Wind Tunnel Measurements of Flow Characteristics Using an Ultrasonic Wind Anemometer, Influenced by the Passive Vortex Generator and Blockage From Circular Obstacles

Abstract

This study investigates wind tunnel experiments on flow characteristics assessed by an ultrasonic wind anemometer under varying upstream conditions. The impact of four circular cylinders arranged in a diamond pattern, simulating a virtual lattice wind mast, with a passive vortex generator at the entrance of the wind tunnel, is examined. Measurements were taken at wind speeds of 5 m/s and 10 m/s, with windward angles of 45, 135, 180, 225, and 315 degrees, to assess their impact on turbulence intensity and gust characteristics. The results indicate that both the circular cylinders and the vortex generator markedly enhance turbulence intensity, with the arrangement of the cylinders producing the most significant impacts. The examination of the Probability Density Function (PDF) for turbulence intensity and gust factor indicates minimal variability and low standard deviations in the base condition. Nevertheless, the diamond-configured cylinders result in an expanded PDF distribution, especially with the lateral turbulence component. The vortex generator, by contrast, induces a more regulated increase in turbulence, exhibiting smaller standard deviations compared to the circular obstacles. The investigation of peak factor and cumulative power spectral density further highlights these effects. In the base case measurements, peak factors are generally concentrated around 1, while cylinder obstruction decreases peak factor values. Cumulative power spectrum density analysis reveals decreased energy levels in the base scenario, whereas the vortex generator elevates spectral density across several frequencies, indicating increased turbulence effects.