WorldWideScience

Sample records for anemometers

  1. Cup Anemometer Overspeeding

    DEFF Research Database (Denmark)

    Busch, N. E.; Kristensen, Leif

    1976-01-01

    Statistical considerations are applied to a general equation of motion for cup anemometers in a turbulent wind. It is shown that the relative overspeeding ΔS/S can be expressed as ΔS/S = Ih2 · Js(l0/Λs) + cIw2, where Is and Iw are the horizontal and the vertical turbulence intensifies, respectively...

  2. Field calibration of cup anemometers

    DEFF Research Database (Denmark)

    Schmidt Paulsen, Uwe; Mortensen, Niels Gylling; Hansen, Jens Carsten;

    2007-01-01

    A field calibration method and results are described along with the experience gained with the method. The cup anemometers to be calibrated are mounted in a row on a 10-m high rig and calibrated in the free wind against a reference cup anemometer. The method has been reported [1] to improve the...... statistical bias on the data relative to calibrations carried out in a wind tunnel. The methodology is sufficiently accurate for calibration of cup anemometers used for wind resource assessments and provides a simple, reliable and cost-effective solution to cup anemometer calibration, especially suited for...

  3. Wind Speed Measurement by Paper Anemometer

    Science.gov (United States)

    Zhong, Juhua; Cheng, Zhongqi; Guan, Wenchuan

    2011-01-01

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

  4. Field calibration of cup anemometers

    DEFF Research Database (Denmark)

    Kristensen, L.; Jensen, G.; Hansen, A.;

    2001-01-01

    . It is concluded that the method has the advantage that many anemometers can be calibrated accurately with a minimum of work and cost. The obvious disadvantage is that the calibration of a set of anemometersmay take more than one month in order to have wind speeds covering a sufficiently large magnitude range...... in a wind direction sector where we can be sure that the instruments are exposed to identical, simultaneous wind flows. Another main conclusion is thatstatistical uncertainty must be carefully evaluated since the individual 10 minute wind-speed averages are not statistically independent....

  5. Sphere anemometer - a faster alternative solution to cup anemometry

    Science.gov (United States)

    Hölling, M.; Schulte, B.; Barth, S.; Peinke, J.

    2007-07-01

    We present an anemometer technique characterized by an instrument in a sealed enclosure without moving parts. Measurements taken with our improved sphere anemometer in comparison to cup anemometer and hot-wire anemometer data subjected to wind gusts are discussed. The hot-wire anemometer serves as a reference with high temporal and spacial resolution. A manually driven "gust generator" produced gusts at low frequencies of about 1Hz. All measurements were carried out in the wind tunnel at the University of Oldenburg.

  6. Tethersonde and kite anemometer evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Chow, W.Y.; Kirchhoff, R.H.

    1988-10-01

    The responses of kite anemometers and tethersonde balloons to the dynamics of the wind are investigated in this study. A three-phase effort of theoretical development, experimental measurement, and comparison of data and theory was undertaken to provide further understanding of how a kite or balloon responds to atmospheric turbulence. Understanding the effect on wind velocity measurements obtained using these instruments is important to their use in, for example, identifying optimum wind turbine sites. The theoretical development included: (1) an extension of double theodolite theory, to provide a mechanism for calculating instrument displacement, and (2) linear small perturbation analysis of the effect of atmospheric turbulence on kite or balloon motion. The results of the small perturbation analyses were response equations that analyze the movement of the kite or balloon as a function of the mean elevation angle of the kite or balloon and turbulence parameters of the wind. The response equations provide the ratio of the fluctuating string tension to the mean string tension (for the kite) and the fluctuating elevation angle for the kite and balloon. 18 refs., 66 figs., 22 tabs.

  7. ACCUWIND - Methods for classification of cup anemometers

    Energy Technology Data Exchange (ETDEWEB)

    Dahlberg, J.Aa.; Friis Pedersen, T.; Busche, P.

    2006-05-15

    Errors associated with the measurement of wind speed are the major sources of uncertainties in power performance testing of wind turbines. Field comparisons of well-calibrated anemometers show significant and not acceptable difference. The European CLASSCUP project posed the objectives to quantify the errors associated with the use of cup anemometers, and to develop a classification system for quantification of systematic errors of cup anemometers. This classification system has now been implemented in the IEC 61400-12-1 standard on power performance measurements in annex I and J. The classification of cup anemometers requires general external climatic operational ranges to be applied for the analysis of systematic errors. A Class A category classification is connected to reasonably flat sites, and another Class B category is connected to complex terrain, General classification indices are the result of assessment of systematic deviations. The present report focuses on methods that can be applied for assessment of such systematic deviations. A new alternative method for torque coefficient measurements at inclined flow have been developed, which have then been applied and compared to the existing methods developed in the CLASSCUP project and earlier. A number of approaches including the use of two cup anemometer models, two methods of torque coefficient measurement, two angular response measurements, and inclusion and exclusion of influence of friction have been implemented in the classification process in order to assess the robustness of methods. The results of the analysis are presented as classification indices, which are compared and discussed. (au)

  8. Flow distortion on boom mounted cup anemometers

    DEFF Research Database (Denmark)

    Lindelöw, Per Jonas Petter; Friis Pedersen, Troels; Gottschall, Julia;

    in the measurement of wind turbine power performance, wind resource assessment and for providing purposeful in-field comparisons between different sensors, e.g. lidar anemometers. With the proposed method, direction dependent errors can be extracted and the mast flow distortion effect on the wind measurements......In this report we investigate on wind direction dependent errors in the measurement of the horizontal wind speed by boom mounted cup anemometers. The boom mounting on the studied lattice tower is performed according to IEC standard design rules, yet, larger deviations than predicted by flow models...... are observed. The errors on the measurements are likely caused by an underestimation of the flow distortions around the tower. In this paper an experimental method for deriving a correction formula and an in-field calibration is suggested. The method is based on measurements with two cup anemometers mounted...

  9. Rugged constant-temperature thermal anemometer

    CERN Document Server

    Palma, J

    2016-01-01

    Here we report a robust thermal anemometer which can be easily built. It was conceived to measure outdoor wind speeds, and for airspeed monitoring in wind tunnels and other indoor uses. It works at a constant, low temperature of approximately 90$^\\circ$C, so that an independent measurement of the air temperature is required to give a correct speed reading. Despite the size and high thermal inertia of the probe, the test results show that this anemometer is capable of measuring turbulent fluctuations up to ~100 Hz in winds of ~14 m/s, which corresponds to a scale similar to the length of the probe.

  10. Industry guidelines for the calibration of maximum anemometers

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, B.H. [AWS Scientific, Inc., Albany, NY (United States)

    1996-12-31

    The purpose of this paper is to report on a framework of guidelines for the calibration of the Maximum Type 40 anemometer. This anemometer model is the wind speed sensor of choice in the majority of wind resource assessment programs in the U.S. These guidelines were established by the Utility Wind Resource Assessment Program. In addition to providing guidelines for anemometers, the appropriate use of non-calibrated anemometers is also discussed. 14 refs., 1 tab.

  11. Flow distortion on boom mounted cup anemometers

    Energy Technology Data Exchange (ETDEWEB)

    Lindeloew-Marsden, P.; Pedersen, Troels F.; Gottschall, J.; Vesth, A.; Paulsen, R.W.U.; Courtney, M.S.

    2010-08-15

    In this report we investigate on wind direction dependent errors in the measurement of the horizontal wind speed by boom mounted cup anemometers. The boom mounting on the studied lattice tower is performed according to IEC standard design rules, yet, larger deviations than predicted by flow models are observed. The errors on the measurements are likely caused by an underestimation of the flow distortions around the tower. In this paper an experimental method for deriving a correction formula and an in-field calibration is suggested. The method is based on measurements with two cup anemometers mounted with booms at the same height but pointing in 60 deg. different directions. In the examined case of a 1.9 m wide equilateral triangular lattice tower with booms protruding 4.1 m at 80 m height the measurement errors are observed to reach up to +- 2 %. Errors of this magnitude are severely problematic in the measurement of wind turbine power performance, wind resource assessment and for providing purposeful in-field comparisons between different sensors, e.g. lidar anemometers. With the proposed method, direction dependent errors can be extracted and the mast flow distortion effect on the wind measurements corrected to an uncertainty estimated to better than 0.5%. This level of uncertainty is probably acceptable for the above mentioned applications. (author)

  12. Validation of 3D sonic-anemometer against cup anemometer response

    DEFF Research Database (Denmark)

    Hansen, Kurt Schaldemose; Larsen, Gunner Chr.; Courtney, Michael

    2004-01-01

    Determination and validation of wind turbine power curves traditionally rely on single point wind speed measurements recorded with a calibrated cup-anemometer. The power curve verification process, which is typically performed in different terrain types, does not always result in satisfactory...... agreement between measures- and predicted power curves. The observed disagreement is premarily believed to relate to the cup-anemometers being sensitive to tilted flow i.e. that the measurement of the horizontal flow component is sensible to flow in a plane perpendicular to the horizontal plane. Furthermore......, the limited cup-anemometer response due to high turbulence can explain some of the diviations. The present paper investigates this problem, by analysing full-scale time series data extracted from "Database on Wind Characteristics" (http://www.winddata.com/), which represents a wide range of sites...

  13. Distance constant of the Risø cup anemometer

    DEFF Research Database (Denmark)

    Kristensen, L.; Frost Hansen, O.

    2002-01-01

    The theory for cup-anemometer dynamics is presented in some detail and two methods of obtaining the distance constant lo are discussed. The first method is based on wind tunnel measurements: with a constant wind speed the cup anemometer is released from alocked position of the rotor and the incre......The theory for cup-anemometer dynamics is presented in some detail and two methods of obtaining the distance constant lo are discussed. The first method is based on wind tunnel measurements: with a constant wind speed the cup anemometer is released from alocked position of the rotor...... resolution which is significantly better than that which can be obtained by a cup anemometer. The ratio between the measured power spectra of the horizontal windspeed by the two instruments contains the necessary information for determining the response characteristics of the cup anemometer and thereby lo...

  14. Quality, precision and accuracy of the maximum No. 40 anemometer

    Energy Technology Data Exchange (ETDEWEB)

    Obermeir, J. [Otech Engineering, Davis, CA (United States); Blittersdorf, D. [NRG Systems Inc., Hinesburg, VT (United States)

    1996-12-31

    This paper synthesizes available calibration data for the Maximum No. 40 anemometer. Despite its long history in the wind industry, controversy surrounds the choice of transfer function for this anemometer. Many users are unaware that recent changes in default transfer functions in data loggers are producing output wind speed differences as large as 7.6%. Comparison of two calibration methods used for large samples of Maximum No. 40 anemometers shows a consistent difference of 4.6% in output speeds. This difference is significantly larger than estimated uncertainty levels. Testing, initially performed to investigate related issues, reveals that Gill and Maximum cup anemometers change their calibration transfer functions significantly when calibrated in the open atmosphere compared with calibration in a laminar wind tunnel. This indicates that atmospheric turbulence changes the calibration transfer function of cup anemometers. These results call into question the suitability of standard wind tunnel calibration testing for cup anemometers. 6 refs., 10 figs., 4 tabs.

  15. Development of a classification system for cup anemometers - CLASSCUP

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels

    2003-01-01

    Errors associated with the measurements of the wind speed are the major sources of uncertainties in power performance testing of wind turbines. Field comparisons of well-calibrated anemometers show a significant and not acceptable difference. TheEuropean CLASSCUP research project posed......). The classification of three commercial cup anemometersshowed that for the normal category, the best class for horizontal wind speed measurements was class 2 and for vector measurements class 3. The CLASSCUP prototype anemometer got a class 2 as a horizontal anemometer and class 1 as a vector anemometer. Forthe...

  16. A Procedure for Classification of Cup-Anemometers

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Paulsen, Uwe Schmidt

    1997-01-01

    The paper proposes a classification procedure for cup-anemometers based on similar principles as for power converters. A range of operational parameters are established within which the response of the cup-anemometer is evaluated. The characteristics of real cup-anemometers are fitted to a...... realistic 3D cup-anemometer model. Afterwards, the model is used to calculate the response under the range of operational conditions which are set up for the classification. Responses are compared to the normal linear calibration relationship, derived from Wind tunnel calibrations. Results of the 3D cup...

  17. Sonic anemometers in aeolian sediment transport research

    Science.gov (United States)

    van Boxel, J. H.; Sterk, G.; Arens, S. M.

    2004-04-01

    Fast-response wind and turbulence instruments, including sonic anemometers, are used more and more in aeolian sediment transport research. These instruments give information on mean wind, but also on fluctuations and turbulent statistics, such as the uw covariance, which is a direct measure of Reynolds' stress (RS) and friction velocity. This paper discusses the interpretation of sonic anemometer data, the transformations needed to get proper results and turbulence spectra, and how they are influenced by instrument size, sampling frequency, and measurement height. Turbulence spectra characterize how much the different frequencies in the turbulent signals contribute to the variance of wind speed, or to the covariance of horizontal and vertical wind speed. They are important in determining the measurement strategy when working with fast-response instruments, such as sonic anemometers, and are useful for interpreting the measurement results. Choices on the type of sonic anemometer, observation height, sampling period, sampling frequency, and filtering can be made on the basis of expected high and low-frequency losses in turbulent signals, which are affected by those variables, as well as wind speed and atmospheric stability. Friction velocity and RS, important variables in aeolian sediment transport research, are very sensitive to tilt or slope errors. During a field experiment, the slope sensitivity of the RS was established as 9% per degree of slope, which is 1.5 times the value reported in literature on the basis of theoretical considerations. An important reason for the difference probably is the large influence of streamline curvature on turbulence statistics and thereby on the slope sensitivity of the RS. An error of 9% per degree of slope in the RS will translate into an error of approximately 4% per degree of slope in the calculated friction velocity. Space-time correlation of the horizontal wind speed is much larger than that of the vertical wind speed and

  18. ACCUWIND - Methods for classification of cup anemometers

    DEFF Research Database (Denmark)

    Dahlberg, J.-Å.; Friis Pedersen, Troels; Busche, P.

    2006-01-01

    of assessment of systematic deviations. The present report focuses on methods that can beapplied for assessment of such systematic deviations. A new alternative method for torque coefficient measurements at inclined flow have been developed, which have then been applied and compared to the existing methods...... developed in the CLASSCUP projectand earlier. A number of approaches including the use of two cup anemometer models, two methods of torque coefficient measurement, two angular response measurements, and inclusion and exclusion of influence of friction have been implemented in theclassification process...

  19. Feature Extraction and Pattern Identification for Anemometer Condition Diagnosis

    Directory of Open Access Journals (Sweden)

    Longji Sun

    2012-01-01

    Full Text Available Cup anemometers are commonly used for wind speed measurement in the wind industry. Anemometer malfunctions lead to excessive errors in measurement and directly influence the wind energy development for a proposed wind farm site. This paper is focused on feature extraction and pattern identification to solve the anemometer condition diagnosis problem of the PHM 2011 Data Challenge Competition. Since the accuracy of anemometers can be severely affected by the environmental factors such as icing and the tubular tower itself, in order to distinguish the cause due to anemometer failures from these factors, our methodologies start with eliminating irregular data (outliers under the influence of environmental factors. For paired data, the relation between the relative wind speed difference and the wind direction is extracted as an important feature to reflect normal or abnormal behaviors of paired anemometers. Decisions regarding the condition of paired anemometers are made by comparing the features extracted from training and test data. For shear data, a power law model is fitted using the preprocessed and normalized data, and the sum of the squared residuals (SSR is used to measure the health of an array of anemometers. Decisions are made by comparing the SSRs of training and test data. The performance of our proposed methods is evaluated through the competition website. As a final result, our team ranked the second place overall in both student and professional categories in this competition.

  20. Optimization of Wind Turbine Operation by Use of Spinner Anemometer

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Sørensen, Niels N.; Vita, Luca;

    A prototype spinner anemometer was developed from a standard scientific sonic anemometer with specially designed 1D sonic sensors. A model spinner anemometer was tested in wind tunnel with two sensor head configurations. The tests showed that the sonic sensors responded with a high influence factor...... that the calculations were almost insensitive to rotation and to wind speeds. For all flow angles up to 60º the azimuth variation was a pure sinus. The shape of the responses was found to be described with a simple function that over one revolution decreases the average value with a cosine to the flow angle...

  1. Wind Powering America Anemometer Loan Program: A Retrospective

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, T.

    2013-05-01

    This white paper details the history, mechanics, status, and impact of the Native American Anemometer Loan Program (ALP) conducted by the U.S. Department of Energy's Wind Powering America (WPA) initiative. Originally conceived in 2000 and terminated (as a WPA activity) at the end of FY 2011, the ALP has resulted in the installation of anemometers at 90 locations. In addition, the ALP provided support for the installation of anemometers at 38 additional locations under a related ALP administered by the Western Area Power Administration.

  2. Can a cup anemometer 'underspeed'? A heretical question

    DEFF Research Database (Denmark)

    Kristensen, L.

    2002-01-01

    calibration function is included. The conclusion is that neither longitudinal nor lateral velocity fluctuations can contribute significantly to a negative bias. However, if a cup anemometer has an angular response that falls below the ideal cosine response, there will, as demonstrated in the concluding......An analysis of cup-anemometer dynamics has been carried out in order to determine whether the mean-wind velocity can have a negative bias. This would be contrary to the general belief that cup anemometers always overspeed. Compared to prior analyses, the effect of a possible nonlinearity of the...... discussion, be a negative contribution from the vertical velocity fluctuations to the total bias, and this contribution may even outbalance the positive contributions from the longitudinal velocity fluctuations. Concrete evidence of such exotic cup anemometer behaviour has not been reported in the literature....

  3. Optimization of wind turbine operation by use of spinner anemometer

    Energy Technology Data Exchange (ETDEWEB)

    Pedersen, T.F.; Soerensen, N.N.; Vita, L.; Enevoldsen, P.

    2008-08-15

    A prototype spinner anemometer was developed from a standard scientific sonic anemometer with specially designed 1D sonic sensors. A model spinner anemometer was tested in wind tunnel with two sensor head configurations. The tests showed that the sonic sensors responded with a high influence factor on yaw errors, and that the sensors responded with sinusoidal behaviour to rotation of the spinner. The tests also revealed a significant 'sensor head flow distortion effect' from the classic sensor heads. A full CFD analysis of the model spinner anemometer was made. The results showed that the calculations were almost insensitive to rotation and to wind speeds. For all flow angles up to 60 deg. C the azimuth variation was a pure sinus. The shape of the responses was found to be described with a simple function that over one revolution decreases the average value with a cosine to the flow angle and increases the amplitude with a sine to the flow angle. The relation can be used in a conversion algorithm for the spinner anemometer. Field measurements were made with the model spinner anemometer. The spinner anemometer measurements were compared to measurements from a standard 3D sonic anemometer. The results showed time traces of the two instruments that were very similar. The prototype spinner anemometer was mounted on a 3.6MW prototype wind turbine. Statistics of the yaw error showed an average of about 10 deg. C. The average flow inclination angle was about 1 deg. C. The spinner anemometer measurements were correlated with wind speed and wind direction from a free meteorology mast. The results showed that the gain factor of the yaw error was only 0.80, which indicates that the yaw error measurements were overestimated with the use of the K factors from the CFD analysis. The wind speed at the free mast ahead of the wind turbine was compared to the wind speed measured by the spinner anemometer while the wind turbine was yawing while idling or stopped. The results

  4. Classification of operational characteristics of commercial cup-anemometers

    Energy Technology Data Exchange (ETDEWEB)

    Friis Pedersen, T.; Schmidt Paulsen, U. [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)

    1999-03-01

    The present classification of cup-anemometers is based on a procedure for classification of operational characteristics of cup-anemometers that was proposed at the EWEC `97 conference in Dublin 1997. Three definitions of wind speed are considered. The average longitudinal wind speed (ID), the average horizontal wind speed (2D) and the average vector wind speed (3D). The classification is provided in these terms, and additionally, the turbulence intensities, which are defined from the same wind speed definitions. The commercial cup-anemometers have all been calibrated in wind tunnel for the normal calibrations and angular characteristics. Friction was measured by blywheel testing, where the surrounding temperatures were varied over a wide range. The characteristics of the cup-anemometers have been fitted to the heuristic dynamic model, and the response has been calculated in time domain for prescribed ranges of external operational conditions. The results are presented in ranges of maximum deviations of `measured` average wind speed. For each definition of wind speed and turbulence intensity, the cup-anemometers are ranked according to the most precise instrument. Finally, the most important systematic error sources are commented. (au)

  5. Characterisation and classification of RISØ P2546 cup anemometer

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels

    2003-01-01

    The characteristics of the RISØ P2546 cup anemometer were investigated in detail by wind tunnel and laboratory tests. The characteristics include accredited calibration, tilt response measurements for tilt angles between -40° to 40°, gust responsemeasurements at 8m/s and turbulence intensities of...... 10%, 16% and 23%, step response measurements at step wind speeds 3,7, 8, 11,9 and 15,2m/s, measurement of torque characteristics at 8m/s, rotor inertia measurements and measurements of friction ofbearings at temperatures -20°C to 40°C. Characteristics were fitted to a time domain cup anemometer model....... The characteristics were transformed into the CLASSCUP classification scheme, and were related to the cup anemometer requirements in the Danishcertification system and in the IEC 61400-121 Committee Draft....

  6. Characterisation and classification of RISØ P2546 cup anemometer

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels

    2004-01-01

    The characteristics of the RISØ P2546 cup anemometer were investigated in detail by wind tunnel and laboratory tests. The characteristics include accredited calibration, tilt response measurements for tilt angles between -40° to 40°, gust responsemeasurements at 8m/s and turbulence intensities of...... 10%, 16% and 23%, step response measurements at step wind speeds 3,7, 8, 11,9 and 15,2m/s, measurement of torque characteristics at 8m/s, rotor inertia measurements and measurements of friction ofbearings at temperatures -20°C to 40°C. Characteristics were fitted to a time domain cup anemometer model....... The characteristics were transformed into the CLASSCUP classification scheme, and were related to the cup anemometer requirements in the Danishcertification system and in the IEC 61400-121 Committee Draft....

  7. Calibration of a spinner anemometer for yaw misalignment measurements

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Demurtas, Giorgio; Zahle, Frederik

    2015-01-01

    from the generic spinner anemometer conversion algorithm. Five different methods were evaluated for calibration of a spinner anemometer on a 500 kW wind turbine. The first three methods used rotor yaw direction as reference angular, while the wind turbine, was yawed in and out of the wind. The fourth...... method used a hub height met-mast wind vane as reference. The fifth method used computational fluid dynamics simulations. Method 1 utilizing yawing of the wind turbine in and out of the wind in stopped condition was the preferred method for calibration of kα. The uncertainty of the yaw misalignment...

  8. Fourier analysis of the aerodynamic behavior of cup anemometers

    International Nuclear Information System (INIS)

    The calibration results (the transfer function) of an anemometer equipped with several cup rotors were analyzed and correlated with the aerodynamic forces measured on the isolated cups in a wind tunnel. The correlation was based on a Fourier analysis of the normal-to-the-cup aerodynamic force. Three different cup shapes were studied: typical conical cups, elliptical cups and porous cups (conical-truncated shape). Results indicated a good correlation between the anemometer factor, K, and the ratio between the first two coefficients in the Fourier series decomposition of the normal-to-the-cup aerodynamic force. (paper)

  9. Total uncertainty of low velocity thermal anemometers for measurement of indoor air movements

    DEFF Research Database (Denmark)

    Jørgensen, F.; Popiolek, Z.; Melikov, Arsen Krikor;

    2004-01-01

    developed mathematical model of the anemometer in combination with a large database of representative room flows measured with a 3-D Laser Doppler anemometer (LDA). A direct comparison between measurements with a thermal anemometer and a 3-D LDA in flows of varying velocity and turbulence intensity shows...

  10. Influence of the Meteorology Mast on a Cup Anemometer

    DEFF Research Database (Denmark)

    Hansen, Martin O. L.; Pedersen, B.M.

    1999-01-01

    The actuator disc model is applied on lattice-type meteorological masts to estimate the influence of the tower on the accuracy of the measured wind speed. Combining the results with corrections for the boom, on which the anemometer is mounted, good agreement is found for measurements made...

  11. An innovative method to calibrate a spinner anemometer without the use of yaw position sensor

    DEFF Research Database (Denmark)

    Demurtas, Giorgio; Janssen, Nick Gerardus Cornelis

    2016-01-01

    A spinner anemometer can be used to measure the yaw misalignment and flow inclination experienced by a wind turbine. Previous calibration methods used to calibrate a spinner anemometer for flow angle measurements were based on measurements of a spinner anemometer with default settings (arbitrary...... values, generally k1,d  =  1 and k2,d  =  1) and a reference yaw misalignment signal measured with a yaw position sensor. The yaw position sensor is normally present in wind turbines for control purposes; however, such a signal is not always available for a spinner anemometer calibration. Therefore......, an additional yaw position sensor was installed prior to the spinner anemometer calibration. An innovative method to calibrate the spinner anemometer without a yaw positions sensor was then developed. It was noted that a non-calibrated spinner anemometer that overestimates (underestimates) the inflow angle...

  12. All semiconductor laser Doppler anemometer at 1.55 microm.

    Science.gov (United States)

    Hansen, René Skov; Pedersen, Christian

    2008-10-27

    We report to our best knowledge the first all semiconductor Laser Doppler Anemometer (LIDAR) for wind speed determination. We will present the design and first experimental results on a focusing coherent cw laser Doppler anemometer for measuring atmospheric wind velocities in the 10 meters to 300 meters distance range. Especially, we will demonstrate that both the output power as well as the demanding coherence properties required from the laser source can be accomplished by an all semiconductor laser. Preliminary tests at a distance of 40 meters indicate a typical signal to noise ratio of 9 dB. This result is obtained at a clear day with an up-date rate of 12 Hz. PMID:18958105

  13. The Sphere Anemometer - A Fast Alternative to Cup Anemometry

    Science.gov (United States)

    Heißelmann, Hendrik; Hölling, Michael; Peinke, Joachim

    The main problem of cup anemometry is the different response time for increasing and decreasing wind velocities due to its moment of inertia. This results in an overestimation of wind speed under turbulent wind conditions, the so-called over-speeding. Additionally, routine calibrations are necessary due to the wear of bearings. Motivated by these problems the sphere anemometer, a new simple and robust sensor for wind velocity measurements without moving parts, was developed at the University of Oldenburg. In contrast to other known thrust-based sensors, the sphere anemometer uses the light pointer principle to detect the deflection of a bending tube caused by the drag force acting on a sphere mounted at its top. This technique allows the simultaneous determination of wind speed and direction via a two-dimensional position sensitive detector.

  14. ACCUWIND - Accurate wind speed measurements in wind energy - Summary report[Cup and sonic anemometers

    Energy Technology Data Exchange (ETDEWEB)

    Friis Pedersen, T.; Dahlberg, J.Aa.; Cuerva, A.; Mouzakis, F.; Busche, P.; Eecen, P.; Sanz-Andres, A.; Franchini, S.; Markkilde Petersen, S.

    2006-07-15

    The cup anemometer is at present the standard instrument used for mean wind speed measurement in wind energy. It is being applied in high numbers around the world for wind energy assessments. It is also applied exclusively for accredited power performance measurements for certification and verification purposes, and for purposes of optimisation in research and development. The revised IEC standard on power performance measurements has now included requirements for classification of cup anemometers. The basis for setting up such requirements of cup anemometers is two EU projects SITEPARIDEN and CLASSCUP from which the proposed classification method for cup anemometers was developed for the IEC standard. While cup anemometers at present are the standard anemometer being used for average wind speed measurements, sonic anemometers have been developed significantly over the last years, and prices have come down. The application of sonic anemometers may increase in wind energy if they prove to have comparable or better operational characteristics compared to cup anemometers, and if similar requirements to sonic anemometers are established as for cup anemometers. Sonic anemometers have historically been used by meteorologists for turbulence measurements, but have also found a role on wind turbine nacelles for wind speed and yaw control purposes. The report on cup and sonic anemometry deals with establishment of robustness in assessment and classification by focus on methods and procedures for analysis of characteristics of cup and sonic anemometers. The methods and procedures provide a platform, hopefully for use in meeting the requirements of the IEC standard on power performance measurements, as well as for development of improved instruments. (au)

  15. Determining the velocity fine structure by a laser anemometer with fixed orientation

    Energy Technology Data Exchange (ETDEWEB)

    Kristensen, Leif; Kirkegaard, P.; Mikkelsen, Torben

    2011-02-15

    We have studied the velocity structure functions and spectra which can be determined by a CW-laser anemometer and a (pulsed) lidar anemometer. We have found useful theoretical expressions for both types of anemometers and compared their filtering of the along-beam turbulent velocity. The purpose has been to establish a basis for remote determining of turbulence fine-structure in terms of the rate of dissipation of specific kinetic energy in the atmospheric boundary layer. (Author)

  16. SiC-Based Miniature High-Temperature Cantilever Anemometer

    Science.gov (United States)

    Okojie, Robert S.; Fralick, Gustave; Saad, George J.

    2004-01-01

    The figure depicts a miniature cantilever-type anemometer that has been developed as a prototype of compact, relatively nonintrusive anemometers that can function at temperatures up to 600 C and that can be expected to be commercially mass-producible at low cost. The design of this anemometer, and especially the packaging aspect of the design, is intended to enable measurement of turbulence in the high-temperature, high-vibration environment of a turbine engine or in any similar environment. The main structural components of the anemometer include a single-crystal SiC cantilever and two polycrystalline SiC clamping plates, all made from chemical-vapor-deposited silicon carbide. Fabrication of these components from the same basic material eliminates thermal-expansion mismatch, which has introduced spurious thermomechanical stresses in cantilever-type anemometers of prior design. The clamping plates are heavily oxidized to improve electrical insulation at high temperature. A cavity that serves as a receptacle for the clamped end of the cantilever is etched into one end of one clamping plate. Trenches that collectively constitute a socket for a multipin electrical plug (for connection to external electronic circuitry) are etched into the opposite end of this clamping plate. Metal strips for electrical contact are deposited on one face of the other clamping plate. Piezoresistive single-crystal SiC thin-film strain gauges are etched in the n-type SiC epilayer in a Wheatstone-bridge configuration. Metal contact pads on the cantilever that extend into the clamping-receptacle area, are obtained by deposition and patterning using standard semiconductor photolithography and etching methods. The cantilever and the two clamping plates are assembled into a sandwich structure that is then clamped in a stainless-steel housing. The Wheatstone- bridge carrying SiC cantilever with the metal contact pads on the piezoresistors is slid into the receptacle in the bottom clamping plate

  17. Spectral coherence along a lidar-anemometer beam

    Energy Technology Data Exchange (ETDEWEB)

    Kristensen, Leif; Kirkegaard, P.; Mann, J.; Mikkelsen, Torben; Nielsen, Morten; Sjoeholm, M.

    2010-10-15

    The theory of measuring the spectral coherence by means of a lidar anemometer has been outlined. It is based on the assumption that the turbulent velocity field can be considered statistically locally isotropic and on the validity of Taylor's hypothesis. This implies that the longitudinal coherence cannot be predicted realistically. Special emphasis has been placed on the effect of line average along the beam. One section has been devoted to the effect of spectral aliasing, which may cause severe problems in the interpretation of measured data. This work is considered the theoretical background for the understanding of the coherences calculated on basis of real date. (Author)

  18. Calibration of a spinner anemometer for wind speed measurements

    DEFF Research Database (Denmark)

    Demurtas, Giorgio; Friis Pedersen, Troels; Zahle, Frederik

    2016-01-01

    of the spinner anemometer is based on the flow distortion caused by the wind turbine spinner. The flow on the spinner surface is measured by means of three 1D sonic sensors mounted on the spinner and a conversion algorithm to convert the wind velocity components measured by the three sonic sensors to horizontal...... wind speed, yaw misalignment and flow inclination angle. The algorithm utilizes two calibration constants that are specific to the spinner shape, blade root design and to the mounting positions of the sonic sensors on the spinner. The present analysis describes methods to determine the calibration...... constant related to wind speed measurements. The first and preferred method is based on the definition of the calibration constant and uses wind speed measurements during the stopped condition of the wind turbine. Two alternative methods that did not require the turbine to be stopped were investigated: one...

  19. Measurements of laboratory turbulence with the 2d-Laser Cantilever Anemometer

    Science.gov (United States)

    Puczylowski, Jaroslaw; Peinke, Joachim; Hoelling, Michael

    2013-11-01

    A newly developed anemometer, the 2d-Laser Cantilever Anemometer, was used to measure the two-dimensional wind speed vector in laboratory-generated turbulence. The anemometer provides a temporal and spatial resolution comparable or even higher to those of commercial hot-wires and thus is an excellent alternative for high-resolution measurements. The 2d-Laser Cantilever Anemometer uses a previously unseen measurement technique in the range of anemometers. The principle is adopted from atomic force microscopes (AFM). A tiny micro-structured cantilever is brought into the airflow, where it experiences a drag force due to the moving fluid. The resulting deflection is measured using the laser pointer principle. Unlike the measuring principle of hot-wires this technique can be applied in challenging environments such as in liquids or very close to walls. Our comparing measurements with the 2d-Laser Cantilever Anemometer and an x-wire were carried out in the wake of rigid bodies and grids. The results show a great agreement with regards to the increment statistics on various scales, power spectra and turbulence intensity, thus proving the new anemometer.

  20. Deviation of Cup and Propeller Anemometer Calibration Results with Air Density

    Directory of Open Access Journals (Sweden)

    Santiago Pindado

    2012-03-01

    Full Text Available The effect of air density variations on the calibration constants of several models of anemometers has been analyzed. The analysis was based on a series of calibrations between March 2003 and February 2011. Results indicate a linear behavior of both calibration constants with the air density. The effect of changes in air density on the measured wind speed by an anemometer was also studied. The results suggest that there can be an important deviation of the measured wind speed with changes in air density from the one at which the anemometer was calibrated, and therefore the need to take this effect into account when calculating wind power estimations.

  1. An Auto-Associative Residual Processing and K-means Clustering Approach for Anemometer Health Assessment

    Directory of Open Access Journals (Sweden)

    David Siegel

    2011-01-01

    Full Text Available This paper presents a health assessment methodology, as well as specific residual processing and figure of merit algorithms for anemometers in two different configurations. The methodology and algorithms are applied to data sets provided by the Prognostics and Health Management Society 2011 Data Challenge. The two configurations consist of the “paired” data set in which two anemometers are positioned at the same height, and the “shear” data set which includes an array of anemometers at different heights. Various wind speed statistics, wind direction, and ambient temperature information are provided, in which the objective is to classify the anemometer health status during a set of samples from a 5 day period. The proposed health assessment methodology consists of a set of data processing steps that include: data filtering and pre-processing, a residual or difference calculation, and a k-means clustering based figure of merit calculation. The residual processing for the paired data set was performed using a straightforward difference calculation, while the shear data set utilized an additional set of algorithm processing steps to calculate a weighted residual value for each anemometer. The residual processing algorithm for the shear data set used a set of auto-associative neural network models to learn the underlying correlation relationship between the anemometer sensors and to calculate a weighted residual value for each of the anemometer wind speed measurements. A figure of merit value based on the mean value of the smaller of the two clusters for the wind speed residual is used to determine the health status of each anemometer. Overall, the proposed methodology and algorithms show promise, in that the results from this approach resulted in the top score for the PHM 2011 Data Challenge Competition. Using different clustering algorithms or density estimation methods for the figure of merit calculation is being considered for future work.

  2. Measurement of air velocity in animal occupied zones using an ultrasonic anemometer

    OpenAIRE

    Wagenberg, van, A.V.; Leeuw, van der, R.

    2003-01-01

    The air velocity in the animal occupied zone (AOZ) of a pig facility influences the thermal comfort of pigs and is affected by the ventilation system in the building. Little is known about the relationship between the air velocity in the AOZ and the ventilation system design. This article describes the development and a practical test of an air velocity measuring system in the AOZ using ultrasonic anemometers. The anemometers were protected by a wire protection cage, which resulted in a lower...

  3. Highly resolved measurements of atmospheric turbulence with the new 2d-Atmospheric Laser Cantilever Anemometer

    Science.gov (United States)

    Jeromin, A.; Schaffarczyk, A. P.; Puczylowski, J.; Peinke, J.; Hölling, M.

    2014-12-01

    For the investigation of atmospheric turbulent flows on small scales a new anemometer was developed, the so-called 2d-Atmospheric Laser Cantilever Anemometer (2d-ALCA). It performs highly resolved measurements with a spatial resolution in millimeter range and temporal resolution in kHz range, thus detecting very small turbulent structures. The anemometer is a redesign of the successfully operating 2d-LCA for laboratory application. The new device was designed to withstand hostile operating environments (rain and saline, humid air). In February 2012, the 2d-ALCA was used for the first time in a test field. The device was mounted in about 53 m above ground level on a lattice tower near the German North Sea coast. Wind speed was measured by the 2d-ALCA at 10 kHz sampling rate and by cup anemometers at 1 Hz. The instantaneous wind speed ranged from 8 m/s to 19 m/s at an average turbulence level of about 7 %. Wind field characteristics were analyzed based on cup anemometer as well as 2d-ALCA. The combination of both devices allowed the study of atmospheric turbulence over several magnitudes in turbulent scales.

  4. Effects of precipitation on sonic anemometer measurements of turbulent fluxes in the atmospheric surface layer

    Science.gov (United States)

    Zhang, Rongwang; Huang, Jian; Wang, Xin; Zhang, Jun A.; Huang, Fei

    2016-06-01

    Effects caused by precipitation on the measurements of three-dimensional sonic anemometer are analyzed based on a field observational experiment conducted in Maoming, Guangdong Province, China. Obvious fluctuations induced by precipitation are observed for the outputs of sonic anemometer-derived temperature and wind velocity components. A technique of turbulence spectra and cospectra normalized in the framework of similarity theory is utilized to validate the measured variables and calculated fluxes. It is found that the sensitivity of sonic anemometer-derived temperature to precipitation is significant, compared with that of the wind velocity components. The spectra of wind velocity and cospectra of momentum flux resemble the standard universal shape with the slopes of the spectra and cospectra at the inertial subrange, following the -2/3 and -4/3 power law, respectively, even under the condition of heavy rain. Contaminated by precipitation, however, the spectra of temperature and cospectra of sensible heat flux do not exhibit a universal shape and have obvious frequency loss at the inertial subrange. From the physical structure and working principle of sonic anemometer, a possible explanation is proposed to describe this difference, which is found to be related to the variations of precipitation particles. Corrections for errors of sonic anemometer-derived temperature under precipitation is needed, which is still under exploration.

  5. ACCUWIND - Classification of five cup anemometers according to IEC61400-12-1

    Energy Technology Data Exchange (ETDEWEB)

    Friis Pedersen, T.; Dahlberg, J.Aa.; Busche, P.

    2006-05-15

    The characteristics of five cup anemometers were investigated in detail, and data are presented in figures and tables. The characteristics include: normal wind tunnel calibrations; angular response measurements at 5, 8 and 11m/s; torque coefficient curve measurements from combined tilt and ramp-gust tests, torque coefficient curve measurements for non-tilted conditions; rotor inertia measurements and measurements of friction of bearings at temperatures -10 deg. C to 40 deg. C. The characteristics are fitted to two different time domain cup anemometer models, and simulations of the cup anemometers are made with artificial wind generators to make classifications according to annex I and J of the standard IEC 61400-12-1 on power performance measurements. Results of classification are shown in graphs of systematic deviations and class index tables. (au)

  6. All semiconductor laser Doppler anemometer at 1.55 μm

    DEFF Research Database (Denmark)

    Hansen, Rene Skov; Pedersen, Christian

    2008-01-01

    We report to our best knowledge the first all semiconductor Laser Doppler Anemometer (LIDAR) for wind speed determination. We will present the design and first experimental results on a focusing coherent cw laser Doppler anemometer for measuring atmospheric wind velocities in the 10 meters to 300...... meters distance range. Especially, we will demonstrate that both the output power as well as the demanding coherence properties required from the laser source can be accomplished by an all semiconductor laser. Preliminary tests at a distance of 40 meters indicate a typical signal to noise ratio of 9 d...

  7. Mathematical analysis of the effect of rotor geometry on cup anemometer response.

    Science.gov (United States)

    Sanz-Andrés, Ángel; Pindado, Santiago; Sorribes-Palmer, Félix

    2014-01-01

    The calibration coefficients of two commercial anemometers equipped with different rotors were studied. The rotor cups had the same conical shape, while the size and distance to the rotation axis varied. The analysis was based on the 2-cup positions analytical model, derived using perturbation methods to include second-order effects such as pressure distribution along the rotating cups and friction. The comparison with the experimental data indicates a nonuniform distribution of aerodynamic forces on the rotating cups, with higher forces closer to the rotating axis. The 2-cup analytical model is proven to be accurate enough to study the effect of complex forces on cup anemometer performance.

  8. Power curve measurement with Spinner Anemometer according to IEC 61400-12-2

    DEFF Research Database (Denmark)

    Demurtas, Giorgio

    In wind industry power performance measurements on site is an increasing challenge due to the larger and larger rotors. An IEC standard on power performance verification with nacelle anemometry, IEC61400-12-2 [1], has been developed and was published 2013. However, nacelle anemometry has a number...... anemometer measurements from two adjacent wind turbines and a met-mast. Due to the site layout, it is possible with the met-mast to measure the power curve of both turbines. The report also presents a method for evaluation of uncertainty related to the spinner anemometer....

  9. The Cup Anemometer, a Fundamental Meteorological Instrument for the Wind Energy Industry. Research at the IDR/UPM Institute

    Directory of Open Access Journals (Sweden)

    Santiago Pindado

    2014-11-01

    Full Text Available The results of several research campaigns investigating cup anemometer performance carried out since 2008 at the IDR/UPM Institute are included in the present paper. Several analysis of large series of calibrations were done by studying the effect of the rotor’s geometry, climatic conditions during calibration, and anemometers’ ageing. More specific testing campaigns were done regarding the cup anemometer rotor aerodynamics, and the anemometer signals. The effect of the rotor’s geometry on the cup anemometer transfer function has been investigated experimentally and analytically. The analysis of the anemometer’s output signal as a way of monitoring the anemometer status is revealed as a promising procedure for detecting anomalies.

  10. Comparison of 3D turbulence measurements using three staring wind lidars and a sonic anemometer

    DEFF Research Database (Denmark)

    Mann, Jakob; Cariou, J.-P.; Courtney, Michael;

    2008-01-01

    Three pulsed lidars were used in staring, non-scanning mode, placed so that their beams crossed close to a 3D sonic anemometer. The goal is to compare lidar volume averaged wind measurement with point measurement reference sensors and to demonstrate the feasibility of performing 3D turbulence...

  11. A Phase-Locked Loop Continuous Wave Sonic Anemometer-Thermometer

    DEFF Research Database (Denmark)

    Larsen, Søren Ejling; Weller, F. W.; Busings, J. A.

    1979-01-01

    A continuous wake sonic anemometer-thermometer has been developed for simultaneous measurements of vertical velocity and temperature. The phase angle fluctuations are detected by means of a monolithic integrated phase-locked loop, the latter feature providing for inexpensive and accurate...

  12. Time-of-Flight Laser Anemometer for Velocity Measurements in the Atmosphere

    DEFF Research Database (Denmark)

    Lading, Lars; Jensen, A. Skov; Fog, C.;

    1978-01-01

    In the system described, a 1W CW Ar II laser operates over a range of 70 m with spatial and temporal resolutions of mm and 10-100 m sec, respectively. Mean wind velocities obtained with a cup-anemometer agree within 10%...

  13. Calibration of a spinner anemometer for flow angle measurements by use of wind turbine yawing

    DEFF Research Database (Denmark)

    Demurtas, Giorgio; Friis Pedersen, Troels

    The present report describes a method to calibrate a spinner anemometer ow angle measurements. The turbine is yawed several times (5 times approximately 60 with respect to the wind direction) in steady wind (> 6 m/s) and measurements of yaw position (measured by a yaw position sensor) and yaw...

  14. Final report on EURAMET project No. 827: LDA-based intercomparison of anemometers

    Science.gov (United States)

    Müller, Harald

    2013-01-01

    A regional air speed comparison between six EURAMET laboratories used an ultrasonic anemometer and a laser Doppler anemometer (LDA) at air speeds between 0.2 m s-1 and 40 m s-1. Based on periodic calibrations at the pilot laboratory (PTB), the uncertainty contributed to the comparison by the LDA was 0.2% and the uncertainty contributed by the ultrasonic anemometer depended on the air speed and varied between 2.95% and 0.11%. The degrees of equivalence between the participants were notably better for the laser Doppler anemometer data than for the ultrasonic anemometer data. For example, using the 95% chi-squared consistency check, 16 of the original 59 participant data points were removed as discrepant from the ultrasonic data set, but only one point was discrepant in the LDA data. A possible explanation is that the LDA is non-intrusive and therefore does not alter the velocity field in the wind tunnel whereas the ultrasonic device does produce blockage effects. The results of this comparison (and prior EURAMET and CIPM comparisons) indicate a need for more attention to blockage effects during air speed calibrations and their effect on air speed uncertainty statements. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  15. On the Use of Hot-Sphere Anemometers in a Highly Transient Flow in a Double-Skin Facade

    DEFF Research Database (Denmark)

    Jensen, Rasmus Lund; Kalyanova, Olena; Hyldgård, Carl-Erik

    2007-01-01

    from the measurement of air velocity in the occupied zone. The velocity is higher and the flow is more transient, the anemometer is subjected to high loads of direct solar radiation and wide temperature ranges and, finally, the direction of the flow is important. The flow in the double-skin façade...... measured by the anemometer. Temperature compensation is the working principle of anemometers. The ability to compensate for different temperatures when exposed to solar radiation is investigated in a controlled environment using a powerful lamp as a radiant heat source. In the double-skin façade, both...... upward and downward flow will occur and therefore, it is important to determine the direction of the flow. A simple method using two hot-sphere anemometers separated by a small plate is discussed....

  16. Pointwise and scanning laser anemometer measurements in steady and unsteady separated turbulent boundary layers

    Science.gov (United States)

    Simpson, R. L.; Chehroudi, B.; Shivaprasad, B. G.

    1982-01-01

    The physical features of steady and unsteady freestream separating turbulent boundary layers that have been determined by pointwise laser anemometer measurements are outlined. It is seen that the large-scale structures control the outer region's backflow behavior. Near the wall, the mean backflow velocity profile for both the steady and unsteady cases is found to scale on the maximum negative mean velocity and its distance from the wall. A description is given of a scanning laser anemometer that produces nearly instantaneous velocity profiles for examing the temporal features of these large-scale structures. Also described is a 'zero-wake' seeder that supplies particles to the outer shear layer and freestream flow with a minimal disturbance.

  17. Fiber optic anemometer based on silicon Fabry-Pérot interferometer

    Science.gov (United States)

    Liu, Guigen; Hou, Weilin; Qiao, Wei; Han, Ming

    2015-05-01

    Flowmeters have been finding vast applications in all kinds of industrial processes, such as process control, food quality surveillance, wind turbines, environment monitoring, etc. In this paper, we propose a new anemometer which consists of a Fabry-Pérot interferometer (FPI) implemented using a thin silicon mounted on the tip of an optical fiber. The anemometer takes advantage of the superior thermal and optical properties of silicon. Silicon is transparent to infrared wavelength, while it absorbs visible light. Thus, the silicon FPI can be heated by a beam injected from a red diode laser while the infrared signals go through it without any interference from the heating light. The heat loss from the silicon film will increase when the sensor is placed in stronger flow (wind), which induces a decrease in the optical path of the silicon FPI, which lead to blueshifts the output spectrum. A higher wind speed corresponds to a larger wavelength shift. By tuning the heating power, the response range and sensitivity of the anemometer is changed. Experimental results demonstrate that a wavelength shift -0.574 nm was observed for a wind speed of 4 m/s. Better sensitivity is to be expected when stronger heating applied. The proposed sensor also features simple structure, low cost and fast response.

  18. Assessing indoor low velocity measurements. Pt. 1: Effect of measuring method on quantifying room air flow - comparison LDA - thermal anemometers; Messtechnische Erfassung characteristischer Kenngroessen von Raumluftstroemungen. T. 1: Einfluss der Messmethode bei der Bewertung von Raumluftstroemungen - Vergleich LDA - thermische Anemometer

    Energy Technology Data Exchange (ETDEWEB)

    Sefker, T.; Wolters, T. [Gebr. Trox GmbH, Neukirchen-Vluyn (Germany)

    2004-03-01

    Within the scope of an EU research project, Thermal Anemometers (TA) from different manufacturers were compared by means of a 'Laser Doppler Anemometer' (LDA) under model room conditions. Comparisons were carried out with different kinds of aerodynamic room flows, air change rates and heat loads. This article presents the measuring principle of thermal and 'Laser Doppler Anemometers', it demonstrates the measurements in the scale 1:1, it also demonstrates how the measured air velocities for the estimation of the aerodynamic room flows by means of statistical methods are developed and it presents the results of these measurements. (orig.) [German] Im Rahmen eines EU-Forschungsprojekts wurden Thermische Anemometer (TA) verschiedener Hersteller unter Modellraumbedingungen mit einem Laser Doppler Anemometer (LDA) verglichen. Vergleiche wurden fuer verschiedene Raumstroemungsarten, Luftwechsel und Raumlasten durchgefuehrt. Dieser Beitrag stellt das Messprinzip von thermischen und Laser Doppler Anemometern vor, demonstriert die Messungen im Massstab 1:1, zeigt wie die gemessenen Luftgeschwindigkeiten zur Beurteilung der Raumstroemung mittels statistischen Methoden weiterverarbeitet wurden und praesentiert die Ergebnisse dieser Betrachtungen. (orig.)

  19. Numerical Simulation on Floating Behavior of Buoyancy Tank Foundation of Anemometer Tower

    Institute of Scientific and Technical Information of China (English)

    丁红岩; 韩艳丽; 张浦阳

    2014-01-01

    The intact stability and damage stability of a model of an anemometer tower with buoyancy tank founda-tion are computed by the finite element software MOSES in this paper. The natural period of the anemometer tower is discussed through frequency domain analysis. The influence of a single factor, such as towing point position, wave height, wave direction and wave period, on towing stability is discussed through time domain analysis. At the same time, the towing stability under the condition of various combinations of many factors is analyzed based on the meas-ured data of the target area. Computer simulation results show that the intact stability is preferable and the damage stability is sufficient under the condition of plenty of subdivisions. Within the scope of the buoyancy tank foundation, the higher the towing point position is, the better the stability is. Wave height has a great impact on the motion ampli-tude of buoyancy tank foundation, but the effect on the acceleration is not obvious;wave period has a great impact on the acceleration, while the effect on the motion amplitude is not obvious;following-waves towing is more conducive to safety than atry.

  20. Determining the Velocity Fine Structure by a Laser Anemometer in VAD operation

    DEFF Research Database (Denmark)

    Kristensen, Leif; Kirkegaard, Peter; Mikkelsen, Torben

    The theoretical basis for determining the dissipation ε, by measuring the velocity structure function with a CW-laser anemometer has been derived in the case of calm wind conditions. If there is a well defined mean wind speed the structure function can be obtained by having the laser beam pointing....... Then it is necessary to “create” a mean wind by turning the laser beam. Since the instrument is not moved the beam will describe a cone which could be a VAD-scanning. In any case the measured velocity components will not be parallel and this implies that the measured structure function will contain a...... term which is proportional to the total variance. The theoretical expression for the line-filtered structure function is derived in two equivalent ways, one in physical space and one in wave-number space, of which the last can be reliably evaluated by numerical integration. Also a practical approximate...

  1. Phase doppler anemometer - commissioning tests for measurement of water aerosol sizes and velocities in flashing jets

    International Nuclear Information System (INIS)

    A state-of-the-art phase Doppler Anemometer (PDA) has been commissioned at AECL Research, Whiteshell Laboratories to undertake the measurement of size and velocity of water droplets generated in flashing jets. Experimental data on size and velocity distribution of water aerosols in flashing jets are required to support licensing of current multi-unit and single-unit CANDU (CANada Deuterium Uranium) stations. This paper presents the methodology involved in choosing the magnitudes of the various operating parameters of the PDA such as laser power and sensitivity of photomultiplier tubes in obtaining the experimental data. The various calibration and validation procedures used are also discussed. Size and velocity distributions in a typical flashing jet are presented. (author)

  2. Note: Signal conditioning of a hot-film anemometer for a periodic flow rate monitoring system.

    Science.gov (United States)

    Mantovani, Federico; Tagliaferri, Cristian

    2011-12-01

    A flow monitoring system based on a constant temperature hot-film anemometer is presented. The device has been designed to monitor a dispensing process of extremely low quantities of adhesive material. The monitoring device presented in this paper is useful in industrial applications where exact flow speed tracking is not needed, but reliability and tolerance to parameters variability are essential. During the design of the device, problems related to the physical characteristic of the calorimetric sensor, in particular its thermal capacitance, and to the periodic nature of the monitored flow have been taken into account and suitable solutions have been implemented. The schematic representation of the monitoring device together with the experimental results obtained by monitoring fluids with different physical characteristics are presented.

  3. Automation of the positioning of a laser anemometer flow rate measurement bench

    International Nuclear Information System (INIS)

    The laser anemometry technique is commonly used by the Core Hydraulics Laboratory of the CEA for the determination of the field of flow rates inside fuel rod bundles. The adjustment of measurement point coordinates represents an important part of the velocimetry campaign. In order to increase the number of measurements and the preciseness of the positioning operation, the automation of these preliminary tasks was decided. This work describes first the principle of Doppler laser velocimetry, the components of the measurement system and their functioning conditions. Then, the existing software for tuning and measurement is presented. A new software, called PAMELA, for the automatic positioning of the laser anemometer using a moving table with 5 degrees of freedom, has been developed and tested. This software, written with the LabView language, advises the operator, drives the bench and executes the tunings with a greater precision than manually. (J.S.)

  4. Using sonic anemometer temperature to measure sensible heat flux in strong winds

    Directory of Open Access Journals (Sweden)

    S. P. Burns

    2012-09-01

    Full Text Available Sonic anemometers simultaneously measure the turbulent fluctuations of vertical wind (w' and sonic temperature (Ts', and are commonly used to measure sensible heat flux (H. Our study examines 30-min heat fluxes measured with a Campbell Scientific CSAT3 sonic anemometer above a subalpine forest. We compared H calculated with Ts to H calculated with a co-located thermocouple and found that, for horizontal wind speed (U less than 8 m s−1, the agreement was around ±30 W m−2. However, for U ≈ 8 m s−1, the CSAT H had a generally positive deviation from H calculated with the thermocouple, reaching a maximum difference of ≈250 W m−2 at U ≈ 18 m s−1. With version 4 of the CSAT firmware, we found significant underestimation of the speed of sound and thus Ts in high winds (due to a delayed detection of the sonic pulse, which resulted in the large CSAT heat flux errors. Although this Ts error is qualitatively similar to the well-known fundamental correction for the crosswind component, it is quantitatively different and directly related to the firmware estimation of the pulse arrival time. For a CSAT running version 3 of the firmware, there does not appear to be a significant underestimation of Ts; however, a Ts error similar to that of version 4 may occur if the CSAT is sufficiently out of calibration. An empirical correction to the CSAT heat flux that is consistent with our conceptual understanding of the Ts error is presented. Within a broader context, the surface energy balance is used to evaluate the heat flux measurements, and the usefulness of side-by-side instrument comparisons is discussed.

  5. Software corrected hot wire thermal lag for the constant voltage anemometer featuring a constant bandwidth at the selected compensation setting

    OpenAIRE

    Sarma, Garimella,; Comte-Bellot, Geneviève; Faure, Thierry M.

    1998-01-01

    International audience Software compensation correction for thermal lag of a hot wire in the application of a constant voltage anemometer (CVA) for turbulence measurements in the boundary layer of a supersonic wind tunnel has been demonstrated. The CVA was used with a fixed compensation setting while measuring the in situ thermal lag (time constant) of the hot wire. Using the measured time constant, corrections are applied to the fixed compensation output of the CVA in postprocessing of th...

  6. Is the nacelle mounted anemometer an acceptable option in performance testing?

    Energy Technology Data Exchange (ETDEWEB)

    Dahlberg, J.A. [FFA, The Aeronautical Research Inst. of Sweden, Bromma (Sweden); Frandsen, S.; Madsen, H.A; Antoniou, I.; Friis Pedersen, T. [Risoe National Lab., Roskilde (Denmark); Hunter, R. [RES, Renewable Energy Systems, Glasgow, Scotland (United Kingdom); Klug, H. [DEWI, Wilhelmshaven (Germany)

    1999-03-01

    Although the nacelle anemometer method has been used for power verification purposes for several years, it is only relatively recently that a full understanding of its limitations has emerged. the technique is totally dependent upon the assumption that the nacelle to free wind speed relationship established for a reference turbine in free air can be applied universally to other turbines. Facts emerged from research projects have shown that this assumption is unjustified. In the present paper facts are presented of which some have not been identified nor presented before. E.g. the effect related to wake conditions is novel as a phenomena and the size of the effect can be considerable. The analysis shows that the total error caused by the effects considered in this paper can, in the worst case reach unacceptable high values, 24%, but by taking precautionary measures the errors can be kept at acceptable low levels, 4%. It is found probable that the future use of nacelle anemometry for power performance verification will be subject to strong restrictions. (au)

  7. Investigation on Characterizing Heated Pulsating Flows with Hot Wire Anemometers - A Hands-On Approach

    Directory of Open Access Journals (Sweden)

    Marius Alexandru PANAIT

    2014-06-01

    Full Text Available The pulsating heated flows are traditionally a difficult subject to treat with conventional hot wire or film methods. Special factors that complicate matters are flow reversal and non linear flow effects of vortices and wire probe wake disturbances on the heat transfer to the hot film or wire sensor in heated pulsating flows. The presence of these strongly nonlinear and unknown terms leads to great difficulties in calibration of hot film probes in this particular regime. The paper analyses the current state of matters in the field and reports a series of solutions that have been practically tested in a case of a high speed pulsated heated flow. Normally such measurements are made in a non-contact fashion using a LDV system or various visualization techniques but there have been recent attempts to use a constant temperature hot wire anemometer system (CTA.To obtain meaningful calibration for hot wire films in hot pulsating flows, a comparison system on other principles (LDV was used, as well as a specially designed nozzle to replace the calibrator unit that could not be operated with heated fluid due to structural integrity reasons. The method as described below works well for the expected speed range that could be generated using the special nozzle.

  8. Laser Anemometer Measurements of the Flow Field in a 4:1 Pressure Ratio Centrifugal Impeller

    Science.gov (United States)

    Skoch, G. J.; Prahst, P. S.; Wernet, M. P.; Wood, J. R.; Strazisar, A. J.

    1997-01-01

    A laser-doppler anemometer was used to obtain flow-field velocity measurements in a 4:1 pressure ratio, 4.54 kg/s (10 lbm/s), centrifugal impeller, with splitter blades and backsweep, which was configured with a vaneless diffuser. Measured through-flow velocities are reported for ten quasi-orthogonal survey planes at locations ranging from 1% to 99% of main blade chord. Measured through-flow velocities are compared to those predicted by a 3-D viscous steady flow analysis (Dawes) code. The measurements show the development and progression through the impeller and vaneless diffuser of a through-flow velocity deficit which results from the tip clearance flow and accumulation of low momentum fluid centrifuged from the blade and hub surfaces. Flow traces from the CFD analysis show the origin of this deficit which begins to grow in the inlet region of the impeller where it is first detected near the suction surface side of the passage. It then moves toward the pressure side of the channel, due to the movement of tip clearance flow across the impeller passage, where it is cut by the splitter blade leading edge. As blade loading increases toward the rear of the channel the deficit region is driven back toward the suction surface by the cross-passage pressure gradient. There is no evidence of a large wake region that might result from flow separation and the impeller efficiency is relatively high. The flow field in this impeller is quite similar to that documented previously by NASA Lewis in a large low-speed backswept impeller.

  9. Investigation of noise in Lightwave Synthesized Frequency Sweeper seeded LIDAR anemometers from leakage through the Acousto Optic Modulators

    DEFF Research Database (Denmark)

    Pedersen, Anders Tegtmeier; Lindelöw, Per Jonas Petter

    2009-01-01

    Lightwave Synthesized Frequency Sweepers (LSFS) have potential use as lightsources in lidar anemometers. In this paper noise due to leakage in the acousto optic modulators in an LSFS is investigated. Theoretical expressions describing the build-up of noise in the LSFS due to leakage are derived...... Train (FSPT) modulated lidars the leakage will give rise to rapidly growing noise in the bins which corresponds to the signal from low radial wind velocities. It is likely that noise canceling techniques similar to those used for RIN removal has to be deployed for measurements of low wind velocities....

  10. Aircraft-based in-situ calibration of a hot-wire anemometer in a compressible flow

    Science.gov (United States)

    Hugo, Ronald J.; Nowlin, Scott R.; Hahn, Ila L.; Bishop, Kenneth P.; McCrae, Kimberley A.

    1999-08-01

    High-bandwidth measurements of atmospheric velocity and temperature fluctuations in the high troposphere/low stratosphere using aircraft-based hot-wire anemometers requires calibration. An in-situ calibration characterizing wire sensitivity at high subsonic Mach numbers and relatively low temperatures and pressures was performed. Custom designed constant-temperature and constant-current anemometer equipment has been used for these atmospheric measurements. Two sets of calibration experiments are described, one in a controlled laboratory environment where the Mach number and temperature were varied and the other on board a C-135E aircraft. The aircraft test were conducted by varying the flight Mach number at different pressure altitudes while flying into an upper-level low pressure area, achieving variability in velocity, temperature, and pressure. Results obtained indicate increased sensitivity to velocity while operating the wire at a low overheat ratio. The calibration data was fit to a form of King's law which was found to work well for in-situ calibrations.

  11. The measurement of sperm motility by the fibre optic Doppler anemometer as a prediction of bovine fertility

    Science.gov (United States)

    Bullock, J. G.; Ross, D. A.

