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. Field calibration of cup anemometers

    DEFF Research Database (Denmark)

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

    2001-01-01

    An outdoor calibration facility for cup anemometers, where the signals from 10 anemometers of which at least one is a reference can be can be recorded simultaneously, has been established. The results are discussed with special emphasis on the statisticalsignificance of the calibration expressions...

  4. ACCUWIND - Methods for classification of cup anemometers

    OpenAIRE

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

    2006-01-01

    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 EuropeanCLASSCUP 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 imple...

  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. ACCUWIND - Methods for classification of cup anemometers

    DEFF Research Database (Denmark)

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

    2006-01-01

    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 implementedin 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 categoryclassification is connected to reasonably flat sites, and another Class B category is connected to complex terrain, General classification indices are the...... theclassification process in order to assess the robustness of methods. The results of the analysis are presented as classification indices, which are compared and discussed....

  9. Flow distortion on boom mounted cup anemometers

    DEFF Research Database (Denmark)

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

    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...

  10. 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.

  11. 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.

  12. 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)

  13. 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...

  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. 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...... increasing rotation rate recorded. It is concluded that the rapid increase in rotation rate makes the method very inaccurate. The second method consists of an analysis of turbulent, atmospheric of wind speed asmeasured by the cup anemometer and a fast-responding sonic anemometer with a spatial eddy...... 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...

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

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels

    2003-01-01

    objectives to quantify the errors associated with the use of cup anemometers, and to determine the requirements for an optimum design of a cup anemometer, and to develop a classification system forquantification of systematic errors of cup anemometers. The present report describes this proposed...... classification system. A classification method for cup anemometers has been developed, which proposes general external operational ranges to be used. Anormal category range connected to ideal sites of the IEC power performance standard was made, and another extended category range for complex terrain was...... proposed. General classification indices were proposed for all types of cup anemometers. As a resultof the classification, the cup anemometer will be assigned to a certain class: 0.5, 1, 2, 3 or 5 with corresponding intrinsic errors (%) as a vector instrument (3D) or as a horizontal instrument (2D). The...

  17. 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...

  18. Two ways factorial design for round robin test of anemometers

    International Nuclear Information System (INIS)

    This work presents a way to carry out an inter-comparison between different cup anemometers that are tested in different wind tunnels. The method applied is known as Factorial design and allows determining the influence in the test of different factors in this case the anemometer itself and the wind tunnel where it is tested. (Author) 4 refs

  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. 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.

  1. 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....

  2. 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

  3. Calibration of a spinner anemometer for yaw misalignment measurements

    OpenAIRE

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

    2015-01-01

    The spinner anemometer is an instrument for yaw misalignment measurements without the drawbacks of instruments mounted on the nacelle top. The spinner anemometer uses a non-linear conversion algorithm that converts the measured wind speeds by three sonic sensors on the spinner to horizontal wind speed, yaw misalignment and flow inclination angle. The conversion algorithm utilizes two constants that are specific to the spinner and blade root design and to the mounting positions of the sonic se...

  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. Optimization of Wind Turbine Operation by Use of Spinner Anemometer

    DEFF Research Database (Denmark)

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

    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 showed that average wind speeds compared well within about 1%. The power of the 3,6MW wind turbine was analysed for varying yaw error but though 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 and...... 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°. The average flow inclination angle was about 1°. The spinner anemometer measurements were...

  6. 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....

  7. 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....

  8. 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...

  9. 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)

  10. 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...

  11. 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 on the ...

  12. 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.

  13. 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)

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

    OpenAIRE

    David Siegel; Jay Lee

    2011-01-01

    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 differ...

  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. 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)

  17. Effects of turbulence and flow inclination on the performance of cup anemometers in the field

    DEFF Research Database (Denmark)

    Papadopoulos, K.H.; Stefantos, N.C.; Schmidt Paulsen, U.; Morfiadakis, E.

    2001-01-01

    Four commercial and one research cup anemometers were comparatively tested in a complex terrain site to quantify the effects of turbulence and flow inclination on the wind speed measurements. The difference of the mean wind speed reading between the anemometers was as much as 2% for wind directio...

  18. Comparing the sphere anemometer to standard sensors for 2D wind measurements

    Science.gov (United States)

    Heisselmann, Hendrik; Hoelling, Michael; Peinke, Joachim

    2011-11-01

    The cup anemometers commonly used for wind energy applications are fairly robust, but suffer from several drawbacks like their limited temporal resolution, a systematic overestimation of the wind speed in turbulent flows and the inability to measure the wind direction. While sonic anemometers can measure the wind vector at a higher temporal resolution, they are more fragile and significantly more expensive. Therefore, we propose the sphere anemometer as a robust and highly-resolving alternative to standard anemometers. Designed without wearing parts, the sphere anemometer provides simultaneous wind speed and direction measurements as needed for wind turbine operation especially under challenging conditions such as offshore installation. In our contribution, we introduce the setup of the sphere anemometer which is based on the velocity-dependent deflection of a flexible tube with a sphere mounted atop. The deflection is measured in two dimensions using a light pointer, which allows for the simultaneous determination of wind speed and direction via calibration. Experimental results from wind tunnel measurements with sonic anemometer and sphere anemometer are presented, as well as first comparative measurements from the operation on the nacelle of a near-shore wind turbine.

  19. Particle size and velocity measurement in flames by laser anemometer

    Science.gov (United States)

    Chigier, N. A.; Ungut, A.; Yule, A. J.

    1979-01-01

    Simultaneous droplet size and velocity measurements by a particle counting Laser Doppler Anemometer (LDA) in kerosene fuel sprays under burning and non-burning conditions are presented. Particle sizes are derived from pulse height analysis of the mean LDA signals and velocities are simultaneously determined by measuring Doppler shift frequencies. The measurements show that droplet velocity is a function of droplet diameter for burning and non-burning conditions, and spatially averaged size distributions are derived from velocity data. A comparison of results obtained under burning and non-burning conditions show changes in size distribution due to preferential vaporization of small droplets, acceleration due to thermal expansion of gases, and corresponding changes in droplet momentum.

  20. 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.

  1. 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.

  2. 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.

  3. Zoom lens compensator for a cylindrical window in laser anemometer uses

    Science.gov (United States)

    Wernet, Mark P.; Seasholtz, Richard G.

    1987-01-01

    In laser anemometer systems, the flow fields under study are typically enclosed by a window. Aberration of a flat window can be corrected by a shift of the object distance. A zooming correction lens elimates the astigmatism caused by a thick cylindrical window and yields diffraction-limited performance for a monochromatic laser anemometer system. The effects of residual anamorphic distortion are discussed, and procedures for correcting these effects are presented.

  4. 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...

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

    OpenAIRE

    Santiago Pindado; Alfredo Sanz; Alain Wery

    2012-01-01

    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 ...

  6. The cup anemometer, a fundamental meteorological instrument for the wind energy industry

    OpenAIRE

    Pindado Carrion, Santiago; Cubas Cano, Javier; Sorribes Palmer, Felix

    2014-01-01

    The cup anemometer has been used widely by the wind energy industry since its early beginning, covering two fundamental aspects: wind mill performance control and wind energy production forecast. Furthermore, despite modern technological advances such as LIDAR and SODAR, the cup anemometer remains clearly the most used instrument by the wind energy industry. Together with the major advantages of this instrument (precision, robustness), some issues must be taken into account by scientists a...

  7. 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.

  8. 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)

  9. 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....

  10. 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.

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

    DEFF Research Database (Denmark)

    Demurtas, Giorgio; Friis Pedersen, Troels

    misalignment (measured by the spinner anemometer under calibration) are recorded. The tangent of the two angles is plotted in a scatter plot. A linear fitting is made, and the slope coefficient is the correction factor Fα. The method applied to a Nordtank 500kW wind turbine erected at the Risø test site is...

  12. 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...

  13. 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%...

  14. 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 is...... 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....

  15. 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. In a...... pilot study in Lysefjord, Norway, a pulsed long-range lidar and two short-range WindScanners were installed at the bridge site, together with a long-term monitoring system based on sonic anemometers. The deployment of the two types of lidars is described in more details and the complementary value of...... the data from all three types of the instruments is illustrated. The emphasis is on the lidars’ potential to map the wind conditions along the whole span of a bridge in a complex terrain, as opposed to ”point” measurements achievable by sonic anemometers. The challenging balance between the spatial...

  16. 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.

  17. Four spot laser anemometer and optical access techniques for turbine applications

    International Nuclear Information System (INIS)

    A time-of-flight anemometer (TOFA) system, utilizing a spatial lead-lag filter for bipolar pulse generation was constructed and tested. This system, called a Four Spot Laser Anemometer, was specifically designed for use in high speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe type anemometer. The tightly focused spots used in the Four Spot yield excellent flare light rejection capabilities. Good results were obtained to 75 microns normal to a surface, with a f/2.5 collecting lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence

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

    DEFF Research Database (Denmark)

    Mann, Jakob; Cariou, Jean-Pierre; Courtney, Michael; Parmentier, Remy; Mikkelsen, Torben; Wagner, Rozenn; Lindelöw, Per Jonas Petter; Sjöholm, Mikael; Enevoldsen, Karen

    2009-01-01

    The goals are to compare lidar volume averaged wind measurement with point measurement reference sensors and to demonstrate the feasibility of performing 3D turbulence measurements with lidars. For that purpose three pulsed lidars were used in staring mode, placed so that their beams crossed close...... to a 3D sonic anemometer mounted at 78 m above the ground. The results show generally very good correlation between the lidar and the sonic times series, except that the variance of the velocity measured by the lidar is attenuated due to spatial filtering. The amount of attenuation can however be...

  19. Investigation of measuring wind speed using anemometers on a measuring mast

    Energy Technology Data Exchange (ETDEWEB)

    Gjerding, J.B.; Dyre Jespersen, K.; Langhans, F.

    1998-01-01

    The report describes a project carried out by Tripod Wind Energy from September 1996 to September 1997 comprising wind measurements and data analyses. The aim of the project was to investigate the possible influence of the anemometer position on the measuring mast on the measured wind speed. The investigation is of special interest in connection with wind turbines, where the result from wind speed measurements forms the basis of the majority of economic calculations. The report therefore in particular describes the conditions in connection with the measuring wind turbine power curves. The conclusion of the work is that even small variations of the wind speed measuring set up have a significant effect on the measured wind speed. An influence which in turn has an impact of the calculated energy output of a wind turbine and/or wind farm. Varying measurements set-ups are acceptable within the frames of existing and acknowledged codes and recommendations. The work indicates that the frames are too wide leading to ambiguous wind speed measurements. In order to eliminate this ambiguousness it is recommended that it is carefully considered to revise the mentioned documents, particularly with respect to specification of anemometer positioning. The work presented had been funded by The Danish Energy Agency. (au)

  20. 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.

  1. 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...

  2. 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)

  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. A directional cylindrical anemometer with four sets of differential pressure sensors

    Science.gov (United States)

    Liu, C.; Du, L.; Zhao, Z.

    2016-03-01

    This paper presents a solid-state directional anemometer for simultaneously measuring the speed and direction of a wind in a plane in a speed range 1-40 m/s. This instrument has a cylindrical shape and works by detecting the pressure differences across diameters of the cylinder when exposed to wind. By analyzing our experimental data in a Reynolds number regime 1.7 × 103-7 × 104, we figure out the relationship between the pressure difference distribution and the wind velocity. We propose a novel and simple solution based on the relationship and design an anemometer which composes of a circular cylinder with four sets of differential pressure sensors, tubes connecting these sensors with the cylinder's surface, and corresponding circuits. In absence of moving parts, this instrument is small and immune of friction. It has simple internal structures, and the fragile sensing elements are well protected. Prototypes have been fabricated to estimate performance of proposed approach. The power consumption of the prototype is less than 0.5 W, and the sample rate is up to 31 Hz. The test results in a wind tunnel indicate that the maximum relative speed measuring error is 5% and the direction error is no more than 5° in a speed range 2-40 m/s. In theory, it is capable of measuring wind up to 60 m/s. When the air stream goes slower than 2 m/s, the measuring errors of directions are slightly greater, and the performance of speed measuring degrades but remains in an acceptable range of ±0.2 m/s.

  5. 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.

  6. Assessment of Performances of Ultrasonic Anemometers as One Step Ahead in Wind Measurements of Energy Production of a Wind Turbine

    OpenAIRE

    Cuerva Tejero, Alvaro; Bezdenejnykh, N.A.; Perales Perales, José Manuel; Sanz Andres, Angel Pedro

    1998-01-01

    The most important uncertainties in the tests oriented to estimate the Annual Energy Production of a type of wind turbine, come from the wind measurements, in the determination of the power curve of the machine. The existing Standards indicate that wind measurements shall be taken by cup anemometers. These sensors are not able to measure some wind properties that affect power performance and that arc proposed to be included in the future Standard's revision, by recent research projects (mainl...

  7. 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...

  8. A novel design and analysis of a MEMS ceramic hot-wire anemometer for high temperature applications

    International Nuclear Information System (INIS)

    This paper attempts to prove the feasibility of high temperature MEMS hot-wire anemometer for gas turbine environment. No such sensor exists at present. Based on the latest improvement in a new type of Polymer-Derived Ceramic (PDC) material, the authors present a Novel design, structural and thermal analysis of MEMS hot-wire anemometer (HWA) based on PDC material, and show that such a sensor is indeed feasible. This MEMS Sensor is microfabricated by using three types of PDC materials such as SiAlCN, SiCN (lightly doped) and SiCN (heavily doped) for sensing element (hot-wire), support prongs and connecting leads respectively. This novel hot wire anemometer can perform better than a conventional HWA in which the hot wire is made of tungsten or platinum-iridium. This type of PDC-HWA can be used in harsh environment due to its high temperature resistance, tensile strength and resistance to oxidation. This HWA is fabricated using microstereolithography as a novel microfabrication technique to manufacture the proposed MEMS Sensor

  9. A novel design and analysis of a MEMS ceramic hot-wire anemometer for high temperature applications

    Science.gov (United States)

    Nagaiah, N. R.; Sleiti, A. K.; Rodriguez, S.; Kapat, J. S.; An, L.; Chow, L.

    2006-04-01

    This paper attempts to prove the feasibility of high temperature MEMS hot-wire anemometer for gas turbine environment. No such sensor exists at present. Based on the latest improvement in a new type of Polymer-Derived Ceramic (PDC) material, the authors present a Novel design, structural and thermal analysis of MEMS hot-wire anemometer (HWA) based on PDC material, and show that such a sensor is indeed feasible. This MEMS Sensor is microfabricated by using three types of PDC materials such as SiAlCN, SiCN (lightly doped) and SiCN (heavily doped) for sensing element (hot-wire), support prongs and connecting leads respectively. This novel hot wire anemometer can perform better than a conventional HWA in which the hot wire is made of tungsten or platinum-iridium. This type of PDC-HWA can be used in harsh environment due to its high temperature resistance, tensile strength and resistance to oxidation. This HWA is fabricated using microstereolithography as a novel microfabrication technique to manufacture the proposed MEMS Sensor.

  10. Fast-response fiber-optic anemometer with temperature self-compensation.

    Science.gov (United States)

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

    2015-05-18

    We report a novel fiber-optic anemometer with self-temperature compensation capability based on a Fabry-Pérot interferometer (FPI) formed by a thin silicon film attached to the end face of a single-mode fiber. Guided in the fiber are a visible laser beam from a 635 nm diode laser used to heat the FPI and a white-light in the infrared wavelength range as the signal light to interrogate the optical length of the FPI. Cooling effects on the heated sensor head by wind is converted to a wavelength blueshift of the reflection spectral fringes of the FPI. Self-temperature-compensated measurement of wind speed is achieved by recording the difference in fringe wavelengths when the heating laser is turned on and then off. Large thermal-optic coefficient and thermal expansion coefficient of silicon render a high sensitivity that can also be easily tuned by altering the heating laser power. Furthermore, the large thermal diffusivity and the small mass of the thin silicon film endow a fast sensor response. PMID:26074604

  11. 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)

  12. 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.

  13. Hot-film anemometer measurements in adiabatic two-phase flow through a vertical duct

    International Nuclear Information System (INIS)

    A hot-film anemometer (HFA) probe was used to obtain local measurements of void fraction and bubble frequency in a vertically oriented, high aspect ratio duct containing R-134a under selected adiabatic two-phase flow conditions. Data were obtained along a narrow dimension scan over the range 0.03 ≤ bar Z ≤ 0.80, where bar Z is the distance from the wall normalized with the duct spacing dimension. The void fraction profiles displayed large gradients in the near-wall regions and broad maxima near the duct centerline. The trends in the bubble frequency data generally follow those for the local void fraction data. However, the relatively large number of bubbles at higher pressure implies a larger magnitude of the interfacial area concentration, for the same cross-sectional average void fraction. For the two annular flow conditions tested, analysis of the HFA output voltage signal enabled identification of three distinct regions of the flow field; liquid film with dispersed bubbles, interfacial waves, and continuous vapor with dispersed droplets

  14. 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.

  15. 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

    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.......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...

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Study of in situ calibration performance of co-located multi-sensor hot-film and sonic anemometers using a ‘virtual probe’ algorithm

    International Nuclear Information System (INIS)

    The performance of an in situ calibration technique, implementing neural network (NN) algorithms for co-located multi-wire hot-film and sonic anemometers, is studied. The NN-based calibration technique, proposed by Kit et al (2010 J. Atmos. Ocean. Technol. 27 23–41), allows performing direct measurement of fine scales in turbulent air flow, and offers a robust tool for measurements of micro-scale properties in atmospheric flows. Accuracy of the suggested calibration technique is examined in view of isotropic and anisotropic flow fields of various turbulence intensity (TI). Anisotropic velocity datasets of various TIs were generated using a ‘virtual probe’ simulating hot-film anemometer response to the sensed flow, while a kinematic model of homogeneous isotropic turbulent flow was implemented to generate isotropic flow datasets. NN calibration performance is examined by quantitative comparison between the original and reconstructed velocity components, using a specially constructed norm and by visual comparison of original and reconstructed time series. The examined NN calibration technique performance is shown to be of reasonable accuracy for all TI velocity fields examined, while a notable drop in accuracy is detected with the increase in TI. The reconstruction of isotropic velocity fields, using the NN algorithm for calibration, is apparently of slightly lower accuracy than in the case of anisotropic flows. The results are discussed in view of possible implementation of the suggested technique in direct field measurements of atmospheric turbulence fine scales. (paper)

  3. 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.

  4. 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)

  5. 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.

  6. 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.

  7. 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.

  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. Calibration Experiments with a DISA Hot-Wire Anemometer

    International Nuclear Information System (INIS)

    From Collis' law and the direction sensitivity relation proposed by Hinze it is possible to derive the following relation between the voltage over the wire, the velocity and the angle of incidence of the flow: (V2 - V20)/R(R-Ra) = b(ρu)c (sin2ψ + k2cos2ψ)c/2. T values of the exponent c and the direction sensitivity coefficient k were determined experimentally in the range 20 2. It was found that, if V0 is the voltage measured with no net flow past the wire, c and k are decreasing with increasing values of ρu. In order to check these calibration experiments, shear stress and turbulence measurements were made in a circular channel. For this geometry the shear stress distribution can be estimated theoretically and several earlier experiments can be used for comparisons. These experiments were made at Reynolds numbers 3 x 105 - 106, Mach numbers 0.1 - 0.3 and a channel length of 61 diameters. Excellent agreement with the theoretical shear stress distribution (corrected for compressibility effects) and earlier data for the axial and radial turbulence components was obtained when the results of the calibration experiments were used for the evaluation of these measurements Evaluation with a constant value of c or with k2 equal to zero (as often recommended) gave less good agreement

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

    OpenAIRE

    Fischer, Andreas

    2012-01-01

    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 intensit...

  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. 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...

  17. 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.

  18. 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.

  19. 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.

  20. Wind measurements for wind energy applications. A review

    OpenAIRE

    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 turbulent nature of the wind, but these errors can be neglected in many applications if a well-designed, fast-responding anemometer is used. The response characteristics of sonic anemometers are fair...

  1. 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...

  2. 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 t...

  3. Wind measurements for wind energy applications. A review

    DEFF Research Database (Denmark)

    Mortensen, N.G.

    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...

  4. ACCUWIND - Accurate wind speed measurements in wind energy - Summary report

    DEFF Research Database (Denmark)

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

    2006-01-01

    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. Thebasis for setting up such requirements of cup anemometers is two EU projects SITEPARIDEN and......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 performancemeasurements for certification and...... 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 improvedinstruments....

