Abstract
The following conclusions are made for the configurations tested. 1) Flow entrainment caused by the exhaust jet affects boattail flow significantly. This may, in part, explain why experimenters have had only varying success in duplicating jet effects with solid, plume-shaped extensions. Solid extensions may adequately simulate exhaust jets which entrain relatively little external flow as, for example, can be the case in ejector-type nozzles. Since an ejector nozzle pumps internal secondary flow, its ability to entrain boattail flow is diminished. However, as seen in the General Dynamics tests, jet entrainment of the nonejector nozzles tested readily affects boattail flow whereas solid extensions do not reproduce this effect. 2) The boattail tested has three to four times more drag with conical plug exhaust flow than with axially directed convergent flow. This illustrates the strong effect of plume shape on boattail flowfield. 3) Drag levels on the typical force-model nozzle are misleading. The flow-through-nacelle nozzle tested exhibits different drag levels than do counterpart engine nozzles. This result is explained by particular differences in plume shape and entrainment effects.
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