Abstract In this study, the flow field distribution around an isolated stepped flat roof building and the influence of snow cover on flow fields are investigated by wind tunnel experiments based on particle image velocimetry (PIV) technology. Firstly, the stable snow cover, which is obtained based on the previous wind tunnel test of snowdrift on stepped flat roofs, is made by using 3D printing technology. Then two groups of models with and without snow cover on roofs are used in a low-speed wind tunnel and the experiments of flow around buildings are carried out. The significant differences of flow characteristic on roofs between without and with snow cover are that when there exists a snow cover, the reverse flow on the lower roof almost disappears and the recirculation vortex only exists at the rear region of lower roof. In addition, when there is with snow cover on roofs, the strength of flow separation and the peak value of vorticity at the higher roof is enhanced. With the existence of snow cover on roofs, turbulent kinetic energy significantly decreases by 51.1% compared with that without snow cover. Finally, the relationship between the distribution coefficient of snow depth and flow patterns is analyzed, and it is found that the linear relationship is fitted well in the front and rear regions on the lower roof.

中文翻译：

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孤立阶梯式平屋顶建筑周围气流的实验研究：积雪对流场的影响

摘要 本研究通过基于粒子图像测速（PIV）技术的风洞实验研究了孤立阶梯式平屋顶建筑物周围的流场分布以及积雪对流场的影响。首先，利用3D打印技术，根据此前阶梯式平屋顶积雪风洞试验得到的稳定积雪。然后在低速风洞中使用两组屋顶积雪和无积雪模型，进行了建筑物周围流动的实验。无积雪与有积雪屋顶流动特性的显着差异在于，当有积雪覆盖时，下屋顶的逆流几乎消失，回流涡仅存在于下屋顶的后部。此外，当屋顶有积雪时，较高屋顶处的流动分离强度和涡量峰值增强。屋顶有积雪存在时，湍动能比无积雪时显着降低51.1%。最后，对雪深分布系数与流型的关系进行了分析，发现下屋顶前后区域线性关系拟合较好。