data without recourse to conventional probabilistic approaches. In the first study of its kind, we test a nonlinear dynamics approach in an application to Sugarland Wind-the first utility-scale wind project proposed in Florida, USA. We find empirical evidence of a low-dimensional and nonlinear wind-speed attractor characterized by strong temporal patterns that match up well with regular daily and seasonal electricity demand patterns. PMID:25617767

  19. Hourly Wind Speed Interval Prediction in Arid Regions

    NASA Astrophysics Data System (ADS)

    Chaouch, M.; Ouarda, T.

    2013-12-01

    The long and extended warm and dry summers, the low rate of rain and humidity are the main factors that explain the increase of electricity consumption in hot arid regions. In such regions, the ventilating and air-conditioning installations, that are typically the most energy-intensive among energy consumption activities, are essential for securing healthy, safe and suitable indoor thermal conditions for building occupants and stored materials. The use of renewable energy resources such as solar and wind represents one of the most relevant solutions to overcome the increase of the electricity demand challenge. In the recent years, wind energy is gaining more importance among the researchers worldwide. Wind energy is intermittent in nature and hence the power system scheduling and dynamic control of wind turbine requires an estimate of wind energy. Accurate forecast of wind speed is a challenging task for the wind energy research field. In fact, due to the large variability of wind speed caused by the unpredictable and dynamic nature of the earth's atmosphere, there are many fluctuations in wind power production. This inherent variability of wind speed is the main cause of the uncertainty observed in wind power generation. Furthermore, producing wind power forecasts might be obtained indirectly by modeling the wind speed series and then transforming the forecasts through a power curve. Wind speed forecasting techniques have received substantial attention recently and several models have been developed. Basically two main approaches have been proposed in the literature: (1) physical models such as Numerical Weather Forecast and (2) statistical models such as Autoregressive integrated moving average (ARIMA) models, Neural Networks. While the initial focus in the literature has been on point forecasts, the need to quantify forecast uncertainty and communicate the risk of extreme ramp events has led to an interest in producing probabilistic forecasts. In short term

  20. QBO in solar wind speed and its relation to ENSO

    NASA Astrophysics Data System (ADS)

    Hocke, Klemens

    2009-02-01

    Corotating coronal holes of the Sun induce fluctuations of the solar wind speed in the vicinity of the Earth. The fluctuations of solar wind speed are closely correlated with geomagnetic activity. Solar wind speed has been monitored by satellites since the mid 1960s. The long-term series of solar wind speed show enhanced amplitudes at the solar rotation period 27.3 days and at its harmonics 13.6 and 9.1 days. The amplitude series are modulated by a quasi-biennial oscillation (QBO) with a period of 1.75a (21 months) as bispectral analysis reveals. A 1.75a QBO component is also present in the equatorial, zonal wind of the stratosphere at 30 hPa, in addition to the well-known QBO component at the period 2.4a (29 months). The solar wind QBO may influence the stratospheric QBO, the global electric circuit, and cloud cover by modulation of ionospheric electric fields, cosmic ray flux, and particle precipitation. For a further analysis, the series of solar wind speed fluctuations are bandpass-filtered at the period 1.75a. The filtered series provide the amplitude of the solar wind QBO as function of time. The maxima of the solar wind QBO series are correlated with those of the ENSO index. The analysis indicate that the solar wind QBO may trigger the ENSO activity. This result is speculative at the moment. However, the focus of the study is on the investigation of the long-term modulations of the short-term (4-45 days) oscillations of the solar wind speed which are quite unexplored yet.

  1. A Nonlinear Dynamics Approach for Incorporating Wind-Speed Patterns into Wind-Power Project Evaluation

    PubMed Central

    Huffaker, Ray; Bittelli, Marco

    2015-01-01

    Wind-energy production may be expanded beyond regions with high-average wind speeds (such as the Midwest U.S.A.) to sites with lower-average speeds (such as the Southeast U.S.A.) by locating favorable regional matches between natural wind-speed and energy-demand patterns. A critical component of wind-power evaluation is to incorporate wind-speed dynamics reflecting documented diurnal and seasonal behavioral patterns. Conventional probabilistic approaches remove patterns from wind-speed data. These patterns must be restored synthetically before they can be matched with energy-demand patterns. How to accurately restore wind-speed patterns is a vexing problem spurring an expanding line of papers. We propose a paradigm shift in wind power evaluation that employs signal-detection and nonlinear-dynamics techniques to empirically diagnose whether synthetic pattern restoration can be avoided altogether. If the complex behavior of observed wind-speed records is due to nonlinear, low-dimensional, and deterministic system dynamics, then nonlinear dynamics techniques can reconstruct wind-speed dynamics from observed wind-speed data without recourse to conventional probabilistic approaches. In the first study of its kind, we test a nonlinear dynamics approach in an application to Sugarland Wind—the first utility-scale wind project proposed in Florida, USA. We find empirical evidence of a low-dimensional and nonlinear wind-speed attractor characterized by strong temporal patterns that match up well with regular daily and seasonal electricity demand patterns. PMID:25617767

  2. Variable speed generator technology options for wind turbine generators

    NASA Technical Reports Server (NTRS)

    Lipo, T. A.

    1995-01-01

    The electrical system options for variable speed operation of a wind turbine generator are treated in this paper. The key operating characteristics of each system are discussed and the major advantages and disadvantages of each are identified

  3. Effect of Wind Speed on Aerosol Optical Depth over Remote Oceans, Based on Data from the Maritime Aerosol Network

    NASA Technical Reports Server (NTRS)

    Smirnov, A.; Sayer, A. M.; Holben, B. N.; Hsu, N. C.; Sakerin, S. M.; Macke, A.; Nelson, N. B.; Courcoux, Y.; Smyth, T. J.; Croot, P.; Quinn, P. K.; Sciare, J.; Gulev, S. K.; Piketh, S.; Losno, R.; Kinne, S.; Radionov, V. F.

    2012-01-01

    The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (approx. 0.004 - 0.005), even for strong winds over 10m/s. The relationships show significant scatter (correlation coefficients typically in the range 0.3 - 0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used

  4. A comparison between a hydro-wind plant and wind speed forecasting using ARIMA models

    NASA Astrophysics Data System (ADS)

    Bayón, L.; Grau, J. M.; Ruiz, M. M.; Suárez, P. M.

    2014-10-01

    In this paper, we will present a comparison between two options for harnessing wind power. We will first analyze the behaviour of a wind farm that goes to the electricity market, having previously made a forecast of wind speed while accepting the deviation penalties that these may incur. Second, we will study the possibility of the wind farm not going to the market individually, but as part of a hydro-wind plant.

  5. Wind speed power spectrum analysis for Bushland, Texas

    SciTech Connect

    Eggleston, E.D.

    1996-12-31

    Numerous papers and publications on wind turbulence have referenced the wind speed spectrum presented by Isaac Van der Hoven in his article entitled Power Spectrum of Horizontal Wind Speed Spectrum in the Frequency Range from 0.0007 to 900 Cycles per Hour. Van der Hoven used data measured at different heights between 91 and 125 meters above the ground, and represented the high frequency end of the spectrum with data from the peak hour of hurricane Connie. These facts suggest we should question the use of his power spectrum in the wind industry. During the USDA - Agricultural Research Service`s investigation of wind/diesel system power storage, using the appropriate wind speed power spectrum became a significant issue. We developed a power spectrum from 13 years of hourly average data, 1 year of 5 minute average data, and 2 particularly gusty day`s 1 second average data all collected at a height of 10 meters. While the general shape is similar to the Van der Hoven spectrum, few of his peaks were found in the Bushland spectrum. While higher average wind speeds tend to suggest higher amplitudes in the high frequency end of the spectrum, this is not always true. Also, the high frequency end of the spectrum is not accurately described by simple wind statistics such as standard deviation and turbulence intensity. 2 refs., 5 figs., 1 tab.

  6. Plant Gas Exchange at High Wind Speeds 1

    PubMed Central

    Caldwell, Martyn M.

    1970-01-01

    High altitude Rhododendron ferrugineum L. and Pinus cembra L. seedlings were exposed to winds at 15 meters per second for 24-hour periods. Wind-sensitive stomata of Rhododendron seedlings immediately initiated a closing response which resulted in decreased photosynthesis and an even greater reduction in transpiration. Stomatal aperture and transpiration rates of P. cembra were only slightly reduced by high speed winds. However, photosynthesis was substantially reduced because of changes in needle display to available irradiation. PMID:16657501

  7. Evaluation of SEASAT-A SMMR derived wind speed measurements

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Wind speeds derived from versions of the least-squares and regression algorithms developed after the JASIN Workshop were evaluated. The accuracy of scanning multichannel microwave radiometer (SMMR) wind retrievals was determined in terms of the intrinsic accuracy of a baseline surface truth data set in favorable conditions. Effects which degrade the wind retrievals or introduce biases were identified and assessed. The performance of the SMMR in storms was ascertained with particular emphasis on the effects of rain.

  8. Influence of Speed Governors of Hydropower Stations on Frequency Stabilization of Fixed-Speed Wind Farm

    NASA Astrophysics Data System (ADS)

    AL Jowder, Fawzi A. Rahman

    2013-05-01

    This paper uses a small power system, consisting of two hydropower stations and a fixed-speed wind farm as sources of power, to study the influence of type of speed governor of hydropower stations on the frequency stabilization of the fixed-speed wind farm. As an example, two types of speed governors are selected which are (1) mechanical-hydraulic speed governor and (2) electrical-hydraulic speed governor. Rest of the speed governors can be also examined following the same methodology presented in the research. Two transfer functions, which correspond to the two speed governors, are developed for each hydropower station. The overall transfer function of the test power system is developed, and different study cases are presented. The frequency response analysis of the different transfer functions is used to compare the two speed governors based on their ability to stabilize the frequency deviation of the fixed-speed wind resulting from electrical or mechanical disturbances in the power systems. Time-domain simulations under a mechanical disturbance, represented by a wind gust, and an electrical disturbance, represented by three-phase to ground fault, are performed to validate the results of the frequency response analysis.

  9. Variable speed operation of generators with rotor-speed feedback in wind power applications

    SciTech Connect

    Muljadi, E.; Butterfield, C.P.; Migliore, P.

    1995-11-01

    The use of induction generators in wind power applications has been common since the early development of the wind industry. Most of these generators operate at fixed frequency and are connected directly to the utility grid. Unfortunately, this mode of operation limits the rotor speed to a specific rpm. Variable-speed operation is preferred in order to facilitate maximum energy capture over a wide range of wind speeds. This paper explores variable-speed operating strategies for wind turbine applications. The objectives are to maximize energy production, provide controlled start-up and reduce torque loading. This paper focuses on optimizing the energy captured by operating at maximum aerodynamic efficiency at any wind speed. The control strategy we analyze uses rotor speed and generator power as the feedback signals. In the normal operating region, rotor speed is used to compute a target power that corresponds to optimum operation. With power as the control objective, the power converter and generator are controlled to track the target power at any rpm. Thus, the torque-speed characteristic of the generator is shaped to optimize the energy capture. The target power is continuously updated at any rpm. in extreme areas of the operating envelope, during start-up, shutdown, generator overload, or overspeed, different strategies driven by other system considerations must be used.

  10. Comparison of a simple logarithmic and equivalent neutral wind approaches for converting buoy-measured wind speed to the standard height: special emphasis to North Indian Ocean

    NASA Astrophysics Data System (ADS)

    Singh, Prem; Parekh, Anant; Attada, Raju

    2013-02-01

    The difference between the transferred wind speed to 10-m height based on the equivalent neutral wind approach ( U n) and the logarithmic approach ( U log) is studied using in situ observations from the Indian, Pacific, and Atlantic Oceans, with special emphasis given to the North Indian Ocean. The study included U n - U log variations with pressure, relative humidity, wind speed, air temperature, and sea surface temperature (SST). U n - U log variation with respect to air temperature ( T a) reveals that U n - U log is out of phase with air temperature. Further analysis found that U n - U log is in phase with SST ( T s) - T a and varies between -1.0 and 1.0 m/s over the North Indian Ocean, while for the rest of the Oceans, it is between -0.3 and 0.8 m/s. This higher magnitude of U n - U log over the North Indian Ocean is due to the higher range of T s - T a (-4 to 6 °C) in the North Indian Ocean. Associated physical processes suggested that the roughness length and friction velocity dependence on the air-sea temperature difference contributes to the U n - U log difference. The study is further extended to evaluate the behavior of U n - U log under cyclonic conditions (winds between 15 and 30 m/s), and it was found that the magnitude of Un - U log varies 0.5-1.5 m/s under the cyclonic wind conditions. The increasing difference with the wind speed is due to the increase in the momentum transfer coefficient with wind speed, which modifies the friction velocity significantly, resulting in U n higher than U log. Thus, under higher wind conditions, U n - U log can contribute up to half the retrieval error (5 % of the wind speed magnitude) to the satellite validation exercise.

  11. Indexed semi-Markov process for wind speed modeling.

    NASA Astrophysics Data System (ADS)

    Petroni, F.; D'Amico, G.; Prattico, F.

    2012-04-01

    The increasing interest in renewable energy leads scientific research to find a better way to recover most of the available energy. Particularly, the maximum energy recoverable from wind is equal to 59.3% of that available (Betz law) at a specific pitch angle and when the ratio between the wind speed in output and in input is equal to 1/3. The pitch angle is the angle formed between the airfoil of the blade of the wind turbine and the wind direction. Old turbine and a lot of that actually marketed, in fact, have always the same invariant geometry of the airfoil. This causes that wind turbines will work with an efficiency that is lower than 59.3%. New generation wind turbines, instead, have a system to variate the pitch angle by rotating the blades. This system able the wind turbines to recover, at different wind speed, always the maximum energy, working in Betz limit at different speed ratios. A powerful system control of the pitch angle allows the wind turbine to recover better the energy in transient regime. A good stochastic model for wind speed is then needed to help both the optimization of turbine design and to assist the system control to predict the value of the wind speed to positioning the blades quickly and correctly. The possibility to have synthetic data of wind speed is a powerful instrument to assist designer to verify the structures of the wind turbines or to estimate the energy recoverable from a specific site. To generate synthetic data, Markov chains of first or higher order are often used [1,2,3]. In particular in [1] is presented a comparison between a first-order Markov chain and a second-order Markov chain. A similar work, but only for the first-order Markov chain, is conduced by [2], presenting the probability transition matrix and comparing the energy spectral density and autocorrelation of real and synthetic wind speed data. A tentative to modeling and to join speed and direction of wind is presented in [3], by using two models, first

  12. Validation of solar wind high-speed stream predictions

    NASA Astrophysics Data System (ADS)

    Reiss, Martin; Temmer, Manuela; Veronig, Astrid; Nikolic, Ljubomir; Schöngassner, Florian; Vennerstrøm, Susanne

    2016-04-01

    Solar wind high-speed streams emanating from coronal holes are frequently impinging on the Earth's magnetosphere causing recurrent, medium-level geomagnetic storm activity. As major contributors to space weather disturbances at times of low solar activity, prediction models of solar wind high-speed streams are becoming highly desirable. We present a verification analysis of two operational solar wind prediction models (empirical model, Wang-Sheeley-Arge like model) by comparing the model runs for the period 2011 to 2014 with in-situ plasma measurements from the ACE spacecraft located at 1 AU. We find that both prediction models achieve a similar accuracy but demonstrate the tendency to under-predict and over-predict events of solar wind high-speed streams, respectively. General advantages and disadvantages of both models are diagnosed and outlined.

  13. Wind tunnel experiments to prove a hydraulic passive torque control concept for variable speed wind turbines

    NASA Astrophysics Data System (ADS)

    Diepeveen, N. F. B.; Jarquin-Laguna, A.

    2014-12-01

    In this paper the results are presented of experiments to prove an innovative concept for passive torque control of variable speed wind turbines using fluid power technology. It is demonstrated that by correctly configuring the hydraulic drive train, the wind turbine rotor operates at or near maximum aerodynamic efficiency for below rated wind speeds. The experiments with a small horizontal-axis wind turbine rotor, coupled to a hydraulic circuit, were conducted at the Open Jet Facility of the Delft University of Technology. In theory, the placement of a nozzle at the end of the hydraulic circuit causes the pressure and hence the rotor torque to increase quadratically with flow speed and hence rotation speed. The rotor torque is limited by a pressure relief valve. Results from the experiments proved the functionality of this passive speed control concept. By selecting the correct nozzle outlet area the rotor operates at or near the optimum tip speed ratio.

  14. Rotor equivalent wind speed for power curve measurement - comparative exercise for IEA Wind Annex 32

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Cañadillas, B.; Clifton, A.; Feeney, S.; Nygaard, N.; Poodt, M.; St. Martin, C.; Tüxen, E.; Wagenaar, J. W.

    2014-06-01

    A comparative exercise has been organised within the International Energy Agency (IEA) Wind Annex 32 in order to test the Rotor Equivalent Wind Speed (REWS) method under various conditions of wind shear and measurement techniques. Eight organisations from five countries participated in the exercise. Each member of the group has derived both the power curve based on the wind speed at hub height and the power curve based on the REWS. This yielded results for different wind turbines, located in diverse types of terrain and where the wind speed profile was measured with different instruments (mast or various lidars). The participants carried out two preliminary steps in order to reach consensus on how to implement the REWS method. First, they all derived the REWS for one 10 minute wind speed profile. Secondly, they all derived the power curves for one dataset. The main point requiring consensus was the definition of the segment area used as weighting for the wind speeds measured at the various heights in the calculation of the REWS. This comparative exercise showed that the REWS method results in a significant difference compared to the standard method using the wind speed at hub height in conditions with large shear and low turbulence intensity.

  15. MEASUREMENT OF WIND SPEED FROM COOLING LAKE THERMAL IMAGERY

    SciTech Connect

    Garrett, A; Robert Kurzeja, R; Eliel Villa-Aleman, E; Cary Tuckfield, C; Malcolm Pendergast, M

    2009-01-20

    The Savannah River National Laboratory (SRNL) collected thermal imagery and ground truth data at two commercial power plant cooling lakes to investigate the applicability of laboratory empirical correlations between surface heat flux and wind speed, and statistics derived from thermal imagery. SRNL demonstrated in a previous paper [1] that a linear relationship exists between the standard deviation of image temperature and surface heat flux. In this paper, SRNL will show that the skewness of the temperature distribution derived from cooling lake thermal images correlates with instantaneous wind speed measured at the same location. SRNL collected thermal imagery, surface meteorology and water temperatures from helicopters and boats at the Comanche Peak and H. B. Robinson nuclear power plant cooling lakes. SRNL found that decreasing skewness correlated with increasing wind speed, as was the case for the laboratory experiments. Simple linear and orthogonal regression models both explained about 50% of the variance in the skewness - wind speed plots. A nonlinear (logistic) regression model produced a better fit to the data, apparently because the thermal convection and resulting skewness are related to wind speed in a highly nonlinear way in nearly calm and in windy conditions.

  16. Measurement of wind speed from cooling lake thermal imagery

    NASA Astrophysics Data System (ADS)

    Garrett, Alfred J.; Tuckfield, R. Cary; Villa-Aleman, Eliel; Kurzeja, Robert J.; Pendergast, Malcolm M.

    2009-05-01

    The Savannah River National Laboratory (SRNL) collected thermal imagery and ground truth data at two commercial power plant cooling lakes to investigate the applicability of laboratory empirical correlations between surface heat flux and wind speed, and statistics derived from thermal imagery. SRNL demonstrated in a previous paper [1] that a linear relationship exists between the standard deviation of image temperature and surface heat flux. In this paper, SRNL will show that the skewness of the temperature distribution derived from cooling lake thermal images correlates with instantaneous wind speed measured at the same location. SRNL collected thermal imagery, surface meteorology and water temperatures from helicopters and boats at the Comanche Peak and H. B. Robinson nuclear power plant cooling lakes. SRNL found that decreasing skewness correlated with increasing wind speed, as was the case for the laboratory experiments. Simple linear and orthogonal regression models both explained about 50% of the variance in the skewness - wind speed plots. A nonlinear (logistic) regression model produced a better fit to the data, apparently because the thermal convection and resulting skewness are related to wind speed in a highly nonlinear way in nearly calm and in windy conditions.

  17. Variable-Speed Wind System Design : Final Report.

    SciTech Connect

    Lauw, Hinan K.; Weigand, Claus H.; Marckx, Dallas A.; Electronic Power Conditioning, Inc.

    1993-10-01

    Almost from the onset of the development of wind energy conversion systems (WECS), it was known that variable-speed operation of the turbine would maximize energy capture. This study was commissioned to assess the cost, efficiency gain, reduction of the cost of energy (COE), and other operating implications of converting the existing hardware of a modern fixed-speed wind energy conversion system to variable-speed operation. The purpose of this study was to develop a preliminary design for the hardware required to allow variable-speed operation using a doubly-fed generator with an existing fixed-speed wind turbine design. The turbine selected for this study is the AWT-26 designed and built by Advanced Wind Turbines Inc. of Redmond, Washington. The lowest projected COE using this variable-speed generation system is projected to be $0.0499/kWh, compared to the lowest possible COE with fixed-speed generation which is projected to be $0.0546/kWh. This translates into a 8.6% reduction of the COE using this variable-speed generation option. The preliminary system design has advanced to where the printed circuit boards can be physically laid out based on the schematics and the system software can be written based on the control flow-charts. The core of hardware and software has been proven to be successful in earlier versions of VSG systems. The body of this report presents the results of the VSWG system development. Operation under normal and fault conditions is described in detail, the system performance for variable-speed operation is estimated and compared to the original fixed-speed system performance, and specifications for all system components (generator, power electronic converter, and system controller) are given. Costs for all components are estimated, and incremental system cost is compared to incremental energy production. Finally, operational features of the VSWG which are not available in the existing FSWG system are outlined.

  18. An Automatic Speed Control for Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1928-01-01

    Described here is an automatic control that has been used in several forms in wind tunnels at the Washington Navy Yard. The form now in use with the 8-foot tunnel at the Navy Yard is considered here. Details of the design and operation of the automatic control system are given. Leads from a Pitot tube are joined to an inverted cup manometer located above a rheostat. When the sliding weight of this instrument is set to a given notch, say for 40 m.p.h, the beam tip vibrates between two electric contacts that feed the little motor. Thus, when the wind is too strong or too weak, the motor automatically throws the rheostat slide forward and backward. If it failed to function well, the operator would notice the effect on his meniscus, and would operate the hand control by merely pressing the switch.

  19. Two Capacitive Micro-Machined Ultrasonic Transducers for Wind Speed Measurement

    PubMed Central

    Bui, Gia Thinh; Jiang, Yu-Tsung; Pang, Da-Chen

    2016-01-01

    This paper presents a new wind speed measurement method using a single capacitive micro-machined ultrasonic transducer (CMUT). The CMUT was arranged perpendicular to the direction of the wind flow, and a reflector was set up a short distance away, facing the CMUT. To reduce the size, weight, cost, and power consumption of conventional ultrasonic anemometers this study proposes two CMUT designs for the measurement of wind speed using either the amplitude of the signal or the time of flight (TOF). Each CMUT with a double array element design can transmit and receive signals in five different operation modes. Experiments showed that the two CMUT designs utilizing the TOF were better than those utilizing the amplitude of the signal for wind speed measurements ranging from 1 m/s to 10 m/s, providing a measurement error of less than 0.2 m/s. These results indicate that the sensitivity of the TOF is independent of the five operation modes. PMID:27271625

  20. Two Capacitive Micro-Machined Ultrasonic Transducers for Wind Speed Measurement.

    PubMed

    Bui, Gia Thinh; Jiang, Yu-Tsung; Pang, Da-Chen

    2016-01-01

    This paper presents a new wind speed measurement method using a single capacitive micro-machined ultrasonic transducer (CMUT). The CMUT was arranged perpendicular to the direction of the wind flow, and a reflector was set up a short distance away, facing the CMUT. To reduce the size, weight, cost, and power consumption of conventional ultrasonic anemometers this study proposes two CMUT designs for the measurement of wind speed using either the amplitude of the signal or the time of flight (TOF). Each CMUT with a double array element design can transmit and receive signals in five different operation modes. Experiments showed that the two CMUT designs utilizing the TOF were better than those utilizing the amplitude of the signal for wind speed measurements ranging from 1 m/s to 10 m/s, providing a measurement error of less than 0.2 m/s. These results indicate that the sensitivity of the TOF is independent of the five operation modes. PMID:27271625

  1. Multifractal and local correlation of simultaneous wind speed-power output from a single wind trubine

    NASA Astrophysics Data System (ADS)

    Calif, Rudy; Schmitt, François G.; Huang, Yongxiang

    2014-05-01

    The wind energy production is a nonlinear and no stationary resource, due to the intermittent statistics of atmospheric wind speed at all spatial and temporal scales ranging from large scale variations to very short scale variations. Recently, Rudy et al.[1] observed the intermittent and multifractal properties of wind energy production. Classically, IEC standard 4100 is used by the wind energy community, for modeling the interactions of wind speed with the wind turbine. However, this model reflects gaussian statistics contrary to observed wind and energy production measurements. Modeling of power curve of a single wind turbine remains a challenge. The precise understanding of the dynamics of nonlinear power curve over very short time scales, is necessary. Hence, multifractal cross-correlation methods such as Generalized Correlations Exponents (GCE), multifractal detrended cross-correlation analysis (MFXDFA), multifractal detrending moving average cross-correlation analysis (MFXDMA) are applied to simultaneous wind speed power output from a single wind turbine to determine the nature of scaling correlation behavior. Furthermore, in order to detect eventual local correlation, an application of empirical mode decomposition based on time dependent intrinsic correlation to simultaneous measurements is performed. The simultaneous wind speed-power output measurements are recorded continuously with a sampling rate f = 1Hz, during 115 days in 2006. The wind speed measurements are obtained at 31 m above the ground, and the power output is delivered by 500 kW Nordtank wind turbine positionned at the Technical University, Risœ, Denmark. References [1] Calif, R., Schmitt, F.G., Huang, Y., Multifractal description of wind power fluctuations using arbitrary order Hilbert spectral analysis, Physica, 392, 4106-4120, 2013.

  2. Results and validation of marine surface wind speed obtained from SAC-D/Aquarius MWR

    NASA Astrophysics Data System (ADS)

    Tauro, C. B.; Etala, P.; Echevarría, P.; Hejazin, Y.; Jacob, M. M.; Jones, L.

    2012-12-01

    MWR (MicroWave Radiometer) is a radiometer on board SAC-D/Aquarius satellite, launched in June 2011. The SAC-D/Aquarius science mission was developed jointly by the Nacional Space Agency of Argentina (CONAE, Comisión Nacional de Actividades Espaciales) and the National Aeronautics and Space Administration of USA (NASA), that focuses on understanding the interaction between the global water cycle, ocean circulation and climate by measuring sea surface salinity. MWR is a three channel push broom, Dicke radiometer, that has 16 beams, 8 forward-looking at 36.5 GHz (in vertical and horizontal polarization) and 8 aft-looking at 23.8 GHz (in horizontal polarization), with a swath of approximately 380 Km. The beams are arranged to have two incidence angles, one of 52° (odd beams) and one of 58° (even beams) for both forward and aft-looks. Since recently, CONAE with collaboration of CFRSL (Central Florida Remote Sensing Laboratory), are generating geophysical parameters, all over the sea surface, using brightness temperature measurements from MWR. These parameters include columnar water vapor, wind speed, sea ice concentration and rain rate, which are ancillary data for the Aquarius salinity measurements. We present in this paper the first results of wind speed over the sea, obtained using the MWR data. The wind speed retrieval algorithm is based on the microwave radiative transfer theory by Wentz [1]. The algorithm developed uses MWR brigthness temperature at 36.5 GHz in both polarizations and sea surface temperature obtained from GDAS. As a result, the neutral stability ocean surface wind speed at 10 m height and the atmospheric trasnmissivity at 36.5 GHz are retrieved. In addition, a validation process in collaboration with the Naval Hydrographic Service of Argentina (SHN) has started. The final goal of this on-going work is to assess the quality of MWR wind data in conjunction with surface wind observations from other sources in a data assimilation system. At this

  3. Credibility of statistical modeling of extreme wind speed

    NASA Astrophysics Data System (ADS)

    Pop, L.

    2009-09-01

    This paper deals with credibility of statistical modeling of extreme wind speed. The work has been done in the framework of Project KJB300420905 - Analysis of extreme wind speed in the Czech Republic (2009-2011, AV0/KJ). Statistical modeling of extreme wind speed is based on the extremal types theorem. The theorem states that extreme values converge to so-called Generalized extreme value (GEV). Depending on one parameter, usually called k, the distribution is usually called Fréchet (k > 0), Gumbel (k = 0) or Weibull (k < 0). Using upper tail of these distributions, it is simple to estimate wind speed with return period N years. The most important value for technical applications is the case N = 50. Fréchet distribution has an upper limit, while Gumbel and Weibull distributions have not. Consequently, Fréchet distribution is considered not to be suitable for extreme wind speed applications, because there is no physical reason for such an upper limit However, the extreme wind speed based on Fréchet distribution enables arbitrary high upper tail of distribution, so the previous reason is by not sufficient for excllusion of the distribution from extreme wind modeling by some authors. The most applied method is Gumbel distribution. There is not any theoretical reason for this fact. But the value of wind speed with return period of 50 years is strongly affected by thickness of right tail of GEV distribution and, consequently, by value of parameter k. Limitation of Gumbell distribution is keeping this value equal to zero, so estimated values of extreme wind are expected to be less scattered. Extremal types theorem has two presumptions: stationarity and extremity of modeled data. Stationarity strongly depends on quality of the measured data, however this issue will not be addressed here. Instead we will suppose that all measured data are of good quality Other problems preventing stationarity are due to time correlations of wind speed. Possible reasons are as follows: 1

  4. Reduced Wind Speed Improves Plant Growth in a Desert City

    PubMed Central

    Bang, Christofer; Sabo, John L.; Faeth, Stanley H.

    2010-01-01

    Background The often dramatic effects of urbanization on community and ecosystem properties, such as primary productivity, abundances, and diversity are now well-established. In most cities local primary productivity increases and this extra energy flows upwards to alter diversity and relative abundances in higher trophic levels. The abiotic mechanisms thought to be responsible for increases in urban productivity are altered temperatures and light regimes, and increased nutrient and water inputs. However, another abiotic factor, wind speed, is also influenced by urbanization and well known for altering primary productivity in agricultural systems. Wind effects on primary productivity have heretofore not been studied in the context of urbanization. Methodology/Principal Findings We designed a field experiment to test if increased plant growth often observed in cities is explained by the sheltering effects of built structures. Wind speed was reduced by protecting Encelia farinosa (brittlebush) plants in urban, desert remnant and outlying desert localities via windbreaks while controlling for water availability and nutrient content. In all three habitats, we compared E. farinosa growth when protected by experimental windbreaks and in the open. E. farinosa plants protected against ambient wind in the desert and remnant areas grew faster in terms of biomass and height than exposed plants. As predicted, sheltered plants did not differ from unprotected plants in urban areas where wind speed is already reduced. Conclusion/Significance Our results indicate that reductions in wind speed due to built structures in cities contribute to increased plant productivity and thus also to changes in abundances and diversity of higher trophic levels. Our study emphasizes the need to incorporate wind speed in future urban ecological studies, as well as in planning for green space and sustainable cities. PMID:20548790

  5. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 6 2014-07-01 2014-07-01 false Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration...

  6. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 6 2012-07-01 2012-07-01 false Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration...

  7. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 6 2013-07-01 2013-07-01 false Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration...

  8. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 5 2011-07-01 2011-07-01 false Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration...

  9. Laser Velocimetry In Low-Speed Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Orloff, Kenneth L.; Snyder, Philip K.; Reinath, Michael S.

    1990-01-01

    Design and performance of three-dimensional and two-dimensional backscatter laser velocimeter, both used in low-speed wind tunnels, described in report together with historical overview of development of laser velocimetry (LV). Provides measurements of airflow in wind-tunnel tests without perturbing effects of probes and probe-supporting structures. Applicable in such related fields as ventilation engineering and possibly in detection of wing vortexes from large aircraft at airports.

  10. ARE660 Wind Generator: Low Wind Speed Technology for Small Turbine Development

    SciTech Connect

    Robert W. Preus; DOE Project Officer - Keith Bennett

    2008-04-23

    This project is for the design of a wind turbine that can generate most or all of the net energy required for homes and small businesses in moderately windy areas. The purpose is to expand the current market for residential wind generators by providing cost effective power in a lower wind regime than current technology has made available, as well as reduce noise and improve reliability and safety. Robert W. Preus’ experience designing and/or maintaining residential wind generators of many configurations helped identify the need for an improved experience of safety for the consumer. Current small wind products have unreliable or no method of stopping the wind generator in fault or high wind conditions. Consumers and their neighbors do not want to hear their wind generators. In addition, with current technology, only sites with unusually high wind speeds provide payback times that are acceptable for the on-grid user. Abundant Renewable Energy’s (ARE) basic original concept for the ARE660 was a combination of a stall controlled variable speed small wind generator and automatic fail safe furling for shutdown. The stall control for a small wind generator is not novel, but has not been developed for a variable speed application with a permanent magnet alternator (PMA). The fail safe furling approach for shutdown has not been used to our knowledge.

  11. Higher-than-predicted saltation threshold wind speeds on Titan.

    PubMed

    Burr, Devon M; Bridges, Nathan T; Marshall, John R; Smith, James K; White, Bruce R; Emery, Joshua P

    2015-01-01

    Titan, the largest satellite of Saturn, exhibits extensive aeolian, that is, wind-formed, dunes, features previously identified exclusively on Earth, Mars and Venus. Wind tunnel data collected under ambient and planetary-analogue conditions inform our models of aeolian processes on the terrestrial planets. However, the accuracy of these widely used formulations in predicting the threshold wind speeds required to move sand by saltation, or by short bounces, has not been tested under conditions relevant for non-terrestrial planets. Here we derive saltation threshold wind speeds under the thick-atmosphere, low-gravity and low-sediment-density conditions on Titan, using a high-pressure wind tunnel refurbished to simulate the appropriate kinematic viscosity for the near-surface atmosphere of Titan. The experimentally derived saltation threshold wind speeds are higher than those predicted by models based on terrestrial-analogue experiments, indicating the limitations of these models for such extreme conditions. The models can be reconciled with the experimental results by inclusion of the extremely low ratio of particle density to fluid density on Titan. Whereas the density ratio term enables accurate modelling of aeolian entrainment in thick atmospheres, such as those inferred for some extrasolar planets, our results also indicate that for environments with high density ratios, such as in jets on icy satellites or in tenuous atmospheres or exospheres, the correction for low-density-ratio conditions is not required. PMID:25487154

  12. Higher-than-predicted saltation threshold wind speeds on Titan

    NASA Astrophysics Data System (ADS)

    Burr, Devon M.; Bridges, Nathan T.; Marshall, John R.; Smith, James K.; White, Bruce R.; Emery, Joshua P.

    2015-01-01

    Titan, the largest satellite of Saturn, exhibits extensive aeolian, that is, wind-formed, dunes, features previously identified exclusively on Earth, Mars and Venus. Wind tunnel data collected under ambient and planetary-analogue conditions inform our models of aeolian processes on the terrestrial planets. However, the accuracy of these widely used formulations in predicting the threshold wind speeds required to move sand by saltation, or by short bounces, has not been tested under conditions relevant for non-terrestrial planets. Here we derive saltation threshold wind speeds under the thick-atmosphere, low-gravity and low-sediment-density conditions on Titan, using a high-pressure wind tunnel refurbished to simulate the appropriate kinematic viscosity for the near-surface atmosphere of Titan. The experimentally derived saltation threshold wind speeds are higher than those predicted by models based on terrestrial-analogue experiments, indicating the limitations of these models for such extreme conditions. The models can be reconciled with the experimental results by inclusion of the extremely low ratio of particle density to fluid density on Titan. Whereas the density ratio term enables accurate modelling of aeolian entrainment in thick atmospheres, such as those inferred for some extrasolar planets, our results also indicate that for environments with high density ratios, such as in jets on icy satellites or in tenuous atmospheres or exospheres, the correction for low-density-ratio conditions is not required.

  13. Wind Speed Preview Measurement and Estimation for Feedforward Control of Wind Turbines

    NASA Astrophysics Data System (ADS)

    Simley, Eric J.

    Wind turbines typically rely on feedback controllers to maximize power capture in below-rated conditions and regulate rotor speed during above-rated operation. However, measurements of the approaching wind provided by Light Detection and Ranging (lidar) can be used as part of a preview-based, or feedforward, control system in order to improve rotor speed regulation and reduce structural loads. But the effectiveness of preview-based control depends on how accurately lidar can measure the wind that will interact with the turbine. In this thesis, lidar measurement error is determined using a statistical frequency-domain wind field model including wind evolution, or the change in turbulent wind speeds between the time they are measured and when they reach the turbine. Parameters of the National Renewable Energy Laboratory (NREL) 5-MW reference turbine model are used to determine measurement error for a hub-mounted circularly-scanning lidar scenario, based on commercially-available technology, designed to estimate rotor effective uniform and shear wind speed components. By combining the wind field model, lidar model, and turbine parameters, the optimal lidar scan radius and preview distance that yield the minimum mean square measurement error, as well as the resulting minimum achievable error, are found for a variety of wind conditions. With optimized scan scenarios, it is found that relatively low measurement error can be achieved, but the attainable measurement error largely depends on the wind conditions. In addition, the impact of the induction zone, the region upstream of the turbine where the approaching wind speeds are reduced, as well as turbine yaw error on measurement quality is analyzed. In order to minimize the mean square measurement error, an optimal measurement prefilter is employed, which depends on statistics of the correlation between the preview measurements and the wind that interacts with the turbine. However, because the wind speeds encountered by

  14. SSMI Wind Speed Climatology of the Time of Monsoon Wind Offset in the Western Arabian Sea

    NASA Technical Reports Server (NTRS)

    Halpern, David

    2000-01-01

    Forecasting the time of onset of monsoon wind in the western Arabian Sea, which is believed to precede the onset of rainfall along the west coast of India, is an important unsolved problem. Prior to measurements of the surface wind field by satellite, there was an absence of suitable surface wind observations. NASA scatterometer (NSCAT) surface wind vectors revealed that the time of the 1997 onset of 12 m/s southwest monsoon wind speeds in the western Arabian Sea preceded the onset of monsoon rainfall in Goa, India, by 3 - 4 days. Wind speed and direction data were necessary to establish a dynamical mechanism between times of onset of 12 m/s wind speed off Somalia and rainfall in Goa. Except for NSCAT, no satellite scatterometer wind product recorded adequately sampled 2-day 1deg x 1deg averaged wind vectors, which are the required space and time scales, to examine the wind-rain relationship in other years. However, the greater-than-95% steadiness of summer monsoon winds allows an opportunity to use satellite measurements of surface wind speed. The Special Sensor Microwave Imager (SSMI) recorded surface wind speed with adequate sampling to produce a 1-day, 1deg x 1deg data product during 1988 - 1998. SSMI data had been uniformly processed throughout the period. Times of onset of 12 m/s wind speed off Somalia determined with the SSMI data set were 21 May 1988, 24 May 1989, 17 May 1990, 28 May 1991, 8 June 1992, 28 May 1993, 30 May 1994, 7 June 1995, 29 May 1996, 12 June 1997, and 15 May 1998. Uncertainty of the 1992 and 1996 times of onset were increased because of the absence of SSMI data on 6 and 7 June 1992 and on 30 May 1996. Correlations of timing of monsoon wind onset with El Nino will be described. Variability of the time difference between times of onset of 12 m/s wind speed and Goa rainfall will be discussed. At the time of submission of the abstract, the Goa rainfall data have not arrived from the India Meteorological Department.

  15. Examples of the Influence of Turbine Wakes on Downwind Power Output, Surface Wind Speed, Turbulence and Flow Convergence in Large Wind Farms

    NASA Astrophysics Data System (ADS)

    Takle, E. S.; Rajewski, D. A.; Lundquist, J. K.; Doorenbos, R. K.

    2014-12-01

    We have analyzed turbine power and concurrent wind speed, direction and turbulence data from surface 10-m flux towers in a large wind farm for experiments during four summer periods as part of the Crop Wind Energy Experiment (CWEX). We use these data to analyze surface differences for a near-wake (within 2.5 D of the turbine line), far wake (17 D downwind of the turbine line), and double wake (impacted by two lines of turbines about 34 D downwind of the first turbine line) locations. Composites are categorized by10 degree directional intervals and three ambient stability categories as defined by Rajewski et al. (2013): neutral (|z/L|<0.05), stable (z/L>0.05) and unstable (z/L<-0.05), where z is the height of the measurement and L is the Monin-Obhukov length. The dominant influence of the turbines is under stably stratified conditions (i. e., mostly at night). A 25% to 40% increase in mean wind speed occurs when turbine wakes are moving over the downwind station at a distance of 2.8 D and 5.4 D (D = fan diameter). For the double wake condition (flux station leeward of two lines of turbines) we find a daytime (unstable conditions) speed reduction of 20% for southerly wind, but for nighttime (stable conditions) the surface speeds are enhancedby 40-60% for SSW-SW winds. The speedup is reduced as wind directions shift to the west. We interpret these speed variations as due to the rotation of the wake and interaction (or not) with higher speed air above the rotor layer in highly sheared nocturnal low-level jet conditions. From a cluster of flux stations and three profiling lidars deployed within and around a cluster of turbines in 2013 (CWEX-13) we found evidence of mesoscale influences. In particular, surface convergence (wind direction deflection of 10-20 degrees) was observed during periods of low nighttime winds (hub-height winds of 4-6 m/s) with power reduction of 50-75%. This is consistent with a similar range of deflection observed from a line of turbines in CWEX

  16. Modulation of Saturn's radio clock by solar wind speed.

    PubMed

    Zarka, Philippe; Lamy, Laurent; Cecconi, Baptiste; Prangé, Renée; Rucker, Helmut O

    2007-11-01

    The internal rotation rates of the giant planets can be estimated by cloud motions, but such an approach is not very precise because absolute wind speeds are not known a priori and depend on latitude: periodicities in the radio emissions, thought to be tied to the internal planetary magnetic field, are used instead. Saturn, despite an apparently axisymmetric magnetic field, emits kilometre-wavelength (radio) photons from auroral sources. This emission is modulated at a period initially identified as 10 h 39 min 24 +/- 7 s, and this has been adopted as Saturn's rotation period. Subsequent observations, however, revealed that this period varies by +/-6 min on a timescale of several months to years. Here we report that the kilometric radiation period varies systematically by +/-1% with a characteristic timescale of 20-30 days. Here we show that these fluctuations are correlated with solar wind speed at Saturn, meaning that Saturn's radio clock is controlled, at least in part, by conditions external to the planet's magnetosphere. No correlation is found with the solar wind density, dynamic pressure or magnetic field; the solar wind speed therefore has a special function. We also show that the long-term fluctuations are simply an average of the short-term ones, and therefore the long-term variations are probably also driven by changes in the solar wind. PMID:17994092

  17. Numerical study on the impact of ground heating and ambient wind speed on flow fields in street canyons

    NASA Astrophysics Data System (ADS)

    Li, Lei; Yang, Lin; Zhang, Li-Jie; Jiang, Yin

    2012-11-01

    The impact of ground heating on flow fields in street canyons under different ambient wind speed conditions was studied based on numerical methods. A series of numerical tests were performed, and three factors including height-to-width (H/W) ratio, ambient wind speed and ground heating intensity were taken into account. Three types of street canyon with H/W ratios of 0.5, 1.0 and 2.0, respectively, were used in the simulation and seven speed values ranging from 0.0 to 3.0 m s-1 were set for the ambient wind speed. The ground heating intensity, which was defined as the difference between the ground temperature and air temperature, ranged from 10 to 40 K with an increase of 10 K in the tests. The results showed that under calm conditions, ground heating could induce circulation with a wind speed of around 1.0 m s-1, which is enough to disperse pollutants in a street canyon. It was also found that an ambient wind speed threshold may exist for street canyons with a fixed H/W ratio. When ambient wind speed was lower than the threshold identified in this study, the impact of the thermal effect on the flow field was obvious, and there existed a multi-vortex flow pattern in the street canyon. When the ambient wind speed was higher than the threshold, the circulation pattern was basically determined by dynamic effects. The tests on the impact of heating intensity showed that a higher ground heating intensity could strengthen the vortical flow within the street canyon, which would help improve pollutant diffusion capability in street canyons.

  18. An atlas of monthly mean distributions of GEOSAT sea surface height, SSMI surface wind speed, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1988

    NASA Technical Reports Server (NTRS)

    Halpern, D.; Zlotnicki, V.; Newman, J.; Brown, O.; Wentz, F.

    1991-01-01

    Monthly mean global distributions for 1988 are presented with a common color scale and geographical map. Distributions are included for sea surface height variation estimated from GEOSAT; surface wind speed estimated from the Special Sensor Microwave Imager on the Defense Meteorological Satellite Program spacecraft; sea surface temperature estimated from the Advanced Very High Resolution Radiometer on NOAA spacecrafts; and the Cartesian components of the 10m height wind vector computed by the European Center for Medium Range Weather Forecasting. Charts of monthly mean value, sampling distribution, and standard deviation value are displayed. Annual mean distributions are displayed.

  19. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 5 2010-07-01 2010-07-01 false Particle Sizes and Wind Speeds for Full... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test Primary Partical Mean Size a (µm) Full Wind Tunnel Test 2 km/hr 24 km/hr...

  20. Performance of Statistical Temporal Downscaling Techniques of Wind Speed Data Over Aegean Sea

    NASA Astrophysics Data System (ADS)

    Gokhan Guler, Hasan; Baykal, Cuneyt; Ozyurt, Gulizar; Kisacik, Dogan

    2016-04-01

    Wind speed data is a key input for many meteorological and engineering applications. Many institutions provide wind speed data with temporal resolutions ranging from one hour to twenty four hours. Higher temporal resolution is generally required for some applications such as reliable wave hindcasting studies. One solution to generate wind data at high sampling frequencies is to use statistical downscaling techniques to interpolate values of the finer sampling intervals from the available data. In this study, the major aim is to assess temporal downscaling performance of nine statistical interpolation techniques by quantifying the inherent uncertainty due to selection of different techniques. For this purpose, hourly 10-m wind speed data taken from 227 data points over Aegean Sea between 1979 and 2010 having a spatial resolution of approximately 0.3 degrees are analyzed from the National Centers for Environmental Prediction (NCEP) The Climate Forecast System Reanalysis database. Additionally, hourly 10-m wind speed data of two in-situ measurement stations between June, 2014 and June, 2015 are considered to understand effect of dataset properties on the uncertainty generated by interpolation technique. In this study, nine statistical interpolation techniques are selected as w0 (left constant) interpolation, w6 (right constant) interpolation, averaging step function interpolation, linear interpolation, 1D Fast Fourier Transform interpolation, 2nd and 3rd degree Lagrange polynomial interpolation, cubic spline interpolation, piecewise cubic Hermite interpolating polynomials. Original data is down sampled to 6 hours (i.e. wind speeds at 0th, 6th, 12th and 18th hours of each day are selected), then 6 hourly data is temporally downscaled to hourly data (i.e. the wind speeds at each hour between the intervals are computed) using nine interpolation technique, and finally original data is compared with the temporally downscaled data. A penalty point system based on

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

    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 distortion by the ship's hull and superstructure introducing biases into the measured wind speed. The effect of airflow distortion on estimates of the transfer velocity was examined by modelling the airflow around the three-dimensional geometries of the research vessels Hakuho Maru and Mirai, using the Large Eddy Simulation code GERRIS. For airflows within ±45° of the bow the maximum bias was +16%. For wind speed of 10 m s-1 to 15 m s-1, a +16% bias in wind speed would cause an overestimate in the calculated value of k of 30% to 50%, depending on which k parameterisation is used. This is due to the propagation of errors when using quadratic or cubic parameterizations. Recommendations for suitable anemometer locations on research vessels are given. The errors in transfer velocity may be much larger for typical merchant ships, as the anemometers are generally not as well-exposed as those on research vessels. Flow distortion may also introduce biases in the wind speed dependent k parameterizations themselves, since these are obtained by relating measurements of the CO2 flux to measurements of the wind speed and the CO2 concentration difference. To investigate this, flow distortion effects were estimated for three different platforms from which wind speed dependent parameterizations are published. The estimates ranged from -4% to +14% and showed that flow distortion may have a significant impact on wind speed dependent parameterizations. However, the wind biases are not large enough to explain the differences at high wind speeds in parameterizations which are based on eddy covariance and

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

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    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 due to air flow distortion by the ship's hull and superstructure introducing biases into the measured wind speed. The effect of airflow distortion on estimates of the transfer velocity was examined by modelling the airflow around the three-dimensional geometries of the research vessels Hakuho Maru and Mirai, using the Large Eddy Simulation code GERRIS. For airflows within ±45° of the bow the maximum bias was +16%. For wind speed of 10 m s-1 to 15 m s-1, a +16% bias in wind speed would cause an overestimate in the calculated value of k of 30% to 50%, depending on which k parameterisation is used. This is due to the propagation of errors when using quadratic or cubic parameterisations. Recommendations for suitable anemometer locations on research vessels are given. The errors in transfer velocity may be much larger for typical merchant ships, as the anemometers are generally not as well-exposed as those on research vessels. Flow distortion may also introduce biases in the wind speed dependent k parameterisations themselves, since these are obtained by relating measurements of the CO2 flux to measurements of the wind speed and the CO2 concentration difference. To investigate this, flow distortion effects were estimated for three different platforms from which wind speed dependent parameterisations are published. The estimates ranged from -4% to +14% and showed that flow distortion may have a significant impact on wind speed dependent parameterisations. However, the wind biases are not large enough to explain the differences at high wind speeds in parameterisations which are based on eddy

  3. Hi-Q Rotor - Low Wind Speed Technology

    SciTech Connect

    Todd E. Mills; Judy Tatum

    2010-01-11

    The project objective was to optimize the performance of the Hi-Q Rotor. Early research funded by the California Energy Commission indicated the design might be advantageous over state-of-the-art turbines for collecting wind energy in low wind conditions. The Hi-Q Rotor is a new kind of rotor targeted for harvesting wind in Class 2, 3, and 4 sites, and has application in areas that are closer to cities, or 'load centers.' An advantage of the Hi-Q Rotor is that the rotor has non-conventional blade tips, producing less turbulence, and is quieter than standard wind turbine blades which is critical to the low-wind populated urban sites. Unlike state-of-the-art propeller type blades, the Hi-Q Rotor has six blades connected by end caps. In this phase of the research funded by DOE's Inventions and Innovation Program, the goal was to improve the current design by building a series of theoretical and numeric models, and composite prototypes to determine a best of class device. Development of the rotor was performed by aeronautical engineering and design firm, DARcorporation. From this investigation, an optimized design was determined and an 8-foot diameter, full-scale rotor was built and mounted using a Bergey LX-1 generator and furling system which were adapted to support the rotor. The Hi-Q Rotor was then tested side-by-side against the state-of-the-art Bergey XL-1 at the Alternative Energy Institute's Wind Test Center at West Texas State University for six weeks, and real time measurements of power generated were collected and compared. Early wind tunnel testing showed that the cut-in-speed of the Hi-Q rotor is much lower than a conventional tested HAWT enabling the Hi-Q Wind Turbine to begin collecting energy before a conventional HAWT has started spinning. Also, torque at low wind speeds for the Hi-Q Wind Turbine is higher than the tested conventional HAWT and enabled the wind turbine to generate power at lower wind speeds. Based on the data collected, the results of

  4. Variability of Wind Speeds and Power over Europe

    NASA Astrophysics Data System (ADS)

    Tambke, J.; von Bremen, L.; de Decker, J.; Schmidt, M.; Steinfeld, G.; Wolff, J.-O.

    2010-09-01

    This study comprises two parts: First, we describe the vertical wind speed and turbulence profiles that result from our improved PBL scheme and compare it to observations and 1-dimensional approaches (Monin-Obukhov etc.). Second, we analyse the spatio-temporal correlations in our meso-scale simulations for the years 2004 to 2007 over entire Europe, with special focus on the Irish, North and Baltic Sea. 1.) Vertical Wind Speed Profiles The vertical wind profile above the sea has to be modelled with high accuracy for tip heights up to 160m in order to achieve precise wind resource assessments, to calculate loads and wakes of wind turbines as well as for reliable short-term wind power forecasts. We present an assessment of different models for wind profiles in unstable, neutral and stable thermal stratification. The meso-scale models comprise MM5, WRF and COSMO-EU (LME). Both COSMO-EU from the German Weather Service DWD and WRF use a turbulence closure of 2.5th order - and lead to similar results. Especially the limiting effect of low boundary layer heights on the wind shear in very stable stratification is well captured. In our new WRF-formulation for the mixing length in the Mellor-Yamada-Janjic (MYJ) parameterisation of the Planetary Boundary Layer (PBL-scheme), the master length scale itself depends on the Monin-Obukhov-Length as a parameter for the heat flux effects on the turbulent mixing. This new PBL-scheme shows a better performance for all weather conditions than the original MYJ-scheme. Apart from the low-boundary-layer-effect in very stable situations (which are seldom), standard Monin-Obukhov formulations in combination with the Charnock relation for the sea surface roughness show good agreement with the FINO1-data (German Bight). Interesting results were achieved with two more detailed micro-scale approaches: - the parameterization proposed by Pena, Gryning and Hasager [BLM 2008] that depends on the boundary layer height - our ICWP-model, were the flux

  5. Short-term wind speed predictions with machine learning techniques

    NASA Astrophysics Data System (ADS)

    Ghorbani, M. A.; Khatibi, R.; FazeliFard, M. H.; Naghipour, L.; Makarynskyy, O.

    2016-02-01

    Hourly wind speed forecasting is presented by a modeling study with possible applications to practical problems including farming wind energy, aircraft safety and airport operations. Modeling techniques employed in this paper for such short-term predictions are based on the machine learning techniques of artificial neural networks (ANNs) and genetic expression programming (GEP). Recorded values of wind speed were used, which comprised 8 years of collected data at the Kersey site, Colorado, USA. The January data over the first 7 years (2005-2011) were used for model training; and the January data for 2012 were used for model testing. A number of model structures were investigated for the validation of the robustness of these two techniques. The prediction results were compared with those of a multiple linear regression (MLR) method and with the Persistence method developed for the data. The model performances were evaluated using the correlation coefficient, root mean square error, Nash-Sutcliffe efficiency coefficient and Akaike information criterion. The results indicate that forecasting wind speed is feasible using past records of wind speed alone, but the maximum lead time for the data was found to be 14 h. The results show that different techniques would lead to different results, where the choice between them is not easy. Thus, decision making has to be informed of these modeling results and decisions should be arrived at on the basis of an understanding of inherent uncertainties. The results show that both GEP and ANN are equally credible selections and even MLR should not be dismissed, as it has its uses.

  6. High resolution reanalysis of wind speeds over the British Isles for wind energy integration

    NASA Astrophysics Data System (ADS)

    Hawkins, Samuel Lennon

    The UK has highly ambitious targets for wind development, particularly offshore, where over 30GW of capacity is proposed for development. Integrating such a large amount of variable generation presents enormous challenges. Answering key questions depends on a detailed understanding of the wind resource and its temporal and spatial variability. However, sources of wind speed data, particularly offshore, are relatively sparse: satellite data has low temporal resolution; weather buoys and met stations have low spatial resolution; while the observations from ships and platforms are affected by the structures themselves. This work uses a state-of-the art mesoscale atmospheric model to produce a new high-resolution wind speed dataset over the British Isles and surrounding waters. This covers the whole region at a resolution of 3km for a period of eleven consecutive years, from 2000 to 2010 inclusive, and is thought to be the first high resolution re-analysis to represent a true historic time series, rather than a statistically averaged climatology. The results are validated against observations from met stations, weather buoys, offshore platforms and satellite-derived wind speeds, and model bias is reduced offshore using satellite derived wind speeds. The ability of the dataset to predict power outputs from current wind farms is demonstrated, and the expected patterns of power outputs from future onshore and offshore wind farms are predicted. Patterns of wind production are compared to patterns of electricity demand to provide the first conclusive combined assessment of the ability of future onshore and offshore wind generation meet electricity demand and contribute to secure energy supplies..

  7. An Improved Wind Speed Retrieval Algorithm For The CYGNSS Mission

    NASA Astrophysics Data System (ADS)

    Ruf, C. S.; Clarizia, M. P.

    2015-12-01

    The NASA spaceborne Cyclone Global Navigation Satellite System (CYGNSS) mission is a constellation of 8 microsatellites focused on tropical cyclone (TC) inner core process studies. CYGNSS will be launched in October 2016, and will use GPS-Reflectometry (GPS-R) to measure ocean surface wind speed in all precipitating conditions, and with sufficient frequency to resolve genesis and rapid intensification. Here we present a modified and improved version of the current baseline Level 2 (L2) wind speed retrieval algorithm designed for CYGNSS. An overview of the current approach is first presented, which makes use of two different observables computed from 1-second Level 1b (L1b) delay-Doppler Maps (DDMs) of radar cross section. The first observable, the Delay-Doppler Map Average (DDMA), is the averaged radar cross section over a delay-Doppler window around the DDM peak (i.e. the specular reflection point coordinate in delay and Doppler). The second, the Leading Edge Slope (LES), is the leading edge of the Integrated Delay Waveform (IDW), obtained by integrating the DDM along the Doppler dimension. The observables are calculated over a limited range of time delays and Doppler frequencies to comply with baseline spatial resolution requirements for the retrieved winds, which in the case of CYGNSS is 25 km. In the current approach, the relationship between the observable value and the surface winds is described by an empirical Geophysical Model Function (GMF) that is characterized by a very high slope in the high wind regime, for both DDMA and LES observables, causing large errors in the retrieval at high winds. A simple mathematical modification of these observables is proposed, which linearizes the relationship between ocean surface roughness and the observables. This significantly reduces the non-linearity present in the GMF that relate the observables to the wind speed, and reduces the root-mean square error between true and retrieved winds, particularly in the high wind

  8. Adaptive torque control of variable speed wind turbines

    NASA Astrophysics Data System (ADS)

    Johnson, Kathryn E.

