A Note on the Causes of Thin Aerofoil Stall

Abstract

Recent Researches have led to some possible explanations for thin aerofoil stalling behaviour. Apart from the Owen Klanfer criterion these are the reverse flow breakdown hypothesis of McGregor and Wallis's turbulent separation theory.This note describes simple theoretical boundary layer calculations which indicate the feasibility of Wallis's hypothesis. In addition the results of some experiments on a thin two-dimensional aerofoil with various leading edge configurations with Reynolds number, based on model chord, of 1.8 million and 1 million support either of these hypotheses, depending on the leading edge configuration. It is concluded that thin aerofoil stall can occur broadly, through either of the suggested mechanisms, depending on conditions in the nose region.