At the relatively high takeoff speeds of supersonic transport aircraft, external air flowing across the exhaust nozzles may affect their jet noise characteristics. To investigate this, a series of flyover and static tests were conducted using an F-106B aircraft modified to carry two underwing nacelles each containing a calibrated J85-GE-13 turbojet engine. A flyover altitude of 300 feet and a Mach number.of 0.4 provided acoustic data that were repeatable to within ±1.5 PNdB. Comparisons of flyover and static data indicated that external flow reduced the noise of an auxiliary inlet ejector nozzle. An unsuppressed plug nozzle was not affected whereas the plug suppressor configurations were not as effective in flight.

Engine inlets for subsonic V/STOL aircraft must operate over a wide range of conditions without internal flow separation. An experimental and an analytical investigation were conducted to evaluate the effectiveness of tangential blowing to maintain attached flow to high angles of attack. The inlet had a relatively thin lip with a blowing slot located either on the lip or in the diffuser. The height and width of these slots were varied. Experimentally determined flow separation boundaries showed that lip blowing achieved higher angle-of-attack capability than diffuser blowing. This capability was achieved with the largest slot circumferential extent and either of the two slot heights. Predicted (analytical) separation boundaries showed good agreement except at the highest angles of attack. xlO 4 Nomenclature A = area CR = contraction ratio D = diameter h = blowing slot height L -inlet length m = mass flow rate P = total pressure p = static pressure , 'R = Reynolds number m R [/Pa \ (T-//T) "1 RBP = relative blowing power,--( --) -1\ fflf L.\PQ / J T = total temperature V.= velocity x = axial length from inlet highlight y = rake height 7 = ratio of specific heats 6 = blowing slot circumferential extent = viscosity p = density \l/-= circumferential location Subscripts B = blowing d = diffuser rake de = diffuser exit e^ = edge of boundary layer F -fan face HL = highlight / = inlet max .= maximum 0 -freestream t = throat

Nozzle performance may be sensitive to the type of airframe-nozzle installation. An installation that is of general interest is a podded engine mounted near the aft lower surface of the wing. The effect of this installation on nozzle performance in the transonic speed range is currently being investigated at the Lewis Research will discuss some of the significant results obtained with two of these nozzle types: auxiliary inlet ejector and conical plug. Both of them approximate subsonic cruise geometries of nozzles designed for efficient operation in the Mach 2.8 range.

The rehabilitation of the AWT at the NASA Lewis Research Center is under study with the goal of providing a modern subsonic wind tunnel for conducting propulsion system/airframe integration, isolated propulsion system, propulsion acoustics and adverse weather tests. Because of the . o increased Mach number capability (from Mach 0.6 to S 0.9 plus) and the incorporation of acoustic and adverse weather capabilities into an existing tunnel, the AWT rehabilitation represents a significant technical challenge. In order to reduce the risk associated with such an undertaking, an extensive AWT modeling program is being conducted to guide and verify the tunnel design. Significant, findings and progress in this modeling program are the subject of this paper.

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