Study on the Influence of Vortex Generator on Aerodynamic and Stealth Characteristics of Serpentine Inlet

Abstract

Serpentine inlet is widely used in military aircraft worldwide because of its good electromagnetic stealth performance. However, the large curvature of the serpentine inlet makes them prone to flow separation, causing significant total pressure loss and swirl distortion at the Aerodynamic Interface Plane (AIP), thereby affecting engine operational stability. Moreover, since the vortex generator can change the three-dimensional shape of the inlet and affect the electromagnetic scattering characteristics of the inlet, it is necessary to study the influence of the vortex generator on the electromagnetic scattering characteristics of the serpentine inlet. However, there is no relevant research in this field. In this paper, the numerical simulation method was conducted to explore the mechanism and effect of the vortex generator on the aerodynamic characteristics and electromagnetic scattering characteristics of the serpentine inlet. Specifically, a serpentine inlet was designed by the curvature control parametric design method, and straight plate vortex generator scheme with four installation positions, four quantities and six heights were also designed. The calculation results showed that vortex generator significantly improved the inlet flow field distortion. Compared with the inlet without vortex generator, the circumferential total pressure distortion and swirl distortion were reduced by 57.8% and 53.3% respectively after the vortex generators were installed, and the total pressure recovery coefficient reduced by 1.4% at the maximum, which was acceptable. The installation position, height and quantity of vortex generator affected each other and had a coupling relationship. The Iterative Physical Optics (IPO) method compiled by C++ program was used to explore the influence of the vortex generator on the electromagnetic scattering characteristics of the serpentine inlet. It was found that electromagnetic wave reflect multiple times between the vortex generator and the outlet wall, which ultimately led to the increase of the peak and average value of Radar Cross Section(RCS) of the serpentine inlet, and the RCS angular distribution curve oscillates more violently.