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جریان خارجی
Actually, pressure drops of this magnitude or higher normally correspond to flight with outlet flaps extended, for which tho accompanying energy losses in the external flow may result in a drag power that is several tires the pump power.
Inlet is placed too high, the internal, flow will separate from the lower lip In climb and the external flow will separate over the upper lip:at high angles of attaok and thereby induce a premature stall-(fig. 7(b)).
The static pressure, for an exit like that of figure 12, is simply the static pressure of.the external flow in its vicinity.
A cowl flap extended at an angle of 15° to 30° to the surfaoe provides within the flap opening a static pressure less than the static pressure of the external flow by about 0.4 to 0.6 of the local external dynamic pressure (references 12 and 13), depending on the flap chord.
, results with outlets like "that of figure 16 Indicate that the" Inertia of the. external flow- has an appreciable effect in reducing the e^lt ¦ flow; that Is, If the exit dynamic pressure Is taken as the dif-. farenoe between the: Internal total pressure and the external statlo -pressure, It Is necessary to use an orifice coefficient of 0.5 •to'0.9, depending on the ratio of the exit velocity to'--*the Veloo- ' lty of the external flow.
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