Experimental and numerical evaluation of wind flow in a compact urban area : validation and sensitivity analysis

Given the rapid increase of urbanization and urban population worldwide, the urban air quality, wind and thermal comfort have become increasingly important matters. In this perspective, an accurate prediction of urban wind flow is of high importance. The 3D steady Reynolds-Averaged Navier-Stokes (RANS) approach is widely used in CFD simulations of wind flow in urban areas. However, there is a lack of basic knowledge on the performance of 3D steady RANS for this application. This paper presents a systematic evaluation of 3D steady RANS CFD simulations of wind flow in a compact heterogeneous urban area, most commonly encountered in old historical city centers. In addition, the impact of different turbulence models is investigated. The study area selected for this investigation is the old city of Nicosia, Cyprus. The evaluation is based on validation with wind-tunnel measurements of mean wind speed performed in an atmospheric boundary layer wind-tunnel at scale 1:250. The results show that steady RANS, in spite of its limitations, can accurately reproduce the mean wind speed distributions. For all of the turbulence models the average deviations of all the measuring points, from the wind-tunnel measurements are within 10%, where none of the models is superior.