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

    DEFF Research Database (Denmark)

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

    2010-01-01

    -sets. These features of the investigated sonic anemometers make them unsuitable for measuring vertical velocities over highly turbulent forested terrain. By comparing the sonic anemometer results to that of a conically scanning Doppler lidar (Dellwik et al., 2010b), sonic anemometer accuracy for measuring...... mean flow tilt angles was estimated to between 2° and 3°. Use of planar fit algorithms, where the mean vertical velocity is calculated as the difference between the neutral and non-neutral flow, does not solve this problem of low accuracy and is not recommended. Because of the large uncertainties...... caused by flow distortion and vertical alignment, it was only possible to a limited extent to relate sonic anemometer flow tilt angles to upwind forest edges, but the results by the lidar indicated that an internal boundary layer affect flow tilt angles at 21m above the forest. This is in accordance with...

  6. Power curve measurement with a nacelle mounted lidar

    DEFF Research Database (Denmark)

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

    2014-01-01

    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 the...... wind measured by the mast. Finally, the lidar is never in the wake of the turbine under test contrary to the cup anemometer; therefore, the wind sector usable for power curve measurement was larger than the sector for which the cup anemometer was not disturbed by any obstacle. The power curve obtained...

  7. 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

  8. 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 ...

  9. Low-speed airspeed calibration data for a single-engine research-support aircraft

    Science.gov (United States)

    Holmes, B. J.

    1980-01-01

    A standard service airspeed system on a single engine research support airplane was calibrated by the trailing anemometer method. The effects of flaps, power, sideslip, and lag were evaluated. The factory supplied airspeed calibrations were not sufficiently accurate for high accuracy flight research applications. The trailing anemometer airspeed calibration was conducted to provide the capability to use the research support airplane to perform pace aircraft airspeed calibrations.

  10. Accurate Monitoring and Fault Detection in Wind Measuring Devices through Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Komal Saifullah Khan

    2014-11-01

    Full Text Available Many wind energy projects report poor performance as low as 60% of the predicted performance. The reason for this is poor resource assessment and the use of new untested technologies and systems in remote locations. Predictions about the potential of an area for wind energy projects (through simulated models may vary from the actual potential of the area. Hence, introducing accurate site assessment techniques will lead to accurate predictions of energy production from a particular area. We solve this problem by installing a Wireless Sensor Network (WSN to periodically analyze the data from anemometers installed in that area. After comparative analysis of the acquired data, the anemometers transmit their readings through a WSN to the sink node for analysis. The sink node uses an iterative algorithm which sequentially detects any faulty anemometer and passes the details of the fault to the central system or main station. We apply the proposed technique in simulation as well as in practical implementation and study its accuracy by comparing the simulation results with experimental results to analyze the variation in the results obtained from both simulation model and implemented model. Simulation results show that the algorithm indicates faulty anemometers with high accuracy and low false alarm rate when as many as 25% of the anemometers become faulty. Experimental analysis shows that anemometers incorporating this solution are better assessed and performance level of implemented projects is increased above 86% of the simulated models.

  11. 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.

  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. Experimental Investigation of Particle Deagglomeration using Turbulence

    International Nuclear Information System (INIS)

    The effect of turbulence on powder aerosol deagglomeration was investigated. Two impinging jets were used to generate turbulence. Lactose particles, whose fully dispersed fine particle fraction (FPF) - number percentage of the particles whose diameter smaller than 5 μm- is above 90 %, were applied as aerosol powder. The particle size distribution after the dispersion unit were measured by using phase Doppler anemometer (PDA) and turbulence level were quantified at the impingement point of two jets with laser Doppler anemometer. As the turbulence level increases turbulent time and length scales decrease, and the ratio of fine particle fraction (FPF) increases from 36% to 86%.

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

    DEFF Research Database (Denmark)

    Smith, D.A.; Harris, M.; Coffey, A.S.; Mikkelsen, Torben; Ejsing Jørgensen, Hans; Mann, Jakob; Danielian, G.

    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....

  15. Study of the correlation between the velocity fluctuation and the droplet size in a non evaporative type diesel spray; Estudio de la correlacion entre las fluctuaciones de la velocidad y el tamano de gota en un chorro tipo diesel no evaporativo

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, M.L.; Castro, F.; Garicano, A.; Melgar, A. [Univerdad de Valladolid (Spain). Dept. de Ingenieria Energetica y Fluidomecanica

    1995-07-01

    The interaction between a diesel spray and a low velocity crossflow has been investigated. The crossflow has been characterized by a two component hot wire anemometer. Instantaneous spray two component velocity, and diameter fields for different cross flow Reynolds number, and turbulent intensities have been obtained by means of a Phase Doppler Anemometer (PDA). Results show no influence of the turbulence intensity, while variations with Reynolds number occur in the spray region where the disperse phase shows a higher equilibrium with the gaseous phase. (author)

  16. Experimental methods in natural convection

    International Nuclear Information System (INIS)

    Some common experimental techniques to determine local velocities and to visualize temperature fields in natural convection research are discussed. First the physics and practice of anemometers are discussed with emphasis put on optical anemometers. In the second and third case the physics and practice of the most developed interferometers are discussed; namely differential interferometry for visualization of temperature gradient fields and holographic interferometry for visualization of temperature fields. At the Institut fuer Reaktorbauelemente these three measuring techniques are applied for convection and pipe flow studies. (orig.)

  17. 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...

  18. 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...

  19. Accuracy limitations for low velocity measurements and draft assessment in rooms

    DEFF Research Database (Denmark)

    Melikov, Arsen Krikor; Popiolek, Zbigniew J.; Silva, M.G.;

    2007-01-01

    The measurement of air temperature, mean air speed, and turbulence intensity is required in order to assess air distribution and draft discomfort in ventilated rooms. The measurements are also used for validation of computational fluid dynamics (CFD) predictions. The uncertainty of the measurements...... measurement and of the draft risk determination can be affected by numerous factors, for example, directional sensitivity of the velocity sensor, natural convection flow generated by the heated velocity sensor, dynamic response of the anemometer, calibration of the anemometer, velocity and temperature....... Thus, the definition of realistic requirements in thermal comfort standards as well as validation of CFD predictions is made possible....

  20. 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....

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

    DEFF Research Database (Denmark)

    Koukoura, Christina

    from 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...

  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. 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...

  4. 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...

  5. 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.

  6. 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. T...

  7. 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

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

    DEFF Research Database (Denmark)

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

    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...

  9. 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...

  10. 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...

  11. 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...

  12. 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)

  13. 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)

  14. 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

  15. 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...

  16. 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

  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. 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...

  19. 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

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

    DEFF Research Database (Denmark)

    Branlard, Emmanuel; Pedersen, Anders Tegtmeier; Mann, Jakob; Angelou, Nikolas; Fischer, Andreas; Mikkelsen, Torben; Harris, M.; Slinger, C.; Montes, B. F.

    2013-01-01

    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....

  1. CFD Calculations of the Flow Around a Wind Turbine Nacelle

    Energy Technology Data Exchange (ETDEWEB)

    Varela, J.; Bercebal, D. [Ciemat, Madrid (Spain)

    2000-07-01

    The purpose of this work is to identify the influence of a MADE AE30 wind turbine nacelle on the site calibration anemometer placed on the upper back of the nacelle by means of flow simulations around the nacelle using FLUENT, a Commercial Computational Fluid Dynamics code (CFD), which provides modeling capabilities for the simulation of wide range laminar and turbulent fluid flow problems. Different 2D and 3D simulations were accomplished in order to estimate the effects of the complex geometry on the flow behavior. The speed up and braking values of the air flow at the anemometer position are presented for different flow conditions. Finally some conclusions about the accuracy of results are mentioned. (Author) 5 refs.

  2. 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)

  3. 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...

  4. 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...

  5. Remote sensing used for power curves

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Ejsing Jørgensen, Hans; Schmidt Paulsen, Uwe;

    2008-01-01

    Power curve measurement for large wind turbines requires taking into account more parameters than only the wind speed at hub height. Based on results from aerodynamic simulations, an equivalent wind speed taking the wind shear into account was defined and found to reduce the power standard...... deviation in the power curve significantly. Two LiDARs and a SoDAR are used to measure the wind profile in front of a wind turbine. These profiles are used to calculate the equivalent wind speed. The comparison of the power curves obtained with the three instruments to the traditional power curve, obtained...... using a cup anemometer measurement, confirms the results obtained from the simulations. Using LiDAR profiles reduces the error in power curve measurement, when these are used as relative instrument together with a cup anemometer. Results from the SoDAR do not show such promising results, probably...

  6. CFD Calculations of the Flow Around a Wind Turbine Nacelle

    International Nuclear Information System (INIS)

    The purpose of this work is to identify the influence of a MADE AE30 wind turbine nacelle on the site calibration anemometer placed on the upper back of the nacelle by means of flow simulations around the nacelle using FLUENT, a Commercial Computational Fluid Dynamics code (CFD), which provides modeling capabilities for the simulation of wide range laminar and turbulent fluid flow problems. Different 2D and 3D simulations were accomplished in order to estimate the effects of the complex geometry on the flow behavior. The speed up and braking values of the air flow at the anemometer position are presented for different flow conditions. Finally some conclusions about the accuracy of results are mentioned. (Author) 5 refs

  7. 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...

  8. 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.

  9. 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...

  10. 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...

  11. A wind tunnel study of the mean airflow around a simple representation of a merchant ship

    OpenAIRE

    Moat, B. I.; Molland, A.F.; M. J. Yelland

    2004-01-01

    An investigation has been carried out to measure mean velocities above a solid block located in a wind tunnel. A Particle Image Velocimetry (PIV) system was used. The purpose of the investigation was to quantify the change in the mean flow speed caused by the bluff body and hence to determine the possible bias in wind speed measurement made from anemometers located above the superstructure of merchant ships. Possible sources of experimental error were investigated and resulted in; a) a blocka...

  12. 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...

  13. 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 ...

  14. 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...

  15. UpWind D1. Uncertainties in wind assessment with LIDAR

    Energy Technology Data Exchange (ETDEWEB)

    Lindeloew-Marsden, P.

    2009-01-15

    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 state 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. (author)

  16. 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...

  17. СИСТЕМА АВТОМАТИЗИРОВАННОГО КОНТРОЛЯ И ПРОГНОЗИРОВАНИЯ ОСТОЙЧИВОСТИ МАЛОМЕРНОГО СУДНА

    Directory of Open Access Journals (Sweden)

    ТИМЧЕНКО Виктор Леонидович

    2014-05-01

    Full Text Available Based multifunctional anemometer system, block modeling of sea waves and a system of sensors (inclinometers developed an automated system that allows to forecast parameters of rolling small vessel on a given interval of pre-emption, whereby the skipper receives information on the projected values of the roll angles, which will reduce the level of accidents operating small vessels in adverse weather conditions.

  18. Sofware de simulación en CSharp para el cálculo de la relación a ruido de un sistema 2D-LDA

    OpenAIRE

    Cobo González, Susana

    2010-01-01

    A computer program has been developed to evaluate the performance parameters of a general fringe mode two-dimensonal Laser Doppler Anemometer system or 2D-LDA for the detection and estimation of the speed of a fluid using the Mie scattering theory for spherical scattering particles. The evaluated performance parameters include Doppler signal strength, pedestal signal strength, and signal-to-shot noise ratio. Variable parameters in this program are the particle size and...

  19. 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....

  20. 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...

  1. 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....

  2. 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...

  3. 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.

  4. 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...

  5. Local measurements in turbulent bubbly flows

    International Nuclear Information System (INIS)

    Local measurements methods in bubbly flows are discussed. Concerning liquid velocity measurement, problems linked to HFA and LDA are first analysed. Then simultaneously recorded velocity signals obtained by both anemometers are compared. New signal processing are developed for the two techniques. Bubble sizes and velocities measurements methods using intrusive double optical sensor probe are presented. Plane bubbly mixing layer has been investigated. Local measurements using the described methods are presented as examples. (author)

  6. 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.

  7. 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...

  8. 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.

  9. 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...

  10. 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...

  11. 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.

  12. A Plume Tracing, Source Identifying Technique for Mars Rovers

    Science.gov (United States)

    Banfield, Don; Lamb, Brian; Hovde, Chris; Ferrara, Tom

    2015-11-01

    We have developed and field-tested a technique to identify and characterize the source of an effluent plume (biogenic or otherwise) on Mars, using a slow-moving vehicle like a Mars Rover. The technique is based on terrestrial plume characterization methods (EPA Method 33a), and uses puff models of variable complexity to predict the plume behavior for a given source. The technique is developed assuming that a Mars Rover would be equipped with a high-performance eddy-sensing 3-D anemometer (e.g., a Martian Sonic Anemometer), as well as a fast-response tracer molecule-specific sensor (e.g., a TLS methane sensor). The platform is assumed to move only once a day, but have the ability to observe throughout the day and night. Data obtained from any one sol while the effluent plume meanders across the rover can be used to estimate the azimuth, range and strength of the source, but combining observations from multiple sols and locations is used to improve the estimate of the souce location and strength.We have conducted preliminary field tests using a Sonic Anemometer (Gill and Campbell) and fast-response methane sensors (LICOR and Picarro) on mobile platforms using both controlled and existing methane releases to prove our algorithm in simple terrain, and with varying atmospheric stability. We will discuss our results and the efficacy of our algorithm in real world conditions.

  13. Stratospheric Flight of Three Mars Surface Instrument Prototypes

    Science.gov (United States)

    Hudson, T. L.; Neidholdt, E.; Banfield, D. J.; Kokorowski, M.; Kobie, B.; Diaz, E.; Gordon, S.; Doan, D.; Salami, M.

    2012-12-01

    The Analog Site Testbed for Readiness Advancement (ASTRA) is a high-altitude balloon platform for the testing of Mars surface instrument systems. In September 2012 three prototype instruments, a mass spectrometer and two anemometers, were taken to the 6 mbar pressure level of Earth's stratosphere (~34.5 km) above New Mexico to demonstrate their current capabilities and identify the critical path-to-flight steps for future advancement. Each of the instrument systems deployed on ASTRA were rated at TRL 4 at the start of the project. Through laboratory development, environmental testing, and the ASTRA balloon flight, each has advanced to an overall system TRL of 5, with specific subsystems reaching TRL 6. The results from the Rapid Acquisition Mass Spectrometer (RAMS), the Hot-Wire Anemometer (HWA), and the Single-Axis Sonic Anemometer (SASA) from the mid-September flight are presented, with focus given to both scientific results of the terrestrial atmospheric investigations, and the engineering and technical performance of the individual instrument systems and the balloon platform. The RAMS instrument has unique ion-imaging optics which permit the acquisition of a complete mass spectrum in a single CCD frame (~50 ms minimum). This allows RAMS to see rapid fluctuations in atmospheric constituents (necessary for the study of, for instance, vapor fluxes to and from the Mars surface) and has potential applications for laser ablation mass spectroscopy. The HWA is the latest generation of hot-wire anemometer, with heritage from the Mars Pathfinder MET instrument, and the ATMIS sensors developed for the Mars Polar Lander and the NetLander project. In addition to wind speed, a thermocouple cage around the hot filament detects heat plume direction, thus permitting 2-D wind vectors to be established. The SASA is a proof-of-capability device for an eventual three-axis sonic anemometer design. Developed under PIDDP funding by Dr. Don Banfield of Cornell (thus a contributed

  14. Analyzing the Effects of Temporal Wind Patterns on the Value ofWind-Generated Electricity at Different Sites in California and theNorthwest

    Energy Technology Data Exchange (ETDEWEB)

    Fripp, Matthias; Wiser, Ryan

    2006-05-31

    Wind power production varies on a diurnal and seasonal basis. In this report, we use wind speed data modeled by TrueWind Solutions, LLC (now AWS Truewind) to assess the effects of wind timing on the value of electric power from potential wind farm locations in California and the Northwest. (Data from this dataset are referred to as ''TrueWind data'' throughout this report.) The intra-annual wind speed variations reported in the TrueWind datasets have not previously been used in published work, however, so we also compare them to a collection of anemometer wind speed measurements and to a limited set of actual wind farm production data. The research reported in this paper seeks to answer three specific questions: (1) How large of an effect can the temporal variation of wind power have on the value of wind in different wind resource areas? (2) Which locations are affected most positively or negatively by the seasonal and diurnal timing of wind speeds? (3) How compatible are wind resources in the Northwest and California with wholesale power prices and loads in either region? The latter question is motivated by the fact that wind power projects in the Northwest could sell their output into California (and vice versa), and that California has an aggressive renewable energy policy that may ultimately yield such imports. Based on our research, we reach three key conclusions. (1) Temporal patterns have a moderate impact on the wholesale market value of wind power and a larger impact on the capacity factor during peak hours. The best-timed wind power sites have a wholesale market value that is up to 4 percent higher than the average market price, while the worst-timed sites have a market value that is up to 11 percent below the average market price. The best-timed wind sites could produce as much as 30-40 percent more power during peak hours than they do on average during the year, while the worst timed sites may produce 30-60 percent less power during

  15. 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.

  16. 2d-LCA - an alternative to x-wires

    Science.gov (United States)

    Puczylowski, Jaroslaw; Hölling, Michael; Peinke, Joachim

    2014-11-01

    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 150 kHz. 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.

  17. 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.

  18. OPTMAIN- A FORTRAN CODE FOR THE CALCULATION OF PROBE VOLUME GEOMETRY CHANGES IN A LASER ANEMOMETRY SYSTEM CAUSED BY WINDOW REFRACTION

    Science.gov (United States)

    Owen, A. K.

    1994-01-01

    The laser anemometer has provided the fluid dynamicist with a powerful tool for nonintrusively measuring fluid velocities. One of the more common types of laser anemometers, the laser fringe anemometer, divides a single laser beam into two parallel beams and then focuses them on a point in space called the "probe volume" (PV) where the fluid velocity is measured. Many applications using this method for measuring fluid velocities require the observation of fluids through a window. The passage of the laser beams through materials having different indices of refraction has the following effects: 1) the position of the probe volume will change; 2) the beams will uncross, i.e., no longer lie in the same plane at the probe volume location; and 3) for nonflat plate windows, the crossing angle of the two beams will change. OPTMAIN uses a ray tracing technique, which is not restricted to special cases, to study the changes in probe volume geometry and position due to refraction effects caused by both flat and general smooth windows. Input parameters are the indices of refraction on both sides of the window and of the window itself, the window shape, the assumed position of the probe volume and the actual position of the focusing lens relative to the window, the orientation of the plane which contains the laser beams, the beam crossing angle, and the laser beam wavelength. OPTMAIN is written in FORTRAN 77 for interactive execution. It has been implemented on a DEC VAX 11/780 under VMS 5.0 with a virtual memory requirement of 50K. OPTMAIN was developed in 1987.

  19. Wind observations above an urban river using a new lidar technique, scintillometry and anemometry

    International Nuclear Information System (INIS)

    Airflow along rivers might provide a key mechanism for ventilation in cities: important for air quality and thermal comfort. Airflow varies in space and time in the vicinity of rivers. Consequently, there is limited utility in point measurements. Ground-based remote sensing offers the opportunity to study 3D airflow in locations which are difficult to observe with conventional approaches. For three months in the winter and spring of 2011, the airflow above the River Thames in central London was observed using a scanning Doppler lidar, a scintillometer and sonic anemometers. First, an inter-comparison showed that lidar-derived mean wind-speed estimates compare almost as well to sonic anemometers (root-mean-square error (rmse) 0.65–0.68 m s−1) as comparisons between sonic anemometers (0.35–0.73 m s−1). Second, the lidar duo-beam operating strategy provided horizontal transects of wind vectors (comparison with scintillometer rmse 1.12–1.63 m s−1) which revealed mean and turbulent airflow across the river and surrounds; in particular, channelled airflow along the river and changes in turbulence quantities consistent with the roughness changes between built and river environments. The results have important consequences for air quality and dispersion around urban rivers, especially given that many cities have high traffic rates on roads located on riverbanks. -- Highlights: ► An inter-comparison was made between lidar-derived winds and regular anemometry. ► A new lidar operating technique was developed. ► Airflow features above an urban river included channelling of wind.

  20. Accuracy limitations for low velocity measurements and draft assessment in rooms

    DEFF Research Database (Denmark)

    Melikov, Arsen Krikor; Popiolek, Zbigniew J.; Silva, M.G.; Care, I.; Sefker, T.

    2007-01-01

    The measurement of air temperature, mean air speed, and turbulence intensity is required in order to assess air distribution and draft discomfort in ventilated rooms. The measurements are also used for validation of computational fluid dynamics (CFD) predictions. The uncertainty of the measurements...... must be known in order to perform reliable assessment and validation. At present, a low-velocity thermal anemometer (LVTA) with an omnidirectional (spherical) sensor is most often used in practice for measuring air speed due to its low price and easy and convenient operation. The accuracy of the speed...

