INVESTIGATION OF WIND FLOW CHARACTERISTICS USING PASSIVE DEVICES IN BOUNDARY LAYER WIND TUNNEL

Abstract

Atmospheric boundary layer (ABL) flow can be generated in an open-loop boundary layer wind tunnel (BLWT) to simulate a realistic rough-wall condition imposed on the natural wind. An open-loop BLWT experiment is performed in this work using a wall barrier and roughness elements as passive devices to create a rough-wall condition and reproduce a realistic neutral ABL flow. The roughness elements used are homogeneous cubic blocks with a side length of 25 mm arranged in a staggered layout at 12.5% packing density. Wind velocity data is measured in the upstream test section of the BLWT using a hot-wire anemometer (HWA) to obtain the wind velocity profiles, i.e., mean wind velocity, standard deviation, and skewness. The height z was measured from z = 7 mm from the test section floor to z = 800 mm. The mean vertical velocity profile of the rough wall indicates a significant decrease within the height interval of z/z_ref < 1.0 due to the surface roughness. Additionally, the normalized mean wind velocity is approaching unity at z/z_ref = 1 with the rough wall, whereas the smooth wall (no roughness elements) is observed at z/z_ref = 0.1. Moreover, the standard deviation profile of the rough wall shows higher values in the near-wall region (z/z_ref ≤ 0.4), suggesting a higher level of turbulence in the wind flow due to surface roughness. Finally, the rough wall skewness profile is left-skewed, suggesting a non-Gaussian feature. The study found that roughness parameters affect vertical velocity profiles and create realistic atmospheric boundary layer flows.