Facility for calibrating anemometers as a function of air velocity vector and turbulence (original) (raw)
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A new approach to highly resolved measurements of turbulent flow
Measurement Science and Technology, 2015
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.
Calibration and Quality Assurance of an Airborne Turbulence Probe in an Aeronautical Wind Tunnel
Journal of Atmospheric and Oceanic Technology, 2013
The Best Aircraft Turbulence (BAT) probe is used by multiple research groups worldwide. To promote an accurate interpretation of the data obtained from the probe’s unusual nine-port design, a detailed understanding of the BAT probe’s function along with a characterization and minimization of its systematic anomalies is necessary. This paper describes recent tests to enhance understanding of the probe’s behavior. The tests completed in the Wright Brothers Wind Tunnel at the Massachusetts Institute of Technology (MIT) built on earlier findings at Purdue University. Overall the true-vertical wind relative to the probe was found to have a systematic anomaly of about 10%–15%, an acceptable value borne out by considerable field experience and further reducible by modeling and removing. However, significant departure from theoretical behavior was found, making detailed generalization to other BAT probes still inadvisable. Based on these discoveries, recommendations are made for further exp...
A rapid-response 2-D drag anemometer for atmospheric turbulence measurements
Boundary-Layer Meteorology, 1991
A rapid response drag anemometer for measuring streamwise and lateral components of horizontal windspeed is described. Theory of operation, design and calibration are discussed with emphasis on the electronic preconditioning of signals and problems associated with using a mechanically resonant system as a sensor. Field comparisons showed half-hourly means and standard deviations of the streamwise component to be within 8% and 5% of respective values obtained from a 3-dimensional sonic anemometer. The lateral component from the drag anemometer was significantly more noisy than that from the 3-D sonic due to induced oscillations arising from vortex shedding. After mechanical and electronic filtering, half-hourly standard deviation comparisons agreed to within 6% for this component. Friction velocities obtained from the drag anemometer in combination with a 1-D sonic, agreed with measurements from the 3-D sonic anemometer to within 4% over a measured range of 0.05 to 1.2 m s-l.
Calibration Methodology of a F101-F201 Global Flow Probe Using a Laser Doppler Anemometer
Random uncertainties caused by the environment conditions, system operator as well as the measurement system itself, are factors that interfere in measurements. Concerning the uncertainty generated by the instrument interference, the use of non-invasive instruments, which are not introduced in the environment, is supported. However, these instruments are generally very costly and require specific work conditions which disable their use in certain tests, mainly in the field test. With the objective of correcting the interference caused by the invasive measurement system, its calibration is done using only non-invasive measurement systems as standards. This paper presents the calibration methodology of an invasive flow probe, the F101-F201 Global Flow Probe, with the required correction of the instrument interference on the true velocity measurement in the system. This methodology can also be applied on the calibration of other invasive type velocity measurement systems.
(NFAC) 40 foot by 80 foot wind tunnel at NASA Ames Research Center in the summer of 2011. The development of two measurement techniques is discussed in this work, both with the objective of making measurements on AMELIA for CFD validation. First, the work on the application of the Fringe-Imaging Skin Friction (FISF) technique to AMELIA is discussed. The FISF technique measures the skin friction magnitude and direction by applying oil droplets on a surface, exposing them to flow, measuring their thickness, and correlating their thickness to the local skin friction. The technique has the unique ability to obtain global skin friction measurements. A two foot, nickel plated, blended wing section test article has been manufactured specifically for FISF. The model is illuminated with mercury vapor lamps and imaged with a Canon 50D with a 546 nm bandpass filter. Various tests are applied to the wing in order to further characterize uncertainties related with the FISF technique. Human repeatability has uncertainties of ±2.3% of fringe spacing and ±2.0° in skin friction vector direction, while image post processing yields ±25% variation in skin friction coefficient. A method for measuring photogrammetry uncertainty is developed. The effect of filter variation and test repeatability was found to be negligible. A validation against a Preston tube was found to have 1.8% accuracy. Second, the validation of a micro flow measurement device is investigated. Anemometers have always had limited capability in making near wall measurements, driving the design of new devices capable of measurements with increased wall proximity. Utilizing a thermocouple boundary layer rake, wall measurements within 0.0025 inches of the surface have been made. A Cross Correlation Rake (CCR) has the advantage of not requiring calibration but obtaining the same proximity and resolution as the thermocouple boundary layer rake. The flow device utilizes time of flight measurements computed via cross correlation to calculate wall velocity profiles. The CCR was designed to be applied to AMELIA to measure flow velocities above a flap in a transonic flow regime. The validation of the CCR was unsuccessful. Due to the fragile construction of the CCR, only one data point at 0.10589 inches from the surface was available for validation. The subsonic wind tunnel's variable frequency drive generated noise which could not be filtered or shielded, requiring the use of a flow bench for validation testing. Since velocity measurements could not be made in the flow bench, a v comparison of a fast and slow velocity was made. The CCR was not able to detect the difference between the two flow velocities. Currently, the CCR cannot be applied on AMELIA due to the unsuccessfully validation of the device.
Characterization of Low Turbulence Wind Tunnel
2006
Wind tunnels with uniform velocity profiles and low turbulence are used to calibrate air velocity sensors such as anemometers and Pitot tubes among others. These wind velocity sensors are used in cases such as, for example, eolic turbines towers, meteorological stations, hospitals, etc. To make calibrations with high precision and accuracy it is necessary a wind tunnel with low turbulence (less than 0.4%) and uniform velocity profile in the test section. This study presents a characterization of the low turbulence wind tunnel of the Anemometry Laboratory of IPT (Institute for Technological Research), in which the calibrations are done in the discharge of the wind tunnel and the working range is from 2 m/s up to 40 m/s. A turbulence intensity less than 0.4% and a mean velocity variation of ± 0.2 % was obtained.
Turbulence measurements by the DC‐8 Meteorological Measurement System
Geophysical Research Letters, 1998
The instrumentation of a new MMS on the NASA DC-8 aircraft is briefly described. A method to compute the turbulent dissipation rate, e, is discussed in light of some apparent inconsistencies between high and medium altitude aircraft data and available theory. Examples of turbulence measurements during encounters of a wake vortex, a field of wave clouds, and persistent contrails are illustrated.
A Discussion of the Results of an In-Situ Comparison of Three Full-Vector Anemometers
1990
Extensive field measurements and the numerical modeling of dynamic responses associated with wind turbine rotor blades have pointed to strong interactions with coherent turbulent structures in the turbine inflow. These interactions are thought to be a major source of high-cycle fatigue in the primary structural components of wind turbines. The sources of such turbulent structures are not only natural terrain features but also the wakes from upwind turbines. Many unsteady aerodynamic processes are excited by turbulent eddies ranging in size from several rotor diameters down to the dimensions of the mean blade chord. These processes are responsible for inducing large, fluctuating 'loads on the turbine rotor blades. For the wind turbine generators now in use, this encompasses a spatial range of about 0.1 to 300 m. To assess our ability to measure the coherent properties of inflow turbulence over such a wide range of spatial range, we performed a study to compare three full-vector anemometers. We believe that to identify the dominant fluid dynamic properties of such flows, the instrumentation used must be capable of good fidelity measurements over the desired spatial range. The sonic anemometer is a primary candidate; we also wanted to compare the results associated with a well-designed mechanical instrument which is available at considerably less cost. Two sonic designs and a propeller-bivane were exposed to turbulent flows downstream of both extremely complex and moderately rolling terrain. This paper discusses some of the results of these comparisons With an emphasis on the measurements of turbulent fluctuations.