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闪电负先导通道上起始再激活过程的数值模拟研究

Numerical simulation study of the reactivation process initiated from lightning negative leader channels

  • 摘要: 针对闪电负先导通道再激活过程认知十分匮乏的问题,本研究通过改进自持电中性闪电模型,在经典雷暴三极电荷结构下实现了对负先导端再激活过程的模拟,并对其放电特征进行分析。结果表明,闪电负先导端能够起始两种类型再激活过程:一种是自发起始型,对应电场呈“累积型”变化,与所在负先导通道向外延伸转移异极性电荷有关,对负先导头部电场增强及分支后续延伸影响微弱。另一种是触发起始型,对应电场呈“跃增型”变化,由正先导端起始的再激活过程触发,可连续起始直至将转移而来的静电能耗尽。总体而言,负先导端起始的再激活过程不论是始发数量、放电强度还是对先导通道的影响都要弱于正先导端,且其对应的通道电场强度通常只略高于再激活起始阈值,难以维持再激活过程在导电性差的通道中持续击穿。本研究不仅提升了数值模型对闪电精细化放电过程的模拟能力,还为揭示造成正、负先导端再激活过程显著差异的关键机制提供有效手段。

     

    Abstract: Given the limited understanding of the reactivation initiated from the lightning negative leader end, this study, by improving a self-sustained charge neutrality lightning model, successfully simulated the reactivation process initiated from negative leader channel under a classic tripole thunderstorm charge structure, and analyzed its discharge characteristics. The results show that two types of reactivation processes were initiated from the negative leader end: one is spontaneous initiation, corresponding to a “cumulative” pattern of electric field change. This is related to the outward extension of the negative leader channel, which transfers charges of opposite polarity to cutoff points. The simulated reactivation process of this type has a very limited effect on enhancing the electric field at the active negative leader head and does not significantly impact the subsequent extension of negative leader branches. The other is triggered initiation, corresponding to a “jump-increase” pattern of electric field change, which is triggered by the reactivation process initiated from the positive leader end. This type can be continuously initiated from the negative leader end until the electrostatic energy transferred from the positive leader end was fully dissipated. Overall, the reactivation processes initiated from the negative leader end are weaker than those initiated from the positive leader end in terms of initiation frequency, discharge intensity, and impact on the leader channel. Additionally, the electric field strength in the discharge channel corresponding to the reactivation process initiated from the negative leader end is typically only slightly above the reactivation initiation threshold, making it unable to sustain continuous breakdown in poorly conductive channels. This study not only enhances the capability of numerical models to simulate refined lightning discharge processes but also provides an effective means to reveal the key mechanisms causing significant differences between reactivation processes initiated from the positive and negative leader ends.

     

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