Effects of geometrical parameters of two height-unequal adjacent objects on corona discharges from their tips during a thunderstorm

A two-dimensional time-dependent numerical model in Cartesian coordinate system has been developed to evaluate the mutual effect of two height-unequal adjacent objects on corona discharge occurring on their tips during a negative charging process of thundercloud. The results show that the higher object has a significant effect on the corona discharge of the shorter one. The relationships between the three geometric parameters (the height of the shorter object (h), the height difference (Δh) and the horizontal distance (d) between them) and the two corona properties of the shorter object (the background electric field for corona onset (Eonset) and the peak value of the corona current (Ip)) are investigated. When d is fixed (d = 30 m), the variation of Eonset of the shorter object varies with h orΔh is linear and the rate of the variation no matter with or without the presence of the taller object is the same. The only difference is that Eonset with the presence of the taller object is about 10% greater than without. Ip of the shorter object also has a linear variation with h or Δh no matter with or without the presence of the taller object, but the rate of the variation when the taller object is present is smaller than absent. When the heights of the two objects are fixed as 70 m and 100 m respectively, Eonset of the shorter object with the presence of the taller object decreases exponentially and Ip increases exponentially with increasing d. When d is more than 70 m, the effect of the taller object on Eonset and Ip of the shorter object is so weak that can be neglected. Furthermore, it is interesting to find out in the study that Eonset of the shorter object in the presence of a taller object is affected strongly by the geometric parameters of the two objects and weakly by the corona space charges generated from the taller object, while Ip is affected not only by the geometric parameters of the two objects but also by the corona generated from the two objects.