    The fibre optic Doppler anemometer (FODA) has been used to develop an accurate quantitative method of routinely assessing bull fertility. This method is of importance to the artificial insemination industry because the present qualitative estimation, performed by viewing semen using a microscope, can only set broad limits of quality. Laser light from the FODA was directed into diluted semen samples and the back scattered light was measured. A digital correlator was used to calculate the signal correlation of the back scattered light. The resultant data curves were interpreted in terms of the collective motility and swimming speed of the spermatozoa using a microcomputer. These two parameters are accepted as being indicative of fertility. The accuracy of this method is demonstrated by examination of results obtained in an experiment where enzymes, thought to alter fertility, were added to semen. The effect of the enzymes on the swimming speed and motility was clearly demonstrated.

  12. Accuracy of Sonic Anemometers: Laminar Wind-Tunnel Calibrations Compared to Atmospheric In Situ Calibrations Against a Reference Instrument

    Science.gov (United States)

    Högström, Ulf; Smedman, Ann-Sofi

    Two Gill Solent Ultrasonic anemometers, models 1012R2 and 1210R3, weretested in field parallel measurements against a windvane based hot-film anemometerwith additional sensors for temperature and wet-bulb temperature, the MIUU (MIUU:Meteorology Institute, Uppsala University) instrument. This instrument was shown toretain its precision from laminar wind-tunnel tests when used in atmospheric turbulentflow. This contrasts strongly to the observed results for the two sonic anemometers,which were first calibrated in laminar wind-tunnel flow. Individual three-dimensionalcalibration matrices were constructed, and were shown to reduce the remaining calibration uncertainty for the wind speed to 0.4-0.8% for all azimuths and for angles of attack within ±40°. In the field intercomparison tests of the sonics against the MIUU instrument, it was found that the precision not only of the mean wind speed but of all second-order moments studied (variances and covariances, with and without temperature) deteriorated by a factor of typically three to four. Most of the scatter appears to be random, but in the case of the wind speed, a clear dependence on wind direction is found as well. It is concluded that the correction for the effect of the vertical supporting rods of the R2 and R3 instruments, which gives nearly perfect agreement for laminar flow, does not work entirely satisfactory in the natural turbulent flow. This, in turn, is likely to be so because of high sensitivity of the wake behind the cylindrical supporting rods to the character of the approach flow.

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

    Directory of Open Access Journals (Sweden)

    Y. Narita

    2009-09-01

    Full Text Available Data from research vessels and merchant ships are used to estimate ocean CO2 uptake via parameterizations of the gas transfer velocity (k and measurements of the difference between the concentration of CO2 in the ocean (pCO2sw and atmosphere (pCO2atm and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be in error due to air flow distortion by the ship's hull and superstructure introducing biases into the measured wind speed. The effect of airflow distortion on estimates of the transfer velocity was examined by modelling the airflow around the three-dimensional geometries of the research vessels Hakuho Maru and Mirai, using the Large Eddy Simulation code GERRIS. For airflows within ±45° of the bow the maximum bias was +16%. For wind speed of 10 m s−1 to 15 m s−1, a +16% bias in wind speed would cause an overestimate in the calculated value of k of 30% to 50%, depending on which k parameterisation is used. This is due to the propagation of errors when using quadratic or cubic parameterizations. Recommendations for suitable anemometer locations on research vessels are given. The errors in transfer velocity may be much larger for typical merchant ships, as the anemometers are generally not as well-exposed as those on research vessels. Flow distortion may also introduce biases in the wind speed dependent k parameterizations themselves, since these are obtained by relating measurements of the CO2 flux to measurements of the wind speed and the CO2 concentration difference. To investigate this, flow distortion effects were estimated for three different platforms from which wind speed dependent parameterizations are published. The estimates ranged from –4% to +14% and showed that flow distortion may have a significant impact on wind speed dependent parameterizations. However, the wind biases are not large enough to explain the differences at high wind speeds in parameterizations which are based on

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

    Directory of Open Access Journals (Sweden)

    Y. Narita

    2010-06-01

    Full Text Available Data from platforms, research vessels and merchant ships are used to estimate ocean CO2 uptake via parameterisations of the gas transfer velocity (k and measurements of the difference between the partial pressures of CO2 in the ocean (pCO2 sw and atmosphere (pCO2 atm and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be in error due to air flow distortion by the ship's hull and superstructure introducing biases into the measured wind speed. The effect of airflow distortion on estimates of the transfer velocity was examined by modelling the airflow around the three-dimensional geometries of the research vessels Hakuho Maru and Mirai, using the Large Eddy Simulation code GERRIS. For airflows within ±45° of the bow the maximum bias was +16%. For wind speed of 10 m s−1 to 15 m s−1, a +16% bias in wind speed would cause an overestimate in the calculated value of k of 30% to 50%, depending on which k parameterisation is used. This is due to the propagation of errors when using quadratic or cubic parameterisations. Recommendations for suitable anemometer locations on research vessels are given. The errors in transfer velocity may be much larger for typical merchant ships, as the anemometers are generally not as well-exposed as those on research vessels. Flow distortion may also introduce biases in the wind speed dependent k parameterisations themselves, since these are obtained by relating measurements of the CO2 flux to measurements of the wind speed and the CO2 concentration difference. To investigate this, flow distortion effects were estimated for three different platforms from which wind speed dependent parameterisations are published. The estimates ranged from −4% to +14% and showed that flow distortion may have a significant impact on wind speed dependent parameterisations. However, the wind biases are not large enough to explain the differences at high wind speeds in parameterisations

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

    Science.gov (United States)

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

    2010-06-01

    Data from platforms, research vessels and merchant ships are used to estimate ocean CO2 uptake via parameterisations of the gas transfer velocity (k) and measurements of the difference between the partial pressures of CO2 in the ocean (pCO2 sw) and atmosphere (pCO2 atm) and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be in error due to air flow distortion by the ship's hull and superstructure introducing biases into the measured wind speed. The effect of airflow distortion on estimates of the transfer velocity was examined by modelling the airflow around the three-dimensional geometries of the research vessels Hakuho Maru and Mirai, using the Large Eddy Simulation code GERRIS. For airflows within ±45° of the bow the maximum bias was +16%. For wind speed of 10 m s-1 to 15 m s-1, a +16% bias in wind speed would cause an overestimate in the calculated value of k of 30% to 50%, depending on which k parameterisation is used. This is due to the propagation of errors when using quadratic or cubic parameterisations. Recommendations for suitable anemometer locations on research vessels are given. The errors in transfer velocity may be much larger for typical merchant ships, as the anemometers are generally not as well-exposed as those on research vessels. Flow distortion may also introduce biases in the wind speed dependent k parameterisations themselves, since these are obtained by relating measurements of the CO2 flux to measurements of the wind speed and the CO2 concentration difference. To investigate this, flow distortion effects were estimated for three different platforms from which wind speed dependent parameterisations are published. The estimates ranged from -4% to +14% and showed that flow distortion may have a significant impact on wind speed dependent parameterisations. However, the wind biases are not large enough to explain the differences at high wind speeds in parameterisations which are based on eddy

  16. Three Dimensional Wind Speed and Flux Measurement over a Rain-fed Soybean Field Using Orthogonal and Non-orthogonal Sonic Anemometer Designs

    Science.gov (United States)

    Thomas, T.; Suyker, A.; Burba, G. G.; Billesbach, D.

    2014-12-01

    The eddy covariance method for estimating fluxes of trace gases, energy and momentum in the constant flux layer above a plant canopy fundamentally relies on accurate measurements of the vertical wind speed. This wind speed is typically measured using a three dimensional ultrasonic anemometer. These anemometers incorporate designs with transducer sets that are aligned either orthogonally or non-orthogonally. Previous studies comparing the two designs suggest differences in measured 3D wind speed components, in particular vertical wind speed, from the non-orthogonal transducer relative to the orthogonal design. These differences, attributed to additional flow distortion caused by the non-orthogonal transducer arrangement, directly affect fluxes of trace gases, energy and momentum. A field experiment is being conducted over a rain-fed soybean field at the AmeriFlux site (US-Ne3) near Mead, Nebraska. In this study, ultrasonic anemometers featuring orthogonal transducer sets (ATI Vx Probe) and non-orthogonal transducer sets (Gill R3-100) collect high frequency wind vector and sonic temperature data. Sensible heat and momentum fluxes and other key sonic performance data are evaluated based on environmental parameters including wind speed, wind direction, temperature, and angle of attack. Preliminary field experiment results are presented.

  17. Radiator cooling flow measurement method with propeller type anemometer; Radiator reikyaku furyo sokuteiho (propeller shiki fusokukei wo mochiita sokutei hoho no kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    Oguma, T.; Takada, H.; Yahashi, Y. [Isuzu Motors Ltd., Tokyo (Japan); Komatsubara, T. [Tokyo Radiator MFG. Co. Ltd., Tokyo (Japan)

    1995-04-20

    An examination was carried out for the accurate measurement method of a radiator cooling flow in order to design an engine cooling system for automobiles. An I-type hot-wire anemometer used to be employed conventionally, but a small propeller type anemometer was developed for this examination. This measurement device was such that the revolution of a propeller type sensor was read by an optical cable and that the number of revolution thus obtained was converted to a wind velocity by an arithmetic unit. In addition, the device was capable of recording data for the maximum of 64 items simultaneously, and also capable of measuring the distribution and average value of wind velocity. It showed superiority to the conventional method in the comparison of directivity, accuracy, wind velocity distribution, vehicle adaptability and durability. The I-type hot-wire anemometer showed excessive measurements since it had a tendency of measuring a wind velocity component other than vertical inflow component into a radiator on account of its directivity. The directivity of the sensor developed this time was so reliable that, if the yaw of the wind velocity vector was within 45 degrees, only the vertical inflow component was measured with errors within 10%. Pressure loss was 1 to 8% of a radiator, which was negligible taking a whole vehicle into consideration. 2 refs., 11 figs., 1 tab.

  18. Using an optical fibre anemometer to measure the speed of the electric wind in a negative polarity, atmospheric corona discharge

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, A; Lamb, D W [Physics and Electronics, School of Biological, Biomedical and Molecular Sciences, University of New England, Armidale, NSW 2351 (Australia)

    2005-01-01

    Coronas are partial discharges that occur in regions of non-uniform electric fields adjacent to conductors stressed to high voltages. Negative, Trichel-pulse coronas in air occur when a dc, negative-polarity, high voltage is applied to a conductor. Trichel pulses in atmospheric air generate significant amounts of ozone as well as electrical and acoustic noise. Under the right conditions these coronas can be a precursor to complete electrical breakdown of the air gap due to a reduction in the density of neutral molecules resulting from a combination of localised heating and convective air flow generated by the movement of negative ions. An optical fibre anemometer, based on a Mach-Zehnder interferometer has been constructed to measure the speed of the wind generated in the point-plane gap of a negative, Trichel-pulse corona discharge in atmospheric air. The sensing arm of the fibre interferometer is subjected to controlled, repetitive bursts of infrared radiation from a CO{sub 2} laser and the combination of localised heating and convective cooling by the corona wind results in fringe shifts which are directly calibrated to the speed of the wind. This paper reports on the nature of the calibration process and presents some radial profiles of wind speed in the corona gap.

  19. Using an optical fibre anemometer to measure the speed of the electric wind in a negative polarity, atmospheric corona discharge

    International Nuclear Information System (INIS)

    Coronas are partial discharges that occur in regions of non-uniform electric fields adjacent to conductors stressed to high voltages. Negative, Trichel-pulse coronas in air occur when a dc, negative-polarity, high voltage is applied to a conductor. Trichel pulses in atmospheric air generate significant amounts of ozone as well as electrical and acoustic noise. Under the right conditions these coronas can be a precursor to complete electrical breakdown of the air gap due to a reduction in the density of neutral molecules resulting from a combination of localised heating and convective air flow generated by the movement of negative ions. An optical fibre anemometer, based on a Mach-Zehnder interferometer has been constructed to measure the speed of the wind generated in the point-plane gap of a negative, Trichel-pulse corona discharge in atmospheric air. The sensing arm of the fibre interferometer is subjected to controlled, repetitive bursts of infrared radiation from a CO2 laser and the combination of localised heating and convective cooling by the corona wind results in fringe shifts which are directly calibrated to the speed of the wind. This paper reports on the nature of the calibration process and presents some radial profiles of wind speed in the corona gap

  20. Measurements of Flow Distortion within the IRGASON Integrated Sonic Anemometer and CO_2/H_2O Gas Analyzer

    Science.gov (United States)

    Horst, T. W.; Vogt, R.; Oncley, S. P.

    2016-07-01

    Wind-tunnel and field measurements are analyzed to investigate flow distortion within the IRGASON integrated sonic anemometer and CO_2/H_2O gas analyzer as a function of wind speed, wind direction and attack angle. The wind-tunnel measurements are complimentary to the field measurements, and the dependence of the wind-tunnel mean-wind-component flow-distortion errors on wind direction agrees well with that of the field measurements. The field measurements exhibit significant overestimation of the crosswind variance and underestimation of the momentum flux with respect to an adjacent CSAT3 sonic, as well as a transfer of turbulent kinetic energy from the streamwise wind component to the cross-stream wind components. In contrast, we find attenuation of only a few percent in the vertical velocity variance and the vertical flux of sonic temperature. The attenuation of the fluxes appears to be caused to a large extent by decorrelation between the horizontal and vertical-velocity components and between the vertical velocity and sonic temperature. Additional flow distortion due to transducer shadowing reduces to some extent the overestimation, but also increases the underestimation of the IRGASON turbulence statistics.

  1. 1.5 μm lidar anemometer for true air speed, angle of sideslip, and angle of attack measurements on-board Piaggio P180 aircraft

    Science.gov (United States)

    Augere, B.; Besson, B.; Fleury, D.; Goular, D.; Planchat, C.; Valla, M.

    2016-05-01

    Lidar (light detection and ranging) is a well-established measurement method for the prediction of atmospheric motions through velocity measurements. Recent advances in 1.5 μm Lidars show that the technology is mature, offers great ease of use, and is reliable and compact. A 1.5 μm airborne Lidar appears to be a good candidate for airborne in-flight measurement systems. It allows measurements remotely, outside aircraft aerodynamic disturbance, and absolute air speed (no need for calibration) with great precision in all aircraft flight domains. In the framework of the EU AIM2 project, the ONERA task has consisted of developing and testing a 1.5 μm anemometer sensor for in-flight airspeed measurements. The objective of this work is to demonstrate that the 1.5 μm Lidar sensor can increase the quality of the data acquisition procedure for aircraft flight test certification. This article presents the 1.5 μm anemometer sensor dedicated to in-flight airspeed measurements and describes the flight tests performed successfully on-board the Piaggio P180 aircraft. Lidar air data have been graphically compared to the air data provided by the aircraft flight test instrumentation (FTI) in the reference frame of the Lidar sensor head. Very good agreement of true air speed (TAS) by a fraction of ms‑1, angle of sideslip (AOS), and angle of attack (AOA) by a fraction of degree were observed.

  2. 1.5 μm lidar anemometer for true air speed, angle of sideslip, and angle of attack measurements on-board Piaggio P180 aircraft

    International Nuclear Information System (INIS)

    Lidar (light detection and ranging) is a well-established measurement method for the prediction of atmospheric motions through velocity measurements. Recent advances in 1.5 μm Lidars show that the technology is mature, offers great ease of use, and is reliable and compact. A 1.5 μm airborne Lidar appears to be a good candidate for airborne in-flight measurement systems. It allows measurements remotely, outside aircraft aerodynamic disturbance, and absolute air speed (no need for calibration) with great precision in all aircraft flight domains. In the framework of the EU AIM2 project, the ONERA task has consisted of developing and testing a 1.5 μm anemometer sensor for in-flight airspeed measurements. The objective of this work is to demonstrate that the 1.5 μm Lidar sensor can increase the quality of the data acquisition procedure for aircraft flight test certification. This article presents the 1.5 μm anemometer sensor dedicated to in-flight airspeed measurements and describes the flight tests performed successfully on-board the Piaggio P180 aircraft. Lidar air data have been graphically compared to the air data provided by the aircraft flight test instrumentation (FTI) in the reference frame of the Lidar sensor head. Very good agreement of true air speed (TAS) by a fraction of ms−1, angle of sideslip (AOS), and angle of attack (AOA) by a fraction of degree were observed. (special issue article)

  3. A micro-scale hot wire anemometer based on low stress (Ni/W) multi-layers deposited on nano-crystalline diamond for air flow sensing

    Science.gov (United States)

    Talbi, A.; Gimeno, L.; Gerbedoen, J.-C.; Viard, R.; Soltani, A.; Mortet, V.; Preobrazhensky, V.; Merlen, A.; Pernod, P.

    2015-12-01

    A linear array of microscale thermal anemometers has been designed, fabricated and characterized. The sensitive element consists of a self-compensated-stress multilayer (Ni/W) patterned to form a wire with length, width, and thickness close to 200 μm, 5 μm and 2 μm respectively. The wire is deposited and supported by prongs made of nano-crystalline diamond (NCD) of about 2 μm in thickness. Due to its high Young’s modulus, NCD allows a very high mechanical toughness without the need for thicker support for the hot wire. Also, depending on grain size, the NCD is able to present thermal conductivity smaller than 10 W mK-1, providing good thermal insulation from the substrate and less conductive end losses to the prongs. The sensor was characterized experimentally. Its electrical and thermal properties were obtained first in the absence of fluid flow. The results confirm the effectiveness of thermal insulation and the mechanical robustness of the structure. The fluidic characterizations were performed and analysed in the case of an airflow with velocities of up to 30 m s-1.

  4. Analysis of the air flow generated by an air-assisted sprayer equipped with two axial fans using a 3D sonic anemometer.

    Science.gov (United States)

    García-Ramos, F Javier; Vidal, Mariano; Boné, Antonio; Malón, Hugo; Aguirre, Javier

    2012-01-01

    The flow of air generated by a new design of air assisted sprayer equipped with two axial fans of reversed rotation was analyzed. For this goal, a 3D sonic anemometer has been used (accuracy: 1.5%; measurement range: 0 to 45 m/s). The study was divided into a static test and a dynamic test. During the static test, the air velocity in the working vicinity of the sprayer was measured considering the following machine configurations: (1) one activated fan regulated at three air flows (machine working as a traditional sprayer); (2) two activated fans regulated at three air flows for each fan. In the static test 72 measurement points were considered. The location of the measurement points was as follow: left and right sides of the sprayer; three sections of measurement (A, B and C); three measurement distances from the shaft of the machine (1.5 m, 2.5 m and 3.5 m); and four measurement heights (1 m, 2 m, 3 m and 4 m). The static test results have shown significant differences in the module and the vertical angle of the air velocity vector in function of the regulations of the sprayer. In the dynamic test, the air velocity was measured at 2.5 m from the axis of the sprayer considering four measurement heights (1 m, 2 m, 3 m and 4 m). In this test, the sprayer regulations were: one or two activated fans; one air flow for each fan; forward speed of 2.8 km/h. The use of one fan (back) or two fans (back and front) produced significant differences on the duration of the presence of wind in the measurement point and on the direction of the air velocity vector. The module of the air velocity vector was not affected by the number of activated fans.

  5. Automation of the positioning of a laser anemometer flow rate measurement bench; Automatisation du positionnement d`un banc de mesure de vitesses d`ecoulements par anemometrie laser

    Energy Technology Data Exchange (ETDEWEB)

    Gobillot, G

    1998-01-24

    The laser anemometry technique is commonly used by the Core Hydraulics Laboratory of the CEA for the determination of the field of flow rates inside fuel rod bundles. The adjustment of measurement point coordinates represents an important part of the velocimetry campaign. In order to increase the number of measurements and the preciseness of the positioning operation, the automation of these preliminary tasks was decided. This work describes first the principle of Doppler laser velocimetry, the components of the measurement system and their functioning conditions. Then, the existing software for tuning and measurement is presented. A new software, called PAMELA, for the automatic positioning of the laser anemometer using a moving table with 5 degrees of freedom, has been developed and tested. This software, written with the LabView language, advises the operator, drives the bench and executes the tunings with a greater precision than manually. (J.S.) 16 refs.

  6. Sensor Tip Optimization for a Thermal Anemometer for Determining Convection Intensity in Quench Baths%测定淬火槽对流强度的热流速仪探头的优化设计

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Due to the occurrence of complex fluid flow patterns in a quench tank which will significantly impact hardening results,it is important to develop a compact flow measuring device.A typical quench process involves immersion of austenitized steel into a quench bath which affects the circulation of the fluid and results in non-uniform flow and thermal striations in the quenchant.This non-uniformity of fluid flow patterns therefore results in variations of heat transfer and subsequent inconsistent hardening of the parts.In this paper,the systematic optimization of the tip of a thermal anemometer used to measure flow rates in a quench tank are reviewed.%淬火槽中复杂的液流形态会明显影响淬硬结果,因此开发一套结构紧凑的液流测量装置就显得很重要了.一个典型的淬火过程包括把已奥氏体化了的钢浸没在淬火槽中,这一过程势必影响液流的循环,使其形成不均匀的液流和热波动,由此而引起传热变化,导致零件的不均匀淬火.本文介绍了用于测量淬火槽中液流速率的热风仪探头的系统优化设计.

  7. Measurement of the local void fraction in two-phase air-water flow with a hot-film anemometer; Mesure du taux de vide local en ecoulement diphasique eau-air par un anemometre a film chaud

    Energy Technology Data Exchange (ETDEWEB)

    Delhaye, J. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1968-07-01

    The experimental knowledge of the local void-fraction is basic for the derivation of the constitutive equations of two-phase flows. This report deals with measurements of the local void-fraction based on the use of a constant temperature hot-film anemometer associated with a multichannel analyser. After determining the void-fraction profile along a diameter of a vertical pipe (40 mm I.D.), in which air and water flow upwards, we compare the void-fraction averaged over the diameter with the average value measured directly by a {gamma}-ray method. Two runs were made in bubble flow and a third in slug flow. The two methods give results in a good agreement especially for bubble flow. The void-fraction averaged over the cross-section was also calculated from the different profiles and compared in a good manner with the experimental results of R. ROUMY. For bubble flow we verified the theory of S.G. BANKOFF about the shape of the void-fraction profiles. (author) [French] Nous proposons une methode de mesure du taux de vide local a en ecoulement diphasique, basee sur l'emploi d'un anemometre a film chaud a temperature constante dont on etudie la repartition du signal en amplitude dans un analyseur multicanaux. Ayant trace un profil de taux de vide local suivant un diametre d'une conduite verticale de section circulaire parcourue par un ecoulement ascendant d'eau et d'air, nous avons compare la moyenne de {alpha} sur ce diametre a la valeur obtenue par une methode d'absorption de rayons {gamma}. Les essais ont ete faits en ecoulements a bulles et a bouchons. Les deux methodes donnent des resultats concordants en particulier pour les ecoulements a bulles. Le taux de vide moyenne dans la section, calcule a partir des differents profils, a egalement ete compare avec succes aux resultats experimentaux de R. ROUMY. Dans l'etude de la structure radiale des ecoulements a bulles, nous avons verifie l'hypothese de S.G. BAJMKOFF. (auteur)

  8. Arkansas' Anemometer Loan Program

    Energy Technology Data Exchange (ETDEWEB)

    Fernando Vego

    2012-10-11

    The measurement campaign had one year duration from 04/01/2011 to 03/31/2012 and was taken at 20m and 34m with NRG instrumentation. The data was analyzed weekly to check inconsistencies and validity and processed using Excel, Flexpro and Windographer standard Edition Version 2.04. The site analyzed is located in the Waldron, Arkansas in Scott County. It is an open site for most of the direction sectors with immediate roughness class of 1.5. It has seasonally directional winds, of which the most energetic come from the southern direction. The vertical wind profile shows moderate wind shear that varies by season as well.

  9. Reviews Book: Voyage to the Heart of the Matter: The ATLAS Experiment at CERN Equipment: SEP Spectroscope Books: Quantum Gods / The Universe Places to visit: The Royal Institution of Great Britain Book: What is this Thing Called Science? Book: Don't be Such a Scientist: Talking Substance in the Age of Style Equipment: La Crosse Anemometer Book: Wonder and Delight Web Watch

    Science.gov (United States)

    2010-05-01

    WE RECOMMEND SEP Spectroscope Flatpacked classroom equipment for pupils aged 10 and over Quantum Gods Book attacks spiritualism and religion with physics The Universe Study of whether physics alone can explain origin of universe La Crosse Anemometer Handheld monitor is packed with useful features Wonder and Delight Essays in science education in honour of Eric Rogers WORTH A LOOK Voyage to the Heart of the Matter: The ATLAS Experiment at CERN Pop-up book explains background to complex physics The Royal Institution of Great Britain RI museum proves interesting but not ideal for teaching What is this Thing Called Science? Theory and history of science in an opinionated study Don't be Such a Scientist: Talking Substance in the Age of Style Explanation of how science is best communicated to the public WEB WATCH Particle physics simulations vary in complexity, usefulness and how well they work

  10. Design and Calibration of an Inexpensive Digital Anemometer

    Science.gov (United States)

    Hernandez-Walls, R.; Rojas-Mayoral, E.; Baez-Castillo, L.; Rojas-Mayoral, B.

    2008-01-01

    An inexpensive and easily implemented device to measure wind velocity is proposed. This prototype has the advantage of being able to measure both the speed and the direction of the wind in two dimensions. The device utilizes a computational interface commonly referred to as a "mouse." The mouse proposed for this prototype contains an optical…

  11. Potential errors in using one anemometer to characterize the wind power over an entire rotor disk

    Science.gov (United States)

    Simon, R. L.

    1982-01-01

    Wind data collected at four levels on a 90-m tower in a prospective wind farm area are used to evaluate how well the 10-m wind speed data with and without intermittent vertical profile measurements compare with the 90-m tower data. If a standard, or even predictable, wind speed profile existed, there would be no need for a large, expensive tower. This cost differential becomes even more significant if several towers are needed to study a prospective wind farm.

  12. Temperature corrections for constant temperature and constant current hot-wire anemometers

    International Nuclear Information System (INIS)

    Changes in the ambient fluid temperature change the calibration curve for velocity measurements taken using hot-wire anemometry. New correction methods are proposed to account for the effects of relatively large temperature changes in the heat-transfer process and on the fluid properties. The corrections do not assume any particular heat-transfer correlation, and they do not require multiple calibrations over a range of temperatures. The corrections are derived for the constant temperature and constant current modes of operation

  13. Evaluation of Tower Shadowing on Anemometer Measurements at Los Alamos National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Bruggeman, David Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-14

    The objective of this study is to evaluate the effect of tower shadowing from the meteorology towers at LANL during 2014. This study is in response to the Department of Energy Meteorological Coordinating Council visit in 2015 that recommended an evaluation of any biases in the wind data introduced by the tower and boom alignment at all meteorology towers.

  14. Assessment of dispersion parameterizations through wind data measured by three sonic anemometers in a urban canopy

    Directory of Open Access Journals (Sweden)

    L. Mortarini

    2009-05-01

    Full Text Available One year of continuous wind and turbulence measurements at three levels (5, 9 and 25 m on a mast located in the suburb of the city of Turin were collected. Those recorded during April 2007 are analyzed and their main characteristics are presented and discussed. The analysis includes, at each level, mean, standard deviation, Skewness, Kurtosis for the 3-D wind components and sonic temperature. The integral time scales for the 3-D wind components are also computed and friction velocity and Monin-Obukhov length are determined as well. In particular, the wind standard deviation profiles as a function of stability are compared to the literature predictions for flat undisturbed terrain. It is found that, while the vertical component agrees reasonably well, the horizontal components deviate from the prescribed values, as expected considering the buildings and other obstacles effects and the high percentage of low-wind conditions. Also the integral time scales, estimated by the autocorrelation functions, are compared to the literature predictions, finding significant differences, again attributed to the low-wind speed occurrences.

  15. Development of a "Digital Bridge" Thermal Anemometer for Turbulence Measurements Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Thermal anemometry (a.k.a. hot-wire anemometry) has been a key experimental technique in fluid mechanics for many decades. Due to the small physical size and high...

  16. Assessment of wind conditions at a fjord inlet by complementary use of sonic anemometers and lidars

    DEFF Research Database (Denmark)

    Jakobsen, Jasna Bogunovic; Cheynet, Etienne; Snæbjörnsson, Jonas;

    2015-01-01

    Wind velocity measurement devices based on the remote optical sensing, lidars, are extensively applied in wind energy research and wind farm operation. The present paper demonstrates the relevance and potential of lidar measurements for other windsensitive structures such as long-span bridges...

  17. Hot Wire Anemometer Turbulence Measurements in the wind Tunnel of LM Wind Power

    DEFF Research Database (Denmark)

    Fischer, Andreas

    Flow measurements were carried out in the wind tunnel of LM Wind Power A/S with a Dantec Streamline CTA system to characterize the flow turbulence. Besides the free tunnel flow with empty test section we also investigated the tunnel flow when two grids with different mesh size were introduced...... downstream of the nozzle contraction. We used two different hot wire probes: a dual sensor miniature wire probe (Dantec 55P61) and a triple sensor fiber film probe (Dantec 55R91). The turbulence intensity measured with the dual sensor probe in the empty tunnel section was significantly lower than the one...

  18. Laser anemometer measurements in an annular cascade of core turbine vanes and comparison with theory

    Science.gov (United States)

    Goldman, L. J.; Seashultz, R. G.

    1982-01-01

    Laser measurements were made in an annular cascade of stator vanes operating at an exit critical velocity ratio of 0.78. Velocity and flow angles in the blade to blade plane were obtained at every 10 percent of axial chord within the passage and at 1/2 axial chord downstream of the vanes for radial positions near the hub, mean and tip. Results are presented in both plot and tabulated form and are compared with calculations from an inviscid, quasi three dimensional computer program. The experimental measurements generally agreed well with these theoretical calculations, an indication of the usefulness of this analytic approach.

  19. Multi-mode fibre laser Doppler anemometer (LDA) with high spatial resolution for the investigation of boundary layers

    Energy Technology Data Exchange (ETDEWEB)

    Buettner, L.; Czarske, J. [Group Laser Metrology, Laser Zentrum Hannover e.V., Hollerithallee 8, 30419, Hannover (Germany)

    2004-01-01

    A novel LDA system using laser diode arrays and multi-mode fibers in the transmitting optics is presented. The use of high numerical aperture multi-mode step-index fibres results in measurement volumes with, for example, 80 {mu}m length and minimal speckle effects. Because of the high spatial resolution and low relative fringe spacing variation of {delta}d/d{approx}5 x 10{sup -4} the multi-mode fibre LDA is predestined for investigating turbulent flows. Boundary layer measurements carried out show excellent agreement with theoretical velocity profiles. (orig.)

  20. Acoustic and Laser Doppler Anemometer Results for Confluent, 22-Lobed, and Unique-Lobed Mixer Exhaust Systems for Subsonic Jet Noise Reduction

    Science.gov (United States)

    Salikuddin, M.; Martens, S.; Shin, H.; Majjigi, R. K.; Krejsa, Gene (Technical Monitor)

    2002-01-01

    The objective of this task was to develop a design methodology and noise reduction concepts for high bypass exhaust systems which could be applied to both existing production and new advanced engine designs. Special emphasis was given to engine cycles with bypass ratios in the range of 4:1 to 7:1, where jet mixing noise was a primary noise source at full power takeoff conditions. The goal of this effort was to develop the design methodology for mixed-flow exhaust systems and other novel noise reduction concepts that would yield 3 EPNdB noise reduction relative to 1992 baseline technology. Two multi-lobed mixers, a 22-lobed axisymmetric and a 21-lobed with a unique lobe, were designed. These mixers along with a confluent mixer were tested with several fan nozzles of different lengths with and without acoustic treatment in GEAE's Cell 41 under the current subtask (Subtask C). In addition to the acoustic and LDA tests for the model mixer exhaust systems, a semi-empirical noise prediction method for mixer exhaust system is developed. Effort was also made to implement flowfield data for noise prediction by utilizing MGB code. In general, this study established an aero and acoustic diagnostic database to calibrate and refine current aero and acoustic prediction tools.

  1. Izmerenie vektora skorosti lazernym dopplerovskim anemometrom (LDA s volokonno-opticheskimi traktami[Measurement of the velocity vector of the laser Doppler anemometer (LDA with fiber-optic tracts

    Directory of Open Access Journals (Sweden)

    S. N. Khotyaintsev

    1982-12-01

    Full Text Available The problems encountered in the development of laser Doppler velocity vector meter optical fiber paths. The scheme of the meter, including three-dimensional velocity meter made by differential circuit. Describes the experimental setup and the results of the experiment by measuring the two projections of the velocity vector.

  2. Stable atmospheric boundary-layer experiment in Spain (SABLES 98): A report

    DEFF Research Database (Denmark)

    Cuxart, J.; Yague, C.; Morales, G.;

    2000-01-01

    boundary layer (SBL). Instrumentation deployed on two meteorological masts (of heights 10 m and 100 m) included five sonic anemometers, 15 thermocouples, five cup anemometers and three propeller anemometers, humidity sensors and radiometers. A Sensitron mini-sodar and a tethered balloon were also operated...

  3. Design and Study of a Low-Cost Laboratory Model Digital Wind Power Meter

    Science.gov (United States)

    Radhakrishnan, Rugmini; Karthika, S.

    2010-01-01

    A vane-type low-cost laboratory model anemometer cum power meter is designed and constructed for measuring low wind energy created from accelerating fluids. The constructed anemometer is a device which records the electrical power obtained by the conversion of wind power using a wind sensor coupled to a DC motor. It is designed for its…

  4. Wind measurements for wind energy applications. A review

    DEFF Research Database (Denmark)

    Mortensen, N.G.

    1994-01-01

    A review is given of the error sources and uncertainties in cup and sonic anemometry. In both cases the effects of the tower, boom and other mounting arrangements, as well as the siting of the anemometer, should be considered carefully. Cup anemometer measurements are inherently biased due to the...

  5. Conversion of Measured Turbulence Spectra from Temporal to Spatial Domain

    DEFF Research Database (Denmark)

    Buchhave, Preben; Velte, Clara Marika

    2017-01-01

    number of turbulence measurements results in time records from stationary probes, either hot-wire probes (hot-wire anemometers, HWA) or laser beam probes (laser Doppler anemometers, LDA). The spatial structure of the turbulent velocity field is then inferred by “Taylor’s hypothesis,”as first presented...

  6. Aerodynamical errors on tower mounted wind speed measurements due to the presence of the tower

    Energy Technology Data Exchange (ETDEWEB)

    Bergstroem, H. [Uppsala Univ. (Sweden). Dept. of Meteorology; Dahlberg, J.Aa. [Aeronautical Research Inst. of Sweden, Bromma (Sweden)

    1996-12-01

    Field measurements of wind speed from two lattice towers showed large differences for wind directions where the anemometers of both towers should be unaffected by any upstream obstacle. The wind speed was measured by cup anemometers mounted on booms along the side of the tower. A simple wind tunnel test indicates that the boom, for the studied conditions, could cause minor flow disturbances. A theoretical study, by means of simple 2D flow modelling of the flow around the mast, demonstrates that the tower itself could cause large wind flow disturbances. A theoretical study, based on simple treatment of the physics of motion of a cup anemometer, demonstrates that a cup anemometer is sensitive to velocity gradients across the cups and responds clearly to velocity gradients in the vicinity of the tower. Comparison of the results from the theoretical study and field tests show promising agreement. 2 refs, 8 figs

  7. 高速噴霧流と周囲流の流動特性 : 第2報, ノズル形状の影響

    OpenAIRE

    細谷, 肇; 小保方, 富夫

    1993-01-01

    There have been many experiments to characterize Diesel fuel spray under steady-state conditions. However, the appropriate number of holes and the hole position on the sac to be used in the experiment are not clear. To address this subject, we investigate Diesel type spray flows using a laser Doppler anemometer (LDA) and a phase Doppler anemometer (PDA). Spray flow characteristics such as mean and fluctuating two-component velocities, two-dimensional distribution of particle diameter and the ...

  8. Thermal flow micro sensors

    OpenAIRE

    Elwenspoek, M

    1999-01-01

    A review is given on sensors fabricated by silicon micromachining technology using the thermal domain for the measurement of fluid flow. Attention is paid especially to performance and geometry of the sensors. Three basic types of thermal flow sensors are discussed: anemometers, calorimetric flow sensors and time of flight flow sensors. Anemometers may comprise several heaters and temperature sensors and from a geometric point of view are similar sometimes for calorimetric flow sensors. We fi...

  9. Description of the Columbia Basin Wind Energy Study (CBWES)

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Larry K.; Pekour, Mikhail S.; Nelson, Danny A.

    2012-10-01

    The purpose of this Technical Report is to provide background information about the Columbia Basin Wind Energy Study (CBWES). This study, which was supported by the U.S. Department of Energy’s Wind and Water Power Program, was conducted from 16 November 2010 through 21 March 2012 at a field site in northeastern Oregon. The primary goal of the study was to provide profiles of wind speed and wind direction over the depth of the boundary layer in an operating wind farm located in an area of complex terrain. Measurements from propeller and vane anemometers mounted on a 62 m tall tower, Doppler Sodar, and Radar Wind Profiler were combined into a single data product to provide the best estimate of the winds above the site during the first part of CBWES. An additional goal of the study was to provide measurements of Turbulence Kinetic Energy (TKE) near the surface. To address this specific goal, sonic anemometers were mounted at two heights on the 62 m tower on 23 April 2011. Prior to the deployment of the sonic anemometers on the tall tower, a single sonic anemometer was deployed on a short tower 3.1 m tall that was located just to the south of the radar wind profiler. Data from the radar wind profiler, as well as the wind profile data product are available from the Atmospheric Radiation Measurements (ARM) Data Archive (http://www.arm.gov/data/campaigns). Data from the sonic anemometers are available from the authors.

  10. Full-Scale Spectrum of Boundary-Layer Winds

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo; Larsen, Søren Ejling; Lundtang Petersen, Erik

    2016-01-01

    Extensive mean meteorological data and high frequency sonic anemometer data from two sites in Denmark, one coastal onshore and one offshore, have been used to study the full-scale spectrum of boundary-layer winds, over frequencies f from about 1 yr−1 to10 Hz. 10-min cup anemometer data are used...... to estimate the spectrum from about 1 yr−1 to 0.05 min−1; in addition, using 20-Hz sonic anemometer data, an ensemble of 1-day spectra covering the range 1 day−1 to 10 Hz has been calculated. The overlapping region in these two measured spectra is in good agreement. Classical topics regarding the various...... of the three velocity components over a wide range from 1 day−1 to 10 Hz, which is useful in determining the necessary sample duration when measuring turbulence statistics in the boundary layer....

  11. Flow tilt angles near forest edges - Part 1: Sonic anemometry

    DEFF Research Database (Denmark)

    Dellwik, Ebba; Mann, Jakob; Larsen, Klaus Steenberg

    2010-01-01

    An analysis of flow tilt angles from a fetch-limited beech forest site with clearings is presented in the context of vertical advection of carbon dioxide. Flow angles and vertical velocities from two sonic anemometers by different manufacturers were analyzed. Instead of using rotations, where zero......-flow angles were assumed for neutral flow, the data was interpreted in relation to upstream and downstream forest edges. Uncertainties caused by flow distortion, vertical misalignment and limited sampling time (statistical uncertainty) were evaluated and found to be highly significant. Since the attack angle...... distribution of the wind on the sonic anemometer is a function of atmospheric stratification, an instrumental error caused by imperfect flow distortion correction is also a function of the atmospheric stratification. In addition, it is discussed that the sonic anemometers have temperature dependent off...

  12. High resolution climatological wind measurements for wind energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Bergstroem, H. [Uppsala Univ. (Sweden). Dept. of Meteorology

    1996-12-01

    Measurements with a combined cup anemometer/wind vane instrument, developed at the Department of Meteorology in Uppsala, is presented. The instrument has a frequency response of about 1 Hz, making it suitable not only for mean wind measurements, but also for studies of atmospheric turbulence. It is robust enough to be used for climatological purposes. Comparisons with data from a hot-film anemometer show good agreement, both as regards standard deviations and the spectral decomposition of the turbulent wind signal. The cup anemometer/wind vane instrument is currently used at three sites within the Swedish wind energy research programme. These measurements are shortly described, and a few examples of the results are given. 1 ref, 10 figs

  13. Wind lidar evaluation at the Danish wind test site in Høvsøre

    DEFF Research Database (Denmark)

    Smith, D.A.; Harris, M.; Coffey, A.S.;

    2006-01-01

    Initial assessments of a wind lidar have shown the technology to have significant potential for wind field measurements in the wind energy industry. A more extended evaluation is now reported using a scanning lidar next to a meteorological mast with calibrated anemometers at the Risø wind test si...... in Høvsøre on the windy northwest coast of Denmark. Results are presented of wind speed comparisons at heights up to 100 m above ground level showing excellent correlation between the lidar and the cup anemometers. Copyright © 2006 John Wiley & Sons, Ltd....

  14. Atmospheric stability and turbulence fluxes at Horns Rev—an intercomparison of sonic, bulk and WRF model data

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo; Hahmann, Andrea N.

    2012-01-01

    Direct estimations of turbulent fluxes and atmospheric stability were performed from a sonic anemometer at 50 m height on a meteorological mast at the Horns Rev wind farm in the North Sea. The stability and flux estimations from the sonic measurements are compared with bulk results from a cup...... anemometer at 15 m height and potential temperature differences between the water and the air above. Surface flux estimations from the advanced weather research and forecast (WRF) model are also validated against the sonic and bulk data. The correlation between the sonic and bulk estimates of friction...

  15. Meso- and Micro-scale modelling in China: Wind measurements at 12 meteorological stations in NE China (Dongbei)

    DEFF Research Database (Denmark)

    Lindelöw-Marsden, Petter; Enevoldsen, Karen

    This report is part of the presentation of the results obtained during the CMA component of the Wind Energy Development (WED) program. It describes the techniques and results of the project “A02 Measurements” which produced wind measurements from mast mounted anemometers and vanes in Dongbei...... in North-East China during 2008 to 2010. Main focus is given to the equipment supplied by Risø and the measurements taken by these systems. Specifically it shows the results of a comparison between the P2546A and EL15-1A cup anemometer....

  16. 沙漠環境風洞の特性計測 (定常風と脈動風)

    OpenAIRE

    林,農; 原, 豊; 康, 仁勝; 加藤, 優; 藤本,裕己; 若,良二; 田川, 公太朗; 神近,牧男

    2007-01-01

    Wind characteristics generated by the wind tunnel named Desert Environment Wind Tunnel, which can generate arbitrary pattern of wind speed variation by changing the angle of pitch of the blower blades, were investigated with both of a hot-wire anemometer and a ultrasonic anemometer. Distributions of the wind velocity components (v, w) in a plane perpendicular to the mainstream (u-direction), whose wind speed varies like a sine wave, were measured downstream at x = 1.5m from the exit of wind t...

  17. Experimental Study of Near Wake Flow Behind a Rectangular Cylinder

    OpenAIRE

    Abdollah Shadaram; Mahdi A. Fard; Noorallah Rostamy

    2008-01-01

    The turbulence characteristics of the near wake flow behind a rectangular cylinder is investigated in a two-dimensional analysis using a hot-wire anemometer. The time-averaged and fluctuating components of the velocity are measured for a cylinder having various width-to-height (b h-1) ratios. The measurements are carried out in a low-speed wind tunnel. Data from hot-wire anemometer is collected by a data acquisition system. The results show that the turbulence intensity in the flow wake decre...

  18. Power curve investigation

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Gómez Arranz, Paula

    This report describes the analysis carried out with data from a given turbine in a wind farm and a chosen period. The purpose of the analysis is to correlate the power output of the wind turbine to the wind speed measured by a nacelle-mounted anemometer. The measurements and analysis are not perf...

  19. Telltale wind indicator for the Mars Phoenix lander

    DEFF Research Database (Denmark)

    Gunnlaugsson, H.P.; Honstein-Rathlou, C.; Merrison, J.P.;

    2008-01-01

    The Telltale wind indicator is a mechanical anemometer designed to operate on the Martian surface as part of the meteorological package on the NASA Phoenix lander. It consists of a lightweight cylinder suspended by Kevlar fibers and is deflected under the action of wind. Imaging of the Telltale d...

  20. Hot film anemometry. Citations from the NTIS data base

    Science.gov (United States)

    Habercom, G. E., Jr.

    1980-08-01

    The principles of hot film anemometer operation are summarized; wind tunnel and laboratory tests are described; flow field dynamics are discussed involving turbulence, boundary layers, separation, shock waves, and stresses; mathematical models and analysis are presented; computer techniques are outlined; and a number of applications are given. This updated bibliography contains 58 citations, 3 of which are new entries to the previous edition.

  1. Inter comparison of two commercially available SODARS

    DEFF Research Database (Denmark)

    Ejsing Jørgensen, Hans; Antoniou, I.

    2002-01-01

    In the present work two SODARs of the phased array type are compared indirectly using the top anemometer readings from the Risoe 125m instrumented meteorology mast. The two SODARs are the AeroVironment 4000 and the Metek DSDPA.90-24....

  2. Inclined test of nacelle wind lidar

    DEFF Research Database (Denmark)

    Courtney, Michael

    A nacelle wind lidar, placed at ground level, is tested by inclining the laser beams to bisect a measurement mast at a known distance and height. The horizontal wind speed reported by the lidar is compared to a reference cup anemometer mounted on the mast at the comparison height....

  3. Comparison test of WLS200S-22 (Final)

    DEFF Research Database (Denmark)

    Wagner, Rozenn

    This report presents the result of the test on a sector scanning Windcube WLS200S simulating offshore measurements from a coastal site. A comparison is made between the lidar measurements and those of a cup anemometer and a vane mounted on an on-shore met mast at a distance of 1.6 km....

  4. スワール噴射弁における燃料噴射率と噴霧性状の相互評価法の研究

    OpenAIRE

    石間, 経章; 助名, 亮一; 小保方, 富夫; 河内, 勝義; 小林, 一光

    2003-01-01

    Characteristics of spray injected from the five types of swirl nozzle, which were the same design however differed in the static flow rates as 600, 700, 800, 900 and 1 000 cc/min respectively, have been evaluated by a phase Doppler anemometer (PDA) and a

  5. 40 CFR 59.208 - Charcoal lighter material testing protocol.

    Science.gov (United States)

    2010-07-01

    ... monoxide poisoning and the reduction of oxygen.) (2) Test structure components. The following test... digital air velocity meter, DavisΔ DTA 4000 vane anemometer, or equivalent to method 1A of 40 CFR part 60... ring—Rigid metal cylinder 21.6 centimeters (8.5 inches) in diameter with indicators to determine...

  6. Velocity and turbulence measurements of impellers discharge flow for multi-stage centrifugal blower

    International Nuclear Information System (INIS)

    This paper assesses some results of an experimental investigation on a 4-stage centrifugal blower. The two-dimensional velocity and turbulence field at the exit of the first and fourth stage was measured in some working conditions of the machine, by a single hot-wire anemometer rotated twice about its own axis

  7. Flow Dynamics In Eccentrically Rotating Flasks Used For Dispersant Effectiveness Testing

    Science.gov (United States)

    The evaluation of dispersant effectiveness used for oil spills is commonly done using tests conducted in laboratory flasks. We used a Hot Wire Anemometer (HWA) to characterize mixing dynamics in the Swirling Flask (SF) and the Baffled Flask (BF), the latter is being considered b...

  8. Eddy Correlation Measurements of Sea Spray Aerosol Fluxes

    NARCIS (Netherlands)

    Leeuw, G. de; Moerman, M.M.; Zappa, C.J.; McGillis, W.R.; Norris, S.; Smith, M.

    2007-01-01

    Fluxes of primary marine aerosol in the sub-micron fraction were measured using a flux package consisting of a sonic anemometer, a Condensation Particle Counter (CPC) and an optical particle counter (OPC) equipped with a heated inlet. Whereas the CPC provides the total particle number flux of partic

  9. Laser scanning of a recirculation zone on the Bolund escarpment

    DEFF Research Database (Denmark)

    Mann, Jakob; Angelou, Nikolas; Sjöholm, Mikael;

    2012-01-01

    Rapid variations in the height of the recirculation zone are measured with a scanning wind lidar over a small escarpment on the Bolund Peninsula. The lidar is essentially a continuous-wave laser Doppler anemometer with the capability of rapidly changing the focus distance and the beam direction...... scanning systems is done primarily for that purpose....

  10. Hub Height Ocean Winds over the North Sea Observed by the NORSEWInD Lidar Array: Measuring Techniques, Quality Control and Data Management

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Stein, Detlef; Courtney, Michael;

    2013-01-01

    In the North Sea, an array of wind profiling wind lidars were deployed mainly on offshore platforms. The purpose was to observe free stream winds at hub height. Eight lidars were validated prior to offshore deployment with observations from cup anemometers at 60, 80, 100 and 116 m on an onshore m...

  11. Thermal flow micro sensors

    NARCIS (Netherlands)

    Elwenspoek, M.

    1999-01-01

    A review is given on sensors fabricated by silicon micromachining technology using the thermal domain for the measurement of fluid flow. Attention is paid especially to performance and geometry of the sensors. Three basic types of thermal flow sensors are discussed: anemometers, calorimetric flow se

  12. Sensing the wind profile

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo

    observations from cup anemometers with lidars. The lidar is necessary to extend the measurements on masts at the Horns Rev offshore wind farm and over at land at Høvsøre, Denmark. Both sensing techniques show a high degree of agreement for wind speed measurements performed at either sites. The wind speed...

  13. Two-Component Horizontal Motion Vectors from Scanning Eye-Safe Aerosol Lidar

    OpenAIRE

    Mayor, Shane; Dérian, Pierre; Héas, Patrick; Memin, Etienne

    2011-01-01

    This poster was presented at the 19th Symposium on Boundary Layers and Turbulence, August 2010, Keystone, CO. Session P1.4. Derive the two-component vector motion field from pairs of aerosol backscatter lidar images and compare results with observations from a co-located sonic anemometer. Two methods will be tested: correlations and dense estimation.

  14. 75 FR 12796 - Petitions for Modification

    Science.gov (United States)

    2010-03-17

    ... calibrated anemometer. Methane gas or other harmful, noxious, or poisonous gases will not be permitted to... the cleaned out borehole produces an excessive amount of methane gas, a mechanical bridge plug will be...), (c), (d), (k), and (l) will be used to continuously monitor methane, oxygen and carbon...

  15. A Tall-Tower Instrument for Mean and Fluctuating Velocity, Fluctuating Temperature and Sensible Heat Flux Measurements

    DEFF Research Database (Denmark)

    Gryning, Sven-Erik; Thomson, D. W.

    1979-01-01

    For an ongoing elevated-source, urban-scale tracer experiment, an instrument system to measure the three-dimensional wind velocity and the turbulent sensible heat flux was developed. The wind velocity was measured with a combination of cup anemometer, propeller (vertical) and vane sensor. The...

  16. The Bolund experiment - design of measurement campaign using CFD

    DEFF Research Database (Denmark)

    Bechmann, Andreas; Johansen, Jeppe; Sørensen, Niels N.

    upcoming measurement campaign. The simulation results are used for estimating rational positions of measuring masts and instrumentation. A total of ten measuring masts are proposed consisting of two 16 m masts, six 9 m masts and two 5 m masts. The masts are instrumented with 12 cup anemometers for mean...

  17. NEW VERSATILE AEROSOL GENERATION SYSTEM DEVELOPED FOR USE IN A LARGE WIND TUNNEL

    Science.gov (United States)

    A new aerosol generation system was developed to accommodate a variety of research activities performed within a large wind tunnel. Because many of the velocity measurements are taken in the wind tunnel with a laser Doppler anemometer (LDA), it is necessary to maintain an aero...

  18. The Effect of a Finite Measurement Volume on Power Spectra from a Burst Type LDA

    DEFF Research Database (Denmark)

    Buchhave, Preben; Velte, Clara Marika; K. George, William

    2014-01-01

    We analyze the effects of a finite size measurement volume on the power spectrum computed fromdata acquired with a burst-type laser Doppler anemometer. The finite measurement volume causes temporal distortions in acquisition of the data resulting in phenomena such as finite processing time and de...

  19. Experimental and theoretical study of the atmospheric boundary layer over the paris area; Etude experimentale et theorique de la couche limite atmospherique en agglomeration parisienne

    Energy Technology Data Exchange (ETDEWEB)

    Menut, L

    1997-12-15

    This thesis studied the urban boundary layer dynamic behaviour over the Paris area by comparing urban (Paris) and suburban (Palaiseau) dynamic data such as lidars, sodars, sonic anemometers. All the data were obtained during the ECLAP experiment, specifically performed to characterize the differences between a city and its near environment. (author)

  20. Experimental and theoretical study of the atmospheric boundary layer over the paris area

    International Nuclear Information System (INIS)

    This thesis studied the urban boundary layer dynamic behaviour over the Paris area by comparing urban (Paris) and suburban (Palaiseau) dynamic data such as lidars, sodars, sonic anemometers. All the data were obtained during the ECLAP experiment, specifically performed to characterize the differences between a city and its near environment. (author)

  1. 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 ...

  2. Conventional measurement data: good enough for offshore meteorology?

    Science.gov (United States)

    Schmidt, Michael; Tambke, Jens; Steinfeld, Gerald; Heinemann, Detlev

    2014-05-01

    The analysis of marine boundary layer properties is an fundamental task of energy meteorology. The determination of atmospheric stability and momentum fluxes out of measurement data is, for example, important for the validation of mesoscale models such as WRF and COSMO, but also for the validation of microscale models like PALM large eddy simulations. From them, major conclusions are drawn for the design of wind turbines and the layout design of entire offshore wind farms with 20 to more than 100 turbines. Up to now, high-resolution measurements of the vertical wind are usually carried out with sonic anemometers, which are known to provide simultaneously (sound-) temperature signals. Recent investigations of data from different met masts in the North Sea have revealed errors now, which can be corrected only partially. A method will be shown for visualization of a sonic anemometers influence on the mean vertical wind speed and how it can be adjusted. Another sonic anemometer dysfunction, the striking, not by meteorology explainable underestimation of vertical wind events for lots of fine wind direction segments can only be demonstrated so far, but not explained or actually corrected. The quality of sonic anemometer measurements of mean temperatures is proved to be poor to mediocre - depending on the type of the device. Furthermore, there is no evidence about the quality of the high-frequency temperature fluctuation measurements, simply because comparative measurements are missing. Temperature measurements with sonic anemometers under controlled laboratory conditions and comparisons with other fast temperature measurements techniques must be performed in order to gain more certainty on this issue. Temperature difference sensors are producing data in agreement with theory. Such a sensor is already installed on a North Sea met mast. Some new temperature difference sensor results will be presented. New methods, especially for high-frequency and high-quality measurements

  3. Calibration of a system for measuring low air flow velocity in a wind tunnel

    Science.gov (United States)

    Krach, Andrzej; Kruczkowski, Janusz

    2016-08-01

    This article presents the calibration of a system for measuring air flow velocity in a wind tunnel with a multiple-hole orifice. The comparative method was applied for the calibration. The method consists in equalising the air flow velocity in a test section of the tunnel with that of the hot-wire anemometer probe which should then read zero value. The hot-wire anemometer probe moves reciprocally in the tunnel test section with a constant velocity, aligned and opposite to the air velocity. Air velocity in the tunnel test section is adjusted so that the minimum values of a periodic hot-wire anemometer signal displayed on an oscilloscope screen reach the lowest position (the minimum method). A sinusoidal component can be superimposed to the probe constant velocity. Then, the air flow velocity in the tunnel test section is adjusted so that, when the probe moves in the direction of air flow, only the second harmonic of the periodically variable velocity superimposed on the constant velocity (second harmonic method) remains at the output of the low-pass filter to which the hot-wire anemometer signal, displayed on the oscilloscope screen, is supplied. The velocity of the uniform motion of the hot-wire anemometer probe is measured with a magnetic linear encoder. The calibration of the system for the measurement of low air velocities in the wind tunnel was performed in the following steps: 1. Calibration of the linear encoder for the measurement of the uniform motion velocity of the hot-wire anemometer probe in the test section of the tunnel. 2. Calibration of the system for measurement of low air velocities with a multiple-hole orifice for the velocities of 0.1 and 0.25 m s‑1: - (a) measurement of the probe movement velocity setting; - (b) measurement of air velocity in the tunnel test section with comparison according to the second harmonic method; - (c) measurement of air velocity in the tunnel with comparison according to the minimum method. The calibration

  4. Flow Characterization of a Piezo-Electric High Speed Valve

    Directory of Open Access Journals (Sweden)

    T. Takiya

    2012-03-01

    Full Text Available Injecting a gas into fusion reactors or semiconductor manufacturing systems, one has to quickly control the flow rate by a piezoelectric valve. In order to construct a gas injection system with high speed valves in the future, performance tests have been conducted on a commercial piezoelectric valve. An orifice flowmeter for measuring time average flowrate and a hot wire anemometer for instantaneous flowrate were manufactured. The total flow coefficient of the orifice flowmeter was obtained experimentally under a low pressure of a 10-2 Pa and a low flowrate of a few mg/s, although they are smaller than the values specified by Japanese Industrial Standards. It is found that the hot wire anemometer installed downstream in the vicinity of the valve is suitable for detecting the change in flowrate with the response time of less than 1 ms.

  5. Modelling and measurements of power losses and turbulence intensity in wind turbine wakes at Middelgrunden offshore wind farm

    DEFF Research Database (Denmark)

    Barthelmie, Rebecca Jane; Frandsen, Sten Tronæs; Nielsen, Niels Morten;

    2007-01-01

    Understanding of power losses and turbulence increase due to wind turbine wake interactions in large offshore wind forms is crucial to optimizing wind farm design. Power losses and turbulence increase due to wakes are quantified based on observations from Middel-grunden and state-of-the-art models....... Observed power losses due solely to wakes are approximately 10% on average. These are relatively high for a single line of wind turbines due in part to the close spacing of the wind farm. The wind form model Wind Analysis and Application Program (WAsP) is shown to capture wake losses despite operating...... beyond its specifications for turbine spacing. The paper describes two methods of estimating turbulence intensity. one based on the mean and standard deviation (SD) of wind speed from the nacelle anemometer, the other from mean power output and its SD. Observations from the nacelle anemometer indicate...

  6. Power curve measurement with a nacelle mounted lidar

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Friis Pedersen, Troels; Courtney, Michael;

    2014-01-01

    Nacelle-based lidars are an attractive alternative to conventional mast base reference wind instrumentation where the erection of a mast is expensive, for example offshore. In this paper, the use of this new technology for the specific application of wind turbine power performance measurement...... mean wind speed measured by the lidar to that measured by the cup anemometer showed a deviation of about 1.4% on average. The power curve measured with the lidar was very similar to that measured with the cup anemometer although the lidar power curve was slightly distorted because of the deviation...... in wind speed measurements. A lower scatter in the power curve was observed for the lidar than for the mast. Since the lidar follows the turbine nacelle as it yaws, it always measures upwind. The wind measured by the lidar therefore shows a higher correlation with the turbine power fluctuations than...

  7. Investigation of turbulence measurements with a continuous wave, conically scanning LiDAR

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Mikkelsen, Torben; Courtney, Michael

    LIDAR systems are getting more and more accurate and reliable. It has been shown many times that the mean horizontal wind speed measured by a lidar over flat terrain compares very well with that measured by a cup anemometer. But can a lidar measure turbulence? Here we investigate the case of a...... continuous wave, conically scanning Zephir lidar. First, the wind speed standard deviation measured by such a lidar gives on average 80% of the standard deviation measured by a cup anemometer. This difference is due to the spatial averaging inherently made by a cw conically scanning lidar. The spatial...... averaging is done in two steps: 1) the weighted averaging of the wind speed in the probe volume of the laser beam; 2) the averaging of the wind speeds occurring on the circular path described by the conically scanning lidar. Therefore the standard deviation measured by a lidar resolves only the turbulence...

  8. Momentum and Turbulent Kinetic Energy Budgets Within the Park Avenue Street Canyon During the Joint Urban 2003 Field Campaign

    Science.gov (United States)

    Nelson, Matthew A.; Pardyjak, Eric R.; Klein, Petra

    2011-07-01

    Very few attempts have so far been made to quantify the momentum and turbulent kinetic energy (TKE) budgets within real urban canopies. In this study, sonic anemometer data obtained during the Joint Urban 2003 field campaign in Oklahoma City, U.S.A. were used for calculating the momentum and TKE budgets within a real-world urban street canyon. Sonic anemometers were deployed on multiple towers in the lower half of the canyon. Gradients in all three principal directions were included in the analyses. The storage and buoyancy terms were found to have negligible contributions to both the momentum and TKE budgets. The momentum budgets were generally found to be more complex than a simple balance of two physical processes. The horizontal terms were found to have significant and sometimes dominant contributions to the momentum and TKE budgets.

  9. Recent trends in technology for underground mine safety measuring instruments, plus some practical applications (II): ventilation measurements - air speed and pressure

    Energy Technology Data Exchange (ETDEWEB)

    Noda, K.; Sagisaka, M.

    1983-01-01

    Air speed is measured either by an anemometer in which the speed of a vaned wheel rotated by the air current indicates ventilation speed, or by a hot wire anemometer, which utilizes changes in the electrical resistance of a hot filament due to heat loss. Explanations are given of these types of instruments, and of various sorts of air pressure gauge: the strain gauge type which is based on the changes in electrical resistance which occur when an external force is applied to a metal or a semiconductor; and the capacitance type pressure gauge, in which changes in capacitance between two fixed electrodes and a moving electrode fitted between them are differentially processed and converted to electric current. 3 references

  10. Offshore wind profiling using light detection and ranging measurements

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo; Hasager, Charlotte Bay; Gryning, Sven-Erik;

    2009-01-01

    The advantages and limitations of the ZephlR (R), a continuous-wave, focused light detection and ranging (LiDAR) wind profiler, to observe offshore winds and turbulence characteristics were tested during a 6 month campaign at the tronsformer/platform of Hams Rev, the world's largest wind form....... The LiDAR system is a ground-based sensing technique which avoids the use of high and costly meteorological masts. Three different inflow conditions were selected to perform LiDAR wind profiling. Comparisons of LiDAR mean wind speeds against cup anemometers from different masts showed high correlations...... for the open sea sectors and good agreement with their longitudinal turbulence characteristics. Cup anemometer mean wind speed profiles were extended with LiDAR profiles up to 161 m on each inflow sector. The extension resulted in a good profile match for the three surrounding masts. These extended profiles...

