| Zugriffsnummer | 50704 |
| Dokumenttyp | Zeitschriftenartikel |
| Peer Review | mit Peer Review |
| Sprache | Englisch |
| Titel | Effect of the insertion depth on calibration results of vane anemometers |
| Autor(in); Institution |
Pachinger, Dietmar; BEV/E+E Elektronik GesmBH, Engerwitzdorf, AUSTRIA
Kampe, Jessica; 1.4, Gase, PTB-Braunschweig
Roß, Alina; Deutsche WindGuard Wind Tunnel Services GmbH, Varel, GERMANY
Kouba, Pavel; Czech Hydrometeorological Institute, Prague, CZECH REPUBLIC
|
| Quelle/Jahr | Measurement: 222 (2023) |
| Artikelnummer | 113630 |
| ISSN | 0263-2241 (print) ; 1873-412X (online) |
| DOI | |
| Verlag | Amsterdam: Elsevier |
| Freie Schlagworte | vane anemometer calibration ; effect of mounting rod ; air speed ; interlaboratory comparisons ; transfer standard ; insertion depth |
| Zusammenfassung | When calibrating anemometers in wind tunnels significant differences in calibration results can be observed depending on the size of the wind tunnel’s test section. Such differences appear not only for large size meters with a large blockage effect but also for small size meters of certain construction where the effect cannot be assigned to the meter’s dimensions. In this case it turns out hat the effect is caused by a flow pattern in neighbourhood of the anemometer’s mounting rod which influences the sensor placed at the tip of the rod whereas the magnitude of the effect depends on how long part of the mounting rod is exposed to flow. In this work we tested four vane anemometers of different dimensions (propeller diameter from 16 mm to 107 mm) mounted on a thin tube with a diameter of 10 mm or 12 mm. Tests have been performed in a wind tunnel of Czech Metrology Institute which has an open circular test section with a diameter of 45 cm and uses LDA as a reference. Position of the anemometers’ propellers in the wind tunnel has been consecutively shifted from one side of the test section to another increasing their insertion depth (i.e. the length of the anemometer and mounting immersed to the air stream) with a step of 15 mm and changes in the anemometers’ readings have been observed for 5 velocities from 2 m/s to 20 m/s set in the wind tunnel. It was shown that the smaller anemometers are more sensitive to the effect and their reading can change by up to 5% when changing their insertion depth by around 10 cm. Such deviation is an order of magnitude larger than a typical measurement uncertainty declared by air speed laboratories of national metrology institutes. Physical background of the effect was further investigated by changing the mounting rod profile from a circle to an airfoil which lead to significant flattening of the insertion depth dependencies of the anemometers’ indication. Flow behind a propeller of one of the tested anemometers was also visualised using paper flags demonstrating how the flow direction changes with increasing insertion depth. Finally an interlaboratory comparison with two of the tested meters is presented showing how the effect influences the calibration results in six different wind tunnels with test section diameters/widths ranging from 25.5 cm to 100 cm. |
| Kostenfreier Zugang | Open Access Hybrid |
| Rechteinformation | CC BY 4.0 ; Creative Commons Attribution 4.0 License |
| Themenbereich der Metrologie | Durchfluss |