The general trend in missile development is towards longer, faster, high-maneuverability missiles. This makes missiles increasingly more flexible and therefore more susceptible to aeroelastic effects, such as static and dynamic aeroelastic instability, and stability problems due to thrust misalignment. While most past problems of missile aeroelasticity were of control surfaces flutter, modern missile configurations experience static aeroelastic phenomena, which are not addressed much in the literature. The current study focuses on nonlinear aerodynamic effects on the flight of elastic missiles and examines these effects for a range of angle of attack and Mach number values. The investigation is based on static aeroelastic analyses of flexible missile configurations that are performed using linear and nonlinear aerodynamic models. The nonlinear aeroelastic solution is based on the solution of the Navier-Stokes equations on the elastically deformed missile in a Computational Fluid Dynamics (CFD) code. It serves to study the load distribution over the missile, the resulting deformed shape of the missile, and the integral aerodynamic coefficients compared to those computed with linear aerodynamics.
The study proposes a computationally efficient approach for the aeroelastic analysis of flexible missiles via a Nonlinear Strip Model (NSM). In the NSM, the nonlinear aerodynamic force coefficients in each strip (segment) over the missile’s body are computed for the rigid configuration. A database of coefficients, computed for various Mach numbers and angle of attack values, is used together with the structural modal model to provide the aeroelastic solution.
The test case of this study is that of a generic, flexible missile configuration in various flight conditions. The elastic deformation of the missile’s body significantly reduces the stability of the configuration, which, at some conditions, becomes unstable. Nonlinear aerodynamic effects further reduce the missile’s stability and are critical for accurate prediction of the stability margin. The NSM accurately predicts the nonlinear aeroelastic solution without relying on a computational expensive aeroelastic simulation in a CFD code.
