Investigation on control characteristics of zero-net-mass-flux jet for transonic shock buffeting of airfoil

Transonic shock buffeting poses a significant threat to aircraft safety and performance. This paper presents a novel approach utilizing a zero-net-mass-flux (ZNMF) jet method, implemented through trailing edge blowing/suction on the NASA SC(2)-0714 airfoil, to tackle the critical issue of transonic shock buffeting control. The fundamental characteristics of transonic shock buffeting were obtained through wind tunnel experiments. Numerical simulations, validated against experimental data, were carried out to investigate the control effects by the unsteady Reynolds-averaged Navier-Stokes equations based on the Reynolds stress model. Key parameters including jet intervention timing, angle of attack, free stream Mach number, and the jet strength, were analyzed to optimize the suppression of transonic shock buffeting. Results show that the ZNMF jet can completely suppress the airfoil transonic shock buffeting, independent of the specific jet intervention timing. This suppression is maintained across a range of angles of attack and free stream Mach numbers, yielding significant improvement in aerodynamic characteristics. Specifically, the standard deviation of the pitching moment coefficient is reduced by more than an order of magnitude, and the lift-drag ratio is increased by more than 10% on average. Furthermore, the study identifies a critical threshold for the jet strength in suppressing the transonic shock buffeting. Sub-critical jet strengths result in reduced shock wave oscillation, while application of jet strengths above this threshold completely suppresses shock wave oscillation, offering valuable insights for pratical implementation in aircraft design and operation.