The Effect of Base Bleed on a Periodic Wake

Summary:— Measurements of profile drag, base pressure, wake turbulence and vortex shedding frequency have been made on a 9 per cent thick aerofoil in the presence of a secondary air flow, ejected from the blunt trailing edge. It is shown that the decrease in profile drag caused by the base bleed is associated with a decrease in the strength of the vortex street. The initial formation of the vortices occurs further downstream as the bleed quantity is increased. As a result, a greater proportion of the shed vorticity is diffused before the street is formed.