    Wind is a clean, renewable resource that has become more popular in recent years due to numerous advances in technology and public awareness. Wind energy is quickly becoming cost competitive with fossil fuels, but further reductions in the cost of wind energy are necessary before it can grow into a fully mature technology. One reason for higher-than-necessary cost of the wind energy is uncertainty in the aerodynamic parameters, which leads to inefficient controllers. This thesis explores an adaptive control technique designed to reduce the negative effects of this uncertainty. The primary focus of this work is a new adaptive controller that is designed to resemble the standard non-adaptive controller used by the wind industry. The standard controller was developed for variable speed wind turbines operating below rated power. The new adaptive controller uses a simple, highly intuitive gain adaptation law intended to seek out the optimal gain for maximizing the turbine's energy capture. It is designed to work even in real, time-varying winds. The adaptive controller has been tested both in simulation and on a real turbine, with numerous experimental results provided in this work. Simulations have considered the effects of erroneous wind measurements and time-varying turbine parameters, both of which are concerns on the real turbine. The adaptive controller has been found to operate as desired under realistic operating conditions, and energy capture has increased on the real turbine as a result. Theoretical analyses of the standard and adaptive controllers were performed, as well, providing additional insight into the system. Finally, a few extensions were made with the intent of making the adaptive control idea even more appealing in the commercial wind turbine market.

  9. 11. INTERIOR VIEW OF 8FOOT HIGH SPEED WIND TUNNEL. SAME ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. INTERIOR VIEW OF 8-FOOT HIGH SPEED WIND TUNNEL. SAME CAMERA POSITION AS VA-118-B-10 LOOKING IN THE OPPOSITE DIRECTION. - NASA Langley Research Center, 8-Foot High Speed Wind Tunnel, 641 Thornell Avenue, Hampton, Hampton, VA

  10. An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1991

    NASA Technical Reports Server (NTRS)

    Halpern, D.; Knauss, W.; Brown, O.; Wentz, F.

    1993-01-01

    The following monthly mean global distributions for 1991 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 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) spacecraft; Cartesian components of free-drifting buoys which are tracked by the ARGOS navigation system on NOAA satellites; and Cartesian components of the 10-m height wind vector computed by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of monthly mean value, sampling distribution, and standard deviation value are displayed. Annual mean distributions are displayed.

  11. An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1990

    NASA Technical Reports Server (NTRS)

    Halpern, D.; Knauss, W.; Brown, O.; Wentz, F.

    1993-01-01

    The following monthly mean global distributions for 1990 are proposed 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 (US) 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) spacecraft; Cartesian components of free drifting buoys which are tracked by the ARGOS navigation system on NOAA satellites; and Cartesian components on the 10-m height wind vector computed by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of monthly mean value, sampling distribution, and standard deviation values are displayed. Annual mean distributions are displayed.

  12. Neptune's Wind Speeds Obtained by Tracking Clouds in Voyager Images.

    PubMed

    Hammel, H B; Beebe, R F; De Jong, E M; Hansen, C J; Howell, C D; Ingersoll, A P; Johnson, T V; Limaye, S S; Magalhaes, J A; Pollack, J B; Sromovsky, L A; Suomi, V E; Swift, C E

    1989-09-22

    Images of Neptune obtained by the narrow-angle camera of the Voyager 2 spacecraft reveal large-scale cloud features that persist for several months or longer. The features' periods of rotation about the planetary axis range from 15.8 to 18.4 hours. The atmosphere equatorward of -53 degrees rotates with periods longer than the 16.05-hour period deduced from Voyager's planetary radio astronomy experiment (presumably the planet's internal rotation period). The wind speeds computed with respect to this radio period range from 20 meters per second eastward to 325 meters per second westward. Thus, the cloud-top wind speeds are roughly the same for all the planets ranging from Venus to Neptune, even though the solar energy inputs to the atmospheres vary by a factor of 1000. PMID:17798743

  13. Satellite retrieved cloud optical thickness sensitive to surface wind speed in the subarctic marine boundary layer

    NASA Astrophysics Data System (ADS)

    Glantz, Paul

    2010-07-01

    The optical and microphysical properties of low level marine clouds, presented over the Norwegian Sea and Barents Sea, have been investigated for the period 2000-2006. The air masses were transported for more or less seven days over the warmer North Atlantic before they arrived at the area investigated. The main focus in this study is on investigating the relationship between cloud optical thickness (COT) and surface wind speed (U10 m) using satellite retrievals in combination with operational meteorological data. A relatively strong correlation (R2 = 0.97) is obtained for wind speeds up to 12 m s - 1, in air masses that were probably to a major degree influenced by wind shears and to a minor degree by buoyancy. The relationship (U2.5) is also in between those most commonly found in the literature for water vapor (~U1) and sea salt (~U3.4). The present results highlight the magnitude of marine sea-spray influence on COT and their global climatic importance.

  14. Efficient Low-Speed Flight in a Wind Field

    NASA Technical Reports Server (NTRS)

    Feldman, Michael A.

    1996-01-01

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

  15. Wind Tunnel Studies in Aerodynamic Phenomena at High Speed

    NASA Technical Reports Server (NTRS)

    Caldwell, F W; Fales, E N

    1921-01-01

    A great amount of research and experimental work has been done and fair success obtained in an effort to place airplane and propeller design upon an empirical basis. However, one can not fail to be impressed by the apparent lack of data available toward establishing flow phenomena upon a rational basis, such that they may be interpreted in terms of the laws of physics. With this end in view it was the object of the authors to design a wind tunnel differing from the usual type especially in regard to large power and speed of flow. This report describes the wind tunnel at Mccook Field and gives the results of experiments conducted in testing the efficiency of the wind tunnel.

  16. Ulysses Composition, Plasma and Magnetic Field Observations of High Speed Solar wind Streams

    NASA Technical Reports Server (NTRS)

    Smith, E. J.

    1997-01-01

    During 1992-3 as the Ulysses spacecraft passed in and out of the southern high speed solar wind stream, the Solar Wind Ion Spectrometer, SWICS made continuous composition and temperature measurements of all major solar wind ions.

  17. Validation of Special Sensor Microwave Imager monthly-mean wind speed from July 1987 to December 1989

    NASA Technical Reports Server (NTRS)

    Halpern, David

    1993-01-01

    Since July 1987, the Remote Sensing Systems (Santa Rosa, California) routinely computes from first principles the wind speed from Special Sensor Microwave Imager (SSM/I) measurements of the intensity of microwave radiation emitted at the ocean surface. The accuracy of monthly-mean SSM/I wind speeds is determined by comparisons with moored-buoy wind measurements, which were recorded by four different institutions at 44 sites in the Atlantic and Pacific Oceans during July 1987 to December 1989. All results for 1988 were virtually identical with 1989. The range of monthly mean moored-buoy wind speeds was 2-10 m/s. The rms difference of 697 monthly-mean matchups of the composite 1988 and 1989 data set was 1.2 m/s. The rms differences were smaller in the equatorial zone and higher in middle latitudes, in accord with the monthly standard deviation. At middle latitudes, the time series of rms differences displayed an annual cycle. In the equatorial zone, the agreement between SSM/I and in situ data was better in regions with a lesser amount of clouds, and vice versa. For SSM/I monthly standard deviations of 1-2, 2-3, and 3-4 m/s, the average absolute values of the monthly-mean difference between SSM/I and moored-buoy wind speeds were 0.6, 0.9, and 1.4 m/s, respectively.

  18. Wind farm induced changes in wind speed and surface fluxes over the North Sea

    NASA Astrophysics Data System (ADS)

    Chatterjee, Fabien; van Lipzig, Nicole; Meyers, Johan

    2016-04-01

    Offshore wind farm deployment in the North Sea is foreseen to expand dramatically in the coming years. The strong expansion of offshore wind parks is likely to affect the regional climatology on the North Sea. We assess this impact by conducting a regional climate model simulation over future wind farms built near the German coast. In order to achieve this, the wind farm parameterisation of Fitch et al. 2012, where wind farms are parameterised as elevated sources of turbulent kinetic energy and sinks of momentum ( Blahak et al 2010 and Fitch et al 2012) is implemented in COSMO-CLM at a 1.5 km resolution. As a first step, COSMO-CLM's ability to reproduce wind profiles over the North Sea is evaluated using wind speed data from the FINO1 meteorological mast, toghether with QuikScat scatterometer data, for a time period of 2000-2008. Subsequently, the impact of windfarms on the regional climate over a period of ten years (1999-2008) is assessed. A large scale wind farm can create wakes which depending on the wind direction could affect the power production of a neighbouring farm. Furthermore, wind farms decelerate the flow and create a vertical circulation in the inflow region. As a result, changes in vertical fluxes of moisture are observed. This leads to enhanced low level cloud cover which may trigger changes in precipitation.

  19. Systematic Controller Design Methodology for Variable-Speed Wind Turbines

    SciTech Connect

    Hand, M. M.; Balas, M. J.

    2002-02-01

    Variable-speed, horizontal axis wind turbines use blade-pitch control to meet specified objectives for three operational regions. This paper provides a guide for controller design for the constant power production regime. A simple, rigid, non-linear turbine model was used to systematically perform trade-off studies between two performance metrics. Minimization of both the deviation of the rotor speed from the desired speed and the motion of the actuator is desired. The robust nature of the proportional-integral-derivative controller is illustrated, and optimal operating conditions are determined. Because numerous simulation runs may be completed in a short time, the relationship between the two opposing metrics is easily visualized.

  20. Effects of wind speed on leaf energy and gas exchange

    NASA Astrophysics Data System (ADS)

    Schymanski, Stanislaus J.; Or, Dani

    2013-04-01

    The common practice of modelling transpiration from plant leaves as an isothermal process (assuming equal leaf and air temperatures) may introduce significant bias into estimates of transpiration rates and energy partitioning. In a recent study (Schymanski et al., 2013, PLOS ONE, in print) we investigated effects of fluctuating irradiance (sunflecks) on leaf thermal regime and transpiration rates using a physically-based leaf model. Results suggest that leaf temperatures may deviate substantially from air temperature, leading to greatly modified transpiration rates compared to isothermal conditions, even under steady-state conditions. The results also highlighted the importance of intrinsic thermal protection imparted by transpiration flux. In this study we consider leaf energy balance to systematically investigate effects of wind speed on plant heat and gas exchange. Surprisingly, under certain conditions increasing wind speeds can result in a decrease in transpiration rates. This is due to the feedbacks between sensible heat flux, leaf temperature and latent heat flux. The model predicts that for high wind velocities the same leaf conductance (for water vapour and carbon dioxide) can be maintained with less evaporative losses. This may have profound implications for estimates of water use efficiency (WUE, the amount of carbon gained by photosynthesis per unit of water lost by transpiration), and the interpretation of changes in "Potential Evaporation" in relation to plant water use.

  1. Contraction design for small low-speed wind tunnels

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Mehta, Rabindra D.

    1988-01-01

    An iterative design procedure was developed for two- or three-dimensional contractions installed on small, low-speed wind tunnels. The procedure consists of first computing the potential flow field and hence the pressure distributions along the walls of a contraction of given size and shape using a three-dimensional numerical panel method. The pressure or velocity distributions are then fed into two-dimensional boundary layer codes to predict the behavior of the boundary layers along the walls. For small, low-speed contractions it is shown that the assumption of a laminar boundary layer originating from stagnation conditions at the contraction entry and remaining laminar throughout passage through the successful designs if justified. This hypothesis was confirmed by comparing the predicted boundary layer data at the contraction exit with measured data in existing wind tunnels. The measured boundary layer momentum thicknesses at the exit of four existing contractions, two of which were 3-D, were found to lie within 10 percent of the predicted values, with the predicted values generally lower. From the contraction wall shapes investigated, the one based on a fifth-order polynomial was selected for installation on a newly designed mixing layer wind tunnel.

  2. Contraction design for small low-speed wind tunnels

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Mehta, Rabindra D.

    1988-01-01

    An iterative design procedure was developed for 2- or 3-dimensional contractions installed on small, low speed wind tunnels. The procedure consists of first computing the potential flow field and hence the pressure distributions along the walls of a contraction of given size and shape using a 3-dimensional numerical panel method. The pressure or velocity distributions are then fed into 2-dimensional boundary layer codes to predict the behavior of the boundary layers along the walls. For small, low speed contractions, it is shown that the assumption of a laminar boundary layer originating from stagnation conditions at the contraction entry and remaining laminar throughout passage through the successful designs is justified. This hypothesis was confirmed by comparing the predicted boundary layer data at the contraction exit with measured data in existing wind tunnels. The measured boundary layer momentum thicknesses at the exit of four existing contractions, two of which were 3-D, were found to lie within 10 percent of the predicted values, with the predicted values generally lower. From the contraction wall shapes investigated, the one based on a 5th order polynomial was selected for newly designed mixing wind tunnel installation.

  3. Scatterometer wind speed bias induced by the large-scale component of the wave field

    NASA Technical Reports Server (NTRS)

    Glazman, R. E.; Pihos, G. G.; Ip, J.

    1988-01-01

    In order to determine if an environmental bias exists in the winds measured by the Seasat A satellite scatterometer (SASS), the SASS wind speed observations, U(s), colocated with the buoy wind speed data, U(b), were analyzed. There was a trend in the SASS wind speed error, U(b) - U(s), which was found to be related to the degree of the development of wind-generated gravity waves; this trend (estimated to be 0.5 m/sec per 100 km of the generalized wind fetch) is capable of introducing a well-pronounced environmental bias into the scatterometer-produced global distributions of wind.

  4. Gas exchange-wind speed relation measured with sulfur hexafluoride on a lake

    NASA Technical Reports Server (NTRS)

    Wanninkhof, R.; Broecker, W. S.; Ledwell, J. R.

    1985-01-01

    Gas-exchange processes control the uptake and release of various gases in natural systems such as oceans, rivers, and lakes. Not much is known about the effect of wind speed on gas exchange in such systems. In the experiment described here, sulfur hexafluoride was dissolved in lake water, and the rate of escape of the gas with wind speed (at wind speeds up to 6 meters per second) was determined over a 1-month period. A sharp change in the wind speed dependence of the gas-exchange coefficient was found at wind speeds of about 2.4 meters per second, in agreement with the results of wind-tunnel studies. However the gas-exchange coefficients at wind speeds above 3 meters per second were smaller than those observed in wind tunnels and are in agreement with earlier lake and ocean results.

  5. A review of satellite altimeter measurement of sea surface wind speed - With a proposed new algorithm

    NASA Technical Reports Server (NTRS)

    Chelton, D. B.; Mccabe, P. J.

    1985-01-01

    The scheduled February 1985 launch of a radar altimeter aboard the U.S. Navy satellite Geosat has motivated an in-depth investigation of wind speed retrieval from satellite altimeters. The accuracy of sea surface wind speed estimated by the Seasat altimeter is examined by comparison with wind speed estimated by the Seasat scatterometer. The intercomparison is based on globally distributed spatial and temporal averages of the estimated wind speed. It is shown that there are systematic differences between altimeter and scatterometer wind speed estimates. These differences are traced to errors in the Seasat altimeter geophysical data record wind speed algorithm. A new algorithm is proposed which yields consistent estimates from the two satellite sensors. Using this new algorithm, the rms difference between spatial and temporal averages of the two wind speed estimates is less than 1 m/s, and their correlation is greater than 0.9.

  6. Magnitude and frequency of wind speed shears from 3 to 150 meters

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    An analysis is presented of high resolution wind profile measurements recorded at the NASA 150-m ground winds tower facility, showing wind speed shear frequency and magnitude distributions for six vertical layers of the atmosphere and one vertical distance. Vertical wind shear is defined as the change of wind speed with height, and its magnitudes were derived by algebraically subtracting lower level wind speeds from those of higher levels and dividing the distance between levels. Horizontal wind shear is understood to be change of wind speed with horizontal distance, and its magnitudes were derived by algebraically subtracting the wind speed at a short tower from that at a tall one and dividing by the distance between towers.

  7. Radial variation of the solar wind speed between 1 and 15 AU

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Pioneer 10 and 11 solar wind speeds measured between 1.4 and 15.2 AU are compared with those of IMP 6, 7, and 8 measured at 1 AU for 90-day intervals centered on six solar radial alignments between 1973 and 1978. The time profile of the solar wind speed undergoes change as the distance from the sun increases, which is due to interaction of adjacent solar wind streams. Speed variations are smaller at greater radial distance and both the highest and lowest speeds disappear as radial distance increases. For periods with extremely high speed solar wind streams, the mean solar wind speed decreases as the distance from the sun increases, which must be due to the disappearance of the highest speeds of the streams with increasing distance. It is concluded that at distances from the sun greater than 30-40 AU, the solar wind behavior may closely resemble that of a radially expanding constant speed plasma.

  8. Relationship between gas exchange, wind speed, and radar backscatter in a large wind-wave tank

    NASA Technical Reports Server (NTRS)

    Wanninkhof, Richard H.; Bliven, L. F.

    1991-01-01

    The relationships between the gas exchange, wind speed, friction velocity, and radar backscatter from the water surface was investigated using data obtained in a large water tank in the Delft (Netherlands) wind-wave tunnel, filled with water supersaturated with SF6, N2O, and CH4. Results indicate that the gas-transfer velocities of these substances were related to the wind speed with a power law dependence. Microwave backscatter from water surface was found to be related to gas transfer velocities by a relationship in the form k(gas) = a 10 exp (b A0), where k is the gas transfer velocity for the particular gas, the values of a and b are obtained from a least squares fit of the average backscatter cross section and gas transfer at 80 m, and A0 is the directional (azimuthal) averaged return.

  9. Low Speed PSP Testing in Production Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Bell, James; Mehta, Rabi; Schairer, Ed; Hand, Larry; Nixon, David (Technical Monitor)

    1998-01-01

    The brightness signal from a pressure-sensitive paint varies inversely with absolute pressure. Consequently high signal-to-noise ratios are required to resolve aerodynamic pressure fields at low speeds, where the pressure variation around an object might only be a few percent of the mean pressure. This requirement is unavoidable, and implies that care must be taken to minimize noise sources present in the measurement. This paper discusses and compares the main noise sources in low speed PSP testing using the "classical" intensity-based single-luminophore technique. These are: temperature variation, model deformation, and lamp drift/paint degradation. Minimization of these error sources from the point of view of operation in production wind tunnels is discussed, with some examples from recent tests in NASA Ames facilities.

  10. Evaluating the effects of land use and cover change on the decrease of surface wind speed over China in recent 30 years using a statistical downscaling method

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Zha, Jinlin; Zhao, Deming

    2016-03-01

    The long-term decrease of surface wind speed (SWS) has been revealed by previous studies in China in recent decades, but the reasons for the SWS decrease remain uncertain. In this paper, we evaluated the effects of land use and cover change (LUCC) on the SWS decrease during 1980-2011 over the Eastern China Plain (ECP) region using a combined method of statistical downscaling and observation minus reanalysis data, which was used to improve the climate prediction of general circulation models and to evaluate the influence of LUCC on climate change. To exclude the potential influence of LUCC on SWS observation, a statistical downscaling model (SDM) was established during 1980-1992 because a lower extent of LUCC occurred during this period than in later periods. The skill of the SDM was checked by comparing the results of different predictor combinations. Then, SDM was used to improve the wind speed data at 10 m above the surface in the ERA-Interim reanalysis data (V10m-ERA) during 1993-2011, which decreased the error in the reanalysis wind speed as far as possible. Then, the difference between the station observed SWS (V10m-OBV) and the downscaled SWS (V10m-SDM) during 1993-2011 (SWSD) was considered the quantitative estimation of the influence of the LUCC on SWS in this period. The V10m-SDM can capture both the large-scale and local characteristics in the observation, and their patterns are very similar. V10m-SDM has better performance in the spatial-temporal changes than does V10m-ERA with respect to V10m-OBV. The impact of LUCC on the SWS was pronounced, the SWSD was -0.24 m s-1 in 1993, and the SWSD reached -0.56 m s-1 in 2011. LUCC could induce a 0.17 m s-1 wind speed decrease per 10 year in the ECP region during 1993-2011. Furthermore, each 10 % rise of the urbanization rate could cause an approximately 0.12 m s-1 decrease in wind speed. Additionally, pressure-gradient force was eliminated as the primary cause of the observed long-term decrease of SWS in ECP by

  11. Effective wind speed estimation: Comparison between Kalman Filter and Takagi-Sugeno observer techniques.

    PubMed

    Gauterin, Eckhard; Kammerer, Philipp; Kühn, Martin; Schulte, Horst

    2016-05-01

    Advanced model-based control of wind turbines requires knowledge of the states and the wind speed. This paper benchmarks a nonlinear Takagi-Sugeno observer for wind speed estimation with enhanced Kalman Filter techniques: The performance and robustness towards model-structure uncertainties of the Takagi-Sugeno observer, a Linear, Extended and Unscented Kalman Filter are assessed. Hence the Takagi-Sugeno observer and enhanced Kalman Filter techniques are compared based on reduced-order models of a reference wind turbine with different modelling details. The objective is the systematic comparison with different design assumptions and requirements and the numerical evaluation of the reconstruction quality of the wind speed. Exemplified by a feedforward loop employing the reconstructed wind speed, the benefit of wind speed estimation within wind turbine control is illustrated. PMID:26725505

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    In recent years, the wind farm sizes have increased tremendously and with increasing installed capacity, the wind farms are requested to downregulate from their maximum possible power more frequently, especially in the offshore environment. Determination of the possible (or available) power is crucial not only because the reserve power has considerable market value but also for wind farm developers to be properly compensated for the loss during downregulation. While the available power calculation is straightforward for a single turbine, it gets rather complicated for the whole wind farm due to the change in the wake characteristics. In fact, the wake losses generated by the upstream turbine(s) decrease during downregulation and the downstream turbines therefore see more wind compared to the normal operation case. Currently, the Transmission System Operators (TSOs) have no real way to determine exactly the available power of a whole wind farm which is downregulated. Therefore, the PossPOW project aims to develop a verified and internationally accepted way to determine the possible power of a down-regulated offshore wind farm. The first phase of the project is to estimate the rotor effective wind speed. Since the nacelle anemometers are not readily available and are known to have reliability issues, the proposed method is to use power, pitch angle and rotational speed as inputs and combine it with a generic Cp model to estimate the wind speed. The performance of the model has been evaluated for both normal operation and downregulation periods using two different case studies: Horns Rev-I wind farm and NREL 5MW single turbine. During downregulation, the wake losses are not as severe and the velocity deficits at the downstream turbines are smaller as if also the wake is "downregulated". On the other hand, in order to calculate the available power, the wakes that would have been produced normally (if the turbines were not curtailed) are of importance, not the

  13. Variable Speed Wind Turbine Generator with Zero-sequence Filter

    DOEpatents

    Muljadi, Eduard

    1998-08-25

    A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility.

  14. Variable speed wind turbine generator with zero-sequence filter

    DOEpatents

    Muljadi, E.

    1998-08-25

    A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility. 14 figs.

  15. Variable speed wind turbine generator with zero-sequence filter

    DOEpatents

    Muljadi, Eduard

    1998-01-01

    A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility.

  16. NRO 10-m submillimeter telescope

    NASA Astrophysics Data System (ADS)

    Ukita, Nobuharu; Kawabe, Ryohei; Ishiguro, Masato; Ezawa, Hajime; Sekimoto, Yutaro; Hasegawa, Tatsuo; Yamamoto, Satoshi; Miyawaki, Keizo; Matsumoto, Soichi

    2000-07-01

    A 10-m submillimeter telescope designed for interferometric observations at bands from 3 to 0.3 mm has constructed at Nobeyama Radio Observatory. The telescope is an engineering model for a large millimeter and sub-millimeter array, and will be operated for developments of sub-millimeter observation techniques at a remote site. We have fabricated lightweight machined aluminum panels (15 kg m-2) that have a surface accuracy of 5 micrometer rms. They have a typical size of 0.8 m X 0.6 m, and are supported with three motorized screws. The back-up structure is constructed of a central hub of low thermal expansion alloy, and CFRP honeycomb boards and tubes. Holography measurements will be made with a nearby transmitter at 3 mm. The overall surface accuracy is expected to be < 25 micrometer rms; the goal being 17 micrometer rms. We have achieved an accuracy of 0.03' rms for angle encoders. The drive and control system is designed to achieve a pointing error of 1'.0 rms with no wind and at night. Under a wind velocity of 7 m s-1, the pointing error increases to 2'.0 rms. An optical telescope of 10-cm diameter mounted on the center hub will be used to characterize pointing and tracking accuracy. Thermal effects on the pointing and surface accuracy will be investigated using temperature measurements and FEM analyses. The fast position switching capability is also demanded to cancel atmospheric fluctuations. The antenna is able to drive both axes at a maximum velocity of 3 deg s-2 with a maximum acceleration of 6 deg. s-2. The telescope is currently equipped with SIS receivers for 100, 150, 230, and 345 GHz and a continuum backend and an FX-type digital autocorrelator with an instantaneous bandwidth of 512 MHz and 1024 channel outputs.

  17. Predictions of the solar wind speed by the probability distribution function model

    NASA Astrophysics Data System (ADS)

    Bussy-Virat, C. D.; Ridley, A. J.

    2014-06-01

    The near-Earth space environment is strongly driven by the solar wind and interplanetary magnetic field. This study presents a model for predicting the solar wind speed up to 5 days in advance. Probability distribution functions (PDFs) were created that relate the current solar wind speed and slope to the future solar wind speed, as well as the solar wind speed to the solar wind speed one solar rotation in the future. It was found that a major limitation of this type of technique is that the solar wind periodicity is close to 27 days but can be from about 22 to 32 days. Further, the optimum lag between two solar rotations can change from day to day, making a prediction of the future solar wind speed based solely on the solar wind speed approximately 27 days ago quite difficult. It was found that using a linear combination of the solar wind speed one solar rotation ago and a prediction of the solar wind speed based on the current speed and slope is optimal. The linear weights change as a function of the prediction horizon, with shorter prediction times putting more weight on the prediction based on the current solar wind speed and the longer prediction times based on an even spread between the two. For all prediction horizons from 8 h up to 120 h, the PDF Model is shown to be better than using the current solar wind speed (i.e., persistence), and better than the Wang-Sheeley-Arge Model for prediction horizons of 24 h.

  18. Flying with the wind: scale dependency of speed and direction measurements in modelling wind support in avian flight

    USGS Publications Warehouse

    Safi, Kamran; Kranstauber, Bart; Weinzierl, Rolf P.; Griffin, Larry; Reese, Eileen C.; Cabot, David; Cruz, Sebastian; Proaño, Carolina; Takekawa, John Y.; Newman, Scott H.; Waldenström, Jonas; Bengtsson, Daniel; Kays, Roland; Wikelski, Martin; Bohrer, Gil

    2013-01-01

    Background: Understanding how environmental conditions, especially wind, influence birds' flight speeds is a prerequisite for understanding many important aspects of bird flight, including optimal migration strategies, navigation, and compensation for wind drift. Recent developments in tracking technology and the increased availability of data on large-scale weather patterns have made it possible to use path annotation to link the location of animals to environmental conditions such as wind speed and direction. However, there are various measures available for describing not only wind conditions but also the bird's flight direction and ground speed, and it is unclear which is best for determining the amount of wind support (the length of the wind vector in a bird’s flight direction) and the influence of cross-winds (the length of the wind vector perpendicular to a bird’s direction) throughout a bird's journey. Results: We compared relationships between cross-wind, wind support and bird movements, using path annotation derived from two different global weather reanalysis datasets and three different measures of direction and speed calculation for 288 individuals of nine bird species. Wind was a strong predictor of bird ground speed, explaining 10-66% of the variance, depending on species. Models using data from different weather sources gave qualitatively similar results; however, determining flight direction and speed from successive locations, even at short (15 min intervals), was inferior to using instantaneous GPS-based measures of speed and direction. Use of successive location data significantly underestimated the birds' ground and airspeed, and also resulted in mistaken associations between cross-winds, wind support, and their interactive effects, in relation to the birds' onward flight. Conclusions: Wind has strong effects on bird flight, and combining GPS technology with path annotation of weather variables allows us to quantify these effects for

  19. Substorm probabilities are best predicted from solar wind speed

    NASA Astrophysics Data System (ADS)

    Newell, P. T.; Liou, K.; Gjerloev, J. W.; Sotirelis, T.; Wing, S.; Mitchell, E. J.

    2016-08-01

    Most measures of magnetospheric activity - including auroral power (AP), magnetotail stretching, and ring current intensity - are best predicted by solar wind-magnetosphere coupling functions which approximate the frontside magnetopause merging rate. However radiation belt fluxes are best predicted by a simpler function, namely the solar wind speed, v. Since most theories of how these high energy electrons arise are associated with repeated rapid dipolarizations such as associated with substorms, this apparent discrepancy could be reconciled under the hypothesis that the frequency of substorms tracks v rather than the merging rate - despite the necessity of magnetotail flux loading prior to substorms. Here we investigate this conjecture about v and substorm probability. Specifically, a continuous list of substorm onsets compiled from SuperMAG covering January 1, 1997 through December 31, 2007 are studied. The continuity of SuperMAG data and near continuity of solar wind measurements minimize selection bias. In fact v is a much better predictor of onset probability than is the overall merging rate, with substorm odds rising sharply with v. Some loading by merging is necessary, and frontside merging does increase substorm probability, but nearly as strongly as does v taken alone. Likewise, the effects of dynamic pressure, p, are smaller than simply v taken by itself. Changes in the solar wind matter, albeit modestly. For a given level of v (or Bz), a change in v (or Bz) will increase the odds of a substorm for at least 2 h following the change. A decrease in driving elevates substorm probabilities to a greater extent than does an increase, partially supporting external triggering. Yet current v is the best single predictor of subsequently observing a substorm. These results explain why geomagnetically quiet years and active years are better characterized by low or high v (respectively) than by the distribution of merging estimators. It appears that the flow of energy

  20. Ozone gradients in a spruce forest stand in relation to wind speed and time of the day

    NASA Astrophysics Data System (ADS)

    Pleijel, H.; Wallin, G.; Karlsson, P. E.; Skärby, L.

    Ozone concentrations were measured outside and inside a 60-year-old 15-20 m tall spruce forest at a wind-exposed forest edge in southwest Sweden, at 3 and 13 m height 15 m outside the forest, and at 3 and 13 m height inside the forest 45 m from the forest edge. Measurements at 3 m were made with three replicate tubes on each site, the replicates being separated by 10 m. In addition, horizontal and vertical wind speeds were measured at 8 m height outside and inside the forest. During daytime, the concentrations inside the forest were generally slightly lower. Negative ozone concentration gradients from the open field into the forest were observed at 3 m height when the wind speed was below approximately 1.5 m s -1. At very low wind speeds, mainly occurring during the night, the ozone concentrations at 3 m height were frequently higher inside the forest than outside the forest. This may be caused by a very large aerodynamic resistance to ozone deposition, due to very small air movements inside the forest under stable conditions. It is concluded that ozone uptake by the trees is likely to be very small at night, even if stomata are not entirely closed. Results from open-top chamber experiments are also discussed.

  1. Experimental investigation of the dependence of radar backscattering on wind speed, wind stress and wave height

    NASA Technical Reports Server (NTRS)

    Gogineni, S. P.; Katsaros, K. B.

    1989-01-01

    During summer 1988, radar measurements were performed in conjunction with detailed environmental observations on Lake Washington at the University of Washington Sand Point field station. Radar data were collected at 5.3 and 10 GHz for incidence angles between 30 and 60 deg with VV-polarization. The environmental measurements included wind speed and direction, large-wave heights, the high-frequency portion of the wave spectrum, humidity, and air and water temperatures. The small-scale wave spectrum was measured using a resistance wire gauge. The results show that backscatter increased with wind speed as expected. However, little difference was observed in the scattering coefficient for upwind and crosswind directions. The results also indicated an increase in the amplitude of small waves with friction velocity.

  2. A Novel Empirical Mode Decomposition With Support Vector Regression for Wind Speed Forecasting.

    PubMed

    Ren, Ye; Suganthan, Ponnuthurai Nagaratnam; Srikanth, Narasimalu

    2016-08-01

    Wind energy is a clean and an abundant renewable energy source. Accurate wind speed forecasting is essential for power dispatch planning, unit commitment decision, maintenance scheduling, and regulation. However, wind is intermittent and wind speed is difficult to predict. This brief proposes a novel wind speed forecasting method by integrating empirical mode decomposition (EMD) and support vector regression (SVR) methods. The EMD is used to decompose the wind speed time series into several intrinsic mode functions (IMFs) and a residue. Subsequently, a vector combining one historical data from each IMF and the residue is generated to train the SVR. The proposed EMD-SVR model is evaluated with a wind speed data set. The proposed EMD-SVR model outperforms several recently reported methods with respect to accuracy or computational complexity. PMID:25222957

  3. Snow fences on slopes at high wind speed: physical modelling in the CSTB cold wind tunnel

    NASA Astrophysics Data System (ADS)

    Naaim-Bouvet, F.; Naaim, M.; Michaux, J.-L.

    In order to determine the effect of steep slopes on snowdrift generated by snow fences, we have conducted physical modeling experiments in the CSTB (Centre Scientifique et Technique du Bâtiment) cold wind tunnel as part of the European project "Access to Large Facilities". After an overview of previous studies and an accurate description of the drifting snow process inside the experimental chamber, we present the main results obtained. (1) On flat areas, even for high wind speed, the acknowledged results for moderate wind are still valid: the porous snow fence (50%) is the most efficacious and the bottom gap increases the efficacy of the dense snow fence. (2) The steeper the slope is, the less effective all tested snow fences are. Their effectiveness decreases considerably: the snow catch is approximately divided by two for a slope of 10°. (3) Contrary to flat areas, on steep slopes, the "efficacy" is greater for a dense snow fence.

  4. Mistral and Tramontane wind speed and wind direction patterns in regional climate simulations

    NASA Astrophysics Data System (ADS)

    Obermann, Anika; Bastin, Sophie; Belamari, Sophie; Conte, Dario; Gaertner, Miguel Angel; Li, Laurent; Ahrens, Bodo

    2016-03-01

    The Mistral and Tramontane are important wind phenomena that occur over southern France and the northwestern Mediterranean Sea. Both winds travel through constricting valleys before flowing out towards the Mediterranean Sea. The Mistral and Tramontane are thus interesting phenomena, and represent an opportunity to study channeling effects, as well as the interactions between the atmosphere and land/ocean surfaces. This study investigates Mistral and Tramontane simulations using five regional climate models with grid spacing of about 50 km and smaller. All simulations are driven by ERA-Interim reanalysis data. Spatial patterns of surface wind, as well as wind development and error propagation along the wind tracks from inland France to offshore during Mistral and Tramontane events, are presented and discussed. To disentangle the results from large-scale error sources in Mistral and Tramontane simulations, only days with well simulated large-scale sea level pressure field patterns are evaluated. Comparisons with the observations show that the large-scale pressure patterns are well simulated by the considered models, but the orographic modifications to the wind systems are not well simulated by the coarse-grid simulations (with a grid spacing of about 50 km), and are reproduced slightly better by the higher resolution simulations. On days with Mistral and/or Tramontane events, most simulations underestimate (by 13 % on average) the wind speed over the Mediterranean Sea. This effect is strongest at the lateral borders of the main flow—the flow width is underestimated. All simulations of this study show a clockwise wind direction bias over the sea during Mistral and Tramontane events. Simulations with smaller grid spacing show smaller biases than their coarse-grid counterparts.

  5. A Comparison of GPS and Scatterometer Sensing of Ocean Wind Speed and Direction

    NASA Technical Reports Server (NTRS)

    Armatys, Michael; Komjathy, Attila; Axelrad, Penina; Katzberg, Stephen J.

    2000-01-01

    Initial estimates of ocean surface wind speed and direction based on observations of reflected Global Positioning System (GPS) signals are presented and compared to QuikSCAT wind fields. The two wind speed estimates are generally in agreement to within 2-3 m/s, and under favorable conditions of well developed seas and stable winds, direction estimates agree to within 10 deg. An overview of the GPS technique is presented as well as a presentation and discussion of these first results.

  6. 11- and 22-year variations of the cosmic ray density and of the solar wind speed

    NASA Technical Reports Server (NTRS)

    Chirkov, N. P.

    1985-01-01

    Cosmic ray density variations for 17-21 solar activity cycles and the solar wind speed for 20-21 events are investigated. The 22-year solar wind speed recurrence was found in even and odd cycles. The 22-year variations of cosmic ray density were found to be opposite that of solar wind speed and solar activity. The account of solar wind speed in 11-year variations significantly decreases the modulation region of cosmic rays when E = 10-20 GeV.

  7. The Impacts of Wind Speed Trends and 30-Year Variability in Relation to Hydroelectric Reservoir Inflows on Wind Power in the Pacific Northwest

    PubMed Central

    Cross, Benjamin D.; Kohfeld, Karen E.; Bailey, Joseph; Cooper, Andrew B.

    2015-01-01

    In hydroelectric dominated systems, the value and benefits of energy are higher during extended dry periods and lower during extended or extreme wet periods. By accounting for regional and temporal differences in the relationship between wind speed and reservoir inflow behavior during wind farm site selection, the benefits of energy diversification can be maximized. The goal of this work was to help maximize the value of wind power by quantifying the long-term (30-year) relationships between wind speed and streamflow behavior, using British Columbia (BC) and the Pacific Northwest (PNW) as a case study. Clean energy and self-sufficiency policies in British BC make the benefits of increased generation during low streamflow periods particularly large. Wind density (WD) estimates from a height of 10m (North American Regional Reanalysis, NARR) were correlated with cumulative usable inflows (CUI) for BC (collected from BC Hydro) for 1979–2010. The strongest WD-CUI correlations were found along the US coast (r ~0.55), whereas generally weaker correlations were found in northern regions, with negative correlations (r ~ -0.25) along BC’s North Coast. Furthermore, during the lowest inflow years, WD anomalies increased by up to 40% above average values for the North Coast. Seasonally, high flows during the spring freshet were coincident with widespread negative WD anomalies, with a similar but opposite pattern for low inflow winter months. These poorly or negatively correlated sites could have a moderating influence on climate related variability in provincial electricity supply, by producing greater than average generation in low inflow years and reduced generation in wet years. Wind speed and WD trends were also analyzed for all NARR grid locations, which showed statistically significant positive trends for most of the PNW and the largest increases along the Pacific Coast. PMID:26271035

  8. The Impacts of Wind Speed Trends and 30-Year Variability in Relation to Hydroelectric Reservoir Inflows on Wind Power in the Pacific Northwest.

    PubMed

    Cross, Benjamin D; Kohfeld, Karen E; Bailey, Joseph; Cooper, Andrew B

    2015-01-01

    In hydroelectric dominated systems, the value and benefits of energy are higher during extended dry periods and lower during extended or extreme wet periods. By accounting for regional and temporal differences in the relationship between wind speed and reservoir inflow behavior during wind farm site selection, the benefits of energy diversification can be maximized. The goal of this work was to help maximize the value of wind power by quantifying the long-term (30-year) relationships between wind speed and streamflow behavior, using British Columbia (BC) and the Pacific Northwest (PNW) as a case study. Clean energy and self-sufficiency policies in British BC make the benefits of increased generation during low streamflow periods particularly large. Wind density (WD) estimates from a height of 10m (North American Regional Reanalysis, NARR) were correlated with cumulative usable inflows (CUI) for BC (collected from BC Hydro) for 1979-2010. The strongest WD-CUI correlations were found along the US coast (r ~0.55), whereas generally weaker correlations were found in northern regions, with negative correlations (r ~ -0.25) along BC's North Coast. Furthermore, during the lowest inflow years, WD anomalies increased by up to 40% above average values for the North Coast. Seasonally, high flows during the spring freshet were coincident with widespread negative WD anomalies, with a similar but opposite pattern for low inflow winter months. These poorly or negatively correlated sites could have a moderating influence on climate related variability in provincial electricity supply, by producing greater than average generation in low inflow years and reduced generation in wet years. Wind speed and WD trends were also analyzed for all NARR grid locations, which showed statistically significant positive trends for most of the PNW and the largest increases along the Pacific Coast. PMID:26271035

  9. Low Wind Speed Turbine Developments in Convoloid Gearing: Final Technical Report, June 2005 - October 2008

    SciTech Connect

    Genesis Partners LP

    2010-08-01

    This report presents the results of a study conducted by Genesis Partners LP as part of the United States Department of Energy Wind Energy Research Program to develop wind technology that will enable wind systems to compete in regions having low wind speeds. The purpose of the program is to reduce the cost of electricity from large wind systems in areas having Class 4 winds to 3 cents per kWh for onshore systems or 5 cents per kWh for offshore systems. This work builds upon previous activities under the WindPACT project, the Next Generation Turbine project, and Phase I of the Low Wind Speed Turbine (LWST) project. This project is concerned with the development of more cost-effective gearing for speed increasers for wind turbines.

  10. Long term variability of the solar wind speed

    NASA Technical Reports Server (NTRS)

    Gazis, P. R.; Ahluwalia, H. S.; Fikani, M. M.; Xue, S. .S.

    1995-01-01

    We have reviewed the solar wind data obtained over a period of more than three decades. The data coverage on the Omnitape begins on 27 November 1963 and ends on 31 December 1993, for the version used by us. The coverage is very uneven, ranging from less than 40% to greater than 80%. We find that a correlation continues to exist between the measured values of the solar wind speed (V) and the geomagnetic index Ap. For the period when the coverage is greater than or equal to 85%, the data fit the equation: V (km/s) = 11.7 A(sub p) + 260. The correlation coefficient is 0.8, at a confidence level of 99.95%. However, we find that the predicted value of V may differ from the observed value by as much as 15% for a year in which the coverage is poorer. A comparison of IMP 8 with Pioneer Venus Orbiter (PVO) data indicates that the average values at the former are systematically higher by as much as 35 km/s (approximately 8%) for an overlapping time period. Also, we draw attention to the observed three solar cycle periodicity in A(sub p) data for the 1932 to 1994 period and its implications for forecasting the parameters for solar cycle 23 as well as on the computations of the modulation parameters for cosmic rays.

  11. Multiple and variable speed electrical generator systems for large wind turbines

    NASA Technical Reports Server (NTRS)

    Andersen, T. S.; Hughes, P. S.; Kirschbaum, H. S.; Mutone, G. A.

    1982-01-01

    A cost effective method to achieve increased wind turbine generator energy conversion and other operational benefits through variable speed operation is presented. Earlier studies of multiple and variable speed generators in wind turbines were extended for evaluation in the context of a specific large sized conceptual design. System design and simulation have defined the costs and performance benefits which can be expected from both two speed and variable speed configurations.

  12. A conceptual framework for evaluating variable speed generator options for wind energy applications

    NASA Technical Reports Server (NTRS)

    Reddoch, T. W.; Lipo, T. A.; Hinrichsen, E. N.; Hudson, T. L.; Thomas, R. J.

    1995-01-01

    Interest in variable speed generating technology has accelerated as greater emphasis on overall efficiency and superior dynamic and control properties in wind-electric generating systems are sought. This paper reviews variable speed technology options providing advantages and disadvantages of each. Furthermore, the dynamic properties of variable speed systems are contrasted with synchronous operation. Finally, control properties of variable speed systems are examined.

  13. Chandrayaan-1 observations of backscattered solar wind protons from the lunar regolith: Dependence on the solar wind speed

    NASA Astrophysics Data System (ADS)

    Lue, Charles; Futaana, Yoshifumi; Barabash, Stas; Wieser, Martin; Bhardwaj, Anil; Wurz, Peter

    2014-05-01

    We study the backscattering of solar wind protons from the lunar regolith using the Solar Wind Monitor of the Sub-keV Atom Reflecting Analyzer on Chandrayaan-1. Our study focuses on the component of the backscattered particles that leaves the regolith with a positive charge. We find that the fraction of the incident solar wind protons that backscatter as protons, i.e., the proton-backscattering efficiency, has an exponential dependence on the solar wind speed that varies from ~0.01% to ~1% for solar wind speeds of 250 km/s to 550 km/s. We also study the speed distribution of the backscattered protons in the fast (~550 km/s) solar wind case and find both a peak speed at ~80% of the solar wind speed and a spread of ~85 km/s. The observed flux variations and speed distribution of the backscattered protons can be explained by a speed-dependent charge state of the backscattered particles.

  14. Assessing the Impact of Different Measurement Time Intervals on Observed Long-Term Wind Speed Trends

    NASA Astrophysics Data System (ADS)

    Azorin-Molina, C.; Vicente-Serrano, S. M.; McVicar, T.; Jerez, S.; Revuelto, J.; López Moreno, J. I.

    2014-12-01

    During the last two decades climate studies have reported a tendency toward a decline in measured near-surface wind speed in some regions of Europe, North America, Asia and Australia. This weakening in observed wind speed has been recently termed "global stilling", showing a worldwide average trend of -0.140 m s-1 dec-1 during last 50-years. The precise cause of the "global stilling" remains largely uncertain and has been hypothetically attributed to several factors, mainly related to: (i) an increasing surface roughness (i.e. forest growth, land use changes, and urbanization); (ii) a slowdown in large-scale atmospheric circulation; (iii) instrumental drifts and technological improvements, maintenance, and shifts in measurements sites and calibration issues; (iv) sunlight dimming due to air pollution; and (v) astronomical changes. This study proposed a novel investigation aimed at analyzing how different measurement time intervals used to calculate a wind speed series can affect the sign and magnitude of long-term wind speed trends. For instance, National Weather Services across the globe estimate daily average wind speed using different time intervals and formulae that may affect the trend results. Firstly, we carried out a comprehensive review of wind studies reporting the sign and magnitude of wind speed trend and the sampling intervals used. Secondly, we analyzed near-surface wind speed trends recorded at 59 land-based stations across Spain comparing monthly mean wind speed series obtained from: (a) daily mean wind speed data averaged from standard 10-min mean observations at 0000, 0700, 1300 and 1800 UTC; and (b) average wind speed of 24 hourly measurements (i.e., wind run measurements) from 0000 to 2400 UTC. Thirdly and finally, we quantified the impact of anemometer drift (i.e. bearing malfunction) by presenting preliminary results (1-year of paired measurements) from a comparison of one new anemometer sensor against one malfunctioned anenometer sensor due

  15. CFD based design and modelling of wind fence to mitigate high-speed wind loading on a modular data center

    NASA Astrophysics Data System (ADS)

    Gorrepati, Devi Prasad

    A Modular Data Center (MDC) is a portable method of deploying a data center's capacity. As an alternative to the traditional data center, an MDC can be placed anywhere data capacity is required. The purpose of this study is to reduce the damage or loss of performance caused to the data centers that use free cooling, by mitigating high-speed winds. The Modular Data centers which use free cooling and that are located in open regions are subjected to various environmental risks such as very high-speed winds. As this wind blows over these data centers, the pressure difference generated within and outside the enclosure can have a drastic effect on the free cooling. Therefore, by using a wind fence which basically acts as a barrier to the upstream wind and reduces the mean velocity of air downstream of the wind fence, we reduce the pressure difference created and also the wind induced loading on the objects situated behind the fence. Although wind fences are used in many agricultural and farming practices, their usage pertaining to MDCs is very limited. The challenge is to reduce wind speed from 100 mph to 10 mph. This has been achieved by iteratively designing and analyzing a wind fence using CFD simulations to come up with a few wind fence options that have defined properties such as height, perforation and location (distance from the inlet of MDC) of the wind fence.

  16. Coronal Holes and Solar Wind High-Speed Streams: I. Forecasting the Solar Wind Parameters

    NASA Astrophysics Data System (ADS)

    Vršnak, Bojan; Temmer, Manuela; Veronig, Astrid M.

    2007-02-01

    We analyze the relationship between the coronal hole (CH) area/position and physical characteristics of the associated corotating high-speed stream (HSS) in the solar wind at 1 AU. For the analysis we utilize the data in the period DOY 25 125 of 2005, characterized by a very low coronal mass ejection (CME) activity. Distinct correlations between the daily averaged CH parameters and the solar wind characteristics are found, which allows us to forecast the solar wind velocity v, proton temperature T, proton density n, and magnetic field strength B, several days in advance in periods of low CME activity. The forecast is based on monitoring fractional areas A, covered by CHs in the meridional slices embracing the central meridian distance ranges [-40°,-20°], [-10°,10°], and [20°,40°]. On average, the peaks in the daily values of n, B, T, and v appear delayed by 1, 2, 3, and 4 days, respectively, after the area A attains its maximum in the central-meridian slice. The peak values of the solar wind parameters are correlated to the peak values of A, which provides also forecasting of the peak values of n, B, T, and v. The most accurate prediction can be obtained for the solar wind velocity, for which the average relative difference between the calculated and the observed peak values amounts to overline{\\vertδ\\vert}≈10 %. The forecast reliability is somewhat lower in the case of T, B, and n ( overline{\\vertδ\\vert}≈20 , 30, and 40%, respectively). The space weather implications are discussed, including the perspectives for advancing the real-time calculation of the Sun Earth transit times of coronal mass ejections and interplanetary shocks, by including more realistic real-time estimates of the solar wind characteristics.

  17. Study on the operational safety of high-speed trains exposed to stochastic winds

    NASA Astrophysics Data System (ADS)

    Yu, Meng-Ge; Zhang, Ji-Ye; Zhang, Ke-Yue; Zhang, Wei-Hua

    2014-06-01

    The characteristic wind curve (CWC) was commonly used in the previous work to evaluate the operational safety of the high-speed trains exposed to crosswinds. However, the CWC only provide the dividing line between safety state and failure state of high-speed trains, which can not evaluate the risk of derailment of high-speed trains when exposed to natural winds. In the present paper, a more realistic approach taking into account the stochastic characteristics of natural winds is proposed, which can give a reasonable and effective assessment of the operational safety of high-speed trains under stochastic winds. In this approach, the longitudinal and lateral components of stochastic winds are simulated based on the Cooper theory and harmonic superposition. An algorithm is set up for calculating the unsteady aerodynamic forces (moments) of the high-speed trains exposed to stochastic winds. A multi-body dynamic model of the rail vehicle is established to compute the vehicle system dynamic response subjected to the unsteady aerodynamic forces (moments) input. Then the statistical method is used to get the mean characteristic wind curve (MCWC) and spread range of the high-speed trains exposed to stochastic winds. It is found that the CWC provided by the previous analytical method produces over-conservative limits. The methodology proposed in the present paper can provide more significant reference for the safety operation of high-speed trains exposed to stochastic winds.

  18. Effect of wind speed on performance of a solar-pv array

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Thousands of solar photovoltaic (PV) arrays have been installed over the past few years, but the effect of wind speed on the predicted performance of PV arrays is not usually considered by installers. An increase in wind speed will cool the PV array, and the electrical power of the PV modules will ...

  19. Flow-Visualization Techniques Used at High Speed by Configuration Aerodynamics Wind-Tunnel-Test Team

    NASA Technical Reports Server (NTRS)

    Lamar, John E. (Editor)

    2001-01-01

    This paper summarizes a variety of optically based flow-visualization techniques used for high-speed research by the Configuration Aerodynamics Wind-Tunnel Test Team of the High-Speed Research Program during its tenure. The work of other national experts is included for completeness. Details of each technique with applications and status in various national wind tunnels are given.

  20. Observed and Projected Ocean Wind Speed Trends and Marine Boundary Layer Clouds

    NASA Astrophysics Data System (ADS)

    Kazil, J.; Feingold, G.

    2013-12-01

    Marine boundary layer clouds respond to wind speed, inter alia, via the wind speed dependence of surface fluxes of heat, moisture, and sea spray aerosol. Wind speed trends have the potential to change the properties and radiative forcing of marine boundary layer clouds in the 21st century. Satellite observations show a trend in mean ocean surface wind speed over the period 1991-2008, with increases by at least 5-10 %, depending on region. This observed trend in ocean surface wind speed is not necessarily related to anthropogenic climate forcing, but could arise from decadal internal variability of the climate system. Climate simulations project a decrease in surface wind speed in the north Pacific and Atlantic Oceans, and an increase in the Southern Ocean over the 21st century in response to anthropogenic climate forcing. This presentation addresses the response of cloud properties and cloud radiative forcing in the large, climatically relevant stratocumulus decks along the western shores of continents to the observed and projected trends in ocean wind speed. Results of cloud-system-resolving simulations of marine stratocumulus clouds are presented, in which the response of cloud properties and of cloud radiative forcing to the observed and projected changes in surface wind speed is quantified.

  1. Interplanetary gas. XX - Does the radial solar wind speed increase with latitude

    NASA Technical Reports Server (NTRS)

    Brandt, J. C.; Harrington, R. S.; Roosen, R. G.

    1975-01-01

    The astrometric technique used to derive solar wind speeds from ionic comet-tail orientations has been used to test the suggestion that the radial solar wind speed is higher near the solar poles than near the equator. We find no evidence for the suggested latitude variation.

  2. Analysis of the Flicker Level Produced by a Fixed-Speed Wind Turbine

    NASA Astrophysics Data System (ADS)

    Suppioni, Vinicius; P. Grilo, Ahda

    2013-10-01

    In this article, the analysis of the flicker emission during continuous operation of a mid-scale fixed-speed wind turbine connected to a distribution system is presented. Flicker emission is investigated based on simulation results, and the dependence of flicker emission on short-circuit capacity, grid impedance angle, mean wind speed, and wind turbulence is analyzed. The simulations were conducted in different programs in order to provide a more realistic wind emulation and detailed model of mechanical and electrical components of the wind turbine. Such aim is accomplished by using FAST (Fatigue, Aerodynamics, Structures, and Turbulence) to simulate the mechanical parts of the wind turbine, Simulink/MatLab to simulate the electrical system, and TurbSim to obtain the wind model. The results show that, even for a small wind generator, the flicker level can limit the wind power capacity installed in a distribution system.

  3. Nonparametric Stochastic Model for Uncertainty Quantifi cation of Short-term Wind Speed Forecasts

    NASA Astrophysics Data System (ADS)

    AL-Shehhi, A. M.; Chaouch, M.; Ouarda, T.

    2014-12-01

    Wind energy is increasing in importance as a renewable energy source due to its potential role in reducing carbon emissions. It is a safe, clean, and inexhaustible source of energy. The amount of wind energy generated by wind turbines is closely related to the wind speed. Wind speed forecasting plays a vital role in the wind energy sector in terms of wind turbine optimal operation, wind energy dispatch and scheduling, efficient energy harvesting etc. It is also considered during planning, design, and assessment of any proposed wind project. Therefore, accurate prediction of wind speed carries a particular importance and plays significant roles in the wind industry. Many methods have been proposed in the literature for short-term wind speed forecasting. These methods are usually based on modeling historical fixed time intervals of the wind speed data and using it for future prediction. The methods mainly include statistical models such as ARMA, ARIMA model, physical models for instance numerical weather prediction and artificial Intelligence techniques for example support vector machine and neural networks. In this paper, we are interested in estimating hourly wind speed measures in United Arab Emirates (UAE). More precisely, we predict hourly wind speed using a nonparametric kernel estimation of the regression and volatility functions pertaining to nonlinear autoregressive model with ARCH model, which includes unknown nonlinear regression function and volatility function already discussed in the literature. The unknown nonlinear regression function describe the dependence between the value of the wind speed at time t and its historical data at time t -1, t - 2, … , t - d. This function plays a key role to predict hourly wind speed process. The volatility function, i.e., the conditional variance given the past, measures the risk associated to this prediction. Since the regression and the volatility functions are supposed to be unknown, they are estimated using

  4. Stochastic simulation and forecasting of hourly average wind speed sequences in Jamaica

    SciTech Connect

    Daniel, A.R.; Chen, A.A. )

    1991-01-01

    Stochastic simulation and forecast models of hourly average wind speeds are presented in this paper. The models take into account several basic features of wind speed data including autocorrelation, non-Gaussian distribution, and diurnal nonstationarity. The positive correlation between consecutive wind speed observations is taken into account by fitting an autoregressive moving average (ARMA) process to wind speed data which were transformed to make their distribution approximately Gaussian and standardized to remove diurnal nonstationarity. Based on three years of data, separate models were obtained for the months of June, July, and August. Tests were performed to verify the adequacy of the models and comparisons were made between generated and real series and between forecasted and real series to check if the wind speed behavior was faithfully reproduced. Good results were obtained.

  5. Dependence of US hurricane economic loss on maximum wind speed and storm size

    NASA Astrophysics Data System (ADS)

    Zhai, Alice R.; Jiang, Jonathan H.

    2014-05-01

    Many empirical hurricane economic loss models consider only wind speed and neglect storm size. These models may be inadequate in accurately predicting the losses of super-sized storms, such as Hurricane Sandy in 2012. In this study, we examined the dependences of normalized US hurricane loss on both wind speed and storm size for 73 tropical cyclones that made landfall in the US from 1988 through 2012. A multi-variate least squares regression is used to construct a hurricane loss model using both wind speed and size as predictors. Using maximum wind speed and size together captures more variance of losses than using wind speed or size alone. It is found that normalized hurricane loss (L) approximately follows a power law relation with maximum wind speed (V max) and size (R), L = 10c V maxa R b , with c determining an overall scaling factor and the exponents a and b generally ranging between 4-12 and 2-4 respectively. Both a and b tend to increase with stronger wind speed. Hurricane Sandy’s size was about three times of the average size of all hurricanes analyzed. Based on the bi-variate regression model that explains the most variance for hurricanes, Hurricane Sandy’s loss would be approximately 20 times smaller if its size were of the average size with maximum wind speed unchanged. It is important to revise conventional empirical hurricane loss models that are only dependent on maximum wind speed to include both maximum wind speed and size as predictors.

  6. Wind Speed Measurement from Bistatically Scattered GPS Signals

    NASA Technical Reports Server (NTRS)

    Garrison, James L.; Komjathy, Attila; Zavorotny, Valery U.; Katzberg, Stephen J.

