Three-dimensional Numerical Simulation of Side Flash on Buildings

Lightning is among the top ten kinds of natural disasters. Observations show that the connecting of downward leader and upward leader happen on the corner of tall buildings, a few take place on the side of buildings, but the damage of side flash shouldn't be ignored. As the side of the lightning protection is relatively weak, the side flash brings huge shock wave and strong electromagnetic radiation, causing great threat to buildings and human securities. Therefore, it is necessary to discuss processes and causes of side flash.On the basis of the existing leader developing random pattern of three-dimensional near-ground lightning, keeping other model settings unchanged, by changing initial potential of downward leader and geometrical property, many model studies on the development of occurrence of side flash are carried out, and statistics of the probability of side flash in various circumstances are performed. Results show that electric field strength of the top corner of the building is an important condition for the occurrence of side flash. When the downward leader is close to the building and below the height of the building, the value of electric field will reach the triggering threshold value, and the side flash is prone to take place. Moreover, initial potential of the downward leader and geometrical properties (height and width) of the building are important factors affecting the probability of side flash occurrence. When initial potential of the downward leader is between-9 MV and-3 MV, the probability of side flash increases at first and then decreases. When the initial potential of downward leader is-4.5 MV, the probability of side flash reaches a maximum. When the height of the building is between 50 m and 150 m, the probability of side flash increases at first and then decreases. When the height of the building is 100 m, the probability of side flash reaches a maximum. When the width of the building is between 30 m and 70 m, the probability of side flash decreases with the increase of the width. When the width of the building is 30 m, the probability of side flash reaches a maximum.These results are beneficial for the three-dimensional simulation of different connecting behavior and modifications of the electric field at the building corner, as well as the research on causes and influencing factors of side flash.