  11. Retrieving wind statistics from average spectrum of continuous-wave lidar

    Directory of Open Access Journals (Sweden)

    E. Branlard

    2013-02-01

    Full Text Available The aim of this study is to experimentally demonstrate that the time-average Doppler spectrum of a continuous-wave lidar is proportional to the probability density function of the line-of-sight velocities. This would open the possibility of using cw lidars for a precise determination of the second-order atmospheric turbulence statistics. An atmospheric field campaign and a wind tunnel experiment are carried out to show that the use of an average Doppler spectrum instead of a time series of velocities determined from individual Doppler spectra significantly reduces the differences with the standard deviation measured using ordinary anemometers, such as ultra-sonic anemometers or hotwires. The proposed method essentially removes the spatial averaging effect intrinsic to the cw lidar systems.

  12. Retrieving wind statistics from average spectrum of continuous-wave lidar

    Directory of Open Access Journals (Sweden)

    E. Branlard

    2013-07-01

    Full Text Available The aim of this study is to experimentally demonstrate that the time-average Doppler spectrum of a continuous-wave (cw lidar is proportional to the probability density function of the line-of-sight velocities. This would open the possibility of using cw lidars for the determination of the second-order atmospheric turbulence statistics. An atmospheric field campaign and a wind tunnel experiment are carried out to show that the use of an average Doppler spectrum instead of a time series of velocities determined from individual Doppler spectra significantly reduces the differences with the standard deviation measured using ordinary anemometers, such as ultra-sonic anemometers or hotwires. The proposed method essentially removes the spatial averaging effect intrinsic to the cw lidar systems.

  13. A new approach to highly resolved measurements of turbulent flow

    International Nuclear Information System (INIS)

    In this paper we present the design and principle of a new anemometer, namely the 2d-Laser Cantilever Anemometer (2d-LCA), which has been developed for highly resolved flow speed measurements of two components (2d) under laboratory conditions. We will explain the working principle and demonstrate the sensor’s performance by means of comparison measurements of wake turbulence with a commercial X-wire. In the past we have shown that the 2d-LCA is capable of being applied in liquid and particle-laden domains, but we also believe that other challenging areas of operation such as near-wall flows can become accessible. (paper)

  14. Experimental Study of Near Wake Flow Behind a Rectangular Cylinder

    Directory of Open Access Journals (Sweden)

    Abdollah Shadaram

    2008-01-01

    Full Text Available The turbulence characteristics of the near wake flow behind a rectangular cylinder is investigated in a two-dimensional analysis using a hot-wire anemometer. The time-averaged and fluctuating components of the velocity are measured for a cylinder having various width-to-height (b h-1 ratios. The measurements are carried out in a low-speed wind tunnel. Data from hot-wire anemometer is collected by a data acquisition system. The results show that the turbulence intensity in the flow wake decreases as the width-to-height ratio of the cylinder increases. In addition, the characteristics of the flow field in a few sections are evaluated. Spectral analysis of the velocity signals is carried out for two different Reynolds numbers. The spectral analysis shows that Strouhal number remains nearly constant in high Reynolds numbers. The results of present experiments are in close agreement with the most widely accepted results in the literature.

  15. Power curve investigation

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Vesth, Allan

    This report describes the analysis carried out with data from a given turbine in a wind farm and a chosen period. The purpose of the analysis is to correlate the power output of the wind turbine to the wind speed measured by a nacelle-mounted anemometer. The measurements and analysis are not perf......This report describes the analysis carried out with data from a given turbine in a wind farm and a chosen period. The purpose of the analysis is to correlate the power output of the wind turbine to the wind speed measured by a nacelle-mounted anemometer. The measurements and analysis...... are not performed according to IEC 61400-12-1 [1]. Therefore, the results presented in this report cannot be considered a power curve according to the reference standard, and are referred to as “power curve investigation” instead. The measurements have been performed by a customer and the data analysis has been...

  16. A thermistor based sensor for flow measurement in water

    OpenAIRE

    Moore, John P.

    2003-01-01

    There is limited experimental data describing the mixing processes and coherent velocity structures near the surface of the ocean. These play an important part in the interactions between the atmosphere and the ocean and thus affect the climate of the earth. A robust, low cost thermistor based sensor suitable for use in the detection and quantification of velocity structures has been designed and developed. The flow sensor, a thermal anemometer, consists of a self-heated thermistor that is ma...

  17. Turbulence Measurements in Swirling Flows

    Directory of Open Access Journals (Sweden)

    V. M. Domkundwar

    1981-10-01

    Full Text Available Investigation have been conducted to find out the region of high turbulent intensities in a swirling jet passing through a divergent passage. A hot wire anemometer is used to measure the turbulence intensity using a four position method. It has been concluded that the jet spreads with increasing diffuser angle and the region of high turbulent intensity also spreads. The high turbulence intensity region lies around the recirculation zone and it decays rapidly along the main flow direction.

  18. SUBMERGED IMPINGING JETS WITHIN A FINITE WATER DEPTH

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By use of the sheet of laser light and the trac-ing particle technology, flow visualization tests of complexflow structures for submerged impinging jets within finite wa-ter depths are conducted. Typical flow patterns of submergeimpinging jets are analysed by the singular topology method.In order to reveal the mechanism of these flows, the diffusivecharacteristics and turbulent fluctuations of submerged impin-ging jets are measured by the hot-film anemometer.

  19. Optimization Controller for Mechatronic Sun Tracking System to Improve Performance

    OpenAIRE

    Mustafa Engin; Dilşad Engin

    2013-01-01

    An embedded system that contains hardware and software was developed for two-axis solar tracking system to improve photovoltaic panel utilization. The hardware section of the embedded system consists of a 32-bit ARM core microcontroller, motor driver circuits, a motion control unit, pyranometer, GPS receiver, and an anemometer. The real-time control algorithm enables the solar tracker to operate automatically without external control as a stand-alone system, combining the advantages of the op...

  20. The design and instrumentation of the Purdue annular cascade facility with initial data acquisition and analysis

    Science.gov (United States)

    Stauter, R. C.; Fleeter, S.

    1982-01-01

    Three dimensional aerodynamic data, required to validate and/or indicate necessary refinements to inviscid and viscous analyses of the flow through turbomachine blade rows, are discussed. Instrumentation and capabilities for pressure measurement, probe insertion and traversing, and flow visualization are reviewed. Advanced measurement techniques including Laser Doppler Anemometers, are considered. Data processing is reviewed. Predictions were correlated with the experimental data. A flow visualization technique using helium filled soap bubbles was demonstrated.

  1. Integrated micro-liquid dosing systems

    OpenAIRE

    Theo S.J. Lammerink; Elwenspoek, Miko; Fluitman, Jan H.J

    1993-01-01

    An integrated micro-liquid dosing system consisting of a micropump and a microliquid flow sensor is demonstrated. The dosing system allows accurate dosing of liquid in the microliter regime and can easily be integrated with components such as mixers and detectors in micro-liquid handling systems. The liquid pump is of the reciprocating type with a thermopneumatic actuator. The microliquid flow sensor is based on the thermal anemometer type. Both pump and flow sensor are realized in a 3-in (10...

  2. Field performance of an all-semiconductor laser coherent Doppler lidar

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Pedersen, Christian

    2012-01-01

    measured by our instrument at an 80 m distance to those simultaneously obtained from an industry-standard sonic anemometer (SA). An excellent degree of correlation (R2=0.994 and slope=0.996) is achieved from a linear regression analysis of the CDL versus SA wind speed data. The lidar system is capable...... general class of low-cost, portable remote sensors based on all-SL emitters for applications that require demanding laser stability and coherence....

  3. Numerical study of a wind tunnel setup for measuring train slipstream with Detached Eddy Simulation

    OpenAIRE

    Dhanabalan, Yogeshwar

    2013-01-01

    High speed trains have become an integral part of the transportation systems around the world. With increasing speed, very high velocities are generated in the region around the train known as slipstream. Experimental studies have been conducted over the last few decades to study the effect of these phenomena. Slipstream velocities have been measured using anemometers placed near real trains running on the tracks and model trains running on rigs like moving model rig and rotating rail rig. Ho...

  4. Turbulence in vertical axis wind turbine canopies

    OpenAIRE

    Kinzel, Matthias; Araya, Daniel B.; Dabiri, John O.

    2015-01-01

    Experimental results from three different full scale arrays of vertical-axis wind turbines (VAWTs) under natural wind conditions are presented. The wind velocities throughout the turbine arrays are measured using a portable meteorological tower with seven, vertically staggered, three-component ultrasonic anemometers. The power output of each turbine is recorded simultaneously. The comparison between the horizontal and vertical energy transport for the different turbine array sizes shows the i...

  5. Inference of thermal models for sensors

    OpenAIRE

    Novio Vázquez, Santiago

    2016-01-01

    The presence of thermal diffusivity in a spherical thermal anemometer gives it long-memory dependence. The identification problem and state realisation of this model is addressed by using diffusive representation (DR). In order to do that, an ideal thermal sphere quadrupole model and its corresponding finite differences model are proposed and simulated. From those models and the non-rational Cole-Cole transfer function, the identification problem is discussed. PRBS as an input signal is also ...

  6. 高速噴霧流と周囲流の流動特性 : 第1報, 定常噴霧流の場合

    OpenAIRE

    細谷, 肇; 小保方, 富夫

    1992-01-01

    Diesel fuel spray from a single-hole-type injection nozzle is investigated under steady and atmospheric conditions in order to understand the unsteady Diesel spray. Axial and radial velocity components of the spray at two constant injection pressures of 9.8MPa and 4.9MPa are measured by laser Doppler anemometer (LDA), and turbulence characteristics of the spray flow velocities are analyzed. Distributions of mean velocity and turbulence characteristics in the spray flow are compared with gas j...

  7. Upwind D1. Uncertainties in wind assessment with LIDAR

    DEFF Research Database (Denmark)

    Lindelöw, Per Jonas Petter

    In this report sources influencing wind assessments with lidars are listed and discussed. Comparisons with mast mounted cup anemometers are presented and the magnitudes of the errors from the listed error sources are estimated. Finally an attempt to define uncertainty windows for the current stat...... of the two commercial wind sensing lidars is presented. The results in this report give important feedback on system improvements to manufacturers and an estimation of the current ability for wind farm developers which are potential users....

  8. Analysis of Signal-to-Noise Ratio of the Laser Doppler Velocimeter

    DEFF Research Database (Denmark)

    Lading, Lars

    1973-01-01

    The signal-to-shot-noise ratio of the photocurrent of a laser Doppler anemometer is calculated as a function of the parameters which describe the system. It is found that the S/N is generally a growing function of receiver area, that few large particles are better than many small ones, and that...... generally the "fringe" or l"differential" mode configuration is equal to, or better than, the "reference beam" mode....

  9. Rotary slanted single wire CTA – a useful tool for 3D flows investigations

    OpenAIRE

    Jonáš P.

    2013-01-01

    The procedure is described of experimental investigation of a statistically stationary generally nonisothermal 3D flow by means of a constant temperature anemometer (CTA) using single slanted heated wire, rotary round the fixed axis. The principle of this procedure is quite clear. The change of the heated wire temperature modifies ratio of CTA sensitivities to temperature and velocity fluctuations. Turning the heated wire through a proper angle changes the sensitivity to components of the ins...

  10. Characteristics of Flow Field around NACA 0012 Airfoil with DBD plasma Actuator at Low Reynolds Number

    OpenAIRE

    簗瀬, 祐太; Yanase, Yuta; 大竹, 智久; Otake, Tomohisa; 村松, 旦典; Muramatsu, Akinori; 本橋, 龍郎; Motohashi, Tatsuo

    2012-01-01

    Aerodymamic performance of NACA0012 airfoil is enhanced with suppression of boundary layer separation due to operation of DBD plasma actuator at low Reynolds numbers. We carried out flow field measurements using hot-wire anemometer around the airfoil which applied to the actuator to investigate relationship between aerodynamics and flow field around the airfoil at Reymolds number of 10,000. Results of velocity profiles of the boundary layer show suppression of laminar separation on the airfoi...

  11. Qualitative comparison of concurrent vertical optical turbulence profiles from an aircraft and balloons over White Sands Missile Range

    Science.gov (United States)

    Nowlin, Scott R.; Hahn, Ila L.; Hugo, Ronald J.; Bishop, Kenneth P.

    1999-08-01

    We report simultaneous balloon-borne thermosonde/airborne constant-current anemometer measurements made over a portion of White Sands Missile Range, NM. For the first time, vertical profiles of the refractive index structure parameter (Cn2) data generated from shallow slant aircraft flight paths are compared to the balloons vertical Cn2 distributions. We discuss possible adverse effects of meteorology and atmospheric velocity fluctuations. We present conclusions and make recommendations for future similar experimental efforts.

  12. Interazione tra superficie libera e turbolenza di forte intensità

    OpenAIRE

    Chiapponi, Luca

    2010-01-01

    In this work the experimental analysis of the interaction between turbulence and free surface is detailed. The topic is interesting in many natural flows and industrial processes. Turbulence is generated by a vertically oscillating grid moving beneath the free surface, as widely reported in several experiments. Fluid velocity is measured through a hot film anemometer. This instrument is able to measure vertical velocity fluctuation to within 0.5 mm of the surface, from which profiles of r.m.s...

  13. Tall Tower Wind Energy Monitoring and Numerical Model Validation in Northern Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Koracin, D. [Desert Research Inst. (DRI), Las Vegas, NV (United States); Kaplan, M. [Desert Research Inst. (DRI), Las Vegas, NV (United States); Smith, C. [Desert Research Inst. (DRI), Las Vegas, NV (United States); McCurdy, G. [Desert Research Inst. (DRI), Las Vegas, NV (United States); Wolf, A. [Desert Research Inst. (DRI), Las Vegas, NV (United States); McCord, T. [Desert Research Inst. (DRI), Las Vegas, NV (United States); King, K. [Desert Research Inst. (DRI), Las Vegas, NV (United States); Belu, R. [Drexel Univ., Philadelphia, PA (United States); Horvath, K. [Croatian Meteorological and Hydrological Service, Zagreb (Croatia)

    2015-10-01

    The main objectives of this project were to conduct a tall-tower and sodar field campaign in complex terrain, investigate wind properties relevant to wind energy assessment, and evaluate high-resolution models with fixed and adaptive grid structures. Two 60-m towers at Virginia Peak ridges near Washoe Valley, Nevada, were instrumented with cup and vane anemometers as well as sonic anemometers, and an acoustic sounder (hereafter sodar) was installed near one of the towers. The towers were located 2,700 m apart with a vertical distance of 140 m elevation between their bases. Each tower had a downhill exposure of rolling complex terrain, with the nearby valley floor 3,200 m to the west and 800 m below the summit. Cup anemometers were installed at both towers at 20, 40, and 60 m, wind vanes at 20 and 60 m, and sonic anemometers at 20 and 60 m. The sodar measurements were nominally provided every 10 m in vertical distance from 40 to 200 m with the quality of the data generally decreasing with height. Surface air temperature, atmospheric pressure, and radiation measurements were conducted at 1.5 m AGL at both of the towers. Although the plan was to conduct a 1-year period of data collection, we extended the period (October 5, 2012 through February 24, 2014) to cover for possible data loss from instrument or communication problems. We also present a preliminary analysis of the towers and sodar data, including a detailed inventory of available and missing data as well as outliers. The analysis additionally includes calculation of the Weibull parameters, turbulence intensity, and initial computation of wind power density at various heights.

  14. VHF Data Telemetry

    OpenAIRE

    Birch, K.G.; Clayson, C. H.; R. W. Pascal

    1994-01-01

    The objective of the VHF Data Telemetry system was the collection of continuous raw data from the Solent Sonic anemometer, whist the sensor was deployed at sea, on the Sonic Buoy. The aims of the development project were achieved within short timescales and the successful sea trial proved the overall system operationally viable. The success of the system exceeded that expected, with 98% of data blocks received without errors. Analysis of the data success rates is shown, and areas fo...

  15. Estimating the role of a ditch network in groundwater recharge in a Mediterranean catchment using a water balance approach

    OpenAIRE

    Dages, C.; Voltz, Marc; Bsaibes, A.; Prévot, L.; Huttel, O.; Louchart, X.; Garnier, F.; Negro, S.

    2009-01-01

    Water balance variables were monitored in a farmed Mediterranean catchment characterized by a dense ditch network to allow for the separate estimation of the diffuse and concentrated recharge terms during flood events. The 27 ha central part of the catchment was equipped with (i) rain gauges, (ii) ditch gauge stations, (iii) piezometers, (iv) neutron probes, and (v) an eddy covariance mast including a 3D sonic anemometer and a fast hygrometer. The water balance was calculated for two autumnal...

  16. Single card PC compatible computer

    OpenAIRE

    Smith, P K

    1994-01-01

    This report details the construction and assembly of a single Eurocard PC (AT) compatible computer. The card has a 80386SX processor, maths co-processor, floppy disk controller, IDE standard hard disk controller, two serial ports and a printer port. It is manufactured by DSP Design. The advantage of this design is that any type of interface can be designed and fitted to the computer. This report includes an interface for the Sonic Anemometer and the Magnavox MX4200 GPS navigation system....

  17. On the Analytical Approach to Present Engineering Problems: Photovoltaic Systems Behavior, Wind Speed Sensors Performance, and High-Speed Train Pressure Wave Effects in Tunnels

    Directory of Open Access Journals (Sweden)

    Santiago Pindado

    2015-01-01

    Full Text Available At present, engineering problems required quite a sophisticated calculation means. However, analytical models still can prove to be a useful tool for engineers and scientists when dealing with complex physical phenomena. The mathematical models developed to analyze three different engineering problems: photovoltaic devices analysis; cup anemometer performance; and high-speed train pressure wave effects in tunnels are described. In all cases, the results are quite accurate when compared to testing measurements.

  18. REMOTE RECORDING ANNULAR VANE ASSEMBLY

    Science.gov (United States)

    Wehmann, G.

    1963-06-25

    A weather vane apparatus is described which is capable of movement in horizontal and vertical planes. Associated with the vane are tangent potentiometers, commutators, and other electrical apparatus for deriving electrical output voltages as a function of the wind direction. The apparatus is particularly adapted for use with an anemometer to provide an electrical output indicating the amount and direction of an up or down draft. (AEC)

  19. Holographic flow visualization of time-varying shock waves

    Science.gov (United States)

    Decker, A. J.

    1981-01-01

    Rapid-double-exposure, diffuse-illumination holography is evaluated analytically and experimentally as a flow visualization method for time-varying shock waves. Conditions are determined that minimize the distance (localization error) between the surface or curve of interference-fringe localization and the shock surface. Treated specifically are the cases of shock waves in a transonic compressor rotor for which there is laser anemometer data for comparison and shock waves in a flutter cascade.

  20. Heat balance of a multistage spray-dryer: principles and example of application

    OpenAIRE

    Bimbenet, Jean-Jacques; Schuck, Pierre; Roignant, Michel; Brulé, Gérard; Méjean, Serge

    2002-01-01

    International audience The authors present the principles of isenthalpic air drying, the use in drying of the enthalpic diagram of air and mass and enthalpy balances. As an application of these principles, a pilot multistage spray-dryer, operating on skim milk, was experimentally studied. Air flow rates were measured by a hot wire anemometer at different positions of the air pipes. It was checked that the mass flow rate of air delivered by a fan was independent of air temperature. A thermo...

  1. Technical Training on High-Order Spectral Analysis and Thermal Anemometry Applications

    Science.gov (United States)

    Maslov, A. A.; Shiplyuk, A. N.; Sidirenko, A. A.; Bountin, D. A.

    2003-01-01

    The topics of thermal anemometry and high-order spectral analyses were the subject of the technical training. Specifically, the objective of the technical training was to study: (i) the recently introduced constant voltage anemometer (CVA) for high-speed boundary layer; and (ii) newly developed high-order spectral analysis techniques (HOSA). Both CVA and HOSA are relevant tools for studies of boundary layer transition and stability.

  2. Time series analysis of continuous-wave coherent Doppler Lidar wind measurements

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Mikkelsen, Torben; Mann, Jakob;

    2008-01-01

    The influence of spatial volume averaging of a focused 1.55 mu m continuous-wave coherent Doppler Lidar on observed wind turbulence measured in the atmospheric surface layer over homogeneous terrain is described and analysed. Comparison of Lidar-measured turbulent spectra with spectra...... simultaneously obtained from a mast-mounted sonic anemometer at 78 meters height at the test station for large wind turbines at Hovsore in Western Jutland, Denmark is presented for the first time....

  3. Wind-farm power performance verification

    Energy Technology Data Exchange (ETDEWEB)

    Dutilleux, P. [DEWI German Wind Energy Institute, Wilhelmshaven (Germany)

    2005-07-01

    Details of wind farm power performance verification procedures were presented. Verifications were performed at the DEWI test site at Wilhelmhaven, Germany. Types of power performance guarantees included power performance of individual turbines with IEC verification measurement, and Nacelle anemometer verification. In addition, availability guarantees were examined, as well as issues concerning energy production guarantees of complete wind farms in relation to nearby meteorology masts. An evaluation of power curve verification measurements was presented as well as measurement procedures relating to IEC standards. Methods for Nacelle anemometry verification included calibration of the anemometer; documentation of its exact position and chain signal; and end-to-end calibration from sensor to SCADA data base. Classification of anemometers included impact of dynamical effects; and influence on annual energy production. An example of a project for performance verification of a wind farm with 9 identical wind turbines was presented. The significance of status signals was discussed, as well as alternative methods for power-curve measurements. Evaluation procedures for energy yield and power curve verifications were presented. The upcoming set of IEC standards concerning power curve measurements was discussed. Various alternative verification procedures for wind farm power performance were reviewed. refs., tabs., figs.

  4. Turbulence assessment at potential turbine sites

    Energy Technology Data Exchange (ETDEWEB)

    Daniels, A. [Univ. of Hawaii, Honolulu, HI (United States)

    1996-12-31

    As opposed to a fixed anemometer, the Tala kite is free to move in the air. The motion of the kite is not random, it moves with or against the speed gradient towards the center of passing turbulence events of higher or lower speeds thus allowing the kite to measure event maximum or minimum speed rather than the speed at some unknown distance from the event center like a fixed anemometer. This behavior is confirmed both by a theoretical aerodynamics analysis of the kite motion and by data from a field study where kite and hot film anemometer (HFA) events, defined by the rain flow count method, were compared with flap events on a rotating turbine blade. The HFAs simulated too few events lasting too long while the kites reproduced both the number of events and event periods remarkably close. It is concluded that the kite is the optimal tool for measuring turbulence at potential turbine sites. Kite turbulence can form the bases for economic return estimates and an example is given where less windy sites could be more economical than other more turbulent higher speed sites. 13 refs., 8 figs.

  5. 层流翼型三维边界层横流驻波精确测量方法研究%On the Accurate Measurement Method of Standing Cross-flow for Three-dimensional Laminar Airfoil Boundary Layer

    Institute of Scientific and Technical Information of China (English)

    马彪; 白存儒; 杨广珺; 李栋

    2011-01-01

    Laminar flow control (LFC) of swept-back wing is a complex but very significant topic for drag reduction. The study of standing cross-flow has a great significance for LFC. For this reason, the experimental method of standing cross-flow measurement was analyzed and studied by using hot wire anemometer and sublimation method in a low turbulence wind tunnel. Corresponding technical details about the setup of hot wire anemometer system and process of sublimation surface spray are elaborated in this paper. The velocity profile curve in boundary layer, the image of sublimation result, the distance between standing waves and the wedge transition line were obtained in experiment. Synthetical analysis of experimental results shows that there is a high agreement between hot wire anemometer and sublimation method. This indicates that flow state in a 3-D boundary layer can be measured conveniently by hot wire anemometer; that at a suitable angle, the hot wire anemometer support does not impact the measurement; that hot wire probe has less effect on flow in boundary layer. So the results measured by hot wire anemometer may be regarded as actual flow in boundary layer. Analysis of experimental data shows that the combination of hot wire anemometer and sublimation method is a very effective method.%后掠机翼的层流控制对于气动减阻有着重要的意义,同时也是非常复杂的研究课题.而对横流驻波的研究是实现层流翼型的一个关健.为此,本文分析并研究了在低湍流度风洞中,采用热线风速仪(CTA)与表面升华法相结合研究由横流不稳定性产生的驻波及其对转捩影响的实验技术,阐述了该实验中架设热线测量系统与升华法表面喷涂的相关技术与细节.实验得到了边界层内的速度剖面图、升华法图形、驻波间距和楔形转捩线.实验结果的综合分析表明热线和升华法一致性很高.说明通过热线风速仪可以方便地测得三维边界层内的流动

  6. AC plasma anemometer—characteristics and design

    Science.gov (United States)

    Marshall, Curtis; Matlis, Eric; Corke, Thomas; Gogineni, Sivaram

    2015-08-01

    The characteristics and design of a high-bandwidth flow sensor that uses an AC glow discharge (plasma) as the sensing element is presented. The plasma forms in the air gap between two protruding low profile electrodes attached to a probe body. The output from the anemometer is an amplitude modulated version of the AC voltage input that contains information about the mean and fluctuating velocity components. The anemometer circuitry includes resistance and capacitance elements that simulate a dielectric-barrier to maintain a diffuse plasma, and a constant-current feedback control that maintains operation within the desired glow discharge regime over an extended range of air velocities. Mean velocity calibrations are demonstrated over a range from 0 to 140 m s-1. Over this velocity range, the mean output voltage varied linearly with air velocity, providing a constant static sensitivity. The effect of the electrode gap and input AC carrier frequency on the anemometer static sensitivity and dynamic response are investigated. Experiments are performed to compare measurements obtained with a plasma sensor operating at two AC carrier frequencies against that of a constant-temperature hot-wire. All three sensors were calibrated against the same known velocity reference. An uncertainty based on the standard deviation of the velocity calibration fit was applied to the mean and fluctuating velocity measurements of the three sensors. The motivation is not to replace hot-wires as a general measurement tool, but rather as an alternative to hot-wires in harsh environments or at high Mach numbers where they either have difficulty in surviving or lack the necessary frequency response.

  7. Capacitive Ultrasonic Transducer Development for Acoustic Anemometry on Mars

    Science.gov (United States)

    Leonard-Pugh, Eurion; Wilson, C.; Calcutt, S.; Davis, L.

    2012-10-01

    Previous Mars missions have used either mechanical or thermal anemometry techniques. The moving parts of mechanical anemometers are prone to damage during launch and landing and their inertia makes them unsuited for turbulence studies. Thermal anemometers have been used successfully on Mars but are difficult to calibrate and susceptible to varying ambient temperatures. In ultrasonic anemometry, wind speed and sound speed are calculated from two-way time-of-flight measurements between pairs of transducers; three pairs of transducers are used to return a 3-D wind vector. These high-frequency measurements are highly reliable and immune from drift. Piezo-electric ultrasonic anemometers are widely used on Earth due to their full-range accuracy and high measurement frequency. However these transducers have high acoustic impedances and would not work on Mars. We are developing low-mass capacitive ultrasonic transducers for Mars missions which have significantly lower acoustic impedances and would therefore have a much stronger coupling to the Martian atmosphere. These transducers consist of a metallised polymer film pulled taught against a machined metal backplane. The film is drawn towards the backplane by a DC bias voltage. A varying signal is used on top of the DC bias to oscillate the film; generating acoustic waves. This poster will look at the operation of such sensors and the developments necessary to operate the devices under Martian conditions. Transducer performance is determined primarily by two elements; the front film and the backplane. The sensitivity of the transducer is affected by the thickness of the front film; as well as the diameter, curvature and roughness of the metal backplane. We present data on the performance of the sensors and instrument design considerations including signal shapes and transducer arrangements.

  8. The 2d-LCA as an alternative to x-wires

    Science.gov (United States)

    Puczylowski, Jaroslaw; Hölling, Michael; Peinke, Joachim

    2015-11-01

    The 2d-Laser Cantilever Anemometer (2d-LCA) is an innovative sensor for two-dimensional velocity measurements in fluids. It uses a micostructured cantilever made of silicon and SU-8 as a sensing element and is capable of performing mesurements with extremly high temporal resolutions up to 150kHz. The size of the cantilever defines its spatial resolution, which is in the order of 150 μm only. Another big feature is a large angular range of 180° in total. The 2d-LCA has been developed as an alternative measurement method to x-wires with the motivation to create a sensor that can operate in areas where the use of hot-wire anemometry is difficult. These areas include measurements in liquids and in near-wall or particle-laden flows. Unlike hot-wires, the resolution power of the 2d-LCA does not decrease with increasing flow velocity, making it particularly suitable for measurements in high speed flows. Comparative measurements with the 2d-LCA and hot-wires have been carried out in order to assess the performance of the new anemometer. The data of both measurement techniques were analyzed using the same stochastic methods including a spectral analysis as well as an inspection of increment statistics and structure functions. Furthermore, key parameters, such as mean values of both velocity components, angles of attack and the characteristic length scales were determined from both data sets. The analysis reveals a great agreement between both anemometers and thus confirms the new approach.

  9. Droplet velocity in horizontal two-phase air/water free jet flow in stagnant ambient

    Energy Technology Data Exchange (ETDEWEB)

    Surma, R.; Friedel, L. [Wissenschaftlicher Arbeitsbereich Stroemungsmechanik, TU Hamburg-Harburg, Eissendorferstr. 38, D-21073 Hamburg (Germany)

    2004-08-01

    For the case of an isothermal free jet flow the velocity and the size of the drops were measured with a Phase-Doppler-Anemometer. The axial velocity decay downstream from the nozzle outlet and the radial drop velocity profile are reproducible within reasonable limits, if a so-called homogeneous flow mixture density in the nozzle outlet is introduced. In case of low mass flow qualities an adjustment of the entrainment coefficient and a virtual jet origin as well as a reduced exponent for the Gaussian function type radial velocity profile is required. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  10. Free jet water flow in Pelton turbines; Freistrahlstroemungen in Peltonturbinen

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.; Casey, M.

    2003-07-01

    This short article presents the results of experimental investigations made on the flow processes found in the jets of water in Pelton turbines. The results can be used to improve basic knowledge on the design of nozzles and the interaction between the jet and the cups on the Pelton turbine's wheel and thus help improve the efficiency of Pelton turbine systems. Brief details are given on the experimental arrangement and the measurement methods used, which included a Laser-Doppler-Anemometer system.

  11. In vitro calibration of a system for measurement of in vivo convective heat transfer coefficient in animals

    OpenAIRE

    Webster John G; Chachati Louay; Tangwongsan Chanchana; Farrell Patrick V

    2006-01-01

    Abstract Background We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver. Methods We built a minimally invasive instrument to measure the in vivo convective heat transfer coefficient, h in animals, using a Wheatstone-bridge circuit, similar to a hot-wire anemometer circuit. One arm is connected to a steerable catheter sensor whose tip is a 1.9 mm × 3.2 mm thin film resistive temperature detector (RTD) sensor. We used a circulation system t...

  12. Tests of a robust eddy correlation system for sensible heat flux

    Science.gov (United States)

    Blanford, J. H.; Gay, L. W.

    1992-03-01

    Sensible heat flux estimates from a simple, one-propeller eddy correlation system (OPEC) were compared with those from a sonic anemometer eddy correlation system (SEC). In accordance with similarity theory, the performance of the OPEC system improved with increasing height of the sensor above the surface. Flux totals from the two systems at sites with adequate fetch were in excellent agreement after frequency response corrections were applied. The propeller system appears suitable for long periods of unattended measurement. The sensible heat flux measurements can be combined with net radiation and soil heat flux measurements to estimate latent heat as a residual in the surface energy balance.

  13. ISEE - Information system for renewables on the Internet; ISEE - Informationssystem fuer Erneuerbare Energien im Internet

    Energy Technology Data Exchange (ETDEWEB)

    Rohrig, K. [ISET - Institut fuer Solare Energieversorgungstechnik e.V., Kassel (Germany)

    1997-12-31

    Since 1988 ISET has been operating a central information system for components of solar energy plants called ISEE. At present this online data base offers technical data, cost data, and manufacturers` information on photovoltaic modules, solar collectors, aerogenerators, inverters, DC chopper converters, batteries, solar charge control devices, solar irradiance measuring devices, and anemometers. (HW) [Deutsch] Seit 1988 betreibt das ISET ein zentrales Informationssystem fuer Komponenten solarer Energieversorgungsanlagen ISEE. Aktuell stehen in dieser Online-Datenbank technische Daten, Kostendaten sowie Herstellerinformationen zu Photovoltaikmodulen, Sonnenkollektoren, Windenergieanlagen, Stromrichtern, Gleichstromstellern, Batterien, Solarladereglern, Solarstrahlungsmessgeraeten und Windmessgeraeten zur Verfuegung. (HW)

  14. MPPT Algorithm for Small Wind Systems based on Speed Control Strategy

    Directory of Open Access Journals (Sweden)

    Ciprian VLAD

    2008-07-01

    Full Text Available This paper presents experimental results of an autonomous low-power wind energy conversion system (WECS, based on a permanent-magnet synchronous generator (PMSG connected directly to the wind turbine. The purpose of this paper is to present an improving method for MPPT (Maximum Power Point Tracking algorithm based shaft rotational speed optimal control. The proposed method concern the variable delay compensation between measured wind speed from anemometer and wind shaft rotational speed proportional signal. Experimental results aiming to prove the efficiency of the proposed method are presented.

  15. Maximum-likelihood estimates of the frequency and other parameters of signals of laser Doppler measuring systems operating in the one-particle-scattering mode

    International Nuclear Information System (INIS)

    Maximum-likelihood equations are presented for estimates of the Doppler frequency (speed) and other unknown parameters of signals of laser Doppler anemometers and lidars operating in the one-particle-scattering mode. Shot noise was assumed to be the main interfering factor of the problem. The error correlation matrix was calculated and the Rao - Cramer bounds were determined. The results are confirmed by the computer simulation of the Doppler signal and the numerical solution of the maximum-likelihood equations for the Doppler frequency. The obtained estimate is unbiased, and its dispersion coincides with the Rao-Cramer bound. (laser applications and other topics in quantum electronics)

  16. Geographically distributed environmental sensor system

    Science.gov (United States)

    French, Patrick; Veatch, Brad; O'Connor, Mike

    2006-10-03

    The present invention is directed to a sensor network that includes a number of sensor units and a base unit. The base station operates in a network discovery mode (in which network topology information is collected) in a data polling mode (in which sensed information is collected from selected sensory units). Each of the sensor units can include a number of features, including an anemometer, a rain gauge, a compass, a GPS receiver, a barometric pressure sensor, an air temperature sensor, a humidity sensor, a level, and a radiant temperature sensor.

  17. FSO and radio link attenuation: meteorological models verified by experiment

    Science.gov (United States)

    Brazda, Vladimir; Fiser, Ondrej; Svoboda, Jaroslav

    2011-09-01

    Institute of Atmospheric Physics of Czech Academy measures atmospheric attenuation on 60 m experimental FSO link on 830 and 1550 nm for more than three years. Visibility sensors and two 3D sonic anemometers on both transmitting and receiving site, rain gauge and many sensors enabling the refractivity index computation are spaced along the optical link. Meteorological visibility, wind turbulent energy, sonic temperature, structure index and rain rate are correlated with measured attenuation. FSO link attenuation dependence on the above mentioned parameters is analyzed. The paper shows also basic statistical behavior of the long-term FSO signal level and also the simulation of hybrid link techniques.

  18. Quantifying the Effect of Lidar Turbulence Error on Wind Power Prediction

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Jennifer F.; Clifton, Andrew

    2016-01-01

    Currently, cup anemometers on meteorological towers are used to measure wind speeds and turbulence intensity to make decisions about wind turbine class and site suitability; however, as modern turbine hub heights increase and wind energy expands to complex and remote sites, it becomes more difficult and costly to install meteorological towers at potential sites. As a result, remote-sensing devices (e.g., lidars) are now commonly used by wind farm managers and researchers to estimate the flow field at heights spanned by a turbine. Although lidars can accurately estimate mean wind speeds and wind directions, there is still a large amount of uncertainty surrounding the measurement of turbulence using these devices. Errors in lidar turbulence estimates are caused by a variety of factors, including instrument noise, volume averaging, and variance contamination, in which the magnitude of these factors is highly dependent on measurement height and atmospheric stability. As turbulence has a large impact on wind power production, errors in turbulence measurements will translate into errors in wind power prediction. The impact of using lidars rather than cup anemometers for wind power prediction must be understood if lidars are to be considered a viable alternative to cup anemometers.In this poster, the sensitivity of power prediction error to typical lidar turbulence measurement errors is assessed. Turbulence estimates from a vertically profiling WINDCUBE v2 lidar are compared to high-resolution sonic anemometer measurements at field sites in Oklahoma and Colorado to determine the degree of lidar turbulence error that can be expected under different atmospheric conditions. These errors are then incorporated into a power prediction model to estimate the sensitivity of power prediction error to turbulence measurement error. Power prediction models, including the standard binning method and a random forest method, were developed using data from the aeroelastic simulator FAST

  19. Measurement of velocity fluctuations in microfluidics with simultaneously ultrahigh spatial and temporal resolution

    Science.gov (United States)

    Zhao, Wei; Yang, Fang; Khan, Jamil; Reifsnider, Ken; Wang, Guiren

    2016-01-01

    Although unsteady and electrokinetic flows are widely used in microfluidics, there is unfortunately no velocimeter today that can measure the random velocity fluctuation at high temporal and spatial resolution simultaneously in microfluidics. Here we, for the first time, theoretically study the temporal resolution of laser induced fluorescence photobleaching anemometer (LIFPA) and experimentally verify that LIFPA can have simultaneously ultrahigh temporal ({˜ } 4 \\upmu s) and spatial ({˜ }203 nm) resolution and can measure velocity fluctuation up to at least 2 kHz, whose corresponding wave number is about 6× 10^6 {/}m in an electrokinetically forced unsteady flow in microfluidics.

  20. Efficiency of small wind generator powered water pumping systems; Rendimento de unidade de bombeamento de agua acionada por gerador eolico de pequeno porte

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Mendeleyev Guerreiro; Carvalho, Paulo Cesar Marques de; Costa, Levy Ferreira [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Engenharia Eletrica; Borges Neto, Manuel Rangel [Centro Federal de Educacao Tecnologica de Petrolina (CEFET), PE (Brazil)

    2008-07-01

    The present paper aims to evaluate the efficiency of a small wind generator powered water pumping system; the generator is a permanent magnet generator of 1 kw of axial flow, using three fiber glass blades with 2.46 m diameter. The used centrifugal pump is connected to a 0.5 c v motor, three-phase, frequency of 60 Hz, rotational speed of 3450 rpm. For the efficiency evaluation a shell anemometer, a flow and pressure sensor were used, connected to a data logger to the collection and storage of the data. An energy analyzer was also used to collect the current, voltage and power generated from the wind generator. (author)

  1. Wind measurements by optical remote sensing; Windmessung mit optischer Fernerkundung

    Energy Technology Data Exchange (ETDEWEB)

    Emeis, S. [Inst. fuer Meteorologie und Klimaforschung - Atmosphaerische Umweltforschung (IMK-IFU), Forschungszentrum Karlsruhe GmbH, Garmisch-Partenkirchen (Germany)

    2006-08-15

    The use of wind energy requires precise wind measurements. The hitherto existing in situ-techniques with cup anemometers mounted on masts will meet mechanical and financial limits at future hub heights. Ground-based optical remote sensing methods that measure the vertical profile of wind speed up to some hundred metres height may be a way out from these problems. This paper will discuss the basic principles of anemometry by remote sensing and will present some optical methods (lidar, lidar-Doppler-anemometry) in more detail. (orig.)

  2. Rotary slanted single wire CTA - a useful tool for 3D flows investigations

    Science.gov (United States)

    Jonáš, P.

    2013-04-01

    The procedure is described of experimental investigation of a statistically stationary generally nonisothermal 3D flow by means of a constant temperature anemometer (CTA) using single slanted heated wire, rotary round the fixed axis. The principle of this procedure is quite clear. The change of the heated wire temperature modifies ratio of CTA sensitivities to temperature and velocity fluctuations. Turning the heated wire through a proper angle changes the sensitivity to components of the instantaneous velocity vector. Some recommendations are presented based on long time experiences, e.g. on the choice of probe, on the probe calibration, to the measurement organization and to the evaluation of results.

  3. Rotary slanted single wire CTA – a useful tool for 3D flows investigations

    Directory of Open Access Journals (Sweden)

    Jonáš P.

    2013-04-01

    Full Text Available The procedure is described of experimental investigation of a statistically stationary generally nonisothermal 3D flow by means of a constant temperature anemometer (CTA using single slanted heated wire, rotary round the fixed axis. The principle of this procedure is quite clear. The change of the heated wire temperature modifies ratio of CTA sensitivities to temperature and velocity fluctuations. Turning the heated wire through a proper angle changes the sensitivity to components of the instantaneous velocity vector. Some recommendations are presented based on long time experiences, e.g. on the choice of probe, on the probe calibration, to the measurement organization and to the evaluation of results.

  4. Analysis of solar radiation and other variables for the evaluation of locations of thermo solar power stations; Analisis de radiacion solar y otras vairables para la evaluacion de emplazamientos de centrales termosolares

    Energy Technology Data Exchange (ETDEWEB)

    Montero, I.; Miranda, M. T.; Rojas, S.; Bolinaga, B.; Tierra, C.; Pico, J. del

    2008-07-01

    This paper presents the characteristics of various measuring weather stations located in future CCP thermal plants, showing the different systems they are equipped with, among others, pyrheliometer, pyrano meter, anemometers, thermo-hygrometer and data transmission system. Some results of solar radiation and other climate variables obtained in these stations are presented and analyzed in relation to existing data in the area, taking into account different external parameters that can influence the direct radiation obtained and, therefore, the future operation of the thermal plant. (Author)

  5. Meso-scale modeling of a forested landscape

    DEFF Research Database (Denmark)

    Dellwik, Ebba; Arnqvist, Johan; Bergström, Hans;

    2014-01-01

    Meso-scale models are increasingly used for estimating wind resources for wind turbine siting. In this study, we investigate how the Weather Research and Forecasting (WRF) model performs using standard model settings in two different planetary boundary layer schemes for a forested landscape and how...... this performance is changed when enhancing the roughness by a factor four in one of the schemes. The model simulations were evaluated using data from a 138 m tall mast in southeastern Sweden, where an experiment with six sonic anemometers and standard meteorological instrumentation was performed 2010...

  6. Roughness Effects on Wind-Turbine Wake Dynamics in a Boundary-Layer Wind Tunnel

    DEFF Research Database (Denmark)

    Barlas, Emre; Buckingham, Sophia; van Beeck, Jeroen

    2016-01-01

    Increasing demand in wind energy has resulted in increasingly clustered wind farms, and raised the interest in wake research dramatically in the last couple of years. To this end, the present work employs an experimental approach with scaled three-bladed wind-turbine models in a large boundary......-layer windtunnel. Time-resolved measurements are carried out with a three-component hot-wire anemometer in the mid-vertical plane of the wake up to a downstream distance of eleven turbine diameters. The major issue addressed is the wake dynamics i.e. the flow and turbulence characteristics as well as spectral...

  7. Air mass flow estimation in turbocharged diesel engines from in-cylinder pressure measurement

    Energy Technology Data Exchange (ETDEWEB)

    Desantes, J.M.; Galindo, J.; Guardiola, C.; Dolz, V. [CMT - Motores Termicos, Universidad Politecnica de Valencia (Spain)

    2010-01-15

    Air mass flow determination is needed for the control of current internal combustion engines. Current methods are based on specific sensors (as hot wire anemometers) or indirect estimation through manifold pressure. With the availability of cylinder pressure sensors for engine control, methods based on them can be used for replacing or complementing standard methods. Present paper uses in cylinder pressure increase during the intake stroke for inferring the trapped air mass. The method is validated on two different turbocharged diesel engines and compared with the standard methods. (author)

  8. Network Wind Power Over the Pacific Northwest. Progress Report, October 1979-September 1980.

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Robert W.; Hewson, E. Wendell

    1980-10-01

    The research in FY80 is composed of six primary tasks. These tasks include data collection and analysis, wind flow studies around an operational wind turbine generator (WTG), kite anemometer calibration, wind flow analysis and prediction, the Klickitat County small wind energy conversion system (SWECS) program, and network wind power analysis. The data collection and analysis task consists of four sections, three of which deal with wind flow site surveys and the fourth with collecting and analyzing wind data from existing data stations. This report also includes an appendix which contains mean monthly wind speed data summaries, wind spectrum summaries, time series analysis plots, and high wind summaries.

  9. Low-energy house in Sisimiut - Measurement equipment

    DEFF Research Database (Denmark)

    Andersen, Philip Hvidthøft Delff; Rode, Carsten; Madsen, Henrik

    This paper documents the measurement equipment in a low-energy house in Sisimiut, Greenland. Detailed measurements are being taken on energy consumption, indoor temperatures, floor heating, ventilation, open/closed state of doors and windows, and indoors climate. Equipped with a central control...... on the power generated by the solar thermal system. A weather station equipped with thermometer, pyranometer and anemometer is installed on the building as well. Finally, it is described how to retrieve data from an SQL server which is configured to take monthly backups. R functions have been implemented...

  10. Improved interpretation and validation of CFD predictions

    DEFF Research Database (Denmark)

    Popiolek, Z.; Melikov, Arsen Krikor

    2004-01-01

    The mean velocity in rooms predicted by CFD simulations based on RANS equations differs from the mean (in time) magnitude of the velocity, i.e. the mean speed, in rooms measured by low velocity thermal anemometers with omnidirectional sensor. This discrepancy results in incorrect thermal comfort...... assessment by the CFD predictions as well as incorrect validation of the predicted velocity field. In this paper the discrepancies are discussed and identified, and a method for estimating of the mean speed based on the CFD predictions of mean velocity and kinetic turbulence energy is suggested. The method...

  11. Use of the WEST-1 wind turbine simulator to predict blade fatigue load distribution

    Science.gov (United States)

    Janetzke, D. C.

    1983-01-01

    To test the ability of WEST-1 to predict blade fatigue load distribution, actual wind signals were fed into the simulator and the response data were recorded and processed in the same manner as actual wind turbine data. The WEST-1 simulator was operated in a stable, unattended mode for six hours. The probability distribution of the cyclic flatwise bending moment for the blade was comparable to that for an actual wind turbine in winds with low turbulence. The input from a stationary anemometer was found to be inadequate for use in the prediction of fatigue load distribution for blade design purposes and modifications are necessary.

  12. ALEX2014: The Alqueva Hydro-Meteorological Experiment

    OpenAIRE

    Salgado, Rui; Potes, Miguel; Albino, André; Apolinário, João; Barbosa, Susana; Bárias, Samuel; Beliche, Paulo; Bortoli, Daniel; Canhoto, Paulo; Costa, Maria João; Fernandes, Rui; Harrison, Giles; Ilhéu, Ana; Le Moigne, Patrick; Lima, Raul

    2015-01-01

    During the four months of the ALEX 2014, the over water fluxes of momentum, heat and mass (H2O and CO2) were obtained with an integrated Open-Path CO2 /H2O Gas Analyser and 3D Sonic Anemometer, mounted on a floating platform (Fig.1) belonging to the Portuguese Environment Agency. The short and long wave, up and down, radiative fluxes were measured at the same place, as well as the water temperature profile. Eight near surface weather stations were operating during the field campaign, two in f...

  13. Lidar Scanning of Momentum Flux in and above the Atmospheric Surface Layer

    DEFF Research Database (Denmark)

    Mann, Jakob; Pena Diaz, Alfredo; Bingöl, Ferhat;

    2010-01-01

    Methods to measure the vertical flux of horizontal momentum using both continuous wave and pulsed Doppler lidar profilers are evaluated. The lidar measurements are compared to momentum flux observations performed with sonic anemometers over flat terrain at Høvsøre, Denmark, and profile......-derived vertical momentum flux observations at the Horns Rev wind farm in the North Sea. Generally, the momentum fluxes are reduced because of the finite measuring volume of the instruments, and the filtering is crudely accounted for theoretically. The essential parameter for the estimation of the reduction...

  14. Lidar Scanning of Momentum Flux in the Marine Boundary Layer

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo; Mann, Jakob; Courtney, Michael;

    Momentum flux measurements are important for describing the wind profile in the atmospheric boundary layer, modeling the atmospheric flow over water, the accounting of exchange processes between air and sea, etc. It is also directly related to the friction velocity, which is a velocity scale...... turbulence measurements from a sonic anemometer, showing high agreement. In this study, a conical scanning lidar is used to derive the momentum flux, which compares well to the estimations from the bulk-derived method, but it also shows a filtering effect due to the large spatial-averaging volume...

  15. 風力エネルギーデータ収集装置の開発

    OpenAIRE

    西本,澄

    1992-01-01

    A Data acquisiton system developed for wind energy applications will be described in this paper. This system is composed of an anemometer with two blades downwind and a computer which processes wind data. Wind energy calculated from an average wind speed is inaccurate, since wind power increases with the cube of wind velocity. To decide the design and the site for a wind turbine system, it is very important to consider wind data on a long term basis, that is the total wind energy and distribu...

  16. プロペラファンの翼先端相対流れ場と周期的な空力騒音に関する研究

    OpenAIRE

    佐々木, 壮一; 日高, 央也

    2015-01-01

    In order to clarify the main factor of the periodical aerodynamic noise in the off-design point of the propeller fan, the relative flow field in the blade tip is measured by the hot-wire anemometer with the phase-lock method. In particular, we discuss the influence of the rotational speed of the impeller experimentally for clarifying the relationship between the relative flow field and the periodical aerodynamic noise. When the propeller fan is operated at the off-design point, the periodaica...

  17. Local time estimation for the slotted correlation function of randomly sampled LDA data

    Energy Technology Data Exchange (ETDEWEB)

    Nobach, H. [Fachgebiet Stroemungslehre und Aerodynamik, Technische Universitaet Darmstadt (Germany)

    2002-03-01

    The task of autocorrelation and power spectral density estimation from velocity data sampled irregularly in time by a laser-Doppler anemometer (LDA) is addressed in this article. A new method based on the slotting technique was found to be a very reliable estimator. This article describes specific improvements of the slotting technique, the model-based variance estimation and the spectral transform leading to more accurate estimates of the autocorrelation function and the power spectral density. Furthermore, the new method yields more information especially at short time lags of the autocorrelation function, which can be used to derive improved estimates of the Taylor time scale. (orig.)

  18. Reconstruction of 3D flow structures in a cylindrical cavity with a rotating lid

    DEFF Research Database (Denmark)

    Meyer, Knud Erik

    will also be based on time-resolved stereoscopic PIV measurements in a vertical plane through the cylinder axis as shown in figure 1. Compared to Meyer et al (2008) the measurements will be expanded by adding measurements in several points outside the PIV data plane with a Laser Doppler Anemometer (LDA......). LDA has a very good time resolution and the synchronized PIV and LDA measurements will therefore resolve the ambiguity in the interpretation of PIV data with respect to whether the flow variations are caused by rotation of a three-dimensional structure or is a real transient phenomenon....

  19. Estimation of Wind Speed in Connection to a Wind Turbine

    DEFF Research Database (Denmark)

    Ma, Xin; Poulsen, Niels Kjølstad; Bindner, Henrik

    The wind speed varies over the rotor plane of wind turbine making it impossible to determine from a single wind speed measurement taken by an anemometer. However, in this paper the wind speed on the rotor plane will be estimated by using a wind turbine as a wind measuring device. To realize...... the idea, a knowledge of the system characteristics is required, therefore the fundamental relations and principles of system dynamics will be presented. Several estimation methods such as Newton-Raphson method, Kalman filter method and extended Kalman filter method will be investigated in the paper....

  20. The effects of propeller tip vane on flow-field behavior

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, T. [Fujitsu Labs. Ltd., Kanagawa (Japan); Nigim, H.H. [Dept. of Mech. Engineering, Faculty of Engineering, Birzeit University, P.O. Box 14, Birzeit, West Bank, Palestine (Israel); Koyama, H.S. [Dept. of Mech. Engineering, Tokyo Denki University, 2-2 Kanda-Nishikicho, Chiyoda-ku, Tokyo 101 (Japan)

    1997-11-01

    This paper investigates the effects of attaching a tip vane to a propeller blade on the development and propagation of a tip vortex. The study employed a two-bladed propeller operating with and without a tip vane. Evaluation of the tip vortex was studied by using both smoke-wire flow visualization, hot wire anemometer, and strain gauge load-cell techniques. The mean velocity distributions and the velocity unsteadiness data as well as thrust, input power and efficiencies were obtained. Experiments were repeated at various rotating speeds ranging from 2000 to 5000 rpm. (orig.) With 10 figs., 1 tab., 15 refs.

  1. Measurement of velocity in rotational flows using ultrasonic anemometry: the flowmeter

    Science.gov (United States)

    Franchini, S.; Sanz-Andrés, A.; Cuerva, A.

    2007-06-01

    In this paper a previously developed theoretical model of the measurement process performed by a transit-time ultrasonic anemometer is applied to a fluid flowing through a circular section pipe. This model considers the influence of the shift of the acoustic pulse trajectory from straight propagation due to the flow on the measured speed. The aim of this work is to estimate the errors induced in the measured velocity by the shift of the acoustic pulse trajectory. Using different duct’s flow models, laminar and turbulent regimes have been analyzed. The results show that neglecting the effect of shift of the acoustic pulse trajectory leads to flow rate measurement underestimation.

  2. An introduction to turbulence and its measurement

    CERN Document Server

    Bradshaw, P

    1971-01-01

    An Introduction to Turbulence and Its Measurement is an introductory text on turbulence and its measurement. It combines the physics of turbulence with measurement techniques and covers topics ranging from measurable quantities and their physical significance to the analysis of fluctuating signals, temperature and concentration measurements, and the hot-wire anemometer. Examples of turbulent flows are presented. This book is comprised of eight chapters and begins with an overview of the physics of turbulence, paying particular attention to Newton's second law of motion, the Newtonian viscous f

  3. Wind Speed Estimation and Parameterization of Wake Models for Downregulated Offshore Wind Farms

    DEFF Research Database (Denmark)

    Göçmen Bozkurt, Tuhfe; Giebel, Gregor; Poulsen, Niels Kjølstad;

    The estimation of possible (or available) power of a downregulated offshore wind farm is the content of the PossPOW project (See PossPOW Poster ID: 149). The main challenges of this estimation process are: 1) to determine the free stream equivalent wind speed at the turbine level since the accuracy...... of nacelle anemometers are in question and power curve derivation is no longer applicable during downregulation 2) to apply a real-time wake model which can calculate the power production as if the wind farm was operating normally even in short downregulation periods. However, most existing wake...

  4. Turbulence Time Series Data Hole Filling using Karhunen-Loeve and ARIMA methods

    CERN Document Server

    Chang, M P J L; Font, C O; Gilbreath, G C; Oh, E

    2007-01-01

    Measurements of optical turbulence time series data using unattended instruments over long time intervals inevitably lead to data drop-outs or degraded signals. We present a comparison of methods using both Principal Component Analysis, which is also known as the Karhunen--Loeve decomposition, and ARIMA that seek to correct for these event-induced and mechanically-induced signal drop-outs and degradations. We report on the quality of the correction by examining the Intrinsic Mode Functions generated by Empirical Mode Decomposition. The data studied are optical turbulence parameter time series from a commercial long path length optical anemometer/scintillometer, measured over several hundred metres in outdoor environments.

  5. Hot-Film and Hot-Wire Anemometry for a Boundary Layer Active Flow Control Test

    Science.gov (United States)

    Lenahan, Keven C.; Schatzman, David M.; Wilson, Jacob Samuel

    2013-01-01

    Unsteady active flow control (AFC) has been used experimentally for many years to minimize bluff-body drag. This technology could significantly improve performance of rotorcraft by cleaning up flow separation. It is important, then, that new actuator technologies be studied for application to future vehicles. A boundary layer wind tunnel was constructed with a 1ft-x-3ft test section and unsteady measurement instrumentation to study how AFC manipulates the boundary layer to overcome adverse pressure gradients and flow separation. This unsteady flow control research requires unsteady measurement methods. In order to measure the boundary layer characteristics, both hot-wire and hot-film Constant Temperature Anemometry is used. A hot-wire probe is mounted in the flow to measure velocity while a hot-film array lays on the test surface to measure skin friction. Hot-film sensors are connected to an anemometer, a Wheatstone bridge circuit with an output that corresponds to the dynamic flow response. From this output, the time varying flow field, turbulence, and flow reversal can be characterized. Tuning the anemometers requires a fan test on the hot-film sensors to adjust each output. This is a delicate process as several variables drastically affect the data, including control resistance, signal input, trim, and gain settings.

  6. High-resolution wind speed measurements using actively heated fiber optics

    Science.gov (United States)

    Sayde, Chadi; Thomas, Christoph K.; Wagner, James; Selker, John

    2015-11-01

    We present a novel technique to simultaneously measure wind speed (U) at thousands of locations continuously in time based on measurement of velocity-dependent heat transfer from a heated surface. Measuring temperature differences between paired passive and actively heated fiber-optic (AHFO) cables with a distributed temperature sensing system allowed estimation of U at over 2000 sections along the 230 m transect (resolution of 0.375 m and 5.5 s). The underlying concept is similar to that of a hot wire anemometer extended in space. The correlation coefficient between U measured by two colocated sonic anemometers and the AHFO were 0.91 during the day and 0.87 at night. The combination of classical passive and novel AHFO provides unprecedented dynamic observations of both air temperature and wind speed spanning 4 orders of magnitude in spatial scale (0.1-1000 m) while resolving individual turbulent motions, opening new opportunities for testing basic theories for near-surface geophysical flows.

  7. Preliminary analysis of the Nocturnal Atmospheric Boundary Layer during the experimental campaign CIBA 2008

    Science.gov (United States)

    Yagüe, C.; Maqueda, G.; Ramos, D.; Sastre, M.; Viana, S.; Serrano, E.; Morales, G.; Ayarzagüena, B.; Viñas, C.; Sánchez, E.

    2009-04-01

    An Atmospheric Boundary Layer campaign was developed in Spain along June 2008 at the CIBA (Research Centre for the Lower Atmosphere) site which is placed on a fairly homogeneous terrain in the centre of an extensive plateau (41°49' N, 4°56' W). Different instrumentation at several levels was available on a new 10m meteorological mast, including temperature and humidity sensors, wind vanes and cup anemometers, as well as one sonic anemometer. Besides, two quartz-based microbarometers were installed at 50 and 100m on the main permanent 100m tower placed at CIBA. Three additional microbarometers were deployed on the surface on a triangular array of approximately 200 m side, and a tethered balloon was used in order to record vertical profiles of temperature, wind and humidity up to 1000m. Finally, a GRIMM particle monitor (MODEL 365), which can be used to continuously measure each six seconds simultaneously the PM10, PM2.5 and PM1 values, was deployed at 1.5m. This work will show some preliminary results from the campaign CIBA 2008, analysing the main physical processes present in the atmospheric Nocturnal Boundary Layer (NBL), the different stability periods observed and the corresponding turbulent parameters, as well as the coherent structures detected. The pressure perturbations measured from the surface and tower levels make possible to study the main wave parameters from wavelet transform, and compared the structures detected by the microbarometers with those detected in the wind and particles records.

  8. Evaluation of turbulent dissipation rate retrievals from Doppler Cloud Radar

    Directory of Open Access Journals (Sweden)

    M. D. Shupe

    2012-06-01

    Full Text Available Turbulent dissipation rate retrievals from cloud radar Doppler velocity measurements are evaluated using independent, in situ observations in Arctic stratocumulus clouds. In situ validation data sets of dissipation rate are derived using sonic anemometer measurements from a tethered balloon and high frequency pressure variation observations from a research aircraft, both flown in proximity to stationary, ground-based radars. Modest biases are found among the data sets in particularly low- or high-turbulence regimes, but in general the radar-retrieved values correspond well with the in situ measurements. Root mean square differences are typically a factor of 4–6 relative to any given magnitude of dissipation rate. These differences are no larger than those found when comparing dissipation rates computed from tethered-balloon and meteorological tower-mounted sonic anemometer measurements made at spatial distances of a few hundred meters. Temporal lag analyses suggest that approximately half of the observed differences are due to spatial sampling considerations, such that the anticipated radar-based retrieval uncertainty is on the order of a factor of 2–3. Moreover, radar retrievals are clearly able to capture the vertical dissipation rate structure observed by the in situ sensors, while offering substantially more information on the time variability of turbulence profiles. Together these evaluations indicate that radar-based retrievals can, at a minimum, be used to determine the vertical structure of turbulence in Arctic stratocumulus clouds.

  9. Observational study of atmospheric surface layer and coastal weather in northern Qatar

    Science.gov (United States)

    Samanta, Dhrubajyoti; Sadr, Reza

    2016-04-01

    Atmospheric surface layer is the interaction medium between atmosphere and Earth's surface. Better understanding of its turbulence nature is essential in characterizing the local weather, climate variability and modeling of turbulent exchange processes. The importance of Middle East region, with its unique geographical, economical and weather condition is well recognized. However, high quality micrometeorological observational studies are rare in this region. Here we show experimental results from micrometeorological observations from an experimental site in the coastal region of Qatar during August-December 2015. Measurements of winds are obtained from three sonic anemometers installed on a 9 m tower placed at Al Ghariyah beach in northern Qatar (26.08 °N, 51.36 °E). Different surface layer characteristics is analyzed and compared with earlier studies in equivalent weather conditions. Monthly statistics of wind speed, wind direction, temperature, humidity and heat index are made from concurrent observations from sonic anemometer and weather station to explore variations with surface layer characteristics. The results also highlights potential impact of sea breeze circulation on local weather and atmospheric turbulence. The observed daily maximum temperature and heat index during morning period may be related to sea breeze circulations. Along with the operational micrometeorological observation system, a camera system and ultrasonic wave measurement system are installed recently in the site to study coastline development and nearshore wave dynamics. Overall, the complete observational set up is going to provide new insights about nearshore wind dynamics and wind-wave interaction in Qatar.

