Numerical Simulation on Multiple Upward Leader Attachment Process of Tall and Low Buildings

Abstract

The multiple upward leader's attachment process on buildings is an important topic in lightning physics research, but the research on its physical mechanism is still insufficient. An improved 3D high-resolution multiple upward leader's stochastic method is used to simulate the development and attachment process of downward negative cloud-to-ground lightning in the near-ground area. The model allows upward leaders to be initiated on both tall and low buildings. The attachment process is analyzed when the multiple upward leaders are initiated and connected from both high and low buildings. The results show that low buildings have very small probability of initiating upward leaders directly and being struck, while high buildings have a clear influence on the initiation of upward leader of low buildings. Once low buildings initiate upward leaders, they are more likely to be stricken. The height difference between buildings is the main factor affecting the lightning attachment process. When the height difference between buildings is not large, the shielding effect of high buildings on the low buildings is not obvious, and the relative position of the downward leader channel will affect whether the low buildings can first initiate the upward leader. With the increase of the height difference between buildings, it is difficult for low buildings to preferentially initiate the upward leader. Only when the downward leader channel is obviously closer to low buildings, low buildings can initiate the upward leader and have a certain probability to connect with the downward leader to form a return stroke. When the height difference between buildings is large enough to a certain extent, the space form of the downward leader has little influence on the lightning attachment process. The low buildings will not be struck without initiating an upward leader. After the upward leader is initiated, it will have a certain inhibitory effect on the electric field intensity of the surrounding top angle. This inhibitory effect is related to the number of upward leaders and the horizontal distance between the top angle of the initiating upward leader and other top angles. The inhibitory effect is positively correlated with the amount of upward leaders while negatively correlated with the horizontal distance.

Keywords

• numerical simulation
• cloud-to-ground lightning attachment process
• multiple upward leader
• height difference between buildings