    1999-01-01

    Instrumentation and retrieval algorithms are described which use the forward, or bistatically scattered range-coded signals from the Global Positioning System (GPS) radio navigation system for the measurement of sea surface roughness. This roughness is known to be related directly to the surface wind speed. Experiments were conducted from aircraft along the TOPEX ground track, and over experimental surface truth buoys. These flights used a receiver capable of recording the cross correlation power in the reflected signal. The shape of this power distribution was then compared against analytical models derived from geometric optics. Two techniques for matching these functions were studied. The first recognized the most significant information content in the reflected signal is contained in the trailing edge slope of the waveform. The second attempted to match the complete shape of the waveform by approximating it as a series expansion and obtaining the nonlinear least squares estimate. Discussion is also presented on anomalies in the receiver operation and their identification and correction.

  7. Control algorithms for effective operation of variable-speed wind turbines

    NASA Astrophysics Data System (ADS)

    1993-10-01

    This report describes a computer code, called ASYM, and provides results from its application in simulating the control of the 34-m Test Bed vertical-axis wind turbine (VAWT) in Bushland, Texas. The code synthesizes dynamic wind speeds on a second-by-second basis in the time domain. The wind speeds conform to a predetermined spectral content governed by the hourly average wind speed that prevails at each hour of the simulation. The hourly average values are selected in a probabilistic sense through the application of Markov chains, but their cumulative frequency of occurrence conforms to a Rayleigh distribution that is governed by the mean annual wind speed of the site selected. The simulated wind speeds then drive a series of control algorithms that enable the code to predict key operational parameters such as number of annual starts and stops, annual energy production, and annual fatigue damage at a critically stressed joint on the wind turbine. This report also presents results from the application of ASYM that pertain to low wind speed cut-in and cut-out conditions and controlled operation near critical speed ranges that excite structural vibrations that can lead to accelerated fatigue damage.

  8. Control algorithms for effective operation of variable-speed wind turbines

    SciTech Connect

    Not Available

    1993-10-01

    This report describes a computer code, called ASYM and provides results from its application in simulating the control of the 34-m Test Bed vertical-axis wind turbine (VAWT) in Bushland, Texas. The code synthesizes dynamic wind speeds on a second-by-second basis in the time domain. The wind speeds conform to a predetermined spectral content governed by the hourly average wind speed that prevails at each hour of the simulation. The hourly average values are selected in a probabilistic sense through the application of Markov chains, but their cumulative frequency of occurrence conforms to a Rayleigh distribution that is governed by the mean annual wind speed of the site selected. The simulated wind speeds then drive a series of control algorithms that enable the code to predict key operational parameters such as number of annual starts and stops, annual energy production, and annual fatigue damage at a critically stressed joint on the wind turbine. This report also presents results from the application of ASYM that pertain to low wind speed cut-in and cut-out conditions and controlled operation near critical speed ranges that excite structural vibrations that can lead to accelerated fatigue damage.

  9. Variation of the average 'freezing-in' temperature of oxygen ions with solar wind speed

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Vogt, C.

    1980-01-01

    Observations of the average oxygen ionization equilibrium as a function of speed of the solar wind are presented. At low solar wind speeds they indicate a coronal temperature at the freezing-in point of (1.6 + or - 0.2) x 10 to the 6th K. At speeds above 450 km/sec the apparent temperature starts to rise rapidly. This rise is tentatively interpreted in terms of a lack of thermodynamic equilibrium in the source region.

  10. Numerical Study of the High-Speed Leg of a Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Nayani, Sudheer; Sellers, William L., III; Brynildsen, Scott E.; Everhart, Joel L.

    2015-01-01

    The paper describes the numerical study of the high-speed leg of the NASA Langley 14 by 22-foot Low Speed Wind Tunnel. The high-speed leg consists of the Settling Chamber, Contraction, Test Section, and First Diffuser. Results are shown comparing two different exit boundary conditions and two different methods of determining the surface geometry.

  11. Winds, Bubbles, ...but Magnetized: Solutions for High Speed Post-AGB Winds and Their Extreme Collimation

    NASA Astrophysics Data System (ADS)

    García-Segura, G.; López, J. A.; Franco, J.

    2003-01-01

    This paper provides solutions for the origin of post-AGB winds, their acceleration up to high speed, and the subsequent formation of extremely collimated proto-planetary nebulae. Several wind models with terminal velocities from a few tens of km/s up to 10^3km/s are calculated, which produce proto-planetary nebulae with linear momenta in the range 10^36 to 10^40gcm/s and with kinetic energies in the range 10^42 to 10^47 erg. These results match available observations of proto-planetary nebulae. In the present simplistic scheme, the driver of the wind is just the magnetic pressure at the stellar surface. Other forces are not taken into account in this study, except gravity. We conclude that mass-loss rates of post-AGB stars and transition times from late AGB up to planetary nebula central stars could be directly linked with the production of magnetic field at the stellar core. As an example, mass-loss rates as large as 8×10^-5 M[ sun ]/yr and transition times as short as 5000 years are predicted.

  12. Reconstruction of Helio-Latitudinal Structure of the Solar Wind Proton Speed and Density

    NASA Astrophysics Data System (ADS)

    Sokół, Justyna M.; Swaczyna, Paweł; Bzowski, Maciej; Tokumaru, Munetoshi

    2015-09-01

    The modeling of the heliosphere requires continuous three-dimensional solar wind data. The in-situ out-of-ecliptic measurements are very rare, so that other methods of solar wind detection are needed. We use the remote-sensing data of the solar wind speed from observations of interplanetary scintillation (IPS) to reconstruct spatial and temporal structures of the solar wind proton speed from 1985 to 2013. We developed a method of filling the data gaps in the IPS observations to obtain continuous and homogeneous solar wind speed records. We also present a method to retrieve the solar wind density from the solar wind speed, utilizing the invariance of the solar wind dynamic pressure and energy flux with latitude. To construct the synoptic maps of the solar wind speed we use the decomposition into spherical harmonics of each of the Carrington rotation map. To fill the gaps in time we apply the singular spectrum analysis to the time series of the coefficients of spherical harmonics. We obtained helio-latitudinal profiles of the solar wind proton speed and density over almost three recent solar cycles. The accuracy in the reconstruction is, due to computational limitations, about 20 %. The proposed methods allow us to improve the spatial and temporal resolution of the model of the solar wind parameters presented in our previous paper (Sokół et al., Solar Phys. 285, 167, 2013) and give a better insight into the time variations of the solar wind structure. Additionally, the solar wind density is reconstructed more accurately and it fits better to the in-situ measurements from Ulysses.

  13. On the relationship of radar backscatter to wind speed and fetch. [ocean wave generation

    NASA Technical Reports Server (NTRS)

    Ross, D.; Jones, W. L.

    1978-01-01

    The physics of the interaction of electromagnetic waves with the ocean surface has been an active area of research for a number of years. This paper contains the results of satellite and aircraft experiments to investigate the ability of active microwave radars to infer surface wind speeds remotely. Data obtained from the recent National Aeronautics and Space Administration (NASA) Skylab experiment are compared with surface wind speeds measured by low-flying aircraft and ships-of-opportunity and found to give useful estimates of the ocean wind field. Also investigated was the influence of varying wave height on radar measurements of wind speed by measuring the backscattering cross-section for constant wind speed but variable wave conditions. It is found that this effect is of little importance.

  14. Recent recovery of surface wind speed after decadal decrease: a focus on South Korea

    NASA Astrophysics Data System (ADS)

    Kim, JongChun; Paik, Kyungrock

    2015-09-01

    We investigate the multi-decadal variability of observed surface wind speed around South Korea. It is found that surface wind speed exhibits decreasing trend from mid-1950s until 2003, which is similar with the trends reported for other parts of the world. However, the decreasing trend ceases and becomes unclear since then. It is revealed that decreasing wind speed until 2003 is strongly associated with the decreasing trend of the spatial variance in both atmospheric pressure and air temperature across the East Asia for the same period. On the contrary, break of decreasing trend in surface wind speed since 2003 is associated with increasing spatial variance in surface temperature over the East Asia. Ground observation shows that surface wind speed and air temperature exhibit highly negative correlations for both summer and winter prior to 2003. However, since 2003, the correlations differ between seasons. We suggest that mechanisms behind the recent wind speed trend are different between summer and winter. This is on the basis of an interesting finding that air temperature has decreased while surface temperature has increased during winter months since 2003. We hypothesize that such contrasting temperature trends indicate more frequent movement of external cold air mass into the region since 2003. We also hypothesize that increasing summer wind speed is driven by intrusion of warm air mass into the region which is witnessed via increasing spatial variance in surface temperature across East Asia and the fact that both air and surface temperature rise together.

  15. Ulysses at 50 deg south: Constant immersion in the high-speed solar wind

    NASA Technical Reports Server (NTRS)

    Phillips, J. L.; Balogh, A.; Bame, S. J.; Goldstein, B. E.; Gosling, J. T.; Hoeksema, J. T.; Mccomas, D. J.; Neugebauer, M.; Sheeley, N. R., Jr.; Wang, Y.-M.

    1994-01-01

    We present speed observations from the Ulysses solar wind plasma experiment through 50 deg south latitude. The pronounced speed modulation arising from solar rotation and the tilt of the heliomagnetic current sheet has nearly disappeared. Ulysses is now observing wind speeds in the 700 to 800 km/s range, with a magnetic polarity indicating an origin in the large south polar coronal hole. The strong compressions, rarefractions, and shock waves previously seen have weakened or disappeared. Occasional coronal mass ejections characterized by low plasma density caused by radial expansion have been observed. The coronal configuration was simple and stable in 1993, indicating that the observed solar wind changes were caused by increasing spacecraft latitude. Trends in prevailing speed with increasing latitude support previous findings. A decrease in peak speed southward of 40 deg latitude may indicate that the fastest solar wind comes from the equatorial extensions of the polar coronal holes.

  16. Stability Augmentation of Wind Farm using Variable Speed Permanent Magnet Synchronous Generator

    NASA Astrophysics Data System (ADS)

    Rosyadi, Marwan; Muyeen, S. M.; Takahashi, Rion; Tamura, Junji

    This paper presents a new control strategy of variable speed permanent magnet wind generator for stability augmentation of wind farm including fixed speed wind turbine with Induction Generator (IG). A new control scheme is developed for two levels back-to-back converters of Permanent Magnet Synchronous Generator (PMSG), by which both active and reactive powers delivered to the grid can be controlled easily. To avoid the converter damage, the DC link protection controller is also proposed in order to protect the dc link circuit during fault condition. To evaluate the control capability of the proposed controllers, simulations are performed on two model systems composed of wind farms connected to an infinite bus. From transient and steady state analyses by using PSCAD/EMTDC, it is concluded that the proposed control scheme is very effective to improve the stability of wind farm for severe network disturbance and randomly fluctuating wind speed.

  17. Wind speed affects prey-catching behaviour in an orb web spider

    NASA Astrophysics Data System (ADS)

    Turner, Joe; Vollrath, Fritz; Hesselberg, Thomas

    2011-12-01

    Wind has previously been shown to influence the location and orientation of spider web sites and also the geometry and material composition of constructed orb webs. We now show that wind also influences components of prey-catching behaviour within the web. A small wind tunnel was used to generate different wind speeds. Araneus diadematus ran more slowly towards entangled Drosophila melanogaster in windy conditions, which took less time to escape the web. This indicates a lower capture probability and a diminished overall predation efficiency for spiders at higher wind speeds. We conclude that spiders' behaviour of taking down their webs as wind speed increases may therefore not be a response only to possible web damage.

  18. Flight measurement and analysis of AAFE RADSCAT wind speed signature of the ocean

    NASA Technical Reports Server (NTRS)

    Schroeder, L. C.; Jones, W. L.; Schaffner, P. R.; Mitchell, J. L.

    1984-01-01

    The advanced aerospace flight experiment radiometer scatterometer (AAFE RADSCAT) which was developed as a research tool to evaluate the use of microwave frequency remote sensors to provide wind speed information at the ocean surface is discussed. The AAFE RADSCAT helped establish the feasibility of the satellite scatterometer for measuring both wind speed and direction. The most important function of the AAFE RADSCAT was to provide a data base of ocean normalized radar cross section (NRCS) measurements as a function of surface wind vector at 13.9 GHz. The NRCS measurements over a wide parametric range of incidence angles, azimuth angles, and winds were obtained in a series of RADSCAT aircraft missions. The obtained data base was used to model the relationship between k sub u band radar signature and ocean surface wind vector. The models developed therefrom are compared with those used for inversion of the SEASAT-A satellite scatterometer (SASS) radar measurements to wind speeds.

  19. A Hybrid Approach for Short-Term Forecasting of Wind Speed

    PubMed Central

    Tatinati, Sivanagaraja; Veluvolu, Kalyana C.

    2013-01-01

    We propose a hybrid method for forecasting the wind speed. The wind speed data is first decomposed into intrinsic mode functions (IMFs) with empirical mode decomposition. Based on the partial autocorrelation factor of the individual IMFs, adaptive methods are then employed for the prediction of IMFs. Least squares-support vector machines are employed for IMFs with weak correlation factor, and autoregressive model with Kalman filter is employed for IMFs with high correlation factor. Multistep prediction with the proposed hybrid method resulted in improved forecasting. Results with wind speed data show that the proposed method provides better forecasting compared to the existing methods. PMID:24453872

  20. On the Relationship Between Solar Wind Speed, Geomagnetic Activity, and the Solar Cycle Using Annual Values

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2008-01-01

    The aa index can be decomposed into two separate components: the leading sporadic component due to solar activity as measured by sunspot number and the residual or recurrent component due to interplanetary disturbances, such as coronal holes. For the interval 1964-2006, a highly statistically important correlation (r = 0.749) is found between annual averages of the aa index and the solar wind speed (especially between the residual component of aa and the solar wind speed, r = 0.865). Because cyclic averages of aa (and the residual component) have trended upward during cycles 11-23, cyclic averages of solar wind speed are inferred to have also trended upward.

  1. Flux-tube geometry and solar wind speed during an activity cycle

    NASA Astrophysics Data System (ADS)

    Pinto, R. F.; Brun, A. S.; Rouillard, A. P.

    2016-07-01

    Context. The solar wind speed at 1 AU shows cyclic variations in latitude and in time which reflect the evolution of the global background magnetic field during the activity cycle. It is commonly accepted that the terminal (asymptotic) wind speed in a given magnetic flux-tube is generally anti-correlated with its total expansion ratio, which motivated the definition of widely used semi-empirical scaling laws relating one to the other. In practice, such scaling laws require ad hoc corrections (especially for the slow wind in the vicinities of streamer/coronal hole boundaries) and empirical fits to in situ spacecraft data. A predictive law based solely on physical principles is still missing. Aims: We test whether the flux-tube expansion is the controlling factor of the wind speed at all phases of the cycle and at all latitudes (close to and far from streamer boundaries) using a very large sample of wind-carrying open magnetic flux-tubes. We furthermore search for additional physical parameters based on the geometry of the coronal magnetic field which have an influence on the terminal wind flow speed. Methods: We use numerical magneto-hydrodynamical simulations of the corona and wind coupled to a dynamo model to determine the properties of the coronal magnetic field and of the wind velocity (as a function of time and latitude) during a whole 11-yr activity cycle. These simulations provide a large statistical ensemble of open flux-tubes which we analyse conjointly in order to identify relations of dependence between the wind speed and geometrical parameters of the flux-tubes which are valid globally (for all latitudes and moments of the cycle). Results: Our study confirms that the terminal (asymptotic) speed of the solar wind depends very strongly on the geometry of the open magnetic flux-tubes through which it flows. The total flux-tube expansion is more clearly anti-correlated with the wind speed for fast rather than for slow wind flows, and effectively controls the

  2. Wind speed estimation using C-band compact polarimetric SAR for wide swath imaging modes

    NASA Astrophysics Data System (ADS)

    Denbina, Michael; Collins, Michael J.

    2016-03-01

    We have investigated the use of C-band compact polarimetric synthetic aperture radar for estimation of ocean surface wind speeds. Using 1399 buoy observations collocated with Radarsat-2 scenes, compact polarimetric data was simulated for two of the Radarsat Constellation's planned wide swath imaging modes. Provided the wind direction is known or can be estimated, our results demonstrate that wind speed can be estimated from the right-vertical polarization channel of the compact polarimetry using a combination of the CMOD5 geophysical model function and a linear model. If wind speed estimation without wind direction input is desired, the randomly-polarized component of the backscattered power can be used in a similar fashion to that of the linear cross-polarizations, but is less affected by increases in the noise effective sigma-zero of the data. A model is proposed for the randomly-polarized power as a function of incidence angle and wind speed, independent of wind direction. The results suggest that compact polarimetry is a strong alternative to linearly polarized synthetic aperture radar data for wind speed estimation applications, particularly for wide swath imaging modes with a high noise floor.

  3. Identification and Attribution of Global Wind Speed Trends at 100m

    NASA Astrophysics Data System (ADS)

    McGraw, Zachary; Smith, Ronald; Storelvmo, Trude

    2016-04-01

    Recent studies have found evidence that global climate change significantly alters the strength of large-scale wind patterns. Any enduring trends over large regions are potentially of value to understand due to their implications for the wind energy industry. In this study we identify and evaluate global wind speed trends at the wind turbine hub height (~100m) through the use of CMIP5 models, standard reanalyses (ERA-Interim, NCEP2) and a uniquely high-resolution analysis dataset (Vestas Mesoscale Library). By analyzing how wind speeds change across the globe throughout the period 1900-2100 (with emphasis on the satellite era, 1979-2014), we assess the significance of multi-decadal wind speed trends in the context of natural spatial and temporal variability. Our results show substantial differences in regional trends between different datasets though several regions including the Southern Hemisphere mid-latitudes and the Caribbean show consistently substantial changing wind speeds during the satellite era. Wind speed trends tend to diminish over large time scales and follow spatial patterns that link multi-decadal trends to the evolving behaviors of internal variability modes, especially those of ENSO and the Southern Annular Mode (SAM).

  4. An Analysis of Peak Wind Speed Data from Collocated Mechanical and Ultrasonic Anemometers

    NASA Technical Reports Server (NTRS)

    Short, David A.; Wells, Leonard A.; Merceret, Francis J.; Roeder, William P.

    2005-01-01

    This study focuses on a comparison of peak wind speeds reported by mechanical and ultrasonic anemometers at Cape Canaveral Air Force Station and Kennedy Space Center (CCAFS/KSC) on the east central coast of Florida and Vandenberg Air Force Base (VAFB) on the central coast of California. The legacy mechanical wind instruments on CCAFS/KSC and VAFB weather towers are being changed from propeller-and-vane (CCAFS/KSC) and cup-and-vane (VAFB) sensors to ultrasonic sensors under the Range Standardization and Automation (RSA) program. The wind tower networks on KSC/CCAFS and VAFB have 41 and 27 towers, respectively. Launch Weather Officers, forecasters, and Range Safety analysts at both locations need to understand the performance of the new wind sensors for a myriad of reasons that include weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The Legacy sensors measure wind speed and direction mechanically. The ultrasonic RSA sensors have no moving parts. Ultrasonic sensors were originally developed to measure very light winds (Lewis and Dover 2004). The technology has evolved and now ultrasonic sensors provide reliable wind data over a broad range of wind speeds. However, because ultrasonic sensors respond more quickly than mechanical sensors to rapid fluctuations in speed, characteristic of gusty wind conditions, comparisons of data from the two sensor types have shown differences in the statistics of peak wind speeds (Lewis and Dover 2004). The 45th Weather Squadron (45 WS) and the 30 WS requested the Applied Meteorology Unit (AMU) to compare data from RSA and Legacy sensors to determine if there are significant differences in peak wind speed information from the two systems.

  5. Ulysses at 50{degrees} south: Constant immersion in the high-speed solar wind

    SciTech Connect

    Phillips, J.L.; Bame, S.J.; Gosling, J.T.; McComas, D.J.; Balogh, A.; Goldstein, B.E.; Neugebauer, M.; Hoeksema, J.T.; Sheeley, N.R. Jr.; Wang, Y.M.

    1994-06-15

    The authors present speed observations from the Ulysses solar wind plasma experiment through 50{degrees} south latitude. The pronounced speed modulation arising from solar rotation and the tilt of the heliomagnetic current sheet has nearly disappeared. Ulysses is now observing wind speeds in the 700 to 800 km s{sup {minus}1} range, with a magnetic polarity indicating an origin in the large south polar coronal hole. The strong compressions, rarefactions, and shock waves previously seen have weakened or disappeared. Occasional coronal mass ejections characterized by low plasma density caused by radial expansion have been observed. The coronal configuration was simple and stable in 1993, indicating that the observed solar wind changes were caused by increasing latitude support previous findings. A decrease in peak speed southward of 40{degrees} latitude may indicate that the fastest solar wind comes from the equatorial extensions of the polar coronal holes. 16 refs., 4 figs.

  6. Solar Wind Speed Structure in the Inner Corona at 3-12R(sub)O

    NASA Technical Reports Server (NTRS)

    Woo, R.

    1995-01-01

    Estimates of solar wind speed obtained by Armstrong et al. [1986] based on 1983 VLA multiple-station intensity scintillation measurements inside 12 R(sub)O have been compared with white light coronagraph measurements.

  7. An efficient method for distributing wind speeds over heterogeneous terrain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High spatial variability of wind over mountain landscapes can create strong gradients in mass and in energy fluxes at the scale of tens of meters. Variable winds are often cited as the cause of high heterogeneity in snow distribution in non-forested mountain locations. Distributed models capable o...

  8. Future hub-height wind speed distributions from statistically downscaled CMIP5 simulations

    NASA Astrophysics Data System (ADS)

    Devis, A.; Demuzere, M.; van Lipzig, N.

    2013-12-01

    In order to realistically estimate wind-power yields, we need to know the hub-height wind speed under future climate conditions. Climate conditions of the upper atmosphere are commonly simulated using general circulation models (GCMs). However their typical resolutions are too coarse to assess the climate at the height of a wind turbine. This study simulates the hub-height wind speed probability distributions (PDFs) over Europe under future climate conditions. The analysis is based on the simulations of the CMIP5 earth system models, which are the latest development of GCMs. They include more components and feedbacks and their runs are performed at higher resolutions. In a first step, the ensemble of GCMs is evaluated on their representation of the wind speed PDFs in the lower atmosphere using ERA-Interim data. The evaluation indicates that GCMs are skillful down to their lowest model levels apart for the south of Europe, which is affected by a large scale winter bias and for certain coastal and orographical regions. Secondly, a statistical approach is developed which downscales the GCM output to the wind speed PDF at the height of the wind turbine hub. Since the evaluation analysis shows that GCMs are also skillful at the lower model levels, the statistical downscaling uses GCM variables describing the lower atmosphere, instead of the commonly used large scale circulation variables of the upper atmosphere. By doing so less uncertainty will be added trough the downscaling implementation. The downscaling methodology is developed for an observational site in the Netherlands, using hub-height wind speed observations and ERA-Interim data for the period 1989-2009. The statistical approach is based on a regression analysis of the parameters of the PDFs. Results indicate that the predictor selection is very much defined by the stability conditions of the atmospheric boundary layer. During convective summer-day conditions, the observed hub-height wind speed can skillfully

  9. Wind tunnel results of the high-speed NLF(1)-0213 airfoil

    NASA Technical Reports Server (NTRS)

    Sewall, William G.; Mcghee, Robert J.; Hahne, David E.; Jordan, Frank L., Jr.

    1987-01-01

    Wind tunnel tests were conducted to evaluate a natural laminar flow airfoil designed for the high speed jet aircraft in general aviation. The airfoil, designated as the High Speed Natural Laminar Flow (HSNLF)(1)-0213, was tested in two dimensional wind tunnels to investigate the performance of the basic airfoil shape. A three dimensional wing designed with this airfoil and a high lift flap system is also being evaluated with a full size, half span model.

  10. Comparison Between Sea Surface Wind Speed Estimates From Reflected GPS Signals and Buoy Measurements

    NASA Technical Reports Server (NTRS)

    Garrison, James L.; Katzberg, Steven J.; Zavorotny, Valery U.

    2000-01-01

    Reflected signals from the Global Positioning System (GPS) have been collected from an aircraft at approximately 3.7 km altitude on 5 different days. Estimation of surface wind speed by matching the shape of the reflected signal correlation function against analytical models was demonstrated. Wind speed obtained from this method agreed with that recorded from buoys to with a bias of less than 0.1 m/s, and with a standard derivation of 1.3 meters per second.

  11. How Well Can We Measure the Vertical Wind Speed? Implications for Fluxes of Energy and Mass

    NASA Astrophysics Data System (ADS)

    Kochendorfer, John; Meyers, Tilden P.; Frank, John; Massman, William J.; Heuer, Mark W.

    2012-11-01

    Sonic anemometers are capable of measuring the wind speed in all three dimensions at high frequencies (10-50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a non-orthogonal transducer orientation were estimated for over 100 combinations of angle-of-attack and wind direction using a novel technique to measure the true angle-of-attack and wind speed within the turbulent atmospheric surface layer. Corrections to the vertical wind speed varied from -5 to 37% for all angles-of-attack and wind directions examined. When applied to eddy-covariance data from three NOAA flux sites, the wind-velocity corrections increased the magnitude of CO2 fluxes, sensible heat fluxes, and latent heat fluxes by ≈11%, with the actual magnitude of flux corrections dependent upon sonic anemometer, surface type, and scalar. A sonic anemometer that uses vertically aligned transducers to measure the vertical wind speed was also tested at four angles-of-attack, and corrections to the vertical wind speed measured using this anemometer were within ±1% of zero. Sensible heat fluxes over a forest canopy measured using this anemometer were 15% greater than sensible heat fluxes measured using a sonic anemometer with a non-orthogonal transducer orientation. These results indicate that sensors with a non-orthogonal transducer orientation, which includes the majority of the research-grade three-dimensional sonic anemometers currently in use, should be redesigned to minimize sine errors by measuring the vertical wind speed using one pair of vertically aligned transducers.

  12. Sectoral Analysis of Wind Speed and Turbulence Intensity over Forest and Open Land

    NASA Astrophysics Data System (ADS)

    Beyer, Elisabeth

    2015-04-01

    More and more wind turbines are built onshore and reduce the available areas for wind energy. Forests are an additional potential for wind energy priority areas. But the high roughness of wooden areas and the resulting turbulences make it difficult to assess sites in forests. In order to cope with this problem some measurements, using Lidar and met masts were done inside and outside wooden areas. Therefore, two posters were created, dealing with the dependence of turbulence intensity on wind speed and wind direction. This poster summarises the existing results, concentrating on the sectoral analysis of wind speed and turbulence intensity. Furthermore it investigates the differences of inflow over landcover with low and high surface roughnesses.

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

    SciTech Connect

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

    1994-01-01

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

  14. Ensemble Nonlinear Autoregressive Exogenous Artificial Neural Networks for Short-Term Wind Speed and Power Forecasting.

    PubMed

    Men, Zhongxian; Yee, Eugene; Lien, Fue-Sang; Yang, Zhiling; Liu, Yongqian

    2014-01-01

    Short-term wind speed and wind power forecasts (for a 72 h period) are obtained using a nonlinear autoregressive exogenous artificial neural network (ANN) methodology which incorporates either numerical weather prediction or high-resolution computational fluid dynamics wind field information as an exogenous input. An ensemble approach is used to combine the predictions from many candidate ANNs in order to provide improved forecasts for wind speed and power, along with the associated uncertainties in these forecasts. More specifically, the ensemble ANN is used to quantify the uncertainties arising from the network weight initialization and from the unknown structure of the ANN. All members forming the ensemble of neural networks were trained using an efficient particle swarm optimization algorithm. The results of the proposed methodology are validated using wind speed and wind power data obtained from an operational wind farm located in Northern China. The assessment demonstrates that this methodology for wind speed and power forecasting generally provides an improvement in predictive skills when compared to the practice of using an "optimal" weight vector from a single ANN while providing additional information in the form of prediction uncertainty bounds. PMID:27382627

  15. Simple and Computationally Efficient Modeling of Surface Wind Speeds Over Heterogeneous Terrain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind speeds vary dramatically over short distances in mountain settings. Snow distribution is strongly affected by these disparate winds with drifts containing meters of snow-water-equivalence (SWE) often found adjacent to windward slopes containing minimal amounts of SWE. The heterogeneous snow d...

  16. Ensemble Nonlinear Autoregressive Exogenous Artificial Neural Networks for Short-Term Wind Speed and Power Forecasting

    PubMed Central

    Lien, Fue-Sang; Yang, Zhiling; Liu, Yongqian

    2014-01-01

    Short-term wind speed and wind power forecasts (for a 72 h period) are obtained using a nonlinear autoregressive exogenous artificial neural network (ANN) methodology which incorporates either numerical weather prediction or high-resolution computational fluid dynamics wind field information as an exogenous input. An ensemble approach is used to combine the predictions from many candidate ANNs in order to provide improved forecasts for wind speed and power, along with the associated uncertainties in these forecasts. More specifically, the ensemble ANN is used to quantify the uncertainties arising from the network weight initialization and from the unknown structure of the ANN. All members forming the ensemble of neural networks were trained using an efficient particle swarm optimization algorithm. The results of the proposed methodology are validated using wind speed and wind power data obtained from an operational wind farm located in Northern China. The assessment demonstrates that this methodology for wind speed and power forecasting generally provides an improvement in predictive skills when compared to the practice of using an “optimal” weight vector from a single ANN while providing additional information in the form of prediction uncertainty bounds. PMID:27382627

  17. Consideration of tip speed limitations in preliminary analysis of minimum COE wind turbines

    NASA Astrophysics Data System (ADS)

    Cuerva-Tejero, A.; Yeow, T. S.; Lopez-Garcia, O.; Gallego-Castillo, C.

    2014-12-01

    A relation between Cost Of Energy, COE, maximum allowed tip speed, and rated wind speed, is obtained for wind turbines with a given goal rated power. The wind regime is characterised by the corresponding parameters of the probability density function of wind speed. The non-dimensional characteristics of the rotor: number of blades, the blade radial distributions of local solidity, twist, angle, and airfoil type, play the role of parameters in the mentioned relation. The COE is estimated using a cost model commonly used by the designers. This cost model requires basic design data such as the rotor radius and the ratio between the hub height and the rotor radius. Certain design options, DO, related to the technology of the power plant, tower and blades are also required as inputs. The function obtained for the COE can be explored to find those values of rotor radius that give rise to minimum cost of energy for a given wind regime as the tip speed limitation changes. The analysis reveals that iso-COE lines evolve parallel to iso-radius lines for large values of limit tip speed but that this is not the case for small values of the tip speed limits. It is concluded that., as the tip speed limit decreases, the optimum decision for keeping minimum COE values can be: a) reducing the rotor radius for places with high weibull scale parameter or b) increasing the rotor radius for places with low weibull scale parameter.

  18. A Diagnostic Diagram to Understand the Marine Atmospheric Boundary Layer at High Wind Speeds

    NASA Astrophysics Data System (ADS)

    Kettle, Anthony

    2014-05-01

    Long time series of offshore meteorological measurements in the lower marine atmospheric boundary layer show dynamical regimes and variability that are forced partly by interaction with the underlying sea surface and partly by the passage of cloud systems overhead. At low wind speeds, the dynamics and stability structure of the surface layer depend mainly on the air-sea temperature difference and the measured wind speed at a standard height. The physical processes are mostly understood and the quantified through Monin-Obukhov (MO) similarity theory. At high wind speeds different dynamical regimes become dominant. Breaking waves contribute to the atmospheric loading of sea spray and water vapor and modify the character of air-sea interaction. Downdrafts and boundary layer rolls associated with clouds at the top of the boundary layer impact vertical heat and momentum fluxes. Data from offshore meteorological monitoring sites will typically show different behavior and the regime shifts depending on the local winds and synoptic conditions. However, the regular methods to interpret time series through spectral analysis give only a partial view of dynamics in the atmospheric boundary layer. Also, the spectral methods have limited use for boundary layer and mesoscale modellers whose geophysical diagnostics are mostly anchored in directly measurable quantities: wind speed, temperature, precipitation, pressure, and radiation. Of these, wind speed and the air-sea temperature difference are the most important factors that characterize the dynamics of the lower atmospheric boundary layer and they provide a dynamical and thermodynamic constraint to frame observed processes, especially at high wind speeds. This was recognized in the early interpretation of the Froya database of gale force coastal winds from mid-Norway (Andersen, O.J. and J. Lovseth, Gale force maritime wind. The Froya data base. Part 1: Sites and instrumentation. Review of the data base, Journal of Wind

  19. Angular resampling for vibration analysis in wind turbines under non-linear speed fluctuation

    NASA Astrophysics Data System (ADS)

    Villa, Luisa F.; Reñones, Aníbal; Perán, Jose R.; de Miguel, Luis J.

    2011-08-01

    This work presents the development of an angular resampling algorithm for applying in conditions of high speed variability, as occurs in wind turbines, and the results obtained when applied to simulated signals, bearings diagnostic test-beds and wind turbines. The results improve the accuracy of similar resampling algorithms offered by the consulted bibliography. This algorithm is part of the wind turbine diagnostic system developed by the authors.

  20. Quantifying trends in surface roughness and the effect on surface wind speed observations

    NASA Astrophysics Data System (ADS)

    Wever, N.

    2012-06-01

    Many studies analyzing surface wind speed observations find a decrease in wind speed over the last 30 to 50 years. A cause sometimes proposed is increasing surface roughness, although to date the evidence that this is the primary factor is still inconclusive. In this study, changes in surface roughness are investigated for 20 stations in the Netherlands and 137 stations in 7 other European countries. From the Dutch data set, local aerodynamic roughness lengths were calculated from hourly gust factors. Trends in wind speed for individual stations and wind direction sectors correlate negatively with trends in surface roughness. For 1962-2009, typically a doubling of the local roughness length was found, with the strongest increase after 1981. An accompanying average decrease in wind speed by 3.1% (0.13 m/s) per decade was found for 1981-2009. A conceptual boundary layer model was used to show that 70% of the wind speed trend can be attributed to surface roughness changes; the remaining 30% of the trend remains unresolved. Changes in land use, including urbanization, forestation, and a decrease in pasture land area, are probable causes for the increasing surface roughness. For the European station data from the European Climate Assessment and Dataset (ECA&D) and the Swiss Federal Office of Meteorology and Climatology (MeteoSwiss), the analysis was restricted to daily gust factors. Observed trends in wind speed at stations correlate negatively with trends in gust factors. Averaged over all stations, the wind speed decreased 1.2% (0.05 m/s) per decade over 1982-2009, consistent with increasing surface roughness.

  1. Comparison of Drop and Wind-Tunnel Experiments on Bomb Drag at High Subsonic Speeds

    NASA Technical Reports Server (NTRS)

    Gothert, B.

    1948-01-01

    The drag coefficients of bombs at high velocities velocity of fall was 97 percent of the speed of sound) (the highest are determined by drop tests and compared with measurements taken in the DVL high-speed closed wind tunnel and the open jet at AVA - Gottingen.

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

    DOE PAGESBeta

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

    2015-07-14

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

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

    SciTech Connect

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

    2015-07-14

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

  4. Control of the variable speed generator on the Sandia 34-metre vertical axis wind turbine

    NASA Astrophysics Data System (ADS)

    Ralph, Mark E.

    The DOE/Sandia 34-meter VAWT Test Bed is a 500kW variable-speed wind turbine. The turbine is operated between 25 and 38 rpm and has been characterized from a structural and aerodynamic standpoint. A preliminary variable speed control algorithm has been implemented on the Test Bed. This paper describes the initial variable-speed control algorithm developed for the Test Bed and the performance of that algorithm to date. Initial performance comparisons between variable-speed and fixed-speed operation are made as well as some thoughts on the expansion of the operating envelope of the Test Bed.

  5. Control of the variable speed generator on the Sandia 34-metre vertical axis wind turbine

    SciTech Connect

    Ralph, M.E.

    1989-01-01

    The DOE/Sandia 34-metre VAWT Test Bed is a 500kW variable-speed wind turbine. The turbine is operated between 25 and 38 rpm and has been characterized from a structural and aerodynamic stand point. A preliminary variable speed control algorithm has been implemented on the Test Bed. This paper describes the initial variable-speed control algorithm developed for the Test Bed and the performance of that algorithm to date. Initial performance comparisons between variable-speed and fixed-speed operation are made as well as some thoughts on the expansion of the operating envelope of the Test Bed. 7 refs., 4 figs.

  6. Effect of sea wave age on scatterometer measurements and wind speed retrieval accuracy

    NASA Astrophysics Data System (ADS)

    Panfilova, Maria; Karaev, Vladimir; Jie, Guo

    2015-04-01

    Radiolocation data is widely used for the wind field retrieval over the sea surface. Wind speed is obtained from the radar cross-section. The backscattered signal contains information about the sea surface but not about the wind vector. This means that at the fixed wind speed the radar backscattering cross-section (RCS) depends on the sea maturity. In the present work the influence of the sea state at RCS and wind speed retrieval accuracy was investigated. The collocated array of ERS scatterometer and sea buoys data was processed. Buoy data were used to determine the wave age and all the dataset was separated into three parts: developing wind waves, fully developed waves and mixed sea. It was shown that error of wind retrieval algorithms for scatterometers (CMOD in this case) depends on the sea state. Wind speed is overestimated for swell-dominant sea and underestimated for developing waves. The direct problem of RCS dependence on the wind vector and sea state was also concidered. The large-scale waves slope variance is a very important parameter that implicitly influences the RCS in case of Bragg scattering and depends on the sea state. The buoy data were used to estimate the slope variance. The algorithm based on artificial neural networks taking into account the slope variance for RCS retrieval was proposed and performed better agreement with the measured RCS than CMOD5. It was shown that RCS increases with the slope variance growth other conditions being equal. Thus wind speed retrieval accuracy can be increased by taking into account sea waves parameters and regional peculiarities. Acknowledgments. This work was supported by Russian Foundation for Basic Research grants 130500852a, 14-05-31517mol-a.

  7. Dual measurement terminal fall speeds and multiple Doppler winds

    NASA Technical Reports Server (NTRS)

    Grosh, R. C.

    1983-01-01

    It is shown that radar-derived terminal fall speed measurements can be useful in determining vertical air velocity in the middle troposphere by means of a network of Doppler radars. The theoretical principles of the dual measurement technique are described, and the relationship between measurement accuracies and theoretical estimates of terminal fall speeds is discussed. It is demonstrated that the use of differential reflectivity to estimate terminal fall speeds can reduce the standard error of vertical velocity estimates by 40-50 percent.

  8. A new approach for determining fully empirical altimeter wind speed model functions

    NASA Astrophysics Data System (ADS)

    Freilich, Michael H.; Challenor, Peter G.

    1994-12-01

    A statistical technique is developed for determining fully empirical model functions relating altimeter radar backscatter (σ0) measurements to near-surface neutral stability wind speed. By assuming that σ0 varies monotonically and uniquely with wind speed, the method requires knowledge only of the separate, rather than joint, distribution functions of σ0 and wind speed. Analytic simplifications result from using a Weibull distribution to approximate the global ocean wind speed distribution; several different wind data sets are used to demonstrate the validity of the Weibull approximation. The technique has been applied to 1 year of Geosat data. Validation of the new and historical model functions using an independent buoy data set demonstrates that the present model function not only has small overall bias and RMS errors, but yields smaller systematic error trends with wind speed and pseudowave age than previously published models. The present analysis suggests that generally accurate altimeter model functions can be derived without the use of collocated measurements, nor is additional significant wave height information measured by the altimeter necessary.

  9. Fixed-Speed and Variable-Slip Wind Turbines Providing Spinning Reserves to the Grid: Preprint

    SciTech Connect

    Muljadi, E.; Singh, M.; Gevorgian, V.

    2012-11-01

    As the level of wind penetration increases, wind turbine technology must move from merely generating power from wind to taking a role in supporting the bulk power system. Wind turbines should have the capability to provide inertial response and primary frequency (governor) response so they can support the frequency stability of the grid. To provide governor response, wind turbines should be able to generate less power than the available wind power and hold the rest in reserve, ready to be accessed as needed. This paper explores several ways to control wind turbine output to enable reserve-holding capability. This paper focuses on fixed-speed (also known as Type 1) and variable-slip (also known as Type 2) turbines.

  10. Adaptive pitch control for variable speed wind turbines

    DOEpatents

    Johnson, Kathryn E.; Fingersh, Lee Jay

    2012-05-08

    An adaptive method for adjusting blade pitch angle, and controllers implementing such a method, for achieving higher power coefficients. Average power coefficients are determined for first and second periods of operation for the wind turbine. When the average power coefficient for the second time period is larger than for the first, a pitch increment, which may be generated based on the power coefficients, is added (or the sign is retained) to the nominal pitch angle value for the wind turbine. When the average power coefficient for the second time period is less than for the first, the pitch increment is subtracted (or the sign is changed). A control signal is generated based on the adapted pitch angle value and sent to blade pitch actuators that act to change the pitch angle of the wind turbine to the new or modified pitch angle setting, and this process is iteratively performed.

  11. Worldwide influence of Lamb Weather Types on Temperature, Precipitation and Wind Speed

    NASA Astrophysics Data System (ADS)

    Cortesi, Nicola; Torralba, Veronica; Bretonnière, Pierre-Antoine; Gonzalez-Reviriego, Nube; Peña-Angulo, Dhais; Doblas-Reyes, Francisco Javier

    2016-04-01

    One of the main objectives of synoptic climatology is the detection of large-scale atmospheric drivers determining local climate variability. Especially in the extra-tropical regions, synoptic circulation plays an important role in driving local climate; for example, it is known that Atlantic weather fronts are responsible of a high amount of winter precipitation in Europe. In this research, the Weather Type catalogue developed by Lamb to classify the continuum of the atmospheric circulation in 10-26 classes was obtained individually at each grid point of the mean sea level pressure Era-Interim dataset (spatial resolution 0.7°), spanning the whole world. Although the analysis was performed globally, Tropical and Polar regions were excluded, the former because the Coriolis effect is weak at 0-23° N-S (nullifying the vorticity index), and the latter due to the spatial distortion of the Lamb grid at very high latitudes. Each resulting Weather Type was related to the local observed average daily 2-m Temperature, Precipitation and 10-m Wind speed anomalies from Era-Interim during last 30 years (1985-2014) to identify the Weather Types that behave as climate drivers at seasonal and yearly time scale. While some countries and regions have already been analysed in detail individually at higher spatial and/or temporal resolutions, this study provides a global view, filling the existing gap in literature, particularly in the Southern Hemisphere (South Africa, South America, Australia) and over oceans, providing a bigger picture of the influence of Weather Types on climate.

  12. CONSTRAINING HIGH-SPEED WINDS IN EXOPLANET ATMOSPHERES THROUGH OBSERVATIONS OF ANOMALOUS DOPPLER SHIFTS DURING TRANSIT

    SciTech Connect

    Miller-Ricci Kempton, Eliza; Rauscher, Emily

    2012-06-01

    Three-dimensional (3D) dynamical models of hot Jupiter atmospheres predict very strong wind speeds. For tidally locked hot Jupiters, winds at high altitude in the planet's atmosphere advect heat from the day side to the cooler night side of the planet. Net wind speeds on the order of 1-10 km s{sup -1} directed towards the night side of the planet are predicted at mbar pressures, which is the approximate pressure level probed by transmission spectroscopy. These winds should result in an observed blueshift of spectral lines in transmission on the order of the wind speed. Indeed, Snellen et al. recently observed a 2 {+-} 1 km s{sup -1} blueshift of CO transmission features for HD 209458b, which has been interpreted as a detection of the day-to-night (substellar to anti-stellar) winds that have been predicted by 3D atmospheric dynamics modeling. Here, we present the results of a coupled 3D atmospheric dynamics and transmission spectrum model, which predicts the Doppler-shifted spectrum of a hot Jupiter during transit resulting from winds in the planet's atmosphere. We explore four different models for the hot Jupiter atmosphere using different prescriptions for atmospheric drag via interaction with planetary magnetic fields. We find that models with no magnetic drag produce net Doppler blueshifts in the transmission spectrum of {approx}2 km s{sup -1} and that lower Doppler shifts of {approx}1 km s{sup -1} are found for the higher drag cases, results consistent with-but not yet strongly constrained by-the Snellen et al. measurement. We additionally explore the possibility of recovering the average terminator wind speed as a function of altitude by measuring Doppler shifts of individual spectral lines and spatially resolving wind speeds across the leading and trailing terminators during ingress and egress.

  13. A Study of Hydrogen Generation with Doubly-Fed Adjustable Speed Wind Generator

    NASA Astrophysics Data System (ADS)

    Kinoshita, Hirotaka; Takahashi, Rion; Murata, Toshiaki; Tamura, Junji; Sugimasa, Masatoshi; Komura, Akiyoshi; Futami, Motoo; Ichinose, Masaya; Ide, Kazumasa

    This paper presents a combination system of wind power generator and hydrogen generator. In the proposed system, Doubly-Fed Synchronous Generator (DFSG) is used as an adjustable speed wind generator, and an electrolyzer is connected to its terminal for hydrogen generation, which is controlled by power electronic converters. Output power from the wind generator is smoothed and supplied to the power system as well as to the electrolyzer to generate hydrogen under a cooperative control of the wind generator and the electrolyzer. The performance of the proposed system is investigated by simulation analyses, in which simulations are performed by using PSCAD/EMTDC.

  14. Data-Driven Topographic Feature Selection for Mean Wind Speed Mapping

    NASA Astrophysics Data System (ADS)

    Foresti, L.; Pozdnoukhov, A.; Kanevski, M.

    2009-04-01

    Accurate spatial mapping of long term mean wind speeds is of great importance for renewable resources evaluation and wind farm location planning. This task is conventionally approached with a physical model further corrected with some geostatistical or semi-empirical method to take into account local topography and land cover effects. In mountainous regions of complex topographies, however, the evaluation of mean wind speed with this procedure is less precise. A variety of small-scale topographic features has to be incorporated into the model to take into account the factors affecting the wind speed, such as hill and tunnel effects. Large number of topographic features can be computed from digital elevation models to be integrated into a prediction model. Spatial prediction of the wind speeds by using a large set of input features is a high dimensional and non-linear problem. In conventional scheme, one relies here on many empirical correction coefficients and various topographic indices to take into account the influence of terrain. However, there is an emerging field of machine learning algorithms, which are the data-driven methods well-suited to solve such problems. They are aimed at modelling the non-linear dependencies between the high dimensional input features and a target variable such as the wind speed. There is a noticeable interest for using these methods for wind mapping. The presented research provides an application of machine learning methods (neural networks and support vector methods) for spatial prediction of mean wind speeds with a particular attention paid to the problem of feature selection. The number of features which can be generated from digital elevation model is countless as the features can be computed at various spatial scales. For example, a difference of terrains smoothed at different spatial scales enables to highlight the ridges and valleys. Feature selection methods allow finding the features and correspondingly the spatial scales

  15. Efficacy of spatial averaging of infrasonic pressure in varying wind speeds.

    PubMed

    DeWolf, Scott; Walker, Kristoffer T; Zumberge, Mark A; Denis, Stephane

    2013-06-01

    Wind noise reduction (WNR) is important in the measurement of infrasound. Spatial averaging theory led to the development of rosette pipe arrays. The efficacy of rosettes decreases with increasing wind speed and only provides a maximum of ~20 dB WNR due to a maximum size limitation. An Optical Fiber Infrasound Sensor (OFIS) reduces wind noise by instantaneously averaging infrasound along the sensor's length. In this study two experiments quantify the WNR achieved by rosettes and OFISs of various sizes and configurations. Specifically, it is shown that the WNR for a circular OFIS 18 m in diameter is the same as a collocated 32-inlet pipe array of the same diameter. However, linear OFISs ranging in length from 30 to 270 m provide a WNR of up to ~30 dB in winds up to 5 m/s. The measured WNR is a logarithmic function of the OFIS length and depends on the orientation of the OFIS with respect to wind direction. OFISs oriented parallel to the wind direction achieve ~4 dB greater WNR than those oriented perpendicular to the wind. Analytical models for the rosette and OFIS are developed that predict the general observed relationships between wind noise reduction, frequency, and wind speed. PMID:23742329

  16. Compensation of vector and volume averaging bias in lidar wind speed measurements

    NASA Astrophysics Data System (ADS)

    Clive, P. J. M.

    2008-05-01

    A number of vector and volume averaging considerations arise in relation to remote sensing, and in particular, Lidar. 1) Remote sensing devices obtain vector averages. These values are often compared to the scalar averages associated with cup anemometry. The magnitude of a vector average is less than or equal to the scalar average obtained over the same period. The use of Lidars in wind power applications has entailed the estimation of scalar averages by vector averages and vice versa. The relationship between the two kinds of average must therefore be understood. It is found that the ratio of the averages depends upon wind direction variability according to a Bessel function of the standard deviation of the wind direction during the averaging interval. 2) The finite probe length of remote sensing devices also incurs a volume averaging bias when wind shear is non-linear. The sensitivity of the devices to signals from a range of heights produces volume averages which will be representative of wind speeds at heights within that range. One can distinguish between the effective or apparent height the measured wind speeds represent as a result of volume averaging bias, and the configuration height at which the device has been set to measure wind speeds. If the wind shear is described by a logarithmic wind profile the apparent height is found to depend mainly on simple geometrical arguments concerning configuration height and probe length and is largely independent of the degree of wind shear. 3) The restriction of the locus of points at which radial velocity measurements are made to the circumference of a horizontally oriented disc at a particular height is seen to introduce ambiguity into results when dealing with wind vector fields which are not irrotational.

  17. Compensating for volume and vector averaging biases in lidar wind speed measurements

    NASA Astrophysics Data System (ADS)

    Clive, Peter J. M.

    2008-10-01

    A number of vector and volume averaging considerations arise in relation to remote sensing, and in particular, Lidar. 1) Remote sensing devices obtain vector averages. These values are often compared to the scalar averages associated with cup anemometry. The magnitude of a vector average is less than or equal to the scalar average obtained over the same period. The use of Lidars in wind power applications has entailed the estimation of scalar averages by vector averages and vice versa. The relationship between the two kinds of average must therefore be understood. It is found that the ratio of the averages depends upon wind direction variability according to a Bessel function of the standard deviation of the wind direction during the averaging interval. 2) The finite probe length of remote sensing devices also incurs a volume averaging bias when wind shear is non-linear. The sensitivity of the devices to signals from a range of heights produces volume averages which will be representative of wind speeds at heights within that range. One can distinguish between the effective or apparent height the measured wind speeds represent as a result of volume averaging bias, and the configuration height at which the device has been set to measure wind speeds. If the wind shear is described by a logarithmic wind profile the apparent height is found to depend mainly on simple geometrical arguments concerning configuration height and probe length and is largely independent of the degree of wind shear. 3) The restriction of the locus of points at which radial velocity measurements are made to the circumference of a horizontally oriented disc at a particular height is seen to introduce ambiguity into results when dealing with wind vector fields which are not irrotational.

  18. Wind speed and temperature trends impacts on reference evapotranspiration in Southern Italy

    NASA Astrophysics Data System (ADS)

    Liuzzo, Lorena; Viola, Francesco; Noto, Leonardo V.

    2016-01-01

    In this study, the impacts of both temperature and wind speed trends on reference evapotranspiration have been assessed using as a case study the Southern Italy, which present a wide variety of combination of such climatic variables trends in terms of direction and magnitude. The existence of statistically significant trends in wind speed and temperature from observational datasets, measured in ten stations over Southern Italy during the period 1968-2004, has been investigated. Time series have been examined using the Mann-Kendall nonparametric statistical test in order to detect possible evidences of wind speed and temperature trends at different temporal resolution and significance level. Once trends have been examined and quantified, the effects of these trends on seasonal reference evapotranspiration have been evaluated using the FAO-56 Penman-Monteith equation. Results quantified the effects of extrapolated temperature and wind speed trends on reference evapotranspiration. Where these climatic drivers are on the same direction, reference evapotranspiration generally increases during the growing season due to a nonlinear overlapping of effects. Whereas wind speed decreases and temperature increases, there is a sort of counterbalancing effect between the two considered climatic forcing in determining future reference evapotranspiration.

  19. A prediction model for wind speed ratios at pedestrian level with simplified urban canopies

    NASA Astrophysics Data System (ADS)

    Ikegaya, N.; Ikeda, Y.; Hagishima, A.; Razak, A. A.; Tanimoto, J.

    2015-10-01

    The purpose of this study is to review and improve prediction models for wind speed ratios at pedestrian level with simplified urban canopies. We adopted an extensive database of velocity fields under various conditions for arrays consisting of cubes, slender or flattened rectangles, and rectangles with varying roughness heights. Conclusions are summarized as follows: first, a new geometric parameter is introduced as a function of the plan area index and the aspect ratio so as to express the increase in virtual density that causes wind speed reduction. Second, the estimated wind speed ratios in the range 0.05 < z/h < 0.3, where h is the building height, are consistent with those derived from the database to within an error of ±25%. Lastly, the effects of the spatial distribution of the flow were investigated by classifying the regions near building models into areas in front of, to the side of, or behind the building. The correlation coefficients between the wind speeds averaged over the entire region, and the front or side region values are larger than 0.8. In contrast, in areas where the influence of roughness elements is significant, such as behind a building, the wind speeds are weakly correlated.

  20. The Relationship between Wind Speed and Precipitation in the Pacific ITCZ.

    NASA Astrophysics Data System (ADS)

    Back, Larissa E.; Bretherton, Christopher S.

    2005-10-01

    The relationship between wind speed and precipitation in the Pacific ITCZ is analyzed using 4 yr of daily Special Sensor Microwave Imager (SSM/I) and Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) satellite passive microwave retrievals averaged over 2.5° boxes. Throughout the ITCZ, at high-column relative humidities (conditions under which deep convection is likely to occur), faster winds are associated with substantially more precipitation, explaining a small, but highly statistically significant fraction of daily rainfall variability. The slope of this relationship varies geographically and rapidly increases as the atmosphere becomes moister. Analysis of other data sources, including vector mean winds computed from QuikSCAT and area-averaged radar-derived precipitation estimates from Kwajalein Island, shows that the wind speed precipitation correlation is robust.This relation provides a test of large-scale forecast models and insight into conceptual models of deep convection. The observed increases in precipitation are much greater than evaporation changes associated with the increased wind speed; this implies a convergence feedback by which evaporation induces moisture convergence that feeds increases in precipitation. The authors study whether the 40-yr ECMWF Re-Analysis (ERA-40) and NCEP NCAR reanalysis show the observed wind speed precipitation correlation and explore mechanisms for convergence feedback using column-integrated moist static energy budgets computed from the reanalyses.

  1. Satellite retrieval of hurricane wind speeds using the AMSR2 microwave radiometer

    NASA Astrophysics Data System (ADS)

    Yao, Panpan; Wan, Jianhua; Wang, Jin; Zhang, Jie

    2015-09-01

    The AMSR2 microwave radiometer is the main payload of the GCOM-W1 satellite, launched by the Japan Aerospace Exploration Agency in 2012. Based on the pre-launch information extraction algorithm, the AMSR2 enables remote monitoring of geophysical parameters such as sea surface temperature, wind speed, water vapor, and liquid cloud water content. However, rain alters the properties of atmospheric scattering and absorption, which contaminates the brightness temperatures measured by the microwave radiometer. Therefore, it is difficult to retrieve AMSR2-derived sea surface wind speeds under rainfall conditions. Based on microwave radiative transfer theory, and using AMSR2 L1 brightness temperature data obtained in August 2012 and NCEP reanalysis data, we studied the sensitivity of AMSR2 brightness temperatures to rain and wind speed, from which a channel combination of brightness temperature was established that is insensitive to rainfall, but sensitive to wind speed. Using brightness temperatures obtained with the proposed channel combination as input parameters, in conjunction with HRD wind field data, and adopting multiple linear regression and BP neural network methods, we established an algorithm for hurricane wind speed retrieval under rainfall conditions. The results showed that the standard deviation and relative error of retrievals, obtained using the multiple linear regression algorithm, were 3.1 m/s and 13%, respectively. However, the standard deviation and relative error of retrievals obtained using the BP neural network algorithm were better (2.1 m/s and 8%, respectively). Thus, the results of this paper preliminarily verified the feasibility of using microwave radiometers to extract sea surface wind speeds under rainfall conditions.

  2. Long-term wind speed variations for three midwestern U.S. cities.

    PubMed

    Abhishek, A; Lee, Joo-Youp; Keener, Tim C; Yang, Y Jeffery

    2010-09-01

    Long-term wind speed variations were investigated for three midwestern cities including Indianapolis, IN; Cincinnati, OH; and Little Rock, AR in the continental United States. These cities were chosen because their topography is relatively flat and unaffected by large mountain ranges or other topographical features, they represent important regional economic centers, and they have all undergone major air quality management efforts over the past 35 yr to attempt to meet the National Ambient Air Quality Standards. The hourly data were obtained from the National Climatic Data Center from 1943 to 2008 for Indianapolis and Little Rock and from 1948 to 2008 for Cincinnati. The analysis included calculating the frequency of calms and wind speeds over five different bins for the respective cities. The results indicate a significant increase in the frequency of calms (statistical significance > 99.999%) and a decrease in the overall frequency of other wind speeds for all three cities. Increasing trend in calms is more predominant during the ozone season (April through October). The results from regression analysis, significance testing, and spatial correlation analysis support the argument that a common "midwestern" large-scale atmospheric forcing is influencing surface wind speed in this area. It was found that for all three cities the Pacific North American (PNA) teleconnection pattern has the highest relative association with the trends in wind speed. The results support large-scale continental effects (like teleconnections) as a hypothesis to be examined more closely along with already established evidence of the influence of the Pacific and Atlantic teleconnection anomalies. Reduced wind speed may have implications on air quality management efforts in the region. Increases in the frequency of calms would affect ozone distribution patterns and may suggest a need to make changes to their ozone mitigation strategy. Weaker winds would ventilate pollutants from these areas

  3. A reward semi-Markov process with memory for wind speed modeling

    NASA Astrophysics Data System (ADS)

    Petroni, F.; D'Amico, G.; Prattico, F.