  10. Automation&Characterization of US Air Force Bench Top Wind Tunnels - Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, J.E.

    2006-03-23

    The United States Air Force Precision Measurement Equipment Laboratories (PMEL) calibrate over 1,000 anemometer probes per year. To facilitate a more efficient calibration process for probe-style anemometers, the Air Force Metrology and Calibration Program underwent an effort to modernize the existing PMEL bench top wind tunnels. Through a joint effort with the Department of Energy's Oak Ridge National Laboratory, the performance of PMEL wind tunnels was improved. The improvement consisted of new high accuracy sensors, automatic data acquisition, and a software-driven calibration process. As part of the wind tunnel upgrades, an uncertainty analysis was completed, laser Doppler velocimeter profiling was conducted to characterize the velocities at probe locations in the wind tunnel, and pitot tube calibrations of the wind tunnel were verified. The bench top wind tunnel accuracy and repeatability has been measured for nine prototype wind tunnel systems and valuable field experience has been gained with these wind tunnels at the PMELs. This report describes the requirements for the wind tunnel improvements along with actual implementation strategies and details. Lessons-learned from the automation, the velocity profiling, and the software-driven calibration process will also be discussed.

  11. MPPT for PM wind generator using gradient approximation

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Ying-Yi; Lu, Shiue-Der; Chiou, Ching-Sheng [Department of Electrical Engineering, Chung Yuan Christian University, 200, Chung-Pei Road, Chung Li 320 (China)

    2009-01-15

    This paper applies new maximum-power-point tracking (MPPT) algorithms to a wind-turbine generator system (WTGS). In this paper, the WTGS is a direct-drive system and includes the wind-turbine, permanent-magnet (PM) synchronous generator, three-phase full bridge rectifier, buck-boost converter and load. The new MPPT method uses gradient approximation (GA) algorithm. Three methods based on GA for achieving MPPT are discussed in this paper: (1) full-sensor control with anemometer and tachometer, (2) rule-based method and (3) adaptive duty cycle method. The third method has merits of no PID parameters, proportional constant, anemometer, tachometer and characteristics of WTGS required. This method enables the permanent-magnet synchronous generator (PMSG) to operate at variable speeds to achieve good performance. Simulation results show that the tip-speed ratio (TSR) and power coefficient obtained by the adaptive duty cycle method with GA can be almost identical to the optimal values. (author)

  12. Helicity and potential vorticity in the surface boundary layer turbulence

    Science.gov (United States)

    Chkhetiani, Otto; Kurgansky, Michael; Koprov, Boris; Koprov, Victor

    2016-04-01

    An experimental measurement of all three components of the velocity and vorticity vectors, as well as the temperature and its gradient, and potential vorticity, has been developed using four acoustic anemometers. Anemometers were placed at vertices of a tetrahedron, the horizontal base of which was a rectangular triangle with equal legs, and the upper point was exactly above the top of the right angle. The distance from the surface to the tetrahedron its base was 5.5 m, and the lengths of legs and a vertical edge were 5 m. The measurements were carried out of total duration near 100 hours both in stable and unstable stratification conditions (at the Tsimlyansk Scientific Station in a uniform area of virgin steppe 700 x 650 m, August 2012). A covariance-correlation matrix for turbulent variations in all measured values has been calculated. In the daytime horizontal and vertical components of the helicity are of the order of -0.03 and +0.01 m s-2, respectively. The nighttime signs remain unchanged, but the absolute values are several times smaller. It is confirmed also by statistics of a relative helicity. The cospectra and spectral correlation coefficients have been calculated for all helicity components. The time variations in the components of "instantaneous" relative helicity and potential vorticity are considered. Connections of helicity with Monin-Obukhov length and the wind vertical profile structure are discussed. This work was supported by the Russian Science Foundation (Project No 14-27-00134).

  13. Wind shear proportional errors in the horizontal wind speed sensed by focused, range gated lidars

    DEFF Research Database (Denmark)

    Lindelöw, Per Jonas Petter; Courtney, Michael; Parmentier, R.;

    2008-01-01

    The 10-minute average horizontal wind speeds sensed with lidar and mast mounted cup anemometers, at 60 to 116 meters altitude at Hovsore, are compared. The lidar deviation from the cup value as a function of wind velocity and wind shear is studied in a 2-parametric regression analysis which revea...... for wind velocity and wind shear dependent errors are discussed. The 2-parametric regression analysis described in this paper is proven to be a better approach when acceptance testing and calibrating lidars.......The 10-minute average horizontal wind speeds sensed with lidar and mast mounted cup anemometers, at 60 to 116 meters altitude at Hovsore, are compared. The lidar deviation from the cup value as a function of wind velocity and wind shear is studied in a 2-parametric regression analysis which reveals...... an altitude dependent relation between the lidar error and the wind shear. A likely explanation for this relation is an error in the intended sensing altitude. At most this error is estimated to 9 in which induced errors in the horizontal wind velocity of up to 0.5 m/s as compared to a cup at the intended...

  14. Inertial-Dissipation flux measurements over south Bay of Bengal during BOBMEX— Pilot experiment

    Indian Academy of Sciences (India)

    M Venkataramana; K SenGupta; G S Bhat; S Ameenulla; J V S Raju

    2000-06-01

    This paper describes measurement of air-sea parameters and estimation of sensible and latent heat fluxes by the ``Inertial-Dissipation'' technique over south Bay of Bengal. The data were collected on ORV Sagar Kanya during BOBMEX-Pilot cruise during the period 23rd October 1998 to 12th November 1998 over south Bay of Bengal. The fluxes are estimated using the data collected through fast response sensors namely Gill anemometer, Sonic anemometer and IR Hygrometer. In this paper the analyses carried out for two days, one relatively cloud free day on November 3rd and the other cloudy with rain on November 1st, are presented. Sea surface and air temperatures are higher on November 3rd than on November 1st. Sensible heat flux for both the days does not show any significant variation over the period of estimation, whereas latent heat flux is more for November 3rd than November 1st. An attempt is made to explain the variation of latent heat flux with a parameter called thermal stability on the vapor transfer from the water surface, which depends on wind speed and air to sea surface temperature difference.

  15. Measured and predicted rotor performance for the SERI advanced wind turbine blades

    Science.gov (United States)

    Tangler, J.; Smith, B.; Kelley, N.; Jager, D.

    1992-02-01

    Measured and predicted rotor performance for the Solar Energy Research Institute (SERI) advanced wind turbine blades were compared to assess the accuracy of predictions and to identify the sources of error affecting both predictions and measurements. An awareness of these sources of error contributes to improved prediction and measurement methods that will ultimately benefit future rotor design efforts. Propeller/vane anemometers were found to underestimate the wind speed in turbulent environments such as the San Gorgonio Pass wind farm area. Using sonic or cup anemometers, good agreement was achieved between predicted and measured power output for wind speeds up to 8 m/sec. At higher wind speeds an optimistic predicted power output and the occurrence of peak power at wind speeds lower than measurements resulted from the omission of turbulence and yaw error. In addition, accurate two-dimensional (2-D) airfoil data prior to stall and a post stall airfoil data synthesization method that reflects three-dimensional (3-D) effects were found to be essential for accurate performance prediction.

  16. Comparative study of the behavior of wind-turbines in a wind farm

    Energy Technology Data Exchange (ETDEWEB)

    Migoya, Emilio; Crespo, Antonio; Garcia, Javier; Manuel, Fernando; Jimenez, Angel [Universidad Politecnica de Madrid (UPM), Madrid (Spain). Departamento de Ingenieria Energetica y Fluidomecanica, Laboratorio de Mecanica de Fluidos; Moreno, Fermin [Comision Nacional de la Energia, Madrid (Spain); Costa, Alexandre [Energia Eolica, Division de Energias Renovables, CIEMAT, Madrid (Spain)

    2007-10-15

    The Sotavento wind farm is an experimental wind farm which has different types of wind turbines. It is located in an area whose topography is moderately complex, and where wake effects can be significant. One of the objectives of Sotavento wind farm is to compare the performances of the different machines; particularly regarding power production, maintenance and failures. However, because of wakes and topography, the different machines are not working under identical conditions. Two linearized codes have been used to estimate topography effects: UPMORO and WAsP. For wind directions in which topography is abrupt, the non-linear flow equations have been solved with the commercial code FLUENT, although the results are only qualitatively used. For wake effects, the UPMPARK code has been applied. As a result, the incident velocity over each wind turbine is obtained, and the power production is estimated by means of the power curve of each machine. Experimental measurements give simultaneously the wind characteristics at the measuring stations, the wind velocity, at the nacelle anemometer, and the power production of each wind turbine. These experimental results are employed to validate the numerical predictions. The main objective of this work is to deduce and validate a relationship between the wind characteristics measured in the anemometers and the wind velocity and the power output in each machine. (author)

  17. 风向变化对高海拔山地风电场发电效益的影响%Effect of Wind Direction Variation on Beneift In Wind Farm In Mountain Area At High Altitude

    Institute of Scientific and Technical Information of China (English)

    黄劲明

    2016-01-01

    Wind direction difference in different area in a wind farm causes that data from anemometer tower is unrepresentative. Especially, in mountain platform wind farm, wind forming condition complexity due to the micro topography leads to the wind direction variety. Data deviation from the main anemometer tower often affects the generation and the economics of a wind turbine. In this paper, it is analyzed that wind direction variation due to the micro topography in a wind farm leads to generation reduction and affects the economics as well. To avoid of generation reduction due to wind direction difference in mountain area fringe, strengthening measuring wind in this area for wind turbines layout is proposed.%本文通过某山地风电场由于微观地形对风电场局部风向的改变,导致该区域风机发电量的减少,影响风电场经济性的问题,提出了在高山台地风电场布机应加强对场址边缘区域的测风观测,避免由于微地形风向差异的影响导致风机发电量下降的措施及建议。

  18. Turbine Inflow Characterization at the National Wind Technology Center: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Clifton, A.; Schreck, S.; Scott, G.; Kelley, N.; Lundquist, J.

    2012-01-01

    Utility-scale wind turbines operate in dynamic flows that can vary significantly over timescales from less than a second to several years. To better understand the inflow to utility-scale turbines, two inflow towers were installed and commissioned at the National Renewable Energy Laboratory's (NREL) National Wind Technology Center near Boulder, Colorado, in 2011. These towers are 135 m tall and instrumented with a combination of sonic anemometers, cup anemometers, wind vanes, and temperature measurements to characterize the inflow wind speed and direction, turbulence, stability and thermal stratification to two utility-scale turbines. Herein, we present variations in mean and turbulent wind parameters with height, atmospheric stability, and as a function of wind direction that could be important for turbine operation as well as persistence of turbine wakes. Wind speed, turbulence intensity, and dissipation are all factors that affect turbine performance. Our results shown that these all vary with height across the rotor disk, demonstrating the importance of measuring atmospheric conditions that influence wind turbine performance at multiple heights in the rotor disk, rather than relying on extrapolation from lower levels.

  19. Evaluating wind power potential in the Spanish Antarctic Base (BAE); Evaluacion del Potencial Eolico en la Base Antartica Espanola Juan Carlos I

    Energy Technology Data Exchange (ETDEWEB)

    Arribas de Paz, L. M.; Garcia Barquero, C.; Navarro Montesinos, J.; Cuerva Tejero, A.; Cruz Cruz, I.; Roque Lopez, V.; Marti Perez, I. [Ciemat. Madrid (Spain)

    2000-07-01

    The objective of the work is to model wind field in the surroundings of the Spanish Antarctic Base (BAE in the following). The need of such a work comes from the necessity of an energy source able to supply the energy demand in the BAE during the Antarctic winter. When the BAE is in operation (in the Antarctic summer) the energy supply comes from a diesel engine. In the Antartic winter the base is closed, but the demand of energy supply is growing up every year because of the increase in the number of technical and scientific machines that remain in the BAE taking different measurements. For this purpose the top of a closed hill called Pico Radio, not perturbed by close obstacles, has been chosen as the better site for the measurements. The measurement station is made up with a sonic an-emometer and a small wind generator to supply the energy needed by the sensors head heating of the anemometer. this way, it will be also used as a proof for the suitability of a wind generator in the new chosen site, under those special climactic conditions. (Author) 3 refs.

  20. Investigation of turbulence measurements with a continuous wave, conically scanning LiDAR

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, R.; Mikkelsen, T.; Courtney, M.

    2009-03-15

    LIDAR systems are getting more and more accurate and reliable. It has been shown many times that the mean horizontal wind speed measured by a lidar over flat terrain compares very well with that measured by a cup anemometer. But can a lidar measure turbulence? Here we investigate the case of a continuous wave, conically scanning Zephir lidar. First, the wind speed standard deviation measured by such a lidar gives on average 80% of the standard deviation measured by a cup anemometer. This difference is due to the spatial averaging inherently made by a cw conically scanning lidar. The spatial averaging is done in two steps: 1) the weighted averaging of the wind speed in the probe volume of the laser beam; 2) the averaging of the wind speeds occurring on the circular path described by the conically scanning lidar. Therefore the standard deviation measured by a lidar resolves only the turbulence structures larger than a length scale depending on the circle diameter and the mean wind speed (range of magnitude: 100m). However, the Zephir lidar gives another turbulence quantity, the so-called turbulence parameter, which can resolve turbulence structures with a smaller length scale. In this paper, we suggest a volumetric filtering of the turbulence to represent the effect of the spatial averaging operated by a lidar when measuring the wind speed. We then evaluate this model by comparing the theoretical results to experimental data obtained with several Zephir systems, for both turbulence quantities. (au)

  1. Velocity statistics and spectra over a forested site measured with a tall mast

    Science.gov (United States)

    Segalini, Antonio; Alfredsson, Henrik; Dellwik, Ebba; Arnqvist, Johan; Bergström, Hans

    2012-11-01

    In the large expansion of wind power it becomes necessary to use also non-ideal sites for the placement of turbines. Such sites may have a complex terrain in terms of surface elevation as well as being forested. The atmospheric boundary layer is assumed to be severely different as compared to the one over flat, low-vegetation areas, which changes the mean velocity distribution as well as the turbulence intensity, thereby negatively affecting both the power production and loads on the turbines. In this study we use data from a 140 m tall mast in a forest in South-Eastern Sweden, where a unique measurement campaign with sonic anemometers has been running since November 2010 for 16 months. The sonic anemometers give the three velocity components with a frequency resolution of about 10 Hz. The site is covered by approximately 20 m high trees and a 40 degree sector, representative of an approximately homogeneous forest flow, is selected for the analysis of the velocity statistics. The screening of the results indicates the presence of a constant stress layer up to 3-5 canopy heights from the ground. An evaluation of the turbulence statistics in this layer and the levels above is presented. In addition, the spectra are evaluated and compared with the commonly used turbulence models.

  2. A comparison of selected vertical wind measurement techniques on basis of the EUCAARI IMPACT observations

    Science.gov (United States)

    Arabas, S.; Baehr, C.; Boquet, M.; Dufournet, Y.; Pawlowska, H.; Siebert, H.; Unal, C.

    2009-04-01

    The poster presents a comparison of selected methods for determination of the vertical wind in the boundary layer used during the EUCAARI IMPACT campaign that took place in May 2008 in The Netherlands. The campaign covered a monthlong intensified ground-based and airborne measurements in the vicinity of the CESAR observatory in Cabauw. Ground-based vertical wind remote sensing was carried out using the Leosphere WindCube WLS70 IR Doppler lidar, Vaisala LAP3000 radar wind-profiler and the TUDelft TARA S-band radar. In-situ airborne measurements were performed using an ultrasonic anemometer (on the ACTOS helicopter underhung platform) and a 5-hole pressure probe (on the SAFIRE ATR-42 airplane radome). Several in-situ anemometers were deployed on the 200-meter high tower of the CESAR observatory. A summary of the characteristics and principles of the considered techniques is presented. A comparison of the results obtained from different platforms depicts the capabilities of each technique and highlights the time, space and velocity resolutions.

  3. Evaluating Wind Power Potential in the Spanish Antarctic Base (BAE)

    International Nuclear Information System (INIS)

    The objective of the work is to model wind field in the surroundings of the Spanish Antarctic Base (BAE in the following). The need of such a work comes from the necessity of an energy source able to supply the energy demand in the BAE during the Antarctic winter. When the BAE is in operation (in the Antarctic summer) the energy supply comes from a diesel engine. In the Antarctic winter the base is closed, but the demand of energy supply is growing up every year because of the increase in the number of technical and scientific machines that remain in the BAE taking different measurements. For this purpose the top of a closed hill called Pico Radio, not perturbed by close obstacles, has been chosen as the better site for the measurements. The measurement station is made up with a sonic anemometer and a small wind generator to supply the energy needed by the sensors head heating of the anemometer. This way, it will be also used as a proof for the suitability of a wind generator in the new chosen site, under those special climatic conditions.(Author) 3 refs

  4. Advancements in Wind Energy Metrology - UPWIND 1A2.3

    Energy Technology Data Exchange (ETDEWEB)

    Pedersen, Troels F.; Wagner, R.

    2011-02-15

    An overview of wind related metrology research made at Risoe DTU over the period of the UPWIND project is given. A main part of the overview is devoted to development of the Lidar technology with several sub-chapters considering different topics of the research. Technical problems are not rare for this new technology, and testing against a traditional met mast have shown to be efficient for gaining confidence with the ground based Lidar technology and for trust in accuracy of measurements. In principle, Lidar measurements could be traceable through the fundamental measurement principles, but at this stage of development it is not found feasible. Instead, traceability is secured through comparison with met masts that are traceable through wind tunnel calibrations of cup anemometers. The ground based Lidar measurement principle works almost acceptable in flat terrain. In complex terrain and close to woods the measurement volume is disturbed because the flow is no longer horizontally homogeneous. These conditions require special attention and correction methods. Due to the large measurement volume, ground based Lidars perform a spatial averaging which has the effect of a low pass filter on turbulence measurements. Theory and measurements seem to be in good agreement. Lidar measurements from a rotating spinner have been performed. The analysis show good perspectives for scanning the incoming wind, which may lead to better controlled wind turbines. Lidars have also been used to scan the wake of wind turbines. These measurements document the meandering wake pattern. The second part of the overview considers power performance measurements. A new investigation on the influence of wind shear points to a revision of the definition of a power curve. A new measurement method has been developed which has a good chance of being implemented in the present revision of the IEC performance standard. Also, a turbulence normalization method has been tested but not found efficient

  5. Three-Dimensional Venturi Sensor for Measuring Extreme Winds

    Science.gov (United States)

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

    2003-01-01

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

  6. Combining Wind-Tunnel and Field Measurements of Street-Canyon Flow via Stochastic Estimation

    Science.gov (United States)

    Perret, Laurent; Blackman, Karin; Savory, Eric

    2016-06-01

    We demonstrate how application of the stochastic estimation method can be employed to combine spatially well-resolved wind-tunnel particle image velocimetry measurements with instantaneous velocity signals from a limited number of sensors (six sonic anemometers located within the canyon in the present case) to predict full-scale flow dynamics in an entire street-canyon cross-section. The investigated configuration corresponds to a street-canyon flow in a neutrally stratified atmospheric boundary layer with the oncoming flow being perpendicular to the main canyon axis. Data were obtained during both full-scale and 1:200-scale wind-tunnel experiments. The performance of the proposed method is investigated using both wind-tunnel data and signals from five sonic anemometers to predict the velocity from the sixth one. In particular, based on analysis of the influence of the high-frequency velocity fluctuations on the quality of the reconstruction, it is shown that stochastic estimation is able to correctly reproduce the large-scale temporal features of the flow with the present set-up. The full dataset is then used to spatially extrapolate the instantaneous flow measured by the six sonic anemometers and perform detailed analysis of instantaneous flow features. The main features of the flow, such as the presence of the shear layer that develops over the canyon and the intermittent ejection and penetration events across the canyon opening, are well predicted by stochastic estimation. In addition, thanks to the high spatial resolution made possible by the technique, the intermittency of the main vortical structure existing within the canyon is demonstrated, as well as its meandering motion in the canyon cross-section. It is also shown that the canyon flow, particularly its spanwise component, is affected by large-scale fluctuations of low temporal frequency along the canyon axis. Finally, the proposed techniques based on wind-tunnel data can prove useful for a priori

  7. Surface Layer Turbulence During a Frontal Passage

    Energy Technology Data Exchange (ETDEWEB)

    Piper, M; Lundquist, J K

    2004-06-15

    Some recent investigations have begun to quantify turbulence and dissipation in frontal zones to address the question of what physical mechanism counteracts the intensification of temperature and velocity gradients across a developing front. Frank (1994) examines the turbulence structure of two fronts that passed a 200m instrumented tower near Karlsruhe, Germany. In addition to showing the mean vertical structure of the fronts as they pass the tower, Frank demonstrates that there is an order of magnitude or more increase in turbulent kinetic energy across the frontal zone. Blumen and Piper (1999) reported turbulence statistics, including dissipation rate measurements, from the MICROFRONTS field experiment, where high-frequency turbulence data were collected from tower-mounted hotwire and sonic anemometers in a cold front and in a density current. Chapman and Browning (2001) measured dissipation rate in a precipitating frontal zone with high-resolution Doppler radar. Their measurements were conducted above the surface layer, to heights of 5km. The dissipation rate values they found are comparable to those measured in Kennedy and Shapiro (1975) in an upper-level front. Here, we expand on these recent studies by depicting the behavior of the fine scales of turbulence near the surface in a frontal zone. The primary objective of this study is to quantify the levels of turbulence and dissipation occurring in a frontal zone through the calculation of kinetic energy spectra and dissipation rates. The high-resolution turbulence data used in this study are taken during the cold front that passed the MICROFRONTS site in the early evening hours of 20 March 1995. These new measurements can be used as a basis for parameterizing the effects of surface-layer turbulence in numerical models of frontogenesis. We present three techniques for calculating the dissipation rate: direct dissipation technique, inertial dissipation technique and Kolmogorov's four-fifths law. Dissipation

  8. ROUGHNESS LENGTHS FOR THE SAVANNAH RIVER SITE

    Energy Technology Data Exchange (ETDEWEB)

    Hunter, C.

    2012-03-28

    Surface roughness values for the areas surrounding the H, D and N-Area meteorological towers were computed from archived 2010 meteorological data. These 15-minute-averaged data were measured with cup anemometers and bidirectional wind vanes (bivanes) 61 m above the surface. The results of the roughness calculation using the standard deviation of elevation angle {sigma}{sub E}, and applying the simple formula based on tree canopy height, gave consistent estimates for roughness around the H-Area tower in the range of 1.76 to 1.86 m (95% confidence interval) with a mean value of 1.81 m. Application of the {sigma}{sub E} method for the 61-m level at D and N-Areas gave mean values of 1.71 and 1.81 with confidence ranges of 1.62-1.81 and 1.73-1.88 meters, respectively. Roughness results are azimuth dependent, and thus are presented as averages over compass sectors spanning 22.5 degrees. Calculated values were compared to other methods of determining roughness, including the standard deviation of the azimuth direction, {sigma}{sub A}, and standard deviation of the wind speed, {sigma}{sub U}. Additional data was obtained from a sonic anemometer at 61-m on the H-Area tower during a period of a few weeks in 2010. Results from the sonic anemometer support our use of {sigma}{sub E} to calculate roughness. Based on the H-Area tower results, a surface roughness of 1.8 m using is recommended for use in dispersion modeling applications that consider the impacts of a contaminant release to individuals along the Site boundary. The canopy surrounding the H-Area tower is relatively uniform (i.e., little variance in roughness by upwind direction), and data supplied by the U.S. Forest Service at Savannah River show that the canopy height and composition surrounding the H-Area tower is reasonably representative of forested areas throughout the SRS reservation. For dispersion modeling analyses requiring assessments of a co-located worker within the respective operations area, recommended

  9. EXPERIMENTAL AND NUMERICAL INVESTIGATION OF TURBULENT AIR-CUSHION-CASCADE

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Experimental and numerical studies of air-cushion-cascade were conducted and described. The SIMPLE algorithm combined with the normal k-ε turbulence model was adopted to simulate the air-phase flow. The experiment was carried out an IFA 300 anemometer. The flow field was measured for different ratios of main-stream velocity to jet velocity, different numbers of gaps and a couple of gap widths. The contur of the air-cushion was obtained, and the numerical calculations gave a closed-form result. The results show that the air-cushion thickness would increase with the increase of the jet volcoity, gap width and gap number mainly determined by the jet in the former half cascade. The possibility to achieve anti-erosion by the turbulent jet was examined and confirmed.

  10. Particle modulations to turbulence in two-phase round jets

    Institute of Scientific and Technical Information of China (English)

    Bing Wang; Huiqiang Zhang; Yi Liu; Xiaofen Yan; Xilin Wang

    2009-01-01

    The particle modulations to turbulence in round jets were experimentally studied by means of two-phase velocity measurements with Phase Doppler Anemometer (PDA). Laden with very large particles, no significant attenuations of turbulence intensities were measured in the far-fields, due to small two-phase slip velocities and particle Reynolds number. The gas-phase turbulence is enhanced by particles in the near-fields, but it is significantly attenuated by the small particles in the far-fields. The smaller particles have a more profound effect on the attenuation of turbulence intensities. The enhancements or attenuations of turbulence intensities in the far-fields depends on the energy production, transport and dissipation mechanisms between the two phases, which are determined by the particle prop-erties and two-phase velocity slips. The non-dimensional parameter CTI is introduced to represent the change of turbulence intensity.

  11. The Høvsøre Tall Wind-Profile Experiment: A Description of Wind Profile Observations in the Atmospheric Boundary Layer

    DEFF Research Database (Denmark)

    Peña, Alfredo; Floors, Rogier Ralph; Gryning, Sven-Erik

    2014-01-01

    for the analysis of vertical wind-speed profiles under a wide range of atmospheric stability, turbulence, and forcing conditions. One of the objectives of the campaign was to serve as a benchmark for flow over flat terrain models. The observations consist of combined wind lidar and sonic anemometer measurements...... at a meteorological mast. The sonic measurements cover the first 100mand the wind lidar measures above 100m every 50min the vertical. Results of the analysis of observations of the horizontal wind-speed components in the range 10–1200 m and surface turbulence fluxes are illustrated in detail, combined with forcing...... conditions derived from mesoscale model simulations. Ten different cases are presented. The observed wind profiles approach well the simulated gradient and geostrophic winds close to the simulated boundary-layer height during both barotropic and baroclinic conditions, respectively, except for a low-level jet...

  12. Determining the power-law wind-profile exponent under near-neutral stability conditions at sea

    Science.gov (United States)

    Hsu, S. A.; Meindl, Eric A.; Gilhousen, David B.

    1994-01-01

    On the basis of 30 samples from near-simultaneous overwater measurements by pairs of anemometers located at different heights in the Gulf of Mexico and off the Chesapeake Bay, Virginia, the mean and standard deviation for the exponent of the power-law wind profile over the ocean under near-neutral atmospheric stability conditions were determined to be 0.11 +/- 0.03. Because this mean value is obtained from both deep and shallow water environments, it is recommended for use at sea to adjust the wind speed measurements at different heights to the standard height of 10 m above the mean sea surface. An example to apply this P value to estimate the momentum flux or wind stress is provided.

  13. Microclimate Influence on Bird Arrival Behavior Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Herman, R. [Radford Univ., VA (United States); O’Brien, S. [Radford Univ., VA (United States)

    2016-03-01

    Using our own prototype sensor arrays that were deployed to collect microclimate data, we were able to visualize distinct differences in temperature, wind speed, and humidity over very small ranges of distance. We collected data across four polygons within the Barrow Environmental Observatory site. Our prototype microclimate arrays were based on an Arduino microcontroller, DS18B20 temperature sensors, DHT11 relative humidity/temperature sensors, and Vernier anemometers. Data were obtained in a small grid pattern with four sensors spaced 60 cm apart along the x-axis, and moved at 60 cm increments along a y-line across a polygon. Overlaying bird nest location with such data has allowed us to better answer our research question, “How do Arctic birds choose where to nest to maximize fitness in harsh Arctic environments?”

  14. Options of microclimate optimization in stable objects with respect to thermal comfort

    Directory of Open Access Journals (Sweden)

    Anna Šimková

    2013-05-01

    Full Text Available The study was carried out at the farm in Petrovice. Dairy cows and heifers were included in the experiment. The relative humidity, temperature, cooling value environment and flow rate in stables were measured. The flow rate was measured by the handheld anemometer. The relative humidity and the temperature were obtained by the data logger with sensors. The cooling value environment was obtained by the psychrometer. The rectal temperature was measured simultaneously as further value. It was rated 3 different groups of dairy cows and heifers in 2 stables. The aim of this work was finding how this values impact thermal comfort of the animals. The temperature is the most significant factor because it is very variable value. The animals immediately react for change of this. All these measured values are important for optimal welfare of animals. They influence the productivity of dairy cows and heifers, milk quality, reproduction and health of animals.

  15. Numerical and experimental investigation of flow and scour around a half-buried sphere

    DEFF Research Database (Denmark)

    Dixen, Martin; Sumer, B. Mutlu; Fredsøe, Jørgen

    2013-01-01

    The paper describes the results of a numerical and experimental investigation of flow and scour around a half-buried sphere exposed to a steady current. Hot-film bed shear stress and Laser Doppler Anemometer measurements were made with a half sphere mounted on the smooth bed in an open channel....... The hydrodynamic model is a 3-D general purpose N–S flow solver. The k-omega SST turbulence model was used for closure. The flow model was used to study the horseshoe vortex and lee-wake vortex flow processes around the sphere. The flow model was coupled with a morphologic model to calculate scour around the half...... by the horseshoe-vortex flow and the lee-wake flow processes) on sediment transport. The results show that the scour depth increases and time scale decreases when the effect of externally-generated turbulence is incorporated in the calculations. Empirical expressions representing the numerically obtained data...

  16. Coolant mixing in LMFBR rod bundles and outlet plenum mixing transients. Progress report, March 1, 1978--May 31, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Todreas, N.E.; Golay, M.W.; Wolf, L.

    1978-01-01

    An optical technique has been developed for the measurement of the eddy diffusivity of heat in a transparent flowing medium. The method uses a combination of two established measurement tools: a Mach--Zehnder interferometer for the monitoring of turbulently fluctuating temperature and a Laser Doppler Anemometer (LDA) for the measurement of turbulent velocity fluctuations. The technique is applied to the investigation of flow fields characteristic of the LMFBR outlet plenum. The study is accomplished using air as the working fluid in a small scale Plexiglas test section. Flows are introduced into both the 1/15 scale FFTF outlet plenum and the 3/80 scale CRBR geometry plenum at inlet Reynolds numbers of 22,000.

  17. Wind turbine condition monitoring based on SCADA data using normal behavior models

    DEFF Research Database (Denmark)

    Schlechtingen, Meik; Santos, Ilmar

    2014-01-01

    ) a hydraulic oil leakage; (2) cooling system filter obstructions; (3) converter fan malfunctions; (4) anemometer offsets and (5) turbine controller malfunctions. Moreover, the graphical user interface (GUI) developed to access, analyze and visualize the data and results is presented.......This paper is part two of a two part series. The originality of part one was the proposal of a novelty approach for wind turbine supervisory control and data acquisition (SCADA) data mining for condition monitoring purposes. The novelty concerned the usage of adaptive neuro-fuzzy interference......) proposed the prediction errors provide information about the condition of the monitored components.Part two presents application examples illustrating the efficiency of the proposed method. The work is based on continuously measured wind turbine SCADA data from 18 modern type pitch regulated wind turbines...

  18. Point and planar LIF for velocity-concentration correlations in a jet in cross flow

    DEFF Research Database (Denmark)

    Meyer, Knud Erik; Özcan, Oktay; Larsen, Poul Scheel;

    2002-01-01

    (LDA). The flow considered is the mixing of a jet in a fully developed cross flow in a square duct with a width of 10 jet diameters. Both a laminar flow case, Re=675, and a turbulent flow case, Re=33750, are presented . For both flows, the ratio jet-to-duct mean velocities was R=3.3. Result of mean......, since these involve areas with high velocity- and concentration gradients, which in turn amplifies the effect of a finite measurement volume in the two measurement systems. In addition, the concentration measurement was realized by injecting clean water into the dye seeded main flow. This "inverse......Simultaneous measurements of velocities and concentration with Planar Laser Induced Fluorescense (PLIF) combined with Particle Image Velocimetry (PIV) are compared to similar measurements with pointwise Laser Induced Fluorescense (LIF) made with a slightly modified standard Laser Doppler Anemometer...

  19. Lidar measurements of plume statistics

    DEFF Research Database (Denmark)

    Ejsing Jørgensen, Hans; Mikkelsen, T.

    1993-01-01

    Surface-layer aerosol diffusion experiments have been conducted using artificial smoke plume releases at ground level over flat and homogeneously vegetated terrain at the Meppen proving grounds in the Federal Republic of Germany (1989). At fixed downwind locations in the range out to 800 m from...... the source, instantaneous crosswind plume profiles were detected repetitively at high spatial (1.5 m) and temporal (3 sec) intervals by use of a mini LIDAR system. The experiments were accompanied by measurement of the surface-layer mean wind and turbulence quantities by sonic anemometers. On the basis...... of measured crosswind concentration profiles, the following statistics were obtained: 1) Mean profile, 2) Root mean square profile, 3) Fluctuation intensities,and 4)Intermittency factors. Furthermore, some experimentally determined probability density functions (pdf's) of the fluctuations are presented. All...

  20. Effect of blood flow parameters on flow patterns at arterial bifurcations--studies in models.

    Science.gov (United States)

    Liepsch, D W

    1990-01-01

    Atherosclerotic lesions are found primarily at arterial bends and bifurcations. Flow disturbances at these anatomic sites play a major role in atherogenesis. How hemodynamic factors such as vessel geometry, the pulsatile nature of blood flow, vessel wall elasticity and the non-Newtonian flow behavior of blood influence the flow field at these sites must be clarified. We have performed fundamental studies using a birefringent solution in a simplified rigid 90 degree T-bifurcation and pulsatile flow. The velocity distribution was measured with a laser Doppler anemometer. Flow in an elastic abdominal aorta model has been visualized using magnetic resonance imaging. In both flow studies, zones with negative velocity were found. These model measurements demonstrate that no flow parameter can be neglected. Further detailed studies are necessary to examine the interaction between fluid dynamic and cellular surface properties. PMID:2404201

  1. Simulation and Feasibility Study of Flow Sensor on Flexible Polymer for Healthcare Application.

    Science.gov (United States)

    Maji, Debashis; Das, Soumen

    2013-12-01

    Development of microfabrication technology, along with an ever-increasing demand for reliable, low-cost clinical healthcare has led to the realization of various BioMEMS devices. Present study aims at developing a flexible flow sensor on polymer substrate to monitor real-time blood flow and determine plague formation satisfying sensitivity, biocompatibility, and reliability requirements. Transient simulation of temperature and velocity profile of the thermal-anemometer-based sensor wrapped around the catheter has been studied. Initial fabrication of the sensor over polydimethylsiloxane (PDMS) polymer along with thermal coefficient of resistance (TCR) measurement and flow sensing over straight heater has also been performed. The simulation and fabrication works show promising results toward successful development of a flow sensor for effective healthcare delivery.

  2. Turbulence regime near the forest floor of a mixed broad leaved/Korean pine forest in Changbai Mountains

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The measurement and observation for this study were carried out by using a three-dimensional (u, v, w) Sonic anemometer (IAP-SA 485), at Forest Ecosystem Opened Research Station of Changbai Mountains (128(28'E and 42(24' N, Jilin Province, P. R. China) in August 2001. The basic characteristics of turbulence, such as turbulence intensity, atmospheric stability, time scales, and convection state, near the forest floor were analyzed. It is concluded that the airflow near forest floor is characterized by high intermittence and asymmetry, and the active and upward movement takes the leading position. Near forest floor, the vertical turbulence is retained and its time scale and length scale are much less than that of u, v components. The eddy near forest floor shows a flat structure and look like a 'Disk'. Buoyancy plays a leading role in the generation and maintenance of local turbulence

  3. Low level wind measurement technique for wind turbine generator siting

    Energy Technology Data Exchange (ETDEWEB)

    Baker, R.W.; Whitney, R.L.; Hewson, E.W.

    1979-01-01

    Large wind turbine generators to be constructed soon will have rotors as great as 100 m in diameter. Strong and persistent winds are needed if these aerogenerators are to be cost effective. Preliminary site surveys in mountainous terrain to locate such large machines require inexpensive, portable and reasonably accurate methods for measuring winds at heights up to 100 m or more above the ground. Of the various methods available, the recently developed Tethered Aerodynamically Lifting Anemometer (TALA) has been tested and found to be the most satisfactory. The TALA system consists of a kite with tail, tethering line, reel, and either a spring scale for direct measurements of the line tension or a recording strain gauge. Atmospheric density corrections are applied to the basic wind tunnel calibration.

  4. Wind shear over the Nice Côte d'Azur airport: case studies

    Directory of Open Access Journals (Sweden)

    A. Boilley

    2013-04-01

    Full Text Available The Nice Côte d'Azur international airport is subject to horizontal low-level wind shears. Detecting and predicting these hazards is a major concern for aircraft security. A measurement campaign took place over the Nice airport in 2009 including 4 anemometers, 1 wind lidar and 1 wind profiler. Two wind shear events were observed during this measurement campaign. Numerical simulations were carried out with Meso-NH in a configuration compatible with near-real time applications to determine the ability of the numerical model to predict these events and to study the meteorological situations generating a horizontal wind shear. A comparison between numerical simulation and the observation dataset is conducted in this paper.

  5. Experimental Study of Tunnel Fire with Natural Ventilation

    Institute of Scientific and Technical Information of China (English)

    YUAN Zhong-yuan; LEI Bo; CHEN Peng-Yun

    2009-01-01

    The 1/15 reduced-scale experiments using Froude scaling were designed to study the effect on the smoke control efficiency for subway tunnel fires with natural ventilation mode.The propane gas fires with heat release rate 11.48 kW was used,which corresponds to the heat release rate 10 MW in the full-scale tunnel.The temperature distributions under the ceiling were measured by K-type thermocouples to investigate smoke move-ment,and the velocity of smoke in shafts was measured by hot-wire anemometer to obtain the smoke extract amount of ventilation shafts.The results show that the smoke temperature under the ceiling varies with the lon-gitudinal different distance from fire Source.The results also show that the smoke temperature distributions and the smoke control efficiency in tunnel vary with the space between ventilation shafts and vary with the area and the height of ventilation shaft.

  6. The phase reversal phenomenon at flow separation and reattachment

    Science.gov (United States)

    Stack, J. Pete; Mangalam, S. M.; Kalburgi, V.

    1988-01-01

    Tests were conducted on two different airfoils, one of them in a low-turbulence tunnel, to detect laminar separation and turbulent reattachment locations. A 'nonintrusive' multielement sensor consisting of a large number of closely spaced individual nickel films was vacuum deposited on a thin substrate and bonded to the airfoil model surface. Each sensor element was a part of an independent constant temperature anemometer system. Time history as well as spectral analysis of signals from surface film gauges were used to determine the surface shear flow characteristics. A major breakthrough was achieved with the discovery of phase reversal in low-frequency dynamic shear stress signals across regions of flow separation and reattachment.

  7. Experimental studies of flow separation and stalling on two-dimensional airfoils at low speeds. Phase 2: Studies with Fowler flap extended

    Science.gov (United States)

    Seetharam, H. C.; Wentz, W. H., Jr.

    1975-01-01

    Results were given on experimental studies of flow separation and stalling on a two-dimensional GA(W)-1 17 percent thick airfoil with an extended Fowler flap. Experimental velocity profiles obtained from a five tube probe survey with optimum flap gap and overlap setting (flap at 40 deg) are shown at various stations above, below, and behind the airfoil/flap combination for various angles of attack. The typical zones of steady flow, intermittent turbulence, and large scale turbulence were obtained from a hot wire anemometer survey and are depicted graphically for an angle of attack of 12.5 deg. Local skin friction distributions were obtained and are given for various angles of attack. Computer plots of the boundary layer profiles are shown for the case of the flap at 40 deg. Static pressure contours are also given. A GA(W)-2 section model was fabricated with 30 percent Fowler flaps and with pressure tabs.

  8. Shear and Turbulence Effects on Lidar Measurements

    DEFF Research Database (Denmark)

    Courtney, Michael; Sathe, Ameya; Gayle Nygaard, Nicolai

    Wind lidars are now used extensively for wind resource measurements. It is known that lidar wind speed measure-ments are affected by both turbulence and wind shear. This report explains the mechanisms behind these sensitivities. For turbulence, it is found that errors in the scalar mean speed...... are usually only small. However, particularly in re-spect of a lidar calibration procedure, turbulence induced errors in the cup anemometer speed are seen to be signifi-cantly larger. Wind shear is shown to induce measurement errors both due to possible imperfections in the lidar sensing height and due...... to the averaging of a non-linear speed profile. Both effects in combination have to be included when modelling the lidar error. Attempts to evaluate the lidar error from ex-perimental data have not been successful probably due to a lack of detailed knowledge of both the wind shear and the actual lidar sensing...

  9. 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;

    comparison campaigns with ultrasonic anemometer (METEK USA-1, Germany) measurements at a distance of about 80 meters from the lidar instrument. The influence of the finite spatial sampling volume at this range on the measured wind spectra is demonstrated. The sampling volume in the latest version......The wind energy industry is gaining interest in prevision of the rotor inflow for turbine control. The potential benefits are increased power production due to better alignment of the rotor to the mean wind direction as well as prolonged lifetime of the turbine due to load reductions. Several lidar......-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...

  10. Cold Gas-particle Flows in a New Swirl Pulverized-coal Burner by PDPA Measurement

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new type of swirl burner has been developed to stabilize pulverized-coal combustion by burning different types of coal at different loads and to reduce NOx formation during combustion. The burner uses a device to concentrate the coal powder in the primary-air tube that divides the primary coal-air into two streams with different pulverized-coal concentrations. This paper reports the measurement of gas-particle flows at the exit of the different swirl burners using a 3-D Phase Doppler Particle Anemometer (PDPA). The effect of different geometrical configurations on the two-phase flow field is studied. The results that give the two-phase flow fields and particle concentrations show the superiority of the new swirl burner.

  11. Lidar observations of marine boundary-layer winds and heights: a preliminary study

    DEFF Research Database (Denmark)

    Peña, Alfredo; Gryning, Sven-Erik; Floors, Rogier Ralph

    2015-01-01

    Here we describe a nearly 1-yr meteorological campaign, which was carried out at the FINO3 marine research platform on the German North Sea, where a pulsed wind lidar and a ceilometer were installed besides the platform's 105-m tower and measured winds and the aerosol backscatter in the entire...... marine atmospheric boundary layer. The campaign was the last phase of a research project, in which the vertical wind profile in the atmospheric boundary layer was firstly investigated on a coastal and a semi-urban site. At FINO3 the wind lidar, which measures the wind speed up to 2000 m, shows...... the highest data availability (among the three sites) and a very good agreement with the observations of wind speed and direction from cup anemometers and vanes from the platform's tower. The wind lidar was also able to perform measurements under a winter storm where 10-s gusts were observed above 60 m s 1...

  12. Modelling of extreme gusts for design calculations (NewGust)

    Energy Technology Data Exchange (ETDEWEB)

    Bierbooms, W.; Po-Wen Cheng [Delft Univ. of Technology, Inst. for Wind Energy, Delft (Netherlands); Larsen, G. [Risoe National Lab., Roskilde (Denmark); Juul Pedersen, B. [Vestas Wind Systems A/S, Lem (Denmark); Hansen, K. [Tecnical Univ. of Denmark (Denmark)

    1999-03-01

    The main objective of the NewGust project is to come to a realistic and verified description of extreme gusts based on the stochastic properties of wind. In this paper the first results of the project are presented. Theoretical considerations indicate that the shape of extreme gusts is very sharp. Based on simulated wind time series, mean gust shapes (for several amplitudes and mean wind speeds) are determined and compared with the theoretical curves. The resemblance turned out to be very good. Furthermore, the influence of the sampling rate and the dynamics of a cup anemometer on the empirical mean gust shape are examined. The promising results are confirmed by a (preliminary) verification based on measured wind time series, available from the database on wind characteristics. The mean shape of gusts, of certain amplitude, together with their probability of occurrence can be used to obtain the distribution of the extreme response of wind turbines to gust loading. (au)

  13. Experimental studies of the effect of wall roughness on particle behavior in gas-particle flows%壁面粗糙度对气粒两相流动中颗粒行为影响的实验研究

    Institute of Scientific and Technical Information of China (English)

    周力行; 张夏

    2004-01-01

    The effect of wall roughness on particle behavior in two-phase flows in a horizontal backward-facing step is studied using a phase-Doppler particle anemometer.The results show that the wall roughness widens the particle velocity probability density distribution,enhances the redistribution of particle velocity into different directions,reduces the particle longitudinal mean velocity and increases the longitudinal and transverse fluctuation velocities and Reynolds shear stress.The effect of roughness on particle motion in the recirculation zone is weaker than that in the fully developed flow region.The effect of roughness for small particles is restricted only in the near-wall region,while that for large particles diffuses to the whole flow field.

  14. Reduction of noise and bias in randomly sampled power spectra

    DEFF Research Database (Denmark)

    Buchhave, Preben; Velte, Clara Marika

    2015-01-01

    by modifications of the ideal Poisson sample rate caused by dead time effects and correlations between velocity and sample rate. The noise and dead time effects for finite records are shown to tend to previous results for infinite time records and ensemble averages. For finite records, we show that the measured......We consider the origin of noise and distortion in power spectral estimates of randomly sampled data, specifically velocity data measured with a burst-mode laser Doppler anemometer. The analysis guides us to new ways of reducing noise and removing spectral bias, e.g., distortions caused...... sampling function can be used to correct the spectra for noise and dead time effects by a deconvolution process. We also describe a novel version of a power spectral estimator based on a fast slotted autocovariance algorithm....

  15. Airflow attenuation and bed net utilization: observations from Africa and Asia

    DEFF Research Database (Denmark)

    von Seidlein, Lorenz; Ikonomidis, Konstantin; Bruun, Rasmus;

    2012-01-01

    for one night from 21.00 to 6.00 hrs inside and outside of bed nets using sensors and omni-directional thermo-anemometers. An investigator set up a bed net with a mesh size of 220 holes per inch2 in each study household and slept under the bed net to simulate a realistic environment. The attenuation...... of airflow caused by bed nets of different mesh sizes was also measured in an experimental wind tunnel. Results The highest indoor temperatures (49.0 C) were measured in The Gambia. During the hottest months of the year the mean temperature at night (9 pm) was between 33.1 C (The Gambia) and 26.2 C (Thailand...

  16. Low-energy house in Sisimiut - Measurement equipment

    Energy Technology Data Exchange (ETDEWEB)

    Hvidthoeft Delff Andersen, P.; Rode, C.; Madsen, Henrik

    2013-08-15

    This paper documents the measurement equipment in a low-energy house in Sisimiut, Greenland. Detailed measurements are being taken on energy consumption, indoor temperatures, floor heating, ventilation, open/closed state of doors and windows, and indoors climate. Equipped with a central control unit, experiments can be designed in order to study heat dynamics of the building. It is described how to plan and execute such experiments in one apartment in the building. The building also features both a solar thermal system and extra buffer tank facilitating testing of storage strategies on the power generated by the solar thermal system. A weather station equipped with thermometer, pyranometer and anemometer is installed on the building as well. Finally, it is described how to retrieve data from an SQL server which is configured to take monthly backups. R functions have been implemented to fetch and prepare the data for time series analysis. Examples are given on the use of these. (Author)

  17. Acoustic source location in the secondary mixing region of a jet-blown flap using a cross-correlation technique

    Science.gov (United States)

    Becker, R. S.; Maus, J. R.

    1977-01-01

    An experimental investigation of the acoustic sources in the secondary mixing region of a laboratory-scale jet-flap was made using a causality correlation technique. The processed signal of a hot-film anemometer probe was cross correlated with the output signal of a far-field microphone. Axial acoustic source strength distributions were measured for three far-field microphone locations: plus or minus 45 deg in the flyover plane and 45 deg in the sideline plane. These measurements showed that the acoustic sources in the secondary mixing region are highly directional, radiating much more effectively to the -45 deg-microphone, located below the plane of the flap surface. A relative maximum in the acoustic source strength measured for the microphones in the flyover plane occurred very near the flap trailing edge, which may be due to an edge amplification effect predicted by the theoretical work of Ffowcs Williams and Hall.

  18. On the parameterization of the roughness length for the air-sea interface in free convection for the coastal site Tarapur, India

    International Nuclear Information System (INIS)

    The roughness length at air-sea interface during free convection (Z0fc) is mainly related to the convective velocity (w) rather than the friction velocity (u). The parameterization of Z0fc with (w)2/g as proposed by Abdella and D'Alessio (2003) is evaluated. It is shown that the field measurements at MM Lab, Tarapur Maharashtra Site (TMS) coastal site using Metek GmbH, Ultra sonic anemometers are consistent with the proposed formula. In order to avoid self-correlation by using u, a new parameterization of w with σu and σv and gustiness parameter as given by Fairall et al. (1996) is used. The mean values of w and Z0fc estimated using new parameterization were observed to be 0.97 m/s and 2.3E-4 m respectively for the year 2009 at TMS. (author)

  19. Mapping flow distortion on oceanographic platforms using computational fluid dynamics

    Directory of Open Access Journals (Sweden)

    N. O'Sullivan

    2013-10-01

    Full Text Available Wind speed measurements over the ocean on ships or buoys are affected by flow distortion from the platform and by the anemometer itself. This can lead to errors in direct measurements and the derived parametrisations. Here we computational fluid dynamics (CFD to simulate the errors in wind speed measurements caused by flow distortion on the RV Celtic Explorer. Numerical measurements were obtained from the finite-volume CFD code OpenFOAM, which was used to simulate the velocity fields. This was done over a range of orientations in the test domain from −60 to +60° in increments of 10°. The simulation was also set up for a range of velocities, ranging from 5 to 25 m s−1 in increments of 0.5 m s−1. The numerical analysis showed close agreement to experimental measurements.

  20. Microelectrokinetic turbulence in microfluidics at low Reynolds number

    Science.gov (United States)

    Wang, Guiren; Yang, Fang; Zhao, Wei

    2016-01-01

    There is commonly no turbulence in microfluidics, and the flows are believed to be either laminar or chaotic, since Reynolds number (Re) in microflows is usually on the order of unity or lower. However, we recently demonstrated that it is possible to achieve turbulence with low Re (based on the measured flow velocity and the width of the channel entrance) when a pressure-driven flow is electrokinetically forced in a quasi T-microchannel. To be able to measure high frequency velocity fluctuations in microchannels, a velocimeter with submicrometer spatial resolution and microsecond temporal resolution, called a laser-induced fluorescence photobleaching anemometer, is developed. Here we characterize the microelectrokinetic turbulence and observe some typical and important features of high Re flows, such as Kolmogorov -5 /3 spectrum of velocity fluctuation, which usually can be realized only at very high Re in macroturbulent flows.

  1. Hot wire in low Reynolds number flow

    Science.gov (United States)

    Kolb, M. A.; Covert, E. E.

    1984-01-01

    Progress reports were issued on the following experiments: (1) low Reynolds number flow phenomenon of periodic vortex shedding in the wake behind a cylinder as studied by applying the hot wire anemometer technique of flow measurement. The downstream diffusion of these shed vortices was of prime concern. An evaluation of the performance of the hot wire at low Reynolds number is also considered. (2) A brief examination of the back sections of the Wright Brothers wind tunnel circuits were conducted to establish whether or not gross flow deviations were present at corners, or turning vane regions. A calibration of the test sections was done. (3) The attractiveness of using rembedded grids for airfoil calculations modeled by the Euler equations was explored. These calculations were extended to C-type grids and then to Navier-Stokes calculations,

  2. Spectral tensor parameters for wind turbine load modeling from forested and agricultural landscapes

    DEFF Research Database (Denmark)

    Chougule, Abhijit S.; Mann, Jakob; Segalini, A.;

    2015-01-01

    A velocity spectral tensor model was evaluated from the single-point measurements of wind speed. The model contains three parameters representing the dissipation rate of specific turbulent kinetic energy, a turbulence length scale and the turbulence anisotropy. Sonic anemometer measurements taken...... over a forested and an agricultural landscape were used to calculate the model parameters for neutral, slightly stable and slightly unstable atmospheric conditions for a selected wind speed interval. The dissipation rate above the forest was nine times that at the agricultural site. No significant...... constant with height at the forest site, whereas the turbulence became more isotropic with height for the agricultural site. Using the three parameters as inputs, we quantified the performance of the model in coherence predictions for vertical separations. The model coherence of all the three velocity...

  3. Nacelle lidar for power curve measurement - Avedøre campaign

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Davoust, Samuel

    measurement of the wind speed away from the instrument. In the first phase of the EUDP project: “Nacelle lidar for power performance measurement”, a measurement campaign with a na-celle lidar prototype placed on an onshore turbine demonstrated the poten-tial of the technology for power curve measurement...... anemometer, requiring the erection of a tall met mast, then becomes more and more challenging and expensive. A forward looking lidar, mounted on the turbine nacelle, combines the advantages of a nacelle based instrument - no mast/platform installation difficulties - and those of the lidar technology - remote....... The main deviations of this method to the requirement of the IEC 61400-12-1 were identified and a procedure was established for the use of a nacelle lidar specifically for power curve measurement. This report describes the results of a sec-ond measurement campaign aiming at testing and finalising...

  4. Uncertainty of power curve measurement with a two-beam nacelle-mounted lidar

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Courtney, Michael Stephen; Friis Pedersen, Troels;

    2015-01-01

    already been demonstrated to be suitable for use in power performance measurements. To be considered as a professional tool, however, power curve measurements performed using these instruments require traceable calibrated measurements and the quantification of the wind speed measurement uncertainty. Here...... lies between 1 and 2% for the wind speed range between cut-in and rated wind speed. Finally, the lidar was mounted on the nacelle of a wind turbine in order to perform a power curve measurement. The wind speed was simultaneously measured with a mast-top mounted cup anemometer placed two rotor diameters...... upwind of the turbine. The wind speed uncertainty related to the lidar tilting was calculated based on the tilt angle uncertainty derived from the inclinometer calibration and the deviation of the measurement height from hub height. The resulting combined uncertainty in the power curve using the nacelle...

  5. Advanced Exploration Technologies: Micro and Nano Technologies Enabling Space Missions in the 21st Century

    Science.gov (United States)

    Krabach, Timothy

    1998-01-01

    Some of the many new and advanced exploration technologies which will enable space missions in the 21st century and specifically the Manned Mars Mission are explored in this presentation. Some of these are the system on a chip, the Computed-Tomography imaging Spectrometer, the digital camera on a chip, and other Micro Electro Mechanical Systems (MEMS) technology for space. Some of these MEMS are the silicon micromachined microgyroscope, a subliming solid micro-thruster, a micro-ion thruster, a silicon seismometer, a dewpoint microhygrometer, a micro laser doppler anemometer, and tunable diode laser (TDL) sensors. The advanced technology insertion is critical for NASA to decrease mass, volume, power and mission costs, and increase functionality, science potential and robustness.

  6. Carbon Dioxide Flux Measurement Systems (CO2Flux) Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, M

    2005-01-01

    The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The fluxes are obtained by the eddy covariance technique, which computes the flux as the mean product of the vertical wind component with CO2 and H2O densities, or estimated virtual temperature. A three-dimensional sonic anemometer is used to obtain the orthogonal wind components and the virtual (sonic) temperature. An infrared gas analyzer is used to obtain the CO2 and H2O densities. A separate sub-system also collects half-hour average measures of meteorological and soil variables from separate 4-m towers.

  7. Sudden distortion of turbulence at a forest edge

    DEFF Research Database (Denmark)

    Mann, Jakob; Dellwik, Ebba

    2014-01-01

    Dellwik et al. (2013) presented data from a forest edge experiment based on two meteorological towers instrumented with sonic anemometers. The experiment was performed at a dense edge of the Tromnæs Forest, which is a 24 m tall mature beech stand on the island Falster, Denmark. The topography...... at the site is flat. The towers were placed approximately 1.5 canopy heights upwind and downwind of the edge, respectively, and were two canopy heights tall. For near-neutral, near-perpendicular flow towards the edge, one finding concerned that although the wind speed gradients were similar before and after...... the edge, the momentum flux was strongly reduced above the canopy. This is contrary to the results by standard Reynolds' averaged Navier-Stokes models that predict an overshoot of the momentum flux. Further, a reduction of the vertical variance of the flow was largely compensated by an increase...

  8. Flow distortion at a dense forest edge

    DEFF Research Database (Denmark)

    Dellwik, Ebba; Bingöl, Ferhat; Mann, Jakob

    2014-01-01

    The flow near tall forest edges is complex, yet poorly described. A field experiment using two meteorological masts equipped with sonic anemometers and a horizontally staring lidar was performed upwind and downwind of the interface between an open flat farmland and a tall (hc = 24 m) beech forest......, relative to the measurements upwind of the edge. The lidar data taken at several positions between the masts at 1.25hc show that the minimum wind speed occurred just upwind of the edge. At the 1.25hc level, at the forest mast, the momentum flux (\\documentclass...... qualitatively be explained with the concept of eddy‐blocking by the canopy top, which could also explain the observed increase in lateral variance and the decrease in the vertical variance. Despite the short distance to the edge of approximately 1.5hc, the beginning of a new internal boundary layer was visible...

  9. ICIASF '85 - International Congress on Instrumentation in Aerospace Simulation Facilities, 11th, Stanford University, CA, August 26-28, 1985, Record

    Science.gov (United States)

    1985-12-01

    Developments related to laser Doppler velocimetry are discussed, taking into account a three-component dual beam laser-Doppler-anemometer to be operated in large wind tunnels, a new optical system for three-dimensional laser-Doppler-anemometry using an argon-ion and a dye laser, and a two-component laser Doppler velocimeter by switching fringe orientation. Other topics studied are concerned with facilities, instrumentation, control, hot wire/thin film measurements, optical diagnostic techniques, signal and data processing, facilities and adaptive wall test sections, data acquisition and processing, ballistic instrument systems, dynamic testing and material deformation measurements, optical flow measurements, test techniques, force measurement systems, and holography. Attention is given to nonlinear calibration of integral wind tunnel balances, a microcomputer system for real time digitized image compression, and two phase flow diagnostics in propulsion systems.

  10. A STUDY OF INDOOR AIR QUALITY IN UNIVERSITY LABORATORY BUILDINGS

    Directory of Open Access Journals (Sweden)

    ADE ASMI

    2012-09-01

    Full Text Available This paper is a study of Indoor Air Quality (IAQ of laboratory in university buildings at faculty of civil and environmental engineering, Universiti Tun Hussein Onn Malaysia (UTHM. This study assessed the existing indoor air quality in two selected laboratory buildings, which equipped with natural ventilation. The importantIAQ parameters considered in this study are temperature, relative humidity, air movement, and airborne particles. However, airborne particles were categorized based on its size characterization concentration of particles ≥ 0.3 μm and particles ≥ 5.0 μm. The measurements were carried out during the peak hours within these laboratories using Met One GT-521 particle counter and Anemometer. Ultimately, area, time of measurement conducted, the number of activities, ventilation, air movement, and materials, were found as the major contributors to the IAQ performance in these laboratories.

  11. Experimental studies of the boundary layer on an airfoil at low Reynolds numbers

    Science.gov (United States)

    Jansen, B. J., Jr.; Mueller, T. J.

    1983-01-01

    An experimental wind tunnel investigation was carried out to study the effect of laminar separation bubbles on a NACA 66(3)-018 airfoil for Reynolds numbers less than 4.0 x 10 to the 5th. Leading edge laminar separation bubbles formed for angles of attack of approximately 7 to 12 deg. To study the leading edge separation bubble more closely, hotwire anemometer measurements were made in the airfoil a Reynolds number of 8.0 x 10 to the 4th. Velocity and turbulence intensity profiles were obtained and boundary layer parameters were calculated. Frequency spectra were also calculated at key points in the airfoil boundary layer for this case. Correlation of the anemometry data with static pressure distributions, and flow visualization data provided insight into laminar separation bubble behavior at low Reynolds numbers.

  12. Boundary layer transition determination for periodic and static flows using phase-averaged pressure data

    Science.gov (United States)

    Gardner, A. D.; Richter, K.

    2015-06-01

    A method of boundary layer transition measurement is presented for wind tunnel models instrumented with surface pressure taps. The measurement relies on taking a number of theoretically identical measurements at different times and then analysing the standard deviation of the pressures. Due to the slight unsteady movement of the transition position, a peak in the standard deviation of pressure is found at the transition position, and this is correlated with measurements of the transition position with an infrared camera and hot-film anemometers. In contrast to microphone measurements, it is shown that the transition detection works for data which have been low-pass filtered with a cut-off of 1 Hz. The application to static and dynamic transition measurements on static and periodically pitching helicopter rotor blade airfoils at Mach 0.3-0.5 is demonstrated.

  13. Concurrent aerial and ground-based optical turbulence measurements along a long elevated path

    Science.gov (United States)

    Nowlin, Scott R.; Hahn, Ila L.; Hugo, Ronald J.; Bishop, Kenneth P.

    1999-08-01

    We report concurrent ground-based scintillator/airborne constant-current anemometer (CCA) measurements made along a 51.4 km-long slant path between Salinas and North Oscura peaks, NM. Simultaneous path-averaged refractive index structure parameter (Cn2) measurements from the CCA and the scintillometer show good agreement, with deviations apparently due to localized effects of underlying topography and metrology. Statistics from both data sets are presented in the form of histograms and cumulative distribution functions. CCA Cn2 point measurements are compared to underlying surface topography. We discuss possible effects of instruments anomalies, analysis methods, and atmospheric velocity fluctuation levels. We present conclusions and made recommendations for future similar experimental efforts.

