On wind-tunnel and CFD techniques and their accuracy for pedestrian-level wind comfort around buildings

Information on pedestrian-level wind (PLW) speed for wind comfort assessment can be obtained with wind-tunnel measurements or Computational Fluid Dynamics (CFD). Wind-tunnel measurements for PLW are routinely performed with low-cost techniques such as hot-wire or hot-film anemometers, Irwin probes or sand erosion, while Laser-Doppler Anemometry (LDA) and Particle-Image Velocimetry (PIV) are less often used because they are more expensive. CFD simulations are routinely performed by the relatively low-cost steady Reynolds-Averaged Navier-Stokes (RANS) approach. Large-Eddy Simulation (LES) is less often used because of its larger complexity and cost. This paper first briefly addressed wind-tunnel and CFD techniques to determine PLW speed, and some comparative studies that systematically indicate that the low-cost wind-tunnel techniques and steady RANS simulations can provide accurate results (?10%) in high wind speed regions while their accuracy strongly deteriorates in low wind speed regions. Next, it is argued that this does not necessarily compromise the accuracy of PLW comfort assessment, because the higher wind speed regions provide the largest contribution to the discomfort exceedance probability in the comfort criterion. Although LDA, PIV and LES are inherently and potentially more accurate techniques, this paper supports the continued use of faster and cheaper techniques for PLW comfort assessment.