An experimental investigation was performed at the Large Low-speed Facility of the German-Dutch wind tunnels (DNW-LLF) to study the pylon interactions associated with pusher propellers. The aerodynamic and aeroacoustic effects of pylon trailing edge blowing and swirl recovery van
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An experimental investigation was performed at the Large Low-speed Facility of the German-Dutch wind tunnels (DNW-LLF) to study the pylon interactions associated with pusher propellers. The aerodynamic and aeroacoustic effects of pylon trailing edge blowing and swirl recovery vanes (SRVs) were evaluated. The pylon installation increased the summed tonal noise levels by up to 13 dB in unblown conditions, while the propulsive performance was affected in asymmetric inflow conditions only. At a sideslip angle of +6°, pre-swirl of the flow due to the pylon tip vortex led to a thrust increase of 10% at high thrust up to 45% at a low thrust setting. Stereoscopic PIV measurements showed the beneficial effect of pylon blowing in compensating the momentum deficit in the pylon wake. At the optimal blowing rate, a recovery effect of about 80% was obtained compared to the unblown case. Application of the blowing system eliminated the pylon installation penalty, recovering the noise levels to those measured for the isolated propeller. Installation of the SRVs downstream of the isolated propeller resulted in a swirl recovery of 50%, at the cost of a 2 dB tonal noise increase.