The Effect of Mean Loading on the Fluctuating Loads Induced on Aerofoils by a Turbulent Stream

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Abstract
Summary: This paper analyses the unsteady lift produced on a thin aerofoil by an arbitrary three-dimensional gust. In particular, it evaluates the effects of α, the angle of incidence of the aerofoil to the mean stream. A thin aerofoil theory which includes the effects of distortion of the turbulence by the mean flow field of the aerofoil is applied to the case of an aerofoil in isotropic turbulence. Some computed results are compared with measurements made on a NACA 0015 aerofoil in grid turbulence in a wind tunnel. It is shown that for isotropic turbulence the effect of mean incidence on the lift spectrum is of order α2, and is significant at low frequencies for the length scale ratios tested.