Browsing by Author "Harris, K. D."

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    The effect of transition wires on the pressure distribution over a NACA 63A215 aerofoil section
    (College of Aeronautics, 1956-02) Harris, K. D.
    Pressure distributions have been measured over the surface of a N.A.C.A. 63A215 aerofoil section to determine the effect of transition wires on the lift and pitching moment characteristics. These tests, which were made at Reynolds numbers of 3 x 10-) and 8 x 10J, showed that with transition left free laminar separation, followed by turbulent re-attachment, occurred at about 604 chord at low incidences. At medium incidence the position of laminar separation and turbulent re-attachment moved rapidly forward giving rise to kinks or non-linearities in the lift curve. The addition of transition wires at 271% chord eliminated the laminar separation at low incidences and thereby caused the lift curve to become more nearly linear. However, the wires resulted in a reduction in the lift-curve slope at the design CL, and a reduction in Climax. Transition wires at 8%, /a or 1% chord were found to have very adverse effects on the aerofoil characteristics. In particular the lift curves were made very non-linear, and CL max was reduced. The non-linearity was caused by sudden changes in the boundary layer with change of incidence.
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    An experimental investigation of the subsonic drag and pitching moment characteristics of slender cambered bodies with pointed noses and tails
    (College of Aeronautics, 1958-09) Harris, K. D.
    It is known that supersonic aircraft are liable to possess some trim drag under cruise conditions. Fuselage camber has been suggested as one means of reducing this component of the drag, and the purpose of this investigation was to obtain quantitative data on the pitching moment increments obtainable from fuselage camber and incidence, and the associated increments in fuselage drag. Lift, drag and moment measurements have been made on a body representative of the fuselage of a supersonic transport aeroplane. The fineness ratio of the body was 15:1, the cross-sectional area distribution being of modified Sears-Haack form. Parabolic nose and tail camber was used, the nose and tail portions being made removable so that a variety of different configurations could be tested. The Reynolds number of the tests was 14.1 x 106 based on the length of the model, and the Mach number was 0.2. The tests were made with a transition wire attached to the model at 10% of the length from the nose. A preliminary investigation indicated that the Reynolds number was probably sufficiently large to ensure that the results would give a good guide to the full scale characteristics. The experiments showed that nose camber produces a pitching moment increment in very close agreement with the predictions of inviscid slender body theory. The increments in lift and drag, whilst not zero as predicted by inviscid theory, axe small. Tail camber on the other hand gives rise to much larger lift and drag increments, and the increment in pitching moment is quite different from that predicted by inviscid theory. In the present tests the pitching moment increment due to tail camber amounted to about 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, the indications are that an uncambered fuselage at incidence will provide a given pitching moment for less drag than any cambered fuselage. This however neglects the interference effects of the wing and tail unit on the fuselage, 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. Some indication of the fuselage drag penalties likely to be sustained by these modifications of the fuselage are given by the results of this experiment.
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    Measurement of the derivative 'ZW' for an oscillating aerofoil
    (College of Aeronautics, 1950-06) Buchan, A. L.; Harris, K. D.
    This report presents the results of experimental measurements of the damping derivative coefficient zw for constant chord rigid wings of various aspect ratios having sweepback angles of zero and 450. The results for the rectangular wings Flow substantial agreement with the unsteady aerofoil theory developed by TI.P. Jones $2) The dependence of Zvi upon frequency parameter is as given by theory and is much less than for two dimensional flow, but the numerical results are approximately 10 per cent below the theoretical. This is attributed to the large trailing edge angle 22° of the N.A.C.A. 0020 section used for the model aerofoils. The effect of sweepback is to decrease the numerical value of z , but this effect is much less pronounced, for low than for high aspect ratios. For aspect ratios 5 and 3 the numerical value is greater than would be given by a factor of proportionality equal to the cosine of the angle of sweepback. The measurements were corrected for tunnel interference by a method based on the theoretical work of 7.P.Jones.(1)
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    Measurements of lift, drag and pitching moment on a low speed rocket fitted with tail fins of various spans
    (College of Aeronautics, 1955-05) Harris, K. D.
    Measurements of lift, drag and pitching moment have been made in the. No. lA Wind Tunnel at the College of Aeronautics at a speed of 132 f.p.s. on a model rocket supplied by the Armament Research Establishment, Woolwich. The model was tested with three different tail spans, and with no tail. The tests made showed that the increase in static stability was almost directly proportional to the net span of the tail fins. For small angles of incidence the fin effectiveness was the same for the fins mounted vertically and horizontally, and for the fin assembly rotated through 45°. The model vas found to be statically stable about its point of suspension for all three fin sizes, and no unsatisfactory characteristics were Observed over the test range of incidence from -12° to +18°. The experimental results have been compared with estimates based on slender body theory.