Wind-tunnel setup for investigating the response characteristics of anemometers

Trabajo presentado en EGU General Assembly, celebrada en modalidad virtual del 19 al 30 de abril de 2021.The study aims to outline the wind-tunnel setup and testing procedure in a currently ongoing project designed to compare the response characteristics of various anemometers widely used across the world during different historic periods. The variations of several parameters, including gust and peak factors, and turbulence intensities measured by the anemometers as a function of the averaging duration (i.e. gust duration), and turbulence intensity and wind speed of the incoming airflow will be investigated. The outputs of the study will play an essential role in the understanding of historical wind data, and how to account for the changes in anemometers and gust duration in order to eliminate the breakpoints and shifts in wind speed time series, and to produce homogenised wind records. The tests will be carried out in the boundary-layer wind tunnel at the University of Auckland, New Zealand. This boundary-layer wind tunnel is a closed-circuit wind tunnel with two fans, a maximum wind speed of 20 m s‒1, and a large cross-section of 3.6 m × 2.5 m (width × height), which makes the tunnel suitable for the proposed experiment. The calibration of the anemometers will be conducted in the empty wind tunnel, which has a relatively low turbulence intensity of about 1% – 1.5%. The calibration is carried out according to the recommendations of ASTM D5096-02 (2017) and using a 3D Cobra wind sensor as the reference. Turbulence-inducing elements, such as grids and blocks, are used in the wind tunnel to replicate the random fluctuations of wind in nature, such that high turbulence intensities broadly replicate turbulence in urban areas, and low turbulence intensities are similar to those of exposed open-country and sea surface terrains. Details of the calibration and testing procedures as well as analysing the measured data in the wind tunnel will be presented. In addition, the advantages and limitations of wind-tunnel experiments in studying anemometers compared with theoretical approaches and full-scale field measurements will be discussed