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Taro Nakai - One of the best experts on this subject based on the ideXlab platform.
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ultrasonic anemometer Angle of Attack errors under turbulent conditions
Agricultural and Forest Meteorology, 2012Co-Authors: Taro Nakai, K ShimoyamaAbstract:Abstract Measurements of eddy fluxes are premised on the assumption that wind velocities are measured accurately by an ultrasonic anemometer. Recently, Gill ultrasonic anemometers have been shown to suffer errors depending on the Angle of Attack, which is the Angle between the wind vector and the horizontal. The correction of these errors results in general eddy flux increases. However, since calibration for error dependent on Angle of Attack was carried out in a wind tunnel experiment under conditions of nearly laminar flow, the applicability of this correction to the field data under turbulent conditions has been questioned. In this study, Angle of Attack errors from a Gill WindMaster ultrasonic anemometer were assessed by field experiment, over meadow and under turbulent conditions. By using five identical anemometers, two configurations were evaluated: two pairs of anemometers for reference and one between the pairs for tilt. The dependence of anemometer (co)sine response on 0 to −90° Angles of Attack in 10° steps and at 45° were checked. It was clarified that errors dependent on Angle of Attack occur even under turbulent conditions, with results similar to the wind tunnel experiments. Sine responses of vertical wind velocities here depended not only on vertical Angle of Attack but also on horizontal wind direction, a dynamic not considered in previous studies. For a more robust correction, alternative calibration functions were obtained empirically, so as to reasonably explain our field experimental results. Applying this new correction, eddy fluxes increased substantially even over meadow, which is somewhat aerodynamically smooth compared with forests or agricultural fields.
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correction of sonic anemometer Angle of Attack errors
Agricultural and Forest Meteorology, 2006Co-Authors: Taro Nakai, John H. C. Gash, M K Van Der Molen, Yuji KodamaAbstract:An improved method of correcting for the Angle of Attack error resulting from the imperfect (co)sine response of ultrasonic anemometers is proposed. The Angle of Attack, which was calculated as the arctangent of observed wind vectors, contains the Angle of Attack errors in the vectors themselves, and hence this Angle was ‘false’. The ‘true’ Angle of Attack should be calculated from the corrected or ‘true’ wind vectors. In the improved method, the ‘true’ Angle of Attack is derived by solving a nonlinear equation which connects the ‘false’ Angle of Attack to the ‘true’ one. In applying this method to the case of R2- and R3-type Solent ultrasonic anemometers, the fit of the function for the sine responses to wind tunnel data was improved, and the cosine response function was also improved to consider the effect of the difference of the vertical positions of the transducers. The nonlinear equation was solved using the Steffensen method; robustly and adequately fast for practical use in calculating eddy fluxes. The accuracy of the correction method is improved over a previous one, especially at large Angles of Attack. Applying our correction method to field data from two forests and one peat bog, the eddy fluxes of sensible heat, latent heat and CO2were increased and the energy balance closure rates were improved. These results indicate that a large portion of energy imbalance can be accounted for by the ultrasonic anemometer Angle of Attack dependent errors.
Joanna Michalowska - One of the best experts on this subject based on the ideXlab platform.
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wind tunnel testing of plasma actuator with two mesh electrodes to boundary layer control at high Angle of Attack
Sensors, 2021Co-Authors: Ernest Gnapowski, Jaroslaw Pytka, Jerzy Jozwik, Jan Laskowski, Joanna MichalowskaAbstract:The manuscript presents experimental research carried out on the wing model with the SD 7003 profile. A plasma actuator with DBD (Dielectric Barrier Discharge) discharges was placed on the wing surface to control boundary layer. The experimental tests were carried out in the AeroLab wind tunnel where the forces acting on the wing during the tests were measured. The conducted experimental research concerns the analysis of the phenomena that take place on the surface of the wing with the DBD plasma actuator turned off and on. The plasma actuator used during the experimental tests has a different structure compared to the classic plasma actuator. The commonly tested plasma actuator uses solid/impermeable electrodes, while in the research, the plasma actuator uses a new type of electrodes, two mesh electrodes separated by an impermeable Kapton dielectric. The experimental research was carried out for the Angle of Attack α = 15° and several air velocities V = 5–15 m/s with a step of 5 m/s for the Reynolds number Re = 87,500–262,500. The critical Angle of Attack at which the SD 7003 profile has the maximum lift coefficient is about 11°; during the experimental research, the Angle was 15°. Despite the high Angle of Attack, it was possible to increase the lift coefficient. The use of a plasma actuator with two mesh electrodes allowed to increase the lift by 5%, even at a high Angle of Attack. During experimental research used high voltage power supply for powering the DBD plasma actuator in the voltage range from 7.5 to 15 kV.
