Abstract:

Charts are presented for estimating drag-rise Mach number as a function of lift coefficient and thickness/chord ratio for a family of aerofoils characterised in viscous flow by a particular form of upper-surface pressure distribution at the drag-rise condition and a given form of thickness distribution. The particular form of pressure distribution has a flat roof-top extending from the immediate vicinity of the leading-edge to a given chordwise station followed by a linear rise to the trailing-edge. The thickness distributions are chosen from the RAE 101 to 104 series. The specification thus implies a camber line and incidence uniquely derived for each point on the charts which were constructed by deriving aerofoils by an inverse process for a chosen range of conditions corresponding to a number of such discrete points. Further charts indicate the threshold beyond which the linear pressure rise over the rear of the aerofoil would, at the drag-rise condition, cause the boundary layer to separate upstream of the trailing-edge. The derivation of the charts is described, and their accuracy and inherent limitations indicated. The means is then outlined whereby an aerofoil implicit in the charts may be developed to obtain improved drag-rise characteristics.