  1. 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.

  2. Improvement of Wind Farm Performance by Means of Spinner Anemometry

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Demurtas, Giorgio; Gottschall, Julia; Højstrup, Jørgen; Degn Nielsen, Jesper; Christiansen, Wolfgang; Weich, Günther; Sommer, Anders; Kristoffersen, Jesper Runge

    powerful microprocessor and heating was added to the sonic sensor arms plus a range of smaller redesigns. Software was revised with an improved internal calibration procedure. The improved system was tested on a 2MW wind turbine at Tjæreborg wind farm. Measurements on this turbine includes calibration of K......This report is a project report on the EUDP research project SpinnerFarm. The objectives of the project were to improve software and hardware on the spinner anemometer concept and to demonstrate improvement of wind farm performance by opitmized yaw control. The hardware was improved by a more...

  3. Nacelle lidar for power curve measurement - Avedøre campaign

    OpenAIRE

    Wagner, Rozenn; Davoust, Samuel

    2013-01-01

    Wind turbine power performance requires the measurement of the free wind speed at hub height upstream of the turbine. For modern multi-megawatt wind turbines, this means that the wind speed needs to be measured at great heights, from 80m to 150m. The standard wind speed measurement with a cup 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 ...

  4. 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...

  5. 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)

  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. 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

    -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 is the......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...

  8. 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.)

  9. 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.

  10. 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...... 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...

  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. Measurements of velocity and temperature in the region downstream of a sudden pipe expansion

    International Nuclear Information System (INIS)

    The results of detailed velocity and temperature measurements are presented for the recirculating region downstream of a sudden pipe expansion in water. The velocity measurements, made using a laser doppler anemometer, also include a limited amount of turbulence information to assist in the formulation of a suitable turbulence model for a computational procedure, temperature measurements, buoyancy, and Reynolds number effects have been investigated over a limited range. No noticeable dependency was found. It is concluded that the data forms a good basis upon which to develop theoretical prediction methods. (author)

  13. Design of high-Reynolds-number flat-plate experiments in the NTF

    Science.gov (United States)

    Saric, William S.

    1988-01-01

    The design of an experiment to measure skin friction and turbulent boundary layer characteristics at Reynolds numbers exceeding 1 x 10 to the 9th is described. The experiment will be conducted in a zero-pressure-gradient flow on a flat plate in the National Transonic Facility (NTF). The development of computational codes to analyze the aerodynamic loads and the blockage is documented. Novel instrumentation techniques and models, designed to operate in cryogenic environments, are presented. Special problems associated with aerodynamic loads, surface finish, and hot-wire anemometers are discussed.

  14. 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)

  15. Large amplitude waves detected with balloons near the Andes Mountains

    Science.gov (United States)

    de la Torre, A.; Alexander, P.; Giraldez, A.

    Spectral results from a vertical sounding of temperature and wind velocity performed with an open stratospheric balloon in Argentina near the Andes mountains between 12 and 25 km of altitude, are reported. The use of sonic anemometers allows for a higher resolution than in previous experiments. The data records are studied in successive subintervals, yielding a good spectral correlation between the ascent and the descent around and below the tropopause. The possibilities of an orographic origin for large amplitude modes observed in the spectra and of wave generation by non linear interactions between them are discussed.

  16. Calculation of guaranteed mean power from wind turbine generators

    Science.gov (United States)

    Spera, D. A.

    1981-01-01

    A method for calculating the 'guaranteed mean' power output of a wind turbine generator is proposed. The term 'mean power' refers to the average power generated at specified wind speeds during short-term tests. Correlation of anemometers, the method of bins for analyzing non-steady data, the PROP Code for predicting turbine power, and statistical analysis of deviations in test data from theory are discussed. Guaranteed mean power density for the Clayton Mod-OA system was found to be 8 watts per square meter less than theoretical power density at all power levels, with a confidence level of 0.999. This amounts to 4 percent of rated power.

  17. 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...

  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. 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)

  20. 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.)

  1. 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...

  2. 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...

  3. Flow field analysis

    Science.gov (United States)

    Cliff, W. C.; Verholek, M. G.

    1978-01-01

    The average mean wind speed integrated over a disk is shown to be extremely close to the mean value of wind speed which would be measured at the center of a disk for most geometries in which a WECS (Wind Energy Conversion System) would operate. Field test results are presented which compare instantaneous records of wind speed integrated over a disk with the wind speed measured at the center of the disk. The wind field that a rotating element would experience is presented which was synthesized from the outputs of an array of anemometers.

  4. 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.

  5. 3D heterostructures and systems for novel MEMS/NEMS

    Directory of Open Access Journals (Sweden)

    Victor Yakovlevich Prinz, Vladimir Alexandrovich Seleznev, Alexander Victorovich Prinz and Alexander Vladimirovich Kopylov

    2009-01-01

    Full Text Available In this review, we consider the application of solid micro- and nanostructures of various shapes as building blocks for micro-electro-mechanical or nano-electro-mechanical systems (MEMS/NEMS. We provide examples of practical applications of structures created by MEMS/NEMS fabrication. Novel devices are briefly described, such as a high-power electrostatic nanoactuator, a fast-response tubular anemometer for measuring gas and liquid flows, a nanoprinter, a nanosyringe and optical MEMS/NEMS. The prospects are described for achieving NEMS with tunable quantum properties.

  6. 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.

  7. 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.

  8. 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.

  9. The presence of interstellar turbulence could explain the velocity flattening in galaxies

    CERN Document Server

    Vatistas, Georgios H

    2010-01-01

    Expanding our previous work on turbulent whirls [1] we have uncovered a similarity within the similarity shared by intense vortices. Using the new information we compress the tangential velocity profiles of a diverse set of vortices into one and thus identify those that belong to the same genus. Examining the Laser Doppler Anemometer (LDA) results of mechanically produced vortices and radar data of several tropical cyclones, we find that the uplift and flattening effect of tangential velocity is a consequence of turbulence. Reasoning by analogy we conclude that turbulence in the interstellar medium could indeed introduce a flattening effect in the galactic rotation curves.

  10. Executive summary. Wind-energy assessment studies in the Goodnoe Hills and Cape Blanco areas. Progress report, October 1980-September 1981

    Energy Technology Data Exchange (ETDEWEB)

    Baker, R W; Wade, J E; Persson, P O.G.; Katz, R W

    1981-12-01

    Work performed in FY81 on Wind Energy Assessment Studies in the Goodnoe Hills and Cape Blanco Areas is summarized. The research centers on defining the extent of the wind resource at site specific locations that have been documented earlier as having good wind power potential. The work consists of spatial wind surveys in the Goodnoe Hills and Cape Blanco area, wind turbine generator wake measurements at the Goodnoe Hills site, and developing a methodology for sampling the wind flow using a kite anemometer. (LEW)

  11. 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)

  12. Impact of sea breeze of the sea off Goa, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Neetu, S.; Shetye, S.R.; Chandramohan, P.

    coast oj I"dia. Twenty minute averaged spectra, collected ollce eVelY three hOllrs, during thefirst two ,'.·eeks ofApril 1997 (whell sea breeze was well developed Oil most days) show tlra/the spectra ofthe sea breeze related sea peaked at 0.22 ± 0.05 Hz... of the anemometer due to veering from frictional effects in the atmospheric boundary layer. Fig. J: Location ofthe wave and wind observations reported in the paper. 446 Proceedings ofthe International Conference on Coastal and Ocean Technology Fig.2: Upper panel...

  13. Characteristics of airflow turbulence behind HEPA filter

    International Nuclear Information System (INIS)

    The characteristics of airflow turbulence in unidirectional cleanroom are described in this paper. First, the airflow turbulence distribution is measured in a cleanbooth with a hot-wire anemometer. Through the analysis of turbulence intensity, the shape of pleated HEPA filter is found out to be an important factor of eddy generation in airflow, Secondly, turbulence distribution behind HEPA filter is measured in detail. It concludes that the shear stress, caused by the airflow difference between pleated concave and convex part of HEPA filter, makes eddy generation in airflow behind HEPA filter

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

    DEFF Research Database (Denmark)

    Meyer, Knud Erik

    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....

  15. A Review of Sodar Accuracy

    DEFF Research Database (Denmark)

    Bradley, Stuart; Mikkelsen, Torben

    large. On a uniform terrain site, differences between a SODAR and a mastmounted cup anemometer will arise due to turbulent fluctuations and wind components being measured in different spaces, as well as to variable background noise. We develop theories for turbulence-related random fluctuations due to...... different spaces. We show some field results which reinforce this view. Both the turbulencerelated random fluctuations and systematic errors in complex terrain (where systematic wind shears arise) can potentially be removed by use of a vertical column geometry. Field results from a new bistatic receiver...

  16. An evaluation of the WindEye wind lidar

    OpenAIRE

    Dellwik, Ebba; Sjöholm, Mikael; Mann, Jakob

    2015-01-01

    Prevision of the wind field by remote sensing wind lidars has the potential to improve the performance of wind turbines. The functionality of a WindEye lidar developed by Windar Photonics A/S (Denmark) for the wind energy market was tested in a two months long field experiment. The WindEye sensor measures the wind speed along two beams to determine the wind direction of the incoming wind field. The field experiment utilized two sonic anemometers located in the two centers of the measurement v...

  17. 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.

  18. 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.

  19. Near Wall Investigation of Three Dimensional Turbulent Boundary Layers

    OpenAIRE

    Kuhl, David Derieg

    2001-01-01

    This report documents the experimental study for four different three-dimensional turbulent flows. The investigation focuses on near wall measurements in these flows. Several experimental techniques are used in the studies; however, the bulk of the investigation focuses on a three-orthogonal-velocity-component fiber-optic laser Doppler anemometer (3D-LDA) system. The control volume of the 3D-LDA is on the order of 50 micro-meter in size, or a y+ distance of around 2.3 units (using average v...

  20. 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.

  1. 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

  2. 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...

  3. 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.

  4. The Myres Hill remote sensing intercomparison study: preliminary results

    Science.gov (United States)

    Clive, P. J. M.; Chindurza, I.; Ravey, I.; Bass, J.; Boyle, R. J.; Jones, P.; Lang, S. J.; Bradley, S.; Hay, L.; Oldroyd, A.; Stickland, M.

    2008-05-01

    Two remote sensing techniques (SODAR and LIDAR) have been developed for measuring wind speed and turbulence from ground level up to altitudes of 300 m or higher. Although originally developed in the defence sector, these techniques are now generating considerable interest in the renewable energy and meteorological sectors. Despite the benefits of these instruments they are not yet generally accepted for due diligence measurements by wind energy developers and financial institutions. There is a requirement for a series of independent assessments of these new metrology techniques, comparing their measurements with the approved cup-type anemometer readings. This is being addressed at TUV NEL's Myres Hill wind turbine test site in a measurement programme supported by the DIUS National Measurement Systems Measurement for Innovators scheme and a consortium of 21 industrial collaborators. Data from SODAR and LIDAR systems are being compared with results from cup-type anemometers mounted at different heights on an 80m meteorological mast. An ultrasonic sensor is also mounted on the mast. The objective of the test programme is to assess the effectiveness of SODAR and LIDAR wind speed measurement techniques under different operating regimes and atmospheric conditions. Results from the measurements will provide definitive data on the performance of the remote wind speed sensing techniques under test on complex terrain typical of many wind farm sites. Preliminary measurements based on data acquired during the initial measurement campaign are presented.

  5. 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

  6. Turbulence measurements in the compressor exit flow of a General Electric CF6-50 engine

    Science.gov (United States)

    Taylor, J. R.

    1979-01-01

    Ruggedized cooled film probes were used to measure CF6-50 compressor exit turbulence properties at three different engine idle condition test points. The turbulence probe was coupled to a constant temperature anemometer and signal conditioning system. An on-line readout system connected to the anemometer was used to check the data as it was acquired. At engine idle conditions, the turbulence intensity ranged from 4.8 percent to 5.6 percent and the length scale ranged from 5.64 cm to 6.95 cm. The length scale values are somewhat larger than the passage height at the measurement plane (5.54 cm), which indicates that the shape of the turbulent eddies are elongated in the axial direction. The microscale values range from about 0.73 cm to about 0.98 cm. Power spectral density distributions show that a large proportion of the turbulent energy at the measurement plane is concentrated at frequencies below one kilohertz.

  7. 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.

  8. 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)

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

    International Nuclear Information System (INIS)

    The measurement of inflow to a wind turbine rotor was made with a spinner anemometer on a 2 MW wind turbine in a wind farm of eight wind turbines. The wind speed, yaw misalignment and flow inclination angle was measured during a five months measurement campaign. Angular measurements were calibrated by yawing the wind turbine in and out of the wind in stopped conditions. Wind speed was calibrated relative to a met mast in a wake-free wind sector during operation. The calibration measurements were used to determine the basic k1 and k2 constants of the spinner anemometer and a four parameter induction factor function. Yaw measurements and turbulence measurements, where the average wind speed was corrected to the far field with the induction function, showed good correlation with mast measurements. The yaw misalignment measurements showed a significant yaw misalignment for most of the wind speed range, and also a minor symmetric yaw misalignment pattern. The flow inclination angle showed slight variation of inflow angle with wind speed and clear wake swirl patterns in the wakes of the other wind turbines. Turbulence intensity measurements showed clear variations from low turbulence in the wake-free wind sector to high turbulence in the wakes of the other wind turbines

  10. Atmospheric Turbulence Estimates from a Pulsed Lidar

    Science.gov (United States)

    Pruis, Matthew J.; Delisi, Donald P.; Ahmad, Nash'at N.; Proctor, Fred H.

    2013-01-01

    Estimates of the eddy dissipation rate (EDR) were obtained from measurements made by a coherent pulsed lidar and compared with estimates from mesoscale model simulations and measurements from an in situ sonic anemometer at the Denver International Airport and with EDR estimates from the last observation time of the trailing vortex pair. The estimates of EDR from the lidar were obtained using two different methodologies. The two methodologies show consistent estimates of the vertical profiles. Comparison of EDR derived from the Weather Research and Forecast (WRF) mesoscale model with the in situ lidar estimates show good agreement during the daytime convective boundary layer, but the WRF simulations tend to overestimate EDR during the nighttime. The EDR estimates from a sonic anemometer located at 7.3 meters above ground level are approximately one order of magnitude greater than both the WRF and lidar estimates - which are from greater heights - during the daytime convective boundary layer and substantially greater during the nighttime stable boundary layer. The consistency of the EDR estimates from different methods suggests a reasonable ability to predict the temporal evolution of a spatially averaged vertical profile of EDR in an airport terminal area using a mesoscale model during the daytime convective boundary layer. In the stable nighttime boundary layer, there may be added value to EDR estimates provided by in situ lidar measurements.

  11. 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)

  12. The Myres Hill remote sensing intercomparison study: preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Clive, P J M; Chindurza, I [SgurrEnergy Ltd, 79 Coplaw Street, Glasgow G42 7JG, Scotland (United Kingdom); Ravey, I; Bass, J [RES Group Ltd, James Blyth House, 7000 Academy Park, Glasgow, Scotland (United Kingdom); Boyle, R J; Jones, P [TUV NEL Ltd, East Kilbride, Glasgow G75 0QF, Scotland (United Kingdom); Lang, S J [Sustainable Energy Research Group, University College Cork (Ireland); Bradley, S [Mighty River Power, Level 14, 23-29 Albert Street, Auckland (New Zealand); Hay, L [Garrad Hassan and Partners Ltd, 2064 Maryhill Road, Glasgow G20 0AB, Scotland (United Kingdom); Oldroyd, A [Oldbaum Services Ltd, Schoolhouse, Brig o' Turk, Callander, Scotland (United Kingdom); Stickland, M [University of Strathclyde, 16 Richmond Street, Glasgow G1 1XQ, Scotland (United Kingdom)], E-mail: peter.clive@sgurrenergy.com

    2008-05-01

    Two remote sensing techniques (SODAR and LIDAR) have been developed for measuring wind speed and turbulence from ground level up to altitudes of 300 m or higher. Although originally developed in the defence sector, these techniques are now generating considerable interest in the renewable energy and meteorological sectors. Despite the benefits of these instruments they are not yet generally accepted for due diligence measurements by wind energy developers and financial institutions. There is a requirement for a series of independent assessments of these new metrology techniques, comparing their measurements with the approved cup-type anemometer readings. This is being addressed at TUV NEL's Myres Hill wind turbine test site in a measurement programme supported by the DIUS National Measurement Systems Measurement for Innovators scheme and a consortium of 21 industrial collaborators. Data from SODAR and LIDAR systems are being compared with results from cup-type anemometers mounted at different heights on an 80m meteorological mast. An ultrasonic sensor is also mounted on the mast. The objective of the test programme is to assess the effectiveness of SODAR and LIDAR wind speed measurement techniques under different operating regimes and atmospheric conditions. Results from the measurements will provide definitive data on the performance of the remote wind speed sensing techniques under test on complex terrain typical of many wind farm sites. Preliminary measurements based on data acquired during the initial measurement campaign are presented.

  13. The Myres Hill remote sensing intercomparison study: preliminary results

    International Nuclear Information System (INIS)

    Two remote sensing techniques (SODAR and LIDAR) have been developed for measuring wind speed and turbulence from ground level up to altitudes of 300 m or higher. Although originally developed in the defence sector, these techniques are now generating considerable interest in the renewable energy and meteorological sectors. Despite the benefits of these instruments they are not yet generally accepted for due diligence measurements by wind energy developers and financial institutions. There is a requirement for a series of independent assessments of these new metrology techniques, comparing their measurements with the approved cup-type anemometer readings. This is being addressed at TUV NEL's Myres Hill wind turbine test site in a measurement programme supported by the DIUS National Measurement Systems Measurement for Innovators scheme and a consortium of 21 industrial collaborators. Data from SODAR and LIDAR systems are being compared with results from cup-type anemometers mounted at different heights on an 80m meteorological mast. An ultrasonic sensor is also mounted on the mast. The objective of the test programme is to assess the effectiveness of SODAR and LIDAR wind speed measurement techniques under different operating regimes and atmospheric conditions. Results from the measurements will provide definitive data on the performance of the remote wind speed sensing techniques under test on complex terrain typical of many wind farm sites. Preliminary measurements based on data acquired during the initial measurement campaign are presented

  14. 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.

  15. Experimental investigation of turbulent mixed convection in the wake of a heated sphere

    International Nuclear Information System (INIS)

    The axisymmetric wake of a heated sphere under conditions of turbulent mixed convection is investigated in the water test section FLUTMIK. The sphere is located in a vertical channel with forced convective upward flow. The influence of buoyancy forces to the flow field is studied by comparison with the unheated wake. The theoretical fundamentals describing turbulent flows and different versions of the k-ε turbulence model extended by buoyancy terms are described in detail. The quantities to be determined experimentally are derived. The temperature and the components of the velocity vector in axial and radial directions are measured simultaneously by means of a thermocouple probe and a two component, two color laser Doppler anemometer. The flow quantities are determined at axial distances between 5 and 106 sphere diameters. The functional principle and the basis of the laser Doppler anemometer are explained. The mean velocity, the mean temperature, the intensities of their fluctuations and the turbulent exchange quantities of momentum and heat transport are calculated. The decay laws of the quantities along the axis of the channel and the radial profiles are indicated and discussed. The applicability of the experimental results of the axisymmetric buoyancy influenced turbulent wake with respect to the turbulence models presented are shown. (orig.)

  16. 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.

  17. Effect of the sea-breeze on the atmospheric stability at the sea-board

    International Nuclear Information System (INIS)

    For the study on the effect of sea breeze on the atmospheric stability in sea-board, a meteorological observation tower of 10 m height was built on the hill which is 30 m high above the sea level, located westward 400 m away from the coast. The tower was provided with anemometers at the top and 6 thermometers at 1.5-70 m above the ground. A phrhelis-radiometer and an anemometer were put around the ground 700 m away from there. By using the data from those instruments, attempt was made to analyze the relationship between wind near the coastline and several stability categories. Pasquille's atomospheric stability category is not always same as the other category for the state of atmospheric stability. The fluctuation of wind direction and the stability categorization by Richardson numbers agreed with Pasquille's stability to some extent in neutral range, but the disagreement developed conspicuously in stable and unstable sides. The three kinds of the stability categolization agree often each other. The relationship between the fluctuation of wind direction and Richardson numbers shows similar tendency. As a means to estimate the stability, particularly to estimate the fluctuation in wind direction, the Pasquille's stability categorization seems to be appropriate for practical use, since the neutral and stable cases arise in high frequency. (Kobatake, H.)

  18. 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。

  19. 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.

  20. 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).

