建筑物尖端上行正先导始发过程的模拟研究

Simulation Study on the Initiation Process of Upward-Going Positive Leader on the Tip of Building

在热力学模型基础上,考虑了空间电荷屏蔽作用的二次电晕起始过程,认为流注茎(电晕区与流注-先导转化区)温度达到1 500 K同时二次电晕起始即新生迎面先导起始。并且根据纹影仪对先导通道根部的观测结果,流注茎假设为类圆锥状。通过Comsol软件对地面高大建筑物尖端处上行正极性先导的始发过程进行了数值模拟研究,并分析了锥形流注茎和二次电晕起始过程对先导始发过程的影响。最终得到了锥形流注茎长度与流注茎半径的关系,证明了随着电流的注入,根部优先转化为先导;计算的建筑物尖端处在最大半径(R=0.24 mm)情况下的流注茎-先导的转化时间为120μs;在正极性先导起始的过程中,初始先导并不是一个固定值,计算的初始先导的长度为0.03 m。

On the basis of the thermodynamic model, considering the initial corona process of space charge shielding effect, it is considered that the temperature of the streamer （corona zone and streamer-leader conversion zone） reaches 1500 K while the secondary corona begins leader initiation. And accord- ing to the schlieren device＇s observation of the root of the leader channel, stems are assumed to be quasi- conical. The Comsol software is used to simulate the initiation process of upward positive leader on the tip of tall buildings in the ground, and the influence of tapered streamer and the initial process of secondary corona on the initiation process of leader are analyzed. Finally, the relationship between the length and the diameter of tapered streamer was obtained. It was proved that the root was preferentially converted to a leader with the injection of current; The streamer-leader conversion time is calculated, the result is 120 s, on the tip of the building, and under the maximum radius（R=0.24 mm） ; in the initiation process of the positive polarity leader, the initial leader is not a fixed value, and the length of the initial leader calculated is 0.03 m.