WorldWideScience

Sample records for wind field patterns

  1. Calm before the spawn: global coral spawning patterns are explained by regional wind fields.

    Science.gov (United States)

    van Woesik, R

    2010-03-07

    Most corals in tropical localities broadcast their gametes into the water column, yet we have a poor understanding of what forces reproductive schedules. Moreover, recent studies show considerable geographical variation in the duration of the coral spawning season. For example, on the Great Barrier Reef, corals display tight coupling, while corals in Kenya spawn over seven months. This study reconciles the regional variance by testing the hypothesis that regional wind fields are the corals' ultimate reproductive proxy. Regions with short calm periods should be more tightly coupled than regions with calm periods extending for several months. Regional wind fields were assessed at seven localities, between 1997 and 2006, using the 11 GHz channel radiometer tropical microwave imager (TMI) onboard the tropical rainfall measuring mission (TRMM). There was a direct positive relationship between the duration of regional calm periods and the coupling of mass coral spawning. Ultimate long-term evolutionary advantages of releasing gametes during calm periods ensure fertilization and facilitate larval retention and local recruitment. Coupling mass spawning with seasonally calm periods agrees strongly with recent genetic evidence of local dispersal and high local retention.

  2. Dynamical downscaling of wind fields for wind power applications

    Science.gov (United States)

    Mengelkamp, H.-T.; Huneke, S.; Geyer, J.

    2010-09-01

    Dynamical downscaling of wind fields for wind power applications H.-T. Mengelkamp*,**, S. Huneke**, J, Geyer** *GKSS Research Center Geesthacht GmbH **anemos Gesellschaft für Umweltmeteorologie mbH Investments in wind power require information on the long-term mean wind potential and its temporal variations on daily to annual and decadal time scales. This information is rarely available at specific wind farm sites. Short-term on-site measurements usually are only performed over a 12 months period. These data have to be set into the long-term perspective through correlation to long-term consistent wind data sets. Preliminary wind information is often asked for to select favourable wind sites over regional and country wide scales. Lack of high-quality wind measurements at weather stations was the motivation to start high resolution wind field simulations The simulations are basically a refinement of global scale reanalysis data by means of high resolution simulations with an atmospheric mesoscale model using high-resolution terrain and land-use data. The 3-dimensional representation of the atmospheric state available every six hours at 2.5 degree resolution over the globe, known as NCAR/NCEP reanalysis data, forms the boundary conditions for continuous simulations with the non-hydrostatic atmospheric mesoscale model MM5. MM5 is nested in itself down to a horizontal resolution of 5 x 5 km². The simulation is performed for different European countries and covers the period 2000 to present and is continuously updated. Model variables are stored every 10 minutes for various heights. We have analysed the wind field primarily. The wind data set is consistent in space and time and provides information on the regional distribution of the long-term mean wind potential, the temporal variability of the wind potential, the vertical variation of the wind potential, and the temperature, and pressure distribution (air density). In the context of wind power these data are used

  3. Wind Turbines Adaptation to the Variability of the Wind Field

    Science.gov (United States)

    Ulianov, Yuriy; Martynenko, Gennadii; Misaylov, Vitaliy; Soliannikova, Iuliia

    2010-05-01

    WIND TURBINES ADAPTATION TO THE VARIABILITY OF THE WIND FIELD The subject of our scientific research is wind power turbines (WPT) with the horizontal axis which were now common in the world. Efficient wind turbines work is largely determined by non-stationarity of the wind field, expressed in its gustiness, the presence of vertical and horizontal shifts of wind speed and direction. At critical values of the wind parameters WPT has aerodynamic and mechanical overload, leading to breakdowns, premature wear and reduce the life of the wind turbine. To prevent accidents at the peak values of wind speed it is used the regulatory system of windwheels. WPT control systems provide a process orientation of the wind turbine rotor axis in the line of the mean wind. Wind turbines are also equipped with braking device used to protect against breakdowns when a significant increase in the wind. In general, all these methods of regulation are not always effective. Thus, in practice there may be situations when the wind speed is many times greater than the stated limit. For example, if there are microbursts in the atmospheric boundary layer, low-level wind shears caused by its gust front, storms, etc. It is required for a wind power turbine adaptation to intensive short-term wind impulses and considerable vertical wind shifts that the data about them shall be obtained ahead of time. To do this it is necessary to have the information on the real structure of the wind field in the area of the blade sweep for the minimum range against the wind that is determined by the mean speed and the system action time. The implementation of acoustic and laser traditional wind sounding systems is limited by ambient acoustic noise, by heavy rain, snowfall and by fog. There are free of these disadvantages the inclined radioacoustic sounding (IRASS) technique which works for a system of remote detection and control of wind gusts. IRASS technique is realized as low-potential Doppler pulse radar

  4. Development and validation of computational wind field model (Wind scape)

    OpenAIRE

    Kim, D.; Kim, B. -Y

    2012-01-01

    Wind field data is essential for the accurate prediction of forest fire spread. For the accurate prediction of local wind field we developed computational fluid dynamics simulation procedure. Using terrain and wind information as input data three dimensional computational mesh is automatically generated. GIS data of the format DEM(Digital Elevation Map) is directly converted to quad surface mesh and full hexahedral space mesh is automatically generated. Around this mesh we made extended compu...

  5. LIDAR Wind Speed Measurements of Evolving Wind Fields

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Wide Area Wind Field Monitoring Status & Results

    Energy Technology Data Exchange (ETDEWEB)

    Alan Marchant; Jed Simmons

    2011-09-30

    Volume-scanning elastic has been investigated as a means to derive 3D dynamic wind fields for characterization and monitoring of wind energy sites. An eye-safe volume-scanning lidar system was adapted for volume imaging of aerosol concentrations out to a range of 300m. Reformatting of the lidar data as dynamic volume images was successfully demonstrated. A practical method for deriving 3D wind fields from dynamic volume imagery was identified and demonstrated. However, the natural phenomenology was found to provide insufficient aerosol features for reliable wind sensing. The results of this study may be applicable to wind field measurement using injected aerosol tracers.

  7. A combinatorial wind field model

    DEFF Research Database (Denmark)

    Soleimanzadeh, Maryam; Wisniewski, Rafal; Sloth, Christoffer

    2010-01-01

    This report is the deliverable 2.4 in the project Distributed Control of Large-Scale Oshore Wind Farms with the acronym Aeolus. The objective of this deliverable is to provide an understanding of the wind eld model and dynamic variations superimposed on the mean eld. In this report a dynamical mo...

  8. Ocean Wave Simulation Based on Wind Field.

    Science.gov (United States)

    Li, Zhongyi; Wang, Hao

    2016-01-01

    Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates.

  9. Exploring the offshore wind farm far field

    Science.gov (United States)

    Platis, Andreas; Emeis, Stefan; Siedersleben, Simon; Neumann, Tom; Canadillas, Beatriz; Lampert, Astrid; Djath, Nathacha; Schulz-Stellenfleth, Johannes; Bärfuss, Konrad; Bange, Jens

    2017-04-01

    Offshore wind farms contribute a considerable part of today's production of renewable electric energy. In the last years a massive built-up in offshore wind energy farms has occurred with a concentration of the wind farms in group and cluster. This arrangement affects one another through increased wake losses. The German Government is presently funding a research project called WIPAFF (WInd PArk Far Field) which is dedicated to the the analysis of properties and impacts of offshore wind park far fields and wake losses. The focus is on the analysis of wind farm wakes, their interaction among each other and their regional climate impact. This is done by in-situ, extensive aircraft and satellite measurements and by operating meso-scale wind field models and an analytical wind farm model. We will present this project and show preliminary results of the the first in situ evidence by airborne measurements of these wakes behind off shore windfarms with a wind deficit zones and enhanced turbulence.

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

    Science.gov (United States)

    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.

  11. Mod-2 wind turbine field operations experience

    Science.gov (United States)

    Gordon, L. H.

    The Mod-2 wind turbine is now in a 2-year research/experimental operations phase which offers a unique opportunity to study the effects of single and multiple wind turbines interacting with each other, the power grid, and the environment. This paper addresses the field operations and research testing experienced at the Mod-2 Cluster Goodnoe Hills Research Test Site near Goldendale, WA. Field operation, both routine and nonroutine, are discussed as well as the role of the participating utility. Technical areas discussed pertain to system performance and loads. Specific research tests relating to acoustics, TV interference, and wake effects are also discussed.

  12. Experimental Wind Field Estimation and Aircraft Identification

    OpenAIRE

    Condomines, Jean-Philippe; Bronz, Murat; Hattenberger, Gautier; Erdelyi, Jean-François

    2015-01-01

    International audience; The presented work is focusing on the wind estimation and airframe identification based on real flight experiments as part of the SkyScanner project. The overall objective of this project is to estimate the local wind field in order to study the formation of cumulus-type clouds with a fleet of autonomous mini-UAVs involving many aspects including flight control and energy harvesting. For this purpose, a small UAV has been equipped with airspeed and angle of attack sens...

  13. Cooperative field test program for wind systems

    Energy Technology Data Exchange (ETDEWEB)

    Bollmeier, W.S. II; Dodge, D.M.

    1992-03-01

    The objectives of the Federal Wind Energy Program, managed by the US Department of Energy (DOE), are (1) to assist industry and utilities in achieving a multi-regional US market penetration of wind systems, and (2) to establish the United States as the world leader in the development of advanced wind turbine technology. In 1984, the program conducted a series of planning workshops with representatives from the wind energy industry to obtain input on the Five-Year Research Plan then being prepared by DOE. One specific suggestion that came out of these meetings was that the federal program should conduct cooperative research tests with industry to enhance the technology transfer process. It was also felt that the active involvement of industry in DOE-funded research would improve the state of the art of wind turbine technology. DOE established the Cooperative Field Test Program (CFTP) in response to that suggestion. This program was one of the first in DOE to feature joint industry-government research test teams working toward common objectives.

  14. Temporal and spatial patterns in wind stress and wind stress curl over the central Southern California Bight

    Science.gov (United States)

    Noble, Marlene A.; Rosenberger, Kurt J.; Rosenfeld, Leslie K.; Robertson, George L.

    2012-01-01

    In 2001, the U.S. Geological Survey, together with several other federal and municipal agencies, began a series of field programs to determine along and cross-shelf transport patterns over the continental shelves in the central Southern California Bight. As a part of these programs, moorings that monitor winds were deployed off the Palos Verdes peninsula and within San Pedro Bay for six 3–4 month summer and winter periods between 2001 and 2008. In addition, nearly continuous records of winds for this 7-year period were obtained from a terrestrial site at the coast and from a basin site offshore of the long-term coastal site. The mean annual winds are downcoast at all sites. The alongshelf components of wind stress, which are the largest part of the low-frequency wind stress fields, are well correlated between basin, shelf and coastal sites. On average, the amplitude of alongshelf fluctuations in wind stress are 3–4 times larger over the offshore basin, compared to the coastal site, irrespective of whether the fluctuations represent the total, or just the correlated portion of the wind stress field. The curl in the large-scale wind stress tends to be positive, especially in the winter season when the mean wind stress is downcoast and larger at the offshore basin site than at the beach. However, since the fluctuation in wind stress amplitudes are usually larger than the mean, periods of weak negative curl do occur, especially in the summer season when the largest normalized differences in the amplitude of wind stress fluctuations are found in the nearshore region of the coastal ocean. Even though the low-frequency wind stress field is well-correlated over the continental shelf and offshore basins, out to distances of 35 km or more from the coast, winds even 10 km inshore of the beach do not represent the coastal wind field, at least in the summer months. The seasonal changes in the spatial structures in wind stress amplitudes suggest that an assessment of the

  15. Field verification program for small wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Windward Engineering, LLC

    2003-11-30

    In 1999 Windward Engineering (Windward) was awarded a Cooperative Agreement under the Field Verification Program with the Department of Energy (DOE) to install two Whisper H40 wind turbines, one at the NREL National Wind Technology Center (NWTC) and one at a test site near Spanish Fork, Utah. After installation, the turbine at the NWTC was to be operated, maintained, and monitored by NREL while the turbine in Spanish Fork was to be administered by Windward. Under this award DOE and Windward defined the primary objectives of the project as follows: (1) Determine and demonstrate the reliability and energy production of a furling wind turbine at a site where furling will be a very frequent event and extreme gusts can be expected during the duration of the tests. (2) Make engineering measurements and conduct limited computer modeling of the furling behavior to improve the industry understanding of the mechanics and nature of furling. We believe the project has achieved these objectives. The turbine has operated for approximately three and a half years. We have collected detailed engineering data approximately 75 percent of that time. Some of these data were used in an ADAMS model validation that highlighted the accuracies and inaccuracies of the computer modeling for a passively furling wind turbine. We also presented three papers at the American Wind Energy Association (AWEA) Windpower conferences in 2001, 2002, and 2003. These papers addressed the following three topics: (a) general overview of the project [1], (b) furling operation during extreme wind events [2], and (c) extrapolation of extreme (design) loads [3]. We believe these papers have given new insight into the mechanics and nature of furling and have set the stage for future research. In this final report we will highlight some of the more interesting aspects of the project as well as summarize the data for the entire project. We will also present information on the installation of the turbines as well as

  16. Modulated Field Synchronous Generator for Wind Turbines

    Directory of Open Access Journals (Sweden)

    Petru Chioncel

    2013-01-01

    Full Text Available This paper presents a modern electromechanical conversion systemsolution as the modulated field synchronous generator, offering on theone hand, an output voltage with constant frequency in terms of speedvariation of the wind turbine and on the other hand an advantagepower / weight ratio due to the high frequency for which the magneticcircuit of the electric machine is sized. The mathematical model of the modulated field synchronous generator is implemented in MatLABmodeling language, highlighting the command structure on thetransistors bases of the inverter transistors, through which thefunctioning of the electric machine can be studied, especially in terms of the frequency of the delivered voltage.

  17. Comparisons of Wind Field Effects on Radar Rainfall Adjustments

    Science.gov (United States)

    Song, Y.; Han, D.; Rico-Ramirez, M. A.

    2016-12-01

    Weather radar-based rainfall estimates are prone to many sources of uncertainties due to its complicated measurement procedure and intricate synoptic regimes. Rain gauge measurement as the "ground-truth" is widely implemented in radar data adjustments, which is crucial and essential to reduce their systematic bias in hydrological applications, especially for radar bias corrections in spatial matching of precipitation patterns with rain gauge. The conventional practice is to build radar-gauge pairs on the basis of their vertical projection on the ground, which assumes the rainfall observed by radar falls vertically to the ground and should be in accordance with the surface rainfall directly below each radar pixel. Since wind is a typical weather factor, which not only incurs measurement error of rain gauge, but also induces the raindrops observed by radar drifting to the ground, consequently, it could contribute inconsistent spatial relationship between radar and gauge measurements. As a result, this study explores the trajectory of raindrops in the air based on the previous study which incorporates the wind field effect into a bias correlation scheme using downscaled 3-D wind data from weather research and forecasting model (WRF). The new prompted adjustment method is to simulate the raindrop trajectory by implementing the 3-D wind field created by WRF directly. The displacement of rainfall is estimated and radar-gauge spatial relationships are reconstructed and compared. Based on these, this study attempts to compare and evaluate two different adjustment methods on radar data with and without consideration of the wind-drift effect in different rainfall events and locations. The proposed adjustment method is expected to be a promising improvement to minimize wind-drift effect.

  18. Mesoscale wind field modifications over the Baltic Sea

    DEFF Research Database (Denmark)

    Källstrand, B.; Bergström, H.; Højstrup, J.

    2000-01-01

    For two consecutive days during spring 1997, the wind field over the Baltic Sea has been studied. The strength of the geostrophic wind speed is the major difference in synoptic conditions between these two days. During both days, the mesoscale wind field over most of the Baltic Sea is quite heter...

  19. Spectral analysis of wind field in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rashmi, R.; Samiksha, S.V.; Polnikov, V.; Pogarskii, F.; Sudheesh, K.; Vethamony, P.

    To study the variability in wind fields over the Indian Ocean, we used ERA INTERIM daily winds for the period 1979-2012 In order to analyse the temporal variation of wind field, we partitioned the whole Indian Ocean into 6 zones based on spatial...

  20. Cluster Analysis of the Wind Events and Seasonal Wind Circulation Patterns in the Mexico City Region

    Directory of Open Access Journals (Sweden)

    Susana Carreón-Sierra

    2015-07-01

    Full Text Available The residents of Mexico City face serious problems of air pollution. Identifying the most representative scenarios for the transport and dispersion of air pollutants requires the knowledge of the main wind circulation patterns. In this paper, a simple method to recognize and characterize the wind circulation patterns in a given region is proposed and applied to the Mexico City winds (2001–2006. This method uses a lattice wind approach to model the local wind events at the meso-β scale, and hierarchical cluster analysis to recognize their agglomerations in their phase space. Data of the meteorological network of Mexico City was used as input for the lattice wind model. The Ward’s clustering algorithm with Euclidean distance was applied to organize the model wind events in seasonal clusters for each year of the period. Comparison of the hourly population trends of these clusters permitted the recognition and detailed description of seven circulation patterns. These patterns resemble the qualitative descriptions of the Mexico City wind circulation modes reported by other authors. Our method, however, permitted also their quantitative characterization in terms of the wind attributes of velocity, divergence and vorticity, and an estimation of their seasonal and annual occurrence probabilities, which never before were quantified.

  1. Wind loads on flat plate photovoltaic array fields (nonsteady winds)

    Science.gov (United States)

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

    1981-01-01

    Techniques to predict the dynamic response and the structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence were analyzed. Guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays are presented. The dynamic response and the loads dynamic magnification factor of the two array configurations are similar. The magnification factors at a mid chord and outer chord location on the array illustrated and at four points on the chord are shown. The wind tunnel test experimental rms pressure coefficient on which magnification factors are based is shown. It is found that the largest response and dynamic magnification factor occur at a mid chord location on an array and near the trailing edge. A technique employing these magnification factors and the wind tunnel test rms fluctuating pressure coefficients to calculate design pressure loads due to wind turbulence is presented.

  2. Comparison of field and wind-tunnel Darrieus wind-turbine data

    Science.gov (United States)

    Sheldahl, R. E.

    1981-08-01

    A 2-m-diam Darrieus vertical axis wind turbine with NACA-0012 airfoil blades was tested in the field and in a 4.6 x 6.1-m low speed wind tunnel for a direct comparison. Comparisons were made with field data of equivalent chord Reynolds number, and at equivalent rotational field. Maximum values of the power coefficients compared favorably, and an examination of performance coefficients showed complete agreement between wind tunnel and field data. Due to excellent agreement in the first two comparisons, no further field testing was done, and the accuracy of the wind-tunnel test data was believed verified.

  3. Using wind-deformed conifers to measure wind patterns in alpine transition at GLEES

    Science.gov (United States)

    Robert C. Musselman; Gene L. Wooldridge; Douglas G. Fox; Bernadette H. Connell

    1990-01-01

    The Glacier Lakes Ecosystem Experiments Site (GLEES) is a high-elevation ecosystem in the Snowy Range west of Laramie, WY, that is perceived to be highly sensitive to changes in chemical and physical climate. Deposition of atmospheric chemicals to this ecosystem is, in part, governed by the wind pattern. The GLEES has numerous wind-swept areas where the coniferous...

  4. Mod-2 wind turbine field operations experiment

    Science.gov (United States)

    Gordon, L. H.

    1985-12-01

    The three-machine, 7.5 MW Goodnoe Hills located near Goldendale, Washington and is now in a research/experimental operations phase that offers a unique opportunity to study the effects of single and multiple wind turbines interacting with each other, the power grid; and the environment. Following a brief description of the turbine and project history, this paper addresses major problem areas and research and development test results. Field operations, both routine and nonroutine, are discussed. Routine operation to date has produced over 13,379,000 KWh of electrical energy during 11,064 hr of rotation. Nonroutine operation includes suspended activities caused by a crack in the low speed shaft that necessitated a redesign and reinstallation of this assembly on all three turbines. With the world's largest cluster back in full operation, two of the turbines will be operated over the next years to determine their value as energy producer. The third unit will be used primarily for conducting research tests requiring configuration changes to better understand the wind turbine technology. Technical areas summarized pertain to system performance and enhancements. Specific research tests relating to acoustics, TV interference, and wake effects conclude the paper.

  5. Fourier Simulation of a Non-Isotropic Wind Field Model

    DEFF Research Database (Denmark)

    Mann, J.; Krenk, S.

    Realistic modelling of three dimensional wind fields has become important in calculation of dynamic loads on same spatially extended structures, such as large bridges, towers and wind turbines. For some structures the along wind component of the of the turbulent flow is important while for others...

  6. Apparatus and method for using radar to evaluate wind flow fields for wind energy applications

    Science.gov (United States)

    Schroeder, John; Hirth, Brian; Guynes, Jerry

    2017-02-21

    The present invention provides an apparatus and method for obtaining data to determine one or more characteristics of a wind flow field using one or more radars. Data is collected from the one or more radars, and analyzed to determine the one or more characteristics of the wind flow field. The one or more radars are positioned to have a portion of the wind flow field within a scanning sector of the one or more radars.

  7. Mars Global Digital Dune Database (MGD3): Global dune distribution and wind pattern observations

    Science.gov (United States)

    Hayward, Rosalyn K.; Fenton, Lori; Titus, Timothy N.

    2014-01-01

    The Mars Global Digital Dune Database (MGD3) is complete and now extends from 90°N to 90°S latitude. The recently released south pole (SP) portion (MC-30) of MGD3 adds ∼60,000 km2 of medium to large-size dark dune fields and ∼15,000 km2 of sand deposits and smaller dune fields to the previously released equatorial (EQ, ∼70,000 km2), and north pole (NP, ∼845,000 km2) portions of the database, bringing the global total to ∼975,000 km2. Nearly all NP dunes are part of large sand seas, while the majority of EQ and SP dune fields are individual dune fields located in craters. Despite the differences between Mars and Earth, their dune and dune field morphologies are strikingly similar. Bullseye dune fields, named for their concentric ring pattern, are the exception, possibly owing their distinctive appearance to winds that are unique to the crater environment. Ground-based wind directions are derived from slipface (SF) orientation and dune centroid azimuth (DCA), a measure of the relative location of a dune field inside a crater. SF and DCA often preserve evidence of different wind directions, suggesting the importance of local, topographically influenced winds. In general however, ground-based wind directions are broadly consistent with expected global patterns, such as polar easterlies. Intriguingly, between 40°S and 80°S latitude both SF and DCA preserve their strongest, though different, dominant wind direction, with transport toward the west and east for SF-derived winds and toward the north and west for DCA-derived winds.

  8. Wind loads on flat plate photovoltaic array fields

    Science.gov (United States)

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

    1981-01-01

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

  9. Magnetic fields and wind variability in massive stars

    NARCIS (Netherlands)

    Schnerr, R.S.; Henrichs, H.F.; Hamann, W.-R.; Feldmeier, A.; Oskinova, L.

    2008-01-01

    This paper describes the thesis work of Schnerr (2007) entitled "Magnetic fields and mass loss in massive stars", which aimed at a better understanding of the impact of magnetic fields on the winds of massive stars.

  10. Wind tunnel-based assessment of wind field in complex topographic terrain

    Energy Technology Data Exchange (ETDEWEB)

    Hangan, Horia [WindEEE Research Institute (Canada)

    2011-07-01

    This paper gives an overview of the assessment of wind fields in complex topographic terrain based on wind tunnels. It comprises mesoscale modeling, wind tunnel simulation, benchmarking microscale simulations and the windEEE dome. The modeling is categorized into maps for complex terrain, linear models limited to generic topography, measurement techniques for wind tunnel testing and CFD simulations linked with wind tunnel test results required for benchmarking. The wind tunnel testing is discussed in detail using topographic features like valleys, hills and ridges. Instantaneous and mean velocity vectors are calculated for the ridge and mean velocity and turbulence intensity profiles are presented for a hill. Flow is measured over the whole domain using both qualitative and quantitative techniques. These techniques can also be used to simulate low-level nocturnal currents, downbursts and tornados in the actual physical environment. The impact on wind farms and turbines of these local storms can also be calculated.

  11. Field test of a lidar wind profiler

    NARCIS (Netherlands)

    Kunz, G.J.

    1996-01-01

    Wind speeds and wind directions are measured remotely using an incoherent backscatter lidar system operating at a wavelength of 1.06 mm with a maximum repetition rate of 13 Hz. The principle of the measurements is based on following detectable atmospheric structures, which are transported by the

  12. Improvement of wind field hindcasts for tropical cyclones

    Directory of Open Access Journals (Sweden)

    Yi Pan

    2016-01-01

    Full Text Available This paper presents a study on the improvement of wind field hindcasts for two typical tropical cyclones, i.e., Fanapi and Meranti, which occurred in 2010. The performance of the three existing models for the hindcasting of cyclone wind fields is first examined, and then two modification methods are proposed to improve the hindcasted results. The first one is the superposition method, which superposes the wind field calculated from the parametric cyclone model on that obtained from the cross-calibrated multi-platform (CCMP reanalysis data. The radius used for the superposition is based on an analysis of the minimum difference between the two wind fields. The other one is the direct modification method, which directly modifies the CCMP reanalysis data according to the ratio of the measured maximum wind speed to the reanalyzed value as well as the distance from the cyclone center. Using these two methods, the problem of underestimation of strong winds in reanalysis data can be overcome. Both methods show considerable improvements in the hindcasting of tropical cyclone wind fields, compared with the cyclone wind model and the reanalysis data.

  13. Improvement of wind field hindcasts for tropical cyclones

    Directory of Open Access Journals (Sweden)

    Yi Pan

    2016-01-01

    Full Text Available This paper presents a study on the improvement of wind field hindcasts for two typical tropical cyclones, i.e., Fanapi and Meranti, which occurred in 2010. The performance of the three existing models for the hindcasting of cyclone wind fields is first examined, and then two modification methods are proposed to improve the hindcasted results. The first one is the superposition method, which superposes the wind field calculated from the parametric cyclone model on that obtained from the Cross-Calibrated Multi-Platform (CCMP reanalysis data. The radius used for the superposition is based on an analysis of the minimum difference between the two wind fields. The other one is the direct modification method, which directly modifies the CCMP reanalysis data according to the ratio of the measured maximum wind speed to the reanalyzed value as well as the distance from the cyclone center. Using these two methods, the problem of underestimation of strong winds in reanalysis data can be overcome. Both methods show considerable improvements in the hindcasting of tropical cyclone wind fields, compared with the cyclone wind model and the reanalysis data.

  14. Probabilistic Motion Planning of Balloons in Strong, Uncertain Wind Fields

    Science.gov (United States)

    Wolf, Michael T.; Blackmore, Lars; Kuwata, Yoshiaki; Fathpour, Nanaz; Elfes, Alberto; Newman, Claire

    2010-01-01

    This paper introduces a new algorithm for probabilistic motion planning in arbitrary, uncertain vector fields, with emphasis on high-level planning for Montgolfiere balloons in the atmosphere of Titan. The goal of the algorithm is to determine what altitude--and what horizontal actuation, if any is available on the vehicle--to use to reach a goal location in the fastest expected time. The winds can vary greatly at different altitudes and are strong relative to any feasible horizontal actuation, so the incorporation of the winds is critical for guidance plans. This paper focuses on how to integrate the uncertainty of the wind field into the wind model and how to reach a goal location through the uncertain wind field, using a Markov decision process (MDP). The resulting probabilistic solutions enable more robust guidance plans and more thorough analysis of potential paths than existing methods.

  15. Brushless exciters using a high temperature superconducting field winding

    Science.gov (United States)

    Garces, Luis Jose [Schenectady, NY; Delmerico, Robert William [Clifton Park, NY; Jansen, Patrick Lee [Scotia, NY; Parslow, John Harold [Scotia, NY; Sanderson, Harold Copeland [Tribes Hill, NY; Sinha, Gautam [Chesterfield, MO

    2008-03-18

    A brushless exciter for a synchronous generator or motor generally includes a stator and a rotor rotatably disposed within the stator. The rotor has a field winding and a voltage rectifying bridge circuit connected in parallel to the field winding. A plurality of firing circuits are connected the voltage rectifying bridge circuit. The firing circuit is configured to fire a signal at an angle of less than 90.degree. or at an angle greater than 90.degree.. The voltage rectifying bridge circuit rectifies the AC voltage to excite or de-excite the field winding.

  16. Seasonal and interannual variability in wind field and commercial ...

    African Journals Online (AJOL)

    The impact of deviations in the direction and strength of the wind field on the spatial, seasonal and interannual variability in catch rates of Agulhas sole Austroglossus pectoralis was investigated. Temporal variability in the wind cycle on the Agulhas Bank during the period 1981–1996 was deduced mainly from trends in the ...

  17. Beryllium-7 measurements of wind erosion on sloping fields in the wind-water erosion crisscross region on the Chinese Loess Plateau.

    Science.gov (United States)

    Zhang, Jiaqiong; Yang, Mingyi; Deng, Xinxin; Liu, Zhang; Zhang, Fengbao; Zhou, Weiying

    2018-02-15

    Soil erosion is complex in the wind-water erosion crisscross region of the Chinese Loess Plateau, as interleaving of wind and water erosion occurs on both temporal and spatial scales. It is difficult to distinguish wind erosion from the total erosion in previous studies due to the untraceable of aeolian particles and the limitation of feasible methods and techniques. This study used beryllium-7 measurements to study wind erosion in the wind-water erosion crisscross region on the Chinese Loess Plateau arms to delineate wind erosion distribution, to analyze its implication to erosive winds and surface microrelief, and to determine correlations between erosion rates and slope gradients. Results obtained using beryllium-7 measurements based on observation plots were verified with saltating particle collection method, and were also verified on a field scale. Results indicated that the effective resultant erosion wind was from northward, which was proved by the eight-directional distributed saltating particles. The microrelief of the ground surface contributed to the formation of high or low erosion centers. Wind erosion rates increased with a linear (R 2 ≥0.95) or exponential (R 2 ≥0.83) fitting increase in the slope gradients as reported in previous studies. Compared to wind erosion on field scale, both the plots and fields exhibited similar distribution patterns in wind erosion isolines. We also determined that the wind erosion rate for two fields estimated, based on equations developed from plot scale was acceptable. This study validates the feasibility of beryllium-7 measurements for soil-wind erosion field experiments and the potential to expand this approach to real field conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. IMPER: Characterization of the wind field over a large wind turbine rotor - final report; Improved performance

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt Paulsen, U.; Wagner, R.

    2012-01-15

    A modern wind turbine rotor with a contemporary rotor size would easily with the tips penetrate the air between 116 m and 30 m and herby experience effects of different wind. With current rules on power performance measurements such as IEC 61400-121 the reference wind speed is measured at hub height, an oversimplification of the wind energy power over the rotor disk area is carried out. The project comprised a number of innovative and coordinated measurements on a full scale turbine with remote sensing technology and simulations on a 500 kW wind turbine for the effects of wind field characterization. The objective with the present report is to give a short overview of the different experiments carried out and results obtained within the final phase of this project. (Author)

  19. The Interplanetary Magnetic Field and Solar Wind Driven Magnetospheric Reconfiguration

    OpenAIRE

    Savov, Eugene

    2002-01-01

    The magnetic disturbances are associated with electric currents as it is well checked at laboratory room scales and described by the Maxwell's equations of electromagnetic field. The analysis of spacecraft observations for more than a quarter of a century failed to provide a self-consistent three-dimensional picture of the solar wind-magnetosphere dynamo generated magnetospheric and ionospheric current systems. The proposed solar wind and the interplanetary magnetic field (IMF) driven reconfi...

  20. Scaling up from field to region for wind erosion prediction using a field-scale wind erosion model and GIS

    Science.gov (United States)

    Zobeck, T.M.; Parker, N.C.; Haskell, S.; Guoding, K.

    2000-01-01

    Factors that affect wind erosion such as surface vegetative and other cover, soil properties and surface roughness usually change spatially and temporally at the field-scale to produce important field-scale variations in wind erosion. Accurate estimation of wind erosion when scaling up from fields to regions, while maintaining meaningful field-scale process details, remains a challenge. The objectives of this study were to evaluate the feasibility of using a field-scale wind erosion model with a geographic information system (GIS) to scale up to regional levels and to quantify the differences in wind erosion estimates produced by different scales of soil mapping used as a data layer in the model. A GIS was used in combination with the revised wind erosion equation (RWEQ), a field-scale wind erosion model, to estimate wind erosion for two 50 km2 areas. Landsat Thematic Mapper satellite imagery from 1993 with 30 m resolution was used as a base map. The GIS database layers included land use, soils, and other features such as roads. The major land use was agricultural fields. Data on 1993 crop management for selected fields of each crop type were collected from local government agency offices and used to 'train' the computer to classify land areas by crop and type of irrigation (agroecosystem) using commercially available software. The land area of the agricultural land uses was overestimated by 6.5% in one region (Lubbock County, TX, USA) and underestimated by about 21% in an adjacent region (Terry County, TX, USA). The total estimated wind erosion potential for Terry County was about four times that estimated for adjacent Lubbock County. The difference in potential erosion among the counties was attributed to regional differences in surface soil texture. In a comparison of different soil map scales in Terry County, the generalised soil map had over 20% more of the land area and over 15% greater erosion potential in loamy sand soils than did the detailed soil map. As

  1. Differences in simulated fire spread over Askervein Hill using two advanced wind models and a traditional uniform wind field

    Science.gov (United States)

    Jason Forthofer; Bret Butler

    2007-01-01

    A computational fluid dynamics (CFD) model and a mass-consistent model were used to simulate winds on simulated fire spread over a simple, low hill. The results suggest that the CFD wind field could significantly change simulated fire spread compared to traditional uniform winds. The CFD fire spread case may match reality better because the winds used in the fire...

  2. Evaluating winds aloft by a simplified field technique

    Science.gov (United States)

    Melvin K. Hull

    1966-01-01

    A field technique for evaluating winds aloft is described. It can be used at remote places--even at the site of a wildfire. It has proved accurate as any known single theodolite technique, and is time-saving because the winds aloft are evaluated in miles per hour from direct readout. The tools required are much lower in cost, more portable, and more multi-purpose than...

  3. MATHEW: a mass-consistent wind field model

    Energy Technology Data Exchange (ETDEWEB)

    Sherman, C.S.

    1978-05-01

    MATHEW, a regional three-dimensional time-independent wind field model, utilizes a variational analysis technique to determine a three-component non-divergent velocity field which can be used to provide the advection velocities in atmospheric pollutant transport and diffusion models. The regions of interest have horizontal distances of 10 to 200 km and extend less than 2 km above topography.

  4. Doppler radar wind field retrieval over the Po Valley

    Directory of Open Access Journals (Sweden)

    Y. K. Goh

    2006-01-01

    Full Text Available Although methods of using multiple Doppler radars to study wind fields have long been proposed, and many research studies have been made, very few operational radar operators adopt methods which require the use of specific scanning strategies to allow the extraction of wind information. Here we report a collaborative study on dual-Doppler radars based on two Doppler radars in the Po valley, Italy. Unusually, the radars are only about 90 km apart, though operated by the same authority. The wind field syntheses are carried out on a 30 km by 30 km region where the two radars have overlapping scan coverage. An iterative method based on the linear wind model and the equation of mass continuity is used to construct the wind fields. The methodology has been validated by two different methods. The first method is to reconstruct the radial wind observed by each radar, and the second method is calculating and comparing the along-track component with that derived from the observations. Both two comparisons show good agreement with the original data.

  5. CO2 Jets and Wind Patterns on Mars

    Science.gov (United States)

    Hatcher, Chase; Aye, K.-Michael; Portyankina, Ganna

    2017-10-01

    In Martian winters, the poles get covered by a layer of transparent CO2 ice. In spring, sunlight causes substrate under the ice to heat up which sublimates CO2 under the ice. The accumulating gas eventually causes the ice above it to rupture and the CO2 and substrate mixture spews out like a geyser and settles back down on the surface. The shape, size, and alignment of the deposits on the surface as viewed by the HiRISE camera are related to physical processes like sublimation, weather, and wind on Mars. The jet deposits are identified by citizen scientists on a website called Planet Four. Users are shown sections of HiRISE images and asked to mark different surface features with different tools. The markings are averaged, filtered, and sorted to ensure that the data accurately represents the images. By analyzing trends in the change of different characteristics of these surface features over time, we conclude that different regions on Mars have different sublimation processes and different wind patterns. We also conclude that wind and weather patterns generally repeat from year to year, and that sediment deposits affect local weather as well.

  6. Examination of climatological wind patterns and simulated pollen dispersion in a complex island environment.

    Science.gov (United States)

    Viner, Brian J; Arritt, Raymond W; Westgate, Mark E

    2017-03-29

    Complex terrain creates small-scale circulations which affect pollen dispersion but may be missed by meteorological observing networks and coarse-grid meteorological models. On volcanic islands, these circulations result from differing rates of surface heating between land and sea as well as rugged terrain. We simulated the transport of bentgrass, ryegrass, and maize pollen from 30 sources within the agricultural regions of the Hawaiian island Kaua'i during climatological conditions spanning season conditions and the La Niña, El Niño, and neutral phases of the El Niño-Southern Oscillation. Both pollen size and source location had major effects on predicted dispersion over and near the island. Three patterns of pollen dispersion were identified in response to prevailing wind conditions: southwest winds transported pollen inland, funneling pollen grains through valleys; east winds transported pollen over the ocean, with dispersive tails for the smallest pollen grains following the mean wind and extending as far as the island of Ni'ihau 35 km away; and northeast winds moved pollen inland counter to the prevailing flow due to a sea breeze circulation that formed over the source region. These results are the first to predict the interactions between complex island terrain and local climatology on grass pollen dispersion. They demonstrate how numerical modeling can provide guidance for field trials by illustrating the common flow regimes present in complex terrain, allowing field trials to focus on areas where successful sampling is more likely to occur.

  7. Examination of climatological wind patterns and simulated pollen dispersion in a complex island environment

    Science.gov (United States)

    Viner, Brian J.; Arritt, Raymond W.; Westgate, Mark E.

    2017-08-01

    Complex terrain creates small-scale circulations which affect pollen dispersion but may be missed by meteorological observing networks and coarse-grid meteorological models. On volcanic islands, these circulations result from differing rates of surface heating between land and sea as well as rugged terrain. We simulated the transport of bentgrass, ryegrass, and maize pollen from 30 sources within the agricultural regions of the Hawaiian island Kaua'i during climatological conditions spanning season conditions and the La Niña, El Niño, and neutral phases of the El Niño-Southern Oscillation. Both pollen size and source location had major effects on predicted dispersion over and near the island. Three patterns of pollen dispersion were identified in response to prevailing wind conditions: southwest winds transported pollen inland, funneling pollen grains through valleys; east winds transported pollen over the ocean, with dispersive tails for the smallest pollen grains following the mean wind and extending as far as the island of Ni'ihau 35 km away; and northeast winds moved pollen inland counter to the prevailing flow due to a sea breeze circulation that formed over the source region. These results are the first to predict the interactions between complex island terrain and local climatology on grass pollen dispersion. They demonstrate how numerical modeling can provide guidance for field trials by illustrating the common flow regimes present in complex terrain, allowing field trials to focus on areas where successful sampling is more likely to occur.

  8. Scaling Characteristics of Mesoscale Wind Fields in the Lower Atmospheric Boundary Layer: Implications for Wind Energy

    Science.gov (United States)

    Kiliyanpilakkil, Velayudhan Praju

    Atmospheric motions take place in spatial scales of sub-millimeters to few thousands of kilometers with temporal changes in the atmospheric variables occur in fractions of seconds to several years. Consequently, the variations in atmospheric kinetic energy associated with these atmospheric motions span over a broad spectrum of space and time. The mesoscale region acts as an energy transferring regime between the energy generating synoptic scale and the energy dissipating microscale. Therefore, the scaling characterizations of mesoscale wind fields are significant in the accurate estimation of the atmospheric energy budget. Moreover, the precise knowledge of the scaling characteristics of atmospheric mesoscale wind fields is important for the validation of the numerical models those focus on wind forecasting, dispersion, diffusion, horizontal transport, and optical turbulence. For these reasons, extensive studies have been conducted in the past to characterize the mesoscale wind fields. Nevertheless, the majority of these studies focused on near-surface and upper atmosphere mesoscale regimes. The present study attempt to identify the existence and to quantify the scaling of mesoscale wind fields in the lower atmospheric boundary layer (ABL; in the wind turbine layer) using wind observations from various research-grade instruments (e.g., sodars, anemometers). The scaling characteristics of the mesoscale wind speeds over diverse homogeneous flat terrains, conducted using structure function based analysis, revealed an altitudinal dependence of the scaling exponents. This altitudinal dependence of the wind speed scaling may be attributed to the buoyancy forcing. Subsequently, we use the framework of extended self-similarity (ESS) to characterize the observed scaling behavior. In the ESS framework, the relative scaling exponents of the mesoscale atmospheric boundary layer wind speed exhibit quasi-universal behavior; even far beyond the inertial range of turbulence (Delta

  9. Construction of Solar-Wind-Like Magnetic Fields

    Science.gov (United States)

    Roberts, Dana Aaron

    2012-01-01

    Fluctuations in the solar wind fields tend to not only have velocities and magnetic fields correlated in the sense consistent with Alfven waves traveling from the Sun, but they also have the magnitude of the magnetic field remarkably constant despite their being broadband. This paper provides, for the first time, a method for constructing fields with nearly constant magnetic field, zero divergence, and with any specified power spectrum for the fluctuations of the components of the field. Every wave vector, k, is associated with two polarizations the relative phases of these can be chosen to minimize the variance of the field magnitude while retaining the\\random character of the fields. The method is applied to a case with one spatial coordinate that demonstrates good agreement with observed time series and power spectra of the magnetic field in the solar wind, as well as with the distribution of the angles of rapid changes (discontinuities), thus showing a deep connection between two seemingly unrelated issues. It is suggested that using this construction will lead to more realistic simulations of solar wind turbulence and of the propagation of energetic particles.

  10. A verification study and trend analysis of simulated boundary layer wind fields over Europe

    Energy Technology Data Exchange (ETDEWEB)

    Lindenberg, Janna

    2011-07-01

    Simulated wind fields from regional climate models (RCMs) are increasingly used as a surrogate for observations which are costly and prone to homogeneity deficiencies. Compounding the problem, a lack of reliable observations makes the validation of the simulated wind fields a non trivial exercise. Whilst the literature shows that RCMs tend to underestimate strong winds over land these investigations mainly relied on comparisons with near surface measurements and extrapolated model wind fields. In this study a new approach is proposed using measurements from high towers and a robust validation process. Tower height wind data are smoother and thus more representative of regional winds. As benefit this approach circumvents the need to extrapolate simulated wind fields. The performance of two models using different downscaling techniques is evaluated. The influence of the boundary conditions on the simulation of wind statistics is investigated. Both models demonstrate a reasonable performance over flat homogeneous terrain and deficiencies over complex terrain, such as the Upper Rhine Valley, due to a too coarse spatial resolution ({proportional_to}50 km). When the spatial resolution is increased to 10 and 20 km respectively a benefit is found for the simulation of the wind direction only. A sensitivity analysis shows major deviations of international land cover data. A time series analysis of dynamically downscaled simulations is conducted. While the annual cycle and the interannual variability are well simulated, the models are less effective at simulating small scale fluctuations and the diurnal cycle. The hypothesis that strong winds are underestimated by RCMs is supported by means of a storm analysis. Only two-thirds of the observed storms are simulated by the model using a spectral nudging approach. In addition ''False Alarms'' are simulated, which are not detected in the observations. A trend analysis over the period 1961 - 2000 is conducted

  11. Research on wind field algorithm of wind lidar based on BP neural network and grey prediction

    Science.gov (United States)

    Chen, Yong; Chen, Chun-Li; Luo, Xiong; Zhang, Yan; Yang, Ze-hou; Zhou, Jie; Shi, Xiao-ding; Wang, Lei

    2018-01-01

    This paper uses the BP neural network and grey algorithm to forecast and study radar wind field. In order to reduce the residual error in the wind field prediction which uses BP neural network and grey algorithm, calculating the minimum value of residual error function, adopting the residuals of the gray algorithm trained by BP neural network, using the trained network model to forecast the residual sequence, using the predicted residual error sequence to modify the forecast sequence of the grey algorithm. The test data show that using the grey algorithm modified by BP neural network can effectively reduce the residual value and improve the prediction precision.

  12. SMART wind turbine rotor. Design and field test

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Jonathan Charles; Resor, Brian Ray; Paquette, Joshua A.; White, Jonathan Randall

    2014-01-01

    The Wind Energy Technologies department at Sandia National Laboratories has developed and field tested a wind turbine rotor with integrated trailing-edge flaps designed for active control of rotor aerodynamics. The SMART Rotor project was funded by the Wind and Water Power Technologies Office of the U.S. Department of Energy (DOE) and was conducted to demonstrate active rotor control and evaluate simulation tools available for active control research. This report documents the design, fabrication, and testing of the SMART Rotor. This report begins with an overview of active control research at Sandia and the objectives of this project. The SMART blade, based on the DOE / SNL 9-meter CX-100 blade design, is then documented including all modifications necessary to integrate the trailing edge flaps, sensors incorporated into the system, and the fabrication processes that were utilized. Finally the test site and test campaign are described.

  13. Flow Field Analysis of Wind Power Generation System

    Science.gov (United States)

    Zhou, Chao; Huang, Wei; Zhu, Daohua; Li, Yan; Wu, Liwei

    2017-10-01

    The purpose is to solve the problem of wind power curtailment in the wind power generation system. A new type of wind power generation system made of flexible blades is proposed. Combined with the experimental method and numerical simulation method, the impeller blades are analyzed by flow field. The values of the lift coefficient of the leaves under different working conditions were obtained and analyzed. The optimum curvature and the range of the best angle of attack are determined. The influence of the parameters such as the curvature of the blade and the angle of attack on the hydrodynamic performance of the blade and impeller in the power generation system is obtained. The results showed that the best curvature K was 0.019 and the best angle of attack was 20°. Therefore, it can be concluded that it reveals the influence of blade curvature and angle of attack on the lift coefficient.

  14. Cooperative field test program for wind systems. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Bollmeier, W.S. II; Dodge, D.M.

    1992-03-01

    The objectives of the Federal Wind Energy Program, managed by the US Department of Energy (DOE), are (1) to assist industry and utilities in achieving a multi-regional US market penetration of wind systems, and (2) to establish the United States as the world leader in the development of advanced wind turbine technology. In 1984, the program conducted a series of planning workshops with representatives from the wind energy industry to obtain input on the Five-Year Research Plan then being prepared by DOE. One specific suggestion that came out of these meetings was that the federal program should conduct cooperative research tests with industry to enhance the technology transfer process. It was also felt that the active involvement of industry in DOE-funded research would improve the state of the art of wind turbine technology. DOE established the Cooperative Field Test Program (CFTP) in response to that suggestion. This program was one of the first in DOE to feature joint industry-government research test teams working toward common objectives.

  15. Statistics-Based Compression of Global Wind Fields

    KAUST Repository

    Jeong, Jaehong

    2017-02-07

    Wind has the potential to make a significant contribution to future energy resources. Locating the sources of this renewable energy on a global scale is however extremely challenging, given the difficulty to store very large data sets generated by modern computer models. We propose a statistical model that aims at reproducing the data-generating mechanism of an ensemble of runs via a Stochastic Generator (SG) of global annual wind data. We introduce an evolutionary spectrum approach with spatially varying parameters based on large-scale geographical descriptors such as altitude to better account for different regimes across the Earth\\'s orography. We consider a multi-step conditional likelihood approach to estimate the parameters that explicitly accounts for nonstationary features while also balancing memory storage and distributed computation. We apply the proposed model to more than 18 million points of yearly global wind speed. The proposed SG requires orders of magnitude less storage for generating surrogate ensemble members from wind than does creating additional wind fields from the climate model, even if an effective lossy data compression algorithm is applied to the simulation output.

  16. Ripple Field AC Losses in 10-MW Wind Turbine Generators With a MgB2 Superconducting Field Winding

    DEFF Research Database (Denmark)

    Liu, Dong; Polinder, Henk; Magnusson, Niklas

    2016-01-01

    and an excessive cooling budget. To determine the applicability of different design solutions in terms of ac losses, this paper estimates the ac loss level of 10-MW wind generator designs employing a MgB2 SC field winding. The effects on ac losses are compared between nonmagnetic and ferromagnetic teeth...... with different numbers of slots per pole per phase. The necessity of an electromagnetic shield is then discussed based on the obtained loss levels. The results show that the total ac loss is so small that ferromagnetic teeth can be applied in the generator design without using an electromagnetic shield....

  17. Atmospheric circulation patterns associated with strong wind events in Catalonia

    Science.gov (United States)

    Peña, J. C.; Aran, M.; Cunillera, J.; Amaro, J.

    2011-01-01

    The benefit of having a daily synoptic weather type catalogue and even more, a detailed catalogue for high impact weather events is well recognised by both climatologist and meteorologist communities. In this way the Meteorological Service of Catalonia (SMC) has produced some accurate classifications for extreme events, such as hailstorms or strong winds (SW). Within the framework of the MEDEX project, the SMC has been collaborating to increase the level of awareness about these events. Following this line of work, the aim of this study is to characterise the SW events in Catalonia. According to the guidelines of the MEDEX project we worked with its SW event database for the period June 1995 to May 2004. We also used the period 2005-2009 to test the methodology. The methodology is based on principal component, cluster and discriminant analyses and applied to four variables: SLP, temperature at 850 hPa and geopotential at 500 hPa on a synoptic-scale and local gust wind. We worked with ERA-Interim reanalysis and applied discriminant analysis to test the quality of the methodology and to classify the events of the validation period. We found seven patterns for the SW events. The strongest event corresponds to NW-Flow with the Azores Anticyclone and the passing of a low pressure through the Pyrenees. This methodology has distinguished the summer events in an independent cluster. The results obtained encourage us to follow this line of work.

  18. Electromagnetic Simulation of the Near-Field Distribution around a Wind Farm

    Directory of Open Access Journals (Sweden)

    Shang-Te Yang

    2013-01-01

    Full Text Available An efficient approach to compute the near-field distribution around and within a wind farm under plane wave excitation is proposed. To make the problem computationally tractable, several simplifying assumptions are made based on the geometry problem. By comparing the approximations against full-wave simulations at 500 MHz, it is shown that the assumptions do not introduce significant errors into the resulting near-field distribution. The near fields around a 3×3 wind farm are computed using the developed methodology at 150 MHz, 500 MHz, and 3 GHz. Both the multipath interference patterns and the forward shadows are predicted by the proposed method.

  19. The use of energy pattern factor (EPF) in estimating wind power ...

    African Journals Online (AJOL)

    The Energy Pattern Factor (EPF) method is a less computational method of estimating the available wind power density of an area and wind speed variation account for the energy power density throughout a given period. Using the Average daily wind speed data for an 11 year period (2004-2014) obtained from the ...

  20. IMF dependence of high-latitude thermospheric wind pattern derived from CHAMP cross-track measurements

    Directory of Open Access Journals (Sweden)

    M. Förster

    2008-06-01

    Full Text Available Neutral thermospheric wind pattern at high latitudes obtained from cross-track acceleration measurements of the CHAMP satellite above both North and South polar regions are statistically analyzed in their dependence on the Interplanetary Magnetic Field (IMF direction in the GSM y-z plane (clock angle. We compare this dependency with magnetospheric convection pattern obtained from the Cluster EDI plasma drift measurements under the same sorting conditions. The IMF-dependency shows some similarity with the corresponding high-latitude plasma convection insofar that the larger-scale convection cells, in particular the round-shaped dusk cell for ByIMF+ (ByIMF− conditions at the Northern (Southern Hemisphere, leave their marks on the dominant general transpolar wind circulation from the dayside to the nightside. The direction of the transpolar circulation is generally deflected toward a duskward flow, in particular in the evening to nighttime sector. The degree of deflection correlates with the IMF clock angle. It is larger for ByIMF+ than for ByIMF− and is systematically larger (~5° and appear less structured at the Southern Hemisphere compared with the Northern. Thermospheric cross-polar wind amplitudes are largest for BzIMF−/ByIMF− conditions at the Northern Hemisphere, but for BzIMF−/ByIMF+ conditions at the Southern because the magnetospheric convection is in favour of largest wind accelerations over the polar cap under these conditions. The overall variance of the thermospheric wind magnitude at Southern high latitudes is larger than for the Northern. This is probably due to a larger "stirring effect" at the Southern Hemisphere because of the larger distance between the geographic and geomagnetic frameworks.

  1. Basin-scale wind transport during the MILAGRO field campaign and comparison to climatology using cluster analysis

    Directory of Open Access Journals (Sweden)

    B. de Foy

    2008-03-01

    Full Text Available The MILAGRO field campaign was a multi-agency international collaborative project to evaluate the regional impacts of the Mexico City air pollution plume as a means of understanding urban impacts on the global climate. Mexico City lies on an elevated plateau with mountains on three sides and has complex mountain and surface-driven wind flows. This paper asks what the wind transport was in the basin during the field campaign and how representative it was of the climatology. Surface meteorology and air quality data, radiosondes and radar wind profiler data were collected at sites in the basin and its vicinity. Cluster analysis was used to identify the dominant wind patterns both during the campaign and within the past 10 years of operational data from the warm dry season. Our analysis shows that March 2006 was representative of typical flow patterns experienced in the basin. Six episode types were identified for the basin-scale circulation providing a way of interpreting atmospheric chemistry and particulate data collected during the campaign. Decoupling between surface winds and those aloft had a strong influence in leading to convection and poor air quality episodes. Hourly characterisation of wind circulation during the MILAGRO, MCMA-2003 and IMADA field campaigns enables the comparisons of similar air pollution episodes and the evaluation of the impact of wind transport on measurements of the atmospheric chemistry taking place in the basin.

  2. Field Measurement of Wind Speeds and Wind-Induced Responses atop the Shanghai World Financial Center under Normal Climate Conditions

    Directory of Open Access Journals (Sweden)

    Yong Quan

    2013-01-01

    Full Text Available Field measurement data on wind velocities and wind-induced acceleration responses at the top of the 492 m high Shanghai World Financial Center (SWFC under normal climate conditions are studied. Characteristics of the mean wind speeds and turbulence intensities, gust factors, power spectral densities, and turbulence integral scales of the fluctuating wind speed are analyzed in different observation time intervals. Power spectral densities of wind-induced acceleration are also investigated. The basic natural frequencies and structural damping ratios of the building are identified based on Hilbert-Huang transform method and random decrement method. The field measurement results of wind-induced responses of the SWFC are finally compared with those from the corresponding high-frequency force balance wind tunnel test study.

  3. Cyclones causing wind storms in the Mediterranean: characteristics, trends and links to large-scale patterns

    Directory of Open Access Journals (Sweden)

    K. M. Nissen

    2010-07-01

    Full Text Available A climatology of cyclones with a focus on their relation to wind storm tracks in the Mediterranean region (MR is presented. Trends in the frequency of cyclones and wind storms, as well as variations associated with the North Atlantic Oscillation (NAO, the East Atlantic/West Russian (EAWR and the Scandinavian variability pattern (SCAND are discussed.

    The study is based on the ERA40 reanalysis dataset. Wind storm tracks are identified by tracking clusters of adjacent grid boxes characterised by extremely high local wind speeds. The wind track is assigned to a cyclone track independently identified with an objective scheme.

    Areas with high wind activity – quantified by extreme wind tracks – are typically located south of the Golf of Genoa, south of Cyprus, southeast of Sicily and west of the Iberian Peninsula. About 69% of the wind storms are caused by cyclones located in the Mediterranean region, while the remaining 31% can be attributed to North Atlantic or Northern European cyclones.

    The North Atlantic Oscillation, the East Atlantic/West Russian pattern and the Scandinavian pattern all influence the amount and spatial distribution of wind inducing cyclones and wind events in the MR. The strongest signals exist for the NAO and the EAWR pattern, which are both associated with an increase in the number of organised strong wind events in the eastern MR during their positive phase. On the other hand, the storm numbers decrease over the western MR for the positive phase of the NAO and over the central MR during the positive phase of the EAWR pattern. The positive phase of the Scandinavian pattern is associated with a decrease in the number of winter wind storms over most of the MR.

    A third of the trends in the number of wind storms and wind producing cyclones during the winter season of the ERA40 period may be attributed to the variability of the North Atlantic Oscillation.

  4. Convex optimisation of gradient and shim coil winding patterns.

    Science.gov (United States)

    Poole, Michael S; Shah, N Jon

    2014-07-01

    Gradient and shim coils were designed using boundary element methods with convex optimisation. The convex optimisation framework permits the prototyping of many different cost functions and constraints, for example ℓ(p)-norms of the current density. Several examples of gradients and shims were designed and simulated to demonstrate this, as well as to investigate the behaviour of new cost functions. A mixture of ℓ(1)- and ℓ(∞)-norms of the current density, when used as a regularisation term in the field synthesis problem, was found to produce coils with bunches of equally spaced windings that do not take up all of the available surface. This is thought to be beneficial in the design of coils that will be manufactured from wire with a fixed cross-section. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. X-band COSMO-SkyMed wind field retrieval, with application to coastal circulation modeling

    Directory of Open Access Journals (Sweden)

    A. Montuori

    2013-02-01

    Full Text Available In this paper, X-band COSMO-SkyMed© synthetic aperture radar (SAR wind field retrieval is investigated, and the obtained data are used to force a coastal ocean circulation model. The SAR data set consists of 60 X-band Level 1B Multi-Look Ground Detected ScanSAR Huge Region COSMO-SkyMed© SAR data, gathered in the southern Tyrrhenian Sea during the summer and winter seasons of 2010. The SAR-based wind vector field estimation is accomplished by resolving both the SAR-based wind speed and wind direction retrieval problems independently. The sea surface wind speed is retrieved by means of a SAR wind speed algorithm based on the azimuth cut-off procedure, while the sea surface wind direction is provided by means of a SAR wind direction algorithm based on the discrete wavelet transform multi-resolution analysis. The obtained wind fields are compared with ground truth data provided by both ASCAT scatterometer and ECMWF model wind fields. SAR-derived wind vector fields and ECMWF model wind data are used to construct a blended wind product regularly sampled in both space and time, which is then used to force a coastal circulation model of a southern Tyrrhenian coastal area to simulate wind-driven circulation processes. The modeling results show that X-band COSMO-SkyMed© SAR data can be valuable in providing effective wind fields for coastal circulation modeling.

  6. Relating immission alarms with wind patterns in La Oroya valleys, Peru

    OpenAIRE

    Doolan, Ryan Lee

    2016-01-01

    This work aims to use collected wind data and collected emission data to correlate wind patterns with air pollution levels. This can then be compared against the three level 'emergency'air pollution indicators to determine if certain wind patterns are more susceptible to bringing spikes in pollution levels. This information could then be used to design a mitigation strategy to reduce the pollution effects.

  7. Design, construction and calibration of a portable boundary layer wind tunnel for field use

    Science.gov (United States)

    Wind tunnels have been used for several decades to study wind erosion processes. Portable wind tunnels offer the advantage of testing natural surfaces in the field, but they must be carefully designed to insure that a logarithmic boundary layer is formed and that wind erosion processes may develop ...

  8. Assimilation of Typhoon Wind Field Retrieved from Scatterometer and SAR Based on the Huber Norm Quality Control

    National Research Council Canada - National Science Library

    Boheng Duan; Weimin Zhang; Xiaofeng Yang; Haijin Dai; Yi Yu

    2017-01-01

    Observations of sea surface wind field are critical for typhoon prediction. The scatterometer observation is one of the most important sources of sea surface winds, which provides both wind speed and wind direction information...

  9. Enhanced gauge symmetry and winding modes in double field theory

    Energy Technology Data Exchange (ETDEWEB)

    Aldazabal, G. [Centro Atómico Bariloche,8400 S.C. de Bariloche (Argentina); Instituto Balseiro (CNEA-UNC) and CONICET,8400 S.C. de Bariloche (Argentina); Graña, M. [Institut de Physique Théorique, CEA/ Saclay,91191 Gif-sur-Yvette Cedex (France); Iguri, S. [Instituto de Astronomía y Física del Espacio (CONICET-UBA), Universidad de Buenos Aires,1428 Buenos Aires (Argentina); Mayo, M. [Centro Atómico Bariloche,8400 S.C. de Bariloche (Argentina); Instituto Balseiro (CNEA-UNC) and CONICET,8400 S.C. de Bariloche (Argentina); Nuñez, C. [Instituto de Astronomía y Física del Espacio (CONICET-UBA), Universidad de Buenos Aires,1428 Buenos Aires (Argentina); Departamento de Física, FCEN, Universidad de Buenos Aires,C.C. 67 - Suc. 28, 1428 Buenos Aires (Argentina); Rosabal, J.A. [Departamento de Física, FCEN, Universidad de Buenos Aires,C.C. 67 - Suc. 28, 1428 Buenos Aires (Argentina)

    2016-03-15

    We provide an explicit example of how the string winding modes can be incorporated in double field theory. Our guiding case is the closed bosonic string compactified on a circle of radius close to the self-dual point, where some modes with non-zero winding or discrete momentum number become massless and enhance the U(1)×U(1) symmetry to SU(2)×SU(2). We compute three-point string scattering amplitudes of massless and slightly massive states, and extract the corresponding effective low energy gauge field theory. The enhanced gauge symmetry at the self-dual point and the Higgs-like mechanism arising when changing the compactification radius are examined in detail. The extra massless fields associated to the enhancement are incorporated into a generalized frame with ((O(d+3,d+3))/(O(d+3)×O(d+3))) structure, where d is the number of non-compact dimensions. We devise a consistent double field theory action that reproduces the low energy string effective action with enhanced gauge symmetry. The construction requires a truly non-geometric frame which explicitly depends on both the compact coordinate along the circle and its dual.

  10. Computations of wind-driven ocean-induced magnetic fields

    Science.gov (United States)

    Sachl, Libor; Einspigel, David; Martinec, Zdenek

    2016-04-01

    We present the results of computations of the secondary magnetic field induced by ocean motions. Ocean velocities are computed using the baroclinic ocean model LSOMG. The velocities are then used to determine the Lorentz force which is plugged into the magnetic induction code TLAM as a principal forcing. The TLAM is a 2D magnetic induction code based on the thin-shell approximation (Vivier et al., 2004; Tyler et al., 1997). In this approximation, the equation of magnetic induction simplifies significantly, time derivatives of main and induced magnetic fields are neglected as well as the self-induction term. The price for simplification of governing equations is the limited applicability of the resulting system. It is only suitable for slowly evolving processes. In order to meet the condition, we restrict ourselves to the wind (buoyancy) driven ocean circulation, although the LSOMG model is able to model both tidally- and wind-driven circulations. We assess the accuracy of thin-shell approximation in our setup by comparing the results with the Swarm satellite magnetic data. References Tyler, R. H., Mysak, L. A., and Oberhuber, J. M, 1997. Electromagnetic fields generated by a three dimensional global ocean circulation. J. Geophys. Res., 102, 5531-5551. Vivier, F., Meier-Reimer, E., and Tyler, R. H., 2004. Simulations of magnetic fields generated by the Antarctic Circumpolar Current at satellite altitude: Can geomagnetic measurements be used to monitor the flow? Geophys. Res. Lett., 31, L10306, doi:10.1029/2004GL019804.

  11. Stratosphere and lower mesosphere wind observation and gravity wave activities of the wind field in China using a mobile Rayleigh Doppler lidar

    Science.gov (United States)

    Zhao, Ruocan; Dou, Xiankang; Xue, Xianghui; Sun, Dongsong; Han, Yuli; Chen, Chong; Zheng, Jun; Li, Zimu; Zhou, Anran; Han, Yan; Wang, Guocheng; Chen, Tingdi

    2017-08-01

    Since the mobile Rayleigh Doppler lidar of the University of Science and Technology of China was developed in 2013, more than 100 days of valid nighttime wind data from 15 to 60 km altitude were obtained during recent 3 years. The observation locations cover the northwest (midlatitude) of China: Delingha (37.371°N, 97.374°E), Xinzhou (38.425°N, 112.729°E), and Jiuquan (39.741°N, 98.495°E). Recently, we have extracted perturbations of the wind profiles from the wind field measurements and we have found that inertia gravity waves and mountain waves existed at the same time. The results of wind field and several gravity waves cases are shown in this paper. Typical characteristics of the gravity waves are analyzed in this midlatitude area of China. A 2-D fast Fourier transform of the wind perturbation shows that a dominant stationary wave mode and a downward wave mode exist simultaneously in the spectrum. A band-pass 2-D filter was applied to the spectrum followed by inverse fast Fourier transform to separate inertia gravity waves from stationary mountain waves. The horizontal wavelength is retrieved using hodograph methods, indicating that the inertia waves are generated thousands of kilometers away. Observed mountain waves from a combination of vertical wind and leaned line of sight wind measurements show a small-angle leaned wave front from the horizontal direction. This kind of gravity wave observation of the stratospheric wind field and its wave patterns is rare and significant for the study of atmospheric dynamics.

  12. Numerical simulation of the aerodynamic field in complex terrain wind farm based on actuator disk model

    DEFF Research Database (Denmark)

    Xu, Chang; Li, Chen Qi; Han, Xing Xing

    2015-01-01

    Study on the aerodynamic field in complex terrain is significant to wind farm micro-sitting and wind power prediction. This paper modeled the wind turbine through an actuator disk model, and solved the aerodynamic field by CFD to study the influence of meshing, boundary conditions and turbulence ...