  1. Three-dimensional æolian dynamics within a bowl blowout during offshore winds: Greenwich Dunes, Prince Edward Island, Canada

    Science.gov (United States)

    Hesp, Patrick A.; Walker, Ian J.

    2012-01-01

    This paper examines the æolian dynamics of a deep bowl blowout within the foredune of the Greenwich Dunes, on the northeastern shore or Prince Edward Island, Canada. Masts of cup anemometers and sonic anemometers were utilized to measure flow velocities and directions during a strong regional ESE (offshore) wind event. The flow across the blowout immediately separated at the upwind rim crest, and within the blowout was strongly reversed. High, negative vertical flows occurred down the downwind (but seaward) vertical scarp which projected into the separation envelope and topographically forced flow back into the blowout. A pronounced, accelerated jet flow existed near the surface across the blowout basin, and the flow exhibited a complex, anti-clockwise structure with the near-surface flow following the contours around the blowout basin and lower slopes. Significant æolian sediment transport occurred across the whole bowl basin and sediment was delivered by saltation and suspension out the blowout to the east. This study demonstrates that strong offshore winds produce pronounced topographically forced flow steering, separation, reversal, and more complex three-dimensional motions within a bowl blowout, and that such winds within a bowl blowout play a notable role in transporting sediment within and beyond deep topographic hollows in the foredune.

  2. 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.

  3. 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

  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. Calibration, Data Acquisition, and Post Analysis of Turbulent Fluid Flow in a Calibration Jet Using Hot-wire Anemometry

    Science.gov (United States)

    Moreno, Michelle

    2004-01-01

    The Turbine Branch concentrates on the following areas: Computational Fluid Dynamics (CFD), and implementing experimental procedures to obtain physical modeling data. Hot-wire Anemometry is a valuable tool for obtaining physical modeling data. Hot-wire Anemometry is likely to remain the principal research tool for most turbulent air/gas flow studies. The Hot-wire anemometer consists of a fine wire heated by electric current. When placed in a fluid stream, the hot-wire loses heat to the fluid by forced convection. In forced convection, energy transfer is due to molecular motion imposed by an extraneous force moving fluid parcels. When the hot-wire is in "equilibrium", the rate of heat input to the wire is equal to the rate of heat loss at the wire ends. The equality between heat input and heat loss is the basis for King s equation, which relates the electrical parameters of the hot-wire to the flow parameters of the fluid. Hot-wire anemometry is based on convective heat transfer from a heated wire element placed in a fluid flow. Any change in the fluid flow condition that affects the heat transfer from the heated element will be detected virtually instantaneously by a constant-temperature Hot-wire anemometry system. The system implemented for this research is the IFA 300. The system is a fully-integrated, thermal anemometer-based system that measures mean and fluctuating velocity components in air, water, and other fluids. It also measures turbulence and makes localized temperature measurements. A constant-temperature anemometer is a bridge and amplifier circuit that controls a tiny wire at constant temperature. As a fluid flow passes over the heated sensor, the amplifier senses the bridge off-balance and adjusts the voltage to the top of the bridge, keeping the bridge in balance. The voltage on top of the bridge can then be related to the velocity of the flow. The bridge voltage is sensitive to temperature as well as velocity and so the built-in thermocouple

  8. 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

  9. 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

  10. Velocity field measurement of a round jet using quantitative schlieren

    International Nuclear Information System (INIS)

    This paper utilizes the background oriented schlieren (BOS) technique to measure the velocity field of a variable density round jet. The density field of the jet is computed based on the light deflection created during the passage of light through the understudy jet. The deflection vector estimation was carried out using phase-based optical flow algorithms. The density field is further exploited to extract the axial and radial velocity vectors with the aid of continuity and energy equations. The experiment is conducted at six different jet-exit temperature values. Additional turbulence parameters, such as velocity variance and power spectral density of the vector field, are also computed. Finally, the measured velocity parameters are compared with the hot wire anemometer measurements and their correlation is displayed.

  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. Nacelle lidar for power curve measurement - Avedøre campaign

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Davoust, Samuel

    Wind turbine power performance requires the measurement of the free wind speed at hub height upstream of the turbine. For modern multi-megawatt wind turbines, this means that the wind speed needs to be measured at great heights, from 80m to 150m. The standard wind speed measurement with a cup...... 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. The...... 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...

  13. 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.

  14. 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.

  15. 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.

  16. 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...

  17. A Computational Study of a Data Assimilation Algorithm for the Two-dimensional Navier-Stokes Equations

    Science.gov (United States)

    Gesho, Masakazu; Olson, Eric; Titi, Edriss S.

    2016-04-01

    We study the numerical performance of a continuous data assimilation (downscaling) algorithm, based on ideas from feedback control theory, in the context of the two-dimensional incompressible Navier--Stokes equations. Our model problem is to recover an unknown reference solution, asymptotically in time, by using continuous-in-time coarse-mesh nodal-point observational measurements of the velocity field of this reference solution (subsampling), as might be measured by an array of weather vane anemometers. Our calculations show that the required nodal observation density is remarkably less that what is suggested by the analytical study; and is in fact comparable to the {\\it number of numerically determining Fourier modes}, which was reported in an earlier computational study by the authors. Thus, this method is computationally efficient and performs far better than the analytical estimates suggest.

  18. 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?”

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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...

  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. 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.

  7. 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

  8. 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)

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

    DEFF Research Database (Denmark)

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

    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......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 for...... 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...

  10. Alignment of stress, mean wind, and vertical gradient of the velocity vector

    DEFF Research Database (Denmark)

    Berg, Jacob; Mann, Jakob; Patton, E.G.

    2012-01-01

    is supposedly a good approximation. High resolution large-eddy simulation (LES) data show that it is indeed the case. Through analysis of WindCube lidar measurements accompanied by sonic measurements we show that this is, on the other hand, rarely the case in the real atmosphere. This might indicate...... that large scale mechanisms play an important role in the misalignment observed in the atmosphere. Baroclinicity is one candidate of a such, instationarity another. In this contribution we will present ongoing work: data from both a WindCube lidar, sonic anemometers and LES and discuss the results in...... the context of atmospheric boundary layer modeling. The measurements are from the Danish wind turbine test sites at Høvsøre. With theWindCube lidar we are able to reach heights of 250 meters and hence capture the entire atmospheric surface layer both in terms of wind speed and the direction of the...

  11. 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

    influence on temperature and humidity. The discomfort associated with bed nets is likely to be most intolerable during the hottest and most humid period of the year, which frequently coincides with the peak of malaria vector densities and the force of pathogen transmission. Conclusions These observations......Background/Methods Qualitative studies suggest that bed nets affect the thermal comfort of users. To understand and reduce this discomfort the effect of bed nets on temperature, humidity, and airflow was measured in rural homes in Asia and Africa, as well as in an experimental wind tunnel. Two...... 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...

  12. Flow mapping of heart valves: Natural and prosthetic

    International Nuclear Information System (INIS)

    Over the past decade there have been many in vitro studies conducted on the velocity and turbulence fields in the vicinity of prosthetic aortic heart valves. A vast majority of these studies have utilized one dimensional laser Doppler anemometer (LDA) systems. Recently, two dimensional LDA systems have been utilized to directly measure turbulent shear stresses under pulsatile flow conditions. LDA is considered the gold standard for in vitro velocity and turbulence measurements. In addition, numerical models have also been developed to simulate flow through prosthetic heart valves. With the advent of more powerful computers these simulation techniques have become more and more sophisticated, and are beginning to provide more realistic and useful information standards. In this session there are presentations made by engineers, scientists and physicians, that encompass in vitro LDA studies, computer simulation techniques, and ultrasound Doppler studies in animals and human subjects

  13. 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.

  14. 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)

  15. Heat transfer enhancement on thin wires in superfluid helium forced flows

    CERN Document Server

    Duri, Davide; Moro, Jean-Paul; Roche, Philippe-Emmanuel; Diribarne, Pantxo

    2014-01-01

    In this paper, we report the first evidence of an enhancement of the heat transfer from a heated wire by an external turbulent flow of superfluid helium. We used a standard Pt-Rh hot-wire anemometer and overheat it up to 21 K in a pressurized liquid helium turbulent round jet at temperatures between 1.9 K and 2.12 K. The null-velocity response of the sensor can be satisfactorily modeled by the counter flow mechanism while the extra cooling produced by the forced convection is found to scale similarly as the corresponding extra cooling in classical fluids. We propose a preliminary analysis of the response of the sensor and show that -contrary to a common assumption- such sensor can be used to probe local velocity in turbulent superfluid helium.

  16. Surface Stress with Non-stationary Weak Winds and Stable Stratification

    Science.gov (United States)

    Mahrt, L.; Thomas, Christoph K.

    2016-04-01

    The behaviour of turbulent transport in the weak-wind, stably-stratified, boundary layer over land is examined in terms of the non-stationarity of the wind field using measurements from three field programs. These field programs include towers ranging from 12 to 20 m in height and an extensive horizontal network of sonic anemometers. The relationship of the friction velocity to the stratification and non-stationary submeso motions is investigated from several points of view and nominally quantified. The relationship of the turbulence to the stratification is less systematic than expected partly due to enhancement of the turbulence by submeso motions. 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 in the downward transport of momentum.

  17. Heat transfer from cylinders in subsonic slip flows

    Science.gov (United States)

    Nagabushana, K. A.; Stainback, P. C.

    1992-01-01

    The heat transfer in heated wires was measured using a constant temperature anemometer over a Mach number range from 0.05 to 0.4 and pressures from 0.5 to 8.0 atmospheres. The total temperature ranged from 80 to 120 F and the wire diameters were 0.00015, 0.00032, and 0.00050 inch. The heat transfer data is presented in the form of a corrected Nusselt number. Based on suggested criteria, much of the data was obtained in the slip flow regime. Therefore, the data is compared with data having comparable flow conditions. The possible application of the heat transfer data to hot wire anemometry is discussed. To this end, the sensitivity of the wires to velocity, density, and total temperature is computed and compared using two different types of correlations.

  18. 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)

  19. 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,

  20. 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.

  1. 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.

  2. 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.

  3. Flow velocities and bed shear stresses in a stone cover under an oscillatory flow

    DEFF Research Database (Denmark)

    Stenanato, F.; Nielsen, Anders Wedel; Sumer, B. Mutlu;

    2010-01-01

    I order to get a better understanding of the interaction between the wave-induced, near-bed oscillatory flow, the stome cover and the sea bed, physical model tests were carried out. The tests were conducted in an oscillating water tunnel. The bottom of the tunnes was covered by one, two and three...... layers of stones. The flow velocities in the pores of the stones were measured using LDA (Laser Doppler Anemometer). In addition to the velocity measurements, the bed shear stresses were also measured using a hotfilm (Constant Temperature Anemometry). It is found that the boundary layer of the outer flow...... current boundary layer without any externally generated turbulence. The bd shear stress is found to be very low, more than ten times smaller than in the case of a smooth base bottom without stone cover....

  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...... uncertainty 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...

  5. WindScanner.eu - a new Remote Sensing Research Infrastructure for On- and Offshore Wind Energy

    DEFF Research Database (Denmark)

    Mikkelsen, Torben; Siggaard Knudsen, Søren; Sjöholm, Mikael;

    2012-01-01

    disseminated throughout Europe to pilot European wind energy research centers. The new research infrastructure will become an open source infrastructure that also invites collaboration with wind energy related atmospheric scientists and wind energy industry overseas. Recent achievements with 3D Wind...... and a rotor diameter of 154 meters; hence its blade tips reaches almost 200 meters into the sky. The wind speed profiles over the rotor planes are consequently no longer representatively measured by a single cup anemometer at hub height from a nearby met-mast; power curve assessment as well as turbine...... control call for multi-height multi point measurement strategies of wind speed and wind shear within the turbines entire rotor plane. The development of our new remote sensing-based WindScanner.dk facility as well as the first measurement results obtained to date are here presented, including a first wind...

  6. Sonic Thermometer for High-Altitude Balloons

    Science.gov (United States)

    Bognar, John

    2012-01-01

    The sonic thermometer is a specialized application of well-known sonic anemometer technology. Adaptations have been made to the circuit, including the addition of supporting sensors, which enable its use in the high-altitude environment and in non-air gas mixtures. There is a need to measure gas temperatures inside and outside of superpressure balloons that are flown at high altitudes. These measurements will allow the performance of the balloon to be modeled more accurately, leading to better flight performance. Small thermistors (solid-state temperature sensors) have been used for this general purpose, and for temperature measurements on radiosondes. A disadvantage to thermistors and other physical (as distinct from sonic) temperature sensors is that they are subject to solar heating errors when they are exposed to the Sun, and this leads to issues with their use in a very high-altitude environment

  7. 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.

  8. 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.

  9. 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

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

    DEFF Research Database (Denmark)

    Buchhave, Preben; Velte, Clara Marika

    2015-01-01

    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...... 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.......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 by...

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

    Observatory tower. The approximate magnitude of the error due to spatial and temporal pulse volume separation is presented as a function of mean wind angle relative to the sodar configuration and for several antenna pulsing orders. Sodar-derived standard deviations of the lateral wind component, before and......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...... after the application of the spatial and temporal volume separation correction, are presented. The improvement appears to be significant. The effects of correcting for pulse volume averaging derived in part I are also discussed...

  20. Evaluation of thermal overload in boiler operators.

    Science.gov (United States)

    Braga, Camila Soares; Rodrigues, Valéria Antônia Justino; Campos, Julio César Costa; de Souza, Amaury Paulo; Minette, Luciano José; de Moraes, Angêlo Casali; Sensato, Guilherme Luciano

    2012-01-01

    The Brazilians educational institutions need a large energy demand for the operation of laundries, restaurants and accommodation of students. Much of that energy comes from steam generated in boilers with wood fuel. The laboral activity in boiler may present problems for the operator's health due to exposure to excessive heat, and its operation has a high degree of risk. This paper describes an analysis made the conditions of thermal environment in the operation of a B category boiler, located at a Higher Education Institution, located in the Zona da Mata Mineira The equipments used to collect data were Meter WBGT of the Heat Index; Meter of Wet Bulb Index and Globe Thermometer (WBGT); Politeste Instruments, an anemometer and an Infrared Thermometer. By the application of questionnaires, the second phase consisted of collecting data on environmental factors (temperature natural environment, globe temperature, relative humidity and air velocity). The study concluded that during the period evaluated, the activity had thermal overload. PMID:22316768

  1. Experimental and numerical investigation of turbulent natural convection in a large air-filled cavity

    International Nuclear Information System (INIS)

    We investigate experimentally and numerically the turbulent natural convection flow that develops in a differentially heated cavity of height H=1 m, width W=H and depth D=0.32H, submitted to a temperature difference between the active vertical walls equal to 15 K resulting in a characteristic Rayleigh number equal to 1.5 x 109. In the experiment temperature is measured by 25 μm micro-thermocouples and velocity by a Laser Doppler Anemometer. Both 2D and 3D LES and 3D DNS are performed. DNS uses a Chebyshev spectral method and LES a finite volume method with a local subgrid diffusivity model. Numerical simulations are performed for both adiabatic conditions and experimentally measured temperature on the horizontal walls. Time-averaged quantities and turbulent statistics in the median vertical plane are presented and compared

  2. 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...

  3. Evaluation of wind flow with a nacelle-mounted, continuous wave wind lidar

    DEFF Research Database (Denmark)

    Medley, John; Barker, Will; Harris, Mike;

    2014-01-01

    ZephIR DM lidar mounted on the nacelle of a 550 kW turbine at the Risø campus of the Technical University of Denmark (DTU). Lidar measurements of wind speed and turbulence were compared against those made by anemometers on a high-quality traditional mast. Analysis showed excellent correlation between......Nacelle-mounted lidar is becoming widely recognized as a tool with potential for assessing power curves, understanding wind flow characteristics, and controlling turbines. As rotor diameters continue to increase, and the deployment of turbines in complex terrain becomes more widespread, knowledge...... mast and ZephIR, increasing the confidence in the ZephIR for measuring wind parameters in this configuration. SCADA data from the turbine was combined with measured wind speeds and directions to derive power curves from the mast data (hub-height) and from ZephIR data (hub-height and rotor...

  4. Evaluation of wind flow with a nacelle-mounted continuous-wave lidar

    DEFF Research Database (Denmark)

    Medley, John; Slinger, Chris; Barker, Will;

    ZephIR DM lidar mounted on the nacelle of a 550 kW turbine at the Risø campus of the Technical University of Denmark (DTU). Lidar measurements of wind speed and turbulence were compared against those made by anemometers on a high-quality traditional mast. Analysis showed excellent correlation between......Nacelle-mounted lidar is becoming widely recognized as a tool with potential for assessing power curves, understanding wind flow characteristics, and controlling turbines. As rotor diameters continue to increase, and the deployment of turbines in complex terrain becomes more widespread, knowledge...... mast and ZephIR, increasing the confidence in the ZephIR for measuring wind parameters in this configuration. SCADA data from the turbine was combined with measured wind speeds and directions to derive power curves from the mast data (hub-height) and from ZephIR data (hub-height and rotor...

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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)

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

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Pedersen, Christian

    2012-01-01

    We implement and test what, to our knowledge, is the first deployable coherent Doppler lidar (CDL) system based on a compact, inexpensive all-semiconductor laser (SL). To demonstrate the field performance of our SL-CDL remote sensor, we compare a 36 h time series of averaged radial wind speeds...... providing high data availability, ranging from 85% to 100% even under varying outdoor (temperature and humidity) conditions during the test period. We also show the use of our SL-CDL for monitoring the dependence of aerosol backscatter on relative humidity. This work points to the feasibility of a more...... 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 of...

  12. 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.

  13. 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...

  14. On the theory of SODAR measurement techniques

    DEFF Research Database (Denmark)

    Antoniou, I.; Ejsing Jørgensen, Hans; Bradley, S.

    2003-01-01

    The need for alternative means to measure the wind speed for wind energy purposes has increased with the increase of the size of wind turbines. The cost and the technical difficulties for performing wind speed measurements has also increased with the sizeof the wind turbines, since it is demanded...... that the wind speed has to be measured at the rotor centre of the turbine and the size of both the rotor and the hub height have grown following the increase in the size of the wind turbines. The SODAR (SOundDetection And Ranging) is an alternative to the use of cup anemometers and offers the...... possibility of measuring both the wind speed distribution with height and the wind direction. At the same time the SODAR presents a number of serious drawbacks such asthe low number of measurements per time period, the dependence of the ability to measure on the atmospheric conditions and the difficulty of...

  15. 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.

  16. The entrainment rate for a row of turbulent jets. M.S. Thesis Final Report

    Science.gov (United States)

    Gordon, Eliott B.; Greber, Isaac

    1990-01-01

    Entrainment rates for a row of isothermal circular air jets issuing into a quiescent environment are found by integrating velocity distributions measured by a linearized hot-wire anemometer. Jet spacing to jet diameter ratios of 2.5, 5, 10, and 20 are studied at jet Reynold's numbers ranging from 5110 to 12070. Velocity distributions are determined at regular downstream intervals at axial distances equal to 16.4 to 164 jet diameters from the jet source. The entrainment rates for the four spacing configurations vary monotonically with increasing spacing/diameter between the limiting case of the slot jet entrainment rate (where the jet spacing to diameter ratio is zero) and the circular jet entrainment rate (in which the spacing to diameter ratio is infinity).

  17. Effects of gas properties and inclination angle on exchange flow through a rectangular channel

    International Nuclear Information System (INIS)

    This study deals with the exchange flow of two different gases (He-air, Ar-air, and SF6-air) through a rectangular channel that has a 5-mm width, a 50-mm height, and a 200-mm length. The net exchange flow rate is measured by an electronic mass balance, and velocity distribution is measured by a laser-Doppler anemometer. Flow patterns of the exchange flow are made visual with a tracer method using smoke. The effects of gas densities, molecular diffusion coefficients, inclination angles (θ) of the channel, on the flow patterns and the net exchange flow rates, are discussed. Based on the experimental results, the net exchange flow data are correlated by the equation derived by dimensional analysis: Q*=2.87 x 10-7 Gr2.17Sc0.41θ-1.09. (author)

  18. Laser Doppler technology applied to atmospheric environmental operating problems

    Science.gov (United States)

    Weaver, E. A.; Bilbro, J. W.; Dunkin, J. A.; Jeffreys, H. B.

