## 3 Results and Discussion  
### Experimental Results  
In the present study, the ice layer was assumed to be distributed evenly along the cylinder axis, due to the short cylinder height of only 20 mm. Therefore, at any cross section of the icing cylinder perpendicular to the axis, the profile of the icing shape can be selected as the icing shape on the cylinder surface. For convenience in recording the icing shape, the profile of the icing shape at the end face of the cylinder was used to explore and analyze the icing characteristics. Pictures of the icing on the rotating cylinder surfaces taken from the end face of the cylinder are shown in Figure 5.  
Figure 5 shows the distributions of icing on the cylinder with a diameter of 40 mm under different TSR conditions. When the TSR is low, e.g., 0.2 or 0.6, the type of icing is prime, and the whole cylinder surface is covered by the ice layer. In contrast, when the TSR is high, e.g., 2.5 or 3.5, the type of icing is glaze, and only part of the cylinder surface is covered by the ice layer. The reasons for these results are discussed in later sections. Similarly, icing distributions on the other sizes of cylinders were also captured in the present study. After each icing test, the pictures showing the sectional icing shapes were imported into CAD software, and the size of the cylinder in the picture was adjusted to the same size as the sample. Then, the icing shape could be extracted using the SPLINE command in the CAD software, as shown in Figure 6. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**TSR** & **Rotational Speed (\(u\)/min)** & **Experimental Temperature (\({}^{\circ}\)C)** & **LWC (\(\upmu\)m)** & **MVD (\(\upmu\)m)** & **Wind Speed (\(\upmu\)m)** & **Time Interval of (\(\upmu\)m)** & **Total Icing Shape (\(\upmu\)f)** \\ \hline
0.2 & 25.4 & & & & & 5 min & 30 min \\
0.6 & 76.39 & & & & & 5 min & 30 min \\
1.0 & 127.4 & \(-\)16 \({}^{\circ}\)C & 0.58 & 50 & 4 & 90 s & 270 s \\
1.5 & 191.1 & & & & & 50 s & 150 s \\
2.5 & 318.5 & & & & & 30 s & 90 s \\
3.5 & 445.9 & & & & & & \\ \hline \end{tabular}
\end{table} 
Table 1: Experimental scheme and conditions. Figure 5: Lcing on the cylinder with a diameter of 40 mm. Figure 6: Cont. The surface of the cylinder can be classified into two regions, i.e., the front surface and the back surface, as shown in Figure 7.  
When the cylinder is rotating, the front surface is the windward side, and the back surface is the leeward side. When the TSR was 0.2, the ice layer covered the whole cylinder surface, and the icing shape was approximately circular. The ice shape was symmetrically distributed between the left part of the surface and the right part of the surface. With an increase in the rotational speed or the TSR, the icing shape became irregular, and the thickness of the ice layer on the front surface clearly increased. In contrast, the thickness of the ice layer on the back surface decreased and gradually disappeared. As the TSR  
Figure 7: Sketch map of the cylinder surface regions. reached 1, the icing shape became irregular and coarse, and the cylinder surface was not completely covered by the ice layer. The icing region contracted towards the horizontal center line, which is the demarcation between the front surface and the back surface, from the back surface. When the TSR was higher than 1, the ice layer on the cylinder surface was distributed more regularly and evenly in comparison with the case for a TSR of 1. In addition, with a further increase in the rotational speed or the TSR, the thickness of the ice layer on the left surface of the cylinder became larger than that on the right surface, and a bulge occurred on the left surface of the ice layer. The icing region on the cylinder surface contracted towards the front surface of the cylinder. Moreover, the icing time also affected the process of icing. With the other conditions held constant, it was found that the amount of icing on the rotating cylinder increased.