Browsing by Author "Harris, K. D."
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Item Open Access 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.Item Open Access 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)Item Open Access 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.