    1976-01-01

    Carbon dioxide laser Doppler ground wind data were very favorably compared with data from standard anemometers. As a result of these measurements, two breadboard systems were developed for taking research data: a continuous wave velocimeter and a pulsed Doppler system. The scanning continuous wave laser Doppler velocimeter developed for detecting, tracking and measuring aircraft wake vortices was successfully tested at an airport where it located vortices to an accuracy of 3 meters at a range of 150 meters. The airborne pulsed laser Doppler system was developed to detect and measure clear air turbulence (CAT). This system was tested aboard an aircraft, but jet stream CAT was not encountered. However, low altitude turbulence in cumulus clouds near a mountain range was detected by the system and encountered by the aircraft at the predicted time.

  19. 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)....

  20. 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.

  1. 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.

  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. 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

  4. 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)

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. On the theory of SODAR measurement techniques[SOund Detection And Ranging

    Energy Technology Data Exchange (ETDEWEB)

    Antoniou, I.; Joergensen, H.E. [Risoe National Lab. (Denmark); Ormel, F. [Energy Research Center of the Netherlands (Netherlands); Bradley, S.; Huenerbein, S. von [University of Salford (United Kingdom); Emeis, S. [Forschungszentrum Karlsruhe GmbH (Germany); Warmbier, G. [GWU-Umwelttechnik Gmbh (Germany)

    2003-04-01

    The need for alternative means to measure the wind speed for wind energy purposes has increased with the increase of the size of wind turbines. The cost and the technical difficulties for performing wind speed measurements has also increased with the size of the wind turbines, since it is demanded that the wind speed has to be measured at the rotor centre of the turbine and the size of both the rotor and the hub height have grown following the increase in the size of the wind turbines. The SODAR (SOund Detection And Ranging) is an alternative to the use of cup anemometers and offers the possibility of measuring both the wind speed distribution with height and the wind direction. At the same time the SODAR presents a number of serious drawbacks such as the low number of measurements per time period, the dependence of the ability to measure on the atmospheric conditions and the difficulty of measuring at higher wind speeds due to either background noise or the neutral condition of the atmosphere. Within the WISE project (EU project number NNE5-2001-297), a number of work packages have been defined in order to deal with the SODAR. The present report is the result of the work package 1. Within this package the objective has been to present and achieve the following: 1) An accurate theoretic model that describes all the relevant aspects of the interaction of the sound beam with the atmosphere in the level of detail needed for wind energy applications. 2) Understanding of dependence of SODAR performance on hard- and software configuration. 3) Quantification of principal difference between SODAR wind measurement and wind speed measurements with cup anemometers with regard to power performance measurements.

  11. 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

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

    Science.gov (United States)

    Fujita, Shigetaka; Harima, Takashi

    2016-03-01

    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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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

  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. 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

  20. 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

  1. 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

  2. Direct Measurement of Turbulent Particle and Gas Fluxes by Eddy Covariance Technique

    Science.gov (United States)

    Kondo, F.; Griessbaum, F.; Tsukamoto, O.; Uematsu, M.

    2010-12-01

    Direct Measurement of Turbulent Particle and Gas Fluxes by Eddy Covariance Technique Fumiyoshi KONDO (The University of Tokyo) Frank GRIESSBAUM (Universität Münster) Osamu TSUKAMOTO (Okayama University) Mitsuo UEMATSU (The University of Tokyo) The oceans play major key roles in global energy transport, element cycles, and atmospheric radiation balance. The study of the processes at the interface of ocean and atmosphere is essential to develop profound understanding of the mechanisms driving ocean-atmosphere interaction and climate. Eddy covariance technique is the only direct measurement of air-sea particle and gas fluxes. This technique has little assumption (constant flux layer and steady state), and may evaluate small spatial and temporal particle and gas fluxes. For these reasons, we hope that the eddy covariance technique investigates uncertain processes that control the air-sea particle (aerosol) and gas (CO2) fluxes. The understanding of processes controlling both the CO2 uptake to the ocean and the oceans as major source of aerosols is vital for quantifying the role of the global oceans in the climate system. We developed the simultaneous measurement system of turbulent particle and gas fluxes by eddy covariance technique and installed with ship motion correction system on the top of the foremast of R/V Hakuho-Maru and Mirai. The turbulent flux system on the top of the foremast consisted of a sonic anemometer-thermometer (Gill, HS-50), an infrared CO2/H2O gas analyzer (LI-COR, LI-7500), a water-based condensation particle counter (TSI, WCPC3785), and Fog Monitor (Droplet Measurement, FM-100). The ship motion correction system consisted of a three-axis accelerometer and a three-axis rate gyro (Systron Donner, MotionPak II). The sonic anemometer measures three-dimensional wind components relative to the ship including apparent wind velocity due to the ship motion. Then, the ship motion correction system measures the ship motions by time integral of

  3. An experimental methodology to quantify the spray cooling event at intermittent spray impact

    International Nuclear Information System (INIS)

    The present paper describes an experimental methodology devised to study spray cooling with multiple-intermittent sprays as those found in fuel injection systems of spark-ignition and diesel engines, or in dermatologic surgery applications. The spray characteristics and the surface thermal behaviour are measured by combining a two-component phase-Doppler anemometer with fast response surface thermocouples. The hardware allows simultaneous acquisition of Doppler and thermocouple signals which are processed in Matlab to estimate the time-varying heat flux and fluid-dynamic characteristics of the spray during impact. The time resolution of the acquisition system is limited by the data rate of validation of the phase-Doppler anemometer, but it has been shown to be accurate for the characterization of spray-cooling processes with short spurt durations for which the transient period of spray injection plays an important role. The measurements are processed in terms of the instantaneous heat fluxes, from which phase-average values of the boiling curves are obtained. Two of the characteristic parameters used in the thermal analysis of stationary spray cooling events, the critical heat flux (CHF) and Leidenfrost phenomenon, are then inferred in terms of operating conditions of the multiple-intermittent injections, such as the frequency, duration and pressure of injection. An integral method is suggested to describe the overall process of heat transfer, which accounts for the fluid-dynamic heterogeneities induced by multiple and successive droplet interactions within the area of spray impact. The method considers overall boiling curves dependant on the injection conditions and provides an empirical tool to characterize the heat transfer processes on the impact of multiple-intermittent sprays. The methodology is tested in a preliminary study of the effect of injection conditions on the heat removed by a fuel spray striking the back surface of the intake valve as in spark

  4. 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

  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. 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

  7. Comparing laser-based open- and closed-path gas analyzers to measure methane fluxes using the eddy covariance method

    Science.gov (United States)

    Detto, M.; Verfaillie, J.; Anderson, F.; Xu, L.; Baldocchi, D.

    2011-01-01

    Closed- and open-path methane gas analyzers are used in eddy covariance systems to compare three potential methane emitting ecosystems in the Sacramento-San Joaquin Delta (CA, USA): a rice field, a peatland pasture and a restored wetland. The study points out similarities and differences of the systems in field experiments and data processing. The closed-path system, despite a less intrusive placement with the sonic anemometer, required more care and power. In contrast, the open-path system appears more versatile for a remote and unattended experimental site. Overall, the two systems have comparable minimum detectable limits, but synchronization between wind speed and methane data, air density corrections and spectral losses have different impacts on the computed flux covariances. For the closed-path analyzer, air density effects are less important, but the synchronization and spectral losses may represent a problem when fluxes are small or when an undersized pump is used. For the open-path analyzer air density corrections are greater, due to spectroscopy effects and the classic Webb-Pearman-Leuning correction. Comparison between the 30-min fluxes reveals good agreement in terms of magnitudes between open-path and closed-path flux systems. However, the scatter is large, as consequence of the intensive data processing which both systems require. ?? 2011.

  8. 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)

  9. 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.

  10. 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...

  11. Investigation of three-dimensional flow field in a turbine including rotor/stator interaction. I - Design development and performance of the research facility

    Science.gov (United States)

    Lakshminarayana, B.; Camci, C.; Halliwell, I.; Zaccaria, M.

    1992-01-01

    A description of the Axial Flow Turbine Research Facility (AFTRF) installed at the Turbomachinery Laboratory of the Pennsylvania State University is presented in this paper. The facility diameter is 91.66 cm (3 feet) and the hub-to-tip ratio of the blading is 0.73. The flow path consists of turbulence generating grid, 23 nozzle vane and 29 rotor blades followed by outlet guide vanes. The blading design, carried out by General Electric Company personnel, embody modern HP turbine design philosophy, loading and flow coefficient, reaction, aspect ratio, and blade turning angles; all within the current aircraft engine design turbine practice. State-of-the-art quasi-3D blade design techniques were used to design the vane and the blade shapes. The vanes and blades are heavily instrumented with fast response pressure, shear stress, and velocity probes and have provision for flow visualization and laser Doppler anemometer measurement. Furthermore, provision has been made for detailed nozzle wake, rotor wake and boundary layer surveys. A 150 channel slip ring unit is used for transmitting the rotor data to a stationary instrumentation system. All the design objectives have been met.

  12. Flowfield And Download Measurements And Computation of a Tiltrotor Aircraft In Hover

    Science.gov (United States)

    Brand, Albert G.; Peryea, Martin A.; Wood, Tom L.; Meakin, Robert L.

    2001-01-01

    A multipart study of the V-22 hover flowfield was conducted. Testing involved a 0.15-scale semispan model with multiple independent force balance systems. The velocity flowfield surrounding the airframe was measured using a robotic positioning system and anemometer. Both time averaged and cycle-averaged results are reported. It is shown that the fuselage download in hover can be significantly reduced using a small download reduction device. Measurements indicate that the success of the device is attributed to the substantial elimination of tiltrotor fountain flow. As part of.the study, an unsteady CFD prediction is time-averaged, and shown to have excellent agreement in predicting the baseline configuration fountain flow. Some discrepancies at the outboard edge of the rotor are discussed. An &&sessment of an advanced tip shape rotor comp"'Ietes the study. Derived from a nonrotating study, the advanced tip shape rotor was developed and tested on the Bell 0.15 scale semi-span V-22 model. The tip shape was intended to diffuse the tip vortex and reduce BVI noise. Rotor wake vorticity is extracted from the measured velocity dam to show that the advanced tip shape produces a tip vortex that is only slightly more diffuse than the baseline tip blade. The results indicate that nonrotating tests may overpredict the amount of tip vortex diffusion achieved by tip shape design in a rotating environment.

  13. 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

  14. 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.

  15. 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.

  16. 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)

  17. 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.

  18. Gas/particle flow characteristics of two swirl burners

    International Nuclear Information System (INIS)

    A three-component particle-dynamics anemometer is used to measure, in the near-burner region, the characteristics of gas/particle two-phase flows with a centrally fuel rich swirl coal combustion burner and enhanced ignition-dual register burner, on a gas/particle two-phase test facility. Velocities, RMS velocities, particle mean diameters and particle volume flux profiles were obtained. For the centrally fuel rich burner, particles penetrate the central recirculation zone partially, and are then deflected radially. For the enhanced ignition-dual register burner, particles completely penetrate the central recirculation zone. Compared with the enhanced ignition-dual register burner, in the same cross-section, the particle volume flux peak value for the centrally fuel rich burner is much closer to the chamber axis and much larger near the chamber axis. In six cross-sections from x/d = 0.3 to 2.5, the particle volume flux in the central recirculation zone for the centrally fuel rich burner is much larger than that for the enhanced ignition-dual register burner. For the centrally fuel rich burner, most of bigger particles are resident in the region near the chamber axis and the residence time is prolonged. The influence of gas/particle flow characteristics on combustion has been analyzed.

  19. 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.

  20. Utilizing the energy from induced wind produce by highway vehicle motion

    International Nuclear Information System (INIS)

    A research work has been conducted at the Faculty of mechanical Engineering, Universiti Teknologi Malaysia to utilize energy from airflow induced by moving vehicles along the highway for advertising and signboard lighting. Series of data collections have been made at Km 20 Johor Bahru - Kuala Lumpur Plus Highway. Wind anemometer equipped with data recorder has been placed at the highway divider to measure the wind speed induced by the vehicles moving from Johor Bahru to Kuala Lumpur and vice versa. From the data analysis it has been found that the to and from Kuala Lumpur motion of the vehicles induced a stable and continuous source of airflow (wind) ranges from 2 to 4 m/s. The energy in this induced wind has been estimated and has the potential to be used for the above said purpose. Five design models have been tested in the Faculty of mechanical Engineering Low Speed Wind Tunnel and the twisted vertical blades with circular end covers has proven to be the most efficient and suitable. The optimum sizing of the vertical axis wind turbine has also been determined. The details of the collection of wind induced data and analysis, estimation of energy content, the vertical axis wind turbine models testing and results are presented in this paper. (Author)

  1. 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.

  2. 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.

  3. 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.

  4. 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...

  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. The Stand-alone Heliostat; El Heliostato Autonomo

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Navajas, G.; Egea Gea, A. [Ciemat. Madrid (Spain)

    2000-07-01

    The first Autonomous Heliostat has been developed by CIEMAT at PSA facilities in Almeria. This heliostat is an innovative approach to reducing the civil engineering work costs in heliostat fields of central tower plants. Channels, cables and other electric elements have been eliminated in the new heliostat. Thus, one 70-m''2, classical T glass/metal heliostat has been adapted to include all the new stand-alone concept components. A PV system is able to drive two sun-tracking DC motors between 5 and 24 Vdc, 0 and 15A. The heliostat communicates with the control room 400-m away by using a radio-modern working at 9600 baud. An anemometer, a wind switcher, light and ambient temperature sensors have been installed on the heliostat for self-protection decision-making. A PV panel integrated into the heliostat reflecting surface, eliminates cabling and other elements required for a conventional power supply. Communication lines between master control and local control have been replaced by radio-modern. Testing has validated the technical feasibility of the prototype and quantified the real consumption and efficiencies of new elements. The extra costs produced by the autonomous concepts are compared with the cost of civil work in conventional heliostat field. (Author) 8 refs.

  7. Experimental gas/particle flow characteristics of a down-fired 600 MWe supercritical utility boiler at different staged-air ratios

    International Nuclear Information System (INIS)

    To acquire the gas/particle flow characteristics of an in-assembly down-fired 600-MWe supercritical utility boiler, experiments were conducted by using particle dynamics anemometer (PDA) measurement within a two-phase small-scale model at various staged-air ratio settings (i.e., 0%, 6%, and 12%). The mean velocity, particle volume flux, and particle number concentration along several cross sections, were discussed well in the present work, in addition to the decay and trajectories of the downward gas/particle flow. For all three settings, asymmetric gas/particle flow characteristics appeared in the lower furnace, with the gas/particle flow in the front-half furnace penetrating greatly further and occupying much more furnace volume than that in the rear-half furnace. The longitudinal-velocity components are clearly higher near the front wall than near the rear wall. Decreasing the staged-air ratio can only weaken the gas/particle flow asymmetries to some extent. An estimation on the furnace performance, i.e., severe asymmetric combustion, low burnout, and high NOx emissions, is given out for the boiler's commercial operation in the near future. -- Highlights: ► Asymmetric gas/particle flow characteristics appeared at various staged-air ratio settings. ► Decreasing the staged-air ratio only weakens the gas/particle flow asymmetries to some extent. ► An evaluation of asymmetric combustion, low burnout, and high NOx emissions is given out for the boiler.

  8. Regional Approaches to Climate Change (REACCH) in the Inland Pacific Northwest: Micrometeorological Measurements of Nitrous Oxide Fluxes over a Wheat Cropping System

    Science.gov (United States)

    Lamb, B. K.; Waldo, S.; Chi, J.; Pressley, S. N.; Allwine, G.; O'Keeffe, P.; Huggins, D. R.; Pan, W.; Stockle, C.; Uberuaga, D.

    2012-12-01

    It is becoming increasingly important to investigate the relationship between global climate and agriculture in the face of ongoing climate change and the need to feed a growing global population. The REgional Approaches to Climate CHange (REACCH) USDA project is focused on Inland Pacific Northwest cereal cropping systems with an overarching goal to develop strategies for regional agriculture to mitigate and adapt to climate change. An important component of REACCH is to establish a baseline of greenhouse gas (GHG) fluxes for current and alternate management practices. While cropping systems have the potential to sequester carbon in the soils, they are a net source of nitrous oxide (N2O), a greenhouse gas with three hundred times the warming potential of CO2. We report here initial micrometeorological flux measurements of N2O over a high rainfall, annual cropping system under no-tillage management. The measurements were collected from three-meter eddy covariance towers. Each tower is equipped with a sonic anemometer and peripheral meteorological instruments. Closed-path cavity ring down spectroscopy instruments were used to measure N2O fluxes via two techniques: eddy covariance and the modified Bowen ratio gradient method. The flux data from the two techniques are compared to each other and also to enclosure chamber measurements to determine viability and the range of uncertainty in the measurements. They are also analyzed for patterns associated with management events and meteorological conditions.

  9. 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.

  10. 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.

  11. 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.

  12. 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. ...

  13. Nacelle lidar for power curve measurement - Avedoere campaign

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, R.; Davoust, S.

    2013-01-15

    Wind turbine power performance requires the measurement of the free wind speed at hub height upstream of the turbine. For modern multi-megawatt wind turbines, this means that the wind speed needs to be measured at great heights, from 80m to 150m. The standard wind speed measurement with a cup 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 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 nacelle lidar prototype placed on an onshore turbine demonstrated the potential of the technology for power curve measurement. 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 second measurement campaign aiming at testing and finalising the procedure. (Author)

  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. 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).

  16. 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.

  17. 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 ...

  18. DEVELOPMENT OF AN EXPERIMENTAL TEST BED DESIGNATED FOR MODEL STUDIES OF AERODYNAMICS OF PREMISES USING METHOD OF DIGITAL FLOW VISUALIZATION

    Directory of Open Access Journals (Sweden)

    Varapaev Vladimir Nikolaevich

    2012-12-01

    Full Text Available In the article, the authors present their findings generated at the laboratory of aerodynamic and aero-acoustic testing of structural units of MGSU. The authors provide information about the principle of operation and a brief description of the experimental test bed designated for the physical research of patterns of air flows arising inside building premises of various geometric shapes. The authors also demonstrate the basic parameters of the test bed, the principle of operation of its recording devices and some of its characteristics. The test bed is designated for the identification of characteristics of three-dimensional flows of models under research and for the verification of results of numerical studies. The measurement bed has advanced measurement and registration units. The management principle is based on the method of digital flow visualization, PIV method and Doppler flow meter implemented in the LDA anemometer. The test stand generates two or three component vector fields of turbulent gas flow velocities. It may be applicable to the study of liquids in case of research of hydraulics-related problems. Some results of the flow study are provided in the article, as well.

  19. 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

  20. Helioseismology in a bottle: an experimental technique

    Science.gov (United States)

    Triana, S. A.; Zimmerman, D. S.; Nataf, H.; Thorette, A.; Cabanes, S.; Roux, P.; Lekic, V.; Lathrop, D. P.

    2013-12-01

    Measurement of the differential rotation of the Sun's interior is one of the great achievements of helioseismology, providing important constraints for stellar physics. The technique relies on observing and analyzing rotationally-induced splittings of p-modes in the star. Here we demonstrate the first use of the technique in a laboratory setting. We apply it in a spherical cavity with a spinning central core (spherical Couette flow) to determine the azimuthal velocity of the air filling the cavity. We excite a number of acoustic resonances (analogous to p-modes in the Sun) using a speaker and record the response with an array of small microphones and/or accelerometers on the outer sphere. Many observed acoustic modes show rotationally-induced splittings which allow us to perform an inversion to determine the air's azimuthal velocity as a function of both radius and latitude. We validate the method by comparing the velocity field obtained through inversion against the velocity profile measured with a calibrated hot film anemometer. The technique has great potential for laboratory setups involving rotating fluids in axisymmetric cavities, and we hope it will be especially useful in liquid metals. Acoustic spectra showing rotationally induced splittings. Top figure is the spectra recorded from a microphone near the equator and lower figure from a microphone at high latitude. Color indicates core's rotation rate in Hz.

  1. Helioseismology in a bottle: modal acoustic velocimetry

    Science.gov (United States)

    Triana, Santiago Andrés; Zimmerman, Daniel S.; Nataf, Henri-Claude; Thorette, Aurélien; Lekic, Vedran; Lathrop, Daniel P.

    2014-11-01

    Measurement of the differential rotation of the Sun's interior is one of the great achievements of helioseismology, providing important constraints for stellar physics. The technique relies on observing and analyzing rotationally-induced splittings of p-modes in the star. Here, we demonstrate the first use of the technique in a laboratory setting. We apply it in a spherical cavity with a spinning central core (spherical-Couette flow) to determine the mean azimuthal velocity of the air filling the cavity. We excite a number of acoustic resonances (analogous to p-modes in the Sun) using a speaker and record the response with an array of small microphones on the outer sphere. Many observed acoustic modes show rotationally-induced splittings, which allow us to perform an inversion to determine the air's azimuthal velocity as a function of both radius and latitude. We validate the method by comparing the velocity field obtained through inversion against the velocity profile measured with a calibrated hot film anemometer. This modal acoustic velocimetry technique has great potential for laboratory setups involving rotating fluids in axisymmetric cavities. It will be useful especially in liquid metals where direct optical methods are unsuitable and ultrasonic techniques very challenging at best.

