# Snow Load Shape Coefficients and Snow Prevention Method for Stepped Flat Roofs
## 4 Results and Discussion  
### The Final Pattern of Snow Accumulation  
The corresponding wind speed and temperature in the field measurements are illustrated in Figure 9. When the lower roof was on the windward side, the mean wind speed was 4.68 m/s, and the mean temperature was \(-\)10.3 \({}^{\circ}\)C. It took about 13 min to reach the final pattern of snow distribution. On the other hand, the windward snowdrift reached its final pattern in about 18 min, during which the mean wind speed was 4.91 m/s, and the mean temperature was \(-\)9.3 \({}^{\circ}\)C. The field measurements were conducted from 13:07 to 14:13, and the wind speed and temperature were relatively stable.  
Figure 10 presents the measured snow deposition on the roof. In Figure 11, the horizontal axis denotes the distance from the upper wall \(x\) normalized by the level difference  
\begin{table}
\begin{tabular}{c c} \hline \hline  & **Calculation Settings** \\ \hline Computational domain & 8000 mm (16 L) \(\times\) 3000 mm (15 H\({}_{2}\)) \\ \hline \multirow{4}{*}{Mesh division} & Minimum grid height: 5 mm. Grid growth rate: 1.1. \\  & Total grid: 30,000. \(y^{+}\): 80. \\  & Mesh quality: the quality and orthogonality are \\  & about 1, and the aspect ratio is less than 13. \\ \hline \multirow{2}{*}{Inlet boundary} & Air phase: Equation (1) and Equations (12) and (13). \\  & Snow phase: Equations (14)–(16). \\ \hline Ground and model boundary & Wall: \(C_{S}\) = 2.0, \(K_{S}\) = 2 mm. \\ \hline Outlet boundary & Pressure outlet \\ \hline Upper boundary & Symmetry \\ \hline \hline \end{tabular}
\end{table}
Table 2: Calculation settings of the numerical simulation.  
Figure 8: Methodological flow diagram.  
Figure 10: Wind environment and temperature in the field measurements.  
Figure 9: Wind environment and temperature in the field measurements.  
H, and the vertical axis denotes the dimensionless height \(h/\mathrm{H}\). The origin of the horizontal axis is located at the junction of the upper roof and the lower roof.  
As indicated in Figures 10a and 11a, when the lower roof was on the windward side, there was almost no snow accumulation on the upper roof. The final snow deposition on the lower roof was similar to a triangle, with the peak snow depth located at the roof junction (\(x/\mathrm{H}=0\)) and aligned with the outer edge of the upper roof (\(h/\mathrm{H}=2.0\)). The snow accumulation leveled off at \(x/\mathrm{H}=1.4\). Due to the wind separation and acceleration occurring at \(x/\mathrm{H}=3\), the lower roof presented a snow-free condition at \(x/\mathrm{H}=2.95\)-\(3\).  
Figures 10b and 11b show the snow distribution when the upper roof was on the windward side. There was a small amount of snow on the upper roof. The peak snow depth was about \(1/2\mathrm{H}\) at \(x/\mathrm{H}=0\). Similar to the appearance in Figures 10a and 11a, the wind accelerated at the windward corner of the lower roof (\(x/\mathrm{H}=-2\)), and the snow-free area occurred at \(x/\mathrm{H}=-2\)\(\sim\)\(-1.8\). The snow distribution on the lower roof was approximately uniform, and the dimensionless snow depth was around \(0.4\) at \(x/\mathrm{H}=0.2\)-\(2.4\).