  14. Multi-Sensor Integration to Map Odor Distribution for the Detection of Chemical Sources.

    Science.gov (United States)

    Gao, Xiang; Acar, Levent

    2016-01-01

    This paper addresses the problem of mapping odor distribution derived from a chemical source using multi-sensor integration and reasoning system design. Odor localization is the problem of finding the source of an odor or other volatile chemical. Most localization methods require a mobile vehicle to follow an odor plume along its entire path, which is time consuming and may be especially difficult in a cluttered environment. To solve both of the above challenges, this paper proposes a novel algorithm that combines data from odor and anemometer sensors, and combine sensors' data at different positions. Initially, a multi-sensor integration method, together with the path of airflow was used to map the pattern of odor particle movement. Then, more sensors are introduced at specific regions to determine the probable location of the odor source. Finally, the results of odor source location simulation and a real experiment are presented. PMID:27384568

  15. Estimation of the Lagrangian structure function constant ¤C¤0 from surface-layer wind data

    DEFF Research Database (Denmark)

    Anfossi, D.; Degrazia, G.; Ferrero, E.;

    2000-01-01

    Eulerian turbulence observations, made in the surface layer under unstable conditions (z/L > 0), by a sonic anemometer were used to estimate the Lagrangian structure function constant C(0). Two methods were considered. The first one makes use of a relationship, widely used in the Lagrangian...... stochastic dispersion models, relating C(0) to the turbulent kinetic energy dissipation rate epsilon, wind velocity variance and Lagrangian decorrelation time. The second one employs a novel equation, connecting C(0) to the constant of the second-order Eulerian structure function. Before estimating C(0), the......-order longitudinal Eulerian structure function. The first method was preferred and applied to the subsequent part of the analysis. Both methods predict the partitioning of C(0) in different spatial components as a consequence of the directional dependence of the Eulerian correlation functions due to the isotropy...

  16. Quantitative measurement of blood flow dynamics in chorioallantoic membrane of chicken embryo using laser Doppler anemometry

    Science.gov (United States)

    Borozdova, M. A.; Stiukhina, E. S.; Sdobnov, A. A.; Fedosov, I. V.; Postnov, D. E.; Tuchin, V. V.

    2016-04-01

    We report the results on in ovo application of developed Laser Doppler Anemometer (LDA) device. The chorioallantoic membrane (CAM) of 9-13 days chicken embryos was used as a biological model that allows an easy access to both arterial and venous vessels of different size. The key point of our study was to find out how the periodic and aperiodic pulsations of blood flow (which are inevitable in living organism) will affect the LDA functions and measuring capability. Specifically, we (i) developed the technique to extract and refine the pulse rhythm from the signal received from a vessel, and (ii) analyzed the changes in power spectra of LDA signal that are caused by heart beating and considerably complicate the reliable measurement of Doppler shift. Our main conclusion is that the algorithm of LDA data processing need to be improved, and this possibly can be done by counting the information on current phase of cardiac cycle.

  17. Vorticity Measurements Using a 6-Sensor Hot-Wire Probe in a Tangentially-Fired Furnace

    Institute of Scientific and Technical Information of China (English)

    何伯述; 刁永发; 许晋源; 陈昌和

    2003-01-01

    Vorticity, which represents the rotation of a fluid element, is an important characteristic of turbulence. Various methods have been used to measure vorticity. A hot-wire/hot-film anemometer (HWA) was used here to measure the vorticity in turbulent flows. The velocity components and their partial derivatives were simultaneously measured with a new 6-sensor hot-wire (HW) probe assuming ideal yaw and pitch factors with Jorgensen's expression and Taylor's hypothesis to analyze the data. The accurate 6-sensor hot-wire probe results for the velocity field were used to determine the velocity gradients and, therefore, the vorticity vector field. The data was measured in an isothermal model of a tangentially fired furnace. The experimental results in the tangentially fired furnace agree with numerical results.

  18. Advancements in Wind Energy Metrology – UPWIND 1A2.3

    DEFF Research Database (Denmark)

    Angelou, Nikolas; Bingöl, Ferhat; Courtney, Michael;

    An overview of wind related metrology research made at Risø DTU over the period of the UPWIND project is given. A main part of the overview is devoted to development of the Lidar technology with several sub-chapters considering different topics of the research. Technical problems are not rare...... on turbulence measurements. Theory and measurements seem to be in good agreement. Lidar measurements from a rotating spinner have been performed. The analysis show good perspectives for scanning the incoming wind, which may lead to better controlled wind turbines. Lidars have also been used to scan the wake...... of nacelle anemometry, IEC61400- 12-2-CD, nacelle anemometry has been studied, both with experiments and in theory. An alternative to nacelle anemometry has been developed, the socalled spinner anemometer. This type of sensor measures yaw-error with high absolute accuracy, and avoids the draw...

  19. A case study of air quality above an urban roof top vegetable farm.

    Science.gov (United States)

    Tong, Zheming; Whitlow, Thomas H; Landers, Andrew; Flanner, Benjamin

    2016-01-01

    The effect of elevation and rooftop configuration on local air quality was investigated at the Brooklyn Grange rooftop farm during a short-term observational campaign. Using multiple particle counters and sonic anemometers deployed along vertical gradients, we found that PM2.5 concentration decayed with height above the street. Samples adjacent to the street had the highest average PM2.5 concentration and frequent stochastic spikes above background. Rooftop observations 26 m above ground showed 7-33% reductions in average PM2.5 concentration compared with the curbside and had far fewer spikes. A relationship between the vertical extinction rate of PM2.5 and atmospheric stability was found whereby less unstable atmosphere and greater wind shear led to greater PM2.5 extinction due to damped vertical motion of air. PMID:26272830

  20. A case study of air quality above an urban roof top vegetable farm.

    Science.gov (United States)

    Tong, Zheming; Whitlow, Thomas H; Landers, Andrew; Flanner, Benjamin

    2016-01-01

    The effect of elevation and rooftop configuration on local air quality was investigated at the Brooklyn Grange rooftop farm during a short-term observational campaign. Using multiple particle counters and sonic anemometers deployed along vertical gradients, we found that PM2.5 concentration decayed with height above the street. Samples adjacent to the street had the highest average PM2.5 concentration and frequent stochastic spikes above background. Rooftop observations 26 m above ground showed 7-33% reductions in average PM2.5 concentration compared with the curbside and had far fewer spikes. A relationship between the vertical extinction rate of PM2.5 and atmospheric stability was found whereby less unstable atmosphere and greater wind shear led to greater PM2.5 extinction due to damped vertical motion of air.

  1. The turning of the wind in the atmospheric boundary layer

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo; Gryning, Sven-Erik; Floors, Rogier Ralph

    2014-01-01

    at the Høvsøre site in Denmark, which is a flat farmland area with a nearly homogeneous easterly upstream sector. Therefore, within that sector, the turning of the wind is caused by a combination of atmospheric stability, Coriolis, roughness, horizontal pressure gradient and baroclinity effects. Atmospheric......Here we use accurate observations of the wind speed vector to analyze the behavior with height of the wind direction. The observations are a combination of tall meteorological mast and long-range wind lidar measurements covering the entire atmospheric boundary layer. The observations were performed...... stability was measured using sonic anemometers placed at different heights on the mast. Horizontal pressure gradients and baroclinity are derived from outputs of a numerical weather prediction model and are used to estimate the geostrophic wind. It is found, for these specific and relatively short periods...

  2. Vortex shedding by a Savonius rotor

    Science.gov (United States)

    Botrini, M.; Beguier, C.; Chauvin, A.; Brun, R.

    1984-05-01

    A series of flow visualizations was performed to characterize the wake vortices of a Savonius rotor. The trials were undertaken in an attempt to account for discrepancies between theoretical and experimentally-derived power coefficients. The Savonius examined was two-bladed with a center offset. All tests were made in a water tunnel. Dye injection provided the visualization, and average velocities and velocity fluctuations were measured using a laser Doppler anemometer. A system of three vortices was found to be periodically shed by the rotor. Flow velocity fluctuation intensity peaked as a vortex was shed. The vortex shedding alternated from blade to blade, so that one was shed from a blade moving upstream.

  3. The properties of isolated and coupled Savonius rotors

    Science.gov (United States)

    Bowden, G. J.; McAleese, S. A.

    Some measurments on the Queensland optimum S-shaped rotor are presented. In particular it is shown that the efficiency of the turbine is about 18 percent, which is lower than the figure of about 23 percent given by earlier workers. In addition, detailed measurements of the pulsating wind-flow around a Savonius rotor are presented. These results were obtained using (1) tell-tales and a stroboscope, (2) a hot-wire anemometer (0-5 kHz response), and (3) a turbulence meter. This data can be used to suggest that 'active coupling' between Savonius rotors might be useful in 'redirecting' the wind-flow more efficiently. In particular, it is shown that if two counter-rotating rotors are placed side by side in a wind-tunnel, a natural phase locking occurs.

  4. Impact of supersonic versus propeller wind data on dispersion estimates for nuclear plants

    International Nuclear Information System (INIS)

    Statistical analyses and comparisons of the wind data obtained by the propeller and supersonic anemometers at the Japan Atomic Energy Research Institute (JAERI) were performed. For wind speeds less than 1 ms-1, the propeller readings are inaccurate and are generally 0.5 ms-1 less than the supersonic readings. Thus, the number of calms recorded differs. These differences affect the sum of the inverse of wind speed, frequency distribution of wind direction, and the annual percentage frequency distribution of stability categories. The resultant average air concentrations and ground-level gamma exposure rates due to the normal operational releases from a nuclear plant are overestimated when calculated using the propeller wind data

  5. Performance evaluation of an all-fiber image-reject homodyne coherent Doppler wind lidar

    Directory of Open Access Journals (Sweden)

    C. F. Abari

    2015-04-01

    Full Text Available The main purpose of this study is to evaluate the near-zero wind velocity measurement performance of two separate 1.5 μm all-fiber coherent Doppler lidars (CDL. The performance characterization is performed through the presentation of the results from two separate atmospheric field campaigns. In one campaign, a recently developed continuous wave (CW CDL benefiting from an image-reject front-end was deployed. The other campaign utilized a different CW CDL, benefiting from a heterodyne receiver with intermediate frequency (IF sampling. In both field campaigns the results are compared against a sonic anemometer, as the reference instrument. The measurements clearly show that the image-reject architecture results in more accurate measurements of radial wind velocities close to zero. Close-to-zero velocities are usually associated with the vertical component of the wind and are important to characterize.

  6. Bisecting Microfluidic Channels with Metallic Nanowires Fabricated by Nanoskiving.

    Science.gov (United States)

    Kalkman, Gerard A; Zhang, Yanxi; Monachino, Enrico; Mathwig, Klaus; Kamminga, Machteld E; Pourhossein, Parisa; Oomen, Pieter E; Stratmann, Sarah A; Zhao, Zhiyuan; van Oijen, Antoine M; Verpoorte, Elisabeth; Chiechi, Ryan C

    2016-02-23

    This paper describes the fabrication of millimeter-long gold nanowires that bisect the center of microfluidic channels. We fabricated the nanowires by nanoskiving and then suspended them over a trench in a glass structure. The channel was sealed by bonding it to a complementary poly(dimethylsiloxane) structure. The resulting structures place the nanowires in the region of highest flow, as opposed to the walls, where it approaches zero, and expose their entire surface area to fluid. We demonstrate active functionality, by constructing a hot-wire anemometer to measure flow through determining the change in resistance of the nanowire as a function of heat dissipation at low voltage (wires. We measure rates of flow and show that, compared to surface-bound DNA strands, elongation saturates at lower rates of flow and background fluorescence from nonspecific binding is reduced. PMID:26836373

  7. Specific Properties of Air Flow Field Within the Grinding Zone

    Institute of Scientific and Technical Information of China (English)

    ZHENG Junyi; JIANG Zhengfeng; ZHAO Liang

    2006-01-01

    Air barrier of grinding means a boundary layer of air existing at the circumference of the rotating wheel, which hinders coolant from entry. This paper makes a research on air flow field of the grinding zone through experiments and numerical simulations, focusing on acquainting with the specific properties of the air flow field. Finite volume method is applied to analyze air flow field within grinding wheel in the course of numerical calculations. The test devices such as Hot-wire anemometer and Betz manometer are used during the experiments of testing the pressure and velocity within grinding zone. Results of experiments agree by and large with numerical results of calculations. The conclusions obtained in this paper, the distribution of wall pressure and the distribution of air flow velocity, are important and useful to navigate the delivery of coolant into the grinding zone. In conclusion, some recommendations are made for further study and practical applications in such field.

  8. Wind-driven water motions in wetlands with emergent vegetation

    CERN Document Server

    Tse, Ian C; Variano, Evan A

    2016-01-01

    Wetland biogeochemical transformations are affected by flow and mixing in wetland surface water. We investigate the influence of wind on wetland water flow by simultaneously measuring wind and surface water velocities in an enclosed freshwater wetland during one day of strong-wind conditions. Water velocities are measured using a Volumetric Particle Imager while wind velocities are measured via sonic-anemometer. Our measurements indicate that the wind interacting with the vegetation canopy generates coherent billows and that these billows are the dominant source of momentum into the wetland water column. Spectral analysis of velocity timeseries shows that the spectral peak in water velocity is aligned with the spectral peak of in-canopy wind velocity, and that this peak corresponds with the Kelvin-Helmholtz billow frequency predicted by mixing layer theory. We also observe a strong correlation in the temporal pattern of velocity variance in the air and water, with high variance events having similar timing an...

  9. Ventilation measurements at underground-mine regulators

    Energy Technology Data Exchange (ETDEWEB)

    Smith, R.L.; Haney, R.A.

    1981-01-01

    Two studies were conducted to investigate practical and accurate methods for computing the air volumes passing through underground mine regulators and rectangular openings in stoppings. The first series of tests produced a revised regulator formula using the static pressure drop at the regulator and the area of the opening to calculate the volumetric flow through the regulator. An overall discharge coefficient was determined experimentally for all pressure losses at regulators. The second set of observations used 4-inch rotating vane anemometers to develop methods factors for velocity readings at underground regulators. Methods factors were determined by comparing the corrected measured velocity at the centerline of the openings with the average air velocity passing through the regulators. Methods factors were dependent on the size of the opening, the location of the reading (inlet or discharge side of the regulator), and the type of instrument support (rod-mounted or hand-held); they showed little dependence on the air velocity.

  10. Development of semiconductor laser based Doppler lidars for wind-sensing applications

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Hu, Qi; Pedersen, Christian

    2015-01-01

    We summarize the progress we have made in the development of semiconductor laser (SL) based Doppler lidar systems for remote wind speed and direction measurements. The SL emitter used in our wind-sensing lidar is an integrated diode laser with a tapered (semiconductor) amplifier. The laser source...... is low-cost and compact - enhancing the potential of lidar wind sensors for mass production. This paper describes two embodiments of the patented wind lidar technology and presents experimental results that evaluate the wind sensors' performance. Due to compactness, portability and cost-efficiency, SL...... based wind sensors have a strong potential in a number of applications such as wind turbine control, wind resource assessment, and micrometeorology (e.g. as alternative to the construction of meteorological towers with anemometers and wind vanes)....

  11. Heat and momentum transfer from an atmospheric argon hydrogen plasma jet to spherical particles

    International Nuclear Information System (INIS)

    In this thesis the author describes the energy and momentum transfer from the plasma jet to the spray particles. This is done both experimentally and theoretically. Also the internal energy process of the recombining plasma is discussed. All elastic and inelastic collisional and radiative processes, as well as transport effects within the plasma are considered. In the next section, the so called passive spectroscopy is treated. It describes the diagnostics of electron density and temperature measurement, as well as the investigation on heat content of the particles. Spatially resolved electron density and temperature profiles are presented. Next, the active spectroscopy, i.e. the laser Doppler anemometer is dealt with. With this diagnostic, axial spray-particle velocities inside the plasma jet were determined. The author also presents heat and momentum transfer modelling of the plasma, related to the plasma particle interaction. Finally, a one dimensional model verification is made, using the experimentally determined particle velocity and plasma temperature profiles. (Auth.)

  12. Application of rotor mounted pressure transducers to analysis of inlet turbulence. [flow distortion in turbofan engine inlet

    Science.gov (United States)

    Hanson, D. B.

    1976-01-01

    Miniature pressure transducers installed near the leading edge of a fan blade were used to diagnose the non-uniform flow entering a subsonic tip speed turbofan on a static test stand. The pressure response of the blade to the inlet flow variations was plotted in a form which shows the space-time history of disturbances ingested by the rotor. Also, periodically sampled data values were auto- and cross-correlated as if they had been acquired from fixed hot wire anemometers at 150 equally spaced angles around the inlet. With a clean inlet and low wind, evidence of long, narrow turbulence eddies was easily found both in the boundary layer of the fan duct and outside the boundary layer. The role of the boundary layer was to follow and amplify disturbances in the outer flow. These eddies frequently moved around the inlet with a corkscrew motion as they passed through.

  13. Attenuation characteristics of nonlinear pressure waves propagating in pipes

    Science.gov (United States)

    Shih, C. C.

    1974-01-01

    A series of experiments was conducted to investigate temporal and spatial velocity distributions of fluid flow in 3-in. open-end pipes of various lengths up to 210 ft, produced by the propagation of nonlinear pressure waves of various intensities. Velocity profiles across each of five sections along the pipes were measured as a function of time with the use of hot-film and hot-wire anemometers for two pressure waves produced by a piston. Peculiar configurations of the velocity profiles across the pipe section were noted, which are uncommon for steady pipe flow. Theoretical consideration was given to this phenomenon of higher velocity near the pipe wall for qualitative confirmation. Experimentally time-dependent velocity distributions along the pipe axis were compared with one-dimensional theoretical results obtained by the method of characteristics with or without diffusion term for the purpose of determining the attenuation characteristics of the nonlinear wave propagation in the pipes.

  14. Wind Noise Reduction in a Non-Porous Subsurface Windscreen

    Science.gov (United States)

    Zuckerwar, Allan J.; Shams, Qamar A.; Knight, H. Keith

    2012-01-01

    Measurements of wind noise reduction were conducted on a box-shaped, subsurface windscreen made of closed cell polyurethane foam. The windscreen was installed in the ground with the lid flush with the ground surface. The wind was generated by means of a fan, situated on the ground, and the wind speed was measured at the center of the windscreen lid with an ultrasonic anemometer. The wind speed was controlled by moving the fan to selected distances from the windscreen. The wind noise was measured on a PCB Piezotronics 3†electret microphone. Wind noise spectra were measured with the microphone exposed directly to the wind (atop the windscreen lid) and with the microphone installed inside the windscreen. The difference between the two spectra comprises the wind noise reduction. At wind speeds of 3, 5, and 7 m/s, the wind noise reduction is typically 15 dB over the frequency range of 0.1-20 Hz.

  15. Validated Loads Prediction Models for Offshore Wind Turbines for Enhanced Component Reliability

    DEFF Research Database (Denmark)

    Koukoura, Christina

    in the aero-servo-hydro-elastic code HAWC2. The results are validated with full scale measurements from a 3.6MW Siemens offshore wind turbine installed in the Walney Offshore Wind Farm 1 at the west coast of England. Damping estimation, wind-wave misalignment cases and storm loads are analyzed. The findings...... are used for the modification of the sub-structure/foundation design for possible material savings. First, the background of offshore wind engineering, including wind-wave conditions, support structure, blade loading and wind turbine dynamics are presented. Second, a detailed description of the site...... a nacelle mounted cup-anemometer. The model setup is based on the downscaled 5MW NREL reference wind turbine. Modifications on the downscaled model to match the actual full-scale wind turbine (mass and natural frequency) are applied. Extreme and mean measured loads from the free wind and the wake sectors...

  16. Investigation into the feasibility of wind as an alternate energy resource at selected North Georgia sites

    Energy Technology Data Exchange (ETDEWEB)

    Brock, D.L.

    1982-10-26

    Anemometers were placed at four selected sites in North Georgia during the period July, 1980, to June, 1982. Regular wind speed readings were taken using accumulating recorders and average daily wind speeds calculated for each location. Three wind speed categories were determined: (a) average below 7 mph; (b) average between 7 and 25 mph; (c) average above 25 mph. One site was abandoned after seven months due to lack of expected wind; another site was closed after 4.5 months due to continuing excessive and damaging winds. Two sites were determined, after 12 to 20 months of data collecting respectively, to have sufficient wind resources in a usable time pattern to merit further investigation.

  17. 计算大型塔板效率的区域贡献法%Local Contribution Method for Efficiency of Large Plates

    Institute of Scientific and Technical Information of China (English)

    许松林; 王惠媛; 徐世民

    2005-01-01

    From the measurement of liquid flow field on a large plate by a hot-film anemometer, three different regions on the large plate were presented, including a liquid circulation area near the inlet down-comer, a region with very slow moving or stagnant liquid on the side of the tray and an active flow region at the center of the plate.According to the contribution of the three regions, the tray efficiency for large plates was proposed. The prediction plate efficiency by the present model are compared with the experimental data in the literature and those calculated by other models. It is shown that the present model is more accurate for prediction of efficiency of large plates, and the calculation is simpler.

  18. The Bistatic Sodar ''Heimdall'', You blow, I listen

    DEFF Research Database (Denmark)

    Mikkelsen, Torben; Ejsing Jørgensen, Hans; Kristensen, Leif

    With the increased exploitation of wind energy, remote sensing of wind profiles in the atmospheric boundary layer has come in focus as an attractive alternative to the operation of tall instrumented masts for wind energy siting and assessment studies. Project “Heimdall” describes a recent...... conditions in a neutrally stratified atmospheric conditions, characteristic for wind energy applications. Here we first describe the theoretical developments for sound wave scattering theory within a bistatic configuration. We calculate the Doppler shifts and returned power for the proposed new Heimdall...... bistatic configuration, implemented for measurements at 60 meters height above the ground. The bistatic “Heimdall” sodar was subsequently built and set in operation adjacent to the 123 meter tall met tower at Risø National, which we had equipped with a sonic reference anemometer installed at the 60 meters...

  19. Fast Ice Detection for Wind Turbine Blades via the Langevin Equation

    Science.gov (United States)

    Fang, Haijun; Wang, Linpeng

    2016-09-01

    In this paper, a software-based algorithm for fast detection of ice on wind turbine blades is developed. The Langevin equation is used to create an entire or partial power curve with the high frequency data of wind speed and electrical power. Such a power curve is called the Langevin Power Curve (LPC). The LPC is obtained periodically. The period can be adjusted to be from 1 minute to 1 hour. For our application, the period is set to 5 minutes to allow enough data to generate an entire or partial LPC and then ice may be detected within a short period of time. The obtained LPC is compared to a reference power curve and then an ice index is calculated given that the condition for ice accretion is met. If the ice index is much higher or lower than 1, it may be concluded that there is ice on the anemometer or the blades of a wind turbine.

  20. Heat Transfer in a Forced Wall Jet on a heated Rough Surface

    Institute of Scientific and Technical Information of China (English)

    Marie-FrancoiseScibilia

    2000-01-01

    In this paper,an experimental investigation of a laminar wall jet in the presence of a heated wall with stationary particles on its surface,is reproted.The wall jet was submitted to external acoustic vibration amplifying the coherent structures appearing in the laminar region.A wind tunnel was used at very low Reynolds number,Mean velocity and turbulence intensity were measured by a constant temperature anemometer .Measurements were taken in the transition and turbulent regions.Embedded particles were outside the vissous sublayer and it was observed that their presence modifies significantly the flow characteristics in particular the boundary layer is thickened.This study can bring a better understanding of the structure of a flow when it is heated and forced on a rough wall.

  1. Effects of Bell Speed and Flow Rate on Evaporation of Water Spray from a Rotary Bell Atomizer

    Directory of Open Access Journals (Sweden)

    Rajan Ray

    2015-05-01

    Full Text Available A phase doppler anemometer (PDA was used to determine the effects of evaporation on water spray for three rotary bell atomizer operational variable parameters: shaping air, bell speed and liquid flow. Shaping air was set at either 200 standard liters per minute (L/min or 300 L/min, bell speed was set to 30, 40 or 50 thousand rotations per minute (krpm and water flow rate was varied between 100, 200 or 300 cubic centimeters per minute (cm3/min. The total evaporation between 22.5 and 37.5 cm from the atomizer (cm3/s was calculated for all the combinations of those variables. Evaporation rate increased with higher flow rate and bell speed but no statistically significant effects were obtained for variable shaping air on interactions between parameters.

  2. Designing, Constructing, And Testing A Low – Speed Open – Jet Wind Tunnel

    Directory of Open Access Journals (Sweden)

    Nguyen Quoc Y

    2014-01-01

    Full Text Available A low-speed wind tunnel has been built and tested in the Laboratory of Fluid Mechanics at the Hochiminh City University of Technology for teaching and doing research. The wind tunnel is an open-jet type with the nozzle area of 1m x 1m and the maximum wind speed of 14 m/s. To evaluate quality of the wind flow created by the tunnel, velocity distribution and turbulence intensity of airflow were measured at the nozzle by a thermal-couple anemometer. The measurements indicated that the turbulence intensity was less than two percent while the uniformity of wind speed across the nozzle is more than ninety five percent.

  3. Blade-to-Blade Flow at Centrifugal Impeller Exit Under Rotating Stall

    Science.gov (United States)

    Shin, You Hwan; Kim, Kwang Ho

    This study presents the unsteady fluctuation measurements of impeller discharge flow for a centrifugal compressor in unstable operating region. The characteristics of the blade-to-blade flow under rotating stall were investigated by measuring unsteady velocity fluctuations at several different diffuser axial distances using a hot wire anemometer and high frequency pressure transducers mounted on the shroud wall. The flow characteristics in terms of the radial and tangential velocity components and turbulence intensity at the impeller exit were analyzed by using double phase-locked ensemble averaging techniques. During one stall period, a deep wake core was observed on the suction surface near the hub for the maximum radial velocity instant. On the other hand, large wake region existed in the middle of the passage near the shroud side. For the radial velocity increasing instant a quite strong core flow was generated at the pressure side, however, for the decreasing instant comparatively strong core flow was developed near the suction side.

  4. LDA measurement of the passage flow field in a 3-D airfoil cascade

    Science.gov (United States)

    Stauter, R. C.; Fleeter, S.

    1986-01-01

    Three-dimensional internal flow computational models are currently being developed to predict the flow through turbomachinery blade rows. For these codes to be of quantitative value, they must be verified with data obtained in experiments which model the fundamental flow phenomena. In this paper, the complete three-dimensional flow field through a subsonic annular cascade of cambered airfoils is experimentally quantified. In particular, detailed three-dimensional data are obtained to quantify the inlet velocity profile, the cascade passage velocity field, and the exit region flow field. The primary instrumentation for acquiring these data is a single-channel Laser Doppler Anemometer operating in the backscatter mode, with chordwise distributions of airfoil surface static pressure taps also utilized. Appropriate data are correlated with predictions from the MERIDL/TSONIC codes.

  5. Dead time effects in laser Doppler anemometry measurements

    DEFF Research Database (Denmark)

    Velte, Clara Marika; Buchhave, Preben; George, William K.

    2014-01-01

    We present velocity power spectra computed by the so-called direct method from burst-type laser Doppler anemometer (LDA) data, both measured in a turbulent round jet and generated in a computer. Using today’s powerful computers, we have been able to study more properties of the computed spectra...... frequency range, starting around the cutoff frequency due to the finite size of the MV. Using computer-generated data mimicking the LDA data, these effects have previously been shown to appear due to the effect of dead time, i.e., the finite time during which the system is not able to acquire new...... measurements. These dead times can be traced back to the fact that the burst-mode LDA cannot measure more than one signal burst at a time. Since the dead time is approximately equal to the residence time for a particle traversing a measurement volume, we are dealing with widely varying dead times, which...

  6. Optical guidelines and signal quality for LDA applications in circular pipes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. [Sulzer Innotec, 8401, Winterthur (Switzerland); Faculty of Science and Technology, University of Applied Sciences Aargau, 5210, Windisch (Switzerland)

    2004-07-01

    The optical performance of laser Doppler anemometer (LDA) technology in applications to circular pipes with an external plane wall has been clarified and quantified. It is shown that optical aberration is a persistent feature in such LDA measurements and measurements from each direction along a full pipe diameter are needed to obtain the flow distribution. For measurements of axial velocities in a circular pipe no special care has to be taken, even if the optical plane deviates from the pipe axis. For measurements of tangential and radial velocities detailed operating guidelines have been presented with respect to the shift of the measurement volume, its optical properties and the beam waist dislocations. The analysis reveals the possible influences on both the signal quality and the measurement accuracy. (orig.)

  7. An improved sample-and-hold reconstruction procedure for estimation of power spectra from LDA data

    Energy Technology Data Exchange (ETDEWEB)

    Simon, Laurent [Laboratoire d' Acoustique de l' Universite du Maine, UMR-CNRS 6613, Avenue Messiaen, 72085, Le Mans (France); Fitzpatrick, John [Mechanical Engineering Department, Trinity College, Dublin 2 (Ireland)

    2004-08-01

    Techniques for deriving the auto or power spectrum (PSD) of turbulence from laser Doppler anemometry (LDA) measurements are reviewed briefly. The low pass filter and step noise errors associated with the sample-and-hold process are considered and a discrete version of the low pass filter for the resampled signal is derived. This is then used to develop a procedure by which the PSD estimates obtained from sample and hold measurements can be corrected. The application of the procedures is examined using simulated data and the results show that the frequency range of the analysis can be extended beyond the Nyquist frequency based on the mean sample rate. The results are shown to be comparable to those obtained using the method of Nobach et al. (1998) but the new procedures are more straightforward to implement. The technique is then used to determine the PSD of real LDA data and the results are compared with those from a hot wire anemometer. (orig.)

  8. Assessing the local windfield with instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Zambrano, T.G.

    1980-10-01

    This report concerns the development and testing of a technique for the initial screening and evaluation of potential sites for wind-energy conversion systems (WECS). The methodology was developed through a realistic siting exercise. The siting exercise involved measurements of winds along the surface and winds aloft using a relatively new instrument system, the Tethered Aerodynamic Lifting Anemometer (TALA) kite; notation of ecological factors such as vegetation flagging, soil erosion and site exposure, and verification of an area best suited for wind-energy development by establishing and maintaining a wind monitoring network. The siting exercise was carried out in an approximately 100-square-mile region of the Tehachapi Mountains of Southern California. The results showed that a comprehensive site survey involving field measurements, ecological survey, and wind-monitoring can be an effective tool for preliminary evaluation of WECS sites.

  9. Experimental measurements of surface turbulent flows

    Science.gov (United States)

    Afanasiev, Alexey L.; Rostov, Andrey P.; Shefer, Nadezhda A.

    2014-11-01

    Results of processing data obtained with the help of multi-parameter meter of turbulent micropulsation of wind speed components, temperature, humidity, pressure, and concentration of aerosol particles are discussed. The results of statistical processing of experimental time series of the aerosol scattering coefficient (nephelometer), wind speed components and temperature (ultrasonic anemometer-thermometer), are presented. Registration of the relative and absolute humidity, incoming and outgoing radiation was carried out in parallel. On the basis of the pulsation method of observations from the obtained data, dispersion of fluctuations of optical and meteorological parameters; auto-spectra fluctuations of wind speed, temperature, humidity and scattering coefficient; turbulent flows of momentum, heat and aerosol particles; the spectra of turbulent flows were calculated.

  10. Characterization of sprays

    Science.gov (United States)

    Chigier, N.; Mao, C.-P.

    1984-01-01

    It is pointed out that most practical power generation and propulsion systems involve the burning of different types of fuel sprays, taking into account aircraft propulsion, industrial furnaces, boilers, gas turbines, and diesel engines. There has been a lack of data which can serve as a basis for spray model development and validation. A major aim of the present investigation is to fill this gap. Experimental apparatus and techniques for studying the characteristics of fuel sprays are discussed, taking into account two-dimensional still photography, cinematography, holography, a laser diffraction particle sizer, and a laser anemometer. The considered instruments were used in a number of experiments, taking into account three different types of fuel spray. Attention is given to liquid fuel sprays, high pressure pulsed diesel sprays, and coal-water slurry sprays.

  11. Multi-Sensor Integration to Map Odor Distribution for the Detection of Chemical Sources

    Science.gov (United States)

    Gao, Xiang; Acar, Levent

    2016-01-01

    This paper addresses the problem of mapping odor distribution derived from a chemical source using multi-sensor integration and reasoning system design. Odor localization is the problem of finding the source of an odor or other volatile chemical. Most localization methods require a mobile vehicle to follow an odor plume along its entire path, which is time consuming and may be especially difficult in a cluttered environment. To solve both of the above challenges, this paper proposes a novel algorithm that combines data from odor and anemometer sensors, and combine sensors’ data at different positions. Initially, a multi-sensor integration method, together with the path of airflow was used to map the pattern of odor particle movement. Then, more sensors are introduced at specific regions to determine the probable location of the odor source. Finally, the results of odor source location simulation and a real experiment are presented. PMID:27384568

  12. Flow measurement in mechanical ventilation: a review.

    Science.gov (United States)

    Schena, Emiliano; Massaroni, Carlo; Saccomandi, Paola; Cecchini, Stefano

    2015-03-01

    Accurate monitoring of flow rate and volume exchanges is essential to minimize ventilator-induced lung injury. Mechanical ventilators employ flowmeters to estimate the amount of gases delivered to patients and use the flow signal as a feedback to adjust the desired amount of gas to be delivered. Since flowmeters play a crucial role in this field, they are required to fulfill strict criteria in terms of dynamic and static characteristics. Therefore, mechanical ventilators are equipped with only the following kinds of flowmeters: linear pneumotachographs, fixed and variable orifice meters, hot wire anemometers, and ultrasonic flowmeters. This paper provides an overview of these sensors. Their working principles are described together with their relevant advantages and disadvantages. Furthermore, the most promising emerging approaches for flowmeters design (i.e., fiber optic technology and three dimensional micro-fabrication) are briefly reviewed showing their potential for this application. PMID:25659299

  13. Aerodynamic and acoustic environment of a highly supersonic hot jet; Environnement aerodynamique et acoustique d'un jet chaud et fortement supersonique

    Energy Technology Data Exchange (ETDEWEB)

    Varnier, J.; Gely, D. [Office National d' Etudes et de Recherches Aerospatiales (ONERA), Dept. DSNA, 92 - Chatillon (France); Foulon, H. [CEAT, 86 - Poitiers (France)

    2001-07-01

    In the context of the spatial launchers, the prediction of noise radiated by highly supersonic hot jets is generally made from empirical methods. More recently, simulation methods based on computational fluid dynamics have been developed. In the two cases, in order to specify the parameters of the computer codes, it is necessary to know the actual aerodynamic and acoustic data of the flow. In the MARTEL facilities of CNES, ONERA has carried out tests with a 1200 m/s hot jet, free or impinging on a large plate. Acoustic near field and aerodynamic configuration of the free jet and of the wall jet have been characterized by measurements. Particularly, the supersonic core length and the location of the sound power peak on the jet axis have been determined. Other measurements, made with anemometers and wind cocks in the vicinity of the jet and of the plate, have allowed to characterize the drive of the ambient air by the jet. (authors)

  14. Multi-Sensor Integration to Map Odor Distribution for the Detection of Chemical Sources

    Directory of Open Access Journals (Sweden)

    Xiang Gao

    2016-07-01

    Full Text Available This paper addresses the problem of mapping odor distribution derived from a chemical source using multi-sensor integration and reasoning system design. Odor localization is the problem of finding the source of an odor or other volatile chemical. Most localization methods require a mobile vehicle to follow an odor plume along its entire path, which is time consuming and may be especially difficult in a cluttered environment. To solve both of the above challenges, this paper proposes a novel algorithm that combines data from odor and anemometer sensors, and combine sensors’ data at different positions. Initially, a multi-sensor integration method, together with the path of airflow was used to map the pattern of odor particle movement. Then, more sensors are introduced at specific regions to determine the probable location of the odor source. Finally, the results of odor source location simulation and a real experiment are presented.

  15. Operation in the turbulent jet field of a linear array of multiple rectangular jets using a two-dimensional jet (Variation of mean velocity field

    Directory of Open Access Journals (Sweden)

    Fujita Shigetaka

    2016-01-01

    Full Text Available The mean flowfield of a linear array of multiple rectangular jets run through transversely with a two-dimensional jet, has been investigated, experimentally. The object of this experiment is to operate both the velocity scale and the length scale of the multiple rectangular jets using a two-dimensional jet. The reason of the adoption of this nozzle exit shape was caused by the reports of authors in which the cruciform nozzle promoted the inward secondary flows strongly on both the two jet axes. Aspect ratio of the rectangular nozzle used in this experiment was 12.5. Reynolds number based on the nozzle width d and the exit mean velocity Ue (≅ 39 m / s was kept constant 25000. Longitudinal mean velocity was measured using an X-array Hot-Wire Probe (lh = 3.1 μm in diameter, dh = 0.6 mm effective length : dh / lh = 194 operated by the linearized constant temperature anemometers (DANTEC, and the spanwise and the lateral mean velocities were measured using a yaw meter. The signals from the anemometers were passed through the low-pass filters and sampled using A.D. converter. The processing of the signals was made by a personal computer. Acquisition time of the signals was usually 60 seconds. From this experiment, it was revealed that the magnitude of the inward secondary flows on both the y and z axes in the upstream region of the present jet was promoted by a two-dimensional jet which run through transversely perpendicular to the multiple rectangular jets, therefore the potential core length on the x axis of the present jet extended 2.3 times longer than that of the multiple rectangular jets, and the half-velocity width on the rectangular jet axis of the present jet was suppressed 41% shorter compared with that of the multiple rectangular jets.

  16. A direct method of measuring gaseous emissions from naturally ventilated dairy barns

    Science.gov (United States)

    Joo, H. S.; Ndegwa, P. M.; Heber, A. J.; Bogan, B. W.; Ni, J.-Q.; Cortus, E. L.; Ramirez-Dorronsoro, J. C.

    2014-04-01

    Air pollutant emission rates from mechanically ventilated (MV) dairy barns are determined from the product of the differences in concentrations of pollutants in air at the inlet and exhaust points and the corresponding ventilation rates. In contrast to well defined entry and exit points in MV barns, large area air inlets or outlets characterize naturally ventilated (NV) freestall dairy barns. Complicating this scenario even more, pertinent airflow characteristics (velocity and direction) necessary for determining ventilation rates vary continuously, both temporally and spatially. This paper describes implementation of a direct method, generally equivalent to the approach used for MV barns, for determining air emission rates of NV barns. Ultrasonic anemometers (sonics) located at salient points in the barn openings mapped air inflow and outflow velocities necessary to calculate ventilation rates. Pollutant concentrations in the air entering or leaving the barn during a given period were measured at sampling points located next to the anemometers. The air inflow rates were, in general, higher than the air outflow rates from the barns, but diurnal profiles were similar. The observed ventilation characteristics were consistent with prevailing wind directions. Air inflows were observed predominantly at windward openings of the barn, while the outflows were mainly at the barn's leeward openings. Results indicated that either: (i) the average of the air inflow and outflow rates (averaging approach), or (ii) the air inflow rates (inflow-only approach) were credible representations of ventilation rates. Results also revealed use of an on-site weather station and one sonic mounted in the middle of each wall of the barn as a possible approach for determining barn ventilation rates. The suggested use of ventilation rates for interpolating missing concentrations from intermittent gas measurements could potentially increase the integrity of emission rates at significantly lower

  17. 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.

  18. State of the Art and Trends in Wind Resource Assessment

    Directory of Open Access Journals (Sweden)

    Oliver Probst

    2010-06-01

    Full Text Available Given the significant rise of the utilization of wind energy the accurate assessment of the wind potential is becoming increasingly important. Direct applications of wind assessment techniques include the creation of wind maps on a local scale (typically 5 20 km and the micrositing of wind turbines, the estimation of vertical wind speed variations, prospecting on a regional scale (>100 km, estimation of the long-term wind resource at a given site, and forecasting. The measurement of wind speed and direction still widely relies on cup anemometers, though sonic anemometers are becoming increasingly popular. Moreover, remote sensing by Doppler techniques using the backscattering of either sonic beams (SODAR or light (LIDAR allowing for vertical profiling well beyond hub height are quickly moving into the mainstream. Local wind maps are based on the predicted modification of the regional wind flow pattern by the local atmospheric boundary layer which in turn depends on both topographic and roughness features and the measured wind rose obtained from one or several measurement towers within the boundaries of the planned development site. Initial models were based on linearized versions of the Navier-Stokes equations, whereas more recently full CFD models have been applied to wind farm micrositing. Linear models tend to perform well for terrain slopes lower than about 25% and have the advantage of short execution times. Long-term performance is frequently estimated from correlations with nearby reference stations with concurrent information and continuous time series over a period of at least 10 years. Simple methods consider only point-to-point linear correlations; more advanced methods like multiple regression techniques and methods based on the theory of distributions will be discussed. Both for early prospecting in regions where only scarce or unreliable reference information is available, wind flow modeling on a larger scale (mesoscale is becoming

  19. Exploring the influence of surface waves in the carbon dioxide transfer velocity between the ocean and atmosphere in the coastal region

    Science.gov (United States)

    Ocampo-Torres, Francisco Javier; Francisco Herrera, Carlos; Gutiérrez-Loza, Lucía; Osuna, Pedro

    2016-04-01

    Field measurements have been carried out in order to better understand the possible influence of ocean surface waves in the transfer of carbon dioxide between the ocean and atmosphere in the coastal zone. The CO2 fluxes are being analysed and results are shown in a contribution by Gutiérrez-Loza et al., in this session. Here we try to highlight the findings regarding the transfer velocity (kCO2) once we have incorporated direct measurements of carbon dioxide concentration in the water side. In this study direct measurements of CO2 fluxes were obtained with an eddy covariance tower located in the shoreline equipped with an infrared open-path gas analyzer (LI-7500, LI-COR) and a sonic anemometer (R3-100 Professional Anemometer, Gill Instruments), both at about 13 m above the mean sea level, and sampling at 20 Hz. For some period of time simultaneous information of waves was recorded with a sampling rate of 2 Hz using an Acoustic Doppler Current Profiler (Workhorse Sentinel, Teledyne RD Instruments) at 10 m depth and 350 m away from the tower. Besides, recently the concentration of CO2 in water has also been recorded making use of a SAMI-CO2 instrument. A subtle effect of the wave field is detected in the estimated kCO2. Looking into details of the surface currents being detected very near the air-sea interface through an ADPC, a certain association can be found with the gas transfer velocity. Furthermore, some of the possible effects of breaking wave induced turbulence in the coastal zone is to be addressed. This work represents a RugDiSMar Project (CONACYT 155793) contribution. The support from CB-2011-01-168173 CONACYT project is greatly acknowledged.

  20. An experimental study of mixed convection; Contribution a l'etude experimentale de la convection mixte

    Energy Technology Data Exchange (ETDEWEB)

    Saez, M.

    1998-10-20

    The aim of our study is to establish a reliable database for improving thermal hydraulic codes, in the field of turbulent flows with buoyancy forces. The flow considered is mixed convection in the Reynolds and Richardson number range: Re = 10{sup 3} to 6.10{sup 4} and Ri = 10{sup -4} to 1. Experiments are carried out in an upward turbulent flow between vertical parallel plates at different wall temperatures. Part 1 gives a detailed database of turbulent mixed flow of free and forced convection. Part 2 presents the installation and the calibration system intended for probes calibration. Part 3 describes the measurement technique (constant temperature probe and cold-wire probe) and the method for measuring the position of the hot-wire anemometer from the wall surface. The measurement accuracy is within 0.001 mm in the present system. Part 4 relates the development of a method for near wall measurements. This correction procedure for hot-wire anemometer close to wall has been derived on the basis of a two-dimensional numerical study. The method permits to obtain a quantitative correction of the wall influence on hot-wires and takes into account the velocity profile and the effects the wall material has on the heat loss. Part 5 presents the experimental data obtained in the channel in forced and mixed convection. Results obtained in the forced convection regime serve as a verification of the measurement technique close to the wall and give the conditions at the entrance of the test section. The effects of the buoyancy force on the mean velocity and temperature profiles are confirmed. The buoyancy strongly affects the fluid structure and deforms the distribution of mean velocity. The velocity profiles are asymmetric. The second section of part 5 gives an approach of analytical wall functions with buoyancy forces, on the basis of the experimental data obtained in the test section. (author)

  1. A comparison of Lagrangian model estimates to light detection and ranging (LIDAR) measurements of dust plumes from field tilling.

    Science.gov (United States)

    Wang, Junming; Hiscox, April L; Miller, David R; Meyer, Thomas H; Sammis, Ted W

    2009-11-01

    A Lagrangian particle model has been adapted to examine human exposures to particulate matter elastic LIDAR (light detection and ranging). For the first time, the LIDAR measurements allowed spatially distributed and time dynamic measurements to be used to test the predictions of a field-scale model. The model outputs, which are three-dimensional concentration distribution maps from an agricultural disking operation, were compared with the LIDAR-scanned images. The peak cross-correlation coefficient and the offset distance of the measured and simulated plumes were used to quantify both the intensity and location accuracy. The appropriate time averaging and changes in accuracy with height of the plume were examined. Inputs of friction velocity, Monin-Obukhov length, and wind direction (1 sec) were measured with a three-axis sonic anemometer at a single point in the field (at 1.5-m height). The Lagrangian model of Wang et al. predicted the near-field concentrations of dust plumes emitted from a field disking operation with an overall accuracy of approximately 0.67 at 3-m height. Its average offset distance when compared with LIDAR measurements was approximately 38 m, which was 6% of the average plume moving distance during the simulation periods. The model is driven by weather measurements, and its near-field accuracy is highest when input time averages approach the turbulent flow time scale (3-70 sec). The model accuracy decreases with height because of smoothing and errors in the input wind field, which is modeled rather than measured at heights greater than the measurement anemometer. The wind steadiness parameter (S) can be used to quantify the combined effects of wind speed and direction on model accuracy. PMID:19947118

  2. Evolution of planetary boundary layer under different weather conditions, and its impact on aerosol concentrations

    Institute of Scientific and Technical Information of China (English)

    Jiannong Quan; Yang Gao; Qiang Zhang; Xuexi Tie; Junji Cao; Suqin Han; Junwang Meng

    2013-01-01

    A field experiment was conducted in Tianjin,China from September 9-30,2010,focused on the evolution of Planetary Boundary Layer (PBL) and its impact on surface air pollutants.The experiment used three remote sensing instruments,wind profile radar (WPR),microwave radiometer (MWR) and micro-pulse lidar (MPL),to detect the vertical profiles of winds,temperature,and aerosol backscattering coefficient and to measure the vertical profiles of surface pollutants (aerosol,CO,SO2,NOx),and also collected sonic anemometers data from a 255-m meteorological tower.Based on these measurements,the evolution of the PBL was estimated.The averaged PBL height was about 1000-1300 m during noon/afternoon-time,and 200-300 m during night-time.The PBL height and the aerosol concentrations were anti-correlated during clear and haze conditions.The averaged maximum PBL heights were 1.08 and 1.70 km while the averaged aerosol concentrations were 52 and 17 μg/m3 under haze and clear sky conditions,respectively.The influence of aerosols and clouds on solar radiation was observed based on sonic anemometers data collected from the 255-m meteorological tower.The heat flux was found significantly decreased by haze (heavy pollution) or cloud,which tended to depress the development of PBL,while the repressed structure of PBL further weakened the diffusion of pollutants,leading to heavy pollution.This possible positive feedback cycle (more aerosols → lower PBL height → more aerosols) would induce an acceleration process for heavy ground pollution in megacities.

  3. Mapping flow distortion on oceanographic platforms using computational fluid dynamics

    Directory of Open Access Journals (Sweden)

    N. O'Sullivan

    2012-11-01

    Full Text Available Ocean-Atmosphere Fluxes Eddy correlation (EC is the most direct method to measure fluxes of trace gases over the Earth's surface. In its simplest form, an EC setup consists of a gas sensor and a sonic anemometer. EC is commonly used on land, but its adaptation at sea has proven difficult because of the marine environment, the motion of the research platform (ship or buoy, and flow distortion. Flow distortion occurs when streamlines circumvent the research platform, which may lead to significant errors in the calculation of the gas transfer velocity. This paper uses computational fluid dynamics (CFD to simulate the errors in wind speed measurements caused by flow distortion on the R/V Celtic Explorer. Numerical measurements were obtained from the finite volume CFD code OpenFOAM, which was used to simulate the velocity fields. This was done over a range of orientations in the test domain from −60° to +60°, in increments of 10°. The simulation was also set up for a range of velocities, ranging from 5 m s−1 to 25 m s−1 in increments of 0.5 m s−1 The numerical analysis showed close agreement to experimental measurements to within a 12% mean difference prediction of flow distortion effects. Other aspects resulting from flow distortion that were investigated using the CFD tools included development of a correction method for flow distortion effects for in situ wind speed measurements; analysis of ideal positioning of anemometers; vertical tilt orientation of the vessel to inflow; meteorological mast design; and mast instrumentation setups.

  4. An experimental and numerical study of the urban wind field at the university site Tübingen

    Science.gov (United States)

    El Bahlouli, Asmae; Bange, Jens

    2015-04-01

    This study examines the wind energy potential close to energy consumers inside cities, i.e. between buildings at the university site in the city of Tübingen. The study area is characterized by cubic shaped buildings, related to the university and located on top of a hill in an outlying district in the city of Tübingen. A majority of the buildings is higher than 20 meters with 3 of them around 50 meters. This investigation combines a full-scale experiment and a numerical study. A common technique to calculate the energy potential includes wind measurements at least for an annual cycle. For our study, the measurement campaign started in April 2014 and should last until mid of 2015. Six stations with sonic anemometers were installed. These anemometers are providing measurements of wind speed and wind direction with a high temporal resolution (10 Hz). On the one hand, the measured data are used for a determination of the inflow boundary conditions for our simulations. On the other hand, the wind data will be used to verify the numerical model inside the domain. A wide variety of numerical simulations based on Reynolds Averaged Navier-Stokes Equations (RANS) and large eddy simulation (LES) models have been conducted (cf. Tutar and Oguz (2002)). From these numerical studies it has been concluded that the LES approach seems to be more suitable for studies of airflows around buildings. Consequently we decided to conduct our calculations by means of a LES using OpenFOAM software. This study will help us to identify locations with the most qualified conditions for producing electrical energy using small building-mounted wind turbines. Tutar, M., Oguz, G. (2002). Large eddy simulation of flow around parallel buildings with varying configurations. Fluid Dynamic Research 31, p289-315.

  5. Transition from downward to upward air-sea momentum transfer in swell-dominated light wind condition

    Science.gov (United States)

    Smedman, Ann-Sofi; Högström, Ulf; Rutgersson, Anna

    2016-04-01

    Atmospheric and surface wave data from two oceanic experiments carried out on FLIP and ASIS platforms are analysed in order to identify swell-related effects on the momentum exchange during low wind speed conditions. The RED experiment was carried out on board an R/P Floating Instrument Platform, FLIP, anchored north east of the Hawaiian island Oahu with sonic anemometers at four levels: 5.1 m, 6.9 m, 9.9 m and 13.8 m respectively. The meteorological conditions were characterized by north- easterly trade wind and with swell present during most of the time. During swell the momentum flux was directed downwards meaning a positive contribution to the stress. The FETCH experiment was carried out in the Gulf of Lion in the north-western Mediterranean Sea. On the ASIS (air-sea interaction spar) buoy a sonic anemometer was mounted at 7 m above the mean surface level. During strong swell conditions the momentum flux was directed upwards meaning a negative contribution to the stress in this case. The downward momentum flux is shown to be a function of the orbital circulation while the upward momentum flux is a function of wave height. The dividing wind speed is found to be 3.5 m/s Conclusion: Wind speed > 3.5 m/s creates waves (ripples) and thus roughness. Combination of orbital motion and asymmetric structure of ripples lead to flow perturbation and downward transport of negative momentum. With low wind speed (no ripples but viscosity) circulations will form above the crest and the trough with opposite direction which will cause a pressure drop in the vertical direction and an upward momentum transport from the water to the air.

  6. Design and use of a sparged platform for energy flux measurements over lakes

    Science.gov (United States)

    Gijsbers, S.; Wenker, K.; van Emmerik, T.; de Jong, S.; Annor, F.; Van De Giesen, N.

    2012-12-01

    Energy flux measurements over lakes or reservoirs demand relatively stable platforms. Platforms can not be stabilized by fixing them on the bottom of the lake when the water body is too deep or when water levels show significant fluctuations. We present the design and first operational results of a sparged platform. The structure consists of a long PVC pipe, the sparge, which is closed at the bottom. On the PVC pipe rests an aluminum frame platform that carries instrumentation and solar power panel. In turn, the platform rests partially on a large inflated tire. At the bottom of the PVC pipe, lead weights and batteries were placed to ensure a very low point of gravity to minimize wave impact on the platform movement. The tire ensures a large second moment of the water plane. The overall volume of displacement is small in this sparged design. The combination of large second momentum of the water plane and small displacement ensure a high placement of the metacenter. The distance between the point of gravity and the metacenter is relatively long and the weight is large due to the weights and batteries. This ensures that the eigenfrequency of the platform is very low. The instrumentation load consisted of a WindMaster Pro (sonic anemometer for 3D wind speed and air temperature to perform eddy covariance measurements of sensible heat flux), a NR Lite (net radiometer), and air temperature and relative humidity sensors. The platform had a wind vane and the sparge could turn freely around its anchor cable to ensure that the anemometer always faced upwind. A compass in the logger completed this setup. The stability was measured with an accelerometer. In addition to the design and its stability, some first energy flux results will be presented.

  7. SENSOR ULTRASONIK SEBAGAI ALAT PENGUKUR KECEPATAN ALIRAN UDARA DALAM PIPA

    Directory of Open Access Journals (Sweden)

    K.G. Suastika

    2014-08-01

    Full Text Available ABSTRAKEra perkembangan teknologi saat ini telah banyak ditemukan alat-alat inovasi terbaru terutama pada penggunaan gelombang ultrasonik. Gelombang ultrasonik merupakan gelombang bunyi yang frekuensinya di atas 20.000 Hz dan biasanya digunakan dalam bidang kelautan (SONAR, kedokteran (USG maupun dalam bidang industri. Penelitian yang dilakukan adalah penelitian tentang pengukuran kecepatan aliran udara dalam pipa menggunakan sensor ultrasonik dan gelombang ultrasonik yang digunakan pada penelitian ini adalah gelombang ultrasonik yang memiliki frekuensi kerja sebesar 300 kHz. Prinsip pengukuran yang digunakan dalam penelitian ini menggunakan metode waktu tempuh gelombang ultrasonik (time of flight dengan memanfaatkan perubahan karakteristik gelombang ultrasonik ketika melewati kondisi aliran udara yang berbeda yaitu upstream dan downstream. Selain itu, sebagai pembanding (tingkat akurasi dalam penelitian ini digunakan alat pengukur kecepatan aliran udara standar yaitu anemometer. Dari hasil penelitian didapat bahwa tingkat akurasi sebesar 99% dan dengan korelasi sebesar 0,99 (korelasi sangat tinggi. Berdasarkan hasil tersebut, dapat disimpulkan bahwa sensor ultrasonik valid dan dapat digunakan sebagai perangkat pengukur kecepatan aliran udara dalam pipa. ABSTRACTThe newest innovation instruments applying ultrasonic wave have been found in this technology era. Ultrasonic wave is the sound of wave is the sound wave having frequency above 20.000 Hz and is usually used in oceanic field (SONAR, medical (USG and industrial fields. This research measured the air velocity in pipe by using ultrasonic sensor. The ultrasonic wave used was the one which has frequency of 300 kHz. The Principle of measurement applied the method of elapsed time of ultrasonic wave (time of flight by considering the change of ultrasonic wave when passing different air flow condition: upstream and downstream. Besides, the anemometer was used as the accuracy comparator. The

  8. An experimental investigation of the three-dimensional boundary layer on a rotating disk

    Science.gov (United States)

    Littell, Howard Steven

    The velocity field above a large spinning disk has been studied using pressure probes and hotwire anemometers. The flowfield consists of a three-dimensional boundary layer due to a crossflow caused by centrifugal forces. The disk was 1 m in diameter and was spun at speeds up to 1500 rpm, giving momentum thickness Reynolds numbers in excess of 6000. The mean flow in both the laminar and turbulent regimes compares well with previous studies of 'infinite' smooth rotating disks. All six Reynolds stresses and the ten triple products have been measured using established crosswire anemometry techniques. These results are compared to previous three-dimensional boundary layer measurements and several key differences are noted. The ratio of the shear stress vector magnitude to the turbulent kinetic energy is a common descriptor of boundary layer flow and is used in many modeling efforts because it is usually a constant over most of a two-dimensional boundary layer. Three-dimensionality has been observed to depress this parameter near the wall in many pressure-driven boundary layers. In the disk flow, this parameter was at a maximum near the wall at close to the 2-D value, but dropped off almost linearly away from the wall. Two-point velocity correlations were also measured using a pair of crosswire anemometers to gain insight into the structure of the turbulence. These measurements were obtained at two different heights at momentum thickness Reynolds numbers of 2650 and 5000 to test for possible scaling effects. These measurements showed that the turbulence exhibits asymmetry in the crossflow direction, which cannot occur in two-dimensional boundary layers. A mechanism by which the crossflow may be modifying the turbulence structure is proposed which exhibits several features of the asymmetric two-point correlations.

  9. Using of standard marine radar for determination of a water surface and an atmosphere near-surface layer parameters

    Science.gov (United States)

    Bogatov, Nikolay A.; Bakhanov, Victor V.; Ermoshkin, Aleksei V.; Kazakov, Vasily I.; Kemarskaya, Olga N.; Titov, Victor I.; Troitskaya, Yulia I.

    2014-10-01

    At present time radar methods of the seas and oceans diagnostics are actively developing. Using of the radar stations based on satellites and planes allows to receive information on a sea surface and a atmosphere near-surface layer with coverage of big water surface areas independently of day time. The developed methods of satellite radio images processing can be applied to marine radar stations. In Institute of Applied Physics RAS works on sea surface diagnostics systems development on the basis of standard marine radar are actively conducted. Despite smaller coverage of the territory in comparison with satellite data, marine radar have possibility to record spatially temporary radar images and to receive information on a surrounding situation quickly. This work deals with results of the researches which were conducted within the international expedition in the Atlantic Ocean in the autumn of 2012 on a route Rotterdam (Netherlands) - Ushuaya (Argentina) - Antarctica — Ushuaya. During this expedition a complex measurements of a sea surface, a atmosphere near-surface layer parameters and subsurface currents in the wide range of hydroweather conditions, including the storm were carried out. The system developed in IAP RAS on the basis of a marine radar ICOM MR-1200RII and the ADC (Analog Digital Converter) block for data recording on the personal computer was used. Display of a non-uniform near-surface current on sea surface radar images in storm conditions is shown. By means of the high-speed anemometer and meteorological station the measurements of the atmosphere parameters were carried out. Comparison of the anemometer data with calculated from radar images is carried out. Dependence of radar cross section from wind speed in the wide range of wind speeds, including storm conditions is investigated. Possibility of marine radar using for surface waves intensity and ice situation estimates also as icebergs detection is shown.

  10. 基于ANFIS模型的风功率超短期预测研究%Study of Ultra-Short-Term Forecasting Method for Wind Power

    Institute of Scientific and Technical Information of China (English)

    王艳艳; 尹少平; 王灵梅; 张志华

    2016-01-01

    提出一种基于自适应神经模糊推理系统(ANFIS)模型的风功率超短期预测方法。该方法以测风塔在层高70m测得的风向、风速和在层高20m测得的气温为输入,以风场的实际有功出力为输出,选取山西某风场的历史数据进行训练,建立了风功率超短期ANFIS预测模型。最后将ANFIS预测结果与基于BP神经网络的预测结果进行了对比分析,结果表明本文提出的预测方法预测精度较高。%An ultra-short-term forecasting method is proposed based on ANFIS for wind power. The wind direction, wind speed which are measured in height of 70m from anemometer tower and temperature which is measured in height of 20m from anemometer tower, take these data as input and actual active power of the wind farm as output. The ultra-short-term forecasting model is established on the basis of ANFIS for wind power by training the historical data of a wind farm in Shanxi. The experimental results are compared with that of BP neural networks. And result from the study shows that ANFIS may give a high precision.

  11. Stably Stratified Flow in a Shallow Valley

    Science.gov (United States)

    Mahrt, L.

    2016-07-01

    Stratified nocturnal flow above and within a small valley of approximately 12-m depth and a few hundred metres width is examined as a case study, based on a network of 20 sonic anemometers and a central 20-m tower with eight levels of sonic anemometers. Several regimes of stratified flow over gentle topography are conceptually defined for organizing the data analysis and comparing with the existing literature. In our case study, a marginal cold pool forms within the shallow valley in the early evening but yields to larger ambient wind speeds after a few hours, corresponding to stratified terrain-following flow where the flow outside the valley descends to the valley floor. The terrain-following flow lasts about 10 h and then undergoes transition to an intermittent marginal cold pool towards the end of the night when the larger-scale flow collapses. During this 10-h period, the stratified terrain-following flow is characterized by a three-layer structure, consisting of a thin surface boundary layer of a few metres depth on the valley floor, a deeper boundary layer corresponding to the larger-scale flow, and an intermediate transition layer with significant wind-directional shear and possible advection of lee turbulence that is generated even for the gentle topography of our study. The flow in the valley is often modulated by oscillations with a typical period of 10 min. Cold events with smaller turbulent intensity and duration of tens of minutes move through the observational domain throughout the terrain-following period. One of these events is examined in detail.

  12. New Instrument for Measuring Size-resolved Submicron Sea Spray Particle Production From Ocean

    Science.gov (United States)

    Meskhidze, N.; Petters, M. D.; Reed, R. E.; Dawson, K. W.; Phillips, B.; Royalty, T. M.