  2. Helioseismology in a bottle: modal acoustic velocimetry

    International Nuclear Information System (INIS)

    Measurement of the differential rotation of the Sun's interior is one of the great achievements of helioseismology, providing important constraints for stellar physics. The technique relies on observing and analyzing rotationally-induced splittings of p-modes in the star. Here, we demonstrate the first use of the technique in a laboratory setting. We apply it in a spherical cavity with a spinning central core (spherical-Couette flow) to determine the mean azimuthal velocity of the air filling the cavity. We excite a number of acoustic resonances (analogous to p-modes in the Sun) using a speaker and record the response with an array of small microphones on the outer sphere. Many observed acoustic modes show rotationally-induced splittings, which allow us to perform an inversion to determine the air's azimuthal velocity as a function of both radius and latitude. We validate the method by comparing the velocity field obtained through inversion against the velocity profile measured with a calibrated hot film anemometer. This modal acoustic velocimetry technique has great potential for laboratory setups involving rotating fluids in axisymmetric cavities. It will be useful especially in liquid metals where direct optical methods are unsuitable and ultrasonic techniques very challenging at best. (paper)

  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. Clear air boundary layer spaced antenna wind measurement with the Multiple Antenna Profiler (MAPR

    Directory of Open Access Journals (Sweden)

    S. A. Cohn

    Full Text Available Spaced antenna (SA wind measurement techniques are applied to Multiple Antenna Profiler (MAPR data to evaluate its performance in clear air conditions. MAPR is a multiple antenna 915 MHz wind profiler developed at the National Center for Atmospheric Research (NCAR and described in Cohn et al. (1997, designed to make high resolution wind measurements. Previous reported measurements with MAPR were restricted to precipitation because of low signal to noise (SNR and signal to ground-clutter (SCR ratios. By using a standard pulse-coding technique and upgrading the profiler control software, increases in average power and SNR were achieved, making routine measurements in clear air possible. Comparison of winds measured by MAPR and by a sonic anemometer on a nearby 300 m tower show correlation coefficients in the range of R2 = 0.75 – 0.80, and an average absolute error of ~ 1.4 m s - 1 . This compares favorably with the agreement typically found in wind profiler comparisons. We also consider the use of the parameter ah , which is related to the value of the cross-correlation function at its zero crossing. This parameter is a data quality indicator and possibly a key component in a ground clutter removal technique.

    Key words. Meteorology and atmospheric dynamics (mesoscale meteorology; instruments and techniques – Radio science (remote sensing

  5. 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

  6. Scanning of wind turbine upwind conditions: numerical algorithm and first applications

    Science.gov (United States)

    Calaf, Marc; Cortina, Gerard; Sharma, Varun; Parlange, Marc B.

    2014-11-01

    Wind turbines still obtain in-situ meteorological information by means of traditional wind vane and cup anemometers installed at the turbine's nacelle, right behind the blades. This has two important drawbacks: 1-turbine misalignment with the mean wind direction is common and energy losses are experienced; 2-the near-blade monitoring does not provide any time to readjust the profile of the wind turbine to incoming turbulence gusts. A solution is to install wind Lidar devices on the turbine's nacelle. This technique is currently under development as an alternative to traditional in-situ wind anemometry because it can measure the wind vector at substantial distances upwind. However, at what upwind distance should they interrogate the atmosphere? A new flexible wind turbine algorithm for large eddy simulations of wind farms that allows answering this question, will be presented. The new wind turbine algorithm timely corrects the turbines' yaw misalignment with the changing wind. The upwind scanning flexibility of the algorithm also allows to track the wind vector and turbulent kinetic energy as they approach the wind turbine's rotor blades. Results will illustrate the spatiotemporal evolution of the wind vector and the turbulent kinetic energy as the incoming flow approaches the wind turbine under different atmospheric stability conditions. Results will also show that the available atmospheric wind power is larger during daytime periods at the cost of an increased variance.

  7. 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.

  8. 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)

  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. A sound budget for the southeastern Bering Sea: measuring wind, rainfall, shipping, and other sources of underwater sound.

    Science.gov (United States)

    Nystuen, Jeffrey A; Moore, Sue E; Stabeno, Phyllis J

    2010-07-01

    Ambient sound in the ocean contains quantifiable information about the marine environment. A passive aquatic listener (PAL) was deployed at a long-term mooring site in the southeastern Bering Sea from 27 April through 28 September 2004. This was a chain mooring with lots of clanking. However, the sampling strategy of the PAL filtered through this noise and allowed the background sound field to be quantified for natural signals. Distinctive signals include the sound from wind, drizzle and rain. These sources dominate the sound budget and their intensity can be used to quantify wind speed and rainfall rate. The wind speed measurement has an accuracy of +/-0.4 m s(-1) when compared to a buoy-mounted anemometer. The rainfall rate measurement is consistent with a land-based measurement in the Aleutian chain at Cold Bay, AK (170 km south of the mooring location). Other identifiable sounds include ships and short transient tones. The PAL was designed to reject transients in the range important for quantification of wind speed and rainfall, but serendipitously recorded peaks in the sound spectrum between 200 Hz and 3 kHz. Some of these tones are consistent with whale calls, but most are apparently associated with mooring self-noise. PMID:20649201

  11. Performance evaluation of stand alone hybrid PV-wind generator

    Science.gov (United States)

    Nasir, M. N. M.; Saharuddin, N. Z.; Sulaima, M. F.; Jali, Mohd Hafiz; Bukhari, W. M.; Bohari, Z. H.; Yahaya, M. S.

    2015-05-01

    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.

  12. Performance evaluation of stand alone hybrid PV-wind generator

    International Nuclear Information System (INIS)

    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

  13. State-of-the-Art Report on Five-hole Pitot tube

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Hyuk; Hwang, D. H.; Seo, K. W

    2007-03-15

    Five-hole pitot tube is an effective detector that could measure a three dimensional average flow field on a complex geometry. At the present study, have been mainly used in the field of aerodynamics and nautics, the five-hole pitot tube is extensively investigated to apply on the nuclear engineering. Five-hole pitot tube could measure the three dimensional velocity to make use of a relationship between pressure energy and kinetic energy from Bernoulli's equation; therefore, the report shortly overviewed the definition, units, and transducers of pressure and then detaily was described about the pitot tube. For five-hole pitot tube, history, kinds and fabrication methods were briefly provided. The calibration methods for the five-hole pitot tube were deeply introduced in various methods according to simple concept but complex process. Additionally, causeses of detection errors and estimation of uncertainty were included in the present report. Optical measurement and how wire anemometers are difficult to detect the flow velocity under environmental such as tight lattice bundle geometry, dusty flow and high temperature fluid. One of alternatives to overcome the diffculty is the five-hole pitot tube.

  14. Variation of 222Rn concentration in outdoor air due to variation of the atmospheric boundary layer

    International Nuclear Information System (INIS)

    Variation of 222Rn concentration in outdoor air, returns of a monostatic acoustic sounder and sensible heat flux are simultaneously observed at Okayama-shi in Japan. The sensible heat flux is measured with an eddy correlation method using a sonic anemometer and a copper-constantan thermocouple thermometer. Using height of a surface-based inversion layer obtained by the acoustic sounder returns and two 222Rn concentrations during the presence of the surface-based inversion layer, the exhalation rate of 222Rn at this site is estimated to be about 0.01 Bq.m-2.s-1, which agrees well within the exhalation rate of 222Rn estimated at Nagoya-shi in Japan. Using the estimated exhalation rates of 222Rn and the variation of the 222Rn concentration in the daytime, heights of mixing layers are estimated. These heights of the mixing layers are larger than the height of the mixing layer estimated using the sensible heat flux and the representative vertical profile of the autumnal night time air temperature in this area. (author)

  15. 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)

  16. Flow measurement and characterization in shallow geothermal systems used for downhole heat exchanger applications

    Energy Technology Data Exchange (ETDEWEB)

    Churchill, D.; Culver, G.G.; Reistad, G.M.

    1977-01-01

    In the largest non-electrical application of geothermal energy presently occurring in the United States, over 400 relatively shallow wells are being used for extraction of energy with downhole heat exchangers. Despite this large amount of application, the exact nature of the flows in the wells has not before been characterized. Knowledge to date on the nature of flows in the systems is summarized, and an ongoing experimental program for making appropriate downhole measurements to determine flows is described in detail. Flow characterization was a principal object of this study. Horizontal cross-flows of geothermal fluid may occur at upper and/or lower levels in the well where perforations in the well casing are situated. In addition, natural convection may induce vertical flows within the well casing which would be influenced by the presence or absence of a heat exchanger. Three main aspects of the experimental program are reported on: (i) a review of potentially applicable methods for measuring vertical and horizontal flows in wells, (ii) the limitations and preliminary results of using a vane anemometer for measuring vertical flows, and (iii) the description of the selected hot-film probe, its associated pressurized calibration facility, and means of making well measurements.

  17. Severe wind hazard using dynamically downscaled climate simulations

    International Nuclear Information System (INIS)

    Tropical cyclones, thunderstorms and sub-tropical storms can generate extreme winds that can cause significant economic loss. Severe wind is one of the major natural hazards in Australia. In this study, regional return period gust wind hazard (10 meter height over open terrain) is determined using a new methodology developed by Geoscience Australia. The methodology involves a combination of three models: A Statistical Model (ie. data-based model) to quantify wind hazard using extreme value distributions. A methodology to extract gridded hourly maximum mean (time-step) wind speed and direction fields from a high-resolution regional climate model (RCM). Area-averaged measurements from the RCM are 'corrected' for point measurement exposure by applying a regional factor to the RCM values. And a Monte Carlo method to calculate gust wind from RCM mean wind, the former is the value of interest in wind hazard. To assess accuracy, model results were compared against three wind recording stations in Tasmania. These sites were selected because their weather stations and anemometer measurements are located at airports, avoiding the problem of houses or trees affecting the instruments, and also due to these sites having wind gust records. The model works only with synoptic gust wind speeds. A methodology to calculate severe wind gusts associated with thunderstorm down-burst winds is under development.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Significance of face velocity fluctuation in relation to laboratory fume hood performance.

    Science.gov (United States)

    Tseng, Li-Ching; Huang, Rong Fung; Chen, Chih-Chieh

    2010-01-01

    In order to recognize the problems associated with the transport mechanism of containment during the ventilation process of a laboratory fume hood, a transparent, full scale chemical fume hood is constructed for experimental studies. Distributions of mean velocity and velocity fluctuation in the sash plane are measured using a thermal anemometer. Flow patterns and tracer-gas concentration leakages are respectively diagnosed via the laser-assisted flow visualization method and the EN 14175-3 test protocol. The magnitudes of measured velocity fluctuations exhibit a sharp peak along the perimeter of the sash opening. The results of flow visualization verify that the elevated turbulence fluctuations are induced by the boundary-layer separation when the flow passes over the edges of sash perimeter. The tracer gas experiment shows that the regions where high degree containment leakages detected are located along the perimeter of hood aperture. Eleven commercial hoods which are claimed with fine aerodynamic design are further tested for confirmation of these observations. The results show similar correlations. Conclusions thus are made that large-scale vortex structures occurring around the perimeters of hood aperture due to the boundary-layer separation could induce strong turbulence, and therefore enhance dispersion of the hood containment. PMID:20160407

  3. RTDS-based modelling and analysis of grid-connected fixed speed wind generator system

    Energy Technology Data Exchange (ETDEWEB)

    Park, D.J.; Kim, Y.J.; Park, M.; Yu, I.K. [Changwon National Univ., Bangladesh (Korea, Republic of). Dept. of Electrical Engineering; Ali, M.H. [Ryerson Polytechnic Univ., Toronto, ON (Canada). Dept. of Electrical and Computer Engineering

    2008-07-01

    Wind power is the most attractive renewable energy source in terms of energy efficiency and cost. This paper presented an innovative real-time simulation method for a grid connected wind generator system using a real time digital simulator (RTDS) based modeling and simulation technique. A 3 MW fixed-speed wind generator system was connected to the power grid and modeled using RSCAD. The simulated wind generator system was then interfaced with the RTDS in order to carry out simulations in real time. Random wind speed variations were considered. Transient stability analysis was carried out considering the speed control mode of the pitch angle control system. The responses of the wind generator terminal voltage, real power and rotor speed were observed and analyzed. Real wind speed data extracted from an anemometer was used in this work. The validity of the developed wind generator system was confirmed through simulation results. It was concluded that fluctuations in the wind generator can be minimized by changing the blade pitch angle. Future studies will include a comparison of the performance of the pitch angle control system with other methods for stabilizing wind generators. 8 refs., 2 tabs., 14 figs.

  4. 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.

  5. 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

    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 of the......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...... 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 of the...

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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).

  11. Field intercomparison of two optical analyzers for CH4 eddy covariance flux measurements

    Directory of Open Access Journals (Sweden)

    L. Emmenegger

    2010-07-01

    Full Text Available Fast response optical analyzers based on laser absorption spectroscopy are the preferred tools to measure field-scale mixing ratios and fluxes of a range of trace gases. Several state-of-the-art instruments have become commercially available and are gaining in popularity. This paper aims for a critical field evaluation and intercomparison of two compact, cryogen-free and fast response instruments: a quantum cascade laser based absorption spectrometer from Aerodyne Research, Inc., and an off-axis integrated cavity output spectrometer from Los Gatos Research, Inc. In this paper, both analyzers are characterized with respect to precision, accuracy, response time and also their sensitivity to water vapour. The instruments were tested in a field campaign to assess their behaviour under various meteorological conditions. The instrument's suitability for eddy covariance flux measurements was evaluated by applying an artificial flux of CH4 generated above a managed grassland with otherwise very low methane flux. This allowed an independent verification of the flux measurements accuracy, including the overall eddy covariance setup and data treatment. The retrieved fluxes were in good agreement with the known artificial emission flux, which is more than satisfactory, given that the analyzers were attached to separate sonic anemometers placed on individual eddy towers with different data acquisition systems but similar data treatment that are specific to the best practice used by the involved research teams.

  12. Field intercomparison of two optical analyzers for CH4 eddy covariance flux measurements

    Directory of Open Access Journals (Sweden)

    L. Emmenegger

    2010-11-01

    Full Text Available Fast response optical analyzers based on laser absorption spectroscopy are the preferred tools to measure field-scale mixing ratios and fluxes of a range of trace gases. Several state-of-the-art instruments have become commercially available and are gaining in popularity. This paper aims for a critical field evaluation and intercomparison of two compact, cryogen-free and fast response instruments: a quantum cascade laser based absorption spectrometer from Aerodyne Research, Inc., and an off-axis integrated cavity output spectrometer from Los Gatos Research, Inc. In this paper, both analyzers are characterized with respect to precision, accuracy, response time and also their sensitivity to water vapour. The instruments were tested in a field campaign to assess their behaviour under various meteorological conditions. The instrument's suitability for eddy covariance flux measurements was evaluated by applying an artificial flux of CH4 generated above a managed grassland with otherwise very low methane exchange. This allowed an independent verification of the flux measurements accuracy, including the overall eddy covariance setup and data treatment. The retrieved fluxes were in good agreement with the known artificial emission flux, which is more than satisfactory, given that the analyzers were attached to separate sonic anemometers placed on individual eddy towers with different data acquisition systems but similar data treatment that are specific to the best practice used by the involved research teams.

  13. Control of Vortex Shedding on an Airfoil using Mini Flaps at Low Reynolds Number

    Science.gov (United States)

    Oshiyama, Daisuke; Numata, Daiju; Asai, Keisuke

    2015-11-01

    In this study, the effects of mini flaps (MFs) on a NACA0012 airfoil were investigated experimentally at low Reynolds number. MFs are small flat plates attached to the trailing edge of an airfoil perpendicularly. All the tests were conducted at the Tohoku-University Basic Aerodynamic Research Tunnel at the chord Reynolds number of 25,000. Aerodynamic forces were measured using a 3-component balance and the surface flow was visualized by luminescent oil film technique. The results of force measurement show that attachment of MFs enhances lift and the enhanced lift increases with MF height. On the other hand, the results of oil flow visualization show that attachment of MFs enlarges the separated region on the airfoil rather than diminishes it. To understand the physical mechanism of MFs for lift enhancement, the flow around the airfoil was visualized by the smoke-wire method and the wake profile behind the airfoil was measured using a hot wire anemometer. It was found that vortices shed periodically from the tip of the MFs and interact with the separated shear layer from the upper surface. This unsteady vortex shedding forms a low-pressure region on the upper surface, generating higher lift. These results suggest that the height of MFs controls the frequency of vortex shedding behind the MF, forcing the separated shear layer on the upper surface flow in unsteady manner.

  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. 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.

  16. 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

  17. Experimental and analytical study of axial turbulent flows in an interior subchannel of a bare rod bundle

    International Nuclear Information System (INIS)

    Reactor fuel elements generally consist of rod bundles with the coolant flowing axially through the bundles in the space between the rods. Heat transfer calculations form an important part in the design of such elements, which can only be carried out if information of the velocity field is available. A one-equation statistical model of turbulence is applied to compute the detailed description of velocity field (axial and secondary flows) and the wall shear stress distribution of steady, fully developed turbulent flows with incompressible, temperature-independent fluid, flowing through triangular arrays of rods with different aspect ratios (P/D). Also experimental measurements of the distributions of the axial velocity, turbulence kinetic energy, and Reynolds stresses were performed using a laser Doppler anemometer (LDA), operating in a ''fringe'' mode with forward scattering, in a simulated interior subchannel of a triangular rod array with P/D = 1.123 and L/D/sub H/ = 77. From the experimental results, a new mixing length distribution is proposed. Comparisons between the analytical results and the results of this experiment as well as other experimental data available in the literature are presented. The results are in good agreement

  18. RSA/Legacy Wind Sensor Comparison. Part 2; Eastern Range

    Science.gov (United States)

    Short, David A.; Wheeler, Mark M.

    2006-01-01

    This report describes a comparison of data from ultrasonic and propeller-and-vane anemometers on 5 wind towers at Kennedy Space Center and Cape Canaveral Air Force Station. The ultrasonic sensors are scheduled to replace the Legacy propeller-and-vane sensors under the Range Standardization and Automation (RSA) program. Because previous studies have noted differences between peak wind speeds reported by mechanical and ultrasonic wind sensors, the latter having no moving parts, the 30th and 45th Weather Squadrons wanted to understand possible differences between the two sensor types. The period-of-record was 13-30 May 2005, A total of 357,626 readings of 1-minute average and peak wind speed/direction from each sensor type were used. Statistics of differences in speed and direction were used to identify 15 out of 19 RSA sensors having the most consistent performance, with respect to the Legacy sensors. RSA average wind speed data from these 15 showed a small positive bias of 0.38 kts. A slightly larger positive bias of 0.94 kts was found in the RSA peak wind speed.

  19. RSA/Legacy Wind Sensor Comparison. Part 1; Western Range

    Science.gov (United States)

    Short, David A.; Wheeler, Mark M.

    2006-01-01

    This report describes a comparison of data from ultrasonic and cup-and-vane anemometers on 5 wind towers at Vandenberg AFB. The ultrasonic sensors are scheduled to replace the Legacy cup-and-vane sensors under the Range Standardization and Automation (RSA) program. Because previous studies have noted differences between peak wind speeds reported by mechanical and ultrasonic wind sensors, the latter having no moving parts, the 30th and 45th Weather Squadrons wanted to understand possible differences between the two sensor types. The period-of-record was 13-30 May 2005. A total of 153,961 readings of I-minute average and peak wind speed/direction from each sensor type were used. Statistics of differences in speed and direction were used to identify 18 out of 34 RSA sensors having the most consistent performance, with respect to the Legacy sensors. Data from these 18 were used to form a composite comparison. A small positive bias in the composite RSA average wind speed increased from +0.5 kts at 15 kts, to +1 kt at 25 kts. A slightly larger positive bias in the RSA peak wind speed increased from +1 kt at 15 kts, to +2 kts at 30 kts.

  20. Presentations from 'The Bolund Experiment: Workshop' 3-4th December 2009

    Energy Technology Data Exchange (ETDEWEB)

    Bechmann, A.

