where U is the phase-averaged axial jet velocity at the nozzle exit plane, T is the period, and An is the nozzle exit area
. The average velocity on the centerline is used to define a jet Reynolds number, given by
Please keep in mind that the nozzle exit area of the WTA was reduced by the inlet area of the boundary layer scoop - 144 [10.sup.-3] [m.sup.2] - that "cuts off" the lower part of the flow through the nozzle.
While the wind tunnel at the TUM featured a nozzle exit area of about 4.32 [m.sup.2] - and hence was only suited for model-scale testing of passenger cars - the wind tunnel at Audi had a nozzle exit of about 11 [m.sup.2] and was almost exclusively used for full-scale testing of typical passenger cars.
The major diameter of the nozzle was a = 6mm and the minor diameter was b = 2, 1 and 0.6mm corresponding to a nozzle exit area
(A=37.69911, 18.84956 and 11.30973 [mm.sup.2]) respectively.
"Today's engine suffers from a modest compromise in internal engine performance because the nozzle exit area
is linked mechanically to the throat in a fixed ratio, meaning you don't get full expansion in all conditions," he said.
The nozzle exit areas
are significantly reduced under these flight conditions, while the length and maximum diameter are unchanged, leading to very high boattail drags.