    2012-04-01

    The increasing interest in renewable energy leads scientific research to find a better way to recover most of the available energy. Particularly, the maximum energy recoverable from wind is equal to 59.3% of that available (Betz law) at a specific pitch angle and when the ratio between the wind speed in output and in input is equal to 1/3. The pitch angle is the angle formed between the airfoil of the blade of the wind turbine and the wind direction. Old turbine and a lot of that actually marketed, in fact, have always the same invariant geometry of the airfoil. This causes that wind turbines will work with an efficiency that is lower than 59.3%. New generation wind turbines, instead, have a system to variate the pitch angle by rotating the blades. This system able the wind turbines to recover, at different wind speed, always the maximum energy, working in Betz limit at different speed ratios. A powerful system control of the pitch angle allows the wind turbine to recover better the energy in transient regime. A good stochastic model for wind speed is then needed to help both the optimization of turbine design and to assist the system control to predict the value of the wind speed to positioning the blades quickly and correctly. The possibility to have synthetic data of wind speed is a powerful instrument to assist designer to verify the structures of the wind turbines or to estimate the energy recoverable from a specific site. To generate synthetic data, Markov chains of first or higher order are often used [1,2,3]. In particular in [1] is presented a comparison between a first-order Markov chain and a second-order Markov chain. A similar work, but only for the first-order Markov chain, is conduced by [2], presenting the probability transition matrix and comparing the energy spectral density and autocorrelation of real and synthetic wind speed data. A tentative to modeling and to join speed and direction of wind is presented in [3], by using two models, first

  4. High-speed-propeller wind-tunnel aeroacoustic results

    NASA Technical Reports Server (NTRS)

    Jeracki, R. J.; Dittmar, J. H.

    1980-01-01

    Some aerodynamic concepts are presented together with an explanation of how these concepts are applied to advanced propeller design. The unique features of this propulsion system are addressed with emphasis on the design concepts being considered for the high speed turboprop. More particular emphasis is given to the blade sweep, long blade chords, and the large number of blades.

  5. Wind noise at microphones within and across hearing aids at wind speeds below and above microphone saturation.

    PubMed

    Zakis, Justin A

    2011-06-01

    The variation of wind noise at hearing-aid microphones with wind speed, wind azimuth, and hearing-aid style was investigated. Comparisons were made across behind-the-ear (BTE) and completely-in-canal (CIC) devices, and between microphones within BTE devices. One CIC device and two BTE devices were placed on a Knowles Electronics Manikin for Acoustic Research. The smaller BTE device had vented plastic windshields around its microphone ports while the larger BTE device had none. The microphone output signals were digitally recorded in wind generated at 0, 3, 6, and 12 m/s at 8 wind azimuths. The microphone output signals were saturated at 12 m/s with wind-noise levels of up to 116 dB SPL at the microphone output. Wind-noise levels differed by up to 12 dB between microphones within the same BTE device, and across BTE devices by up to 6 or 8 dB for front or rear microphones, respectively. On average, wind-noise levels were lowest with the CIC device and highest at the rear microphone of the smaller BTE device. Engineering and clinical implications are discussed. PMID:21682412

  6. Comparison of sea surface wind speed fields by SEASAT radar altimeter, scatterometer and scanning multichannel microwave radiometer with an emphasis on the Southern Ocean

    NASA Technical Reports Server (NTRS)

    Mognard, N. M.; Campbell, W. J.

    1984-01-01

    The SEASAT altimeter (ALT), scatterometer (SASS), and scanning microwave multichannel radiometer (SMMR) measured sea surface wind speed. During the satellite lifetime from June to October 1978, the Austral winter, the highest wind speeds were recorded in the Southern Ocean. Three-month, monthly, and three-day surface wind speed fields deduced from the three Seasat wind speed sensors are compared. The monthly and three-day fields show a pronounced mesoscale (1000 km) variability in wind speed. At all space and time scales analyzed, differences of 40% are found in the magnitude of the wind speed features, with the ALT consistently yielding the lowest wind speed and the SMMR the highest.

  7. The speeds of coronal mass ejections in the solar wind at mid heliographic latitudes: Ulysses

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Bame, S. J.; Mccomas, D. J.; Phillips, J. L.; Goldstein, B. E.; Neugebauer, M.

    1994-01-01

    Six CMEs (coronal mass ejections) have been detected in the Ulysses plasma observations poleward of S31 deg. The most striking aspect of these mid-latitude CMEs was their high speeds; the overall average speed of these CMEs was approximately 740 km/s, which was comparable to that of the rest of the solar wind at these latitudes. This average CME speed is much higher than average CME speeds observed in the solar wind in the ecliptic or in the corona close to the Sun. The evidence indicates that the CMEs were not pushed up to high speeds in interplanetary space by interaction with trailing high-speed plasma. Rather, they simply seem to have received the same basic acceleration as the rest of the solar wind at these mid-latitudes. Our results suggest that the basic acceleration process for many CMEs at all latitudes is essentially the same as for the normal solar wind. Frequently most of this acceleration must occur well beyond 6 solar radii from Sun center.

  8. The speeds of coronal mass ejections in the solar wind at mid heliographic latitudes: Ulysses

    SciTech Connect

    Gosling, J.T.; Bame, S.J.; McComas, D.J.; Phillips, J.L.; Goldstein, B.E.; Neugebauer, M.

    1994-06-15

    Six CMEs have been detected in the Ulysses plasma observations poleward of S31{degrees}. The most striking aspect of these mid-latitude CMEs was their high speeds; the overall average speed of these CMEs was {approximately}740 km s{sup {minus}1}, which was comparable to that of the rest of the solar wind at these latitudes. This average CME speed is much higher than average CME speeds observed in the solar wind in the ecliptic or in the corona close to the Sun. The evidence indicates that the CMEs were not pushed up to high speeds in interplanetary space by interaction with trailing high-speed plasma. Rather, they simply seem to have received the same basic acceleration as the rest of the solar wind at these mid-latitudes. These results suggest that the basic acceleration process for many CMEs at all latitudes is essentially the same as for the normal solar wind. Frequently most of this acceleration must occur well beyond 6 solar radii from Sun`sj center. 18 refs., 4 figs.

  9. Solar Wind Speed Structure in the Inner Corona at 3-12 Ro

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    1995-01-01

    Estimates of solar wind speed obtained by Armstrong et al. [1986] based on 1983 VLA multiple-station intensity scintillation measurements inside 12 R(sub o) have been correlated with the electron density structure observed in white-light coronagraph measurements. The observed large- scale and apparently systematic speed variations are found to depend primarily on changes in heliographic latitude and longitude, which leads to the first results on large-scale speed structure in the acceleration region of the solar wind. Over an equatorial hole, solar wind speed is relatively steady, with peak-to-peak variations of 50 km/s and an average of 230 km/s. In contrast, the near-Sun flow speed across the streamer belt shows regular large-scale variations in the range of 100-300 km/s. Based on four groups of data, the gradient is 36 km/s per degree in heliocentric coordinates (corresponding to a rise of 260 km/s over a spatial distance on the Sun of two arcmin) with a standard deviation of 2.4 km/s per degree. The lowest speeds most likely coincide with the stalks of coronal streamers observed in white-light measurements. The detection of significant wind shear over the streamer belt is consistent with in situ and scintillation measurements showing that the density spectrum has a power-law form characteristic of fully developed turbulence over a much broader range of scales than in neighboring regions.

  10. Study of wind speed attenuation at Kavaratti Island using land-based, offshore, and satellite measurements

    NASA Astrophysics Data System (ADS)

    Joseph, Antony; Rivonkar, Pradhan; Balakrishnan Nair, T. M.

    2012-06-01

    The role of dense coconut palms in attenuating the wind speed at Kavaratti Island, which is located in the southeastern Arabian Sea, is examined based on land-based and offshore wind measurements (U10) using anchored-buoy-mounted and satellite-borne sensors (QuikSCAT scatterometer and TMI microwave imager) during an 8-year period (2000-2007). It is found that round the year monthly-mean wind speed measurements from the Port Control Tower (PCT) located within the coconut palm farm at the Kavaratti Island are weaker by 15-61% relative to those made from the nearby offshore region. Whereas wind speed attenuation at the island is ~15-40% in the mid-June to mid-October south-west monsoon period, it is ~41-61% during the rest of the year. Wind direction measurements from all the devices overlapped, except in March-April during which the buoy measurements deviated from the other measurements by ~20°. U10 wind speed measurements from PCT during the November 2009 tropical cyclone "Phyan" indicated approximately 50-80% attenuation relative to those from the seaward boundary of the island's lagoon (and therefore least influenced by the coconut palms). The observed wind speed attenuation can be understood through the theory of free turbulent flow jets embodied in the boundary-layer fluid dynamics, according to which both the axial and transverse components of the efflux of flows discharged through the inter-leaves porosity (orifice) undergo increasing attenuation in the downstream direction with increasing distance from the orifice. Thus, the observed wind speed attenuation at Kavaratti Island is attributable to the decline in wind energy transmission from the seaward boundary of the coconut palm farm with distance into the farm. Just like mangrove forests function as bio-shields against forces from oceanic waves and stormsurges through their large above-ground aerial root systems and standing crop, and thereby playing a distinctive role in ameliorating the effects of

  11. Wind Plant Capacity Credit Variations: A Comparison of Results Using Multiyear Actual and Simulated Wind-Speed Data

    SciTech Connect

    Milligan, M.

    1997-06-01

    Although it is widely recognized that variations in annual wind energy capture can be significant, it is not clear how significant this effect is on accurately calculating the capacity credit of a wind plant. An important question is raised concerning whether one year of wind data is representative of long-term patters. This report calculates the range of capacity credit measures based on 13 years of actual wind-speed data. The results are compared to those obtained with synthetic data sets that are based on one year of data. Although the use of synthetic data sets is a considerable improvement over single-estimate techniques, this report finds that the actual inter-annual variation in capacity credit is still understated by the synthetic data technique.

  12. Wind plant capacity credit variations: A comparison of results using multiyear actual and simulated wind-speed data

    SciTech Connect

    Milligan, M.R.

    1997-12-31

    Although it is widely recognized that variations in annual wind energy capture can be significant, it is not clear how significant this effect is on accurately calculating the capacity credit of a wind plant. An important question is raised concerning whether one year of wind data is representative of long-term patterns. This paper calculates the range of capacity credit measures based on 13 years of actual wind-speed data. The results are compared to those obtained with synthetic data sets that are based on one year of data. Although the use of synthetic data sets is a considerable improvement over single-estimate techniques, this paper finds that the actual inter-annual variation in capacity credit is still understated by the synthetic data technique.

  13. High speed video shooting with continuous-wave laser illumination in laboratory modeling of wind - wave interaction

    NASA Astrophysics Data System (ADS)

    Kandaurov, Alexander; Troitskaya, Yuliya; Caulliez, Guillemette; Sergeev, Daniil; Vdovin, Maxim

    2014-05-01

    Three examples of usage of high-speed video filming in investigation of wind-wave interaction in laboratory conditions is described. Experiments were carried out at the Wind - wave stratified flume of IAP RAS (length 10 m, cross section of air channel 0.4 x 0.4 m, wind velocity up to 24 m/s) and at the Large Air-Sea Interaction Facility (LASIF) - MIO/Luminy (length 40 m, cross section of air channel 3.2 x 1.6 m, wind velocity up to 10 m/s). A combination of PIV-measurements, optical measurements of water surface form and wave gages were used for detailed investigation of the characteristics of the wind flow over the water surface. The modified PIV-method is based on the use of continuous-wave (CW) laser illumination of the airflow seeded by particles and high-speed video. During the experiments on the Wind - wave stratified flume of IAP RAS Green (532 nm) CW laser with 1.5 Wt output power was used as a source for light sheet. High speed digital camera Videosprint (VS-Fast) was used for taking visualized air flow images with the frame rate 2000 Hz. 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 using conditional in phase averaging like in [1]. In the experiments on the LASIF more powerful Argon laser (4 Wt, CW) was used as well as high-speed camera with higher sensitivity and resolution: Optronics Camrecord CR3000x2, frame rate 3571 Hz, frame size 259×1696 px. In both series of experiments spherical 0.02 mm polyamide particles with inertial time 7 ms were used for seeding airflow. New particle seeding system based on utilization of air pressure is capable of injecting 2 g of particles per second for 1.3 - 2.4 s without flow disturbance. Used in LASIF this system provided high particle density on PIV-images. In combination with high-resolution camera it allowed us to obtain momentum fluxes directly from

  14. On the high correlation between long-term averages of solar wind speed and geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Crooker, N. U.; Feynman, J.; Gosling, J. T.

    1977-01-01

    Six-month and yearly averages of solar-wind speed from 1962 to 1975 are shown to be highly correlated with geomagnetic activity as measured by averages of the Ap index. On the same time scale the correlation between the southward component of the interplanetary magnetic field and geomagnetic activity is poor. Previous studies with hourly averages gave opposite results. The better correlation with the southward component on an hourly time scale is explained by its large variation compared with the relatively constant solar-wind speed. However, on a yearly time scale the magnitude of the variations in both parameters are about the same. This problem can be solved by invoking an energy transfer mechanism which is proportional to the first power of the southward component and a higher power of the solar-wind speed.

  15. Mesoscale Near-Surface Wind Speed Variability Mapping with Synthetic Aperture Radar

    PubMed Central

    Young, George; Sikora, Todd; Winstead, Nathaniel

    2008-01-01

    Operationally-significant wind speed variability is often observed within synthetic aperture radar-derived wind speed (SDWS) images of the sea surface. This paper is meant as a first step towards automated distinguishing of meteorological phenomena responsible for such variability. In doing so, the research presented in this paper tests feature extraction and pixel aggregation techniques focused on mesoscale variability of SDWS. A sample of twenty eight SDWS images possessing varying degrees of near-surface wind speed variability were selected to serve as case studies. Gaussian high- and low-pass, local entropy, and local standard deviation filters performed well for the feature extraction portion of the research while principle component analysis of the filtered data performed well for the pixel aggregation. The findings suggest recommendations for future research.

  16. Fuzzy logic based intelligent control of a variable speed cage machine wind generation system

    SciTech Connect

    Simoes, M.G.; Bose, B.K.; Spiegel, R.J.

    1997-01-01

    The paper describes a variable speed wind generation system where fuzzy logic principles are used for efficiency optimization and performance enhancement control. A squirrel cage induction generator feeds the power to a double-sided pulse width modulated converter system which pumps power to a utility grid or can supply to an autonomous system. The generation system has fuzzy logic control with vector control in the inner loops. A fuzzy controller tracks the generator speed with the wind velocity to extract the maximum power. A second fuzzy controller programs the machine flux for light load efficiency improvement, and a third fuzzy controller gives robust speed control against wind gust and turbine oscillatory torque. The complete control system has been developed, analyzed, and validated by simulation study. Performances have then been evaluated in detail.

  17. Polar summer mesospheric extreme horizontal drift speeds during interplanetary corotating interaction regions (CIRs) and high-speed solar wind streams: Coupling between the solar wind and the mesosphere

    NASA Astrophysics Data System (ADS)

    Lee, Young-Sook; Kirkwood, Sheila; Kwak, Young-Sil; Kim, Kyung-Chan; Shepherd, Gordon G.

    2014-05-01

    We report the observation of echo extreme horizontal drift speed (EEHS, ≥ 300 m s-1) during polar mesospheric (80-90 km) summer echoes (PMSEs) by the VHF (52 MHz) radar at Esrange, Sweden, in years of 2006 and 2008. The EEHS occur in PMSEs as correlated with high-speed solar wind streams (HSSs), observed at least once in 12-17% of all hours of observation for the two summers. The EEHS rate peaks occur either during high solar wind speed in the early part of the PMSE season or during the arrival of interplanetary corotating interaction regions (CIRs) followed by peaks in PMSE occurrence rate after 1-4 days, in the latter part of the 2006 summer. The cause of EEHS rate peaks is likely under the competition between the interval of the CIR and HSS passage over the magnetosphere. A candidate process in producing EEHS is suggested to be localized strong electric field, which is caused by solar wind energy transfer from the interaction of CIR and HSS with the magnetosphere in a sequential manner. We suggest that EEHS are created by strong electric field, estimated as > 10-30 V m-1 at 85 km altitude, exceeding the mesospheric breakdown threshold field.

  18. Dual stator winding variable speed asynchronous generator: optimal design and experiments

    NASA Astrophysics Data System (ADS)

    Tutelea, L. N.; Deaconu, S. I.; Popa, G. N.

    2015-06-01

    In the present paper is carried out a theoretical and experimental study of dual stator winding squirrel cage asynchronous generator (DSWA) behavior in the presence of saturation regime (non-sinusoidal) due to the variable speed operation. The main aims are the determination of the relations of calculating the equivalent parameters of the machine windings to optimal design using a Matlab code. Issue is limited to three phase range of double stator winding cage-induction generator of small sized powers, the most currently used in the small adjustable speed wind or hydro power plants. The tests were carried out using three-phase asynchronous generator having rated power of 6 [kVA].

  19. Desirable airfoil characteristics for large variable-speed horizontal axis wind turbines

    SciTech Connect

    Giguere, P.; Selig, M.S.

    1997-08-01

    In an effort to define the desirable airfoil characteristics for large variable-speed wind turbines, a systematic study was performed using a series of airfoils designed to have similar aerodynamic properties, except for the amount of lift, which varied over a wide range. For several airfoil combinations, blade shapes were designed for a 750-kW wind turbine with a 48.8-m diameter rotor using the optimization code PROPGA together with PROPID, which is an inverse design method for horizontal-axis wind turbines. Roughness effects, including the consideration of dirty-blade performance in the blade-shape optimization process, were also considered and are discussed. The results and conclusions reveal practical design implications that should aid in the aerodynamic blade design of not only large but also other sizes of variable-speed wind turbines.

  20. Self streamlining wind tunnel: Further low speed testing and final design studies for the transonic facility

    NASA Technical Reports Server (NTRS)

    Wolf, S. W. D.

    1978-01-01

    Work was continued with the low speed self streamlining wind tunnel (SSWT) using the NACA 0012-64 airfoil in an effort to explain the discrepancies between the NASA Langley low turbulence pressure tunnel (LTPT) and SSWT results obtained with the airfoil stalled. Conventional wind tunnel corrections were applied to straight wall SSWT airfoil data, to illustrate the inadequacy of standard correction techniques in circumstances of high blockage. Also one SSWT test was re-run at different air speeds to investigate the effects of such changes (perhaps through changes in Reynold's number and freestream turbulence levels) on airfoil data and wall contours. Mechanical design analyses for the transonic self-streamlining wind tunnel (TSWT) were completed by the application of theoretical airfoil flow field data to the elastic beam and streamline analysis. The control system for the transonic facility, which will eventually allow on-line computer operation of the wind tunnel, was outlined.

  1. Dual stator winding variable speed asynchronous generator: magnetic equivalent circuit with saturation, FEM analysis and experiments

    NASA Astrophysics Data System (ADS)

    Tutelea, L. N.; Muntean, N.; Deaconu, S. I.; Cunţan, C. D.

    2016-02-01

    The authors carried out a theoretical and experimental study of dual stator winding squirrel cage asynchronous generator (DSWA) behaviour in the presence of saturation regime (non-sinusoidal) due to the variable speed operation. The main aims are the determination of the relations of calculating the equivalent parameters of the machine windings, FEM validation of parameters and characteristics with free FEMM 4.2 computing software and the practice experimental tests for verifying them. Issue is limited to three phase range of double stator winding cage-asynchronous generator of small sized powers, the most currently used in the small adjustable speed wind or hydro power plants. The tests were carried out using three-phase asynchronous generator having rated power of 6 [kVA].

  2. Nature and Variability of Coronal Streamers and Their Relationship to the Slow Speed Wind

    NASA Technical Reports Server (NTRS)

    Strachan, Leonard

    2004-01-01

    NASA Grant NAGS12781 is a study on the "Nature and Variability of Coronal Streamers and their Relationship to the Slow Speed Wind." The two main goals of this study are to identify: I ) Where in the streamer structure does the solar wind originate, and 2 ) What coronal conditions are responsible for the variability of the slow speed wind. These goals are to be accomplished by carrying out the following activities: I ) Developing models for inferring the plasma outflow velocities in the extended solar corona based on UV spectroscopic and white light coronagraph data. 2 ) Producing UVCS Carrington Maps for the period around solar minimum 1996-1998. 3) Producing electron density profiles from the corresponding LASCO-C2 observations. 4) Identifying and selecting in situ data sets to be used for characterizing the solar wind from the streamers observed with UVCS. 5) Developing new visualization tools for using the UVCS synoptic data.

  3. A storm severity index based on return levels of wind speeds

    NASA Astrophysics Data System (ADS)

    Becker, Nico; Nissen, Katrin M.; Ulbrich, Uwe

    2015-04-01

    European windstorms related to extra-tropical cyclones cause considerable damages to infrastructure during the winter season. Leckebusch et al. (2008) introduced a storm severity index (SSI) based on the exceedances of the local 98th percentile of wind speeds. The SSI is based on the assumption that (insured) damage usually occurs within the upper 2%-quantile of the local wind speed distribution (i.e. if the 98th percentile is exceeded). However, critical infrastructure, for example related to the power network or the transportation system, is usually designed to withstand wind speeds reaching the local 50-year return level, which is much higher than the 98th percentile. The aim of this work is to use the 50-year return level to develop a modified SSI, which takes into account only extreme wind speeds relevant to critical infrastructure. As a first step we use the block maxima approach to estimate the spatial distribution of return levels by fitting the generalized extreme value (GEV) distribution to the wind speeds retrieved from different reanalysis products. We show that the spatial distributions of the 50-year return levels derived from different reanalyses agree well within large parts of Europe. The differences between the reanalyses are largely within the range of the uncertainty intervals of the estimated return levels. As a second step the exceedances of the 50-year return level are evaluated and compared to the exceedances of the 98th percentiles for different extreme European windstorms. The areas where the wind speeds exceed the 50-year return level in the reanalysis data do largely agree with the areas where the largest damages were reported, e.g. France in the case of "Lothar" and "Martin" and Central Europe in the case of "Kyrill". Leckebusch, G. C., Renggli, D., & Ulbrich, U. (2008). Development and application of an objective storm severity measure for the Northeast Atlantic region. Meteorologische Zeitschrift, 17(5), 575-587.

  4. Relationships among daily mean and maximum wind speeds, with application to data quality assurance

    NASA Astrophysics Data System (ADS)

    Graybeal, Daniel Y.

    2006-01-01

    A growing number of climate change and variability studies, as well as applied research toward improving engineering design climatographies, require high-quality, long-term, extreme-value climate data sets for accurate and reliable estimates and assessments. As part of a historical weather data rescue project of the US government, new data quality control procedures are being developed and applied for daily maximum wind speeds. Not only are existing quality assurance procedures mostly lacking for such data but the climatological relationships upon which such quality checks may be based are also grossly underexploited. Therefore, this study seeks to elucidate relationships among peak-gust, fastest-mile, and fastest 5-min wind speeds, utilizing the peak gust factor model but generalizing it for these and other extreme wind-speed elements. The relationship between peak-gust factor and daily mean wind speed is also adapted for quality assurance and for a wider range of climates than previously studied. Fastest-interval wind-speed factors are found to follow Gaussian, gamma, or Weibull probability distributions, included within mixed models to handle zeros. Resistant prediction interval estimates about a resistant regression were developed for quality assurance of peak-gust factor, given the daily mean wind speed. Flagging thresholds were estimated using parametric bootstrapping. Flag rates from 0.05 to 0.5% are in line with rates reported in the literature, from work with similar data sets; overall Type I and Type II error rates are in the range 0.03-0.3%. The approach outlined lends itself straightforwardly to application in data quality assurance.

  5. Elimination of temperature stratification in a low-speed open-return wind tunnel

    NASA Astrophysics Data System (ADS)

    Cimbala, J. M.; Park, W. J.

    1989-06-01

    It is noted that temperature stratification can be a significant source of error during hot-wire measurements in low-speed, open-return wind tunnels that operate in an enclosed room. The stratification is suggested to be eliminated by resort to a thorough mixing of the air just upstream of the wind-tunnel inlet. Since the facility is equipped with adequate turbulence management, mixing can be accomplished without reduction of flow quality.

  6. Slotted-wall research with disk and parachute models in a low-speed wind tunnel

    SciTech Connect

    Macha, J.M.; Buffington, R.J.; Henfling, J.L. ); Every, D. Van; Harris, J.L. )

    1990-01-01

    An experimental investigation of slotted-wall blockage interference has been conducted using disk and parachute models in a low speed wind tunnel. Test section open area ratio, model geometric blockage ratio, and model location along the length of the test section were systematically varied. Resulting drag coefficients were compared to each other and to interference-free measurements obtained in a much larger wind tunnel where the geometric blockage ratio was less than 0.0025. 9 refs., 10 figs.

  7. An Intelligent Ensemble Neural Network Model for Wind Speed Prediction in Renewable Energy Systems

    PubMed Central

    Ranganayaki, V.; Deepa, S. N.

    2016-01-01

    Various criteria are proposed to select the number of hidden neurons in artificial neural network (ANN) models and based on the criterion evolved an intelligent ensemble neural network model is proposed to predict wind speed in renewable energy applications. The intelligent ensemble neural model based wind speed forecasting is designed by averaging the forecasted values from multiple neural network models which includes multilayer perceptron (MLP), multilayer adaptive linear neuron (Madaline), back propagation neural network (BPN), and probabilistic neural network (PNN) so as to obtain better accuracy in wind speed prediction with minimum error. The random selection of hidden neurons numbers in artificial neural network results in overfitting or underfitting problem. This paper aims to avoid the occurrence of overfitting and underfitting problems. The selection of number of hidden neurons is done in this paper employing 102 criteria; these evolved criteria are verified by the computed various error values. The proposed criteria for fixing hidden neurons are validated employing the convergence theorem. The proposed intelligent ensemble neural model is applied for wind speed prediction application considering the real time wind data collected from the nearby locations. The obtained simulation results substantiate that the proposed ensemble model reduces the error value to minimum and enhances the accuracy. The computed results prove the effectiveness of the proposed ensemble neural network (ENN) model with respect to the considered error factors in comparison with that of the earlier models available in the literature. PMID:27034973

  8. Influence of wind speed averaging on estimates of dimethylsulfide emission fluxes

    SciTech Connect

    Chapman, E. G.; Shaw, W. J.; Easter, R. C.; Bian, X.; Ghan, S. J.

    2002-12-03

    The effect of various wind-speed-averaging periods on calculated DMS emission fluxes is quantitatively assessed. Here, a global climate model and an emission flux module were run in stand-alone mode for a full year. Twenty-minute instantaneous surface wind speeds and related variables generated by the climate model were archived, and corresponding 1-hour-, 6-hour-, daily-, and monthly-averaged quantities calculated. These various time-averaged, model-derived quantities were used as inputs in the emission flux module, and DMS emissions were calculated using two expressions for the mass transfer velocity commonly used in atmospheric models. Results indicate that the time period selected for averaging wind speeds can affect the magnitude of calculated DMS emission fluxes. A number of individual marine cells within the global grid show DMS emissions fluxes that are 10-60% higher when emissions are calculated using 20-minute instantaneous model time step winds rather than monthly-averaged wind speeds, and at some locations the differences exceed 200%. Many of these cells are located in the southern hemisphere where anthropogenic sulfur emissions are low and changes in oceanic DMS emissions may significantly affect calculated aerosol concentrations and aerosol radiative forcing.

  9. Long term behavior of trapped relativistic electrons and their correlation with solar wind speed

    SciTech Connect

    Belian, R.D.; Cayton, T.E.; Christensen, R.A.; Ingraham, J.C.; Reeves, G.D.

    1995-12-31

    We examine Los Alamos energetic electron data from 1979 through the present to show long term trends in the trapped relativistic electron populations at geosynchronous Earth orbit. Such populations are thought to be associated with high-speed solar wind structures typically present near solar minimum. We will show that high-energy electron fluxes, E > 1.4 MeV, displayed a solar-like cycle of about 10.5 years, but that the behavior is out of phase with the sunspot cycle. We will also compare relativistic electrons during the cycle with solar wind speed from the MIT plasma analyzers on IMP-8. It will be shown that relativistic electrons correlate well with high solar winds only during limited, short periods of time. We will also confirm the observation that the higher-energy electrons occur with a longer delay after the establishment of the high-speed solar wind. Comparison of our data with previously published data indicate that the higher the solar wind speed, the sooner the relativistic electrons occur.

  10. An Intelligent Ensemble Neural Network Model for Wind Speed Prediction in Renewable Energy Systems.

    PubMed

    Ranganayaki, V; Deepa, S N

    2016-01-01

    Various criteria are proposed to select the number of hidden neurons in artificial neural network (ANN) models and based on the criterion evolved an intelligent ensemble neural network model is proposed to predict wind speed in renewable energy applications. The intelligent ensemble neural model based wind speed forecasting is designed by averaging the forecasted values from multiple neural network models which includes multilayer perceptron (MLP), multilayer adaptive linear neuron (Madaline), back propagation neural network (BPN), and probabilistic neural network (PNN) so as to obtain better accuracy in wind speed prediction with minimum error. The random selection of hidden neurons numbers in artificial neural network results in overfitting or underfitting problem. This paper aims to avoid the occurrence of overfitting and underfitting problems. The selection of number of hidden neurons is done in this paper employing 102 criteria; these evolved criteria are verified by the computed various error values. The proposed criteria for fixing hidden neurons are validated employing the convergence theorem. The proposed intelligent ensemble neural model is applied for wind speed prediction application considering the real time wind data collected from the nearby locations. The obtained simulation results substantiate that the proposed ensemble model reduces the error value to minimum and enhances the accuracy. The computed results prove the effectiveness of the proposed ensemble neural network (ENN) model with respect to the considered error factors in comparison with that of the earlier models available in the literature. PMID:27034973

  11. GPS Signal Scattering from Sea Surface: Wind Speed Retrieval Using Experimental Data and Theoretical Model

    NASA Technical Reports Server (NTRS)

    Komjathy, Attila; Zavorotny, Valery U.; Axelrad, Penina; Born, George H.; Garrison, James L.

    2000-01-01

    Global Positioning System (GPS) signals reflected from the ocean surface have potential use for various remote sensing purposes. Some possibilities arc measurements of surface roughness characteristics from which ware height, wind speed, and direction could be determined. For this paper, GPS-reflected signal measurements collected at aircraft altitudes of 2 km to 5 km with a delay-Doppler mapping GPS receiver arc used to explore the possibility of determining wind speed. To interpret the GPS data, a theoretical model has been developed that describes the power of the reflected GPS signals for different time delays and Doppler frequencies as a function of geometrical and environmental parameters. The results indicate a good agreement between the measured and the modeled normalized signal power waveforms during changing surface wind conditions. The estimated wind speed using surface- reflected GPS data, obtained by comparing actual and modeled waveforms, shows good agreement (within 2 m/s) with data obtained from a nearby buoy and independent wind speed measurements derived from the TOPEX/Poseidon altimetric satellite.

  12. Control strategy for a variable-speed wind energy conversion system

    NASA Technical Reports Server (NTRS)

    Jacob, A.; Veillette, D.; Rajagopalan, V.

    1979-01-01

    A control concept for a variable-speed wind energy conversion system is proposed, for which a self-exited asynchronous cage generator is used along with a system of thyristor converters. The control loops are the following: (1) regulation of the entrainment speed as function of available mechanical energy by acting on the resistance couple of the asynchronous generator; (2) control of electric power delivered to the asynchronous machine, functioning as a motor, for start-up of the vertical axis wind converter; and (3) limitation of the slip value, and by consequence, of the induction currents in the presence of sudden variations of input parameters.

  13. Linear retrieval and global measurements of wind speed from the Seasat SMMR

    NASA Technical Reports Server (NTRS)

    Pandey, P. C.

    1983-01-01

    Retrievals of wind speed (WS) from Seasat Scanning Multichannel Microwave Radiometer (SMMR) were performed using a two-step statistical technique. Nine subsets of two to five SMMR channels were examined for wind speed retrieval. These subsets were derived by using a leaps and bound procedure based on the coefficient of determination selection criteria to a statistical data base of brightness temperatures and geophysical parameters. Analysis of Monsoon Experiment and ocean station PAPA data showed a strong correlation between sea surface temperature and water vapor. This relation was used in generating the statistical data base. Global maps of WS were produced for one and three month periods.

  14. a New Method to Detect Regions Endangered by High Wind Speeds

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Ehrensperger, S.; Krauß, T.

    2016-06-01

    In this study we evaluate whether the methodology of Boosted Regression Trees (BRT) suits for accurately predicting maximum wind speeds. As predictors a broad set of parameters derived from a Digital Elevation Model (DEM) acquired within the Shuttle Radar Topography Mission (SRTM) is used. The derived parameters describe the surface by means of quantities (e.g. slope, aspect) and quality (landform classification). Furthermore land cover data from the CORINE dataset is added. The response variable is maximum wind speed, measurements are provided by a network of weather stations. The area of interest is Switzerland, a country which suits perfectly for this study because of its highly dynamic orography and various landforms.

  15. An experimental study of several wind tunnel wall configurations using two V/STOL model configurations. [low speed wind tunnels

    NASA Technical Reports Server (NTRS)

    Binion, T. W., Jr.

    1975-01-01

    Experiments were conducted in the low speed wind tunnel using two V/STOL models, a jet-flap and a jet-in-fuselage configuration, to search for a wind tunnel wall configuration to minimize wall interference on V/STOL models. Data were also obtained on the jet-flap model with a uniform slotted wall configuration to provide comparisons between theoretical and experimental wall interference. A test section configuration was found which provided some data in reasonable agreement with interference-free results over a wide range of momentum coefficients.

  16. First and second order semi-Markov chains for wind speed modeling

    NASA Astrophysics Data System (ADS)

    Prattico, F.; Petroni, F.; D'Amico, G.

    2012-04-01

    The increasing interest in renewable energy leads scientific research to find a better way to recover most of the available energy. Particularly, the maximum energy recoverable from wind is equal to 59.3% of that available (Betz law) at a specific pitch angle and when the ratio between the wind speed in output and in input is equal to 1/3. The pitch angle is the angle formed between the airfoil of the blade of the wind turbine and the wind direction. Old turbine and a lot of that actually marketed, in fact, have always the same invariant geometry of the airfoil. This causes that wind turbines will work with an efficiency that is lower than 59.3%. New generation wind turbines, instead, have a system to variate the pitch angle by rotating the blades. This system able the wind turbines to recover, at different wind speed, always the maximum energy, working in Betz limit at different speed ratios. A powerful system control of the pitch angle allows the wind turbine to recover better the energy in transient regime. A good stochastic model for wind speed is then needed to help both the optimization of turbine design and to assist the system control to predict the value of the wind speed to positioning the blades quickly and correctly. The possibility to have synthetic data of wind speed is a powerful instrument to assist designer to verify the structures of the wind turbines or to estimate the energy recoverable from a specific site. To generate synthetic data, Markov chains of first or higher order are often used [1,2,3]. In particular in [3] is presented a comparison between a first-order Markov chain and a second-order Markov chain. A similar work, but only for the first-order Markov chain, is conduced by [2], presenting the probability transition matrix and comparing the energy spectral density and autocorrelation of real and synthetic wind speed data. A tentative to modeling and to join speed and direction of wind is presented in [1], by using two models, first

  17. Aerodynamic Characteristics of High Speed Trains under Cross Wind Conditions

    NASA Astrophysics Data System (ADS)

    Chen, W.; Wu, S. P.; Zhang, Y.

    2011-09-01

    Numerical simulation for the two models in cross-wind was carried out in this paper. The three-dimensional compressible Reynolds-averaged Navier-Stokes equations(RANS), combined with the standard k-ɛ turbulence model, were solved on multi-block hybrid grids by second order upwind finite volume technique. The impact of fairing on aerodynamic characteristics of the train models was analyzed. It is shown that, the flow separates on the fairing and a strong vortex is generated, the pressure on the upper middle car decreases dramatically, which leads to a large lift force. The fairing changes the basic patterns around the trains. In addition, formulas of the coefficient of aerodynamic force at small yaw angles up to 24° were expressed.

  18. Wind Speed and Mortality Rate of a Marine Fish, the Northern Anchovy (Engraulis mordax).

    PubMed

    Peterman, R M; Bradford, M J

    1987-01-16

    Large variability in recruitment of marine fishes creates challenging management problems. In northern anchovy (Engraulis mordax), there is a significant linear relation between larval mortality rate and the frequency of calm, low wind speed periods during the spawning season, possibly because calm winds permit maintenance of concentrated patches of larval food. Neither cannibalism on larvae nor offshore transport contributed significantly to interannual variation in early larval mortality. These results are consistent with the hypothesis that wind-driven turbulent mixing affects variability in survival of young fish larvae. However, abundance of recruits does not necessarily reflect abundance of larvae surviving through this early stage. PMID:17750387

  19. Quantification of rain gauge measurement undercatch and wind speed correction

    NASA Astrophysics Data System (ADS)

    Pollock, Michael; Quinn, Paul; Dutton, Mark; Wilkinson, Mark

    2014-05-01

    Hydrological processes are adversely affected by systematic rain gauge inaccuracy due to wind induced undercatching. The implications of this are discussed and addressed. Despite evidence of the undercatch problem being cited in the past and the difficulty in solving such a complex problem; it has become an inconvenient truth to hydrologists that major inaccuracies in rainfall measurement exist. A two year long experiment using new equipment and improved data logging and telemetery techniques enriches this formative work to redress the wilful neglect with which accurate rainfall measurement has been treated in recent decades. Results from this work suggest that the annual systematic undercatch can be in the order of 20 percent in the UK. During specific periods (measured at high temporal resolution), this can rise to as high as 50 percent for a single wind impacted event. As one organisation, responsible for the environment in the UK, moves towards using fewer instruments (15 percent fewer in the next year), it is scarcely possible to overstate the importance in solving this problem. It had been hoped that new equipment, such as acoustic distrometer and weighing gauge technologies, would be able to reduce the magnitude of the bias. However, through data gathered in the 2 year experiment and through secondary sources from the 1970s and 1980s, it is demonstrated that this is not the case and that the same problems with undercatching remain now as they did then. We further postulate that wider, denser networks of inexpensive telemetered equipment are now possible but they must still address the undercatch issue. There is little merit in pointing out an age old problem if no solution is put forward to fix it. The aforementioned experiment has furnished new ideas and further work has been commissioned to address this problem. This will be achieved via the medium of a Knowledge Transfer Partnership between Newcastle University and an innovative equipment manufacturer

  20. Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

    2013-05-01

    Shipboard measurements of eddy covariance DMS air/sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air/sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near surface water side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air/sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

  1. Error Correction Method for Wind Speed Measured with Doppler Wind LIDAR at Low Altitude

    NASA Astrophysics Data System (ADS)

    Liu, Bingyi; Feng, Changzhong; Liu, Zhishen

    2014-11-01

    For the purpose of obtaining global vertical wind profiles, the Atmospheric Dynamics Mission Aeolus of European Space Agency (ESA), carrying the first spaceborne Doppler lidar ALADIN (Atmospheric LAser Doppler INstrument), is going to be launched in 2015. DLR (German Aerospace Center) developed the A2D (ALADIN Airborne Demonstrator) for the prelaunch validation. A ground-based wind lidar for wind profile and wind field scanning measurement developed by Ocean University of China is going to be used for the ground-based validation after the launch of Aeolus. In order to provide validation data with higher accuracy, an error correction method is investigated to improve the accuracy of low altitude wind data measured with Doppler lidar based on iodine absorption filter. The error due to nonlinear wind sensitivity is corrected, and the method for merging atmospheric return signal is improved. The correction method is validated by synchronous wind measurements with lidar and radiosonde. The results show that the accuracy of wind data measured with Doppler lidar at low altitude can be improved by the proposed error correction method.

  2. Predicting extreme wind speeds on a tropical island for multi-peril catastrophe modelling

    NASA Astrophysics Data System (ADS)

    Thornton, James; Moncoulon, David; Millinship, Ian; Raven, Emma

    2013-04-01

    Catastrophe models are important tools used by the reinsurance industry for assessing and managing risk. Here, we present the methods used to develop high-resolution wind hazard maps for the Indian Ocean island of La Réunion. As the recent Cyclone Dumile (January 2013) reminded us, the island is at considerable risk from the extreme weather associated with tropical cyclones. It also contains a significant proportion of the total value insured in French overseas territories. The wind maps, alongside flood and storm surge maps, were ultimately combined with exposure information in a multi-peril catastrophe model to provide probabilistic estimates of insured loss. Our wind mapping methodology used established extreme value theory statistics to estimate the annual probability of extreme wind speeds, including those exceeding the observed maxima of our 19 year record, at meteorological stations. This gave approximate wind speeds for a range of return periods at these specific locations. Since the spatial density of the stations was insufficient to resolve the numerous potential effects of the complex island topography, geographically weighted regression (GWR) models were then developed to interpolate these cyclonic wind speeds across the entire island. Factors known to affect local wind speed such as elevation, surface roughness and coastal proximity were explicitly accounted for. Using this advanced interpolation method, wind hazard maps were produced for six return periods between 1 in 10 and 1 in 1000 years. Our maps compared favourably with those of historical events, and also showed patterns of wind speed in agreement with the findings of other studies investigating the effects of topography. Leave-one-out cross-validation (LOOCV) further confirmed the satisfactory performance of the models in providing a robust and comprehensive description of wind patterns during cyclone passage. Uncertainty increased with return period as more extrapolation of the limited

  3. A New Height Error Revision Method of Predicting Long-Term Wind Speed with MCP Algorithm

    NASA Astrophysics Data System (ADS)

    Liu, Yujue; Hu, Fei

    2013-04-01

    Wind energy technology is one of the fastest in growing rate in new and renewable energy technologies. It is very important to select stronger windy sites in a country for the purpose of producing more electricity. Measure-Correlate-Predict (MCP) algorithms are used to predict the wind resource at target site for wind power development. MCP method model bases on a relationship between wind data (speed and direction) measured at the target site and concurrent wind data at reference site nearby. The model is then used with long-term data from the reference site to predict the long-term wind speed and direction distributions at the target site. MCP method is in order to be able to determine the annual energy capture of a wind farm located at the target site. Over the last 15 years well over a half dozen of MCP methods in the literature. The MCP algorithms differ in terms of overall approach, model definition, use of direction sectors, and length of the data. Such as 1)a linear regression model; 2)a model using distributions of ratios of wind speeds at two sites; 3)a vector regression method; 4)a method based on the ratio of standard deviations of two data sets, etc. Unfortunately, none of these MCP algorithms can predict wind speed from two sites at different altitudes. If the target site is much higher or lower than the reference site, the result accuracy will be much poorer. Inner Mongolia grassland is known as one of the regions that rich in wind resource in China. The data we use is from three wind measurements, consisting of nearly one year of six layers in XiLinGuoLe of Inner Mongolia . Firstly, we use the maximum likelihood method to estimate k, shape parameter and c, scale parameter of the Weibull function for different time periods. And then we find out that c has a power law function of height, and that k varies as the form of a quadratic function of height and obtains the max value in the height of 10 to100 meters. Finally, we add the height distribution

  4. Statistical Short-Range Guidance for Peak Wind Speed Forecasts at Edwards Air Force Base, CA

    NASA Technical Reports Server (NTRS)

    Dreher, Joseph; Crawford, Winifred; Lafosse, Richard; Hoeth, Brian; Burns, Kerry

    2008-01-01

    The peak winds near the surface are an important forecast element for Space Shuttle landings. As defined in the Shuttle Flight Rules (FRs), there are peak wind thresholds that cannot be exceeded in order to ensure the safety of the shuttle during landing operations. The National Weather Service Spaceflight Meteorology Group (SMG) is responsible for weather forecasts for all shuttle landings. They indicate peak winds are a challenging parameter to forecast. To alleviate the difficulty in making such wind forecasts, the Applied Meteorology Unit (AMTJ) developed a personal computer based graphical user interface (GUI) for displaying peak wind climatology and probabilities of exceeding peak-wind thresholds for the Shuttle Landing Facility (SLF) at Kennedy Space Center. However, the shuttle must land at Edwards Air Force Base (EAFB) in southern California when weather conditions at Kennedy Space Center in Florida are not acceptable, so SMG forecasters requested that a similar tool be developed for EAFB. Marshall Space Flight Center (MSFC) personnel archived and performed quality control of 2-minute average and 10-minute peak wind speeds at each tower adjacent to the main runway at EAFB from 1997- 2004. They calculated wind climatologies and probabilities of average peak wind occurrence based on the average speed. The climatologies were calculated for each tower and month, and were stratified by hour, direction, and direction/hour. For the probabilities of peak wind occurrence, MSFC calculated empirical and modeled probabilities of meeting or exceeding specific 10-minute peak wind speeds using probability density functions. The AMU obtained and reformatted the data into Microsoft Excel PivotTables, which allows users to display different values with point-click-drag techniques. The GUT was then created from the PivotTables using Visual Basic for Applications code. The GUI is run through a macro within Microsoft Excel and allows forecasters to quickly display and

  5. A 3-D High Speed Photographic Survey For Bomb Dropping In The Wind Tunnel

    NASA Astrophysics Data System (ADS)

    Junren, Chen; Liangyi, Chen; Yuxian, Nie; Wenxing, Chen

    1989-06-01

    High speed Stereophotography may obtain 3-D information of the motion object. This paper deals with a high speed stereophotographic survey of dropping bomb in wind tunnel and measurement of its displacement, velocity, acceleration, angle of attack and yaw angle. Two high speed cinecameras are used, the two optical axes of the cameras are perpendicular to each other and in a plane being vertical to the plumb line. The optical axis of a camera (front camera) is parallel with the aircraft body, and the another (side camera) is perpendicular. Before taking the object and image distance of the two cameras must be measured by photographic method. The photographic rate is 304 fps.

  6. Numerical Study of the High-Speed Leg of a Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Nayani, Sudheer; Sellers, William L, III; Brynildsen, Scott E.; Everhart, Joel L.

    2015-01-01

    The paper describes a numerical study of the high-speed leg of the NASA Langley 14 x 22-ft Low-Speed Wind Tunnel. The high-speed leg consists of the settling chamber, contraction, test section, and first diffuser. Results are shown comparing two different sources of surface geometry, and two different unstructured grid solvers for the flow characteristics. Numerical simulations of the flow on the tunnel centerline, boundary layer profiles on the floor, and wall static pressures have been compared with experiment. Flow angularities along the test section length have also been determined.

  7. Solar-wind-magnetosphere coupling, including relativistic electron energization, during high-speed streams

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Lee, D.-Y.; Kim, H.-J.; Hwang, J. A.; Thorne, R. M.; Horne, R. B.; Smith, A. J.

    2009-07-01

    High geomagnetic activity occurs continuously during high-speed solar wind streams, and fluxes of relativistic electrons observed at geosynchronous orbit enhance significantly. High-speed streams are preceded by solar wind compression regions, during which time there are large losses of relativistic electrons from geosynchronous orbit. Weak to moderate geomagnetic storms often occur during the passage of these compression regions; however, we find that the phenomena that occur during the ensuing high-speed streams do not depend on whether or not a preceding storm develops. Large-amplitude Alfvén waves occur within the high-speed solar wind streams, which are expected to lead to intermittent intervals of significantly enhanced magnetospheric convection and to thus also lead to repetitive substorms due to repetitively occurring reductions in the strength of convection. We find that such repetitive substorms are clearly discernible in the LANL geosynchronous energetic particle data during high-speed stream intervals. Global auroral images are found to show unambiguously that these events are indeed classical substorms, leading us to conclude that substorms are an important contributor to the enhanced geomagnetic activity during high-speed streams. We used the onsets of these substorms as indicators of preceding periods of enhanced convection and of reductions in convection, and we have used ground-based chorus observations from the VELOX instrument at Halley station as an indicator of magnetospheric chorus intensities. These data show evidence that it is the periods of enhanced convection that precede substorm expansions, and not the expansions themselves, that lead to the enhanced dawn-side chorus wave intensity that has been postulated to cause the energization of relativistic electrons. If this inference is correct, and if it is chorus that energizes the relativistic electrons, then high-speed solar wind streams lead to relativistic electron flux enhancements

  8. Heliolatitude structure of the solar wind proton speed and density at 1 AU for heliospheric modeling

    NASA Astrophysics Data System (ADS)

    Sokol, Justyna Maria; Swaczyna, Pawel; Bzowski, Maciej; Tokumaru, Munetoshi

    2014-05-01

    The heliolatitudinal structure of solar wind proton speed and density varies with solar activity. A model of its variation with time is needed for heliospheric studies and modeling. It is important for the global heliospheric structure, allows for an assessment of ionization rates of neutral species in the heliosphere and interpretation of observations of the energetic neutral atoms and neutral interstellar atoms. Sokół et al. 2013 presented a model of the heliolatitudinal and time variations of solar wind structure based on results of the computer assisted tomography analysis of the solar wind speed enabled by remote-sensing observations of interplanetary scintillations, in-situ measurements from Ulysses, and in-ecliptic measurements from various missions gathered in the OMNI2 database. They determined the 3D structure of solar wind on a yearly time grid from 1990 to 2011. Now we increase the time resolution of the grid used in the model. Because of the weather conditions in Japan, where the interplanetary scintillation observations are carried out, the solar wind data sets contain systematic gaps. For the purposes of the increase of the time resolution of the model for heliospheric studies the method of filling of these gap is needed. We present a comparison of various methods of gap filling. We present results of the investigation of the procedures of reconstruction of the solar wind density with the use of the solar wind invariants published in the literature. Additionally we study various algorithms of extrapolation of the heliolatitudinal time series of the solar wind proton speed and number density in time.

  9. Modeling Heteroscedasticity of Wind Speed Time Series in the United Arab Emirates

    NASA Astrophysics Data System (ADS)

    Kim, H. Y.; Marpu, P. R.; Ouarda, T.

    2014-12-01

    There has been a growing interest in wind resources in the Gulf region, not only for evaluating wind energy potential, but also for understanding and forecasting changes in wind, as a regional climate variable. In particular, time varying variance—the second order moment—or heteroscedasticity in wind time series is important to investigate since high variance causes turbulence, which affects wind power potential and may lead to structural changes in wind turbines. Nevertheless, the conditional variance of wind time series has been rarely explored, especially in the Gulf region. Therefore, the seasonal autoregressive integrated moving average-generalized autoregressive conditional heteroscedasticity (SARIMA-GARCH) model is applied to observed wind data in the United Arab Emirates (UAE). This model allows considering apparent seasonality which is present in wind time series and the heteroscedasticity in residuals indicated with the Engle test, to understand and forecast changes in the conditional variance of wind time series. In this study, the autocorrelation function of daily average wind speed time series obtained from seven stations within the UAE—Al Aradh, Al Mirfa, Al Wagan, East of Jebel Haffet, Madinat Zayed, Masdar City, Sir Bani Yas Island—is inspected to fit a SARIMA model. The best SARIMA model is selected according to the minimum Akaike Information Criteria (AIC) and based on residuals of the model. Then, the GARCH model is applied to the remaining residuals to capture the conditional variance of the SARIMA model. Results indicate that the SARIMA-GARCH model provides a good fir to wind data in the UAE.

  10. Conceptions of Tornado Wind Speed and Land Surface Interactions among Undergraduate Students in Nebraska

    ERIC Educational Resources Information Center

    Van Den Broeke, Matthew S.; Arthurs, Leilani

    2015-01-01

    To ascertain novice conceptions of tornado wind speed and the influence of surface characteristics on tornado occurrence, 613 undergraduate students enrolled in introductory science courses at a large state university in Nebraska were surveyed. Our findings show that students lack understanding of the fundamental concepts that (1) tornadoes are…

  11. Evaluation of spray drift using low speed wind tunnel measurements and dispersion modeling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this work was to evaluate the EPA’s proposed Test Plan for the validation testing of pesticide spray drift reduction technologies (DRTs) for row and field crops, focusing on the evaluation of ground application systems using the low-speed wind tunnel protocols and processing the dat...

  12. Microwave Remote Sensing of Ocean Surface Wind Speed and Rain Rates over Tropical Storms

    NASA Technical Reports Server (NTRS)

    Swift, C. T.; Dehority, D. C.; Black, P. G.; Chien, J. Z.

    1984-01-01

    The value of using narrowly spaced frequencies within a microwave band to measure wind speeds and rain rates over tropical storms with radiometers is reviewed. The technique focuses on results obtained in the overflights of Hurricane Allen during 5 and 8 of August, 1980.

  13. Process model for ammonia volatilization from anaerobic swine lagoons incorporating varying wind speeds and biogas bubbling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ammonia volatilization from treatment lagoons varies widely with the total ammonia concentration, pH, temperature, suspended solids, atmospheric ammonia concentration above the water surface, and wind speed. Ammonia emissions were estimated with a process-based mechanistic model integrating ammonia ...

  14. Evaluation of the EPA Drift Reduction Technology (DRT) low-speed wind tunnel protocol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The EPA’s proposed Drift Reduction Technology low-speed wind tunnel evaluation protocol was tested across a series of modified ASAE reference nozzles. Both droplet size and deposition and flux volume measurements were made downwind from the nozzles operating in the tunnel at airspeeds of 1 and 2.5 ...

  15. Hurricane Imaging Radiometer Wind Speed and Rain Rate Retrievals during the 2010 GRIP Flight Experiment

    NASA Technical Reports Server (NTRS)

    Sahawneh, Saleem; Farrar, Spencer; Johnson, James; Jones, W. Linwood; Roberts, Jason; Biswas, Sayak; Cecil, Daniel

    2014-01-01

    Microwave remote sensing observations of hurricanes, from NOAA and USAF hurricane surveillance aircraft, provide vital data for hurricane research and operations, for forecasting the intensity and track of tropical storms. The current operational standard for hurricane wind speed and rain rate measurements is the Stepped Frequency Microwave Radiometer (SFMR), which is a nadir viewing passive microwave airborne remote sensor. The Hurricane Imaging Radiometer, HIRAD, will extend the nadir viewing SFMR capability to provide wide swath images of wind speed and rain rate, while flying on a high altitude aircraft. HIRAD was first flown in the Genesis and Rapid Intensification Processes, GRIP, NASA hurricane field experiment in 2010. This paper reports on geophysical retrieval results and provides hurricane images from GRIP flights. An overview of the HIRAD instrument and the radiative transfer theory based, wind speed/rain rate retrieval algorithm is included. Results are presented for hurricane wind speed and rain rate for Earl and Karl, with comparison to collocated SFMR retrievals and WP3D Fuselage Radar images for validation purposes.

  16. FUZZY LOGIC BASED INTELLIGENT CONTROL OF A VARIABLE SPEED CAGE MACHINE WIND GENERATION SYSTEM

    EPA Science Inventory

    The paper describes a variable-speed wind generation system where fuzzy logic principles are used to optimize efficiency and enhance performance control. A squirrel cage induction generator feeds the power to a double-sided pulse width modulated converter system which either pump...

  17. FUZZY LOGIC BASED INTELLIGENT CONTROL OF A VARIABLE SPEED CAGE MACHINE WIND GENERATION SYSTEM

    EPA Science Inventory

    The report gives results of a demonstration of the successful application of fuzzy logic to enhance the performance and control of a variable-speed wind generation system. A squirrel cage induction generator feeds the power to either a double-sided pulse-width modulation converte...

  18. Two Machine Learning Approaches for Short-Term Wind Speed Time-Series Prediction.

    PubMed

    Ak, Ronay; Fink, Olga; Zio, Enrico

    2016-08-01

    The increasing liberalization of European electricity markets, the growing proportion of intermittent renewable energy being fed into the energy grids, and also new challenges in the patterns of energy consumption (such as electric mobility) require flexible and intelligent power grids capable of providing efficient, reliable, economical, and sustainable energy production and distribution. From the supplier side, particularly, the integration of renewable energy sources (e.g., wind and solar) into the grid imposes an engineering and economic challenge because of the limited ability to control and dispatch these energy sources due to their intermittent characteristics. Time-series prediction of wind speed for wind power production is a particularly important and challenging task, wherein prediction intervals (PIs) are preferable results of the prediction, rather than point estimates, because they provide information on the confidence in the prediction. In this paper, two different machine learning approaches to assess PIs of time-series predictions are considered and compared: 1) multilayer perceptron neural networks trained with a multiobjective genetic algorithm and 2) extreme learning machines combined with the nearest neighbors approach. The proposed approaches are applied for short-term wind speed prediction from a real data set of hourly wind speed measurements for the region of Regina in Saskatchewan, Canada. Both approaches demonstrate good prediction precision and provide complementary advantages with respect to different evaluation criteria. PMID:25910257

  19. Prediction of Wind Speeds Based on Digital Elevation Models Using Boosted Regression Trees

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Etienne, C.; Tian, J.; Krauß, T.

    2015-12-01

    In this paper a new approach is presented to predict maximum wind speeds using Gradient Boosted Regression Trees (GBRT). GBRT are a non-parametric regression technique used in various applications, suitable to make predictions without having an in-depth a-priori knowledge about the functional dependancies between the predictors and the response variables. Our aim is to predict maximum wind speeds based on predictors, which are derived from a digital elevation model (DEM). The predictors describe the orography of the Area-of-Interest (AoI) by various means like first and second order derivatives of the DEM, but also higher sophisticated classifications describing exposure and shelterness of the terrain to wind flux. In order to take the different scales into account which probably influence the streams and turbulences of wind flow over complex terrain, the predictors are computed on different spatial resolutions ranging from 30 m up to 2000 m. The geographic area used for examination of the approach is Switzerland, a mountainious region in the heart of europe, dominated by the alps, but also covering large valleys. The full workflow is described in this paper, which consists of data preparation using image processing techniques, model training using a state-of-the-art machine learning algorithm, in-depth analysis of the trained model, validation of the model and application of the model to generate a wind speed map.