  13. Mean wind field in the urban atmospheric boundary layer by sodar data

    Science.gov (United States)

    Yushkov, V. P.

    2008-05-01

    Two-year uninterrupted sodar measurements of vertical profiles of wind speed and direction in the height range 40 to 250-500 m were carried out in two points of Moscow megalopolis. Seasonal and diurnal courses of mean speed profiles, wind speed distributions, wind roses and occurrence of strong and weak wind speed events are shown. Influence of urban heat island and orography on wind field is discussed.

  14. Field Measurement of Wind Characteristics of Typhoon Muifa on the Shanghai World Financial Center

    National Research Council Canada - National Science Library

    An, Y; Quan, Y; Gu, M

    2012-01-01

      Field measurement is considered to be the most reliable method to obtain wind characteristics of typhoon, and it is of essential value of further understanding of wind-resistant design of super tall buildings...

  15. A Study of the Effects of Different Urban Wind Models on Dispersion Patterns Using Joint Urban 2003 Data

    Energy Technology Data Exchange (ETDEWEB)

    Gowardhan, A A; Brown, M J

    2012-02-21

    The Quick Urban & Industrial Complex (QUIC) Dispersion Modeling System has been developed to rapidly compute the transport and dispersion of toxic agent releases in the vicinity of buildings. It is composed of a wind solver, an 'urbanized' Lagrangian random-walk model, and a graphical user interface. QUIC has two different wind models: (a) The QUIC-URB wind solver, an empirically-based diagnostic wind model and (b) The QUIC-CFD (RANS) solver, based on the 3D Reynolds-Averaged Navier-Stokes (RANS) equations. In this paper, we discuss the effect of different wind models on dispersion patterns in dense built-up areas. The model-computed wind from the two urban wind models- QUIC-URB and QUIC-CFD are used to drive the dispersion model. The concentration fields are then compared to measurements from the Oklahoma City Joint Urban 2003 field experiment. QUIC produces high-resolution 3-D mean wind and concentration fields around buildings, in addition to deposition on the ground and building surfaces. It has options for different release types, including point, moving point, line, area, and volumetric sources, as well as dense gas, explosive buoyant rise, multi-particle size, bioslurry, and two-phase releases. Other features include indoor infiltration, a pressure solver, outer grid simulations, vegetative canopies, and population exposure calculations. It has been used for biological agent sensor siting in cities, vulnerability assessments for heavier-than-air chemical releases at industrial facilities, and clean-up assessments for radiological dispersal device (RDD) releases in cities (e.g., see Linger et al., 2005; Brown, 2006a, b). QUIC has also been used for dust transport studies (Bowker et al., 2007a) and for the impact of highway sound barriers on the transport and dispersion of vehicle emissions (Bowker et al., 2007b).

  16. Turbulent wind field characterization and re-generation based on pitot tube measurements mounted on a wind turbine

    DEFF Research Database (Denmark)

    Pedersen, Mads Mølgaard; Larsen, Torben J.; Aagaard Madsen, Helge

    2015-01-01

    This paper describes a new method to estimate the undisturbed inflow field of a wind turbine based on measurements obtained from one or more five-hole pitot tubes mounted directly on the blades. Based on the measurements, the disturbance caused by the wind turbine is estimated using aerodymanic m...

  17. Field measurement of wind pressure and wind-induced vibration of large-span spatial cable-truss system under strong wind or typhoon

    Directory of Open Access Journals (Sweden)

    ZHANG Zhihong

    2013-10-01

    Full Text Available In order to ensure wind-resistance safety of large-span pre-stressed flexible system in southeast coast area of China,and to prepare something for revising of current codes of practice or technical standards,the present paper conducts field measurement of wind pressure and wind-induced vibration of a practical and typical large-span spatial cable-truss system-lunar stadium in Yueqing city.Wind loading and wind effects on full-scale structure under strong wind or typhoon in real architectural environment can be obtained directly and effectively.Field measurement is the best way to investigate the wind loading property,wind effects,and wind-structure interactions of large-span flexible system.Measured data will be highly valuable for scientific research and practical design.On the other hand,it also provides the basis of wind-resistance safety design of this kind of tension structures.If any creative development,it would dramatically improve the research level of large-span pre-stressed flexible system in our country.

  18. Field evaluation of remote wind sensing technologies: Shore-based and buoy mounted LIDAR systems

    Energy Technology Data Exchange (ETDEWEB)

    Herrington, Thomas [Stevens Inst. of Technology, Hoboken, NJ (United States)

    2017-11-03

    will be transferred to the Garrad Hassan (a subcontractor to Fishermen’s Energy) for incorporation in to the validation database, which is accessible to other scientific team members. Data collection times and durations will be determined by the PI and Co-PIs in consultation with instrument engineers to ensure the capture of data representative of the expected range of mid-Atlantic atmospheric conditions (e.g., temperature, moisture, coastal low pressure systems, tropical systems, rain, snow, fog). The collection and processing of the data is a function of site specific measurement requirements (Kelley et.al. 2007; Hannon et.al. 2008). To determine the optimal profiles of wind speed and direction from the LIDAR radial velocities as a function of azimuth angle, rigorous estimates of the bias and random error of each radial velocity estimate are required. Lockheed Martin Coherent Technologies, Inc., under contract with Fishermen’s Energy, will provide analyses of raw and processed data using various scan patterns to determine optimal performance settings for the pulsed scanning LIDAR. Once optimized, appropriate processing and analyses techniques will be evaluated by Garrad Hassan for use in validating the accuracy of the LIDAR wind field measurements against the standard anemometer measurements from the meteorological masts. The most attractive capability of the scanning LIDAR is the ability to provide high spatial resolution observations in a three-dimensional volume which provides superior statistical accuracy due to the large number of samples obtained. Each radial scan provides measurements in 100 range gates over a distance of 10 to 12 km at an update rate of 5 to 10 Hz and rotation of 2.5° per second. Each rotation at a fixed azimuth requires 2.4 minutes. Depending on the number of azimuths desired a complete scan can take up to 10 minutes or longer to complete. Once collected the radial velocities are processed to produce vector wind velocity estimates based

  19. Springtime connections between the large-scale sea-level pressure field and gust wind speed over Iberia and the Balearics

    Science.gov (United States)

    Martín, M. L.; Valero, F.; Pascual, A.; Morata, A.; Luna, M. Y.

    2011-01-01

    This paper investigates, by means of Singular Value Decomposition analysis, the springtime relationships between the mean sea-level pressure field over the North Atlantic and the regional wind gusts over the Iberian Peninsula, identifying the main atmospheric circulation patterns linked to gust wind speed anomaly configurations. The statistical significance of the obtained modes is investigated by means of Monte Carlo approach. The analysis highlighted that the covariability is dominated by two main large-scale features of the atmospheric circulation over the North Atlantic. The first mode relates to Iberian gust wind speeds to the Scandinavian pattern (SCAND), linking the large-scale pattern to above-normal wind gusts. The second covariability mode, associated with the North Atlantic Oscillation (NAO) pattern, correlates with maximum wind speeds over Iberia. An enhanced spring NAO pattern is related to positive (negative) wind gust correlations over northern (southern) Iberia. To find true relationships between large-scale atmospheric field and the gust wind speeds, composite maps were built up to give an average atmospheric circulation associated with coherent wind gust variability over Iberia.

  20. Springtime connections between the large-scale sea-level pressure field and gust wind speed over Iberia and the Balearics

    Directory of Open Access Journals (Sweden)

    M. L. Martín

    2011-01-01

    Full Text Available This paper investigates, by means of Singular Value Decomposition analysis, the springtime relationships between the mean sea-level pressure field over the North Atlantic and the regional wind gusts over the Iberian Peninsula, identifying the main atmospheric circulation patterns linked to gust wind speed anomaly configurations. The statistical significance of the obtained modes is investigated by means of Monte Carlo approach. The analysis highlighted that the covariability is dominated by two main large-scale features of the atmospheric circulation over the North Atlantic. The first mode relates to Iberian gust wind speeds to the Scandinavian pattern (SCAND, linking the large-scale pattern to above-normal wind gusts. The second covariability mode, associated with the North Atlantic Oscillation (NAO pattern, correlates with maximum wind speeds over Iberia. An enhanced spring NAO pattern is related to positive (negative wind gust correlations over northern (southern Iberia. To find true relationships between large-scale atmospheric field and the gust wind speeds, composite maps were built up to give an average atmospheric circulation associated with coherent wind gust variability over Iberia.

  1. Spatial interpolation of fine particulate matter concentrations using the shortest wind-field path distance.

    Directory of Open Access Journals (Sweden)

    Longxiang Li

    Full Text Available Effective assessments of air-pollution exposure depend on the ability to accurately predict pollutant concentrations at unmonitored locations, which can be achieved through spatial interpolation. However, most interpolation approaches currently in use are based on the Euclidean distance, which cannot account for the complex nonlinear features displayed by air-pollution distributions in the wind-field. In this study, an interpolation method based on the shortest path distance is developed to characterize the impact of complex urban wind-field on the distribution of the particulate matter concentration. In this method, the wind-field is incorporated by first interpolating the observed wind-field from a meteorological-station network, then using this continuous wind-field to construct a cost surface based on Gaussian dispersion model and calculating the shortest wind-field path distances between locations, and finally replacing the Euclidean distances typically used in Inverse Distance Weighting (IDW with the shortest wind-field path distances. This proposed methodology is used to generate daily and hourly estimation surfaces for the particulate matter concentration in the urban area of Beijing in May 2013. This study demonstrates that wind-fields can be incorporated into an interpolation framework using the shortest wind-field path distance, which leads to a remarkable improvement in both the prediction accuracy and the visual reproduction of the wind-flow effect, both of which are of great importance for the assessment of the effects of pollutants on human health.

  2. Three Dimensional Dynamic Model Based Wind Field Reconstruction from Lidar Data

    Science.gov (United States)

    Raach, Steffen; Schlipf, David; Haizmann, Florian; Cheng, Po Wen

    2014-06-01

    Using the inflowing horizontal and vertical wind shears for individual pitch controller is a promising method if blade bending measurements are not available. Due to the limited information provided by a lidar system the reconstruction of shears in real-time is a challenging task especially for the horizontal shear in the presence of changing wind direction. The internal model principle has shown to be a promising approach to estimate the shears and directions in 10 minutes averages with real measurement data. The static model based wind vector field reconstruction is extended in this work taking into account a dynamic reconstruction model based on Taylor's Frozen Turbulence Hypothesis. The presented method provides time series over several seconds of the wind speed, shears and direction, which can be directly used in advanced optimal preview control. Therefore, this work is an important step towards the application of preview individual blade pitch control under realistic wind conditions. The method is tested using a turbulent wind field and a detailed lidar simulator. For the simulation, the turbulent wind field structure is flowing towards the lidar system and is continuously misaligned with respect to the horizontal axis of the wind turbine. Taylor's Frozen Turbulence Hypothesis is taken into account to model the wind evolution. For the reconstruction, the structure is discretized into several stages where each stage is reduced to an effective wind speed, superposed with a linear horizontal and vertical wind shear. Previous lidar measurements are shifted using again Taylor's Hypothesis. The wind field reconstruction problem is then formulated as a nonlinear optimization problem, which minimizes the residual between the assumed wind model and the lidar measurements to obtain the misalignment angle and the effective wind speed and the wind shears for each stage. This method shows good results in reconstructing the wind characteristics of a three dimensional

  3. A review of wind field models for atmospheric transport

    Energy Technology Data Exchange (ETDEWEB)

    Ramsdell, J.V. Jr.; Skyllingstad, E.D.

    1993-06-01

    The primary objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation dose that individuals could have received as a result of emissions since 1944 from the US Department of Energy`s (DOE) Hanford Site near Richland, Washington. The HEDR Project is developing a computer code to estimate these doses and their uncertainties. The code, known as the HEDR integrated Code (HEDRIC), consists of four separate component codes. One of the component codes, called the Regional Atmospheric Transport Code for Hanford Emission Tracking (RATCHET) combines meteorological and release data to estimate time-integrated air concentrations and surface contamination at specific locations in the vicinity of the Hanford Site. The RATCHET domain covers approximately 75,000 square miles, extending from the crest of the Cascade Mountains on the west to the eastern edge of the Idaho panhandle and from central Oregon on the south to the Canadian border. This letter report explains the procedures in RATCHET that transform observed wind data into the wind fields used in atmospheric transport calculations. It also describes and evaluates alternative procedures not selected for use in RATCHET.

  4. Prediction of Wind Environment and Indoor/Outdoor Relationships for PM2.5 in Different Building–Tree Grouping Patterns

    Directory of Open Access Journals (Sweden)

    Bo Hong

    2018-01-01

    Full Text Available Airflow behavior and indoor/outdoor PM2.5 dispersion in different building–tree grouping patterns depend significantly on the building–tree layouts and orientation towards the prevailing wind. By using a standard k-ε model and a revised generalized drift flux model, this study evaluated airflow fields and indoor/outdoor relationships for PM2.5 resulting from partly wind-induced natural ventilation in four hypothetical building–tree grouping patterns. Results showed that: (1 Patterns provide a variety of natural ventilation potential that relies on the wind influence, and buildings that deflect wind on the windward facade and separate airflow on the leeward facade have better ventilation potential; (2 Patterns where buildings and trees form a central space and a windward opening side towards the prevailing wind offer the best ventilation conditions; (3 Under the assumption that transported pollution sources are diluted through the inlet, the aerodynamics and deposition effects of trees cause the lower floors of a multi-storey building to be exposed to lower PM2.5 compared with upper floors, and lower indoor PM2.5 values were found close to the tree canopy; (4 Wind pressure differences across each flat showed a poor correlation (R2 = 0.059, with indoor PM2.5 concentrations; and (5 Patterns with the long facade of buildings and trees perpendicular to the prevailing wind have the lowest indoor PM2.5 concentrations.

  5. System and method for evaluating wind flow fields using remote sensing devices

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, John; Hirth, Brian; Guynes, Jerry

    2016-12-13

    The present invention provides a system and method for obtaining data to determine one or more characteristics of a wind field using a first remote sensing device and a second remote sensing device. Coordinated data is collected from the first and second remote sensing devices and analyzed to determine the one or more characteristics of the wind field. The first remote sensing device is positioned to have a portion of the wind field within a first scanning sector of the first remote sensing device. The second remote sensing device is positioned to have the portion of the wind field disposed within a second scanning sector of the second remote sensing device.

  6. Effects of El Niño-driven changes in wind patterns on North Pacific albatrosses

    Science.gov (United States)

    Thorne, L. H.; Conners, M. G.; Hazen, E. L.; Bograd, S. J.; Antolos, M.; Costa, D. P.; Shaffer, S. A.

    2016-01-01

    Changes to patterns of wind and ocean currents are tightly linked to climate change and have important implications for cost of travel and energy budgets in marine vertebrates. We evaluated how El Niño-Southern Oscillation (ENSO)-driven wind patterns affected breeding Laysan and black-footed albatross across a decade of study. Owing to latitudinal variation in wind patterns, wind speed differed between habitat used during incubation and brooding; during La Niña conditions, wind speeds were lower in incubating Laysan (though not black-footed) albatross habitat, but higher in habitats used by brooding albatrosses. Incubating Laysan albatrosses benefited from increased wind speeds during El Niño conditions, showing increased travel speeds and mass gained during foraging trips. However, brooding albatrosses did not benefit from stronger winds during La Niña conditions, instead experiencing stronger cumulative headwinds and a smaller proportion of trips in tailwinds. Increased travel costs during brooding may contribute to the lower reproductive success observed in La Niña conditions. Furthermore, benefits of stronger winds in incubating habitat may explain the higher reproductive success of Laysan albatross during El Niño conditions. Our findings highlight the importance of considering habitat accessibility and cost of travel when evaluating the impacts of climate-driven habitat change on marine predators. PMID:27278360

  7. Changes in wind pattern alter albatross distribution and life-history traits.

    Science.gov (United States)

    Weimerskirch, Henri; Louzao, Maite; de Grissac, Sophie; Delord, Karine

    2012-01-13

    Westerly winds in the Southern Ocean have increased in intensity and moved poleward. Using long-term demographic and foraging records, we show that foraging range in wandering albatrosses has shifted poleward in conjunction with these changes in wind pattern, while their rates of travel and flight speeds have increased. Consequently, the duration of foraging trips has decreased, breeding success has improved, and birds have increased in mass by more than 1 kilogram. These positive consequences of climate change may be temporary if patterns of wind in the southern westerlies follow predicted climate change scenarios. This study stresses the importance of foraging performance as the key link between environmental changes and population processes.

  8. Short-range dynamics and prediction of mesoscale flow patterns in the MISTRAL field experiment

    Energy Technology Data Exchange (ETDEWEB)

    Weber, R.O.; Kaufmann, P.; Talkner, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    In a limited area of about 50 km by 50 km with complex topography, wind measurements on a dense network were performed during the MISTRAL field experiment in 1991-1992. From these data the characteristic wind fields were identified by an automated classification method. The dynamics of the resulting twelve typical regional flow patterns is studied. It is discussed how transitions between the flow patterns take place and how well the transition probabilities can be described in the framework of a Markov model. Guided by this discussion, a variety of prediction models were tested which allow a short-term forecast of the flow pattern type. It is found that a prediction model which uses forecast information from the synoptic scale has the best forecast skill. (author) 2 figs., 7 refs.

  9. Investigation of the relationship between main-bearing loads and wind field characteristics

    Science.gov (United States)

    Hart, E.; Turnbull, A.; McMillan, D.; Feuchtwang, J.; Golysheva, E.; Elliott, R.

    2017-11-01

    This paper investigates the relationship between main bearing loads and the characteristics of the incident wind field in which a wind turbine is operating. For a 2MW wind turbine model, fully aeroelastic multibody simulations are performed in 3D turbulent wind fields across the wind turbines operational envelope. Hub loads are extracted and then injected into a simplified drivetrain model of a single main-bearing configuration whose parameters are determined using finite element software. The main bearing reaction loads and load ratios from the simplified model are presented and analysed. The results indicate that there is a strong link between wind field characteristics and the loading experienced by a single main-bearing, with more damaging load ratios seen to occur in low turbulence and high shear wind conditions.

  10. A Pattern Recognition Approach to Acoustic Emission Data Originating from Fatigue of Wind Turbine Blades.

    Science.gov (United States)

    Tang, Jialin; Soua, Slim; Mares, Cristinel; Gan, Tat-Hean

    2017-11-01

    The identification of particular types of damage in wind turbine blades using acoustic emission (AE) techniques is a significant emerging field. In this work, a 45.7-m turbine blade was subjected to flap-wise fatigue loading for 21 days, during which AE was measured by internally mounted piezoelectric sensors. This paper focuses on using unsupervised pattern recognition methods to characterize different AE activities corresponding to different fracture mechanisms. A sequential feature selection method based on a k-means clustering algorithm is used to achieve a fine classification accuracy. The visualization of clusters in peak frequency-frequency centroid features is used to correlate the clustering results with failure modes. The positions of these clusters in time domain features, average frequency-MARSE, and average frequency-peak amplitude are also presented in this paper (where MARSE represents the Measured Area under Rectified Signal Envelope). The results show that these parameters are representative for the classification of the failure modes.

  11. IMPER: Characterization of the Wind Field over a Large Wind Turbine Rotor

    DEFF Research Database (Denmark)

    Schmidt Paulsen, Uwe; Wagner, Rozenn

    A modern wind turbine rotor with a contemporary rotor size would easily with the tips penetrate the air between 116 m and 30 m and herby experience effects of different wind. With current rules on power performance measurements such as IEC 61400-121 the reference wind speed is measured at hub...

  12. Wide Field Coverage for Juno (WFCJ): Jupiter's 2D Wind Field and Cloud Structure

    Science.gov (United States)

    Wong, Michael

    2017-08-01

    Juno will take novel measurements in the jovian system during HST Cycles 23, 24, and 25. This proposal supports Juno's neutral atmospheric investigation, which includes measurements with an IR imager/spectrometer (JIRAM) and the Microwave Radiometer (MWR). Both will achieve high spatial resolution as the orbiter swoops past Jupiter, in between the radiation belts and the cloud tops. But instrument fields of view are small compared to the planet, so HST observations would provide valuable context and complementary information.We propose to measure Jupiter's 2D wind field, as well as UV/optical cloud colors (and their evolution). We will measure winds using sets of global maps that cover two of Juno's perijove passes, characterizing the time-varying dynamics of waves, jets, vortices, and storms. The remaining perijove passes will be covered by snapshot (1-orbit) visits, sufficient to characterize feature morphology along each Juno track at high resolution. These observations will give crucial context for MWR observations and enable more precise retrievals from MWR data. Earth-based support is particularly important for Juno, due to its highly eccentric orbit and specialized instrumentation. WFC3/UVIS imaging can play an important role in the effort, since no other facility can obtain precise 2D wind fields and UV/optical photometry at high spatial resolution. Without the HST component of this campaign, key dynamical constraints will be missing.

  13. Wind Patterns of Coastal Tanzania: Their Variability and Trends

    African Journals Online (AJOL)

    tropospheric circulation has very low speeds which are also modified by the system of land and sea breezes at individual locations. In coastal Tanzania, most authors consider the NE Monsoon to prevail from November to March, and the SE Monsoon from April to. October (Iversen et al., 1984; Newell, 1957). The NE winds ...

  14. 3D wake measurements from a scanning wind lidar in combination with a fast wind field reconstruction model

    DEFF Research Database (Denmark)

    Mikkelsen, Torben Krogh; Herges, T. G.; Astrup, Poul

    2017-01-01

    -Stokes CFD code “Lincom Cyclop-buster model,”3 the corresponding 3D wind vector field (u, v, w) can be reconstructed under constraints for conservation of mass and momentum. The resulting model calculated line-of-sight projections of the 3D wind velocity vectors will become consistent with the line......High-resolution lidar wake measurements are part of an ongoing field campaign being conducted at the Scaled Wind Farm Technology (SWiFT) facility1 by Sandia National Laboratories and the National Renewable Energy Laboratory using a customized scanning “DTU SpinnerLidar”2 from the Technical...... University of Denmark. The purpose of the SpinnerLidar measurements at SWIFT is to measure the response of a V27 turbine wake to varying inflow conditions and turbine operating states. Although our fast scanning SpinnerLidar is able to measure the line-of-sight projected wind speed at up to 400 points per...

  15. Combined Experiment Phase 1. [Horizontal axis wind turbines: wind tunnel testing versus field testing

    Energy Technology Data Exchange (ETDEWEB)

    Butterfield, C.P.; Musial, W.P.; Simms, D.A.

    1992-10-01

    How does wind tunnel airfoil data differ from the airfoil performance on an operating horizontal axis wind turbine (HAWT) The National Renewable Energy laboratory has been conducting a comprehensive test program focused on answering this question and understanding the basic fluid mechanics of rotating HAWT stall aerodynamics. The basic approach was to instrument a wind rotor, using an airfoil that was well documented by wind tunnel tests, and measure operating pressure distributions on the rotating blade. Based an the integrated values of the pressure data, airfoil performance coefficients were obtained, and comparisons were made between the rotating data and the wind tunnel data. Care was taken to the aerodynamic and geometric differences between the rotating and the wind tunnel models. This is the first of two reports describing the Combined Experiment Program and its results. This Phase I report covers background information such as test setup and instrumentation. It also includes wind tunnel test results and roughness testing.

  16. Mexico City basin wind circulation during the MCMA-2003 field campaign

    Directory of Open Access Journals (Sweden)

    B. de Foy

    2005-01-01

    Full Text Available MCMA-2003 was a major field campaign investigating the atmospheric chemistry of the Mexico City Metropolitan Area (MCMA in April of 2003. This paper describes the wind circulation patterns during the campaign both within the Mexico City basin and on the regional scale. ''Time roses'' are introduced to concisely analyze the diurnal wind patterns. Three episode types were identified that explain the conditions encountered: ''O3-South'', ''Cold Surge'' and ''O3-North''. These can be diagnosed from a combination of synoptic and basin observations based on whether the day was predominantly cloudy, or whether the O3 peak was in the north or south of the basin. O3-South days have weak synoptic forcing due to an anti-cyclone over the eastern Pacific. Strong solar heating leads to northerly flows in the basin and an evening shift due to a gap flow from the south-east. Peak ozone concentrations are in the convergence zone in the south of the city. Cold Surge days are associated with ''El Norte'' events, with strong surface northerlies bringing cold moist air and rain. Stable conditions lead to high concentrations of primary pollutants and peak ozone in the city center. O3-North days occur when the sub-tropical jet is closer to Mexico City. With strong westerlies aloft, the circulation pattern is the same as O3-South days except for a wind shift in the mid-afternoon leading to ozone peaks in the north of the city. This classification is proposed as a means of understanding pollutant transport in the Mexico City basin and as a basis for future meteorological and chemical analysis. Furthermore, model evaluation and design of policy recommendations will need to take into account the three episode types.

  17. Multivariate multifractal detrended fluctuation analysis of 3D wind field signals

    Science.gov (United States)

    Zhang, Xiaonei; Zeng, Ming; Meng, Qinghao

    2018-01-01

    Characterizing the dynamic behavior underlying wind field from experimental multivariate signals is a challenging problem of continuous interest. In this work, we propose the multivariate multifractal detrended fluctuation analysis (MV-MFDFA) method to directly study the fractal dynamics of multichannel data in a complex system. By conducting several simulations on synthetic multivariate series, the validity of the proposed MV-MFDFA is illustrated. Then we utilize MV-MFDFA to analyze the 3D wind field signals collected at two different airflow environments, i.e., indoor and outdoor environments. Results show that the indoor and outdoor three wind vectors show multifractal properties, and the multifractal degrees of outdoor three wind vectors are stronger than those of corresponding indoor three wind vectors. By analyzing the indoor and outdoor multivariate wind speed, we find that the indoor and outdoor multivariate wind speed are antipersistent long-range correlation, and the indoor multivariate wind speed exhibits weaker multifractal properties than that of outdoor multivariate wind speed. Moreover, the multifractality of indoor multivariate wind speed depends mainly on the large fluctuations, while the multifractality of outdoor multivariate wind speed depends mainly on the small fluctuations. These findings indicate that the MV-MFDFA allows better understanding the dynamical mechanisms governing 3D wind variability.

  18. Surface Wind Speed Patterns from Synoptic Pressure Series employing different soft-computing algorithms

    Science.gov (United States)

    Kirchner Bossi, N.; Salcedo Sanz, S.; Carro Calvo, L.; Prieto, L.; Garcia Herrera, R.

    2012-04-01

    Two methods for establishing a daily wind-characterizing surface flux classification are introduced and compared in this work. They are based on several geostrophic flow indexes and have been derived from a NCEP/NCAR reanalysis of Mean Sea Level Pressure data (MSLP). In the task of parametrization and design of wind pattern classifiers, several soft-computing tools were developed: an evolutionary algorithm and a greedy-based technique were chosen to tackle the geostrophic flow vs. real wind approaching issue. Both algorithms work by optimizing the borders between clusters in the velocity space of the geostrophic flow (training experiment). Then the cluster configuration is assessed by linking the synoptic geostrophic wind signal with the corresponding real wind data (testing experiment) obtained from measurement towers at six wind farms located in Spain. The results obtained through these approaches were compared with those obtained by a widely reviewed, daily circulation weather types (WT) method, outperforming the later in all the instances considered. The main application of the proposed techniques is the accurate reconstruction of observational wind speed data series, which represents an interesting problem to consider at wind farms specially in periods without wind measurements available.

  19. Physically-based modeling of topographic effects on spatial evapotranspiration and soil moisture patterns through radiation and wind

    Directory of Open Access Journals (Sweden)

    M. Liu

    2012-02-01

    Full Text Available In this paper, simulations with the Soil Water Atmosphere Plant (SWAP model are performed to quantify the spatial variability of both potential and actual evapotranspiration (ET, and soil moisture content (SMC caused by topography-induced spatial wind and radiation differences. To obtain the spatially distributed ET/SMC patterns, the field scale SWAP model is applied in a distributed way for both pointwise and catchment wide simulations. An adapted radiation model from r.sun and the physically-based meso-scale wind model METRAS PC are applied to obtain the spatial radiation and wind patterns respectively, which show significant spatial variation and correlation with aspect and elevation respectively. Such topographic dependences and spatial variations further propagate to ET/SMC. A strong spatial, seasonal-dependent, scale-relevant intra-catchment variability in daily/annual ET and less variability in SMC can be observed from the numerical experiments. The study concludes that topography has a significant effect on ET/SMC in the humid region where ET is a energy limited rather than water availability limited process. It affects the spatial runoff generation through spatial radiation and wind, therefore should be applied to inform hydrological model development. In addition, the methodology used in the study can serve as a general method for physically-based ET estimation for data sparse regions.

  20. A modelling framework to predict bat activity patterns on wind farms: An outline of possible applications on mountain ridges of North Portugal.

    Science.gov (United States)

    Silva, Carmen; Cabral, João Alexandre; Hughes, Samantha Jane; Santos, Mário

    2017-03-01

    Worldwide ecological impact assessments of wind farms have gathered relevant information on bat activity patterns. Since conventional bat study methods require intensive field work, the prediction of bat activity might prove useful by anticipating activity patterns and estimating attractiveness concomitant with the wind farm location. A novel framework was developed, based on the stochastic dynamic methodology (StDM) principles, to predict bat activity on mountain ridges with wind farms. We illustrate the framework application using regional data from North Portugal by merging information from several environmental monitoring programmes associated with diverse wind energy facilities that enable integrating the multifactorial influences of meteorological conditions, land cover and geographical variables on bat activity patterns. Output from this innovative methodology can anticipate episodes of exceptional bat activity, which, if correlated with collision probability, can be used to guide wind farm management strategy such as halting wind turbines during hazardous periods. If properly calibrated with regional gradients of environmental variables from mountain ridges with windfarms, the proposed methodology can be used as a complementary tool in environmental impact assessments and ecological monitoring, using predicted bat activity to assist decision making concerning the future location of wind farms and the implementation of effective mitigation measures. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Toward Isolation of Salient Features in Stable Boundary Layer Wind Fields that Influence Loads on Wind Turbines

    Directory of Open Access Journals (Sweden)

    Jinkyoo Park

    2015-04-01

    Full Text Available Neutral boundary layer (NBL flow fields, commonly used in turbine load studies and design, are generated using spectral procedures in stochastic simulation. For large utility-scale turbines, stable boundary layer (SBL flow fields are of great interest because they are often accompanied by enhanced wind shear, wind veer, and even low-level jets (LLJs. The generation of SBL flow fields, in contrast to simpler stochastic simulation for NBL, requires computational fluid dynamics (CFD procedures to capture the physics and noted characteristics—such as shear and veer—that are distinct from those seen in NBL flows. At present, large-eddy simulation (LES is the most efficient CFD procedure for SBL flow field generation and related wind turbine loads studies. Design standards, such as from the International Electrotechnical Commission (IEC, provide guidance albeit with simplifying assumptions (one such deals with assuming constant variance of turbulence over the rotor and recommend standard target turbulence power spectra and coherence functions to allow NBL flow field simulation. In contrast, a systematic SBL flow field simulation procedure has not been offered for design or for site assessment. It is instructive to compare LES-generated SBL flow fields with stochastic NBL flow fields and associated loads which we evaluate for a 5-MW turbine; in doing so, we seek to isolate distinguishing characteristics of wind shear, wind veer, and turbulence variation over the rotor plane in the alternative flow fields and in the turbine loads. Because of known differences in NBL-stochastic and SBL-LES wind fields but an industry preference for simpler stochastic simulation in design practice, this study investigates if one can reproduce stable atmospheric conditions using stochastic approaches with appropriate corrections for shear, veer, turbulence, etc. We find that such simple tuning cannot consistently match turbine target SBL load statistics, even though

  2. Joint Offshore Wind Field Monitoring with Spaceborne SAR and Platform-Based Doppler LIDAR Measurements

    Science.gov (United States)

    Jacobsen, S.; Lehner, S.; Hieronimus, J.; Schneemann, J.; Kuhn, M.

    2015-04-01

    The increasing demand for renewable energy resources has promoted the construction of offshore wind farms e.g. in the North Sea. While the wind farm layout consists of an array of large turbines, the interrelation of wind turbine wakes with the remaining array is of substantial interest. The downstream spatial evolution of turbulent wind turbine wakes is very complex and depends on manifold parameters such as wind speed, wind direction and ambient atmospheric stability conditions. To complement and validate existing numerical models, corresponding observations are needed. While in-situ measurements with e.g. anemometers provide a time-series at the given location, the merits of ground-based and space- or airborne remote sensing techniques are indisputable in terms of spatial coverage. Active microwave devices, such as Scatterometer and Synthetic Aperture Radar (SAR), have proven their capabilities of providing sea surface wind measurements and particularly SAR images reveal wind variations at a high spatial resolution while retaining the large coverage area. Platform-based Doppler LiDAR can resolve wind fields with a high spatial coverage and repetition rates of seconds to minutes. In order to study the capabilities of both methods for the investigation of small scale wind field structures, we present a direct comparison of observations obtained by high resolution TerraSAR-X (TS-X) X-band SAR data and platform-based LiDAR devices at the North Sea wind farm alpha ventus. We furthermore compare the results with meteorological data from the COSMO-DE model run by the German Weather Service DWD. Our study indicates that the overall agreement between SAR and LiDAR wind fields is good and that under appropriate conditions small scale wind field variations compare significantly well.

  3. Appendix I1-2 to Wind HUI Initiative 1: Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    John Zack; Deborah Hanley; Dora Nakafuji

    2012-07-15

    This report is an appendix to the Hawaii WindHUI efforts to dev elop and operationalize short-term wind forecasting and wind ramp event forecasting capabilities. The report summarizes the WindNET field campaign deployment experiences and challenges. As part of the WindNET project on the Big Island of Hawaii, AWS Truepower (AWST) conducted a field campaign to assess the viability of deploying a network of monitoring systems to aid in local wind energy forecasting. The data provided at these monitoring locations, which were strategically placed around the Big Island of Hawaii based upon results from the Oahu Wind Integration and Transmission Study (OWITS) observational targeting study (Figure 1), provided predictive indicators for improving wind forecasts and developing responsive strategies for managing real-time, wind-related system events. The goal of the field campaign was to make measurements from a network of remote monitoring devices to improve 1- to 3-hour look ahead forecasts for wind facilities.

  4. The relationship between wind power, electricity demand and winter weather patterns in Great Britain

    Science.gov (United States)

    Thornton, Hazel E.; Scaife, Adam A.; Hoskins, Brian J.; Brayshaw, David J.

    2017-06-01

    Wind power generation in Great Britain has increased markedly in recent years. However due to its intermittency its ability to provide power during periods of high electricity demand has been questioned. Here we characterise the winter relationship between electricity demand and the availability of wind power. Although a wide range of wind power capacity factors is seen for a given demand, the average capacity factor reduces by a third between low and high demand. However, during the highest demand average wind power increases again, due to strengthening easterly winds. The nature of the weather patterns affecting Great Britain are responsible for this relationship. High demand is driven by a range of high pressure weather types, each giving cold conditions, but variable wind power availability. Offshore wind power is sustained at higher levels and offers a more secure supply compared to that onshore. However, during high demand periods in Great Britain neighbouring countries may struggle to provide additional capacity due to concurrent low temperatures and low wind power availability.

  5. Field Validation of IEC 61400-27-1 Wind Generation Type 3 Model with Plant Power Factor Controller

    DEFF Research Database (Denmark)

    Göksu, Ömer; Altin, Müfit; Fortmann, Jens

    2016-01-01

    Generic electrical simulation models of wind power generation have been developed as standards, such as the IEC 61400-27-1, to be used by wind industry, system operators, and academia for power system stability studies. In this paper, the IEC type 3 wind turbine model with wind turbine level...... voltage controller and with wind power plant level power factor controller is validated based on field measurements from a 52-MW wind power plant. In addition to the validation of the IEC type 3 wind turbine and wind power plant controller models, a comparison of the validation approaches, which...... of the reference wind power plant model are given....

  6. Theoretical and Observational Consequences of Rotation and Magnetic Fields in Stellar Winds

    Science.gov (United States)

    Ignace, Richard

    1996-05-01

    My dissertation concerns the study of stellar winds from theoretical modeling of the wind structure and the development of observational diagnostics. First, I have investigated the effects of stellar rotation for the wind structure of stars across the H-R Diagram. The effect of rotation is to increase the wind density at the equator while decreasing the density near the poles. The model, known as the Wind-Compressed Zone (WCZ) model, predicts that equatorial wind compressions are most likely to occur for stars with rapid rotation, low terminal speeds, and/or radial velocity distributions that increase gradually from the base of the wind. It is found that in favorable cases, stellar rotation can play a significant role in shaping the winds of Wolf Rayet stars, B supergiants, Asymptotic Giant Branch stars, and even some novae. The second major part of my thesis relates to the fact that the WCZ model will predict the magnetic field structure in the wind, if the field strength is relatively weak. However, there are generally no good diagnostics of stellar magnetic fields in the weak field limit, where Zeeman splitting is smaller than Doppler broadening. Thus, I have explored applications of the Hanle effect for probing magnetic fields in stellar winds. This effect (which has been used in studies of the solar atmosphere) deals with the modification of resonance line scattering polarization by a magnetic field. Solutions for the Hanle effect in optically thin axisymmetric extended stellar envelopes have been derived. Relative to the zero field case, the Hanle effect can result in significant changes of the line polarization, in some cases causing a position angle flip of 90(deg) . With multiline observations the Hanle effect is a viable diagnostic of stellar magnetic fields in the range 1-1000 Gauss. This thesis work was completed under the supervision of Joseph Cassinelli and in collaboration with Kenneth Nordsieck and Jon Bjorkman.

  7. Wind field re-construction of 3D Wake measurements from a turbine-installed scanning lidar

    DEFF Research Database (Denmark)

    Mikkelsen, Torben Krogh; Herges, Tommy; Astrup, Poul

    fields in the scan planes consisting of all three wind components. The combination of a fast-scanning wind lidar and a corresponding fast wind field reconstruction model is shown to be able to provide detailed wind data useful for proactive steering of wakes in real time and also for advanced feed......High-resolution wake flow measurements obtained from a turbine-mounted scanning lidar have been obtained from 1D to 5D behind a V27 test turbine. The measured line-of-sight projected wind speeds have, in connection with a fast CFD wind field reconstruction model, been used to generate 3D wind...

  8. EFFECT OF THE FLOW FIELD DEFORMATION IN THE WIND TUNNEL ON THE AERODYNAMIC COEFFICIENTS

    Directory of Open Access Journals (Sweden)

    Dušan Maturkanič

    2015-06-01

    Full Text Available The flow field quality has a principal signification at wind tunnel measurement. The creation of the flow field of air by fan leads to the rotation of entire flow field which is, moreover, deformed at the bends of the wind tunnel with close circulation. Despite the wind tunnels are equipped with the devices which eliminate these non-uniformities, in the most of cases, the air flow field has not ideal parameters in the test section. For the evaluation of the measured results of the model in the wind tunnel, the character of flow field deformation is necessary. The following text describes the possible general forms of the flow field nonuniformity and their effect on the aerodynamic coefficients calculation.

  9. Magnetic fields in the solar system planets, moons and solar wind interactions

    CERN Document Server

    Wicht, Johannes; Gilder, Stuart; Holschneider, Matthias

    2018-01-01

    This book addresses and reviews many of the still little understood questions related to the processes underlying planetary magnetic fields and their interaction with the solar wind. With focus on research carried out within the German Priority Program ”PlanetMag”, it also provides an overview of the most recent research in the field. Magnetic fields play an important role in making a planet habitable by protecting the environment from the solar wind. Without the geomagnetic field, for example, life on Earth as we know it would not be possible. And results from recent space missions to Mars and Venus strongly indicate that planetary magnetic fields play a vital role in preventing atmospheric erosion by the solar wind. However, very little is known about the underlying interaction between the solar wind and a planet’s magnetic field. The book takes a synergistic interdisciplinary approach that combines newly developed tools for data acquisition and analysis, computer simulations of planetary interiors an...

  10. Armature reaction effects on HTS field winding in HTS machine

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Jensen, Bogi Bech

    2013-01-01

    This paper presents experimental results from the Superwind laboratory setup. Particular focus in the paper has been placed on describing and quantifying the in influence of armature reaction on performance of the HTS fled winding. Presented experimental results have confrmed the HTS feld winding...... sensitivity to both armature reaction intensity and angular position with respect to the HTS coils. Furthermore, the characterization of the HTS feld winding has been correlated to the electromagnetic torque of the machine where the maximal Ic reduction of 21% has been observed for the maximum torque....

  11. FEM Analysis of Magnetic Field and Forces in Area ARC Fault of Autotransformer HV Winding

    Directory of Open Access Journals (Sweden)

    Koteras Dariusz

    2014-12-01

    Full Text Available In this paper the electric arc fault in the high voltage winding turn of the power autotransformer has been investigated. 3D magnetic field distributions in the leakage domain and electrodynamic forces acting on high voltage winding have been calculated. Finite Element Method was used for the magnetic flux density simulation. The elctrodynamic force value under the fault exceed significantly the nominal mechanical stresses of the winding.

  12. Acoustic Tweezing and Patterning of Concentration Fields in Microfluidics

    DEFF Research Database (Denmark)

    Karlsen, Jonas Tobias; Bruus, Henrik

    2017-01-01

    We demonstrate theoretically that acoustic forces acting on inhomogeneous fluids can be used to pattern and manipulate solute concentration fields into spatiotemporally controllable configurations stabilized against gravity. A theoretical framework describing the dynamics of concentration fields ...

  13. Estimation of the optimal wind factor of drifting objects from field experiments

    Science.gov (United States)

    Choi, Jung-Woon; Choi, Jin-Yong; Kwon, Jae-Il

    2017-04-01

    Particle tracking models (PTM) are used to calculate the trajectory of drifting objects for search and rescue in case of marine accidents. During marine accidents, the rescue team needs to predict a possible path of the objects in the ocean to implement an effective plan of dealing with the rescue. In this study, we try to improve the accuracy of PTM throughout a series of field experiments. Field experiments were conducted using drift buoys and mannequin with/without life jacket. The drift buoys and mannequin were designed to be easily influenced by wind and current in the sea. For PTM we used the module embedded on MOHID (Modelo Hidrodinâmico) and the results of WRF (Weather Research Forecasting) and MOHID are used as wind and current input data, respectively. This study aims to find the optimal wind factor according to the objects by using new method to improve the PTM accuracy. In order to estimate an optimal wind factor, we simulated iteratively on the different wind factor from 2 to 5% by increasing 0.2%. However we found the optimal wind factor varies with the wind speed. So, we divided into 16 sections from 2.5 to 10 m/s of wind speed and extracted the best accuracy at each section. Finally we made a formula with wind speed and wind factor. Using this formula, the accuracy of search and rescue was improved by about 10% compared to that in the usual method.

  14. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2007-06-01

    Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  15. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2007-06-01

    Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  16. SMART Wind Turbine Rotor: Design and Field Test

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Jonathan C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Resor, Brian R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Paquette, Joshua A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); White, Jonathan R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-01-29

    This report documents the design, fabrication, and testing of the SMART Rotor. This work established hypothetical approaches for integrating active aerodynamic devices (AADs) into the wind turbine structure and controllers.

  17. Local ionospheric electrodynamics associated with neutral wind fields at low latitudes: Kelvin-Helmholtz billows

    Directory of Open Access Journals (Sweden)

    J. P. St.-Maurice

    2006-07-01

    Full Text Available The Gadanki radar observation of plasma irregularities bearing the signature of Kelvin-Helmholtz billows above 100 km altitude raises the question of the electrodynamical mechanism that would allow the structures to drift with the neutral wind. We show that for locally varying neutral wind fields with the right geometry at night, multiple Hall effects in the electron gas lead to a situation where ions, electrons, and neutrals move together along the component of the wind that changes most rapidly in space. The species must not move together along all directions, however. If this were the case the plasma would be stable and a radar would be unable to observe the wind field. We discuss the stability of the plasma itself for Es layers affected by the Kelvin-Helmholtz wind field and show that a variety of factors have to be taken into account beyond the study of the zeroth order mechanism.

  18. Geosynchronous magnetic field responses to fast solar wind dynamic pressure enhancements: MHD field model

    Directory of Open Access Journals (Sweden)

    T. R. Sun

    2012-08-01

    Full Text Available We performed global MHD simulations of the geosynchronous magnetic field in response to fast solar wind dynamic pressure (Pd enhancements. Taking three Pd enhancement events in 2000 as examples, we found that the main features of the total field B and the dominant component Bz can be efficiently predicted by the MHD model. The predicted B and Bz varies with local time, with the highest level near noon and a slightly lower level around mid-night. However, it is more challenging to accurately predict the responses of the smaller component at the geosynchronous orbit (i.e., Bx and By. In contrast, the limitations of T01 model in predicting responses to fast Pd enhancements are presented.

  19. Field experiments on seed dispersal by wind in ten umbelliferous species (Apiaceae)

    NARCIS (Netherlands)

    Jongejans, E.; Telenius, A.

    2001-01-01

    This report presents data from experiments on seed dispersal by wind for ten species of the family Apiaceae. Seed shadows were obtained in the field under natural conditions, using wind speeds between four and ten m/s. The flight of individual seeds was followed by eye, and seed shadows were

  20. Analysis of Hurricane Irene’s Wind Field Using the Advanced Research Weather Research and Forecast (WRF-ARW Model

    Directory of Open Access Journals (Sweden)

    Alfred M. Klausmann

    2014-01-01

    Full Text Available Hurricane Irene caused widespread and significant impacts along the U.S. east coast during 27–29 August 2011. During this period, the storm moved across eastern North Carolina and then tracked northward crossing into Long Island and western New England. Impacts included severe flooding from the mid-Atlantic states into eastern New York and western New England, widespread wind damage and power outages across a large portion of southern and central New England, and a major storm surge along portions of the Long Island coast. The objective of this study was to conduct retrospective simulations using the Advanced Research Weather Research and Forecast (WRF-ARW model in an effort to reconstruct the storm’s surface wind field during the period of 27–29 August 2011. The goal was to evaluate how to use the WRF modeling system as a tool for reconstructing the surface wind field from historical storm events to support storm surge studies. The results suggest that, with even modest data assimilation applied to these simulations, the model was able to resolve the detailed structure of the storm, the storm track, and the spatial surface wind field pattern very well. The WRF model shows real potential for being used as a tool to analyze historical storm events to support storm surge studies.

  1. Near-surface wind pattern in regional climate projections over the broader Adriatic region

    Science.gov (United States)

    Belušić, Andreina; Telišman Prtenjak, Maja; Güttler, Ivan; Ban, Nikolina; Leutwyler, David; Schär, Christoph

    2017-04-01

    The Adriatic region is characterized by the complex coastline, strong topographic gradients and specific wind regimes. This represents excellent test area for the latest generation of the regional climate models (RCMs) applied over the European domain. The most famous wind along the Adriatic coast is bora, which due to its strength, has a strong impact on all types of human activities in the Adriatic region. The typical bora wind is a severe gusty downslope flow perpendicular to the mountains. Besides bora, in the Adriatic region, typical winds are sirocco (mostly during the wintertime) and sea/land breezes (dominantly in the warm part of the year) as a part of the regional Mediterranean wind system. Thus, it is substantial to determine future changes in the wind filed characteristics (e.g., changes in strength and frequencies). The first step was the evaluation of a suite of ten EURO- and MED-CORDEX models (at 50 km and 12.5 km resolution), and two additional high resolution models from the Swiss Federal Institute of Technology in Zürich (ETHZ, at 12.5 km and 2.2. km resolution) in the present climate. These results provided a basis for the next step where wind field features, in an ensemble of RCMs forced by global climate models (GCMs) in historical and future runs are examined. Our aim is to determine the influence of the particular combination of RCMs and GCMs, horizontal resolution and emission scenario on the future changes in the near-surface wind field. The analysis reveals strong sensitivity of the simulated wind flow and its statistics to both season and location analyzed, to the horizontal resolution of the RCM and on the choice of the particular GCM that provides boundary conditions.

  2. Decadal Patterns of Westerly Winds, Temperatures, Ocean Gyre Circulations and Fish Abundance: A Review

    Directory of Open Access Journals (Sweden)

    Candace Oviatt

    2015-10-01

    Full Text Available The purpose of this review is to describe the global scope of the multidecadal climate oscillations that go back at least, through several hundred years. Literature, historic data, satellite data and global circulation model output have been used to provide evidence for the zonal and meridional jet stream patterns. These patterns were predominantly zonal from the 1970s to 1990s and switched since the 1990s to a meridional wind phase, with weakening jet streams forming Rossby waves in the northern and southern hemispheres. A weakened northern jet stream has allowed northerly winds to flow down over the continents in the northern hemisphere during the winter period, causing some harsh winters and slowing anthropogenic climate warming regionally. Wind oscillations impact ocean gyre circulation affecting upwelling strength and pelagic fish abundance with synchronous behavior in sub Arctic gyres during phases of the oscillation and asynchronous behavior in subtropical gyres between the Atlantic and Pacific oceans.

  3. Weaving the history of the solar wind with magnetic field lines

    Science.gov (United States)

    Alvarado Gomez, Julian

    2017-08-01

    Despite its fundamental role for the evolution of the solar system, our observational knowledge of the wind properties of the young Sun comes from a single stellar observation. This unexpected fact for a field such as astrophysics arises from the difficulty of detecting Sun-like stellar winds. Their detection relies on the appearance of an astrospheric signature (from the stellar wind-ISM interaction region), visible only with the aid of high-resolution HST Lyman-alpha spectra. However, observations and modelling of the present day Sun have revealed that magnetic fields constitute the main driver of the solar wind, providing guidance on how such winds would look like back in time. In this context we propose observations of four young Sun-like stars in order to detect their astrospheres and characterise their stellar winds. For all these objects we have recovered surface magnetic field maps using the technique of Zeeman Doppler Imaging, and developed detailed wind models based on these observed field distributions. Even a single detection would represent a major step forward for our understanding of the history of the solar wind, and the outflows in more active stars. Mass loss rate estimates from HST will be confronted with predictions from realistic models of the corona/stellar wind. In one of our objects the comparison would allow us to quantify the wind variability induced by the magnetic cycle of a star, other than the Sun, for the first time. Three of our targets are planet hosts, thus the HST spectra would also provide key information on the high-energy environment of these systems, guaranteeing their legacy value for the growing field of exoplanet characterisation.

  4. Anomalous Arctic surface wind patterns and their impacts on September sea ice minima and trend

    Directory of Open Access Journals (Sweden)

    Bingyi Wu

    2012-05-01

    Full Text Available We used monthly mean surface wind data from the National Centers for Environmental Prediction/National Centers for Atmospheric Research (NCEP/NCAR reanalysis dataset during the period 1979–2010 to describe the first two patterns of Arctic surface wind variability by means of the complex vector empirical orthogonal function (CVEOF analysis. The first two patterns respectively account for 31 and 16% of its total anomalous kinetic energy. The leading pattern consists of the two subpatterns: the northern Laptev Sea (NLS pattern and the Arctic dipole (AD pattern. The second pattern contains the northern Kara Sea (NKS pattern and the central Arctic (CA pattern. Over the past two decades, the combined dynamical forcing of the first two patterns has contributed to Arctic September sea ice extent (SIE minima and its declining trend. September SIE minima are mainly associated with the negative phase of the AD pattern and the positive phase of the CA pattern during the summer (July to September season, and both phases coherently show an anomalous anticyclone over the Arctic Ocean. Wind patterns affect September SIE through their frequency and intensity. The negative trend in September SIE over the past two decades is associated with increased frequency and enhanced intensity of the CA pattern during the melting season from April to September. Thus, it cannot be simply attributed to the AD anomaly characterised by the second empirical orthogonal function mode of sea level pressure north of 70°N. The CA pattern exhibited interdecadal variability in the late 1990s, and an anomalous cyclone prevailed before 1997 and was then replaced by an anomalous anticyclone over the Arctic Ocean that is consistent with the rapid decline trend in September SIE. This paper provides an alternative way to identify the dominant patterns of climate variability and investigate their associated Arctic sea ice variability from a dynamical perspective. Indeed, this study

  5. Power and loads for wind turbines in yawed conditions. Analysis of field measurements and aerodynamic predictions

    Energy Technology Data Exchange (ETDEWEB)

    Boorsma, K. [ECN Wind Energy, Petten (Netherlands)

    2012-11-15

    A description is given of the work carried out within the framework of the FLOW (Far and Large Offshore Wind) project on single turbine performance in yawed flow conditions. Hereto both field measurements as well as calculations with an aerodynamic code are analyzed. The rotors of horizontal axis wind turbines follow the changes in the wind direction for optimal performance. The reason is that the power is expected to decrease for badly oriented rotors. So, insight in the effects of the yaw angle on performance is important for optimization of the yaw control of each individual turbine. The effect of misalignment on performance and loads of a single 2.5 MW wind turbine during normal operation is investigated. Hereto measurements at the ECN Wind Turbine Test Site Wieringermeer (EWTW) are analyzed from December 2004 until April 2009. Also, the influence of yaw is studied using a design code and results from this design code are compared with wind tunnel measurements.

  6. Diffraction patterns in ferrofluids: Effect of magnetic field and gravity

    Energy Technology Data Exchange (ETDEWEB)

    Radha, S., E-mail: radhasri12@gmail.com [Department of Physics, University of Mumbai, Mumbai 400098 (India); Mohan, Shalini [Department of Physics, University of Mumbai, Mumbai 400098 (India); UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, Mumbai 400098 (India); Pai, Chintamani [Department of Physics, University of Mumbai, Mumbai 400098 (India)

    2014-09-01

    In this paper, we report the experimental observation of diffraction patterns in a ferrofluid comprising of Fe{sub 3}O{sub 4} nanoparticles in hexane by a 10 mW He–Ne laser beam. An external dc magnetic field (0–2 kG) was applied perpendicular to the beam. The diffraction pattern showed a variation at different depths of the sample in both zero and applied magnetic field. The patterns also exhibit a change in shape and size as the external field is varied. This effect arises due to thermally induced self-diffraction under the influence of gravity and external magnetic field.

  7. Advanced Modeling System for Optimization of Wind Farm Layout and Wind Turbine Sizing Using a Multi-Level Extended Pattern Search Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    DuPont, Bryony; Cagan, Jonathan; Moriarty, Patrick

    2016-07-01

    This paper presents a system of modeling advances that can be applied in the computational optimization of wind plants. These modeling advances include accurate cost and power modeling, partial wake interaction, and the effects of varying atmospheric stability. To validate the use of this advanced modeling system, it is employed within an Extended Pattern Search (EPS)-Multi-Agent System (MAS) optimization approach for multiple wind scenarios. The wind farm layout optimization problem involves optimizing the position and size of wind turbines such that the aerodynamic effects of upstream turbines are reduced, which increases the effective wind speed and resultant power at each turbine. The EPS-MAS optimization algorithm employs a profit objective, and an overarching search determines individual turbine positions, with a concurrent EPS-MAS determining the optimal hub height and rotor diameter for each turbine. Two wind cases are considered: (1) constant, unidirectional wind, and (2) three discrete wind speeds and varying wind directions, each of which have a probability of occurrence. Results show the advantages of applying the series of advanced models compared to previous application of an EPS with less advanced models to wind farm layout optimization, and imply best practices for computational optimization of wind farms with improved accuracy.

  8. Field Plot Points for Wind Cave National Park Vegetation Mapping Project

    Data.gov (United States)

    National Park Service, Department of the Interior — Vegetation field plots at Wind Cave NP were visited, described, and documented in a digital database. The database consists of 2 parts - (1) Physical Descriptive...

  9. Regional Field Verification -- Operational Results from Four Small Wind Turbines in the Pacific Northwest: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, K.; Raker, J.

    2006-08-01

    This paper describes four small wind turbines installed in the Pacific Northwest under DOE/NREL's Regional Field Verification Program between 2003 and 2004 and summarizes operational data from each site.

  10. Operational Generation of Urban Wind Fields to Support Transport and Dispersion Modeling

    Science.gov (United States)

    Copeland, J. H.; Sheu, R.; Brown, M. J.

    2007-12-01

    A realistic wind field is a key component to any transport and dispersion model simulation. In the urban environment observing the wind field accurately is complicated by the presence of the building structures themselves. In situ measurements are only representative over a limited area near the point of observation due to the influence of nearby buildings. Winds observed remotely, via radar or lidar, have good spatial resolution, but are limited to making measurements above rooftop. The Urban Shield project is an emergency response system for hazardous atmospheric releases in Arlington County Virginia. To provide building aware wind fields over a 100 square kilometer area for transport and dispersion modeling we use a combined approach of remotely sensed wind observations and very high resolution, ~10 meters, diagnostic wind modeling. In brief, the system uses 3-D wind analyses from Doppler radar and lidar as input to Los Alamos National Laboratory's QUIC-Urb empirical wind model. An overview of the system and results will be presented.

  11. Surface drag effects on simulated wind fields in high-resolution atmospheric forecast model

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Kyo Sun; Lim, Jong Myoung; Ji, Young Yong [Environmental Radioactivity Assessment Team,Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Shin, Hye Yum [NOAA/Geophysical Fluid Dynamics Laboratory, Princeton (United States); Hong, Jin Kyu [Yonsei University, Seoul (Korea, Republic of)

    2017-04-15

    It has been reported that the Weather Research and Forecasting (WRF) model generally shows a substantial over prediction bias at low to moderate wind speeds and winds are too geostrophic (Cheng and Steenburgh 2005), which limits the application of WRF model in the area that requires the accurate surface wind estimation such as wind-energy application, air-quality studies, and radioactive-pollutants dispersion studies. The surface drag generated by the subgrid-scale orography is represented by introducing a sink term in the momentum equation in their studies. The purpose of our study is to evaluate the simulated meteorological fields in the high-resolution WRF framework, that includes the parameterization of subgrid-scale orography developed by Mass and Ovens (2010), and enhance the forecast skill of low-level wind fields, which plays an important role in transport and dispersion of air pollutants including radioactive pollutants. The positive bias in 10-m wind speed is significantly alleviated by implementing the subgrid-scale orography parameterization, while other meteorological fields including 10-m wind direction are not changed. Increased variance of subgrid- scale orography enhances the sink of momentum and further reduces the bias in 10-m wind speed.

  12. Spatial patterns in tactile perception: is there a tactile field?

    Science.gov (United States)

    Haggard, Patrick; Giovagnoli, Giulia

    2011-05-01

    Previous studies of tactile spatial perception focussed either on a single point of stimulation, on local patterns within a single skin region such as the fingertip, on tactile motion, or on active touch. It remains unclear whether we should speak of a tactile field, analogous to the visual field, and supporting spatial relations between stimulus locations. Here we investigate this question by studying perception of large-scale tactile spatial patterns on the hand, arm and back. Experiment 1 investigated the relation between perception of tactile patterns and the identification of subsets of those patterns. The results suggest that perception of tactile spatial patterns is based on representing the spatial relations between locations of individual stimuli. Experiment 2 investigated the spatial and temporal organising principles underlying these relations. Experiment 3 showed that tactile pattern perception makes reference to structural representations of the body, such as body parts separated by joints. Experiment 4 found that precision of pattern perception is poorer for tactile patterns that extend across the midline, compared to unilateral patterns. Overall, the results suggest that the human sense of touch involves a tactile field, analogous to the visual field. The tactile field supports computation of spatial relations between individual stimulus locations, and thus underlies tactile pattern perception. 2011. Published by Elsevier B.V. All rights reserved.

  13. Regional Field Verification -- Case Study of Small Wind Turbines in the Pacific Northwest: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, K.

    2005-05-01

    The U.S. Department of Energy/National Renewable Energy Laboratory's (DOE/NREL) Regional Field Verification (RFV) project supports industry needs for gaining initial field operation experience with small wind turbines and verify the performance, reliability, maintainability, and cost of small wind turbines in diverse applications. In addition, RFV aims to help expand opportunities for wind energy in new regions of the United States by tailoring projects to meet unique regional requirements and document and communicate the experience from these projects for the benefit of others in the wind power development community and rural utilities. Between August 2003 and August 2004, six turbines were installed at different host sites. At least one year of data has been collected from five of these sites. This paper describes DOE/NREL's RFV project, reviews some of the lessons learned with regards to small wind turbine installations, summarizes operations data from these sites, and provides preliminary BOS costs.

  14. Modeling and analysis of solar wind generated contributions to the near-Earth magnetic field

    DEFF Research Database (Denmark)

    Vennerstrøm, Susanne; Moretto, T.; Rastatter, L.

    2006-01-01

    Solar wind generated magnetic disturbances are currently one of the major obstacles for improving the accuracy in the determination of the magnetic field due to sources internal to the Earth. In the present study a global MHD model of solar wind magnetosphere interaction is used to obtain...... of identifying the most important aspects of the solar wind disturbances in an internal field modeling context. The contribution from the distant magnetospheric currents is found to consist of two, mainly opposing, contributions from respectively the dayside magnetopause currents and the cross-tail current...

  15. A Pattern Recognition Approach to Acoustic Emission Data Originating from Fatigue of Wind Turbine Blades

    Directory of Open Access Journals (Sweden)

    Jialin Tang

    2017-11-01

    Full Text Available The identification of particular types of damage in wind turbine blades using acoustic emission (AE techniques is a significant emerging field. In this work, a 45.7-m turbine blade was subjected to flap-wise fatigue loading for 21 days, during which AE was measured by internally mounted piezoelectric sensors. This paper focuses on using unsupervised pattern recognition methods to characterize different AE activities corresponding to different fracture mechanisms. A sequential feature selection method based on a k-means clustering algorithm is used to achieve a fine classification accuracy. The visualization of clusters in peak frequency−frequency centroid features is used to correlate the clustering results with failure modes. The positions of these clusters in time domain features, average frequency−MARSE, and average frequency−peak amplitude are also presented in this paper (where MARSE represents the Measured Area under Rectified Signal Envelope. The results show that these parameters are representative for the classification of the failure modes.

  16. Localized magnetic fields in arbitrary directions using patterned nanomagnets

    DEFF Research Database (Denmark)

    McNeil, Robert P G; Schneble, Jeff; Kataoka, Masaya

    2010-01-01

    Control of the local magnetic fields desirable for spintronics and quantum information technology is not well developed. Existing methods produce either moderately small local fields or one held orientation. We present designs of patterned magnetic elements that produce remanent fields of 50 mT (...

  17. Electromagnetic field patterning or crystal light

    Science.gov (United States)

    Słupski, Piotr; Wymysłowski, Artur; Czarczyński, Wojciech

    2016-12-01

    Using the orbital angular momentum of light for the development of a vortex interferometer, the underlying physics requires microwave/RF models,1 as well as quantum mechanics for light1, 2 and fluid flow for semiconductor devices.3, 4 The combination of the aforementioned physical models yields simulations and results such as optical lattices,1 or an Inverse Farday effect.5 The latter is explained as the absorption of optical angular momentum, generating extremely high instantenous magnetic fields due to radiation friction. An algorithmic reduction across the computational methods used in microwaves, lasers, quantum optics and holography is performed in order to explain electromagnetic field interactions in a single computational framework. This work presents a computational model for photon-electron interactions, being a simplified gauge theory described using differentials or disturbances (photons) instead of integrals or fields. The model is based on treating the Z-axis variables as a Laplace fluid with spatial harmonics, and the XY plane as Maxwell's equations on boundaries. The result is a unified, coherent, graphical computational method of describing the photon qualitatively, quantitatively and with proportion. The model relies on five variables and is described using two equations, which use emitted power, cavity wavelength, input frequency, phase and time. Phase is treated as a rotated physical dimension under gauge theory of Feynmann's QED. In essence, this model allows the electromagnetic field to be treated with it's specific crystallography. The model itself is described in Python programming language. PACS 42.50.Pq, 31.30.J-, 03.70.+k, 11.10.-z, 67.10.Hk

  18. Spatial-temporal analysis of coherent offshore wind field structures measured by scanning Doppler-lidar

    Science.gov (United States)

    Valldecabres, L.; Friedrichs, W.; von Bremen, L.; Kühn, M.

    2016-09-01

    An analysis of the spatial and temporal power fluctuations of a simplified wind farm model is conducted on four offshore wind fields data sets, two from lidar measurements and two from LES under unstable and neutral atmospheric conditions. The integral length scales of the horizontal wind speed computed in the streamwise and the cross-stream direction revealed the elongation of the structures in the direction of the mean flow. To analyse the effect of the structures on the power output of a wind turbine, the aggregated equivalent power of two wind turbines with different turbine spacing in the streamwise and cross-stream direction is analysed at different time scales under 10 minutes. The fact of considering the summation of the power of two wind turbines smooths out the fluctuations of the power output of a single wind turbine. This effect, which is stronger with increasing spacing between turbines, can be seen in the aggregation of the power of two wind turbines in the streamwise direction. Due to the anti-correlation of the coherent structures in the cross-stream direction, this smoothing effect is stronger when the aggregated power is computed with two wind turbines aligned orthogonally to the mean flow direction.

  19. Interplanetary Magnetic Field Power Spectrum Variations in the Inner Heliosphere: A Wind and MESSENGER Study

    Science.gov (United States)

    Szabo, Adam; Koval, A.

