Most likely N794BA, one of the Dreamlifter conversions.
Looks like it’s an old Korean Air plane they acquired.
boeing-test-flights.blogspot.com … flown.html
Not the DreamLifters at all. The Lifters are a former Air China aircraft and two former China Airlines aircraft the 4th one being a former Malaysia Airlines aircraft. Registrations are N747BC, N780BA, N249BA, and N718BA
The one your seeing is one being used for the Vortex testing. Its also used for other test purposes. Its painted in the boeing Swoop livery now.
My mistake 
Everyone is wrong. It’s a 747-800. Your answer with video even is here:
thekathrynreport.com/2010/09 … -over.html
Frank Holbert
160knots.com
.
Frank
Actually 2 airplanes are there doing Vortex testing
The 747-8 (Not -800)
and the 747-400 we are using former HL7412
and the OP is the -400 in question not the -8.
the -8 is using Boeing 503
Boe573 is N794BA. Is a former KAL 747-4 freighter. It’s a converted PAX aircraft. Boeing is using it and a 747-8 to conduct wake turbulence studies. The study is measuring the wake intensity and duration of the two aircraft. The outcome will be used to determine if the 747-8 will require greater in trail seperation with other aircraft.