高矮建筑物多上行先导连接过程的数值模拟

运用改进后的三维多先导模型, 允许高矮建筑物上均可以始发上行先导, 对多次地闪的连接过程进行模拟。结果表明: 矮建筑物始发上行先导和被击中的概率较小, 高建筑物对矮建筑物上行先导的始发具有较明确影响。建筑物间的高度差是影响上述连接过程的主要因子, 当建筑物间高度差较小时, 高建筑物对矮建筑物的屏蔽效应不明显, 下行先导通道的相对位置对矮建筑物是否优先始发上行先导存在影响; 随着建筑物间高度差的增加, 矮建筑物难以优先始发上行先导, 只在下行先导通道明显偏向矮建筑物时, 矮建筑物才可能始发上行先导, 并有一定概率与下行先导连接形成回击; 当建筑物间高度差超过某阈值后, 矮建筑物既不会始发上行先导, 更不会被击中。

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

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.