    2011-01-01

    The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the similar observations made by the MESSENGER spacecraft in the inner heliosphere affords an opportunity to compare magnetic field power spectral density variations as a function of radial distance from the Sun under different solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the approx.2 Hz limit above which digitization noise becomes apparent. The powe'r spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions. Wind and MESSENGER magnetic fluctuations are compared for times when the two spacecraft are close to radial and Parker field alignment. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed.

  20. Measuring electromagnetic fields (EMF) around wind turbines in Canada: is there a human health concern?

    Science.gov (United States)

    McCallum, Lindsay C; Whitfield Aslund, Melissa L; Knopper, Loren D; Ferguson, Glenn M; Ollson, Christopher A

    2014-02-15

    The past five years has seen considerable expansion of wind power generation in Ontario, Canada. Most recently worries about exposure to electromagnetic fields (EMF) from wind turbines, and associated electrical transmission, has been raised at public meetings and legal proceedings. These fears have not been based on any actual measurements of EMF exposure surrounding existing projects but appear to follow from worries from internet sources and misunderstanding of the science. The study was carried out at the Kingsbridge 1 Wind Farm located near Goderich, Ontario, Canada. Magnetic field measurements were collected in the proximity of 15 Vestas 1.8 MW wind turbines, two substations, various buried and overhead collector and transmission lines, and nearby homes. Data were collected during three operational scenarios to characterize potential EMF exposure: 'high wind' (generating power), 'low wind' (drawing power from the grid, but not generating power) and 'shut off' (neither drawing, nor generating power). Background levels of EMF (0.2 to 0.3 mG) were established by measuring magnetic fields around the wind turbines under the 'shut off' scenario. Magnetic field levels detected at the base of the turbines under both the 'high wind' and 'low wind' conditions were low (mean = 0.9 mG; n = 11) and rapidly diminished with distance, becoming indistinguishable from background within 2 m of the base. Magnetic fields measured 1 m above buried collector lines were also within background (≤ 0.3 mG). Beneath overhead 27.5 kV and 500 kV transmission lines, magnetic field levels of up to 16.5 and 46 mG, respectively, were recorded. These levels also diminished rapidly with distance. None of these sources appeared to influence magnetic field levels at nearby homes located as close as just over 500 m from turbines, where measurements immediately outside of the homes were ≤ 0.4 mG. The results suggest that there is nothing unique to wind farms with respect to EMF exposure; in

  1. Implementing a wind measurement Doppler Lidar based on a molecular iodine filter to monitor the atmospheric wind field over Beijing

    Science.gov (United States)

    Du, Li-fang; Yang, Guo-tao; Wang, Ji-hong; Yue, Chuan; Chen, Lin-xiang

    2017-02-01

    A wind measurement Doppler Lidar system was developed, in which injection seeded laser was used to generate narrow linewidth laser pulse. Frequency stabilization was achieved through absorption of iodine molecules. Commands that control the instrumental system were based on the PID algorithm and coded using VB language. The frequency of the seed laser was locked to iodine molecular absorption line 1109 which is close to the upper edge of the absorption range,with long-time (>4 h) frequency-locking accuracy being ≤0.5 MHz and long-time frequency stability being 3.55×10-9. Design the continuous light velocity measuring system, which concluded the cure about doppler frequency shift and actual speed of chopped wave plate, the velocity error is less than 0.4 m/s. The experiment showed that the stabilized frequency of the seed laser was different from the transmission frequency of the Lidar. And such frequency deviation is known as Chirp of the laser pulse. The real-time measured frequency difference of the continuous and pulsed lights was about 10 MHz, long-time stability deviation was around 5 MHz. When the temporal and spatial resolutions were respectively set to 100 s and 96 m, the wind velocity measurement error of the horizontal wind field at the attitude of 15-35 km was within ±5 m/s, the results showed that the wind measurement Doppler Lidar implemented in Yanqing, Beijing was capable of continuously detecting in the middle and low atmospheric wind field at nighttime. With further development of this technique, system measurement error could be lowered, and long-run routine observations are promising.

  2. Meteorological field measurements at potential and actual wind turbine sites

    Energy Technology Data Exchange (ETDEWEB)

    Renne, D.S.; Sandusky, W.F.; Hadley, D.L.

    1982-09-01

    An overview of experiences gained in a meteorological measurement program conducted at a number of locations around the United States for the purpose of site evaluation for wind energy utilization is provided. The evolution of the measurement program from its inception in 1976 to the present day is discussed. Some of the major accomplishments and areas for improvement are outlined. Some conclusions on research using data from this program are presented.

  3. International co-operation in the field of wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Wolff, J. [VTT Energy, Espoo (Finland)

    1998-10-01

    The use of wind energy is expanding rapidly worldwide. At the end of 1996 over 6000 MW was installed and the annual increase has during the last years exceeded 1000 MW. The development is also reaching more and more countries. In order to maintain technical and commercial development international co-operation is needed to secure cost-effectiveness, reliability and safety of the technology. International recommendations, harmonisation and standardisation is promoted by several international organizations like IEA, IEC and the classification organisations

  4. Wind tunnel test of 1/30 scale heliostat field array model. Test report

    Energy Technology Data Exchange (ETDEWEB)

    Brown, G. L.

    1978-02-22

    From 9 January through 20 January 1978, Honeywell conducted a wind tunnel test on a 1/30 scale partial heliostat field. The heliostats were per Honeywell's design developed under the 10 megawatt central receiver pilot electrical power plant subsystem research experiment contract. Likewise, the scaled section of the field geometry duplicated the proposed circular layout. Testing was conducted at the Georgia Institute of Technology's 9 foot subsonic tunnel. The objective of the test was to ascertain from a qualitative standpoint the field effects upon wind loading within a heliostat field. To accomplish this, numerous pressure tap measurements at different heights and at different field positions were taken with varying wind speeds, fence designs, and heliostat gimbal orientations. The Department of Energy specified boundary layer profile was also scaled by 1/30 in order to simulate the total wind effects as accurately as possible taking into account the potentially severe scaling or Reynolds number effects at a 1/30 scale. After initial model set-up within the tunnel and scaled boundary layer generated, 91 separate runs were accomplished. The results do demonstrate the high sensitivity of wind loading upon the collector field due to the actual heliostat orientation and fence geometry. Vertical pressure gradients within the model field and flow reentry angles provide a good qualitative feel as to the full scale environment that might be expected and point to the need for specific additional testing to further explore potentially dangerous conditions.

  5. A wind-tunnel study of sea breeze effects. [diffusion pattern simulation

    Science.gov (United States)

    Ogawa, Y.; Griffiths, R.; Hoydysh, W. G.

    1975-01-01

    A wind-tunnel simulation of the diffusion patterns in a sea breeze has been attempted. No attempt was made to reproduce the recirculation that characterizes a sea breeze, but the results indicate that the low-level onshore flow was well simulated for neutral, stable, unstable, and elevated inversion conditions. Velocity, turbulence, shear stress, and temperature data were taken, and the spread of emissions from ground-level sources was investigated. Comparison is made with theoretical predictions by Inoue (1960) and with the open, countryside results of Pasquill. Agreement with the predictions by Inoue is good. The comparison with Pasquill's results shows that the wind-tunnel flows are shifted two categories towards more stable. The discrepancy may be explained as a lack of mesoscale turbulence in the wind tunnel.

  6. Radar sensitivity and antenna scan pattern study for a satellite-based Radar Wind Sounder (RAWS)

    Science.gov (United States)

    Stuart, Michael A.

    1992-01-01

    Modeling global atmospheric circulations and forecasting the weather would improve greatly if worldwide information on winds aloft were available. Recognition of this led to the inclusion of the LAser Wind Sounder (LAWS) system to measure Doppler shifts from aerosols in the planned for Earth Observation System (EOS). However, gaps will exist in LAWS coverage where heavy clouds are present. The RAdar Wind Sensor (RAWS) is an instrument that could fill these gaps by measuring Doppler shifts from clouds and rain. Previous studies conducted at the University of Kansas show RAWS as a feasible instrument. This thesis pertains to the signal-to-noise ratio (SNR) sensitivity, transmit waveform, and limitations to the antenna scan pattern of the RAWS system. A dop-size distribution model is selected and applied to the radar range equation for the sensitivity analysis. Six frequencies are used in computing the SNR for several cloud types to determine the optimal transmit frequency. the results show the use of two frequencies, one higher (94 GHz) to obtain sensitivity for thinner cloud, and a lower frequency (24 GHz) to obtain sensitivity for thinner cloud, and a lower frequency (24 GHz) for better penetration in rain, provide ample SNR. The waveform design supports covariance estimation processing. This estimator eliminates the Doppler ambiguities compounded by the selection of such high transmit frequencies, while providing an estimate of the mean frequency. the unambiguous range and velocity computation shows them to be within acceptable limits. The design goal for the RAWS system is to limit the wind-speed error to less than 1 ms(exp -1). Due to linear dependence between vectors for a three-vector scan pattern, a reasonable wind-speed error is unattainable. Only the two-vector scan pattern falls within the wind-error limits for azimuth angles between 16 deg to 70 deg. However, this scan only allows two components of the wind to be determined. As a result, a technique is

  7. Near Field HF Antenna Pattern Measurement Method Using an Antenna Pattern Range

    Science.gov (United States)

    2015-12-01

    TECHNICAL REPORT 3006 December 2015 Near-Field HF Antenna Pattern Measurement Method Using an Antenna Pattern Range Ani Siripuram Michael Daly...link budget. This report focuses on computing absolute gain for HF antennas measured on the APR. Recent research efforts by SSC Pacific’s Applied...Electromagnetics Branch (Code 52250) show that the APR extends to accurate measurement of normalized far-field radiation patterns of HF antennas. The

  8. Field-based observations confirm linear scaling of sand flux with wind stress

    CERN Document Server

    Martin, Raleigh L

    2016-01-01

    Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the sand flux scales with wind speed, largely because models do not agree on how particle speed changes with wind shear velocity. Here, we present comprehensive measurements from three new field sites and three published studies, showing that characteristic saltation layer heights, and thus particle speeds, remain approximately constant with shear velocity. This result implies a linear dependence of saltation flux on wind shear stress, which contrasts with the nonlinear 3/2 scaling used in most aeolian process predictions. We confirm the linear flux law with direct measurements of the stress-flux relationship occurring at each site. Models for dust generation, dune migration, and other processes driven by wind-blown sand on Earth, Mars, and several other planetary surfaces should be modified to account for linear stress-flux scaling.

  9. Performance of a prototype micro wind turbine in the manmade wind field from air conditioner of buildings

    Directory of Open Access Journals (Sweden)

    K. H. Goh

    2012-03-01

    Full Text Available Harnessing waste energy from the manmade air fields of buildings presents a new area of renewable energy to explore. Due to the unpredictability of the natural wind, this study is to evaluate the practicality for harnessing waste energy from the air conditioner exhaust units which are a more constant and predictable source available in the buildings. A prototype of the micro wind turbine has been designed to minimize the negative effect of the exhaust sources. After the micro wind turbine was manufactured, the performance of the turbine was tested in the selected air conditioner exhaust unit. Increasing the rotor solidity and decreasing the resistance of the generator contribute to improved starting torque and decreased generator break in torque respectively in the design. The power generation of the micro wind turbine increases with an increase of the rotor speed. The 24-hour operation of the prototype presents an observation for both exhaust performance and power generation prediction when the prototype is mounted on the exhaust unit.

  10. Geosynchronous magnetic field responses to fast solar wind dynamic pressure enhancements: MHD field model

    Directory of Open Access Journals (Sweden)

    T. R. Sun

    2012-08-01

    Full Text Available We performed global MHD simulations of the geosynchronous magnetic field in response to fast solar wind dynamic pressure (Pd enhancements. Taking three Pd enhancement events in 2000 as examples, we found that the main features of the total field B and the dominant component Bz can be efficiently predicted by the MHD model. The predicted B and Bz varies with local time, with the highest level near noon and a slightly lower level around mid-night. However, it is more challenging to accurately predict the responses of the smaller component at the geosynchronous orbit (i.e., Bx and By. In contrast, the limitations of T01 model in predicting responses to fast Pd enhancements are presented.

  11. Estimating the solar wind pressure at comet 67P from Rosetta magnetic field measurements

    Science.gov (United States)

    Nemeth, Z.; Dósa, M.; Goetz, C.; Madanian, H.; Opitz, A.; Richter, I.; Szego, K.; Timar, A.

    2017-09-01

    The solar wind pressure is an important parameter of planetary space weather, which plays a crucial role in the interaction of the solar wind with the planetary plasma environment. Unfortunately, it is not always possible to measure its value at every locations where it would be useful or needed. Spacecraft observing the internal dynamics of a planetary magnetosphere, for example, would benefit greatly from solar wind pressure data, but as the solar wind does not penetrate to their locations, direct measurements are impossible. It is well known that the maximum of the magnetic field in the pile-up region of a magnetosphere is proportional to the square root of the solar wind pressure. Recent investigation of Rosetta data revealed that the maximum of the magnetic field in the pile-up region can be approximated by magnetic field measurements performed in the inner regions of the cometary magnetosphere close to the boundary of the diamagnetic cavity. This relationship holds for several months spanning from June 2015 to January 2016. Here we investigate the possibility to use this relationship to determine a solar wind pressure proxy for this time interval using magnetic field data measured by the Rosetta Magnetometer. This pressure proxy would be useful not only for other Rosetta related studies, but could also serve as a new independent input database for space weather propagation to other locations in the Solar System.

  12. 8000 Ways to Model a Vortex: A Review of Hindcast Wind Field Methodologies

    Science.gov (United States)

    Sweeney, J.

    2014-12-01

    Hindcasts of cyclonic wind fields are crucial for extreme analysis in the oil and gas industry. Recent scientific developments have increased the number of parameterization options for tropical cyclone vortices, leading to well over 8000 permutations of model choices. Which is best? Also problematic is how best to blend modelled vortex winds into a global wind model (such as the Climate Forecast System Reanalysis (CFSR)) in order to resolve tropical cyclones to sufficient detail for wave modelling. Standard blending schemes can leave a 'moat' between the vortex and the CFSR circulation (see Figure 1 from TC Olivia 1996). Using a 35-year track database from the Australian Bureau of Meteorology, this study assesses model configurations and blending schemes against the most extensive measured meteorological dataset in the north-east Indian Ocean (largely commercial-in-confidence). The Holland profile models of 1980 and 2008 are two starting points, with other options examined for radius to maximum wind calculations, pressure-wind relationships, averaging periods, atmospheric profiles, gust factors, and asymmetry methods. Once a vortex is modelled, the winds are then fitted to the radius of gales and blended into the CFSR before further verification. Initial results support recent theoretical developments by Hu et al (2012), with additional results that call for a new asymmetry method and the separation of pressure and wind field modelling.

  13. Interplanetary and Interstellar Dust Observed by the Wind/WAVES Electric Field Instrument

    Science.gov (United States)

    Malaspina, David; Horanyi, M.; Zaslavsky, A.; Goetz, K.; Wilson, L. B., III; Kersten, K.

    2014-01-01

    Observations of hypervelocity dust particles impacting the Wind spacecraft are reported here for the first time using data from the WindWAVES electric field instrument. A unique combination of rotating spacecraft, amplitude-triggered high-cadence waveform collection, and electric field antenna configuration allow the first direct determination of dust impact direction by any spacecraft using electric field data. Dust flux and impact direction data indicate that the observed dust is approximately micron-sized with both interplanetary and interstellar populations. Nanometer radius dust is not detected by Wind during times when nanometer dust is observed on the STEREO spacecraft and both spacecraft are in close proximity. Determined impact directions suggest that interplanetary dust detected by electric field instruments at 1 AU is dominated by particles on bound trajectories crossing Earths orbit, rather than dust with hyperbolic orbits.

  14. A combined aeroelastic-aeroacoustic model for wind turbine noise: Verification and analysis of field measurements

    DEFF Research Database (Denmark)

    Bertagnolio, Franck; Aagaard Madsen, Helge; Fischer, Andreas

    2017-01-01

    In this paper, semi-empirical engineering models for the three main wind turbine aerodynamic noise sources, namely, turbulent inflow, trailing edge and stall noise, are introduced. They are implemented into the in-house aeroelastic code HAWC2 commonly used for wind turbine load calculations...... and design. The results of the combined aeroelastic and aeroacoustic model are compared with field noise measurements of a 500kW wind turbine. Model and experimental data are in fairly good agreement in terms of noise levels and directivity. The combined model allows separating the various noise sources...

  15. Numerical Modeling and Simulation of Wind Blown Sand Morphology under Complex Wind-Flow Field

    National Research Council Canada - National Science Library

    Abdikerem, Xamxinur; Wang, Lei; Jin, Afang; Geni, Mamtimin

    2014-01-01

    ... the road surface height and air stream flow field, then three kinds of different models with different complex air flow fields are made for simulating the sand ripple formation process by weak coupling...

  16. Magnetic field measurements and wind-line variability of OB-type stars

    NARCIS (Netherlands)

    Schnerr, R.S.; Henrichs, H.F.; Neiner, C.; Verdugo, E.; de Jong, J.; Geers, V.C.; Wiersema, K.; van Dalen, B.; Tijani, A.; Plaggenborg, B.; Rygl, K.L.J.

    2008-01-01

    Context. The first magnetic fields in O- and B-type stars that do not belong to the Bp-star class, have been discovered. The cyclic UV wind-line variability, which has been observed in a significant fraction of early-type stars, is likely to be related to such magnetic fields. Aims. We attempt to

  17. Patterns of glaucomatous visual field loss in sita fields automatically identified using independent component analysis.

    Science.gov (United States)

    Goldbaum, Michael H; Jang, Gil-Jin; Bowd, Chris; Hao, Jiucang; Zangwill, Linda M; Liebmann, Jeffrey; Girkin, Christopher; Jung, Tzyy-Ping; Weinreb, Robert N; Sample, Pamela A

    2009-12-01

    To determine if the patterns uncovered with variational Bayesian-independent component analysis-mixture model (VIM) applied to a large set of normal and glaucomatous fields obtained with the Swedish Interactive Thresholding Algorithm (SITA) are distinct, recognizable, and useful for modeling the severity of the field loss. SITA fields were obtained with the Humphrey Visual Field Analyzer (Carl Zeiss Meditec, Inc, Dublin, California) on 1,146 normal eyes and 939 glaucoma eyes from subjects followed by the Diagnostic Innovations in Glaucoma Study and the African Descent and Glaucoma Evaluation Study. VIM modifies independent component analysis (ICA) to develop separate sets of ICA axes in the cluster of normal fields and the 2 clusters of abnormal fields. Of 360 models, the model with the best separation of normal and glaucomatous fields was chosen for creating the maximally independent axes. Grayscale displays of fields generated by VIM on each axis were compared. SITA fields most closely associated with each axis and displayed in grayscale were evaluated for consistency of pattern at all severities. The best VIM model had 3 clusters. Cluster 1 (1,193) was mostly normal (1,089, 95% specificity) and had 2 axes. Cluster 2 (596) contained mildly abnormal fields (513) and 2 axes; cluster 3 (323) held mostly moderately to severely abnormal fields (322) and 5 axes. Sensitivity for clusters 2 and 3 combined was 88.9%. The VIM-generated field patterns differed from each other and resembled glaucomatous defects (eg, nasal step, arcuate, temporal wedge). SITA fields assigned to an axis resembled each other and the VIM-generated patterns for that axis. Pattern severity increased in the positive direction of each axis by expansion or deepening of the axis pattern. VIM worked well on SITA fields, separating them into distinctly different yet recognizable patterns of glaucomatous field defects. The axis and pattern properties make VIM a good candidate as a preliminary process for

  18. Analysis of Wind Vorticity and Divergence in the High-latitude Lower Thermosphere: Dependence on the Interplanetary Magnetic Field (IMF

    Directory of Open Access Journals (Sweden)

    Young-Sil Kwak

    2008-12-01

    Full Text Available To better understand the physical processes that control the high-latitude lower thermospheric dynamics, we analyze the divergence and vorticity of the high-latitude neutral wind field in the lower thermosphere during the southern summertime for different IMF conditions. For this study the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEG CM is used. The analysis of the large-scale vorticity and divergence provides basic understanding flow configurations to help elucidate the momentum sources that ultimately determine the total wind field in the lower polar thermosphere and provides insight into the relative strengths of the different sources of momentum responsible for driving winds. The mean neutral wind pattern in the high-latitude lower thermosphere is dominated by rotational flow, imparted primarily through the ion drag force, rather than by divergent flow, imparted primarily through Joule and solar heating. The difference vorticity, obtained by subtracting values with zero IMF from those with non-zero IMF, in the high-latitude lower thermosphere is much larger than the difference divergence for all IMF conditions, indicating that a larger response of the thermospheric wind system to enhancement in the momentum input generating the rotational motion with elevated IMF than the corresponding energy input generating the divergent motion. the difference vorticity in the high-latitude lower thermosphere depends on the direction of the IMF. The difference vorticity for negative and positive B_y shows positive and negative, respectively, at higher magnetic latitudes than -70°. For negative B_z, the difference vorticities have positive in the dusk sector and negative in the dawn sector. The difference vorticities for positive B_z have opposite sign. Negative IMF B_z has a stronger effect on the vorticity than does positive B_z.

  19. Localized magnetic fields in arbitrary directions using patterned nanomagnets.

    Science.gov (United States)

    McNeil, Robert P G; Schneble, R Jeff; Kataoka, Masaya; Ford, Christopher J B; Kasama, Takeshi; Dunin-Borkowski, Rafal E; Feinberg, Joshua M; Harrison, Richard J; Barnes, Crispin H W; Tse, Desmond H Y; Trypiniotis, Theodossis; Bland, J Anthony C; Anderson, David; Jones, Geb A C; Pepper, Michael

    2010-05-12

    Control of the local magnetic fields desirable for spintronics and quantum information technology is not well developed. Existing methods produce either moderately small local fields or one field orientation. We present designs of patterned magnetic elements that produce remanent fields of 50 mT (potentially 200 mT) confined to chosen, submicrometer regions in directions perpendicular to an external initializing field. A wide variety of magnetic-field profiles on nanometer scales can be produced with the option of applying electric fields, for example, to move a quantum dot between regions where the magnetic-field direction or strength is different. We have confirmed our modeling by measuring the fields in one design using electron holography.

  20. Wind-driven circulation patterns in a shallow estuarine lake: St Lucia, South Africa

    Science.gov (United States)

    Schoen, Julia H.; Stretch, Derek D.; Tirok, Katrin

    2014-06-01

    The spatiotemporal structure of wind-driven circulation patterns and associated water exchanges or residence times can drive important bio-hydrodynamic interactions in shallow lakes and estuaries. The St Lucia estuarine lake in South Africa is an example of such a system. It is a UNESCO World Heritage Site and RAMSAR wetland of international importance but no detailed research on its circulation patterns has previously been undertaken. In this study, a hydrodynamic model was used to investigate the structure of these circulations to provide insights into their role in transport and water exchange processes. A strong diurnal temporal pattern of wind speeds, together with directional switching between two dominant directions, drives intermittent water exchanges and mixing between the lake basins. “High speed flows in shallow nearshore areas with slower upwind counter-flows in deeper areas, linked by circulatory gyres, are key features of the circulation”. These patterns are strongly influenced by the complex geometry of St Lucia and constrictions in the system. Water exchange time scales are non-homogeneous with some basin extremities having relatively long residence times. The influence of the circulation patterns on biological processes is discussed.

  1. Reduction of the Random Variables of the Turbulent Wind Field

    DEFF Research Database (Denmark)

    Sichani, Mahdi Teimouri; Nielsen, Søren R.K.

    2012-01-01

    Applicability of the Probability Density Evolution Method (PDEM) for realizing evolution of the probability density for the wind turbines has rather strict bounds on the basic number of the random variables involved in the model. The efficiency of most of the Advanced Monte Carlo (AMC) methods, i.......e. Importance Sampling (IS) or Subset Simulation (SS), will be deteriorated on problems with many random variables. The problem with PDEM is that a multidimensional integral has to be carried out over the space defined by the random variables of the system. The numerical procedure requires discretization...... of the integral domain; this becomes increasingly difficult as the dimensions of the integral domain increase. On the other hand efficiency of the AMC methods is closely dependent on the design points of the problem. Presence of many random variables may increase the number of the design points, hence affects...

  2. Interaction of solar wind with Mercury and its magnetic field. [as observed by Mariner 10 space probe

    Science.gov (United States)

    Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

    1976-01-01

    A brief review is presented of magnetic field and solar wind electron observations by Mariner 10 spacecraft. The intrinsic magnetic field of the planet Mercury and the implications of such a field for the planetary interior are also discussed.

  3. Suspended sediment diffusion mechanisms in the Yangtze Estuary influenced by wind fields

    Science.gov (United States)

    Wang, Lihua; Zhou, Yunxuan; Shen, Fang

    2018-01-01

    The complexity of suspended sediment concentration (SSC) distribution and diffusion has been widely recognized because it is influenced by sediment supply and various hydrodynamic forcing conditions that vary over space and over time. Sediment suspended by waves and transported by currents are the dominant sediment transport mechanisms in estuarine and coastal areas. However, it is unclear to what extent the SSC distribution is impacted by each hydrodynamic factor. Research on the quantitative influence of wind fields on the SSC diffusion range will contribute to a better understanding of the characteristics of sediment transport change and sedimentary geomorphic evolution. This study determined SSC from three Envisat Medium-Resolution Imaging Spectrometer acquisitions, covering the Yangtze Estuary and adjacent water area under the same season and tidal conditions but with varying wind conditions. SSC was examined based on the Semi-Empirical Radiative Transfer model, which has been well validated with the observation data. Integrating the corresponding wind field information from European Centre for Medium-Range Weather Forecasts further facilitated the discussion of wind fields affecting SSC, and in turn the influence of water and suspended sediment transportation and diffusion in the Yangtze estuarine and coastal area. The results demonstrated that the SSC present much more distinctive fluvial features in the inner estuary and wind fields are one of the major factors controlling the range of turbid water diffusion.

  4. Bidirectional ionic wind in nonpremixed counterflow flames with DC electric fields

    KAUST Repository

    Park, Daegeun

    2016-05-05

    Under an electric field, ions in the reaction zone of a flame generate a bulk flow motion called ionic wind. Because the majority of ions are positive, ionic wind is commonly considered to be unidirectional toward the cathode. A more thorough understanding of the effects of electric fields on flames could be obtained by clarifying the role of minor negative ions in the ionic wind. Here, we report on the effects of direct current on nonpremixed counterflow flames by visualizing the ionic wind. We found that the original flow field separates near the flame when it locates at a flow stagnation plane, resulting in a double-stagnant flow configuration. This evidences a bidirectional ionic wind blowing from the flame to both the cathode and the anode due to the positive and the negative ions, respectively. Meanwhile, an electric body force pulls the flame toward the cathode. Thus, the electric field affects the strain rate and the axial location of the stoichiometry, which are important for characterizing nonpremixed counterflow flames. In addition, measurement of the electric current density roughly showed a nearly saturated current when these flames restabilized under relatively high voltage. Detailed explanations of flame behavior, electric currents, and flow characteristics of various fuels are discussed in this study.

  5. Patterns of visual field changes in thyroid eye disease.

    Science.gov (United States)

    Choi, Catherine J; Oropesa, Susel; Callahan, Alison B; Glass, Lora R; Teo, Livia; Cestari, Dean M; Kazim, Michael; Freitag, Suzanne K

    2017-08-01

    This article provides a systematic description of visual field changes in thyroid eye disease-compressive optic neuropathy (TED-CON). A retrospective, non-comparative chart review of patients with TED-CON and documented Humphrey Visual Field 24-2 or 30-2 testing was conducted with IRB approval. Ninety-six visual fields in 68 patients were classified into 7 broad categories (superior, inferior, diffuse, temporal, nasal, central/paracentral, enlarged blind spot) and 17 mutually exclusive patterns from the Ocular Hypertension Treatment Study (OHTS) or "other." Fifty-three of 96 visual fields (55%) showed an inferior defect using the broad categories, with the remaining 6 categories ranging from 2% to 14%. The five most common OHTS patterns were other (28%), partial arcuate (28%), partial peripheral rim (9%), arcuate (8%) and altitudinal (7%). Further sub-classification showed a predominance of inferior visual field defects, ranging from 33% to 93% of each category. Of the 78 visual fields in these five categories combined, 52 (67%) were inferior defects. Inferior defect is the most typical TED-CON-associated visual field change. While the OHTS categories are geared toward classification of glaucomatous patterns, the overall predominance of inferior field defects in TED-CON was clearly demonstrated. These "other" visual field changes showing central inferior defect up to but not crossing the horizontal meridian and not contiguous from blind spot to nasal meridian should be designated as "TED-CON pattern." The high proportion of visual fields falling under the "other" category, however, does demonstrate the need for a more specific and tailored visual field classification system for TED-CON.

  6. Circulation Patterns identified by spatial rainfall and ocean wave fields in Southern Africa

    Directory of Open Access Journals (Sweden)

    Andras eBardossy

    2015-04-01

    Full Text Available This paper presents the applications of Fuzzy Rule Based Circulation Patterns (CPs classification in the description and modelling of two different physical consequences of their form: Rainfall regimes and Wind generated Ocean Waves. The choice of the CP groupings is made by searching for those CPs which generate (i different daily rainfall patterns over mesoscale regions and (ii wave directions and heights at chosen shoreline locations. The method used to choose the groupings of CPs is a bottom-up methodology using simulated annealing, ensuring that the causative CPs are responsible for the character of the results. This approach is in marked distinction to the top-down approaches such as k-means clustering or Self Organising Maps (SOMS to identify several classes of CPs and then finding the effects of those CPs on the variables of choice on given historical days. The CP groups we define are quite different for the two phenomena rainfall and waves, simply because different details of the pressure fields are responsible for wind and for precipitation. Large ocean waves are typically generated over fetches of the order of thousands of kilometres far off shore, whereas rainfall is generated by local atmospheric variables including temperature, humidity, wind speed and radiation over the area of concern. The spatial representativeness of the CPs is discussed and classifications obtained for different regions are compared. The paper gives examples of applications of the ideas over South Africa.

  7. Winds in the high-latitude lower thermosphere: Dependence on the interplanetary magnetic field

    DEFF Research Database (Denmark)

    Richmond, A.D.; Lathuillere, C.; Vennerstrøm, Susanne

    2003-01-01

    /s. The correlation between the IMF B-z component and the diurnal harmonic of the winds is generally best when the IMF is averaged over the preceding 1-4.5 hours. The magnetic-zonal-mean zonal wind below 120 km correlates best with the IMF B-y component when the latter is averaged over approximately the preceding 20...... of similar to20 hours, a B-y-dependent magnetic-zonal-mean zonal wind generally exists, with maximum wind speeds at 80 magnetic latitude, typically 10 m/s at 105 km, increasing to about 60 m/s at 123 km and 80 m/s at 200 km. In the southern hemisphere the wind is cyclonic when the time-averaged B......[1] Wind observations in the summertime lower thermosphere at high southern latitudes, measured by the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite, are statistically analyzed in magnetic coordinates and correlated with the interplanetary magnetic field (IMF...

  8. Filament formation in wind-cloud interactions- II. Clouds with turbulent density, velocity, and magnetic fields

    Science.gov (United States)

    Banda-Barragán, W. E.; Federrath, C.; Crocker, R. M.; Bicknell, G. V.

    2018-01-01

    We present a set of numerical experiments designed to systematically investigate how turbulence and magnetic fields influence the morphology, energetics, and dynamics of filaments produced in wind-cloud interactions. We cover 3D, magnetohydrodynamic systems of supersonic winds impacting clouds with turbulent density, velocity, and magnetic fields. We find that lognormal density distributions aid shock propagation through clouds, increasing their velocity dispersion and producing filaments with expanded cross-sections and highly magnetized knots and subfilaments. In self-consistently turbulent scenarios, the ratio of filament to initial cloud magnetic energy densities is ∼1. The effect of Gaussian velocity fields is bound to the turbulence Mach number: Supersonic velocities trigger a rapid cloud expansion; subsonic velocities only have a minor impact. The role of turbulent magnetic fields depends on their tension and is similar to the effect of radiative losses: the stronger the magnetic field or the softer the gas equation of state, the greater the magnetic shielding at wind-filament interfaces and the suppression of Kelvin-Helmholtz instabilities. Overall, we show that including turbulence and magnetic fields is crucial to understanding cold gas entrainment in multiphase winds. While cloud porosity and supersonic turbulence enhance the acceleration of clouds, magnetic shielding protects them from ablation and causes Rayleigh-Taylor-driven subfilamentation. Wind-swept clouds in turbulent models reach distances ∼15-20 times their core radius and acquire bulk speeds ∼0.3-0.4 of the wind speed in one cloud-crushing time, which are three times larger than in non-turbulent models. In all simulations, the ratio of turbulent magnetic to kinetic energy densities asymptotes at ∼0.1-0.4, and convergence of all relevant dynamical properties requires at least 64 cells per cloud radius.

  9. On the flow, thermal field and winds along the western continental shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Shenoi, S.S.C.

    Research, Vt}l. 13, No. 4, pp. 425439, 1993. 027~4343/93 $6.00 + 0.00 Printed in Great Britain. Q 1993 Pergamon Press Ltd On the flow, thermal field and winds along the western continental shelf of India M. K. ANTONY* and S. S. C. SHENOI* (Received 14... continental shelf of India were analysed for mean flow characteristics and for their possible relationship with wind and mass field. The analyses show that the mean alongshore flows IV) during May and March are towards south and during November, towards...

  10. Denmarks future as leading centre of competence within the field of wind power

    Energy Technology Data Exchange (ETDEWEB)

    2008-07-01

    Megavind has developed the present report with the intention of assessing the challenges involved, if Denmark is to maintain its position as an internationally leading centre of competence within the field of wind power. Furthermore, with the report, the partnership Megavind also wishes to point out specific initiatives within testing, demonstration, innovation and research as well as presenting recommendations for a strengthened effort within education that can take part in developing Denmark as an internationally leading centre of competence within the field of wind power. (au)

  11. Full-Scale Field Test of a Blade-Integrated Dual-Telescope Wind Lidar

    DEFF Research Database (Denmark)

    Pedersen, Anders Tegtmeier; Sjöholm, Mikael; Angelou, Nikolas

    -dimensional plane upwind was installed in the turbine and the first results from these experiments will be presented in another EWEA 2013 contribution. The lidar logged the raw Doppler spectra and the wind speed estimation was done subsequently using software designed specifically for the blade-mounted lidar......-rotation of the telescopes and the wind turbine blade. Because of the placement 15 m down the blade the measured speeds are high, typically in excess of 25 m/s. However, the lidar can measure up to about 40 m/s and has no difficulties measuring the required speeds. In addition to providing interesting information about...... in the top and bottom of the rotor plane. Conclusion We present here what we believe is the first successful wind speed measurements from a dual-telescope lidar installed on the blade of an operating wind turbine. The full-scale field test performed in the summer of 2012 has clearly demonstrated...

  12. Temporally-patterned magnetic fields induce complete fragmentation in planaria.

    Directory of Open Access Journals (Sweden)

    Nirosha J Murugan

    Full Text Available A tandem sequence composed of weak temporally-patterned magnetic fields was discovered that produced 100% dissolution of planarian in their home environment. After five consecutive days of 6.5 hr exposure to a frequency-modulated magnetic field (0.1 to 2 µT, immediately followed by an additional 6.5 hr exposure on the fifth day, to another complex field (0.5 to 5 µT with exponentially increasing spectral power 100% of planarian dissolved within 24 hr. Reversal of the sequence of the fields or presentation of only one pattern for the same duration did not produce this effect. Direct video evidence showed expansion (by visual estimation ∼twice normal volume of the planarian following the first field pattern followed by size reduction (estimated ∼1/2 of normal volume and death upon activation of the second pattern. The contortions displayed by the planarian during the last field exposure suggest effects on contractile proteins and alterations in the cell membrane's permeability to water.

  13. Effect of stellar wind induced magnetic fields on planetary obstacles of non-magnetized hot Jupiters

    Science.gov (United States)

    Erkaev, N. V.; Odert, P.; Lammer, H.; Kislyakova, K. G.; Fossati, L.; Mezentsev, A. V.; Johnstone, C. P.; Kubyshkina, D. I.; Shaikhislamov, I. F.; Khodachenko, M. L.

    2017-10-01

    We investigate the interaction between the magnetized stellar wind plasma and the partially ionized hydrodynamic hydrogen outflow from the escaping upper atmosphere of non-magnetized or weakly magnetized hot Jupiters. We use the well-studied hot Jupiter HD 209458b as an example for similar exoplanets, assuming a negligible intrinsic magnetic moment. For this planet, the stellar wind plasma interaction forms an obstacle in the planet's upper atmosphere, in which the position of the magnetopause is determined by the condition of pressure balance between the stellar wind and the expanded atmosphere, heated by the stellar extreme ultraviolet radiation. We show that the neutral atmospheric atoms penetrate into the region dominated by the stellar wind, where they are ionized by photoionization and charge exchange, and then mixed with the stellar wind flow. Using a 3D magnetohydrodynamic (MHD) model, we show that an induced magnetic field forms in front of the planetary obstacle, which appears to be much stronger compared to those produced by the solar wind interaction with Venus and Mars. Depending on the stellar wind parameters, because of the induced magnetic field, the planetary obstacle can move up to ≈0.5-1 planetary radii closer to the planet. Finally, we discuss how estimations of the intrinsic magnetic moment of hot Jupiters can be inferred by coupling hydrodynamic upper planetary atmosphere and MHD stellar wind interaction models together with UV observations. In particular, we find that HD 209458b should likely have an intrinsic magnetic moment of 10-20 per cent that of Jupiter.

  14. Wind-induced transmission tower foundation loads. A field study-design code comparison

    Energy Technology Data Exchange (ETDEWEB)

    Savory, E. [Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ont. (Canada); Parke, G.A.R.; Disney, P.; Toy, N. [School of Engineering, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

    2008-06-15

    This paper presents a comparison between the wind-induced foundation loads measured on a type L6 transmission line tower during a field study in the UK and those computed using the UK Code of Practice for lattice tower and transmission line design (BS8100). In this work, the Code provisions have been generalised to give the wind-induced strain in each of the tower legs immediately above the foundation as a function of wind direction and wind speed at the top of the tower. The complete data set from the field monitoring has been decomposed to provide a similar formulation for comparison purposes. The analysis shows excellent agreement between the Code calculations and the measured results, within the overall accuracy of the field data. This indicates that, at least for the tower type examined here, the existing design Code provides a reliable transformation of the local wind speed at the top of the tower into tension and compression loads on the foundations. (author)

  15. Configuration and Evaluation of a Dual-Doppler 3-D Wind Field System

    Science.gov (United States)

    Crawford, Winifred C.

    2014-01-01

    Current LSP, GSDO, and SLS space vehicle operations are halted when wind speeds from specific directions exceed defined thresholds and when lightning is a threat. Strong winds and lightning are difficult parameters for the 45th Weather Squadron (45 WS) to forecast, yet are important in the protection of customer vehicle operations and the personnel that conduct them. A display of the low-level horizontal wind field to reveal areas of high winds or convergence would be a valuable tool for forecasters in assessing the timing of high winds, or convection initiation and subsequent lightning occurrence. This is especially important for areas where no weather observation platforms exist. Developing a dual-Doppler radar capability would provide such a display to assist forecasters in predicting high winds and convection initiation. The wind fields can also be used to initialize a local mesoscale numerical weather prediction model to help improve the model forecast winds, convection initiation, and other phenomena. The 45 WS and NWS MLB tasked the Applied Meteorology Unit (AMU) to develop a dual- Doppler wind field display using data from the 45th Space Wing radar, known as the Weather Surveillance Radar (WSR), NWS MLB Weather Surveillance Radar 1988 Doppler (KMLB), and the Orlando International Airport Terminal Doppler Weather Radar (KMCO). They also stipulated that the software used should be freely available. The AMU evaluated two software packages and, with concurrence from NWS MLB and the 45 WS, chose the Warning Decision Support System-Integrated Information (WDSS-II). The AMU collected data from two significant weather cases: a tornadic event on 14 April 2013 and a severe wind and hail event on 12 February 2014. For the 14 April case, the data were from WSR and KMLB. For the 12 February case, the data were from KMCO and KMLB. The AMU installed WDSS-II on a Linux PC, then processed and quality controlled the radar data for display and analysis using WDSS-II tools

  16. Recognizing patterns of visual field loss using unsupervised machine learning.

    Science.gov (United States)

    Yousefi, Siamak; Goldbaum, Michael H; Zangwill, Linda M; Medeiros, Felipe A; Bowd, Christopher

    2014-03-21

    Glaucoma is a potentially blinding optic neuropathy that results in a decrease in visual sensitivity. Visual field abnormalities (decreased visual sensitivity on psychophysical tests) are the primary means of glaucoma diagnosis. One form of visual field testing is Frequency Doubling Technology (FDT) that tests sensitivity at 52 points within the visual field. Like other psychophysical tests used in clinical practice, FDT results yield specific patterns of defect indicative of the disease. We used Gaussian Mixture Model with Expectation Maximization (GEM), (EM is used to estimate the model parameters) to automatically separate FDT data into clusters of normal and abnormal eyes. Principal component analysis (PCA) was used to decompose each cluster into different axes (patterns). FDT measurements were obtained from 1,190 eyes with normal FDT results and 786 eyes with abnormal (i.e., glaucomatous) FDT results, recruited from a university-based, longitudinal, multi-center, clinical study on glaucoma. The GEM input was the 52-point FDT threshold sensitivities for all eyes. The optimal GEM model separated the FDT fields into 3 clusters. Cluster 1 contained 94% normal fields (94% specificity) and clusters 2 and 3 combined, contained 77% abnormal fields (77% sensitivity). For clusters 1, 2 and 3 the optimal number of PCA-identified axes were 2, 2 and 5, respectively. GEM with PCA successfully separated FDT fields from healthy and glaucoma eyes and identified familiar glaucomatous patterns of loss.

  17. [Distribution of Regional Pollution and the Characteristics of Vertical Wind Field in the Pearl River Delta].

    Science.gov (United States)

    Liu, Jian; Wu, Dui; Fan, Shao-jia

    2015-11-01

    Based on the data of hourly PM2.5 concentration of 56 environmental monitoring stations and 9 cities over the Pearl River Delta (PRD) region, the distributions of PM2.5 pollution in PRD region were analyzed by systematic cluster analysis and correlational analysis. It was found that the regional pollution could be divided into 3 types. The first type was the pollution occurred in Dongguan, Guangzhou, Foshan and Jiangmen (I type), and the second type was the pollution occurred in Zhongshan, Zhuhai, Shenzhen and Huizhou (II type), while the last type was the pollution only occurred in Zhaoqing (III type). During the study period, they occurred 47, 7 and 128 days, respectively. During events of pollution type I, except Zhuhai, Shenzhen and Huizhou, the PM2.5 concentrations of other cities were generally high, while the PM2.5 concentration in whole PRD region was over 50.0 μg x m(-3) during events of pollution type II. The regions with higher PM2.5 concentration was mainly concentrated in Zhaoqing, Guangzhou and Foshan during events of pollution type III. The wind data from 4 wind profile radars located in PRD region was used to study the characteristics of vertical wind field of these 3 pollution types. It was found that the wind profiles of type I and III were similar that low layer and high layer were controlled by the southeast wind and the southwest wind, respectively. For type II, the low layer and high layer were influenced by northerly wind and westerly wind, respectively. Compared with other types, the wind speed and ventilation index of type II. were much higher, and the variation of wind direction at lower-middle-layer was much smaller. When PRD region was influenced by northerly winds, the PM2.5 concentration in the entire PRD region was higher. When PRD region was controlled by southeast wind, the PM2.5 concentrations of I and II areas were relatively lower, while the pollution in III area was relatively heavier.

  18. Measuring electromagnetic fields (EMF) around wind turbines in Canada: is there a human health concern?

    Science.gov (United States)

    2014-01-01

    Background The past five years has seen considerable expansion of wind power generation in Ontario, Canada. Most recently worries about exposure to electromagnetic fields (EMF) from wind turbines, and associated electrical transmission, has been raised at public meetings and legal proceedings. These fears have not been based on any actual measurements of EMF exposure surrounding existing projects but appear to follow from worries from internet sources and misunderstanding of the science. Methods The study was carried out at the Kingsbridge 1 Wind Farm located near Goderich, Ontario, Canada. Magnetic field measurements were collected in the proximity of 15 Vestas 1.8 MW wind turbines, two substations, various buried and overhead collector and transmission lines, and nearby homes. Data were collected during three operational scenarios to characterize potential EMF exposure: ‘high wind’ (generating power), ‘low wind’ (drawing power from the grid, but not generating power) and ‘shut off’ (neither drawing, nor generating power). Results Background levels of EMF (0.2 to 0.3 mG) were established by measuring magnetic fields around the wind turbines under the ‘shut off’ scenario. Magnetic field levels detected at the base of the turbines under both the ‘high wind’ and ‘low wind’ conditions were low (mean = 0.9 mG; n = 11) and rapidly diminished with distance, becoming indistinguishable from background within 2 m of the base. Magnetic fields measured 1 m above buried collector lines were also within background (≤ 0.3 mG). Beneath overhead 27.5 kV and 500 kV transmission lines, magnetic field levels of up to 16.5 and 46 mG, respectively, were recorded. These levels also diminished rapidly with distance. None of these sources appeared to influence magnetic field levels at nearby homes located as close as just over 500 m from turbines, where measurements immediately outside of the homes were ≤ 0.4 mG. Conclusions The results suggest that there is

  19. Flow field and load characteristics of the whole MEXICO wind turbine

    DEFF Research Database (Denmark)

    Xu, Haoran; Yang, Hua; Liu, Chao

    2017-01-01

    CFD(Computational Fluid Dynamics) method was used to perform steady numerical simulation investigation on the flow field and load characteristics of MEXICO(Model EXperiment In Controlled cOnditions) wind turbine under non-yawed condition. Circumferentially-Averaged method was used to extract the ...

  20. Armature reaction effects on a high temperature superconducting field winding of an synchronous machine: experimental results

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Jensen, Bogi Bech

    2014-01-01

    sensitivity to both armature reaction intensity and angular position with respect to the HTS coils. Furthermore, the characterization of the HTS field winding has been correlated to the electromagnetic torque of the machine where the maximal Ic reduction of 21% has been observed for the maximum torque....

  1. Near-field to far-field characterization of speckle patterns generated by disordered nanomaterials

    CERN Document Server

    Parigi, Valentina; Binard, Guillaume; Bourdillon, Céline; Maître, Agnès; Carminati, Rémi; Krachmalnicoff, Valentina; De Wilde, Yannick

    2016-01-01

    We study the intensity spatial correlation function of optical speckle patterns above a disordered dielectric medium in the multiple scattering regime. The intensity distributions are recorded by scanning near-field optical microscopy (SNOM) with sub-wavelength spatial resolution at variable distances from the surface in a range which spans continuously from the near-field (distance $ \\ll \\lambda $) to the far-field regime (distance $\\gg \\lambda $). The non-universal behavior at sub-wavelength distances reveals the connection between the near-field speckle pattern and the internal structure of the medium.

  2. Near-field to far-field characterization of speckle patterns generated by disordered nanomaterials.

    Science.gov (United States)

    Parigi, Valentina; Perros, Elodie; Binard, Guillaume; Bourdillon, Céline; Maître, Agnès; Carminati, Rémi; Krachmalnicoff, Valentina; De Wilde, Yannick

    2016-04-04

    We study the intensity spatial correlation function of optical speckle patterns above a disordered dielectric medium in the multiple scattering regime. The intensity distributions are recorded by scanning near-field optical microscopy (SNOM) with sub-wavelength spatial resolution at variable distances from the surface in a range which spans continuously from the near-field (distance ≪ λ) to the far-field regime (distance ≫ λ). The non-universal behavior at sub-wavelength distances reveals the connection between the near-field speckle pattern and the internal structure of the medium.

  3. Long-term variations of the mesospheric wind field at mid-latitudes

    Directory of Open Access Journals (Sweden)

    D. Keuer

    2007-08-01

    Full Text Available Continuous MF radar observations at the station Juliusruh (54.6° N; 13.4° E have been analysed for the time interval between 1990 and 2005, to obtain information about solar activity-induced variations, as well as long-term trends in the mesospheric wind field. Using monthly median values of the zonal and the meridional prevailing wind components, as well as of the amplitude of the semidiurnal tide, regression analyses have been carried out with a dependence on solar activity and time. The solar activity causes a significant amplification of the zonal winds during summer (increasing easterly winds and winter (increasing westerly winds. The meridional wind component is positively correlated with the solar activity during summer but during winter the correlation is very small and non significant. Also, the solar influence upon the amplitude of the semidiurnal tidal component is relatively small (in dependence on height partly positive and partly negative and mostly non-significant.

    The derived trends in the zonal wind component during summer are below an altitude of about 83 km negative and above this height positive. During the winter months the trends are nearly opposite compared with the trends in summer (transition height near 86 km. The trends in the meridional wind components are below about 85 km positive in summer (significant and near zero (nonsignificant in winter; above this height during both seasons negative trends have been detected. The trends in the semidiurnal tidal amplitude are at all heights positive, but only partly significant.

    The detected trends and solar cycle dependencies are compared with other experimental results and model calculations. There is no full agreement between the different results, probably caused by different measuring techniques and evaluation methods used. Also, different heights and observation periods investigated may contribute to the detected differences.

  4. Experience with field testing for model validation of GE wind plants

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N.; Hannett, L.; Clark, K.; MacDowell, J.; Barton, W. [GE Energy, Mississauga, ON (Canada)

    2007-07-01

    GE Energy recently conducted field tests on wind turbines using a suite of controls and electronics. Zero voltage ride through (ZVRT) and Volt/Var tests were performed on operating wind turbine generators (WTG) to determine fault tolerance. The Western Electricity Coordinating Council's (WECC) model validation results were used to examine voltage regulation and VAR management issues. GE's WindCONTROL supervisor controller system regulates voltage and power in real time. It supplies reactive power to the grid to regulate system voltage and stabilize grids. It was emphasized that model validation is becoming increasingly important as wind penetration increases. Development of stability models is ongoing and grid codes are driving increased functionality in wind plants. This presentation included graphs indicating WTG reactive power response; WTG voltage response; plant level Volt/Var tests; and, Volt/Var control. Field test simulation results were also presented. It was revealed that ZVRT test results met grid requirements. Volt/Var response of WTGs was extremely fast and stable. It was determined that the response to significant grid disturbances will produce maximum (or minimum) reactive power output within 200 ms. The stability models were shown to closely replicate plant performance. figs.

  5. Agent-based modelling of shifting cultivation field patterns, Vietnam

    DEFF Research Database (Denmark)

    Jepsen, Martin Rudbeck; Leisz, S.; Rasmussen, K.

    2006-01-01

    costs associated with fencing of fields, and are faced with physical constraints. The simulation results are compared with land-cover data obtained from remote sensing. Comparisons are made on patterns as detected visually and using the mean nearest-neighbour ratio. Baseline simulation outputs show high...

  6. Two-Dimensional Rotorcraft Downwash Flow Field Measurements by Lidar-Based Wind Scanners with Agile Beam Steering

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Angelou, Nikolas; Hansen, Per

    2014-01-01

    , and there is a need for instruments that can measure flow fields on scales larger than a few meters with good resolution. This paper reports on the use of synchronized continuous-wave Doppler lidars for rotorcraft downwash flow field studies. Built from a modified ZephIR wind lidar and a double-prism arrangement...... for agile beam steering, a wind scanner—WindScanner—has been developed at the Department ofWind Energy at the Technical University of Denmark (DTU) Risø campus. The WindScanner measures the line-of-sight component of the airflow remotely and by rapid steering, the line-of-sight direction and the focus...... and rescue helicopter are presented. Since the line-of-sight directions of the two synchronized WindScanners were scanned within the plane of interest, the influence of the wind component perpendicular to the plane was avoided. The results also demonstrate the possibilities within less demanding flows...

  7. Field and numerical study of wind and surface waves at short fetches

    Science.gov (United States)

    Baydakov, Georgy; Kuznetsova, Alexandra; Sergeev, Daniil; Papko, Vladislav; Kandaurov, Alexander; Vdovin, Maxim; Troitskaya, Yuliya

    2016-04-01

    Measurements were carried out in 2012-2015 from May to October in the waters of Gorky Reservoir belonging to the Volga Cascade. The methods of the experiment focus on the study of airflow in the close proximity to the water surface. The sensors were positioned at the oceanographic Froude buoy including five two-component ultrasonic sensors WindSonic by Gill Instruments at different levels (0.1, 0.85, 1.3, 2.27, 5.26 meters above the mean water surface level), one water and three air temperature sensors, and three-channel wire wave gauge. One of wind sensors (0.1 m) was located on the float tracking the waveform for measuring the wind speed in the close proximity to the water surface. Basic parameters of the atmospheric boundary layer (the friction velocity u∗, the wind speed U10 and the drag coefficient CD) were calculated from the measured profiles of wind speed. Parameters were obtained in the range of wind speeds of 1-12 m/s. For wind speeds stronger than 4 m/s CD values were lower than those obtained before (see eg. [1,2]) and those predicted by the bulk parameterization. However, for weak winds (less than 3 m/s) CD values considerably higher than expected ones. The new parameterization of surface drag coefficient was proposed on the basis of the obtained data. The suggested parameterization of drag coefficient CD(U10) was implemented within wind input source terms in WAVEWATCH III [3]. The results of the numerical experiments were compared with the results obtained in the field experiments on the Gorky Reservoir. The use of the new drag coefficient improves the agreement in significant wave heights HS [4]. At the same time, the predicted mean wave periods are overestimated using both built-in source terms and adjusted source terms. We associate it with the necessity of the adjusting of the DIA nonlinearity model in WAVEWATCH III to the conditions of the middle-sized reservoir. Test experiments on the adjusting were carried out. The work was supported by the

  8. Acoustic Tweezing and Patterning of Concentration Fields in Microfluidics

    Science.gov (United States)

    Karlsen, Jonas T.; Bruus, Henrik

    2017-03-01

    We demonstrate theoretically that acoustic forces acting on inhomogeneous fluids can be used to pattern and manipulate solute concentration fields into spatiotemporally controllable configurations stabilized against gravity. A theoretical framework describing the dynamics of concentration fields that weakly perturb the fluid density and speed of sound is presented and applied to study manipulation of concentration fields in rectangular-channel acoustic eigenmodes and in Bessel-function acoustic vortices. In the first example, methods to obtain horizontal and vertical multilayer stratification of the concentration field at the end of a flow-through channel are presented. In the second example, we demonstrate acoustic tweezing and spatiotemporal manipulation of a local high-concentration region in a lower-concentration medium, thereby extending the realm of acoustic tweezing to include concentration fields.

  9. Possibilities of Utilization the Risk – Based Techniques in the Field of Offshore Wind Power Plants

    Directory of Open Access Journals (Sweden)

    Przemysław Kacprzak

    2014-09-01

    Full Text Available In the article the risk-based concept that may be applicable to offshore wind power plants has been presented. The aim of the concept is to aid designers in the early design and retrofit phases of the project in case of lack or insufficient information in relevant international standards. Moreover the initial classification of components within main system parts of offshore wind power plant has been performed. Such classification is essential in order to apply risk-based concept. However further scientific researches need to be performed in that field to develop detailed concept useful for future practical applications.

  10. ValidWind applications: wind power prospecting, aerosol transport

    Science.gov (United States)

    Wilkerson, T.; Marchant, A.; Apedaile, T.; Scholes, D.; Simmons, J.; Bradford, B.

    2010-10-01

    The ValidWind™ system employs an XL200 laser rangefinder to track small, lightweight, helium-filled balloons (0.33 meters, 0.015 kg). We record their trajectories (range resolution 0.5 meters) and automatically produce local wind profiles in real time. Tracking range is enhanced beyond 2 km by applying retro-reflector tape to the balloons. Aerodynamic analysis shows that ValidWind balloon motion is well coupled to the local wind within relaxation times { 1 second, due to drag forces at subcritical Reynolds numbers Re wind as opposed to being fixed in space. In a field campaign involving many balloons, slight variations in ground level winds at launch lead to trajectory patterns that we analyze to derive 3D maps of the vertical and horizontal wind profiles downwind of the launch area. Field campaigns are focused on likely sites for wind power generation and on facilities from which airborne particulates are emitted. We describe results of wind measurements in Utah near the cities of Clarkston, Logan, and Ogden. ValidWind is a relatively inexpensive wind sensor that is easily and rapidly transported and deployed at remote sites. It is an ideal instrument for wind prospecting to support early decisions required, for example, in siting meteorology towers. ValidWind provides high-resolution, real time characterization of the average and changing 3D wind fields in which wind power turbines and other remote sensors must operate.

  11. Application of simulated lidar scanning patterns to constrained Gaussian turbulence fields for load validation

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Natarajan, Anand

    2017-01-01

    of this study, we assess the influence of the proposed method on the statistical uncertainty in wind turbine extreme and fatigue loads. The main conclusion is that introducing lidar measurements as turbulence constraints in load simulations may bring significant reduction in load and energy production...... uncertainty, not accounting for any additional uncertainty from real measurements. The constrained turbulence method is most efficient for prediction of energy production and loads governed by the turbulence intensity and the thrust force, while for other load components such as tower base side-to-side moment...... generated Gaussian turbulence fields in compliance with the Mann model for neutral stability. The expected efficiency of various scanning patterns is estimated by means of the explained variance associated with the constrained field. A numerical study is made using the HAWC2 aeroelastic software, whereby...

  12. Montgomery Potential and Wind Fields on Isentropic Surfaces from GPS Radio Occultation

    Science.gov (United States)

    Scherllin-Pirscher, Barbara; Steiner, Andrea; Kirchengast, Gottfried; Leroy, Stephen

    2015-04-01

    Atmospheric profiles from Global Positioning System (GPS) radio occultation (RO) measurements provide precise and accurate information on the thermal structure of the troposphere and lower stratosphere. Since altitude (and also geopotential height) is based on accurate knowledge of the position and velocity vectors of the transmitter and receiver satellites involved, it is possible to obtain highly resolved and accurate vertical information from RO. In this study we use observational data from 2007 to 2013 from the RO missions CHAMP, SAC-C, GRACE-A, and Formosat-3/COSMIC. Using potential temperature as the vertical coordinate we calculate monthly means of the Montgomery potential on isentropic surfaces from 300 K to 600 K (approximately 12 km to 24 km in altitude) with a horizontal resolution of 5° in latitude and 5° in longitude. Contours of the Montgomery potential on isentropic surfaces correspond to a stream-function for adiabatic, geostrophic flow. Subsequently we derive monthly mean geostrophic wind fields (outside the tropics) from sampling error-corrected fields of the Montgomery potential on isentropic surfaces. We find that these climatological RO wind fields clearly capture all of the main wind features with departures from analysis winds being, in general, smaller than 2 m s-1. Larger biases close to the subtropical jet and at high latitudes'biases rarely exceed 10 %'are caused by the geostrophic approximation. We present monthly mean wind fields, their annual cycle as well as inter-annual variability related to the El Niño-Southern Oscillation. This three-dimensional information of high quality from RO data can subsequently be utilized to investigate atmospheric dynamics close to the tropopause.

  13. Local and regional effects of large scale atmospheric circulation patterns on winter wind power output in Western Europe

    Science.gov (United States)

    Zubiate, Laura; McDermott, Frank; Sweeney, Conor; O'Malley, Mark

    2014-05-01

    Recent studies (Brayshaw, 2009, Garcia-Bustamante, 2010, Garcia-Bustamante, 2013) have drawn attention to the sensitivity of wind speed distributions and likely wind energy power output in Western Europe to changes in low-frequency, large scale atmospheric circulation patterns such as the North Atlantic Oscillation (NAO). Wind speed variations and directional shifts as a function of the NAO state can be larger or smaller depending on the North Atlantic region that is considered. Wind speeds in Ireland and the UK for example are approximately 20 % higher during NAO + phases, and up to 30 % lower during NAO - phases relative to the long-term (30 year) climatological means. By contrast, in southern Europe, wind speeds are 15 % lower than average during NAO + phases and 15 % higher than average during NAO - phases. Crucially however, some regions such as Brittany in N.W. France have been identified in which there is negligible variability in wind speeds as a function of the NAO phase, as observed in the ERA-Interim 0.5 degree gridded reanalysis database. However, the magnitude of these effects on wind conditions is temporally and spatially non-stationary. As described by Comas-Bru and McDermott (2013) for temperature and precipitation, such non-stationarity is caused by the influence of two other patterns, the East Atlantic pattern, (EA), and the Scandinavian pattern, (SCA), which modulate the position of the NAO dipole. This phenomenon has also implications for wind speeds and directions, which has been assessed using the ERA-Interim reanalysis dataset and the indices obtained from the PC analysis of sea level pressure over the Atlantic region. In order to study the implications for power production, the interaction of the NAO and the other teleconnection patterns with local topography was also analysed, as well as how these interactions ultimately translate into wind power output. The objective is to have a better defined relationship between wind speed and power

  14. Unexpected bat fatality patterns at a northeast BC wind energy facility

    Energy Technology Data Exchange (ETDEWEB)

    Paterson, Brian; Palmer, Charlie [Hemmera (Canada)

    2011-07-01

    This paper discusses bat fatality patterns due to wind energy projects, taking the North East BC wind energy project as an example. Migratory tree bats in that region include the hoary bat and the silver-haired bat. There were other bats which were seasonal migrants. The paper presents the inquiry process for estimating the fatality patterns. The results for 2010 showed 156 bat and 82 bird fatalities, of which 55% were non-migratory birds. This number increased to 75% in 2011, which was quite unexpected. It was noticed that migrant fatalities took place during the breeding season. The graph shows silver-haired bats and big brown bats had the highest number of fatalities among the migratory and non-migratory categories respectively. The fatality demographics reveal that the ratio of male sex local bats was high and the proportion female silver-haired bats was high. It is suggested that potential bat habitat should be identified and monitored from spring through fall and that the researched data be made available.

  15. On the use of mass-conserving wind fields in chemistry-transport models

    Directory of Open Access Journals (Sweden)

    B. Bregman

    2003-01-01

    Full Text Available A new method has been developed that provides mass-conserving wind fields for global chemistry-transport models. In previous global Eulerian modeling studies a mass-imbalance was found between the model mass transport and the surface pressure tendencies. Several methods have been suggested to correct for this imbalance, but so far no satisfactory solution has been found. Our new method solves these problems by using the wind fields in a spherical harmonical form (divergence and vorticity by mimicing the physics of the weather forecast model as closely as possible. A 3-D chemistry-transport model was used to show that the calculated ozone fields with the new processing method agree remarkably better with ozone observations in the upper troposphere and lower stratosphere. In addition, the calculated age of air in the lower stratosphere show better agreement with observations, although the air remains still too young in the extra-tropical stratosphere.

  16. Design of Offshore Wind Turbine Support Structures: Selected topics in the field of geotechnical engineering

    DEFF Research Database (Denmark)

    Bakmar, Christian LeBlanc

    .D. thesis was to enable low-cost and low-risk support structures to be designed in order to improve the economic feasibility of future offshore wind farms. The research work was divided in the following four selected research topics in the field of geotechnical engineering, relating to the monopile......-cost and low-risk support structures to be put into use. Overall, these outcomes are an important contribution to increase the economic feasibility of future offshore wind farms.......Breaking the dependence on fossil fuels offers many opportunities for strengthened competitiveness, technological development and progress. Offshore wind power is a domestic, sustainable and largely untapped energy resource that provides an alternative to fossil fuels, reduces carbon emissions...

  17. Particle Velocity Distributions and Large-Scale Electric Field in Solar Wind

    Science.gov (United States)

    Pavan, J.; Vinas, A. F.

    2016-12-01

    Velocity distributions of particles are key elements in the study of solar wind. The physical mechanisms that regulate their many features are a matter of debate. The present work addresses the subject with a fully analytical method in order to establish the shape of particle velocity distributions in solar wind. The method consists in solving the steady-state kinetic equation for particles and the related fluid equations, assigning spatial profiles for density and temperature matching observational data. The model is one-dimensional in configuration-space and two-dimensional in velocity-space, and accounts for large-scale processes, namely, advection, gravity, magnetic mirroring and the large-scale ambipolar electric field, without the aid of wave-particle interactions or collisions. The findings reported add to the general understanding of regulation of particle distributions in solar wind and to the predictions of their shape in regions restricted for in situ measurements.

  18. Wind tunnel and field assessment of pollen dispersal in soybean [Glycine max (L.) Merr.].

    Science.gov (United States)

    Yoshimura, Yasuyuki

    2011-01-01

    Although genetically modified (GM) soybean has never been cultivated commercially in Japan, it is essential to set up the isolation distance required to prevent out-crossing between GM and conventional soybean in preparation for any future possibility of pollen transfer. The airborne soybean pollen was sampled using some Durham pollen samplers located in the range of 20 m from the field edge. In addition, the dispersal distance was assessed in a wind tunnel under constant air flow and then it was compared with the anticipated distances based on the pollen diameter. In the field, the maximum pollen density per day observed was 1.235 grains cm(-2) day(-1) at three observation points within 2.5 m from the field and inside the field the mean density did not reach the rate of 1 grain cm(-2 )day(-1) during 19 flowering days. The results of the wind tunnel experiment also showed that the plants had almost no airborne release of pollen and the dispersal distance was shorter than theoretical value due to clustered dispersal. This study showed little airborne pollen in and around the soybean field and the dispersal is restricted to a small area. Therefore, wind-mediated pollination appears to be negligible.

