Numerical analysis of surface jets for load alleviation on transport aircraft

Abstract

Effective alleviation of aerodynamic peak loads - caused by gusts or maneuvers - allows significant wing-structure mass reduction and lower energy consumption. Traditional control surfaces, like trailing-edge flaps, are limited by deflection rates, whereas fluidic actuators, such as wall-normal surface jets, use pressurized air to achieve much faster response. This study selects and evaluates a surface-jet design for elastic 3D aircraft wings. First, a 2D RANS-based parametric study shows that using narrow slots of 0.05% chord width cuts mass flow requirements by 40% at fixed pressure ratios, compared to prior designs, despite lower efficiency at supersonic jet speeds. Chordwise positioning at x/c = 0.8 yields greater lift reduction on a stiff 2D wing section, while x/c = 0.6 enhances decoupling between lift and pitching moment control, which is beneficial for flexible wings and outboard locations. Two selected actuator geometries were evaluated over varying Reynolds numbers, Mach numbers, and angles of attack to generate a CFD dataset from which a reduced-order model is derived. Implemented in a low-fidelity aeroelastic framework, results confirm that chordwise placement at x/c = 0.6 balances lift control and pitching moment, achieving 20% wing-root ending-moment reduction compared to the trim load at less than 1.5 kg/s mass flow, while the most effective spanwise location is at 75% span.