Active Flow Control Applied at the Engine-Wing Junction
The integration of UHBR (Ultra High Bypass Ratio) engines mounted under backward swept wings may lead at low speed to local flow separations on the wing suction side in the wake of the nacelle. These local flow separations can trigger the total wing stall which degrades the total aircraft performance. This paper presents a numerical study of AFC (active flow control) applied at the engine-wing junction of a generic full scale wind tunnel model to suppress the local flow separations. The AFC method is based on the principle of fluidic actuation and assembles a pulsed blowing with a 180° phase shift between the neighbouring nozzles. Its working principle is the production of vortices that enhance the mixing of the boundary layer and the free stream flow. The free stream flow in the wake of the nacelle is compromised due to the wakes of local flow separations and longitudinal vortices such as the strake vortex. The computation results show that pulsed blowing is capable of suppressing the local separations. It is shown that a certain blowing velocity exists that is required for the suppression of the nacelle-wake separation. Additionally the influence of the pulse frequency was analysed with a parameter study. It was shown that the local flow separations were suppressed by both low and high pulse frequencies.