    2015-12-01

    Marine aerosols play an important role in controlling the Earth's radiation balance, cloud formation and microphysical properties, and the chemistry of the marine atmosphere. As aerosol effects on climate are estimated from the difference between model simulations with present-day and with preindustrial aerosol and precursor emissions, accurate knowledge of size- and composition-dependent production flux of sea spray particles is important for correct assessment of the role of anthropogenic aerosols in climate change. One particular knowledge gap in sea spray particle emissions resides in yet uncharacterized contributions of sea spray to the cloud condensation nuclei (CCN) budget over the marine boundary layer. The chemical composition of 50 to 200 nm sized sea spray particles, most critical to modeling CCN concentration from size distribution data is often simplified as purely organic, purely sea-salt or mixture of both. The lack of accurate information of the size-dependent production flux of sub-micron sea spray particles prevents the modeling community from resolving discrepancies between model-predicted and measured CCN number concentration in the marine boundary layer. We designed a new system for size-selected sea spray aerosol flux measurement that is composed of a 3D sonic anemometer, two thermodenuders, three differential mobility analyzers, two condensation particle counters, and a CCN counter. The system is designed to operate in both Eddy Covariance (EC) and Relaxed Eddy Accumulation (REA) modes. The system is based on the volatility/humidified tandem differential mobility analyzer technique and is therefore designed to measure the size-resolved turbulent fluxes of sub-micron sized sea-salt particles for a wide range of meteorological, hydrological and ocean chemical/biological conditions. The method and the setup will be presented along with some results from a recent field-deployment of the instrument at the North Carolina coast. This presentation

  13. Sensors for Using Times of Flight to Measure Flow Velocities

    Science.gov (United States)

    Fralick, Gutave; Wrbanek, John D.; Hwang, Danny; Turso, James

    2006-01-01

    Thin-film sensors for measuring flow velocities in terms of times of flight are undergoing development. These sensors are very small and can be mounted flush with surfaces of airfoils, ducts, and other objects along which one might need to measure flows. Alternatively or in addition, these sensors can be mounted on small struts protruding from such surfaces for acquiring velocity measurements at various distances from the surfaces for the purpose of obtaining boundary-layer flow-velocity profiles. These sensors are related to, but not the same as, hot-wire anemometers. Each sensor includes a thin-film, electrically conductive loop, along which an electric current is made to flow to heat the loop to a temperature above that of the surrounding fluid. Instantaneous voltage fluctuations in segments of the loop are measured by means of electrical taps placed at intervals along the loop. These voltage fluctuations are caused by local fluctuations in electrical resistance that are, in turn, caused by local temperature fluctuations that are, in turn, caused by fluctuations in flow-induced cooling and, hence, in flow velocity. The differential voltage as a function of time, measured at each pair of taps, is subjected to cross-correlation processing with the corresponding quantities measured at other pairs of taps at different locations on the loop. The cross-correlations yield the times taken by elements of fluid to travel between the pairs of taps. Then the component of velocity along the line between any two pairs of taps is calculated simply as the distance between the pairs of taps divided by the travel time. Unlike in the case of hot-wire anemometers, there is no need to obtain calibration data on voltage fluctuations versus velocity fluctuations because, at least in principle, the correlation times are independent of the calibration data.

  14. Mean vertical velocities and flow tilt angles at a fetch-limited forest site in the context of carbon dioxide vertical advection

    Directory of Open Access Journals (Sweden)

    E. Dellwik

    2009-08-01

    Full Text Available An analysis of flow angles from a fetch-limited beech forest site with clearings is presented. Flow angles and vertical velocities from two types of sonic anemometers as well as a ground based remote sensing lidar were analysed. Instead of using rotations, where zero-flow angles were assumed for neutral flow, the data from the instruments were interpreted in relation to the terrain.

    Uncertainties regarding flow distortion and limited sampling time (statistical uncertainty were evaluated and found to be significant. Especially for one of the sonic anemometers, relatively small changes in the flow distortion correction could change the sign of mean vertical velocities taken during stable atmospheric stratification relative to the neutral flow. Despite the uncertainties, it was possible to some extent to relate both positive and negative mean flow angles to features in the terrain.

    Conical and linear scans with a remote sensing lidar were evaluated for estimation of vertical velocities and flow angles. The results of the vertical conical scans were promising, and yielded negative flow angles for a sector where the forest is fetch-limited. However, more data and analysis is needed for a complete evaluation of the technique. The horizontal linear scans showed the variability of the mean wind speed field. A vertical velocity was calculated from different focusing distances, but this estimate yielded unrealistically high vertical velocities, due to neglect of the transversal wind component.

    The vertical advection term was calculated using the measured mean flow angles at the mast and profile measurements of carbon dioxide, but it is not recommended to use in relation with the flux measurement as the vertical velocity measured at the mast is most likely not representative for the whole forest.

  15. Expanding Spatial and Temporal Coverage of Arctic CH4 and CO2 Fluxes

    Science.gov (United States)

    Murphy, P.; Oechel, W. C.; Moreaux, V.; Losacco, S.; Zona, D.

    2013-12-01

    Carbon storage and exchange in Arctic ecosystems is the subject of intensive study focused on determining rates, controls, and mechanisms of CH4 and CO2 fluxes. The Arctic contains more than 1 Gt of Carbon in the upper meter of soil, both in the active layer and permafrost (Schuur et al., 2008; Tarnocai et al., 2009). However, the annual pattern and controls on the release of CH4 is inadequately understood in Arctic tundra ecosystems. Annual methane budgets are poorly understood, and very few studies measure fluxes through the freeze-up cycle during autumn months (Mastepanov et al., 2008; Mastepanov et al., 2010; Sturtevant et al., 2012). There is no known, relatively continuous, CH4 flux record for the Arctic. Clearly, the datasets that currently exist for budget calculations and model parameterization and verification are inadequate. This is likely due to the difficult nature of flux measurements in the Arctic. In September 2012, we initiated a research project towards continuous methane flux measurements along a latitudinal transect in Northern Alaska. The eddy-covariance (EC) technique is challenging in such extreme weather conditions due to the effects of ice formation and precipitation on instrumentation, including gas analyzers and sonic anemometers. The challenge is greater in remote areas of the Arctic, when low power availability and limited communication can lead to delays in data retrieval or data loss. For these reasons, a combination of open- and closed-path gas analyzers, and several sonic anemometers (including one with heating), have been installed on EC towers to allow for cross-comparison and cross-referencing of calculated fluxes. Newer instruments for fast CH4 flux determination include: the Los Gatos Research Fast Greenhouse Gas Analyzer and the Li-Cor LI-7700. We also included the self-heated Metek Class-A uSonic-3 Anemometer as a new instrument. Previously existing instruments used for comparison include the Li-Cor LI-7500; Li-Cor LI-7200

  16. Real-time on-line meteorological and radiological environmental survey system

    International Nuclear Information System (INIS)

    The National Research Institute for Nuclear Physics and Engineering has an ultimate survey system for meteorological and radiation situation. With the help of IAEA and of the Romanian Government a modern computerized survey system was design, built, equipped, calibrated and put into operation. For the first time in Romania real-time information on meteorology and radiation is obtained and transmitted on-line to be used by on-site emergency systems. The site survey system was designed to accomplish the following tasks: i) radioprotection (continuous monitoring); ii) training for accident management; iii) pilot for data acquisition and transmission to RODOS system; iv) studies on environmental physics (influence of meteorological factors on external dose, influence of soil roughness on intermediate boundary layers); v) studies for nuclear safety (meteorological database and preprocessing for probabilistic studies - PSA level III); vi) studies on climate influence on plant growth and pollutant transfer (tritium); vii) studies on nuclear meteorology with focus on technology transfer to Cernavoda NPP. The measurement system consists of the following meteorological sensors positioned at four height levels on our meteorological-radiological (MR) surveying tower: i) on the ground levels: raingauge - for level of rainfalls per known area; ii) at 10 m height: anemometer; windvane; solar energy sensor; relative humidity - meter; temperature air sensor; iii) at 30 m height: anemometer; windvane; iv) at 60 m height: anemometer; windvane; temperature air sensor. The radiological measurement system consists of Geiger-Mueller counters. The three G-M counters positioned at three levels on meteo tower (1 m, 10 m and 60 m. Other instruments will be soon incorporated to the system among which an Alpha-Beta Airborne Monitor, an Iodine Monitor and a Double GM Area Monitor to enlarge its sensing coverage. Primary MR data are acquired and stored by a programmable data logging device

  17. Scaling Anisotropy and Convective Instability of the Atmospheric Surface-Layer

    Science.gov (United States)

    Fitton, G. F.; Tchiguirinskaia, I.; Schertzer, D. J.; Lovejoy, S.

    2013-12-01

    In this study we use the scaling exponents, often called Hurst exponents, of the horizontal velocity and the temperature to classify the stability of the atmospheric surface-layer, including in the wake of a turbine. For this study we use two datasets for comparison. In the Growian experiment two 150m masts were constructed on coastal terrain with propeller anemometers positioned at the heights 10, 50, 75, 100, 125 and 150m measuring wind speed and direction. The measurements were taken at 2.5Hz over twenty-minutes with 300 measuring runs done in total. In addition, temperature was measured also at 2.5Hz over twenty minutes but only at the heights 10, 50, 100 and 150m. The second dataset consisted of three sonic anemometers positioned at 22, 23 and 43m on a single mast situated in a wind turbine test site in a mountainous part of Corsica France. The sonic anemometers measured three dimensional velocities and temperature at 10Hz over a period of six-months. The samples are separated into daily sub-samples, 180 in total. We find that the stability of the atmospheric surface-layer strongly depends on whether or not the temperature scales passively as the velocity. When the two scaling exponents remain of the same order, the scaling of both the velocity and temperature is consistent with surface-layer literature. However, when the scaling exponent of the temperature becomes larger than the scaling exponent of the velocity, the corresponding time-scales exhibit a strong, scaling anisotropy. To avoid shadow effects from masts, we are compelled to deal with samples whose `mean' velocity is near-perpendicular to the masts. The anisotropy of these samples turns out to be beyond a trivial component-wise anisotropy corresponding to pre-factors depending on the direction, i.e., the scaling exponents themselves (in particular the Hurst exponent) depend on the direction. We use a rotated frame of reference to better analyse this behaviour and put forward analytical expression of

  18. Multifractal Analysis of Velocity Vector Fields and a Continuous In-Scale Cascade Model

    Science.gov (United States)

    Fitton, G.; Tchiguirinskaia, I.; Schertzer, D.; Lovejoy, S.

    2012-04-01

    In this study we have compared the multifractal analyses of small-scale surface-layer wind velocities from two different datasets. The first dataset consists of six-months of wind velocity and temperature measurements at the heights 22, 23 and 43m. The measurements came from 3D sonic anemometers with a 10Hz data output rate positioned on a mast in a wind farm test site subject to wake turbulence effects. The location of the test site (Corsica, France) meant the large scale structures were subject to topography effects that therefore possibly caused buoyancy effects. The second dataset (Germany) consists of 300 twenty minute samples of horizontal wind velocity magnitudes simultaneously recorded at several positions on two masts. There are eight propeller anemometers on each mast, recording velocity magnitude data at 2.5Hz. The positioning of the anemometers is such that there are effectively two grids. One grid of 3 rows by 4 columns and a second of 5 rows by 2 columns. The ranges of temporal scale over which the analyses were done were from 1 to 103 seconds for both datasets. Thus, under the universal multifractal framework we found both datasets exhibit parameters α ≈ 1.5 and C1 ≈ 0.1. The parameters α and C1, measure respectively the multifractality and mean intermittency of the scaling field. A third parameter, H, quantifies the divergence from conservation of the field (e.g. H = 0 for the turbulent energy flux density). To estimate the parameters we used the ratio of the scaling moment function of the energy flux and of the velocity increments. This method was particularly useful when estimating the parameter α over larger scales. In fact it was not possible to obtain a reasonable estimate of alpha using the usual double trace moment method. For each case the scaling behaviour of the wind was almost isotropic when the scale ranges remained close to the sphero-scale. For the Corsica dataset this could be seen by the agreement of the spectral exponents of

  19. Multifractal Analysis of the Small Time-Scale Boundary-Layer Characteristics of the Wind: the Anisotropy and Extremes

    Science.gov (United States)

    Fitton, G. F.; Tchiguirinskaia, I.; Schertzer, D. J.; Lovejoy, S.

    2012-12-01

    Under various physical conditions (mean temperature and velocity gradients, stratification and rotation) atmospheric turbulent flows remain intrinsically anisotropic. The immediate vicinity of physical boundaries rises to a greater complexity of the anisotropy effects. In this paper we address the issue of the scaling anisotropy of the wind velocity fields within the atmospheric boundary layer (ABL). Under the universal multifractal (UM) framework we compare the small time-scale (0.1 to 1,000 seconds) boundary-layer characteristics of the wind for two different case studies. The first case study consisted of a single mast located within a wind farm in Corsica, France. Three sonic anemometers were installed on the mast at 22, 23 and 43m, measuring three-dimensional wind velocity data at 10Hz. Wakes, complex terrain and buoyancy forces influenced the measurements. The second case study (GROWIAN experiment in Germany) consisted of an array of propeller anemometers measuring wind speed inflow data at 2.5Hz over flat terrain. The propeller anemometers were positioned vertically at 10, 50, 75, 100, 125 and 150m with four horizontal measurements taken at 75, 100 and 125m. The spatial distribution allowed us to calculate the horizontal and vertical shear structure functions of the horizontal wind. Both case studies are within a kilometre from the sea. For the first case study (10Hz measurements in a wind farm test site) the high temporal resolution of the data meant we observed Kolmogorov scaling from 0.2 seconds (with intermittency correction) right up to 1,000 seconds at which point a scaling break occurred. After the break we observed a scaling power law of approximately 2, which is in agreement with Bolgiano-Obukhov scaling theory with intermittency correction. However, for the second case study (2.5Hz on flat terrain) we only observed Kolmogorov scaling from 6.4 seconds (also with intermittency correction). The spectra of horizontal velocity components remain

  20. Volumetric LiDAR scanning of a wind turbine wake and comparison with a 3D analytical wake model

    Science.gov (United States)

    Carbajo Fuertes, Fernando; Porté-Agel, Fernando

    2016-04-01

    A correct estimation of the future power production is of capital importance whenever the feasibility of a future wind farm is being studied. This power estimation relies mostly on three aspects: (1) a reliable measurement of the wind resource in the area, (2) a well-established power curve of the future wind turbines and, (3) an accurate characterization of the wake effects; the latter being arguably the most challenging one due to the complexity of the phenomenon and the lack of extensive full-scale data sets that could be used to validate analytical or numerical models. The current project addresses the problem of obtaining a volumetric description of a full-scale wake of a 2MW wind turbine in terms of velocity deficit and turbulence intensity using three scanning wind LiDARs and two sonic anemometers. The characterization of the upstream flow conditions is done by one scanning LiDAR and two sonic anemometers, which have been used to calculate incoming vertical profiles of horizontal wind speed, wind direction and an approximation to turbulence intensity, as well as the thermal stability of the atmospheric boundary layer. The characterization of the wake is done by two scanning LiDARs working simultaneously and pointing downstream from the base of the wind turbine. The direct LiDAR measurements in terms of radial wind speed can be corrected using the upstream conditions in order to provide good estimations of the horizontal wind speed at any point downstream of the wind turbine. All this data combined allow for the volumetric reconstruction of the wake in terms of velocity deficit as well as turbulence intensity. Finally, the predictions of a 3D analytical model [1] are compared to the 3D LiDAR measurements of the wind turbine. The model is derived by applying the laws of conservation of mass and momentum and assuming a Gaussian distribution for the velocity deficit in the wake. This model has already been validated using high resolution wind-tunnel measurements

  1. Field measurement and analysis of turbulence coherence for Typhoon Nuri at Macao Friendship Bridge

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    For the purpose of investigating the turbulent and spatial coherent characteristics of strong wind during typhoon landing period,two 3-dimensional ultrasonic anemometer stations were set up 30 m horizontally apart on the Macao Friendship Bridge to caputure the turbulent wind velocities of Typhoon Nuri. Based on the reliable and representative field measured data,the mean wind speed and direction,turbulence intensity,turbulence integral scale,turbulence power spectra,spatial correlation coefficient and coherence function were statistically evaluated. The field measurement analysis have presented the following results: 1) Two anemometer stations provided consistent results. The mean wind speed variation in time domain presented typical M-shape curves. The strong wind (10-minute mean wind speed higher than 8th grade in Beaufort wind scale) direction changed in a big range up to 122-degrees-angle,indicating the field measurements scoped over the typhoon landing period. 2) The ratio of the longitudinal,lateral and vertical turbulence intensities of the strong wind in the typhoon eye wall region was 1:0.96:0.36. Compared with the code defined ratio 1:0.88:0.5,the lateral component was larger and the vertical component was smaller. 3) The value of integral scale increased when the eye wall of Typhoon Nuri passed over the field measurement site. Before the center of Typhoon Nuri arrived,the integral scale of the strong typhoon wind was about twice compared with that for the non-typhoon wind. 4) The spatial correlation of the turbulent wind,coherence function curve and the decay factor had significant differences at different times during the typhoon process. In the eye wall of the typhoon,the horizontal spatial correlation was relatively strong and horizontally spatial correlation spectrum decayed slower with frequency increase. The minimum regressed coefficient C in coherence function model was 4.67,which is lower than the code defined low limit. The maximum decay factor

  2. Improving Lidar-Derived Turbulence Estimates for Wind Energy

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Jennifer F.; Clifton, Andrew

    2016-07-08

    Remote sensing devices such as lidars are currently being investigated as alternatives to cup anemometers on meteorological towers. Although lidars can measure mean wind speeds at heights spanning an entire turbine rotor disk and can be easily moved from one location to another, they measure different values of turbulence than an instrument on a tower. Current methods for improving lidar turbulence estimates include the use of analytical turbulence models and expensive scanning lidars. While these methods provide accurate results in a research setting, they cannot be easily applied to smaller, commercially available lidars in locations where high-resolution sonic anemometer data are not available. Thus, there is clearly a need for a turbulence error reduction model that is simpler and more easily applicable to lidars that are used in the wind energy industry. In this work, a new turbulence error reduction algorithm for lidars is described. The algorithm, L-TERRA, can be applied using only data from a stand-alone commercially available lidar and requires minimal training with meteorological tower data. The basis of L-TERRA is a series of corrections that are applied to the lidar data to mitigate errors from instrument noise, volume averaging, and variance contamination. These corrections are applied in conjunction with a trained machine-learning model to improve turbulence estimates from a vertically profiling WINDCUBE v2 lidar. L-TERRA was tested on data from three sites -- two in flat terrain and one in semicomplex terrain. L-TERRA significantly reduced errors in lidar turbulence at all three sites, even when the machine-learning portion of the model was trained on one site and applied to a different site. Errors in turbulence were then related to errors in power through the use of a power prediction model for a simulated 1.5 MW turbine. L-TERRA also reduced errors in power significantly at all three sites, although moderate power errors remained for periods when

  3. 3D-calibration of three- and four-sensor hot-film probes based on collocated sonic using neural networks

    Science.gov (United States)

    Kit, Eliezer; Liberzon, Dan

    2016-09-01

    High resolution measurements of turbulence in the atmospheric boundary layer (ABL) are critical to the understanding of physical processes and parameterization of important quantities, such as the turbulent kinetic energy dissipation. Low spatio-temporal resolution of standard atmospheric instruments, sonic anemometers and LIDARs, limits their suitability for fine-scale measurements of ABL. The use of miniature hot-films is an alternative technique, although such probes require frequent calibration, which is logistically untenable in field setups. Accurate and truthful calibration is crucial for the multi-hot-films applications in atmospheric studies, because the ability to conduct calibration in situ ultimately determines the turbulence measurements quality. Kit et al (2010 J. Atmos. Ocean. Technol. 27 23-41) described a novel methodology for calibration of hot-film probes using a collocated sonic anemometer combined with a neural network (NN) approach. An important step in the algorithm is the generation of a calibration set for NN training by an appropriate low-pass filtering of the high resolution voltages, measured by the hot-film-sensors and low resolution velocities acquired by the sonic. In Kit et al (2010 J. Atmos. Ocean. Technol. 27 23-41), Kit and Grits (2011 J. Atmos. Ocean. Technol. 28 104-10) and Vitkin et al (2014 Meas. Sci. Technol. 25 75801), the authors reported on successful use of this approach for in situ calibration, but also on the method’s limitations and restricted range of applicability. In their earlier work, a jet facility and a probe, comprised of two orthogonal x-hot-films, were used for calibration and for full dataset generation. In the current work, a comprehensive laboratory study of 3D-calibration of two multi-hot-film probes (triple- and four-sensor) using a grid flow was conducted. The probes were embedded in a collocated sonic, and their relative pitch and yaw orientation to the mean flow was changed by means of motorized

  4. High pressure annular two-phase flow in a narrow duct. Part 1: Local measurements in the droplet field, and Part 2: Three-field modeling

    Energy Technology Data Exchange (ETDEWEB)

    Trabold, T.A.; Kumar, R. [Lockheed Martin Corp., Schenectady, NY (United States)

    1999-07-01

    In Part 1, detailed measurements were made in a high pressure, adiabatic (boiled at the inlet) annular flow in a narrow, high aspect ratio duct using a gamma densitometer, hot-film anemometer and high-speed video photography. Measurements of void fraction, droplet frequency, velocity, drop size, and interfacial area concentration have been made to support the three field computational capability. An important aspect of this testing is the use of a modeling fluid (R-134a) in a vertical duct which permits visual access in annular flow. This modeling fluid accurately simulates the low liquid-to-vapor density ratio of steam-water flows at high pressures. These measurements have been taken in a narrow duct of hydraulic diameter 4.85 mm, and a cross-section aspect ratio of 22.5. However, the flow displays profiles of various shapes not only in the narrow dimension, but also in the width dimension. In particular, the shape of the droplet profiles depends on the entrained droplet flux from the edges in the vapor core. The average diameter from these profiles compare well with the models developed in the literature. Interfacial area concentration for these low density ratio flows is higher than the highest concentration reported for air-water flows. Video records show that along with the bow-shaped waves, three-dimensional {lambda}-shaped waves appear in annular flows for high flow rates. Part 2 outlines the development of a three-field modeling approach in annular flow and the predictive capability of an analysis code. Models have been developed here or adapted from the literature for the thin film near the wall as well as the droplets in the vapor core, and have been locally applied in a fully developed, two-phase adiabatic boiling annular flow in a duct heated at the inlet at high pressure. Numerical results have been obtained using these models that are required for the closure of the continuity and momentum equations. The two-dimensional predictions are compared with

  5. 3D-calibration of three- and four-sensor hot-film probes based on collocated sonic using neural networks

    Science.gov (United States)

    Kit, Eliezer; Liberzon, Dan

    2016-09-01

    High resolution measurements of turbulence in the atmospheric boundary layer (ABL) are critical to the understanding of physical processes and parameterization of important quantities, such as the turbulent kinetic energy dissipation. Low spatio-temporal resolution of standard atmospheric instruments, sonic anemometers and LIDARs, limits their suitability for fine-scale measurements of ABL. The use of miniature hot-films is an alternative technique, although such probes require frequent calibration, which is logistically untenable in field setups. Accurate and truthful calibration is crucial for the multi-hot-films applications in atmospheric studies, because the ability to conduct calibration in situ ultimately determines the turbulence measurements quality. Kit et al (2010 J. Atmos. Ocean. Technol. 27 23–41) described a novel methodology for calibration of hot-film probes using a collocated sonic anemometer combined with a neural network (NN) approach. An important step in the algorithm is the generation of a calibration set for NN training by an appropriate low-pass filtering of the high resolution voltages, measured by the hot-film-sensors and low resolution velocities acquired by the sonic. In Kit et al (2010 J. Atmos. Ocean. Technol. 27 23–41), Kit and Grits (2011 J. Atmos. Ocean. Technol. 28 104–10) and Vitkin et al (2014 Meas. Sci. Technol. 25 75801), the authors reported on successful use of this approach for in situ calibration, but also on the method’s limitations and restricted range of applicability. In their earlier work, a jet facility and a probe, comprised of two orthogonal x-hot-films, were used for calibration and for full dataset generation. In the current work, a comprehensive laboratory study of 3D-calibration of two multi-hot-film probes (triple- and four-sensor) using a grid flow was conducted. The probes were embedded in a collocated sonic, and their relative pitch and yaw orientation to the mean flow was changed by means of

  6. Optimizing Lidar Scanning Strategies for Wind Energy Measurements (Invited)

    Science.gov (United States)

    Newman, J. F.; Bonin, T. A.; Klein, P.; Wharton, S.; Chilson, P. B.

    2013-12-01

    Environmental concerns and rising fossil fuel prices have prompted rapid development in the renewable energy sector. Wind energy, in particular, has become increasingly popular in the United States. However, the intermittency of available wind energy makes it difficult to integrate wind energy into the power grid. Thus, the expansion and successful implementation of wind energy requires accurate wind resource assessments and wind power forecasts. The actual power produced by a turbine is affected by the wind speeds and turbulence levels experienced across the turbine rotor disk. Because of the range of measurement heights required for wind power estimation, remote sensing devices (e.g., lidar) are ideally suited for these purposes. However, the volume averaging inherent in remote sensing technology produces turbulence estimates that are different from those estimated by a sonic anemometer mounted on a standard meteorological tower. In addition, most lidars intended for wind energy purposes utilize a standard Doppler beam-swinging or Velocity-Azimuth Display technique to estimate the three-dimensional wind vector. These scanning strategies are ideal for measuring mean wind speeds but are likely inadequate for measuring turbulence. In order to examine the impact of different lidar scanning strategies on turbulence measurements, a WindCube lidar, a scanning Halo lidar, and a scanning Galion lidar were deployed at the Southern Great Plains Atmospheric Radiation Measurement (ARM) site in Summer 2013. Existing instrumentation at the ARM site, including a 60-m meteorological tower and an additional scanning Halo lidar, were used in conjunction with the deployed lidars to evaluate several user-defined scanning strategies. For part of the experiment, all three scanning lidars were pointed at approximately the same point in space and a tri-Doppler analysis was completed to calculate the three-dimensional wind vector every 1 second. In another part of the experiment, one of

  7. An application of ensemble/multi model approach for wind power production forecast.

    Science.gov (United States)

    Alessandrini, S.; Decimi, G.; Hagedorn, R.; Sperati, S.

    2010-09-01

    The wind power forecast of the 3 days ahead period are becoming always more useful and important in reducing the problem of grid integration and energy price trading due to the increasing wind power penetration. Therefore it's clear that the accuracy of this forecast is one of the most important requirements for a successful application. The wind power forecast is based on a mesoscale meteorological models that provides the 3 days ahead wind data. A Model Output Statistic correction is then performed to reduce systematic error caused, for instance, by a wrong representation of surface roughness or topography in the meteorological models. The corrected wind data are then used as input in the wind farm power curve to obtain the power forecast. These computations require historical time series of wind measured data (by an anemometer located in the wind farm or on the nacelle) and power data in order to be able to perform the statistical analysis on the past. For this purpose a Neural Network (NN) is trained on the past data and then applied in the forecast task. Considering that the anemometer measurements are not always available in a wind farm a different approach has also been adopted. A training of the NN to link directly the forecasted meteorological data and the power data has also been performed. The normalized RMSE forecast error seems to be lower in most cases by following the second approach. We have examined two wind farms, one located in Denmark on flat terrain and one located in a mountain area in the south of Italy (Sicily). In both cases we compare the performances of a prediction based on meteorological data coming from a single model with those obtained by using two or more models (RAMS, ECMWF deterministic, LAMI, HIRLAM). It is shown that the multi models approach reduces the day-ahead normalized RMSE forecast error of at least 1% compared to the singles models approach. Moreover the use of a deterministic global model, (e.g. ECMWF deterministic

  8. PENGARUH BENTUK ATAP BANGUNAN TRADISIONAL DI JAWA TENGAH UNTUK PENINGKATAN KENYAMANAN (Sebuah pencarian model arsitektur tropis untuk aplikasi desain arsitektur

    Directory of Open Access Journals (Sweden)

    Ridwan Sanjaya

    2006-01-01

    Full Text Available In the architectural development recently, form of Java traditional roof is still commonly interested. While it is full of philosophic value, form of Java traditional roof also varies. On the other hand, Java traditional architecture concerns deeply in environmental aspect, which is formed in macro and micro concept as well, in order to become harmony and be comfort to dwell in. However, in the development and the application to modern buildings, which uses modern building materials, the thermal comfort aspect and the sturdy of construction are not considered. Therefore, it is necessary to understand well the basic concept of the forming traditional architecture in the context of trophical architecture and the sturdy of construction.This research aims to give descriptions to society, students and architects, in order to understand the importantance of thermal comfort, which can be achieved by well-designed roof.To achieve the expected result, the research is approached through analizing the sturdy of construction, to the original traditional buildings and the modern buildings using the Java traditional roof as well. The thermal comfort analysis is done with some equipments such as digital thermometer, digital hygrometer and digital anemometer. The research result is design recommendation to adjust the modern material to the form of Java traditional roof. By computer program using Visual Basic, it is expected that the research will be easily understood by society and it can be applied in building design. Abstract in Bahasa Indonesia : Dalam perkembangan arsitektur saat ini, bentuk atap tradisional Jawa masih diminati oleh masyarakat. Selain sarat muatan filosofis, bentuk atap tradisional juga bervariasi. Di sisi lain, arsitektur tradisional Jawa sangat memperhatikan aspek lingkungan, yang tertuang dalam konsep makro dan mikro kosmosnya, sehingga selaras dan nyaman untuk dihuni. Namun dalam perkembangan dan penerapan pada bangunan modern, yang

  9. Observed winds, turbulence, and dispersion in built-up downtown areas of Oklahoma City and Manhattan

    Science.gov (United States)

    Hanna, Steven; White, John; Zhou, Ying

    2007-12-01

    Wind and tracer data from the Oklahoma City Joint Urban 2003 (JU2003) and the Manhattan Madison Square Garden 2005 (MSG05) urban field experiments are being analyzed to aid in understanding air flow and dispersion near street-level in built-up downtown areas. The mean winds are separately calculated for groups of anemometers having similar exposures such as “near street level” and “on building top”. Several general results are found, such as the scalar wind speed at street level is about 1/3 of that at building top. Turbulent standard deviations of wind speed components and temperature, and vertical fluxes of momentum and sensible heat, are calculated from sonic anemometers near street level at 20 locations in JU2003 and five locations in MSG05, and from two rooftop locations in MSG05. The turbulence observations are consistent with observations in the literature at other cities, although the JU2003 and MSG05 data are unique in that many data are available near street level. For example, it is found that the local (i.e., at the measuring height) σw/u_{ast} averages about 1.5 and the local u_{ast}/u averages about 0.25 in the two cities, where σw is the standard deviation of vertical velocity fluctuations, u_{ast} is the friction velocity, and u is the wind speed. The ratio of temperature fluctuations to temperature scale, σT/T_{ast} , averages about -3 in both cities, consistent with similarity theory for slightly unstable conditions, where σT is the standard deviation of temperature fluctuations, and T_{ast} is the temperature scale. The calculated Obukhov length, L, is also consistent with slightly unstable conditions near street level, even at night during JU2003. The SF6 tracer concentration observations from JU2003 are analyzed. Values of uC_{max}/Q for the continuous releases are calculated for each release and arc distance, where C_{max} is the 30-min average arc maximum concentration, Q is the continuous source emission rate, and u is the

  10. Chambers versus Relaxed Eddy Accumulation: an intercomparison study of two methods for short-term measurements of biogenic CO2 fluxes

    Science.gov (United States)

    Jasek, Alina; Zimnoch, Miroslaw; Gorczyca, Zbigniew; Chmura, Lukasz; Necki, Jaroslaw

    2014-05-01

    The presented work is a part of comprehensive study aimed at thorough characterization of carbon cycle in the urban environment of Krakow, southern Poland. In the framework of this study two independent methods were employed to quantify biogenic CO2 flux in the city: (i) closed chambers, and (ii) Relaxed Eddy Accumulation (REA). The results of a three-day intensive intercomparison campaign performed in July 2013 and utilizing both measurement methods are reported here. The chamber method is a widely used approach for measurements of gas exchange between the soil and the atmosphere. The system implemented in this study consisted of a single chamber operating in a closed-dynamic mode, combined with Vaisala CarboCAP infrared CO2 sensor in a mobile setup. An alternative flux measurement method, covering larger area is represented by REA, which is a modification of the eddy covariance method. It consists of a 3D anemometer (Gill Windmaster Pro) and the system collecting updraft and downdraft samples to 5-litre Tedlar bags. The CO2 mixing ratios in the collected samples are measured by Picarro G2101i analyzer. The setup consists of two sets of bags so that the sampling can be performed continuously with 15-min temporal resolution. A 48-hectares open meadow located close the city center was chosen as a test site for comparison of the two methods of CO2 flux measurements outlined above. In the middle of the meadow a 3-metre high tripod was installed with the anemometer and REA inlet system. For a period of 46 hours the system was measuring net CO2 flux from the surrounding area. A meteorological conditions and intensity of photosynthetically active radiation (PAR) were also recorded. In the same time, CO2 flux from several points around the REA inlet was measured with the chamber system, resulting in 93 values for both respiration and net CO2 flux. Chamber results show rather homogenous distribution of the soil CO2 flux (the mean value equal to 40.9 ± 2.2 mmol/m2h), with

  11. Acidity of vapor plume from cooling tower mixed with flue gases emitted from coal-fired power plant.

    Science.gov (United States)

    Hlawiczka, Stanislaw; Korszun, Katarzyna; Fudala, Janina

    2016-06-01

    Acidity of products resulting from the reaction of flue gas components emitted from a coal-fired power plant with water contained in a vapor plume from a wet cooling tower was analyzed in a close vicinity of a power plant (710 m from the stack and 315 m from the cooling tower). Samples of this mixture were collected using a precipitation funnel where components of the mixed plumes were discharged from the atmosphere with the rainfall. To identify situations when the precipitation occurred at the same time as the wind directed the mixed vapor and flue gas plumes above the precipitation funnel, an ultrasound anemometer designed for 3D measurements of the wind field located near the funnel was used. Precipitation samples of extremely high acidity were identified - about 5% of samples collected during 12 months showed the acidity below pH=3 and the lowest recorded pH was 1.4. During the measurement period the value of pH characterizing the background acidity of the precipitation was about 6. The main outcome of this study was to demonstrate a very high, and so far completely underestimated, potential of occurrence of episodes of extremely acid depositions in the immediate vicinity of a coal-fired power plant. PMID:26950639

  12. Volume reconstruction optimization for tomo-PIV algorithms applied to experimental data

    International Nuclear Information System (INIS)

    Tomographic PIV is a three-component volumetric velocity measurement technique based on the tomographic reconstruction of a particle distribution imaged by multiple camera views. In essence, the performance and accuracy of this technique is highly dependent on the parametric adjustment and the reconstruction algorithm used. Although synthetic data have been widely employed to optimize experiments, the resulting reconstructed volumes might not have optimal quality. The purpose of the present study is to offer quality indicators that can be applied to data samples in order to improve the quality of velocity results obtained by the tomo-PIV technique. The methodology proposed can potentially lead to significantly reduction in the time required to optimize a tomo-PIV reconstruction, also leading to better quality velocity results. Tomo-PIV data provided by a six-camera turbulent boundary-layer experiment were used to optimize the reconstruction algorithms according to this methodology. Velocity statistics measurements obtained by optimized BIMART, SMART and MART algorithms were compared with hot-wire anemometer data and velocity measurement uncertainties were computed. Results indicated that BIMART and SMART algorithms produced reconstructed volumes with equivalent quality as the standard MART with the benefit of reduced computational time. (paper)

  13. Contribution to the Experimental and Numerical Dynamic Study of a Turbulent Jet Issued from Lobed Diffuser

    Directory of Open Access Journals (Sweden)

    A. Bennia

    2016-01-01

    Full Text Available In the present work, we are interested to the experimental and numerical study of the free turbulent lobed jet, used in residential heating and air conditioning. The objective of our study is the improvement of the diffusion performance of the ventilation driving air flow, in the occupancy zone. The experiments have been conducted in a room where the dimensions enables a better execution in the conditions of free and hot vertical jet at unfavorable pushing forces. The installation contains a hot air blowing diffuser oriented from top to bottom. The velocities of the flow were measured by a multi-functional thermo-anemometer. The probe is supported by a stem guided vertically and horizontally in order to sweep a maximum space. Experimentally, we measured the axial and radial velocity field. The dynamics field analysis, show that in the potential core region, the dynamic profiles are more spread at the principal plane and this is due to the widening of the lobes’ opening. While, in the transition zone and in the region where the flow is fully developed, these profiles are not influenced by the type of plane and then the jet will be similar to the circular one. Numerically, we used the commercial software Fluent. The obtained numerical results with turbulence method, (RNG k-ε, were in good accordance with the experimental one.

  14. Experimental Investigation on Mixing Enhancement Mechanism of Turbulent Jet Flow with Tabbed Nozzle

    Institute of Scientific and Technical Information of China (English)

    LIU Wei; JIANG Nan

    2008-01-01

    Flow visualization and hot-wire measurement techniques were combined to Investigate the influence of the size and number of tabs on jet flow field and vortex structure generation mechanism. Stream wise vortices generated by the tabs of different sizes and numbers were observed from the flow visualization images. Combined with flow visualization, hot-wire measurement gave a quantitative insight of the effect of various tabbed jet flows. Instantaneous two-component velocity signals (longitudinal and transverse velocity components) at different cross sections along radius direction and stream wise direction with different tabbed jet nozzles were measured using hot-wire anemometer. Average flow field parameters of tabbed jet flow such as mean velocity, turbulence intensity, vorticity were analyzed and the effects of tabs with different sizes and numbers were compared with that of circular no-tab jet flow. It is revealed that the generation of a series of counter-rotating quasi-stream wise vortices, azimuthal vortices and double-row azimuthal vortex are the reasons for mixing enhancement of tabbed turbulent jet flow.

  15. Experimental investigation of flow instabilities in a laminar separation bubble

    Science.gov (United States)

    Simoni, D.; Ubaldi, M.; Zunino, P.

    2014-06-01

    The present paper reports the results of a detailed experimental study aimed at investigating the dynamics of a laminar separation bubble, from the origin of separation up to the breakdown to turbulence of the large scale coherent structures generated as a consequence of the Kelvin-Helmholtz instability process. Measurements have been performed along a flat plate installed within a double contoured test section, designed to produce an adverse pressure gradient typical of Ultra-High-Lift turbine blade profiles, which induces the formation of a laminar separation bubble at low Reynolds number condition. Measurements have been carried out by means of complementary techniques: hot-wire (HW) anemometry, Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV). The high accuracy 2-dimensional LDV results allow investigating reverse flow magnitude and both Reynolds normal and shear stress distributions along the separated flow region, while the high frequency response of the HW anemometer allows analyzing the amplification process of flow oscillations induced by instability mechanisms. PIV results complement the flow field analysis providing information on the generation and evolution of the large scale coherent structures shed as a consequence of the separated shear layer roll-up, through instantaneous velocity vector maps. The simultaneous analysis of the data obtained by means of the different measuring techniques allows an in depth view of the instability mechanisms involved in the transition/reattachment processes of the separated shear layer.

  16. Performance evaluation of stand alone hybrid PV-wind generator

    Energy Technology Data Exchange (ETDEWEB)

    Nasir, M. N. M.; Saharuddin, N. Z.; Sulaima, M. F.; Jali, Mohd Hafiz; Bukhari, W. M.; Bohari, Z. H. [Faculty of Electrical Engineering, Universiti Teknikal Malaysia Melaka (UTeM), Hang Tuah Jaya, 76100 Melaka (Malaysia); Yahaya, M. S. [Faculty of Engineering Technology, Universiti Teknikal Malaysia Melaka (UTeM), Hang Tuah Jaya, 76100 Melaka (Malaysia)

    2015-05-15

    This paper presents the performance evaluation of standalone hybrid system on Photovoltaic (PV)-Wind generator at Faculty of Electrical Engineering (FKE), UTeM. The hybrid PV-Wind in UTeM system is combining wind turbine system with the solar system and the energy capacity of this hybrid system can generate up to charge the battery and supply the LED street lighting load. The purpose of this project is to evaluate the performance of PV-Wind hybrid generator. Solar radiation meter has been used to measure the solar radiation and anemometer has been used to measure the wind speed. The effectiveness of the PV-Wind system is based on the various data that has been collected and compared between them. The result shows that hybrid system has greater reliability. Based on the solar result, the correlation coefficient shows strong relationship between the two variables of radiation and current. The reading output current followed by fluctuate of solar radiation. However, the correlation coefficient is shows moderate relationship between the two variables of wind speed and voltage. Hence, the wind turbine system in FKE show does not operate consistently to produce energy source for this hybrid system compare to PV system. When the wind system does not fully operate due to inconsistent energy source, the other system which is PV will operate and supply the load for equilibrate the extra load demand.

  17. Push-Pull Air Curtain Performances for VOCs Containment in an Industrial Process

    Directory of Open Access Journals (Sweden)

    A. Aubert

    2011-01-01

    Full Text Available The aim of this study is to analyze the efficiency of a Volatile Organic Compounds (VOCs containment system using an air curtain (push-pull type on a manual workstation. This work combines CFD numerical simulations of the air curtain system and experimental studies on a real scale test bench. The point is to evaluate whether the actual worker protection can be replaced by an air curtain system, without weakening human safety. The new system could considerably reduce energetic consumption (ventilation, heating and VOCs emissions into the atmosphere. Experimental studies of the flow using a Particle Image Velocimetry anemometer (PIV have been carried out to validate the numerical model kinematics. The containment quality obtained by the model has been validated with experimental concentration fields given by a gaseous analyzer using flame ionization (FID. Numerical simulation provides an overview of the containment efficiency in the global area of the system. Thus, it is possible to evaluate numerically, but accurately, the quality of the containment of the system. Moreover, an energetic study proves the economic benefit of the push-pull system.

  18. 风能

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    [篇名] A case study on energy saving and new energy services in Japan, [篇名] A linear dynamic model for asynchronous wind turbines with mechanical fluctuations, [篇名] A method of tracking the peak power points for a variable speed wind energy conversion system, [篇名] A new model for short-term wind electric power forecasting, [篇名] A new simulation platform to model, optimize and design wind turbines, [篇名 ] A New Vertical Axis Wind Rotor using Convergent Nozzles, [ 篇名 ] A Novel Doubly-fed Induction Wind Generato Control Scheme for Reactive Power Control and Torque Pulsation Compensation Under Unbalanced Grid Voltage Conditions, [ 篇名 ] A review on recent advances on wind energy system, [ 篇名 ] A Sensorless Integrated Doubly-Fed Electric Alternator/Active Filter (IDEA) for Variable Speed Wind Energy System, [ 篇名 ] A Simple Maximum Power Point Tracker for Grid connected Variablc Spccd Wind Energy Convcrsion System with Reduced Switch Count Power Converters, [ 篇名] A STOCHASTIC MARKOV CHAIN MODEL FOR SIMULATING WIND SPEED TIME SERIES at Tangiers, MOROCCO, [ 篇名 ] A switched reluctance wind power generator with the excitation of low voltage, [篇名] A technology assessment system of the alternative energy sources (sun and wind) for rural communities in Mexico, [ 篇名 ] A virtual instrument for automatic anemometer calibration with ANN based supervision.

  19. Is it always windy somewhere? Occurrence of low-wind-power events over large areas

    CERN Document Server

    Handschy, Mark A; Apt, Jay

    2016-01-01

    The incidence of widespread low-wind conditions is important to the reliability and economics of electric grids with large amounts of wind power. In order to investigate a future in which wind plants are geographically widespread but interconnected, we examine how frequently low generation levels occur for wind power aggregated from distant, weakly-correlated wind generators. We simulate the wind power using anemometer data from nine tall-tower sites spanning the contiguous United States. We find that the number of low-power hours per year declines exponentially with the number of sites being aggregated. Hours with power levels below 5% of total capacity, for example, drop by a factor of about 60, from 2140 h/y for the median single site to 36 h/y for the generation aggregated from all nine sites; the standard deviations drops by a factor of 3. The systematic dependence of generation-level probability distribution "tails" on both number and power threshold is well described by the theory of Large Deviations. ...

  20. The cost of hovering and forward flight in a nectar-feeding bat, Glossophaga soricina, estimated from aerodynamic theory

    DEFF Research Database (Denmark)

    Norberg, U M; Kunz, T H; Steffensen, J F;

    1993-01-01

    Energy expenditure during flight in animals can best be understood and quantified when both theoretical and empirical approaches are used concurrently. This paper examines one of four methods that we have used to estimate the cost of flight in a neotropical nectar-feeding bat Glossophaga soricina...... (Phyllostomidae), namely the use of kinematic and morphological data and aerodynamic theory to estimate the mechanical power requirements (power output) for hovering and horizontal forward flight. A hot-wire anemometer was used to measure induced velocity (the velocity of air accelerated by the wings) during...... power for hovering is 0.34 W or 32.4 W kg-1. The mechanical power required for horizontal forward flight, near the minimum power flight speed (4.2 ms-1) for a 0.0117 kg bat is 0.14 W (12.3 W kg-1), of which 0.10 W is aerodynamic power and 0.042 W is inertial power. Comparison with our results...

  1. EXPERIMENTAL STUDY OF MEASUREMENT FOR DISSIPATION RATE SCALING EXPONENT IN HEATED WALL TURBULENCE

    Institute of Scientific and Technical Information of China (English)

    姜楠; 王玉春; 舒玮; 王振东

    2002-01-01

    Experimental investigations have been devoted to the study of scaling law of coarse-grained dissipation rate structure function for velocity and temperature fluctuation of non-isotropic and inhomogeneous turbulent flows at moderate Reynolds number. Much attention has been paid to the case of turbulent boundary layer, which is typically the nonistropic and inhomogeneous trubulence because of the dynamically important existence of organized coherent structure burst process in the near wall region. Longitudinal velocity and temperature have been measured at different vertical positions in turbulent boundary layer over a heated and unheated flat plate in a wind tunnel using hot wire anemometer. The influence of non-isotropy and inhomogeneity and heating the wall on the scaling law of the dissipation rate structure function is studied because of the existence of organized coherent structure burst process in the near wall region. The scaling law of coarse-grained dissipation rate structure function is found to be independent of the mean velocity shear strain and the heating wall boundary condition. The scaling law of the dissipation rate structure function is verified to be in agreement with the hierarchical structure model that has been verified valid for isotropic and homogeneous turbulence.

  2. Compensated intruder-detection systems

    Science.gov (United States)

    McNeilly, David R.; Miller, William R.

    1984-01-01

    Intruder-detection systems in which intruder-induced signals are transmitted through a medium also receive spurious signals induced by changes in a climatic condition affecting the medium. To combat this, signals received from the detection medium are converted to a first signal. The system also provides a reference signal proportional to climate-induced changes in the medium. The first signal and the reference signal are combined for generating therefrom an output signal which is insensitive to the climatic changes in the medium. An alarm is energized if the output signal exceeds a preselected value. In one embodiment, an acoustic cable is coupled to a fence to generate a first electrical signal proportional to movements thereof. False alarms resulting from wind-induced movements of the fence (detection medium) are eliminated by providing an anemometer-driven voltage generator to provide a reference voltage proportional to the velocity of wind incident on the fence. An analog divider receives the first electrical signal and the reference signal as its numerator and denominator inputs, respectively, and generates therefrom an output signal which is insensitive to the wind-induced movements in the fence.

  3. In vitro calibration of a system for measurement of in vivo convective heat transfer coefficient in animals

    Directory of Open Access Journals (Sweden)

    Webster John G

    2006-10-01

    Full Text Available Abstract Background We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver. Methods We built a minimally invasive instrument to measure the in vivo convective heat transfer coefficient, h in animals, using a Wheatstone-bridge circuit, similar to a hot-wire anemometer circuit. One arm is connected to a steerable catheter sensor whose tip is a 1.9 mm × 3.2 mm thin film resistive temperature detector (RTD sensor. We used a circulation system to simulate different flow rates at 39°C for in vitro experiments using distilled water, tap water and saline. We heated the sensor approximately 5°C above the fluid temperature. We measured the power consumed by the sensor and the resistance of the sensor during the experiments and analyzed these data to determine the value of the convective heat transfer coefficient at various flow rates. Results From 0 to 5 L/min, experimental values of h in W/(m2·K were for distilled water 5100 to 13000, for tap water 5500 to 12300, and for saline 5400 to 13600. Theoretical values were 1900 to 10700. Conclusion We believe this system is the smallest, most accurate method of minimally invasive measurement of in vivo h in animals and provides the least disturbance of flow.

  4. Measurement of the dry deposition rates on trees by using the natural radioactivity as a tracer

    International Nuclear Information System (INIS)

    Measurement of the dry deposition rates on trees by using the natural radioactivity as a tracer. The direct measurement of dry deposition fluxes into a canopy or onto single branches or leaves is difficult. The natural particle bound radioactivity in the ground-level air can be used as a tracer to gain information on this process in small scales of time and space. γ- and α-spectroscopy of radioactive daughters of Rn and Tn deposited on filters and on leaves, needles and surrogate acceptors have been developed as highly mobile field-methods. Applying Radon daughters as tracers leads to information on deposition velocities during short time intervals. The evaluation of meteorological effects in the field thus becomes possible. The main factors influencing the deposition velocity are the particle size and the wind speed. Therefore size fractionating sampling devices and anemometer arrangements are needed, both small, light-weight and cheap. We prefered filter and impactor combinations to gain 4 size fractions suitable for radioactivity and composition measurements. The concentration values of compounds and elements have been evaluated by X-ray fluorescence and ionchromatography. Numerous results of measurements on natural leaves and surrogates are presented, showing the state of developement now attained and proving the applicability of this method. (orig.). 41 figs., 108 refs., 28 tabs

  5. Real time Markov chains: Wind states in anemometric data

    CERN Document Server

    Sanchez, P A; Jaramillo, O A

    2015-01-01

    The description of wind phenomena is frequently based on data obtained from anemometers, which usually report the wind speed and direction only in a horizontal plane. Such measurements are commonly used either to develop wind generation farms or to forecast weather conditions in a geographical region. Beyond these standard applications, the information contained in the data may be richer than expected and may lead to a better understanding of the wind dynamics in a geographical area. In this work we propose a statistical analysis based on the wind velocity vectors, which we propose may be grouped in "wind states" associated to binormal distribution functions. We found that the velocity plane defined by the anemometric velocity data may be used as a phase space, where a finite number of states may be found and sorted using standard clustering methods. The main result is a discretization technique useful to model the wind with Markov chains. We applied such ideas in anemometric data for two different sites in M...

  6. Laboratory Proposal for Studies on Poultry Environment

    Directory of Open Access Journals (Sweden)

    Schiassi, L

    2014-09-01

    Full Text Available The goal of the present work was the instrumentation and validation of a laboratory equipped with a control system for air temperature (tair, relative air humidity (RH and air velocity (V to study the environment for small animals. An experimental was equipped with two air conditioners to manage basic tair and RH in order to work. Four wind tunnels, with partial recirculation of air were installed in the room. Each tunnel features two electric heaters and two humidifiers divided into two operation stages. The air velocity is manually controlled by potentiometers connected to exhaust fans. A system to acquire data and control climatic variables was installed in the laboratory and it consisted of a datalogger, a multiplexer channel, a relay controller , tair and RH sensors, sensors for measuring water temperature and digital helix anemometer to measure air velocity. The results showed that the system presented deviations of ± 0.19 °C, ± 0.75% and ± 0.05 m s-1 for tair, RH and V, respectively, when comparing the values measured inside the tunnels to those previously established (setpoints.

  7. Experimental study on airflow fluctuation characteristic of an underfloor air supply terminal unit

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jinping [School of Electric Power, South China University of Technology, Guangzhou 510640 (China); State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou 510640 (China); Wu, Yanfang [Design Institute of Guangzhou Metro Corporation, Guangzhou 510010 (China)

    2010-11-15

    In order to investigate dynamic characteristic of underfloor air supply terminal unit, an IFV900A hot-wire anemometer was used to measure the corresponding velocity field. Turbulence intensity and power spectrum density exponent of air velocity signal were analyzed. The result showed that the outlet velocity distribution of underfloor air supply terminal unit was uniform. With increment of height, the velocity distribution trends to be uniform. Two velocity attenuation regions appear during airflow development. Turbulence intensity changes obviously with height. It is lower than that of mechanical wind. Turbulence intensity goes up with the increment of jetting distance. Power spectrum density exponent trends to the value of natural wind with increase of jetting distance and decrease of wind velocity. The exponent value approaches to the value of typical natural wind for the air velocity is 0.5 m/s under high supply air rate. With airflow diffusion, the fluctuation characteristic of airflow varies obviously with the jetting direction. The fluctuation characteristic of airflow changes to that of natural wind with the increase of height which can improve comfort of indoor environment. (author)

  8. 风量罩罩体选择及摆放对测量的影响%INFLUENCE OF THE FLOW HOOD SHAPE AND THE PLACED POSITION ON THE MEASUREMENT

    Institute of Scientific and Technical Information of China (English)

    王成凤; 王智超

    2012-01-01

    Anemometer and flow hood are used to measure air volume at present, flow hood is known and used by more and more people because its simple and convenient usage. But some factors are not taken into consideration such as the validity of the measuring method, the rightness of the indicated number, the matching of flow hood shape with the dimension of air port as well as the placed position and whether revise is needed. This leads to the measurement inaccuracy. This paper considered some frequently-used flow hood on market and illustrated the influence of the choice of flow hood and the placed position.%目前测量风量的方法有风速仪法和风量罩法,风量罩因其使用的简便快捷,已越来越多被人们了解和使用.但对测量方法是否正确,读出来的数值是否合适,罩体形状与风口尺寸是否匹配,位置摆放是否合理,是否需要修正等并不多加考虑,这势必造成测量的不准确.本文将针对市场上常用的几种风量罩体进行实验,说明罩体的选择及不同摆放位置对测量的影响.

  9. Comparison of Sensible Heat Flux from Eddy Covariance and Scintillometer over different land surface conditions

    Science.gov (United States)

    Zeweldi, D. A.; Gebremichael, M.; Summis, T.; Wang, J.; Miller, D.

    2008-12-01

    The large source of uncertainty in satellite-based evapotranspiration algorithm results from the estimation of sensible heat flux H. Traditionally eddy covariance sensors, and recently large-aperture scintillometers, have been used as ground truth to evaluate satellite-based H estimates. The two methods rely on different physical measurement principles, and represent different foot print sizes. In New Mexico, we conducted a field campaign during summer 2008 to compare H estimates obtained from the eddy covariance and scintillometer methods. During this field campaign, we installed sonic anemometers; one propeller eddy covariance (OPEC) equipped with net radiometer and soil heat flux sensors; large aperture scintillometer (LAS); and weather station consisting of wind speed, direction and radiation sensors over three different experimental areas consisting of different roughness conditions (desert, irrigated area and lake). Our results show the similarities and differences in H estimates obtained from these various methods over the different land surface conditions. Further, our results show that the H estimates obtained from the LAS agree with those obtained from the eddy covariance method when high frequency thermocouple temperature, instead of the typical weather station temperature measurements, is used in the LAS analysis.

  10. Thermistor based, low velocity isothermal, air flow sensor

    International Nuclear Information System (INIS)

    The semiconductor thermistor technology is applied as a flow sensor to measure low isothermal air velocities (<2 ms−1). The sensor is subjected to heating and cooling cycles controlled by a multifunctional timer. In the heating stage, the alternating current of a main AC power supply source guarantees a uniform thermistor temperature distribution. The conditioning circuit assures an adequate increase of the sensors temperature and avoids the thermal disturbance of the flow. The power supply interruption reduces the consumption from the source and extends the sensors life time. In the cooling stage, the resistance variation of the flow sensor is recorded by the measuring chain. The resistive sensor parameters proposed vary significantly and feature a high sensitivity to the flow velocity. With the aid of a computer, the data transfer, storage and analysis provides a great advantage over the traditional local anemometer readings. The data acquisition chain has a good repeatability and low standard uncertainties. The proposed method measures isothermal air mean velocities from 0.1 ms−1 to 2 ms−1 with a standard uncertainty error less than 4%. (paper)

  11. Locating a compact odor source using a four-channel insect electroantennogram sensor

    International Nuclear Information System (INIS)

    Here we demonstrate the feasibility of using an array of live insects to detect concentrated packets of odor and infer the location of an odor source (∼15 m away) using a backward Lagrangian dispersion model based on the Langevin equation. Bayesian inference allows uncertainty to be quantified, which is useful for robotic planning. The electroantennogram (EAG) is the biopotential developed between the tissue at the tip of an insect antenna and its base, which is due to the massed response of the olfactory receptor neurons to an odor stimulus. The EAG signal can carry tens of bits per second of information with a rise time as short as 12 ms (K A Justice 2005 J. Neurophiol. 93 2233-9). Here, instrumentation including a GPS with a digital compass and an ultrasonic 2D anemometer has been integrated with an EAG odor detection scheme, allowing the location of an odor source to be estimated by collecting data at several downwind locations. Bayesian inference in conjunction with a Lagrangian dispersion model, taking into account detection errors, has been implemented resulting in an estimate of the odor source location within 0.2 m of the actual location.

  12. Experimental observation of the collision of three vortex rings

    Science.gov (United States)

    Hernández, R. H.; Monsalve, E.

    2015-06-01

    We investigate for the first time the motion, interaction and simultaneous collision between three initially stable vortex rings arranged symmetrically, making an angle of 120 degrees between their straight path lines. We report results with laminar vortex rings in air and water obtained through measurements of the ring velocity field with a hot-wire anemometer, both in free flight and during the entire collision. In the air experiment, our flow visualizations allowed us to identify two main collision stages. A first ring-dominated stage where the rings slowdown progressively, increasing their diameter rapidly, followed by secondary vortex structures resulting after the rings make contact. Local portions of the vortex tubes of opposite circulation are coupled together thus creating local arm-like vortex structures moving radially in outward directions, rapidly dissipating kinetic energy. From a similar water experiment, we provide detailed shadowgraph visualizations of both the ring bubble and the full size collision, showing clearly the final expanding vortex structure. It is accurately resolved that the physical contact between vortex ring tubes gives rise to three symmetric expanding vortex arms but also the vortex reconnection of the top and lower vortex tubes. The central collision zone was found to have the lowest kinetic energy during the entire collision and therefore it can be identified as a safe zone. The preserved collision symmetries leading to the weak kinematic activity in the safe zone is the first step into the development of an intermittent hydrodynamic trap for small and lightweight particles.

  13. SWiFT site atmospheric characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, Christopher Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ennis, Brandon Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-01-01

    Historical meteorological tall tower data are analyzed from the Texas Tech University 200 m tower to characterize the atmospheric trends of the Scaled Wind Farm Technologies (SWiFT) site. In this report the data are analyzed to reveal bulk atmospheric trends, temporal trends and correlations of atmospheric variables. Through this analysis for the SWiFT turbines the site International Electrotechnical Commission (IEC) classification is determined to be class III-C. Averages and distributions of atmospheric variables are shown, revealing large fluctuations and the importance of understanding the actual site trends as opposed to simply using averages. The site is significantly directional with the average wind speed from the south, and particularly so in summer and fall. Site temporal trends are analyzed from both seasonal (time of the year) to daily (hour of the day) perspectives. Atmospheric stability is seen to vary most with time of day and less with time of year. Turbulence intensity is highly correlated with stability, and typical daytime unstable conditions see double the level of turbulence intensity versus that experienced during the average stable night. Shear, veer and atmospheric stability correlations are shown, where shear and veer are both highest for stable atmospheric conditions. An analysis of the Texas Tech University tower anemometer measurements is performed which reveals the extent of the tower shadow effects and sonic tilt misalignment.

  14. Air speeds of migrating birds observed by ornithodolite and compared with predictions from flight theory.

    Science.gov (United States)

    Pennycuick, C J; Åkesson, Susanne; Hedenström, Anders

    2013-09-01

    We measured the air speeds of 31 bird species, for which we had body mass and wing measurements, migrating along the east coast of Sweden in autumn, using a Vectronix Vector 21 ornithodolite and a Gill WindSonic anemometer. We expected each species' average air speed to exceed its calculated minimum-power speed (Vmp), and to fall below its maximum-range speed (Vmr), but found some exceptions to both limits. To resolve these discrepancies, we first reduced the assumed induced power factor for all species from 1.2 to 0.9, attributing this to splayed and up-turned primary feathers, and then assigned body drag coefficients for different species down to 0.060 for small waders, and up to 0.12 for the mute swan, in the Reynolds number range 25 000-250 000. These results will be used to amend the default values in existing software that estimates fuel consumption in migration, energy heights on arrival and other aspects of flight performance, using classical aeronautical theory. The body drag coefficients are central to range calculations. Although they cannot be measured on dead bird bodies, they could be checked against wind tunnel measurements on living birds, using existing methods. PMID:23804440

  15. Experimental Study and CFD modeling of high speed water jets in air

    Science.gov (United States)

    Guha, Anirban; Barron, R. M.; Balachandar, R.

    2007-11-01

    High speed turbulent water jets are extensively used in industrial cleaning applications. They interact vigorously with the surrounding air and loose mass in the form of water droplets which moves along with the entrained air stream. The transfer of momentum to the surroundings reduces the jet velocity and thus the pressure at the impinging surface is significantly lower than the supply pressure. Laser Doppler Anemometer (LDA) measurements of velocity field and pressure measurements at different axial and radial locations were performed. The potential core of the jet was found to extend to around 100 nozzle diameters. The dynamic pressure along the centerline was found to decay linearly, which can be used to estimate the decay of water volume fraction along the centerline. An empirical formulation of mass transfer (in the form of droplets) from water phase to the surroundings has been developed and incorporated into the commercial CFD code FLUENT. The flow was simulated using the RNG k-ɛ turbulence model and Eulerian-Eulerian multiphase model. The predicted pressure distribution at the impinging surface was found to match closely with the experimental findings.

