An experimental investigation of the subsonic drag and pitching moment characteristics of slender cambered bodies with pointed noses and tails

摘要

It is known that supersonic aircraft are liable to possess some trimdrag under cruise conditions. Fuselage camber has been suggested as onemeans of reducing this component of the drag, and the purpose of thisinvestigation was to obtain quantitative data on the pitching momentincrements obtainable from fuselage camber and incidence, and the associatedincrements in fuselage drag.Lift, drag and moment measurements have been made on a body representativeof the fuselage of a supersonic transport aeroplane. The finenessratio of the body was 15:1, the cross-sectional area distribution beingof modified Sears-Haack form. Parabolic nose and tail camber was used,the nose and tail portions being made removable so that a variety ofdifferent configurations could be tested. The Reynolds number of thetests was 14.1 x 106 based on the length of the model, and the Mach numberwas 0.2. The tests were made with a transition wire attached to the modelat 10% of the length from the nose. A preliminary investigation indicatedthat the Reynolds number was probably sufficiently large to ensure thatthe results would give a good guide to the full scale characteristics.The experiments showed that nose camber produces a pitching momentincrement in very close agreement with the predictions of inviscid slenderbody theory. The increments in lift and drag, whilst not zero as predictedby inviscid theory, axe small. Tail camber on the other hand gives riseto much larger lift and drag increments, and the increment in pitchingmoment is quite different from that predicted by inviscid theory. In thepresent tests the pitching moment increment due to tail camber amounted toabout 10% of the theoretical value.The scope of the experiment was insufficient to answer the question“What is the optimum fuselage shape for minimum trim drag?" However, theindications are that an uncambered fuselage at incidence will provide agiven pitching moment for less drag than any cambered fuselage. Thishowever neglects the interference effects of the wing and tail unit on thefuselage, and of the fuselage on the wing and tail unit. For reasons of(i) tail clearance on take-off and landing, (ii) cockpit layout and view,and (iii) cabin layout, fuselages with camber may be required. Someindication of the fuselage drag penalties likely to be sustained by thesemodifications of the fuselage are given by the results of this experiment.