  19. A model to relate wind tunnel measurements to open field odorant emissions from liquid area sources

    Science.gov (United States)

    Lucernoni, F.; Capelli, L.; Busini, V.; Sironi, S.

    2017-05-01

    Waste Water Treatment Plants are known to have significant emissions of several pollutants and odorants causing nuisance to the near-living population. One of the purposes of the present work is to study a suitable model to evaluate odour emissions from liquid passive area sources. First, the models describing volatilization under a forced convection regime inside a wind tunnel device, which is the sampling device that typically used for sampling on liquid area sources, were investigated. In order to relate the fluid dynamic conditions inside the hood to the open field and inside the hood a thorough study of the models capable of describing the volatilization phenomena of the odorous compounds from liquid pools was performed and several different models were evaluated for the open field emission. By means of experimental tests involving pure liquid acetone and pure liquid butanone, it was verified that the model more suitable to describe precisely the volatilization inside the sampling hood is the model for the emission from a single flat plate in forced convection and laminar regime, with a fluid dynamic boundary layer fully developed and a mass transfer boundary layer not fully developed. The proportionality coefficient for the model was re-evaluated in order to account for the specific characteristics of the adopted wind tunnel device, and then the model was related with the selected model for the open field thereby computing the wind speed at 10 m that would cause the same emission that is estimated from the wind tunnel measurement furthermore, the field of application of the proposed model was clearly defined for the considered models during the project, discussing the two different kinds of compounds commonly found in emissive liquid pools or liquid spills, i.e. gas phase controlled and liquid phase controlled compounds. Lastly, a discussion is presented comparing the presented approach for emission rates recalculation in the field, with other approaches

  20. Report on the field test project for wind power development at Oshima Village (wind characteristics investigation); Oshimamura ni okeru furyoku kaihatsu field test jigyo (fukyo seisa) hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-11-01

    Wind characteristics are observed for a year at Oshima City, Fukuoka Prefecture. The annual average wind speed is 6.7m/s at 20m above ground, reflecting the general trend in Japan's climate that wind is strong in the cold season and weak in the warm season. The wind direction occurrence rate is the highest of 13.2% in the ENE direction. Now that the occurrence of the NE, SW, and WSW directions occupying the same wind axis is also high throughout the year, Oshima Village is suitable for wind turbine installation. Since the wind speed is high in the high-occurrence NE-ESE directions, the relation between the wind direction occurrence rate and wind speed is said to be convenient. The conditions for a success in wind power development, that the wind speed be 5.8m/s or more and energy density 215W/m{sup 2} or more at an altitude of 20m above the ground, are satisfied at this observation station. As for the operation rate and capacity ratio of each of 150kW, 300kW, and 750kW wind turbine models, they are all over the reference values. The site is highly promising as a wind power development site because all the wind turbine availability conditions, such as the annual average wind speed, annual wind energy density, operating rate, and capacity ratio are found to be better than the reference values.

  1. On the Use of Coupled Wind, Wave, and Current Fields in the Simulation of Loads on Bottom-Supported Offshore Wind Turbines during Hurricanes: March 2012 - September 2015

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eungsoo [Univ. of Texas, Austin, TX (United States); Manuel, Lance [Univ. of Texas, Austin, TX (United States); Curcic, Milan [Univ. of Miami, Coral Gables, FL (United States); Chen, Shuyi S. [Univ. of Miami, Coral Gables, FL (United States); Phillips, Caleb [National Renewable Energy Lab. (NREL), Golden, CO (United States); Veers, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-06-01

    In the United States, potential offshore wind plant sites have been identified along the Atlantic seaboard and in the Gulf of Mexico. It is imperative that we define external conditions associated with hurricanes and severe winter storms and consider load cases for which wind turbines may need to be designed. We selected two hurricanes, Ike (2008) and Sandy (2012), and investigated the effect these tropical storms would have on bottom-supported offshore wind turbines that were hypothetically in or close to their path as they made landfall. For realistic turbine loads assessment, it is important that the coupled influences of the changing wind, wave, and current fields are simulated throughout the evolution of the hurricanes. We employed a coupled model--specifically, the University of Miami Coupled Model (UMCM)--that integrates atmospheric, wave, and ocean components to produce needed wind, wave, and current data. The wind data are used to generate appropriate vertical wind profiles and full wind velocity fields including turbulence; the current field over the water column is obtained by interpolated discrete output current data; and short-crested irregular second-order waves are simulated using output directional wave spectra from the coupled model. We studied two monopile-supported offshore wind turbines sited in 20 meters of water in the Gulf of Mexico to estimate loads during Hurricane Ike, and a jacket space-frame platform-supported offshore wind turbine sited in 50 meters of water in the mid-Atlantic region to estimate loads during Hurricane Sandy. In this report we discuss in detail how the simulated hurricane wind, wave, and current output data are used in turbine loads studies. In addition, important characteristics of the external conditions are studied, including the relative importance of swell versus wind seas, aerodynamic versus hydrodynamic forces, current velocity effects, yaw control options for the turbine, hydrodynamic drag versus inertia forces

  2. Simulations of Wind Field Effect on Two-Stream Waves in the Equatorial Electrojet

    Directory of Open Access Journals (Sweden)

    Chi-Lon Fern

    2009-01-01

    Full Text Available The wind field effect on the phase veloc i ties of 3- to 10-me ter Farley-Buneman two-stream waves in the equato rial E region ion o sphere at al titudes in the range of 95 - 110 km is stud ied by nu mer i cal simu la tion. The behav ior of this two-stream wave in the uni form wind field Un in a plane per pen dic u lar to the Earth’s mag netic field is simu lated with a two-di men sional two-fluid code in which elec tron in er tia is ne glected while ion in er tia is re tained. It is con firmed that, the thresh old con di tion for the ap pear ance of two-stream waves is VD C U th » + s + n (1 / cos Y0 q ; and the phase ve loc ity of the two-stream wave at the thresh old con di tion is Vp » Cs + Un cos q, where q is the ele va tion an gle of the wave prop a ga tion in a limited range and Y0 = ninnen / WiWe. The first formula in di cates that the wind field paral lel (anti-par al lel to the elec tron drift ve loc ity will raise (lower the thresh old drift ve loc ity by the amount of the wind speed. This means that par al lel wind is a sta ble fac tor, while anti-paral lel wind is an un sta ble fac tor of two-stream waves. This may ex plain why high speed (larger than acous tic speed two-stream waves were rarely ob served, since larger thresh old drift veloc ity de mands larger po larization elec tric field. The result of the simu la tions at the sat u ra tion stage show that when VD was only slightly larger than VD th , the hor i zon tal phase ve loc ity of the two-stream wave would grad u ally down-shift to the thresh old phase ve loc ity Cs + Un. The physical implications of which are discussed

  3. Predicting spatial patterns of eagle migration using a mesoscale atmospheric model: a case study associated with a mountain-ridge wind development.

    Science.gov (United States)

    Ainslie, B; Alexander, N; Johnston, N; Bradley, J; Pomeroy, A C; Jackson, P L; Otter, K A

    2014-01-01

    velocity fields are in general agreement with the observed flight track patterns. Our results suggest that use of high resolution meteorological fields to locate the occurrence of updrafts in proposed ridge-line wind installations could aid in predicting, and mitigating for, convergence points in raptor migrations.

  4. New Subarray Readout Patterns for the ACS Wide Field Channel

    Science.gov (United States)

    Golimowski, D.; Anderson, J.; Arslanian, S.; Chiaberge, M.; Grogin, N.; Lim, Pey Lian; Lupie, O.; McMaster, M.; Reinhart, M.; Schiffer, F.; Serrano, B.; Van Marshall, M.; Welty, A.

    2017-04-01

    At the start of Cycle 24, the original CCD-readout timing patterns used to generate ACS Wide Field Channel (WFC) subarray images were replaced with new patterns adapted from the four-quadrant readout pattern used to generate full-frame WFC images. The primary motivation for this replacement was a substantial reduction of observatory and staff resources needed to support WFC subarray bias calibration, which became a new and challenging obligation after the installation of the ACS CCD Electronics Box Replacement during Servicing Mission 4. The new readout patterns also improve the overall efficiency of observing with WFC subarrays and enable the processing of subarray images through stages of the ACS data calibration pipeline (calacs) that were previously restricted to full-frame WFC images. The new readout patterns replace the original 512×512, 1024×1024, and 2048×2046-pixel subarrays with subarrays having 2048 columns and 512, 1024, and 2048 rows, respectively. Whereas the original square subarrays were limited to certain WFC quadrants, the new rectangular subarrays are available in all four quadrants. The underlying bias structure of the new subarrays now conforms with those of the corresponding regions of the full-frame image, which allows raw frames in all image formats to be calibrated using one contemporaneous full-frame "superbias" reference image. The original subarrays remain available for scientific use, but calibration of these image formats is no longer supported by STScI.

  5. Quantifying scaling in the velocity field of the anisotropic\\ud turbulent solar wind

    OpenAIRE

    Chapman, Sandra C.; Hnat, B.

    2007-01-01

    Solar wind turbulence is dominated by Alfvénic fluctuations with power spectral exponents that somewhat surprisingly evolve toward the Kolmogorov value of −5/3, that of hydrodynamic turbulence. We analyze in situ satellite observations at 1AU and show that the turbulence decomposes linearly into two coexistent components perpendicular and parallel to the local average magnetic field and determine their distinct intermittency independent scaling exponents. The first of these is consistent with...

  6. Magnetic field assisted programming of particle shapes and patterns.

    Science.gov (United States)

    Xu, Wenwen; Yao, Yuyu; Klassen, John S; Serpe, Michael J

    2015-09-28

    Anisotropic particles have generated an enormous amount of research interest due to their applications for drug delivery, electronic displays and as micromotors. However, up till now, there is no single protocol capable of generating particles of "patchy" composition with a variety of well-defined and predictable shapes. To address this, in this submission we dispersed magnetic nanoparticles (MNPs) in a non-magnetic fluid containing monomer and crosslinker. This solution was added to the surface of Teflon, which was submerged in the solvent 2,2,4-trimethylpentane. Under these conditions a round, stable droplet was formed on the Teflon. Upon exposure to a permanent magnet, the MNPs self-assembled into clusters with a variety shapes and sizes. The shape and size of the clusters depended on the magnetic field strength, which we controlled by systematically varying the distance between the magnet and the droplet. Interestingly, the shape of the liquid droplet was also influenced by the magnetic field. Upon polymerization, the MNP patterns and the droplet shape was preserved. We also show that very complex MNP patterns and particle shapes could be generated by controlling the distance between the drop and both a magnet above and below the droplet. In this case, the resulting patterns depended on whether the magnets were attracting or repelling each other, which was capable of changing the field lines that the MNPs align with. Overall, this approach is capable of generating particles with predictable MNP patterns and particle shapes without the use of any templates or complex synthetic steps. Furthermore, by using a sprayer (or similar approaches, e.g., ink jet printing) this technique can be easily scaled up to produce many complex anisotropic particles in a short amount of time.

  7. Report on the field test project for wind power development at Kamiyaku Town (wind characteristics investigation); Kamiyakucho ni okeru furyoku kaihatsu field test jigyo (fukyo seisa) hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-11-01

    Wind characteristics are observed for a year at the above town located at the northern end of the Yakushima island, Kagoshima Prefecture. The exponential index of the wind speed distribution in the vertical direction is 6.06 with all the directions averaged, and is so high as 8.4/13.6 in the wind directions (W/E). Prudence should be exercised, when to estimate the wind speed at the wind turbine hub altitude, against disjunction from the simple exponential law due to geographical peculiarities of the observation location. Turbulence intensity is low and is 0.15 when the wind speed is 2m/s or more, not exerting an ill effect on wind power development. As for the total wind direction occurrence rate on the prevalent wind axis, 78.2% is recorded, which is much higher than the reference value (60%). The average wind speed on this wind axis is high, and this shows that the location is quite suitable for wind power development. The annual average wind speed of 6.3m/s is much higher than the reference value, this again promising a success. The wind energy density of 478W/m{sup 2} is sufficiently high, as compared with the reference value (215W/m{sup 2}). Since there are possibilities of a maximum instantaneous wind speed of over 60m/s, caution is to be used in determining wind endurance for the wind turbine design. The annual capacity ratios for the 150/300/750kW wind turbine models are 33.8/36.5/36.9%, respectively, higher than the NEDO-provided reference value (17% or higher) and predicting sufficient power generation. (NEDO)

  8. Field-oriented control of five-phase induction motor with open-end stator winding

    OpenAIRE

    Listwan Jacek; Pieńkowski Krzysztof

    2016-01-01

    The mathematical model of the five-phase squirrel-cage induction motor and the system of the dual five-phase voltage source inverter have been presented. The control methods and control systems of the field-oriented control of the five-phase induction motor with an open-end stator winding are described. The structures of the direct fieldoriented control system (DFOC) and the Indirect Field-oriented control system (IFOC) with PI controllers in outer and inner control loops are analyzed. A meth...

  9. Impact of solar wind depression on the dayside magnetosphere under northward interplanetary magnetic field

    Directory of Open Access Journals (Sweden)

    S. Baraka

    2011-01-01

    Full Text Available We present a follow up study of the sensitivity of the Earth's magnetosphere to solar wind activity using a particles-in-cell model (Baraka and Ben Jaffel, 2007, but here during northward Interplanetary Magnetic Field (IMF. The formation of the magnetospheric cavity and its elongation around the planet is obtained with the classical structure of a magnetosphere with parallel lobes. An impulsive disturbance is then applied to the system by changing the bulk velocity of the solar wind to simulate a decrease in the solar wind dynamic pressure followed by its recovery. In response to the imposed drop in the solar wind velocity, a gap (abrupt depression in the incoming solar wind plasma appears moving toward the Earth. The gap's size is a ~15 RE and is comparable to the sizes previously obtained for both Bz<0 and Bz=0. During the initial phase of the disturbance along the x-axis, the dayside magnetopause (MP expands slower than the previous cases of IMF orientations as a result of the abrupt depression. The size of the MP expands nonlinearly due to strengthening of its outer boundary by the northward IMF. Also, during the initial 100 Δt, the MP shrank down from 13.3 RE to ~9.2 RE before it started expanding, a phenomenon that was also observed for southern IMF conditions but not during the no IMF case. As soon as they felt the solar wind depression, cusps widened at high altitude while dragged in an upright position. For the field's topology, the reconnection between magnetospheric and magnetosheath fields is clearly observed in both the northward and southward cusps areas. Also, the tail region in the northward IMF condition is more confined, in contrast to the fishtail-shape obtained in the southward IMF case. An X-point is formed in the tail at ~110 RE compared to ~103 RE and ~80 RE for Bz=0 and Bz<0, respectively. Our findings are consistent with existing reports from many space observatories (Cluster, Geotail, Themis, etc. for which predictions

  10. Computational study: The influence of omni-directional guide vane on the flow pattern characteristic around Savonius wind turbine

    Science.gov (United States)

    Wicaksono, Yoga Arob; Tjahjana, D. D. D. P.

    2017-01-01

    Standart Savonius wind turbine have a low performance such as low coefficient of power and low coefficient of torque compared with another type of wind turbine. This phenomenon occurs because the wind stream can cause the negative pressure at the returning rotor. To solve this problem, standard Savonius combined with Omni Directional Guide Vane (ODGV) proposed. The aim of this research is to study the influence of ODGV on the flow pattern characteristic around of Savonius wind turbine. The numerical model is based on the Navier-Stokes equations with the standard k-ɛ turbulent model. This equation solved by a finite volume discretization method. This case was analyzed by commercial computational fluid dynamics solver such as SolidWorks Flow Simulations. Simulations were performed at the different wind directions; there are 0°, 30°,60° at 4 m/s wind speed. The numerical method validated with the past experimental data. The result indicated that the ODGV able to augment air flow to advancing rotor and decrease the negative pressure in the upstream of returning rotor compared to the bare Savonius wind turbine.

  11. Velocity field and coherent structures in the near wake of a utility-scale wind turbine

    Science.gov (United States)

    Hong, Jiarong; Dasari, Teja; Wu, Yue; Liu, Yun

    2017-11-01

    Super-large-scale particle image velocity (SLPIV) and the associated flow visualization technique using natural snowfall have been shown as an effective tool to probe turbulent velocity field and coherent structures around utility-scale wind turbines (Hong et al. Nature Comm. 2014). Here we present a follow-up study using the data collected during multiple deployments from 2014 to 2016 around the 2.5 MW turbine at EOLOS field station. The data include SLPIV measurements in the near wake of the turbine in a field of view of 120 m (height) x 60 m (width), and the visualization of tip vortex behavior near the bottom blade tip over a broad range of turbine operational conditions. SLPIV results indicate a highly intermittent flow field in the near wake, consisting of both intense wake expansion and contraction events. Such intermittent states of the near wake are shown to be influenced by both the incoming wind conditions and the turbine operation. The visualization of tip vortex behavior demonstrates the presence of the state of consistent vortex formation as well as various types of disturbed vortex states. The occurrence of these states is statistically analyzed and is shown to be correlated with turbine operational and response parameters under different field conditions. National Science Foundation Fluid Dynamics Program.

  12. Wind reduction patterns around isolated biomass for wind erosion control in a desertified area of Central Sudan

    NARCIS (Netherlands)

    Nasr Al-amin, N.K.; Stigter, C.J.; El-Tayeb Mohammed, A.

    2010-01-01

    The aim of this study was to assess the effectiveness of sparse vegetation, feature common in arid zone, to reduce wind force (velocity) and hence protect the surface and regions downwind from drifting sand and their consequences. Respectively 4 (with heights h of 4, 3.2, 2 and 1.66 m), 2 (with h of

  13. Prediction of far-field wind turbine noise propagation with parabolic equation.

    Science.gov (United States)

    Lee, Seongkyu; Lee, Dongjai; Honhoff, Saskia

    2016-08-01

    Sound propagation of wind farms is typically simulated by the use of engineering tools that are neglecting some atmospheric conditions and terrain effects. Wind and temperature profiles, however, can affect the propagation of sound and thus the perceived sound in the far field. A better understanding and application of those effects would allow a more optimized farm operation towards meeting noise regulations and optimizing energy yield. This paper presents the parabolic equation (PE) model development for accurate wind turbine noise propagation. The model is validated against analytic solutions for a uniform sound speed profile, benchmark problems for nonuniform sound speed profiles, and field sound test data for real environmental acoustics. It is shown that PE provides good agreement with the measured data, except upwind propagation cases in which turbulence scattering is important. Finally, the PE model uses computational fluid dynamics results as input to accurately predict sound propagation for complex flows such as wake flows. It is demonstrated that wake flows significantly modify the sound propagation characteristics.

  14. Validating coronal magnetic field reconstruction methods using solar wind simulations and synthetic imagery

    Science.gov (United States)

    Pinto, Rui; Rouillard, Alexis; Génot, Vincent; Amari, Tahar; Buchlin, Eric; Arge, Nick; Sasso, Clementina; Andretta, Vincenzo; Bemporad, Alessandro

    2017-04-01

    We present an ongoing effort within the ESA Modeling and Data Analysis Working Group (MADAWG) to determine automatically the magnetic connectivity between the solar surface and any point in interplanetary space. The goal is to produce predictions of the paths and propagation delays of plasma and energetic particle propagation. This is a key point for the data exploitation of the Solar Orbiter and Solar Probe Plus missions, and for establishing connections between remote and in-situ data. The background coronal magnetic field is currently determined via existing surface magnetograms and PFSS extrapolations, but the interface is ready to include different combinations of coronal field reconstruction methods (NLFFF, Solar Models), wind models (WSA, MULTI-VP), heliospheric models (Parker spiral, ENLIL, EUHFORIA). Some model realisations are also based on advanced magnetograms based on data assimilation techniques (ADAPT) and the HELCATS catalogue of simulations. The results from the different models will be combined in order to better assess the modelling uncertainties. The wind models provide synthetic white-light and EUV images which are compared to coronographic imagery, and the heliospheric models provide estimations of synthetic in-situ data wich are compared to spacecraft data. A part of this is work (wind modelling) is supported by the FP7 project #606692 (HELCATS).

  15. Performance and Economics of a Wind-Diesel Hybrid Energy System: Naval Air Landing Field, San Clemente Island, California

    Energy Technology Data Exchange (ETDEWEB)

    McKenna, E. (National Renewable Energy Laboratory); Olsen, T. (Timothy Olsen Consulting)

    1999-07-06

    This report provides an overview of the wind resource, economics and operation of the recently installed wind turbines in conjunction with diesel power for the Naval Air Landing Field (NALF), San Clemente Island (SCI), California Project. The primary goal of the SCI wind power system is to operate with the existing diesel power plant and provide equivalent or better power quality and system reliability than the existing diesel system. The wind system is also intended to reduce, as far as possible, the use of diesel fuel and the inherent generation of nitrogen-oxide emissions and other pollutants. The first two NM 225/30 225kW wind turbines were installed and started shake-down operations on February 5, 1998. This report describes the initial operational data gathered from February 1998 through January 1999, as well as the SCI wind resource and initial cost of energy provided by the wind turbines on SCI. In support of this objective, several years of data on the wind resources of San Clemente Island were collected and compared to historical data. The wind resource data were used as input to economic and feasibility studies for a wind-diesel hybrid installation for SCI.

  16. Field Verification Project for Small Wind Turbines, Quarterly Report: April - June 2001; 2nd Quarter, Issue No.5

    Energy Technology Data Exchange (ETDEWEB)

    2002-04-01

    This newsletter provides a brief overview of the Field Verification Project for Small Wind Turbines conducted out of the NWTC and a description of current activities. The newsletter also contains case studies of current projects.

  17. Field Verification Program for Small Wind Turbines: Quarterly Report for January-March 2001; 1st Quarter, Issue No.4

    Energy Technology Data Exchange (ETDEWEB)

    Forsyth, T.; Cardinal, J.

    2001-10-30

    This newsletter provides a brief overview of the Field Verification Program for Small Wind Turbines conducted out of the NWTC and a description of current activities. The newsletter also contains case studies of current projects.

  18. Field Verification Program for Small Wind Turbines: Quarterly Report for October-December 2000; 4th Quarter, Iss. No.3

    Energy Technology Data Exchange (ETDEWEB)

    Cardinal, J.

    2001-07-03

    This newsletter provides a brief overview of the Field Verification Program for Small Wind Turbines conducted out of the NWTC and a description of current activities. The newsletter also contains case studies of current projects.

  19. Field Verification Project for Small Wind Turbines Quarterly Report; July-September 2001, 3rd Quarter, Issue#6

    Energy Technology Data Exchange (ETDEWEB)

    2003-04-01

    This newsletter provides a brief overview of the Field Verification Project for Small Wind Turbines conducted at the NWTC and a description of current activities. The newsletter also contains case studies of current projects.

  20. Field Verification Program for Small Wind Turbines, Quarterly Report: 3rd Quarter, Issue No.2, July-September 2000

    Energy Technology Data Exchange (ETDEWEB)

    Cardinal. J.; Tu, P.

    2001-05-16

    This newsletter provides a brief overview of the Field Verification Program for Small Wind Turbines conducted out of the NWTC and a description of current activities. The newsletter also contains case studies of current projects.

  1. Reaching saturation in patterned source vertical organic field effect transistors

    Science.gov (United States)

    Greenman, Michael; Sheleg, Gil; Keum, Chang-min; Zucker, Jonathan; Lussem, Bjorn; Tessler, Nir

    2017-05-01

    Like most of the vertical transistors, the Patterned Source Vertical Organic Field Effect Transistor (PS-VOFET) does not exhibit saturation in the output characteristics. The importance of achieving a good saturation is demonstrated in a vertical organic light emitting transistor; however, this is critical for any application requiring the transistor to act as a current source. Thereafter, a 2D simulation tool was used to explain the physical mechanisms that prevent saturation as well as to suggest ways to overcome them. We found that by isolating the source facet from the drain-source electric field, the PS-VOFET architecture exhibits saturation. The process used for fabricating such saturation-enhancing structure is then described. The new device demonstrated close to an ideal saturation with only 1% change in the drain-source current over a 10 V change in the drain-source voltage.

  2. Comparison of computational modelling and field testing of a small wind turbine operating in unsteady flows

    Science.gov (United States)

    Bradney, D. R.; Evans, S. P.; Salles Pereira Da Costa, M.; Clausen, P. D.

    2016-09-01

    Small horizontal-axis wind turbines are likely to operate in a broad range of operating flow conditions, often in highly turbulent flow, due, in part, to their varied site placements. This paper compares the computational simulations of the performance of a 5 kW horizontal-axis wind turbine to detailed field measurements, with a particular focus on the impact of unsteady operating conditions on the drivetrain performance and generator output. Results indicate that the current Blade Element Momentum Theory based aerodynamic models under-predict the effect of high turbine yaw on the rotor torque, leading to a difference between predicted and measured shaft speed and power production. Furthermore, the results show discrepancies between the predicted instantaneous turbine yaw performance and measurements.

  3. On the fractal nature of the magnetic field energy density in the solar wind

    Science.gov (United States)

    Hnat, B.; Chapman, S. C.; Kiyani, K.; Rowlands, G.; Watkins, N. W.

    2007-08-01

    The solar wind exhibits scaling typical of intermittent turbulence in the statistics of in situ fluctuations in both the magnetic and velocity fields. Intriguingly, quantities not directly accessed by theories of ideal, incompressible, MHD turbulence, such as magnetic energy density, B 2, nevertheless show evidence of simple fractal (self-affine) statistical scaling. We apply a novel statistical technique which is a sensitive discriminator of fractality to the B 2 timeseries from WIND and ACE. We show that robust fractal behaviour occurs at solar maximum and determine the scaling exponents. The probability density function (PDF) of fluctuations at solar maximum and minimum are distinct. Power law tails are seen at maximum, and the PDF is reminiscent of a Lévy flight.

  4. Reflection driven wave turbulence in an open field and the structure of solar wind

    Science.gov (United States)

    Asgari-Targhi, M.; van Ballegooijen, A. A.

    2016-12-01

    We present results from an extensive study of an open magnetic field line positioned at the center of a coronal hole. We test the hypothesis that reflection-driven wave turbulence can provide the energy needed for heating the coronal plasma in the acceleration region of the fast solar wind. We use the reduced magnetohydrodynamic simulations to describe the wave turbulence where the simulated wave dissipation rates are compared with those needed to sustain the background atmosphere. We consider the effects of density fluctuations, which may significantly increase the turbulent heating rate. These density variations simulate the effects of compressive MHD waves on the Alfvén waves. We find that such variations significantly enhance the wave reflection and thereby the turbulent dissipation rates, producing enough heat to maintain the background atmosphere. We conclude that interactions between Alfvén and compressive waves may play an important role in the turbulent heating of the fast solar wind.

  5. Diel variation in feeding and movement patterns of juvenile Atlantic cod at offshore wind farms

    Science.gov (United States)

    Reubens, Jan T.; De Rijcke, Maarten; Degraer, Steven; Vincx, Magda

    2014-01-01

    Atlantic cod (Gadus morhua) is a commercially important fish species suffering from overexploitation in the North-East Atlantic. In recent years, their natural environment is being intensively altered by the construction of offshore wind farms in many coastal areas. These constructions form artificial reefs influencing local biodiversity and ecosystem functioning. It has been demonstrated that Atlantic cod is present in the vicinity of these constructions. However, empirical data concerning the diel activity and feeding behaviour of Atlantic cod in the vicinity of these artificial reefs is lacking. Atlantic cod has a flexible diel activity cycle linked to spatio-temporal variations in food availability and predation risk. In this study we integrated acoustic telemetry with stomach content analysis to quantify diel activity and evaluate diel feeding patterns at a windmill artificial reef (WAR) in the Belgian part of the North Sea. Atlantic cod exhibited crepuscular movements related to feeding activity; a 12 h cycle was found and the highest catch rates and stomach fullness were recorded close to sunset and sunrise. It is suggested that the observed diel movement pattern is related to the prey species community and to predation pressure. Foraging at low ambient light levels (i.e. at dusk and dawn) probably causes a trade-off between foraging success and reducing predation pressure. Fish did not leave the area in-between feeding periods. Hence other benefits (i.e. shelter against currents and predators) besides food availability stimulate the aggregation behaviour at the WARs.

  6. Wind-driven Snow Distribution Patterns Over an Antarctic Ice Floe

    Science.gov (United States)

    Trujillo, E.; Leonard, K. C.; Maksym, T.; Lehning, M.

    2015-12-01

    Sea ice, snow and atmosphere interactions are major drivers of the spatial distribution of snow over sea ice in polar regions. Here, we combine measurements of the wind flow, atmospheric conditions and blowing snow at two locations on an Antarctic sea ice floe, with terrestrial laser scanning to characterize a blowing snow storm and its influence on the spatial patterns of snow distribution at resolutions of 1-10 cm over an area of 100 m x 100 m. The datasets were obtained during the SIPEX II (Sea Ice Physics and Ecosystem eXperiment II) research voyage to East Antarctica (September-November 2012). The pre-storm surface (2012-10-20) exhibits multi-directional elongated snow dunes behind aerodynamic obstacles likely formed during previous snowstorms. The post-storm surface (2012-10-23) exhibits clear new deposition dunes elongated along the predominant wind direction. The new deposition areas amount to 38% of the total surveyed area. Patterns of erosion are less evident but cover a larger portion of the area. This results in a total volume of change near zero with a mean elevation difference of 0.02 m indicating that net erosion or deposition from snowfall was small despite of large mass relocation. After the storm, the statistical distributions of elevation and the 2D correlation functions remain similar to those of the pre-storm surface. The pre- and post-storm surfaces also exhibit power-law relationships in the power spectrum with little change between pre- and post-storm slopes. These observations suggest that despite the significant change observed in the snow surface patterns, the change does not translate into significant changes in the spatial statistical and scaling properties of the surface morphology. Such an observation is important for sea-ice model representations of the sub-pixel variability of sea ice surfaces, particularly between snowstorm events, although more datasets will be required to extend these results to a wider range of sea ice surface

  7. Addressing Spatial Variability of Surface-Layer Wind with Long-Range WindScanners

    DEFF Research Database (Denmark)

    Berg, Jacob; Vasiljevic, Nikola; Kelly, Mark C.

    2015-01-01

    This paper presents an analysis of mean wind measurements from a coordinated system of long-range WindScanners. From individual scan patterns the mean wind field was reconstructed over a large area, and hence it highlights the spatial variability. From comparison with sonic anemometers, the quality...

  8. Conditional Random Fields for Pattern Recognition Applied to Structured Data

    Directory of Open Access Journals (Sweden)

    Tom Burr

    2015-07-01

    Full Text Available Pattern recognition uses measurements from an input domain, X, to predict their labels from an output domain, Y. Image analysis is one setting where one might want to infer whether a pixel patch contains an object that is “manmade” (such as a building or “natural” (such as a tree. Suppose the label for a pixel patch is “manmade”; if the label for a nearby pixel patch is then more likely to be “manmade” there is structure in the output domain that can be exploited to improve pattern recognition performance. Modeling P(X is difficult because features between parts of the model are often correlated. Therefore, conditional random fields (CRFs model structured data using the conditional distribution P(Y|X = x, without specifying a model for P(X, and are well suited for applications with dependent features. This paper has two parts. First, we overview CRFs and their application to pattern recognition in structured problems. Our primary examples are image analysis applications in which there is dependence among samples (pixel patches in the output domain. Second, we identify research topics and present numerical examples.

  9. Report on the field test project for wind power development at Matsushima (wind characteristics investigation); Matsushima ni okeru furyoku kaihatsu field test jigyo (fukyo seisa) hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-11-01

    The test was conducted at Matsushima, Oseto Town, Nishisonogi-gun, Nagasaki Prefecture, for a year. The annual average wind speed is 4.3m/s at 20m above ground, lower than the reference value (5.8m/s). Wind speed variation is great in the cold season and small in the warm season, which is typical of Japan's climate. A maximum instantaneous wind speed to exceed wind turbine system wind-resisting capacity is not likely to occur. At the site selected for investigation, there is no manifestly prevailing wind direction, and caution needs to be exercised relative to mutual interference in case plural wind turbine systems are built. The exponential value in the wind speed vertical distribution is 7.1. The turbulence intensity index is 0.14 (for 4.0m/s or higher), which indicates a relatively small scale. As for wind energy density, it is short of the level indicated by U.S. Department of Energy. Wind turbines of 150 kW, 300 kW, and 750 kW are assumed, and they all work beyond NEDO (New Energy and Industrial Technology Development Organization) indicated operating rates, and will also satisfy NEDO indicated capacity ratios when their wattage is higher than 300 kW. Although Matsushima is not necessarily an excellent place for wind power development in view of the annual average wind speed, it is concluded that possibilities are that Matsushima will satisfy the requisites for a wind power development site if large wind turbine systems with the hub positioned high are introduced. (NEDO)

  10. Report on the field test project for wind power development at Yajima Town (wind characteristics investigation); Yajimamachi ni okeru furyoku kaihatsu field test jigyo (fukyo seisa)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-11-01

    Wind characteristics are observed at Yajima Town, Akita Prefecture, in the period November 1997 through October 1998. The wind speeds are 5.4m/s and 4.5m/s at altitudes of 20m and 10m above the ground, respectively. They are high in winter and the seasonal difference is great. The wind direction occurrence rate is the highest in the WNW and next in the W under the 16 compass point system, and the two directions prevail except in July and September. The wind direction occurrence rates on the wind axis total as high as 74.0%, offering great convenience to the installation of multiple wind turbine systems. The occurrence rate up to the wind speed of 6m/s or more occupies 10% or more, and the wind speed is higher in wind directions that occur oftener. The intensity of turbulence in wind speed is 0.22 where the average wind speed is 2m/s or higher, and 0.19 where it is 4m/s or higher. The annual operation rate of wind turbines are reckoned to be 65% or higher. The amounts of energy to be collected by the 150kW, 300kW, and 750kW machines are, respectively, 356,563kWh, 837,822kWh, and 2,178,380kWh. Their annual capacity ratios are to be 27.6%, 32.4%, and 33.7%. The figures are rather low for wind turbines on the Japan Sea side of the Tohoku district, but service operation is feasible, dependent upon conditions. It is expected that the installation of wind turbines will do but a little harm on the environment they find themselves in. (NEDO)

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

    Science.gov (United States)

    Jancewicz, Kacper

    2014-06-01

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

  12. Climatologies of nighttime upper thermospheric winds measured by ground-based Fabry-Perot interferometers during geomagnetically quiet conditions: 2. High-latitude circulation and interplanetary magnetic field dependence

    DEFF Research Database (Denmark)

    Emmert, J.T.; Hernandez, G.; Jarvis, M.J.

    2006-01-01

    Stromfjord (67 degrees N, 51 degrees W), and Thule (77 degrees N, 68 degrees W). We examine the wind patterns as a function of magnetic local time and latitude, solar cycle, day of year, and the dawn-dusk and north-south components of the interplanetary magnetic field (IMF B-y and B-z). In magnetic...... By negative winds; this behavior is consistent with the By-dependence of statistical ionospheric convection patterns. The strength of the wind response to By tends to increase with increasing solar EUV irradiation, roughly in proportion to the increased wind speeds. Quiet time By effects are detectable...... at latitudes as low as that of Millstone Hill ( magnetic latitude 53 degrees N). Quiet time Bz effects are negligible except over the magnetic polar cap station of Thule....

  13. Relevance of wildfires on dust emissions via interaction with near-surface wind pattern

    Science.gov (United States)

    Wagner, Robert; Jähn, Michael; Schepanski, Kerstin

    2017-04-01

    Mineral dust is a key player in the Earth system and shows diverse impacts on the radiation budget, cloud microphysics, marine and terrestrial ecosystems. Eventually, it also affects our modern way of life. Not only dust emissions from barren or unvegetated soil surfaces like deserts or uncultivated croplands are important sources of airborne mineral dust. Also, during fire events dust is entrained into the atmosphere and appears to contribute noteworthy to the atmospheric dust burden. The underlying process, which drives dust entrainment during fires, is the so-called pyro-convection. The high temperatures in the center of a fire result in an upward motion of the heated air. Subsequently, air flows towards the fire replacing the raising air. The resulting accelerated winds are able to mobilize soil and dust particles up to a size of several millimeters, depending of both the size and the strength of the fire. Several measurements have shown that up to 80% of the mass fraction of the emitted particles during natural or prescribed fires is related to soil or dust particles. The particles are then mixed externally with the combustion aerosols into the convective updraft and were finally inject into altitudes above the planetary boundary layer where they can be distributed and transported over long distances by the atmospheric circulation. To investigate the impacts of such fires on the near-surface wind pattern and the potential for dust emissions via exceeding typical threshold velocities, high resolved Large-Eddy Simulations (LES) with the All Scale Atmospheric Model (ASAM) were executed. In the framework of this study, the influences of different fire properties (fire intensity, size, and shape) and different atmospheric conditions on the strength and extent of fire-related winds and finally their relevance for dust emissions were investigated using sensitivity studies. Prescribed fires are omnipresent during dry seasons and pyro-convection is a mechanism

  14. Field-oriented control of five-phase induction motor with open-end stator winding

    Directory of Open Access Journals (Sweden)

    Listwan Jacek

    2016-09-01

    Full Text Available The mathematical model of the five-phase squirrel-cage induction motor and the system of the dual five-phase voltage source inverter have been presented. The control methods and control systems of the field-oriented control of the five-phase induction motor with an open-end stator winding are described. The structures of the direct fieldoriented control system (DFOC and the Indirect Field-oriented control system (IFOC with PI controllers in outer and inner control loops are analyzed. A method of space vector modulation used to control the system of the dual five-phase voltage source inverter has been discussed. The results of simulation studies of the field-oriented control methods are presented. Comparative analysis of the simulation results was carried out.

  15. Temperature Field-Wind Velocity Field Optimum Control of Greenhouse Environment Based on CFD Model

    Directory of Open Access Journals (Sweden)

    Yongbo Li

    2014-01-01

    Full Text Available The computational fluid dynamics technology is applied as the environmental control model, which can include the greenhouse space. Basic environmental factors are set to be the control objects, the field information is achieved via the division of layers by height, and numerical characteristics of each layer are used to describe the field information. Under the natural ventilation condition, real-time requirements, energy consumption, and distribution difference are selected as index functions. The optimization algorithm of adaptive simulated annealing is used to obtain optimal control outputs. A comparison with full-open ventilation shows that the whole index can be reduced at 44.21% and found that a certain mutual exclusiveness exists between the temperature and velocity field in the optimal course. All the results indicate that the application of CFD model has great advantages to improve the control accuracy of greenhouse.

  16. Solar wind interaction with the Martian upper atmosphere: Crustal field orientation, solar cycle, and seasonal variations

    Science.gov (United States)

    Dong, Chuanfei; Bougher, Stephen W.; Ma, Yingjuan; Toth, Gabor; Lee, Yuni; Nagy, Andrew F.; Tenishev, Valeriy; Pawlowski, Dave J.; Combi, Michael R.; Najib, Dalal

    2015-09-01

    A comprehensive study of the solar wind interaction with the Martian upper atmosphere is presented. Three global models: the 3-D Mars multifluid Block Adaptive Tree Solar-wind Roe Upwind Scheme MHD code (MF-MHD), the 3-D Mars Global Ionosphere Thermosphere Model (M-GITM), and the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) were used in this study. These models are one-way coupled; i.e., the MF-MHD model uses the 3-D neutral inputs from M-GITM and the 3-D hot oxygen corona distribution from M-AMPS. By adopting this one-way coupling approach, the Martian upper atmosphere ion escape rates are investigated in detail with the combined variations of crustal field orientation, solar cycle, and Martian seasonal conditions. The calculated ion escape rates are compared with Mars Express observational data and show reasonable agreement. The variations in solar cycles and seasons can affect the ion loss by a factor of ˜3.3 and ˜1.3, respectively. The crustal magnetic field has a shielding effect to protect Mars from solar wind interaction, and this effect is the strongest for perihelion conditions, with the crustal field facing the Sun. Furthermore, the fraction of cold escaping heavy ionospheric molecular ions [(O2+ and/or O2+)/Total] are inversely proportional to the fraction of the escaping (ionospheric and corona) atomic ion [O+/Total], whereas O2+ and O2+ ion escape fractions show a positive linear correlation since both ion species are ionospheric ions that follow the same escaping path.

  17. Remnant magnetic fields of Mars and their interaction with the solar wind

    Science.gov (United States)

    Breus, T. K.; Krymskii, A. M.

    2017-07-01

    This work presents a review of studies of the Martian magnetic fields during the early Soviet missions to Mars in 1971-1974, which never approached Mars by closer than 1000 km before the experiment with the Magnetometer/Electronic Reflectometer (MAG/ER) on board the Mars Global Surveyor spacecraft, which could descend to altitudes of 80-100 km. At present, the experiment with the magnetometer (MAG) onboard the American MAVEN spacecraft adds new data, but the map of distribution of remnant magnetic fields of Mars and the picture of their interaction with the solar wind are already formed and, at its core, obviously, will not be revised. Thus, it would be very instructive to consider the following in detail: (a) what is already known regarding the features and distribution of remnant magnetic fields on Mars; (b) how they control the interaction of solar wind with a weakly magnetized planet (Mars); and (c) what is its distinction from another nonmagnetized planet (Venus).

  18. Attempts to Simulate Anisotropies of Solar Wind Fluctuations Using MHD with a Turning Magnetic Field

    Science.gov (United States)

    Ghosh, Sanjoy; Roberts, D. Aaron

    2010-01-01

    We examine a "two-component" model of the solar wind to see if any of the observed anisotropies of the fields can be explained in light of the need for various quantities, such as the magnetic minimum variance direction, to turn along with the Parker spiral. Previous results used a 3-D MHD spectral code to show that neither Q2D nor slab-wave components will turn their wave vectors in a turning Parker-like field, and that nonlinear interactions between the components are required to reproduce observations. In these new simulations we use higher resolution in both decaying and driven cases, and with and without a turning background field, to see what, if any, conditions lead to variance anisotropies similar to observations. We focus especially on the middle spectral range, and not the energy-containing scales, of the simulation for comparison with the solar wind. Preliminary results have shown that it is very difficult to produce the required variances with a turbulent cascade.

  19. Comparison of chaparral regrowth patterns between Santa Ana wind-driven and non-Santa Ana fire areas

    Science.gov (United States)

    Rachels, Diane Helen

    Wildfires are a common occurrence in California shrublands and island forests. Fire has a fundamental role in maintaining the ecosystem functions in chaparral where fire intensity and severity play important roles in the regeneration of species. In San Diego, the Cedar Fire that occurred in the fall of 2003 was unique in that one side was burned with wildfire fueled by dry, strong easterly Santa Ana winds that later died down, burning the remainder of the area under a mild westerly wind, allowing fuel-fed conditions. The objective of this study was to understand the connection between vegetation type and structure and environmental response to extreme fire events by analyzing life form regrowth in chaparral communities from the Santa Ana wind driven, Santa Ana backing, and non-Santa Ana fire types. Environmental factors of slope angle, aspect, elevation and soils were investigated in an effort to isolate shrub regrowth patterns. Fire burn characteristics, anthropogenic disturbance, fire history, and moisture availability were also analyzed to identify additional factors that may have influenced shrub regrowth. Shrub extents before the fire and six year after the fire were examined per slope aspect, slope angle, elevation, and fire characteristic categories. The closed canopy and natural features of the chaparral environment make ground based mapping very difficult. Remote sensing data and methods can be very helpful to evaluate the health of the vegetation and condition of the watershed for flood, erosion, and fire control. This study used high spatial resolution aerial imagery and a machine learning algorithm with a spatial contextual classifier to map three different areas from within the Cedar Fire perimeter. Geographic information science (GIS), field mapping, and image interpretation methods were used to identify vegetation samples for the classification and accuracy assessment of the vegetation maps. Object-based image samples were selected for the classifier

  20. STRONG SOLAR WIND DYNAMIC PRESSURE PULSES: INTERPLANETARY SOURCES AND THEIR IMPACTS ON GEOSYNCHRONOUS MAGNETIC FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Zuo, Pingbing; Feng, Xueshang; Wang, Yi [SIGMA Weather Group, State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing (China); Xie, Yanqiong [College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing (China); Xu, Xiaojun, E-mail: pbzuo@spaceweather.ac.cn, E-mail: fengx@spaceweather.ac.cn [Space Science Institute, Macau University of Science and Technology, Macao (China)

    2015-10-20

    In this investigation, we first present a statistical result of the interplanetary sources of very strong solar wind dynamic pressure pulses (DPPs) detected by WIND during solar cycle 23. It is found that the vast majority of strong DPPs reside within solar wind disturbances. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears to be no systematic investigations on the response of GMFs to negative DPPs. Here, we study both the decompression effects of very strong negative DPPs and the compression from strong positive DPPs on GMFs at different magnetic local time sectors. In response to the decompression of strong negative DPPs, GMFs on the dayside near dawn and near dusk on the nightside, are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of the events when GOES is located at the midnight sector, the GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that under certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here, we find that a stronger pressure enhancement may have a higher probability of producing the exceptional depression of GMF at the midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, which are stronger at the noon sector.

  1. A Multi-layered Model for the Shape, Zonal Winds and Gravitational Field of Jupiter

    Science.gov (United States)

    Schubert, G.; Zhang, K.; Kong, D.

    2016-12-01

    We have developed a three-dimensional, finite-element, multi-layered, non-spheroidal model of Jupiter consisting of an inner core, a metallic dynamo region and an outer molecular electrically insulating envelope. Different polytropic equations of state are used in the metallic and molecular regions. The zonal winds are on cylinders parallel to the rotation axis and are confined within the molecular envelope by magnetic braking. The effect of rotational distortion is fully accounted for; it is not treated as simply a small perturbation on a spherically symmetric state. The model determines the density, size and shape of the inner core, the irregular shape of the 1-bar pressure level, and the internal structure of Jupiter. It produces the known mass, the known equatorial and polar radii, and the known zonal gravitational coefficient J2 of Jupiter within their error bars; it also yields the coefficients J4 and J6 with an accuracy of a few percent. The variation of the gravitational field caused solely by the effect of the zonal winds on the rotationally distorted Jupiter is also determined. Different cases, ranging from a deep wind profile to a very shallow profile, are considered. The model enables accurate interpretation of the zonal gravitational coefficients expected from the Juno mission.

  2. Experimental Simulation of Solar Wind Interactions with Magnetic Dipole Fields above Insulating Surfaces

    Science.gov (United States)

    Munsat, Tobin; Deca, Jan; Han, Jia; Horanyi, Mihaly; Wang, Xu; Werner, Greg; Yeo, Li Hsia; Fuentes, Dominic

    2017-10-01

    Magnetic anomalies on the surfaces of airless bodies such as the Moon interact with the solar wind, resulting in both magnetic and electrostatic deflection of the charged particles and thus localized surface charging. This interaction is studied in the Colorado Solar Wind Experiment with large-cross-section ( 300 cm2) high-energy flowing plasmas (100-800 eV beam ions) that are incident upon a magnetic dipole embedded under various insulating surfaces. Measured 2D plasma potential profiles indicate that in the dipole lobe regions, the surfaces are charged to high positive potentials due to the collection of unmagnetized ions, while the electrons are magnetically shielded. At low ion beam energies, the surface potential follows the beam energy in eV. However, at high energies, the surface potentials in the electron-shielded regions are significantly lower than the beam energies. A series of studies indicate that secondary electrons are likely to play a dominant role in determining the surface potential. Early results will also be presented from a second experiment, in which a strong permanent magnet with large dipole moment (0.55 T, 275 A*m2) is inserted into the flowing plasma beam to replicate aspects of the solar wind interaction with the earth's magnetic field. This work is supported by the NASA SSERVI program.

  3. Stabilization and destabilization effects of the electric field on stochastic precipitate pattern

    NARCIS (Netherlands)

    Lagzi, István; Izsak, F.

    2004-01-01

    Stabilization and destabilization effects of an applied electric field on the Liesegang pattern formation in low concentration gradient were studied with numerical model simulations. In the absence of an electric field pattern formation exhibits increasingly stochastic behaviour as the initial

  4. Two-component wind fields over ocean waves using atmospheric lidar and motion estimation algorithms

    Science.gov (United States)

    Mayor, S. D.

    2016-02-01

    Numerical models, such as large eddy simulations, are capable of providing stunning visualizations of the air-sea interface. One reason for this is the inherent spatial nature of such models. As compute power grows, models are able to provide higher resolution visualizations over larger domains revealing intricate details of the interactions of ocean waves and the airflow over them. Spatial observations on the other hand, which are necessary to validate the simulations, appear to lag behind models. The rough ocean environment of the real world is an additional challenge. One method of providing spatial observations of fluid flow is that of particle image velocimetry (PIV). PIV has been successfully applied to many problems in engineering and the geosciences. This presentation will show recent research results that demonstate that a PIV-style approach using pulsed-fiber atmospheric elastic backscatter lidar hardware and wavelet-based optical flow motion estimation software can reveal two-component wind fields over rough ocean surfaces. Namely, a recently-developed compact lidar was deployed for 10 days in March of 2015 in the Eureka, California area. It scanned over the ocean. Imagery reveal that breaking ocean waves provide copius amounts of particulate matter for the lidar to detect and for the motion estimation algorithms to retrieve wind vectors from. The image below shows two examples of results from the experiment. The left panel shows the elastic backscatter intensity (copper shades) under a field of vectors that was retrieved by the wavelet-based optical flow algorithm from two scans that took about 15 s each to acquire. The vectors, that reveal offshore flow toward the NW, were decimated for clarity. The bright aerosol features along the right edge of the sector scan were caused by ocean waves breaking on the beach. The right panel is the result of scanning over the ocean on a day when wave amplitudes ranged from 8-12 feet and whitecaps offshore beyond the

  5. Photospheric magnetic field of an eroded-by-solar-wind coronal mass ejection

    Science.gov (United States)

    Palacios, J.; Cid, C.; Saiz, E.; Guerrero, A.

    2017-10-01

    We have investigated the case of a coronal mass ejection that was eroded by the fast wind of a coronal hole in the interplanetary medium. When a solar ejection takes place close to a coronal hole, the flux rope magnetic topology of the coronal mass ejection (CME) may become misshapen at 1 AU as a result of the interaction. Detailed analysis of this event reveals erosion of the interplanetary coronal mass ejection (ICME) magnetic field. In this communication, we study the photospheric magnetic roots of the coronal hole and the coronal mass ejection area with HMI/SDO magnetograms to define their magnetic characteristics.

  6. Quantifying scaling in the velocity field of the anisotropic turbulent solar wind

    Science.gov (United States)

    Chapman, S. C.; Hnat, B.

    2007-09-01

    Solar wind turbulence is dominated by Alfvénic fluctuations with power spectral exponents that somewhat surprisingly evolve toward the Kolmogorov value of -5/3, that of hydrodynamic turbulence. We analyze in situ satellite observations at 1AU and show that the turbulence decomposes linearly into two coexistent components perpendicular and parallel to the local average magnetic field and determine their distinct intermittency independent scaling exponents. The first of these is consistent with recent predictions for anisotropic MHD turbulence and the second is closer to Kolmogorov-like scaling.

  7. Topology Optimization of a High-Temperature Superconducting Field Winding of a Synchronous Machine

    DEFF Research Database (Denmark)

    Pozzi, Matias; Mijatovic, Nenad; Jensen, Bogi Bech

    2013-01-01

    This paper presents topology optimization (TO) of the high-temperature superconductor (HTS) field winding of an HTS synchronous machine. The TO problem is defined in order to find the minimum HTS material usage for a given HTS synchronous machine design. Optimization is performed using a modified...... potential HTS savings, which could be achieved using multiple power supplies for the excitation of the machine. Using the TO approach combined with two excitation currents, an additional HTS saving of 9.1% can be achieved....

  8. AN ADJOINT-BASED METHOD FOR THE INVERSION OF THE JUNO AND CASSINI GRAVITY MEASUREMENTS INTO WIND FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Galanti, Eli; Kaspi, Yohai, E-mail: eli.galanti@weizmann.ac.il [Weizmann Institute of Science, Rehovot (Israel)

    2016-04-01

    During 2016–17, the Juno and Cassini spacecraft will both perform close eccentric orbits of Jupiter and Saturn, respectively, obtaining high-precision gravity measurements for these planets. These data will be used to estimate the depth of the observed surface flows on these planets. All models to date, relating the winds to the gravity field, have been in the forward direction, thus only allowing the calculation of the gravity field from given wind models. However, there is a need to do the inverse problem since the new observations will be of the gravity field. Here, an inverse dynamical model is developed to relate the expected measurable gravity field, to perturbations of the density and wind fields, and therefore to the observed cloud-level winds. In order to invert the gravity field into the 3D circulation, an adjoint model is constructed for the dynamical model, thus allowing backward integration. This tool is used for the examination of various scenarios, simulating cases in which the depth of the wind depends on latitude. We show that it is possible to use the gravity measurements to derive the depth of the winds, both on Jupiter and Saturn, also taking into account measurement errors. Calculating the solution uncertainties, we show that the wind depth can be determined more precisely in the low-to-mid-latitudes. In addition, the gravitational moments are found to be particularly sensitive to flows at the equatorial intermediate depths. Therefore, we expect that if deep winds exist on these planets they will have a measurable signature by Juno and Cassini.

  9. Solar wind charge exchange emission in the Chandra deep field north

    Energy Technology Data Exchange (ETDEWEB)

    Slavin, Jonathan D.; Wargelin, Bradford J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Koutroumpa, Dimitra [LATMOS/IPSL, CNRS, Université Versailles Saint Quentin, 11 Boulevard d' Alembert, F-78280, Guyancourt (France)

    2013-12-10

    The diffuse soft X-ray background comes from distant galaxies, from hot Galactic gas, and from within the solar system. The latter emission arises from charge exchange between highly charged solar wind ions and neutral gas. This so-called solar wind charge exchange (SWCX) emission is spatially and temporally variable and interferes with our measurements of more distant cosmic emission while also providing important information on the nature of the solar wind-interstellar medium interaction. We present the results of our analysis of eight Chandra observations of the Chandra Deep Field North (CDFN) with the goal of measuring the cosmic and SWCX contributions to the X-ray background. Our modeling of both geocoronal and heliospheric SWCX emission is the most detailed for any observation to date. After allowing for ∼30% uncertainty in the SWCX emission and subtracting it from the observational data, we estimate that the flux of cosmic background for the CDFN in the O VII Kα, Kβ, and O VIII Lyα lines totals 5.8 ± 1.1 photons s{sup –1} cm{sup –2} sr{sup –1} (or LU). Heliospheric SWCX emission varied for each observation due to differences in solar wind conditions and the line of sight through the solar system, but was typically about half as strong as the cosmic background (i.e., one-third of the total) in those lines. The modeled geocoronal emission was 0.82 LU in one observation but averaged only 0.15 LU in the others. Our measurement of the cosmic background is lower than but marginally consistent with previous estimates based on XMM-Newton data.

  10. Tailoring the Electromagnetic Near Field with Patterned Surfaces: Near-Field Plates

    Science.gov (United States)

    2014-12-10

    estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington...plates [9–16] and evanescent field lenses [9], and later as holographic screens [17], metascreens [18] and spatially beam shifted transmission screens...pattern, its spectral representation can be found E⃗focal(ky) = E0 π q0 Π(ky, q◦)x̂, (2) where Π(ky, q0) is the rectangular function with amplitude one

  11. The Electric Wind of Venus: A global and persistent "polar wind" like ambipolar electric field sufficient for the direct escape of heavy ionospheric ions

    Science.gov (United States)

    Collinson, G.; Frahm, R.; Glocer, A.; Coates, A. J.; Grebowsky, J. M.; Barbash, S.; Fedorov, A.; Futaana, Y.; Gilbert, L.; Khazanov, G. V.; Domagal-Goldman, S. D.; Nordheim, T.; Mitchell, D. L.; Moore, T. E.; Peterson, W.; Winningham, D.; Zhang, T.

    2016-12-01

    Understanding what processes govern atmospheric escape and the loss of planetary water is of paramount importance for understanding how life in the universe can exist. One mechanism thought to be important at all planets is an "ambipolar" electric field that helps ions overcome gravity. We report the discovery and first quantitative extraterrestrial measurements of such a field at the planet Venus. Unexpectedly, despite comparable gravity, we show the field to be five times stronger than in Earth's similar ionosphere. Contrary to our understanding, Venus would still lose heavy ions (including oxygen and all water-group species) to space, even if there were no stripping by the solar wind. We therefore find it is possible for planets to lose heavy ions to space entirely through electric forces in their ionospheres, and such an "electric wind" must be considered when studying the evolution and potential habitability of any planet in any star system

  12. The Electric Wind of Venus: A Global and Persistent Polar Wind -Like Ambipolar Electric Field Sufficient for the Direct Escape of Heavy Ionospheric Ions

    Science.gov (United States)

    Collinson, Glyn A.; Frahm, Rudy A.; Glocer, Alex; Coates, Andrew J.; Grebowsky, Joseph M.; Barabash, Stas; Domagal-Goldman, Shawn D.; Federov, Andrei; Futaana, Yoshifumi; Gilbert, Lin K.; hide

    2016-01-01

    Understanding what processes govern atmospheric escape and the loss of planetary water is of paramount importance for understanding how life in the universe can exist. One mechanism thought to be important at all planets is an ambipolar electric field that helps ions overcome gravity. We report the discovery and first quantitative extraterrestrial measurements of such a field at the planet Venus. Unexpectedly, despite comparable gravity, we show the field to be five times stronger than in Earths similar ionosphere. Contrary to our understanding, Venus would still lose heavy ions (including oxygen and all water-group species) to space, even if there were no stripping by the solar wind. We therefore find that it is possible for planets to lose heavy ions to space entirely through electric forces in their ionospheres and such an electric wind must be considered when studying the evolution and potential habitability of any planet in any star system.

  13. Interplanetary Field Enhancements: The Interaction between Solar Wind and Interplanetary Dusty Plasma Released by Interplanetary Collisions

    Science.gov (United States)

    Lai, Hairong

    Interplanetary field enhancements (IFEs) are unique large-scale structures in the solar wind. During IFEs, the magnetic-field strength is significantly enhanced with little perturbation in the solar-wind plasma. Early studies showed that IFEs move at nearly the solar-wind speed and some IFEs detected at 0.72AU by Pioneer Venus Orbiter (PVO) are associated with material co-orbiting with asteroid Oljato. To explain the observed IFE features, we develop and test an IFE formation hypothesis: IFEs result from interactions between the solar wind and clouds of nanoscale charged dust particles released in interplanetary collisions. This hypothesis predicts that the magnetic field drapes and the solar wind slows down in the upstream. Meanwhile the observed IFE occurrence rate should be comparable with the detectable interplanetary collision rate. Based on this hypothesis, we can use the IFE occurrence to determine the spatial distribution and temporal variation of interplanetary objects which produce IFEs. To test the hypothesis, we perform a systematic survey of IFEs in the magnetic-field data from many spacecraft. Our datasets cover from 1970s to present and from inner than 0.3AU to outer than 5 AU. In total, more than 470 IFEs are identified and their occurrences show clustering features in both space and time. We use multi-spacecraft simultaneous observations to reconstruct the magnetic-field geometry and find that the magnetic field drapes in the upstream region. The results of a superposed epoch study show that the solar wind slows down in the upstream and there is a plasma depletion region near the IFE centers. In addition, the solar-wind slowdown and plasma depletion feature are more significant in larger IFEs. The mass contained in IFEs can be estimated by balancing the solar-wind pressure force exerted on the IFEs against the solar gravity. The solar-wind slowdown resultant from the estimated mass is consistent with the result in superposed epoch study. The

  14. A field application experience of integrating hydrogen technology with wind power in a remote island location

    Science.gov (United States)

    Gazey, R.; Salman, S. K.; Aklil-D'Halluin, D. D.

    This paper aims to share the field application experience related to the development of an innovative stand-alone sustainable energy system known as the PURE project. The PURE project has been developed alongside a Knowledge Transfer Partnership (KTP) scheme, which is supported by the UK Department of Trade and Industry and executed by siGEN in collaboration with The Robert Gordon University. The system has been constructed within an industrial estate on the island of Unst in Shetland, 200 miles north of the Scottish mainland. The energy system now supplies five business properties with clean reliable power and utilises wind turbine and hydrogen technology to provide a sustainable energy source. The stored hydrogen gas generated by the system is used as an energy source for periods when electrical demand within the business properties exceeds wind turbine production. The hydrogen is also utilised as a fuel source for transportation and as a transportable energy source for mobile power generation. The paper therefore gives a detailed description of the PURE project and discusses the field experience accumulated during the development and installation of the system. It also shares a number of practical issues that had to be overcome during its integration and operation. The installation of the PURE project has resulted in a number of unexpected conclusions being identified and marks a significant step forward in the accessible deployment of this technology for community use.

  15. Conjectures Concerning Planetary Deuterium Enrichment from Solar Wind or Galactic Clouds Driven by Planetary Magnetic Fields

    Science.gov (United States)

    Arias, F. J.

    2017-09-01

    In this poster, it is conjectured (and theoretically discussed) the possibility of planetary deuterium enrichment contribution in the past driven by planetary magnetic fields and external sources as solar winds or galactic clouds. The mechanism is interesting because: 1) is in clear contrast with current mechanism where planets and bodies are enriched with deuterium by preferential escape of ordinary hydrogen. 2) is linking deuterium enrichment with body magnetic fields, and then observed deuterium enrichment can be a hint that in the past there was magnetic activity in the body 3) open the possibility that geological records can be find with abrupt increase of deuterium and then the possible transit of the solar system crossing galactic clouds.

  16. Impact of Spatial Resolution on Wind Field Derived Estimates of Air Pressure Depression in the Hurricane Eye

    Directory of Open Access Journals (Sweden)

    Linwood Jones

    2010-03-01

    Full Text Available Measurements of the near surface horizontal wind field in a hurricane with spatial resolution of order 1–10 km are possible using airborne microwave radiometer imagers. An assessment is made of the information content of the measured winds as a function of the spatial resolution of the imager. An existing algorithm is used which estimates the maximum surface air pressure depression in the hurricane eye from the maximum wind speed. High resolution numerical model wind fields from Hurricane Frances 2004 are convolved with various HIRAD antenna spatial filters to observe the impact of the antenna design on the central pressure depression in the eye that can be deduced from it.

  17. Understanding the Internal Magnetic Field Configurations of ICMEs Using More than 20 Years of Wind Observations

    Science.gov (United States)

    Nieves-Chinchilla, T.; Vourlidas, A.; Raymond, J. C.; Linton, M. G.; Al-haddad, N.; Savani, N. P.; Szabo, A.; Hidalgo, M. A.

    2018-02-01

    The magnetic topology, structure, and geometry of the magnetic obstacles embedded within interplanetary coronal mass ejections (ICMEs) are not yet fully and consistently described by in situ models and reconstruction techniques. The main goal of this work is to better understand the status of the internal magnetic field of ICMEs and to explore in situ signatures to identify clues to develop a more accurate and reliable in situ analytical models. We take advantage of more than 20 years of Wind observations of transients at 1 AU to compile a comprehensive database of ICMEs through three solar cycles, from 1995 to 2015. The catalog is publicly available at wind.gsfc.nasa.gov and is fully described in this article. We identify and collect the properties of 337 ICMEs, of which 298 show organized magnetic field signatures. To allow for departures from idealized magnetic configurations, we introduce the term "magnetic obstacle" (MO) to signify the possibility of more complex configurations. To quantify the asymmetry of the magnetic field strength profile within these events, we introduce the distortion parameter (DiP) and calculate the expansion velocity within the magnetic obstacle. Circular-cylindrical geometry is assumed when the magnetic field strength displays a symmetric profile. We perform a statistical study of these two parameters and find that only 35% of the events show symmetric magnetic profiles and a low enough expansion velocity to be compatible with the assumption of an idealized cylindrical static flux rope, and that 41% of the events do not show the expected relationship between expansion and magnetic field compression in the front, with the maximum magnetic field closer to the first encounter of the spacecraft with the magnetic obstacle; 18% show contractions ( i.e. apparent negative expansion velocity), and 30% show magnetic field compression in the back. We derive an empirical relation between DiP and expansion velocity that is the first step toward

  18. Effect of soil crusting on the emission and transport of wind-eroded sediment: field measurements on loamy sandy soil

    NARCIS (Netherlands)

    Goossens, D.

