Xv-11a Description and Preliminary Flight Test

Consideration of clogging in boundary-layer control system design

“…From Ref. 4, the pressure coefficient near midchord at a section lift coefficient of 2.01 was measured to be -2.3, which gives, for a forward speed of 50 mph, a value for U e of 133 fps. Thus, for these conditions, it is found that (p e -p s ) lq e = 2.2, which grossly exceeds the calculated upper limit for no clogging of 0.085.…”

“…The complication introduced by this term results from the fact that rigorous determination of its value requires invoking the momentum equation and can lead to over constraint of the system of equations. The mean pressure for blade row volumes is determined from the empirical relationship where P M =(2P L +P s )/3 (4) P L is the larger of the volume inlet or exit station static pressures, and P s is the smaller of the volume inlet or exit station static pressures. This empirical relationship was developed by examining an exact calculation of the mean pressure in a compression component with no losses and assuming that the relationship developed for lossless blade rows would remain valid for the actual case where blade row losses are taken into account.…”