Numerical investigation of the surface effects on the dwell time during the sweeping of lightning arcs
Résumé
During a lightning strike in flight, the arc sweeps back along the aircraft surface by jump under the effects of the aerodynamic flow. This mechanism is called swept stroke. The dwell times at each attachment point vary according to the nature of the surface; the local geometry and air flow; and the current waveform which could cause reattachment if a current peak occurs. This paper is focused on the effects of the surface on the dwell time value. The parameters studied are the thickness of the boundary layer, and the presence of insulating coatings on the surface. 3D Numerical simulations of DC arcs along planar surfaces in the presence of a flow are carried out based on the Magneto Hydrodynamic (MHD) approach. The dynamics and the arcs instabilities are investigated with a special attention to the expansion radius, the tortuosity, and the internal voltage gradient. The effects of the boundary layer thickness and the presence of insulating layers on the dwell-time are discussed and the criteria for reattachment are examined. Finally, an example of dwell-time estimation is considered and the effects of electric and thermal constraints are discussed.
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