    2004-01-01

    Abstract Field data are reported for the horizontal and vertical flux of wind-eroded sediment on an agricultural field in northern Germany. Measurements were made during a windstorm that hit the region on 18 May 1999. The magnitude of both fluxes was significantly affected by the presence of a

  19. Dynamics and sources of last glacial aeolian deposition in southwest France derived from dune patterns, grain-size gradients and geochemistry, and reconstruction of efficient wind directions

    Science.gov (United States)

    Sitzia, Luca; Bertran, Pascal; Sima, Adriana; Chery, Philippe; Queffelec, Alain; Rousseau, Denis-Didier

    2017-08-01

    Dune pattern, grain-size gradients and geochemistry were used to investigate the sources and dynamics of aeolian deposition during the last glacial in southwest France. The coversands form widespread fields of low-amplitude ridges (zibars), whereas Younger Dryas parabolic dunes mainly concentrate in corridors and along rivers. Spatial modelling of grain-size gradients combined with geochemical analysis points to a genetic relationship between coversands and loess, the latter resulting primarily from dust produced by aeolian abrasion of the coversands. The alluvium of the Garonne river provided also significant amounts of dust at a more local scale. The geochemical composition of loess shows much lower scattering than that of coversands, due to stronger homogenisation during transport in the atmosphere. Overall, sandy loess and loess deposits decrease in thickness away from the coversands. Dune orientation and grain-size gradients suggest that the efficient winds blew respectively from the W to the NW during the glacial, and the W-SW during the Younger Dryas. A comparison between the wind directions derived from the proxy data and those provided by palaeoclimatic simulations suggests a change of the main transport season. Ground surface conditions and their evolution throughout the year, i.e. the length of the season with snow and frozen or moist topsoil, and the seasonal distribution of wind speeds able to cause deflation are thought to have been the main factors that controlled the transport season in the study area.

  20. Pattern recognition techniques and the measurement of solar magnetic fields

    Science.gov (United States)

    Lopez Ariste, Arturo; Rees, David E.; Socas-Navarro, Hector; Lites, Bruce W.

    2001-11-01

    Measuring vector magnetic fields in the solar atmosphere using the profiles of the Stokes parameters of polarized spectral lines split by the Zeeman effect is known as Stokes Inversion. This inverse problem is usually solved by least-squares fitting of the Stokes profiles. However least-squares inversion is too slow for the new generation of solar instruments (THEMIS, SOLIS, Solar-B, ...) which will produce an ever-growing flood of spectral data. The solar community urgently requires a new approach capable of handling this information explosion, preferably in real-time. We have successfully applied pattern recognition and machine learning techniques to tackle this problem. For example, we have developed PCA-inversion, a database search technique based on Principal Component Analysis of the Stokes profiles. Search is fast because it is carried out in low dimensional PCA feature space, rather than the high dimensional space of the spectral signals. Such a data compression approach has been widely used for search and retrieval in many areas of data mining. PCA-inversion is the basis of a new inversion code called FATIMA (Fast Analysis Technique for the Inversion of Magnetic Atmospheres). Tests on data from HAO's Advanced Stokes Polarimeter show that FATIMA isover two orders of magnitude faster than least squares inversion. Initial tests on an alternative code (DIANNE - Direct Inversion based on Artificial Neural NEtworks) show great promise of achieving real-time performance. In this paper we present the latest achievements of FATIMA and DIANNE, two powerful examples of how pattern recognition techniques can revolutionize data analysis in astronomy.

  1. Small wind turbine performance evaluation using field test data and a coupled aero-electro-mechanical model

    Science.gov (United States)

    Wallace, Brian D.

    A series of field tests and theoretical analyses were performed on various wind turbine rotor designs at two Penn State residential-scale wind-electric facilities. This work involved the prediction and experimental measurement of the electrical and aerodynamic performance of three wind turbines; a 3 kW rated Whisper 175, 2.4 kW rated Skystream 3.7, and the Penn State designed Carolus wind turbine. Both the Skystream and Whisper 175 wind turbines are OEM blades which were originally installed at the facilities. The Carolus rotor is a carbon-fiber composite 2-bladed machine, designed and assembled at Penn State, with the intent of replacing the Whisper 175 rotor at the off-grid system. Rotor aerodynamic performance is modeled using WT_Perf, a National Renewable Energy Laboratory developed Blade Element Momentum theory based performance prediction code. Steady-state power curves are predicted by coupling experimentally determined electrical characteristics with the aerodynamic performance of the rotor simulated with WT_Perf. A dynamometer test stand is used to establish the electromechanical efficiencies of the wind-electric system generator. Through the coupling of WT_Perf and dynamometer test results, an aero-electro-mechanical analysis procedure is developed and provides accurate predictions of wind system performance. The analysis of three different wind turbines gives a comprehensive assessment of the capability of the field test facilities and the accuracy of aero-electro-mechanical analysis procedures. Results from this study show that the Carolus and Whisper 175 rotors are running at higher tip-speed ratios than are optimum for power production. The aero-electro-mechanical analysis predicted the high operating tip-speed ratios of the rotors and was accurate at predicting output power for the systems. It is shown that the wind turbines operate at high tip-speeds because of a miss-match between the aerodynamic drive torque and the operating torque of the wind

  2. Low-frequency magnetic field fluctuations in Venus' solar wind interaction region: Venus Express observations

    Directory of Open Access Journals (Sweden)

    L. Guicking

    2010-04-01

    Full Text Available We investigate wave properties of low-frequency magnetic field fluctuations in Venus' solar wind interaction region based on the measurements made on board the Venus Express spacecraft. The orbit geometry is very suitable to investigate the fluctuations in Venus' low-altitude magnetosheath and mid-magnetotail and provides an opportunity for a comparative study of low-frequency waves at Venus and Mars. The spatial distributions of the wave properties, in particular in the dayside and nightside magnetosheath as well as in the tail and mantle region, are similar to observations at Mars. As both planets do not have a global magnetic field, the interaction process of the solar wind with both planets is similar and leads to similar instabilities and wave structures. We focus on the spatial distribution of the wave intensity of the fluctuating magnetic field and detect an enhancement of the intensity in the dayside magnetosheath and a strong decrease towards the terminator. For a detailed investigation of the intensity distribution we adopt an analytical streamline model to describe the plasma flow around Venus. This allows displaying the evolution of the intensity along different streamlines. It is assumed that the waves are generated in the vicinity of the bow shock and are convected downstream with the turbulent magnetosheath flow. However, neither the different Mach numbers upstream and downstream of the bow shock, nor the variation of the cross sectional area and the flow velocity along the streamlines play probably an important role in order to explain the observed concentration of wave intensity in the dayside magnetosheath and the decay towards the nightside magnetosheath. But, the concept of freely evolving or decaying turbulence is in good qualitative agreement with the observations, as we observe a power law decay of the intensity along the streamlines. The observations support the assumption of wave convection through the magnetosheath, but

  3. Influence of hurricane wind field in the structure of directional wave spectra.

    Science.gov (United States)

    Esquivel-Trava, Bernardo; García-Nava, Hector; Osuna, Pedro; Ocampo-Torres, Francisco J.

    2017-04-01

    Three numerical experiments using the spectral wave prediction model SWAN were carried out to gain insight into the mechanism that controls the directional and frequency distributions of hurricane wave energy. One particular objective is to evaluate the effect of the translation speed of the hurricane and the presence of concentric eye walls, on both the wave growth process and the shape of the directional wave spectrum. The HRD wind field of Hurricane Dean on August 20 at 7:30 was propagated at two different velocities (5 and 10 m/s). An idealized concentric eye wall (a Gaussian function that evolve in time along a path in the form of an Archimedean spiral) was imposed to the wind field. The white-capping formulation of Westhuysen et al. (2007) was selected. The wave model represents fairly well the directionality of the energy and the shape of the directional spectra in the hurricane domain. The model results indicate that the forward movement of the storm influences the development of the waves, consistent with field observations. Additionally the same experiments were carried out using the Wave Watch III model with the source terms formulation proposed by Ardhuin et al., 2010, with the aim of making comparisons between the physical processes that represent each formulation, and the latest results will be addressed. References Ardhuin, F., Rogers, E., Babanin, A. V., Filipot, J.-F., Magne, R., Roland, A., van der Westhuysen, A., et al. (2010). Semiempirical Dissipation Source Functions for Ocean Waves. Part I: Definition, Calibration, and Validation. Journal of Physical Oceanography, 40(9), 1917-1941. doi:10.1175/2010JPO4324.1 Van der Westhuysen, A. J., Zijlema, M., & Battjes, J. A. (2007). Nonlinear saturation-based whitecapping dissipation in SWAN for deep and shallow water. Coast. Eng., 54(2), 151-170. doi:10.1016/j.coastaleng.2006.08.006

  4. Laser Interferometer Space Antenna (LISA) Far Field Phase Patterns

    Science.gov (United States)

    Waluschka, Eugene; Obenschain, Arthur F. (Technical Monitor)

    2000-01-01

    The Laser Interferometer Space Antenna (LISA) consists of three spacecraft in orbit about the sun. The orbits are chosen such that the three spacecraft are always at (roughly) the vertices of a equilateral triangle with 5 million kilometer leg lengths. Even though the distances between the three spacecraft are 5 million kilometers, the expected phase shifts between any two beams, due to a gravitational wave, only correspond to a distance change of about 10 pico meters, which is about 10(exp -5) waves for a laser wavelength of 1064 nm. To obtain the best signal-to-noise ratio, noise sources such as changes in the apparent distances due to pointing jitter must be controlled carefully. This is the main reason for determining the far-field phase patterns of a LISA type telescope. Because of torque on the LISA spacecraft and other disturbances, continuous adjustments to the pointing of the telescopes are required. These pointing adjustments will be a "jitter" source. If the transmitted wave is perfectly spherical then rotations (Jitter) about its geometric center will not produce any effect at the receiving spacecraft. However, if the outgoing wave is not perfectly spherical, then pointing jitter will produce a phase variation at the receiving spacecraft. The following sections describe the "brute force" computational approach used to determine the scalar wave front as a function of exit pupil (Zernike) aberrations and to show the results (mostly graphically) of the computations. This approach is straightforward and produces believable phase variations to sub-pico meter accuracy over distances on the order of 5 million kilometers. As such this analyzes the far field phase sensitivity to exit pupil aberrations.

  5. Patterns of migrating soaring migrants indicate attraction to marine wind farms.

    Science.gov (United States)

    Skov, Henrik; Desholm, Mark; Heinänen, Stefan; Kahlert, Johnny A; Laubek, Bjarke; Jensen, Niels Einar; Žydelis, Ramūnas; Jensen, Bo Præstegaard

    2016-12-01

    Monitoring of bird migration at marine wind farms has a short history, and unsurprisingly most studies have focused on the potential for collisions. Risk for population impacts may exist to soaring migrants such as raptors with K-strategic life-history characteristics. Soaring migrants display strong dependence on thermals and updrafts and an affinity to land areas and islands during their migration, a behaviour that creates corridors where raptors move across narrow straits and sounds and are attracted to islands. Several migration corridors for soaring birds overlap with the development regions for marine wind farms in NW Europe. However, no empirical data have yet been available on avoidance or attraction rates and behavioural reactions of soaring migrants to marine wind farms. Based on a post-construction monitoring study, we show that all raptor species displayed a significant attraction behaviour towards a wind farm. The modified migratory behaviour was also significantly different from the behaviour at nearby reference sites. The attraction was inversely related to distance to the wind farm and was primarily recorded during periods of adverse wind conditions. The attraction behaviour suggests that migrating raptor species are far more at risk of colliding with wind turbines at sea than hitherto assessed. © 2016 The Author(s).

  6. Variability of the Magnetic Field Power Spectrum in the Solar Wind at Electron Scales

    Science.gov (United States)

    Roberts, Owen Wyn; Alexandrova, O.; Kajdič, P.; Turc, L.; Perrone, D.; Escoubet, C. P.; Walsh, A.

    2017-12-01

    At electron scales, the power spectrum of solar-wind magnetic fluctuations can be highly variable and the dissipation mechanisms of the magnetic energy into the various particle species is under debate. In this paper, we investigate data from the Cluster mission’s STAFF Search Coil magnetometer when the level of turbulence is sufficiently high that the morphology of the power spectrum at electron scales can be investigated. The Cluster spacecraft sample a disturbed interval of plasma where two streams of solar wind interact. Meanwhile, several discontinuities (coherent structures) are seen in the large-scale magnetic field, while at small scales several intermittent bursts of wave activity (whistler waves) are present. Several different morphologies of the power spectrum can be identified: (1) two power laws separated by a break, (2) an exponential cutoff near the Taylor shifted electron scales, and (3) strong spectral knees at the Taylor shifted electron scales. These different morphologies are investigated by using wavelet coherence, showing that, in this interval, a clear break and strong spectral knees are features that are associated with sporadic quasi parallel propagating whistler waves, even for short times. On the other hand, when no signatures of whistler waves at ∼ 0.1{--}0.2{f}{ce} are present, a clear break is difficult to find and the spectrum is often more characteristic of a power law with an exponential cutoff.

  7. A Calculation Method of Equivalent Circuit Constants of Synchronous Machines Considering Field Transient Characteristics Using DC Decay Testing Method with Open and Shorted Field Windings

    Science.gov (United States)

    Kano, Takashi; Watanabe, Yasutoshi; Ara, Takahiro; Matsumura, Toshiro

    It has been reported that the calculated values of field transient behavior in a synchronous machine differ considerably from the measured values. This discrepancy is caused by the use of equivalent circuit constants in standardized tests provied by JEC2130 and IEC60034-4, in which the mutual leakage reactance between the damper and field windings is not accounted for. The authors have been studying a method for calculating equivalent circuit constants for the accurate simulation of transient behavior including the field winding side, by means of a standstill test with a small-capacity DC power supply (DC decay testing method). The authors have previously presented a calculation method using operational impedances with the field windings opened, shorted, and inserted with an external resistance, obtained by the DC decay test. This paper presents a new method in which the external resistance used in our previous method is no longer needed. Instead, the field winding impedance is determined based on its invariability against slip. The validity of the new method is demonstrated by comparing the calculated and measured values of the armature and field currents during a sudden three-phase short-circuit using 10kVA-200V-31.9A-4P-50Hz test machines.

  8. Statistics of MLT wind field values derived from 11 years of common volume specular meteor observations in northern Norway

    Science.gov (United States)

    Chau, Jorge Luis; Stober, Gunter; Laskar, Fazlul; Hall, Chris M.; Tsutsumi, Masaki

    2016-04-01

    Traditionally mean values of the mesosphere and lower thermosphere winds over the radar volume are obtained using monostatic specular meteor radars. Such observing volume consist of a few hundreds of kilometers in radius. Moreover the differences between measured radial velocities and the expected radial velocities from the measured mean winds are used to derive properties of gravity wave momentum fluxes. Recently, Stober and Chau [2015] have proposed to use a multi-static approach to retrieve horizontally resolved wind fields, where most of the radar volume is observed from different viewing angles. Similar results could be obtained if measurements from close-by monostatic systems are combined. In this work we present the results of the derived wind fields from combining specular meteor radar data between 2004 and 2015 from the Trømso (19.22oW, 69.58oN) and Andenes (16.04oW, 69.27oN) radar systems. Among the directly estimated values are the mean winds and the horizontal and vertical gradients of the zonal and meridional winds. Combining the horizontal gradients, the horizontal divergence, relative vorticity, shear and deformation are derived. The seasonal and annual variability of these parameters are presented and discussed, as well as the planetary wave, tidal, and gravity wave information embedded in these new parameters.

  9. 3D WindScanner lidar measurements of wind and turbulence around wind turbines, buildings and bridges

    Science.gov (United States)

    Mikkelsen, T.; Sjöholm, M.; Angelou, N.; Mann, J.

    2017-12-01

    WindScanner is a distributed research infrastructure developed at DTU with the participation of a number of European countries. The research infrastructure consists of a mobile technically advanced facility for remote measurement of wind and turbulence in 3D. The WindScanners provide coordinated measurements of the entire wind and turbulence fields, of all three wind components scanned in 3D space. Although primarily developed for research related to on- and offshore wind turbines and wind farms, the facility is also well suited for scanning turbulent wind fields around buildings, bridges, aviation structures and of flow in urban environments. The mobile WindScanner facility enables 3D scanning of wind and turbulence fields in full scale within the atmospheric boundary layer at ranges from 10 meters to 5 (10) kilometers. Measurements of turbulent coherent structures are applied for investigation of flow pattern and dynamical loads from turbines, building structures and bridges and in relation to optimization of the location of, for example, wind farms and suspension bridges. This paper presents our achievements to date and reviews briefly the state-of-the-art of the WindScanner measurement technology with examples of uses for wind engineering applications.

  10. Plasma β Scaling of Anisotropic Magnetic Field Fluctuations in the Solar Wind Flux Tube

    Science.gov (United States)

    Sarkar, Aveek; Bhattacharjee, Amitava; Ebrahimi, Fatima

    2014-03-01

    Based on various observations, it has been suggested that at 1 AU, solar wind consists of "spaghetti"-like magnetic field structures that have the magnetic topology of flux tubes. It is also observed that the plasma fluctuation spectra at 1 AU show a plasma β dependence. Reconciling these two sets of observations and using the Invariance Principle, Bhattacharjee et al. suggested that the plasma inside every flux tube may become unstable with respect to pressure-driven instabilities and gives rise to fluctuation spectra that depend on the local plasma β. The present work is the first direct numerical simulation of such a flux tube. We solve the full magnetohydrodynamic equations using the DEBS code and show that if the plasma inside the flux tube is driven unstable by spatial inhomogeneities in the background plasma pressure, the observed nature of the fluctuating power spectra agrees reasonably well with observations, as well as the analytical prediction of Bhattacharjee et al.

  11. Plasma β scaling of anisotropic magnetic field fluctuations in the solar wind flux tube

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Aveek [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States); Bhattacharjee, Amitava; Ebrahimi, Fatima, E-mail: aveek.sarkar@unh.edu, E-mail: amitava@princeton.edu, E-mail: ebrahimi@princeton.edu [Department of Astrophysical Sciences and Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States)

    2014-03-10

    Based on various observations, it has been suggested that at 1 AU, solar wind consists of 'spaghetti'-like magnetic field structures that have the magnetic topology of flux tubes. It is also observed that the plasma fluctuation spectra at 1 AU show a plasma β dependence. Reconciling these two sets of observations and using the Invariance Principle, Bhattacharjee et al. suggested that the plasma inside every flux tube may become unstable with respect to pressure-driven instabilities and gives rise to fluctuation spectra that depend on the local plasma β. The present work is the first direct numerical simulation of such a flux tube. We solve the full magnetohydrodynamic equations using the DEBS code and show that if the plasma inside the flux tube is driven unstable by spatial inhomogeneities in the background plasma pressure, the observed nature of the fluctuating power spectra agrees reasonably well with observations, as well as the analytical prediction of Bhattacharjee et al.

  12. Non-axisymmetric Anisotropy of magnetic field fluctuations in the solar wind dissipation range

    Science.gov (United States)

    Gogoberidze, G.; Turner, A. J.; Chapman, S. C.; Hnat, B.; Muller, W.

    2011-12-01

    Anisotropy is a key topic for theoretical, numerical and observational studies of plasma turbulence in the solar wind. A fundamental assumption of many theoretical descriptions of turbulence, both in the inertial and dissipation range, is that of axisymmetry of the anisotropic fluctuations with respect to the background magnetic field. Intriguingly, there is observational evidence that these fluctuations are ordered both with respect to the background field and flow directions. This level of non-axisymmetry is observed to increases as we move from the inertial range to the dissipation range. This is characterized by minimum variance analysis as well as in observations of the ratio of the Power Spectral Density (PSD) in the perpendicular directions, eBxeR : eBx(eBxeR), where eB is a unit vector in the direction of the average magnetic field and eR is a unit vector in the radial direction away from the sun. Here, we show that this observed non-axisymmetry may arise as a data sampling effect rather than as a result of the physical properties of the turbulent plasma. We first quantify the observed non-axisymmetry through the inertial and dissipation ranges via the PSD ratio in the perpendicular plane for in-situ measurements using the Cluster spacecraft in fast wind where both magnetic field instruments, FGM and STAFF, are operating in burst mode. This allows the small scales of the dissipation range to be investigated. We then show that a spacecraft 'fly through' of a simple analytical model for a field composed of a linear superposition of transverse waves, where Taylor's hypothesis is used and the only variable parameter is the power law index, is sufficient to give the observed non-axisymmetry. In particular, we find that the ratio of power in the perpendicular plane, eBxeR : eBx(eBxeR), depends on the exponent of the PSD. Thus we find that the enhanced non-axisymmetry seen in the dissipation range is a result of the steepening of the PSD slope.

  13. Empirical Doppler Characterization of Signals Scattered by Wind Turbines in the UHF Band under Near Field Condition

    Directory of Open Access Journals (Sweden)

    Itziar Angulo

    2013-01-01

    Full Text Available Time variability of the scattering signals from wind turbines may lead to degradation problems on the communication systems provided in the UHF band, especially under near field condition. In order to analyze the variability due to the rotation of the blades, this paper characterizes empirical Doppler spectra obtained from real samples of signals scattered by wind turbines with rotating blades under near field condition. A new Doppler spectrum model is proposed to fit the spectral characteristics of these signals, providing notable goodness of fit. Finally, the effect of this kind of time variability on the degradation of OFDM signals is studied.

  14. Radiation of Air-Borne Noise in Non-Homogeneous Wind and Temperature Fields using FEM Analysis

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Nielsen, Søren R. K.; Krenk, S.

    1999-01-01

    The paper describes analysis in the time domain of noise propagating in non-homogeneous mean wind or temperature fields. The analysis is based on a field equation for the velocity potential, which contains strong convection terms. In order to circumvent the problem of numerical instability and loss...... by a conventional Galerkin approach. The radiation condition is an impedance condition for wave propagation towards the artificial boundary at an oblique angle. The propagation angle is estimated geometrically with due consideration of the mean wind velocity. The method has been applied to a 2-dimensional point...

  15. Before-after field study of effects of wind turbine noise on polysomnographic sleep parameters

    National Research Council Canada - National Science Library

    Leila Jalali; Philip Bigelow; Mohammad-Reza Nezhad-Ahmadi; Mahmood Gohari; Diane Williams; Steve McColl

    2016-01-01

    .... However, alleged health-related effects of exposure to wind turbine (WT) noise have attracted much public attention and various symptoms, such as sleep disturbance, have been reported by residents living close to wind developments...

  16. Seasonal effects of wind conditions on migration patterns of soaring American white pelican.

    Science.gov (United States)

    Gutierrez Illan, Javier; Wang, Guiming; Cunningham, Fred L; King, D Tommy

    2017-01-01

    Energy and time expenditures are determinants of bird migration strategies. Soaring birds have developed migration strategies to minimize these costs, optimizing the use of all the available resources to facilitate their displacement. We analysed the effects of different wind factors (tailwind, turbulence, vertical updrafts) on the migratory flying strategies adopted by 24 satellite-tracked American white pelicans (Pelecanus erythrorhynchos) throughout spring and autumn in North America. We hypothesize that different wind conditions encountered along migration routes between spring and autumn induce pelicans to adopt different flying strategies and use of these wind resources. Using quantile regression and fine-scale atmospheric data, we found that the pelicans optimized the use of available wind resources, flying faster and more direct routes in spring than in autumn. They actively selected tailwinds in both spring and autumn displacements but relied on available updrafts predominantly in their spring migration, when they needed to arrive at the breeding regions. These effects varied depending on the flying speed of the pelicans. We found significant directional correlations between the pelican migration flights and wind direction. In light of our results, we suggest plasticity of migratory flight strategies by pelicans is likely to enhance their ability to cope with the effects of ongoing climate change and the alteration of wind regimes. Here, we also demonstrate the usefulness and applicability of quantile regression techniques to investigate complex ecological processes such as variable effects of atmospheric conditions on soaring migration.

  17. Seasonal effects of wind conditions on migration patterns of soaring American white pelican.

    Directory of Open Access Journals (Sweden)

    Javier Gutierrez Illan

    Full Text Available Energy and time expenditures are determinants of bird migration strategies. Soaring birds have developed migration strategies to minimize these costs, optimizing the use of all the available resources to facilitate their displacement. We analysed the effects of different wind factors (tailwind, turbulence, vertical updrafts on the migratory flying strategies adopted by 24 satellite-tracked American white pelicans (Pelecanus erythrorhynchos throughout spring and autumn in North America. We hypothesize that different wind conditions encountered along migration routes between spring and autumn induce pelicans to adopt different flying strategies and use of these wind resources. Using quantile regression and fine-scale atmospheric data, we found that the pelicans optimized the use of available wind resources, flying faster and more direct routes in spring than in autumn. They actively selected tailwinds in both spring and autumn displacements but relied on available updrafts predominantly in their spring migration, when they needed to arrive at the breeding regions. These effects varied depending on the flying speed of the pelicans. We found significant directional correlations between the pelican migration flights and wind direction. In light of our results, we suggest plasticity of migratory flight strategies by pelicans is likely to enhance their ability to cope with the effects of ongoing climate change and the alteration of wind regimes. Here, we also demonstrate the usefulness and applicability of quantile regression techniques to investigate complex ecological processes such as variable effects of atmospheric conditions on soaring migration.

  18. Atmospheric stability effects on wind fields and scalar mixing within and just above a subalpine forest in sloping terrain

    Science.gov (United States)

    Burns, Sean P.; Sun, Jielun; Lenschow, D.H.; Oncley, S.P.; Stephens, B.B.; Yi, C.; Anderson, D.E.; Hu, Jiawen; Monson, Russell K.

    2011-01-01

    Air temperature Ta, specific humidity q, CO2 mole fraction ??c, and three-dimensional winds were measured in mountainous terrain from five tall towers within a 1 km region encompassing a wide range of canopy densities. The measurements were sorted by a bulk Richardson number Rib. For stable conditions, we found vertical scalar differences developed over a "transition" region between 0.05 1), the vertical scalar differences reached a maximum and remained fairly constant with increasing stability. The relationships q and ??c have with Rib are explained by considering their sources and sinks. For winds, the strong momentum absorption in the upper canopy allows the canopy sublayer to be influenced by pressure gradient forces and terrain effects that lead to complex subcanopy flow patterns. At the dense-canopy sites, soil respiration coupled with wind-sheltering resulted in CO2 near the ground being 5-7 ??mol mol-1 larger than aloft, even with strong above-canopy winds (near-neutral conditions). We found Rib-binning to be a useful tool for evaluating vertical scalar mixing; however, additional information (e.g., pressure gradients, detailed vegetation/topography, etc.) is needed to fully explain the subcanopy wind patterns. Implications of our results for CO2 advection over heterogenous, complex terrain are discussed. ?? 2010 Springer Science+Business Media B.V.

  19. MODELING OF THE WIND VELOCITY FIELD – RENEWABLE SOURCES OF ENERGY IN KRASNODAR REGION

    Directory of Open Access Journals (Sweden)

    E. A. Kiseleva

    2015-01-01

    Full Text Available Assessment of the potential of wind energy in the Krasnodar region obtained by mapping the wind speed at the height of 50, 80 and 100 meters. The technique of modeling, based on the global experience of assessing the potential of wind energy, including data on the average annual wind speed at the meteorological network and estimates of surface roughness . The algorithm for automated mapping.

  20. BVOC emission pattern from Quercus robur under field conditions

    Science.gov (United States)

    Pokorska, O.; Dewulf, J.; Joó; Šimpraga, M.; Steppe, K.; Amelynck, C.; Schoon, N.; Muller, J. J.; van Langenhove, H.

    2010-12-01

    Over the past decades biogenic volatile organic compounds (BVOC) have been widely studied not only for better understanding their functions, biosynthesis and regulation, but also because they have great impact on regional and global air quality [1]. Since all BVOCs react with hydroxyl radicals (OH●) and may also react with nitrate radicals (NO3●) and ozone (O3), they contribute to the formation of ozone and secondary organic aerosols. In this study we focus on Quercus robur which is a widely spread tree species in Europe and known as a strong isoprene emitter. We aimed to investigate seasonal patterns of BVOC emissions from Quercus robur under field conditions and to explore the intra-species variations within Quercus robur trees as both are of great importance for accurate modeling and regional inventories. Measurements were performed during a period from May till October 2009 at the campus of Ghent University (Belgium) using a dynamic branch enclosure system. Experiments were conducted on four potted Quercus robur trees with a varying 1-1.5 m height. Samples were collected on Tenax TA-Carbotrap adsorbent tubes and analyzed by TD-GC-MS. Isoprene was the predominant compound released by Quercus robur (QR1) with a pronounced seasonal emission. The normalized emission rates for isoprene calculated according to Guenther’s algorithm (standard conditions of temperature 30°C and PAR 1000 µmol m-2 s-1) varied from 29.89 µg h-1 g(DW)-1 in Spring (May) to 28.62 µg h-1 g(DW)-1 in Fall (October) reaching peak of 105.51 µg h-1 g(DW)-1 in August. Apart from isoprene, through the whole measurement period trans-β-ocimene and β-caryophyllene were the only BVOC emitted in detectable range (sum of the emissions varied between 0.15 µg h-1 g(DW)-1 in July and 0.24 µg h-1 g(DW)-1 in October). No clear seasonal pattern was observed for those compounds. In May when acorns where developing on enclosed branch, emissions of limonene and β-farnesene were also observed. The

  1. Experimental investigation of the surface pressure field for prediction of trailing edge noise of wind turbine aerofoils

    DEFF Research Database (Denmark)

    Fischer, Andreas; Aagaard Madsen, Helge; Bertagnolio, Franck

    2015-01-01

    This paper concerns the characterisation of turbulent boundary layer trailing edge noise by measuring the surface pressure field. Two aerofoils typically used at the outer blade section of modern MW wind turbines were tested in an anechoic wind tunnel for Reynolds numbers ranging from 1 million...... to 1.9 million and angles of attack ranging from −10° to 14°. The emitted trailing noise from the aerofoils was measured with a microphone array at a distance of 1.6 m away from the aerofoil. The two-dimensional surface pressure field, which is considered the source of the emitted trailing edge noise......, was measured with pinhole microphones distributed in streamwise and spanwise direction on the surface of the aerofoil. Two acoustic formulations relating the fluctuating surface pressure field to far field trailing edge noise were investigated. The measurements of the fluctuating surface pressure field were...

  2. Visualization of Wind Data on Google Earth for the Three-dimensional Wind Field (3DWF) Model

    Science.gov (United States)

    2012-09-01

    input boxes have been entered, the user can then select one of the seven plot buttons. The seven buttons are labeled, “u”, “v”, ”w”, “Speed”, “ Horiz ...and the terrain elevation contours, respectively. The two vector display buttons, 21 “ Horiz vectors” and “Domain vectors”, produce slightly...different results. As indicated by its label, the “ Horiz vector” button will produce a wind vector plot at the user-defined elevation. The “Domain

  3. RF antenna-pattern visual aids for field use

    Science.gov (United States)

    Williams, J. H.

    1973-01-01

    Series of plots must be made of antenna pattern on polar-coordinate sheet depicting vertical planes. Separate sheets are plotted depicting antenna patterns in vertical plane at azimuth positions. After all polar plots are drawn, they are labeled according to their azimuthal positions. Transparencies are then stiffened with regular wire, cardboard, or molded plastic.

  4. Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

    Directory of Open Access Journals (Sweden)

    Judit Lecina-Diaz

    Full Text Available Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1 determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together and (2 ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires. The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn

  5. Extreme Fire Severity Patterns in Topographic, Convective and Wind-Driven Historical Wildfires of Mediterranean Pine Forests

    Science.gov (United States)

    Lecina-Diaz, Judit; Alvarez, Albert; Retana, Javier

    2014-01-01

    Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR) from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1) determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together) and (2) ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires). The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires) showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn as extreme

  6. Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

    Science.gov (United States)

    Lecina-Diaz, Judit; Alvarez, Albert; Retana, Javier

    2014-01-01

    Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR) from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1) determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together) and (2) ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires). The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires) showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn as extreme

  7. Noise source localization using Matched Field Processing: wind turbines, mofettes and geysirs.

    Science.gov (United States)

    Umlauft, Josefine; Flores Estrella, Hortencia; Christin Obermann, Anne; Korn, Michael

    2017-04-01

    The Matched Field Processing (MFP) is a beamforming method, derived from ocean acoustics, that serves as a noise source localization and exploration tool in applied geophysics. Here, we present three case studies to explore the applicability of MFP in the presence of different source types, and using sensor arrays with different aperture and density. First, we show the localization of a single wind turbine (Saxony, Eastern Germany), which acts as a point source at the surface generating continuous vibrations due to the rotation of their blades. Using 30 vertical sensors (Reftek Texans) randomly distributed within an area of approximately 50 x 50 m2 around the wind turbine, we identified the turbine as the dominant noise source within the array. Therefore we verified that the MFP procedure gives useful results. The second test was performed in Hartouŝov (NW Bohemia, Czech Republic). This area is characterized by several natural degassing areas of mantle-originating fluids and CO2 (mofettes). Mofettes either appear as little sinks filled with bubbling groundwater or more extensive as vegetation anomalies. We located these mofettes, using the collapsing water bubbles as seismic noise source, and compared our results with CO2 flux values of the same field measured by Nickschick et al. (2015). The array consisted of 130 stations in total (30 Reftek Texans, 50 Omnirecs Data-Cubes3 and 50 Summit X-One channels) and covered an area of about 500 x 1000 m2. Additionally to MFP, we perfomed a polarization analysis of surface waves to characterize the wave field generated by the the degassing process. The last example is a geysering system in NE Java (Indonesia) which is called LUSI (Lumpur Sidoarjo). The geysir was surrounded by 5 stations (Trillium Compacts) arranged in a circle with about 1.5 km diameter. Here, we could successfully locate the surface position of the geysir as well as image its feeding channel to a depth of 100 m. This example shows the suitability of MFP

  8. Comparison of aerosol backscatter and wind field estimates from the REAL and the SAMPLE

    Science.gov (United States)

    Mayor, Shane D.; Dérian, Pierre; Mauzey, Christopher F.; Spuler, Scott M.; Ponsardin, Patrick; Pruitt, Jeff; Ramsey, Darrell; Higdon, Noah S.

    2015-09-01

    Although operating at the same near-infrared 1.5- m wavelength, the Raman-shifted Eye-safe Aerosol Lidar (REAL) and the Scanning Aerosol Micro-Pulse Lidar-Eye-safe (SAMPLE) are very different in how they generate and detect laser radiation. We present results from an experiment where the REAL and the SAMPLE were operated side-by-side in Chico, California, in March of 2015. During the non-continuous, eleven day test period, the SAMPLE instrument was operated at maximum pulse repetition frequency (15 kHz) and integrated over the interpulse period of the REAL (0.1 s). Operation at the high pulse repetition frequency resulted in second trip echoes which contaminated portions of the data. The performance of the SAMPLE instrument varied with background brightness--as expected with a photon counting receiver|--yet showed equal or larger backscatter intensity signal to noise ratio throughout the intercomparison experiment. We show that a modest low-pass filter or smooth applied to the REAL raw waveforms (that have 5x higher range resolution) results in significant increases in raw signal-to-noise ratio and image signal-to-noise ratio--a measure of coherent aerosol feature content in the images resulting from the scans. Examples of wind fields and time series of wind estimates from both systems are presented. We conclude by reviewing the advantages and disadvantages of each system and sketch a plan for future research and development activities to optimize the design of future systems.

  9. Incorporating field wind data into FIRETEC simulations of the International Crown Fire Modeling Experiment (ICFME): preliminary lessons learned

    Science.gov (United States)

    Rodman Linn; Kerry Anderson; Judith Winterkamp; Alyssa Broos; Michael Wotton; Jean-Luc Dupuy; Francois Pimont; Carleton Edminster

    2012-01-01

    Field experiments are one way to develop or validate wildland fire-behavior models. It is important to consider the implications of assumptions relating to the locality of measurements with respect to the fire, the temporal frequency of the measured data, and the changes to local winds that might be caused by the experimental configuration. Twenty FIRETEC simulations...

  10. Sandia Wake Imaging System Field Test Report: 2015 Deployment at the Scaled Wind Farm Technology (SWiFT) Facility.

    Energy Technology Data Exchange (ETDEWEB)

    Naughton, Brian Thomas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Herges, Thomas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-10-01

    This report presents the objectives, configuration, procedures, reporting , roles , and responsibilities and subsequent results for the field demonstration of the Sandia Wake Imaging System (SWIS) at the Sandia Scaled Wind Farm Technology (SWiFT) facility near Lubbock, Texas in June and July 2015.

  11. Field Verification Program for Small Wind Turbines, Quartelry Report: 2nd Quarter, Issue No.1, October 2000

    Energy Technology Data Exchange (ETDEWEB)

    Tu, P.; Forsyth, T.

    2000-11-02

    The Field Verification Program for Small Wind Turbines quarterly report provides industry members with a description of the program, its mission, and purpose. It also provides a vehicle for participants to report performance data, activities, and issues during quarterly test periods.

  12. Seasonal patterns of wind-induced upwelling/downwelling in the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Andrew Bakun

    2001-09-01

    Full Text Available The historical file of wind observations from maritime weather reports is summarized to identify the characteristic seasonal distributions of wind-induced Ekman upwelling and downwelling in the Mediterranean Sea. Both coastal upwelling/downwelling and wind-stress curl-driven open ocean upwelling/downwelling are treated in a unified description. Vigorous upwelling zones are found in the eastern Aegean Sea, off the west coast of Greece, and in the Gulf of Lyons. The southern coast of the Mediterranean is found to be primarily a downwelling area, although significant coastal upwelling does appear in the Gulf of Sidra during the spring and summer seasons, and along the Algerian coast during summer.

  13. Sparse Matrix Motivated Reconstruction of Far-Field Radiation Patterns

    Science.gov (United States)

    2015-03-01

    root mean square error (RMSE). In addition, the proposed reconstruction algorithm was evaluated using measured data obtained in an anechoic chamber ...proposed approach for radiation pattern reconstruction, the time required to take measurements in an anechoic chamber can be reduced up to 87%, therefore...13  Fig. 13  2-D radiation pattern of the pyramidal horn ( anechoic chamber ) antenna and measurements used for reconstruction

  14. Bats avoid radar installations: could electromagnetic fields deter bats from colliding with wind turbines?

    Directory of Open Access Journals (Sweden)

    Barry Nicholls

    Full Text Available Large numbers of bats are killed by collisions with wind turbines, and there is at present no direct method of reducing or preventing this mortality. We therefore determine whether the electromagnetic radiation associated with radar installations can elicit an aversive behavioural response in foraging bats. Four civil air traffic control (ATC radar stations, three military ATC radars and three weather radars were selected, each surrounded by heterogeneous habitat. Three sampling points matched for habitat type and structure, dominant vegetation species, altitude and surrounding land class were located at increasing distances from each station. A portable electromagnetic field meter measured the field strength of the radar at three distances from the source: in close proximity (2 volts/metre, an intermediate point within line of sight of the radar (200-400 m and with an EMF strength 400 m and registering an EMF of zero v/m. At each radar station bat activity was recorded three times with three independent sampling points monitored on each occasion, resulting in a total of 90 samples, 30 of which were obtained within each field strength category. At these sampling points, bat activity was recorded using an automatic bat recording station, operated from sunset to sunrise. Bat activity was significantly reduced in habitats exposed to an EMF strength of greater than 2 v/m when compared to matched sites registering EMF levels of zero. The reduction in bat activity was not significantly different at lower levels of EMF strength within 400 m of the radar. We predict that the reduction in bat activity within habitats exposed to electromagnetic radiation may be a result of thermal induction and an increased risk of hyperthermia.

  15. Before?After Field Study of Effects of Wind Turbine Noise on Polysomnographic Sleep Parameters

    OpenAIRE

    Jalali, Leila; Bigelow, Philip; Nezhad-Ahmadi, Mohammad-Reza; Gohari, Mahmood; Williams, Diane; McColl, Steve

    2016-01-01

    Wind is considered one of the most advantageous alternatives to fossil energy because of its low operating cost and extensive availability. However, alleged health-related effects of exposure to wind turbine (WT) noise have attracted much public attention and various symptoms, such as sleep disturbance, have been reported by residents living close to wind developments. Prospective cohort study with synchronous measurement of noise and sleep physiologic signals was conducted to explore the pos...

  16. First in situ evidence of wakes in the far field behind offshore wind farms.

    Science.gov (United States)

    Platis, Andreas; Siedersleben, Simon K; Bange, Jens; Lampert, Astrid; Bärfuss, Konrad; Hankers, Rudolf; Cañadillas, Beatriz; Foreman, Richard; Schulz-Stellenfleth, Johannes; Djath, Bughsin; Neumann, Thomas; Emeis, Stefan

    2018-02-01

    More than 12 GW of offshore wind turbines are currently in operation in European waters. To optimise the use of the marine areas, wind farms are typically clustered in units of several hundred turbines. Understanding wakes of wind farms, which is the region of momentum and energy deficit downwind, is important for optimising the wind farm layouts and operation to minimize costs. While in most weather situations (unstable atmospheric stratification), the wakes of wind turbines are only a local effect within the wind farm, satellite imagery reveals wind-farm wakes to be several tens of kilometres in length under certain conditions (stable atmospheric stratification), which is also predicted by numerical models. The first direct in situ measurements of the existence and shape of large wind farm wakes by a specially equipped research aircraft in 2016 and 2017 confirm wake lengths of more than tens of kilometres under stable atmospheric conditions, with maximum wind speed deficits of 40%, and enhanced turbulence. These measurements were the first step in a large research project to describe and understand the physics of large offshore wakes using direct measurements, together with the assessment of satellite imagery and models.

  17. Wind estimation around the shipwreck of Oriental Star based on field damage surveys and radar observations.

    Science.gov (United States)

    Meng, Zhiyong; Yao, Dan; Bai, Lanqiang; Zheng, Yongguang; Xue, Ming; Zhang, Xiaoling; Zhao, Kun; Tian, Fuyou; Wang, Mingjun

    Based on observational analyses and on-site ground and aerial damage surveys, this work aims to reveal the weather phenomena-especially the wind situation-when Oriental Star capsized in the Yangtze River on June 1, 2015. Results demonstrate that the cruise ship capsized when it encountered strong winds at speeds of at least 31 m s-1 near the apex of a bow echo embedded in a squall line. As suggested by the fallen trees within a 2-km radius around the wreck location, such strong winds were likely caused by microburst straight-line wind and/or embedded small vortices, rather than tornadoes.

  18. On Discrete Killing Vector Fields and Patterns on Surfaces

    KAUST Repository

    Ben-Chen, Mirela

    2010-09-21

    Symmetry is one of the most important properties of a shape, unifying form and function. It encodes semantic information on one hand, and affects the shape\\'s aesthetic value on the other. Symmetry comes in many flavors, amongst the most interesting being intrinsic symmetry, which is defined only in terms of the intrinsic geometry of the shape. Continuous intrinsic symmetries can be represented using infinitesimal rigid transformations, which are given as tangent vector fields on the surface - known as Killing Vector Fields. As exact symmetries are quite rare, especially when considering noisy sampled surfaces, we propose a method for relaxing the exact symmetry constraint to allow for approximate symmetries and approximate Killing Vector Fields, and show how to discretize these concepts for generating such vector fields on a triangulated mesh. We discuss the properties of approximate Killing Vector Fields, and propose an application to utilize them for texture and geometry synthesis. Journal compilation © 2010 The Eurographics Association and Blackwell Publishing Ltd.

  19. Wind Field Reconstruction from Nacelle-Mounted Lidars Short Range Measurements

    DEFF Research Database (Denmark)

    Borraccino, Antoine; Schlipf, David; Haizmann, Florian

    2017-01-01

    at multiple distances close to the rotor, where a wind model is combined with a simple induction model. The method allows robust determination of free-stream wind characteristics. The method was applied to experimental data obtained with two different types of nacelle lidar (five-beam Demonstrator and Zeph...

  20. Field wind tunnel testing of two silt loam soils on the North American Central High Plains

    Science.gov (United States)

    Wind erosion is a soil degrading process that threatens agricultural sustainability and environmental quality globally. Protecting the soil surface with cover crops and plant residues is a highly effective method for shielding the soil surface from the erosive forces of wind. Recently, advances in...

  1. Different injury pattern in goalkeepers compared to field players

    DEFF Research Database (Denmark)

    Eirale, Cristiano; Tol, Johannes L; Whiteley, Rod

    2014-01-01

    Goalkeepers have a specific physiological and biomechanical profile including hip loading with increased frontal plane kinetics and explosive side jumps. The aim of this study is to analyze the injury incidence in professional goalkeepers and to compare this with field players.......Goalkeepers have a specific physiological and biomechanical profile including hip loading with increased frontal plane kinetics and explosive side jumps. The aim of this study is to analyze the injury incidence in professional goalkeepers and to compare this with field players....

  2. Seasonal effects of wind conditions on migration patterns of soaring American white pelican

    OpenAIRE

    Gutierrez Illan, Javier; Wang, Guiming; Cunningham, Fred L.; King, D. Tommy

    2017-01-01

    Energy and time expenditures are determinants of bird migration strategies. Soaring birds have developed migration strategies to minimize these costs, optimizing the use of all the available resources to facilitate their displacement. We analysed the effects of different wind factors (tailwind, turbulence, vertical updrafts) on the migratory flying strategies adopted by 24 satellite-tracked American white pelicans (Pelecanus erythrorhynchos) throughout spring and autumn in North America. We h...

  3. Charged-Particle Transport in the Data-Driven, Non-Isotropic Turbulent Mangetic Field in the Solar Wind

    Science.gov (United States)

    Sun, P.; Jokipii, J. R.; Giacalone, J.

    2016-12-01

    Anisotropies in astrophysical turbulence has been proposed and observed for a long time. And recent observations adopting the multi-scale analysis techniques provided a detailed description of the scale-dependent power spectrum of the magnetic field parallel and perpendicular to the scale-dependent magnetic field line at different scales in the solar wind. In the previous work, we proposed a multi-scale method to synthesize non-isotropic turbulent magnetic field with pre-determined power spectra of the fluctuating magnetic field as a function of scales. We present the effect of test particle transport in the resulting field with a two-scale algorithm. We find that the scale-dependent turbulence anisotropy has a significant difference in the effect on charged par- ticle transport from what the isotropy or the global anisotropy has. It is important to apply this field synthesis method to the solar wind magnetic field based on spacecraft data. However, this relies on how we extract the power spectra of the turbulent magnetic field across different scales. In this study, we propose here a power spectrum synthesis method based on Fourier analysis to extract the large and small scale power spectrum from a single spacecraft observation with a long enough period and a high sampling frequency. We apply the method to the solar wind measurement by the magnetometer onboard the ACE spacecraft and regenerate the large scale isotropic 2D spectrum and the small scale anisotropic 2D spectrum. We run test particle simulations in the magnetid field generated in this way to estimate the transport coefficients and to compare with the isotropic turbulence model.

  4. Seabird aggregative patterns: a new tool for offshore wind energy risk assessment.

    Science.gov (United States)

    Christel, Isadora; Certain, Grégoire; Cama, Albert; Vieites, David R; Ferrer, Xavier

    2013-01-15

    The emerging development of offshore wind energy has raised public concern over its impact on seabird communities. There is a need for an adequate methodology to determine its potential impacts on seabirds. Environmental Impact Assessments (EIAs) are mostly relying on a succession of plain density maps without integrated interpretation of seabird spatio-temporal variability. Using Taylor's power law coupled with mixed effect models, the spatio-temporal variability of species' distributions can be synthesized in a measure of the aggregation levels of individuals over time and space. Applying the method to a seabird aerial survey in the Ebro Delta, NW Mediterranean Sea, we were able to make an explicit distinction between transitional and feeding areas to define and map the potential impacts of an offshore wind farm project. We use the Ebro Delta study case to discuss the advantages of potential impacts maps over density maps, as well as to illustrate how these potential impact maps can be applied to inform on concern levels, optimal EIA design and monitoring in the assessment of local offshore wind energy projects. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Lisbon Urban Heat Island Updated: New Highlights about the Relationships between Thermal Patterns and Wind Regimes

    Directory of Open Access Journals (Sweden)

    António Lopes

    2013-01-01

    Full Text Available Urban growth implies significant modifications in the urban climate. To understand the influence of the city of Lisbon on the urban boundary layer, a mesoscale meteorological network was installed in 2004. The main goals of the present study are to update the results of the research published in 2007 and to bring more precise information about the relationship between the Urban Heat Island (UHI and the regional and local wind systems. The highest frequencies of the UHI were found in the city centre (Restauradores. In the green park of Monsanto, the highest frequency occurred between −2 and 0°C. During the summer, the effect of the breezes was observed in Belém, lowering the temperature. The “strong” UHI (intensity >4°C occurred more often during the summer, with median values of 2°C by night and 1.8°C by day. The highest frequencies of UHI occurred for winds between 2 and 6 m/s and were not associated with atmospheric calm, as pointed out in the literature. Winds above 8 m/s inhibit the occurrence of strong UHI in Lisbon. Summer nighttime strong UHI should be further investigated, due to the heat stress consequences on the population and probable increase of energy consumption.

  6. The effect of wind speed on the statistics of the temperature field of an air/water interface

    Science.gov (United States)

    Saylor, J. R.; Conover, T. A.

    2006-11-01

    An experimental study is presented of the transfer of heat from a warm body of water to an air flow above it. This work was conducted in a wind/water tunnel, permitting these experiments to be conducted over a range of wind speeds and heat fluxes. The temperature field of the air/water interface was measured using an infrared camera. These temperature fields were used to compute the root mean square (rms) of the interfacial temperature. The relationship between the rms and the heat flux was obtained, and the sensitivity of this relationship to the wind speed was determined. The experiments were conducted for conditions where forced convection and natural convection both contribute to the heat transfer rate. Data are presented for cases where the water surface was covered with a soluble and an insoluble surfactant monolayer. Sample infrared images are presented for several wind speeds, and the relevance of this work to the remote sensing of heat flux will be discussed.

  7. Evaluating the Relationship between Field Aerodynamic Roughness and the MODIS BRDF, NDVI, and Wind Speed over Grassland

    Directory of Open Access Journals (Sweden)

    Qiang Xing

    2017-01-01

    Full Text Available Aerodynamic roughness (AR is an important parameter that influences the momentum and energy exchange between the earth’s surface and the atmosphere. In this study, profile wind data observed during the vegetation growing period (April–September in 2013 and 2014 at the A’rou grassland station, which is in the upstream of the Heihe River Basin (HRB, were used to determine the relationship between the field AR and the Moderate-resolution Imaging Spectroradiometer (MODIS near-infrared (NIR bi-directional reflectance distribution function (BRDF R index, the normalized difference vegetation index (NDVI, and a combination of these indices. In addition, the relationship between the average wind speed at a height of 1 m and the field AR is also presented. The results indicate that the MODIS NIR BRDF_R index and the NDVI are both sensitive indicators of the AR over grassland (R2: 0.5228 for NIR BRDF_R; R2: 0.579 for NDVI. Moreover, the combined index shows a significantly increased R2 value of 0.721, which is close to the result inferred from the wind speed (R2: 0.7411. The proposed remote sensing-based combination index (CI has the potential for use in evaluations of the AR over grasslands during growing season and its sensitivity can reach levels that are comparable to considering the effects of wind speed, which usually requires ground-based observations.

  8. Towards general patterns of features in multi-field inflation

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Xian [Department of Physics, Tokyo Institute of Technology,2-12-1 Ookayama, Meguro, Tokyo, 152-8551 (Japan); Gong, Jinn-Ouk [Asia Pacific Center for Theoretical Physics,67 Cheongam-ro, Pohang, 790-784 (Korea, Republic of); Department of Physics, Postech,77 Cheongam-ro, Pohang, 790-784 (Korea, Republic of)

    2015-08-24

    We investigate the consequences of general curved trajectories in multi-field inflation. After setting up a completely general formalism using the mass basis, which naturally accommodates the notion of light and heavy modes, we study in detail the simple case of two successive turns in two-field system. We find the power spectrum of the curvature perturbation receives corrections that exhibit oscillatory features sinusoidal in the logarithm of the comoving wavenumber without slow-roll suppression. We show that this is because of the resonance of the heavy modes inside and outside the mass horizon.

  9. Using Wind and Temperature Fields to Study Dehydration Mechanisms in the Tropical Tropopause Layer

    Science.gov (United States)

    Pittman, Jasna; Miller, Timothy; Robertson, Franklin

    2008-01-01

    The tropics are the main region for troposphere-to-stratosphere transport (TST) of air. One of the dominant mechanisms that control tropical TST of water vapor is freeze-drying by the cold tropical tropopause. This mechanism is supported by evidence from satellite observations of the "tape recorder", where seasonal changes in stratospheric water vapor are in phase with seasonal changes in tropopause temperatures in the tropics. Over the last few years, however, the concept of the tropical tropopause has evolved from a single material surface to a layer called the Tropical Tropopause Layer (TTL). A recent hypothesis on dehydration mechanisms suggests that dehydration and entry point into the stratosphere are not always co-located (Holton and Gettelman, 2001). Instead, dehydration can occur during horizontal advection through Lagrangian 'cold pools', or coldest regions along a parcel's trajectory, as air ascends within the TTL while the entry point into the stratosphere occurs at a different geographical location. In this study, we investigate the impact that these Lagrangian cold pools have on TTL moisture. For this purpose, we use in situ measurements of TTL water vapor obtained aboard NASA's WB-57 aircraft over the Eastern Tropical Pacific, and we compare these measurements to minimum saturation water vapor mixing ratios obtained from three-dimensional backward trajectory calculations. Aircraft measurements show frequent unsaturated conditions, which suggest that the entry value of stratospheric water vapor in this region was not set by local saturation conditions. Trajectory calculations, driven by both ECMWF operational analysis and reanalysis winds and temperature fields, are used to explore the impact (e.g., geographical location, timing, dehydration magnitude) of the Lagrangian cold pools intercepted by the parcels sampled by the aircraft. We find noteworthy differences in the location of the Lagrangian cold pools using the two ECMWF data sets, namely

  10. Patterns of non-embolic transient monocular visual field loss

    NARCIS (Netherlands)

    Petzold, A.; Islam, N.; Plant, G.T.

    2013-01-01

    The aim of this study was to systematically describe the semiology of non-embolic transient monocular visual field loss (neTMVL). We conducted a retrospective case note analysis of patients from Moorfields Eye Hospital (1995-2007). The variables analysed were age, age of onset, gender, past medical

  11. Topological field patterns in the Yang–Mills theory

    Indian Academy of Sciences (India)

    Here, we obtain an expression for the charges of these topological SO(3) gauge field configurations in terms of the Abelian vector potentials. In this formalism we analyse the 't Hooft–Polyakov monopole solution. Keywords. Topological configurations; Yang–Mills theory; monopole. PACS Nos 14.80.Hv; 11.15.-q; 11.15.Tk. 1.

  12. Experimental surface flow patterns and flow-field phenomena of a delta-wing space-shuttle orbiter

    Science.gov (United States)

    Cleary, J. W.

    1972-01-01

    Composite photographs of the surface flow and shadowgraphs of the shock wave pattern are presented that depict the hypersonic flow field of a typical delta wing space shuttle orbiter. Results from a wind tunnel test in air are given in side, oblique, and projected plan views for angles of attack from 0 to 60 deg. The tests were conducted at a Mach number of 7.4 and for Reynolds numbers based on body length of 6,000,000 and 9,000,000. The interrelationship is shown for the intersecting bow and wing leading edge waves with the surface flow for angles of attack for which: (1) the leading edge wave is attached, and (2) the leading edge wave is detached.

  13. Generation of high-resolution wind fields from the dense meteorological station network WegenerNet in South-Eastern Austria

    Science.gov (United States)

    Schlager, Christoph; Kirchengast, Gottfried; Fuchsberger, Jürgen

    2016-04-01

    To investigate weather and climate on a local scale as well as for evaluating regional climate models (RCMs) the Wegener Center at the University of Graz established the long-term field experiment WegenerNet Feldbach region, a dense grid of 153 meteorological stations. The observations of these stations are managed by an automatic WegenerNet Processing system. This system includes a quality check of collected observations and a Data Product Generator (DPG), among other subsystems. Products already implemented in the DPG are gridded weather and climate products, generated from the main parameters temperature, precipitation and relative humidity (Kirchengast et. al., Bull. Amer. Meteor. Soc., 95, 227-242, 2014). Missing elements are gridded wind fields from wind observations. Wind is considered as one of the most difficult meteorological variables to model and depends on many different parameters such as topography and surface roughness. Therefore a simple interpolation can only be performed in case of uniform characteristics of landscape. The presentation introduces our method of generation of wind fields from near real-time observations of the WegenerNet. Purpose of this work is to provide a database with 3D wind fields in a high spatial and time resolution as addition to the existing products, for evaluating convection permitting climate models as well as investigating weather and climate on a local scale. Core of the application is the diagnostic California Meteorological Model (CALMET). This model computes 3D wind fields based on meteorological observational data, a digital elevation model and land use categories. The application generates the required input files from meteorological stations of the WegenerNet Feldbach region and triggers the start of the CALMET model with these input files. In a next step the modeled wind fields are stored automatically every 30 minutes with a spatial resolution of 100 x 100 m in the WegenerNet database. To verify the

  14. Relation between the variations of the solar wind and the noon-time equatorial ionospheric electric fields

    Science.gov (United States)

    Manoj, C.; Maus, S.; Alken, P.; Gentile, L.; Burke, W.

    2007-12-01

    We compare the solar wind measurements from ACE satellite with the vertical plasma drift (observed by JULIA radar) and the EEJ magnetic signals (observed at HUA observatory) from the South American equatorial sector. The aim is to understand the effect of solar wind on the variations of the electric field in the noon time equatorial ionosphere. We restrict our study to local noon time conditions, geomagnetically active days and while interplanetary Bz is negative. The estimates of electric field intensities (E_VS) at equatorial plain of the magnetosphere were made from ACE data using a combination of Volland-Stern and Siscoe-Hill models (Burke et al, 2007). The JULIA and magnetometer data were high-pass filtered to remove the regular daily variations. The relation between the data set will be presented as a coherence spectrum. In addition, the use of the ACE measurements to improve the climatological models of EEJ during geomagnetically active days will be explored.

  15. 9- by 15-Foot Low-Speed Wind Tunnel Acoustic Free Field Evaluation; Part 1: Qualification Report Summary and Part 2: Anechoic Environment Characterization Field Test Report

    Science.gov (United States)

    Schmitt, Jeff G.; Stahnke, Brian

    2017-01-01

    This report describes test results from an assessment of the acoustically treated 9x15 Foot Low Speed Wind Tunnel at the NASA Glenn Research Center in Cleveland, Ohio in July of 2016. The tests were conducted in accordance with the recently adopted international standard ISO 26101-2012 on Qualification of Free Field Test Environments. This method involves moving a microphone relative to a source and comparing the sound pressure level versus distance measurements with theoretical inverse square law spreading.

  16. Field scale experiments to assess the effects of offshore wind farms on marine organisms

    Energy Technology Data Exchange (ETDEWEB)

    Gill, Andrew; Mueller-Blenkle, Christina; McGregor, Peter K.; Andersson, Mathias H.; Metcalfe, Julian; Bendall, Victoria; Sigray, Peter; Wood, Daniel; Wearmouth, Victoria; Thomsen, Frank

    2011-07-01

    Full text: There are different phases in the life of an Offshore Wind Farm (OWF) that need to be considered in terms of how it interacts with the coastal ecosystem: the survey and construction, operation and decommissioning. Taking these phases and identifying the associated effectors and whether they have an effect on coastal organisms is an important step before going on to determine whether actual impact may occur. Hence, we have developed studies focussing first on assessing the effects on species individuals at an appropriate scale and, subsequently looking at the effect across multiple individuals which could then be used to assess effects at the level of the population, thereby providing evidence for an impact (either positive or negative). To obtain ecologically relevant results at a scale appropriate for OWFs, we have taken the experimental approach, incorporating a treatment and control, into the coastal environment using large underwater netted structures (mesocosms) to provide a more realistic setting. To date, our studies have used the mesocosm approach to increase understanding of two relatively unknown effectors on fish: underwater pile-driving noise (Construction Phase) and Electromagnetic Fields (EMF), associated with the production of the electricity by OWFs (Operational Phase). The approach presented here clearly demonstrates that specific effects of OWFs on fish (and potentially other marine organisms) can be determined at a scale that is ecologically relevant. Furthermore, it that provides an important step in assessing what effectors need to be considered in terms of their possible impacts, thereby moving the research agenda forward whilst also meeting the needs of the stake holders involved with OWF. (Author)

  17. Patterning of hydrogenated microcrystalline silicon growth by magnetic field

    Czech Academy of Sciences Publication Activity Database

    Fejfar, Antonín; Stuchlík, Jiří; Mates, Tomáš; Ledinský, Martin; Honda, Shinya; Kočka, Jan

    2005-01-01

    Roč. 87, č. 1 (2005), 011901/1-011901/3 ISSN 0003-6951 R&D Projects: GA AV ČR(CZ) IAA1010316; GA AV ČR(CZ) IAA1010413; GA ČR(CZ) GD202/05/H003 Institutional research plan: CEZ:AV0Z10100521 Keywords : hydrogenated microcrystalline silicon * magnet ic field growth Subject RIV: BM - Solid Matter Physics ; Magnet ism Impact factor: 4.127, year: 2005

  18. Wind energy concentration within vortex flow fields and its utilization for the generation of energy, phase 1

    Science.gov (United States)

    Greff, E.; Holsdeppe, D.

    1983-08-01

    Delta-shaped planforms serving as vortex generators were investigated in a water tunnel where vortex stabilization by spanwise camber was achieved. The velocity field of an optimized wing was measured in a wind tunnel with a five hole probe. Codes for rotor blade design in flows with swirl were derived and a threefold optimum solidity was found. Power measurements on a four blade rotor show an upper limit of loading at a power amplification ratio of two.

  19. Disturbance of the inclined inserting-type sand fence to wind-sand flow fields and its sand control characteristics

    Science.gov (United States)

    Cheng, Jian-jun; Lei, Jia-qiang; Li, Sheng-yu; Wang, Hai-feng

    2016-06-01

    The inclined inserting-type sand fence is a novel sand retaining wall adopted along the Lanxin High-Speed Railway II in Xinjiang for controlling and blocking sand movement. To verify the effectiveness of the new fence structure for sand prevention, a wind tunnel test was used for flow field test simulation of the sand fence. The results indicate that the inclined inserting-type sand fence was able to deflect the flow of the sand and was able to easily form an upward slant acceleration zone on the leeward side of the sand fence. As shown by the percentage change in sand collection rates on the windward side and the leeward side of the sand fence, the sand flux per unit area at 4 m height in the slant upward direction increased on the leeward side of the inclined inserting-type sand fence. By comparing the flow fields, this site is an acceleration zone, which also reaffirms the correspondence of wind-sand flow fields with the spatial distribution characteristic of the wind-carried sand motion. The field sand collection data indicates that under the effects of the inclined inserting-type sand fence, the sandy air currents passing in front and behind the sand fence not only changed in quality, but the grain composition and particle size also significantly changed, suggesting that the inclined inserting-type sand fence has a sorting and filtering effect on the sandy air currents that passed through. The fence retained coarse particulates on the windward side and fine particulates within the shade of the wind on the leeward side.

  20. ORIENTED FOR CAD UNIVERSAL MATHEMATICAL MODEL OF THE EDDY CURRENT PROBE. PART 1. THE RESULTING FIELD OF THE DRIVE WINDING

    Directory of Open Access Journals (Sweden)

    A. G. Dedegkaev

    2015-01-01

    Full Text Available The work relates to the field of CAD methods and means of nondestructive electromagnetic testing of conductive flat products. The problem of constructing mathematical model of the drive winding eddy current probe linearly extended form is polygon in cross section. This allows you to create a universal mathematical model, which includes a model of a simpler shape in cross-section, as a special case. 

  1. Extrapolation of Extreme Response for Wind Turbines based on FieldMeasurements

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    2009-01-01

    The characteristic loads on wind turbines during operation are among others dependent on the mean wind speed, the turbulence intensity and the type and settings of the control system. These parameters must be taken into account in the assessment of the characteristic load. The characteristic load...... is normally determined by statistical extrapolation of the simulated response during operation according to IEC 61400-1 2005. However, this method assumes that the individual 10 min. time series are independent and that peaks extracted are independent. In the present paper two new methods for loads...... extrapolation are presented. The first method is based on the same assumptions as the existing method but the statistical extrapolation is only performed for a limited number of mean wind speeds where the extreme load is likely to occur. For the second method the mean wind speeds are divided into storms which...

  2. Multivariate reconstruction of missing data in sea surface temperature, chlorophyll, and wind satellite fields

    OpenAIRE

    Alvera-Azcarate, A.; A.; Barth; Beckers, J.-M.; Weisberg, R.H.

    2007-01-01

    An empirical orthogonal function-based technique called Data Interpolating Empirical Orthogonal Functions (DINEOF) is used in a multivariate approach to reconstruct missing data. Sea surface temperature (SST), chlorophyll a concentration, and QuikSCAT winds are used to assess the benefit of a multivariate reconstruction. In particular, the combination of SST plus chlorophyll, SST plus lagged SST plus chlorophyll, and SST plus lagged winds have been studied. To assess the quality of the recons...

  3. Solar wind electron interaction with the dayside lunar surface and crustal magnetic fields: Evidence for precursor effects

    Science.gov (United States)

    Halekas, J. S.; Poppe, A.; Delory, G. T.; Farrell, W. M.; Horányi, M.

