An investigation of snow drifting on low-sloped gable roofs: Wind-tunnel tests and CFD simulations

In this paper, a series of wind-tunnel tests and steady Reynolds-averaged Navier-Stokes (RANS) simulations were conducted to investigate the influence of roof slope upon snow drifting and flow characteristics around low sloped gable roofs. First, the fresh-dry-snow-drifting processes on four gable roofs with inclinations of 5 degrees, 10 degrees, 15 degrees and 20 degrees were investigated via wind-tunnel tests using silica sand, and three reference wind velocities (namely 4.7 m/s, 5.85 m/s and 7.0 m/s) were taken into consideration. The snow-redistribution, peak-position, trapping-efficiency and transport-rate characteristics on model roofs were carefully discussed. The results of the wind-tunnel tests showed that roof slope significantly influenced snow depth on the leeward surface, that trapping efficiency increased along with roof slope, and that snow depth on the windward side was more affected by wind velocity. Sensitivity analyses for grid resolutions and inflow profiles were performed; the distributions of friction velocity, streamlines, positions of time-averaged vortex cores, and turbulence kinetic energy around buildings were investigated via numerical simulations. The change in the wind-flow pattern between inclinations of 10 degrees and 15 degrees resulted in the greatest transport-rate difference of all adjacent roof slopes. Finally, an empirical equation was provided that allowed the differential value between friction velocity and threshold friction velocity to estimate the snow-transport rate on the building roof.