空间分辨率对上行先导起始过程数值模拟的影响

Effect of Spatial Resolution on Numerical Simulation of Upward Leader Initiation Process

建筑物上能否触发上行先导是判断其能否被闪电击中的一个重要标准。利用三维变网格有限差分法,建立了三维电场计算模型和上行先导始发模型,讨论了网格大小(即空间分辨率粗细)对电场计算的影响。进而研究了在上行先导始发过程数值模拟中,常用的4种先导始发判据在不同空间分辨率下的适用性。结果表明:使用介质击穿模型和临界半径准则判定先导始发时,即仅以尖端表面电场大小为判据,此类会因空间分辨率过粗或过细,而分别导致模拟的先导始发时刻过晚或过早;而临界长度法和临界电场法,均是以一定区域内的电场或电位大小两个因子作为评判标准,此类判据只要空间分辨率小于判定范围尺寸则不会对结果带来较大影响。

Whether the upward leader can be triggered on a building is an important criterion to judge whether it can be hit by lightning.Three-dimensional finite difference method with variable grid was used to establish a three-dimensional electric field calculation model and an upward leader inception model.The influence of grid size(spatial resolution)on electric field calculation was discussed.Furthermore,the applicability of the four commonly used criteria in the numerical simulation of upward leader inception process under different spatial resolutions was studied.The results show that when the dielectric breakdown model and the critical radius criterion are used to determine the upward leader initiation,that is,only the electric field on the tip surface is used as the criterion,the upward leader initiation time will be too late or too early due to the too coarse or too fine spatial resolution.The critical length method and the critical electric field method both take the electric field or the potential in a certain area as the evaluation criteria.As long as the spatial resolution is less than the size of the judgment range,the results will not be greatly affected.