    2010-08-15

    The Bolund experiment is a measuring campaign from a complex terrain performed in 2007 and 2008 where high frequency data from 35 anemometers provides a unique database designed to validate micro-scale flow models. Since no systematic comparison of micro-scale models existed it was decided to challenge micro-scale modelers to simulate the wind over Bolund and compare the results systematically. Since the Bolund measurements had not been published the comparison could be made blindly, i.e. the participants would not have prior knowledge of the measurement results. To broaden the types of models participating, modelers were invited worldwide from research institutes, universities and industry. More than 40 groups participated in the blind comparison with well over 50 model predictions and the blind comparison therefore gives an overview of the accuracy of micro-scale models anno 2010. On the 3-4 December 2009, 80 specialists in modeling of wind over complex terrain met at a Risoe DTU workshop where the model predictions and the Bolund measurements were revealed. During the workshop, interesting presentations were given about different flow modeling approaches. This report contains copies of the slide presentations given at the workshop. (LN)

  1. 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.

  2. 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.

  3. 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...

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Field measurements in the wake of a model wind turbine

    International Nuclear Information System (INIS)

    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

  9. Effects of wind shear and temperature inversion on sound propagation from wind turbines.

    Energy Technology Data Exchange (ETDEWEB)

    Haan, Henk de [Golder Associates (Canada)], email: Henk_deHaan@golder.com

    2011-07-01

    Noise impact assessment of wind turbines usually takes into account sound speed and propagation at ground level, and those are influenced by wind shear and atmospheric temperature changes. This paper focuses on a week-long monitoring study and presents the observed and anticipated effects of wind shear and temperature on the level of ground sound emitted from a 65m high wind turbine. Working with anemometers at ground level and turbine height, it is shown that wind shear can influence sound propagation, and that atmospheric stability must be taken into account for accurate wind speed calculations to be made. Temperature must also be addressed and the heating of the earth by solar radiation and the re-radiation of that heat in a day-night cycle, resulting in temperature inversion in the atmosphere, must be taken into account. Observations of temperature changes over a week can then yield sound speed and sound power levels with respect to altitude, and show that sound power levels are higher at ground levels during the night.

  10. 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...

  11. Investigation of the drag reducing effect of hydrophobized sand on cylinders

    International Nuclear Information System (INIS)

    Superhydrophobic surfaces show strong potential for drag reducing applications. If such a surface supports a Cassie–Baxter state with low solid surface fraction and when immersed it retains a plastron air layer, large slip can occur across its surface as well as a consequent reduction in drag. In this work we report a facile method for creating hydrophobic cylinders and hydrophobic flat surfaces with varying surface roughness able to support a Cassie–Baxter state. Cylinders of 12 mm diameter were coated in hydrophobized sand with grain sizes in the ranges of 50–100, 212–300, 425–600 and 600–710 µm to produce the varying degrees of roughness. A laser Doppler anemometer was used to measure the velocity profile of the water across their wake in a large water circulating flow chamber. The hydrophobic cylinders in the Cassie–Baxter state show drag reductions of up to 28% compared to the same sample in the Wenzel state for flows with Reynolds numbers of 10 000 to 40 000. These drag reduction results, in combination with confocal microscopy images of the plastron air layer and feature height, show that the thickness of the plastron and the protrusion height of the features combine to give a drag reduction or drag increase depending on the ratio of the two. (paper)

  12. 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)

  13. 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.

  14. 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.

  15. Inverse structure functions in the canonical wind turbine array boundary layer

    Science.gov (United States)

    Viggiano, Bianca; Gion, Moira; Ali, Naseem; Tutkun, Murat; Cal, Raúl Bayoán

    2015-11-01

    Insight into the statistical behavior of the flow past an array of wind turbines is useful in determining how to improve power extraction from the overall available energy. Considering a wind tunnel experiment, hot-wire anemometer velocity signals are obtained at the centerline of a 3 x 3 canonical wind turbine array boundary layer. Two downstream locations are considered referring to the near- and far-wake, and 21 vertical points were acquired per profile. Velocity increments are used to quantify the ordinary and inverse structure functions at both locations and their relationship between the scaling exponents is noted. It is of interest to discern if there is evidence of an inverted scaling. The inverse structure functions will also be discussed from the standpoint of the proximity to the array. Observations will also address if inverted scaling exponents follow a power law behavior and furthermore, extended self-similarity of the second moment is used to obtain the scaling exponent of other moments. Inverse structure functions of moments one through eight are tested via probability density functions and the behavior of the negative moment is investigated as well. National Science Foundation-CBET-1034581.

  16. Hot-wire calibration in a nonisothermal incompressible pressure variant flow

    Science.gov (United States)

    Hugo, Ronald J.; Nowlin, Scott R.; Eaton, Frank D.; Bishop, Kenneth P.; McCrae, Kimberley A.

    1999-08-01

    The calibration procedure for a hot-wire anemometer system operating in a non-isothermal pressure-variant flow field is presented. Sensing of atmospheric velocity and temperature fluctuations from an altitude-variant platform using hot- wire anemometry equipment operating in both constant- temperature and constant-current modes requires calibration for velocity, temperature, and atmospheric pressure variations. Calibration tests to provide the range of velocity, temperature and pressure variations anticipated during Air Force Research Lab, Directed Energy Directorate- sponsored kite/tethered-balloon experiments were conducted and the result of these tests presented. The calibration tests were performed by placing the kite/tethered-balloon sensor package on a vehicle and driving from Kirtland AFB, NM to the top of Sandia Crest, a 10678 ft mountain range to the east of Albuquerque, NM. By varying the velocity of the van and conducting the test at different times of the day, variations in velocity, temperature and pressure within the range of those encountered during the kite/tethered-balloon experiments were obtained. The method of collapsing the calibration data is presented. Problems associated with collecting hot-wire anemometry data in a non-laboratory environment are discussed. Example data sets of temperature and velocity collected during the kite/tethered-balloon experiments are presented.

  17. Thermally Driven Flow in a Mock Street Canyon

    Science.gov (United States)

    Dallman, Ann; Magnusson, Sigurdur; Norford, Leslie; Fernando, Harindra J. S.; Entekhabi, Dara; Britter, Rex; Pan, Shanshan

    2012-11-01

    Under conditions of low synoptic winds and high solar radiation, non-uniform heating of building walls and the ground in an urban street canyon induces thermally-driven airflow. These effects have mainly been studied using wind-tunnel experiments and numerical models, but only a few field-scale experiments have been performed. However, this is an important topic of interest because of its implications for air quality and emergency response planning. A field experiment was carried out in collaboration between the Singapore-MIT Alliance for Research and Technology (SMART) and the University of Notre Dame. The study was conducted on the campus of Nanyang Technical University in Singapore, and consisted of an `idealized' building canyon constructed with two rows of shipping containers aligned in the North-South direction. The site was carefully instrumented with sonic anemometers (for wind speed and direction and virtual temperature), weather stations (wind speed and direction, temperature, relative humidity, pressure, and rain fall), and thermocouples (surface temperature of buildings). Measurements were recorded for 9 days, which included periods of sunshine and high convective activity that created thermal circulation between the buildings. Using a fog machine, flow visualization was carried out to observe circulation patterns. An overview of the experiment and the results will be presented.

  18. Formulation of a wind specification for Titan late polar summer exploration

    Science.gov (United States)

    Lorenz, Ralph D.; Newman, Claire E.; Tokano, Tetsuya; Mitchell, Jonathan L.; Charnay, Benjamin; Lebonnois, Sebastien; Achterberg, Richard K.

    2012-09-01

    Titan's polar regions, and its hydrocarbon lakes in particular, are of interest for future exploration. The polar conditions have considerable seasonal variation and are distinct from the equatorial environment experienced by Huygens. Thus specific environmental models are required for these regions. This paper, informed by Cassini and groundbased observations and four independent Global Circulation Models (GCMs), summarizes northern summer polar conditions (specifically, regions north of 65°N, during the 2023-2024 period, or solar longitude Ls˜150o-170°) and presents a simple analytical formulation of expected, minimum and maximum winds as a function of altitude to aid spacecraft and instrument design for future exploration, with particular reference to the descent dispersions of the Titan Mare Explorer (TiME) mission concept presently under development. We also consider winds on the surface, noting that these (of relevance for impact conditions, for waves, and for wind-driven drift of a floating capsule) are weaker than those in the lowest cell in most GCMs: some previously-reported estimates of 'surface' wind speeds (actually at 90-500 m altitude) should be reduced by 20-35% to refer to the standard 10 m 'anemometer height' applicable for surface phenomena. A Weibull distribution with scale speed C=0.4 m/s and shape parameter k=2.0 embraces the GCM-predicted surface wind speeds.

  19. 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.

  20. One semester course in wind energy for advanced undergraduate and graduate engineering students

    International Nuclear Information System (INIS)

    The recent increase in energy consumption in India is resulting in high levels of greenhouse gas emissions. Attempts to harness new renewable energy sources such as wind power is creating the need for trained manpower in aerospace engineering and mechanical engineering. The course outline for a one semester course in wind energy for advanced undergraduate and graduate engineering students at the Indian Institute of Technology was presented in this paper. A history of wind energy was also presented along with the approaching global environmental crisis. International efforts and conventions to reduce greenhouse gas emissions were discussed. India's geography and relationship to wind resources were presented in terms of its latitude and geostrophic winds. The course outline also includes a section on measuring instruments (anemometers) and organization of wind data using Weibull distribution as well as the impacts of summer and monsoon winds. The aerodynamics of wind turbines including airfoils, airscrew theory, and its application to wind turbines were discussed. Rural and remote area usage of wind turbines as well as the structural design and construction of wind turbine blades using composite materials are also examined in the course. Last, the course presents a video cassette and a 16 mm film on wind energy and advises students that they are exposed to laboratory and field practices and encouraged to do practical projects. The course contains a discussion of policy issues such as reaching the common people, and industry-academia interaction. 8 refs., 10 figs

  1. A new test bench for HWA fluid-dynamic characterization of a two-valved in-piston-bowl production engine

    Energy Technology Data Exchange (ETDEWEB)

    Catania, A.E.; Dongiovanni, C.; Mittica, A.; Molina, G.; Spessa, E. [Politecnico di Torino, Turin (Italy)

    1995-12-31

    A new test bench has been sup up and equipped in order to analyze the air mean motion and turbulence quantities in the combustion system of an automotive diesel engine with one helicoidal intake duct and a conical type in-piston bowl. A sophisticated HWA technique employing single- and dual-sensor probes was applied to the in-cylinder flow investigation under motored conditions. The anemometric probe was also operated as a thermometric sensor. An analytical-numerical procedure, based on the heat balance equations for both anemometric and thermometric wires, was refined and applied to compute the gas velocity from the anemometer output signal. The gas property influence, the thermometric sensor lag and the prong temperature effects were taken into account with this procedure. The in-cylinder velocity data were reduced using both a cycle-resolved approach and the conventional ensemble-averaging procedure, in order to separate the mean flow from the fluctuating motion. New results on the statistical properties of the non-stationary engine turbulence, with particular reference to its time-frequency spectral structure, were obtained at practical engine speeds, in the range of 600--3,000 rpm, and at different locations along the injector axis, one of which was very close to the cylinder-head wall.

  2. Analysis of airborne Doppler lidar, Doppler radar and tall tower measurements of atmospheric flows in quiescent and stormy weather

    Science.gov (United States)

    Bluestein, H. B.; Doviak, R. J.; Eilts, M. D.; Mccaul, E. W.; Rabin, R.; Sundara-Rajan, A.; Zrnic, D. S.

    1986-01-01

    The first experiment to combine airborne Doppler Lidar and ground-based dual Doppler Radar measurements of wind to detail the lower tropospheric flows in quiescent and stormy weather was conducted in central Oklahoma during four days in June-July 1981. Data from these unique remote sensing instruments, coupled with data from conventional in-situ facilities, i.e., 500-m meteorological tower, rawinsonde, and surface based sensors, were analyzed to enhance understanding of wind, waves and turbulence. The purposes of the study were to: (1) compare winds mapped by ground-based dual Doppler radars, airborne Doppler lidar, and anemometers on a tower; (2) compare measured atmospheric boundary layer flow with flows predicted by theoretical models; (3) investigate the kinematic structure of air mass boundaries that precede the development of severe storms; and (4) study the kinematic structure of thunderstorm phenomena (downdrafts, gust fronts, etc.) that produce wind shear and turbulence hazardous to aircraft operations. The report consists of three parts: Part 1, Intercomparison of Wind Data from Airborne Lidar, Ground-Based Radars and Instrumented 444 m Tower; Part 2, The Structure of the Convective Atmospheric Boundary Layer as Revealed by Lidar and Doppler Radars; and Part 3, Doppler Lidar Observations in Thunderstorm Environments.

  3. 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.

  4. 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.

  5. Research on Development Trend of Wind Direction and Wind Speed Sensor of Wind Turbine%风电机组风速风向仪未来发展趋势研究

    Institute of Scientific and Technical Information of China (English)

    梁宇飞

    2013-01-01

    Wind direction and wind speed sensor is the most important element of wind turbine, its working characteristics are directly related to the control strategy and power efciency of fan. In this paper, through the analysis and comparison of the wind turbine mechanical, traditional principle of ultrasonic and ultrasonic resonance wind instrument structure and the advantages and disadvantages, ultrasonic resonance type wind instrument with long service life, high practicability, compact and light and excellent sensitivity and accuracy, will gradually replace the mechanical and the traditional ultrasonic wind anemometer in the future.%风速风向仪是风电机组最重要的传感元件,它的工作特性直接关系到风电机组的控制策略和发电效率。本文通过对风电机组机械式、传统超声波式和超声波共振式风速风向仪结构原理和优缺点的对比分析,超声波共振式风向风速仪因寿命长、实用性高、小而轻的结构及出色的灵敏度和准确性,必将在未来的发展竞争中逐步取代机械式和传统超声波式风向风速仪。

  6. A comparison of wind turbulence simulation models for stochastic loads analysis for horizontal-axis wind turbines

    Science.gov (United States)

    Walker, S. N.; Weber, T. L.; Wilson, R. E.

    1989-06-01

    Four wind turbine turbulence codes, the Pacific Northwest Laboratory (PNL) Rotational Code, the PNL Simulation Code, the Holley Code, and the Sandia National Laboratories Code, were examined. Hub-height simulations were made with each code and were compared to hub-height wind data from the vertical plane array of anemometers at the Howden 330-kW horizontal-axis wind turbine (HAWT). Blade tip simulations were made with each code and were compared to rotational wind data taken from the Howden-330 kW HAWT. The PNL Rotational Code was given an overall rating of satisfactory for large wind turbine applications and an overall rating of good for small wind turbine applications. The PNL Simulation Code was given a rating of good when used with large turbines and a rating of very good when used with small turbines. The Holley Code and the Sandia Code were given ratings of good and satisfactory, respectively, for both large and small wind turbine applications. The Sandia Code could be upgraded if documentation were made available. Further upgrades for any of the codes would require major revision.

  7. A comparison of two-and three-dimensional S809 airfoil properties for rough and smooth HAWT (Horizontal-Axis Wind Tunnel) rotor operation

    Science.gov (United States)

    Musial, W. D.; Butterfield, C. P.; Jenks, M. D.

    1990-02-01

    At the Solar Energy Research Institute (SERI), we carried out tests to measure the effects of leading-edge roughness on an S809 airfoil using a 10-m, three-bladed, horizontal-axis wind turbine (HAWT). The rotor employed a constant-chord (.457 m) blade geometry with zero twist. Blade structural loads were measured with strain gages mounted at 9 spanwise locations. Airfoil pressure measurements were taken at the 80 percent spanwise station using 32 pressure taps distributed around the airfoil surface. Detailed inflow measurements were taken using nine R.M. Young Model 8002 propvane anemometers on a vertical plane array (VPA) located 10 m upwind of the test turbine in the prevailing wind direction. The major objective of this test was to determine the sensitivity of the S809 airfoil to roughness on a rotating wind turbine blade. We examined this effect by comparing several parameters. We compared power curves to show the sensitivity of whole rotor performance to roughness. We used pressure measurements to generate pressure distributions at the 80 percent span which operates at a Reynolds number (Re) of 800,000. We then integrated these distributions to determine the effect of roughness on the section's lift and pressure-drag coefficients.

  8. The Influence of Rotor Configurations on the Energy Production in an Array of Vertical-Axis Wind Turbines

    Science.gov (United States)

    Kinzel, Matthias; Araya, Daniel; Dabiri, John

    2012-11-01

    We analyze the flow field within an array of 18 vertical-axis wind turbines (VAWTs) at full-scale and under natural wind conditions. The emphasis is on the energy flux into the turbine array and the energy extraction by the turbines. The wind velocities throughout the turbine array are measured using a portable meteorological tower with seven, vertically-staggered, three-component ultrasonic anemometers. These measurements yield a detailed insight into the turbine wakes and the recovery of the flow. A high planform kinetic energy flux is detected, which enables the flow velocities to return to 95% of the upwind value within six rotor diameters downwind from a turbine row. This is significantly faster than the recovery behind a typical horizontal-axis wind turbine (HAWT). The Presentation will compare the results for different rotor configurations. Conclusions will be drawn about the influence of these configurations on the power production of the individual turbines as well as the turbine array as a whole. The authors gratefully acknowledge funding from the National Science Foundation Energy for Sustainability program (Grant No. CBET-0725164) and the Gordon and Betty Moore Foundation.

  9. Measurement of Unsteady Aerodynamics Load on the Blade of Field Horizontal Axis Wind Turbine

    Science.gov (United States)

    Kamada, Yasunari; Maeda, Takao; Naito, Keita; Ouchi, Yuu; Kozawa, Masayoshi

    This paper describes an experimental field study of the rotor aerodynamics of wind turbines. The test wind turbine is a horizontal axis wind turbine, or: HAWT with a diameter of 10m. The pressure distributions on the rotating blade are measured with multi point pressure transducers. Sectional aerodynamic forces are analyzed from pressure distribution. Blade root moments are measured simultaneously by a pair of strain gauges. The inflow wind is measured by a three component sonic anemometer, the local inflow of the blade section are measured by a pair of 7 hole Pitot tubes. The relation between the aerodynamic moments on the blade root from pressure distribution and the mechanical moment from strain gauges is discussed. The aerodynamic moments are estimated from the sectional aerodynamic forces and show oscillation caused by local wind speed and direction change. The mechanical moment shows similar oscillation to the aerodynamic excepting the short period oscillation of the blade first mode frequency. The fluctuation of the sectional aerodynamic force triggers resonant blade oscillations. Where stall is present along the blade section, the blade's first mode frequency is dominant. Without stall, the rotating frequency is dominant in the blade root moment.

  10. An approach for measuring methane emissions from whole farms.

    Science.gov (United States)

    McGinn, S M; Flesch, T K; Harper, L A; Beauchemin, K A

    2006-01-01

    Estimates of enteric methane (CH4) emissions from ruminants are typically measured by confining animals in large chambers, using head hoods or masks, or by a ratiometric technique involving sampling respired air of the animal. These techniques are not appropriate to evaluate large-scale farm emissions and the variability between farms that may be partly attributed to different farm management. This study describes the application of an inverse-dispersion technique to calculate farm emissions in a controlled tracer-release experiment. Our study was conducted at a commercial dairy farm in southern Alberta, Canada (total of 321 cattle, including 152 lactating dairy cows). Sulfur hexafluoride (SF6) and CH4 were released from 10 outlet locations (barn and open pens) using mass-flow controllers. A Lagrangian stochastic (LS) dispersion model was then used to infer farm emissions from downwind gas concentrations. Concentrations of SF6 and CH4 were measured by gas chromatography analysis and open path lasers, respectively. Wind statistics were measured with a three-dimensional sonic anemometer. Comparing the inferred emissions with the known release rate showed we recovered 86% of the released CH4 and 100% of the released SF6. The location of the concentration observations downwind of the farm was critically important to the success of this technique. PMID:16391273

  11. 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.

    2016-01-01

    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

  12. Distributed Sensible Heat Flux Measurements for Wireless Sensor Networks

    Science.gov (United States)

    Huwald, H.; Brauchli, T.; Lehning, M.; Higgins, C. W.

    2015-12-01

    The sensible heat flux component of the surface energy balance is typically computed using eddy covariance or two point profile measurements while alternative approaches such as the flux variance method based on convective scaling has been much less explored and applied. Flux variance (FV) certainly has a few limitations and constraints but may be an interesting and competitive method in low-cost and power limited wireless sensor networks (WSN) with the advantage of providing spatio-temporal sensible heat flux over the domain of the network. In a first step, parameters such as sampling frequency, sensor response time, and averaging interval are investigated. Then we explore the applicability and the potential of the FV method for use in WSN in a field experiment. Low-cost sensor systems are tested and compared against reference instruments (3D sonic anemometers) to evaluate the performance and limitations of the sensors as well as the method with respect to the standard calculations. Comparison experiments were carried out at several sites to gauge the flux measurements over different surface types (gravel, grass, water) from the low-cost systems. This study should also serve as an example of spatially distributed sensible heat flux measurements.

