An investigation on external airflow around low-rise building with various roof types: PIV measurements and LES simulations. (February 2020)

• Record Type: Journal Article
• Authors: Liu, Zhixiang; Yu, Zhixiang; Chen, Xiaoxiao; Cao, Ruizhou; Zhu, Fu
• Is Part Of: Building and environment. Volume 169(2020)
• Publication Date: 2020-02
• Subjects: PIV -- LES -- Low-rise building -- Flow topology -- Roof shape; Buildings -- Environmental engineering -- Periodicals; Building -- Research -- Periodicals; Constructions -- Technique de l'environnement -- Périodiques; Electronic journals; 696
• DOI: 10.1016/j.buildenv.2019.106583
• Languages: English
• ISSNs: 0360-1323

Abstract

Abstract: In this study, the influence of different roof shapes on the airflow around isolated low-rise buildings is investigated with particle imaging velocity (PIV) wind tunnel experiments and large eddy simulations (LESs). PIV measurements are conducted in an atmospheric boundary layer wind tunnel for obtaining the mean velocity, fluctuating velocity component and time-averaged vortical structure around three low-rise buildings. The results provide a useful database for validation of an LES numerical model. Next, LES simulations are employed for solving the flow fields. Then, the performance of LES prediction is quantitatively evaluated based on the PIV database. Finally, the influences of the various roofs on the flow characteristics around buildings are analysed. The results illustrate that the LES numerical predictions show good agreement with the experimental results for all models. However, the predicting performance is largely related to the roof shape: A flat roof with a simpler geometry results in better prediction performance than more complex geometries do. The roof shapes remarkably affect the surrounding wind conditions at the pedestrian level. The area of low wind velocity ( R i < 0.2) in the wake region of the stepped model is by far the smallest at a wind direction of 180°. The size of a horseshoe vortex formed at the front of the model is positively correlated with the upwind height. The turbulence energy downstream is approximately concentrated around the non-dimensional frequency of 0.10, and the probability density functions of the velocity component at the monitor points approximately obeyed a normal distribution, with a weak skewness and kurtosis fatness. Highlights: PIV experiments on airflow around low-rise buildings with different roof are conducted to obtain validation database for LES. Sensitivity analyses for grid resolutions and the sampling time are carried out to obtain optimal values in LES studies. The influences of the roof shapes on airflow characteristics around low-rise buildings are carefully analysed and discussed. The prediction performance of LES approach is largely related with the geometric shape of building roof.