    2012-02-01

    Electron distributions measured by Lunar Prospector above the dayside lunar surface in the solar wind often have an energy dependent loss cone, inconsistent with adiabatic magnetic reflection. Energy dependent reflection suggests the presence of downward parallel electric fields below the spacecraft, possibly indicating the presence of a standing electrostatic structure. Many electron distributions contain apparent low energy (<100 eV) upward-going conics (58% of the time) and beams (12% of the time), primarily in regions with non-zero crustal magnetic fields, implying the presence of parallel electric fields and/or wave-particle interactions below the spacecraft. Some, but not all, of the observed energy dependence comes from the energy gained during reflection from a moving obstacle; correctly characterizing electron reflection requires the use of the proper reference frame. Non-adiabatic reflection may also play a role, but cannot fully explain observations. In cases with upward-going beams, we observe partial isotropization of incoming solar wind electrons, possibly indicating streaming and/or whistler instabilities. The Moon may therefore influence solar wind plasma well upstream from its surface. Magnetic anomaly interactions and/or non-monotonic near surface potentials provide the most likely candidates to produce the observed precursor effects, which may help ensure quasi-neutrality upstream from the Moon.

  4. Implications of the UK field trial of building mounted horizontal axis micro-wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    James, P.A.B.; Sissons, M.F.; Myers, L.E.; Bahaj, A.S.; Anwar, A. [Sustainable Energy Research Group, School of Civil Engineering and Environment, University of Southampton, Highfield, Southampton SO19 1BJ (United Kingdom); Bradford, J.; Green, S. [Energy Saving Trust, 21 Dartmouth Street, London SW1H 9BP (United Kingdom)

    2010-10-15

    Building mounted micro-wind turbines and photovoltaics have the potential to provide widely applicable carbon free electricity generation at the building level. Photovoltaic systems are well understood and it is easy to predict performance using software tools or widely accepted yield estimates. Micro-wind, however, is far more complex and in comparison poorly understood. This paper presents the key findings of the building mounted (<2 kWp) turbine component of the UK micro-wind trial undertaken by the Energy Saving Trust in 2008/09. The monitored performance of 39 horizontal axis turbines in urban, suburban and rural locations is discussed alongside the accuracy of predictive wind speed tools for the sites. The performance of urban and suburban micro-wind sites in the trial was poor with annual generation of less than 75 kWh/m{sup 2} swept area, the majority of which were less than 25 kWh/m{sup 2}. Good rural sites had an annual generation of between 100 and 280 kWh/m{sup 2}, far less than the nominal 360 kWh/m{sup 2} (10% load factor for a typical turbine) that is often assumed. In the light of these findings, the potential impact of the UK's latest policy instrument, the 2010 micro-generation tariffs, is considered for both micro-wind and photovoltaics. (author)

  5. ION KINETIC ENERGY CONSERVATION AND MAGNETIC FIELD STRENGTH CONSTANCY IN MULTI-FLUID SOLAR WIND ALFVÉNIC TURBULENCE

    Energy Technology Data Exchange (ETDEWEB)

    Matteini, L.; Horbury, T. S.; Schwartz, S. J. [The Blackett Laboratory, Imperial College London, SW7 2AZ (United Kingdom); Pantellini, F. [LESIA, Observatoire de Paris, CNRS, UPMC, Universit Paris-Diderot, 5 Place Jules Janssen, F-92195 Meudon (France); Velli, M. [Department of Earth, Planetary, and Space Sciences, UCLA, California (United States)

    2015-03-20

    We investigate the properties of plasma fluid motion in the large-amplitude, low-frequency fluctuations of highly Alfvénic fast solar wind. We show that protons locally conserve total kinetic energy when observed from an effective frame of reference comoving with the fluctuations. For typical properties of the fast wind, this frame can be reasonably identified by alpha particles which, due to their drift with respect to protons at about the Alfvén speed along the magnetic field, do not partake in the fluid low-frequency fluctuations. Using their velocity to transform the proton velocity into the frame of Alfvénic turbulence, we demonstrate that the resulting plasma motion is characterized by a constant absolute value of the velocity, zero electric fields, and aligned velocity and magnetic field vectors as expected for unidirectional Alfvénic fluctuations in equilibrium. We propose that this constraint, via the correlation between velocity and magnetic field in Alfvénic turbulence, is the origin of the observed constancy of the magnetic field; while the constant velocity corresponding to constant energy can only be observed in the frame of the fluctuations, the corresponding constant total magnetic field, invariant for Galilean transformations, remains the observational signature in the spacecraft frame of the constant total energy in the Alfvén turbulence frame.

  6. Field Testing of LIDAR-Assisted Feedforward Control Algorithms for Improved Speed Control and Fatigue Load Reduction on a 600-kW Wind Turbine: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Avishek A.; Bossanyi, Ervin A.; Scholbrock, Andrew K.; Fleming, Paul; Boquet, Mathieu; Krishnamurthy, Raghu

    2015-12-14

    A severe challenge in controlling wind turbines is ensuring controller performance in the presence of a stochastic and unknown wind field, relying on the response of the turbine to generate control actions. Recent technologies such as LIDAR, allow sensing of the wind field before it reaches the rotor. In this work a field-testing campaign to test LIDAR Assisted Control (LAC) has been undertaken on a 600-kW turbine using a fixed, five-beam LIDAR system. The campaign compared the performance of a baseline controller to four LACs with progressively lower levels of feedback using 35 hours of collected data.

  7. Laser Interferometer Space Antenna (LISA) Far Field Phase Pattern

    Science.gov (United States)

    Waluschka, Eugene

    1999-01-01

    The Laser Interferometry Space Antenna (LISA) for the detection of Gravitational Waves is a very long baseline interferometer that will measure the changes in the distance of a five million kilometer arm to pico meter accuracies. Knowledge of the phase deviations from a spherical wave and what causes these deviations are needed considerations in (as a minimum) the design of the telescope and in determining pointing requirements. Here we present the far field phase deviations from a spherical wave for given Zernike aberrations and obscurations of the exit pupil.

  8. Centennial eolian cyclicity in the Great Plains, USA: A dominant pattern of wind transport over the past 4000 years?

    Science.gov (United States)

    Schwalb, Antje; Dean, Walter E.; Fritz, C. Sherilyn; Geiss, Christoph E.; Kromer, Bernd

    2010-01-01

    Proxy evidence at decadal resolution from Late Holocene sediments from Pickerel Lake, northeastern South Dakota, shows distinct centennial cycles (400-700 years) in magnetic susceptibility; contents of carbonate, organic carbon, and major elements; abundance in ostracodes; and delta18O and delta13C values in calcite. Proxies indicate cyclic changes in eolian input, productivity, and temperature. Maxima in magnetic susceptibility are accompanied by maxima in aluminum and iron mass accumulation rates (MARs), and in abundances of the ostracode Fabaeformiscandona rawsoni. This indicates variable windy, and dry conditions with westerly wind dominance, including during the Medieval Climate Anomaly. Maxima in carbonates, organic carbon, phosphorous, and high delta13C values of endogenic calcite indicate moister and less windy periods with increased lake productivity, including during the Little Ice Age, and alternate with maxima of eolian transport. Times of the Maunder, Sporer and Wolf sunspot minima are characterized by maxima in delta18O values and aluminum MARs, and minima in delta13C values and organic carbon content. We interpret these lake conditions during sunspot minima to indicate decreases in lake surface water temperatures of up to 4-5 degrees C associated with decreases in epilimnetic productivity during summer. We propose that the centennial cycles are triggered by solar activity, originate in the tropical Pacific, and their onset during the Late Holocene is associated with insolation conditions driven by precession. The cyclic pattern is transmitted from the tropical Pacific into the atmosphere and transported by westerly winds into the North Atlantic realm where they strengthen the Atlantic Meridional Overturning Circulation during periods of northern Great Plains wind maxima. This consequently leads to moister climates in Central and Northern Europe. Thus, Pickerel Lake provides evidence for mechanisms of teleconnections including an atmospheric link

  9. Ground-based Wind Field Construction from Mode-S and ADS-B Data with a Novel Gas Particle Model

    NARCIS (Netherlands)

    Sun, J.; Vû (Student TU Delft), Huy; Ellerbroek, J.; Hoekstra, J.M.

    2017-01-01

    Wind is an important parameter in many air traffic management researches, as it often introduces significant uncertainties in aircraft performance studies and trajectory predictions. Obtaining accurate wind field information has always been a challenge due to the availability of weather sensors.

  10. Learning to Recognize Patterns: Changes in the Visual Field with Familiarity

    Science.gov (United States)

    Bebko, James M.; Uchikawa, Keiji; Saida, Shinya; Ikeda, Mitsuo

    1995-01-01

    Two studies were conducted to investigate changes which take place in the visual information processing of novel stimuli as they become familiar. Japanese writing characters (Hiragana and Kanji) which were unfamiliar to two native English speaking subjects were presented using a moving window technique to restrict their visual fields. Study time for visual recognition was recorded across repeated sessions, and with varying visual field restrictions. The critical visual field was defined as the size of the visual field beyond which further increases did not improve the speed of recognition performance. In the first study, when the Hiragana patterns were novel, subjects needed to see about half of the entire pattern simultaneously to maintain optimal performance. However, the critical visual field size decreased as familiarity with the patterns increased. These results were replicated in the second study with more complex Kanji characters. In addition, the critical field size decreased as pattern complexity decreased. We propose a three component model of pattern perception. In the first stage a representation of the stimulus must be constructed by the subject, and restricting of the visual field interferes dramatically with this component when stimuli are unfamiliar. With increased familiarity, subjects become able to reconstruct a previous representation from very small, unique segments of the pattern, analogous to the informativeness areas hypothesized by Loftus and Mackworth [J. Exp. Psychol., 4 (1978) 565].

  11. Very high-accuracy calibration of radiation pattern and gain of a near-field probe

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Nielsen, Jeppe Majlund; Breinbjerg, Olav

    2014-01-01

    In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission of the Europ......In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission...

  12. 3D WindScanner lidar measurements of wind and turbulence around wind turbines, buildings and bridges

    DEFF Research Database (Denmark)

    Mikkelsen, Torben Krogh; Sjöholm, Mikael; Angelou, Nikolas

    2017-01-01

    structures and of flow in urban environments. The mobile WindScanner facility enables 3D scanning of wind and turbulence fields in full scale within the atmospheric boundary layer at ranges from 10 meters to 5 (10) kilometers. Measurements of turbulent coherent structures are applied for investigation...... of flow pattern and dynamical loads from turbines, building structures and bridges and in relation to optimization of the location of, for example, wind farms and suspension bridges. This paper presents our achievements to date and reviews briefly the state-of-the-art of the WindScanner measurement...

  13. Modeling and Analysis of the Wind-Waves Field Variability in the Indian Ocean During 1998-2009 Years

    CERN Document Server

    Polnikov, V G; Sannasiraj, S A; Sundar, V

    2011-01-01

    To calculate the wind-waves in the Indian Ocean (IO), the wind field for the period from 1998 to 2009 was used, obtained from the NCEP/NOAA archive, and numerical model WAM (Cycle-4) was applied, modified by the new source function proposed in Polnikov (2005). Based on buoy data for the Indian Ocean, the fitting of the modified model WAM was done, which provides the win in accuracy of calculations on 35%, in comparison with the original model. All the further calculations of the wave fields in IO were made for these model settings. At the first stage, the analysis of the simulation results involves a) mapping the fields of the significant wave height and the wave energy , calculated with different scales of averaging in time T and space R; b) estimating the fields of seasonal, annual and long-term variability; and c) determining the 12-year trend of the annually averaged fields. The analysis was carried out taking into account the previously introduced zoning the ocean area, provided by the spatial inhomogen...

  14. Measurement of rotor centre flow direction and turbulence in wind farm environment

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Demurtas, Giorgio; Sommer, A.

    2014-01-01

    The measurement of inflow to a wind turbine rotor was made with a spinner anemometer on a 2 MW wind turbine in a wind farm of eight wind turbines. The wind speed, yaw misalignment and flow inclination angle was measured during a five months measurement campaign. Angular measurements were calibrated...... factor function. Yaw measurements and turbulence measurements, where the average wind speed was corrected to the far field with the induction function, showed good correlation with mast measurements. The yaw misalignment measurements showed a significant yaw misalignment for most of the wind speed range......, and also a minor symmetric yaw misalignment pattern. The flow inclination angle showed slight variation of inflow angle with wind speed and clear wake swirl patterns in the wakes of the other wind turbines. Turbulence intensity measurements showed clear variations from low turbulence in the wake-free wind...

  15. Patterns of bryophyte diversity in arable fields of Lithuania

    Directory of Open Access Journals (Sweden)

    Danguolė Andriušaitytė

    2013-03-01

    Full Text Available The paper presents research data on bryophyte diversity in arable land throughout the territory of Lithuania. The bryoflora was analyzed regarding systematic structure and morphological forms, life-history strategies, mode of reproduction and frequency of species. Bryophyte diversity in arable fields of Lithuania was compared with that of Slovakia and the British Isles, which are positioned in different geographical regions of Europe. A total of 97 species of bryophytes of 25 families and 48 genera were ascertained. Dominance of acrocarpous mosses and thalloid liverworts, high representation of Pottiaceae, Bryaceae, Mielichhoferiaceae and Ricciaceae families as well as Bryum, Dicranella, Pohlia and Riccia genera, wide distribution of annual shuttles and ephemeral colonists, high reproduction effort of the species (frequent sporophytes and asexual propagules were specific features of the bryophytes of the studied habitats as a result of adaptations to regular disturbances. The distribution of species into six frequency groups seemed to be uneven. The most abundant group of species with the lowest frequency (1–3 records covered 53.6% of all species. The group contained about 90% of all many-year potential life span species recorded in the habitat. Species with short life span were distributed quite evenly throughout frequency groups. No regionally-specific species were ascertained in the studied habitat. Most of arable-land-specific species recorded in Lithuania is distributed throughout different regions of Europe.

  16. Spectral discrete probability density function of measured wind turbine noise in the far field

    Directory of Open Access Journals (Sweden)

    Payam eAshtiani

    2015-04-01

    Full Text Available Of interest is the spectral character of wind turbine noise at typical residential set-back distances. In this paper a spectral statistical analysis has been applied to immission measurements conducted at three locations. This method provides discrete probability density functions for the Turbine ONLY component of the measured noise. This analysis is completed for 1/3rd Octave sound levels, at integer wind speeds, and is compared to existing metrics for measuring acoustic comfort as well as previous discussions on low frequency noise sources.

  17. Spectral discrete probability density function of measured wind turbine noise in the far field.

    Science.gov (United States)

    Ashtiani, Payam; Denison, Adelaide

    2015-01-01

    Of interest is the spectral character of wind turbine noise at typical residential set-back distances. In this paper, a spectral statistical analysis has been applied to immission measurements conducted at three locations. This method provides discrete probability density functions for the Turbine ONLY component of the measured noise. This analysis is completed for one-third octave sound levels, at integer wind speeds, and is compared to existing metrics for measuring acoustic comfort as well as previous discussions on low-frequency noise sources.

  18. Short-term forecasting of thunderstorms at Kennedy Space Center, based on the surface wind field

    Science.gov (United States)

    Watson, Andrew I.; Lopez, Raul E.; Holle, Ronald L.; Daugherty, John R.; Ortiz, Robert

    1989-01-01

    Techniques incorporating wind convergence that can be used for the short-term prediction of thunderstorm development are described. With these techniques, the convergence signal is sensed by the wind network array 15 to 90 min before actual storm development. Particular attention is given to the convergence cell technique (which has been applied at the Kennedy Space Center) where each convective region is analyzed independently. It is noted that, while the monitoring of areal and cellular convergence can be used to help locate the seeds of developing thunderstorms and pinpoint the lightning threat areas, this forecasting aid cannot be used in isolation.

  19. The Dependence of the Strength and Thickness of Field-Aligned Currents on Solar Wind and Ionospheric Parameters

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Jay R. [PPPL; Wing, Simon [Johns Hopkins University

    2014-08-01

    Sheared plasma flows at the low-latitude boundary layer correlate well with early afternoon auroral arcs and eld-aligned currents [Sonnerup, 1980; Lundin and Evans, 1985]. We present a simple analytic model that relates solar wind and ionospheric parameters to the strength and thickness of field-aligned currents in a region of sheared velocity, such as the low latitude boundary layer. We compare the predictions of the model with DMSP observations and nd remarkably good scaling of the currents with solar wind and ionospheric parameters. The sheared boundary layer thickness is inferred to be around 3000km consistent with observational studies. The analytic model provides a simple way to organize data and to infer boundary layer structures from ionospheric data.

  20. Analysis of the Uncertainty in Wind Measurements from the Atmospheric Radiation Measurement Doppler Lidar during XPIA: Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Newsom, Rob [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-03-01

    In March and April of 2015, the ARM Doppler lidar that was formerly operated at the Tropical Western Pacific site in Darwin, Australia (S/N 0710-08) was deployed to the Boulder Atmospheric Observatory (BAO) for the eXperimental Planetary boundary-layer Instrument Assessment (XPIA) field campaign. The goal of the XPIA field campaign was to investigate methods of using multiple Doppler lidars to obtain high-resolution three-dimensional measurements of winds and turbulence in the atmospheric boundary layer, and to characterize the uncertainties in these measurements. The ARM Doppler lidar was one of many Doppler lidar systems that participated in this study. During XPIA the 300-m tower at the BAO site was instrumented with well-calibrated sonic anemometers at six levels. These sonic anemometers provided highly accurate reference measurements against which the lidars could be compared. Thus, the deployment of the ARM Doppler lidar during XPIA offered a rare opportunity for the ARM program to characterize the uncertainties in their lidar wind measurements. Results of the lidar-tower comparison indicate that the lidar wind speed measurements are essentially unbiased (~1cm s-1), with a random error of approximately 50 cm s-1. Two methods of uncertainty estimation were tested. The first method was found to produce uncertainties that were too low. The second method produced estimates that were more accurate and better indicators of data quality. As of December 2015, the first method is being used by the ARM Doppler lidar wind value-added product (VAP). One outcome of this work will be to update this VAP to use the second method for uncertainty estimation.

  1. Experimental and Numerical Study of Wind and Turbulence in a Near-Field Dispersion Campaign at an Inhomogeneous Site

    Science.gov (United States)

    Wei, Xiao; Dupont, Eric; Gilbert, Eric; Musson-Genon, Luc; Carissimo, Bertrand

    2016-09-01

    We present a detailed experimental and numerical study of the local flow field for a pollutant dispersion experimental program conducted at SIRTA (Site Instrumental de Recherche par Télédétection Atmosphérique), a complex and intensively instrumented site in a southern suburb of Paris. Global analysis of continuous measurements over 2 years highlights the impact of terrain heterogeneity on wind and turbulence. It shows that the forest to the north of the experimental field induces strong directional shear and wind deceleration below the forest canopy height. This directional shear is stronger with decreasing height and decreasing distance from the forest edge. Numerical simulations are carried out using Code_Saturne, a computational fluid dynamics code, in Reynolds-averaged Navier-Stokes mode with a standard k{-}ɛ closure and a canopy model, in neutral and stable stratifications. These simulations are shown to reproduce globally well the characteristics of the mean flow, especially the directional wind shear in northeasterly and northwesterly cases and the turbulent kinetic energy increase induced by the forest. However, they slightly underestimate wind speed and the directional shear of the flow below the forest canopy height. Sensitivity studies are performed to investigate the influence of leaf area density, inlet stability condition, and roughness length. These studies show that the typical features of the canopy flow become more pronounced as canopy density increases. Performance statistics indicate that the impact of the forest and adequate inlet profiles are the most important factors in the accurate reproduction of flow at the site, especially under stable stratification.

  2. Patterns of orodental injury and mouthguard use in Dutch field hockey

    NARCIS (Netherlands)

    Vucic, S.; Drost, R.W.; van Wijk, A.J.; Wesselink, P.R.; Wolvius, E.B.

    2016-01-01

    Background Orodental injuries in field hockey are a growing cause of concern that requires attention. Objective The objective of this cross-sectional study was to investigate the patterns of orodental injury, and the use of mouthguards in Dutch national field hockey. Materials and methods In the

  3. Statistical prediction of far-field wind-turbine noise, with probabilistic characterization of atmospheric stability

    DEFF Research Database (Denmark)

    Kelly, Mark C.; Barlas, Emre; Sogachev, Andrey

    2018-01-01

    Here we provide statistical low-order characterization of noise propagation from a single wind turbine, as affected by mutually interacting turbine wake and environmental conditions. This is accomplished via a probabilistic model, applied to an ensemble of atmospheric conditions based upon atmosp...

  4. Field Wind Tunnel Testing of Two Silt Loam Soils in the North American Central High Plains

    Science.gov (United States)

    The change from conventional tillage to no-till cropping systems and the emergence of cropping systems with fewer and shorter fallow periods has resulted in reduced wind erosion on the North American Central High Plains. This reduction has been attributed primarily to increased surface coverage by ...

  5. Portable wind tunnels for field testing of soils and natural surfaces

    Science.gov (United States)

    Large stationary wind tunnels have been used to test the erodibility of soils and to study in detail the processes controlling erosion rates. These tunnels require the use of disturbed soil samples which may result in parameter estimations that are not consistent with the natural surface. Several ...

  6. Low-Energy Electron Diffraction Patterns Using Field-Emitted Electrons from Tungsten Tips

    Science.gov (United States)

    Mizuno, Seigi; Rahman, F.; Iwanaga, Masayuki

    2006-02-01

    We have observed low-energy electron diffraction patterns of Cu(001) clean surface using field-emitted electrons from tungsten tips. Only elastically scattered electrons contribute to diffraction patterns. Tip-sample distance, bias voltage, electron beam opening angle and tip apex structure determine the probing diameter and symmetry of diffraction patterns. The emission current, bias voltage and estimated probing diameter for the observed diffraction patterns were 0.15 nA, 75-82 V, and 4-40 μm, respectively.

  7. Spontaneous emission of magnetic field fluctuations in Solar wind-like suprathermal plasmas

    Science.gov (United States)

    Navarro, R.; Munoz, V.; Araneda, J. A.; Vinas, A. F.; Valdivia, J. A.

    2013-12-01

    Heavy ions in solar wind have been observed to flow faster than protons, with temperatures exceeding the mass proportionality respect to protons. The identification and explanation of the physical processes responsible for ion heating may provide the key to explain why the temperature of the outer solar atmosphere and expanding corona forming the solar wind is several orders of magnitude higher than that of the photosphere. Possible explanations of the preferential acceleration and heating of ions often involve linear kinetic theory, which allows for a wide number of heavily damped waves (or higher-order modes), which could play a secondary role in the energization of solar wind plasmas. Also, linear theory predicts instability thresholds in the temperature distribution of protons which are consistent with data from the Solar Wind Experiment (SWE). However, it has also been observed that proton velocity distributions appear to be strongly anisotropic, displaying a pronounced non-Maxwellian profile of particles exceeding thermal energies. These velocity distributions are often modeled with a family of specific functional describing both the low-energy Maxwellian core and the high-energy power-law tails, popularly known in the literature as kappa-distributions. Furthermore, short wavelength magnetic fluctuations with small amplitude are present even in the absence of plasma instabilities. These spontaneous fluctuations are intimately linked to the linear response of perturbations via the fluctuation-dissipation theorem. The various collective modes of fluctuations are constrained by the structure of the higher-order modes determined by the electromagnetic kinetic dispersion relation. In this work, we examine the propagation and excitation of parallel Alfvén-cyclotron waves in a suprathermal proton solar wind-like plasma, as described by a kappa-like distribution function, by taking care of the often ignored higher-order modes which modify the structure of the

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

    Science.gov (United States)

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

    2008-12-03

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

  9. Correlation between the horizontal wind direction and orientation of cross-field anisotropy of small-scale irregularities in the F region of midlatitude ionosphere

    Science.gov (United States)

    Romanova, N. Yu.

    2017-07-01

    Radio sounding of midlatitude ionosphere shows that natural small-scale electron density irregularities in the F region are cross-field anisotropic. The orientation of the cross-field anisotropy is different under different geophysical conditions. The cross-field anisotropy orientation is matched with the horizontal wind direction calculated within the HWM07 model for each event. It is ascertained that natural irregularities in a plane perpendicular to the magnetic field are stretched along the horizontal wind direction under different geophysical conditions.

  10. Objective Tracking of Tropical Cyclones in the North-West Pacific Basin Based on Wind Field Information only

    Science.gov (United States)

    Leckebusch, G. C.; Befort, D. J.; Kruschke, T.

    2016-12-01

    Although only ca. 12% of the global insured losses of natural disasters occurred in Asia, there are two major reasons to be concerned about risks in Asia: a) The fraction of loss events was substantial higher with 39% of which 94% were due to atmospheric processes; b) Asia and especially China, is undergoing quick transitions and especially the insurance market is rapidly growing. In order to allow for the estimation of potential future (loss) impacts in East-Asia, in this study we further developed and applied a feature tracking system based on extreme wind speed occurrences to tropical cyclones, which was originally developed for extra-tropical cyclones (Leckebusch et al., 2008). In principle, wind fields will be identified and tracked once a coherent exceedance of local percentile thresholds is identified. The focus on severe wind impact will allow an objective link between the strength of a cyclone and its potential damages over land. The wind tracking is developed in such a way to be applicable also to course-gridded AOGCM simulation. In the presented configuration the wind tracking algorithm is applied to the Japanese reanalysis (JRA55) and TC Identification is based on 850hPa wind speeds (6h resolution) from 1979 to 2014 over the Western North Pacific region. For validation the IBTrACS Best Track archive version v03r8 is used. Out of all 904 observed tracks, about 62% can be matched to at least one windstorm event identified in JRA55. It is found that the relative amount of matched best tracks increases with the maximum intensity. Thus, a positive matching (hit rate) of above 98% for Violent Typhoons (VTY), above 90% for Very Strong Typhoons (VSTY), about 75% for Typhoons (TY), and still some 50% for less intense TCs (TD, TS, STS) is found. This result is extremely encouraging to apply this technique to AOGCM outputs and to derive information about affected regions and intensity-frequency distributions potentially changed under future climate conditions.

  11. Modeling dynamic stall on wind turbine blades under rotationally augmented flow fields

    DEFF Research Database (Denmark)

    Guntur, Srinivas; Sørensen, Niels N.; Schreck, Scott

    2016-01-01

    This paper presents an investigation of two well-known aerodynamic phenomena, rotational augmentation and dynamic stall, together in the inboard parts of wind turbine blades. This analysis is carried out using the following: (1) the National Renewable Energy Laboratory’s Unsteady Aerodynamics...... a reduced order dynamic stall model that uses rotationally augmented steady-state polars obtained from steady Phase VI experimental sequences, instead of the traditional two-dimensional, non-rotating data. The aim of this work is twofold. First, the blade loads estimated by the DDES simulations are compared...... with those from the dynamic stall model. This allowed the differences between the stall phenomenon on the inboard parts of harmonically pitching blades on a rotating wind turbine and the classic dynamic stall representation in two-dimensional flow to be investigated. Results indicated a good qualitative...

  12. On the impact of wind on the development of wave field during storm Britta

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo; Du, Jianting; Bolaños, Rodolfo

    2017-01-01

    our understanding of these processes, which are essential for a good forecast of similarly important events offshore, this study revisits the development of storm Britta using an atmospheric and wave coupled modeling system, wind and wave measurements from ten stations across the North Sea, cloud......The observation of extreme waves at FINO 1 during storm Britta on the 1st November 2006 has initiated a series of research studies regarding the mechanisms behind. The roles of stability and the presence of the open cell structures have been previously investigated but not conclusive. To improve...... images and Synthetic Aperture Radar (SAR) data. It is found here that a standard state-of-the-art model is capable of capturing the important characteristics of a major storm like Britta, including the storm path, storm peak wind speed, the open cells, and peak significant wave height (H s ) for open sea...

  13. Carbon nanotube field emitters on KOVAR substrate modified by random pattern

    Energy Technology Data Exchange (ETDEWEB)

    Park, Seol Ah; Song, Eun-Ho; Kang, Byung Hyun; Ju, Byeong-Kwon, E-mail: bkju@korea.ac.kr [Korea University, Display and Nanosystem Laboratory, College of Engineering (Korea, Republic of)

    2015-07-15

    We investigated the field emission characteristics of patterned carbon nanotubes (CNTs) on KOVAR substrates with different surface morphologies. The substrate with a micro-sized random pattern was fabricated through chemical wet etching, whereas the substrate with a nano-sized random pattern was formed by surface roughening process of polymer and chemical wet etching. The field emission characteristics of these substrates were the compared with those of non-treated substrates. It was clearly revealed that the field emission characteristics of CNTs were influenced by the surface morphology of the cathode substrate. When the surface of cathode was modified by random pattern, the modified substrate provided a large surface area and a wider print area. Also, the modified surface morphology of the cathode provided strong adhesion between the CNT paste and the cathode. Particularly, the substrate with the nano-sized random pattern showed that the turn-on field value decreases and the field enhancement factor value improves as compared with non-treated substrate.

  14. Radar Wind Profiler for Cloud Forecasting at Brookhaven National Laboratory (BNL) Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, M. P. [Brookhaven National Laboratory (BNL), Upton, NY (United States); Giangrande, S. E. [Brookhaven National Laboratory (BNL), Upton, NY (United States); Bartholomew, M. J. [Brookhaven National Laboratory (BNL), Upton, NY (United States)

    2016-04-01

    The Radar Wind Profiler for Cloud Forecasting at Brookhaven National Laboratory (BNL) [http://www.arm.gov/campaigns/osc2013rwpcf] campaign was scheduled to take place from 15 July 2013 through 15 July 2015 (or until shipped for the next U.S. Department of Energy Atmospheric Radiation Measurement [ARM] Climate Research Facility first Mobile Facility [AMF1] deployment). The campaign involved the deployment of the AMF1 Scintec 915 MHz Radar Wind Profiler (RWP) at BNL, in conjunction with several other ARM, BNL and National Weather Service (NWS) instruments. The two main scientific foci of the campaign were: 1) To provide profiles of the horizontal wind to be used to test and validate short-term cloud advection forecasts for solar-energy applications and 2) to provide vertical profiling capabilities for the study of dynamics (i.e., vertical velocity) and hydrometeors in winter storms. This campaign was a serendipitous opportunity that arose following the deployment of the RWP at the Two-Column Aerosol Project (TCAP) campaign in Cape Cod, Massachusetts and restriction from participation in the Green Ocean Amazon 2014/15 (GoAmazon 2014/15) campaign due to radio-frequency allocation restriction for international deployments. The RWP arrived at BNL in the fall of 2013, but deployment was delayed until fall of 2014 as work/safety planning and site preparation were completed. The RWP further encountered multiple electrical failures, which eventually required several shipments of instrument power supplies and the final amplifier to the vendor to complete repairs. Data collection began in late January 2015. The operational modes of the RWP were changed such that in addition to collecting traditional profiles of the horizontal wind, a vertically pointing mode was also included for the purpose of precipitation sensing and estimation of vertical velocities. The RWP operated well until the end of the campaign in July 2015 and collected observations for more than 20 precipitation

  15. Shape, zonal winds and gravitational field of Jupiter: a fully self-consistent, multi-layered model

    Science.gov (United States)

    Schubert, Gerald; Kong, Dali; Zhang, Keke

    2016-10-01

    We construct a three-dimensional, finite-element, fully self-consistent, multi-layered,non-spheroidal model of Jupiter consisting of an inner core, a metallic electrically conducting dynamo region and an outer molecular electrically insulating envelope. We assume that the Jovian zonal winds are on cylinders parallel to the rotation axis but, due to the effect of magnetic braking, are confined within the outer molecular envelope. Two related calculations are carried out. The first provides an accurate description of the shape and internal density profile of Jupiter; the effect of rotational distortion is not treated as a small perturbation on a spherically symmetric state. This calculation determines the density, size and shape of the inner core, the irregular shape of the 1-bar pressure level, and the internal structure of Jupiter; the full effect of rotational distortion, without the influence of the zonal winds, is accounted for. Our multi-layered model is able to produce the known mass, the known equatorial and polar radii, and the known zonal gravitational coefficient J2 of Jupiter within their error bars; it also yields the coefficients J4 and J6 within about 5% accuracy, and the core equatorial radius 0.09RJ containing 3.73 Earth masses.The second calculation determines the variation of the gravitational field caused solely by the effect of the zonal winds on the rotationally distorted non-spheroidal Jupiter. Four different cases, ranging from a deep wind profile to a very shallow profile, are considered and implications for accurate interpretation of the zonal gravitational coefficients expected from the Juno mission are discussed.

  16. Wind seismic noise introduced by external infrastructure: field data and transfer mechanism

    Science.gov (United States)

    Martysevich, Pavel; Starovoyt, Yuri

    2017-04-01

    Background seismic noise generated by wind was analyzed at six co-located seismic and infrasound arrays with the use of the wind speed data. The main factors affecting the noise level were identified as (a) external structures as antenna towers for intrasite communication, vegetation and heavy solar panels fixtures, (b) borehole casing and (c) local lithology. The wind-induced seismic noise peaks in the spectra can be predicted by combination of inverted pendulum model for antenna towers and structures used to support solar panels, free- or clamped-tube resonance of the borehole casing and is dependent on the type of sedimentary upper layer. Observed resonance frequencies are in agreement with calculated clamped / free tube modes for towers and borehole casings. Improvement of the seismic data quality can be achieved by minimizing the impact of surrounding structures close to seismic boreholes. The need and the advantage of the borehole installation may vanish and appear to be even not necessary at locations with non-consolidated sediments because the impact of surrounding structures on seismic background may significantly deteriorate the installation quality and therefore the detection capability of the array. Several IMS arrays where the radio telemetry antennas are used for data delivery to the central site may benefit from the redesign of the intrasite communication system by its substitute with the fiber-optic net as less harmful engineering solution.

  17. On the impact of wind on the development of wave field during storm Britta

    Science.gov (United States)

    Larsén, Xiaoli Guo; Du, Jianting; Bolaños, Rodolfo; Larsen, Søren

    2017-11-01

    The observation of extreme waves at FINO 1 during storm Britta on the 1st November 2006 has initiated a series of research studies regarding the mechanisms behind. The roles of stability and the presence of the open cell structures have been previously investigated but not conclusive. To improve our understanding of these processes, which are essential for a good forecast of similarly important events offshore, this study revisits the development of storm Britta using an atmospheric and wave coupled modeling system, wind and wave measurements from ten stations across the North Sea, cloud images and Synthetic Aperture Radar (SAR) data. It is found here that a standard state-of-the-art model is capable of capturing the important characteristics of a major storm like Britta, including the storm path, storm peak wind speed, the open cells, and peak significant wave height ( H s ) for open sea. It was also demonstrated that the impact of the open cells has negligible contribution to the development of extreme H s observed at FINO 1. At the same time, stability alone is not sufficient in explaining the development of extreme H s . The controlling conditions for the development of Britta extreme H s observed at FINO 1 are the persistent strong winds and a long and undisturbed fetch over a long period.

  18. Evolution Of The Cloud Field And Wind Structure Of Ntb Disturbance

    Science.gov (United States)

    Barrado-Izagirre, Naiara; Pérez-Hoyos, S.; García-Melendo, E.; Sánchez-Lavega, A.

    2009-09-01

    The banded visual aspect of cloud patterns in Jupiter hides markedly turbulent areas visible in high resolution images. The North Temperate Belt (NTB) at 21° N planetocentric latitude where the most intense Jovian jet resides (with speeds of 160 - 180 m/s) is a region of particular interest because it is known to suffer almost every 15 years an eruption or disturbance which dramatically changes its appearance. This phenomenon is known as NTB Disturbance (NTBD). The last one of such disturbances happened in 2007 and was captured by the Hubble Space Telescope and with lower resolution by the "International Outer Planet Watch” (IOPW) network [Sánchez-Lavega et al., 2008. Depth of a strong Jovian jet from a planetary-scale disturbance driven by storms, Nature 451.]. In this work we make use of these observations to characterize the morphology of the disturbed cloud field in the wake of the plumes which originated the perturbation. This is done mostly in terms of the brightness spectral distribution in order to characterize the typical spatial frequency of the perturbation and its wavy and turbulent nature. In addition we make a comparison of the jet profile in the NTB just after the disturbance ended (June 2007) with one obtained year later (July 2008). It shows that a change occurred in its anticyclonic side producing a reinforced westward jet at 17°N with a speed change of 30 m/s. Acknowledgments: This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07

  19. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    Energy Technology Data Exchange (ETDEWEB)

    Rajnak, Michal; Kopcansky, Peter; Timko, Milan [Institute of Experimental Physics SAS, Watsonova 47, 04001 Košice (Slovakia); Petrenko, Viktor I. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Kyiv Taras Shevchenko National University, Volodymyrska Street 64, Kyiv 01033 (Ukraine); Avdeev, Mikhail V. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Ivankov, Olexandr I. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Kyiv Taras Shevchenko National University, Volodymyrska Street 64, Kyiv 01033 (Ukraine); Moscow Institute of Physics and Technology, Institutskiy per. 9, Dolgoprudniy 141700 (Russian Federation); Feoktystov, Artem [Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85747 Garching (Germany); Dolnik, Bystrik; Kurimsky, Juraj [Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice (Slovakia)

    2015-08-17

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

  20. Advanced structural wind engineering

    CERN Document Server

    Kareem, Ahsan

    2013-01-01

    This book serves as a textbook for advanced courses as it introduces state-of-the-art information and the latest research results on diverse problems in the structural wind engineering field. The topics include wind climates, design wind speed estimation, bluff body aerodynamics and applications, wind-induced building responses, wind, gust factor approach, wind loads on components and cladding, debris impacts, wind loading codes and standards, computational tools and computational fluid dynamics techniques, habitability to building vibrations, damping in buildings, and suppression of wind-induced vibrations. Graduate students and expert engineers will find the book especially interesting and relevant to their research and work.

  1. Wind energy bibliography

    Energy Technology Data Exchange (ETDEWEB)

    None

    1995-05-01

    This bibliography is designed to help the reader search for information on wind energy. The bibliography is intended to help several audiences, including engineers and scientists who may be unfamiliar with a particular aspect of wind energy, university researchers who are interested in this field, manufacturers who want to learn more about specific wind topics, and librarians who provide information to their clients. Topics covered range from the history of wind energy use to advanced wind turbine design. References for wind energy economics, the wind energy resource, and environmental and institutional issues related to wind energy are also included.

  2. Phase-Field Crystal Modeling of Polcrystalline Pattern Evolution in Hard and Soft Matter

    Science.gov (United States)

    Karma, Alain

    2013-03-01

    The phase-field crystal (PFC) model has attracted considerable attention during the past decade for its potential application to model the complex defect-mediated dynamics of hard and soft crystalline materials on diffusive time scales. The model is rooted in earlier models of non-equilibrium pattern formation (Swift-Hohenberg equation), and classical density functional theory that expresses the free-energy of a system as a functional of its density. This talk will discuss progress made to investigate the dynamics for both isolated grain boundaries and complex polycrystalline patterns under the driving forces of boundary curvature and applied stress. The results highlight fundamental differences between polycrystalline pattern evolution in soft matter, including colloid crystals and crystalline non-equilibrium patterns described by the standard PFC dynamics, and crystalline solids described by a reformulation of this dynamics presented in this talk. The results also pave the way for a unified theory of polycrystalline pattern evolution in hard and soft matter.

  3. Before–after field study of effects of wind turbine noise on polysomnographic sleep parameters

    Directory of Open Access Journals (Sweden)

    Leila Jalali

    2016-01-01

    Full Text Available Wind is considered one of the most advantageous alternatives to fossil energy because of its low operating cost and extensive availability. However, alleged health-related effects of exposure to wind turbine (WT noise have attracted much public attention and various symptoms, such as sleep disturbance, have been reported by residents living close to wind developments. Prospective cohort study with synchronous measurement of noise and sleep physiologic signals was conducted to explore the possibility of sleep disturbance in people hosting new industrial WTs in Ontario, Canada, using a pre and post-exposure design. Objective and subjective sleep data were collected through polysomnography (PSG, the gold standard diagnostic test, and sleep diary. Sixteen participants were studied before and after WT installation during two consecutive nights in their own bedrooms. Both audible and infrasound noises were also concurrently measured inside the bedroom of each participant. Different noise exposure parameters were calculated (LAeq, LZeq and analyzed in relation to whole-night sleep parameters. Results obtained from PSG show that sleep parameters were not significantly changed after exposure. However, reported sleep qualities were significantly (P = 0.008 worsened after exposure. Average noise levels during the exposure period were low to moderate and the mean of inside noise levels did not significantly change after exposure. The result of this study based on advanced sleep recording methodology together with extensive noise measurements in an ecologically valid setting cautiously suggests that there are no major changes in the sleep of participants who host new industrial WTs in their community. Further studies with a larger sample size and including comprehensive single-event analyses are warranted.

  4. Wind dispersal of alien plant species into remnant natural vegetation from adjacent agricultural fields

    Directory of Open Access Journals (Sweden)

    Chika Egawa

    2017-07-01

    Full Text Available Knowledge regarding the seed dispersal of alien species is crucial to manage invasion risk in fragmented natural habitats. Focusing on wind dispersal, this study assessed the spatial and quantitative extents to which a remnant natural fen receives the seeds of alien species dispersed from adjacent hay meadows in Hokkaido, northern Japan. I established a total of 80 funnel seed traps in the fen at distances of 1, 2, 5, 10, 20, 30, 50, and 100 m from the meadows. The proportion of alien species in the seed rain at each distance was quantified, and the 99th-percentile dispersal distance from the meadows was estimated for each alien species by constructing dispersal kernels. Despite the presence of a marginal ditch and an elevational difference between the fen and the meadows, five alien species, including four grasses that do not have modified seed structures for wind dispersal, dispersed their seeds into the fen. These alien species accounted for up to 65.9% of the seed rain in terms of quantity. The 99th-percentile dispersal distances of the alien species ranged from 3.8 m to 309.3 m, and these distances were longer than the values predicted on the basis of their functional traits, such as terminal velocity. The results of this study demonstrated that numerous seeds of farmland-derived alien species were transported into the remnant vegetation via wind dispersal, and that simple predictions of dispersal distance based on functional traits could underestimate the potential area that alien species can reach. Continuous management both in farmland (to reduce seed escape and in remnant vegetation (to prevent the establishment of alien species is necessary to protect native vegetation from biological invasion in agricultural landscapes.

  5. Before-after field study of effects of wind turbine noise on polysomnographic sleep parameters.

    Science.gov (United States)

    Jalali, Leila; Bigelow, Philip; Nezhad-Ahmadi, Mohammad-Reza; Gohari, Mahmood; Williams, Diane; McColl, Steve

    2016-01-01

    Wind is considered one of the most advantageous alternatives to fossil energy because of its low operating cost and extensive availability. However, alleged health-related effects of exposure to wind turbine (WT) noise have attracted much public attention and various symptoms, such as sleep disturbance, have been reported by residents living close to wind developments. Prospective cohort study with synchronous measurement of noise and sleep physiologic signals was conducted to explore the possibility of sleep disturbance in people hosting new industrial WTs in Ontario, Canada, using a pre and post-exposure design. Objective and subjective sleep data were collected through polysomnography (PSG), the gold standard diagnostic test, and sleep diary. Sixteen participants were studied before and after WT installation during two consecutive nights in their own bedrooms. Both audible and infrasound noises were also concurrently measured inside the bedroom of each participant. Different noise exposure parameters were calculated (LAeq, LZeq) and analyzed in relation to whole-night sleep parameters. Results obtained from PSG show that sleep parameters were not significantly changed after exposure. However, reported sleep qualities were significantly (P = 0.008) worsened after exposure. Average noise levels during the exposure period were low to moderate and the mean of inside noise levels did not significantly change after exposure. The result of this study based on advanced sleep recording methodology together with extensive noise measurements in an ecologically valid setting cautiously suggests that there are no major changes in the sleep of participants who host new industrial WTs in their community. Further studies with a larger sample size and including comprehensive single-event analyses are warranted.

  6. Before–After Field Study of Effects of Wind Turbine Noise on Polysomnographic Sleep Parameters

    Science.gov (United States)

    Jalali, Leila; Bigelow, Philip; Nezhad-Ahmadi, Mohammad-Reza; Gohari, Mahmood; Williams, Diane; McColl, Steve

    2016-01-01

    Wind is considered one of the most advantageous alternatives to fossil energy because of its low operating cost and extensive availability. However, alleged health-related effects of exposure to wind turbine (WT) noise have attracted much public attention and various symptoms, such as sleep disturbance, have been reported by residents living close to wind developments. Prospective cohort study with synchronous measurement of noise and sleep physiologic signals was conducted to explore the possibility of sleep disturbance in people hosting new industrial WTs in Ontario, Canada, using a pre and post-exposure design. Objective and subjective sleep data were collected through polysomnography (PSG), the gold standard diagnostic test, and sleep diary. Sixteen participants were studied before and after WT installation during two consecutive nights in their own bedrooms. Both audible and infrasound noises were also concurrently measured inside the bedroom of each participant. Different noise exposure parameters were calculated (LAeq, LZeq) and analyzed in relation to whole-night sleep parameters. Results obtained from PSG show that sleep parameters were not significantly changed after exposure. However, reported sleep qualities were significantly (P=0.008) worsened after exposure. Average noise levels during the exposure period were low to moderate and the mean of inside noise levels did not significantly change after exposure. The result of this study based on advanced sleep recording methodology together with extensive noise measurements in an ecologically valid setting cautiously suggests that there are no major changes in the sleep of participants who host new industrial WTs in their community. Further studies with a larger sample size and including comprehensive single-event analyses are warranted. PMID:27569407

  7. Emergency wind erosion control

    Science.gov (United States)

    February through May is the critical time for wind erosion in Kansas, but wind erosion can happen any time when high winds occur on smooth, wide fields with low vegetation and poor soil structure. The most effective wind erosion control is to ensure a protective cover of residue or growing crop thro...

  8. Coastal Ohio Wind Project

    Energy Technology Data Exchange (ETDEWEB)

    Gorsevski, Peter [Bowling Green State Univ., OH (United States); Afjeh, Abdollah [Univ. of Toledo, OH (United States); Jamali, Mohsin [Univ. of Toledo, OH (United States); Bingman, Verner [Bowling Green State Univ., OH (United States)

    2014-04-04

    reduced the wake size and enhanced the vortices in the flow downstream of the turbine-tower compared with the tower alone case. Mean and rms velocity distributions from hot wire anemometer data confirmed that in a downwind configuration, the wake of the tower dominates the flow, thus the flow fields of a tower alone and tower-turbine combinations are nearly the same. For the upwind configuration, the mean velocity shows a narrowing of the wake compared with the tower alone case. The downwind configuration wake persisted longer than that of an upwind configuration; however, it was not possible to quantify this difference because of the size limitation of the wind tunnel downstream of the test section. The water tunnel studies demonstrated that the scale model studies could be used to adequately produce accurate motions to model the motions of a wind turbine platform subject to large waves. It was found that the important factors that affect the platform is whether the platform is submerged or surface piercing. In the former, the loads on the platform will be relatively reduced whereas in the latter case, the structure pierces the wave free surface and gains stiffness and stability. The other important element that affects the movement of the platform is depth of the sea in which the wind turbine will be installed. Furthermore, the wildlife biology component evaluated migratory patterns by different monitoring systems consisting of marine radar, thermal IR camera and acoustic recorders. The types of radar used in the project are weather surveillance radar and marine radar. The weather surveillance radar (1988 Doppler), also known as Next Generation Radar (NEXRAD), provides a network of weather stations in the US. Data generated from this network were used to understand general migratory patterns, migratory stopover habitats, and other patterns caused by the effects of weather conditions. At a local scale our marine radar was used to complement the datasets from NEXRAD and

  9. Errors in second moments estimated from monostatic Doppler sodar winds. II. Application to field measurements

    DEFF Research Database (Denmark)

    Gaynor, J. E.; Kristensen, Leif

    1986-01-01

    For pt.I see ibid., vol.3, no.3, p.523-8 (1986). The authors use the theoretical results presented in part I to correct turbulence parameters derived from monostatic sodar wind measurements in an attempt to improve the statistical comparisons with the sonic anemometers on the Boulder Atmospheric ...... and after the application of the spatial and temporal volume separation correction, are presented. The improvement appears to be significant. The effects of correcting for pulse volume averaging derived in part I are also discussed...

  10. Wake meandering and its relationship with the incoming wind characteristics: a statistical approach applied to long-term on-field observations

    Science.gov (United States)

    Torres Garcia, E.; Aubrun, S.; Boquet, M.; Royer, P.; Coupiac, O.; Girard, N.

    2017-05-01

    In several papers, the importance of the atmospheric flow in the wake development of wind turbines (WT) has been pointed out, making it clear that it is necessary to have long-term on-field observations for an appropriate description of the wake development, its structure and dynamics. This work presents a statistical approach to wake meandering, y w , and the relationship that this behavior has with the incoming wind conditions and neighboring wakes. The work was developed in the framework of the French project SMARTEOLE. The study is based on a 7-month measurement campaign in which a pulsed scanning LiDAR system was used. The ground based LiDAR, measures the flow field in a segment such that the wake of two wind turbines can be captured quasi-horizontally. The analysis filters the incoming wind conditions according to the thermal stability, wind direction and wind velocity at hub height; therefore, the wakes that are developed in periods with similar wind conditions are expected to be analogous, hence meandering can be tracked and statistically analyzed. A well-defined wake evolution was found and the uncertainty analysis made on the wake meandering uncovered some interesting characteristics, including the number of samples required to reach a statistical uncertainty on the mean wake position between 2 × 10-2 D and 8 × 10-2 D for a confidence interval of 95%.

  11. Evaluation of the lifting line vortex model approximation for estimating the local blade flow fields in horizontal-axis wind turbines

    NARCIS (Netherlands)

    Sant, T; Del Campo, V.; Micallef, D.; Simao Ferreira, C.

    2016-01-01

    Lifting line vortex models have been widely used to predict flow fields around wind turbine rotors. Such models are known to be deficient in modelling flow fields close to the blades due to the assumption that blade vorticity is concentrated on a line and consequently the influences of blade

  12. A Second Wind for the Philosophy of Education: The Application of William James's "The Energies of Men" to the Field of Philosophy of Education

    Science.gov (United States)

    Novakowski, Julia T.

    2017-01-01

    In this essay, the author proposes that the field of Philosophy of Education is in search of its own second wind and can find guidance in the work and life of William James. This paper is meant to invite conversation on the challenges faced and provide potential solutions in the field. The goal is to find the "cash-value" of the field…

  13. Wind turbine noise diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Richarz, W. [Aerocoustics Engineering Ltd., Toronto, ON (Canada); Richarz, H.

    2009-07-01

    This presentation proposed a self-consistent model for broad-band noise emitted from modern wind turbines. The simple source model was consistent with the physics of sound generation and considered the unique features of wind turbines. Although the acoustics of wind turbines are similar to those of conventional propellers, the dimensions of wind turbines pose unique challenges in diagnosing noise emission. The general features of the sound field were deduced. Source motion and source directivity appear to be responsible for amplitude variations. The amplitude modulation is likely to make wind-turbine noise more audible, and may be partly responsible for annoyance that has been reported in the literature. Acoustic array data suggests that broad-band noise is emitted predominantly during the downward sweep of each rotor blade. Source motion and source directivity account for the observed pattern. Rotor-tower interaction effects are of lesser importance. Predicted amplitude modulation ranges from 1 dB to 6dB. 2 refs., 9 figs.

  14. Field Demonstration of Real-Time Wind Turbine Foundation Strain Monitoring.

    Science.gov (United States)

    Rubert, Tim; Perry, Marcus; Fusiek, Grzegorz; McAlorum, Jack; Niewczas, Pawel; Brotherston, Amanda; McCallum, David

    2017-12-31

    Onshore wind turbine foundations are generally over-engineered as their internal stress states are challenging to directly monitor during operation. While there are industry drivers to shift towards more economical foundation designs, making this transition safely will require new monitoring techniques, so that the uncertainties around structural health can be reduced. This paper presents the initial results of a real-time strain monitoring campaign for an operating wind turbine foundation. Selected reinforcement bars were instrumented with metal packaged optical fibre strain sensors prior to concrete casting. In this paper, we outline the sensors' design, characterisation and installation, and present 67 days of operational data. During this time, measured foundation strains did not exceed 95 μ ϵ , and showed a strong correlation with both measured tower displacements and the results of a foundation finite element model. The work demonstrates that real-time foundation monitoring is not only achievable, but that it has the potential to help operators and policymakers quantify the conservatism of their existing design codes.

  15. Tuning phase structures of a symmetrical diblock copolymer with a patterned electric field.

    Science.gov (United States)

    Kan, Di; He, Xuehao

    2016-05-11

    Electric fields can induce the orientation of the phase interfaces of block copolymers and provide a potential method to tune polymer phase structures for nanomaterial manufacture. In this work, we applied self-consistent field theory to study the self-assembly of a diblock copolymer confined between two parallel neutral substrates on which a set of electrodes was imposed to form a patterned electric field. The results showed that an alternatively distributed electric field can induce the formation of a parallel lamellar phase structure, which exists stably only in the system with selective substrates. The phase structure was proved to be sensitive to the characteristics of the electric field distribution, such as the strength of the electric field, the size and position of the electrodes, and the corresponding phase diagram was calculated in detail. The transition pathway of the phase structure from the perpendicular layered phase to the parallel layered phase was further analysed using the minimum energy path method. It is shown that the path and the active energy barrier of the phase transition depend on the electric field strength. Compound electric field patterns that can be designed to control the formation of novel and complex microphase structures were also examined.

  16. Spatiotemporal ecohydrological patterns and processes in temperate uplands: linking field observations and model results

    Science.gov (United States)

    Dodd, N. H.; Baird, A. J.; Wainwright, J.; Dunn, S. M.

    2011-12-01

    There are obvious surface expressions - in terms of vegetation patterning - of ecohydrological feedbacks on dryland and peatland hillslopes. Much less is known about subsurface ecohydrological patterns, and whether or not they 'map onto' surface patterns. Likewise, few attempts have been made to investigate how such ecohydrological patterns affect whole-hillslope hydrological behaviour or how widespread they are in non-dryland and non-peatland hillslopes. In this study we investigate surface and near- surface patterning in temperate hillslopes, which to date have been the focus of much hydrological work but little ecohydrological work. In particular, we consider the extent to which the direct and the indirect effects of past and present plant assemblages on local and whole-hillslope soil moisture conditions may contribute to patterning. We have conducted a field study of two temperate upland hillslopes in Northern Scotland, UK, on one of which human intervention plays a major part in shaping the landscape. Repeat measurements have been made of near- surface soil-moisture content, taken at lag distances of 0.25 m to 20 m, under different antecedent hydrological conditions together with characterisation of plant assemblages at the same points through both ground-based vegetation surveys of 1 m × 1 m plots and kite aerial photography (KAP) of > 20 m2 plots. Results from this have indicated that changes in ecohydrological patterns can occur over small spatial scales (images allowed detection of vegetation patterns not obvious from the ground. Comparison of KAP images and historic aerial photographs has highlighted the persistence of vegetation patterns over time at both sites, and that the current structure of the landscape is clearly related to current and past vegetation management practices. Evidence of sustained patterning under relatively steady environmental conditions has prompted us to consider how internal system dynamics such as competition and facilitation

  17. Near-field imaging of interference pattern of counterpropagating evanescent waves

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Bozhevolnaya, Elena A.

    1999-01-01

    It is generally accepted that measurement of of the contrast of the intensity interference pattern formed by two counterpropagating evanescent waves can be used to characterize the resolving power of a collection near-field microscope. We argue that, if the light collected by a fiber probe...

  18. Evolutionary convergence of the patterns of international research collaborations across scientific fields

    NARCIS (Netherlands)

    Wang, L.; Coccia, M.

    2015-01-01

    Frame and Carpenter (1979) analysed the pattern of international research collaboration among scientific fields in 1970s. Starting from this pioneering work, this paper investigates international collaborations over 1997-2012 and compares the critical results with earlier studies to detect the

  19. Precise Patterning of Organic Single Crystals via Capillary-Assisted Alternating-Electric Field.

    Science.gov (United States)

    Zhang, Yedong; Jie, Jiansheng; Sun, Yuning; Jeon, Seok-Gy; Zhang, Xiujuan; Dai, Gaole; Lee, Cheol Jin; Zhang, Xiaohong

    2017-07-01

    Owing to the extraordinary properties, organic micro/nanocrystals are important building blocks for future low-cost and high-performance organic electronic devices. However, integrated device application of the organic micro/nanocrystals is hampered by the difficulty in high-throughput, high-precision patterning of the micro/nanocrystals. In this study, the authors demonstrate, for the first time, a facile capillary-assisted alternating-electric field method for the large-scale assembling and patterning of both 0D and 1D organic crystals. These crystals can be precisely patterned at the photolithography defined holes/channels at the substrate with the yield up to 95% in 1 mm2 . The mechanism of assembly kinetics is systematically studied by the electric field distribution simulation and experimental investigations. By using the strategy, various organic micro/nanocrystal patterns are obtained by simply altering the geometries of the photoresist patterns on substrates. Moreover, ultraviolet photodetectors based on the patterned Alq3 micro/nanocrystals exhibit visible-blind photoresponse with high sensitivity as well as excellent stability and reproducibility. This work paves the way toward high-integration, high-performance organic electronic, and optoelectronic devices from the organic micro/nanocrystals. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Three-dimensional flow field around and downstream of a subscale model rotating vertical axis wind turbine

    Science.gov (United States)

    Ryan, Kevin J.; Coletti, Filippo; Elkins, Christopher J.; Dabiri, John O.; Eaton, John K.

    2016-03-01

    Three-dimensional, three-component mean velocity fields have been measured around and downstream of a scale model vertical axis wind turbine (VAWT) operated at tip speed ratios (TSRs) of 1.25 and 2.5, in addition to a non-rotating case. The five-bladed turbine model has an aspect ratio (height/diameter) of 1 and is operated in a water tunnel at a Reynolds number based on turbine diameter of 11,600. Velocity fields are acquired using magnetic resonance velocimetry (MRV) at an isotropic resolution of 1/50 of the turbine diameter. Mean flow reversal is observed immediately behind the turbine for cases with rotation. The turbine wake is highly three-dimensional and asymmetric throughout the investigated region, which extends up to 7 diameters downstream. A vortex pair, generated at the upwind-turning side of the turbine, plays a dominant role in wake dynamics by entraining faster fluid from the freestream and aiding in wake recovery. The higher TSR case shows a larger region of reverse flow and greater asymmetry in the near wake of the turbine, but faster wake recovery due to the increase in vortex pair strength with increasing TSR. The present measurement technique also provides detailed information about flow in the vicinity of the turbine blades and within the turbine rotor. The details of the flow field around VAWTs and in their wakes can inform the design of high-density VAWT wind farms, where wake interaction between turbines is a principal consideration.

  1. FACILITIES OF MEASURING OF WIND FOR RESEARCHES AND PLANNING OF THE AIR FIELDS AND HELIPORTS

    Directory of Open Access Journals (Sweden)

    А. Бєлятинський

    2012-04-01

    Full Text Available The choice of the place for the future airdrome (heliport construction must satisfy the financial appropriatenessand also exploitation security. For this purpose on the stage of the researches and designing the information is neededabout wind speed and its direction with an error 0,5 m/s and 10 hail accordingly, in a radius up to 15 km, as to heightfrom 2 to 1000 m with resolution 30 m, a spatial interval of measuring in a horizontal plane is not more than 20 km,in time - not rarer, than each 3 hours. Information is needed to be gained for maximal temporal period (it is desirableno less than five years. A device for the receipt of such information must be of low cost. The acoustic andradioacoustic sounding systems answer the indicated requirements most of all

  2. Field test report of the Department of Energy's 100-kW vertical axis wind turbine

    Science.gov (United States)

    Nellums, R. O.

    1985-02-01

    Three second generation Darrieus type vertical axis wind turbines of approximately 120 kW capacity per unit were installed in 1980-1981. Through March 1984, over 9000 hours of operation had been accumulated, including 6600 hours of operation on the unit installed in Bushland, Texas. The turbines were heavily instrumented and have yielded a large amount of test data. Test results of this program, including aerodynamic, structural, drive train, and economic data are presented. Among the most favorable results were an aerodynamic peak performance coefficient of 0.41; fundamental structural integrity requiring few repairs and no major component replacements as of March 1984; and an average prototype fabrication cost of approximately $970 per peak kilowatt of output. A review of potential design improvements is presented.

  3. Multi-field electron emission pattern of 2D emitter: Illustrated with graphene

    Science.gov (United States)

    Luo, Ma; Li, Zhibing

    2016-11-01

    The mechanism of laser-assisted multi-field electron emission of two-dimensional emitters is investigated theoretically. The process is basically a cold field electron emission but having more controllable components: a uniform electric field controls the emission potential barrier, a magnetic field controls the quantum states of the emitter, while an optical field controls electron populations of specified quantum states. It provides a highly orientational vacuum electron line source whose divergence angle over the beam plane is inversely proportional to square root of the emitter height. Calculations are carried out for graphene with the armchair emission edge, as a concrete example. The rate equation incorporating the optical excitation, phonon scattering, and thermal relaxation is solved in the quasi-equilibrium approximation for electron population in the bands. The far-field emission patterns, that inherit the features of the Landau bands, are obtained. It is found that the optical field generates a characteristic structure at one wing of the emission pattern.

  4. Line-patterning of polyaniline coated MWCNT on stepped substrates using DC electric field

    Science.gov (United States)

    Ko, Young Gun; Do, Tae Gu; Oh, Hyun Chul; Lee, Hyun Jeong; Han, Hung-Gu; Kim, Choong Hyun; Choi, Ung Su

    2014-10-01

    Printing electronic components on a chip edge and a stepped substrate with functional inks are an attractive approach for achieving flexible and inexpensive circuits for applications such as flexible displays and large-area chemo/bio/radioactivity sensors. However, it is still challenging because a sufficient cover of the 100 μm high step at the chip edge with a high-resolution pattern is the hardest part of the layer assembling by inkjet printing. Herein, we present a simple and effective strategy to generate electrically conductive line-patterns on stepped substrates by applying the DC electric field. On the surface of flat polyimide substrate, the fine line-pattern (less than 850 nm in line width) is achieved with a polyaniline coated MWCNT dispersed ink. Furthermore, 9.9 μm of line width is successfully patterned on the high stepped poly(dimethylsiloxane) substrate, higher than 100 μm, by printing only 1 time.

  5. Inverse measurement of wall pressure field in flexible-wall wind tunnels using global wall deformation data

    Science.gov (United States)

    Brown, Kenneth; Brown, Julian; Patil, Mayuresh; Devenport, William

    2018-02-01

    The Kevlar-wall anechoic wind tunnel offers great value to the aeroacoustics research community, affording the capability to make simultaneous aeroacoustic and aerodynamic measurements. While the aeroacoustic potential of the Kevlar-wall test section is already being leveraged, the aerodynamic capability of these test sections is still to be fully realized. The flexibility of the Kevlar walls suggests the possibility that the internal test section flow may be characterized by precisely measuring small deflections of the flexible walls. Treating the Kevlar fabric walls as tensioned membranes with known pre-tension and material properties, an inverse stress problem arises where the pressure distribution over the wall is sought as a function of the measured wall deflection. Experimental wall deformations produced by the wind loading of an airfoil model are measured using digital image correlation and subsequently projected onto polynomial basis functions which have been formulated to mitigate the impact of measurement noise based on a finite-element study. Inserting analytic derivatives of the basis functions into the equilibrium relations for a membrane, full-field pressure distributions across the Kevlar walls are computed. These inversely calculated pressures, after being validated against an independent measurement technique, can then be integrated along the length of the test section to give the sectional lift of the airfoil. Notably, these first-time results are achieved with a non-contact technique and in an anechoic environment.

  6. The impact of monsoon winds and mesoscale eddies on thermohaline structures and circulation patterns in the northern South China Sea

    Science.gov (United States)

    Zhao, Ruixiang; Zhu, Xiao-Hua; Guo, Xinyu

    2017-07-01

    We deployed 5 pressure-recording inverted echo sounders (PIES) along a section in the northern South China Sea (NSCS), and estimated well the distributions of temperature, salinity and velocity across the section. Applying the empirical orthogonal function (EOF) method, we found that variability of the estimates is dominated by two modes: one named the seasonal mode affecting strongly on the hydrographic distribution with explained variability of temperature/salinity by 62.9/72.2%; the other named the eddy mode, corresponding to the arrival of mesoscale eddies, affecting strongly on the circulation pattern with explained variability of velocity by 63.2%. Temporal variation of the seasonal mode is highly correlated with the monsoon winds southeast of Vietnam, suggesting a nonlocal forcing mechanism. Case studies looking at the structures and evolutions of three captured eddies, whose impacts were well quantified by the eddy mode. The monsoon (eddies) significantly affects temperature, salinity and velocity shallower than 635 m (860 m), 160 m (150 m) and 1055 m (920 m), respectively. The monsoon (eddies) can induce maximum temperature, salinity and velocity anomalies up to -1.6 to 2.1 °C (-2.5 to 2.2 °C), -0.11 to 0.14 psu (-0.13 to 0.27 psu) and -0.31 to 0.46 m/s (-0.40 to 0.38 m/s), respectively. Mean volume transport (VT) across the section is 1.0 Sv (1 Sv= 1 ×106 m3 s-1, positive to the northeast). Seasonal VT (with eddy impacts removed) is -4.6 Sv, 11.4 Sv, -5.1 Sv and -4.1 Sv for spring, summer, autumn and winter, respectively.

