Experimental investigation of snow drifting on flat roofs during snowfall: Impact of roof span and snowfall intensity

Owing to the controllability and reliability, wind tunnel experiment is considered as a powerful and effective approach for the investigation of snow drifting. Most of the previous experimental studies were mainly concerned with snow drifting on roofs without snowfall, in which a layer of particles was uniformly paved on the roof surface to model the initial snow cover. Hence, a cryogenic wind tunnel experiment using artificial snow particles was conducted to investigate snow drifting on flat roofs during snowfall. The similarity requirement related to snowfall intensity is derived according to the similarities of snow distribution pattern and the development of snow transport. Based on the results of snow distributions and transport rates for different roof spans and snowfall intensities, the features of snow drifting under snowfall conditions are analyzed in detail. The concurrence of snowfall is further revealed to greatly affect the development of snow drifting on flat roofs and thereby result in a reduction in the required fetch for reaching the saturated state. And the typical distribution patterns for snow drifting on flat roofs with and without snowfall are also summarized. Besides, the snow transport rate is found to increase along the roof surface before the achievement of the saturated state, whereas a slight decrease in the degree of snow erosion with roof span is observed. But the location of the crest formed near the windward edge is nearly unaffected by roof span as well as snowfall intensity. The results also indicate obvious linear characteristics in the relationship between the degree of erosion on the roof surface and snowfall intensity. And the normalized development process of snow transport before reaching the saturated state is nearly independent of snowfall intensity, although both the saturated transport rate and the required fetch for saturated drifting are strongly affected in the meantime.