Infrared signature of serpentine nozzle with engine swirl

Serpentine nozzle is used to improve the stealth performance of military aircraft due to its ability to suppress the infrared signature. Investigation of the effect of engine swirl on the infrared signature of the serpentine nozzle is the primary objective of this study. The results showed that the engine swirl could effectively suppress the infrared signature, while inducing a small performance loss. Moreover, the engine swirl mainly contributed to the infrared signature suppression from the gas. The hot streak induced by the engine swirl affected the wall infrared signature level; however, exhibited limited effect on the total infrared signature level of the serpentine nozzle. The swirl angle significantly affected the infrared signature level of the serpentine nozzle. Compared to the no-swirl case, the average reduction of the total infrared signature level increased from 2.29% to 13.84% in the horizontal plane, and from 5.83% to 31.21% in the vertical plane with the increase in the swirl angle from 5° to 20°.