Abstract:
Wind-tunnel tests, at Mach numbers 1.86 and 2.48, have been carried out on two-dimensional unswept double-wedge and circular-arc aerofoils to study the viscous effects which are not accounted for in the linearised and shock-expansion aerofoil theories. The aerofoil characteristics derived from the measured surface pressures are compared with the theoretical values. Schlieren observation was employed to examine the flow and, in particular, the separation near the trailing edges of the aerofoils. In an appendix the results obtained from experiments on breakaway caused by a step on a flat plate are applied to the aerofoil tests as a method of assessing the pressures in the dead-water regions formed by the flow separation, and comparison is made with the measured pressures. Disturbing the boundary layer by means of wires caused a delay in separation; pitot-tube traverses through the boundary layers with and without wires illustrated the change in velocity profile between the two cases. The position of separation was briefly examined also by the use of oil; the point of separation as indicated by this method was in fair agreement with that given by pressure measurements, for cases of considerable separation only.