  20. Application of extreme learning machine for estimation of wind speed distribution

    NASA Astrophysics Data System (ADS)

    Shamshirband, Shahaboddin; Mohammadi, Kasra; Tong, Chong Wen; Petković, Dalibor; Porcu, Emilio; Mostafaeipour, Ali; Ch, Sudheer; Sedaghat, Ahmad

    2016-03-01

    The knowledge of the probabilistic wind speed distribution is of particular significance in reliable evaluation of the wind energy potential and effective adoption of site specific wind turbines. Among all proposed probability density functions, the two-parameter Weibull function has been extensively endorsed and utilized to model wind speeds and express wind speed distribution in various locations. In this research work, extreme learning machine (ELM) is employed to compute the shape ( k) and scale ( c) factors of Weibull distribution function. The developed ELM model is trained and tested based upon two widely successful methods used to estimate k and c parameters. The efficiency and accuracy of ELM is compared against support vector machine, artificial neural network and genetic programming for estimating the same Weibull parameters. The survey results reveal that applying ELM approach is eventuated in attaining further precision for estimation of both Weibull parameters compared to other methods evaluated. Mean absolute percentage error, mean absolute bias error and root mean square error for k are 8.4600 %, 0.1783 and 0.2371, while for c are 0.2143 %, 0.0118 and 0.0192 m/s, respectively. In conclusion, it is conclusively found that application of ELM is particularly promising as an alternative method to estimate Weibull k and c factors.

  1. Influence of wind speed averaging on estimates of dimethylsulfide emission fluxes

    DOE PAGESBeta

    Chapman, E. G.; Shaw, W. J.; Easter, R. C.; Bian, X.; Ghan, S. J.

    2002-12-03

    The effect of various wind-speed-averaging periods on calculated DMS emission fluxes is quantitatively assessed. Here, a global climate model and an emission flux module were run in stand-alone mode for a full year. Twenty-minute instantaneous surface wind speeds and related variables generated by the climate model were archived, and corresponding 1-hour-, 6-hour-, daily-, and monthly-averaged quantities calculated. These various time-averaged, model-derived quantities were used as inputs in the emission flux module, and DMS emissions were calculated using two expressions for the mass transfer velocity commonly used in atmospheric models. Results indicate that the time period selected for averaging wind speedsmore » can affect the magnitude of calculated DMS emission fluxes. A number of individual marine cells within the global grid show DMS emissions fluxes that are 10-60% higher when emissions are calculated using 20-minute instantaneous model time step winds rather than monthly-averaged wind speeds, and at some locations the differences exceed 200%. Many of these cells are located in the southern hemisphere where anthropogenic sulfur emissions are low and changes in oceanic DMS emissions may significantly affect calculated aerosol concentrations and aerosol radiative forcing.« less

  2. A GIS wind resource map with tabular printout of monthly and annual wind speeds for 2,000 towns in Iowa

    SciTech Connect

    Brower, M.C.; Factor, T.

    1997-12-31

    The Iowa Wind Energy Institute, under a grant from the Iowa Energy Center, undertook in 1994 to map wind resources in Iowa. Fifty-meter met towers were erected at 13 locations across the state deemed promising for utility-scale wind farm development. Two years of summarized wind speed, direction, and temperature data were used to create wind resource maps incorporating effects of elevation, relative exposure, terrain roughness, and ground cover. Maps were produced predicting long-term mean monthly and annual wind speeds on a one-kilometer grid. The estimated absolute standard error in the predicted annual average wind speeds at unobstructed locations is 9 percent. The relative standard error between points on the annual map is estimated to be 3 percent. These maps and tabular data for 2,000 cities and towns in Iowa are now available on the Iowa Energy Center`s web site (http.//www.energy.iastate.edu).

  3. Plans for Testing the NREL Unsteady Aerodynamics Experiment 10m Diameter HAWT in the NASA Ames Wind Tunnel: Minutes, Conclusions, and Revised Text Matrix from the 1st Science Panel Meeting

    SciTech Connect

    Simms, D.; Schreck, S.; Hand, M.; Fingersh, L.; Cotrell, J.; Pierce, K.; Robinson, M.

    2000-08-28

    Currently, the NREL Unsteady Aerodynamics Experiment (UAE) research turbine is scheduled to enter the NASA Ames 80-ft x 120-ft wind tunnel in early 2000. To prepare for this 3-week test, a Science Panel meeting was convened at the National Wind Technology Center (NWTC) in October 1998. During this meeting, the Science Panel and representatives from the wind energy community provided numerous detailed recommendations regarding test activities and priorities. The Unsteady Aerodynamics team of the NWTC condensed this guidance and drafted a detailed test plan. This test plan represents an attempt to balance diverse recommendations received from the Science Panel meeting, while taking into account multiple constraints imposed by the UAE research turbine, the NASA Ames 80-ft x 120-ft wind tunnel, and other sources. The NREL-NASA Ames wind tunnel tests will primarily be focused on obtaining rotating blade pressure data. NREL has been making these types of measurements since 1987 and has considerable experience in doing so. The purpose of this wind tunnel test is to acquire accurate quantitative aerodynamic and structural measurements, on a wind turbine that is geometrically and dynamically representative of full-scale machines, in an environment free from pronounced inflow anomalies. These data will be exploited to develop and validate enhanced engineering models for designing and analyzing advanced wind energy machines.

  4. Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations

    NASA Astrophysics Data System (ADS)

    Kazil, J.; Feingold, G.; Yamaguchi, T.

    2015-10-01

    Observed and projected trends in large scale wind speed over the oceans prompt the question: how might marine stratocumulus clouds and their radiative properties respond to future changes in large scale wind speed? Wind speed drives the surface fluxes of sensible heat, moisture, and momentum, and thereby acts on cloud liquid water path (LWP) and cloud radiative properties. We present an investigation of the dynamical response of non-precipitating, overcast marine stratocumulus clouds to different wind speeds, all else equal. In cloud-system resolving simulations, we find that higher wind speed leads to faster boundary layer growth and stronger entrainment. The dynamical driver is enhanced buoyant production of turbulence kinetic energy (TKE) from latent heat release in cloud updrafts. LWP is enhanced during the night and in the morning at higher wind speed, and more strongly suppressed later in the day. Wind speed hence accentuates the diurnal LWP cycle by expanding the morning - afternoon contrast. The higher LWP at higher wind speed does not, however, enhance cloud top cooling because in clouds with LWP ⪆ 50 g m-2, long wave emissions are very insensitive to LWP. This leads to the more general conclusion that in sufficiently thick stratocumulus clouds, additional boundary layer growth and entrainment due to a boundary layer moistening arises by stronger production of TKE from latent heat release in cloud updrafts, rather than from enhanced longwave cooling. We find furthermore that large scale wind modulates boundary layer decoupling. At nighttime and at low wind speed during daytime, it enhances decoupling in part by faster boundary layer growth and stronger entrainment, and in part because circulation driven by shear from large scale wind in the sub-cloud layer hinders vertical moisture transport between the surface and cloud base. With increasing wind speed, however, in decoupled daytime conditions, shear-driven circulation due to large scale wind

  5. Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations

    DOE PAGESBeta

    Kazil, Jan; Feingold, Graham; Yamaguchi, Takanobu

    2016-05-12

    Observed and projected trends in large-scale wind speed over the oceans prompt the question: how do marine stratocumulus clouds and their radiative properties respond to changes in large-scale wind speed? Wind speed drives the surface fluxes of sensible heat, moisture, and momentum and thereby acts on cloud liquid water path (LWP) and cloud radiative properties. We present an investigation of the dynamical response of non-precipitating, overcast marine stratocumulus clouds to different wind speeds over the course of a diurnal cycle, all else equal. In cloud-system resolving simulations, we find that higher wind speed leads to faster boundary layer growth and strongermore » entrainment. The dynamical driver is enhanced buoyant production of turbulence kinetic energy (TKE) from latent heat release in cloud updrafts. LWP is enhanced during the night and in the morning at higher wind speed, and more strongly suppressed later in the day. Wind speed hence accentuates the diurnal LWP cycle by expanding the morning–afternoon contrast. The higher LWP at higher wind speed does not, however, enhance cloud top cooling because in clouds with LWP ⪆ 50 g m−2, longwave emissions are insensitive to LWP. This leads to the general conclusion that in sufficiently thick stratocumulus clouds, additional boundary layer growth and entrainment due to a boundary layer moistening arises by stronger production of TKE from latent heat release in cloud updrafts, rather than from enhanced longwave cooling. We find that large-scale wind modulates boundary layer decoupling. At nighttime and at low wind speed during daytime, it enhances decoupling in part by faster boundary layer growth and stronger entrainment and in part because shear from large-scale wind in the sub-cloud layer hinders vertical moisture transport between the surface and cloud base. With increasing wind speed, however, in decoupled daytime conditions, shear-driven circulation due to large-scale wind takes over

  6. Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations

    DOE PAGESBeta

    Kazil, Jan; Feingold, Graham; Yamaguchi, Takanobu

    2016-05-12

    Observed and projected trends in large-scale wind speed over the oceans prompt the question: how do marine stratocumulus clouds and their radiative properties respond to changes in large-scale wind speed? Wind speed drives the surface fluxes of sensible heat, moisture, and momentum and thereby acts on cloud liquid water path (LWP) and cloud radiative properties. We present an investigation of the dynamical response of non-precipitating, overcast marine stratocumulus clouds to different wind speeds over the course of a diurnal cycle, all else equal. In cloud-system resolving simulations, we find that higher wind speed leads to faster boundary layer growth and strongermore » entrainment. The dynamical driver is enhanced buoyant production of turbulence kinetic energy (TKE) from latent heat release in cloud updrafts. LWP is enhanced during the night and in the morning at higher wind speed, and more strongly suppressed later in the day. Wind speed hence accentuates the diurnal LWP cycle by expanding the morning–afternoon contrast. The higher LWP at higher wind speed does not, however, enhance cloud top cooling because in clouds with LWP ≳50 gm–2, longwave emissions are insensitive to LWP. This leads to the general conclusion that in sufficiently thick stratocumulus clouds, additional boundary layer growth and entrainment due to a boundary layer moistening arises by stronger production of TKE from latent heat release in cloud updrafts, rather than from enhanced longwave cooling. Here, we find that large-scale wind modulates boundary layer decoupling. At nighttime and at low wind speed during daytime, it enhances decoupling in part by faster boundary layer growth and stronger entrainment and in part because shear from large-scale wind in the sub-cloud layer hinders vertical moisture transport between the surface and cloud base. With increasing wind speed, however, in decoupled daytime conditions, shear-driven circulation due to large-scale wind takes over from

  7. Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations

    NASA Astrophysics Data System (ADS)

    Kazil, Jan; Feingold, Graham; Yamaguchi, Takanobu

    2016-05-01

    Observed and projected trends in large-scale wind speed over the oceans prompt the question: how do marine stratocumulus clouds and their radiative properties respond to changes in large-scale wind speed? Wind speed drives the surface fluxes of sensible heat, moisture, and momentum and thereby acts on cloud liquid water path (LWP) and cloud radiative properties. We present an investigation of the dynamical response of non-precipitating, overcast marine stratocumulus clouds to different wind speeds over the course of a diurnal cycle, all else equal. In cloud-system resolving simulations, we find that higher wind speed leads to faster boundary layer growth and stronger entrainment. The dynamical driver is enhanced buoyant production of turbulence kinetic energy (TKE) from latent heat release in cloud updrafts. LWP is enhanced during the night and in the morning at higher wind speed, and more strongly suppressed later in the day. Wind speed hence accentuates the diurnal LWP cycle by expanding the morning-afternoon contrast. The higher LWP at higher wind speed does not, however, enhance cloud top cooling because in clouds with LWP ⪆ 50 g m-2, longwave emissions are insensitive to LWP. This leads to the general conclusion that in sufficiently thick stratocumulus clouds, additional boundary layer growth and entrainment due to a boundary layer moistening arises by stronger production of TKE from latent heat release in cloud updrafts, rather than from enhanced longwave cooling. We find that large-scale wind modulates boundary layer decoupling. At nighttime and at low wind speed during daytime, it enhances decoupling in part by faster boundary layer growth and stronger entrainment and in part because shear from large-scale wind in the sub-cloud layer hinders vertical moisture transport between the surface and cloud base. With increasing wind speed, however, in decoupled daytime conditions, shear-driven circulation due to large-scale wind takes over from buoyancy

  8. Global measurements of sea surface temperature, wind speed and atmospheric water content from satellite microwave radiometry

    NASA Technical Reports Server (NTRS)

    Njoku, E. G.; Swanson, L.

    1983-01-01

    The Scanning Multichannel Microwave Radiometer (SMMR) was launched on the Seasat and Nimbus 7 satellites in 1978. The SMMR has the ability to measure sea surface temperature and wind speed with the aid of microwaves. In addition, the instrument was designed to measure water vapor and cloud liquid water with better spatial resolution than previous microwave radiometers, and to make sea-ice measurements with higher precision. A description is presented of the results of global analyses of sea surface temperature, wind speed, water vapor, and cloud liquid water, taking into account data provided by the SMMR on the Seasat satellite. It is found that the SMMR data show good self-consistency, and can usefully measure global distributions of sea surface temperatures, surface winds, water vapor, and cloud liquid water.

  9. High speed wind tunnel tests of the PTA aircraft. [Propfan Test Assessment Program

    NASA Technical Reports Server (NTRS)

    Aljabri, A. S.; Little, B. H., Jr.

    1986-01-01

    Propfans, advanced highly-loaded propellers, are proposed to power transport aircraft that cruise at high subsonic speeds, giving significant fuel savings over the equivalent turbofan-powered aircraft. NASA is currently sponsoring the Propfan Test Assessment Program (PTA) to provide basic data on the structural integrity and acoustic performance of the propfan. The program involves installation design, wind-tunnel tests, and flight tests of the Hamilton Standard SR-7 propfan in a wing-mount tractor installation on the Gulfstream II aircraft. This paper reports on the high-speed wind-tunnel tests and presents the computational aerodynamic methods that were employed in the analyses, design, and evaluation of the configuration. In spite of the complexity of the configuration, these methods provide aerodynamic predictions which are in excellent agreement with wind-tunnel data.

  10. Self streamlining wind tunnel: Further low speed testing and final design studies for the transonic facility

    NASA Technical Reports Server (NTRS)

    Wolf, S. W. D.

    1977-01-01

    Work has continued with the low speed self streamlining wind tunnel (SSWT) using the NACA 0012-64 airfoil in an effort to explain the discrepancies between the NASA Langley low turbulence pressure tunnel (LTPT) and SSWT results obtained with the airfoil stalled. Conventional wind tunnel corrections were applied to straight wall SSWT airfoil data, to illustrate the inadequacy of standard correction techniques in circumstances of high blockage. Also one SSWT test was re-run at different air speeds to investigate the effects of such changes on airfoil data and wall contours. Mechanical design analyses for the transonic self streamlining wind tunnel (TSWT) were completed by the application of theoretical airfoil flow field data to the elastic beam and streamline analysis. The control system for the transonic facility is outlined.

  11. Towards an improved wind speed scale and damage description adapted for Central Europe

    NASA Astrophysics Data System (ADS)

    Feuerstein, Bernold; Groenemeijer, Pieter; Dirksen, Erik; Hubrig, Martin; Holzer, Alois M.; Dotzek, Nikolai

    2011-06-01

    We propose an updated wind speed scale description adapted for Central Europe considering wind impact to buildings as well as to vegetation. The scale is motivated by the need of a broadly applicable, accurate and consistent tornado or downburst intensity rating system based on a standardised wind speed scale for the purpose of climatological homogeneity. The description comprises building and vegetation damage characteristics, which can be found in Central Europe - but similar in other parts of the world, occurring with the various classes of the Fujita- and T-scales. The scale description is supplemented by photographs of typical damage. For practical application, an ensemble-based use of a decision matrix for specific building structures and vegetation types is suggested.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  13. IPS observations at 140 MHz to study solar wind speeds and density fluctuations by MEXART

    NASA Astrophysics Data System (ADS)

    Chang, Oyuki; Gonzalez-Esparza, J. A.; Mejia-Ambriz, J.

    2016-03-01

    The interplanetary scintillation (IPS) technique is a remote-sensing method for monitoring the inner heliosphere. These observations supply information on solar wind conditions covering heliocentric ranges that no other technique can provide. The Mexican Array Radio Telescope (MEXART) is a single-station instrument operating at 140 MHz, fully dedicated to performing solar-wind studies employing the IPS technique. We present solar-wind parameters (scintillation indices and solar-wind speeds), using the initial measurements from this array of four IPS sources (3C273, 3C283, 3C286, 3C298) detected during October-December 2014. We report the transit of an IPS radio source (3C298), observed at 140 MHz, from weak- to strong-scattering regions at around 0.36 AU, and sky projection maps of solar wind conditions associated presumably with the passing of one or more Coronal Mass Ejections (CMEs). These results show the progress to operate the full array in the near future. The MEXART observations will complement the solar wind IPS studies using other frequencies, and the tracking of solar wind disturbances by other stations located at different longitudes. These solar wind measurements, provided in real time, can have space-weather forecasting applications.

  14. A control strategy for a variable-speed wind energy conversion system

    NASA Astrophysics Data System (ADS)

    Jacob, A.; Rajagopalan, V.; Veillette, D.

    1980-01-01

    In this article, a method of calculating an optimal control strategy for a variable-speed wind power generation scheme incorporating a squirrel cage induction machine and operating in a self-excited induction generator mode is discussed. This scheme also uses a conventional three-phase thyristor rectifier, a line-commutated inverter and an economical auxiliary commutated-voltage-source inverter. The three regulated variables are: (1) drive speed as a function of available mechanical energy by manipulating the resistive torque developed by induction generator; (2) induction motor power consumption during start-up of the wind machine of vertical axis type; (3) operating slip of the induction machine, thereby limiting start-up and braking currents. The developed strategy is also suitable for any other variable-speed drive system incorporating an induction machine.

  15. Solar wind suprathermal electron Stahl widths across high-speed stream structures

    SciTech Connect

    Skoug, Ruth M; Steinberg, John T; Goodrich, Katherine A; Anderson, Brett R

    2011-01-03

    Suprathermal electrons (100-1500 eV) observed in the solar wind typically show a strahl distribution, that is, a beam directed away from the Sun along the magnetic field direction. The strahl width observed at 1 AU is highly variable, ranging from 10-70 degrees. The obsenred finite width of the strahl results from the competition between beam focusing as the interplanetary magnetic field strength drops with distance from the Sun, and pitch-angle scattering as the beam interacts with the solar wind plasma in transit from the sun. Here we examine strahl width, observed with ACE SWEPAM across high-speed stream structures to investigate variations in electron scattering as a function of local plasma characteristics. We find that narrow strahls (less than 20 degrees wide), indicating reduced scattering, are observed within high-speed streams. Narrow strahls are also observed in both very low temperature solar wind, in association with ICMEs. Case studies of high-speed streams typically show the strahl narrowing at the leading edge of the stream. In some cases, the strahl narrows at the reverse shock or pressure wave, in other cases at the stream interface. The narrowing can either occur discontinuously or gradually over a period of hours. Within the high-speed wind, the strahl remains narrow for a period of hours to days, and then gradually broadens. The strahl width is roughly constant at all energies across these structures. For some fraction of high-speed streams, counterstreaming is associated with passage of the corotating interaction region. In these cases, we find the widths of the two counterstreaming beams frequently differ by more than 40 degrees. This dramatic difference in strahl width contrasts with observations in the solar wind as a whole, in which counterstreaming strahls typically differ in width by less than 20 degrees.

  16. A level 2 wind speed retrieval algorithm for the CYGNSS mission

    NASA Astrophysics Data System (ADS)

    Clarizia, Maria Paola; Ruf, Christopher; O'Brien, Andrew; Gleason, Scott

    2014-05-01

    The NASA EV-2 Cyclone Global Navigation Satellite System (CYGNSS) is a spaceborne mission focused on tropical cyclone (TC) inner core process studies. CYGNSS consists of a constellation of 8 microsatellites, which will measure ocean surface wind speed in all precipitating conditions, including those experienced in the TC eyewall, and with sufficient frequency to resolve genesis and rapid intensification. It does so through the use of an innovative remote sensing technique, known as Global Navigation Satellite System-Reflectometry, or GNSS-R. GNSS-R uses signals of opportunity from navigation constellations (e.g. GPS, GLONASS, Galileo), scattered by the surface of the ocean, to retrieve the surface wind speed. The dense space-time sampling capabilities, the ability of L-band signals to penetrate well through rain, and the possibility of simple, low-cost/low-power GNSS receivers, make GNSS-R ideal for the CYGNSS goals. Here we present an overview of a Level 2 (L2) wind speed retrieval algorithm, which would be particularly suitable for CYGNSS, and could be used to estimate winds from GNSS-R in general. The approach makes use of two different observables computed from 1-second Level 2a (L2a) delay-Doppler Maps (DDMs) of radar cross section. The first observable is called Delay-Doppler Map Average (DDMA), and it's the averaged radar cross section over a delay-Doppler window around the DDM peak (i.e. the specular reflection point coordinate in delay and Doppler). The second is called the Leading Edge Slope (LES), and it's the leading edge of the Integrated Delay Waveform (IDW), obtained by integrating the DDM along the Doppler dimension. The observables are calculated over a limited range of delays and Doppler frequencies, to comply with baseline spatial resolution requirements for the retrieved winds, which in the case of CYGNSS is 25 km x 25 km. If the observable from the 1-second DDM corresponds to a resolution higher than the specified one, time-averaging between

  17. Nature and Variability of Coronal Streamers and their Relationship to the Slow Speed Wind

    NASA Technical Reports Server (NTRS)

    Strachan, Leonard

    2005-01-01

    NASA Grant NAG5-12781 is a study on the "Nature and Variability of Coronal Streamers and their Relationship to the Slow Speed Wind." The two main goals of this study are to identify: 1) Where in the streamer structure does the solar wind originate, and 2) What coronal conditions are responsible for the variability of the slow speed wind. To answer the first question, we examined the mostly closed magnetic field regions in streamer cores to search for evidence of outflow. Preliminary results from the OVI Doppler dimming ratios indicates that most of the flow originates from the edges of coronal streamers but this idea should be confirmed by a comparison of the coronal plasma properties with in situ solar wind data. To answer the second question, the work performed thus far suggests that solar minimum streamers have larger perpendicular velocity distributions than do solar maximum streamers. If it can be shown that solar minimum streamers also produce higher solar wind speeds then this would suggest that streamers and coronal holes have similar solar wind acceleration mechanisms. The key to both questions lie in the analysis of the in situ solar wind data sets. This work was not able to be completed during the period of performance and therefore the grant was formally extended for an additional year at no cost to NASA. We hope to have final results and a publication by the end of the calendar year 2004. The SAO personnel involved in the research are Leonard Strachan (PI), Mari Paz Miralles, Alexander Panasyuk, and a Southern University student Michael Baham.

  18. Modified GIT model for predicting wind-speed behavior of low-grazing-angle radar sea clutter

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Shi; Zhang, Jin-Peng; Li, Xin; Wu, Zhen-Sen

    2014-10-01

    A modified GIT model for describing the variational trend of mean clutter reflectivity as a function of wind speed is proposed. It uses two slope adjustment factors and two critical wind-speed factors to define and adjust the increasing slope of reflectivity with respect to wind speed. In addition, it uses a constant factor to compensate the overall amplitude of clutter reflectivity. The performance of the modified GIT model has been verified on the basis of the L-band low-grazing-angle radar sea clutter data. The results are in good agreement with the experimental data, indicating that the model is more effective in predicting the wind-speed behavior of clutter reflectivity than the conventional GIT model, especially for lower and higher wind speeds. We believe that the proposed model can provide deeper insights into the relationship between radar sea clutter reflectivity and sea state conditions.

  19. Application of stochastic methods for wind speed forecasting and wind turbines design at the area of Thessaly, Greece

    NASA Astrophysics Data System (ADS)

    Dimitriadis, Panayiotis; Lazaros, Lappas; Daskalou, Olympia; Filippidou, Ariadni; Giannakou, Marianna; Gkova, Eleni; Ioannidis, Romanos; Polydera, Angeliki; Polymerou, Eleni; Psarrou, Eleftheria; Vyrini, Alexandra; Papalexiou, Simon; Koutsoyiannis, Demetris

    2015-04-01

    Several methods exist for estimating the statistical properties of wind speed, most of them being deterministic or probabilistic, disregarding though its long-term behaviour. Here, we focus on the stochastic nature of wind. After analyzing several historical timeseries at the area of interest (AoI) in Thessaly (Greece), we show that a Hurst-Kolmogorov (HK) behaviour is apparent. Thus, disregarding the latter could lead to unrealistic predictions and wind load situations, causing some impact on the energy production and management. Moreover, we construct a stochastic model capable of preserving the HK behaviour and we produce synthetic timeseries using a Monte-Carlo approach to estimate the future wind loads in the AoI. Finally, we identify the appropriate types of wind turbines for the AoI (based on the IEC 61400 standards) and propose several industrial solutions. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.

  20. Ulysses observations of a recurrent high speed solar wind stream and the heliomagnetic streamer belt

    NASA Technical Reports Server (NTRS)

    Bame, S. J.; Goldstein, B. E.; Gosling, J. T.; Harvey, J. W.; Mccomas, D. J.; Neugebauer, M.; Phillips, J. L.

    1993-01-01

    Near-ecliptic solar wind observations by Ulysses on its way to the polar regions of the Sun, compared with those from IMP 8 at 1 AU, showed that high-speed streams decay and broaden with heliocentric distance from IMP 8 to Ulysses, as expected. In July 1992 while traveling south at approximately 13 deg S and 5.3 AU, Ulysses encountered a recurrent high-speed stream, that may also have been observed at IMP 8. The stream has been observed a total of 14 times, once in each solar rotation through June 1993 at approximately 34 deg S. The source of the high-speed stream is an equatorward extension of the south polar coronal hole. From July 1992 through June 1993, averages of solar wind peak speed increased while density decreased with heliographic latitude. Both the stream and a low-speed, high-density flow, presumably associated with the heliomagnetic (coronal) streamer belt encircling the heliomagnetic equator, crossed Ulysses with the solar rotation period until April 1993 when the spacecraft was at approximately 29 deg S heliographic latitude. After this time, as the spacecraft climbed to higher latitudes, the central portion of the streamer belt with lowest speed and highest density disappeared. Therefore, at its maximum inclination, the belt was tilted at approximately 29 deg to the heliographic equator at this point in the solar cycle.

  1. Power Spectral Density of Fluctuations of Bulk and Thermal Speeds in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Šafránková, J.; Němeček, Z.; Němec, F.; Přech, L.; Chen, C. H. K.; Zastenker, G. N.

    2016-07-01

    This paper analyzes solar wind power spectra of bulk and thermal speed fluctuations that are computed with a time resolution of 32 ms in the frequency range of 0.001–2 Hz. The analysis uses measurements of the Bright Monitor of the Solar Wind on board the Spektr-R spacecraft that are limited to 570 km s‑1 bulk speed. The statistics, based on more than 42,000 individual spectra, show that: (1) the spectra of bulk and thermal speeds can be fitted by two power-law segments; (2) despite their large variations, the parameters characterizing frequency spectrum fits computed on each particular time interval are very similar for both quantities; (3) the median slopes of the bulk and thermal speeds of the segment attributed to the MHD scale are ‑1.43 and ‑1.38, respectively, whereas they are ‑3.08 and ‑2.43 in the kinetic range; (4) the kinetic range slopes of bulk and thermal speed spectra become equal when either the ion density or magnetic field strength are high; (5) the break between MHD and kinetic scales seems to be controlled by the ion β parameter; (6) the best scaling parameter for bulk and thermal speed variations is a sum of the inertial length and proton thermal gyroradius; and (7) the above conclusions can be applied to the density variations if the background magnetic field is very low.

  2. Ulysses observations of a recurrent high speed solar wind stream and the heliomagnetic streamer belt

    SciTech Connect

    Bame, S.J.; Gosling, J.T.; McComas, D.J.; Phillips, J.L. ); Goldstein, B.E.; Neugebauer, M. ); Harvey, J.W.

    1993-11-05

    Near-ecliptic solar wind observations by Ulysses on its way to the polar regions of the Sun, compared with those from IMP 8 at 1 AU, showed that high-speed streams decay and broaden with heliocentric distance from IMP 8 to Ulysses, as expected. In July 1992 while travelling south at [approximately]13[degrees]S and 5.3 AU, Ulysses encountered a recurrent high-speed stream, that may also have been observed at IMP 8. The stream has been observed a total of 14 times, once in each solar rotation through June 1993 at [approximately]34[degrees]S. The source of the high-speed stream is an equatorward extension of the south polar coronal hole. From July 1992 through June 1993, averages of solar wind peak speed increased while density decreased with heliographic latitude. Both the stream and a low-speed, high-density flow, presumably associated with the heliomagnetic (coronal) streamer belt encircling the heliomagnetic equator, crossed Ulysses with the solar rotation period until April 1993 when the spacecraft was at [approximately]29[degrees]S heliographic latitude. After this time, as the spacecraft climbed to higher latitudes, the central portion of the streamer belt with lowest speed and highest density disappeared. Therefore, at its maximum inclination, the belt was tilted at [approximately]29[degrees] to the heliographic equator at this point in the solar cycle. 11 refs., 5 figs.

  3. Experimental investigation of aerodynamic devices for wind turbine rotational speed control. Phase 1

    SciTech Connect

    Miller, L.S.

    1995-02-01

    An investigation was undertaken to identify the aerodynamic performance of five separate trailing-edge control devices, and to evaluate their potential for wind turbine overspeed and power modulation applications. A modular two-dimensional wind tunnel model was constructed and evaluated during extensive wind tunnel testing. Aerodynamic lift, drag, suction, and pressure coefficient data were acquired and analyzed for various control configurations and angles of attack. To further interpret their potential performance, the controls were evaluated numerically using a generic wind turbine geometry and a performance analysis computer program. Results indicated that the Spoiler-Flap control configuration was best softed for turbine braking applications. It exhibited a large negative suction coefficient over a broad angle-of-attack range, and good turbine braking capabilities, especially at low tip-speed ratio.

  4. Multisensor satellite data integration for sea surface wind speed and direction determination

    NASA Technical Reports Server (NTRS)

    Glackin, D. L.; Pihos, G. G.; Wheelock, S. L.

    1984-01-01

    Techniques to integrate meteorological data from various satellite sensors to yield a global measure of sea surface wind speed and direction for input to the Navy's operational weather forecast models were investigated. The sensors were launched or will be launched, specifically the GOES visible and infrared imaging sensor, the Nimbus-7 SMMR, and the DMSP SSM/I instrument. An algorithm for the extrapolation to the sea surface of wind directions as derived from successive GOES cloud images was developed. This wind veering algorithm is relatively simple, accounts for the major physical variables, and seems to represent the best solution that can be found with existing data. An algorithm for the interpolation of the scattered observed data to a common geographical grid was implemented. The algorithm is based on a combination of inverse distance weighting and trend surface fitting, and is suited to combing wind data from disparate sources.

  5. A wave tank study of the dependence of X band cross sections on wind speed and water temperature

    NASA Technical Reports Server (NTRS)

    Keller, Mary Ruth; Keller, William C.; Plant, William J.

    1992-01-01

    The effects of varying the water temperature, wind speed, and wind stress on the values of backscatter were investigated using measurements of normalized radar cross sections of wind-generated waves, made at X band for both vertical and horizontal polarization for incidence angles 10, 28, 48, and 68 deg. The experiment was conducted using the Naval Research Laboratory wind-wave tank. Measurements made for a wide range of wind speeds and water temperatures are compared with results of backscattering models currently in use.

  6. Investigation of load reduction for a variable speed, variable pitch, and variable coning wind turbine

    SciTech Connect

    Pierce, K.

    1997-12-31

    A two bladed, variable speed and variable pitch wind turbine was modeled using ADAMS{reg_sign} to evaluate load reduction abilities of a variable coning configuration as compared to a teetered rotor, and also to evaluate control methods. The basic dynamic behavior of the variable coning turbine was investigated and compared to the teetered rotor under constant wind conditions as well as turbulent wind conditions. Results indicate the variable coning rotor has larger flap oscillation amplitudes and much lower root flap bending moments than the teetered rotor. Three methods of control were evaluated for turbulent wind simulations. These were a standard IPD control method, a generalized predictive control method, and a bias estimate control method. Each control method was evaluated for both the variable coning configuration and the teetered configuration. The ability of the different control methods to maintain the rotor speed near the desired set point is evaluated from the RMS error of rotor speed. The activity of the control system is evaluated from cycles per second of the blade pitch angle. All three of the methods were found to produce similar results for the variable coning rotor and the teetered rotor, as well as similar results to each other.

  7. On the Origin of the Slow Speed Solar Wind: Helium Abundance Variations

    NASA Astrophysics Data System (ADS)

    Rakowski, Cara E.; Laming, J. Martin

    2012-07-01

    The first ionization potential (FIP) effect is the by now well-known enhancement in abundance over photospheric values of Fe and other elements with FIP below about 10 eV observed in the solar corona and slow speed solar wind. In our model, this fractionation is achieved by means of the ponderomotive force, arising as Alfvén waves propagate through or reflect from steep density gradients in the solar chromosphere. This is also the region where low FIP elements are ionized, and high FIP elements are largely neutral leading to the fractionation as ions interact with the waves but neutrals do not. Helium, the element with the highest FIP and consequently the last to remain neutral as one moves upward, can be depleted in such models. Here, we investigate this depletion for varying loop lengths and magnetic field strengths. Variations in this depletion arise as the concentration of the ponderomotive force at the top of the chromosphere varies in response to Alfvén wave frequency with respect to the resonant frequency of the overlying coronal loop, the magnetic field, and possibly also the loop length. We find that stronger depletions of He are obtained for weaker magnetic field, at frequencies close to or just above the loop resonance. These results may have relevance to observed variations of the slow wind solar He abundance with wind speed, with slower slow speed solar wind having a stronger depletion of He.

  8. Performance of Steady-State Dispersion Models Under Low Wind-Speed Conditions

    NASA Astrophysics Data System (ADS)

    Qian, Wenjun; Venkatram, Akula

    2011-03-01

    We examine the performance of two steady-state models, a numerical solution of the advection-diffusion equation and the Gaussian plume-model-based AERMOD (the American Meteorological Society/Environmental Protection Agency Regulatory Model), to predict dispersion for surface releases under low wind-speed conditions. A comparison of model estimates with observations from two tracer studies, the Prairie Grass experiment and the Idaho Falls experiment indicates that about 50% of the concentration estimates are within a factor of two of the observations, but the scatter is large: the 95% confidence interval of the ratio of the observed to estimated concentrations is about 4. The model based on the numerical solution of the diffusion equation in combination with the model of Eckman (1994, Atmos Environ 28:265-272) for horizontal spread performs better than AERMOD in explaining the observations. Accounting for meandering of the wind reduces some of the overestimation of concentrations at low wind speeds. The results deteriorate when routine one-level observations are used to construct model inputs. An empirical modification to the similarity estimate of the surface friction velocity reduces the underestimation at low wind speeds.

  9. Direct Adaptive Control of Utility-Scale Wind Turbine for Speed Regulation

    SciTech Connect

    Frost, S. A.; Balas, M. J.; Wright, A. D.

    2009-01-01

    The accurate modeling of wind turbines is an extremely challenging problem due to the tremendous complexity of the machines and the turbulent and unpredictable conditions in which they operate. Adaptive control techniques are well suited to nonlinear applications, such as wind turbines, which are difficult to accurately model and which have effects from poorly known operating environments. In this paper, we extended the direct model reference adaptive control (DMRAC) approach to track a reference point and to reject persistent disturbances. This approach was then used to design an adaptive collective pitch controller for a high-fidelity simulation of a variable-speed horizontal axis wind turbine. The objective of the adaptive pitch controller was to regulate generator speed in Region 3 and to reject step disturbances. The control objective was accomplished by collectively pitching the turbine blades. The turbine simulation models the controls advanced research turbine (CART) of the National Renewable Energy Laboratory in Golden, Colorado. The CART is a utility-scale wind turbine that has a well-developed and extensively verified simulator. This novel application of adaptive control was compared in simulations with a classical proportional integrator (PI) collective pitch controller. In the simulations, the adaptive pitch controller showed improved speed regulation in Region 3 when compared with the PI pitch controller.

  10. ON THE ORIGIN OF THE SLOW SPEED SOLAR WIND: HELIUM ABUNDANCE VARIATIONS

    SciTech Connect

    Rakowski, Cara E.; Laming, J. Martin

    2012-07-20

    The first ionization potential (FIP) effect is the by now well-known enhancement in abundance over photospheric values of Fe and other elements with FIP below about 10 eV observed in the solar corona and slow speed solar wind. In our model, this fractionation is achieved by means of the ponderomotive force, arising as Alfven waves propagate through or reflect from steep density gradients in the solar chromosphere. This is also the region where low FIP elements are ionized, and high FIP elements are largely neutral leading to the fractionation as ions interact with the waves but neutrals do not. Helium, the element with the highest FIP and consequently the last to remain neutral as one moves upward, can be depleted in such models. Here, we investigate this depletion for varying loop lengths and magnetic field strengths. Variations in this depletion arise as the concentration of the ponderomotive force at the top of the chromosphere varies in response to Alfven wave frequency with respect to the resonant frequency of the overlying coronal loop, the magnetic field, and possibly also the loop length. We find that stronger depletions of He are obtained for weaker magnetic field, at frequencies close to or just above the loop resonance. These results may have relevance to observed variations of the slow wind solar He abundance with wind speed, with slower slow speed solar wind having a stronger depletion of He.

  11. The effect of tip speed ratio on a vertical axis wind turbine at high Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Parker, Colin M.; Leftwich, Megan C.

    2016-05-01

    This work visualizes the flow surrounding a scaled model vertical axis wind turbine at realistic operating conditions. The model closely matches geometric and dynamic properties—tip speed ratio and Reynolds number—of a full-size turbine. The flow is visualized using particle imaging velocimetry (PIV) in the midplane upstream, around, and after (up to 4 turbine diameters downstream) the turbine, as well as a vertical plane behind the turbine. Time-averaged results show an asymmetric wake behind the turbine, regardless of tip speed ratio, with a larger velocity deficit for a higher tip speed ratio. For the higher tip speed ratio, an area of averaged flow reversal is present with a maximum reverse flow of -0.04U_∞. Phase-averaged vorticity fields—achieved by syncing the PIV system with the rotation of the turbine—show distinct structures form from each turbine blade. There were distinct differences in results by tip speed ratios of 0.9, 1.3, and 2.2 of when in the cycle structures are shed into the wake—switching from two pairs to a single pair of vortices being shed—and how they convect into the wake—the middle tip speed ratio vortices convect downstream inside the wake, while the high tip speed ratio pair is shed into the shear layer of the wake. Finally, results show that the wake structure is much more sensitive to changes in tip speed ratio than to changes in Reynolds number.

  12. Using Daily Ocean Wind Vector and Speed Measurements to Estimate the Diurnal Cycle Modes

    NASA Astrophysics Data System (ADS)

    Turk, F. J.; Hristova-Veleva, S. M.; Haddad, Z. S.

    2014-12-01

    Over many oceanic regions, the surface wind varies widely throughout the day, owing to various meteorological forcings, such as land/sea temperature differences near coasts, or variations associated with tropical precipitation processes. Over the tropical oceans, several coarsely spaced buoy networks (TAO/TRITON in the Pacific, PIRATA in the Atlantic, RAMA in the Indian Ocean) are maintained as part of the Global Tropical Moored Buoy Array. For finer global scale analysis, further improvements to the modeling and understanding of physical processes within the coupled atmosphere ocean is based upon analysis of a disparate collection of low Earth orbiting (LEO) satellite based ocean surface wind data records. Since LEO satellite observations represent intermittently spaced, instantaneous snapshots, sampling against the backdrop of continuously changing physical processes, its is important to carefully merge and analyze the multiple satellite datasets in order to extract meaningful information on diurnal and semi-diurnal wind cycles. Early analysis of an investigation are described whereby multi-year collections of global sun-synchronous and asynchronous orbiting satellite ocean wind data are used to investigate the diurnal and semi-diurnal ocean wind vector variability over certain regions. A unique feature of the effort is the utilization of all capable sensors, including both wind speed and wind vector capable sensors, using overlapping asynchronous satellite observations to establish self-consistency, including inter-sensor bias correction to a common reference platform.

  13. Statistical Short-Range Guidance for Peak Wind Speed Forecasts at Edwards Air Force Base, CA

    NASA Technical Reports Server (NTRS)

    Dreher, Joseph G.; Crawford, Winifred; Lafosse, Richard; Hoeth, Brian; Burns, Kerry

    2009-01-01

    The peak winds near the surface are an important forecast element for space shuttle landings. As defined in the Flight Rules (FR), there are peak wind thresholds that cannot be exceeded in order to ensure the safety of the shuttle during landing operations. The National Weather Service Spaceflight Meteorology Group (SMG) is responsible for weather forecasts for all shuttle landings, and is required to issue surface average and 10-minute peak wind speed forecasts. They indicate peak winds are a challenging parameter to forecast. To alleviate the difficulty in making such wind forecasts, the Applied Meteorology Unit (AMU) developed a PC-based graphical user interface (GUI) for displaying peak wind climatology and probabilities of exceeding peak wind thresholds for the Shuttle Landing Facility (SLF) at Kennedy Space Center (KSC; Lambert 2003). However, the shuttle occasionally may land at Edwards Air Force Base (EAFB) in southern California when weather conditions at KSC in Florida are not acceptable, so SMG forecasters requested a similar tool be developed for EAFB.

  14. Pose measurement method and experiments for high-speed rolling targets in a wind tunnel.

    PubMed

    Jia, Zhenyuan; Ma, Xin; Liu, Wei; Lu, Wenbo; Li, Xiao; Chen, Ling; Wang, Zhengqu; Cui, Xiaochun

    2014-01-01

    High-precision wind tunnel simulation tests play an important role in aircraft design and manufacture. In this study, a high-speed pose vision measurement method is proposed for high-speed and rolling targets in a supersonic wind tunnel. To obtain images with high signal-to-noise ratio and avoid impacts on the aerodynamic shape of the rolling targets, a high-speed image acquisition method based on ultrathin retro-reflection markers is presented. Since markers are small-sized and some of them may be lost when the target is rolling, a novel markers layout with which markers are distributed evenly on the surface is proposed based on a spatial coding method to achieve highly accurate pose information. Additionally, a pose acquisition is carried out according to the mentioned markers layout after removing mismatching points by Case Deletion Diagnostics. Finally, experiments on measuring the pose parameters of high-speed targets in the laboratory and in a supersonic wind tunnel are conducted to verify the feasibility and effectiveness of the proposed method. Experimental results indicate that the position measurement precision is less than 0.16 mm, the pitching and yaw angle precision less than 0.132° and the roll angle precision 0.712°. PMID:25615732

  15. Pose Measurement Method and Experiments for High-Speed Rolling Targets in a Wind Tunnel

    PubMed Central

    Jia, Zhenyuan; Ma, Xin; Liu, Wei; Lu, Wenbo; Li, Xiao; Chen, Ling; Wang, Zhengqu; Cui, Xiaochun

    2014-01-01

    High-precision wind tunnel simulation tests play an important role in aircraft design and manufacture. In this study, a high-speed pose vision measurement method is proposed for high-speed and rolling targets in a supersonic wind tunnel. To obtain images with high signal-to-noise ratio and avoid impacts on the aerodynamic shape of the rolling targets, a high-speed image acquisition method based on ultrathin retro-reflection markers is presented. Since markers are small-sized and some of them may be lost when the target is rolling, a novel markers layout with which markers are distributed evenly on the surface is proposed based on a spatial coding method to achieve highly accurate pose information. Additionally, a pose acquisition is carried out according to the mentioned markers layout after removing mismatching points by Case Deletion Diagnostics. Finally, experiments on measuring the pose parameters of high-speed targets in the laboratory and in a supersonic wind tunnel are conducted to verify the feasibility and effectiveness of the proposed method. Experimental results indicate that the position measurement precision is less than 0.16 mm, the pitching and yaw angle precision less than 0.132° and the roll angle precision 0.712°. PMID:25615732

  16. Solar wind-magnetosphere coupling leading to relativistic electron energization during high-speed streams

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Lee, D.-Y.; Thorne, R. M.; Horne, R. B.; Smith, A. J.

    2005-11-01

    Enhancements in relativistic electron fluxes in the outer radiation belt often occur following magnetic storms and have been suggested to result from resonant interactions with enhanced whistler-mode chorus emissions observed on the dawnside. Using observations during a period of persistent high-speed, corotating, solar wind streams, we investigate the aspects of solar wind-magnetosphere coupling that lead to these enhanced chorus emissions. We find that relativistic electron energization occurs in association with large-amplitude Alfvén waves within the high-speed streams. These waves last for multiday periods and cause multiday intervals having intermittent periods of significantly enhanced convection. The enhanced convection periods are followed by repetitive substorm onsets caused by the Alfvén wave related repetitive reductions in convection. We use these substorm onsets, identified using geosynchronous particles and midlatitude H components, as indicators of preceding periods of enhanced convection and of reductions in convection. We use ground-based chorus observations from the Halley station VLF/ELF Logger Experiment (VELOX) instrument to indicate magnetospheric chorus intensities. These data give evidence that the periods of enhanced convection that precede substorm expansions lead to the enhanced dawnside chorus wave. We also see that the enhanced solar wind densities nsw ahead of high-speed streams are associated with significant energetic electron loss at geosynchronous orbit and that the subsequent flux increases appear to not begin until nsw drops below ˜5 cm-3 even if the solar wind speed increases earlier. The sequence of loss during the leading interval of high nsw, followed by energization during high-speed streams, occurs whether or not the high nsw interval leads to a magnetic storm.

  17. Solar wind iron abundance variations at solar wind speeds up to 600 km s sup -1, 1972 to 1976

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    The Fe/H ratios in the peaks of high speed streams (HSS) were analyzed during the decline of Solar Cycle 20 and the following minimum (October 1972 to December 1976). The response of the 50 to 200 keV ion channel of the APL/JHU energetic particle experiment (EPE) on IMP-7 and 8 was utilized to solar wind iron ions at high solar wind speeds (V or = 600 km/sec). Fe measurements with solar wind H and He parameters were compared from the Los Alamos National Laboratory (LANL) instruments on the same spacecraft. In general, the Fe distribution parameters (bulk velocity, flow direction, temperature) are found to be similar to the LANL He parameters. Although the average Fe/H ration in many steady HSS peaks agrees within observational uncertainties with the nominal coronal ratio of 4.7 x 0.00001, abundance variations of a factor of up to 6 are obtained across a given coronal-hole associated HSS.

  18. Electron heating within interaction zones of simple high-speed solar wind streams

    NASA Technical Reports Server (NTRS)

    Feldman, W. C.; Asbridge, J. R.; Bame, S. J.; Gosling, J. T.; Lemons, D. S.

    1978-01-01

    In the present paper, electron heating within the high-speed portions of three simple stream-stream interaction zones is studied to further our understanding of the physics of heat flux regulation in interplanetary space. To this end, the thermal signals present in the compressions at the leading edges of the simple high-speed streams are analyzed, showing that the data are inconsistent with the Spitzer conductivity. Instead, a polynomial law is found to apply. Its implication concerning the mechanism of interplanetary heat conduction is discussed, and the results of applying this conductivity law to high-speed flows inside of 1 AU are studied. A self-consistent model of the radial evolution of electrons in the high-speed solar wind is proposed.

  19. Initial investigations of transonic turbine aerodynamics using the Carleton University High-Speed Wind Tunnel

    NASA Astrophysics Data System (ADS)

    Jeffries, Michael Scott

    In recent years, Carleton University has been commissioning a high-speed blow down wind tunnel. The wind tunnel was commissioned to support on-going axial turbine research efforts and to provide a facility for transonic turbine cascade research. Much effort has been made at Carleton to investigate the performance of axial turbines at off-design conditions and to develop correlations to be used for predicting turbine off-design performance. The current study was a contribution to the off-design work being done at Carleton. This thesis describes the first transonic turbine cascade study conducted using the Carleton University High-Speed Wind Tunnel. To document the Carleton wind tunnel capabilities, cascade measurements were taken and compared to four European wind tunnels using the same cascade at equivalent conditions. The development of experimental procedures used at Carleton and estimates of measurement uncertainties are also presented in this text. Measurements at off-design incidences were made using a transonic turbine cascade to increase the body of published data on off-design turbine performance.

  20. Impedance seen by Distance Relays on Lines Fed from Fixed Speed Wind Turbines

    NASA Astrophysics Data System (ADS)

    Srivastava, Sachin; Shenoy, U. J.; Chandra Biswal, Abhinna; Sethuraman, Ganesan

    2013-05-01

    This paper deals with line protection challenges experienced in a system having substantial wind generation penetration. Two types of generators, thermal synchronous generators and fixed speed wind turbines based on squirrel-cage induction generators, are simulated as thevenin equivalent model, connected to grid with single-circuit transmission line. The paper gives comparative discussion and summarizes analytical investigations carried out on the impedance seen by distance relays by varying fault resistances and grid short circuit MVA, for the protection of such transmission lines during faults.

  1. An Analysis of Peak Wind Speed Data from Collocated Mechanical and Ultrasonic Anemometers

    NASA Technical Reports Server (NTRS)

    Short, David A.; Wells, Leonard; Merceret, Francis J.; Roeder, William P.

    2007-01-01

    This study compared peak wind speeds reported by mechanical and ultrasonic anemometers at Cape Canaveral Air Force Station and Kennedy Space Center (CCAFS/KSC) on the east central coast of Florida and Vandenberg Air Force Base (VAFB) on the central coast of California. Launch Weather Officers, forecasters, and Range Safety analysts need to understand the performance of wind sensors at CCAFS/KSC and VAFB for weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The legacy CCAFS/KSC and VAFB weather tower wind instruments are being changed from propeller-and-vane (CCAFS/KSC) and cup-and-vane (VAFB) sensors to ultrasonic sensors under the Range Standardization and Automation (RSA) program. Mechanical and ultrasonic wind measuring techniques are known to cause differences in the statistics of peak wind speed as shown in previous studies. The 45th Weather Squadron (45 WS) and the 30th Weather Squadron (30 WS) requested the Applied Meteorology Unit (AMU) to compare data between the RSA ultrasonic and legacy mechanical sensors to determine if there are significant differences. Note that the instruments were sited outdoors under naturally varying conditions and that this comparison was not designed to verify either technology. Approximately 3 weeks of mechanical and ultrasonic wind data from each range from May and June 2005 were used in this study. The CCAFS/KSC data spanned the full diurnal cycle, while the VAFB data were confined to 1000-1600 local time. The sample of 1-minute data from numerous levels on five different towers on each range totaled more than 500,000 minutes of data (482,979 minutes of data after quality control). The ten towers were instrumented at several levels, ranging from 12 ft to 492 ft above ground level. The ultrasonic sensors were collocated at the same vertical levels as the mechanical sensors and

  2. Solar Wind Helium Abundance as a Function of Speed and Heliographic Latitude: Variation through a Solar Cycle

    NASA Technical Reports Server (NTRS)

    Kasper, J. C.; Stenens, M. L.; Stevens, M. L.; Lazarus, A. J.; Steinberg, J. T.; Ogilvie, Keith W.

    2006-01-01

    We present a study of the variation of the relative abundance of helium to hydrogen in the solar wind as a function of solar wind speed and heliographic latitude over the previous solar cycle. The average values of A(sub He), the ratio of helium to hydrogen number densities, are calculated in 25 speed intervals over 27-day Carrington rotations using Faraday Cup observations from the Wind spacecraft between 1995 and 2005. The higher speed and time resolution of this study compared to an earlier work with the Wind observations has led to the discovery of three new aspects of A(sub He), modulation during solar minimum from mid-1995 to mid-1997. First, we find that for solar wind speeds between 350 and 415 km/s, A(sub He), varies with a clear six-month periodicity, with a minimum value at the heliographic equatorial plane and a typical gradient of 0.01 per degree in latitude. For the slow wind this is a 30% effect. We suggest that the latitudinal gradient may be due to an additional dependence of coronal proton flux on coronal field strength or the stability of coronal loops. Second, once the gradient is subtracted, we find that A(sub He), is a remarkably linear function of solar wind speed. Finally, we identify a vanishing speed, at which A(sub He), is zero, is 259 km/s and note that this speed corresponds to the minimum solar wind speed observed at one AU. The vanishing speed may be related to previous theoretical work in which enhancements of coronal helium lead to stagnation of the escaping proton flux. During solar maximum the A(sub He), dependences on speed and latitude disappear, and we interpret this as evidence of two source regions for slow solar wind in the ecliptic plane, one being the solar minimum streamer belt and the other likely being active regions.

  3. Orbiting observatory SOHO finds source of high-speed "wind" blowing from the Sun

    NASA Astrophysics Data System (ADS)

    1999-02-01

    "The search for the source of the solar wind has been like the hunt for the source of the Nile," said Dr. Don Hassler of the Southwest Research Institute, Boulder, Colorado, lead author of the paper in Science. "For 30 years, scientists have observed high-speed solar wind coming from regions in the solar atmosphere with open magnetic field lines, called coronal holes. However, only recently, with the observations from SOHO, have we been able to measure the detailed structure of this source region". The solar wind comes in two varieties : high-speed and low-speed. The low-speed solar wind moves at "only" 1.5 million kilometres per hour, while the high-speed wind is even faster, moving at speeds as high as 3 million kilometres per hour. As it flows past Earth, the solar wind changes the shape and structure of the Earth's magnetic field. In the past, the solar wind didn't affect us directly, but as we become increasingly dependent on advanced technology, we become more susceptible to its effects. Researchers are learning that variations in the solar wind flow can cause dramatic changes in the shape of the Earth's magnetic field, which can damage satellites and disrupt communications and electrical power systems. The nature and origin of the solar wind is one of the main mysteries ESA's solar observatory SOHO was designed to solve. It has long been thought that the solar wind flows from coronal holes; what is new is the discovery that these outflows are concentrated in specific patches at the edges of the honeycomb-shaped magnetic fields. Just below the surface of the Sun there are large convection cells, and each cell has a magnetic field associated with it. "If one thinks of these cells as paving stones in a patio, then the solar wind is breaking through like grass around the edges, concentrated in the corners where the paving stones meet", said Dr. Helen Mason, University of Cambridge, England, and co-author of the paper to appear in Science. "However, at speeds

  4. Low-speed wind tunnel performance of high-speed counterrotation propellers at angle-of-attack

    NASA Technical Reports Server (NTRS)

    Hughes, Christopher E.; Gazzaniga, John A.

    1989-01-01

    The low-speed aerodynamic performance characteristics of two advanced counterrotation pusher-propeller configurations with cruise design Mach numbers of 0.72 were investigated in the NASA Lewis 9- by 15-Foot Low-Speed Wind Tunnel. The tests were conducted at Mach number 0.20, which is representative of the aircraft take/off/landing flight regime. The investigation determined the effect of nonuniform inflow on the propeller performance characteristics for several blade angle settings and a range of rotational speeds. The inflow was varied by yawing the propeller mode to angle-of-attack by as much as plus or minus 16 degrees and by installing on the counterrotation propeller test rig near the propeller rotors a model simulator of an aircraft engine support pylon and fuselage. The results of the investigation indicated that the low-speed performance of the counterrotation propeller configurations near the take-off target operating points were reasonable and were fairly insensitive to changes in model angle-of-attack without the aircraft pylon/fuselage simulators installed on the propeller test rig. When the aircraft pylon/fuselage simulators were installed, small changes in propeller performance were seen at zero angle-of-attack, but fairly large changes in total power coefficient and very large changes of aft-to-forward-rotor torque ratio were produced when the propeller model was taken to angle-of-attack. The propeller net efficiency, though, was fairly insensitive to any changes in the propeller flowfield conditions near the take-off target operating points.

  5. Low-speed wind tunnel performance of high-speed counterrotation propellers at angle-of-attack

    NASA Technical Reports Server (NTRS)

    Hughes, Christopher E.; Gazzaniga, John A.

    1989-01-01

    The low-speed aerodynamic performance characteristics of two advanced counterrotation pusher-propeller configurations with cruise design Mach numbers of 0.72 were investigated in the NASA Lewis 9- by 15-Foot Low-Speed Wind Tunnel. The tests were conducted at Mach number 0.20, which is representative of the aircraft take-off/landing flight regime. The investigation determined the effect of nonuniform inflow on the propeller performance characteristics for several blade angle settings and a range of rotational speeds. The inflow was varied by yawing the propeller model to angle-of-attack by as much as plus or minus 16 degrees and by installing on the counterrotation propeller test rig near the propeller rotors a model simulator of an aircraft engine support pylon and fuselage. The results of the investigation indicated that the low-speed performance of the counterrotation propeller configurations near the take-off target operating points were reasonable and were fairly insensitive to changes in model angle-of-attack without the aircraft pylon/fuselage simulators installed on the propeller test rig. When the aircraft pylon/fuselage simulators were installed, small changes in propeller performance were seen at zero angle-of-attack, but fairly large changes in total power coefficient and very large changes of aft-to-forward-rotor torque ratio were produced when the propeller model was taken to angle-of-attack. The propeller net efficiency, though, was fairly insensitive to any changes in the propeller flowfield conditions near the take-off target operating points.

  6. Large-scale Advanced Prop-fan (LAP) high speed wind tunnel test report

    NASA Technical Reports Server (NTRS)

    Campbell, William A.; Wainauski, Harold S.; Arseneaux, Peter J.

