A numerical study on the aerodynamic characteristics of leading-edge vortex controllers on a fighter pertinent to Su-57

Abstract

This study numerically investigated the effects of active flow control devices, LEVCONs and slats, on the aerodynamic characteristics of a triple-delta-wing configuration pertinent to the Su-57. The effects of actuating LEVCONs and slats to different deflection angles on the aerodynamic characteristics were examined individually. It was found that the effects of lift contribution and drag reduction can be superposed. The characteristics of vortex cores were also investigated by using dimensionless axial velocity and dimensionless vorticity to respectively classify vortex cores and quantify the strength of vortical flows. Flow fields were visualized using the isosurfaces of dimensionless Q-criterion and spatial streamlines to facilitate the understanding of the complex flow physics behind the vortical flows. The analysis indicated that the actuation of LEVCONs and slats tended to delay vortex breakdown and shift vortices outboard. This, in turn, spread out different vortex systems more evenly on the upper surface of the model. Pressure coefficients on the model surface along the spanwise direction revealed that the outboard trajectory of vortices induced a rise in local -C_p, signifying the existence of vortex lift, which was responsible for the improvement in aerodynamic characteristics within the angle-of-attack range from 0° to 40° At a higher angle-of-attack range from 26° to 40°, the deflection of LEVCONs and slats by 30° resulted in more than a 10 % increase in lift. Proper actuation of LEVCONs and slats was also found to reduce drag and lessen the unstable pitching moment.