An investigation of dynamic stall onset on a pitching wing

This paper presents an examination of dynamic stall onset on both a rectangular wing and a nominally two-dimensional aerofoil with the same cross-section. The intention is to determine the extent to which the onset of dynamic stall is changed in the three-dimensional case. To do this, three different criteria are applied to measured pressure data to identify both the onset of the stalling process and the formation of the dynamic stall vortex. It is shown that examination of the vorticity flux in the vicinity of the leading edge provides a means of determining vortex formation in the absence of strong three-dimensional effects. It is also shown that this technique is not applicable on outboard sections of the rectangular wing where the phasing of dynamic stall onset with respect to the leading edge response is altered by the three-dimensionality of the flow. It is concluded that the application of two-dimensional stall onset criteria is inappropriate under such conditions.