Control of Flow Separation Using Hemispherical Protuberance on the Leading Edge

The boundary layer separation control by a hemispherical protuberance near the leading edge has been discussed here. The protuberance is placed on the leading edge of a modelled aerofoil at an angle \(60^{\circ }\) from the theoretical stagnation point. The experiments are performed at a Reynolds number (Re) of \(1.6 \times 10^{5}\) and freestream turbulence (fst) of 1.2%. For the surface without protuberance, the flow separates near the leading edge evolving normal vortex shedding and forming a two-dimensional separation bubble. The application of protuberance significantly modifies the flow field by generating the streamwise vortices that interact with the shear layer downstream. These interactions augment the local turbulence, resulting in a three-dimensional separation bubble where the bubble length is reduced by 31–78%. Further, the separation bubble length, vortex shedding, and turbulence statistics become highly asymmetric in the spanwise direction, whilst the influence of protuberance is felt up to 6 k.