    1988-01-01

    High Speed Wind Tunnel testing of the SR-7L Large Scale Advanced Prop-Fan (LAP) is reported. The LAP is a 2.74 meter (9.0 ft) diameter, 8-bladed tractor type rated for 4475 KW (6000 SHP) at 1698 rpm. It was designated and built by Hamilton Standard under contract to the NASA Lewis Research Center. The LAP employs thin swept blades to provide efficient propulsion at flight speeds up to Mach .85. Testing was conducted in the ONERA S1-MA Atmospheric Wind Tunnel in Modane, France. The test objectives were to confirm that the LAP is free from high speed classical flutter, determine the structural and aerodynamic response to angular inflow, measure blade surface pressures (static and dynamic) and evaluate the aerodynamic performance at various blade angles, rotational speeds and Mach numbers. The measured structural and aerodynamic performance of the LAP correlated well with analytical predictions thereby providing confidence in the computer prediction codes used for the design. There were no signs of classical flutter throughout all phases of the test up to and including the 0.84 maximum Mach number achieved. Steady and unsteady blade surface pressures were successfully measured for a wide range of Mach numbers, inflow angles, rotational speeds and blade angles. No barriers were discovered that would prevent proceeding with the PTA (Prop-Fan Test Assessment) Flight Test Program scheduled for early 1987.

  7. North-south asymmetry in global distribution of the solar wind speed during 1985-2013

    NASA Astrophysics Data System (ADS)

    Tokumaru, Munetoshi; Fujiki, Ken'ichi; Iju, Tomoya

    2015-05-01

    Interplanetary scintillation (IPS) observations made between 1985 and 2013 are used to investigate the north-south (N-S) asymmetry in global distribution of the solar wind speed. The IPS observations clearly demonstrate that the global distribution of the solar wind speed systematically changes with the solar activity. This change is found to closely correlate with that in polar magnetic fields of the Sun, while fast wind data at solar minima systematically deviate from this correlation. The IPS observations show that notable N-S asymmetry of polar solar winds occurs at the solar maxima, and small but significant N-S asymmetry exists at the solar minima. The observed asymmetry at the solar maxima is consistent with the time lag in the reversal of polar magnetic fields between north and south hemispheres. We also find that significant N-S asymmetry of the polar fast wind lasts for the period between Cycles 23 and 24 solar maxima, starting from predominance of the fast wind over the north pole and ending with that over the south pole. The N-S asymmetry revealed from IPS observations is found to be generally consistent with Ulysses observations. We compare IPS observations with magnetic field data of the Sun and find that the ratio of the quadrupole to dipole coefficients exhibits a similar time variation to that of the N-S asymmetry revealed from IPS observations. This suggests that higher-order multipole moments play an important role in determining the N-S asymmetry of the solar wind when the dipole moment weakens.

  8. Geosynchronous Relativistic Electron Events Associated with High-Speed Solar Wind Streams in 2006

    NASA Astrophysics Data System (ADS)

    Lee, Sungeun; Hwang, Junga; Lee, Jae-Jin; Cho, Kyung-Suk; Kim, Khan-Hyuk; Yi, Yu

    2009-12-01

    Recurrent enhancements of relativistic electron events at geosynchronous orbit (GREEs) were observed in 2006. These GREE enhancements were associated with high-speed solar wind streams coming from the same coronal hole. For the first six months of 2006, the occurrence of GREEs has 27 day periodicity and the GREEs were enhanced with various flux levels. Several factors have been studied to be related to GREEs: (1) High speed stream, (2) Pc5 ULF wave activity, (3) Southward IMF Bz, (4) substorm occurrence, (5) Whistler mode chorus wave, and (6) Dynamic pressure. In this paper, we have examined the effectiveness about those parameters in selected periods.

  9. Atmospheric Boundary Layer and Clouds wind speed profile measurements with the new compact long range wind Lidar WindCube(TM) WLS70

    NASA Astrophysics Data System (ADS)

    Boquet, M.; Cariou, J. P.; Sauvage, L.; Lolli, S.; Parmentier, R.; Loaec, S.

    2009-04-01

    To fully understand atmospheric dynamics, climate studies, energy transfer, and weather prediction the wind field is one of the most important atmospheric state variables. Small scales variability and low atmospheric layers are not described with sufficient resolution up to now. To answer these needs, the WLS70 long-range wind Lidar is a new generation of wind Lidars developed by LEOSPHERE, derived from the commercial WindCube™ Lidar widely used by the wind power industry and well-known for its great accuracy and data availability. The WLS70 retrieves the horizontal and vertical wind speed profiles as well as the wind direction at various heights simultaneously inside the boundary layer and cloud layers. The amplitude and spectral content of the backscattering signal are also available. From raw data, the embedded signal processing software performs the computation of the aerosol Doppler shift and backscattering coefficient. Higher values of normalized relative backscattering (NRB) are proportional to higher aerosol concentration. At 1540 nm, molecular scattering being negligible, it is then possible to directly retrieve the Boundary Layer height evolution observing the height at which the WindCube NRB drops drastically. In this work are presented the results of the measurements obtained during the LUAMI campaign that took place in Lindenberg, at the DWD (Deutscher WetterDienst) meteorological observatory, from November 2008 to January 2009. The WLS70 Lidar instrument was placed close together with an EZ Lidar™ ALS450, a rugged and compact eye safe aerosol Lidar that provides a real time measurement of backscattering and extinction coefficients, aerosol optical depth (AOD), automatic detection of the planetary boundary layer (PBL) height and clouds base and top from 100m up to more than 20km. First results put in evidence wind shear and veer phenomena as well as strong convective effects during the raise of the mixing layer or before rain periods. Wind speed

  10. Seasonality, Interannual Variability, and Linear Tendency of Wind Speeds in the Northeast Brazil from 1986 to 2011

    PubMed Central

    Santos e Silva, Cláudio Moisés

    2013-01-01

    Wind speed analyses are currently being employed in several fields, especially in wind power generation. In this study, we used wind speed data from records of Universal Fuess anemographs at an altitude of 10 m from 47 weather stations of the National Institute of Meteorology (Instituto Nacional de Meteorologia-INMET) from January 1986 to December 2011. The objective of the study was to investigate climatological aspects and wind speed trends. To this end, the following methods were used: filling of missing data, descriptive statistical calculations, boxplots, cluster analysis, and trend analysis using the Mann-Kendall statistical method. The seasonal variability of the average wind speeds of each group presented higher values for winter and spring and lower values in the summer and fall. The groups G1, G2, and G5 showed higher annual averages in the interannual variability of wind speeds. These observed peaks were attributed to the El Niño and La Niña events, which change the behavior of global wind circulation and influence wind speeds over the region. Trend analysis showed more significant negative values for the G3, G4, and G5 groups for all seasons of the year and in the annual average for the period under study. PMID:24250267

  11. Seasonality, interannual variability, and linear tendency of wind speeds in the northeast Brazil from 1986 to 2011.

    PubMed

    Torres Silva dos Santos, Alexandre; Moisés Santos e Silva, Cláudio

    2013-01-01

    Wind speed analyses are currently being employed in several fields, especially in wind power generation. In this study, we used wind speed data from records of Universal Fuess anemographs at an altitude of 10 m from 47 weather stations of the National Institute of Meteorology (Instituto Nacional de Meteorologia-INMET) from January 1986 to December 2011. The objective of the study was to investigate climatological aspects and wind speed trends. To this end, the following methods were used: filling of missing data, descriptive statistical calculations, boxplots, cluster analysis, and trend analysis using the Mann-Kendall statistical method. The seasonal variability of the average wind speeds of each group presented higher values for winter and spring and lower values in the summer and fall. The groups G1, G2, and G5 showed higher annual averages in the interannual variability of wind speeds. These observed peaks were attributed to the El Niño and La Niña events, which change the behavior of global wind circulation and influence wind speeds over the region. Trend analysis showed more significant negative values for the G3, G4, and G5 groups for all seasons of the year and in the annual average for the period under study. PMID:24250267

  12. Direct radiative effects of sea salt for the Mediterranean region under conditions of low to moderate wind speeds

    NASA Astrophysics Data System (ADS)

    Lundgren, K.; Vogel, B.; Vogel, H.; Kottmeier, Ch.

    2013-02-01

    ABSTRACT This study deals with the direct radiative effect of sea salt on the regional scale, within both the shortwave and longwave ranges. The COSMO-ART model system has been extended and applied for a large part of Europe and adjacent waters within this investigation. For the radiation calculations, we determined the sea salt optical properties based on Mie calculations, giving the optical properties for the three sea salt modes and eight spectral intervals. The simulated sea salt aerosol optical depth is found to show strong dependence on the 10 m wind speed under cloud-free conditions. This relation is best represented by a power law fit and compares well with satellite observations. For clear-sky conditions, the simulated sea salt direct radiative effects on the shortwave and longwave radiative budgets are approximately of the same order of magnitude, but with opposite signs. This causes the net radiative effect to approach zero, which leads to a low impact on the temperature for this area.

  13. Variable speed wind turbine control by discrete-time sliding mode approach.

    PubMed

    Torchani, Borhen; Sellami, Anis; Garcia, Germain

    2016-05-01

    The aim of this paper is to propose a new design variable speed wind turbine control by discrete-time sliding mode approach. This methodology is designed for linear saturated system. The saturation constraint is reported on inputs vector. To this end, the back stepping design procedure is followed to construct a suitable sliding manifold that guarantees the attainment of a stabilization control objective. It is well known that the mechanisms are investigated in term of the most proposed assumptions to deal with the damping, shaft stiffness and inertia effect of the gear. The objectives are to synthesize robust controllers that maximize the energy extracted from wind, while reducing mechanical loads and rotor speed tracking combined with an electromagnetic torque. Simulation results of the proposed scheme are presented. PMID:26804750

  14. A Free-flight Wind Tunnel for Aerodynamic Testing at Hypersonic Speeds

    NASA Technical Reports Server (NTRS)

    Seiff, Alvin

    1954-01-01

    The supersonic free-flight wind tunnel is a facility at the Ames Laboratory of the NACA in which aerodynamic test models are gun-launched at high speed and directed upstream through the test section of a supersonic wind tunnel. In this way, test Mach numbers up to 10 have been attained and indications are that still higher speeds will be realized. An advantage of this technique is that the air and model temperatures simulate those of flight through the atmosphere. Also the Reynolds numbers are high. Aerodynamic measurements are made from photographic observation of the model flight. Instruments and techniques have been developed for measuring the following aerodynamic properties: drag, initial lift-curve slope, initial pitching-moment-curve slope, center of pressure, skin friction, boundary-layer transition, damping in roll, and aileron effectiveness. (author)

  15. Tone Noise of Three Supersonic Helical Tip Speed Propellers in a Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Dittmar, J. H.; Jeracki, R. J.; Blaha, B. J.

    1979-01-01

    Three supersonic helical tip speed propellers were tested in the NASA Lewis 8- by 6-foot wind tunnel. This is a perforated-wall wind tunnel but it does not have acoustic damping material on its walls. The propellers were tested at tunnel through flow Mach numbers of 0.6, 0.7, 0.75, 0.8, and 0.85 with different rotational speeds and blade setting angles. The three propellers, which had approximately the same aerodynamic performance, incorporated different plan forms and different amounts of sweep and yielded different near field noise levels. The acoustically designed propeller had 45 deg of tip sweep and was significantly quieter at M = 0.8 cruise than the straight bladed propeller. The intermediate 30 deg tip sweep propeller, which was swept for aerodynamic purposes, exhibited noise that was between the other two propellers. Noise trends with varying helical tip Mach number and blade loading were also observed.

  16. Small parametric model for nonlinear dynamics of large scale cyclogenesis with wind speed variations

    NASA Astrophysics Data System (ADS)

    Erokhin, Nikolay; Shkevov, Rumen; Zolnikova, Nadezhda; Mikhailovskaya, Ludmila

    2016-07-01

    It is performed a numerical investigation of a self consistent small parametric model (SPM) for large scale cyclogenesis (RLSC) by usage of connected nonlinear equations for mean wind speed and ocean surface temperature in the tropical cyclone (TC). These equations may describe the different scenario of temporal dynamics of a powerful atmospheric vortex during its full life cycle. The numerical calculations have shown that relevant choice of SPMTs incoming parameters allows to describe the seasonal behavior of regional large scale cyclogenesis dynamics for a given number of TC during the active season. It is shown that SPM allows describe also the variable wind speed variations inside the TC. Thus by usage of the nonlinear small parametric model it is possible to study the features of RLSCTs temporal dynamics during the active season in the region given and to analyze the relationship between regional cyclogenesis parameters and different external factors like the space weather including the solar activity level and cosmic rays variations.

  17. The power spectrum of the solar wind speed for periods greater than 10 days

    NASA Technical Reports Server (NTRS)

    Fenimore, E. E.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.

    1978-01-01

    The use of the more than 11 years of solar wind speed data obtained by Vela 2-6 and Imp 6-8 to study the power spectrum of speed variations in the range near the solar rotational frequency is discussed. The broad bands of power near periods of 27 days (corresponding to the rotational period of the sun), 13.5 days, and higher harmonics are characterized, and it is suggested that the described individual peaks in both the solar wind and the geomagnetic spectra are probably not due to differential rotation. The alternate explanation is that the multipeak nature of the power spectra are explained by a wave packet concept in which recurring highspeed streams are described as a series of pulses (separated by a constant period) that last for a varying number of solar rotations.

  18. Proton-driven electromagnetic instabilities in high-speed solar wind streams

    NASA Technical Reports Server (NTRS)

    Abraham-Shrauner, B.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.

    1979-01-01

    Electromagnetic instabilities of the field-aligned, right-hand circularly polarized magnetosonic wave and the left-hand circularly polarized Alfven wave driven by two drifted proton components are analyzed for model parameters determined from Imp 7 solar wind proton data measured during high-speed flow conditions. Growth rates calculated using bi-Lorentzian forms for the main and beam proton as well as core and halo electron velocity distributions do not differ significantly from those calculated using bi-Maxwellian forms. Using distribution parameters determined from 17 measured proton spectra, we show that considering the uncertainties the magnetosonic wave may be linearly stable and the Alfven wave is linearly unstable. Because proton velocity distribution function shapes are observed to persist for times long compared to the proton gyroperiod, the latter result suggests that linear stability theory fails for proton-driven ion cyclotron waves in the high-speed solar wind.

  19. Analysis and Modelling of Extreme Wind Speed Distributions in Complex Mountainous Regions

    NASA Astrophysics Data System (ADS)

    Laib, Mohamed; Kanevski, Mikhail

    2016-04-01

    Modelling of wind speed distributions in complex mountainous regions is an important and challenging problem which interests many scientists from several fields. In the present research, high frequency (10 min) Swiss wind speed monitoring data (IDAWEB service, Meteosuisse) are analysed and modelled with different parametric distributions (Weibull, GEV, Gamma, etc.) using maximum likelihood method. In total, 111 stations placed in different geomorphological units and at different altitude (from 203 to 3580 meters) are studied. Then, this information is used for training machine learning algorithms (Extreme Learning Machines, Support vector machine) to predict the distribution at new places, potentially useful for aeolian energy generation. An important part of the research deals with the construction and application of a high dimensional input feature space, generated from digital elevation model. A comprehensive study was carried out using feature selection approach to get the best model for the prediction. The main results are presented as spatial patterns of distributions' parameters.

  20. Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction

    PubMed Central

    Yonehara, Yoshinari; Goto, Yusuke; Yoda, Ken; Watanuki, Yutaka; Young, Lindsay C.; Weimerskirch, Henri; Bost, Charles-André; Sato, Katsufumi

    2016-01-01

    Ocean surface winds are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface winds measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of wind that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ∼5 km) ocean surface winds. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground speed fluctuated presumably due to tail winds and head winds. Taking advantage of the ground speed difference in relation to flight direction, we reliably estimated wind speed and direction experienced by the birds. These bird-based wind velocities were significantly correlated with wind velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution wind observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface winds, potentially complementing conventional wind measurements by covering spatial and temporal measurement gaps. PMID:27457932

  1. Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction.

    PubMed

    Yonehara, Yoshinari; Goto, Yusuke; Yoda, Ken; Watanuki, Yutaka; Young, Lindsay C; Weimerskirch, Henri; Bost, Charles-André; Sato, Katsufumi

    2016-08-01

    Ocean surface winds are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface winds measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of wind that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ∼5 km) ocean surface winds. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground speed fluctuated presumably due to tail winds and head winds. Taking advantage of the ground speed difference in relation to flight direction, we reliably estimated wind speed and direction experienced by the birds. These bird-based wind velocities were significantly correlated with wind velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution wind observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface winds, potentially complementing conventional wind measurements by covering spatial and temporal measurement gaps. PMID:27457932

  2. Simulation and study of power quality issues in a fixed speed wind farm substation.

    PubMed

    Magesh, T; Chellamuthu, C

    2015-01-01

    Power quality issues associated with the fixed speed wind farm substation located at Coimbatore district are investigated as the wind generators are tripping frequently. The investigations are carried out using two power quality analyzers, Fluke 435 and Dranetz PX5.8, with one of them connected at group control breaker of the 110 kV feeder and the other at the selected 0.69 kV generator busbar during the period of maximum power generation. From the analysis of the recorded data it is found that sag, swell, and transients are the major events which are responsible for the tripping of the generators. In the present study, simulation models for wind, turbine, shaft, pitch mechanism, induction generator, and grid are developed using DIgSILENT. Using the turbine characteristics, a two-dimensional lookup table is designed to generate a reference pitch angle necessary to simulate the power curve of the passive stall controlled wind turbine. Various scenarios and their effects on the performance of the wind farm are studied and validated with the recorded data and waveforms. The simulation model will be useful for the designers for planning and development of the wind farm before implementation. PMID:25950016

  3. Simulation and Study of Power Quality Issues in a Fixed Speed Wind Farm Substation

    PubMed Central

    Magesh, T.; Chellamuthu, C.

    2015-01-01

    Power quality issues associated with the fixed speed wind farm substation located at Coimbatore district are investigated as the wind generators are tripping frequently. The investigations are carried out using two power quality analyzers, Fluke 435 and Dranetz PX5.8, with one of them connected at group control breaker of the 110 kV feeder and the other at the selected 0.69 kV generator busbar during the period of maximum power generation. From the analysis of the recorded data it is found that sag, swell, and transients are the major events which are responsible for the tripping of the generators. In the present study, simulation models for wind, turbine, shaft, pitch mechanism, induction generator, and grid are developed using DIgSILENT. Using the turbine characteristics, a two-dimensional lookup table is designed to generate a reference pitch angle necessary to simulate the power curve of the passive stall controlled wind turbine. Various scenarios and their effects on the performance of the wind farm are studied and validated with the recorded data and waveforms. The simulation model will be useful for the designers for planning and development of the wind farm before implementation. PMID:25950016

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

    NASA Astrophysics Data System (ADS)

    Nadhir, Ahmad; Naba, Agus; Hiyama, Takashi

    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.

  5. Influence of the Solar Wind Speed on the Propagation of Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Yashiro, S.; Tokumaru, M.; Fujiki, K.; Iju, T.; Akiyama, S.; Makela, P. A.; Gopalswamy, N.

    2015-12-01

    We investigate the influence of the solar wind (SW) on the propagation of a set of 191 coronal mass ejections (CMEs) near the Sun during the period 1996-2013. The CMEs were observed by LASCO on board SOHO and their source regions were identified using the CME-associated eruptive features (flares, filament eruptions, dimmings) in X-ray, EUV, microwave, and Hα observations. The SW speeds above the CME source regions were estimated from the interplanetary scintillation (IPS) observations from the Solar Terrestrial Environ Laboratory, Nagoya University. We considered only CMEs from close to the limb in order to avoid the projection effects. We also considered CMEs with at least 10 height-time measurements in order to avoid the large uncertainty in the acceleration measurements. We confirm the well-known CME-SW relationship that the CMEs propagating faster (slower) than the ambient solar wind are likely to decelerate (accelerate). The correlation between the acceleration and the difference of the CME and the SW speeds is high with a correlation coefficient of -0.74, slightly lower compared to the one for CMEs associated with interplanetary radio bursts (Gopalswamy et al. 2001, JGR, 106, 29219). There are many accelerating CMEs in our sample with a speed similar to the ambient solar wind speed. This could be due to selection effect because accelerating CMEs tend to remain visible longer than decelerating ones. We also found that CMEs originating from around the sources of the fast solar wind tend to be faster, indicating that the open magnetic fields above the CME source regions affect the CME propagation.

  6. Analysis And Synthesis Of Model Reference Controller For Variable Speed Wind Generators Inertial Support

    NASA Astrophysics Data System (ADS)

    Bećirović, Elvisa; Osmić, Jakub; Kušljugić, Mirza; Perić, Nedjeljko

    2015-01-01

    Model Reference Controller (MRC) for contribution of Variable Speed Wind Generators (VSWG) in inertial response of Electrical Power System (EPS) is presented and analyzed in this paper. MRC is synthesized based on a model of Generating Unit With non-Reheat Steam Turbine (GUNRST) thus enabling VSWG to emulate GUNRST response during the initial stage of dynamic frequency response ie inertial phase. Very important property of conventional steam generating units is that its contribution to inertial phase response is independent from the initial generating power. By using MRC in VSWG it is accomplished that in most common wind speed region (3-12 m/s) VSWG inertial support is almost independent from wind speed. Since in most EPSs VSWG replaces conventional steam generators, application of MRC algorithm provides that the characteristics of EPS in terms of inertial response are preserved, regardless of the growing trend of introducing VSWG. Evaluation analysis of the proposed MRC is performed on modified nine bus power system when VSWG with MRC is connected to one of the power system buses.

  7. Modeling the Threshold Wind Speed for Saltation Initiation over Heterogeneous Sand Beds

    NASA Astrophysics Data System (ADS)

    Turney, F. A.; Martin, R. L.; Kok, J. F.

    2015-12-01

    Initiation of aeolian sediment transport is key to understanding the formation of dunes, emission of dust into the atmosphere, and landscape erosion. Previous models of the threshold wind speed required for saltation initiation have assumed that the particle bed is monodisperse and homogeneous in arrangement, thereby ignoring what is in reality a distribution of particle lifting thresholds, influenced by variability in soil particle sizes and bed geometry. To help overcome this problem, we present a numerical model that determines the distribution of threshold wind speeds required for particle lifting for a given soil size distribution. The model results are evaluated against high frequency wind speed and saltation data from a recent field campaign in Oceano Dunes in Southern California. The results give us insight into the range of lifting thresholds present during incipient sediment transport and the simplifications that are often made to characterize the process. In addition, this study provides a framework for moving beyond the 'fluid threshold' paradigm, which is known to be inaccurate, especially for near-threshold conditions.

  8. Monitoring the rotation status of wind turbine blades using high-speed camera system

    NASA Astrophysics Data System (ADS)

    Zhang, Dongsheng; Chen, Jubing; Wang, Qiang; Li, Kai

    2013-06-01

    The measurement of the rotating object is of great significance in engineering applications. In this study, a high-speed dual camera system based on 3D digital image correlation has been developed in order to monitor the rotation status of the wind turbine blades. The system allows sequential images acquired at a rate of 500 frames per second (fps). An improved Newton-Raphson algorithm has been proposed which enables detection movement including large rotation and translation in subpixel precision. The simulation experiments showed that this algorithm is robust to identify the movement if the rotation angle is less than 16 degrees between the adjacent images. The subpixel precision is equivalent to the normal NR algorithm, i.e.0.01 pixels in displacement. As a laboratory research, the high speed camera system was used to measure the movement of the wind turbine model which was driven by an electric fan. In the experiment, the image acquisition rate was set at 387 fps and the cameras were calibrated according to Zhang's method. The blade was coated with randomly distributed speckles and 7 locations in the blade along the radial direction were selected. The displacement components of these 7 locations were measured with the proposed method. Conclusion is drawn that the proposed DIC algorithm is suitable for large rotation detection, and the high-speed dual camera system is a promising, economic method in health diagnose of wind turbine blades.

  9. Design of State-Space-Based Control Algorithms for Wind Turbine Speed Regulation: Preprint

    SciTech Connect

    Wright, A.; Balas, M.

    2002-01-01

    Control can improve the performance of wind turbines by enhancing energy capture and reducing dynamic loads.At the National Renewable Energy Laboratory, we are beginning to design control algorithms for regulation of turbine speed and power using state-space control designs. In this paper, we describe the design of such a control algorithm for regulation of rotor speed in full-load operation (region 3) for a two-bladed wind turbine. We base our control design on simple linear models of a turbine, which contain rotor and generator rotation, drivetrain torsion, and rotor flap degrees of freedom (first mode only). We account for wind-speed fluctuations using disturbance-accommodating control. We show the capability of these control schemes to stabilize the modeled turbine modes via pole placement while using state estimation to reduce the number of turbine measurements that are needed for these control algorithms. We incorporate these controllers into the FAST-AD code and show simulation results for various conditions. Finally, we report conclusions to this work and outline future studies.

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

    SciTech Connect

    Zrnic, D.; Istok, M.

    1980-12-01

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

  11. Influence of time scale wind speed data on sustainability analysis for irrigating greenhouse crops

    NASA Astrophysics Data System (ADS)

    Díaz Méndez, Rodrigo; García Llaneza, Joaquín; Peillón, Manuel; Perdigones, Alicia; Sanchez, Raul; Tarquis, Ana M.; Garcia, Jose Luis

    2014-05-01

    Appropriate water supply at crop/farm level, with suitable costs, is becoming more and more important. Energy management is closely related to water supply in this context, being wind energy one of the options to be considered, using wind pumps for irrigation water supply. Therefore, it is important to characterize the wind speed frequency distribution to study the technical feasibility to use its energy for irrigation management purpose. The general objective of this present research is to analyze the impact of time scale recorded wind speed data in the sustainability for tomato (Solanum lycopersicum L.) grown under greenhouse at Cuban conditions using drip irrigation system. For this porpoise, a daily estimation balance between water needs and water availability was used to evaluate the feasibility of the most economic windmill irrigation system. Several factors were included: wind velocity (W, m/s) in function of the time scale averaged, flow supplied by the wind pump as a function of the elevation height (H, m) and daily greenhouse evapotranspiration. Monthly volumes of water required for irrigation (Dr, m3/ha) and in the water tank (Vd, m3), as well as the monthly irrigable area (Ar, ha), were estimated by cumulative deficit water budgeting taking in account these factors. Three-hourly wind velocity (W3h, m/s) data from 1992 till 2008 was available for this study. The original data was grouped in six and twelve hourly data (W6h and W12h respectively) as well as daily data (W24h). For each time scale the daily estimation balance was applied. A comparison of the results points out a need for at least three-hourly data to be used mainly in the months in which mean wind speed are close or below the pumps threshold speed to start-up functioning. References Manuel Esteban Peillon Mesa, Ana Maria Tarquis Alfonso, José Luis García Fernández, and Raúl Sánchez Calvo. The use of wind pumps for irrigating greenhouse tomato crops: a case study in Cuba. Geophysical

  12. Comparison of wind speed measurements over the oceans with the Special Sensor Microwave/Imager and the Geosat altimeter

    NASA Technical Reports Server (NTRS)

    Mognard, Nelly M.; Katsaros, Kristina B.

    1992-01-01

    In order to compare wind speed estimates from the Geosat altimeter and the Special Sensor Microwave/Imager (SSM/I), 25 colocated passes, within 2 hours of each other, were selected and the SSM/I estimates of wind speed and atmospheric parameters extracted along the Geosat track. Both instruments and their algorithms are described. A statistical comparison of wind speed estimates is presented and the effects of the atmospheric parameters from Geosat are analyzed. Quasi-simultaneous measurements by Geosat and SSM/I, along a Geosat track in the North-East Pacific, are also presented.

  13. Wind speeds in lower atmosphere of Venus: Status report on possible measurement via differential VLBI tracking of entry probes

    NASA Technical Reports Server (NTRS)

    Shapiro, I. I.

    1972-01-01

    The potential of very-long-baseline interferometry (VLBI) is examined for use in the determination of wind speeds in Venus' lower atmosphere via the differential tracking of entry probes. A simplified mathematical model is presented in detail. An incomplete error analysis based on this model permits an educated guess to be made: an uncertainty in wind speed determination of no more than about 100/t m/sec, where t l is the corresponding time resolution in seconds, is an achievable goal, without the use of transponders on the miniprobes. If transponders are available on all probes, there should be little difficulty in estimating wind speeds with useful precision.

  14. Spatiotemporal patterns in methane flux and gas transfer velocity at low wind speeds: Implications for upscaling studies on small lakes

    NASA Astrophysics Data System (ADS)

    Schilder, J.; Bastviken, D.; Hardenbroek, M.; Heiri, O.

    2016-06-01

    Lakes contribute significantly to the global natural emissions of methane (CH4) and carbon dioxide. However, to accurately incorporate them into the continental carbon balance more detailed surveys of lacustrine greenhouse gas emissions are needed, especially in respect to spatiotemporal variability and to how this affects the upscaling of results. We investigated CH4 flux from a small, wind-shielded lake during 10 field trips over a 14 month period. We show that floating chambers may be used to calibrate the relationship between gas transfer velocity (k) and wind speed at 10 m height (U10) to the local system, in order to obtain more accurate estimates of diffusive CH4 flux than by applying general models predicting k based on U10. We confirm earlier studies indicating strong within-lake spatial variation in this relationship and in ebullitive CH4 flux within the lake basin. However, in contrast to the pattern reported in other studies, ebullitive CH4 flux was highest in the central parts of the lake. Our results indicate positive relationships between k and U10 at very low U10 (0-3 m s-1), which disagrees with earlier suggestions that this relationship may be negligible at low U10 values. We estimate annually averaged open water CH4 emission from Lake Gerzensee to be 3.6-5.8 mmol m-2 d-1. Our data suggest that estimates of greenhouse gas emissions from aquatic systems to the atmosphere based on the upscaling of short-term and small-scale measurements can be improved if both spatial and temporal variabilities of emissions are taken into account.

  15. Connecting the surface of the Sun to the Heliosphere : wind speed and magnetic field geometry

    NASA Astrophysics Data System (ADS)

    Pinto, Rui

    2016-07-01

    The large-scale solar wind speed distribution varies in time in response to the cyclic variations of the strength and geometry of the magnetic field of the corona. Based on this idea, semi-empirical predictive laws for the solar wind speed (such as in the widely-used WSA law) use simple parameters describing the geometry of the coronal magnetic field. In practice, such scaling laws require ad-hoc corrections and empirical fits to in-situ spacecraft data, and a predictive law based solely on physical principles is still missing. I will discuss improvements to this kind of laws based on the analysis of very large samples of wind acceleration profiles in open flux-tubes (both from MHD simulations and potential-field extrapolations), and possible strategies for corona and heliosphere model coupling. I will, furthermore present an ongoing modelling effort to determine the magnetic connectivity, paths and propagation delays of any type of disturbance (slow/fast solar wind, waves, energetic particles, ballistic propagation) between the solar surface and any point in the interplanetary space at any time. This is a key point for the exploitation of data from Solar Orbiter and Solar Probe Plus, and more generally for establishing connections between remote and in-situ spacecraft data. This is work is supported by the FP7 project #606692 (HELCATS).

  16. Algorithm Determines Wind Speed and Direction from Venturi-Sensor Data

    NASA Technical Reports Server (NTRS)

    Zysko, Jan A.; Perotti, Jose M.; Randazzo, John

    2004-01-01

    An algorithm computes the velocity of wind from the readings of an instrument like the one described in another Tech Brief. To recapitulate: The sensor has no moving parts and is a compact, rugged means of measuring wind vectors having magnitudes of as much as 300 mph (134 m/s). The sensor includes a Venturi gap bounded by a curved upper and a curved lower surface that are axisymmetric with respect to a vertical axis and mirror-symmetric with respect to a horizontal midplane. One of the curved surfaces is instrumented with multiple ports for measuring dynamic pressures. The sensor also incorporates auxiliary sensors for measuring temperature, relative humidity, and static atmospheric pressure. The design and operation of the sensor are based on the concepts of (1) using Bernoulli's equation (which expresses the relationship among variations of speed, density, and pressure along a streamline) to calculate the speed of the wind from differences among the pressure readings at the various ports; and (2) calculating the direction of the wind from the angular positions of ports selected according to comparisons among their pressure readings. The present algorithm performs these calculations.

  17. Statistical analysis of low frequency vibrations in variable speed wind turbines

    NASA Astrophysics Data System (ADS)

    Escaler, X.; Mebarki, T.

    2013-12-01

    The spectral content of the low frequency vibrations in the band from 0 to 10 Hz measured in full scale wind turbines has been statistically analyzed as a function of the whole range of steady operating conditions. Attention has been given to the amplitudes of the vibration peaks and their dependency on rotating speed and power output. Two different wind turbine models of 800 and 2000 kW have been compared. For each model, a sample of units located in the same wind farm and operating during a representative period of time have been considered. A condition monitoring system installed in each wind turbine has been used to register the axial acceleration on the gearbox casing between the intermediate and the high speed shafts. The average frequency spectrum has permitted to identify the vibration signature and the position of the first tower natural frequency in both models. The evolution of the vibration amplitudes at the rotor rotating frequency and its multiples has shown that the tower response is amplified by resonance conditions in one of the models. So, it is concluded that a continuous measurement and control of low frequency vibrations is required to protect the turbines against harmful vibrations of this nature.

  18. Outdoor temperature, precipitation, and wind speed affect physical activity levels in children: a longitudinal cohort study

    PubMed Central

    Edwards, Nicholas M.; Myer, Gregory D.; Kalkwarf, Heidi J.; Woo, Jessica G.; Khoury, Philip R.; Hewett, Timothy E.; Daniels, Stephen R.

    2015-01-01

    Objective Evaluate effects of local weather conditions on physical activity in early childhood. Methods Longitudinal prospective cohort study of 372 children, 3 years old at enrollment, drawn from a major US metropolitan community. Accelerometer-measured (RT3) physical activity was collected every 4 months over 5 years and matched with daily weather measures: day length, heating/cooling degrees (degrees mean temperature < 65°F or ≥ 65°F, respectively), wind, and precipitation. Mixed regression analyses, adjusted for repeated measures, were used to test the relationship between weather and physical activity. Results Precipitation and wind speed were negatively associated with total physical activity and moderate-vigorous physical activity (P<0.0001). Heating and cooling degrees were negatively associated with total physical activity and moderate-vigorous physical activity and positively associated with inactivity (all P<0.0001), independent of age, sex, race, BMI, day length, wind, and precipitation. For every 10 additional heating degrees there was a five-minute daily reduction in moderate-vigorous physical activity. For every additional 10 cooling degrees there was a 17-minute reduction in moderate-vigorous physical activity. Conclusions Inclement weather (higher/lower temperature, greater wind speed, more rain/snow) is associated with less physical activity in young children. These deleterious effects should be considered when planning physical activity research, interventions, and policies. PMID:25423667

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  20. Error estimates for ocean surface winds: Applying Desroziers diagnostics to the Cross-Calibrated, Multi-Platform analysis of wind speed

    NASA Astrophysics Data System (ADS)

    Hoffman, Ross N.; Ardizzone, Joseph V.; Leidner, S. Mark; Smith, Deborah K.; Atlas, Robert M.

    2013-04-01

    The cross-calibrated, multi-platform (CCMP) ocean surface wind project [Atlas et al., 2011] generates high-quality, high-resolution, vector winds over the world's oceans beginning with the 1987 launch of the SSM/I F08, using Remote Sensing Systems (RSS) microwave satellite wind retrievals, as well as in situ observations from ships and buoys. The variational analysis method [VAM, Hoffman et al., 2003] is at the center of the CCMP project's analysis procedures for combining observations of the wind. The VAM was developed as a smoothing spline and so implicitly defines the background error covariance by means of several constraints with adjustable weights, and does not provide an explicit estimate of the analysis error. Here we report on our research to develop uncertainty estimates for wind speed for the VAM inputs and outputs, i.e., for the background (B), the observations (O) and the analysis (A) wind speed, based on the Desroziers et al. [2005] diagnostics (DD hereafter). The DD are applied to the CCMP ocean surface wind data sets to estimate wind speed errors of the ECMWF background, the microwave satellite observations and the resulting CCMP analysis. The DD confirm that the ECMWF operational surface wind speed error standard deviations vary with latitude in the range 0.7-1.5 m/s and that the cross-calibrated Remote Sensing Systems (RSS) wind speed retrievals standard deviations are in the range 0.5-0.8 m/s. Further the estimated CCMP analysis wind speed standard deviations are in the range 0.2-0.4 m/s. The results suggests the need to revise the parameterization of the errors due to the FGAT (first guess at the appropriate time) procedure. Errors for wind speeds < 16 m/s are homogeneous, but for the relatively rare, but critical higher wind speed situations, errors are much larger. Atlas, R., R. N. Hoffman, J. Ardizzone, S. M. Leidner, J. C. Jusem, D. K. Smith, and D. Gombos, A cross-calibrated, multi-platform ocean surface wind velocity product for

  1. Wind tunnel results of advanced high speed propellers in the takeoff, climb, and landing operating regimes

    NASA Technical Reports Server (NTRS)

    Stefko, G. L.; Jeracki, R. J.

    1985-01-01

    Low speed wind tunnel performance tests of two advanced propellers were completed. The 62.2 cm diameter adjustable pitch models were tested at Mach numbers typical of takeoff, initial climbout, and landing speeds in the 10 by 10 ft Supersonic Wind Tunnel. Both models had eight blades and a cruise design point operating condition of 0.80 Mach number, 10.668 km S.A. altitude, 243.8 m/s tip speed and a high power loading of 301 kW sq m. No adverse or unusual low speed operating conditions were found during the test with either the straight blade SR-2 or the 45 deg swept SR-3 propellers. The 45 deg swept propeller efficiency exceeded the straight blade efficiency by 4 to 5 percent. Typical net efficiencies of the straight and 45 deg swept propeller at a Mach 0.20 takeoff condition were 50.2 and 54.9 percent respectively. At a Mach 0.34 climb condition, the efficiencies were 53.7 and 59.1 percent. Reverse thrust data indicates that these propellers are capable of producing more reverse thrust at Mach 0.20 than a high bypass turbofan engine at Mach 0.20.

  2. Wind tunnel results of advanced high speed propellers in the takeoff, climb and landing operating regimes

    NASA Technical Reports Server (NTRS)

    Stefko, G. L.; Jeracki, R. J.

    1985-01-01

    Low speed wind tunnel performance tests of two advanced propellers were completed. The 62.2 cm diameter adjustable pitch models were tested at Mach numbers typical of takeoff, initial climbout, and landing speeds in the 10 by 10 ft Supersonic Wind Tunnel. Both models had eight blades and a cruise design point operating condition of 0.80 Mach number, 10.668 km S.A. altitude, 243.8 m/s tip speed and a high power loading of 301 kW sq m. No adverse or unusual low speed operating conditions were found during the test with either the straight blade SR-2 or the 45 deg swept SR-3 propellers. The 45 deg swept propeller efficiency exceeded the straight blade efficiency by 4 to 5%. Typical net efficiencies of the straight and 45 deg swept propeller at a Mach 0.20 takeoff condition were 50.2 and 54.9% respectively. At a Mach 0.34 climb condition, the efficiencies were 53.7 and 59.1%. Reverse thrust data indicates that these propellers are capable of producing more reverse thrust at Mach 0.20 than a high bypass turbofan engine at Mach 0.20.

  3. Improved Speed Control System for the 87,000 HP Wind Tunnel Drive

    NASA Technical Reports Server (NTRS)

    Becks, Edward A.; Bencic, Timothy J.; Blumenthal, Philip Z.

    1995-01-01

    This paper describes the design, installation, and integrated systems tests for a new drive motor speed control system which was part of a recent rehab project for the NASA Lewis 8x6 Supersonic Wind Tunnel. The tunnel drive consists of three mechanically-coupled 29,000 HP wound rotor induction motors driving an axial flow compressor. Liquid rheostats are used to vary the impedance of the rotor circuits, thus varying the speed of the drive system. The new design utilizes a distributed digital control system with a dual touch screen CRT operator console to provide alarm monitoring, logging, and trending. The liquid rheostats are driven by brushtype servomotor systems with magnetostrictive linear displacement transducers used for position feedback. The new system achieved all goals for speed variations with load, motor load balance, and control of total power.

  4. High Speed Civil Transport in 14x22 Foot Wind Tunnel

    NASA Technical Reports Server (NTRS)

    1993-01-01

    A NASA technician (Michael E. Ramsey) inspects a high-speed civil transport model between wind tunnel tests at NASA's Langley Research Center, Hampton, Virginia. Aerodynamic tests of the 19-foot (5.7m) model in the 14- by 22-Foot Subsonic Tunnel simulate takeoff and landing of a 300-passenger supersonic commercial transport that would cruise at Mach 2.4 (approximately 1,600 mph/2,560 kph). Designated 'Reference H,' the concept was designed by Boeing and presently serves as a common configuration for government-industry technology studies. Langley is NASA's lead center for the agency's High Speed Research program, aimed at developing technology to help U.S. industry compete in the rapidly expanding trans-oceanic transport market. A. U.S. high-speed civil transport is expected to fly in about the year 2010.

  5. Systematic approach for PID controller design for pitch-regulated, variable-speed wind turbines

    SciTech Connect

    Hand, M.M.; Balas, M.J.

    1997-11-01

    Variable-speed, horizontal axis wind turbines use blade-pitch control to meet specified objectives for three regions of operation. This paper focuses on controller design for the constant power production regime. A simple, rigid, non-linear turbine model was used to systematically perform trade-off studies between two performance metrics. Minimization of both the deviation of the rotor speed from the desired speed and the motion of the actuator is desired. The robust nature of the proportional-integral-derivative (PID) controller is illustrated, and optimal operating conditions are determined. Because numerous simulation runs may be completed in a short time, the relationship of the two opposing metrics is easily visualized. 2 refs., 9 figs.

  6. ROWS estimates of wave height, wind speed, and directional wave spectra for SIR-B underflights off Chile, October 11 and 12, 1984

    NASA Technical Reports Server (NTRS)

    Jackson, F. C.; Glazar, W.; Hines, D.; Peng, C. Y.

    1985-01-01

    An account is given of the successful operation of the Goddard Ku-band Radar Ocean Wave Spectrometer (ROWS) on four out of five of the NASA Wallops' P-3 underflights of the Shuttle Imaging Radar-B (SIR-B) off the coast of southern Chile during the period of October 7-12, 1984. ROWS provided surface wind speed, wave height, and directional wave height spectrum estimates from the instrument's nadir altimeter mode and off-nadir spectrometer mode. ROWS estimates of the directional spectra of 300-400-m wavelength swell-dominated 3-5 m seas on October 11 and 12 are presented and compared to SCR (Surface Contour Radar), SIR-B, and Navy GSOWM spectra. Good agreement is found with SCR height spectra for the 12th (when the SCR was operable). Also, surprisingly good agreement is found between ROWS slope spectra and SIR-B image spectra for both the 11th and 12th for both swell and local wind-sea components. ROWS altimeter mode estimates of maximum winds of about 10 m/s on the 11th and 12th are seen to be consistent with the ROWS spectrometer mode observed local wind-sea peak frequencies of about 0.12-0.14 Hz.

  7. High-resolution daily gridded datasets of air temperature and wind speed for Europe

    NASA Astrophysics Data System (ADS)

    Brinckmann, S.; Krähenmann, S.; Bissolli, P.

    2015-08-01

    New high-resolution datasets for near surface daily air temperature (minimum, maximum and mean) and daily mean wind speed for Europe (the CORDEX domain) are provided for the period 2001-2010 for the purpose of regional model validation in the framework of DecReg, a sub-project of the German MiKlip project, which aims to develop decadal climate predictions. The main input data sources are hourly SYNOP observations, partly supplemented by station data from the ECA&D dataset (http://www.ecad.eu). These data are quality tested to eliminate erroneous data and various kinds of inhomogeneities. Grids in a resolution of 0.044° (5 km) are derived by spatial interpolation of these station data into the CORDEX area. For temperature interpolation a modified version of a regression kriging method developed by Krähenmann et al. (2011) is used. At first, predictor fields of altitude, continentality and zonal mean temperature are chosen for a regression applied to monthly station data. The residuals of the monthly regression and the deviations of the daily data from the monthly averages are interpolated using simple kriging in a second and third step. For wind speed a new method based on the concept used for temperature was developed, involving predictor fields of exposure, roughness length, coastal distance and ERA Interim reanalysis wind speed at 850 hPa. Interpolation uncertainty is estimated by means of the kriging variance and regression uncertainties. Furthermore, to assess the quality of the final daily grid data, cross validation is performed. Explained variance ranges from 70 to 90 % for monthly temperature and from 50 to 60 % for monthly wind speed. The resulting RMSE for the final daily grid data amounts to 1-2 °C and 1-1.5 m s-1 (depending on season and parameter) for daily temperature parameters and daily mean wind speed, respectively. The datasets presented in this article are published at http://dx.doi.org/10.5676/DWD_CDC/DECREG0110v1.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  9. Extended Statistical Short-Range Guidance for Peak Wind Speed Analyses at the Shuttle Landing Facility: Phase II Results

    NASA Technical Reports Server (NTRS)

    Lambert, Winifred C.

    2003-01-01

    This report describes the results from Phase II of the AMU's Short-Range Statistical Forecasting task for peak winds at the Shuttle Landing Facility (SLF). The peak wind speeds are an important forecast element for the Space Shuttle and Expendable Launch Vehicle programs. The 45th Weather Squadron and the Spaceflight Meteorology Group indicate that peak winds are challenging to forecast. The Applied Meteorology Unit was tasked to develop tools that aid in short-range forecasts of peak winds at tower sites of operational interest. A seven year record of wind tower data was used in the analysis. Hourly and directional climatologies by tower and month were developed to determine the seasonal behavior of the average and peak winds. Probability density functions (PDF) of peak wind speed were calculated to determine the distribution of peak speed with average speed. These provide forecasters with a means of determining the probability of meeting or exceeding a certain peak wind given an observed or forecast average speed. A PC-based Graphical User Interface (GUI) tool was created to display the data quickly.

  10. Latitudinal variation of speed and mass flux in the acceleration region of the solar wind inferred from spectral broadening measurements

    NASA Technical Reports Server (NTRS)

    Woo, Richard; Goldstein, Richard M.

    1994-01-01

    Spectral broadening measurements conducted at S-band (13-cm wavelength) during solar minimum conditions in the heliocentric distance range of 3-8 R(sub O) by Mariner 4, Pioneer 10, Mariner 10, Helios 1, Helios 2, and Viking have been combined to reveal a factor of 2.6 reduction in bandwidth from equator to pole. Since spectral broadening bandwidth depends on electron density fluctuation and solar wind speed, and latitudinal variation of the former is available from coherence bandwidth measurements, the remote sensing spectral broadening measurements provide the first determination of the latitudinal variation of solar wind speed in the acceleration region. When combined with electron density measurements deduced from white-light coronagraphs, this result also leads to the first determination of the latitudinal variation of mass flux in the acceleration region. From equator to pole, solar wind speed increases by a factor of 2.2, while mass flux decreases by a factor of 2.3. These results are consistent with measurements of solar wind speed by multi-station intensity scintillation measurements, as well as measurements of mass flux inferred from Lyman alpha observations, both of which pertain to the solar wind beyond 0.5 AU. The spectral broadening observations, therefore, strengthen earlier conclusions about the latitudinal variation of solar wind speed and mass flux, and reinforce current solar coronal models and their implications for solar wind acceleration and solar wind modeling.

  11. A 10 year intercomparison between collocated Special Sensor Microwave Imager oceanic surface wind speed retrievals and global analyses

    NASA Astrophysics Data System (ADS)

    Meissner, T.; Smith, D.; Wentz, F.

    2001-06-01

    To evaluate the scalar ocean surface wind speeds obtained from the Special Sensor Microwave Imager (SSM/I), we compare them over the time period from July 1987 through December 1997 with those from two global analyses: the National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) Annual Reanalysis and the European Center for Medium-Range Weather Forecasts (ECMWF)/Tropical Ocean-Global Atmosphere Global Surface Analysis. We perform a statistical analysis for the whole globe and present time series analyses for selected geographical regions in connection with collocated wind speed difference maps. In order to evaluate further geographical biases observed in the SSM/I versus analyses comparisons we use wind speeds from the NASA scatterometer (NSCAT) for the 10 month period from September 1996 through June 1997 as a third data source. The value of the standard deviation for all collocated SSM/I - ECMWF wind speed differences is 2.1 m s-1 and for all collocated SSM/I - NCEP/NCAR reanalyis wind speed differences is 2.4 m s-1. When taking monthly or yearly averages in each pixel, which has the effect of cancelling out small timescale wind speed fluctuations, the values are between 0.8 and 1.2 m s-1, respectively. Global biases range between -0.05 and +0.55 m s-1 for the various SSM/I satellites. Our analysis allows us to identify regional biases for both the SSM/I and analyses winds. The NCEP/NCAR reanalysis wind speeds appear underestimated in the tropical Pacific and tropical Atlantic. ECMWF wind speeds appear underestimated near the southern Pacific islands NE of Australia. The analyses wind speeds are higher than the SSM/I wind speeds near the Argentinean coast. The SSM/I wind speeds appear high in the extratropical central and eastern Pacific and low in certain coastal regions with eastern boundary currents and in the Arabian Sea. The size of some of these biases are seasonally dependent.

  12. World's first telepathology experiments employing WINDS ultra-high-speed internet satellite, nicknamed “KIZUNA”

    PubMed Central

    Sawai, Takashi; Uzuki, Miwa; Miura, Yasuhiro; Kamataki, Akihisa; Matsumura, Tsubasa; Saito, Kenji; Kurose, Akira; Osamura, Yoshiyuki R.; Yoshimi, Naoki; Kanno, Hiroyuki; Moriya, Takuya; Ishida, Yoji; Satoh, Yohichi; Nakao, Masahiro; Ogawa, Emiko; Matsuo, Satoshi; Kasai, Hiroyuki; Kumagai, Kazuhiro; Motoda, Toshihiro; Hopson, Nathan

    2013-01-01

    Background: Recent advances in information technology have allowed the development of a telepathology system involving high-speed transfer of high-volume histological figures via fiber optic landlines. However, at present there are geographical limits to landlines. The Japan Aerospace Exploration Agency (JAXA) has developed the “Kizuna” ultra-high speed internet satellite and has pursued its various applications. In this study we experimented with telepathology in collaboration with JAXA using Kizuna. To measure the functionality of the Wideband InterNet working engineering test and Demonstration Satellite (WINDS) ultra-high speed internet satellite in remote pathological diagnosis and consultation, we examined the adequate data transfer speed and stability to conduct telepathology (both diagnosis and conferencing) with functionality, and ease similar or equal to telepathology using fiber-optic landlines. Materials and Methods: We performed experiments for 2 years. In year 1, we tested the usability of the WINDS for telepathology with real-time video and virtual slide systems. These are state-of-the-art technologies requiring massive volumes of data transfer. In year 2, we tested the usability of the WINDS for three-way teleconferencing with virtual slides. Facilities in Iwate (northern Japan), Tokyo, and Okinawa were connected via the WINDS and voice conferenced while remotely examining and manipulating virtual slides. Results: Network function parameters measured using ping and Iperf were within acceptable limits. However; stage movement, zoom, and conversation suffered a lag of approximately 0.8 s when using real-time video, and a delay of 60-90 s was experienced when accessing the first virtual slide in a session. No significant lag or inconvenience was experienced during diagnosis and conferencing, and the results were satisfactory. Our hypothesis was confirmed for both remote diagnosis using real-time video and virtual slide systems, and also for

  13. On the Relationship Between High Speed Solar Wind Streams and Radiation Belt Electron Fluxes

    NASA Technical Reports Server (NTRS)

    Zheng, Yihua

    2011-01-01

    Both past and recent research results indicate that solar wind speed has a close connection to radiation belt electron fluxes [e.g., Paulikas and Blake, 1979; Reeves et aI., 2011]: a higher solar wind speed is often associated with a higher level of radiation electron fluxes. But the relationship can be very complex [Reeves et aI., 2011]. The study presented here provides further corroboration of this viewpoint by emphasizing the importance of a global perspective and time history. We find that all the events during years 2010 and 2011 where the >0.8 MeV integral electron flux exceeds 10(exp 5) particles/sq cm/sr/s (pfu) at GEO orbit are associated with the high speed streams (HSS) following the onset of the Stream Interaction Region (SIR), with most of them belonging to the long-lasting Corotating Interaction Region (CIR). Our preliminary results indicate that during HSS events, a maximum speed of 700 km/s and above is a sufficient but not necessary condition for the > 0.8 MeV electron flux to reach 10(exp 5) pfu. But in the exception cases of HSS events where the electron flux level exceeds the 10(exp 5) pfu value but the maximum solar wind speed is less than 700 km/s, a prior impact can be noted either from a CME or a transient SIR within 3-4 days before the arrival of the HSS - stressing the importance of time history. Through superposed epoch analysis and studies providing comparisons with the CME events and the HSS events where the flux level fails to reach the 10(exp 5) pfu, we will present the quantitative assessment of behaviors and relationships of various quantities, such as the time it takes to reach the flux threshold value from the stream interface and its dependence on different physical parameters (e.g., duration of the HSS event, its maximum or average of the solar wind speed, IMF Bz, Kp). The ultimate goal is to apply what is derived to space weather forecasting.

  14. Evolution of the Relationships between Helium Abundance, Minor Ion Charge State, and Solar Wind Speed over the Solar Cycle

    NASA Astrophysics Data System (ADS)

    Kasper, J. C.; Stevens, M. L.; Korreck, K. E.; Maruca, B. A.; Kiefer, K. K.; Schwadron, N. A.; Lepri, S. T.

    2012-02-01

    The changing relationships between solar wind speed, helium abundance, and minor ion charge state are examined over solar cycle 23. Observations of the abundance of helium relative to hydrogen (A He ≡ 100 × n He/n H) by the Wind spacecraft are used to examine the dependence of A He on solar wind speed and solar activity between 1994 and 2010. This work updates an earlier study of A He from 1994 to 2004 to include the recent extreme solar minimum and broadly confirms our previous result that A He in slow wind is strongly correlated with sunspot number, reaching its lowest values in each solar minima. During the last minimum, as sunspot numbers reached their lowest levels in recent history, A He continued to decrease, falling to half the levels observed in slow wind during the previous minimum and, for the first time observed, decreasing even in the fastest solar wind. We have also extended our previous analysis by adding measurements of the mean carbon and oxygen charge states observed with the Advanced Composition Explorer spacecraft since 1998. We find that as solar activity decreased, the mean charge states of oxygen and carbon for solar wind of a given speed also fell, implying that the wind was formed in cooler regions in the corona during the recent solar minimum. The physical processes in the coronal responsible for establishing the mean charge state and speed of the solar wind have evolved with solar activity and time.

  15. In situ measurements of wind and current speed and relationship between output power and turbulence

    NASA Astrophysics Data System (ADS)

    Duran Medina, Olmo; Schmitt, François G.; Sentchev, Alexei; Calif, Rudy

    2015-04-01

    In a context of energy transition, wind and tidal energy are sources of clean energy with the potential of partially satisfying the growing demand. The main problem of this type of energy, and other types of renewable energy remains the discontinuity of the electric power produced in different scales, inducing large fluctuations also called intermittency. This intermittency of wind and tidal energy is inherent to the turbulent nature of wind and marine currents. We consider this intermittent power production in strong relation with the turbulent intermittency of the resource. The turbulence theory is multifractal energy cascades models, a classic in physics of turbulence. From earlier studies in atmospheric sciences, we learn that wind speed and the aggregate power output are intermittent and multifractal over a wide range of scales [Calif and Schmitt 2014]. We want to extend this study to a marine current turbine and compare the scaling properties for those renewable energy sources. We consider here coupling between simultaneous velocity time series and output power from a wind turbine and a marine current turbine. Wind turbine data were obtained from Denmark and marine current data from Western Scheldt, Belgium where a prototype of a vertical and horizontal marine current turbines are tested. After an estimation of their Fourier density power spectra, we study their scaling properties in Kolmogorov's theory and the framework of fully developed turbulence. Hence, we employ a Hilbert-based methodology, namely arbitrary-order Hilbert spectral analysis [Calif et al. 2013a, 2013b] to characterize the intermittent property of the wind and marine current velocity in order to characterize the intermittent nature of the fluid. This method is used in order to obtain the spectrum and the corresponding power law for non-linear and non-stationary time series. The goal is to study the non-linear transfer characteristics in a multi-scale and multi-intensity framework.

  16. Forecasting surface wind speeds over offshore islands near Taiwan during tropical cyclones: Comparisons of data-driven algorithms and parametric wind representations

    NASA Astrophysics Data System (ADS)

    Wei, Chih-Chiang

    2015-03-01

    Tropical cyclones often affect the western North Pacific region. Between May and October annually, enormous flood damage is frequently caused by typhoons in Taiwan. This study adopted machine learning techniques to forecast the hourly wind speeds over offshore islands near Taiwan during tropical cyclones. To develop a highly reliable surface wind speed prediction technique, the four kernel-based support vector machines for regression (SVR) models, comprising radial basis function, linear, polynomial, and Pearson VII universal kernels were used. To ensure the accuracy of the SVR model, traditional regressions and the parametric wind representations, comprising the modified Rankine profile, Holland wind profile, and DeMaria wind profile were used to compare wind speed forecasts. The methodology was applied to two islands near Taiwan, Lanyu, and Pengjia Islets. The forecasting horizon ranged from 1 to 6 h. The results indicated that the Pearson VII SVR is the most precise of the kernel-based SVR models, regressions, and parametric wind representations. Additionally, Typhoons Nanmadol and Saola which made landfall over Taiwan during 2011 and 2012 were simulated and examined. The results showed that the Pearson VII SVR yielded more favorable results than did the regressions and Holland wind profile. In addition, we observed that Holland wind profile seems applicable to open ocean but unsuitable for areas affected by topographic effects, such as the Central Mountain Range of Taiwan.

  17. Estimates of oceanic surface wind speed and direction using orthogonal beam scatterometer measurements and comparison of recent sea scattering theories

    NASA Technical Reports Server (NTRS)

    Moore, R. K.; Fung, A. K.; Dome, G. J.; Birrer, I. J.

