Convective Cooling of Lightning Channels
Abstract
We report experimental data which trace the time development of electric discharge channels in air and which demonstrate the turbulent cooling of such channels. These data provide qualitative confirmation of the model proposed and used by Hill, Ranker, and Wilson to calculate the production of nitrogen oxides by lightning. We outline an analytical treatment which identifies asymmetries in the pressure and density gradients of the discharge channel as a significant source of velocity. The vorticity, in turn, causes ambient air to mix into the channel. Our theoretical analysis results in equations from which the vorticity strength and mixing time scale may be calculated. We briefly describe detailed simulations with which have calibrated the theory. Finally, we combine the experimental data with our calibrated formulas to estimate the convective mixing rate in the case of lightning. We obtain a rate of about 300 cc/sec/cc air in the return stroke channel after pressure equilibrium has been achieved.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 14, 1981
- Accession Number
- ADA097994
Entities
People
- J. Michael Picone
- Jay Paul Boris
- Joseph R. Greig
- Michael Raleigh
- Richard F. Fernsler
Organizations
- United States Naval Research Laboratory