Influence of Stores on the Transonic Flutter of a Delta Wing Configuration

Abstract

Transonic and supersonic flutter characteristics of a delta wing configuration with external stores were computationally simulated, and the aerodynamic influence of the stores on the flutter characteristics was investigated. Delta wings with one and two external stores were considered. Unsteady aerodynamics of the wing with external stores were evaluated using Navier-Stokes equations, and equations of motion based on a modal approach were applied to the structural dynamics. These equations were coupled using a subiteration approach. The computational results showed that the flutter dynamic pressures were reduced for a wide range of Mach numbers when the external stores were attached. The flutter dynamic pressures also decreased as the number of external stores increased. In the case of one external store, the aerodynamic influence of the store could be divided into two regions according to the Mach number. It was found that neglecting the aerodynamic influence of the store led to an overestimation of the flutter dynamic pressures in the supersonic flow region. In the case of two external stores, the aerodynamic influence of the stores on the flutter boundary appeared only at one supersonic Mach number, unlike the case of one external store. Additional flutter analysis using a different store size and unsteady aerodynamic analysis with forced oscillations indicated that the interference position of the shock wave generated ahead of the external store on the lower surface was a key factor in determining the flutter boundary, and the shock wave oscillation may have acted as a negative damping on the wing motion.