Measurement of unsteady wind loads in a wind tunnel: Scaling of turbulence spectra

Abstract

Mismatch of turbulence spectra from the corresponding full-scale conditions is a common challenge in wind tunnel modelling of unsteady wind loads on small-scale structures, such as solar panels, heliostats and low-rise buildings. Understanding the effect of this mismatch on the unsteady wind loads is necessary for providing an accurate estimation of wind loads on full-scale structures. The correlation between the turbulence spectra and the unsteady wind loads in wind tunnel measurements is investigated in this study through measurement of unsteady lift and drag forces on horizontal and vertical flat plates. It was found through spectral analysis that the turbulent eddies in the range of reduced frequencies between 0.01 and 1 contributed the most to the unsteady wind loads. An approach for wind tunnel modelling was proposed in which the geometric scaling ratio of each model is determined based on the analysis of the turbulence power spectrum as a function of reduced frequency. The suitable geometric scaling ratio should be then chosen such that the turbulence spectrum as a function of reduced frequency is the closest match to that at full-scale for reduced frequencies between approximately 0.01 and 1.