Numerical and experimental studies on the airflow around the low-rise flat-roof buildings with different stable snowdrifts

摘要

In this study, the airflow characteristics around an isolated flat-roof building with different stable snowdrifts were investigated by adopting the Particle-Image-Velocimetry (PIV) wind tunnel experiments and Large-Eddy Simulations. First, the geometric model to be tested was obtained using a 3D printing technique, where the snowdrift pattern on the roof was provided by the results of previous wind tunnel tests conducted by the authors. Second, PIV wind tunnel experiments were carried out to measure flow information on the middle plane of the tested models (with or without snow cover). The specific physical variables (such as mean wind velocity, turbulence kinetic energy (TKE)) was then systematically analysed, which will be an important validation database to verify the LES method. Finally, the effects of the snowdrift on the time-averaged flow field, the turbulence flow field, and the wind load force acting on the buildings were discussed in detail using the LES method. The relevant research results indicate that the existence of snowdrifts changed the geometrical aerodynamic characteristics of the original roof, rendering the shape more streamlined. Thus, it significantly accelerated the passing velocity of the incoming flow over the roof, which results in the decreasing magnitudes of time-averaged Reynold stresses in the flow field above the roof. Additionally, the existence of snowdrifts can effectively restrain the size of the separation bubbles in the separating-reattachment flow field, which leads to vortices of smaller size and higher frequency being formed on the roof. Furthermore, the mean and fluctuations of wind pressure on the windward side of snowdrifts roof have larger magnitude than a roof without snow, which may increase the risk of damage to local enclosure structures near the windward side of the roof.