  16. Measurements of the fluctuating liquid velocity of a bidisperse suspension of bubbles rising in a vertical channel

    Science.gov (United States)

    Serrano, Juan Carlos; Mendez, Santos; Zenit, Roberto

    2009-11-01

    Experiments were performed in a vertical channel to study the behaviour of a bidisperse suspension of bubbles. Bubbles were produced using capillaries of two distinct inner diameters. The capillaries are small enough to generate bubbles in the range of 1 to 6 mm in diameter. Using water and water-glycerin mixtures, the vertical component of the fluctuating liquid velocity was obtained using a flying hot wire anemometer technique. The system is characterized by the dimensionless Reynolds and Weber numbers in the range of 22

  17. The Impact of Wind Speed Changes on the Surface Stress in the Weak-wind Stable Boundary Layer

    Science.gov (United States)

    Thomas, C. K.

    2015-12-01

    The behaviour of turbulent transport in the weak-wind stably stratified boundary layer is examined in terms of the non-stationarity of the wind field based upon field observations. Extensive sonic anemometer measurements from horizontal networks and vertical towers ranging from 12 to 20 m height were collected from three field programs in moderately sloped terrain with a varying degree of surface heterogeneity, namely the Shallow Cold Pool (SCP) and the Flow Over Snow Surfaces (FLOSS) II experiments in Colorado (USA), and the Advanced Canopy Resolution Experiment (ARCFLO) in Oregon (USA). The relationship of the friction velocity to the stratification and small non-stationary submeso motions is studied from several points of view and nominally quantified. The relationship of the turbulence to the stratification is less systematic than expected due to the important submeso-scale motions. Consequently, the roles of the wind speed and stratification are not adequately accommodated by a single non-dimensional combination, such as the bulk Richardson number. Howver, cause and effect relationships are difficult to isolate because the non-stationary momentum flux significantly modifies the profile of the non-stationary mean flow. The link between the turbulence and accelerations at the surface is examined in terms of the changing vertical structure of the wind profile and sudden increases of downward transport of momentum. The latter may be significant in explaining the small-scale weak turbulence during stable stratification and deviations from conventional flux-profile relationships.

  18. Time-dependent boundary-layer response in a propeller slipstream

    Science.gov (United States)

    Howard, Richard M.; Miley, Stan J.

    1989-01-01

    The time-dependent behavior of a wing boundary layer immersed in a propeller slipstream has been studied experimentally in wind-tunnel tests and in flight. Hot-wire anemometer measurements were made through the boundary layer for time-dependent, ensemble-average velocity and turbulence-intensity profiles at various chord locations. The boundary layer has a coherent, time-dependent cycle of transitional behavior, varying from a laminar to a turbulent-transitional state. Local drag coefficients determined from the velocity profiles for the freewheeling propeller case in flight show that the time-dependent drag in the propeller slipstream varies from the undisturbed laminar value to a value less than that predicted for fully turbulent flow. Local drag coefficients determined from the thrusting propeller case in the wind tunnel indicate that the effects of the slipstream are to enhance the stability of the boundary layer and to reduce the drag coefficient in the laminar portion of the cycle below its undisturbed laminar value.

  19. An investigation of the effects of the propeller slipstream on a wing boundary layer

    Science.gov (United States)

    Howard, Richard Moore

    1987-12-01

    The behavior of a wing boundary layer immersed in a propeller slipstream has been studied experimentally. Airfoil surface static pressure measurements were made for time-averaged effects, and time-dependent measurements were made with hot-film anemometer sensors for the determination of instantaneous velocities. Vertical boundary layer traverses were made at fixed chord locations for the determination of velocity profiles and for values of the turbulence intensity. The boundary layer has a coherent, time-dependent cycle of transitional behavior, varying from laminar to turbulent. This layer shows similarities to those disturbed by high levels of external flow turbulence and to those in a relaminarizing environment. Profile drag coefficients determined from the time-dependent ensemble-average velocity profiles for the freewheeling propeller case show the drag in the propeller slipstream varies from the undisturbed laminar value to a value less than that predicted for fully turbulent flow. Drag values determined from the low Reynolds number thrusting propeller case in the wind tunnel show that the effects of the slipstream are to enhance the stability of the boundary layer and to reduce the drag coefficient in the laminar portion of the slipstream cycle below its undisturbed value.

  20. An Experimental Study on 3—D Flow in an Annular Cascade of High Turning Angle Turbine Blades

    Institute of Scientific and Technical Information of China (English)

    WangWensheng; LiangXizhi; 等

    1994-01-01

    This paper presents an experimental study of the three-dimensional turbulent flow fields in a lowspeed annular cascade of high turning angle turbine blades.Detailed measurements were performed on the blade surfaces and mid-streamsurface in the passage and at three axial planes downstream of the cascade by using wall static pressure taps,a five-hole probe and a hot-wire anemometer,The test data include static pressure distribution on blade surfaces,total pressure loss cofeeicient,mean flow velocity components.radial flow angle,turbulence intensity and Reynolds shear stress.Analyses of the three-dimensional cascade flow characteristics were made on the noset location of high loss vortices.the variation of pressure gradient inside the cascade passage and the properties of endwall boundary layers total pressure loss distributions,secondary vortex turbulent dissipation and wake decay downtream of the cascade.These experimental results are valuable for revealing the details of the complex vortex flow structure in modern highly loaded axial turbomachines and validating the three-dimensional flow numerical computation codes.

  1. Ultimate turbulence experiment: simultaneous measurements of Cn2 near the ground using six devices and eight methods

    Science.gov (United States)

    Yatcheva, Lydia; Barros, Rui; Segel, Max; Sprung, Detlev; Sucher, Erik; Eisele, Christian; Gladysz, Szymon

    2015-10-01

    We have performed a series of experiments in order to simultaneously validate several devices and methods for measurement of the path-averaged refractive index structure constant ( 𝐶𝑛 2). The experiments were carried out along a horizontal urban path near the ground. Measuring turbulence in this layer is particularly important because of the prospect of using adaptive optics for free-space optical communications in an urban environment. On one hand, several commercial sensors were used: SLS20, a laser scintillometer from Scintec AG, BLS900, a largeaperture scintillometer, also from Scintec, and a 3D sonic anemometer from Thies GmbH. On the other hand, we measured turbulence strength with new approaches and devices developed in-house. Firstly, an LED array combined with a high-speed camera allowed for measurement of 𝐶𝑛 2 from raw- and differential image motion, and secondly a two-part system comprising a laser source, a Shack-Hartmann sensor and a PSF camera recoded turbulent modulation transfer functions, Zernike variances and angle-of-arrival structure functions, yielding three independent estimates of 𝐶𝑛 2. We compare the measured values yielded simultaneously by commercial and in-house developed devices and show very good agreement between 𝐶𝑛 2 values for all the methods. Limitations of each experimental method are also discussed.

  2. Predicting wind shear effects: A study of Minnesota wind data collected at heights up to 70 meters

    Energy Technology Data Exchange (ETDEWEB)

    Artig, R. [Minnesota Dept. of Public Service, St. Paul, MN (United States)

    1997-12-31

    The Minnesota Department of Public Service (DPS) collects wind data at carefully selected sites around the state and analyzes the data to determine Minnesota`s wind power potential. DPS recently installed advanced new monitoring equipment at these sites and began to collect wind data at 30, 50, and 70 meters above ground level, with two anemometers at each level. Previously, the Department had not collected data at heights above ground level higher than 30 meters. DPS also, with the U.S. Department of Energy (DOE), installed four sophisticated monitoring sites as part of a Tall Tower Wind Shear Study that is assessing the effects of wind shear on wind power potential. At these sites, wind data are being collected at the 10, 30, 40, 50, 60, and 70 meter heights. This paper presents the preliminary results of the analysis of wind data from all sites. These preliminary results indicate that the traditional 1/7 power law does not effectively predict wind shear in Minnesota, and the result is an underestimation of Minnesota`s wind power potential at higher heights. Using a power factor of 1/5 or 1/4 may be more accurate and provide sound justification for installing wind turbines on taller towers in Minnesota.

  3. Experimental study of turbulence in isothermal jet impingement at intermediate plate spacings

    Science.gov (United States)

    Landfried, D. Tyler; Valentino, Alex; Mazumdar, Sagnik; Jana, Anirban; Kimber, Mark

    2013-11-01

    One fundamental problem in fluid dynamics is that of the axisymmetric round flow impinging on a plate placed some distance downstream of the jet. Impinging jets have a rich history of applications including small plate spacings, H/D ~ 1, such as encountered in electronics cooling, or large plate spacings, H/D ~ 102, such as vertical takeoff aircrafts and rocket engines. However, intermediate plate spacings, such as the lower plenum of the next generation nuclear reactors, are not typically studied. In this paper, an experimental study is conducted investigating the effect of the impingement plate on the flow behavior compared to the near free jet behavior when the plate is removed. Using air as the working fluid, a single jet is considered at jet Reynolds numbers of 10000, 20000, and 30000. A three-wire anemometer probe is used to quantify the mean components of velocities as well as the Reynolds stress and the third-order moments in the flow field at various distances between the jet outlet and the impingement plate. When present, the impingement plate is placed a distance of 8, 11, 14, and 17 diameters downstream of the jet. Additionally trends in the kinetic energy and dissipation are investigated for validation with numerical models.

  4. Mobile monitoring of fugitive methane emissions from natural gas consumer industries

    Science.gov (United States)

    Zhou, X.; Albertson, J. D.; Gaylord, A.; von Fischer, J.; Rudek, J.; Thoma, E. D.

    2015-12-01

    Natural gas is used as a feedstock for major industrial processes, such as ammonia and fertilizer production. However, fugitive methane emissions from many major end-use sectors of the natural gas supply chain have not been quantified yet. This presentation introduces new tools for estimating emission rates from mobile methane measurements, and examines results from recent field measurements conducted downwind of several industrial plants using a specialized vehicle equipped with fast response methane sensor. Using these data along with local meteorological data measured by a 3-D sonic anemometer, a Bayesian approach is applied to probabilistically infer methane emission rates based on a modified Gaussian dispersion model. Source rates are updated recursively with repeated traversals of the downwind methane plume when the vehicle was circling around the targeted facilities. Data from controlled tracer release experiments are presented and used to validate the approach. With access via public roads, this mobile monitoring method is able to quickly assess the emission strength of facilities along the sensor path. This work is developing the capacity for efficient regional coverage of potential methane emission rates in support of leak detection and mitigation efforts.

  5. Issues regarding the modelling and simulation of hybrid micro grid systems

    Science.gov (United States)

    Szeidert, I.; Filip, I.; Prostean, O.

    2016-02-01

    The main followed objectives within control strategies dedicated to hybrid micro grid systems (wind/hydro/solar), that operate based on maximum power point tracking (MPPT) techniques are to improve the conversion systems efficiency and to maintain the quality of the produced electrical energy (the voltage and power factor control). One of the main goals of maximum power point tracking strategy is to achieve the harvesting of the maximal possible energy within a pre-set time period. In order to implement the control strategies for micro grid systems that operate at time variable parameter, there are usually required specific transducers (anemometer for wind speed measurement, optical rotational transducers, taco generators, etc.). In the technical literature there are presented several variants of the MPPT techniques, which are particularized at several applications (wind energy conversion systems, solar systems, hydro plants and micro grid hybrid systems). The maximum power point tracking implementations are mainly based on two-level architecture. The inferior level controls the primary variables, while the superior level represents the MPPT control structure. In the paper, authors present some micro grid structures proposed at Politehnica University Timisoara within the frame of a research grant. The paper is focused on the application of MPPT strategies on hybrid micro grid systems. There are presented several structures and control strategies and are highlighted their advantages and disadvantages, together with practical implementation guidelines.

  6. Heat transfer and velocity measurements in turbulent swirling flows through an abrupt axisymmetric expansion

    Energy Technology Data Exchange (ETDEWEB)

    Dellenback, P.A.

    1986-01-01

    The swirling flow of water through an abrupt 1:2 axisymmetric expansion was examined experimentally. In the upstream tube, the Reynolds number was varied from 30,000 to 100,000 and the swirl number was varied from zero to 1.2. Measurements of mean and RMS velocities were performed with a laser Doppler anemometer. For low swirl levels, as the core flow passed through the expansion, it departed the axis of symmetry and precessed about that axis at frequencies on the order of 1 Hz. As swirl was increased to moderate levels, the flow became axisymmetric with on-axis recirculation marking the onset of vortex breakdown. At the highest swirl levels, flow on the tube centerline was in the same direction as the mean flow, with backflow occurring just off-axis. Turbulence intensities at the highest swirl levels were found to reach 60%. As the swirl was increased from zero to its maximum value, the flow reattachment point moved upstream from 9 to 2 step heights. Experimental data are also presented for local heat transfer rates in the downstream tube. Plots of local Nusselt numbers show a sharply peaked behavior at the point of maximum heat transfer, with increasing swirl greatly exaggerating the peaking.

  7. Factors influencing separation distances against odour annoyance calculated by Gaussian and Lagrangian dispersion models

    Science.gov (United States)

    Piringer, Martin; Knauder, Werner; Petz, Erwin; Schauberger, Günther

    2016-09-01

    Direction-dependent separation distances to avoid odour annoyance, calculated with the Gaussian Austrian Odour Dispersion Model AODM and the Lagrangian particle diffusion model LASAT at two sites, are analysed and compared. The relevant short-term peak odour concentrations are calculated with a stability-dependent peak-to-mean algorithm. The same emission and meteorological data, but model-specific atmospheric stability classes are used. The estimate of atmospheric stability is obtained from three-axis ultrasonic anemometers using the standard deviations of the three wind components and the Obukhov stability parameter. The results are demonstrated for the Austrian villages Reidling and Weissbach with very different topographical surroundings and meteorological conditions. Both the differences in the wind and stability regimes as well as the decrease of the peak-to-mean factors with distance lead to deviations in the separation distances between the two sites. The Lagrangian model, due to its model physics, generally calculates larger separation distances. For worst-case calculations necessary with environmental impact assessment studies, the use of a Lagrangian model is therefore to be preferred over that of a Gaussian model. The study and findings relate to the Austrian odour impact criteria.

  8. Lidar Uncertainty Measurement Experiment (LUMEX) - Understanding Sampling Errors

    Science.gov (United States)

    Choukulkar, A.; Brewer, W. A.; Banta, R. M.; Hardesty, M.; Pichugina, Y.; Senff, Christoph; Sandberg, S.; Weickmann, A.; Carroll, B.; Delgado, R.; Muschinski, A.

    2016-06-01

    Coherent Doppler LIDAR (Light Detection and Ranging) has been widely used to provide measurements of several boundary layer parameters such as profiles of wind speed, wind direction, vertical velocity statistics, mixing layer heights and turbulent kinetic energy (TKE). An important aspect of providing this wide range of meteorological data is to properly characterize the uncertainty associated with these measurements. With the above intent in mind, the Lidar Uncertainty Measurement Experiment (LUMEX) was conducted at Erie, Colorado during the period June 23rd to July 13th, 2014. The major goals of this experiment were the following: Characterize sampling error for vertical velocity statistics Analyze sensitivities of different Doppler lidar systems Compare various single and dual Doppler retrieval techniques Characterize error of spatial representativeness for separation distances up to 3 km Validate turbulence analysis techniques and retrievals from Doppler lidars This experiment brought together 5 Doppler lidars, both commercial and research grade, for a period of three weeks for a comprehensive intercomparison study. The Doppler lidars were deployed at the Boulder Atmospheric Observatory (BAO) site in Erie, site of a 300 m meteorological tower. This tower was instrumented with six sonic anemometers at levels from 50 m to 300 m with 50 m vertical spacing. A brief overview of the experiment outline and deployment will be presented. Results from the sampling error analysis and its implications on scanning strategy will be discussed.

  9. Calibration of a 3-wire-probe for measurements in non-isothermal air flow

    International Nuclear Information System (INIS)

    A method for the measurement of shear stresses, heat fluxes and turbulent Prandtl numbers in axial air flow through heated rod bundles was developed. A hot wire probe was applied consisting of an X-wire with a third wire upstream and perpendicular to the X-wire plane. The calibration method uses look-up tables. For setting up these tables the probe is calibrated through a range of pitch angles, velocities and temperatures in fixed intervalls. During the measurement the three anemometer signals are simultaneously digitized and evaluated by determinating the position in the look-up table which corresponds to the three data. The instantaneous temperature and velocity vectors are found by linear interpolation between the nearest points to the measured data in the look up table. This method is simple, accurate and fast in evaluation and is ideally suited for digital data processing. All RMS-values and correlations are calculated on-line. The report contains an analysis of errors pertaining to the measurement with X-wire probes with a third thermo-wire. The program listings for the evaluation of the look-up tables are included. (orig.)

  10. Flow field analysis of mechanical heart valves. Comparison of Starr-Edwards, Bjork-Shiley c-c, and St. Jude medical prostheses; Kikaiteki jinkoben no nagareba no kaiseki. Starr-Edwards, Bjork-Shiley c-c, oyobi St. Jude Medical ben no hikaku

    Energy Technology Data Exchange (ETDEWEB)

    Akutsu, T. [Kanto Gakuin University, Yokohama (Japan); Bishop, W. [Andronic Inc., Richmond, BC, (Canada); Modi, V. [University of British Columbia, Vancouver, BC (Canada)

    1996-03-25

    Three typical mechanical heart valves (Starr-Edwards, Bjork-Shiley c-c and St. Jude Medical) have been tested in the mitral position under pulsatile flow conditions. The test program included measurements of velocity and turbulent stresses at six downstream locations. The study was carried out using a sophisticated cardiac simulator in conjunction with a highly sensitive two-component laser Doppler anemometer system. The continuous monitoring of parametric time histories revealed useful details about the complex flow and also helped established location and time of the peak parameter values. Based on the experimental data, the following general conclusions can be drawn: (1) all 3 valve designs generated elevated turbulent stresses during acceleration and peak flow phases, presenting a possibility of thromboembolism, and perhaps, hemolysis; (2) valve configuration and valve orientation significantly affect the flow characteristics; (3) the Starr-Edwards valve with relatively a small opening area shows lower turbulent stresses; and (4) the bileaflet design of the St. Jude Medical valve is also associated with lower turbulent stresses, as compared to the Bjork-Shiley c-c valve. 7 refs., 14 figs.

  11. Logarithmic Wind Profile: A Stability Wind Shear Term

    CERN Document Server

    Sakagami, Yoshiaki; Haas, Reinaldo; Passos, Julio C; Taves, Frederico F

    2014-01-01

    A stability wind shear term of logarithmic wind profile based on the terms of turbulent kinetic energy equation is proposed. The fraction influenced by thermal stratification is considered in the shear production term. This thermally affected shear is compared with buoyant term resulting in a stability wind shear term. It is also considered Reynolds stress as a sum of two components associated with wind shear from mechanical and thermal stratification process. The stability wind shear is responsible to Reynolds stress of thermal stratification term, and also to Reynolds stress of mechanical term at no neutral condition. The wind profile and its derivative are validated with data from Pedra do Sal experiment in a flat terrain and 300m from shoreline located in northeast coast of Brazil. It is close to the Equator line, so the meteorological condition are strongly influenced by trade winds and sea breeze. The site has one 100m tower with five instrumented levels, one 3D sonic anemometer, and a medium-range wind...

  12. Winds at the Phoenix landing site

    DEFF Research Database (Denmark)

    Holstein-Rathlou, C.; Gunnlaugsson, H.P.; Merrison, J.P.;

    2010-01-01

    Wind speeds and directions were measured on the Phoenix Lander by a mechanical anemometer, the so-called Telltale wind indicator. Analysis of images of the instrument taken with the onboard imager allowed for evaluation of wind speeds and directions. Daily characteristics of the wind data...... are highly turbulent behavior during midday due to daytime turbulence with more stable conditions during nighttime. From Ls ∼77°–123° winds were generally ∼4 m s−1 from the east, with 360° rotation during midday. From Ls ∼123°–148° daytime wind speeds increased to an average of 6–10 m s−1 and were generally...... from the west. The highest wind speed recorded was 16 m s−1 seen on Ls ∼147°. Estimates of the surface roughness height are calculated from the smearing of the Kapton part of the Telltale during image exposure due to a 3 Hz turbulence and nighttime wind variability. These estimates yield 6 ± 3 mm and 5...

  13. Atmospheric stability and diurnal patterns of aeolian saltation on the Llano Estacado

    Science.gov (United States)

    Lanigan, David; Stout, John; Anderson, William

    2016-06-01

    Aeolian transport is driven by aerodynamic surface stress imposed by turbulent winds in the Earth's atmospheric boundary layer (ABL). ABL regime is influenced by stratification, which can either enhance or suppress production of turbulence by shear associated with the vertical gradient of streamwise velocity. During the day and night, surface heat fluxes induce a negative (unstable) and positive (stable) vertical gradient of potential temperature, respectively, which modifies the role of buoyancy in turbulence production. During the brief morning and evening transition periods, the vertical gradient of potential temperature vanishes (neutral stratification). The Monin-Obukhov similarity theory describes how the vertical gradient of streamwise velocity varies with stratification. Simultaneous field measurement of wind speed and aeolian activity were obtained over a 218-day period on a bare, sandy surface on the high plains of the Llano Estacado region of west Texas. Wind speed was measured at a height of 2 m with a propeller-type anemometer and aeolian activity was measured at the surface with a piezoelectric saltation sensor. We have used the wind speed measurements within the framework of the Monin-Obukhov similarity theory to estimate "typical" shear velocity, u∗ , of the ABL as stratification is varied (characterized with the stability parameter). This approach results in a color flood contour of u∗ against time of day and stability parameter: the procedure demonstrates that aeolian activity is most likely to occur during the day, when buoyancy acts in conjunction with mechanical shear to increase u∗ .

  14. Estimating wind velocity standard deviation values in the inertial sublayer from observations in the roughness sublayer

    Science.gov (United States)

    Falabino, Simona; Trini Castelli, Silvia

    2016-05-01

    In air quality practice, observed data are often input to air pollution models to simulate the pollutants dispersion and to estimate their concentration. When the area of interest includes urban sites, observed data collected at urban or suburban stations can be available, and it can happen to use them for estimating surface layer parameters given in input to the models. In such case, roughness sublayer quantities may enter the parameterizations of the turbulence variables as if they were representative of the inertial sublayer, possibly leading to a not appropriate application of the Monin-Obukhov similarity theory. We investigate whether it is possible to derive suitable values of the wind velocity standard deviations for the inertial sublayer using the friction velocity and stability parameter observed in the roughness sublayer, inside a similarity-like analytical function. For this purpose, an analysis of sonic anemometer data sets collected in suburban and urban sites is proposed. The values derived through this approach are compared to actual observations in the inertial sublayer. The transferability of the empirical coefficients estimated for the similarity functions between different sites, characterized by similar or different morphologies, is also addressed. The derived functions proved to be a reasonable approximation of the actual data. This method was found to be feasible and generally reliable, and can be a reference to keep using, in air pollution models, the similarity theory parameterizations when measurements are available only in the roughness sublayer.

  15. Outer scale and Monin-Obukhov flux relationships of atmospheric turbulence under dry convective conditions

    Science.gov (United States)

    De Bruin, Henk; Hartogensis, Oscar

    2015-04-01

    In this study we will investigate the assumption that in the atmospheric surface layer the outer scale (L0) is proportional to the height above the surface, under dry convective conditions. For this purpose we analyzed raw sonic anemometers data collected at 3.5 m and at 9 m in a field campaign at the Santa Cruz Flats (32040.3190'N, 111032.641'W, 526 m of elevation) near Eloy, Arizona. For simplicity, we define the L0 as that separation distance at which the spatial correlation coefficient of air temperature at two points in the surface layer is 0.5. Then, according to the 2/3-Kolmogorov scaling law in the inertial sub-range, L0 is determined by the variance and the structure parameter of T . It is found that L0 does not scale with height. Possible reasons for this negative result will be discussed, by considering the methodology to determine structure parameters, Taylor's frozen turbulence hypothesis, effects of intermittency and Monin-Obukhov flux relationships for variance and structure parameter for T . The question is asked whether the concept of surface constant flux layer still holds under strong convective condition.

  16. The Tturbulent Structure of the Atmospheric Boundary Layer over Small Northern Lakes

    Science.gov (United States)

    Repina, I.; Stepanenko, V.; Artamonov, A.; Barskov, K.; Polukhov, A.

    2015-12-01

    Wetland and freshwater ecosystems of the Northern Europe are an important natural source of atmospheric methane. Adequate calculation of gas emission from the northern territories requires calculation of balances of heat, moisture, and gases at the surface of water bodies on the sub-grid scale in the climate models. We carried out measurements in North Karelia on the lake Verkhneye (White Sea Biological Station of Moscow State University). The purpose of the study is evaluation of turbulent transport in the system "lake water- near-surface air - surrounding forest" in the winter season. We used an array of acoustic anemometers mounted at different distances from the lake shore. Measurements were taken at two heights in the center of the lake. It was revealed that the intensity of the turbulent transfer essentially depends on the height and location of sensors, and the wind direction. Stratification in the near-to-surface air probably does not play significant role. Besides, there is no constant-flux layer. The later makes Monin and Obukhov similarity theory (which is used in most of the parameterizations for calculating turbulent flows) inapplicable in this case. The work was sponsored by RFBR 14-05-91752, 14-05-91764, 15-35-20958.

  17. Influence of stability on the flux-profile relationships for wind speed, Φm, and temperature, Φh, for the stable atmospheric boundary layer

    Directory of Open Access Journals (Sweden)

    C. Yagüe

    2006-01-01

    Full Text Available Data from SABLES98 experimental campaign have been used in order to study the influence of stability (from weak to strong stratification on the flux-profile relationships for momentum, Φm, and heat, Φh. Measurements from 14 thermocouples and 3 sonic anemometers at three levels (5.8, 13.5 and 32 m for the period from 10 to 28 September 1998 were analysed using the framework of the local-scaling approach (Nieuwstadt, 1984a; 1984b, which can be interpreted as an extension of the Monin-Obukhov similarity theory (Obukhov, 1946. The results show increasing values of Φm and Φh with increasing stability parameter ζ=z/Λ, up to a value of ζ≈1–2, above which the values remain constant. As a consequence of this levelling off in Φm and Φh for strong stability, the turbulent mixing is underestimated when linear similarity functions (Businger et al., 1971 are used to calculate surface fluxes of momentum and heat. On the other hand when Φm and Φh are related to the gradient Richardson number, Ri, a different behaviour is found, which could indicate that the transfer of momentum is greater than that of heat for high Ri. The range of validity of these linear functions is discussed in terms of the physical aspects of turbulent intermittent mixing.

  18. Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

    Directory of Open Access Journals (Sweden)

    W. Choi

    2010-11-01

    Full Text Available In this study the atmospheric boundary layer (ABL height (zi over complex, forested terrain is estimated based on the power spectra and the integral length scale of horizontal winds obtained from a three-axis sonic anemometer during the BEARPEX (Biosphere Effects on Aerosol and Photochemistry Experiment. The zi values estimated with this technique showed very good agreement with observations obtained from balloon tether sonde (2007 and rawinsonde (2009 measurements under unstable conditions (z/L < 0 at the coniferous forest in the California Sierra Nevada. The behavior of the nocturnal boundary layer height (h and power spectra of lateral winds and temperature under stable conditions (z/L > 0 is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007, although it was observed to only vary from 60–80 m during the experiment. Finally, significant directional wind shear was observed during both day and night with winds backing from the prevailing west-southwesterlies in the ABL (anabatic cross-valley circulation to consistent southerlies in a layer ~1 km thick just above the ABL before veering to the prevailing westerlies further aloft. We show that this is consistent with the forcing of a thermal wind driven by the regional temperature gradient directed due east in the lower troposphere.

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

    Science.gov (United States)

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

    2016-04-01

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

  20. LITOS – a new balloon-borne instrument for fine-scale turbulence soundings in the stratosphere

    Directory of Open Access Journals (Sweden)

    A. Theuerkauf

    2011-01-01

    Full Text Available We have developed a new compact balloon payload called LITOS (Leibniz-Institute Turbulence Observations in the Stratosphere for high resolution wind turbulence soundings in the stratosphere up to 35 km altitude. The wind measurements are performed using a constant temperature anemometer (CTA with a vertical resolution of ~2.5 mm, i.e. 2 kHz sampling rate at 5 m/s ascent speed. Thereby, for the first time, it is possible to study the entire turbulence spectrum down to the viscous subrange in the stratosphere. Including telemetry, housekeeping, batteries and recovery unit, the payload weighs less than 5 kg and can be launched from any radiosonde station. Since autumn 2007, LITOS has been successfully launched several times from the Leibniz-Institute of Atmospheric Physics (IAP in Kühlungsborn, Germany (54° N, 12° E. Two additional soundings were carried out in 2008 and 2009 in Kiruna, Sweden (67° N, 21° E as part of the BEXUS program (Balloon-borne EXperiments for University Students. We describe here the basic principle of CTA measurements and prove the validity of this method in the stratosphere. A first case study allows a clear distinction between non-turbulent regions and a turbulent layer with a thickness of some tens of meters. Since our measurements cover the transition between the inertial and viscous subrange, energy dissipation rates can be calculated with high reliability.

  1. Fine-scale turbulence soundings in the stratosphere with the new balloon-borne instrument LITOS

    Directory of Open Access Journals (Sweden)

    A. Theuerkauf

    2010-08-01

    Full Text Available We have developed a new compact balloon payload called LITOS (Leibniz-Institute Turbulence Observations in the Stratosphere for high resolution wind turbulence soundings up to 35 km altitude. The wind measurements are performed applying a constant temperature anemometer (CTA with a vertical resolution of ~2.5 mm, i.e. 2 kHz sampling rate at 5 m/s ascent speed. Thereby, for the first time, it is possible to study the entire turbulence spectrum down to the viscous subrange in the stratosphere. Including telemetry, housekeeping, batteries and recovery unit the payload weighs less than 5 kg and can be launched at any radiosonde station. Since autumn 2007 LITOS has been successfully launched several times from the Leibniz-Institute of Atmospheric Physics (IAP in Kühlungsborn, Germany (54° N, 12° E. Two additional soundings were carried out in 2008 and 2009 at Kiruna, Sweden (67° N, 21° E as part of the BEXUS program (Balloon-borne EXperiments for University Students. We describe here the basic principle of CTA measurements and prove the validity of this method in the stratosphere. First case studies allow a clear distinction between non-turbulent layers and turbulent layers with a thickness of some tens of meters. Since our measurements cover the transition between the inertial and viscous subrange, energy dissipation rates can be calculated with high reliability.

  2. Safe housing ensured by an electric field screen that excludes insect-net permeating haematophagous mosquitoes carrying human pathogens

    Science.gov (United States)

    Matsuda, Y.; Kakutani, K.; Nonomura, T.; Kimbara, J.; Osamura, K.; Kusakar, S.; Toyoda, H.

    2015-10-01

    An electric field screen can be used to keep mosquitoes out of houses with open windows. In this study, doubly charged dipolar electric field screens (DD-screens) were used to capture mosquitoes entering through a window. The screen had two components: three layers of insulated conductor iron wires (ICWs) in parallel arrays and two electrostatic direct current (DC) voltage generators that supplied negative or positive voltages to the ICWs. Within each layer, the ICWs were parallel at 5-mm intervals, and connected to each other and to a negative or positive voltage generator. The negatively and positively charged ICWs are represented as ICW(-) and ICW(+), respectively. The screen consisted of one ICW(+) layer with an ICW(-) layer on either side. The Asian tiger mosquito (Aedes albopictus) and house mosquito (Culex pipiens) were used as models of vectors carrying viral pathogens. Adult mosquitoes were blown into the space between the ICWs by sending compressed air through the tip of an insect aspirator to determine the voltage range that captured all of the test insects. Wind speed was measured at the surface of the ICW using a sensitive anemometer. The result showed that at ≥ 1.2 kV, the force was strong enough that the ICWs captured all of the mosquitoes, despite a wind speed of 7 m/s. Therefore, the DD-screen could serve as a physical barrier to prevent noxious mosquitoes from entering houses with good air penetration.

  3. L2F Anemometry Measurements of the Inter-Row Flow Field Within a Transonic Axial Compressor Provided with Curved Windows

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    When measurements are performed in high speed,small-scale compressors,the use of curved glass windows is required in order to avoid any mismatch between the measurement window and the casing.However,the glass curvature leads to optical distortions,which hinder acceptable measurements and can even prevent the acquisition of any data.Thus,an original optical assembly,which consists in inserting a simple and inexpensive corrective window between the frontal lens of the anemometer and the shroud window,is proposed.The way of determining the geometric characteristics and the position of this corrective window,which restores very acceptable foci,is presented in the paper.The reliability of this corrective optical assembly is highlighted by comparative measurements in a test case .Using such an optical setting,L2F measurements were realised along a section,downstream of the inlet guide vane(IGV) of a transonic compressor stage.The spatial resolution leads to a good description of the interaction of the wake with the oblique shock emanating from the leading edge of the rotor.A phenomenological study of the wake/shock interaction with a change of frame is realised using the streamwise equation of the transport of vorticity.

  4. L2F anemometry measurements of the inter-row flow field within a transonic axial compressor provided with curved windows

    Science.gov (United States)

    Ottavy, Xavier; Trébinjac, Isabelle; Vouillarmet, André

    1999-09-01

    When measurements are performed in high speed, small-scale compressors, the use of curved glass windows is required in order to avoid any mismatch between the measurement window and the casing. However, the glass curvature leads to optical distortions, which hinder acceptable measurements and can even prevent the acquisition of any data. Thus, an original optical assembly, which consists in inserting a simple and inexpensive corrective window between the frontal lens of the anemometer and the shroud window, is proposed. The way of determining the geometric characteristics and the position of this corrective window, which restores very acceptable foci, is presented in the paper. The reliability of this corrective optical assembly is highlighted by comparative measurements in a test case. Using such an optical setting, L2F measurements were realised along a section, downstream of the inlet guide vane (IGV) of a transonic compressor stage. The spatial resolution leads to a good description of the interaction of the wake with the oblique shock emanating from the leading edge of the rotor. A phenomenological study of the wake/shock interaction with a change of frame is realised using the streamwise equation of the transport of vorticity.

  5. Wind turbines in a turbulent wind: energy output and the frequency of shut-downs

    Energy Technology Data Exchange (ETDEWEB)

    Bossanyi, E.A.

    1981-01-01

    The fluctuating nature of the wind affects the design of wind turbines in a number of ways. For instance, the energy output is affected, because the wind turbine is not able to follow the fastest fluctuations in the wind so that some of the available energy is lost. Also the wind turbines must be shut down when the wind is too high or too low, and the number of times that this occurs depends on the nature of the wind speed fluctuations. This may be very important in designing the switchgear for large, grid-connected machines, which may be required to switch on and off quite frequently and must be able to do so for long periods without maintenance. In this paper, these questions are studied by making use of some wind speed data provided by the Meteorological Office. The data consists of one-minute average wind speeds recorded every minute from an anemometer at Stornoway, at an effective height of approximately 12 m. above ground.

  6. Volume reconstruction optimization for tomo-PIV algorithms applied to experimental data

    Science.gov (United States)

    Martins, Fabio J. W. A.; Foucaut, Jean-Marc; Thomas, Lionel; Azevedo, Luis F. A.; Stanislas, Michel

    2015-08-01

    Tomographic PIV is a three-component volumetric velocity measurement technique based on the tomographic reconstruction of a particle distribution imaged by multiple camera views. In essence, the performance and accuracy of this technique is highly dependent on the parametric adjustment and the reconstruction algorithm used. Although synthetic data have been widely employed to optimize experiments, the resulting reconstructed volumes might not have optimal quality. The purpose of the present study is to offer quality indicators that can be applied to data samples in order to improve the quality of velocity results obtained by the tomo-PIV technique. The methodology proposed can potentially lead to significantly reduction in the time required to optimize a tomo-PIV reconstruction, also leading to better quality velocity results. Tomo-PIV data provided by a six-camera turbulent boundary-layer experiment were used to optimize the reconstruction algorithms according to this methodology. Velocity statistics measurements obtained by optimized BIMART, SMART and MART algorithms were compared with hot-wire anemometer data and velocity measurement uncertainties were computed. Results indicated that BIMART and SMART algorithms produced reconstructed volumes with equivalent quality as the standard MART with the benefit of reduced computational time.

  7. Impact of a vortex ring on a conical wall

    Science.gov (United States)

    Hernandez Zapata, Sergio; Lopez Sanchez, Erick Javier; Ruiz Chavarria, Gerardo

    2014-11-01

    In this work we present a numerical and experimental research of a vortex ring impinging a cone. Both the vortex and the conical wall have the same axis of symmetry. For this study we solve the Navier-Stokes and continuity equations in cylindrical coordinates using a finite difference scheme for r, z and time, whereas a Fourier spectral method is used for the angular variable. As initial conditions we assume that velocity is given by the Biot-Savart law for a vorticity distribution of constant magnitude inside a torus. With respect the experiments, measurements of velocity were made with a hot wire anemometer. To have a mapping in space we use a traverse system to place the hot wire probe in points of a grid. Additionally, the measurements of velocity are synchronized with the production of the vortex. Unlike the case of the impact with a flat wall, in this case the diameter of the vortex ring cannot grow. We study the shape of the vortex before the impact, the instabilities and the production of secondary vorticity during the impact. Finally, we made a comparison between experiment and the numerical simulations. Authors acknowledge DGAPA-UNAM by support under Project IIN 116312 (Vorticidad y ondas no lineales en fluidos).

  8. TECNAIRE winter field campaign: turbulent characteristics and their influence on air quality conditions

    Science.gov (United States)

    Yagüe, Carlos; Román Cascón, Carlos; Maqueda, Gregorio; Sastre, Mariano; Arrillaga, Jon A.; Artíñano, Begoña; Diaz-Ramiro, Elías; Gómez-Moreno, Francisco J.; Borge, Rafael; Narros, Adolfo; Pérez, Javier

    2016-04-01

    An urban field campaign was conducted at an air pollution hot spot in Madrid city (Spain) during winter 2015 (from 16th February to 2nd March). The zone selected for the study is a square (Plaza Fernández Ladreda) located in the southern part of the city. This area is an important intersection of several principal routes, and therefore a significant impact in the air quality of the area is found due to the high traffic density. Meteorological data (wind speed and direction, air temperature, relative humidity, pressure, precipitation and global solar radiation) were daily recorded as well as micrometeorological measurements obtained from two sonic anemometers. To characterize this urban atmospheric boundary layer (uABL), micrometeorological parameters (turbulent kinetic energy -TKE-, friction velocity -u∗- and sensible heat flux -H-) are calculated, considering 5-minute average for variance and covariance evaluations. Furthermore, synoptic atmospheric features were analyzed. As a whole, a predominant influence of high pressure systems was found over the Atlantic Ocean and western Spain, affecting Madrid, but during a couple of days (17th and 21st February) some atmospheric instability played a role. The influence of the synoptic situation and specially the evolution of the micrometeorological conditions along the day on air quality characteristics (Particulate Matter concentrations: PM10, PM2.5 and PM1, and NOx concentrations) are analyzed and shown in detail. This work has been financed by Madrid Regional Research Plan through TECNAIRE (P2013/MAE-2972).

  9. Flow visualization of a non-contact transport device by Coanda effect

    Science.gov (United States)

    Iki, Norihiko; Abe, Hiroyuki; Okada, Takashi

    2014-08-01

    AIST proposes new technology of non-contact transport device utilizing Coanda effect. A proposed non-contact transport device has a cylindrical body and circular slit for air. The air flow around non-contact device is turbulent and its flow pattern depends on the injection condition. Therefore we tried visualization of the air flow around non -contact device as the first step of PIV measurement. Several tracer particles were tried such as TiO2 particles, water droplets, potatoes starch, rice starch, corn starch. Hot-wire anemometer is employed to velocity measurement. TiO2 particles deposit inside of a slit and clogging of a slit occurs frequently. Potato starch particles do not clog a slit but they are too heavy to trace slow flow area. Water droplets by ultrasonic atomization also deposit inside of slit but they are useful to visualize flow pattern around a non-contact transport device by being supplied from circumference. Coanda effect of proposed non-contact transport device was confirmed and injected air flow pattern switches by a work. Air flow around non-contact trance port device is turbulent and its velocity range is wide. Therefore flow measurement by tracer part icle has traceability issue. Suitable tracer and exposure condition depends on target area.

  10. Experimental study on flow and heat transfer characteristics of synthetic jet driven by piezoelectric actuator

    Institute of Scientific and Technical Information of China (English)

    ZHANG JingZhou; TAN XiaoMing

    2007-01-01

    To investigate the flow and heat transfer characteristics of a synthetic jet driven by piezoelectric actuator, experimental investigation utilizing particle image velocimetry, hot-wire anemometer and infrared camera was carried out. The results show that: (1) At the jet orifice exit, pairs of vortexes are generated, broken down and merged together periodically, forming a steady jet within a several slot width from distance near the orifice exit. And during the development, the synthetic jet spreads rapidly along the minor axis direction of the orifice. While along the major axis direction, the synthetic jet contracts firstly and then spreads slowly. (2) Excitation frequency forced on the actuator has a great effect on the synthetic jet flow field. There are two resonance frequencies at which the mean velocity and vorticity of the synthetic jet are maximized, especially at the higher resonance frequency.The resonance frequency values obtained by the experiment are lower than the theoretical values. (3) Similarly to the common jet impingement, the convective heat transfer coefficients at the target surface impinged by the synthetic jet also take on up-down tendency varying with the jet-to-surface spacing increment. But the jet-to-surface spacing ratio for optimum cooling achievement is greater and the cooling action region is wider than the former, indicating that the synthetic jet introduces a stronger entrainment and more vigorous penetration in the surrounding fluid.

  11. Experimental study on flow and heat transfer characteristics of synthetic jet driven by piezoelectric actuator

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To investigate the flow and heat transfer characteristics of a synthetic jet driven by piezoelectric actuator, experimental investigation utilizing particle image veloci- metry, hot-wire anemometer and infrared camera was carried out. The results show that: (1) At the jet orifice exit, pairs of vortexes are generated, broken down and merged together periodically, forming a steady jet within a several slot width from distance near the orifice exit. And during the development, the synthetic jet spreads rapidly along the minor axis direction of the orifice. While along the major axis direction, the synthetic jet contracts firstly and then spreads slowly. (2) Exci- tation frequency forced on the actuator has a great effect on the synthetic jet flow field. There are two resonance frequencies at which the mean velocity and vorticity of the synthetic jet are maximized, especially at the higher resonance frequency. The resonance frequency values obtained by the experiment are lower than the theoretical values. (3) Similarly to the common jet impingement, the convective heat transfer coefficients at the target surface impinged by the synthetic jet also take on up-down tendency varying with the jet-to-surface spacing increment. But the jet-to-surface spacing ratio for optimum cooling achievement is greater and the cooling action region is wider than the former, indicating that the synthetic jet in- troduces a stronger entrainment and more vigorous penetration in the surrounding fluid.

  12. Thermo-fluid-dynamic modelling of a cold store for cheese maturation

    Directory of Open Access Journals (Sweden)

    Ferruccio Giametta

    2013-03-01

    Full Text Available In this study, drying tests on fresh cheeses were carried out in a cold store equipped with a Munters MG90 dehumidifier that controls the humidity of the room air. In this system, the condensation/drainage stage is omitted since the humid room air is directed out of the cold store (process air and the dried air is introduced by the dehumidifier inside the cold store. Eight air temperature probes were introduced in the store; two probes (HOBO U12-012, 1 HOBO – Onset Computer Corporation, Cape Cod, MA, USA were also introduced and used to measure relative humidity and temperature together with an anemometer to analyse any changes in thermal and fluid dynamics in the cell environment. COMSOL multiphysics software (Comsol Group, Stockolm, Sweden was used to simulate the store environment based on the finite elements method. This allowed us to compare and discuss the experimental data collected and the results obtained by the thermo- fluid-dynamic simulation.

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

    Science.gov (United States)

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

    2016-01-01

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

  14. Longitudinal Hydraulic Resistance Parameters of Cryocooler and Stirling Regenerators in Periodic Flow

    Science.gov (United States)

    Cha, J. S.; Ghiaasiaan, S. M.; Kirkconnell, C. S.

    2008-03-01

    The results of an on going research program aimed at the measurement and correlation of anisotropic hydrodynamic parameters of widely-used cryocooler regenerator fillers are presented. The hydrodynamic parameters associated with longitudinal periodic flow are addressed in this paper. An experimental apparatus consisting of a cylindrical test section packed with regenerator fillers is used for the measurement of axial permeability and Forchheimer coefficients, with pure helium as the working fluid. The regenerator fillers that are tested include stainless steel 400-mesh screens with 69.2% porosity, stainless steel 325-mesh screens with 69.2% porosity, stainless steel 400-mesh sintered filler with 62% porosity, stainless steel sintered foam metal with 55.47% porosity, and nickel micro-machined disks with 26.8% porosity. The test section is connected to a Stirling type compressor on one end and to a constant volume chamber on the other end. The instrumentation includes piezoelectric pressure transducers at both ends of the regenerator and a hot wire anemometer at the inlet of the regenerator. For each filler material, time histories of local pressures at both ends of the regenerator are measured under steady periodic conditions over a wide range of oscillation frequencies (5—60 Hz). A CFD assisted methodology is then used for the analysis and interpretation of the measured data. The viscous resistance coefficient and the inertial resistance coefficient values obtained in this way are correlated in terms of the relevant dimensionless parameters.

  15. Measurement in multiphase reacting flows

    Science.gov (United States)

    Chigier, N. A.

    1979-01-01

    A survey is presented of diagnostic techniques and measurements made in multiphase reacting flows. The special problems encountered by the presence of liquid droplets, soot and solid particles in high temperature chemically reacting turbulent environments are outlined. The principal measurement techniques that have been tested in spray flames are spark photography, laser anemometry, thermocouples and suction probes. Spark photography provides measurement of drop size, drop size distribution, drop velocity, and angle of flight. Photographs are analysed automatically by image analysers. Photographic techniques are reliable, inexpensive and proved. Laser anemometers have been developed for simultaneous measurement of velocity and size of individual particles in sprays under conditions of vaporization and combustion. Particle/gas velocity differentials, particle Reynolds numbers, local drag coefficients and direct measurement of vaporization rates can be made by laser anemometry. Gas temperature in sprays is determined by direct in situ measurement of time constants immediately prior to measurement with compensation and signal analysis by micro-processors. Gas concentration is measured by suction probes and gas phase chromatography. Measurements of particle size, particle velocity, gas temperature, and gas concentration made in airblast and pressure atomised liquid spray flames are presented.

  16. Field measurement on wind characteristic and buffeting response of the Runyang Suspension Bridge during typhoon Matsa

    Institute of Scientific and Technical Information of China (English)

    WANG Hao; LI AiQun; GUO Tong; XIE Jing

    2009-01-01

    Field measurement on wind characteristic and buffeting response of existing bridge is of great value to the development of bridge wind engineering, and the structural health monitoring system (SHMS) em-ployed in many long-span bridges provide a research basis for the field measurement. In order to pro-vide reliable basis for wind resistant evaluation of Runyang Suspension Bridge (RSB), two anemome-ters and 85 accelerometers were installed in the SliMS of RSB. In August 2005, Typhoon Matsa crossed over Jiangsu, the SHMS timely recorded the typhoon and structural vibration responses. In this paper by using the time-frequency technique and statistical theory, the recorded data were analyzed to obtain the strong wind characteristics, the buffeting response characteristics of the cable and deck, and the variation of buffeting response RMS versus wind speed. Results obtained in this study can be em-ployed to validate the credibility of current buffeting response analysis theory techniques, and provide reference values for wind resistant evaluation of other long-span bridges.

  17. Field measurement on wind characteristic and buffeting response of the Runyang Suspension Bridge during typhoon Matsa

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Field measurement on wind characteristic and buffeting response of existing bridge is of great value to the development of bridge wind engineering,and the structural health monitoring system(SHMS) em-ployed in many long-span bridges provide a research basis for the field measurement.In order to pro-vide reliable basis for wind resistant evaluation of Runyang Suspension Bridge(RSB),two anemome-ters and 85 accelerometers were installed in the SHMS of RSB.In August 2005,Typhoon Matsa crossed over Jiangsu,the SHMS timely recorded the typhoon and structural vibration responses.In this paper by using the time-frequency technique and statistical theory,the recorded data were analyzed to obtain the strong wind characteristics,the buffeting response characteristics of the cable and deck,and the variation of buffeting response RMS versus wind speed.Results obtained in this study can be em-ployed to validate the credibility of current buffeting response analysis theory techniques,and provide reference values for wind resistant evaluation of other long-span bridges.

  18. Description of the airflow produced by an air-assisted sprayer during pesticide applications to citrus

    Directory of Open Access Journals (Sweden)

    Ramon Salcedo

    2015-06-01

    Full Text Available Atmospheric drift of plant protection products is considered a major source of air pollution during pesticide applications. Citrus protection against pests and diseases usually requires application of these products using air-blast sprayers. Many authors have emphasized the influence of vegetation on the risk of spray drift. The aim of this work was to describe in detail how the airflow from an air-blast sprayer behaves when it reaches citrus trees and, in particular, the effect that the tree canopy has on this flow. Tests were conducted at a commercial citrus orchard with conventional machinery, placed parallel to a row of trees. Air velocity and direction was measured using a 3D ultrasonic anemometer in 225 points situated in three parallel planes perpendicular to the equipment. The stability of the airflow at each measuring point was studied and the mean velocities were graphically represented. Two vortexes, one behind the canopy, and another over the tree, have been deducted and never been reported before. Both may have an important influence on the trajectories of the sprayed droplets and, as a consequence, on the way in which plant protection products are diffused into the atmosphere. Observed turbulence intensities were higher than in similar experiments conducted in other tree crops, which may be attributable to the higher air volume generated by the machinery used for citrus protection and to the higher foliage density of citrus orchards.

  19. Measurements of the unsteady flow field within the stator row of a transonic axial-flow fan. I - Measurement and analysis technique

    Science.gov (United States)

    Suder, K. L.; Strazisar, A. J.; Adamczyk, J. J.; Hathaway, M. D.; Okiishi, T. H.

    1987-01-01

    This two-part paper presents laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective is to provide additional insight into unsteady blade-row interactions within highspeed compressors which affect stage efficiency, energy transfer, and other design considerations. Part 1 describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the rotor wake generated and unresolved unsteadiness, respectively. (Rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term unresolved unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctutions, etc.). A procedure for calculating auto and cross correlations of the rotor wake generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper.

  20. Measurements of the unsteady flow field within the stator row of a transonic axial-flow fan. II - Results and discussion

    Science.gov (United States)

    Hathaway, M. D.; Suder, K. L.; Strazisar, A. J.; Adamczyk, J. J.; Okiishi, T. H.

    1987-01-01

    Unsteady velocity field measurements made within the stator row of a transonic axial-flow fan are presented. Measurements were obtained at midspan for two different stator blade rows using a laser anemometer. The first stator row consists of double circular-arc airfoils with a solidity of 1.68. The second features controlled-diffusion airfoils with a solidity of 0.85. Both were tested at design-speed peak efficiency conditions. In addition, the controlled-diffusion stator was also tested at near stall conditions. The procedures developed here are used to identify the rotor wake generated and unresolved unsteadiness from the velocity measurements (rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and unresolved unsteadiness refers to all remaining unsteadiness which contributes to the spread in the distribution of velocities such as vortex shedding, turbulence, etc.). Auto and cross correlations of these unsteady velocity fluctuations are presented to show their relative magnitude and spatial distributions. Amplification and attenuation of both rotor wake generated and unresolved unsteadiness are shown to occur within the stator blade passage.

  1. Measurements of the unsteady flow field within the stator row of a transonic axial-flow fan. Part 2: Results and discussion

    Science.gov (United States)

    Hathaway, M. D.; Suder, K. L.; Okiishi, T. H.; Strazisar, A. J.; Adamczyk, J. J.

    1987-01-01

    Unsteady velocity field measurements made within the stator row of a transonic axial-flow fan are presented. Measurements were obtained at midspan for two different stator blade rows using a laser anemometer. The first stator row consists of double circular-arc airfoils with a solidity of 1.68. The second features controlled-diffusion airfoils with a solidity of 0.85. Both were tested at design-speed peak efficiency conditions. In addition, the controlled-diffusion stator was also tested at near stall conditions. The procedures developed here are used to identify the rotor wake generated and unresolved unsteadiness from the velocity measurements (rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and unresolved unsteadiness refers to all remaining unsteadiness which contributes to the spread in the distribution of velocities such as vortex shedding, turbulence, etc.). Auto and cross correlations of these unsteady velocity fluctuations are presented to show their relative magnitude and spatial distributions. Amplification and attenuation of both rotor wake generated and unresolved unsteadiness are shown to occur within the stator blade passage.

  2. Field investigation of a wake structure downwind of a VAWT in a windfarm array

    Energy Technology Data Exchange (ETDEWEB)

    Liu, H.T.; Buck, J.W.; Germain, A.C.; Hinchee, M.E.; Solt, T.S.; LeRoy, G.M.; Srnsky, R.A.

    1987-10-01

    The effects of upwind turbine wakes on the performance of a FloWind 17-m VAWT were investigated through a series of field experiments conducted at the FloWind windfarm on Cameron Ridge, Tehachapi, California. The field experiment was conducted within a VAWT array consisting of more than nine VAWTs with separations 3D crosswised by 8D downwind (where D is the turbine diameter) in a staggered configuration. The array is the upwind three rows of VAWTS in a total of six rows that are on top of the Cameron Ridge plateau. The terrain features in the vicinity are reasonably regular, with an upslope of 7 deg on the average; however, several local irregularities are present. The annual hourly averaged wind speed exceeds 8 m/s at the site. The wind field and the power-outputs of nine turbines within the array were measured with wind sensors and power transducers. Nine Gill propeller and 18 Maximum cup anemometers and one direction sensor were mounted on portable and stack-up towers installed upwind and within the turbine array. From the field measurements, the velocity and power/energy deficits were derived under various turbine on/off configurations. Much information was provided to characterize the structure of VAWT wakes and to assess their effects on the performance of downwind turbines. Recommendations are made for optimizing windfarm design and operations as well as for wind energy management.

  3. Review of remote-sensor potential for wind-energy studies

    Energy Technology Data Exchange (ETDEWEB)

    Hooke, W.H.

    1981-03-01

    This report evaluates a number of remote-sensing systems such as radars, lidars, and acoustic echo sounders which are potential alternatives to the cup- and propeller anemometers routinely used in wind energy siting. The high costs and demanding operational requirements of these sensors currently preclude their use in the early stages of a multi-phase wind energy siting strategy such as that recently articulated by Hiester and Pennell (1981). Instead, these systems can be used most effectively in the lattermost stages of the siting process - what Hiester and Pennell (1981) refer to as the site development phase, necessary only for the siting of large wind-energy conversion systems (WECS) or WECS clusters. Even for this particular application only four techniques appear to be operational now; that is, if used properly, these techniques should provide the data sets currently considered adequate for wind-energy siting purposes. They are, in rough order of increasing expense and operating demands: optical transverse wind sensors; acoustic Doppler sounders; time-of-flight and continuous wave (CW) Doppler lidar; and frequency-modulated, continuous wave (FM-CW) Doppler radar.

  4. Wind energy under cold climate conditions

    Energy Technology Data Exchange (ETDEWEB)

    Maribo Pedersen, B.

    1999-03-01

    There is an increasing interest in wind energy production under different climatic conditions, among them cold climate and icing conditions. More and more wind turbines are being installed in cold climates and even adapted technology has been developed for that environment. Various national activities are going on in at least Finland, Canada, Italy, Sweden, etc. and international collaboration has been carried out within the European Union's Non-nuclear energy programme. Wind turbine operation is affected by both the cold temperatures and the formation of ice on the blades and the supporting structure. Cold temperatures can be handled by material selections known in other technical fields but to prevent icing, new techniques have to be - and have been - developed. Icing affects the reliability of anemometers, which concerns both turbine control and resource estimation, and changes the aerodynamics of the blades, which eventually stops the turbine. In addition, occasional icing events can locally affect public safety. The development of applied technology has entered some different paths and different solutions are tried out. As the applications are entering a commercial phase, these is a request to gather the experiences and monitor the reliability in a form that can be utilised by developers, manufactureres, consultants and other tenderers. The Topical Experts Meeting will focus on site classification, operational experiences, modelling and mesurements of ice induced loads and safety aspects. (EHS)

  5. The structure of single-phase turbulent flows through closely spaced rod arrays

    International Nuclear Information System (INIS)

    The axial and azimuthal turbulence intensity in the rod gap region has been shown, for developed single-phase turbulent flow through parallel rod arrays, to strongly increase with decreasing rod spacing. Two array geometries are reported, one constructed from a rectangular cross-section duct containing four rods and spaced at five p/d or w/d ratios. The second test section, constructed from six rods set in a regular square-pitch array, represented the interior flow region of a large array. The mean axial velocity, wall shear stress variation and axial pressure distribution were measured, together with hot-wire anemometer measurements of the Reynolds stresses. No significant non-zero secondary flow components were detected, using techniques capable of resolving secondary flow velocities to 1% of the local axial velocity. For the lowest p/d ratio of 1.036, cross-correlation measurements showed the presence of an energetic periodic azimuthal turbulent velocity component, correlated over a significant part of the flow area. The negligible contribution of secondary flows to the axial momentum balance, and the large azimuthal turbulent velocity component in the rod gap area, suggest a different mechanism than Reynolds stress gradient driven secondary flows for the turbulent transport process in the rod gap. (orig.)

  6. Dynamic flow analysis using an OpenFOAM based CFD tool: Validation of Turbulence Intensity in a testing site

    Directory of Open Access Journals (Sweden)

    Casella Livio

    2014-01-01

    Full Text Available The presenting paper investigates on the validation of the turbulence intensity (TI modeled by a CFD tool. Six meteorological masts, equipped with cup anemometers, have been used for the purpose. Three different turbulence closure schemes, which are the SST k-omega and the k-epsilon in two different configurations, have been tested. The flow analysis shows a qualitative agreement between measurements and models, which are capable to simulate the turning of the wind towards South when it comes from SSE. Furthermore, the simulations predict a zone of high turbulence in the northern part of the site that is confirmed by the local measurements. The scores for TI have been quantified by considering the observed directional frequencies in the validation analysis. For the testing site, the SST k-omega scheme achieves the best performance when using the TI definition which is representative of the longitudinal fluctuations of the velocity vector, against the other one, which considers the fluctuation of the horizontal vector. Lastly, the model errors have been used to correct the simulated values using two approaches; the analysis shows that, for the presented case, these correction methods do not always improve the accuracy of the simulations.

  7. Characterization of meteorological and ice conditions at Noranda's abandoned mine site in Murdochville during the 2004-2005 measuring campaign; Characterisation des conditions meteorologiques et du givre sur le site de l'ancienne mine de Noranda a Murdochville durant la campagne de mesure 2004-2005

    Energy Technology Data Exchange (ETDEWEB)

    Fortin, G.; Hochart, C.; Perron, J. [Quebec Univ., Chicoutimi, PQ (Canada). Anti-Icing Materials International Laboratory; Ilinca, A. [Quebec Univ., Rimouski, PQ (Canada). Wind Energy Group

    2005-08-15

    A centre of integrated research and technology regarding wind energy in nordic climates has been established based on meteorological data collected from November 30, 2004 to May 24, 2005 at an abandoned Noranda mine in the town of Murdochville, Quebec. Results were compared with frost accumulation measured on the NACA 63 415 turbine blade profile during refrigerated wind tunnel tests conducted at the Anti-Icing Materials International Laboratory (AMIL) in Chicoutimi, Quebec in late 2005. Loss of lift and increased drag during frost periods were measured during the laboratory tests. Two dome anemometers were used to measure the wind intensity, wind direction, air temperature, relative humidity, barometric pressure, and sunlight. The parameters used to measure frost were the liquid content, diameter of water droplets, the density of the ice, the dew point, and the ice accumulation rate. The degree of potential danger to wind turbines was also calculated from the measured data. During the measuring campaign, there were 13 events of fog during frost periods, and 5 events of sleet that were registered. The month of March was shown to be the most vulnerable to frost followed by April, February, January. It was recommended that the model be modified to estimate the turning speed of wind turbines by adding a factor that keeps track of the increasing air velocity produced by the acceleration of the wind. 100 figs., 28 tabs.

  8. Experimental thermo-aerodynamic characterisation of a jet in crossflow, impacting or not, in channel turbulence

    International Nuclear Information System (INIS)

    This work consists in the experimental study of a jet in crossflow in a closed wind tunnel. Depending on the value of the velocity ratio (r Uj/U∞), this confined rectangular jet can interact or impact with the opposite wall from the one it issues. The jet is slightly heated (∼10 C) in order to stay in the passive scalar case. An improvement of the experimental facility has been done to obtain thermal boundary conditions compatible with the measurements of slight differences of temperature, imposed by the passive scalar. Concerning the metrology, hot and cold wire anemometry and thermometry are used, and all the anemometric devices are developed and built in the lab. Probes made with Wollaston wire (Pt-Rh) of 0.35μm diameter are coupled with an anemometer and a thermometer optimized to maximize the signal to noise ratio. The results are obtained both thanks to visualizations by fast camera shots for several velocity ratios (r between 3 and 12), and thanks to local hot and cold wire measurements, in the particular case of two velocity ratios (r = 3.3 and 9.4). Mixing properties of the scalar are studied by the plot of statistical values of velocity and temperature in different plans, perpendicularly to the three axis. The analysis of spectral densities of the signals on several typical locations emphasizes some features of the dynamic behaviour of the jet. (author)

  9. Short term prediction of the horizontal wind vector within a wake vortex warning system

    Energy Technology Data Exchange (ETDEWEB)

    Frech, M.; Holzaepfel, F.; Gerz, T. [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Wessling (Germany). Inst. fuer Physik der Atmosphaere; Konopka, J. [Deutsche Flugsicherung (DFS) GmbH, Langen (Germany)

    2000-07-14

    A wake vortex warning system (WVWS) has been developed for Frankfurt airport. This airport has two parallel runways which are separated by 518 m, a distance too short to operate them independently because wake vortices may be advected to the adjacent runway. The objective of the WVWS is to enable operation with reduced separation between two aircraft approaching the parallel runways at appropriate wind conditions. The WVWS applies a statistical persistence model to predict the crosswind within a 20 minute period. One of the main problems identified in the old WVWS are discontinuities between successive forecasts. These forecast breakdowns were not acceptable to airtraffic controllers. At least part of the problem was related to the fact that the forecast was solely based on the prediction of crosswind. A new method is developed on the basis of 523 days of sonic anemometer measurements at Frankfurt airport. It is demonstrated that the prediction of the horizontal wind vector avoids these difficulties and significantly improves the system's performance. (orig.)