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

    Directory of Open Access Journals (Sweden)

    Matthew Stickland

    2013-09-01

    Full Text Available 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 met mast situated in flat terrain. The so-called “NORSEWInD standard” for comparing lidar and mast wind data includes the criteria that the slope of the linear regression should lie within 0.98 and 1.01 and the linear correlation coefficient higher than 0.98 for the wind speed range 4–16 m∙s−1. Five lidars performed excellently, two slightly failed the first criterion and one failed both. The lidars were operated offshore from six months to more than two years and observed in total 107 months of 10-min mean wind profile observations. Four lidars were re-evaluated post deployment with excellent results. The flow distortion around platforms was examined using wind tunnel experiments and computational fluid dynamics and it was found that at 100 m height wind observations by the lidars were not significantly influenced by flow distortion. Observations of the vertical wind profile shear exponent at hub height are presented.

  14. Laminar Turbulent Transition in a Boundary Layer Subjected to Weak Free Stream Turbulence

    Science.gov (United States)

    Kenchi, Toshiaki; Matsubara, Masaharu; Ikeda, Toshihiko

    For revealing the transition process in a flat plate boundary layer subjected to a weak free stream turbulence, flow visualization and hot-wire measurements were performed. A weak free stream turbulence was generated by a turbulence grid mounted upstream of the contraction. The flow visualization clearly displayed a transition scenario in which a local two-dimensional wave packet rapidly forms a Λ shape structure and then breaks down to turbulence, resulting in the generation of a turbulent spot. Quantitative measurements performed by using a hot-wire anemometer also confirmed the existence of local Tollmien-Schlichting waves that agreed with the parallel linear theory in terms of their frequency, phase velocity, and the wall-normal distribution of band-pass-filtered fluctuations. For comparison, a boundary layer subjected to a moderate-intensity free stream turbulence was investigated. This investigation showed that streaky structures play an important role in the boundary layer transition, as shown by Matsubara et al. [J. Fluid Mech., 430, (2001), 149-168.] A drastic change occurred in the transition process and this change could be sensitively determined by employing the intensity and/or spectra of the free stream turbulence.

  15. 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.

  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. 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. Analysis environment meteorology data around PPNY using PC with windows system

    International Nuclear Information System (INIS)

    The Installation of a small station to measure some meteorological parameters had been done in Yogyakarta Nuclear Research Centre (PPNY) in order to keep the weather conditions under control, especially wind direction, wind speed, and outdoor temperature. The anemometer with temperature probe (WS-10T) was connected to the game adapter of the Personal Computer (PC) using 40 feet flat cable. A data file entry was automatically written by WS-10T at six minutes interval whenever the program was in operation. The data files are labeled by date as MMDD.log (MM=Months, DD=Day) and if the program is operated continuously. a new file be started each midnight. By the analysis data using SPSS for windows. The range of temperature were 67oF until 97.6oF . he maximum speed of wind was 17.7 Mph and the frequency of wind direction at the most was to the North (18.9 %). The analysis of meteorological data around vicinity was done to get the annual profile of wind speed , wind direction and outdoor temperature. (author)

  1. 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.)

  2. Detection of single microparticles in airflows by edge-filter enhanced self-mixing interferometry.

    Science.gov (United States)

    Contreras, Victor; Lönnqvist, Jan; Toivonen, Juha

    2016-04-18

    A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometry (ESMI) is presented based on speed measurements of single microparticles. The ESMI detection utilizes an acetylene edge-filter that maps the frequency modulation of a semiconductor laser into an intensity modulation as the laser wavelength is tuned to the steep edge of the absorption profile. In this work, the ESMI signal was analyzed for aerosol particles of different sizes from 1 μm to 10 μm at a distance of 2.5 m. At this operation range, the signal from single particles of all sizes was successfully acquired enabling particle velocity measurements through the Doppler shifted frequency along the beam axis. For the particular case of 10 μm particles, single aerosol particles were still detected at an unprecedented range of 10 m. A theoretical treatment describing the relation between Mie scattering theory and the self-mixing phenomenon on single-particle detection is presented supporting the experimental results. The results show that the edge-filter enhanced self-mixing technique opens new possibilities for self-mixing detection where longer ranges, lower backscattering laser powers and higher velocities are involved. For example, it can be used as a robust and inexpensive anemometer for LDV applications for airflows with low-number density of microparticles. PMID:27137321

  3. Effect of the duty cycle on the spark-plug plasma synthetic jet actuator

    Science.gov (United States)

    Seyhan, Mehmet; Erkan Akansu, Yahya; Karakaya, Fuat; Yesildag, Cihan; Akbıyık, Hürrem

    2016-03-01

    A promising novel actuator called Spark-Plug Plasma Synthetic Jet (SPSJ) has been developed in Atmospheric Plasma Research Laboratory at Niğde University. It generates electrothermally high synthetic jet velocity by using high voltage. SPSJ actuator can be utilized to be an active flow control device having some advantages such as no moving parts, low energy consumption and easy to integrate the system. This actuator consists of two main components: semi-surface spark plug (NGK BUHW) as an anode electrode and a cap having an orifice as a cathode electrode. The cap, having a jet exit orifice diameter of 2 mm, has diameter of 4.4 mm and height of 4.65 mm. This study presents the characteristics of SPSJ actuator by using the hot wire anemometer in order to approximately determine jet velocity in quiescent air. Peak velocity as high as 180 m/s was obtained for fe= 100 and duty cycle 50%. The flow visualization indicated that the actuator's jet velocity is enough to penetrate the developed boundary layer.

  4. Effect of the duty cycle on the spark-plug plasma synthetic jet actuator

    Directory of Open Access Journals (Sweden)

    Seyhan Mehmet

    2016-01-01

    Full Text Available A promising novel actuator called Spark-Plug Plasma Synthetic Jet (SPSJ has been developed in Atmospheric Plasma Research Laboratory at Niğde University. It generates electrothermally high synthetic jet velocity by using high voltage. SPSJ actuator can be utilized to be an active flow control device having some advantages such as no moving parts, low energy consumption and easy to integrate the system. This actuator consists of two main components: semi-surface spark plug (NGK BUHW as an anode electrode and a cap having an orifice as a cathode electrode. The cap, having a jet exit orifice diameter of 2 mm, has diameter of 4.4 mm and height of 4.65 mm. This study presents the characteristics of SPSJ actuator by using the hot wire anemometer in order to approximately determine jet velocity in quiescent air. Peak velocity as high as 180 m/s was obtained for fe= 100 and duty cycle 50%. The flow visualization indicated that the actuator’s jet velocity is enough to penetrate the developed boundary layer.

  5. Analysis and optimization of the heat transfer coefficient of a finned heat exchanger submitted to natural convection; Analise e otimizacao do coeficiente de transferencia de calor de um trocador aletado submetido a conveccao natural

    Energy Technology Data Exchange (ETDEWEB)

    Rocha, Alan Carlos Bueno da

    1997-07-01

    A heat transfer (condenser) of a domestic freezer was tested in a vertical channel in order to study the influence of the chimney effect in the optimization of the heat transfer coefficient. The variation of the opening of the channel, position and the heating power of the heat exchanger in the heat transfer coefficient was considered. The influence of the surface emissivity on the heat transfer by thermal radiation was studied with the heat exchanger testes without paint and with black paint. The air velocity entering the channel was measured with a hot wire anemometer. In order to evaluate the chimney effect, the heat exchanger was testes in a open ambient. This situation simulates its operational conditions when installed on the freezer system. The variables collected in the experimental procedures was gathered in the form of dimensionless parameters as Nusselt, Rayleigh, Grashof and Prandtl numbers, and dimensional parameters of the convection. The results showed that the highest heat transfer value occurred when both a specific position and a specific channel opening were used. The experiments pointed out that the radiation contribution must be considered in heat transfer calculations. The conclusions showed that different channel openings can improve the heat transfer coefficient in this heat transfer exchanger. (author)

  6. 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.

  7. 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.)

  8. 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.

  9. 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...

  10. Profiles of Wind and Turbulence in the Coastal Atmospheric Boundary Layer of Lake Erie

    International Nuclear Information System (INIS)

    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

  11. 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.

  12. Turbulence modification in vertical upward annular flow passing through a throat section

    International Nuclear Information System (INIS)

    Experimental studies on the turbulence modification in annular two-phase flow passing through a throat section were carried out. The turbulence modification in multi-phase flow due to the interactions between two-phases is one of the most interesting scientific issues and has attracted research attention. In this study, the gas-phase turbulence modification in annular flow due to the gas-liquid phase interaction is experimentally investigated. The annular flow passing through a throat section is under the transient state due to the changing cross sectional area of the channel and resultantly the superficial velocities of both phases are changed compared with a fully developed flow in a straight pipe. The measurements for the gas-phase turbulence were precisely performed by using a constant temperature hot-wire anemometer, and made clear the turbulence structure such as velocity profiles, fluctuation velocity profiles. The behavior of the interfacial waves in the liquid film flow such as the ripple or disturbance waves was also observed. The measurements for the liquid film thickness by the electrode needle method were also performed to measure the base film thickness, mean film thickness, maximum film thickness and wave height of the ripple or the disturbance waves

  13. Locating a compact odor source using a four-channel insect electroantennogram sensor

    Energy Technology Data Exchange (ETDEWEB)

    Myrick, A J; Baker, T C [Chemical Ecology Laboratory, Department of Entomology, Pennsylvania State University, University Park, PA 16802 (United States)

    2011-03-15

    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 ({approx}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.

  14. Flux measurement of methanol, acetaldehyde and other oxygenated VOCs from crop harvesting using proton-transfer-reaction mass spectrometry and surface layer gradient method

    International Nuclear Information System (INIS)

    PTR-MS technique was used to measure fluxes of various VOC's including oxygenates using surface layer gradient method. The VOC concentrations and temperature were measured at heights of about 0.5 m and 3.9 m above ground at field site in St. Johann in Tirol during and after grass cutting (24th and 25th of May 2000) in order to calculate fluxes. The sensible heat flux was obtained by a sonic anemometer with turbulence data analyzer. The major crop in this part of Austria are perennial grasses used for livestock farming. We observed VOC emission fluxes including methanol and acetaldehyde as the major volatile, C5 and C6 leaf wound compounds with lesser amounts and traces of acetone and butanone. This composition of VOC's is very similar to that released from slashed pasture grass. At the same time, VOC fluxes were measured with PTR-MS and eddy covariance method. Comparing the flux data of methanol and acetaldehyde of both days have shown very similar results. (author)

  15. 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)

  16. 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∗ .

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Automation of radiation exposure dose calculation in the area surrounding reactor of Musashi Institute of Technology

    International Nuclear Information System (INIS)

    The purpose of this study is to develop a system, by which the data on wind direction, wind velocity, temperature, humidity, sunshine, radiation balance, rain fall and others in the vicinity of the stack of the nuclear facility are collected every moment and analyzed, the information not measured so far is extracted, those are continuously digitally recorded, and if the release of radioactive materials out of the stack is assumed, its effects on the surrounding environment are immediately computed and indicated on a graphic display. The system to detect abnormality for the back up of reactor operators and to issue the appropriate instruction is also to be developed in parallel by collecting data on the operating status of the reactor and from the monitors watching the surrounding area. It is considered to unify the data format for carrying out easily mutual comparison of such data and their evaluation in future and to connect the reactor facilities of universities in Japan on-line if possible, by co-developing this system together with these universities making the reactor of Musashi Institute of Technology as a model. In this report, the system configuration and block diagrams and respective satellite functions and operations are described. These satellites include new MK system, reactor-related data collection, weather data collection, colored CRT display, operator console, and packet type data exchanger. Most noteworthy is the data collection with an ultrasonic anemometer, and its construction is illustrated. (Wakatsuki, Y.)

  2. 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.

  3. Effect of Inlet Geometry on Fan Performance and Flow Field in a Half-Ducted Propeller Fan

    Directory of Open Access Journals (Sweden)

    Pin Liu

    2012-01-01

    Full Text Available In order to clarify the effect of rotor inlet geometry of half-ducted propeller fan on performance and velocity fields at rotor outlet, the experimental investigation was carried out using a hotwire anemometer. Three types of inlet geometry were tested. The first type is the one that the rotor blade tip is fully covered by a casing. The second is that the front one-third part of blade tip is opened and the rest is covered. The third is that the front two-thirds are opened and the rest is covered. Fan test and internal flow measurement at rotor outlet were conducted about three types of inlet geometry. At the internal flow measurement, a single slant hotwire probe was used and a periodical multisampling technique was adopted to obtain the three-dimensional velocity distributions. From the results of fan test, the pressure-rise characteristic drops at high flowrate region and the stall point shifts to high flowrate region, when the opened area of blade tip increases. From the results of velocity distributions at rotor outlet, the region with high axial velocity moves to radial inwards, the circumferential velocity near blade tip becomes high, and the flow field turns to radial outward, when the opened area increases.

  4. Investigation of the Airflow inside Realistic and Semi-Realistic Replicas of Human Airways

    Directory of Open Access Journals (Sweden)

    Lizal Frantisek

    2015-01-01

    Full Text Available Measurement of velocity in human lungs during breathing cycle is a challenging task for researchers, since the measuring location is accessible only with significant difficulties. A special measuring rig consisting of optically transparent replica of human lungs, breathing simulator, particle generator and Laser-Doppler anemometer was developed and used for investigation of the velocity in specific locations of lungs during simulated breathing cycle. Experiments were performed on two different replicas of human lungs in corresponding measuring points to facilitate the analysis of the influence of the geometry and its simplification on the flow. The analysis of velocity course and turbulence intensity revealed that special attention should be devoted to the modelling of vocal cords position during breathing, as the position of laryngeal jet created by vocal cords significantly influences velocity profiles in trachea. The shapes of velocity courses during expiration proved to be consistent for both replicas; however magnitudes of peak expiratory velocity differ between the corresponding measuring points in both the replicas.

  5. Experimental study of flow and heat transfer in a rotating chemical vapor deposition reactor

    Science.gov (United States)

    Wong, Sun

    An experimental model was set up to study the rotating vertical impinging chemical vapor deposition reactor. Deposition occurs only when the system has enough thermal energy. Therefore, understanding the fluid characteristic and heat transfer of the system will provide a good basis to understand the full model. Growth rate and the uniformity of the film are the two most important factors in CVD process and it is depended on the flow and thermal characteristic within the system. Optimizing the operating parameters will result in better growth rate and uniformity. Operating parameters such as inflow velocity, inflow diameter and rotational speed are used to create different design simulations. Fluid velocities and various temperatures are recorded to see the effects of the different operating parameters. Velocities are recorded by using flow meter and hot wire anemometer. Temperatures are recorded by using various thermocouples and infrared thermometer. The result should provide a quantitative basis for the prediction, design and optimization of the system and process for design and fabrication of future CVD reactors. Further assessment of the system results will be discuss in detail such as effects of buoyancy and effects of rotation. The experimental study also coupled with a numerical study for further validation of both model. Comparisons between the two models are also presented.

  6. 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.

  7. The Stand-alone Heliostat

    International Nuclear Information System (INIS)

    The first Autonomous Heliostat has been developed by CIEMAT at PSA facilities in Almeria. This heliostat is an innovative approach to reducing the civil engineering work costs in heliostat fields of central tower plants. Channels, cables and other electric elements have been eliminated in the new heliostat. Thus, one 70-nr, classical T glass/metal heliostat has been adapted to include all the new stand-alone concept components. A PV system is able to drive two sun-tracking DC motors between 5 and 24Vdc, 0 and 15A. The heliostat communicates with the control room 400-m away by using a radio-modem working at 9600 baud. An anemometer, a wind switcher, light and ambient temperature sensors have been installed on the heliostat for self-protection decision-making. A PV panel integrated into the heliostat reflecting surface, eliminates cabling and other elements required for a conventional power supply. Communication lines between master control and local control have been replaced by radio-modem. Testing has validated the technical feasibility of the prototype and quantified the real consumption and efficiencies of new elements. The extra costs produced.by the autonomous concepts are compared with the cost of civil work in conventional heliostat field. (Author) 8 refs

  8. 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.

  9. 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.

  10. 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.

  11. Nitrous oxide emissions from a commercial cornfield (Zea mays) measured using the eddy covariance technique

    Science.gov (United States)

    Huang, H.; Wang, J.; Hui, D.; Miller, D. R.; Bhattarai, S.; Dennis, S.; Smart, D.; Sammis, T.; Reddy, K. C.

    2014-12-01

    Increases in observed atmospheric concentrations of the long-lived greenhouse gas nitrous oxide (N2O) have been well documented. However, information on event-related instantaneous emissions during fertilizer applications is lacking. With the development of fast-response N2O analyzers, the eddy covariance (EC) technique can be used to gather instantaneous measurements of N2O concentrations to quantify the exchange of nitrogen between the soil and atmosphere. The objectives of this study were to evaluate the performance of a new EC system, to measure the N2O flux with the system, and finally to examine relationships of the N2O flux with soil temperature, soil moisture, precipitation, and fertilization events. An EC system was assembled with a sonic anemometer and a fast-response N2O analyzer (quantum cascade laser spectrometer) and applied in a cornfield in Nolensville, Tennessee during the 2012 corn growing season (4 April-8 August). Fertilizer amounts totaling 217 kg N ha-1 were applied to the experimental site. Results showed that this N2O EC system provided reliable N2O flux measurements. The cumulative emitted N2O amount for the entire growing season was 6.87 kg N2O-N ha-1. Seasonal fluxes were highly dependent on soil moisture rather than soil temperature. This study was one of the few experiments that continuously measured instantaneous, high-frequency N2O emissions in crop fields over a growing season of more than 100 days.

  12. Effect of unsteady wind on drifting snow

    Science.gov (United States)

    Cierco, F.-X.; Naaim-Bouvet, F.; Naaim, M.

    2003-04-01

    Wind is not always a steady flow. It can oscillate producing blasts. However most of the current numerical models of drifting snow are constrained by one major assumption : forcing winds are steady and uniform. Experiments done in the CSTB climatic wind tunnel (with a data acquisition frequency of 1 Hz both for wind and drifting snow) showed that drifting snow is in a state of permanent disequilibrium in the presence of fluctuating airflows : mass flux and velocity were poorly matched. However, the study of wind and drifting snow gust factors done at Col du Lac Blanc (parameters recorded every 15 min with a scan rate of 1 s) shown that the largest drifting snow episodes appear during periods of roughly constant strong wind whereas a short but strong blast does not produce significant drifting snow. In order to better understand the effect of unsteady wind on drifting snow processes, these first investigations have been completed during winter 2003 by increasing the acquisition frequency during snow storms at Col du Lac Blanc using an ultrasonic anemometer and a profile of six drifting snow acoustic sensors set up side by side.

  13. 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.

  14. Active control of flow around a square prism by slot jet injection

    Directory of Open Access Journals (Sweden)

    Hacıalioğulları M.

    2013-04-01

    Full Text Available The main aim of the experimental study is to determine both the most effective injection surface and rate in order to ensure minimum drag and fluctuating forces on a square prism subjected to crossflow. All predetermined jet injection surfaces i.e. front, side, and rear, tested separately for injection ratios of IR = 0, 1, 1.5, 2 at Reynolds number of Re = 16,000. Surface pressures were measured by differential pressure transducer whereas instantaneous velocity measurements were performed by using multichannel Constant Temperature Anemometer (CTA. It was concluded that jet injection, especially from the rear surface, brought noticeable improvements to the flow characteristics of a square prism. For rear jet configuration with IR = 1.5, the mean drag coefficient (CDT¯$overline {{C_{{m{DT}}}}} $ was reduced to 79.4% and CP RMS level on side surfaces was reduced to 20% of that of the single square prism. In addition, instantaneous flow visualization photographs and Strouhal number (St distribution across the injection ratio were also presented to identify the flow patterns and underlying mechanism of drag and fluctuating force reduction of square prism with rear jet configuration.

  15. 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.

  16. 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

  17. 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.

  18. Meso-scale modeling of a forested landscape

    International Nuclear Information System (INIS)

    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 2010-2012. The land cover around the mast is dominated by forest and for the most common wind direction, the forest extends more than 200 km from the mast. The two low-roughness simulations showed differences both in terms of estimated wind resource and wind shear. The simulation with enhanced roughness results in an improved correlation with measured data for near-neutral situations in the observed height range, whereas the correlation is deteriorated relative to the standard setup for stable atmospheric stratifications for heights above approximately 80 m. The inclusion of the displacement height in the post-processing of the results is also discussed

  19. 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.)

  20. 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.