  7. Low frequency geomagnetic field fluctuations at low latitude during the passage of a higher pressure solar wind region

    Directory of Open Access Journals (Sweden)

    U. Villante

    1997-06-01

    Full Text Available The passage of a higher pressure solar wind region at the Earth's orbit marked the onset of low latitude (L=1.6 fluctuations in the frequency range (0.8–5.5 mHz for both the horizontal geomagnetic field components. Spectral peaks mostly occur at the same frequencies as the spectral enhancements which appeared in the long term analysis of experimental measurements from the same station and were tentatively interpreted in terms of ground signatures of global magnetospheric modes. A comparison with simultaneous observations discussed by previous investigations allows us to conclude that the same set of frequencies is enhanced in a wide portion of the Earth's magnetosphere.

  8. Modeling dynamic stall on wind turbine blades under rotationally augmented flow fields

    Energy Technology Data Exchange (ETDEWEB)

    Guntur, S. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Schreck, S. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sorensen, N. N. [Technical Univ. of Denmark, Lyngby (Denmark); Bergami, L. [Technical Univ. of Denmark, Lyngby (Denmark)

    2015-04-22

    It is well known that airfoils under unsteady flow conditions with a periodically varying angle of attack exhibit aerodynamic characteristics different from those under steady flow conditions, a phenomenon commonly known as dynamic stall. It is also well known that the steady aerodynamic characteristics of airfoils in the inboard region of a rotating blade differ from those under steady two-dimensional (2D) flow conditions, a phenomenon commonly known as rotational augmentation. This paper presents an investigation of these two phenomena together in the inboard parts of wind turbine blades. This analysis is carried out using data from three sources: (1) the National Renewable Energy Laboratory’s Unsteady Aerodynamics Experiment Phase VI experimental data, including constant as well as continuously pitching blade conditions during axial operation, (2) data from unsteady Delayed Detached Eddy Simulations (DDES) carried out using the Technical University of Denmark’s in-house flow solver Ellipsys3D, and (3) data from a simplified model based on the blade element momentum method with a dynamic stall subroutine that uses rotationally augmented steady-state polars obtained from steady Phase VI experimental sequences, instead of the traditional 2D nonrotating data. The aim of this work is twofold. First, the blade loads estimated by the DDES simulations are compared to three select cases of the N sequence experimental data, which serves as a validation of the DDES method. Results show reasonable agreement between the two data in two out of three cases studied. Second, the dynamic time series of the lift and the moment polars obtained from the experiments are compared to those from the dynamic stall subroutine that uses the rotationally augmented steady polars. This allowed the differences between the stall phenomenon on the inboard parts of harmonically pitching blades on a rotating wind turbine and the classic dynamic stall representation in 2D flow to be

  9. Demonstration of synchronised scanning Lidar measurements of 2D velocity fields in a boundary-layer wind tunnel

    DEFF Research Database (Denmark)

    van Dooren, M F; Kühn, M.; Petrovic, V.

    2016-01-01

    compared to hot wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u- and v-components of the wind speed, respectively, validating the 2D measurement capability of the Lidar scanners. Subsequently, the measurement......This paper combines the currently relevant research methodologies of scaled wind turbine model experiments in wind tunnels with remote-sensing short-range WindScanner Lidar measurement technology. The wind tunnel of the Politecnico di Milano was equipped with three wind turbine models and two short......-range WindScanner Lidars to demonstrate the benefits of synchronised scanning Lidars in such experimental surroundings for the first time. The dualLidar system can provide fully synchronised trajectory scans with sampling time scales ranging from seconds to minutes. First, staring mode measurements were...

  10. Generalization of susceptibility of RF systems through far-field pattern superposition

    Science.gov (United States)

    Verdin, B.; Debroux, P.

    2015-05-01

    The purpose of this paper is to perform an analysis of RF (Radio Frequency) communication systems in a large electromagnetic environment to identify its susceptibility to jamming systems. We propose a new method that incorporates the use of reciprocity and superposition of the far-field radiation pattern of the RF system and the far-field radiation pattern of the jammer system. By using this method we can find the susceptibility pattern of RF systems with respect to the elevation and azimuth angles. A scenario was modeled with HFSS (High Frequency Structural Simulator) where the radiation pattern of the jammer was simulated as a cylindrical horn antenna. The RF jamming entry point used was a half-wave dipole inside a cavity with apertures that approximates a land-mobile vehicle, the dipole approximates a leaky coax cable. Because of the limitation of the simulation method, electrically large electromagnetic environments cannot be quickly simulated using HFSS's finite element method (FEM). Therefore, the combination of the transmit antenna radiation pattern (horn) superimposed onto the receive antenna pattern (dipole) was performed in MATLAB. A 2D or 3D susceptibility pattern is obtained with respect to the azimuth and elevation angles. In addition, by incorporating the jamming equation into this algorithm, the received jamming power as a function of distance at the RF receiver Pr(Φr, θr) can be calculated. The received power depends on antenna properties, propagation factor and system losses. Test cases include: a cavity with four apertures, a cavity above an infinite ground plane, and a land-mobile vehicle approximation. By using the proposed algorithm a susceptibility analysis of RF systems in electromagnetic environments can be performed.

  11. Dynamical pattern formation in a low-concentration magnetorheological fluid under two orthogonal sinusoidal fields

    Energy Technology Data Exchange (ETDEWEB)

    Yépez, L.D.; Carrillo, J.L. [Instituto de Física de la Universidad Autónoma de Puebla, Ciudad Universitaria, Edif. 110 A, Puebla 72570 (Mexico); Donado, F.; Sausedo-Solorio, J.M.; Miranda-Romagnoli, P. [Instituto de Ciencias Básicas e Ingeniería Universidad Autónoma del Estado de Hidalgo, Pachuca 42090, Pachuca (Mexico)

    2016-06-15

    The dynamical pattern formation of clusters of magnetic particles in a low-concentration magnetorheological fluid, under the influence of a superposition of two perpendicular sinusoidal fields, is studied experimentally. By varying the frequency and phase shift of the perpendicular fields, this configuration enables us to experimentally analyze a wide range of field configurations, including the case of a pure rotating field and the case of an oscillating unidirectional field. The fields are applied parallel to the horizontal plane where the fluid lies or in the vertical plane. For fields applied in the horizontal plane, we observed that, when the ratio of the frequencies increases, the average cluster size exhibits a kind of periodic resonances. When the phase shift between the fields is varied, the average chain length reaches maximal values for the cases of the rotating field and the unidirectional case. We analyze and discuss these results in terms of a weighted average of the time-dependent Mason number. In the case of a rotating field on the vertical plane, we also observe that the competition between the magnetic and the viscous forces determines the average cluster size. We show that this configuration generates a series of physically meaningful self-organization of clusters and transport phenomena. - Highlights: • A weighted average of the time-dependent Mason number is proposed. • The self-propelling clusters appear when a vertical rotating magnetic field is applied. • The largest average chain lengths are reached when frequencies are multiples one another. • Rotating and unidirectional alternating fields produce the largest average chain length values.

  12. Judicious distribution of laser emitters to shape the desired far-field patterns

    Science.gov (United States)

    Valagiannopoulos, Constantinos A.; Kovanis, Vassilios

    2017-06-01

    The far-field pattern of a simple one-dimensional laser array of emitters radiating into free space is considered. In the course of investigating the inverse problem for their near fields leading to a target beam form, surprisingly, we found that the result is successful when the matrix of the corresponding linear system is not well scaled. The essence of our numerical observations is captured by an elegant inequality defining the functional range of the optical distance between two neighboring emitters. Our finding can restrict substantially the parametric space of integrated photonic systems and simplify significantly the subsequent optimizations.

  13. Report on a wind power development field test project (detailed wind condition investigation) in the city of Choshi; Choshishi ni okeru furyoku kaihatsu field test jigyo (fukyo seisa) hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-11-01

    This paper describes observation on the annual wind condition at the Yokka-ichibadai in the city of Choshi. The average wind velocities were 4.7 and 3.8 m/s at the ground height of 20 and 10 meters, respectively, not having reached the NEDO's criterion values 5.6 and 5.0 m/s. The annual wind direction emergence rate on the wind axis was 70%, meeting the criterion value of 60% or higher, and the wind direction is stable. The exponent for the vertical wind velocity distribution was 3.3, which is similar to that in the urban area. Disturbance in the wind condition was 0.18, meeting the criterion value of 0.30 or lower. The maximum momentary wind velocity was 31.9 m/s, which is well below the criterion of 60 m/s presenting no problem as a wind mill construction site. The wind energy density was 94 W/m{sup 2}, being only 63% of the criterion value, when all the azimuths were used as the object. The result of the investigation is that the average wind velocity is low and the wind energy density is also low. However, if the size of wind mill to be introduced is set to the class B (300 kW), it is possible to attain an annual operation rate of 58%, an annual energy acquisition amount of 515 MWh, and a facility utilization rate of 19.6%. If set to the class C (750 kW), an operation rate of 78%, an annual energy acquisition of 1296 MWh, and a facility utilization rate of 19.7% can be obtained, meeting the criterion value. (NEDO)

  14. Mitigation of pattern sensitivity in full-field electronic dispersion compensation

    OpenAIRE

    Zhao, Jian A.; McCarthy, Mary E.; Gunning, Paul; Ellis, Andrew D.

    2009-01-01

    We investigate the pattern-dependent decoding failures in full-field electronic dispersion compensation (EDC) by offline processing of experimental signals, and find that the performance of such an EDC receiver may be degraded by an isolated "1" bit surrounded by long strings of consecutive "0s". By reducing the probability of occurrence of this kind of isolated "1" and using a novel adaptive threshold decoding method, we greatly improve the compensation performance to achieve 10-Gb/s on-off ...

  15. Distribution pattern assessment of a dual-purpose disc agrochemical applicator for field crops

    Directory of Open Access Journals (Sweden)

    M. S. Abubakar

    2012-08-01

    Full Text Available A dual-purpose disc agrochemical applicator for field crops was developed to boost agricultural mechanization in crop production and also to overcome the safety concern of hazardous spray drift during agrochemical application by the field crop farmers. The dual purpose agrochemical applicator was mounted on a high clearance tractor and tested with respect to the granular fertilizer distribution patterns uniformity/liquid chemical uniformity of droplet sizes in spraying of the agrochemical. Results for NPK granular chemical indicated that, at low (50 kg/ha and high (150 kg/ha application rates with 550 rpm disc speed, distribution patterns skewed to the left whereas the distribution pattern at medium (100 kg/ha application rates was good flattop. Also at high application rate with 1000 rpm disc speed, mean distribution pattern became poor (W-shape. For the liquid chemical herbicide HC 48 amine liquid, the mean values of volume median diameter (VMD and number median diameter (NMD were 108 µm and 80 µm at 90 lt/ha application rate at 5000 rpm rotary disc speed, and also 344 and 222 µm at 30 lt/ha application rate with 2000 rpm rotary disc speed. The mean values of coefficient of uniformity for droplet sizes expressed as VMD/NMD found in this study were in the range of 1.35 to 1.55 for HC amine 48 liquid chemical.

  16. Towards an understanding of microstructure of patterned FePt dots by magnetometry using pulse fields

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Z.J., E-mail: yanzhj@lzu.edu.cn [VBL of Akita University, Gakuen Machi 1-1, Tegata, Akita 010-8502 (Japan); Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Takahashi, S.; Hasegawa, T.; Ishio, S. [VBL of Akita University, Gakuen Machi 1-1, Tegata, Akita 010-8502 (Japan); Kondo, Y.; Ariake, J. [Akita Research Institute of Advanced Technology (AIT), 4-21 Sanuki, Araya, Akita 010-1623 (Japan)

    2014-01-15

    FePt nanodot arrays are patterned and investigated by X-ray magnetic circular dichroism measurements and magneto-optic Kerr effect magnetometry combined with pulse magnetic fields. The experimental results on varied timescale of the applied field are analyzed by Sharrock's formula, showing the emergence of hard and soft magnetic FePt grains with distinct perpendicular anisotropy. While the hard grains in L1{sub 0}-phase can construct the FePt dots with intrinsic perpendicular anisotropy fields around 90 kOe, the exchange coupling between the hard and soft grains in other dots degrades the dot perpendicular coercivity and widens the array switching field distribution, in both the 100 and 30 nm dot arrays. The dot size dependence of the proportion of the hard dot in the array demonstrates that the soft grains originate from the FePt grains of L1{sub 0}-phase with large c-axis misaligning and of fcc phase inside the dots, and the ion etching effects are insignificant. - Highlights: • Patterned FePt dot arrays are studied by XMCD and MOKE with pulse fields. • Results on varied timescale of the applied field indicate the dot microstructure. • Hard magnetic grains are in the L1{sub 0}-phase with perpendicular cell c-axis. • Hard magnetic dots with PMA fields around 90 kOe are found in the 100 and 30 nm dots. • Exchange coupling between the hard and soft grains degrades the soft dot coercivity.

  17. Patterns of failure after involved field radiotherapy for locally advanced esophageal squamous cell carcinoma.

    Science.gov (United States)

    Li, Duo-Jie; Li, Hong-Wei; He, Bin; Wang, Geng-Ming; Cai, Han-Fei; Duan, Shi-Miao; Liu, Jing-Jing; Zhang, Ya-Jun; Cui, Zhen; Jiang, Hao

    2016-01-01

    To retrospectively analyze the patterns of failure and the treatment effects of involved-field irradiation (IFI) on patients treated with locally advanced esophageal squamous cell carcinoma (ESCC) and to determine whether IFI is practicable in these patients. A total of 79 patients with locally advanced ESCC underwent three dimensional conformal (3D)CRT) or intensity modulated radiotherapy (IMRT) using IFI or elective nodal irradiation (ENI) according to the target volume. The patterns of failure were defined as local/regional, in-field, out)of)field regional lymph node (LN) and distant failure. With a median follow)up of 32.0 months, failures were observed in 66 (83.6%) patients. The cumulative incidence of local/regional failure (55.8 vs 52.8%) and in)field regional lymph node failure (25.6 vs 19.4%) showed no statistically significant difference between the IFI and the ENI group (p=0.526 and 0.215, respectively). Out)of)field nodal relapse rate of only 7.0% was seen in the IFI group. Three)year survival rates for the ENI and IFI group were 22.2 and 18.6%, respectively (p=0.240), and 3)year distant metastasis rates were 27.8 and 32.6%, respectively (p=0.180). The lung V10, V20, V30 and mean lung dose of the ENI group were greater than those of the IFI group, while the mean lung dose and V10 had statistically significant difference. The patterns of failure and survival rates in the IFI group were similar as in the ENI group; the regional recurrence and distant metastasis are the main cause of treatment failure. IFI is feasible for locally advanced ESCC. Further investigation is needed to increase local control and decrease distant metastasis in these patients.

  18. Comparisons of Wind Speed Retrievals from an Airborne Microwave Radiometer (AMPR) with Satellite-Based Observations During the OLYMPEX/RADEX Field Campaign

    Science.gov (United States)

    Lang, Timothy J.; Biswas, Sayak

    2017-01-01

    AMPR is an airborne instrument that flew aboard the NASA ER-2 during the OLYMPEX/RADEX field campaign in late 2015. This poster's goal is to explore how well the instrument can retrieve near-surface wind speed over the ocean.

  19. Receptive fields of locust brain neurons are matched to polarization patterns of the sky.

    Science.gov (United States)

    Bech, Miklós; Homberg, Uwe; Pfeiffer, Keram

    2014-09-22

    Many animals, including insects, are able to use celestial cues as a reference for spatial orientation and long-distance navigation [1]. In addition to direct sunlight, the chromatic gradient of the sky and its polarization pattern are suited to serve as orientation cues [2-5]. Atmospheric scattering of sunlight causes a regular pattern of E vectors in the sky, which are arranged along concentric circles around the sun [5, 6]. Although certain insects rely predominantly on sky polarization for spatial orientation [7], it has been argued that detection of celestial E vector orientation may not suffice to differentiate between solar and antisolar directions [8, 9]. We show here that polarization-sensitive (POL) neurons in the brain of the desert locust Schistocerca gregaria can overcome this ambiguity. Extracellular recordings from POL units in the central complex and lateral accessory lobes revealed E vector tunings arranged in concentric circles within large receptive fields, matching the sky polarization pattern at certain solar positions. Modeling of neuronal responses under an idealized sky polarization pattern (Rayleigh sky) suggests that these "matched filter" properties allow locusts to unambiguously determine the solar azimuth by relying solely on the sky polarization pattern for compass navigation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Simulated near-field mapping of ripple pattern supported metal nanoparticles arrays for SERS optimization

    Science.gov (United States)

    Arya, Mahima; Bhatnagar, Mukul; Ranjan, Mukesh; Mukherjee, Subroto; Nath, Rabinder; Mitra, Anirban

    2017-11-01

    An analytical model has been developed using a modified Yamaguchi model along with the wavelength dependent plasmon line-width correction. The model has been used to calculate the near-field response of random nanoparticles on the plane surface, elongated and spherical silver nanoparticle arrays supported on ion beam produced ripple patterned templates. The calculated near-field mapping for elongated nanoparticles arrays on the ripple patterned surface shows maximum number of hot-spots with a higher near-field enhancement (NFE) as compared to the spherical nanoparticle arrays and randomly distributed nanoparticles on the plane surface. The results from the simulations show a similar trend for the NFE when compared to the far field reflection spectra. The nature of the wavelength dependent NFE is also found to be in agreement with the observed experimental results from surface enhanced Raman spectroscopy (SERS). The calculated and the measured optical response unambiguously reveal the importance of interparticle gap and ordering, where a high intensity Raman signal is obtained for ordered elongated nanoparticles arrays case as against non-ordered and the aligned configuration of spherical nanoparticles on the rippled surface.

  1. Delineating the magnetic field line escape pattern and stickiness in a poloidally diverted tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Caroline G. L., E-mail: carolinegameiro@gmail.com, E-mail: ibere@if.usp.br [Departamento de Física, Instituto Tecnológico de Aeronáutica, São José dos Campos, SP 12228-900 (Brazil); Department of Physics, Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States); Roberto, M., E-mail: marisar@ita.br [Departamento de Física, Instituto Tecnológico de Aeronáutica, São José dos Campos, SP 12228-900 (Brazil); Caldas, I. L., E-mail: carolinegameiro@gmail.com, E-mail: ibere@if.usp.br [Universidade de São Paulo, Instituto de Física, São Paulo, SP 05315-970 (Brazil)

    2014-08-15

    We analyze a Hamiltonian model with five wire loops that delineates magnetic surfaces of tokamaks with poloidal divertor. Non-axisymmetric magnetic perturbations are added by external coils, similar to the correction coils that have been installed or designed in present tokamaks. To show the influence of magnetic perturbations on the field line escape, we integrate numerically the field line differential equations and obtain the footprints and deposition patterns on the divertor plate. Moreover, we show that the homoclinic tangle describes the deposition patterns in the divertor plate, agreeing with results observed in sophisticated simulation codes. Additionally, we show that while chaotic lines escape to the divertor plates, some of them are trapped, for many toroidal turns, in complex structures around magnetic islands, embedded in the chaotic region, giving rise to stickiness evidences characteristic of chaotic Hamiltonian systems. Finally, we introduce a random collisional term to the field line mapping to investigate stickiness alterations due to particle collisions. Within this model, we conclude that, even reduced by collisions, the observed trapping still influences the field line transport. The results obtained for our numerical estimations indicate that the reported trapping may affect the transport in present tokamaks.

  2. The Behavior of Surface Wind and Thermodynamic Fields in the Presence of Deep Convection.

    Science.gov (United States)

    1981-05-01

    1975 Intensity #x 10 kg fx 10~ kg Light 8 503.16 14 561 .55 Average 8 62.90 14 40.11 Moderate 9 3278.68 14 3094.59 Average 9 364.30 14 221.04 Heavy 30...Florida peninsula. These case studies illustrate the interaction between storm out- flows and show in detail the makeup of the characteristic signals of...idl I -116- The previous case studies illustrate in some detail: a) The 2-dimensional structure of the divergence fields which makeup the network area

  3. Experimental Investigation of Scalar Patterns in a Spatially Periodic Flow Field

    Science.gov (United States)

    Rajaei, Hadi; Baskan, Ozge; Speetjens, Michel; Clercx, Herman

    2013-11-01

    Spatially persisting patterns that form during the downstream evolution of passive scalars in three-dimensional (3D) spatially periodic flow fields is a fundamental aspect of industrial mixing processes that rely on the static mixing principle. Despite many numerical studies on 3D spatially periodic flow fields, a comprehensive experimental research on the periodic flow field is still scarce. This research focuses on a comparative analysis between laboratory experiments and numerical simulations on the evolution of the periodic flow field and coherent flow structures and concerns the effect of boundary (i.e. inlet) conditions on the periodicity of the flow field in a representative inline mixer consisting of spatially periodic internal elements. The experimental setup is composed of an optically accessible vertical test section with transparent internal elements which is fed by a pressure-driven pipe flow containing tracer particles. The 3D streamlines, hence, the flow field, are measured by 3D Particle-Tracking Velocimetry technique. The streamwise development of the periodicity within few internal elements regardless of the inlet conditions has been proven by preliminary studies.

  4. Evidence for a single stochastic physical process for fast solar wind magnetic field magnitude fluctuations at 1AU across `turbulent' and `1/f' temporal scales

    Science.gov (United States)

    Hnat, B.; Chapman, S. C.; Kiyani, K. H.

    2010-12-01

    The power spectral density of magnetic field components in the fast solar wind on magnetohydrodynamic scales typically shows two power law regions, identified with an inertial range of turbulence, and at lower frequencies, a ~1/f range of coronal origin. The power spectral density of field magnitude shows a single power law region across these scales. We present the first scale-by-scale quantitative comparison of the averaged statistical properties of magnetic field magnitude and component fluctuations over timescales of ~2 minutes to 5.6 hours observed in-situ in the fast quiet solar wind at solar minimum at 1AU with the ACE spacecraft. Fluctuations in the field components show an 'inertial range' of scaling up to ~30 minutes and beyond this, uncorrelated Gaussian statistics. In contrast, the magnetic field magnitude fluctuations show a single scaling behaviour up to 5 hours and are non-Gaussian over this entire range of scales. Thus unlike for the components, a single stochastic process could account for the fluctuations in field magnitude over both the inertial range and 1/f range of timescales the fast solar wind.

  5. Effects of Blade Boundary Layer Transition and Daytime Atmospheric Turbulence on Wind Turbine Performance Analyzed with Blade-Resolved Simulation and Field Data

    Science.gov (United States)

    Nandi, Tarak Nath

    Relevant to utility scale wind turbine functioning and reliability, the present work focuses on enhancing our understanding of wind turbine responses from interactions between energy-dominant daytime atmospheric turbulence eddies and rotating blades of a GE 1.5 MW wind turbine using a unique data set from a GE field experiment and computer simulations at two levels of fidelity. Previous studies have shown that the stability state of the lower troposphere has a major impact on the coherent structure of the turbulence eddies, with corresponding differences in wind turbine loading response. In this study, time-resolved aerodynamic data measured locally at the leading edge and trailing edge of three outer blade sections on a GE 1.5 MW wind turbine blade and high-frequency SCADA generator power data from a daytime field campaign are combined with computer simulations that mimic the GE wind turbine within a numerically generated atmospheric boundary layer (ABL) flow field which is a close approximation of the atmospheric turbulence experienced by the wind turbine in the field campaign. By combining the experimental and numerical data sets, this study describes the time-response characteristics of the local loadings on the blade sections in response to nonsteady nonuniform energetic atmospheric turbulence eddies within a daytime ABL which have spatial scale commensurate with that of the turbine blade length. This study is the first of its kind where actuator line and blade boundary layer resolved CFD studies of a wind turbine field campaign are performed with the motivation to validate the numerical predictions with the experimental data set, and emphasis is given on understanding the influence of the laminar to turbulent transition process on the blade loadings. The experimental and actuator line method data sets identify three important response time scales quantified at the blade location: advective passage of energy-dominant eddies (≈25 - 50 s), blade rotation (1P

  6. Determining volcanic SO2 plume heights in satellite observations using meteorological wind fields

    Science.gov (United States)

    Keicher, Viktoria; Hörmann, Christoph; Sihler, Holger; Platt, Ulrich; Wagner, Thomas

    2016-04-01

    Satellite observations nowadays provide the global monitoring of volcanic plumes via sulphur dioxide (SO2) that is injected into the Earth's atmosphere. In turn, SO2 may lead to the formation of sulphate aerosols that can influence climate via direct and indirect radiative effects. The retrieval of SO2 requires an accurate plume height estimate in order to constrain total amounts for such events. One of the main difficulties for the retrieval is the typically unknown atmospheric profile resulting from unknown initial conditions (individual explosions over an extended time period leading to different gas layer altitudes and influencing the atmospheric transport pattern). In recent years, satellite observations helped to improve global SO2 estimates, but still large uncertainties exist. Passive satellite remote sensing using measurements in the UV/vis spectral range for example offers the opportunity to observe the location of a plume in two dimensions, but information about the corresponding height is sparse. Furthermore, information about these plume profiles is not only interesting in itself (e.g. to assess the radiative effect of volcanic plumes). It is also important for the quantitative interpretation of satellite observations. Here, we present first results for a newly developed approach using the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) in combination with data for different volcanic SO2 plumes as observed by the second generation Global Ozone Monitoring Instrument (GOME-2). The main plume information that can be retrieved by the satellite (i.e. plume location and observation time) are used as initial input parameters in order to estimate the plume's profile at the time of the measurements. For selected case studies we use these trajectories to further estimate values the eruption time and height. The correspondingly modelled values can also be used to verify the results when they are compared to direct local observations and

  7. Comparison of the Dynamic Wake Meandering Model, Large-Eddy Simulation, and Field Data at the Egmond aan Zee Offshore Wind Plant: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Churchfield, M. J.; Moriarty, P. J.; Hao, Y.; Lackner, M. A.; Barthelmie, R.; Lundquist, J.; Oxley, G. S.

    2014-12-01

    The focus of this work is the comparison of the dynamic wake meandering model and large-eddy simulation with field data from the Egmond aan Zee offshore wind plant composed of 36 3-MW turbines. The field data includes meteorological mast measurements, SCADA information from all turbines, and strain-gauge data from two turbines. The dynamic wake meandering model and large-eddy simulation are means of computing unsteady wind plant aerodynamics, including the important unsteady meandering of wakes as they convect downstream and interact with other turbines and wakes. Both of these models are coupled to a turbine model such that power and mechanical loads of each turbine in the wind plant are computed. We are interested in how accurately different types of waking (e.g., direct versus partial waking), can be modeled, and how background turbulence level affects these loads. We show that both the dynamic wake meandering model and large-eddy simulation appear to underpredict power and overpredict fatigue loads because of wake effects, but it is unclear that they are really in error. This discrepancy may be caused by wind-direction uncertainty in the field data, which tends to make wake effects appear less pronounced.

  8. Is Field of Study or Location Associated with College Students' Snacking Patterns?

    Directory of Open Access Journals (Sweden)

    Laura H. McArthur

    2012-01-01

    Full Text Available Objective. To compare on- and off-campus snacking patterns among college students pursuing degrees in health-related fields (HRFs and nonhealth-related fields (NHRFs. Materials and Methods. Snack frequency questionnaire, scales measuring barriers, self-efficacy, and stage of change for healthy snacking, and a snack knowledge test (SKT. Participants. 513 students, 46% HRFs, and 54% NHRFs. The students' mean±SD BMI was 24.1±4.3 kg/m2 (range 14.6 to 43.8, and 32.2% were overweight/obese. Results. Softdrinks (on-campus, lowfat milk (off-campus, and sports drinks were popular among HRFs and NHRFs. Cost and availability were barriers to healthy snacking, students felt least confident to choose healthy snacks when emotionally upset, and 75% (65% of HRFs (NHRFs self-classified in the action stage of change for healthy snacking. The HRFs scored higher on the SKT. Conclusions. Neither location nor field of study strongly influenced snacking patterns, which featured few high-fiber foods.

  9. Is field of study or location associated with college students' snacking patterns?

    Science.gov (United States)

    McArthur, Laura H; Holbert, Donald; Forsythe, William

    2012-01-01

    Objective. To compare on- and off-campus snacking patterns among college students pursuing degrees in health-related fields (HRFs) and nonhealth-related fields (NHRFs). Materials and Methods. Snack frequency questionnaire, scales measuring barriers, self-efficacy, and stage of change for healthy snacking, and a snack knowledge test (SKT). Participants. 513 students, 46% HRFs, and 54% NHRFs. The students' mean ± SD BMI was 24.1 ± 4.3 kg/m(2) (range 14.6 to 43.8), and 32.2% were overweight/obese. Results. Softdrinks (on-campus), lowfat milk (off-campus), and sports drinks were popular among HRFs and NHRFs. Cost and availability were barriers to healthy snacking, students felt least confident to choose healthy snacks when emotionally upset, and 75% (65%) of HRFs (NHRFs) self-classified in the action stage of change for healthy snacking. The HRFs scored higher on the SKT. Conclusions. Neither location nor field of study strongly influenced snacking patterns, which featured few high-fiber foods.

  10. Detection of Wind Evolution and Lidar Trajectory Optimization for Lidar-Assisted Wind Turbine Control

    Directory of Open Access Journals (Sweden)

    David Schlipf

    2015-11-01

    Full Text Available Recent developments in remote sensing are offering a promising opportunity to rethink conventional control strategies of wind turbines. With technologies such as lidar, the information about the incoming wind field - the main disturbance to the system - can be made available ahead of time. Initial field testing of collective pitch feedforward control shows, that lidar measurements are only beneficial if they are filtered properly to avoid harmful control action. However, commercial lidar systems developed for site assessment are usually unable to provide a usable signal for real time control. Recent research shows, that the correlation between the measurement of rotor effective wind speed and the turbine reaction can be modeled and that the model can be used to optimize a scan pattern. This correlation depends on several criteria such as turbine size, position of the measurements, measurement volume, and how the wind evolves on its way towards the rotor. In this work the longitudinal wind evolution is identified with the line-of-sight measurements of a pulsed lidar system installed on a large commercial wind turbine. This is done by staring directly into the inflowing wind during operation of the turbine and fitting the coherence between the wind at different measurement distances to an exponential model taking into account the yaw misalignment, limitation to line-of-sight measurements and the pulse volume. The identified wind evolution is then used to optimize the scan trajectory of a scanning lidar for lidar-assisted feedforward control in order to get the best correlation possible within the constraints of the system. Further, an adaptive filer is fitted to the modeled correlation to avoid negative impact of feedforward control because of uncorrelated frequencies of the wind measurement. The main results of the presented work are a first estimate of the wind evolution in front of operating wind turbines and an approach which manufacturers of

  11. Mean wind patterns and snow depths in an alpine-subalpine ecosystem as measured by damage to coniferous trees

    Science.gov (United States)

    G. L. Wooldridge; R. C. Musselman; R. A. Sommerfeld; D. G. Fox; B. H. Connell

    1996-01-01

    1. Deformations of Engelmann spruce and subalpine fir trees were surveyed for the purpose of determining climatic wind speeds and directions and snow depths in the Glacier Lakes Ecosystem Experiments Site (GLEES) in the Snowy Range of southeastern Wyoming, USA. Tree deformations were recorded at 50- and 100-m grid intervals over areas of c. 30 ha and 300 ha,...

  12. Diurnal pattern and behavior of oviposition of Toxorhynchites theobaldi in the field.

    Science.gov (United States)

    Arredondo-Bernal, H C; Reyes-Villanueva, F

    1989-03-01

    The diurnal pattern and oviposition behavior of Toxorhynchites theobaldi natural populations were studied in 25 artificial containers in the field. The mosquito exhibited a bimodal oviposition pattern with the lower peak at 1100 hr and a mean of 15.7 eggs per container. The higher peak was observed at 1900 hr with a mean of 80.9 eggs per container. Each female flew from 21 to 58 elliptic vertical circles before ejecting one egg upon the surface. In 270 oviposition events, the average was 31.4 ellipses, and the frequency distribution of flights number with different ellipse numbers was fitted to a Poisson distribution. There was a significant linear correlation (r = 0.70) between the oviposition rate and the container surface area.

  13. Study of high speed complex number algorithms. [for determining antenna for field radiation patterns

    Science.gov (United States)

    Heisler, R.

    1981-01-01

    A method of evaluating the radiation integral on the curved surface of a reflecting antenna is presented. A three dimensional Fourier transform approach is used to generate a two dimensional radiation cross-section along a planer cut at any angle phi through the far field pattern. Salient to the method is an algorithm for evaluating a subset of the total three dimensional discrete Fourier transform results. The subset elements are selectively evaluated to yield data along a geometric plane of constant. The algorithm is extremely efficient so that computation of the induced surface currents via the physical optics approximation dominates the computer time required to compute a radiation pattern. Application to paraboloid reflectors with off-focus feeds in presented, but the method is easily extended to offset antenna systems and reflectors of arbitrary shapes. Numerical results were computed for both gain and phase and are compared with other published work.

  14. Demonstration of synchronised scanning Lidar measurements of 2D velocity fields in a boundary-layer wind tunnel

    Science.gov (United States)

    van Dooren, M. F.; Kühn, M.; PetroviĆ, V.; Bottasso, C. L.; Campagnolo, F.; Sjöholm, M.; Angelou, N.; Mikkelsen, T.; Croce, A.; Zasso, A.

    2016-09-01

    This paper combines the currently relevant research methodologies of scaled wind turbine model experiments in wind tunnels with remote-sensing short-range WindScanner Lidar measurement technology. The wind tunnel of the Politecnico di Milano was equipped with three wind turbine models and two short-range WindScanner Lidars to demonstrate the benefits of synchronised scanning Lidars in such experimental surroundings for the first time. The dual- Lidar system can provide fully synchronised trajectory scans with sampling time scales ranging from seconds to minutes. First, staring mode measurements were compared to hot wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u- and v-components of the wind speed, respectively, validating the 2D measurement capability of the Lidar scanners. Subsequently, the measurement of wake profiles on a line as well as wake area scans were executed to illustrate the applicability of Lidar scanning to measuring small scale wind flow effects. The downsides of Lidar with respect to the hot wire probes are the larger measurement probe volume and the loss of some measurements due to moving blades. In contrast, the benefits are the high flexibility in conducting both point measurements and area scanning, and the fact that remote sensing techniques do not disturb the flow while measuring. The research campaign revealed a high potential for using short-range WindScanner Lidar for accurately measuring small scale flow structures in a wind tunnel.

  15. Research on the dq coordinate transform in the six-phase double star windings shifted by 30° synchronous generators with axial magnetic field

    Science.gov (United States)

    Bian, Xiangnan; Ma, Qishuang

    2006-11-01

    As an intermediate frequency power source, the double star windings shifted by 30° synchronous generator with axial magnetic field (DSWAMF) is widely used in the different areas. Using the generalized inverse, the transformation matrix of double windings synchronous generators with two Y-connected 3-phase symmetrical windings displaced in turn by 30° from rotating to stationary axes is proposed. With the transformation matrix, the state-space model of the generators is established. Obtained the relation of interconnection, and optimize the parameter. The kind of machine is simulated by finite element method (FEM), mutual inductance of the simulation is similar to theory. The generator mathematical model is established, the internal parameter of this kind of generator can be obtained easily with transformation matrix.

  16. Changes of dayside auroral distribution caused by a solar wind pressure pulse and associated interplanetary magnetic field disturbances

    Directory of Open Access Journals (Sweden)

    A. Kozlovsky

    2007-05-01

    Full Text Available Global auroral images from the IMAGE satellite were used to study statistically changes of the dayside aurora spatial distribution after an abrupt solar wind pressure increase, or so-called "Sudden Impulse" (SI. Contributions from IMF changes associated with a SI were also investigated. The effects of the IMF and pressure variations were separated using a multi-factor correlation analysis. The first prominent effect due to pressure increase is the auroral intensification equatorward of the middle dayside oval within 6 min after a SI occurred. This is consistent with the midday sub-auroral patches. The second effect due to pressure increase is the auroral intensification at high latitudes in the vicinity of the polar cap boundary. For the first 6 min the auroral intensification is most prominent in the postnoon sector. Later on (6–20 min the intensification occurs in the prenoon sector. The most obvious effect of IMF changes is the "IMF By" effect, an intensification (fading of the most poleward auroral forms when IMF By becomes negative (positive. This effect occurs 6–20 min after changes in the interplanetary medium. Such an effect is consistent with the IMF By-related system of field-aligned currents. No significant motion of the dayside auroral oval was observed associated with IMF Bz variations. This can be explained by a response time to IMF Bz changes larger than 20 min.

  17. Retrieval of convective boundary layer wind field statistics from radar profiler measurements in conjunction with large eddy simulation

    Directory of Open Access Journals (Sweden)

    Danny Scipión

    2009-05-01

    measurements consistent with the LES data fields. First-, second-, and third-order statistics (mean wind, variance, and skewness of vertical velocity obtained from BLR output demonstrate its suitability for validating radar-profiler signal processing algorithms.

  18. Dynamics of verticillium species microsclerotia in field soils in response to fumigation, cropping patterns, and flooding.

    Science.gov (United States)

    Short, Dylan P G; Sandoya, German; Vallad, Gary E; Koike, Steven T; Xiao, Chang-Lin; Wu, Bo-Ming; Gurung, Suraj; Hayes, Ryan J; Subbarao, Krishna V

    2015-05-01

    Verticillium dahliae is a soilborne, economically significant fungal plant pathogen that persists in the soil for up to 14 years as melanized microsclerotia (ms). Similarly, V. longisporum is a very significant production constraint on members of the family Brassicaceae. Management of Verticillium wilt has relied on methods that reduce ms below crop-specific thresholds at which little or no disease develops. Methyl bromide, a broad-spectrum biocide, has been used as a preplant soil fumigant for over 50 years to reduce V. dahliae ms. However, reductions in the number of ms in the vertical and horizontal soil profiles and the rate at which soil recolonization occurs has not been studied. The dynamics of ms in soil before and after methyl bromide+chloropicrin fumigation were followed over 3 years in six 8-by-8-m sites in two fields. In separate fields, the dynamics of ms in the 60-cm-deep vertical soil profile pre- and postfumigation with methyl bromide+chloropicrin followed by various cropping patterns were studied over 4 years. Finally, ms densities were assessed in six 8-by-8-m sites in a separate field prior to and following a natural 6-week flood. Methyl bromide+chloripicrin significantly reduced but did not eliminate V. dahliae ms in either the vertical or horizontal soil profiles. In field studies, increases in ms were highly dependent upon the crop rotation pattern followed postfumigation. In the vertical soil profile, densities of ms were highest in the top 5 to 20 cm of soil but were consistently detected at 60-cm depths. Six weeks of natural flooding significantly reduced (on average, approximately 65% in the total viable counts of ms) but did not eliminate viable ms of V. longisporum.

  19. Masking of Wind Turbine Noise: Influence of wind turbulence on ambient noise fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Fegeant, Olivier

    2002-07-01

    In the issue of noise annoyance generated by wind turbines, masking by ambient noise is of great importance. At wind turbine sites, the main source of ambient noise arises from the wind blowing on the vegetation. However, natural wind can barely be described as a steady flow and 'lulls' and 'gusts' are words used to describe its unsteady component. This latter, also called wind turbulence, may affect the masking effect, as the wind turbine may become audible during short laps of time of low wind speed, that is of low ambient noise. The aim of the present report is to study the influence of wind turbulence on ambient noise fluctuations. It is shown that these latter are governed not only by the turbulence intensity, but also by its temporal and spatial structure. This report provides some elements of atmospheric turbulence as well as techniques for the simulation of turbulent wind fields. Simulation results are given that illustrate how the standard deviation of the vegetation noise can vary as function of the canopy size and turbulence spatial patterns. Finally, ambient noise fluctuations and their statistical descriptions are also discussed, based on both theoretical considerations and empirical results.

  20. Combining dispersion modelling with synoptic patterns to understand the wind-borne transport into the UK of the bluetongue disease vector

    Science.gov (United States)

    Burgin, Laura; Ekström, Marie; Dessai, Suraje

    2017-07-01

    Bluetongue, an economically important animal disease, can be spread over long distances by carriage of insect vectors ( Culicoides biting midges) on the wind. The weather conditions which influence the midge's flight are controlled by synoptic scale atmospheric circulations. A method is proposed that links wind-borne dispersion of the insects to synoptic circulation through the use of a dispersion model in combination with principal component analysis (PCA) and cluster analysis. We illustrate how to identify the main synoptic situations present during times of midge incursions into the UK from the European continent. A PCA was conducted on high-pass-filtered mean sea-level pressure data for a domain centred over north-west Europe from 2005 to 2007. A clustering algorithm applied to the PCA scores indicated the data should be divided into five classes for which averages were calculated, providing a classification of the main synoptic types present. Midge incursion events were found to mainly occur in two synoptic categories; 64.8% were associated with a pattern displaying a pressure gradient over the North Atlantic leading to moderate south-westerly flow over the UK and 17.9% of the events occurred when high pressure dominated the region leading to south-easterly or easterly winds. The winds indicated by the pressure maps generally compared well against observations from a surface station and analysis charts. This technique could be used to assess frequency and timings of incursions of virus into new areas on seasonal and decadal timescales, currently not possible with other dispersion or biological modelling methods.

  1. Effect of electric fields on the stabilization of premixed laminar bunsen flames at low AC frequency: Bi-ionic wind effect

    KAUST Repository

    Kim, Minkuk

    2012-03-01

    The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally by applying AC electric fields at low frequency below 60. Hz together with DC in the single electrode configuration. The blowoff velocity has been measured for varying AC voltage and frequency. A transition frequency between low and high frequency regimes has been identified near 40-50. Hz, where AC electric fields have minimal effect on flame stabilization. In the low frequency regime, the blowoff velocity decreased linearly with AC voltage such that the flames became less stable. This was consistent with the DC result, implying the influence of the ionic wind effect. The variation of blowoff velocity with AC frequency showed a non-monotonic behavior in that the velocity decreased and then increased, exhibiting minimum blowoff velocity near 6-8. Hz. Based on the molecular kinetic theory, the developing degree of ionic wind was derived. By considering the ionic wind effects arising from both positive and negative ions in a flame zone, the bi-ionic wind effect successfully explained the non-monotonic behavior of blowoff velocity with AC frequency in the low frequency regime. © 2011 The Combustion Institute.

  2. RADIO POLARIZATION OBSERVATIONS OF THE SNAIL: A CRUSHED PULSAR WIND NEBULA IN G327.1–1.1 WITH A HIGHLY ORDERED MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y. K.; Ng, C.-Y. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Bucciantini, N. [INAF—Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy); Slane, P. O. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gaensler, B. M. [Dunlap Institute for Astronomy and Astrophysics, The University of Toronto, Toronto, ON M5S 3H4 (Canada); Temim, T., E-mail: ncy@bohr.physics.hku.hk [Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2016-04-01

    Pulsar wind nebulae (PWNe) are suggested to be acceleration sites of cosmic rays in the Galaxy. While the magnetic field plays an important role in the acceleration process, previous observations of magnetic field configurations of PWNe are rare, particularly for evolved systems. We present a radio polarization study of the “Snail” PWN inside the supernova remnant G327.1−1.1 using the Australia Telescope Compact Array. This PWN is believed to have been recently crushed by the supernova (SN) reverse shock. The radio morphology is composed of a main circular body with a finger-like protrusion. We detected a strong linear polarization signal from the emission, which reflects a highly ordered magnetic field in the PWN and is in contrast to the turbulent environment with a tangled magnetic field generally expected from hydrodynamical simulations. This could suggest that the characteristic turbulence scale is larger than the radio beam size. We built a toy model to explore this possibility, and found that a simulated PWN with a turbulence scale of about one-eighth to one-sixth of the nebula radius and a pulsar wind filling factor of 50%–75% provides the best match to observations. This implies substantial mixing between the SN ejecta and pulsar wind material in this system.

  3. Challenges Found When Patterning Semiconducting Polymers with Electric Fields for Organic Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Fernando A. de Castro

    2012-01-01

    Full Text Available A material-independent, contactless structuring method of semiconducting organic materials for the fabrication of interface-enhanced bilayer solar cells is not available so far. Patterning of thin films using electrohydrodynamic instabilities possesses many desired characteristics and has convincingly been used as a simple method to structure and replicate patterns of nonconducting polymers on submicrometer length scales. However, the applicability of this technique to a wider range of materials has not been demonstrated yet. Here, we report attempts to structure poly(p-phenylene vinylene in a similar way. We found that thin films of poly(2-methoxy-5-(2′-ethylhexyl-oxy-1,4-phenylene-vinylene (MEH-PPV and poly(2-methoxy-5-(3′,7′-dimethyloctyloxy-1,4-phenylene-vinylene (MDMO-PPV could not be destabilized at all in the limited accessible range of the experimental parameters set by the delicate chemical nature of these materials. We discuss failure origins and present possible loopholes for the patterning of semiconducting polymers using electric fields.

  4. Changes in muscle coordination patterns induced by exposure to a viscous force field.

    Science.gov (United States)

    Oscari, Fabio; Finetto, Christian; Kautz, Steve A; Rosati, Giulio

    2016-06-16

    Robotic neurorehabilitation aims at promoting the recovery of lost function after neurological injury by leveraging strategies of motor learning. One important aspect of the rehabilitation process is the improvement of muscle coordination patterns, which can be drastically altered after stroke. However, it is not fully understood if and how robotic therapy can address these deficits. The aim of our study was to find how muscle coordination, analyzed from the perspective of motor modules, could change during motor adaptation to a dynamic environment generated by a haptic interface. In our experiment we employed the traditional paradigm of exposure to a viscous force field to subjects that grasped the handle of an actuated joystick during a reaching movement (participants moved directly forward and back by 30 c m). EMG signals of ten muscles of the tested arm were recorded. We extracted motor modules from the pooled EMG data of all subjects and analyzed the muscle coordination patterns. We found that the participants reacted by using a coordination strategy that could be explained by a change in the activation of motor modules used during free motion and by two complementary modules. These complementary modules aggregated changes in muscle coordination, and evolved throughout the experiment eventually maintaining a comparable structure until the late phase of re-adaptation. This result suggests that motor adaptation induced by the interaction with a robotic device can lead to changes in the muscle coordination patterns of the subject.

  5. An Overview of the ASCOT Multi-Laboratory Field Experiments in Relation to Drainage Winds and Ambient Flow.

    Science.gov (United States)

    Orgill, M. M.; Schreck, R. I.

    1985-10-01

    Preliminary analyses of the Atmospheric Studies in Complex Terrain data were conducted by Pacific Northwest Laboratory to determine how the development and persistence of local nocturnal drainage flow are affected by large-scale (synoptic- and mesoscale) pressure and wind systems. The data were collected in the Geysers Geothermal Resource Area of California during July 1979, September 1980, and August 1981. Topics considered in this overview are the local wind cycle, migratory synoptic/mesoscale disturbances, marine-air intrusion, effect of ambient winds and turbulent mixing on drainage conditions, temperature-inversion variations, and transport and dispersion of fluorescent-particle tracer plumes.

  6. Examining In-Cloud Convective Turbulence in Relation to Total Lightning and the 3D Wind Field of Severe Thunderstorms

    Science.gov (United States)

    Al-Momar, S. A.; Deierling, W.; Williams, J. K.; Hoffman, E. G.

    2014-12-01

    Convectively induced turbulence (CIT) is commonly listed as a cause or factor in weather-related commercial aviation accidents. In-cloud CIT is generated in part by shears between convective updrafts and downdrafts. Total lightning is also dependent on a robust updraft and the resulting storm electrification. The relationship between total lightning and turbulence could prove useful in operational aviation settings with the use of future measurements from the geostationary lightning mapper (GLM) onboard the GOES-R satellite. Providing nearly hemispheric coverage of total lightning, the GLM could help identify CIT in otherwise data-sparse locations. For a severe thunderstorm case on 7 June 2012 in northeast Colorado, in-cloud eddy dissipation rate estimates from the NCAR/NEXRAD Turbulence Detection Algorithm were compared with cloud electrification data from the Colorado Lightning Mapping Array and radar products from the Denver, Colorado WSR-88D. These comparisons showed that high concentrations of very high frequency (VHF) source densities emitted by lightning occurred near and downstream of the storm's convective core. Severe turbulence was also shown to occur near this area, extending near the melting level of the storm and spreading upward and outward. Additionally, increases/decreases in VHF sources and turbulence volumes occurred within a few minutes of each other; although, light turbulence was shown to increase near one storm's dissipation. This may be due to increased shear from the now downdraft dominate storm. The 3D wind field from this case, obtained by either a dual-Doppler or a Variational Doppler Radar Assimilation System (VDRAS) analysis, will also be examined to further study the relationships between total lightning and thunderstorm kinematics. If these results prove to be robust, lightning may serve as a strong indicator of the location of moderate or greater turbulence.

  7. Changes of dayside auroral distribution caused by a solar wind pressure pulse and associated interplanetary magnetic field disturbances

    Directory of Open Access Journals (Sweden)

    A. Kozlovsky

    2007-05-01

    Full Text Available Global auroral images from the IMAGE satellite were used to study statistically changes of the dayside aurora spatial distribution after an abrupt solar wind pressure increase, or so-called "Sudden Impulse" (SI. Contributions from IMF changes associated with a SI were also investigated. The effects of the IMF and pressure variations were separated using a multi-factor correlation analysis. The first prominent effect due to pressure increase is the auroral intensification equatorward of the middle dayside oval within 6 min after a SI occurred. This is consistent with the midday sub-auroral patches. The second effect due to pressure increase is the auroral intensification at high latitudes in the vicinity of the polar cap boundary. For the first 6 min the auroral intensification is most prominent in the postnoon sector. Later on (6–20 min the intensification occurs in the prenoon sector. The most obvious effect of IMF changes is the "IMF By" effect, an intensification (fading of the most poleward auroral forms when IMF By becomes negative (positive. This effect occurs 6–20 min after changes in the interplanetary medium. Such an effect is consistent with the IMF By-related system of field-aligned currents. No significant motion of the dayside auroral oval was observed associated with IMF Bz variations. This can be explained by a response time to IMF Bz changes larger than 20 min.

  8. Wind wave source functions in opposing seas

    KAUST Repository

    Langodan, Sabique

    2015-08-26

    The Red Sea is a challenge for wave modeling because of its unique two opposed wave systems, forced by opposite winds and converging at its center. We investigate the different physical aspects of wave evolution and propagation in the convergence zone. The two opposing wave systems have similar amplitude and frequency, each driven by the action of its own wind. Wave patterns at the centre of the Red Sea, as derived from extensive tests and intercomparison between model and measured data, suggest that the currently available wave model source functions may not properly represent the evolution of the local fields that appear to be characterized by a less effective wind input and an enhanced white-capping. We propose and test a possible simple solution to improve the wave-model simulation under opposing winds and waves condition. This article is protected by copyright. All rights reserved.

  9. 77 FR 7601 - Notice of Segregation of Public Lands for the Pattern Energy Group Ocotillo Express Wind Energy...

    Science.gov (United States)

    2012-02-13

    ... Bureau of Land Management Notice of Segregation of Public Lands for the Pattern Energy Group Ocotillo... this segregation totals approximately 12,436 acres. DATES: Effective Date: This segregation is... segregation is necessary to process the ROW application filed by Pattern Energy Group for the Ocotillo Express...

  10. A Semi-analytical Model for Wind-fed Black Hole High-mass X-Ray Binaries: State Transition Triggered by Magnetic Fields from the Companion Star

    Science.gov (United States)

    Yaji, Kentaro; Yamada, Shinya; Masai, Kuniaki

    2017-10-01

    We propose a mechanism of state transition in wind-fed black hole (BH) binaries (high-mass X-ray binaries) such as Cyg X-1 and LMC X-1. Modeling a line-driven stellar wind from the companion by two-dimensional hydrodynamical calculations, we investigate the processes of wind capture by, and accretion onto, the BH. We assume that the wind acceleration is terminated at the He ii ionization front because ions responsible for line-driven acceleration are ionized within the front, i.e., the He iii region. It is found that the mass accretion rate inferred from the luminosity is remarkably smaller than the capture rate. Considering the difference, we construct a model for the state transition based on the accretion flow being controlled by magnetorotational instability. The outer flow is torus-like, and plays an important role to trigger the transition. The model can explain why state transition does occur in Cyg X-1, while not in LMC X-1. Cyg X-1 exhibits a relatively low luminosity, and then the He ii ionization front is located and can move between the companion and BH, depending on its ionizing photon flux. On the other hand, LMC X-1 exhibits too high luminosity for the front to move considerably; the front is too close to the companion atmosphere. The model also predicts that each state of high-soft or low-hard would last fairly long because the luminosity depends weakly on the wind velocity. In the context of the model, the state transition is triggered by a fluctuation of the magnetic field when its amplitude becomes comparable to the field strength in the torus-like outer flow.

  11. Stochastic modeling of complex systems. From the theoretical foundations to the simulation of atmospheric wind fields; Stochastische Modellierung komplexer Systeme. Von den theoretischen Grundlagen zur Simulation atmosphaerischer Windfelder

    Energy Technology Data Exchange (ETDEWEB)

    Kleinhans, David

    2008-06-25

    This thesis investigates various methods for the description and modelling of complex systems. Complex systems can frequently be described by means of the dynamics of a small set of order parameters, that complies with stochastic differential equations. Based on a method for the direct estimation of drift and diffusion functions from measured data by Friedrich and Peinke the focus at first is on the statistical estimation of the dynamics of order parameters. In particular an existing iterative method for data analysis purposes is re ned by means of a 'Maximum-Likelihood' approach. Then the connection between stochastic processes 'in time' and 'in scale' is investigated. Moreover the influence of external noise sources on Markov properties is studied. The compliance with Markov properties is essential for the application of efficient data analysis techniques. It turns out, that Markov properties generally are seriously spoiled by the influence of external noise such as measurement noise. Then 'Continuous Time Random Walks' (CTRWs) are discussed, that form an extension of classic random processes. CTRWs are feasible for the modelling of non- Markov processes exhibiting anomalous difusion properties in the ensemble sense, that frequently are observed in complex amorphous media. At the first instance Fogedby's continuous description of CTRWs is investigated. Based on Fogedby's approach then an algorithm for the generation of continuous trajectories of CTRWs is developed. Additionally, a physical framework for the microscopic dynamics of so-called 'trapping models' is introduced, that are currently used as models for the glass transition. The applicability of CTRWs for simulations of turbulent flows has been an open question. For this reason, the use of CTRWs for the generation of turbulent inflow wind fields for wind turbine simulations is discussed. At first an extensive introduction the special needs of such

  12. Optimal flights of unmanned aerial vehicles utilizing wind energy

    Science.gov (United States)

    Qi, Ying

    Unmanned aerial vehicles (UAVs) are attractive for a wide range of applications where human presence is dangerous or undesirable. Endurance is an important performance attribute in many UAV missions. While UAV flight endurance can be improved through advances in aerodynamics and engine design, it is equally important to examine operational strategies that can enhance UAV flight endurance and other performance. Wind energy may be used to greatly enhance the flight endurance and performances of Unmanned Aerial Vehicles. Glider pilots commonly use wind to improve range, endurance, or cross-country speed. Compared with a glider, UAVs have ad vantages in utilizing energy in atmosphere. By using proper strategies to extract wind energy in the long-duration flights, a UAV's fuel consumption can be reduced and the performance can be extended. The objective of this research is to investigate the potential benefits of utilizing wind energy and develop optimal wind energy efficient flight trajectories for UAVs. In this thesis, the potential benefits and features of the autonomous soaring flights are studied. UAVs are modelled with point-mass equations of motion. Practical constraints from UAV performance and operational constraints are considered. UAV flights through various wind patterns including wind gradients, thermals and downbursts are studied. Linear wind gradient models, two-dimensional thermal models and three-dimensional vortex ring downburst models are used for the calculation of optimal trajectories. UAV flights through wind fields are formulated as nonlinear optimal control problems that minimize the overall fuel consumption. These problems are converted into parameter optimizations and numerical solutions are obtained for a wide range of wind conditions and UAV performance parameters. Basic features and special flight patterns needed for wind energy flights are discovered. Results indicate that significant improvements in UAV endurance can be achieved by

  13. VHF radar observation of atmospheric winds, associated shears and C2n at a tropical location: interdependence and seasonal pattern

    Directory of Open Access Journals (Sweden)

    A. R. Jain

    Full Text Available The turbulence refractivity structure constant (C2n is an important parameter of the atmosphere. VHF radars have been used extensively for the measurements of C2n. Presently, most of such observations are from mid and high latitudes and only very limited observations are available for equatorial and tropical latitudes. Indian MST radar is an excellent tool for making high-resolution measurements of atmospheric winds, associated shears and turbulence refractivity structure constant (C2n. This radar is located at Gadanki (13.45° N, 79.18° E, a tropical station in India. The objective of this paper is to bring out the height structure of C2n for different seasons using the long series of data (September 1995 – August 1999 from Indian MST radar. An attempt is also made to understand such changes in the height structure of C2n in relation to background atmospheric parameters such as horizontal winds and associated shears. The height structure of C2n, during the summer monsoon and post-monsoon season, shows specific height features that are found to be related to Tropical Easterly Jet (TEJ winds. It is important to examine the nature of the radar back-scatterers and also to understand the causative mechanism of such scatterers. Aspect sensitivity of the received radar echo is examined for this purpose. It is observed that radar back-scatterers at the upper tropospheric and lower stratospheric heights are more anisotropic, with horizontal correlation length of 10–20 m, as compared to those observed at lower and middle tropospheric heights.Key words. Meteorology and atmospheric dynamics (climatology; tropical meteorology; turbulence

  14. Wind and ecosystem response at the GLEES

    Science.gov (United States)

    Robert C. Musselman; Gene L. Wooldridge; William J. Massman; Richard A. Sommerfeld

    1995-01-01

    Research was conducted to determine wind patterns and snow deposition at a high elevation alpine/subalpine ecotone site using deformation response of trees to prevailing winds. The research has provided detailed maps of wind speed, wind direction, and snow depth as determined from tree deformation. The effects of prevailing wind on tree blowdown at the site have also...

  15. Evolution of wind towards wind turbine

    NARCIS (Netherlands)

    Giyanani, A.H.; Bierbooms, W.A.A.M.; Van Bussel, G.J.W.

    2015-01-01

    Remote sensing of the atmospheric variables with the use of LiDAR is a relatively new technology field for wind resource assessment in wind energy. The validation of LiDAR measurements and comparisons is of high importance for further applications of the data.

  16. Winds measured by the Rover Environmental Monitoring Station (REMS) during Curiosity's Bagnold Dunes Campaign

    Science.gov (United States)

    Newman, Claire E.; Gomez-Elvira, Javier; Navarro Lopez, Sara; Marin Jimenez, Mercedes; Torres Redondo, Josefina; Richardson, Mark I.

    2016-10-01

    Curiosity's damaged wind sensor has trouble measuring winds coming from behind the rover, due to the loss of its side-pointing boom during landing. During the Bagnold Dunes Campaign, however, the rover was turned to permit measurements of winds from missing directions, capturing upslope/downslope day-night flow on the slopes of Aeolis Mons and blocking of wind in the lee of a dune.The rover's heading is generally determined by the drive direction and often varies little over many tens of sols. Good wind measurements are made when the wind comes from the hemisphere to the front of the rover, but there are sometimes long periods during which winds from certain directions (i.e., at certain times of sol) are largely missed. Since rover turns are often precluded by rover safety and other operational constraints, it is usually not possible to turn to measure such winds properly.During the Bagnold Dunes Campaign, wind measurements were prioritized to provide context for aeolian dune studies. Rover headings were optimized for three wind investigations covering a period of about 90 sols. The first investigation characterized the wind field on approach to the dunes, with the rover turned to face two unusual headings for several sols each and monitoring focused on the 'missing' winds / times of sol. This confirmed the expected primary wind pattern of daytime roughly upslope winds (from ~NW/N) and nighttime downslope winds (from ~S/SE) on the slopes of Aeolis Mons, with significant sol-to-sol variability in e.g. the timing of the reversals. Comparison with the previous year suggests an increasingly upslope-downslope pattern as Curiosity approached the slope.The second investigation studied changes to the wind pattern in the lee of the Namib Dune. This revealed the blocking of northerly winds by the large dune, leaving primarily a westerly component to the daytime winds with weaker wind speeds.The third investigation characterized the wind field at the side of Namib Dune. The

  17. The Effect of Air Density on Sand Transport Structures and the Adobe Abrasion Profile: A Field Wind-Tunnel Experiment Over a Wide Range of Altitude

    Science.gov (United States)

    Han, Qingjie; Qu, Jianjun; Dong, Zhibao; Zu, Ruiping; Zhang, Kecun; Wang, Hongtao; Xie, Shengbo

    2013-11-01

    Aeolian sand transport results from interactions between the surface and the airflow above. Air density strongly constrains airflow characteristics and the resulting flow of sand, and therefore should not be neglected in sand transport models. In the present study, we quantify the influence of air density on the sand flow structure, sand transport rate, adobe abrasion profiles, and abrasion rate using a portable wind-tunnel in the field. For a given wind speed, the flow's ability to transport sand decreases at low air density, so total sand transport decreases, but the saltation height increases. Thus, the damage to human structures increases compared with what occurs at lower altitudes. The adobe abrasion rate by the cloud of blowing sand decreases exponentially with increasing height above the surface, while the wind erosion and dust emission intensity both increase with increasing air density. Long-term feedback processes between air density and wind erosion suggest that the development of low-altitude areas due to long-term deflation plays a key role in dust emission, and will have a profound significance for surface Aeolian processes and geomorphology.

  18. Natural quasy-periodic binary structure with focusing property in near field diffraction pattern.

    Science.gov (United States)

    Mihailescu, Mona

    2010-06-07

    A naturally-inspired phase-only diffractive optical element with a circular symmetry given by a quasi-periodic structure of the phyllotaxis type is presented in this paper. It is generated starting with the characteristic parametric equations which are optimal for the golden angle interval. For some ideal geometrical parameters, the diffracted intensity distribution in near-field has a central closed ring with almost zero intensity inside. Its radius and intensity values depend on the geometry or non-binary phase distribution superposed onto the phyllotaxis geometry. Along propagation axis, the transverse diffraction patterns from the binary-phase diffractive structure exhibit a self-focusing behavior and a rotational motion.

  19. Gaze patterns predicting successful collision avoidance in patients with homonymous visual field defects.

    Science.gov (United States)

    Papageorgiou, Eleni; Hardiess, Gregor; Mallot, Hanspeter A; Schiefer, Ulrich

    2012-07-15

    Aim of the present study was to identify efficient compensatory gaze patterns applied by patients with homonymous visual field defects (HVFDs) under virtual reality (VR) conditions in a dynamic collision avoidance task. Thirty patients with HVFDs due to vascular brain lesions and 30 normal subjects performed a collision avoidance task with moving objects at an intersection under two difficulty levels. Based on their performance (i.e. the number of collisions), patients were assigned to either an "adequate" (HVFD(A)) or "inadequate" (HVFD(I)) subgroup by the median split method. Eye and head tracking data were available for 14 patients and 19 normal subjects. Saccades, fixations, mean number of gaze shifts, scanpath length and the mean gaze eccentricity, were compared between HVFD(A), HVFD(I) patients and normal subjects. For both difficulty levels, the gaze patterns of HVFD(A) patients (N=5) compared to HVFD(I) patients (N=9) were characterized by longer saccadic amplitudes towards both the affected and the intact side, larger mean gaze eccentricity, more gaze shifts, longer scanpaths and more fixations on vehicles but fewer fixations on the intersection. Both patient groups displayed more fixations in the affected compared to the intact hemifield. Fixation number, fixation duration, scanpath length, and number of gaze shifts were similar between HVFD(A) patients and normal subjects. Patients with HVFDs who adapt successfully to their visual deficit, display distinct gaze patterns characterized by increased exploratory eye and head movements, particularly towards moving objects of interest on their blind side. In the context of a dynamic environment, efficient compensation in patients with HVFDs is possible by means of gaze scanning. This strategy allows continuous update of the moving objects' spatial location and selection of the task-relevant ones, which will be represented in visual working memory. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Beyond sunspots: Studies using the McIntosh Archive of global solar magnetic field patterns

    Science.gov (United States)

    Gibson, Sarah E.; Webb, David; Hewins, Ian M.; McFadden, Robert H.; Emery, Barbara A.; Denig, William; McIntosh, Patrick S.

    2017-10-01

    In 1964 (Solar Cycle 20; SC 20), Patrick McIntosh began creating hand-drawn synoptic maps of solar magnetic features, based on Hα images. These synoptic maps were unique in that they traced magnetic polarity inversion lines, and connected widely separated filaments, fibril patterns, and plage corridors to reveal the large-scale organization of the solar magnetic field. Coronal hole boundaries were later added to the maps, which were produced, more or less continuously, into 2009 (i.e., the start of SC 24). The result was a record of ~45 years (~570 Carrington rotations), or nearly four complete solar cycles of synoptic maps. We are currently scanning, digitizing and archiving these maps, with the final, searchable versions publicly available at NOAA's National Centers for Environmental Information. In this paper we present preliminary scientific studies using the archived maps from SC 23. We show the global evolution of closed magnetic structures (e.g., sunspots, plage, and filaments) in relation to open magnetic structures (e.g., coronal holes), and examine how both relate to the shifting patterns of large-scale positive and negative polarity regions.

  1. EM Modeling of Far-Field Radiation Patterns for Antennas on the GMA-TT UAV

    Science.gov (United States)

    Mackenzie, Anne I.

