Experimental Design for NLSI Research Program on Comparative Behavior
of Air Terminals
What air terminal (AT) tip geometry performs better as a preferential
attachment point for lightning? Project No. 199 continues earlier work
on this issue conducted by New Mexico Tech from Moore, Rison, et al (1998).
- Site - The CU INSTAAR site on Niwot Ridge, elevation 12,000
ft., was selected because of the high (100+TDY) assumed level of thunderstorm
days. Travel time from Boulder, CO is about 2+ hours
- Distribution of experimental stations - Ten stations each are
installed on the east (elev. 11,679) and west (elev. 12,284) knolls
of Niwot Ridge, at approx N 39 58 45.2 and W 105 08 38.0. The site is
situated about 30 miles west of Boulder, CO. (see installation details
and examples)st - All of 1999 season and, year 2000 +.
- Equipment - 80 copper-clad steel air terminals, 5/8 dia. X
4 ft high, are mounted in clusters of four rods per wooden sawhorse
platform. 20 amp fused sensors are attached to each platform to provide
lightning attachment verification. 20 sawhorses are deployed. Four AT
tip designs are being studied: blunt; hemispheric, bullet-shaped; and
one of each at each sawhorse. Visual observation of tip arcing
will indicate which geometry was preferred after a lightning strike
has occurred. See installation details.
Equipment will be checked often. Struck terminals will be replaced.
INSTAAR is informed of test results as observations are recorded. Summaries
will be posted periodically. All materials will be removed from Niwot
Ridge at completion of testing.
Proximity to sawhorses during close-in lightning should be avoided.
Plastic-laminated safety signage will be displayed at all sawhorses.
The signage will describe the purpose of the test program, as well basic
lightning safety measures.
Ongoing results are
available. The site has been prepared for winter and will be reopened
in spring when accessible. Stay tuned.