M K Van Der Molen - One of the best experts on this subject based on the ideXlab platform.
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correction of sonic anemometer Angle of Attack errors
Agricultural and Forest Meteorology, 2006Co-Authors: Taro Nakai, John H. C. Gash, M K Van Der Molen, Yuji KodamaAbstract:An improved method of correcting for the Angle of Attack error resulting from the imperfect (co)sine response of ultrasonic anemometers is proposed. The Angle of Attack, which was calculated as the arctangent of observed wind vectors, contains the Angle of Attack errors in the vectors themselves, and hence this Angle was ‘false’. The ‘true’ Angle of Attack should be calculated from the corrected or ‘true’ wind vectors. In the improved method, the ‘true’ Angle of Attack is derived by solving a nonlinear equation which connects the ‘false’ Angle of Attack to the ‘true’ one. In applying this method to the case of R2- and R3-type Solent ultrasonic anemometers, the fit of the function for the sine responses to wind tunnel data was improved, and the cosine response function was also improved to consider the effect of the difference of the vertical positions of the transducers. The nonlinear equation was solved using the Steffensen method; robustly and adequately fast for practical use in calculating eddy fluxes. The accuracy of the correction method is improved over a previous one, especially at large Angles of Attack. Applying our correction method to field data from two forests and one peat bog, the eddy fluxes of sensible heat, latent heat and CO2were increased and the energy balance closure rates were improved. These results indicate that a large portion of energy imbalance can be accounted for by the ultrasonic anemometer Angle of Attack dependent errors.
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sonic anemometer co sine response and flux measurement ii the effect of introducing an Angle of Attack dependent calibration
Agricultural and Forest Meteorology, 2004Co-Authors: M K Van Der Molen, John H. C. Gash, J A ElbersAbstract:The response of R2 and R3-type solent ultrasonic anemometers was tested in a series of wind tunnel experiments. The vertical wind velocity was found to be seriously undermeasured for large Angles of Attack. The error in the horizontal windspeed components was also found to be considerable at large Angles, but the magnitude of the error depends on wind direction. An Angle of Attack dependent calibration is derived to correct for these response errors. Application of this Angle of Attack dependent calibration to data collected over two sites, one a relatively smooth peat bog area and the other a pine forest, shows that the uncorrected covariances representing the fluxes of momentum, sensible and latent heat, and carbon dioxide increase initially by 5–15%. However, interactions between the Angle of Attack dependent calibration and the second axis rotation correction (setting ¯ w = 0) resulted in the final change in momentum flux being −9% on the peat bog area (−4% on the pine forest), but +5% (+15%) for sensible heat flux, +5% (+7%) for latent heat flux and −2% (+9%) for the carbon dioxide flux. The amount of change was related to the vegetation roughness and the flux-Angle distributions. © 2003 Elsevier B.V. All rights reserved.
John H. C. Gash - One of the best experts on this subject based on the ideXlab platform.