    1978-01-01

    The wind direction properties of radar backscatter from the sea were empirically modelled using a cosine Fourier series through the 4th harmonic in wind direction (referenced to upwind). A comparison with 1975 JONSWAP (Joint North Sea Wave Project) scatterometer data, at incidence angles of 40 and 65, indicates that effects to third and fourth harmonics are negligible. Another important result is that the Fourier coefficients through the second harmonic are related to wind speed by a power law expression. A technique is also proposed to estimate the wind speed and direction over the ocean from two orthogonal scattering measurements. A comparison between two different types of sea scatter theories, one type presented by the work of Wright and the other by that of Chan and Fung, was made with recent scatterometer measurements. It demonstrates that a complete scattering model must include some provisions for the anisotropic characteristics of the sea scatter, and use a sea spectrum which depends upon wind speed.

  18. Towards the modelling of pedestrian wind speed using high-resolution digital surface models and statistical methods

    NASA Astrophysics Data System (ADS)

    Johansson, Lars; Onomura, Shiho; Lindberg, Fredrik; Seaquist, Jonathan

    2016-04-01

    Wind is a complex phenomenon and a critical factor in assessing climatic conditions and pedestrian comfort within cities. To obtain spatial information on near-ground wind speed, 3D computational fluid dynamics (CFD) modelling is often used. This is a computationally intensive method which requires extensive computer resources and is time consuming. By using a simpler 2D method, larger areas can be processed and less time is required. This study attempts to model the relationship between near-ground wind speed and urban geometry using 2.5D raster data and variable selection methods. Such models can be implemented in a geographic information system (GIS) to assess the spatial distribution of wind speed at street level in complex urban environments at scales from neighbourhood to city. Wind speed data, 2 m above ground, is obtained from simulations by CFD modelling and used as a response variable. A number of derivatives calculated from high-resolution digital surface models (DSM) are used as potential predictors. A sequential variable selection algorithm followed by all-possible subset regression was used to select candidate models for further evaluation. The results show that the selected models explain general spatial wind speed pattern characteristics but the prediction errors are large, especially so in areas with high wind speeds. However, all selected models did explain 90 % of the wind speed variability (R 2 ≈ 0.90). Predictors adding information on width and height ratio and alignment of street canyons with respect to wind direction are suggested for improving model performance. To assess the applicability of any derived model, the results of the CFD model should be thoroughly evaluated against field measurements.

  19. Low Wind Speed Turbine Project Phase II: The Application of Medium-Voltage Electrical Apparatus to the Class of Variable Speed Multi-Megawatt Low Wind Speed Turbines; 15 June 2004--30 April 2005

    SciTech Connect

    Erdman, W.; Behnke, M.

    2005-11-01

    Kilowatt ratings of modern wind turbines have progressed rapidly from 50 kW to 1,800 kW over the past 25 years, with 3.0- to 7.5-MW turbines expected in the next 5 years. The premise of this study is simple: The rapid growth of wind turbine power ratings and the corresponding growth in turbine electrical generation systems and associated controls are quickly making low-voltage (LV) electrical design approaches cost-ineffective. This report provides design detail and compares the cost of energy (COE) between commercial LV-class wind power machines and emerging medium-voltage (MV)-class multi-megawatt wind technology. The key finding is that a 2.5% reduction in the COE can be achieved by moving from LV to MV systems. This is a conservative estimate, with a 3% to 3.5% reduction believed to be attainable once purchase orders to support a 250-turbine/year production level are placed. This evaluation considers capital costs as well as installation, maintenance, and training requirements for wind turbine maintenance personnel. Subsystems investigated include the generator, pendant cables, variable-speed converter, and padmount transformer with switchgear. Both current-source and voltage-source converter/inverter MV topologies are compared against their low-voltage, voltage-source counterparts at the 3.0-, 5.0-, and 7.5-MW levels.

  20. Structure of Turbulence in Katabatic Flows Below and Above the Wind-Speed Maximum

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Measurements of small-scale turbulence made in the atmospheric boundary layer over complex terrain during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program are used to describe the structure of turbulence in katabatic flows. Turbulent and mean meteorological data were continuously measured on four towers deployed along the east lower slope (2-4°) of Granite Mountain near Salt Lake City in Utah, USA. The multi-level (up to seven) observations made during a 30-day long MATERHORN field campaign in September-October 2012 allowed the study of temporal and spatial structure of katabatic flows in detail, and herein we report turbulence statistics (e.g., fluxes, variances, spectra, and cospectra) and their variations in katabatic flow. 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-slope) heat flux in a slope-following coordinate system change their sign below and above the wind maximum of a katabatic flow. The momentum flux is directed downward (upward) whereas the along-slope heat flux is downslope (upslope) below (above) the wind maximum. This suggests that the position of the jet-speed maximum can be obtained by linear interpolation between positive and negative values of the momentum flux (or the along-slope heat flux) to derive the height where the flux becomes zero. It is shown that the standard deviations of all wind-speed components (and therefore of the turbulent kinetic energy) and the dissipation rate of turbulent kinetic energy have a local minimum, whereas the standard deviation of air temperature has an absolute maximum at the height of wind-speed maximum. We report several cases when the destructive effect of vertical heat flux is completely cancelled by the generation of turbulence due to the along-slope heat flux. Turbulence above the wind-speed

  1. Pulse-burst PIV in a high-speed wind tunnel

    NASA Astrophysics Data System (ADS)

    Beresh, Steven; Kearney, Sean; Wagner, Justin; Guildenbecher, Daniel; Henfling, John; Spillers, Russell; Pruett, Brian; Jiang, Naibo; Slipchenko, Mikhail; Mance, Jason; Roy, Sukesh

    2015-09-01

    Time-resolved particle image velocimetry (TR-PIV) has been achieved in a high-speed wind tunnel, providing velocity field movies of compressible turbulence events. The requirements of high-speed flows demand greater energy at faster pulse rates than possible with the TR-PIV systems developed for low-speed flows. This has been realized using a pulse-burst laser to obtain movies at up to 50 kHz, with higher speeds possible at the cost of spatial resolution. The constraints imposed by use of a pulse-burst laser are limited burst duration of 10.2 ms and a low duty cycle for data acquisition. Pulse-burst PIV has been demonstrated in a supersonic jet exhausting into a transonic crossflow and in transonic flow over a rectangular cavity. The velocity field sequences reveal the passage of turbulent structures and can be used to find velocity power spectra at every point in the field, providing spatial distributions of acoustic modes. The present work represents the first use of TR-PIV in a high-speed ground-test facility.

  2. The Generation of Smooth High Speed Solar Wind From Plume-Interplume Mixing

    NASA Technical Reports Server (NTRS)

    Suess, Steve; Parhi, Shyam; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Ulysses has shown that fast solar wind is extremely smooth, with a variance of less than 5%, in contrast to slow wind with a variance of approximately 30%. Now UVCS has produced the surprising result that the flow speed within coronal holes, the source of fast wind, is not at all smooth. Specifically, Giordano et al. (ApJ, v531, L79-L82, 2000) report that at 1.7 R(sub SUN) the interplume flow speed is typically more than twice the plume flow speed. Other less direct evidence supports this same result, with speeds from less than 300 to over 1000 km/s reported at approximately 5 R(sub SUN). This presents the paradox of how strongly differing plume and interplume flow speeds can exist near the Sun and be absent far from the Sun. The only answer is that plume and interplume material or momentum must be strongly mixed and that the mixing must occur mainly inside 0.3 AU to be consistent with Helios observations of smooth fast wind. Pressure balance structures (PBSs) and He abundance anomalies (Reisenfeld, et al., GRL, v26(13), 1805-1808, 1999) have been identified as interplanetary remnants of plumes, implying momentum mixing is the dominant coronal process. One possible source for plume/interplume momentum mixing is MHD Kelvin-Helmholtz (KH) shear instabilities occurring on the velocity shear interfaces. The velocity shear is a source of free energy and KH fluctuations could, through nonlinear cascade, provide the forcing required for the plasma oscillations (Cranmer, ApJ, v532, 1197-1208, 2000) reported to exist in coronal holes. The physical properties in coronal holes are now sufficiently well known that we can show plume/interplume shear interfaces become unstable to the KH instability at 5 - 10 R(sub SUN). The KH dispersion relation can be used to analyze marginal stability, the most unstable wavelengths, and linear growth rates. Numerical simulations can be used to verify results from the linear analysis and study the nonlinear development of KH modes. Here we

  3. A Comparison of Wind Speed Data from Mechanical and Ultrasonic Anemometers

    NASA Technical Reports Server (NTRS)

    Short, D.; Wells, L.; Merceret, F.; Roeder, W. P.

    2006-01-01

    This study compared the performance of mechanical and ultrasonic anemometers at the Eastern Range (ER; Kennedy Space Center and Cape Canaveral Air Force Station on Florida's Atlantic coast) and the Western Range (WR; Vandenberg Air Force Base on California's Pacific coast). Launch Weather Officers, forecasters, and Range Safety analysts need to understand the performance of wind sensors at the ER and WR for weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The current ER and WR weather tower wind instruments are being changed from the current propeller-and-vane (ER) and cup-and-vane (WR) sensors to ultrasonic sensors through the Range Standardization and Automation (RSA) program. The differences between mechanical and ultrasonic techniques have been found to cause differences in the statistics of peak wind speed in previous studies. The 45th Weather Squadron (45 WS) and the 30th Weather Squadron (30 WS) requested the Applied Meteorology Unit (AMU) to compare data between RSA and current sensors to determine if there are significant differences. Approximately 3 weeks of Legacy and RSA wind data from each range were used in the study, archived during May and June 2005. The ER data spanned the full diurnal cycle, while the WR data was confined to 1000-1600 local time. The sample of 1-minute data from numerous levels on 5 different towers on each range totaled more than 500,000 minutes of data (482,979 minutes of data after quality control). The 10 towers were instrumented at several levels, ranging from 12 ft to 492 ft above ground level. The RSA sensors were collocated at the same vertical levels as the present sensors and typically within 15 ft horizontally of each another. Data from a total of 53 RSA ultrasonic sensors, collocated with present sensors were compared. The 1-minute average wind speed/direction and the 1

  4. Observations During GRIP from HIRAD: Ocean Surface Wind Speed and Rain Rate

    NASA Technical Reports Server (NTRS)

    Miller, Timothy L.; James, M. W.; Jones, L.; Ruf, C. S.; Uhlhorn, E. W.; Bailey, M. C.; Buckley, C. D.; Simmons, D. E.; Johnstone, S.; Peterson, A.; Schultz, L. A.; Biewas, S.; Johnson, J. W.; Shah, G.; Feingstein, D.; Cleveland, W. H.; Johnson, J.; Hood, R. E.

    2011-01-01

    HIRAD (Hurricane Imaging Radiometer) flew on the WB-57 during NASA's GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be inferred. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years. The advantage of HIRAD over SFMR is that HIRAD can observe a +/- 60-degree swath, rather than a single footprint at nadir angle. Results from the flights during the GRIP campaign will be shown, including images of brightness temperatures, wind speed, and rain rate. To the extent possible, comparisons will be made with observations from other instruments on the GRIP campaign, for which HIRAD observations are either directly comparable or are complementary. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  5. Ionospheric Heating Rates Associated with Solar Wind Forcing: Ejecta flow, High Speed Flow and Slow Flow

    NASA Astrophysics Data System (ADS)

    Knipp, D. J.; Kasprzak, B.; Richardson, I.; Paige, T.; Evans, D.

    2001-12-01

    We present estimates of global ionospheric Joule and particle heating as a function of solar wind flow types over solar cycles 21, 22 and the first half of solar cycle 23. Richardson et al., [JGR, 2000] used a variety of techniques to categorize the solar wind flow as ejecta, high-speed stream or slow flow. Their work provides the basis for our catigorization of heating by flow type. The estimates of Joule heating are based on output of the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure, and fits to the Polar Cap Index [Chun et al., GRL, 1999]. Estimates of particle heating are derived from polar orbiting satellites. Although ejecta only account for 19% of the solar wind flow, they account for 27% of the Joule heating. High-speed stream flow accounts for 47% of the flow occurrence and 44% of the Joule heating. We will show similar comparisons for particle heating. Our solar cycle statistics indicate that Joule heating produces a yearly average hemispheric heating rate of 53 GW while particles produce a hemispheric heating rate of 38 GW. Joule heating exhibits more variability than particle heating. During solar cycle maximum years Joule heating accounts for twice the heating associated with particles heating.

  6. Where in the Streamer Belt does the Slow Speed Wind Originate?

    NASA Astrophysics Data System (ADS)

    Strachan, L.; Suleiman, R.; Panasyuk, A. V.; Biesecker, D. A.; Kohl, J. L.

    2001-05-01

    The Ulysses high latitude mission showed that the slow speed wind at solar minimum appears to come from equatorial regions in the heliosphere that are dominated by helmet streamers. However, there are few coronal measurements of the detailed latitudinal variation of the outflow velocity across a streamer. Such measurements are needed to identify the region of the streamer that gives rise to the slow speed wind. For this study we use UVCS and LASCO observations of a solar minimum streamer to make a detailed model of the outflow velocities for O+5 as a function of position angle from the streamer axis. This new work goes beyond using the OVI line ratios to define the boundaries between fast and slow wind. We constrain the coronal plasma parameters (velocities, temperature anisotropies, densities, etc.) using OVI and Ly-alpha line profiles, and white light polarized brightness data. We will discuss various possibilities for the latitudinal profile for the coronal outflow in the streamer belt. This work is supported by NASA Grant NAG5-7822 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency, and by the ESA PRODEX program (Swiss contribution).

  7. Application of Rapid Prototyping Methods to High-Speed Wind Tunnel Testing

    NASA Technical Reports Server (NTRS)

    Springer, A. M.

    1998-01-01

    This study was undertaken in MSFC's 14-Inch Trisonic Wind Tunnel to determine if rapid prototyping methods could be used in the design and manufacturing of high speed wind tunnel models in direct testing applications, and if these methods would reduce model design/fabrication time and cost while providing models of high enough fidelity to provide adequate aerodynamic data, and of sufficient strength to survive the test environment. Rapid prototyping methods utilized to construct wind tunnel models in a wing-body-tail configuration were: fused deposition method using both ABS plastic and PEEK as building materials, stereolithography using the photopolymer SL-5170, selective laser sintering using glass reinforced nylon, and laminated object manufacturing using plastic reinforced with glass and 'paper'. This study revealed good agreement between the SLA model, the metal model with an FDM-ABS nose, an SLA nose, and the metal model for most operating conditions, while the FDM-ABS data diverged at higher loading conditions. Data from the initial SLS model showed poor agreement due to problems in post-processing, resulting in a different configuration. A second SLS model was tested and showed relatively good agreement. It can be concluded that rapid prototyping models show promise in preliminary aerodynamic development studies at subsonic, transonic, and supersonic speeds.

  8. Ion energy equation for the high-speed solar wind: Ulysses observations

    SciTech Connect

    Feldman, W.C.; Barraclough, B.L.; Gosling, J.T.; McComas, D.J.; Riley, P.; Goldstein, B.E.; Balogh, A.

    1998-07-01

    Ulysses data in the high-speed solar wind that cover a wide range of latitudes centered on the solar poles were studied to test whether a polytrope law can be used to close the ion energy equation. Three approaches were taken. We determined the correlation between proton temperature and density (1) in the free expansion of the high-speed solar wind between 1.5 and 4.8 AU, (2) in steepened microstreams at high latitudes, and (3) at the edges of the equatorial band of solar wind variability. Strong correlations were observed in all data subsets that are consistent with a single polytrope relation, T{sub p}=aN{sub p}{sup ({gamma}{sup {asterisk}}{minus}1)}, where our best estimate for {gamma}{sup {asterisk}} is between 1.5 and 1.7. The best fitting relation is T{sub p}=(2.0{plus_minus}0.13){times}10{sup 5} N{sub p}{sup 0.57}. {copyright} 1998 American Geophysical Union

  9. Bivariate ensemble model output statistics approach for joint forecasting of wind speed and temperature

    NASA Astrophysics Data System (ADS)

    Baran, Sándor; Möller, Annette

    2016-06-01

    Forecast ensembles are typically employed to account for prediction uncertainties in numerical weather prediction models. However, ensembles often exhibit biases and dispersion errors, thus they require statistical post-processing to improve their predictive performance. Two popular univariate post-processing models are the Bayesian model averaging (BMA) and the ensemble model output statistics (EMOS). In the last few years, increased interest has emerged in developing multivariate post-processing models, incorporating dependencies between weather quantities, such as for example a bivariate distribution for wind vectors or even a more general setting allowing to combine any types of weather variables. In line with a recently proposed approach to model temperature and wind speed jointly by a bivariate BMA model, this paper introduces an EMOS model for these weather quantities based on a bivariate truncated normal distribution. The bivariate EMOS model is applied to temperature and wind speed forecasts of the 8-member University of Washington mesoscale ensemble and the 11-member ALADIN-HUNEPS ensemble of the Hungarian Meteorological Service and its predictive performance is compared to the performance of the bivariate BMA model and a multivariate Gaussian copula approach, post-processing the margins with univariate EMOS. While the predictive skills of the compared methods are similar, the bivariate EMOS model requires considerably lower computation times than the bivariate BMA method.

  10. Wind speed retrieval from Ku-band Tropical Rainfall Mapping Mission precipitation radar data at low incidence angles

    NASA Astrophysics Data System (ADS)

    Ren, Lin; Yang, Jingsong; Zheng, Gang; Wang, Juan

    2016-01-01

    A Ku-band low incidence backscatter model (KuLMOD) for retrieving wind speeds from Tropical Rainfall Mapping Mission (TRMM) precipitation radar (PR) data is proposed. The data set consisted of TRMM PR observations and collocated National Data Buoy Center (NDBC) and Tropical Ocean Global Atmosphere program buoy-measured wind and wave data. The TRMM PR data properties were analyzed with regard to their dependence on spatial resolution, wind speed, relative wind direction, and significant wave height. The KuLMOD model was developed using incidence angles (0.5 to 6.5 deg) and wind speeds (1.5 to 16.5 m/s) as inputs. The model coefficients were derived by fitting the collocated data. The KuLMOD-derived normalized radar cross section, σ0, was compared with those obtained from the TRMM PR observations and a quasi-specular theoretical model and showed good agreement. With the KuLMOD, the wind speeds were retrieved from the TRMM PR data using the least squares method and validated with the buoy measurements, yielding a root mean square error of 1.45 m/s. The retrieval accuracies for the different incidence angles, wind speeds, and spatial resolutions were obtained.

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

    NASA Astrophysics Data System (ADS)

    Ning, A.; Dykes, K.

    2014-06-01

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

  12. Frequency Regulation and Oscillation Damping Contributions of Variable-Speed Wind Generators in the U.S. Eastern Interconnection (EI)

    SciTech Connect

    Liu, Yong; Gracia, Jose R,; King, Jr, Thomas J.; Liu, Yilu

    2014-05-16

    The U.S. Eastern Interconnection (EI) is one of the largest electric power grids in the world and is expected to have difficulties in dealing with frequency regulation and oscillation damping issues caused by the increasing wind power. On the other side, variable-speed wind generators can actively engage in frequency regulation or oscillation damping with supplementary control loops. This paper creates a 5% wind power penetration simulation scenario based on the 16 000-bus EI system dynamic model and developed the user-defined wind electrical control model in PSS (R) E that incorporates additional frequency regulation and oscillation damping control loops. We evaluated the potential contributions of variable-speed wind generations to the EI system frequency regulation and oscillation damping, and simulation results demonstrate that current and future penetrations of wind power are promising in the EI system frequency regulation and oscillation damping.

  13. Frequency Regulation and Oscillation Damping Contributions of Variable-Speed Wind Generators in the U.S. Eastern Interconnection (EI)

    DOE PAGESBeta

    Liu, Yong; Gracia, Jose R,; King, Jr, Thomas J.; Liu, Yilu

    2014-05-16

    The U.S. Eastern Interconnection (EI) is one of the largest electric power grids in the world and is expected to have difficulties in dealing with frequency regulation and oscillation damping issues caused by the increasing wind power. On the other side, variable-speed wind generators can actively engage in frequency regulation or oscillation damping with supplementary control loops. This paper creates a 5% wind power penetration simulation scenario based on the 16 000-bus EI system dynamic model and developed the user-defined wind electrical control model in PSS (R) E that incorporates additional frequency regulation and oscillation damping control loops. We evaluatedmore » the potential contributions of variable-speed wind generations to the EI system frequency regulation and oscillation damping, and simulation results demonstrate that current and future penetrations of wind power are promising in the EI system frequency regulation and oscillation damping.« less

  14. Effect of blade loading and rotor speed on the optimal aerodynamic performance of wind turbine blades

    NASA Astrophysics Data System (ADS)

    Bryson, Christopher; Hussain, Fazle; Barhorst, Alan

    2015-11-01

    Optimization of wind turbine torque as a function of angle of attack - over the entire speed range from start-up to cut-off - is studied by considering the full trigonometric relations projecting lift and drag to thrust and torque. Since driving force and thrust are geometrically constrained, one cannot be changed without affecting the other. Increasing lift to enhance torque simultaneously increases thrust, which subsequently reduces the inflow angle with respect to the rotor plane via an increased reduction in inflow velocity. Reducing the inflow angle redirects the lift force away from the driving force generating the torque, which may reduce overall torque. Similarly, changes in the tip-speed ratio (TSR) affect the inflow angle and thus the optimal torque. Using the airfoil data from the NREL 5 MW reference turbine, the optimal angle of attack over the operational TSR range (4 to 15) was computed using a BEM model to incorporate the dynamic coupling, namely the interdependency of blade loading and inflow angle. The optimal angle of attack is close to minimum drag during start-up phase (high TSR) and continuously increases toward maximum lift at high wind speeds (low TSR).

  15. Dependence of the Normalized Radar Cross Section of Water Waves on Bragg Wavelength-Wind Speed Sensitivity

    NASA Technical Reports Server (NTRS)

    Long, David G.; Collyer, R. Scott; Reed, Ryan; Arnold, David V.

    1996-01-01

    Measurements of the normalized radar cross section (sigma(sup o)) made by the YSCAT ultrawideband scatterometer during an extended deployment on the Canada Centre for Inland Waters(CCIW) Research Tower located at Lake Ontario are analyzed and compared with anemometer wind measurements to study the sensitivity of (sigma(sup o)) to the wind speed as a function of the Bragg wavelength. This paper concentrates on upwind and downwind azimuth angles in the wind speed range of 4.5-12 m/s. While YSCAT collected measurements of sigma(sup o) at a variety of frequencies and incidence angles, this paper focuses on frequencies of 2.0, 3.05, 5.30, 10.02, and 14.0 GHz and incidence angles within the Bragg regime, 30-50 deg. Adopting a power law model to describe the relationship between sigma(sup o) and wind speed, both wind speed exponents and upwind/downwind (u/d) ratios of sigma(sup o) are found using least squares linear regression. The analysis of the wind speed exponents and u/d ratios show that shorter Bragg wavelengths (Lambda less than 4 cm) are the most sensitive to wind speed and direction. Additionally, vertical polarization (V-pol) sigma(sup o) is shown to be more sensitive to wind speed than horizontal polarization (H-pol) sigma(sup o), while the H-pol u/d ratio is larger than the V-pol u/d ratio.

  16. Infrared thermography for detection of laminar-turbulent transition in low-speed wind tunnel testing

    NASA Astrophysics Data System (ADS)

    Joseph, Liselle A.; Borgoltz, Aurelien; Devenport, William

    2016-05-01

    This work presents the details of a system for experimentally identifying laminar-to-turbulent transition using infrared thermography applied to large, metal models in low-speed wind tunnel tests. Key elements of the transition detection system include infrared cameras with sensitivity in the 7.5- to 14.0-µm spectral range and a thin, insulating coat for the model. The fidelity of the system was validated through experiments on two wind-turbine blade airfoil sections tested at Reynolds numbers between Re = 1.5 × 106 and 3 × 106. Results compare well with measurements from surface pressure distributions and stethoscope observations. However, the infrared-based system provides data over a much broader range of conditions and locations on the model. This paper chronicles the design, implementation and validation of the infrared transition detection system, a subject which has not been widely detailed in the literature to date.

  17. Aeroacoustic response of coaxial wall-mounted Helmholtz resonators in a low-speed wind tunnel.

    PubMed

    Slaton, William V; Nishikawa, Asami

    2015-01-01

    The aeroacoustic response of coaxial wall-mounted Helmholtz resonators with different neck geometries in a low-speed wind tunnel has been investigated. Experimental test results of this system reveal a strong aeroacoustic response over a Strouhal number range of 0.25 to 0.1 for both increasing and decreasing the flow rate in the wind tunnel. Aeroacoustic response in the low-amplitude range O(10(-3)) < Vac/Vflow < O(10(-1)) has been successfully modeled by describing-function analysis. This analysis, coupled with a turbulent flow velocity distribution model, gives reasonable values for the location in the flow of the undulating stream velocity that drives vortex shedding at the resonator mouth. Having an estimate for the stream velocity that drives the flow-excited resonance is crucial when employing the describing-function analysis to predict aeroacoustic response of resonators. PMID:25618056

  18. 9- by 15-Foot Low Speed Wind Tunnel Acoustic Improvements Expanded Overview

    NASA Technical Reports Server (NTRS)

    Stephens, David

    2016-01-01

    The 9- by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) at NASA Glenn Research Center was built in 1969 in the return leg of the 8- by 6-Foot Supersonic Wind Tunnel (8x6 SWT). The 8x6 SWT was completed in 1949 and acoustically treated to mitigate community noise issues in 1950. This treatment included the addition of a large muffler downstream of the 8x6 SWT test section and diffuser. The 9x15 LSWT was designed for performance testing of V/STOL aircraft models, but with the addition of the current acoustic treatment in 1986 the tunnel been used principally for acoustic and performance testing of aircraft propulsion systems. The present document describes an anticipated acoustic upgrade to be completed in 2017.

  19. The Split Window Microwave Radiometer (SWMR) for hurricane wind speed measurement from space

    NASA Technical Reports Server (NTRS)

    Swift, Calvin T.; Black, P. G.

    1992-01-01

    The monitoring of hurricanes demands considerable resources each year by the National Oceanic and Atmospheric Administration. Even with the extensive use of satellite and airborne probing of those storms, there is still much uncertainty involved in predicting landfall for timely evacuation of people subject to the threat. The concept of the Split Window Microwave Radiometer (SWMR) is to add an additional capability of remotely measuring surface winds to hopefully improve prediction capabilities or at least define the severity of the storm while it is far from land. Some of the present science and observational needs are addressed in this report as are remote sensing limitations which impact the design of a minimal system which can be launched into low earth orbit by a low cost launch system. This study has concluded that wind speed and rain rate maps of hurricanes can be generated with an X-Band radiometer system with an antenna whose aperture is 2 m on a side.

  20. Development of the fully digital dc speed regulation system in 8-mX6-m wind tunnel

    NASA Astrophysics Data System (ADS)

    Li, Dexiang; Ye, Jicheng; You, Xi; Zhang, Xiande

    2000-05-01

    The old analog system of speed regulation of 8 m X 6 m wind tunnel has been successfully reformed recently. The new system realized fully digital control on 2600 kW DC motor, through rebuilding two sets of 485 V and 30 A speed regulation equipment used in controlling large power thyristor rectifier of 2-stage serial.

  1. The Generation of Smooth High Speed Solar Wind from Plume-Interplume Mixing

    NASA Technical Reports Server (NTRS)

    Parhi, Shyamsundar; Suess, Steven T.; Sulkanen, Martin E.

    1998-01-01

    Plumes and rays are magnetic field aligned density striations in coronal holes with different values of plasma beta. The overall plasma beta is very small in the low corona but exceeds unity beyond 15-20 solar radius. High speed solar wind reported beyond 0.3 AU is relatively smooth and uniform and known to originate from the much filamented coronal hole. Thus the obvious question is how to generate a smooth solar wind from seemingly filamentary structure. Hence one has to find a mechanism to substantiate this apparent observed (Ulysses) phenomenon. To do this we model plumes as jets (or wakes) of plasma emitted from the solar surface. The shear between a jet and its ambient is known to become unstable to the MHD Kelvin-Helmholtz ("KH") instability if the Alfven Mach number of the jet is greater than one and the uniform external magnetic field is small. Starting with a simple configuration we consider a jet of half thickness R, having uniform density and uniform internal magnetic field. The external medium has also a uniform density and uniform magnetic field. The jet is perturbed at the boundary with a linear amplitude and fixed frequency. We simulate the coronal jet using the 3D ZEUS code. The first results indicate the slab jet is unstable to the MHD KH instability at 5-10 solar radius for some angle of wave propagation. The propagating instability may smooth the filamented flow. It may also produce the entrained Alfvenic fluctuations observed by Ulysses in the high speed wind. We are at present determining the parameters which induce large growth rate. This may clarify the mystery behind the emergence of fast smooth solar wind from very filamentary structures in coronal holes. Also, using the dispersion relation already available for such a flow we obtain some general description of the instability criteria for the KH instability at a jet interface.

  2. Error propagation equations for estimating the uncertainty in high-speed wind tunnel test results

    SciTech Connect

    Clark, E.L.

    1994-07-01

    Error propagation equations, based on the Taylor series model, are derived for the nondimensional ratios and coefficients most often encountered in high-speed wind tunnel testing. These include pressure ratio and coefficient, static force and moment coefficients, dynamic stability coefficients, and calibration Mach number. The error equations contain partial derivatives, denoted as sensitivity coefficients, which define the influence of free-steam Mach number, M{infinity}, on various aerodynamic ratios. To facilitate use of the error equations, sensitivity coefficients are derived and evaluated for five fundamental aerodynamic ratios which relate free-steam test conditions to a reference condition.

  3. F-15 SMTD low speed jet effects wind tunnel test results

    NASA Technical Reports Server (NTRS)

    Blake, William B.

    1988-01-01

    Key results from low speed wind tunnel testing of the F-15 STOL and Maneuver Technology Demonstrator (SMDT) with thrust reversers are presented. Longitudinally, the largest induced increments in the stability and control occur at landing gear height. These generally reflect an induced lift loss and a nose-up pitching moment, and vary with sideslip. Directional stability is reduced at landing gear height with full reverse thrust. Nonlinearities in the horizontal tail effectiveness are found in free air and at landing gear height.

  4. NASA Lewis 9- by 15-foot low-speed wind tunnel user manual

    NASA Technical Reports Server (NTRS)

    Soeder, Ronald H.

    1993-01-01

    This manual describes the 9- by 15-Foot Low-Speed Wind Tunnel at the Lewis Research Center and provides information for users who wish to conduct experiments in this atmospheric facility. Tunnel variables such as pressures, temperatures, available tests section area, and Mach number ranges (0.05 to 0.20) are discussed. In addition, general support systems such as air systems, hydraulic system, hydrogen system, laser system, flow visualization system, and model support systems are described. Instrumentation and data processing and acquisition systems are also discussed.

  5. High speed civil transport in 14x22 foot wind tunnel

    NASA Technical Reports Server (NTRS)

    1993-01-01

    NASA technician Michael E. Ramsey inspects a high speed civil transport model between wind tunnel tests at NASA's Langley Research Center, Hampton, Virginia. Aerodynamic tests of the 19-foot (5.7 meters) model in the 14x22 foot subsonic tunnel simulate takeoff and landing of a 300 passenger supersonic commercial transport that would cruise at Mach 2.4 (approximately 1,600 mph/2,560kph). Designated Reference H, the concept was designed by Boeing and presently serves as a common configuration for government-industry technology studies.

  6. The Acoustic Environment of the NASA Glenn 9- by 15-foot Low-Speed Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Stephens, David B.

    2015-01-01

    The 9- by 15-Foot Low Speed Wind Tunnel is an acoustic testing facility with a long history of aircraft propulsion noise research. Due to interest in renovating the facility to support future testing of advanced quiet engine designs, a study was conducted to document the background noise level in the facility and investigate the sources of contaminating noise. The anechoic quality of the facility was also investigated using an interrupted noise method. The present report discusses these aspects of the noise environment in this facility.

  7. Wind tunnel performance results of swirl recovery vanes as tested with an advanced high speed propeller

    NASA Technical Reports Server (NTRS)

    Gazzaniga, John A.; Rose, Gayle E.

    1992-01-01

    Tests of swirl recovery vanes designed for use in conjunction with advanced high speed propellers were carried out at the NASA Lewis Research Center. The eight bladed 62.23 cm vanes were tested with a 62.23 cm SR = 7A high speed propeller in the NASA Lewis 2.44 x 1.83 m Supersonic Wind Tunnel for a Mach number range of 0.60 to 0.80. At the design operating condition for cruise of Mach 0.80 at an advance ratio of 3.26, the vane contribution to the total efficiency approached 2 percent. At lower off-design Mach numbers, the vane efficiency is even higher, approaching 4.5 percent for the Mach 0.60 condition. Use of the swirl recovery vanes essentially shifts the peak of the high speed propeller efficiency to a higher operating speed. This allows a greater degree of freedom in the selection of rpm over a wider operating range. Another unique result of the swirl recovery vane configuration is their essentially constant torque split between the propeller and the swirl vanes over a wide range of operating conditions for the design vane angle.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Spencer, Roy W.; Braswell, William D.

    2001-01-01

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

  10. Effect of Tip-Speed Constraints on the Optimized Design of a Wind Turbine

    SciTech Connect

    Dykes, K.; Resor, B.; Platt, A.; Guo, Y.; Ning, A.; King, R.; Parsons, T.; Petch, D.; Veers, P.

    2014-10-01

    This study investigates the effect of tip-velocity constraints on system levelized cost of energy (LCOE). The results indicate that a change in maximum tip speed from 80 to 100~m/s could produce a 32% decrease in gearbox weight (a 33% reduction in cost) which would result in an overall reduction of 1%-9% in system LCOE depending on the design approach. Three 100~m/s design cases were considered including a low tip-speed ratio/high-solidity rotor design, a high tip-speed ratio/ low-solidity rotor design, and finally a flexible blade design in which a high tip-speed ratio was used along with removing the tip deflection constraint on the rotor design. In all three cases, the significant reduction in gearbox weight caused by the higher tip-speed and lower overall gear ratio was counterbalanced by increased weights for the rotor and/or other drivetrain components and the tower. As a result, the increased costs of either the rotor or drivetrain components offset the overall reduction in turbine costs from down-sizing the gearbox. Other system costs were not significantly affected, whereas energy production was slightly reduced in the 100~m/s case low tip-speed ratio case and increased in the high tip-speed ratio case. This resulted in system cost of energy reductions moving from the 80~m/s design to the 100~m/s designs of 1.2% for the low tip-speed ratio, 4.6% for the high tip-speed ratio, and 9.5% for the final flexible case (the latter result is optimistic because the impact of deflection of the flexible blade on power production was not modeled). Overall, the results demonstrate that there is a trade-off in system design between the maximum tip velocity and the overall wind plant cost of energy, and there are many trade-offs within the overall system in designing a turbine for a high maximum tip velocity.

  11. X-ray bright points and high-speed wind streams: A preliminary analysis from Yohkoh and Ulysses data

    NASA Technical Reports Server (NTRS)

    Poletto, Giannina; Suess, Steven T.; Khan, J. I.; Uchida, Y.; Hiei, E.; Neugebauer, M.; Goldstein, B. E.; Strong, K. T.; Harvey, K. L.

    1994-01-01

    The following aspect of the solar wind mass flux, and of its variation, is examined: whether coronal plumes might be responsible for the long-term variability of the mass flux in high-speed streams emanating from coronal holes. The assumption that plumes are rooted in coronal bright points (BP's) is made. The behavior of X-ray BP's, imaged by the Yohkoh soft X-ray telescope (SXT), during a seven month period when Ulysses experiments observed a series of recurrent high-speed streams, is analyzed. If plumes/BP's are sources of the wind mass flux, changes in the coronal hole BP density to mimic changes of the mass flux in high-speed streams are expected. SOHO will have the capability of measuring the solar wind speed/density at small heliocentric distances while simultaneously observing coronal BP's and coronal plumes.

  12. Wind Speed Estimation and Parametrization of Wake Models for Downregulated Offshore Wind Farms within the scope of PossPOW Project

    NASA Astrophysics Data System (ADS)

    Göçmen Bozkurt, Tuhfe; Giebel, Gregor; Kjølstad Poulsen, Niels; Mirzaei, Mahmood

    2014-06-01

    With increasing installed capacity, wind farms are requested to downregulate more frequently, especially in the offshore environment. Determination and verification of possible (or available) power of downregulated offshore wind farms are the aims of the PossPOW project (see PossPOW.dtu.dk). Two main challenges encountered in the project so far are the estimation of wind speed and the recreation of the flow inside the downregulated wind farm as if it is operating ideally. The rotor effective wind speed was estimated using power, pitch angle and rotational speed as inputs combined with a generic Cp model. The results have been compared with Horns Rev-I dataset and NREL 5MW simulations under both downregulation and normal operation states. For the real-time flow recreation, the GCLarsen single wake model was re-calibrated using a 1-s dataset from Horns Rev and tested for the downregulated period. The re-calibrated model has to be further parametrized to include dynamic effects such as wind direction variability and meandering also considering different averaging time scales before implemented in full scale wind farms.

  13. Potential errors in using one anemometer to characterize the wind power over an entire rotor disk

    NASA Technical Reports Server (NTRS)

    Simon, R. L.

    1982-01-01

    Wind data collected at four levels on a 90-m tower in a prospective wind farm area are used to evaluate how well the 10-m wind speed data with and without intermittent vertical profile measurements compare with the 90-m tower data. If a standard, or even predictable, wind speed profile existed, there would be no need for a large, expensive tower. This cost differential becomes even more significant if several towers are needed to study a prospective wind farm.

  14. Do thick leaves avoid thermal damage in critically low wind speeds?

    PubMed

    Leigh, A; Sevanto, S; Ball, M C; Close, J D; Ellsworth, D S; Knight, C A; Nicotra, A B; Vogel, S

    2012-04-01

    Transient lulls in air movement are rarely measured, but can cause leaf temperature to rise rapidly to critical levels. The high heat capacity of thick leaves can damp this rapid change in temperature. However, little is known about the extent to which increased leaf thickness can reduce thermal damage, or how thick leaves would need to be to have biological significance. We evaluated quantitatively the contribution of small increases in leaf thickness to the reduction in thermal damage during critically low wind speeds under desert conditions. We employed a numerical model to investigate the effect of thickness relative to transpiration, absorptance and leaf size on damage avoidance. We used measured traits and thermotolerance thresholds of real leaves to calculate the leaf temperature response to naturally occurring variable low wind speed. Our results demonstrated that an increase in thickness of only fractions of a millimetre can prevent excursions to damaging high temperatures. This damping effect of increased thickness was greatest when other means of reducing leaf temperature (transpiration, reflectance or reduced size) were lacking. For perennial desert flora, we propose that increased leaf thickness is important in decreasing the incidence of extreme heat stress and, in some species, in enhancing long-term survival. PMID:22296328

  15. Log-normal distribution based Ensemble Model Output Statistics models for probabilistic wind-speed forecasting

    NASA Astrophysics Data System (ADS)

    Baran, Sándor; Lerch, Sebastian

    2015-07-01

    Ensembles of forecasts are obtained from multiple runs of numerical weather forecasting models with different initial conditions and typically employed to account for forecast uncertainties. However, biases and dispersion errors often occur in forecast ensembles, they are usually under-dispersive and uncalibrated and require statistical post-processing. We present an Ensemble Model Output Statistics (EMOS) method for calibration of wind speed forecasts based on the log-normal (LN) distribution, and we also show a regime-switching extension of the model which combines the previously studied truncated normal (TN) distribution with the LN. Both presented models are applied to wind speed forecasts of the eight-member University of Washington mesoscale ensemble, of the fifty-member ECMWF ensemble and of the eleven-member ALADIN-HUNEPS ensemble of the Hungarian Meteorological Service, and their predictive performances are compared to those of the TN and general extreme value (GEV) distribution based EMOS methods and to the TN-GEV mixture model. The results indicate improved calibration of probabilistic and accuracy of point forecasts in comparison to the raw ensemble and to climatological forecasts. Further, the TN-LN mixture model outperforms the traditional TN method and its predictive performance is able to keep up with the models utilizing the GEV distribution without assigning mass to negative values.

  16. A Complete Catalogue of High-Speed Solar Wind Streams during Solar Cycle 23

    NASA Astrophysics Data System (ADS)

    Xystouris, G.; Sigala, E.; Mavromichalaki, H.

    2014-03-01

    High-speed solar wind streams (HSSWSs) are ejected from the Sun and travel into the interplanetary space. Because of their high speed, they carry out energetic particles such as protons and heavy ions, which leads to an increase in the mean interplanetary magnetic field (IMF). Since the Earth is in the path of those streams, Earth's magnetosphere interacts with the disturbed magnetic field, leading to a significant radiation-induced degradation of technological systems. These interactions provide an enhanced energy transfer from the solar wind/IMF system into the Earth's magnetosphere and initiate geomagnetic disturbances that may have a possible impact on human health. Solar cycle 23 was a particularly unusual cycle with many energetic phenomena during its descending phase and also had an extended minimum. We have identified and catalogued the HSSWSs of this cycle and determined their characteristics, such as their maximum velocity, beginning and ending time, duration, and possible sources. We identified 710 HSSWSs and compared them with the corresponding characteristics of the streams of previous solar cycles. For first time, we used the CME data to study the stream sources, which led to useful results for the monitoring and forecasting of space weather effects.

  17. Wind-Speed Profile and Roughness Sublayer Depth Modelling in Urban Boundary Layers

    NASA Astrophysics Data System (ADS)

    Pelliccioni, Armando; Monti, Paolo; Leuzzi, Giovanni

    2016-03-01

    We propose a new formulation for the wind-speed profile in the urban boundary layer, which can be viewed as a generalisation of the commonly used logarithmic law. The model is based on the assumption that the role played by the classical aerodynamic roughness length and the displacement height in the logarithmic law is taken by a sole variable, the local length scale, which follows a pattern of exponential decrease with height. Starting from wind-speed profiles collected at Villa Pamphili park, Rome, Italy, an empirical fit is used to determine the model parameters. The results show that the local length scale depends also on the friction velocity and that, with appropriate normalization, it reduces to a family of curves that spreads according to the planar area fraction. Another novel aspect is the estimation of the roughness sublayer depth, which can be expressed as a function of the friction velocity and morphometric quantities such as the building height and the planar area fraction. It is also found that the rate of growth with height of the Prandtl mixing length linked to the new formulation is, just above the canopy, lower than the canonical value 0.41, and approaches the latter value well above the roughness sublayer. The model performance is tested by comparison with laboratory and field data reported in the literature.

  18. Wind-Speed Profile and Roughness Sublayer Depth Modelling in Urban Boundary Layers

    NASA Astrophysics Data System (ADS)

    Pelliccioni, Armando; Monti, Paolo; Leuzzi, Giovanni

    2016-08-01

    We propose a new formulation for the wind-speed profile in the urban boundary layer, which can be viewed as a generalisation of the commonly used logarithmic law. The model is based on the assumption that the role played by the classical aerodynamic roughness length and the displacement height in the logarithmic law is taken by a sole variable, the local length scale, which follows a pattern of exponential decrease with height. Starting from wind-speed profiles collected at Villa Pamphili park, Rome, Italy, an empirical fit is used to determine the model parameters. The results show that the local length scale depends also on the friction velocity and that, with appropriate normalization, it reduces to a family of curves that spreads according to the planar area fraction. Another novel aspect is the estimation of the roughness sublayer depth, which can be expressed as a function of the friction velocity and morphometric quantities such as the building height and the planar area fraction. It is also found that the rate of growth with height of the Prandtl mixing length linked to the new formulation is, just above the canopy, lower than the canonical value 0.41, and approaches the latter value well above the roughness sublayer. The model performance is tested by comparison with laboratory and field data reported in the literature.

  19. Low-speed wind tunnel test results of the Canard Rotor/Wing concept

    NASA Technical Reports Server (NTRS)

    Bass, Steven M.; Thompson, Thomas L.; Rutherford, John W.; Swanson, Stephen

    1993-01-01

    The Canard Rotor/Wing (CRW), a high-speed rotorcraft concept, was tested at the National Aeronautics and Space Administration (NASA) Ames Research Center's 40- by 80-Foot Wind Tunnel in Mountain View, California. The 1/5-scale model was tested to identify certain low-speed, fixed-wing, aerodynamic characteristics of the configuration and investigate the effectiveness of two empennages, an H-Tail and a T-Tail. The paper addresses the principal test objectives and the results achieved in the wind tunnel test. These are summarized as: i) drag build-up and differences between the H-Tail and T-Tail configuration, ii) longitudinal stability of the H-Tail and T-Tail configurations in the conversion and cruise modes, iii) control derivatives for the canard and elevator in the conversion and cruise modes, iv) aerodynamic characteristics of varying the rotor/wing azimuth position, and v) canard and tail lift/trim capability for conversion conditions.

  20. In situ observations of the influence of a large onshore wind farm on near-surface temperature, turbulence intensity and wind speed profiles

    NASA Astrophysics Data System (ADS)

    Smith, Craig M.; Barthelmie, R. J.; Pryor, S. C.

    2013-09-01

    Observations of wakes from individual wind turbines and a multi-megawatt wind energy installation in the Midwestern US indicate that directly downstream of a turbine (at a distance of 190 m, or 2.4 rotor diameters (D)), there is a clear impact on wind speed and turbulence intensity (TI) throughout the rotor swept area. However, at a downwind distance of 2.1 km (26 D downstream of the closest wind turbine) the wake of the whole wind farm is not evident. There is no significant reduction of hub-height wind speed or increase in TI especially during daytime. Thus, in high turbulence regimes even very large wind installations may have only a modest impact on downstream flow fields. No impact is observable in daytime vertical potential temperature gradients at downwind distances of >2 km, but at night the presence of the wind farm does significantly decrease the vertical gradients of potential temperature (though the profile remains stably stratified), largely by increasing the temperature at 2 m.

  1. Quasi-periodic (~mHz) dayside auroral brightennings associated with high-speed solar wind

    NASA Astrophysics Data System (ADS)

    Liou, K.

    2013-12-01

    It has been reported that dayside auroral pulsations of a few mHz frequency can occur when variations of solar wind dynamic pressure at the same frequency appear. Magnetospheric compression/decompression is attributed to the auroral pulsations. Here we report another type of dayside auroral pulsations not associated with solar wind dynamic pressure changes by using global auroral images acquired from the Ultraviolet Imager (UVI) on board the Polar satellite. From one periodic (~2 - 8 mHz) auroral event that occurred on February 8, 2000, it is found that the auroral enhancements covered most of the day (~05 - 16 MLT) sector and did not show a latitudinal dependence. Based on in situ particle data from DMSP SSJ/4, the brightennings were associated mainly with enhanced particle precipitations from the central plasma sheet (i.e., diffuse aurora). There was no geomagnetic pulsation on the ground and in the dawn sector of the magnetosheath as indicated by the Geotail measurements. While the auroral pulsations occurred during high solar wind speed (> 600 km/s), they commenced when the interplanetary magnetic field turned northward, suggesting the Kelvin-Helmholtz instability being a source of the pulsations. We will present detail analysis results and discuss other possible mechanisms in the context of current theories.

  2. AE Geomagnetic Index Predictability for High Speed Solar Wind Streams: A Wavelet Decomposition Technique

    NASA Technical Reports Server (NTRS)

    Guarnieri, Fernando L.; Tsurutani, Bruce T.; Hajra, Rajkumar; Echer, Ezequiel; Gonzalez, Walter D.; Mannucci, Anthony J.

    2014-01-01

    High speed solar wind streams cause geomagnetic activity at Earth. In this study we have applied a wavelet interactive filtering and reconstruction technique on the solar wind magnetic field components and AE index series to allowed us to investigate the relationship between the two. The IMF Bz component was found as the most significant solar wind parameter responsible by the control of the AE activity. Assuming magnetic reconnection associated to southward directed Bz is the main mechanism transferring energy into the magnetosphere, we adjust parameters to forecast the AE index. The adjusted routine is able to forecast AE, based only on the Bz measured at the L1 Lagrangian point. This gives a prediction approximately 30-70 minutes in advance of the actual geomagnetic activity. The correlation coefficient between the observed AE data and the forecasted series reached values higher than 0.90. In some cases the forecast reproduced particularities observed in the signal very well.The high correlation values observed and the high efficacy of the forecasting can be taken as a confirmation that reconnection is the main physical mechanism responsible for the energy transfer during HILDCAAs. The study also shows that the IMF Bz component low frequencies are most important for AE prediction.

  3. Binocular videogrammetric system for three-dimensional measurement in low-speed wind tunnel

    NASA Astrophysics Data System (ADS)

    Zhu, Ye; Gu, Yonggang; Zhai, Chao

    2014-11-01

    In order to avoid the defects of contact measurement, such as limited range, complex constructing and disability of 3-D parameter acquisition, we built a binocular videogrammetric system for measuring 3-D geometry parameters of wind tunnel test models, for instance, displacement, rotation angle and vibration, in low-speed wind tunnel. The system is based on the principles of close-range digital photogrammetry. As a non-contact system, it acquires parameters without interference in the experiments, and it has adjustable range and simple structure. It is worth mentioning that this is a Realtime measurement system, so that it can greatly compress the experiment period, furthermore, it is also able to provide some specific experiments with parameters for online adjustment. In this system, images are acquired through two industrial digital cameras and a PCI-E image acquisition card, and they are processed in a PC. The two cameras are triggered by signals come from a function signal generator, so that images of different cameras will have good temporal synchronization to ensure the accuracy of 3-D reconstruction. A two-step stereo calibration technique using planar pattern developed by Zhengyou Zhang is used to calibrate these cameras. Results of wind tunnel test indicate that the system can provide displacement accuracy better than 0.1% and rotation angle accuracy better than 0.1 degree, besides, the vibration frequency accuracy is superior to 0.1Hz in the low-frequency range.

  4. Turbulence measurements in high-speed wind tunnels using focusing laser differential interferometry

    NASA Astrophysics Data System (ADS)

    Fulghum, Matthew R.

    Characterization of freestream disturbances and their effect on laminar boundary layer transition is of great importance in high-speed wind tunnel testing, where significant differences between the behavior of scale-model and free-flight transition have long been noted. However, the methods traditionally used to perform this characterization in low-speed flows present significant difficulties when applied to supersonic and especially hypersonic wind tunnels. The design and theory of a focusing laser differential interferometer (FLDI) instrument, originally invented by Smeets at the Institut Saint-Louis in the 1970s and used recently by Parziale in the CalTech T5 shock tunnel, is presented. It is a relatively-simple, non-imaging common-path interferometer for measuring refractive signals from transition and turbulence, and it has a unique ability to look through facility windows, ignore sidewall boundary-layers and vibration, and concentrate only on the refractive signal near a pair of sharp beam foci in the core flow. The instrument's low cost and ease of implementation make it a promising alternative to traditional hot-wire anemometry and particle-based methods for turbulence characterization. Benchtop experiments using a turbulent supersonic air jet demonstrate its focusing ability, frequency response, unwanted signal rejection, and ease of use. The instrument is used to optically interrogate the flow in the Penn State University Supersonic Wind Tunnel and USAF AEDC Hypervelocity Tunnel 9 for measurement of the overall intensity and spectra of freestream disturbances. Precise characterization of the strength and spectral content of the disturbances provides insight into their nature and potential effect upon boundary layer transition. A special feature of the FLDI instrument used here is the replacement of traditional fixed Wollaston prisms with variable Sanderson prisms for laser-beam separation and recombination.

  5. Quality control of the RMI's AWS wind observations

    NASA Astrophysics Data System (ADS)

    Bertrand, Cédric; González Sotelino, Luis; Journée, Michel

    2016-02-01

    Wind observations are important for a wide range of domains including among others meteorology, agriculture and extreme wind engineering. To ensure the provision of high quality surface wind data over Belgium, a new semi-automated data quality control (QC) has been developed and applied to wind observations from the automated weather stations operated by the Royal Meteorological Institute of Belgium. This new QC applies to 10 m 10 min averaged wind speed and direction, 10 m gust speed and direction, 2 m 10 min averaged wind speed and 30 m 10 min averaged wind speed records. After an existence test, automated procedures check the data for limits consistency, internal consistency, temporal consistency and spatial consistency. At the end of the automated QC, a decision algorithm attributes a flag to each particular data point. Each day, the QC staff analyzes the preceding day's observations in the light of the assigned quality flags.

  6. On the relation between coronal heating, flux tube divergence, and the solar wind proton flux and flow speed

    NASA Technical Reports Server (NTRS)

    Sandbaek, Onulf; Leer, Egil; Hansteen, Viggo H.

    1994-01-01

    A one-fluid solar wind model is used to investigate some relations between coronal heating, the flux tube divergence near the Sun, and the solar wind proton flux and flow speed. The effects of energy addition to the supersonic region of the flow are also studied. We allow for a mechanical energy flux that heats the corona, and an Alfven wave energy flux that adds energy, mainly to the supersonic flow, both as momentum and as heat. We find that the mechanical energy flux determines the solar wind mass flux, and in order to keep an almost constant proton flux at the orbit of Earth with changing flow geometry, that the mechanical energy flux must vary linearly with the magnetic field in the inner corona. This thermally driven wind generally has a low asymptotic flow speed. When Alfven waves are added to the thermally driven flow, the asymptotic flow speed is increased and is determined by the ratio of the Alfven wave and the mechanical energy fluxes at the coronal base. Flow speeds characteristic of recurrent high-speed solar wind streams can be obtained only when the Alfven wave energy flux, deposited in the supersonic flow, is larger than the mechanical energy flux heating the corona.

  7. Variability of daily winter wind speed distribution over Northern Europe during the past millennium in regional and global climate simulations

    NASA Astrophysics Data System (ADS)

    Bierstedt, Svenja E.; Hünicke, Birgit; Zorita, Eduardo; Wagner, Sebastian; José Gómez-Navarro, Juan

    2016-02-01

    We analyse the variability of the probability distribution of daily wind speed in wintertime over Northern and Central Europe in a series of global and regional climate simulations covering the last centuries, and in reanalysis products covering approximately the last 60 years. The focus of the study lies on identifying the link of the variations in the wind speed distribution to the regional near-surface temperature, to the meridional temperature gradient and to the North Atlantic Oscillation. Our main result is that the link between the daily wind distribution and the regional climate drivers is strongly model dependent. The global models tend to behave similarly, although they show some discrepancies. The two regional models also tend to behave similarly to each other, but surprisingly the results derived from each regional model strongly deviates from the results derived from its driving global model. In addition, considering multi-centennial timescales, we find in two global simulations a long-term tendency for the probability distribution of daily wind speed to widen through the last centuries. The cause for this widening is likely the effect of the deforestation prescribed in these simulations. We conclude that no clear systematic relationship between the mean temperature, the temperature gradient and/or the North Atlantic Oscillation, with the daily wind speed statistics can be inferred from these simulations. The understanding of past and future changes in the distribution of wind speeds, and thus of wind speed extremes, will require a detailed analysis of the representation of the interaction between large-scale and small-scale dynamics.

  8. Latitudinal Variation of Solar Wind Speed and Mass Flux in the Acceleration Region of the Solar Wind during Solar Minimum Inferred from Spectral Broadening measurements

    NASA Technical Reports Server (NTRS)

    Woo, R.; Goldstein, R.

    1993-01-01

    In this paper, we use an aggregate of S-band 2.3 GHz (13 cm) spectral broadening observations conducted during solar minimum conditions by the Mariner 4, Pioneer 10, Mariner 10, Helios 1 & 2 and Viking spacecraft to infer the first measurements of the latitudinal variation of solar wind speed and mass flux in the acceleration region of the solar wind at 3-8 R(sub o).

  9. Weibull Wind-Speed Distribution Parameters Derived from a Combination of Wind-Lidar and Tall-Mast Measurements Over Land, Coastal and Marine Sites

    NASA Astrophysics Data System (ADS)

    Gryning, Sven-Erik; Floors, Rogier; Peña, Alfredo; Batchvarova, Ekaterina; Brümmer, Burghard

    2016-05-01

    Wind-speed observations from tall towers are used in combination with observations up to 600 m in altitude from a Doppler wind lidar to study the long-term conditions over suburban (Hamburg), rural coastal (Høvsøre) and marine (FINO3) sites. The variability in the wind field among the sites is expressed in terms of mean wind speed and Weibull distribution shape-parameter profiles. The consequences of the carrier-to-noise-ratio ( CNR) threshold-value choice on the wind-lidar observations are revealed as follows. When the wind-lidar CNR is lower than a prescribed threshold value, the observations are often filtered out as the uncertainty in the wind-speed measurements increases. For a pulsed heterodyne Doppler lidar, use of the traditional -22 dB CNR threshold value at all measuring levels up to 600 m results in a ≈ 7 % overestimation in the long-term mean wind speed over land, and a ≈ 12 % overestimation in coastal and marine environments. In addition, the height of the profile maximum of the shape parameter of the Weibull distribution (so-called reversal height) is found to depend on the applied CNR threshold; it is found to be lower at small CNR threshold values. The reversal height is greater in the suburban (high roughness) than in the rural (low roughness) area. In coastal areas the reversal height is lower than that over land and relates to the internal boundary layer that develops downwind from the coastline. Over the sea the shape parameter increases towards the sea surface. A parametrization of the vertical profile of the shape parameter fits well with observations over land, coastal regions and over the sea. An applied model for the dependence of the reversal height on the surface roughness is in good agreement with the observations over land.