    2015-01-01

    To optimize communication with the Generic Modular Aircraft T-Tail (GMA-TT) unmanned aerial vehicle (UAV), electromagnetic (EM) simulations have been performed to predict the performance of two antenna types on the aircraft. Simulated far-field radiation patterns tell the amount of power radiated by the antennas and the aircraft together, taking into account blockage by the aircraft as well as radiation by conducting and dielectric portions of the aircraft. With a knowledge of the polarization and distance of the two communicating antennas, e.g. one on the UAV and one on the ground, and the transmitted signal strength, a calculation may be performed to find the strength of the signal travelling from one antenna to the other and to check that the transmitted signal meets the receiver system requirements for the designated range. In order to do this, the antenna frequency and polarization must be known for each antenna, in addition to its design and location. The permittivity, permeability, and geometry of the UAV components must also be known. The full-wave method of moments solution produces the appropriate dBi radiation pattern in which the received signal strength is calculated relative to that of an isotropic radiator.

  2. Wind turbine pitch optimization

    DEFF Research Database (Denmark)

    Biegel, Benjamin; Juelsgaard, Morten; Stoustrup, Jakob

    2011-01-01

    We consider a static wind model for a three-bladed, horizontal-axis, pitch-controlled wind turbine. When placed in a wind field, the turbine experiences several mechanical loads, which generate power but also create structural fatigue. We address the problem of finding blade pitch profiles......% compared to any constant pitch profile while sacrificing at most 7% of the maximum attainable output power. Using iterative learning, we show that very similar performance can be achieved by using only load measurements, with no knowledge of the wind field or wind turbine model....... for maximizing power production while simultaneously minimizing fatigue loads. In this paper, we show how this problem can be approximately solved using convex optimization. When there is full knowledge of the wind field, numerical simulations show that force and torque RMS variation can be reduced by over 96...

  3. Wind Braking of Magnetars

    Science.gov (United States)

    Tong, H.; Xu, R. X.; Song, L. M.; Qiao, G. J.

    2013-05-01

    We explore the wind braking of magnetars considering recent observations challenging the traditional magnetar model. There is evidence for strong multipole magnetic fields in active magnetars, but the dipole field inferred from spin-down measurements may be strongly biased by particle wind. Recent observations challenging the traditional model of magnetars may be explained naturally by the wind braking scenario: (1) the supernova energies of magnetars are of normal value; (2) the non-detection in Fermi observations of magnetars; (3) the problem posed by low magnetic field soft gamma-ray repeaters; (4) the relation between magnetars and high magnetic field pulsars; and (5) a decreasing period derivative during magnetar outbursts. Transient magnetars with L_x{<}-\\dot{E}_rot may still be magnetic dipole braking. This may explain why low luminosity magnetars are more likely to have radio emissions. A strong reduction of the dipole magnetic field is possible only when the particle wind is very collimated at the star surface. A small reduction of the dipole magnetic field may result from detailed considerations of magnetar wind luminosity. In the wind braking scenario, magnetars are neutron stars with a strong multipole field. For some sources, a strong dipole field may no longer be needed. A magnetism-powered pulsar wind nebula will be one of the consequences of wind braking. For a magnetism-powered pulsar wind nebula, we should see a correlation between the nebula luminosity and the magnetar luminosity. Under the wind braking scenario, a braking index smaller than three is expected. Future braking index measurement of a magnetar may tell us whether magnetars are wind braking or magnetic dipole braking.

  4. Static and wind tunnel near-field/far-field jet noise measurements from model scale single-flow base line and suppressor nozzles. Summary report. [conducted in the Boeing large anechoic test chamber and the NASA-Ames 40by 80-foot wind tunnel

    Science.gov (United States)

    Jaeck, C. L.

    1977-01-01

    A test program was conducted in the Boeing large anechoic test chamber and the NASA-Ames 40- by 80-foot wind tunnel to study the near- and far-field jet noise characteristics of six baseline and suppressor nozzles. Static and wind-on noise source locations were determined. A technique for extrapolating near field jet noise measurements into the far field was established. It was determined if flight effects measured in the near field are the same as those in the far field. The flight effects on the jet noise levels of the baseline and suppressor nozzles were determined. Test models included a 15.24-cm round convergent nozzle, an annular nozzle with and without ejector, a 20-lobe nozzle with and without ejector, and a 57-tube nozzle with lined ejector. The static free-field test in the anechoic chamber covered nozzle pressure ratios from 1.44 to 2.25 and jet velocities from 412 to 594 m/s at a total temperature of 844 K. The wind tunnel flight effects test repeated these nozzle test conditions with ambient velocities of 0 to 92 m/s.

  5. Influence of magnetic field and ferromagnetic film thickness on domain pattern transfer in multiferroic heterostructures

    Science.gov (United States)

    López González, Diego; Casiraghi, Arianna; Kronast, Florian; Franke, Kévin J. A.; van Dijken, Sebastiaan

    2017-11-01

    We report on domain pattern transfer from a ferroelectric BaTiO3 substrate to a CoFeB wedge film with a thickness of up to 150 nm. Strain coupling to domains in BaTiO3 induces a regular modulation of uniaxial magnetic anisotropy in CoFeB via an inverse magnetostriction effect. As a result, the domain structures of the CoFeB wedge film and BaTiO3 substrate correlate fully and straight ferroelectric domain boundaries in BaTiO3 pin magnetic domain walls in CoFeB. We use X-ray photoemission electron microscopy and magneto-optical Kerr effect microscopy to characterize the spin structure of the pinned domain walls. In a rotating magnetic field, abrupt and reversible transitions between two domain wall types occur, namely, narrow walls where the magnetization vectors align head-to-tail and much broader walls with alternating head-to-head and tail-to-tail magnetization configurations. We characterize variations of the domain wall spin structure as a function of magnetic field strength and CoFeB film thickness and compare the experimental results with micromagnetic simulations.

  6. Electromagnetic Interference on Large Wind Turbines

    Directory of Open Access Journals (Sweden)

    Florian Krug

    2009-11-01

    Full Text Available Electromagnetic interference (EMI can both affect and be transmitted by mega-watt wind turbines. This paper provides a general overview on EMI with respect to mega-watt wind turbines. Possibilities of measuring all types of electromagnetic interference are shown. Electromagnetic fields resulting from a GSM transmitter mounted on a mega-watt wind turbine will be analyzed in detail. This cellular system operates as a real-time communication link. The method-of-moments is used to analytically describe the electro-magnetic fields. The electromagnetic interference will be analyzed under the given boundary condition with a commercial simulation tool. Different transmitter positions are judged on the basis of their radiation patterns. The principal EMI mechanisms are described and taken into consideration.

  7. NWP Forecast Errors of Boundary Layer Flow in Complex Terrain Observed During the Second Wind Forecast Improvement Project (WFIP2) Field Campaign.

    Science.gov (United States)

    Wilczak, James M.

    2017-04-01

    The Second Wind Forecast Improvement Project (WFIP2) is a U.S. Department of Energy and NOAA-led program whose goal is to improve the accuracy of NWP forecasts of wind speed in complex terrain for wind energy applications. WFIP2 includes a field campaign held in the vicinity of the Columbia River Basin in the Pacific Northwest of the U.S., which began in October 2015, and will continue through March, 2017. As part of WFIP2 a large suite of in-situ and remote sensing instrumentation has been deployed, including a network of three 449 MHz radar wind profilers (RWP's) with RASS, eight 915 MHz RWP's with RASS, 18 sodars, 4 profiling microwave radiometers, 5 scanning lidars, 5 profiling lidars, a network of 10 microbarographs, and many surface meteorological stations. Key NWP forecast models utilized for WFIP2 are the 13 km resolution Rapid Refresh (RAP), 3km High Resolution Rapid Refresh (HRRR), 0.75km HRRR-Nest, and the 12 km North American Mesoscale (NAM) forecast system. Preliminary results from WFIP2 will be presented, including seasonal variations of model forecast errors of wind speed, direction, temperature and humidity profiles and boundary layer depths; meteorological phenomena producing large forecast errors; and the relative skill of the various NWP forecasting systems. Diurnal time height cross-sections of the model's mean bias and RMSE are evaluated for each of the models, providing a holistic view of model accuracy at simulating boundary layer structure. Model errors are analyzed as a function of season (3 month averages) and location, and show the impact of increasing model resolution on forecast skill. Seasonal averages of model biases and RMSE provide more robust results than do shorter case study episodes, and can be used to verify that model errors found in shorter case study episodes are in fact representative. The results are used to identify specific model weaknesses and the corresponding parameterization schemes that are in greatest need of

  8. Wind turbine control and monitoring

    CERN Document Server

    Luo, Ningsu; Acho, Leonardo

    2014-01-01

    Maximizing reader insights into the latest technical developments and trends involving wind turbine control and monitoring, fault diagnosis, and wind power systems, 'Wind Turbine Control and Monitoring' presents an accessible and straightforward introduction to wind turbines, but also includes an in-depth analysis incorporating illustrations, tables and examples on how to use wind turbine modeling and simulation software.   Featuring analysis from leading experts and researchers in the field, the book provides new understanding, methodologies and algorithms of control and monitoring, comput

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

    Science.gov (United States)

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

  10. Field test of an all-semiconductor laser-based coherent continuous-wave Doppler lidar for wind energy applications

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Dellwik, Ebba; Hu, Qi

    -based instruments for wind turbine mounting are now commercially available. However, they suffer from high price and bulkiness. Therefore, the Technical University of Denmark has, in collaboration with the Danish company Windar Photonics A/S, developed a compact and low-cost lidar called WindEye based on a mass......-produced all-semiconductor laser. The instrument is a coherent continuous-wave lidar with two fixed-focus telescopes for launching laser beams in two different directions. The alternation between the telescopes is achieved by a novel switching technique without any moving parts. Here, we report results from...

  11. Barotropic wind-driven circulation patterns in a closed rectangular basin of variable depth influenced by a peninsula or an island

    Directory of Open Access Journals (Sweden)

    B. V. Chubarenko

    Full Text Available We study how a coastal obstruction (peninsula or coastal island affects the three-dimensional barotropic currents in an oblong rectangular basin with variable bathymetry across the basin width. The transverse depth profile is asymmetric and the peninsula or island lies in the middle of the long side of the rectangle. A semi-spectral model for the Boussinesq-approximated shallow water equations, developed in Haidvogel et al. and altered for semi-implicit numerical integration in time in Wang and Hutter, is used to find the steady barotropic state circulation pattern to external winds. The structural (qualitative rearrangements and quanti2tative features of the current pattern are studied under four principal wind directions and different lengths of the peninsula and its inclination relative to the shore. The essentially non-linear relationships of the water flux between the two sub-basins (formed by the obstructing peninsula and the corresponding cross-sectional area left open are found and analysed. It is further analysed whether the depth-integrated model, usually adopted by others, is meaningful when applied to the water exchange problems. The flow through the channel narrowing is quantitatively estimated and compared with the three-dimensional results. The dynamics of the vortex structure and the identification of the up-welling/down-welling zones around the obstruction are discussed in detail. The influence of the transformation of the peninsula into a coastal island on the global basin circulation is considered as are the currents in the channel. The geometric and physical reasons for the anisotropy of the current structure which prevail through all obtained solutions are also discussed.

    Key words: Oceanography: general (limnology; numerical modeling - Oceanography: physical (currents

  12. Barotropic wind-driven circulation patterns in a closed rectangular basin of variable depth influenced by a peninsula or an island

    Directory of Open Access Journals (Sweden)

    B. V. Chubarenko

    2000-06-01

    Full Text Available We study how a coastal obstruction (peninsula or coastal island affects the three-dimensional barotropic currents in an oblong rectangular basin with variable bathymetry across the basin width. The transverse depth profile is asymmetric and the peninsula or island lies in the middle of the long side of the rectangle. A semi-spectral model for the Boussinesq-approximated shallow water equations, developed in Haidvogel et al. and altered for semi-implicit numerical integration in time in Wang and Hutter, is used to find the steady barotropic state circulation pattern to external winds. The structural (qualitative rearrangements and quanti2tative features of the current pattern are studied under four principal wind directions and different lengths of the peninsula and its inclination relative to the shore. The essentially non-linear relationships of the water flux between the two sub-basins (formed by the obstructing peninsula and the corresponding cross-sectional area left open are found and analysed. It is further analysed whether the depth-integrated model, usually adopted by others, is meaningful when applied to the water exchange problems. The flow through the channel narrowing is quantitatively estimated and compared with the three-dimensional results. The dynamics of the vortex structure and the identification of the up-welling/down-welling zones around the obstruction are discussed in detail. The influence of the transformation of the peninsula into a coastal island on the global basin circulation is considered as are the currents in the channel. The geometric and physical reasons for the anisotropy of the current structure which prevail through all obtained solutions are also discussed.Key words: Oceanography: general (limnology; numerical modeling - Oceanography: physical (currents

  13. Winds, Waves, Tides, and the Resulting Flow Patterns and Fluxes of Water, Sediment, and Coral Larvae off West Maui, Hawaii

    Science.gov (United States)

    Storlazzi, Curt D.; Field, Michael E.

    2008-01-01

    A series of recent studies has focused on the flow patterns and particle fluxes along the coast of West Maui, Hawaii, USA, from Honolua south to Puumana. From those studies a relatively good understanding has emerged of the physical processes that influence the relative amount of suspended sediment in nearshore waters and the circulation patterns that transport sediment and coral larvae along the coast and between islands. This report is a synthesis of our existing knowledge on the nature of flow and transport off West Maui.

  14. The effect of surface treatments on the field emission characteristics of patterned carbon nanotubes on KOVAR substrate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Keunsoo; Lee, Yang Doo; Kang, Byung Hyun; Dong, Ki-Young; Baek, Jinho; Fai, Vincent Lau Chun [Korea University, Display and Nanosystem Laboratory, College of Engineering (Korea, Republic of); Kim, Won-Seok [Electronic Materials Research Group, Hyosung Corporation, R and D Business Laboratory (Korea, Republic of); Yang, Cheol-Min [Korea Institute of Science and Technology, Institute of Advanced Composite Materials (Korea, Republic of); Ju, Byeong-Kwon, E-mail: bkju@korea.ac.kr [Korea University, Display and Nanosystem Laboratory, College of Engineering (Korea, Republic of)

    2012-07-15

    The field emission characteristics of patterned carbon nanotubes (CNTs) the average diameter of which is 16 nm cathodes on substrates with different surface treatments were investigated. The surface treatments of the substrate were performed by nickel electroless plating and palladium coating, which is an activation procedure of electroless plating. CNTs were patterned on the surface-treated substrate with radius of 200 {mu}m through conventional photolithography process. Two deposition methods, electrophoresis deposition and spray deposition, were used to investigate the effects of deposition methods on field emission characteristics of the cathodes. It was revealed that the two deposition methods showed similar turn-on field trends, which means that the different surface morphologies of the substrates have more influence on the field emission characteristics than the different deposition methods performed in this study. Through the surface treatments, the roughness of the surface increased and cathodes with a high roughness factor showed better field emission characteristics compared to non-treated ones.

  15. Estimation of Wind Turbulence Using Spectral Models

    DEFF Research Database (Denmark)

    Soltani, Mohsen; Knudsen, Torben; Bak, Thomas

    2011-01-01

    The production and loading of wind farms are significantly influenced by the turbulence of the flowing wind field. Estimation of turbulence allows us to optimize the performance of the wind farm. Turbulence estimation is; however, highly challenging due to the chaotic behavior of the wind...... speed outside the wind field. The results show that the method is able to provide estimations which explain more than 50% of the wind turbulence from the distance of about 300 meters....

  16. Electro-hydrodynamic force field and flow patterns generated by a DC corona discharge in the air

    Science.gov (United States)

    Monrolin, Nicolas; Plouraboue, Franck; Praud, Olivier

    2016-11-01

    Ionic wind refers to the electro-convection of ionised air between high voltage electrodes. Microscopic ion-neutral collisions are responsible for momentum transfer from accelerated ions, subjected to the electric field, to the neutral gas molecules resulting in a macroscopic airflow acceleration. In the past decades it has been investigated for various purposes from food drying through aerodynamic flow control and eventually laptop cooling. One consequence of air acceleration between the electrodes is thrust generation, often referred to as the Biefeld-Brown effect or electro-hydrodynamic thrust. In this experimental study, the ionic wind velocity field is measured with the PIV method. From computing the acceleration of the air we work out the electrostatic force field for various electrodes configurations. This enables an original direct evaluation of the force distribution as well as the influence of electrodes shape and position. Thrust computation based on the flow acceleration are compared with digital scale measurements. Complex flow features are highlighted such as vortex shedding, indicating that aerodynamic effects may play a significant role. Furthermore, the aerodynamic drag force exerted on the electrodes is quantified by choosing an appropriate control volume. Authors thank Region Midi-Pyrenee and CNES Launcher Directorate for financial support.

  17. Modeling wind fields and fire propagation following bark beetle outbreaks in spatially-heterogeneous pinyon-juniper woodland fuel complexes

    Science.gov (United States)

    Rodman R. Linn; Carolyn H. Sieg; Chad M. Hoffman; Judith L. Winterkamp; Joel D. McMillin

    2013-01-01

    We used a physics-based model, HIGRAD/FIRETEC, to explore changes in within-stand wind behavior and fire propagation associated with three time periods in pinyon-juniper woodlands following a drought-induced bark beetle outbreak and subsequent tree mortality. Pinyon-juniper woodland fuel complexes are highly heterogeneous. Trees often are clumped, with sparse patches...

  18. DYNAMO: a Mars upper atmosphere package for investigating solar wind interaction and escape processes, and mapping Martian fields

    DEFF Research Database (Denmark)

    Chassefiere, E.; Nagy, A.; Mandea, M.

    2004-01-01

    of periapsis 170 km), and in a lesser extent 2a, offers an unprecedented opportunity to investigate by in situ probing the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, and therefore the present atmospheric escape rate...

  19. Stress Field in Brazil with Focal Mechanism: Regional and Local Patterns

    Science.gov (United States)

    Dias, F.; Assumpcao, M.

    2013-05-01

    The knowledge of stress field is fundamental not only to understand driving forces and plate deformation but also in the study of intraplate seismicity. The stress field in Brazil has been determined mainly using focal mechanisms and a few breakout data and in-situ measurements. However the stress field still is poorly known in Brazil. The focal mechanisms of recent earthquakes (magnitude lower than 5 mb) were studied using waveform modeling. We stacked the record of several teleseismic stations ( delta > 30°) stacked groups of stations separated according to distance and azimuth. Every record was visually inspected and those with a good signal/noise ratio (SNR) were grouped in windows of ten degrees distance and stacked. The teleseismic P-wave of the stacked signals was modeled using the hudson96 program of Herrmann seismology package (Herrmann, 2002) and the consistency of focal mechanism with the first-motion was checked. Some events in central Brazil were recorded by closer stations (~ 1000 km) and the moment tensor was determined with the ISOLA code (Sokos & Zahradnik, 2008). With the focal mechanisms available in literature and those obtained in this work, we were able to identify some patterns: the central region shows a purely compressional pattern (E-W SHmax), which is predicted by regional theoretical models (Richardson & Coblentz, 1996 and the TD0 model of Lithgow & Bertelloni, 2004). Meanwhile in the Amazon we find an indication of SHmax oriented in the SE-NW direction, probably caused by the Caribbean plate interaction (Meijer, 1995). In northern coastal region, the compression rotates following the coastline, which indicates an important local component related to spreading effects at the continental/oceanic transition (Assumpção, 1998) and flexural stresses caused by sedimentary load in Amazon Fan. We determine the focal mechanism of several events in Brazil using different techniques according to the available data. The major difficulty is to

  20. Pattern formation and coarse-graining in two-dimensional colloids driven by multiaxial magnetic fields.

    Science.gov (United States)

    Müller, Kathrin; Osterman, Natan; Babič, Dušan; Likos, Christos N; Dobnikar, Jure; Nikoubashman, Arash

    2014-05-13

    We study the pattern formation in a two-dimensional system of superparamagnetic colloids interacting via spatially coherent induced interactions driven by an external precessing magnetic field. On the pair level, upon changing the opening angle of the external field, the interactions smoothly vary from purely repulsive (opening angle equal to zero) to purely attractive (time-averaged pair interactions at an opening angle of 90°). In the experiments, we observed ordered hexagonal crystals at the repulsive end and coarsening frothlike structures for purely attractive interactions. In both of these limiting cases, the dense colloidal systems can be sufficiently accurately described by assuming pairwise additivity of the interaction potentials. However, for a range of intermediate angles, pronounced many-body depolarization effects compete with the direct induced interactions, resulting in inherently anisotropic effective interactions. Under such conditions, we observed the decay of hexagonal order with the concomitant formation of short chains and percolated networks of chains coexisting with free colloids. In order to describe and investigate these systems theoretically, we developed a coarse-grained model of a binary mixture of patchy and nonpatchy particles with the ratio of patchy and nonpatchy colloids as the order parameter. Combining genetic algorithms with Monte Carlo simulations, we optimized the model parameters and quantitatively reproduced the experimentally observed sequence of colloidal structures. The results offer new insight into the anisotropy induced by the many-body effects. At the same time, they allow for a very efficient description of the system by means of a pairwise-additive Hamiltonian, whereupon the original, one-component system features a two-component mixture of isotropic and patchy colloids.

  1. Detecting Rice Phenology in Paddy Fields with Complex Cropping Pattern Using Time Series MODIS Data

    Directory of Open Access Journals (Sweden)

    Dewi Kania Sari

    2010-09-01

    Full Text Available Monitoring paddy rice phenology and cropping schedules over wide areas is essential for many applications. Remote sensing provides a viable means to meet the requirement of improved regional-scale data set of paddy rice fields, such as phenological stages. A number of methods have been developed for detecting seasonal vegetation changes by using satellite images. Development of such methods to paddy fields with complex cropping pattern is still challenging. In this study, we developed a method for remotely determining phenological stages of paddy rice that uses time series of two vegetation indices (EVI and LSWI obtained from MODIS data. We ran the algorithm to determine the planting date, heading date, and harvesting date of paddy rice in 5 districts of West Java Province, using the 8-day composite MODIS Surface Reflectance products (500-m spatial resolution in 2004. Estimated harvesting dates were then used to calculate paddy rice harvested area. We validated the performance of the method against statistical data in 13 subdistricts. The root mean square errors of the estimated paddy rice harvested area against the statistical data were: 851 Ha for monthly data, 1227 Ha for quarterly data, and 2433 Ha for yearly data. Subdistrict-level comparisons of paddy rice harvested area between the MODIS estimation and statistical data showed moderate correlation, with coefficient of determination (r2 0.6, 0.7, and 0.6 for monthly, quarterly and yearly data, respectively. The results of this study indicated that the MODIS-based paddy rice phenological detection algorithm could potentially be applied at large spatial scales to monitor paddy rice agriculture on a timely and frequent basis.

  2. Modelling of Wind Turbine Loads nearby a Wind Farm

    Science.gov (United States)

    Roscher, B.; Werkmeister, A.; Jacobs, G.; Schelenz, R.

    2017-05-01

    Each wind turbine experiences a variety of loads during its lifetime, especially inside a wind farm due to the wake effect between the turbines. This paper describes a possibility to observe a load spectrum while considering wake effects in a wind farm by through the turbulence intensity. The turbulence intensity is distributed along the wind rose of Alpha Ventus. For each turbulence intensity, a Weibull characteristic is calculated. The resulting wind fields are used to determine the loads through a multibody simulation of an imaginary wind turbine located at FINO-1, representing a closely placed wind turbine at the outer edge of a wind farm. These loads are analyzed and summed up. As expected, the change of the turbulence intensity due to the wake effect has an impact on the internal loading of a wind turbine inside a wind farm. Based on the assumed loading conditions, the maximum loads increased by a factor of almost 2.5.

  3. Evolutionary fields can explain patterns of high-dimensional complexity in ecology.

    Science.gov (United States)

    Wilsenach, James; Landi, Pietro; Hui, Cang

    2017-04-01

    One of the properties that make ecological systems so unique is the range of complex behavioral patterns that can be exhibited by even the simplest communities with only a few species. Much of this complexity is commonly attributed to stochastic factors that have very high-degrees of freedom. Orthodox study of the evolution of these simple networks has generally been limited in its ability to explain complexity, since it restricts evolutionary adaptation to an inertia-free process with few degrees of freedom in which only gradual, moderately complex behaviors are possible. We propose a model inspired by particle-mediated field phenomena in classical physics in combination with fundamental concepts in adaptation, which suggests that small but high-dimensional chaotic dynamics near to the adaptive trait optimum could help explain complex properties shared by most ecological datasets, such as aperiodicity and pink, fractal noise spectra. By examining a simple predator-prey model and appealing to real ecological data, we show that this type of complexity could be easily confused for or confounded by stochasticity, especially when spurred on or amplified by stochastic factors that share variational and spectral properties with the underlying dynamics.

  4. Evolutionary fields can explain patterns of high-dimensional complexity in ecology

    Science.gov (United States)

    Wilsenach, James; Landi, Pietro; Hui, Cang

    2017-04-01

    One of the properties that make ecological systems so unique is the range of complex behavioral patterns that can be exhibited by even the simplest communities with only a few species. Much of this complexity is commonly attributed to stochastic factors that have very high-degrees of freedom. Orthodox study of the evolution of these simple networks has generally been limited in its ability to explain complexity, since it restricts evolutionary adaptation to an inertia-free process with few degrees of freedom in which only gradual, moderately complex behaviors are possible. We propose a model inspired by particle-mediated field phenomena in classical physics in combination with fundamental concepts in adaptation, which suggests that small but high-dimensional chaotic dynamics near to the adaptive trait optimum could help explain complex properties shared by most ecological datasets, such as aperiodicity and pink, fractal noise spectra. By examining a simple predator-prey model and appealing to real ecological data, we show that this type of complexity could be easily confused for or confounded by stochasticity, especially when spurred on or amplified by stochastic factors that share variational and spectral properties with the underlying dynamics.

  5. Offshore wind power in the Aegean Sea

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Badger, Merete; Hahmann, Andrea N.

    winds (SDW). It is planned to combine the Envisat wind fields with Sentinel-1a and Sentinel-1b wind fields to further detail the offshore wind resource within the New European Wind Atlas. The work is in progress. Sentinel-1a images are processed at DTU Wind Energy near-real-time and we are updating our...... wind resource software. A service-based on satellite SAR-derived winds for wind resource estimation is available at DTU Wind Energy. The project was supported by ESA ResGrow and satellite data from ESA Envisat and Copernicus Sentinel-1....... hub heights at around 100 m using a combination of satellite wind fields and the long-term climate of atmospheric stability from the mesoscale model (Badger et al. 2016). The result of the mean wind speed at hub-height for the Aegean Sea is shown in Figure 1. The map shows the stability dependent...

  6. Examining the Effects of Quenching Solution, Post-Treatment Heating, and Magnetic Fields upon the Wear Resistance of Wind Turbine Gearbox Bearings

    Science.gov (United States)

    Jakachira, Takunda; Sapp, Whitley; Somers, Hunter; West, Andrea; Watson, Casey; Paulin, Peter

    We explore modifications to the basic cryogenic procedures utilized by 300 Below Inc. to strengthen 52100 steel - the type of steel used to manufacture wind turbine gearbox bearings. We consider the effects of using two different quenching solutions steel samples, additional heating of samples after 300 Below's standard cryogenic treatment, and the application of both AC and permanent magnetic fields of various strengths to samples before and during the standard cryogenic treatment. We report on the wear-test performance of samples that have undergone these additional processes and compare them to the performance of control samples and samples subjected to the standard cryogenic treatment.

  7. Dark-field illuminated fiber bundle endoscopy with iterative l1-min image reconstruction for honeycomb pattern removal

    Science.gov (United States)

    Liu, Xuan; Zhang, Lijun; Kirby, Mitchell; Raj, Divyaansh; Qi, Shaohai; Zhao, Feng

    2015-03-01

    In this study, we developed a dark-field illuminated reflectance fiber-optic microscope (DRFM) along with an algorithm for l1-norm minimization of fiber bundle image to provide intrinsic endoscopic imaging with cellular resolution. To suppress specular reflection from fiber bundle facets, we adopted a dark-field configuration. To remove the honeycomb pattern of fiber bundle while preserve image resolution and contrast, we chose to minimize the image l1 norm using iterative shrinkage thresholding (IST) algorithm.

  8. The measured field performances of eight different mechanical and air-lift water-pumping wind-turbines

    Energy Technology Data Exchange (ETDEWEB)

    Kentfield, J.A.C. [Univ. of Calgary, Alberta (Canada)

    1996-12-31

    Results are presented of the specific performances of eight, different, water-pumping wind-turbines subjected to impartial tests at the Alberta Renewable Energy Test Site (ARETS), Alberta, Canada. The results presented which were derived from the test data, obtained independently of the equipment manufacturers, are expressed per unit of rotor projected area to eliminate the influence of machine size. Hub-height wind speeds and water flow rates for a common lift of 5.5 m (18 ft) constitute the essential test data. A general finding was that, to a first approximation, there were no major differences in specific performance between four units equipped with conventional reciprocating pumps two of which employed reduction gearing and two of which did not. It was found that a unit equipped with a Moyno pump performed well but three air-lift machines had, as was expected, poorer specific performances than the more conventional equipment. 10 refs., 9 figs.

  9. Long-term observations of the wind field in the Antarctic and Arctic mesosphere and lower-thermosphere at conjugate latitudes

    Science.gov (United States)

    Iimura, H.; Fritts, D. C.; Tsutsumi, M.; Nakamura, T.; Hoffmann, P.; Singer, W.

    2011-10-01

    Mean winds, semidiurnal and diurnal tides, and trends and long-period oscillations spanning a solar cycle (from early 1999 through June 2010) measured by medium frequency (MF) radars at conjugate Antarctic and Arctic latitudes (Syowa, Antarctica, 69°S, 39.6°E, and Andenes, Norway, 69.3°N, 16°E) are described and compared. Zonal mean winds are stronger and more uniform from year to year over the Antarctic, with a stronger eastward winter jet spanning the range of altitudes presented (70 to 96 km). The summer westward jet is also stronger and maximizes at higher altitudes over the Antarctic than over the Arctic. The eastward winter jet over the Arctic, while generally weaker, exhibits a localized maximum in late winter at ˜2 to 3 year intervals. Meridional mean winds likewise achieve somewhat stronger maxima at higher altitudes over the Antarctic than over the Arctic. Semidiurnal tide amplitudes are typically somewhat larger over the Antarctic and similar in the two components, with maxima at ˜85 km or above and narrow responses that tend to cluster from ˜February to May and ˜September to November over the Antarctic and from ˜December to February and ˜June to September over the Arctic. Zonal diurnal tide amplitudes are quite similar between the sites, with maxima extending from ˜70 to 90 km and slightly stronger over the Antarctic. Meridional diurnal amplitudes display more significant growth with altitude, achieve stronger maxima at the highest altitudes presented, and typically exhibit a single and narrow maximum during December to February over the Antarctic and double maxima from ˜May to September over the Arctic. Also discussed are trends and long-period oscillations over a solar cycle observed in these mean and tidal wind fields.

  10. Summertime wind climate in Yerevan: valley wind systems

    Science.gov (United States)

    Gevorgyan, Artur

    2017-03-01

    1992-2014 wind climatology analysis in Yerevan is presented with particular focus given to the summertime thermally induced valley wind systems. Persistence high winds are observed in Yerevan during July-August months when the study region is strongly affected by a heat-driven plain-plateau circulation. The local valley winds arrive in Yerevan in the evening hours, generally, from 1500 to 1800 UTC, leading to rapid enhancement of wind speeds and dramatic changes in wind direction. Valley-winds significantly impact the local climate of Yerevan, which is a densely populated city. These winds moderate evening temperatures after hot and dry weather conditions observed during summertime afternoons. On the other hand, valley winds result in significantly higher nocturnal temperatures and more frequent occurrence of warm nights (tn90p) in Yerevan due to stronger turbulent mixing of boundary layer preventing strong surface cooling and temperature drop in nighttime and morning hours. The applied WRF-ARW limited area model is able to simulate the key features of the observed spatial pattern of surface winds in Armenia associated with significant terrain channeling, wind curls, etc. By contrast, ECMWF EPS global model fails to capture mesoscale and local wind systems over Armenia. However, the results of statistical verification of surface winds in Yerevan showed that substantial biases are present in WRF 18-h wind forecasts, as well as, the temporal variability of observed surface winds is not reproduced adequately in WRF-ARW model.

  11. Muscle co-contraction patterns in robot-mediated force field learning to guide specific muscle group training.

    Science.gov (United States)

    Pizzamiglio, Sara; Desowska, Adela; Shojaii, Pegah; Taga, Myriam; Turner, Duncan L

    2017-01-01

    Muscle co-contraction is a strategy of increasing movement accuracy and stability employed in dealing with force perturbation of movement. It is often seen in neuropathological populations. The direction of movement influences the pattern of co-contraction, but not all movements are easily achievable for populations with motor deficits. Manipulating the direction of the force instead, may be a promising rehabilitation protocol to train movement with use of a co-contraction reduction strategy. Force field learning paradigms provide a well described procedure to evoke and test muscle co-contraction. The aim of this study was to test the muscle co-contraction pattern in a wide range of arm muscles in different force-field directions utilising a robot-mediated force field learning paradigm of motor adaptation. Forty-two participants volunteered to participate in a study utilising robot-mediated force field motor adaptation paradigm with a clockwise or counter-clockwise force field. Kinematics and surface electromyography (EMG) of eight arm muscles were measured. Both muscle activation and co-contraction was earlier and stronger in flexors in the clockwise condition and in extensors in the counter-clockwise condition. Manipulating the force field direction leads to changes in the pattern of muscle co-contraction.

  12. Plants and ventifacts delineate late Holocene wind vectors in the Coachella Valley, USA

    Science.gov (United States)

    Griffiths, P.G.; Webb, R.H.; Fisher, M.; Muth, Allan

    2009-01-01

    Strong westerly winds that emanate from San Gorgonio Pass, the lowest point between Palm Springs and Los Angeles, California, dominate aeolian transport in the Coachella Valley of the western Sonoran Desert. These winds deposit sand in coppice dunes that are critical habitat for several species, including the state and federally listed threatened species Uma inornata, a lizard. Although wind directions are generally defined in this valley, the wind field has complex interactions with local topography and becomes more variable with distance from the pass. Local, dominant wind directions are preserved by growth patterns of Larrea tridentata (creosote bush), a shrub characteristic of the hot North American deserts, and ventifacts. Exceptionally long-lived, Larrea has the potential to preserve wind direction over centuries to millennia, shaped by the abrasive pruning of windward branches and the persistent training of leeward branches. Wind direction preserved in Larrea individuals and clones was mapped at 192 locations. Compared with wind data from three weather stations, Larrea vectors effectively reflect annual prevailing winds. Ventifacts measured at 24 locations record winds 10° more westerly than Larrea and appear to reflect the direction of the most erosive winds. Based on detailed mapping of local wind directions as preserved in Larrea, only the northern half of the Mission-Morongo Creek floodplain is likely to supply sand to protected U. inornata habitat in the Willow Hole ecological reserve.

  13. External magnetic field dependent light transmission and scattered speckle pattern in a magnetically polarizable oil-in-water nanoemulsion

    Science.gov (United States)

    Brojabasi, Surajit; Lahiri, B. B.; Philip, John

    2014-12-01

    We study the magnetic field dependent light transmission and scattered speckle pattern in a magnetically polarizable oil-in-water emulsion of droplet diameter ~220 nm, where the direction of propagation of light is parallel to the direction of the external magnetic field. Up to a magnetic field of 50 Gauss, the nanoemulsion remains opaque due to intense Mie scattering. Above 50 Gauss, the transmitted light intensity increases with external magnetic field up to a critical field (BC). Further increase in the magnetic field leads to a reduction in the transmitted intensity. The BC shifts to a lower magnetic field with increasing volume fraction (ϕ) and follows a power law dependence with ϕ, indicating a disorder-order transition. The scattered light intensity at the lobe part is found to increase with external magnetic field. The analysis of the lobe part reveals that the speckle contrast increases with external magnetic field due to the coarsening of the linear chain-like aggregates formed along the direction of the external magnetic field. The angular speckle correlation coefficient is found to be symmetrical on either side of the transmitted bright spot and decays exponentially with measurement angles.

  14. External magnetic field dependent light transmission and scattered speckle pattern in a magnetically polarizable oil-in-water nanoemulsion

    Energy Technology Data Exchange (ETDEWEB)

    Brojabasi, Surajit; Lahiri, B.B.; Philip, John, E-mail: philip@igcar.gov.in

    2014-12-01

    We study the magnetic field dependent light transmission and scattered speckle pattern in a magnetically polarizable oil-in-water emulsion of droplet diameter ∼220 nm, where the direction of propagation of light is parallel to the direction of the external magnetic field. Up to a magnetic field of 50 Gauss, the nanoemulsion remains opaque due to intense Mie scattering. Above 50 Gauss, the transmitted light intensity increases with external magnetic field up to a critical field (B{sub C}). Further increase in the magnetic field leads to a reduction in the transmitted intensity. The B{sub C} shifts to a lower magnetic field with increasing volume fraction (ϕ) and follows a power law dependence with ϕ, indicating a disorder–order transition. The scattered light intensity at the lobe part is found to increase with external magnetic field. The analysis of the lobe part reveals that the speckle contrast increases with external magnetic field due to the coarsening of the linear chain-like aggregates formed along the direction of the external magnetic field. The angular speckle correlation coefficient is found to be symmetrical on either side of the transmitted bright spot and decays exponentially with measurement angles.

  15. Fabrication and independent control of patterned polymer gate for a few-layer WSe2 field-effect transistor

    Directory of Open Access Journals (Sweden)

    Sung Ju Hong

    2016-08-01

    Full Text Available We report the fabrication of a patterned polymer electrolyte for a two-dimensional (2D semiconductor, few-layer tungsten diselenide (WSe2 field-effect transistor (FET. We expose an electron-beam in a desirable region to form the patterned structure. The WSe2 FET acts as a p-type semiconductor in both bare and polymer-covered devices. We observe a highly efficient gating effect in the polymer-patterned device with independent gate control. The patterned polymer gate operates successfully in a molybdenum disulfide (MoS2 FET, indicating the potential for general applications to 2D semiconductors. The results of this study can contribute to large-scale integration and better flexibility in transition metal dichalcogenide (TMD-based electronics.

  16. Ictal onset patterns of local field potentials, high frequency oscillations, and unit activity in human mesial temporal lobe epilepsy.

    Science.gov (United States)

    Weiss, Shennan Aibel; Alvarado-Rojas, Catalina; Bragin, Anatol; Behnke, Eric; Fields, Tony; Fried, Itzhak; Engel, Jerome; Staba, Richard

    2016-01-01

    To characterize local field potentials, high frequency oscillations, and single unit firing patterns in microelectrode recordings of human limbic onset seizures. Wide bandwidth local field potential recordings were acquired from microelectrodes implanted in mesial temporal structures during spontaneous seizures from six patients with mesial temporal lobe epilepsy. In the seizure onset zone, distinct epileptiform discharges were evident in the local field potential prior to the time of seizure onset in the intracranial EEG. In all three seizures with hypersynchronous (HYP) seizure onset, fast ripples with incrementally increasing power accompanied epileptiform discharges during the transition to the ictal state (p local level. Patterns of incrementally increasing fast ripple power are consistent with observations in rats with experimental hippocampal epilepsy, suggesting that limbic seizures arise when small clusters of synchronously bursting neurons increase in size, coalesce, and reach a critical mass for propagation. Wiley Periodicals, Inc. © 2015 International League Against Epilepsy.

  17. Field evaluation of vegetation and noise barriers for mitigation of near-freeway air pollution under variable wind conditions

    Science.gov (United States)

    Lee, Eon S.; Ranasinghe, Dilhara R.; Ahangar, Faraz Enayati; Amini, Seyedmorteza; Mara, Steven; Choi, Wonsik; Paulson, Suzanne; Zhu, Yifang

    2018-02-01

    Traffic-related air pollutants are a significant public health concern, particularly near freeways. Previous studies have suggested either soundwall or vegetation barriers might reduce the near-freeway air pollution. This study aims to investigate the effectiveness of a combination of both soundwall and vegetation barrier for reducing ultrafine particles (UFPs, diameter ≤ 100 nm) and PM2.5 (diameter ≤ 2.5 μm) concentrations. Concurrent data collection was carried out at both upwind and downwind fixed locations approximately 10-15 m away from the edge of two major freeways in California. This study observed that the reduction of UFP and PM2.5 was generally greater with the combination barrier than with either soundwall or vegetation alone. Since there were no non-barrier sites at the study locations, the reductions reported here are all in relative terms. The soundwall barrier was more effective for reducing PM2.5 (25-53%) than UFPs (0-5%), and was most effective (51-53% for PM2.5) when the wind speed ranged between 1 and 2 m/s. Under the same range of wind speed, the vegetation barrier had little effect (0-5%) on reducing PM2.5; but was effective at reducing UFP (up to 50%). For both types of roadside barrier, decreasing wind speed resulted in greater net reduction of UFPs (i.e., total number particle concentrations; inversely proportional). This trend was observed, however, only within specific particle size ranges (i.e., diameter effects of soundwall and vegetation barriers for near-freeway air pollution mitigation.

  18. Wind Tunnel Measurements at LM Wind Power

    DEFF Research Database (Denmark)

    Bertagnolio, Franck

    2012-01-01

    This section presents the results obtained during the experimental campaign that was conducted in the wind tunnel at LM Wind Power in Lunderskov from August 16th to 26th, 2010. The goal of this study is to validate the so-called TNO trailing edge noise model through measurements of the boundary...... layer turbulence characteristics and the far-field noise generated by the acoustic scattering of the turbulent boundary layer vorticies as they convect past the trailing edge. This campaign was conducted with a NACA0015 airfoil section that was placed in the wind tunnel section. It is equipped with high...

  19. Long-Range WindScanner System

    DEFF Research Database (Denmark)

    Vasiljevic, Nikola; Lea, Guillaume; Courtney, Michael

    2016-01-01

    The technical aspects of a multi-Doppler LiDAR instrument, the long-range WindScanner system, are presented accompanied by an overview of the results from several field campaigns. The long-range WindScanner system consists of three spatially-separated, scanning coherent Doppler LiDARs and a remote......-rangeWindScanner system measures the wind field by emitting and directing three laser beams to intersect, and then scanning the beam intersection over a region of interest. The long-range WindScanner system was developed to tackle the need for high-quality observations of wind fields on scales of modern wind turbine...

  20. THE CHANDRA X-RAY SURVEY OF PLANETARY NEBULAE (CHANPLANS): PROBING BINARITY, MAGNETIC FIELDS, AND WIND COLLISIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kastner, J. H.; Montez, R. Jr.; Rapson, V. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Balick, B. [Department of Astronomy, University of Washington, Seattle, WA (United States); Frew, D. J.; De Marco, O.; Parker, Q. A. [Department of Physics and Astronomy and Macquarie Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney, NSW 2109 (Australia); Miszalski, B. [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Sahai, R. [Jet Propulsion Laboratory, California Institute of Technology, MS 183-900, Pasadena, CA 91109 (United States); Blackman, E.; Frank, A. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Chu, Y.-H. [Department of Astronomy, University of Illinois, Champagne-Urbana, IL (United States); Guerrero, M. A. [Instituto de Astrofisica de Astronomia, Glorieta de la Astronomia s/n, Granada 18008 (Spain); Lopez, J. A. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Campus Ensenada, Apdo. Postal 22860, Ensenada, B. C. (Mexico); Zijlstra, A. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Behar, E. [Department of Physics, Technion (Israel); Bujarrabal, V. [Observatorio Astronomico Nacional, Apartado 112, E-28803, Alcala de Henares (Spain); Corradi, R. L. M. [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Nordhaus, J. [Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623 (United States); Sandin, C., E-mail: jhk@cis.rit.edu, E-mail: soker@physics.technion.ac.il, E-mail: eva.villaver@uam.es [Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); and others

    2012-08-15

    We present an overview of the initial results from the Chandra Planetary Nebula Survey (CHANPLANS), the first systematic (volume-limited) Chandra X-Ray Observatory survey of planetary nebulae (PNe) in the solar neighborhood. The first phase of CHANPLANS targeted 21 mostly high-excitation PNe within {approx}1.5 kpc of Earth, yielding four detections of diffuse X-ray emission and nine detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within {approx}1.5 kpc that have been observed to date, we find an overall X-ray detection rate of {approx}70% for the 35 sample objects. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks-in most cases, 'hot bubbles'-formed by energetic wind collisions is detected in {approx}30%; five objects display both diffuse and point-like emission components. The presence (or absence) of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical nebulae are more likely to display X-ray emission (either point-like or diffuse) than molecule-rich, bipolar, or Ring-like nebulae. All but one of the point-like CSPNe X-ray sources display X-ray spectra that are harder than expected from hot ({approx}100 kK) central stars emitting as simple blackbodies; the lone apparent exception is the central star of the Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest a high frequency of binary companions to CSPNe. Other potential explanations include self-shocking winds or PN mass fallback. Most PNe detected as diffuse X-ray sources are elliptical nebulae that display a nested shell/halo structure and bright ansae; the diffuse X-ray emission regions are confined within inner, sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have inner shell dynamical ages {approx}< 5 Multiplication

  1. CFD analysis of flow fields for shrouded wind turbine’s diffuser model with different flange angles

    Directory of Open Access Journals (Sweden)

    Aly M. El-Zahaby

    2017-03-01

    Present model verification indicates a good agreement between present numerical work and previous published experimental work. The numerical simulation shows the created vortices behind flange that cause pressure drop which increases mass flow rate through the diffuser. The results indicate also that the right flange angle at 15° is the optimum angle that accelerates flow at diffuser entrance. The increase of velocity at this optimum flange angles is higher than the case of normal angle, where the expected increase in the generated power by wind turbine can reach 5% more compared with normal flange.

  2. The pattern of complaints about Australian wind farms does not match the establishment and distribution of turbines: support for the psychogenic, 'communicated disease' hypothesis.

    Directory of Open Access Journals (Sweden)

    Simon Chapman

    Full Text Available BACKGROUND AND OBJECTIVES: With often florid allegations about health problems arising from wind turbine exposure now widespread, nocebo effects potentially confound any future investigation of turbine health impact. Historical audits of health complaints are therefore important. We test 4 hypotheses relevant to psychogenic explanations of the variable timing and distribution of health and noise complaints about wind farms in Australia. SETTING: All Australian wind farms (51 with 1634 turbines operating 1993-2012. METHODS: Records of complaints about noise or health from residents living near 51 Australian wind farms were obtained from all wind farm companies, and corroborated with complaints in submissions to 3 government public enquiries and news media records and court affidavits. These are expressed as proportions of estimated populations residing within 5 km of wind farms. RESULTS: There are large historical and geographical variations in wind farm complaints. 33/51 (64.7% of Australian wind farms including 18/34 (52.9% with turbine size >1 MW have never been subject to noise or health complaints. These 33 farms have an estimated 21,633 residents within 5 km and have operated complaint-free for a cumulative 267 years. Western Australia and Tasmania have seen no complaints. 129 individuals across Australia (1 in 254 residents appear to have ever complained, with 94 (73% being residents near 6 wind farms targeted by anti wind farm groups. The large majority 116/129(90% of complainants made their first complaint after 2009 when anti wind farm groups began to add health concerns to their wider opposition. In the preceding years, health or noise complaints were rare despite large and small-turbine wind farms having operated for many years. CONCLUSIONS: The reported historical and geographical variations in complaints are consistent with psychogenic hypotheses that expressed health problems are "communicated diseases" with nocebo effects likely

  3. The Pattern of Complaints about Australian Wind Farms Does Not Match the Establishment and Distribution of Turbines: Support for the Psychogenic, ‘Communicated Disease’ Hypothesis

    Science.gov (United States)

    Chapman, Simon; St. George, Alexis; Waller, Karen; Cakic, Vince

    2013-01-01

    Background and Objectives With often florid allegations about health problems arising from wind turbine exposure now widespread, nocebo effects potentially confound any future investigation of turbine health impact. Historical audits of health complaints are therefore important. We test 4 hypotheses relevant to psychogenic explanations of the variable timing and distribution of health and noise complaints about wind farms in Australia. Setting All Australian wind farms (51 with 1634 turbines) operating 1993–2012. Methods Records of complaints about noise or health from residents living near 51 Australian wind farms were obtained from all wind farm companies, and corroborated with complaints in submissions to 3 government public enquiries and news media records and court affidavits. These are expressed as proportions of estimated populations residing within 5 km of wind farms. Results There are large historical and geographical variations in wind farm complaints. 33/51 (64.7%) of Australian wind farms including 18/34 (52.9%) with turbine size >1 MW have never been subject to noise or health complaints. These 33 farms have an estimated 21,633 residents within 5 km and have operated complaint-free for a cumulative 267 years. Western Australia and Tasmania have seen no complaints. 129 individuals across Australia (1 in 254 residents) appear to have ever complained, with 94 (73%) being residents near 6 wind farms targeted by anti wind farm groups. The large majority 116/129(90%) of complainants made their first complaint after 2009 when anti wind farm groups began to add health concerns to their wider opposition. In the preceding years, health or noise complaints were rare despite large and small-turbine wind farms having operated for many years. Conclusions The reported historical and geographical variations in complaints are consistent with psychogenic hypotheses that expressed health problems are “communicated diseases” with nocebo effects likely to play an

  4. The pattern of complaints about Australian wind farms does not match the establishment and distribution of turbines: support for the psychogenic, 'communicated disease' hypothesis.

    Science.gov (United States)

    Chapman, Simon; St George, Alexis; Waller, Karen; Cakic, Vince

    2013-01-01

    With often florid allegations about health problems arising from wind turbine exposure now widespread, nocebo effects potentially confound any future investigation of turbine health impact. Historical audits of health complaints are therefore important. We test 4 hypotheses relevant to psychogenic explanations of the variable timing and distribution of health and noise complaints about wind farms in Australia. All Australian wind farms (51 with 1634 turbines) operating 1993-2012. Records of complaints about noise or health from residents living near 51 Australian wind farms were obtained from all wind farm companies, and corroborated with complaints in submissions to 3 government public enquiries and news media records and court affidavits. These are expressed as proportions of estimated populations residing within 5 km of wind farms. There are large historical and geographical variations in wind farm complaints. 33/51 (64.7%) of Australian wind farms including 18/34 (52.9%) with turbine size >1 MW have never been subject to noise or health complaints. These 33 farms have an estimated 21,633 residents within 5 km and have operated complaint-free for a cumulative 267 years. Western Australia and Tasmania have seen no complaints. 129 individuals across Australia (1 in 254 residents) appear to have ever complained, with 94 (73%) being residents near 6 wind farms targeted by anti wind farm groups. The large majority 116/129(90%) of complainants made their first complaint after 2009 when anti wind farm groups began to add health concerns to their wider opposition. In the preceding years, health or noise complaints were rare despite large and small-turbine wind farms having operated for many years. The reported historical and geographical variations in complaints are consistent with psychogenic hypotheses that expressed health problems are "communicated diseases" with nocebo effects likely to play an important role in the aetiology of complaints.

  5. Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) Infestations in Tree Borders and Subsequent Patterns of Abundance in Soybean Fields.

    Science.gov (United States)

    Aigner, B L; Kuhar, T P; Herbert, D A; Brewster, C C; Hogue, J W; Aigner, J D

    2017-04-01

    The invasive brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an important pest of soybean (Glycine max L. Merr.) in the Mid-Atlantic United States. In order to assess the influence of nonmanaged wooded borders on H. halys infestation patterns in soybean, 12 soybean fields in Orange and Madison Counties, VA, were sampled each week from July to October in 2013 or 2014 for H. halys. At each location, five 2-min visual counts of H. halys life stages were made on tree of heaven (Ailanthus altissima Mill.) and other favorable host trees along a wooded border, on the adjacent soybean edge, 15 m into the soybean field, and 30 m into the field. Seasonal data showed a clear trend at all locations of H. halys densities building up on A. altissima-dominated wooded borders in July, then, gradually moving into adjacent soybean field edges later in the summer. Halyomorpha halys did not move far from the invading field edge, with approximately half as many bugs being present at 15 m into the field and very few being detected 30 m into the field. These results have implications for continued monitoring and management using field border sprays, particularly on edges adjacent to woods. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  6. Are there current-sheet-like structures in the Earth's magnetotail as in the solar wind – results and implications from high time resolution magnetic field measurements by Cluster

    Directory of Open Access Journals (Sweden)

    G. Li

    2008-07-01

    Full Text Available Recent studies of solar wind MHD turbulence show that current-sheet-like structures are common in the solar wind and they are a significant source of solar wind MHD turbulence intermittency. While numerical simulations have suggested that such structures can arise from non-linear interactions of MHD turbulence, a recent study by Borovsky (2006, upon analyzing one year worth of ACE data, suggests that these structures may represent the magnetic walls of flux tubes that separate solar wind plasma into distinct bundles and these flux tubes are relic structures originating from boundaries of supergranules on the surface of the Sun. In this work, we examine whether there are such structures in the Earth's magnetotail, an environment vastly different from the solar wind. We use high time resolution magnetic field data of the FGM instrument onboard Cluster C1 spacecraft. The orbits of Cluster traverse through both the solar wind and the Earth's magnetosheath and magnetotail. This makes its dataset ideal for studying differences between solar wind MHD turbulence and that inside the Earth's magnetosphere. For comparison, we also perform the same analysis when Cluster C1 is in the solar wind. Using a data analysis procedure first introduced in Li (2007, 2008, we find that current-sheet-like structures can be clearly identified in the solar wind. However, similar structures do not exist inside the Earth's magnetotail. This result can be naturally explained if these structures have a solar origin as proposed by Borovsky (2006. With such a scenario, current analysis of solar wind MHD turbulence needs to be improved to include the effects due to these curent-sheet-like structures.

  7. Water flow patterns induced by bridge oscillation of magnetic fluid between two permanent magnets subjected to alternating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Sudo, Seiichi, E-mail: sudo@akita-pu.ac.jp [Faculty of Systems Science and Technology, Akita Prefectural University, Ebinokuchi 84-4, Yurihonjo 015-0055 (Japan); Yamamoto, Kazuki [Graduate School of Engineering, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan); Ishimoto, Yukitaka; Nix, Stephanie [Faculty of Systems Science and Technology, Akita Prefectural University, Ebinokuchi 84-4, Yurihonjo 015-0055 (Japan)

    2017-06-01

    This paper describes the characteristics of water flow induced by the bridge oscillation of magnetic fluid between two permanent magnets subject to an external alternating magnetic field. The magnetic fluid bridge is formed in the space between a pair of identical coaxial cylindrical permanent magnets submerged in water. The direction of alternating magnetic field is parallel /antiparallel to the magnetic field produced by two permanent magnets. The magnetic fluid bridge responds to the external alternating magnetic field with harmonic oscillation. The oscillation of magnetic fluid bridge generates water flow around the bridge. Water flow is visualized using a thin milk film at the container bottom. Water flows are observed with a high-speed video camera analysis system. The experimental results show that the flow pattern induced by the bridge oscillation depends on the Keulegan–Carpenter number.

  8. Numerical modeling of present-day stress field and deformation pattern in Anatolia

    OpenAIRE

    Dwivedi, Sunil Kumar; Hayashi, Daigoro; 林, 大五郎

    2010-01-01

    The present-day stress field in the Earth's crust is important and provides insights into mechanisms that drive plate motions. In this study, an elastic plane stress finite element modeling incorporating realistic rock parameters have been used to calculate the stress field, displacement field and deformation of the plate interactions in Anatolia. Modeled stress data for the African-Arabian-Anatolian plate interactions with fixed Eurasian platform correlate well with observed stress indicator...

  9. Effects of Long-term Conservation Tillage on Soil Nutrients in Sloping Fields in Regions Characterized by Water and Wind Erosion

    Science.gov (United States)

    Tan, Chunjian; Cao, Xue; Yuan, Shuai; Wang, Weiyu; Feng, Yongzhong; Qiao, Bo

    2015-12-01

    Conservation tillage is commonly used in regions affected by water and wind erosion. To understand the effects of conservation tillage on soil nutrients and yield, a long-term experiment was set up in a region affected by water and wind erosion on the Loess Plateau. The treatments used were traditional tillage (CK), no tillage (NT), straw mulching (SM), plastic-film mulching (PM), ridging and plastic-film mulching (RPM) and intercropping (In). Our results demonstrate that the available nutrients in soils subjected to non-traditional tillage treatments decreased during the first several years and then remained stable over the last several years of the experiment. The soil organic matter and total nitrogen content increased gradually over 6 years in all treatments except CK. The nutrient content of soils subjected to conservative tillage methods, such as NT and SM, were significantly higher than those in soils under the CK treatment. Straw mulching and film mulching effectively reduced an observed decrease in soybean yield. Over the final 6 years of the experiment, soybean yields followed the trend RPM > PM > SM > NT > CK > In. This trend has implications for controlling soil erosion and preventing non-point source pollution in sloping fields by sacrificing some food production.

  10. Ockham's Razorblade Shaving Wind-Induced Circulation

    Science.gov (United States)

    Bergmann, Juan Carlos

    2010-05-01

    Terrestrial physical oceanography is fortunate because of the existence of the continents that divide the low-latitude oceans into basins. At first glance, the previous statement appears to be not obvious because an ocean-planet should be much simpler to describe. Simple-case explanation is the central aspect of Ockham's Razorblade: If a theory fails to describe the most-simple case properly, the theory is, at least, ‘not good'. Also Descartes' methodical rules take the most-simple case as starting point. The analysis of wind-induced circulation on an ocean-planet will support the initial statement. Earth's south hemisphere is dominated by the oceans. The continents' influence on the zonal-average zonal-wind climate is relatively small. Therefore, South Hemisphere's zonal wind pattern is a relatively good proxy for that of an ocean planet. Application of this wind-stress pattern to an ocean planet yields reasonable meridional mass-flow results from the polar-regions down to the high-pressure belts: Down-welling and up-welling of water-mass are approximately balanced. However, the entire tropical circulation can in principle not be closed because there is only down-welling - even if the extreme down-welling in the equatorial belt (± 8°, with a singularity at the equator) is disregarded. The only input to the calculations is the observed terrestrial south-hemisphere zonal wind-stress pattern. Meridional stress is irrelevant because it produces a closed zonal Ekman-transport around the ocean planet (sic!). Vertical mass-transport is calculated from the divergence of the wind-induced meridional Ekman-mass-transport, which in its turn is a necessary consequence of angular-momentum conservation. No assumptions are made on how the return-flows at depth are forced because the wind-force equations cannot contribute hereto. This circumstance expresses a fundamental difference to atmospheric circulation, where mechanical forcing is caused by the pressure-fields that

  11. The Relationship of High-Latitude Thermospheric Wind With Ionospheric Horizontal Current, as Observed by CHAMP Satellite

    Science.gov (United States)

    Huang, Tao; Lühr, Hermann; Wang, Hui; Xiong, Chao

    2017-12-01

    The relationship between high-latitude ionospheric currents (Hall current and field-aligned current) and thermospheric wind is investigated. The 2-D patterns of horizontal wind and equivalent current in the Northern Hemisphere derived from the CHAMP satellite are considered for the first time simultaneously. The equivalent currents show strong dependences on both interplanetary magnetic field (IMF) By and Bz components. However, IMF By orientation is more important in controlling the wind velocity patterns. The duskside wind vortex as well as the antisunward wind in the morning polar cap is more evident for positive By. To better understand their spatial relation in different sectors, a systematic superposed epoch analysis is applied. Our results show that in the dusk sector, the vectors of the zonal wind and equivalent current are anticorrelated, and both of them form a vortical flow pattern for different activity levels. The currents and zonal wind are intensified with the increase of merging electric field. However, on the dawnside, where the relation is less clear, antisunward zonal winds dominate. Plasma drift seems to play a less important role for the wind than neutral forces in this sector. In the noon sector, the best anticorrelation between equivalent current and wind is observed for a positive IMF By component and it is less obvious for negative By. A clear seasonal effect with current intensities increasing from winter to summer is observed in the noon sector. Different from the currents, the zonal wind intensity shows little dependence on seasons. Our results indicate that the plasma drift and the neutral forces are of comparable influence on the zonal wind at CHAMP altitude in the noon sector.

  12. Combining sprinkling experiments and superconducting gravimetry in the field: a qualitative approach to identify dominant infiltration patterns

    Science.gov (United States)

    Reich, Marvin; Mikolaj, Michal; Blume, Theresa; Güntner, Andreas

    2017-04-01

    Hydrological process research at the plot to catchment scale commonly involves invasive field methods, leading to a large amount of point data. A promising alternative, which gained increasing interest in the hydrological community over the last years, is gravimetry. The combination of its non-invasive and integrative nature opens up new possibilities to approach hydrological process research. In this study we combine a field-scale sprinkling experiment with continuous superconducting gravity (SG) measurements. The experimental design consists of 8 sprinkler units, arranged symmetrically within a radius of about ten meters around an iGrav (SG) in a field enclosure. The gravity signal of the infiltrating sprinkling water is analyzed using a simple 3D water mass distribution model. We first conducted a number of virtual sprinkling experiments resulting in different idealized infiltration patterns and determined the pattern specific gravity response. In a next step we determined which combination of idealized infiltration patterns was able to reproduce the gravity response of our real-world experiment at the Wettzell Observatory (Germany). This process hypothesis is then evaluated with measured point-scale soil moisture responses and the results of the time-lapse electric resistivity survey which was carried out during the sprinkling experiment. This study demonstrates that a controlled sprinkling experiment around a gravimeter in combination with a simple infiltration model is sufficient to identify subsurface flow patterns and thus the dominant infiltration processes. As gravimeters become more portable and can actually be deployed in the field, their combination with sprinkling experiments as shown here constitutes a promising possibility to investigate hydrological processes in a non-invasive way.

  13. Le Conte's sparrows breeding in Conservation Reserve Program fields: precipitation and patterns of population change

    Science.gov (United States)

    Igl, Lawrence D.; Johnson, Douglas H.

    1999-01-01

    ). Like populations of many grassland breeding birds in North America (Fretwell 1986, Igl and Johnson 1997), Le Conte's Sparrow populations exhibit numerical highs and lows depending on local moisture conditions (Peabody 1901, Stewart 1975, Knapton 1979, Zimmer 1979, Madden 1996). This observation, however, is based largely on anecdotal evidence or short-term observations. Long-term studies of Le Conte's Sparrow populations are limited. Le Conte's Sparrow is poorly represented on the North American Breeding Bird Survey (BBS) because of small sample sizes, poor coverage in the northern portion of its breeding range, and the species' furtive behavior (Sauer et al. 1995). Moreover, dramatic fluctuations in Le Conte's Sparrow abundance tend to obscure the species' long-term population trends on the BBS (Sauer et al. 1995). In this paper we examine long-term population changes of Le Conte's Sparrows breeding in perennial grassland fields enrolled in the Conservation Reserve Program (CRP) on the northern Great Plains. We discuss patterns of population change of Le Conte's Sparrows associated with changes in precipitation and moisture conditions.

  14. Husum wind `97. Amiable and powerful. Proceedings; Husum Wind `97. Liebenswert und leistungsstark. Kongressband

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    The Husum Fair and Congress on Wind Energy 97 wants to inform on and demonstrate the state of the art of wind energy and its potentials of development. This conference volume contains 21 papers in seven sections: Wind energy - society and environment; forum of the wind power plant manufacturers represented at the Husum Wind 97; foreign markets for wind power plants; development prospects for wind power; wind power in retrospective and relevant operating experience; panel discussion ``The amendment to the act on remuneration for power fed into the mains - wind power in the lull``; excursion to the test field WINDTEST, Kaiser-Wilhelm-Koog. (AKF)

  15. Impact of Diurnal Variation of Winds on Coastal Waves off South East Coast of India

    Directory of Open Access Journals (Sweden)

    P G Remya

    2013-09-01

    Full Text Available The land-sea breeze systems, the most interesting phenomena observed at coastal regions, have significant impact on the costal wave characteristics. Present study also focuses the diurnal variations of winds and its impact on wave parameters like significant wave height and mean wave period off Ennore port located in the south east coast of India The impact of the diurnal variation of winds on complex wave patterns in the coastal regions of Indian Ocean have been addressed earlier also. In the present study an attempt has been made to explore the impact of diurnal variation of winds on coastal waves using numerical model forced with European Centre for Medium Range Weather Forecasts (ECMWF and National Centre for Environmental Prediction (NCEP blended wind fields. It has been observed that most of the time, the ECMWF blended wind field reproduces the diurnal variation.

  16. Comparison of Field Measurements and EMT Simulation Results on a Multi-Level STATCOM for Grid Integration of London Array Wind Farm

    DEFF Research Database (Denmark)

    Glasdam, Jakob Bærholm; Kocewiak, Lukasz; Hjerrild, Jesper

    2014-01-01

    Simulation results are widely used in the design of electrical systems such as offshore wind power plants (OWPPs) and for determination of grid compliance. Measurements constitute an important part in the evaluation process of the OWPP, including passive and active components such as the static...... compensator (STATCOM). Quality measurement data allow the system designer to obtain real-life knowledge on the operating characteristics of the electrical component(s) for various operating scenarios of both the OWPP and the external grid. Furthermore, measurement data constitute an indispensable part...... of the evaluati