  10. Investigation of the flow field inside the manifold of a real operated fuel cell stack using optical measurements and Computational Fluid Mechanics

    Science.gov (United States)

    Schmieder, Felix; Kinaci, Mustafa E.; Wartmann, Jens; König, Jörg; Büttner, Lars; Czarske, Jürgen; Burgmann, Sebastian; Heinzel, Angelika

    2016-02-01

    The versatility of fuel cells enables a wide range of applications. Usually fuel cells are combined to stacks such that the reactant supply of the single cells is achieved via a pipe branching system, the manifold. The overall performance significantly depends on cell flow rates which are related to the fluidic interaction of the manifold and the cells. Computational Fluid Dynamics (CFD) simulations, which are often used to find a suitable design, lack experimental flow data for validation of the numerical results. To enable flow measurements within the small geometries of the manifold and to provide reliable velocity information inside a real fuel cell stack, a low-coherence Laser Doppler Anemometer (LDA) is applied, which uses multi-mode laser light to achieve a spatial resolution of <100 μm. The use of fluorescent particles and backward scatter mode make the sensor highly suitable for the application in small manifold geometries like in fuel cell stacks. Sensor and measurement technique are validated in simplified stack models and the applicability to air flows is demonstrated. Finally, for the first time, velocity profiles with high spatial resolution inside an operated fuel cell stack are presented, which serve as benchmark for CFD to find an optimal geometry.

  11. Wind energy estimation at Quetta

    Energy Technology Data Exchange (ETDEWEB)

    Nasir, S.M.; Raza, S.M.; Jafri, Y.Z. (Balochistan Univ., Quetta (PK))

    1991-01-01

    Hourly wind data at Quetta airport (Samungli) for the year 1984-1985, were obtained using a standard anemometer height of 10 m, with a view to working out the feasibility of wind energy utilization. Quetta (lat. 30{sup o}11'N long, 66{sup o}57'E) is elevated at 1799 m above sea level. In this paper we analyse the wind energy data by using the Weibull distribution. Scaling and shaping parameters are determined by using the least-squares approximation to a straight line. Actual wind data, weighted Weibull density function and weighted Rayleigh probability density function for regular and continuous periods of 4 weeks up to a year (wind characteristics are being recorded and summarized as diurnal and monthly wind velocity distributions and wind power density roses) are plotted. This shows that the Weibull distribution is generally of the right shape to fit low-averaged wind speed frequency curves. However, a density function of a normal distribution is also determined. Deviations in wind speed distributions at very low-averaged wind speeds and at comparatively large-averaged wind speeds are found. (author).

  12. Wind-driven water motions in wetlands with emergent vegetation

    Science.gov (United States)

    Tse, Ian C.; Poindexter, Cristina M.; Variano, Evan A.

    2016-04-01

    Wetland biogeochemical transformations are affected by flow and mixing in wetland surface water. We investigate the influence of wind on wetland water flow by simultaneously measuring wind and surface water velocities in an enclosed freshwater wetland during 1 day of strong-wind conditions. Water velocities are measured using a Volumetric Particle Imager while wind velocities are measured via sonic-anemometer. Our measurements indicate that the wind interacting with the vegetation canopy generates coherent billows and that these billows are the dominant source of momentum into the wetland water column. Spectral analysis of velocity time series shows that the spectral peak in water velocity is aligned with the spectral peak of in-canopy wind velocity, and that this peak corresponds with the Kelvin-Helmholtz billow frequency predicted by mixing layer theory. We also observe a strong correlation in the temporal pattern of velocity variance in the air and water, with high variance events having similar timing and duration both above and below the air-water interface. Water-side variance appears coupled with air-side variance at least down to 5 cm, while the theoretical Stokes' solution predicts momentum transfer down to only 2 mm assuming transfer via molecular viscosity alone. This suggests that the wind-driven flow contributed to significant mixing in the wetland water column.

  13. A new Wind Sensor for the Beagle 2 Mars Lander

    Science.gov (United States)

    Wilson, C. F.; Calcutt, S. B.; Jones, T. V.

    2001-12-01

    A hot-film anemometer has been developed for Beagle2, a British Mars lander to be launched in 2003. The sensor will measure wind speed (up to 30 m/s) and horizontal component of wind direction. The position of the wind sensor position at the end of Beagle2's motorised arm allows several new possibilities for wind measurement on Mars that were unavailable in previous missions. The height of the wind sensor can be adjusted to any height between ~20 cm and ~110 cm above the lander body, or can be moved laterally at a given height to study the effects of lander interference. Alternatively, the wind sensor may be positioned with its axis horizontal, thus allowing measurements of vertical wind speed. The wind sensor was calibrated in a new wind tunnel facility, in which Martian surface wind conditions are simulated. Wind speeds of 0.5 - 60 m/s can be created in a CO2 or air atmosphere at pressures of 5 - 10 mbar and temperatures of 200 - 300 K. The facility can also be used in its current configuration to simulate stratospheric winds on Earth. >http://www.atm.ox.ac.uk/user/wilson/matacf.html

  14. Evaluation of Noah-LSM for soil hydrology parameters in the Indian summer monsoon conditions

    Science.gov (United States)

    Patil, M. N.; Kumar, Manoj; Waghmare, R. T.; Dharmaraj, T.; Mahanty, N. C.

    2014-10-01

    The micrometeorological observations, collected over a station in Ranchi (23°45'N, 85°30'E) which is under the monsoon trough region of India, were used in the Noah-LSM (NCEP, OSU, Air Force and Office of Hydrology Land Surface Model) to investigate the model performance in wet (2009 and 2011) and dry (2010) conditions during the south-west summer monsoon season. With this analysis, it is seen that the Noah-LSM has simulated the diurnal cycle of heat fluxes (sensible and ground) reasonably. The simulated heat fluxes were compared with its direct measurements by sonic anemometer and soil heat flux plate. The net radiation and sensible heat flux are simulated well by the model, but the simulation of ground heat flux was found to be poor in both dry as well as wet conditions. The soil temperature simulations were also found to be poor in 0-5- and 5-10-cm layers compared to other deeper layers. The observations were also correlated with the Modern Era Retrospective-analysis for Research and Applications (MERRA) data. The correlation between the observations and ground heat flux was better in MERRA dataset than that of the Noah-LSM simulation.

  15. Expérience à Grands Reynolds Cryogéniques : GReC

    CERN Document Server

    Pietropinto, Sylvain

    2002-01-01

    We have developed at CERN, an hydrodynamic experiment using Helium at low temperature as the working fluid (5 K). The very small kinematic viscosity of Helium allows to create highly turbulent flows at Reynolds numbers never reached, within well controlled laboratory conditions (RlÅ 6000). The chosen geometry, known to produce high turbulent rate (30 %), is an open round jet which develops within a 1 m diameter and 2, 5 m high cell. In order to mesure flow-rates from 20 g/s to 300 g/s at 5 K with an accuracy better than10 %, we have built a cryogenic mass flowmeter. To characterize the smallest flow structures, we have manufactured micrometric anemometers. These sensors are made of a 5 um diameter glass fiber covered by a Cr layer. To limit the fiber sensitive area, a superconducting Pb-In alloy is sputtered over the Cr layer, but on a small length (2 to 5 um). Vertical and horizontal moving systems, working at low temperature, allow to make velocity measurements everywhere in the jet. A high performance 10 ...

  16. Effect of Ultrafine particles on Flow Field and Transport Properties near the nterface Around a Moving Bubble

    Institute of Scientific and Technical Information of China (English)

    马友光; 徐世昌; 冯惠生

    2004-01-01

    Laser Doppler Anemometer has been used to measure the flow field characteristics near the interface around a moving bubble in the presence of ultrafine particles. In order to model a moving bubble, the bubble was fixed into the counter-flow liquid by a metal mesh. Experimental materials are air and water, and the particles are complex oxidate powder. Experiments were carried out under the operating conditions: the liquid flow velocity u0 is 12.6 cm/s, the equivalent diameter de is 0.6 cm, the mass concentration of particle is 0.2%,the average particle diameter is about 10 nm and the density is 2 g/cm3. The velocity profiles of both frontal and tail-vortex areas were measured respectively. The experimental results show that the velocity fields are obviously changed in the existence of particles. In the frontal area of the bubble, both tangential and normal velocities decrease due to the presence of particles, but in tail vortex area, the tangential velocities increase remarkably, and normal velocities rise gradually from the center towards the fringe in the opposite tendency to that of no particles. The influences of flow field change in the presence of particles on gas-liquid mass transfer are analyzed and discussed.

  17. Transmission of Mycobacterium chimaera from Heater-Cooler Units during Cardiac Surgery despite an Ultraclean Air Ventilation System.

    Science.gov (United States)

    Sommerstein, Rami; Rüegg, Christian; Kohler, Philipp; Bloemberg, Guido; Kuster, Stefan P; Sax, Hugo

    2016-06-01

    Heater-cooler units (HCUs) were recently identified as a source of Mycobacterium chimaera causing surgical site infections. We investigated transmission of this bacterium from HCUs to the surgical field by using a thermic anemometer and particle counter, videotape of an operating room equipped with an ultraclean laminar airflow ventilation system, and bacterial culture sedimentation plates in a nonventilated room. Smoke from the HCU reached the surgical field in 23 s by merging with ultraclean air. The HCU produced on average 5.2, 139, and 14.8 particles/min in the surgical field at positions Off, On/oriented toward, and On/oriented away, respectively. Culture plates were positive for M. chimaera <5 m from the HCU in the test room. These experiments confirm airborne transmission of M. chimaera aerosols from a contaminated HCU to an open surgical field despite ultraclean air ventilation. Efforts to mitigate infectious risks during surgery should consider contamination from water sources and airflow-generating devices. PMID:27070958

  18. Eddy covariance measurements of sea spray particles over the Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    S. J. Norris

    2008-02-01

    Full Text Available Most estimates of sea spray aerosol source functions have used indirect means to infer the rate of production as a function of wind speed. Only recently has the technology become available to make high frequency measurements of aerosol spectra suitable for direct eddy correlation determination of the sea spray particle flux. This was accomplished in this study by combining a newly developed fast aerosol particle counter with an ultrasonic anemometer which allowed for eddy covariance measurements of size-segregated particle fluxes. The aerosol instrument is the Compact Lightweight Aerosol Spectrometer Probe (CLASP – capable of measuring 8-channel size spectra for mean radii between 0.15 and 3.5 µm at 10 Hz. The first successful measurements were made during the Waves, Air Sea Fluxes, Aerosol and Bubbles (WASFAB field campaign in October 2005 in Duck (NC, USA. The method and initial results are presented and comparisons are made with recent sea spray source functions from the literature.

  19. Profile of the horizontal wind variance near the ground in near neutral flow. K-theory and the transport of the turbulent kinetic energy

    Energy Technology Data Exchange (ETDEWEB)

    Yahaya, S.; Frangi, J.P. [Paris 7 Univ., 75 (France). Equipe Geomateriaux et Environnement

    2009-07-01

    This paper deals with the characteristics of the atmospheric turbulent flow in the vicinity of the ground, and particularly with the profile of the horizontal wind variance. The study is based on experimental measurements performed with fast cup anemometers located near the ground at 5 different levels (from 0.25 to 4 m) and sampled at 1 Hz. The experiment was carried over two agricultural plots with various tillage treatments in a fallow semiarid area (Central Aragon, Spain). The results of this study reveal that near the ground surface and under moderate wind, the horizontal wind variance logarithmically increases with height, in direct relationship with the friction velocity and the roughness length scale. A theoretical development has allowed us to link this behaviour to the modeling of the turbulent kinetic energy (TKE) transport through the eddy diffusivity. Thus, the study proposes a formulation of the similarity universal function of the horizontal wind variance. Besides, the formulation offers a new method for the determination of the friction velocity and the roughness length scale and can be used for the evaluation of the TKE transport rate. (orig.)

  20. Micrometeorological Conditions at the ATTO - Site in the Amazon Basin

    Science.gov (United States)

    Tsokankunku, Anywhere; Sörgel, Matthias; Acevedo, Otávio C.; Araùjo, Alessandro; Berger, Martina; de Abreu Sá, Leonardo D.; de Oliveira Sá, Marta; Dias, Nelson L.; Dlugi, Ralph; Manzi, Antonio O.; Oliveira, Pablo E. S.; Zelger, Michael

    2016-04-01

    The ATTO site is located in a pristine rainforest environment in the Amazon basin about 150 km north east of Manaus. The site is currently equipped with two walk-up towers (325 m and 80 m) and an 80 m high mast. The canopy height is about 35 m. A detailed description of the site and the ongoing measurements is given in the overview paper by Andreae et al. (2015). The 325 m tower was completed in 2015 and will be equipped in 2016. The 80 m walk-up tower is operational since 2012 with a full set of micrometeorological measurements (e.g. wind and temperature profile, radiation, and a few levels for flux measurements). Measurements of vertical profiles of wind velocity components, temperature, humidity, and energy fluxes, together with 3d sonic anemometer measurements at 150 m on the ATTO tower, are analysed to determine characteristics of momentum, heat and water vapour exchange. In addition, the day time influences of secondary circulation on energy fluxes is described, together with the interaction of these circulations with cloud development. The diurnal cycle of stability and the onset and development of convection is shown to be strongly dependent on the onset of cloud formation. Implications on trace gas transport are discussed.

  1. Experimental study of nonlinear processes in a swept-wing boundary layer at the mach number M=2

    Science.gov (United States)

    Yermolaev, Yu. G.; Kosinov, A. D.; Semionov, N. V.

    2014-09-01

    Results of experiments aimed at studying the linear and nonlinear stages of the development of natural disturbances in the boundary layer on a swept wing at supersonic velocities are presented. The experiments are performed on a swept wing model with a lens-shaped airfoil, leading-edge sweep angle of 45°, and relative thickness of 3%. The disturbances in the flow are recorded by a constant-temperature hot-wire anemometer. For determining the nonlinear interaction of disturbances, the kurtosis and skewness are estimated for experimentally obtained distributions of the oscillating signal over the streamwise coordinate or along the normal to the surface. The disturbances are found to increase in the frequency range from 8 to 35 kHz in the region of their linear development, whereas enhancement of high-frequency disturbances is observed in the region of their nonlinear evolution. It is demonstrated that the growth of disturbances in the high-frequency spectral range ( f > 35 kHz) is caused by the secondary instability.

  2. Methods of statistical analysis, dimensioning and determination of production of electric power for description of the scheme applied to wind in Botucatu/ SP region, Brazil; Metodos de analise estatistica, dimensionamento e determinacao da energia eletrica produtivel para descricao do regime eolico aplicados na regiao de Botocatu-SP

    Energy Technology Data Exchange (ETDEWEB)

    Gabriel Filho, Luis Roberto Almeida [Universidade Estadual Paulista Julio de Mesquita Filho (FCA/UNESP), Botucatu, SP (Brazil). Fac. de Ciencias Agronomicas], email: gabrielfilho@tupa.unesp.br; Cremasco, Camila P. [Faculdade de Tecnologia (FATEC), Presidente Prudente, SP (Brazil); Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Botucatu, SP (Brazil). Dept. de Bioestatistica; Verri, Juliano A. [Universidade Estadual Paulista Julio de Mesquita Filho (FCT/UNESP), Presidente Prudente, SP (Brazil). Dept. de Matematica, Estatistica e Computacao; Viais Neto, Daniel dos S. [Faculdade de Tecnologia (FATEC), Presidente Prudente, SP (Brazil); Universidade Estadual Paulista Julio de Mesquita Filho (FCA/UNESP), Botucatu, SP (Brazil). Fac. de Ciencias Agronomicas; Seraphim, Odivaldo J. [Universidade Estadual Paulista Julio de Mesquita Filho (FCA/UNESP), Botucatu, SP (Brazil). Fac. de Ciencias Agronomicas. Dept. de Engenharia Rural

    2011-07-01

    The wind energy is an abundant source of renewable energy, clean and available almost everywhere. For its use, studies are needed to adequately describe its intensity for statistical methods and design for wind turbines. The objective is to structure the mathematical methods used to conduct a general description of the wind, to establish a description of the wind regime using the parameters described using the Weibull function and the analytical model of power from a wind turbine, as well as applications of these methods show. This work was developed at Rural Empowerment Lab of FCA/UNESP in Botucatu-SP. For the application of methods were utilized measurements of wind speed and direction, between 2004 and 2005, obtained by anemometer RM Young Wind Monitor-Campbell. As a result, they estimated the wind behavior and distribution of wind in the region, with 78 kWh of energy production, relatively low potential to supply a small house. Moreover, this energy could possibly be applied in ambient illumination, power supply for electric fences and irrigation of vegetables. (author)

  3. Remote sensing of the nocturnal boundary layer for wind energy applications

    International Nuclear Information System (INIS)

    The fine temporal and spatial resolution of Doppler lidar observations has been highly effective in the study of wind and turbulence dynamic in the nocturnal boundary layer during Lamar Low-Level Project in 2003. The High-Resolution Doppler Lidar (HRDL), designed and developed at the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL), measures range-resolved profiles of line-of sight (LOS) Doppler velocity and aerosol backscatter with a pulse repetition frequency of 200 Hz, velocity precision about 10 cm s-1, and a very narrow beam width. The majority of the lidar-measured wind speed and variance profiles were derived using a vertical-scan mode and the application of a vertical binning technique. The profile data were used to calculate quantities important for wind energy applications, including turbulence intensity, wind and directional shear through the layer of the turbine rotor. Profiles of all quantities show a strong variation with height. The mean wind fields, the turbulence, and turbulence intensities show a good agreement with sonic anemometer sodar high confidence (high SNR) measurements. The ability of HRDL to provide continuous information about wind and turbulence conditions at the turbine height and above the range of the tower measurements made HRDL as a powerful instrument for studies of the nighttime boundary layer features. Such information is needed as turbine rotors continue to rise higher into the boundary layer

  4. Influence of the mass flow rate of secondary air on the gas/particle flow characteristics in the near-burner region of a double swirl flow burner

    Energy Technology Data Exchange (ETDEWEB)

    Jing, J.P.; Li, Z.Q.; Wang, L.; Chen, Z.C.; Chen, L.Z.; Zhang, F.C. [Harbin Institute of Technology, Harbin (China)

    2011-06-15

    The influence of the mass flow rate of secondary air on the gas/particle flow characteristics of a double swirl flow burner, in the near-burner region, was measured by a three-component particle-dynamics anemometer, in conjunction with a gas/particle two-phase test facility. Velocities, particle volume flux profiles, and normalized particle number concentrations were obtained. The relationship between the gas/particle flows and the combustion characteristics of the burners was discussed. For different mass flow rates of secondary air, annular recirculation zones formed only in the region of r/d=0.3-0.6 at x/d=0.1-0.3. With an increasing mass flow rate of secondary air, the peaks of the root mean square (RMS) axial fluctuating velocities, radial mean velocities, RMS radial fluctuating velocities, and tangential velocities all increased, while the recirculation increased slightly. There was a low particle volume flux in the central zone of the burner. At x/d=0.1-0.7, the profiles of particle volume flux had two peaks in the secondary air flow zone near the wall. With an increasing mass flow rate of secondary air, the peak of particle volume flux in the secondary air flow zone decreased, but the peak of particle volume flux near the wall increased. In section x/d=0.1-0.5, the particle diameter in the central zone of the burner was always less than the particle diameter at other locations.

  5. Large scale structures in a turbulent boundary layer and their imprint on wall shear stress

    Science.gov (United States)

    Pabon, Rommel; Barnard, Casey; Ukeiley, Lawrence; Sheplak, Mark

    2015-11-01

    Experiments were performed on a turbulent boundary layer developing on a flat plate model under zero pressure gradient flow. A MEMS differential capacitive shear stress sensor with a 1 mm × 1 mm floating element was used to capture the fluctuating wall shear stress simultaneously with streamwise velocity measurements from a hot-wire anemometer traversed in the wall normal direction. Near the wall, the peak in the cross correlation corresponds to an organized motion inclined 45° from the wall. In the outer region, the peak diminishes in value, but is still significant at a distance greater than half the boundary layer thickness, and corresponds to a structure inclined 14° from the wall. High coherence between the two signals was found for the low-frequency content, reinforcing the belief that large scale structures have a vital impact on wall shear stress. Thus, estimation of the wall shear stress from the low-frequency velocity signal will be performed, and is expected to be statistically significant in the outer boundary layer. Additionally, conditionally averaged mean velocity profiles will be presented to assess the effects of high and low shear stress. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1315138.

  6. EXPERIMENTAL INVESTIGATION OF TIP CLEARANCE FLOW FOR AN AXIAL FLOW FAN ROTOR

    Institute of Scientific and Technical Information of China (English)

    GUO Qiang; ZHU Xiaocheng; DU Zhaohui

    2006-01-01

    The flow field in the tip region of an axial ventilation fan is investigated with a particle image velocimeter (PIV) system at the design condition. Flow fields with three different tip clearances are surveyed on three different circumferential planes, respectively. The phase-locked average method is used to investigate the generation and the development of a tip leakage vortex. The result from PIV system is compared with that from a particle dynamics anemometer(PDA) system. Both data are in good agreement and the structure of the tip leakage vortex for the rotor is illustrated. The characteristic of a leakage vortex is described in both velocity vectors and vortical contours. The unsteadiness of the leakage vortex and the position of the vortex are surveyed in detail, which interprets the discrepancy between the numerical simulation and PDA experimental results to a certain extent. The center loci of tip leakage vortex at different times and the mean center loci of the leakage vortex are displayed particularly. Finally, the trajectories of the tip leakage vortex by the experimental measurement are compared with predictions from the existing models for high speed and high-pressure compressors and turbines when appropriately interpreted. A good agreement is obtained.

  7. Integration of fluidic jet actuators in composite structures

    Science.gov (United States)

    Schueller, Martin; Lipowski, Mathias; Schirmer, Eckart; Walther, Marco; Otto, Thomas; Geßner, Thomas; Kroll, Lothar

    2015-04-01

    Fluidic Actuated Flow Control (FAFC) has been introduced as a technology that influences the boundary layer by actively blowing air through slots or holes in the aircraft skin or wind turbine rotor blade. Modern wing structures are or will be manufactured using composite materials. In these state of the art systems, AFC actuators are integrated in a hybrid approach. The new idea is to directly integrate the active fluidic elements (such as SJAs and PJAs) and their components in the structure of the airfoil. Consequently, the integration of such fluidic devices must fit the manufacturing process and the material properties of the composite structure. The challenge is to integrate temperature-sensitive active elements and to realize fluidic cavities at the same time. The transducer elements will be provided for the manufacturing steps using roll-to-roll processes. The fluidic parts of the actuators will be manufactured using the MuCell® process that provides on the one hand the defined reproduction of the fluidic structures and, on the other hand, a high light weight index. Based on the first design concept, a demonstrator was developed in order to proof the design approach. The output velocity on the exit was measured using a hot-wire anemometer.

  8. Variation of the drag coefficient and its dependence on sea state

    Science.gov (United States)

    Geernaert, G. L.; Katsaros, K. B.; Richter, K.

    1986-01-01

    Using a Gill propeller vane anemometer and resistance wave wires over a water column depth of 15 m, simultaneous measurements of the momentum flux and sea surface wave spectra were acquired from the Pisa mast, 28 km offshore in the German Bight during autumn and winter 1979. These data were analyzed to identify the relationship between wind stress and surface waves. It was found that wind stresses for wind speeds above 15 m/s were regularly higher than open ocean wind stresses as reported by Smith (1980) and by Large and Pond (1981) for the same mean wind speed. These results, when described in terms of the drag coefficient, compared closely with the results of Sheppard et al. (1972), who collected surface layer statistics over Lough Neagh, Northern Ireland. After modeling the surface waves of the North Sea as a function of wave saturation (or wave age), it became evident that variations in the magnitude of the drag coefficient could be explained by coincident variations in the surface wave energy spectrum. By applying the wave dependent roughness length model described by Kitaigorodskii (1973), the North Sea drag coefficient was predicted to be larger than drag coefficients reported from the open sea.

  9. Measurement of turbine inflow with a 3D windscanner system and a spinnerlidar

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Vignaroli, Andrea; Angelou, Nikolas;

    2015-01-01

    of the SpinnerLidar measurements and the 3 dimensional measurements of the short-range WindScanner system. The measurements were first validated against a sonic anemometer mounted on a mast, at 31.5 m a.g.l. and 48.7 m from the turbine. A good agreement was found between the measurements and the CFD model......UniTTe is a research project coordinated by DTU aiming to develop measurement procedures with nacelle mounted lidars for wind turbine power performance and loads assessment based on the inflow close to the rotor, i.e., within the rotor induction zone. This paper is presenting the first measurement...... campaign of UniTTe. Detailed measurements of the inflow to a 500 kW Nordtank wind turbine, at the DTU Risø Campus, have been taken simultaneously with the DTU short-range WindScanner system and the SpinnerLidar. This is a unique measurement campaign, combining high spatial and temporal resolution...

  10. Modeling and measuring neighborhood scale flow, turbulence, and temperature within Chicago heat island

    Science.gov (United States)

    Conry, Patrick; Sharma, Ashish; Leo, Laura; Fernando, H. J. S.; Potosnak, Mark; Hellmann, Jessica

    2013-11-01

    The modeling of urban heat island (UHI) requires a multi-scale approach as it involves numerous physical phenomena spanning a range of scales. We have performed a comprehensive study of Chicago's UHI via coupling of mesoscale Weather Research and Forecasting (WRF) and micro-scale ENVI-met models. The application of the latter model to a Lincoln Park neighborhood and a parallel observational campaign will be the primary focus of this presentation. ENVI-met employs a computational fluid dynamics model to represent heterogeneity of urban areas, providing fine resolution output of UHI dynamics. In the field campaign, two stations located on rooftops of DePaul University buildings were each equipped with a sonic anemometer and vertical array of thermocouples, allowing investigations of spatial variability of flow, turbulent fluxes, and temperature profiles in an urban roughness sublayer. One of these was located above a rooftop garden and the other above a conventional rooftop. Downscaled output from the WRF model or a set of observational data served as initial and boundary conditions for the ENVI-met model. The model's predicative capabilities were assessed through comparison with another set of observational data, and dynamical causes for the model's poor behavior were identified. Funded by NSF Grant No. 0934592 and ND-ECI.

  11. Field measurements in the wake of a model wind turbine

    Science.gov (United States)

    Pol, Suhas; Taylor, Amelia; Bilbao, Argenis; Doostalab, Ali; Novoa, Santiago; Westergaard, Carsten; Hussain, Fazle; Sheng, Jian; Ren, Beibei; Giesselmann, Michael; Glauser, Mark; Castillo, Luciano

    2014-06-01

    As a first step to study the dynamics of a wind farm' we experimentally explored the flow field behind a single wind turbine of diameter 1.17 m at a hub height of 6.25 m. A 10 m tower upstream of the wind farm characterizes the atmospheric conditions and its influence on the wake evolution. A vertical rake of sonic anemometers is clustered around the hub height on a second tower' 6D downstream of the turbine. We present preliminary observations from a 1- hour block of data recorded in near-neutral atmospheric conditions. The ratio of the standard deviation of power to the inflow velocity is greater than three' revealing adverse effects of inflow turbulence on the power and load fluctuations. Furthermore' the wake defect and Reynolds stress and its gradient are pronounced at 6D. The flux of energy due to Reynolds stresses is similar to that reported in wind tunnel studies. The swirl and mixing produces a constant temperature wake which results in a density jump across the wake interface. Further field measurements will explore the dynamics of a model wind farm' including the effects of atmospheric variability.

  12. Underwater Acoustic Measurements to Estimate Wind and Rainfall in the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Sara Pensieri

    2015-01-01

    Full Text Available Oceanic ambient noise measurements can be analyzed to obtain qualitative and quantitative information about wind and rainfall phenomena over the ocean filling the existing gap of reliable meteorological observations at sea. The Ligurian Sea Acoustic Experiment was designed to collect long-term synergistic observations from a passive acoustic recorder and surface sensors (i.e., buoy mounted rain gauge and anemometer and weather radar to support error analysis of rainfall rate and wind speed quantification techniques developed in past studies. The study period included combination of high and low wind and rainfall episodes and two storm events that caused two floods in the vicinity of La Spezia and in the city of Genoa in 2011. The availability of high resolution in situ meteorological data allows improving data processing technique to detect and especially to provide effective estimates of wind and rainfall at sea. Results show a very good correspondence between estimates provided by passive acoustic recorder algorithm and in situ observations for both rainfall and wind phenomena and demonstrate the potential of using measurements provided by passive acoustic instruments in open sea for early warning of approaching coastal storms, which for the Mediterranean coastal areas constitutes one of the main causes of recurrent floods.

  13. Speed control of synchronous machine by changing duty cycle of DC/DC buck converter

    Directory of Open Access Journals (Sweden)

    Rashid Al Badwawi

    2015-11-01

    Full Text Available Renewable energies such as wind or solar energy are naturally intermittent and can create technical challenges to interconnected grid in particular with high integration amounts. In addition, if wind or solar is used to supply power to a stand-alone system, continuous power supply will be met only if sufficient energy storage system is available. The global penetration of renewable energy in power systems is increasing rapidly especially wind and solar photovoltaic (PV systems. Hybrid wind and solar PV generation system becomes very attractive solution in particular for stand-alone applications. It can provide better reliability since the weakness of one system could be complemented by the strength of the other one. When wind energy is integrated into grid, maximum power point tracking control could be used to optimize the output of wind turbine. In variable speed wind turbine, the turbine speed is varied according to the wind speed. This paper presents a comparison between two methods of controlling the speed of a wind turbine in a microgrid namely; Proportional-Integral (PI control of the tip speed ratio and stored power curve. The PI method provides more controllability, but it requires an anemometer to measure the wind speed. The stored power curve method, however, is easier to implement, but the amount of energy extracted can be less. The system has been modelled using Matlab/Simulink.

  14. Aerodynamic pressure and flow-visualization measurement from a rotating wind turbine blade

    Energy Technology Data Exchange (ETDEWEB)

    Butterfield, C P

    1988-11-01

    Aerodynamic, load, flow-visualization, and inflow measurements have been made on a 10-m, three-bladed, downwind, horizontal-axis wind turbine (HAWT). A video camera mounted on the rotor was used to record nighttime and daytime video images of tufts attached to the low-pressure side of a constant-chord, zero-twist blade. Load measurements were made using strain gages mounted at every 10% of the blade's span. Pressure measurements were made at 80% of the blade's span. Pressure taps were located at 32 chordwise positions, revealing pressure distributions comparable with wind tunnel data. Inflow was measured using a vertical-plane array of eight propvane and five triaxial (U-V-W) prop-type anemometers located 10 m upwind in the predominant wind direction. One objective of this comprehensive research program was to study the effects of blade rotation on aerodynamic behavior below, near, and beyond stall. To this end, flow patterns are presented here that reveal the dynamic and steady behavior of flow conditions on the blade. Pressure distributions are compared to flow patterns and two-dimensional wind tunnel data. Separation boundary locations are shown that change as a function of spanwise location, pitch angle, and wind speed. 6 refs., 23 figs., 1 tab.

  15. Eddy Covariance Measurements of the Sea-Spray Aerosol Flu

    Science.gov (United States)

    Brooks, I. M.; Norris, S. J.; Yelland, M. J.; Pascal, R. W.; Prytherch, J.

    2015-12-01

    Historically, almost all estimates of the sea-spray aerosol source flux have been inferred through various indirect methods. Direct estimates via eddy covariance have been attempted by only a handful of studies, most of which measured only the total number flux, or achieved rather coarse size segregation. Applying eddy covariance to the measurement of sea-spray fluxes is challenging: most instrumentation must be located in a laboratory space requiring long sample lines to an inlet collocated with a sonic anemometer; however, larger particles are easily lost to the walls of the sample line. Marine particle concentrations are generally low, requiring a high sample volume to achieve adequate statistics. The highly hygroscopic nature of sea salt means particles change size rapidly with fluctuations in relative humidity; this introduces an apparent bias in flux measurements if particles are sized at ambient humidity. The Compact Lightweight Aerosol Spectrometer Probe (CLASP) was developed specifically to make high rate measurements of aerosol size distributions for use in eddy covariance measurements, and the instrument and data processing and analysis techniques have been refined over the course of several projects. Here we will review some of the issues and limitations related to making eddy covariance measurements of the sea spray source flux over the open ocean, summarise some key results from the last decade, and present new results from a 3-year long ship-based measurement campaign as part of the WAGES project. Finally we will consider requirements for future progress.

  16. Variable Density Turbulence Tunnel Facility

    CERN Document Server

    Bewley, Gregory P; Sinhuber, Michael; Xu, Haitao; Bodenschatz, Eberhard

    2014-01-01

    The Variable Density Turbulence Tunnel (VDTT) at the Max Planck Institute for Dynamics and Self-Organization in G\\"ottingen, Germany produces very high turbulence levels at moderate flow velocities, low power consumption and adjustable kinematic viscosity. To reach the highest Reynolds number, the tunnel can be filled and pressurized up to 15 bar with the dense gas sulfur hexafluoride (SF$_6$). The Reynolds number can be varied by changing the pressure or flow rate of the gas or by using different non-flammable gases including air. Turbulence is generated at the upstream ends of two measurement sections with grids, and the evolution of this turbulence is observed as it moves down the length of the sections. We describe the instrumentation presently in operation, which consists of the tunnel itself, classical grid turbulence generators, and state-of-the-art nano-fabricated hot-wire anemometers provided by Princeton University [Vallikivi et al. (2011) Exp. Fluids 51, 1521]. We report measurements of the charact...

  17. Technologies to support industrial processes

    International Nuclear Information System (INIS)

    Control and measuring techniques applied to industry have the common aim of increasing safety, reliability and plant availability. The industrial monitoring system needs a lot of sensors, whose signals, elaborated and interpreted, allow one to define the best working condition; moreover control instruments perform a diagnosis related to damages and breakages. The Experimental Engineering Division of ENEA's Thermal Reactor Department has developed sensors and measuring apparatus and has acquired advanced control techniques. All these systems, containing an original software, have been applied to industrial process problems and/or to experimental facilities both to increase reliability and to understand better process physics. Division activities are grouped in four sectors: non-destructive examinations (ultrasonic, eddy current, thermography, holographic interpherometry, penetrant liquids and magnetoscopy); innovative sensors (heated thermocouples, optical fiber sensors); advanced measuring systems (laser technology for fluidodynamic measures, nuclear radiation techniques, infrared measuring, mass spectrometer, hot-film anemometer, chromatographic apparatus); advanced technologies for diagnosis and signal analysis (digital image processing, statistical analysis). (author)

  18. Direct Measurements of the Surface-Atmosphere Exchange of Ammonia

    Science.gov (United States)

    Tevlin, A.; Murphy, J. G.; Wentworth, G.; Gregoire, P.

    2012-12-01

    As the dominant atmospheric base, ammonia plays an important role in the formation and growth of inorganic aerosols. Surface-atmosphere exchange of ammonia has been observed to occur as a bidirectional flux governed by the relative magnitudes of atmospheric gas phase concentration and a temperature-dependent surface compensation point. In order to better characterise the links between gas-particle and surface-atmosphere exchanges, more direct measurements of these exchanges are necessary. Eddy Covariance (EC) can provide the most direct surface-atmosphere flux measurements, but its requirement for high frequency data combined with the reactive nature of ammonia have limited its application for this species. In order to address this lack, an investigation into the instrumental sensitivity and time response requirements for EC ammonia flux measurements was carried out using a Quantum Cascade-Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) capable of measuring ammonia concentration at 10 Hz. Time response was additionally improved through the use of a heated sample line and custom glass inlet, and the system was deployed over a short grass field in rural Ontario. The ammonia measurements were used along with three dimensional sonic anemometer wind speed data to calculate EC ammonia fluxes. When combined with simultaneous measurements of the inorganic composition of gas and particle phases made by Ambient Ion Monitor - Ion Chromatography (AIM-IC), these flux measurements can provide insight into the links between gas-particle and surface-atmosphere exchange.

  19. Effect of a Weir-Type Obstruction with Different Geometric and Hydraulic Conditions on Flow Structure in an Open Channel

    Directory of Open Access Journals (Sweden)

    Shahid Ali

    2014-07-01

    Full Text Available This paper presents results from an experimental study which was conducted at Technical University Delft, Netherland. The research was made on obstructions resembling weirs in an open channel. This weir-type obstruction was a representative of groyne/dike in a natural channel. The experimentation was performed in the laboratory for different values of inflow (25 l/sec and 40 l/sec, weir with and without vegetation and with different leeward slopes of the weir (1:4 and 1:7. The results were obtained for Reynolds normal stresses, longitudinal and vertical velocities. A comparison was made between the results of 1:4 and 1:7 leeward slope ratios. The data was collected with a LDA (Laser Doppler Anemometer. The vegetation was modeled with vertical circular rods placed over the crest of the weir. The blockage area due to this vegetation was 25% of the total area. The velocity data was gathered at around ten locations both at upstream and downstream the weir to get an insight into the flow structure. The results have been presented in the shape of vertical profiles both for velocities as well as Reynolds stresses at different locations of the channel.

  20. EXPERIMENTAL RESEARCH ON AERODYNAMIC PERFORMANCE AND EXIT FLOW FIELD OF LOW PRESSURE AXIAL FLOW FAN WITH CIRCUMFERENTIAL SKEWED BLADES

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this article, the low pressure axial flow fan with circumferential skewed rotor blade, including the radial blade, the forward-skewed blade and the backward-skewed blade, was studied with experimental methods. The aerodynamic performance of the rotors was measured. At the design condition at outlet of the rotors, detailed flow measurements were performed with a five-hole probe and a Hot-Wire Anemometer (HWA). The results show that compared to the radial rotor, the forward-skewed rotor demonstrates a wider Stable Operating Range (SOR), is able to reduce the total pressure loss in the hub region and make main loading of blade accumulating in the mid-span region. There is a wider wake in the upper mid-span region of the forward-skewed rotor. Compared to the radial rotor, in the backward-skewed rotor there is higher total pressure loss near the hub and shroud regions and lower loss in the mid-span region. In addition, the velocity deficit in the wake is lower at mid-span of the backward-skewed rotor than the forward-skewed rotor.

  1. Dispersion mechanics in underground mine ventilation

    Energy Technology Data Exchange (ETDEWEB)

    Standish, P.N.

    1988-01-01

    Application of Dispersion Mechanics to mine ventilation surveys is studied using C/sub 2/H/sub 2/ tracer release and detection on the 2 Drill level at Elura Mine, Cobar, NSW. Preliminary calibration work of the measuring systems in the laboratory and in a large test rig together with the results obtained is reported. It is found that the results in these non-mining systems closely follow the results of Dispersion Mechanics theory for a dispersed plug flow model. For the underground conditions studied the results of tracer studies show that the ventilating air flow is layered or segregated in a tube bundle pattern. These tracer results are reproduced by the results of traditional anemometer readings obtained under the same flow conditions. The results also show that the ventilating air flow under actual underground conditions is characterized by transient behavior which appears to be normal behavior of the ventilating air in underground workings. Application of the results to practice is included.

  2. On the turbulent flow around water turbines placed in an open channel: an experimental study

    Science.gov (United States)

    Sotiropoulos, F.; Chamorro, L. P.; Arndt, R.

    2010-12-01

    A growing interest in water turbines (using tidal, river, marine currents) has been observed during the last few years. Fundamental understanding of the turbulent flow around the water turbines is crucial to predict the potential effects of these structures on the local morphology, water flow and power available in the current, among others. In this study, a series of model water turbines (single and an aligned array) of 50 cm rotor diameter were placed in the main channel of the Saint Anthony Falls Laboratory at the University of Minnesota. The main channel is approx 2.5 m wide, 1.8 m height and 85 m long. Flow around the water turbines were analyzed under subcritical conditions. Turbine hub heights coincided with the channel mid height. A series of acoustic Doppler anemometers (ADV) were used to obtain 3 velocity components of the flow at a rate of 200 Hz. Selected streamwise and spanwise vertical planes were measured to describe the kinematics around the water turbines. Potential interactions with the lateral walls were also addressed. High order statistics (mean velocity, turbulence intensities and Reynolds stresses) as well as two point correlations and spectra were computed to infer fundamental differences and similitude with their counterparts, the wind turbines.

  3. Turbulent heat fluxes by profile and inertial dissipation methods: analysis of the atmospheric surface layer from shipboard measurements during the SOFIA/ASTEX and SEMAPHORE experiments

    Directory of Open Access Journals (Sweden)

    H. Dupuis

    Full Text Available Heat flux estimates obtained using the inertial dissipation method, and the profile method applied to radiosonde soundings, are assessed with emphasis on the parameterization of the roughness lengths for temperature and specific humidity. Results from the inertial dissipation method show a decrease of the temperature and humidity roughness lengths for increasing neutral wind speed, in agreement with previous studies. The sensible heat flux estimates were obtained using the temperature estimated from the speed of sound determined by a sonic anemometer. This method seems very attractive for estimating heat fluxes over the ocean. However allowance must be made in the inertial dissipation method for non-neutral stratification. The SOFIA/ASTEX and SEMAPHORE results show that, in unstable stratification, a term due to the transport terms in the turbulent kinetic energy budget, has to be included in order to determine the friction velocity with better accuracy. Using the profile method with radiosonde data, the roughness length values showed large scatter. A reliable estimate of the temperature roughness length could not be obtained. The humidity roughness length values were compatible with those found using the inertial dissipation method.

  4. Measurements of carbon dioxide and heat fluxes during monsoon-2011 season over rural site of India by eddy covariance technique

    Indian Academy of Sciences (India)

    M N Patil; T Dharmaraj; R T Waghmare; T V Prabha; J R Kulkarni

    2014-02-01

    An increase in carbon dioxide (CO2) concentrations in the atmosphere due to anthropogenic activities is responsible for global warming and hence in recent years, CO2 measurement network has expanded globally. In the monsoon season (July–September) of year 2011, we carried out measurements of CO2 and water vapour (H2O) concentrations along with wind and air temperature over a tropical site in southeast India having rural topography. To collect these observations, the instrumentations used were the sonic anemometer for wind and temperature, and the open path H2O/CO2 infrared gas analyzer for CO2 and H2O concentrations. Using these observations, we explored the diurnal variability of CO2 flux along with sensible and latent heat. The CO2 flux was positive during night-time and negative during daytime and in phase with convective instability. The CO2 flux relationships with the meteorological parameters such as wind speed, temperature and heat fluxes have been analysed. The seasonal (monsoon) half hour mean of CO2 flux which was −3.55 mol m−2 s−1 indicated the experimental site as a CO2 sink region (net seasonal uptake). An increase in CO2 concentrations during weekends was not observed due to unavailability of heavy vehicular traffic.

  5. Computational and experimental study of spin coater air flow

    Science.gov (United States)

    Zhu, Xiaoguang; Liang, Faqiu; Haji-Sheikh, A.; Ghariban, N.

    1998-06-01

    An extensive 2- and 3-D analysis of air flow in a POLARISTM 2200 Microlithography Cluster spin coater was conducted using FLUENTTM Computational Fluid Dynamics (CFD) software. To supplement this analysis, direct measurement of air flow velocity was also performed using a DantecTM Hot Wire Anemometer. Velocity measurements were made along two major planes across the entire flow field in the spin coater at various operating conditions. It was found that the flow velocity at the spin coater inlet is much lower than previously assumed and quite nonuniform. Based on this observation, a pressure boundary condition rather than a velocity boundary condition was used for subsequent CFD analysis. A comparison between calculated results and experimental data shows that the 3D model accurately predicts the air flow field in the spin coater. An added advantage of this approach is that the CFD model can be easily generated from the mechanical design database and used to analyze the effect of design changes. The modeled and measured results show that the flow pattern in the spin bowl is affected by interactions between the spinning wafer, exhaust flow, and the gap between the spin head and surrounding baffle. Different operating conditions such as spin speed, inlet pressure, and exhaust pressure were found to generate substantially different flow patterns. It was also found that backflow of air could be generated under certain conditions.

  6. LIDAR and SODAR Measurements of Wind Speed and Direction in Upland Terrain for Wind Energy Purposes

    Directory of Open Access Journals (Sweden)

    Eamon McKeogh

    2011-08-01

    Full Text Available Detailed knowledge of the wind resource is necessary in the developmental and operational stages of a wind farm site. As wind turbines continue to grow in size, masts for mounting cup anemometers—the accepted standard for resource assessment—have necessarily become much taller, and much more expensive. This limitation has driven the commercialization of two remote sensing (RS tools for the wind energy industry: The LIDAR and the SODAR, Doppler effect instruments using light and sound, respectively. They are ground-based and can work over hundreds of meters, sufficient for the tallest turbines in, or planned for, production. This study compares wind measurements from two commercial RS instruments against an instrumented mast, in upland (semi-complex terrain typical of where many wind farms are now being installed worldwide. With appropriate filtering, regression analyses suggest a good correlation between the RS instruments and mast instruments: The RS instruments generally recorded lower wind speeds than the cup anemometers, with the LIDAR more accurate and the SODAR more precise.

  7. Generation of free convection due to changes of the local circulation system

    Directory of Open Access Journals (Sweden)

    T. Foken

    2009-11-01

    Full Text Available Eddy-covariance and Sodar/RASS experimental measurement data of the COPS (Convective and Orographically-induced Precipitation Study field campaign 2007 are used to investigate the generation of near-ground free convection conditions (FCCs in the Kinzig valley, Black Forest, Southwest Germany. The measured high-quality turbulent flux data revealed that FCCs are initiated near the ground in situations where moderate to high buoyancy fluxes and a simultaneously occurring drop of the wind speed were present. The minimum in wind speed – observable by the Sodar measurements through the whole vertical extension of the valley atmosphere – is the consequence of a thermally-induced valley wind system, which changes its wind direction from down to up-valley winds in the morning hours. Buoyancy then dominates over shear within the production of turbulence kinetic energy near the ground. These situations are detected by the stability parameter (ratio of the measurement height to the Obukhov length when the level of free convection, which starts above the Obukhov length, drops below that of the sonic anemometer. An analysis of the scales of turbulent motions during FCCs using wavelet transform shows the occurrence of large-scale turbulence structures. Regarding the entire COPS measurement period, FCCs in the morning hours occur on about 50% of all days. Enhanced surface fluxes of latent and sensible heat are found on these days.

  8. Measurements of Mass, Momentum and Energy fluxes over an ice/snow covered lake

    Science.gov (United States)

    Salgado, Rui; Potes, Miguel; Mammarella, Ivan; Provenzale, Maria

    2016-04-01

    A better understanding of the interactions between ice and snow and the atmosphere requires improved measurements of energy, mass and momentum fluxes, which continue to have a high degree of uncertainty. In this communication, observed near surface fluxes of momentum, heat and mass (H2O and CO2) over a boreal lake during a freezing period (winter 2015/2016) will be analysed and compared with observations over ice free lakes. Continuously measurements of near surface fluxes of momentum, heat and mass (H2O and CO2) are obtained with a new eddy covariance (EC) system, the Campbell Scientific's IRGASON Integrated Open-Path CO2/H2O Gas Analyzer and 3D Sonic Anemometer, over lake Vanajavesi in Finland. The measurement site is located in a tip of narrow peninsula on the lake (61.133935° N ; 24.259119° E), offering very good conditions for eddy covariance flux measurements. The EC system was installed at 2.5m height above the lake surface and was oriented against the prevailing wind direction in the site.

  9. Atmospheric flow measurements using the PIV and HWA techniques

    Directory of Open Access Journals (Sweden)

    Luciana Bassi Marinho Pires

    2010-08-01

    Full Text Available Alcântara Space Center (ASC is the Brazilian gate to the space where rockets of different sizes are launched. At ASC there is a relative topographical variation, coastal cliff, which modifies the atmospheric boundary layer characteristics and can cause interference for operations of rockets. In the present work, a simplified model (mock-up was studied in a wind tunnel. A scale factor of 1:1000 was used and the atmospheric flow was measured using the hot wire anemometer (HWA and particle image velocimetry (PIV techniques. Using of HWA it was possible to calculate values of average wind speed and fluctuations in a set of points of the section of tests that representing the region of the ASC. Through these measures, other meteorological parameters that represent the atmospheric flow, such as the friction velocity (u*, the roughness length (z0 from the logarithmic profile and the alpha exponent (ɑ of the power law were calculated. With the use of the PIV´s technique, the streamlines and the vorticity fields were obtained and it was noticed that the vorticity generated downwind of the coastal cliff has a strong turbulence (vorticities around 2000 sˉ¹. A rectangular building (simulating the mobile integration tower was inserted at the mock-up and the downwind turbulence was similar to the one generated by the coastal cliff.

  10. Turbulent exchange and segregation of HOx radicals and volatile organic compounds above a deciduous forest

    Directory of Open Access Journals (Sweden)

    A. Knaps

    2009-11-01

    Full Text Available The eddy covariance method was applied for the first time to estimate fluxes of OH and HO2 together with fluxes of isoprene, the sum of methyl vinyl ketone (MVK and methacrolein (MACR and the sum of monoterpenes above a mixed deciduous forest. Highly sensitive measurements of OH and HO2 were performed by laser induced fluorescence (LIF, and biogenic volatile organic compounds (BVOCs were measured by Proton-Transfer-Reaction Mass Spectrometry (PTR-MS at a time resolution of 5 s, each. Wind speed was measured by a sonic anemometer at 10 Hz. The one-day feasibility study was conducted at a total height of 37 m, about 7 m above forest canopy, during the ECHO 2003 intensive field study in July 2003. The daytime measurements yielded statistically significant OH fluxes that indicate downward transport of OH into the direction of the canopy and HO2 fluxes mainly upward out of the canopy. This hints towards a significant chemical sink of OH by reaction with BVOCs and conversion of OH to HO2 at the canopy. In addition, the highly time-resolved trace gas measurements were used to calculate the intensity of segregation of OH and BVOCs, demonstrating that the effective reaction rate of isoprene and OH was slowed down as much as 15% due to inhomogeneous mixing of the reactants. The paper describes the applied methods and provides a detailed analysis of possible systematic errors of the covariance products.

  11. Using the morphology and magnetic fields of tailed radio galaxies as environmental probes

    CERN Document Server

    Johnston-Hollitt, M; Pratley, L

    2014-01-01

    Bent-tailed (BT) radio sources have long been known to trace over densities in the Universe up to z ~ 1 and there is increasing evidence this association persists out to redshifts of 2. The morphology of the jets in BT galaxies is primarily a function of the environment that they have resided in and so BTs provide invaluable clues as to their local conditions. Thus, not only can samples of BT galaxies be used as signposts of large-scale structure, but are also valuable for obtaining a statistical measurement of properties of the intra-cluster medium including the presence of cluster accretion shocks & winds, and as historical anemometers, preserving the dynamical history of their surroundings in their jets. We discuss the use of BTs to unveil large-scale structure and provide an example in which a BT was used to unlock the dynamical history of its host cluster. In addition to their use as density and dynamical indicators, BTs are useful probes of the magnetic field on their environment on scales which are...

  12. Profiles of Wind and Turbulence in the Coastal Atmospheric Boundary Layer of Lake Erie

    KAUST Repository

    Wang, H

    2014-06-16

    Prediction of wind resource in coastal zones is difficult due to the complexity of flow in the coastal atmospheric boundary layer (CABL). A three week campaign was conducted over Lake Erie in May 2013 to investigate wind characteristics and improve model parameterizations in the CABL. Vertical profiles of wind speed up to 200 m were measured onshore and offshore by lidar wind profilers, and horizontal gradients of wind speed by a 3-D scanning lidar. Turbulence data were collected from sonic anemometers deployed onshore and offshore. Numerical simulations were conducted with the Weather Research Forecasting (WRF) model with 2 nested domains down to a resolution of 1-km over the lake. Initial data analyses presented in this paper investigate complex flow patterns across the coast. Acceleration was observed up to 200 m above the surface for flow coming from the land to the water. However, by 7 km off the coast the wind field had not yet reached equilibrium with the new surface (water) conditions. The surface turbulence parameters over the water derived from the sonic data could not predict wind profiles observed by the ZephlR lidar located offshore. Horizontal wind speed gradients near the coast show the influence of atmospheric stability on flow dynamics. Wind profiles retrieved from the 3-D scanning lidar show evidence of nocturnal low level jets (LLJs). The WRF model was able to capture the occurrence of LLJ events, but its performance varied in predicting their intensity, duration, and the location of the jet core.

  13. Investigation of scaling characteristics for defining design environments due to transient ground winds and near-field, nonlinear acoustic fields

    Science.gov (United States)

    Shih, C. C.

    1973-01-01

    In order to establish a foundation of scaling laws for the highly nonlinear waves associated with the launch vehicle, the basic knowledge of the relationships among the paramaters pertinent to the energy dissipation process associated with the propagation of nonlinear pressure waves in thermoviscous media is required. The problem of interest is to experimentally investigate the temporal and spacial velocity profiles of fluid flow in a 3-inch open-end pipe of various lengths, produced by the propagation of nonlinear pressure waves for various diaphragm burst pressures of a pressure wave generator. As a result, temporal and spacial characteristics of wave propagation for a parametric set of nonlinear pressure waves in the pipe containing air under atmospheric conditions were determined. Velocity measurements at five sections along the pipes of up to 210 ft. in length were made with hot-film anemometers for five pressure waves produced by a piston. The piston was derived with diaphragm burst pressures at 20, 40, 60, 80 and 100 psi in the driver chamber of the pressure wave generator.

  14. Santa Ana Winds of Southern California: Their Climatology and Variability Spanning 6.5 Decades from Regional Dynamical Modelling

    Science.gov (United States)

    Guzman-Morales, J.; Gershunov, A.

    2015-12-01

    Santa Ana Winds (SAWs) are an integral feature of the regional climate of Southern California/Northern Baja California region. In spite of their tremendous episodic impacts on the health, economy and mood of the region, climate-scale behavior of SAW is poorly understood. In the present work, we identify SAWs in mesoscale dynamical downscaling of a global reanalysis product and construct an hourly SAW catalogue spanning 65 years. We describe the long-term SAW climatology at relevant time-space resolutions, i.e, we developed local and regional SAW indices and analyse their variability on hourly, daily, annual, and multi-decadal timescales. Local and regional SAW indices are validated with available anemometer observations. Characteristic behaviors are revealed, e.g. the SAW intensity-duration relationship. At interdecadal time scales, we find that seasonal SAW activity is sensitive to prominent large-scale low-frequency modes of climate variability rooted in the tropical and north Pacific ocean-atmosphere system that are also known to affect the hydroclimate of this region. Lastly, we do not find any long-term trend in SAW frequency and intensity as previously reported. Instead, we identify a significant long-term trend in SAW behavior whereby contribution of extreme SAW events to total seasonal SAW activity has been increasing at the expense of moderate events. These findings motivate further investigation on SAW evolution in future climate and its impact on wildfires.

  15. Experimental and numerical investigation of flow around a sphere with dimples for various flow regimes

    Directory of Open Access Journals (Sweden)

    Bogdanović-Jovanović Jasmina B.

    2012-01-01

    Full Text Available Flow over a sphere is a typical bluff-body flow with many engineering applications. However, it has not been studied in depth, as compared to flow over a circular cylinder, because of the difficulties in the experimental set-up as well as in the computational approach for studying flow over a sphere. The main challenges are to understand the flow hydrodynamics and to clarify the flow pattern around a dimpled sphere because the flow pattern complying with the dimple structure on its surface is very complicated. In this paper experimental and numerical investigations of the fluid flow around a sphere with dimples, are represented. The sphere with dimples is placed in a quadratic cross section duct (measuring section and numerical simulation results are obtained by solving RANS equations. Furthermore, experimental measurements are carried out using a Laser-Doppler Anemometer (LDA. Experimental and numerical results of flow velocity fields were compared for three different flow regimes (Re=8×103, 2×104 and 4×104. Numerical investigation was performed for wide range of Reynolds numbers (Re=270%106. The final purpose of this paper is experimental and numerical determination of velocity field, separation point, pressure and drag coefficient, the length of reverse flow region in the wake and RANS turbulent model which gives the best results for engineering practice.

  16. Cyclonic Separation Technology: Researches and Developments

    Institute of Scientific and Technical Information of China (English)

    汪华林; 张艳红; 王剑刚; 刘洪来

    2012-01-01

    Centered on thetechniques and industrial applications of the reinforced cyclonic separation process, its principles and mechanism for separation ot ions, molecules and their aggregates using polyalsperse aroplets are discussed generally; the characteristics and influential factors of fish-hook phenomenon of the grade efficiency curve in cyclonic separation for both gas and liquid are analyzed; and the influence of shear force on particle be- havior (or that of particle swarm) is also summarized. A novel idea for cyclonic separation is presented here: enhancing the cyclonic seoaration process of ions, molecules and their aggregates with monodisperse microspheres and their surface grafting, rearranging the distribution of particles by size using centrifugal field, reinforcing the cyclonic separation performance with orderly arranged particle swarm. Also the investigation of the shortcut flow, recirculation flow, the asymmetric structure and non-linear characteristics of the cyclonic flow field with a com-bined method of Volumetric 3-component Velocimetry (V3V) and Phase-Doppler Particle Anemometer (PDPA) are elaborated. It is recommended to develop new systems for the separation of heterogeneous phases with cyclonic technology, in accordance with the capture and reuse of CO2, methanol to olefins (MTO) process, coal transfer, andthe exploitation of oil shale.

  17. Particle-turbulence interaction; Partikkelitihentymien ja turbulenssin vuorovaikutus

    Energy Technology Data Exchange (ETDEWEB)

    Karvinen, R.; Savolainen, K. [Tampere Univ. of Technology (Finland). Energy and Process Technology

    1997-10-01

    In this work the interaction between solid particles and turbulence of the carrier fluid in two-phase flow is studied. The aim of the study is to find out prediction methods for the interaction of particles and fluid turbulence. Accurate measured results are needed in order to develop numerical simulations. There are very few good experimental data sets concerning the particulate matter and its effect on the gas turbulence. Turbulence of the gas phase in a vertical, dilute gas-particle pipe flow has been measured with the laser-Doppler anemometer in Tampere University of Technology. Special attention was paid to different components of the fluctuating velocity. Numerical simulations were done with the Phoenics-code in which the models of two-phase flows suggested in the literature were implemented. It has been observed that the particulate phase increases the rate of anisotropy of the fluid turbulence. It seems to be so that small rigid particles increase the intensity of the axial and decrease the intensity of the radial component in a vertical pipe flow. The change of the total kinetic energy of turbulence obviously depends on the particle size. In the case of 150 ,{mu} spherical glass particles flowing upwards with air, it seems to be slightly positive near the centerline of the pipe. This observation, i.e. the particles decrease turbulence in the radial direction, is very important; because mass and heat transfer in flows is strongly dependent on the component of fluctuating velocity perpendicular to the main flow direction

  18. Coherent and random apparent stresses in periodically unsteady flows

    Science.gov (United States)

    Kehoe, Anthony Byrd

    1990-08-01

    The transitional flow field downstream of a smooth, symmetrically constricted Sylgard pipe was measured with a two color, two component Laser Doppler Anemometer for both pulsatile and steady flows. Vibrations in the flow system were induced with an exciter/shaker and were monitored with an accelerator. The vibration has little effect on the value of the maximum axial and radial turbulence intensities. A frequency domain signal processing technique to separate the disturbance velocity into coherent and random components was modified to guarantee that the sum of the decomposed velocity components equaled the original disturbance velocity. Results of the velocity separation demonstrated that the velocity disturbances prior to turbulent transition consisted almost entirely of coherent velocity fluctuations. The maximum apparent shear stress was found to occur just after the turbulent transition and consisted almost entirely of the random component. The data suggest that if the absolute magnitude of the apparent stress is the determining factor in red blood cell destruction, then the coherent apparent stress is not a significant destruction mechanism. However, the exact mechanism in hemolysis are not identified.

  19. 水垫塘的水流特征和消能规律研究%Study on flow characteristics in water cushion pool and mechanism of energy dissipation

    Institute of Scientific and Technical Information of China (English)

    吕阳泉; 李永祥; 冬俊瑞

    2001-01-01

    结合乌江构皮滩水利枢纽工程消能问题研究,用热膜流速仪在比尺为1∶380的精细模型上量测了拱坝挑跌流在水垫塘内的流速场,并由试验成果分析了淹没射流在水垫塘内的消能过程,计算了消能率。研究表明,要想提高水垫塘的消能效率,就必须设法增大强紊动剪切层区的范围。%Through study on energy dissipation of Goupitang Project on the Wu-jiang River,the velocity field in the water cushion pool downstream ski-jump or drop was measured by hot-film anemometers on a fine model with scale 1∶380. The energy dissipation process in the water cushion pool was analysed using experimental results,and the rate of energy dissipation was calculated.The study showed that if a project requires to raise its rate of energy dissipation,the strong turbulent shear flow region must be extended.

  20. DIREÇÃO E VELOCIDADE DO VENTO EM UMA FLORESTA DE TRANSIÇÃO AMAZÔNIA-CERRADO NO NORTE DE MATO GROSSO, BRASIL

    Directory of Open Access Journals (Sweden)

    Stéfano Teixeira Silva

    2011-08-01

    Full Text Available The objective of the work was to determine the predominant wind direction and speed in a region of rain Amazon-Savanna transition forest, located approximately 50 km from the city of Sinop, in northern Mato Grosso, Brazil.The daily directions wind and speeds were collected by a three-dimensional sonic anemometer-thermometer,installed in a tower at a height of 12 m above the forest canopy. The predominant wind direction was characterizedby a frequency analysis of the daily observations, for each one of the stations and months of the year. In mostof the year there is predominance of south-southeast and south-southwest winds. It was observed that therewas no direct relation between the time and the wind direction, and the same showing a seasonal variation,there is a direct relation just with the wind speed. In the dry season showed that the predominant winddirection was south-southwest. Already in dry-wet and wet seasons the winds flowed in all directions.