The aerodynamic performance of a transonic airfoil with spanwise forcing

TL;DR

This study uses direct numerical simulations to demonstrate that spanwise wall forcing on a transonic airfoil can delay shock waves and reduce drag by influencing shock-boundary layer interactions, extending previous incompressible flow findings.

Contribution

It provides the first detailed analysis of how spanwise forcing affects shock wave behavior and flow separation in transonic conditions, with a parametric study at Mach 0.7.

Findings

Shock wave shifts towards the trailing edge with control

Flow separation length correlates with friction reduction

Transient analysis links shock intensification to flow separation

Abstract

Spanwise wall forcing in the form of streamwise-travelling waves is applied to the suction side of a transonic airfoil with a shock wave to reduce aerodynamic drag. The study, conducted using direct numerical simulations, extends earlier findings by Quadrio et al. (J. Fluid Mech. vol. 942, 2022, R2) and confirms that the wall manipulation shifts the shock wave on the suction side towards the trailing edge of the profile, thereby enhancing its aerodynamic efficiency. A parametric study over the parameters of wall forcing is carried out for the Mach number set at 0.7 and the Reynolds number at 300,000. Similarities and differences with the incompressible plane case are discussed; for the first time, we describe how the interaction between the shock wave and the boundary layer is influenced by flow control via spanwise forcing. With suitable combinations of control parameters, the shock is delayed, and results in a separated region whose length correlates well with friction reduction. The analysis of the transient process following the sudden application of control is used to link flow separation with the intensification of the shock wave.