The study described in this paper was conducted as part of the European Funded CleanSky2 project AFC4TR (Active Flow Control for Tilt-Rotor aircraft). High-Fidelity numerical simulations were made to study various approaches of using Active Flow Control (AFC) actuators to delay flow separation at near stall conditions of the Next Generation Civil Tilt Rotor (NGCTR) VTOL aircraft with a tilted nacelle used during take-off and landing. The study revealed that for this configuration the flow separations travel in the spanwise direction starting from the middle of the wing. Various flow control strategies using Zero Net Mass Flux (ZNMF) actuators (synthetic jets) were then tested. Different number of actuators were integrated on * Postdoc,

This paper discusses the physical dynamics of the use of the Active Flow Control (AFC) actuators embedded in a Vertical Take-Off and Landing (VTOL) aircraft. Results of High-Fidelity numerical simulations are examined at near stall conditions. Different approaches of AFC are proposed to suppress the flow separation at these conditions. First the flow around the VTOL aircraft at high angle of attack in the take-off and landing configurations in real flight conditions at high Reynolds number are examined, then different flow control strategies are investigated. It was found that at these flow condition a flow separation travels along the spanwise direction in the near trailing-edge region of the wing with additional corner vortices between the wing-nacelle and the wing-fuselage junctions. Zero Net Mass Flux (ZNMF) actuators, also called synthetic jets, were then used for Active Flow Control. It was found that these ZNMF devices, when operating at the optimal blowing velocity and activation frequency, and when placed at the correct location enable the flow to re-attach and to delay the flow separation, resulting in an increase in aerodynamic efficiency of the aircraft. This work presented in this paper has been carried out in the context of the European project CleanSky2 Active Flow Control for TiltRotor aircraft (AFC4TR), Grant Agreement 886718.

Purpose This study aims to investigate the physical mechanisms of the use of active flow control (AFC) for a high-lift wing-flap configuration. Design/methodology/approach By means of high-fidelity numerical simulations, the flow dynamics around a high-lift wing-flap system at high Reynolds number (Re/c = 4.6 million) is studied. Adapted turbulence models based on the URANS approach are used to capture the flow separation and the subsequent development of coherent structures. The present study focuses on the use of AFC using a synthetic jet known as zero-net-mass-flux (ZNMF) using the blowing–suction approach. Different parameters (geometry, frequency and velocity) of a ZNMF placed at the cambered flap’s chord are optimized to obtain the most efficient parameter settings to suppress the flow separation. Findings A synthetic jet with the optimal shape and orientation enforces the flow reattachment on the wing-flap surface. This leads to an improvement of the aerodynamic performance of the system. The wake thickness was reduced by 30%, and an increase of 17.6% in lift-to-drag ratio was obtained. Concerning the ZNMF location, they should be installed upstream of the separation point to achieve the best performance. Originality/value The effectiveness of ZNMF devices integrated on a high-lift wing-flap configuration was studied in real flight conditions at high Reynolds number. A detailed analysis of the wake dynamics explains how AFC forces the reattachment of the boundary layer and attenuates the predominant wake instabilities up to −20 dB.