| 摘要 |
610,620. Thick aerofoil sections; boundary layer control. GOLDSTEIN, S., and RICHARDS, E. J. April 11, 1946, No. 11195. [Class 4] An aerofoil is provided on one or each of its surfaces with a boundary layer suction slot located nearer the trailing than the leading edge, the aerofoil section being so shaped that, at all incidences within a prescribed range, the calculated potential flow velocity distribution along the or each slot-containing surface is such as not to provoke boundary layer separation, except at a position coinciding with or closely adjacent the slot, at which position an abrupt decrease of velocity in the downstream direction occurs. The invention is intended for application to very thick aerofoil sections giving low drag at low lift coefficients. Fig. 1 shows a symmetrical section, particulars of the co-ordinates of which are given in the Specification, having a thickness/chord ratio of 30 per cent and in which suction slots S1, S2 on the upper and lower surfaces, located at 80 per cent of the chord from the leading edge, are connected to a suction pump P by ducting D. The calculated velocity distribution is shown in Fig. 2, curve 1 applying to both surfaces at zero incidence, curves 2, 3 and 4 to the upper surface at increasing angles of incidence, and curves 5 and 6 to the lower surface, in all cases a discontinuity occurring in the velocity curve at a point 80 per cent of the chord from the leading edge. Fig. 3 shows an unsymmetrical section having a thickness/chord ratio of 31.5 per cent, and in which a suction slot S3 is provided on the upper surface at 69.11 per cent of the chord from the leading edge. The slots may face forwardly or rearwardly. Specification 578,763 is referred to.
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