Experimental Study on Bidirectional Leader Discharges Initiated From the Floating Conductor

Bidirectional leader discharges initiated from aircraft determine the lightning strike points on aircraft. Understanding the physics underlying the bidirectional leader discharges is fundamental to designing lightning protection systems for aircraft. However, the physical processes of bidirectional leader discharges are still unclear. To deepen the understanding of bidirectional leader discharges, the bidirectional leader discharges initiated from the floating conductors are produced in a laboratory. The development processes of the bidirectional leader are recorded by a high-speed camera with up to 504000 frames/s. The high-speed camera frames and the applied voltage are synchronized in time. Then the initial thresholds of key processes in the bidirectional leader discharges are obtained. The influence of background electric field rise rate and electrode curvature radius on the bidirectional leader discharges are further studied. It is found that the higher the background electric field rise rate, the easier it is for the bipolar discharge to initiate, and the inception condition of positive leader is independent of the electrode curvature radius (diameter in the range of 2050 mm), as is the case for the negative streamer. Finally, a criterion for determining the initiation condition of the bipolar discharge is proposed, and this criterion is validated based on previous instrument aircraft measurement results. This work can serve as a physical basis to support the numerical model for aircraft zoning.