Three-Dimensional Parametric Analysis of a Switchable Vortex Generator for Aerodynamic Load Alleviation at Transonic Speeds

Abstract

This study investigates the aerodynamic performance of switchable vortex generators (SVGs) operated in spoiler configuration for load alleviation at transonic speeds. Using three-dimensional computational fluid dynamics (CFD) simulations, the effects of design parameters - including the height, aspect ratio, and spacing between the vortex vanes - are analysed on a simplified wing geometry, modelled as a straight extrusion of a supercritical airfoil. The analysis demonstrates that finite-span spoiler devices such as SVGs can effectively reduce the generated lift in cruise conditions, but their performance is strongly affected by geometric properties. Distinct aerodynamic regimes can be determined by placing a SVG of varying height and aspect ratio on the wing upper surface, characterised by different degrees of flow separation downstream of the device. Lift reduction becomes significant only when the size of the vortex vane is such to trigger full flow separation. The aerodynamic behaviour induced by a single SVG is further examined under high-speed off-design conditions, showing that larger vortex vanes induce full flow separation at lower angles of attack, while smaller SVGs can lead to sharp lift variations at higher incidence. The interaction between multiple SVGs is found to be significantly influenced by their spacing and aspect ratio, with the wall ratio emerging as a critical parameter. Smaller SVGs are most effective at high wall ratios, where they can generate a more uniform flow separation across the upper surface. In contrast, larger devices perform better at low wall ratios, where they can trigger full flow separation independently of their mutual interaction.