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correction of sonic anemometer Angle of Attack errors
Agricultural and Forest Meteorology, 2006Co-Authors: Taro Nakai, John H. C. Gash, M K Van Der Molen, Yuji KodamaAbstract:An improved method of correcting for the Angle of Attack error resulting from the imperfect (co)sine response of ultrasonic anemometers is proposed. The Angle of Attack, which was calculated as the arctangent of observed wind vectors, contains the Angle of Attack errors in the vectors themselves, and hence this Angle was ‘false’. The ‘true’ Angle of Attack should be calculated from the corrected or ‘true’ wind vectors. In the improved method, the ‘true’ Angle of Attack is derived by solving a nonlinear equation which connects the ‘false’ Angle of Attack to the ‘true’ one. In applying this method to the case of R2- and R3-type Solent ultrasonic anemometers, the fit of the function for the sine responses to wind tunnel data was improved, and the cosine response function was also improved to consider the effect of the difference of the vertical positions of the transducers. The nonlinear equation was solved using the Steffensen method; robustly and adequately fast for practical use in calculating eddy fluxes. The accuracy of the correction method is improved over a previous one, especially at large Angles of Attack. Applying our correction method to field data from two forests and one peat bog, the eddy fluxes of sensible heat, latent heat and CO2were increased and the energy balance closure rates were improved. These results indicate that a large portion of energy imbalance can be accounted for by the ultrasonic anemometer Angle of Attack dependent errors.
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sonic anemometer co sine response and flux measurement ii the effect of introducing an Angle of Attack dependent calibration
Agricultural and Forest Meteorology, 2004Co-Authors: M K Van Der Molen, John H. C. Gash, J A ElbersAbstract:The response of R2 and R3-type solent ultrasonic anemometers was tested in a series of wind tunnel experiments. The vertical wind velocity was found to be seriously undermeasured for large Angles of Attack. The error in the horizontal windspeed components was also found to be considerable at large Angles, but the magnitude of the error depends on wind direction. An Angle of Attack dependent calibration is derived to correct for these response errors. Application of this Angle of Attack dependent calibration to data collected over two sites, one a relatively smooth peat bog area and the other a pine forest, shows that the uncorrected covariances representing the fluxes of momentum, sensible and latent heat, and carbon dioxide increase initially by 5–15%. However, interactions between the Angle of Attack dependent calibration and the second axis rotation correction (setting ¯ w = 0) resulted in the final change in momentum flux being −9% on the peat bog area (−4% on the pine forest), but +5% (+15%) for sensible heat flux, +5% (+7%) for latent heat flux and −2% (+9%) for the carbon dioxide flux. The amount of change was related to the vegetation roughness and the flux-Angle distributions. © 2003 Elsevier B.V. All rights reserved.
Yuji Kodama - One of the best experts on this subject based on the ideXlab platform.
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correction of sonic anemometer Angle of Attack errors
Agricultural and Forest Meteorology, 2006Co-Authors: Taro Nakai, John H. C. Gash, M K Van Der Molen, Yuji KodamaAbstract:An improved method of correcting for the Angle of Attack error resulting from the imperfect (co)sine response of ultrasonic anemometers is proposed. The Angle of Attack, which was calculated as the arctangent of observed wind vectors, contains the Angle of Attack errors in the vectors themselves, and hence this Angle was ‘false’. The ‘true’ Angle of Attack should be calculated from the corrected or ‘true’ wind vectors. In the improved method, the ‘true’ Angle of Attack is derived by solving a nonlinear equation which connects the ‘false’ Angle of Attack to the ‘true’ one. In applying this method to the case of R2- and R3-type Solent ultrasonic anemometers, the fit of the function for the sine responses to wind tunnel data was improved, and the cosine response function was also improved to consider the effect of the difference of the vertical positions of the transducers. The nonlinear equation was solved using the Steffensen method; robustly and adequately fast for practical use in calculating eddy fluxes. The accuracy of the correction method is improved over a previous one, especially at large Angles of Attack. Applying our correction method to field data from two forests and one peat bog, the eddy fluxes of sensible heat, latent heat and CO2were increased and the energy balance closure rates were improved. These results indicate that a large portion of energy imbalance can be accounted for by the ultrasonic anemometer Angle of Attack dependent errors.