  10. Quantifying the benefits of a slender, high tip speed blade for large offshore wind turbiness

    NASA Astrophysics Data System (ADS)

    Blonk, Lindert; Rainey, Patrick; Langston, David A. J.; Vanni, Francesco

    2014-06-01

    An in-depth study has been completed to study the effects of slender, flexible blades in combination with high rotor speed operation on load mitigation, targeted at cost reductions of the structural components of large wind turbines, consequently lowering the levelized cost of energy. An overview of existing theory of sensitivity of turbine fatigue loading to the blade chord and rotor speed was created, and this was supplemented by a proposed theory for aboverated operation including the pitch controller. A baseline jacket-supported offshore turbine (7 MW) was defined, of which the blade was then redesigned to be more slender and flexible, at the same time increasing rotor speed. The blade redesign and optimisation process was guided by cost of energy assessments using a reduced loadset. Thereafter, a full loadset conform IEC61400-3 was calculated for both turbines. The expected support structure load reductions were affirmed, and it was shown that reductions of up to 18.5% are possible for critical load components. Cost modelling indicated that turbine and support structure CapEx could be reduced by 6%. Despite an energy production reduction of 0.44% related to the thicker airfoils used, the blade redesign led to a reduction in Cost of Energy.

  11. Remote Sensing of Solar Wind Speeds using Observations of IPS at 140 and 327 MHz: MEXART and STELab

    NASA Astrophysics Data System (ADS)

    Mejia-Ambriz, J.; Jackson, B. V.; Buffington, A.; Gonzalez-Esparza, A.; Tokumaru, M.

    2013-12-01

    The radio signals from compact radio sources are scattered by the solar wind. This effect is observed by radio telescopes as intensity fluctuations of the sources and known as Interplanetary Scintillation (IPS). IPS can be used as a technique to explore solar wind speeds in the inner heliosphere. The Mexican Array Radio Telescope (MEXART) at 140 MHz and the stations of Solar Terrestrial Environment Laboratory (STELab) at 327 MHz are instruments dedicated to studies of IPS. There exist two techniques to estimate solar wind speeds using analyses from IPS: From multi-station and single-station measurements. In this work we analyze data from one of the radio arrays of STELab and from MEXART to obtain solar wind speeds using the single-station technique. These observations correspond to the minimum and maximum periods of the 24th solar cycle. We compare the speeds we obtain from the single-site technique with speeds from those reported by the multi-station technique provided by STELab. We find that most speeds obtained using both techniques agree within the limits of the errors of each measurement. Large newly-commissioned radio telescopes (LOFAR, in Europe, and MWA in Western Australia) intend IPS surveys at other frequencies, and the single station technique is being used and tested at other locations as well. The conclusions of this work contribute to the understanding of the implementation of the single-station technique for measuring velocities with other radio systems.

  12. EVOLUTION OF THE RELATIONSHIPS BETWEEN HELIUM ABUNDANCE, MINOR ION CHARGE STATE, AND SOLAR WIND SPEED OVER THE SOLAR CYCLE

    SciTech Connect

    Kasper, J. C.; Stevens, M. L.; Korreck, K. E.; Maruca, B. A.; Kiefer, K. K.; Schwadron, N. A.; Lepri, S. T.

    2012-02-01

    The changing relationships between solar wind speed, helium abundance, and minor ion charge state are examined over solar cycle 23. Observations of the abundance of helium relative to hydrogen (A{sub He} {identical_to} 100 Multiplication-Sign n{sub He}/n{sub H}) by the Wind spacecraft are used to examine the dependence of A{sub He} on solar wind speed and solar activity between 1994 and 2010. This work updates an earlier study of A{sub He} from 1994 to 2004 to include the recent extreme solar minimum and broadly confirms our previous result that A{sub He} in slow wind is strongly correlated with sunspot number, reaching its lowest values in each solar minima. During the last minimum, as sunspot numbers reached their lowest levels in recent history, A{sub He} continued to decrease, falling to half the levels observed in slow wind during the previous minimum and, for the first time observed, decreasing even in the fastest solar wind. We have also extended our previous analysis by adding measurements of the mean carbon and oxygen charge states observed with the Advanced Composition Explorer spacecraft since 1998. We find that as solar activity decreased, the mean charge states of oxygen and carbon for solar wind of a given speed also fell, implying that the wind was formed in cooler regions in the corona during the recent solar minimum. The physical processes in the coronal responsible for establishing the mean charge state and speed of the solar wind have evolved with solar activity and time.

  13. On the role played by magnetic expansion factor in the prediction of solar wind speed

    NASA Astrophysics Data System (ADS)

    Riley, Pete; Linker, Jon A.; Arge, C. Nick

    2015-03-01

    Over the last two decades, the Wang-Sheeley-Arge (WSA) model has evolved significantly. Beginning as a simple observed correlation between the expansion factor of coronal magnetic field lines and the measured speed of the solar wind at 1 AU (the Wang-Sheeley (WS) model), the WSA model now drives NOAA's first operational space weather model, providing real-time predictions of solar wind parameters in the vicinity of Earth. Here we demonstrate that the WSA model has evolved so much that the role played by the expansion factor term is now largely minimal, being supplanted by the distance from the coronal hole boundary (DCHB). We illustrate why and to what extent the three models (WS, DCHB, and WSA) differ. Under some conditions, all approaches are able to reproduce the grossest features of the observed quiet time solar wind. However, we show that, in general, the DCHB- and WSA-driven models tend to produce better estimates of solar parameters at 1 AU than the WS model, particularly when pseudostreamers are present. Additionally, we highlight that these empirical models are sensitive to the type and implementation of the magnetic field model used: In particular, the WS model can only reproduce in situ measurements when coupled with the potential field source surface model. While this clarification is important both in its own right and from an operational/predictive standpoint, because of the underlying physical ideas upon which the WS and DCHB models rest, these results provide support, albeit tentatively, for boundary layer theories for the origin of the slow solar wind.

  14. Prediction and analysis of infra and low-frequency noise of upwind horizontal axis wind turbine using statistical wind speed model

    SciTech Connect

    Lee, Gwang-Se; Cheong, Cheolung

    2014-12-15

    Despite increasing concern about low-frequency noise of modern large horizontal-axis wind turbines (HAWTs), few studies have focused on its origin or its prediction methods. In this paper, infra- and low-frequency (the ILF) wind turbine noise are closely examined and an efficient method is developed for its prediction. Although most previous studies have assumed that the ILF noise consists primarily of blade passing frequency (BPF) noise components, these tonal noise components are seldom identified in the measured noise spectrum, except for the case of downwind wind turbines. In reality, since modern HAWTs are very large, during rotation, a single blade of the turbine experiences inflow with variation in wind speed in time as well as in space, breaking periodic perturbations of the BPF. Consequently, this transforms acoustic contributions at the BPF harmonics into broadband noise components. In this study, the ILF noise of wind turbines is predicted by combining Lowson’s acoustic analogy with the stochastic wind model, which is employed to reproduce realistic wind speed conditions. In order to predict the effects of these wind conditions on pressure variation on the blade surface, unsteadiness in the incident wind speed is incorporated into the XFOIL code by varying incident flow velocities on each blade section, which depend on the azimuthal locations of the rotating blade. The calculated surface pressure distribution is subsequently used to predict acoustic pressure at an observing location by using Lowson’s analogy. These predictions are compared with measured data, which ensures that the present method can reproduce the broadband characteristics of the measured low-frequency noise spectrum. Further investigations are carried out to characterize the IFL noise in terms of pressure loading on blade surface, narrow-band noise spectrum and noise maps around the turbine.

  15. Prediction and analysis of infra and low-frequency noise of upwind horizontal axis wind turbine using statistical wind speed model

    NASA Astrophysics Data System (ADS)

    Lee, Gwang-Se; Cheong, Cheolung

    2014-12-01

    Despite increasing concern about low-frequency noise of modern large horizontal-axis wind turbines (HAWTs), few studies have focused on its origin or its prediction methods. In this paper, infra- and low-frequency (the ILF) wind turbine noise are closely examined and an efficient method is developed for its prediction. Although most previous studies have assumed that the ILF noise consists primarily of blade passing frequency (BPF) noise components, these tonal noise components are seldom identified in the measured noise spectrum, except for the case of downwind wind turbines. In reality, since modern HAWTs are very large, during rotation, a single blade of the turbine experiences inflow with variation in wind speed in time as well as in space, breaking periodic perturbations of the BPF. Consequently, this transforms acoustic contributions at the BPF harmonics into broadband noise components. In this study, the ILF noise of wind turbines is predicted by combining Lowson's acoustic analogy with the stochastic wind model, which is employed to reproduce realistic wind speed conditions. In order to predict the effects of these wind conditions on pressure variation on the blade surface, unsteadiness in the incident wind speed is incorporated into the XFOIL code by varying incident flow velocities on each blade section, which depend on the azimuthal locations of the rotating blade. The calculated surface pressure distribution is subsequently used to predict acoustic pressure at an observing location by using Lowson's analogy. These predictions are compared with measured data, which ensures that the present method can reproduce the broadband characteristics of the measured low-frequency noise spectrum. Further investigations are carried out to characterize the IFL noise in terms of pressure loading on blade surface, narrow-band noise spectrum and noise maps around the turbine.

  16. Determination of transport wind speed in the gaussian plume diffusion equation for low-lying point sources

    NASA Astrophysics Data System (ADS)

    Wang, I. T.

    A general method for determining the effective transport wind speed, overlineu, in the Gaussian plume equation is discussed. Physical arguments are given for using the generalized overlineu instead of the often adopted release-level wind speed with the plume diffusion equation. Simple analytical expressions for overlineu applicable to low-level point releases and a wide range of atmospheric conditions are developed. A non-linear plume kinematic equation is derived using these expressions. Crosswind-integrated SF 6 concentration data from the 1983 PNL tracer experiment are used to evaluate the proposed analytical procedures along with the usual approach of using the release-level wind speed. Results of the evaluation are briefly discussed.

  17. Dual-core photonic crystal fiber Doppler velocimeter for small horizontal axis wind turbine blade rotational speed measurement

    NASA Astrophysics Data System (ADS)

    Huang, Xue-Feng; Li, Sheng-Ji; Wang, Wei-Chih

    2014-03-01

    The blades are crucial components of a wind turbine, and its steady and reliable operation is directly related to the power output. Thus, condition monitoring and fault diagnosis of the wind turbine blades is highly beneficial to the operational cost. This paper presents a study of small horizontal axis wind turbine blade rotational speed measurement by laser Doppler velocimeter based on dual-core photonic crystal fiber (DC-PCF). The theory on the DC-PCF Doppler velocimeter is presented, and the measurement system is designed and tested. Experimental results show that the DC-PCF Doppler velocimeter has been proved to work successfully. The uncertainty of the rotational speed is about 0 ~ 4 rpm. The accuracy can meet the requirements for monitoring the rotational operation of the wind turbine.

  18. LIDAR Wind Speed Measurement Analysis and Feed-Forward Blade Pitch Control for Load Mitigation in Wind Turbines: January 2010--January 2011

    SciTech Connect

    Dunne, F.; Simley, E.; Pao, L.Y.

    2011-10-01

    This report examines the accuracy of measurements that rely on Doppler LIDAR systems to determine their applicability to wind turbine feed-forward control systems and discusses feed-forward control system designs that use preview wind measurements. Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feed-forward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. The first half of this report examines the accuracy of different measurement scenarios that rely on coherent continuous-wave or pulsed Doppler LIDAR systems to determine their applicability to feed-forward control. In particular, the impacts of measurement range and angular offset from the wind direction are studied for various wind conditions. A realistic case involving a scanning LIDAR unit mounted in the spinner of a wind turbine is studied in depth with emphasis on choices for scan radius and preview distance. The effects of turbulence parameters on measurement accuracy are studied as well. Continuous-wave and pulsed LIDAR models based on typical commercially available units were used in the studies present in this report. The second half of this report discusses feed-forward control system designs that use preview wind measurements. Combined feedback/feed-forward blade pitch control is compared to industry standard feedback control when simulated in realistic turbulent above-rated winds. The feed-forward controllers are designed to reduce fatigue loads, increasing turbine lifetime and therefore reducing the cost of energy. Three feed-forward designs are studied: non-causal series expansion, Preview Control, and optimized FIR filter. The input to the feed-forward controller is a measurement of

  19. Wind-tunnel results for a modified 17-percent-thick low-speed airfoil section

    NASA Technical Reports Server (NTRS)

    Mcghee, R. J.; Beasley, W. D.

    1981-01-01

    Wind-tunnel tests were conducted in the Langley low-turbulence pressure tunnel to evaluate the effects on performance of modifying a 17-percent-thick low-speed airfoil. The airfoil contour was altered to reduce the pitching-moment coefficient by increasing the forward loading and to increase the climb lift-drag ratio by decreasing the aft upper surface pressure gradient. The tests were conducted over a Mach number range from 0.07 to 0.32, a chord Reynolds number range 1.0 x 10 to the 6th power to 12.0 x 10 to the 6th power, and an angle-of-attack range from about -10 deg to 20 deg.

  20. Wind tunnel investigation of rotor lift and propulsive force at high speed: Data analysis

    NASA Technical Reports Server (NTRS)

    Mchugh, F.; Clark, R.; Soloman, M.

    1977-01-01

    The basic test data obtained during the lift-propulsive force limit wind tunnel test conducted on a scale model CH-47b rotor are analyzed. Included are the rotor control positions, blade loads and six components of rotor force and moment, corrected for hub tares. Performance and blade loads are presented as the rotor lift limit is approached at fixed levels of rotor propulsive force coefficients and rotor tip speeds. Performance and blade load trends are documented for fixed levels of rotor lift coefficient as propulsive force is increased to the maximum obtainable by the model rotor. Test data is also included that defines the effect of stall proximity on rotor control power. The basic test data plots are presented in volumes 2 and 3.

  1. Low-speed wind-tunnel results for symmetrical NASA LS(1)-0013 airfoil

    NASA Technical Reports Server (NTRS)

    Ferris, James C.; Mcghee, Robert J.; Barnwell, Richard W.

    1987-01-01

    A wind-tunnel test has been conducted in the Langley Low-Turbulence Pressure Tunnel to evaluate the performance of a symmetrical NASA LS(1)-0013 airfoil which is a 13-percent-thick, low-speed airfoil. The airfoil contour was obtained from the thickness distribution of a 13-percent-thick, high-performance airfoil developed for general aviation airplanes. The tests were conducted at Mach numbers from 0.10 tp 0.37 over a Reynolds number range from about 0.6 to 12.0 X 10 to the 6th power. The angle of attack varied from about -8 to 20 degrees. The results indicate that the aerodynamic characteristics of the present airfoil are similar to, but slightly better than, those of the NACA 0012 airfoil.

  2. Tracer dispersion simulation in low wind speed conditions with a new 2D Langevin equation system

    NASA Astrophysics Data System (ADS)

    Anfossi, D.; Alessandrini, S.; Trini Castelli, S.; Ferrero, E.; Oettl, D.; Degrazia, G.

    The simulation of atmospheric dispersion in low wind speed conditions (LW) is still recognised as a challenge for modellers. Recently, a new system of two coupled Langevin equations that explicitly accounts for meandering has been proposed. It is based on the study of turbulence and dispersion properties in LW. The new system was implemented in the Lagrangian stochastic particle models LAMBDA and GRAL. In this paper we present simulations with this new approach applying it to the tracer experiments carried out in LW by Idaho National Engineering Laboratory (INEL, USA) in 1974 and by the Graz University of Technology and CNR-Torino near Graz in 2003. To assess the improvement obtained with the present model with respect to previous models not taking into account the meandering effect, the simulations for the INEL experiments were also performed with the old version of LAMBDA. The results of the comparisons clearly indicate that the new approach improves the simulation results.

  3. Design and performance evaluation of a fuzzy-logic-based variable-speed wind generation system

    SciTech Connect

    Simoes, M.G.; Bose, B.K.; Spiegel, R.J.

    1997-07-01

    Artificial intelligence techniques, such as fuzzy logic, neural network, and genetic algorithm, are recently showing a lot of promise in the application of power electronic systems. The paper describes the control strategy development, design, and experimental performance evaluation of a fuzzy-logic-based variable-speed wind generation system that uses a cage-type induction generator and double-sided pulsewidth-modulated (PWM) converters. The system can feed a utility grid maintaining unity power factor at all conditions or can supply an autonomous load. The fuzzy-logic-based control of the system helps to optimize efficiency and enhance performance. A complete 3.5-kW generation system has been developed, designed, and thoroughly evaluated by laboratory tests, in order to validate the predicted performance improvements. The system gives excellent performance and can easily be translated to a larger size in the field.

  4. The proton temperature and the total hourly variance of the magnetic field components in different solar wind speed regions

    NASA Technical Reports Server (NTRS)

    Tu, Chuan-Yi; Freeman, John W.; Lopez, R. E.

    1989-01-01

    A comparison has been made between the predictions of the theory for radial variations of both Alfvenic fluctuations and solar wind proton temperatures proposed by Tu (1987, 1988) and the statistical results of hourly averaged plasma and magnetic field data observed by Helios 1 and 2 from launch through 1980 for different solar wind speed regimes. The comparison shows that for speed ranges between 500-800 km/s, the radial variation of the proton temperature between 0.3 and 1 AU can be explained by heating from the cascade energy which is determined by the radial variation of the total variance of magnetic field vector.

  5. The effects of the variations in sea surface temperature and atmospheric stability in the estimation of average wind speed by SEASAT-SASS

    NASA Technical Reports Server (NTRS)

    Liu, W. T.

    1984-01-01

    The average wind speeds from the scatterometer (SASS) on the ocean observing satellite SEASAT are found to be generally higher than the average wind speeds from ship reports. In this study, two factors, sea surface temperature and atmospheric stability, are identified which affect microwave scatter and, therefore, wave development. The problem of relating satellite observations to a fictitious quantity, such as the neutral wind, that has to be derived from in situ observations with models is examined. The study also demonstrates the dependence of SASS winds on sea surface temperature at low wind speeds, possibly due to temperature-dependent factors, such as water viscosity, which affect wave development.

  6. A leaky magnetohydrodynamic waveguide model for the acceleration of high-speed solar wind streams in coronal holes

    NASA Technical Reports Server (NTRS)

    Davila, J. M.

    1985-01-01

    It is now reasonably well established that there is a correlation between high-speed solar wind streams and coronal holes. It has been concluded that a significant addition of momentum and/or energy in the region of supersonic flow is needed to explain the observed particle flux and flow speed observed in the high-speed streams. The most likely source of this additional momentum appears to be magnetohydrodynamic (MHD) waves propagating up from the solar surface. The present investigation is concerned with the propagation of MHD waves in a structure of finite transverse size, taking into account the consequences for the acceleration of high-speed solar wind streams. A waveguide solution for a model coronal hole is described, giving attention to a geometric or ray analysis of the slab waveguide, a wave mode analysis, an analytic solution of the dispersion relation for high-frequency waves, and the calculation of the time-averaged wave force.

  7. A cm scale electret-based electrostatic wind turbine for low-speed energy harvesting applications

    NASA Astrophysics Data System (ADS)

    Perez, M.; Boisseau, S.; Gasnier, P.; Willemin, J.; Geisler, M.; Reboud, J. L.

    2016-04-01

    This paper presents a small-scale airflow energy harvester built on an axial turbine architecture and exploiting an electret-based electrostatic converter. When the airflow velocity is high enough, the windmill starts rotating and creates a periodic relative motion between a stator and a rotor which induces variations of capacitance. These ones are directly converted into electricity thanks to the use of Teflon electrets charged at -1400 V which polarize the variable capacitors. We focus our study on a 4-blade axial turbine with a diameter of D = 40 mm, a depth of W = 10 mm, for a total volume of 12.6 cm3. This windmill has been tested with various blade angles and different types of electrostatic converters and output powers up to 90 μW at 1.5 m s-1 (7.5 μW cm-3) and 1.8 mW at 10 m s-1 (111 μW cm-3) have been obtained so far. The coefficient of power reaches C p = 5.8% and among the small-scale airflow energy harvesters previously reported, this one has the lowest cut-in speed (1.5 m s-1).

  8. Dependence of SMOS/MIRAS brightness temperatures on wind speed: sea surface effect and latitudinal biases

    NASA Astrophysics Data System (ADS)

    Yin, Xiaobin; Boutin, Jacqueline; Martin, Nicolas; Spurgeon, Paul

    2013-04-01

    SMOS (Soil Moisture and Ocean Salinity) has been successfully launched in November 2009 and its only payload, Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) instrument, is the first interferometric radiometer at L band (1.4GHz) in orbit. MIRAS employs aperture synthesis in 2D with a Y-shaped antenna structure to create an image of emissions from the Earth surface at L-band over a range of incidence angles (0° to 65°) with a spatial resolution of 35 to 110 km. More than two years after launch the level 1C (L1C) brightness temperatures (TBs) reprocessed with the up-to-date ESA level 1 processing version (the Level 1 processor V5.04 and V5.05), have been released. It has been shown during the commissioning phase that the receivers onboard of MIRAS are affected by a short-term drift during each orbit, and a seasonal variation due to the thermal drifts of the antenna patch. Although a new antenna model is incorporated in the ESA L1 V5 processing to account for these variations, latitudinal and seasonal drifts in L1C TBs are still observed. In this presentation, we first investigate the impact of the TB drifts on the sea surface emissivity roughness model we derived in Yin et al. (TGRS 2012) from multi-latitude level 1 V3.17 TBs. We then study dependencies of TBs at multi-incidence angles with wind speed separately for various latitudinal bands and different seasons in order to separate artificial effects of TB drifts from sea surface effects. We then propose a new roughness/foam forward model. We estimate the quality of SMOS retrieved SSS by comparing it with ARGO measurements, and discuss SSS quality given the imprecision of the forward model and of the wind speed used as prior value in the level 2 ocean salinity processor.

  9. Underwater Ambient Noise and Sperm Whale Click Detection during Extreme Wind Speed Conditions

    NASA Astrophysics Data System (ADS)

    Newcomb, Joal J.; Wright, Andrew J.; Kuczaj, Stan; Thames, Rachel; Hillstrom, Wesley R.; Goodman, Ralph

    2004-11-01

    The Littoral Acoustic Demonstration Center (LA DC) deployed three Environmental Acoustic Recording System (EARS) buoys in the northern Gulf of Mexico during the summers of 2001 (LADC 01) and 2002 (LADC 02). The hydrophone of each buoy was approximately 50m from the bottom in water depths of 645m to 1034m. During LADC 01 Tropical Storm Barry passed within 93nmi east of the EARS buoys. During LADC 02 Tropical Storm Isidore and Hurricane Lili passed within approximately 73nmi and 116nmi, respectively, west of the EARS buoys. The proximity of these storm systems to the EARS buoys, in conjunction with wind speed data from three nearby NDBC weather buoys, allows for the direct comparison of underwater ambient noise levels with high wind speeds. These results are compared to the G. M. Wenz spectra at frequencies from 1kHz to 5.5kHz. In addition, the impact of storm conditions on sperm whale clicks was assessed. In particular, although the time period during the closest approach of TS Barry tended to produce lower click rates, this time period did not have the greatest incidence of non-detection at all the EARS buoys. It follows that storm-related masking noise could not have been responsible for all the observed trends. The data suggest that sperm whales may have left the vicinity of the deepest EARS buoy (nearest TS Barry's storm track) during the storm and possibly moved into the shallower waters around the other EARS buoys. It also appears that sperm whales may not have returned to the deepest EARS area, or did not resume normal behavior immediately after the storm, as the click rate did not recover to pre-storm levels during the period after TS Barry had dissipated. Results of these analyses and the ambient noise analysis will be presented. (Research supported by ONR).

  10. A wind-tunnel investigation of parameters affecting helicopter directional control at low speeds in ground effect

    NASA Technical Reports Server (NTRS)

    Yeager, W. T., Jr.; Young, W. H., Jr.; Mantay, W. R.

    1974-01-01

    An investigation was conducted in the Langley full-scale tunnel to measure the performance of several helicopter tail-rotor/fin configurations with regard to directional control problems encountered at low speeds in ground effect. Tests were conducted at wind azimuths of 0 deg to 360 deg in increments of 30 deg and 60 deg and at wind speeds from 0 to 35 knots. The results indicate that at certain combinations of wind speed and wind azimuth, large increases in adverse fin force require correspondingly large increases in the tail-rotor thrust, collective pitch, and power required to maintain yaw trim. Changing the tail-rotor direction of rotation to top blade aft for either a pusher tail rotor (tail-rotor wake blowing away from fin) or a tractor tail rotor (tail-rotor wake blowing against fin) will alleviate this problem. For a pusher tail rotor at 180 deg wind azimuth, increases in the fin/tail-rotor gap were not found to have any significant influence on the overall vehicle directional control capability. Changing the tail rotor to a higher position was found to improve tail-rotor performance for a fin-off configuration at a wind azimuth of 180 deg. A V-tail configuration with a pusher tail rotor with top blade aft direction of rotation was found to be the best configuration with regard to overall directional control capability.

  11. Shelter Index and a simple wind speed parameter to characterize vegetation control of sand transport threshold and Flu

    NASA Astrophysics Data System (ADS)

    Gillies, J. A.; Nield, J. M.; Nickling, W. G.; Furtak-Cole, E.

    2014-12-01

    Wind erosion and dust emissions occur in many dryland environments from a range of surfaces with different types and amounts of vegetation. Understanding how vegetation modulates these processes remains a research challenge. Here we present results from a study that examines the relationship between an index of shelter (SI=distance from a point to the nearest upwind vegetation/vegetation height) and particle threshold expressed as the ratio of wind speed measured at 0.45 times the mean plant height divided by the wind speed at 17 m when saltation commences, and saltation flux. The results are used to evaluate SI as a parameter to characterize the influence of vegetation on local winds and sediment transport conditions. Wind speed, wind direction, saltation activity and point saltation flux were measured at 35 locations in defined test areas (~13,000 m2) in two vegetation communities: mature streets of mesquite covered nebkhas and incipient nebkhas dominated by low mesquite plants. Measurement positions represent the most open areas, and hence those places most susceptible to wind erosion among the vegetation elements. Shelter index was calculated for each measurement position for each 10° wind direction bin using digital elevation models for each site acquired using terrestrial laser scanning. SI can show the susceptibility to wind erosion at different time scales, i.e., event, seasonal, or annual, but in a supply-limited system it can fail to define actual flux amounts due to a lack of knowledge of the distribution of sediment across the surface of interest with respect to the patterns of SI.

  12. MEASUREMENT OF INTERMITTENCY OF ANISOTROPIC MAGNETOHYDRODYNAMIC TURBULENCE IN HIGH-SPEED SOLAR WIND

    SciTech Connect

    Luo, Q. Y.; Wu, D. J.; Yang, L.

    2011-06-01

    We investigate the intermittency of anisotropic magnetohydrodynamic (MHD) turbulence in high-speed solar wind. Using the data recorded by the Ulysses spacecraft, we apply the Castaing function to model the probability density functions of the fluctuating magnetic field and calculate the magnetic structure functions (SFs) S{sup p} of the order p in the coordinates (r, {Theta}), with r being the length scale and {Theta} the direction of the local mean field. The scaling exponent {zeta}, from S{sup p} (r, {Theta}){proportional_to}r {sup {zeta}(p,{Theta})}, has an anomalous nonlinear dependence on p, implying the intermittent scaling of solar wind turbulence, which has been observed for decades. Furthermore, we study the anisotropy of solar wind turbulence introduced by the strong mean magnetic field. From S{sup p} ({Theta} = 0){proportional_to}S{sup p} ({Theta} = {pi}/2), we obtain r{sub perpendicular{proportional_to}r {sup {alpha}}p||} with {alpha}{sub p} = {zeta}{sub ||}/{zeta}{sub perpendicular} denoting the perpendicular-parallel spatial correlation of the moment of the pth order. For the magnetic field difference {delta}B, we find {alpha}{sub 2} = 1.78 {+-} 0.26, consistent with recent theories and observations. However, when the contribution from the intermittent fluctuations begins to dominate the scaling, {alpha} is not a constant but increases with p, e.g., {alpha}{sub 5} = 1.97 {+-} 0.41 and {alpha}{sub 8} {approx} 2.42 {+-} 0.64. This complication of the perpendicular-parallel spatial correlation due to the intermittency raises new questions for MHD turbulence theory.

  13. Acoustical evaluation of the NASA Lewis 9 by 15 foot low speed wind tunnel

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.; Woodward, Richard P.

    1992-01-01

    The test section of the NASA Lewis 9- by 15-Foot Low Speed Wind Tunnel was acoustically treated to allow the measurement of acoustic sources located within the tunnel test section under simulated free field conditions. The treatment was designed for high sound absorption at frequencies above 250 Hz and to withstand tunnel airflow velocities up to 0.2 Mach. Evaluation tests with no tunnel airflow were conducted in the test section to assess the performance of the installed treatment. This performance would not be significantly affected by low speed airflow. Time delay spectrometry tests showed that interference ripples in the incident signal resulting from reflections occurring within the test section average from 1.7 dB to 3.2 dB wide over a 500 to 5150 Hz frequency range. Late reflections, from upstream and downstream of the test section, were found to be insignificant at the microphone measuring points. For acoustic sources with low directivity characteristics, decay with distance measurements in the test section showed that incident free field behavior can be measured on average with an accuracy of +/- 1.5 dB or better at source frequencies from 400 Hz to 10 kHz. The free field variations are typically much smaller with an omnidirectional source.

  14. On the Dependence of Solar Wind Speed on Local Magnetic Field Orientation in Highly Alfvénic Streams

    NASA Astrophysics Data System (ADS)

    Matteini, L.; Horbury, T. S.; Neugebauer, M.; Goldstein, B. E.

    2014-12-01

    Magnetic field fluctuations from the low frequency part of the solar wind turbulent spectrum have typical amplitudes of the order of the underlying mean field, and then result in large random variations in the instantaneous direction associated with the magnetic field vector on the scale of minutes/few hours. At the same time, since fluctuations are Alfvénic, these also introduce variations in solar wind speed, which reflecting the randomness of the process, are not expected to show a dependence on the direction of the magnetic field. On the contrary, and quite surprisingly, we have found that in highly Alfvénic solar wind streams there exists a remarkably strong correlation between the bulk speed of the plasma and the local direction of the magnetic field. This leads to a systematic increase in the solar wind speed when the magnetic field vector is locally transverse to the velocity, and to a decrease in the speed when the field is more aligned with the radial, regardless of the polarity of the underlying magnetic field. We demonstrate that such an effect is a consequence of Alfvénicity for a unidirectional flux of waves propagating away from the Sun and with approximatively constant magnetic field magnitude. This correlation is systematically present in highly Alfvénic streams observed by Ulysses and Helios from 0.3 AU to 5 AU. The variations in the speed being proportional to the local Alfvén speed results in a modulation of the solar wind profile that is particularly relevant close to the Sun.

  15. Air-sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

    2013-11-01

    Shipboard measurements of eddy covariance dimethylsulfide (DMS) air-sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air-sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near-surface water-side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air-sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

  16. Statistical Short-Range Guidance for Peak Wind Speed Forecasts on Kennedy Space Center/Cape Canaveral Air Force Station: Phase I Results

    NASA Technical Reports Server (NTRS)

    Lambert, Winifred C.; Merceret, Francis J. (Technical Monitor)

    2002-01-01

    This report describes the results of the ANU's (Applied Meteorology Unit) Short-Range Statistical Forecasting task for peak winds. The peak wind speeds are an important forecast element for the Space Shuttle and Expendable Launch Vehicle programs. The Keith Weather Squadron and the Spaceflight Meteorology Group indicate that peak winds are challenging to forecast. The Applied Meteorology Unit was tasked to develop tools that aid in short-range forecasts of peak winds at tower sites of operational interest. A 7 year record of wind tower data was used in the analysis. Hourly and directional climatologies by tower and month were developed to determine the seasonal behavior of the average and peak winds. In all climatologies, the average and peak wind speeds were highly variable in time. This indicated that the development of a peak wind forecasting tool would be difficult. Probability density functions (PDF) of peak wind speed were calculated to determine the distribution of peak speed with average speed. These provide forecasters with a means of determining the probability of meeting or exceeding a certain peak wind given an observed or forecast average speed. The climatologies and PDFs provide tools with which to make peak wind forecasts that are critical to safe operations.

  17. Design and control of a variable-speed generator system for a WECS (wind energy conversion system)

    SciTech Connect

    Ralph, M.E.

    1987-01-01

    Sandia National Laboratories has been funded by the Wind/Ocean Technologies Division of the DOE to design and build a 34-meter diameter VAWT research Test Bed incorporating a constant frequency, variable speed generator system (VSGS). The turbine will be utilized to evaluate aerodynamic and structural dynamic technological advances and to develop and test variable speed control algorithms. These algorithms are intended to control the power output and increase the turbine fatigue life. The paper will discuss the design of the power system, VSGS and the control system hardware. The variable speed control algorithm development to date is also discussed. 6 refs., 5 figs.

  18. CO2 exchange coefficients from remotely-sensed wind speed measurements: SSM/I versus QuikSCAT in 2000

    NASA Technical Reports Server (NTRS)

    Carr, M.; Tang, W.; Liu, W. T.

    2002-01-01

    We compare here the air-sea exchange coefficient for C02 estimated with monthly mean wind speed measured by the Special Sensing Microwave Imager (SSM/I), Ks , and by the scatterometer QuikSCAT, Kq, for the year 2000.

  19. Improved process model for ammonia volatilization from anaerobic swine lagoons under varying wind speeds and gas bubbling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ammonia volatilization from treatment lagoons varies widely with the lagoon water total ammonia concentration, pH, temperature, suspended solids, atmospheric ammonia concentration above the water surface, and wind speed. Ammonia emissions were estimated with a process-based mechanistic model using a...

  20. Changes in sea-level pressure over South Korea associated with high-speed solar wind events

    NASA Astrophysics Data System (ADS)

    Cho, Il-Hyun; Kwak, Young-Sil; Marubashi, Katsuhide; Kim, Yeon-Han; Park, Young-Deuk; Chang, Heon-Young

    2012-09-01

    We explore a possibility that the daily sea-level pressure (SLP) over South Korea responds to the high-speed solar wind event. This is of interest in two aspects: first, if there is a statistical association this can be another piece of evidence showing that various meteorological observables indeed respond to variations in the interplanetary environment. Second, this can be a very crucial observational constraint since most models proposed so far are expected to preferentially work in higher latitude regions than the low latitude region studied here. We have examined daily solar wind speed V, daily SLP difference ΔSLP, and daily log(BV2) using the superposed epoch analysis in which the key date is set such that the daily solar wind speed exceeds 800 km s-1. We find that the daily ΔSLP averaged out of 12 events reaches its peak at day +1 and gradually decreases back to its normal level. The amount of positive deviation of ΔSLP is +2.5 hPa. The duration of deviation is a few days. We also find that ΔSLP is well correlated with both the speed of solar wind and log(BV2). The obtained linear correlation coefficients and chance probabilities with one-day lag for two cases are r ≃ 0.81 with P > 99.9%, and r ≃ 0.84 with P > 99.9%, respectively. We conclude by briefly discussing future direction to pursue.

  1. Interstellar flow direction from pickup ion cut-off dependence on longitude, flow and solar wind speed

    NASA Astrophysics Data System (ADS)

    Möbius, Eberhard; Lee, Martin A.; Drews, Christian; Gloeckler, George

    2016-03-01

    The precise interstellar neutral (ISN) flow direction is important because of its strong leverage on the plane subtended by the ISN and magnetic field vectors, which controls the heliospheric shape and interaction with the interstellar medium. IBEX measurements provide a very precise relation between ISN flow longitude and speed via the hyperbolic trajectory equation, forming a 4-dimensional tube in the ISN parameter space, with substantially larger uncertainty along this tube and thus for the longitude alone. As demonstrated before, the interstellar pickup ion (PUI) cut-off speed is a function of the ratio of the radial ISN flow component and the solar wind speed at the observer location. The former is largest precisely upwind and decreases symmetrically with the angle from the upwind direction. Using this functional dependence and the observed solar wind speed, the PUI cut-off can be constructed solely as a function of the ISN flow longitude. From ACE SWICS and STEREO PLASTIC, data sets that span 18+ years are available. We will show, in particular, that by selecting observations for local interplanetary magnetic fields perpendicular to the solar wind and transforming the observed distributions into the solar wind frame, a comparison with data can be devised that is much less sensitive to PUI production and transport effects than methods that rely on pickup ion fluxes.

  2. On the correlation of spatial wind speed and solar irradiance variability above the North Sea

    NASA Astrophysics Data System (ADS)

    Rieke Mehrens, Anna; von Bremen, Lueder

    2016-04-01

    Mesoscale wind fluctuations on a time scale of tens of minutes to several hours lead to high wind power fluctuations. Enhanced mesoscale wind variability emerges during cold air outbreaks and resulting cellular convection. The study investigates spatial wind and solar variability and their correlation during cellular convection. Cellular convection leads to simultaneous high solar and wind variability, but the highest solar or wind variability occurs due to other meteorological phenomena.

  3. Radial forces analysis and rotational speed test of radial permanent magnetic bearing for horizontal axis wind turbine applications

    NASA Astrophysics Data System (ADS)

    Kriswanto, Jamari

    2016-04-01

    Permanent magnet bearings (PMB) are contact free bearings which utilize the forces generated by the magnets. PMB in this work is a type of radial PMB, which functions as the radial bearings of the Horizontal Axis Wind Turbine (HAWT) rotor shaft. Radial PMB should have a greater radial force than the radial force HAWT rotor shaft (bearing load). This paper presents a modeling and experiments to calculate the radial force of the radial PMB. This paper also presents rotational speed test of the radial PMB compared to conventional bearings for HAWT applications. Modeling using COMSOL Multiphysics 4.3b with the magnetic fields physics models. Experiments were conducted by measuring the displacement of the rotor to the stator for a given load variation. Results of the two methods showed that the large displacement then the radial force would be greater. Radial forces of radial PMB is greater than radial forces of HAWT rotor shaft. The rotational speed test results of HAWT that used radial PMB produced higher rotary than conventional bearings with an average increase of 87.4%. Increasing rotational speed occured because radial PMB had no friction. HAWT that used radial PMB rotated at very low wind speeds are 1.4 m/s with a torque of 0.043 Nm, while the HAWT which uses conventional bearing started rotating at a wind speed of 4.4 m/s and required higher torque of 0.104 N.

  4. Remote-Sensing of Solar Wind Speeds from IPS Observations at 140 and 327 MHz Using MEXART and STEL

    NASA Astrophysics Data System (ADS)

    Mejia-Ambriz, J. C.; Jackson, B. V.; Gonzalez-Esparza, J. A.; Buffington, A.; Tokumaru, M.; Aguilar-Rodriguez, E.

    2015-09-01

    Interplanetary scintillation (IPS) is used to probe solar wind speeds in the inner heliosphere by applying either of two generalized data-analysis techniques: model fitting to power spectra (MFPS) from a single station, or cross-correlation functions (CCF) produced by cross-correlating two simultaneous IPS time series from separate stations. The MEXican Array Radio Telescope (MEXART), observing at 140 MHz, is starting to use an MFPS technique. Here we report the first successful solar wind speed determinations with IPS observations by MEXART. Three stations of the Solar-Terrestrial Environment Laboratory (STEL), observing at 327 MHz, use a CCF, and an MFPS technique is also used at one of these sites. We here analyze data from MEXART and from one antenna of STEL to obtain solar wind speeds using an MFPS technique from a single station. The IPS observations were carried out with radio source 3C48 during Solar Cycle 24. The MFPS method we describe here is tested by comparing its obtained speeds with those from the STEL CCF technique. We find that the speeds from the two techniques generally agree within the estimated errors.

  5. The coherent relation between the solar wind proton speed and O7+/O6+ ratio and its coronal sources

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Landi, E.; Fisk, L. A.; Lepri, S. T.

    2016-03-01

    We analyze the two-hour resolution solar wind proton speed (Vp) and charge state ratio of O7+/O6+ measured by ACE (SWICS and SWEPAM) from 1998 to 2011 at 1 AU. By applying a two-step mapping method, we link the solar wind in-situ observations to the corona images captured by SOHO and STEREO, in which we identify the different plasma structures, such as active regions (ARs), coronal holes (CHs) and quiet Sun regions (QS), using a classification scheme based on pixel brightness. Then we determine from which region in the corona the solar wind originates. We examine the in-situ properties of the solar wind streams associated with CHs, ARs and QS regions. We find that more than half of CH associated wind is actually slow wind, and O7+/O6+ ratio has a strong coherent correlation with the location of the solar wind coronal sources. Therefore, we conclude that O7+/O6+ ratio can be used as a much more effective discriminator to identify solar wind coronal sources region than Vp.

  6. Effect of winding layer and speed on kenaf/glass fiber hybrid reinforced acrylonitrile butadiene styrene (ABS) composites

    NASA Astrophysics Data System (ADS)

    Khoni, Norizzahthul Ainaa Abdul; Sharifah Shahnaz S., B.; Ghazali, Che Mohd Ruzaidi

    2016-07-01

    The usage of natural fiber is becoming significant in composite industries due to their good performance. Single and continuous natural fibers have relatively high mechanical properties; especially their young modulus can be as high as glass fibers. Filament winding is a method to produce technically aligned composites which have high fibers content. The properties of filament winding can be tailored to meet the end product requirements. This research studied the compression properties of kenaf/glass fibers hybrid reinforced composites. Kenaf/glass fibers hybrid composite samples were fabricated by filament winding technique and their properties were compared with the properties of neat kenaf fiber and glass fibers composites. The kenaf/glass fiber hybrid composites exhibited higher strength compared to the neat glass fibers composites. Composites of helical pattern, which produced at low winding speed showed better compression resistance than hoop pattern winding, which produced at high winding speed. As predicted, kenaf composite showed highest water absorption; followed by kenaf/glass fiber hybrid composites while neat glass fiber has lowest water absorption capability.

  7. The AEI 10 m prototype interferometer

    NASA Astrophysics Data System (ADS)

    Goßler, S.; Bertolini, A.; Born, M.; Chen, Y.; Dahl, K.; Gering, D.; Gräf, C.; Heinzel, G.; Hild, S.; Kawazoe, F.; Kranz, O.; Kühn, G.; Lück, H.; Mossavi, K.; Schnabel, R.; Somiya, K.; Strain, K. A.; Taylor, J. R.; Wanner, A.; Westphal, T.; Willke, B.; Danzmann, K.

    2010-04-01

    A 10 m prototype interferometer facility is currently being set up at the AEI in Hannover, Germany. The prototype interferometer will be housed inside a 100 m3 ultra-high vacuum envelope. Seismically isolated optical tables inside the vacuum system will be interferometrically interconnected via a suspension platform interferometer. Advanced isolation techniques will be used, such as inverted pendulums and geometrical anti-spring filters in combination with multiple-cascaded pendulum suspensions, containing an all-silica monolithic last stage. The light source is a 35 W Nd:YAG laser, geometrically filtered by passing it through a photonic crystal fibre and a rigid pre-modecleaner cavity. Laser frequency stabilisation will be achieved with the aid of a high finesse suspended reference cavity in conjunction with a molecular iodine reference. Coating thermal noise will be reduced by the use of Khalili cavities as compound end mirrors. Data acquisition and control of the experiments is based on the AdvLIGO digital control and data system. The aim of the project is to test advanced techniques for GEO 600 as well as to conduct experiments in macroscopic quantum mechanics. Reaching standard quantum-limit sensitivity for an interferometer with 100 g mirrors and subsequently breaching this limit, features most prominently among these experiments. In this paper we present the layout and current status of the AEI 10 m Prototype Interferometer project.

  8. The Paradox of Filamented Coronal Hole Flow but Uniform High Speed Wind

    NASA Technical Reports Server (NTRS)

    Suess, Steven T.; Parhi, Shyamsundar; Moore, Ronald L.

    1998-01-01

    Plumes and rays in coronal holes are nearly radially aligned density striations that follow the ambient magnetic field. They have long been known, but have gained new interest with growing awareness that coronal hole flow is inherently filamentary. In retrospect, filamentary flow should have been no surprise. This is because,Beta much less than 1 in coronal holes inside approximately 10 Solar radius, allowing the flow to be filamentary down to the smallest scale of photospheric magnetic activity. While the magnetic field itself is locally smooth across any height above ca. 50,000 km, SOHO/MDI has shown that the photospheric magnetic field is a complex array of rapidly evolving small bipoles that are constantly emerging, evolving, and cancelling. The resulting activity is manifested in microflares, concentrated in the magnetic network, that produce Impulsive injections at the footpoints of coronal field lines. The uneven distribution of this activity in space and time is the source of coronal hole filamentation. What is surprising is that the radial flow speed also exhibits filamentary structure. It is not well described as smooth, spherically symmetric, diverging flow, but instead ranges from 300 to over 1000 km/s at 5.5 Solar radius among field-aligned filaments like those seen in plumes and rays [Feldman et al., JGR, Dec. 1997]. This is completely unlike the constant high speed solar wind reported beyond 0.3 AU. Consequently, plumes and filamentary structure must be strongly mixed, and the mixing must be far along by 0.3 AU to be consistent with Helios observations. The paradox is what causes the mixing? Existing models of coronal heating and solar wind acceleration hardly address this issue. One possibility we are investigating is the MHD Kelvin-Helmholtz instability, to which the shear between plumes and interplume corona is expected to become unstable at 5-10 Solar radius. This instability can be simulated and followed far into the nonlinear regime and may

  9. Inlet Unstart Propulsion Integration Wind Tunnel Test Program Completed for High-Speed Civil Transport

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert

    2000-01-01

    One of the propulsion system concepts to be considered for the High-Speed Civil Transport (HSCT) is an underwing, dual-propulsion, pod-per-wing installation. Adverse transient phenomena such as engine compressor stall and inlet unstart could severely degrade the performance of one of these propulsion pods. The subsequent loss of thrust and increased drag could cause aircraft stability and control problems that could lead to a catastrophic accident if countermeasures are not in place to anticipate and control these detrimental transient events. Aircraft system engineers must understand what happens during an engine compressor stall and inlet unstart so that they can design effective control systems to avoid and/or alleviate the effects of a propulsion pod engine compressor stall and inlet unstart. The objective of the Inlet Unstart Propulsion Airframe Integration test program was to assess the underwing flow field of a High-Speed Civil Transport propulsion system during an engine compressor stall and subsequent inlet unstart. Experimental research testing was conducted in the 10- by 10-Foot Supersonic Wind Tunnel at the NASA Glenn Research Center at Lewis Field. The representative propulsion pod consisted of a two-dimensional, bifurcated inlet mated to a live turbojet engine. The propulsion pod was mounted below a large flat plate that acted as a wing simulator. Because of the plate s long length (nominally 10-ft wide by 18-ft long), realistic boundary layers could form at the inlet cowl plane. Transient instrumentation was used to document the aerodynamic flow-field conditions during an unstart sequence. Acquiring these data was a significant technical challenge because a typical unstart sequence disrupts the local flow field for about only 50 msec. Flow surface information was acquired via static pressure taps installed in the wing simulator, and intrusive pressure probes were used to acquire flow-field information. These data were extensively analyzed to

  10. The Relation Between Wind Speed and Air-Sea Temperature Difference in the Marine Atmospheric Boundary Layer off Northwest Europe

    NASA Astrophysics Data System (ADS)

    Kettle, A. J.

    2014-12-01

    Wind speed and atmospheric stability have an important role in determining the turbulence in the marine atmospheric boundary layer (MABL) as well as the surface wave field. The understanding of MABL dynamics in northwest Europe is complicated by fetch effects, the proximity of coastlines, shallow topography, and larger scale circulation patterns (e.g., cold air outbreaks). Numerical models have difficulty simulating the marine atmospheric boundary layer in coastal areas and partially enclosed seas, and this is partly due to spatial resolution problems at coastlines. In these offshore environments, the boundary layer processes are often best understood directly from time series measurements from fixed platforms or buoys, in spite of potential difficulties from platform flow distortion as well as the spatial sparseness of the data sets. This contribution presents the results of time series measurements from offshore platforms in the North Sea and Norwegian Sea in terms of a summary diagnostic - wind speed versus air-sea temperature difference (U-ΔT) - with important implications for understanding atmospheric boundary layer processes. The U-ΔT diagram was introduced in earlier surveys of data from coastal (Sletringen; O.J. Andersen and J. Løvseth, J. Wind Eng. Ind. Aerodyn., 57, 97-109, 1995) and offshore (Statfjord A; K.J. Eidsvik, Boundary-Layer Meteorol., 32, 103-132, 1985) sites in northwest Europe to summarize boundary layer conditions at a given location. Additional information from a series of measurement purpose-built offshore measurement and oil/gas production platforms from the southern North Sea to the Norwegian Sea illustrates how the wind characteristics vary spatially over large distances, highlighting the influence of cold air outbreaks, in particular. The results are important for the offshore wind industry because of the way that wind turbines accrue fatigue damage in different conditions of atmospheric stability and wind speed.

  11. Low Speed Technology for Small Turbine Development Reaction Injection Molded 7.5 Meter Wind Turbine Blade

    SciTech Connect

    David M. Wright; DOE Project Officer - Keith Bennett

    2007-07-31

    An optimized small turbine blade (7.5m radius) was designed and a partial section molded with the RIM (reaction-injection molded polymer) process for mass production. The intended market is for generic three-bladed wind turbines, 100 kilowatts or less, for grid-assist end users with rural and semi-rural sites, such as the farm/ranch market, having low to moderate IEC Class 3-4 wind regimes. This blade will have substantial performance improvements over, and be cheaper than, present-day 7.5m blades. This is made possible by the injection-molding process, which yields high repeatability, accurate geometry and weights, and low cost in production quantities. No wind turbine blade in the 7.5m or greater size has used this process. The blade design chosen uses a RIM skin bonded to a braided infused carbon fiber/epoxy spar. This approach is attractive to present users of wind turbine blades in the 5-10m sizes. These include rebladeing California wind farms, refurbishing used turbines for the Midwest farm market, and other manufacturers introducing new turbines in this size range.

  12. Techniques for studying gravity waves and turbulence: Vertical wind speed power spectra from the troposphere and stratosphere obtained under light wind conditions

    NASA Technical Reports Server (NTRS)

    Ecklund, W. L.; Balsley, B. B.; Crochet, M.; Carter, D. A.; Riddle, A. C.; Garello, R.

    1983-01-01

    A joint France/U.S. experiment was conducted near the mouth of the Rhone river in southern France as part of the ALPEX program. This experiment used 3 vertically directed 50 MHz radars separated by 4 to 6 km. The main purpose of this experiment was to study the spatial characteristics of gravity waves. The good height resolution (750 meters) and time resolution (1 minute) and the continuous operation over many weeks have yielded high resolution vertical wind speed power spectra under a variety of synoptic conditions. Vertical spectra obtained during very quiet (low wind) conditions in the troposphere and lower stratosphere from a single site are presented.

  13. A case study of effects of atmospheric boundary layer turbulence, wind speed, and stability on wind farm induced temperature changes using observations from a field campaign

    NASA Astrophysics Data System (ADS)

    Xia, Geng; Zhou, Liming; Freedman, Jeffrey M.; Roy, Somnath Baidya; Harris, Ronald A.; Cervarich, Matthew Charles

    2016-04-01

    Recent studies using satellite observations show that operational wind farms in west-central Texas increase local nighttime land surface temperature (LST) by 0.31-0.70 °C, but no noticeable impact is detected during daytime, and that the diurnal and seasonal variations in the magnitude of this warming are likely determined by those in the magnitude of wind speed. This paper further explores these findings by using the data from a year-long field campaign and nearby radiosonde observations to investigate how thermodynamic profiles and surface-atmosphere exchange processes work in tandem with the presence of wind farms to affect the local climate. Combined with satellite data analyses, we find that wind farm impacts on LST are predominantly determined by the relative ratio of turbulence kinetic energy (TKE) induced by the wind turbines compared to the background TKE. This ratio explains not only the day-night contrast of the wind farm impact and the warming magnitude of nighttime LST over the wind farms, but also most of the seasonal variations in the nighttime LST changes. These results indicate that the diurnal and seasonal variations in the turbine-induced turbulence relative to the background TKE play an essential role in determining those in the magnitude of LST changes over the wind farms. In addition, atmospheric stability determines the sign and strength of the net downward heat transport as well as the magnitude of the background TKE. The study highlights the need for better understanding of atmospheric boundary layer and wind farm interactions, and for better parameterizations of sub-grid scale turbulent mixing in numerical weather prediction and climate models.

  14. Measuring Directional Wave Spectra and Wind Speed with a Scanning Radar Altimeter

    NASA Technical Reports Server (NTRS)

    Walsh, E. J.; Vandemark, D.; Wright, C. W.; Swift, R. N.; Scott, J. F.; Hines, D. E.

    1999-01-01

    The geometry for the NASA Scanning Radar Altimeter (SRA) is shown. It transmits a 8-ns duration pulse at Ka-band (8.3 mm) and measures time of flight as it scans a 1 degree (two-way) beam from left to right across the aircraft ground track. The most recent configuration determines the surface elevation at 64 points spaced at uniform angular intervals of about 0.7 across a swath whose width is about 0.8 times the aircraft altitude. The system generates these raster lines of the surface topography beneath the aircraft at about a 10 Hz rate. In postflight processing the SRA wave topographic data are transformed with a two-dimensional Fast Fourier Transformation (FFT) and Doppler corrected to produce directional wave spectra. The SRA is not absolutely calibrated in power, but by measuring the relative fall-off of backscatter with increasing incidence angle, the SRA can also determine the mean square slope (mss) of the sea surface, a surrogate for wind speed. For the slope-dependent specular point model of radar sea surface scattering, an expression approximated by a geometric optics form, for the relative variation with incidence angle of the normalized backscatter radar cross section would be sigma (sup 0) (sub rel) = sec (exp 4) theta exp (-tan squared theta/mss) where theta is the off-nadir incidence angle.

  15. Assessing trophic linkages in and around offshore wind farms using two high-speed optical sensors

    NASA Astrophysics Data System (ADS)

    Dudeck, Tim; Hufnagl, Marc; Auch, Dominik; Eckhardt, André; Möller, Klas-Ove; van Beusekom, Justus; Walter, Bettina; Möllmann, Christian; Floeter, Jens

    2016-04-01

    In search for clean, renewable energy sources European countries have built and planned numerous Offshore Wind Farms (OWF) in the North Sea region. While some research has been carried out on their influence on marine mammals and bottom-dwelling organisms, less is known about fish and lower trophic levels in these areas. Yet, marine mammals purposely seek these structures and there are indications that there are higher chances of fish encounters. However, the local bottom-up effects probably driving these aggregations of higher trophic level organisms are poorly understood. In this study we show preliminary results of primary and secondary production in and around German OWFs in the North Sea using a Laser Optical Particle Counter and a Video Plankton Recorder. With the two sensors working simultaneously on the TRIAXUS system at high speed, we were able to investigate and ground-truth size-spectrum changes on a very high spatial resolution making it possible to detect OWF effects from local to larger scales. Our results show new possibilities in OWF research and the necessity to collect highly resolved field data for meaningful results in these dynamic environments. Furthermore, the use of size spectra simplifies the integration of energy flow through low and medium trophic levels into biogeochemical models by using only a single automatically measurable variable such as size.

  16. Modelling the 2013 Typhoon Haiyan storm surge: Effect of waves, offshore winds, tide phase, and translation speed

    NASA Astrophysics Data System (ADS)

    Bilgera, P. H. T.

    2015-12-01

    Super Typhoon Haiyan, with wind speeds exceeding 300 km h-1 (160 knots) generated a storm surge in San Pedro Bay reaching heights of more than 6m in Tacloban City. Delft Dashboard (DDB), an open-source standalone Matlab based graphical user interface linked to the FLOW and WAVE modeling software of Deltares, was used to develop a coupled flow and wave storm surge model to understand the Typhoon Haiyan storm surge development and propagation. Various experiments were designed to determine the effect of waves, the occurrence of offshore winds prior to the surge, tidal phase, and typhoon translation speed on the surge height. Wave coupling decreased the surge height by about 0.5m probably due to energy dissipation from white capping, bottom friction, and depth-induced breaking. Offshore-directed winds before the arrival of the storm eye resulted to receding of the water level in San Pedro and Cancabato Bay, corroborated by eyewitness and tide gauge data. The experiment wherein the offshore winds were removed resulted to no water receding and a surge with a smaller and gentler surge front, pointing to the importance of the initial water level drawdown in contributing to the destructive power of the wave front. With regard to tides, the effect in Tacloban was actually neither linear nor additive to the surge, with higher surge coincident to low tides and lower surge coincident to high tides. Lastly, the model run with typhoon having a slower translation speed than Haiyan was found to generate higher surges.

  17. Choosing wind power plant locations and sizes based on electric reliability measures using multiple-year wind speed measurements

    SciTech Connect

    Milligan, M.R.; Artig, R.

    1999-07-08

    To project the US potential to meet future electricity demands with wind energy, estimates of available wind resource and costs to access that resource are critical. The US Department of Energy (DOE) Energy Information Administration (EIA) annually estimates the US market penetration of wind in its Annual Energy Outlook series. For these estimates, the EIA uses wind resource data developed by the Pacific Northwest National Laboratory for each region of the country. However, the EIA multiplies the cost of windpower by several factors, some as large as 3, to account for resource quality, market factors associated with accessing the resource, electric grid impacts, and rapid growth in the wind industry. This paper examines the rationale behind these additional costs and suggests alternatives.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  19. Observations During GRIP from HIRAD: Images of C-Band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate

    NASA Technical Reports Server (NTRS)

    Miller, Timothy L.; James, M. W.; Jones, W. L.; Ruf, C. S.; Uhlhorn, E. W.; Biswas, S.; May, C.; Shah, G.; Black, P.; Buckley, C. D.

    2012-01-01

    HIRAD (Hurricane Imaging Radiometer) flew on the WB-57 during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be inferred. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years. The advantage of HIRAD over SFMR is that HIRAD can observe a +/- 60-degree swath, rather than a single footprint at nadir angle. Results from the flights during the GRIP campaign will be shown, including images of brightness temperatures, wind speed, and rain rate. To the extent possible, comparisons will be made with observations from other instruments on the GRIP campaign, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eyewall, location of vortex wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.