基于风雪联合试验系统的风致雪漂移试验相似准则研究

Research on similarity criterion of wind-induced snowdrift experiments based on wind-snow combined experiment facility

风致雪漂移现象导致了建筑屋面积雪的不均匀分布,给建筑结构带来了巨大的安全隐患。风洞试验是研究风致雪漂移的主要方法之一,而相似准则是进行风洞试验的基础,文中对Kind、Iversen和Tabler提出的相似理论进行了介绍,并归类整理了目前国内外学者主要采用的相似参数,包括弗劳德数、雷诺数、时间相似参数、速度相似参数等。应用哈尔滨工业大学自主研发的风雪联合试验系统,以日本学者Oikawa完成的户外实测作为参照原型,以边长0. 5 m立方体为试验模型,人造雪作为模拟颗粒,并在充分考虑不同相似参数的特点基础上,基于优选的相似参数进行了缩尺试验。根据实测结果与缩尺试验结果对比与分析发现,应用基于跃移层质量传输率相似的相似准则所得试验结果的侵蚀区和堆积区与实测结果吻合较好,精确地还原了实测结果的积雪分布形状,且以实测原型的平均风速为标准得出的试验结果优于以实测原型的最大风速为标准的试验结果。

Wind-induced snowdrift phenomenon leads to the unbalanced distribution of snow on the building roofs,which could bring a huge safety hazard to the structure. The wind tunnel test is one of the main methods to study windinduced snowdrift,and similarity theories are the bases of wind tunnel test. In this paper,the similarity theories of Kind,Iversen and Tabler were firstly summarized. After the classification,the main similarity criteria were then summarized,including Froude,Reynold,time similarity criterion and speed similarity criterion,etc. Making use of the wind-snow combined experiment facility,taking artificial snow as the simulating granular material,as well as considering characteristics of different similarity criteria sufficiently,scale experiments on snow distribution around a 0. 5 m cube were conducted according to the selected similarity criterion,with the field observation on snow distribution around a 1 m cube by Oikawa as the prototypes. Finally,according to the comparison of the prototypes and scale experiments,and with a full consideration of the characteristics of each similarity criterion,the similarity criterion based on the mass transfer rate of saltation process is proved to be the most reliable for the reappearance of snow distribution,and the experimental results show better agreement with the prototype when using the mean wind speed of the prototype.