# An Experimental Study on Ice Accretion under Bridge Cable in Different Conditions
## 3 Results and Discussion
### The Effect of Temperature on Bottom Icing Conditions  
In order to quantify the effect of ambient temperature on the length of the maximum icicle, the trend of the top icicle length with temperature is shown in Figure 7. The length of each icicle in the graph represents the distance from the surface of the cable to the top of the icicle at different locations, the zero point of the vertical coordinate corresponds to the case where no icicle is present, and the horizontal coordinate corresponds to the different inclination angles of the cable. As can be seen from the above graph, for the same inclination of the cable, the maximum icicle length increases as the ambient temperature decreases; from \(-5\) \({}^{\circ}\)C to \(-25\) \({}^{\circ}\)C, the rate of increase in the maximum icicle length varies between 152.03% and 610% for the lower part of D1 and D2, while the net increase in the maximum icicle length for the lower part of D3 varies between 12 and 74 mm. This indicates a negative and significant correlation between ambient temperature and maximum icicle length. The low temperature allows more water droplets to collect in the lower part, and the gradually increasing icing surface further increases the heat transfer area between the ice structure and the air, which facilitates the accumulation of more ice structures at the bottom of the diagonal cable. Meanwhile, it can be seen that the icing of the bottom surface of the larger-diameter cable is less influenced by temperature. The more ice formed on the stay cable, the greater the lower cover when the ice falls off, which, to a certain extent, increases the risk of traffic safety below. In order to analyze the influence law of ambient temperature on the icicle, the inclination angle of the stay cable was kept unchanged in the quantitative test, and the variation trend of the icicle quantity with temperature is shown in Figure 8a-c. Under the same inclined angle of the cable (2 m), the number of icicles increases with the decrease in the ambient temperature. When the temperature decreases from \(-5\) \({}^{\circ}\)C to \(-25\) \({}^{\circ}\)C, the growth rate of the number of icicles in D1 varies from 160% to 750%. The growth rate of the number of icicles in D2 ranges from 183.3% to 1400%. For D3, the increased value of icicle quantity with L \(<\) 100 mm is 11-25. The results show a negative correlation between the ambient temperature and the number of icicles. In most cases, the amount of icicle in L \(<\) 100 mm (i.e., L1) is more than 1.7 times that in L \(\geq\) 100 mm (i.e., L2). Under the same pipe diameter condition, the growth rate of the number of tiny icicles is often greater than that of large icicles. This is because the existence of water film on the ice surface makes the liquid water inside icicles only transfer heat upward through the icicle root [25]. In this case, the temperature transfer law determines the relationship between the increase in the number of icicles with the decrease in temperature. In the icing phenomenon, the water film often develops laterally in the plane after accumulation. When the ice rib is formed, water droplets gather into the water flow and gradually freeze during the flow process. In this process, the width and thickness of water droplets increase continuously, forming a cylindrical ice structure distributed on both sides of the stay cable in the shape of ribs. The size of the ice ribs formed in the freezing process of the stay cable is roughly the same, and most of the ice ribs are formed on the windward side [26]. When the ambient temperature is \(-25\) \({}^{\circ}\)C, the ice rib of the cable will further develop into banded ice at the bottom, which is facilitated by low temperature and appropriate inclination angle conditions. Figure 7: _Cont._  
Figure 8: \(Cont.\)  
Figure 7: (a-c) Influence of ambient temperature on maximal length of icicles. Figure 8: (**a–c**) Influence law of temperature on icicles quantity (per meter).