Wind Tunnel Measurement Techniques

Abstract

This chapter discusses different measurement techniques of a low-speed wind tunnel designed and built at the Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM). The fully automated wind tunnel is named Pangkor after an island in Perak, Malaysia. Different measurement techniques are used to understand and validate the flow quality of the turbulent boundary-layer profiles at different locations and directions (wall-normal and spanwise). A hot-wire sensor captures the boundary layer over a smooth, flat surface. These data are then compared with high-quality published data. The flow uniformity shows comparable velocity variations and turbulent intensity. The boundary-layer profiles collapse well in different spanwise locations. Furthermore, the boundary-layer profiles at different Reτ follow the standard boundary-layer profile. Since the wind tunnel is relatively new, the calibration method for the hot-wire anemometry is provided. The approach to spectral analysis is provided using a fast Fourier transform (FFT), revealing the prominence of the energized structure of λx+≈1000 residing in the near-wall, in this analysis, we chose z+≈15. The spectral analysis shows that the compounded effects of small and large-scale do not vary with Reτ. Nonetheless, the outer hump is increasingly visible with increasing Reτ. The proposed measurement technique and findings help validate wind tunnel flow quality and turbulent boundary layer profiles.