Effect of elastic deformation on flight dynamics of projectiles with large slenderness ratio

The elastic deformation of modern projectiles with large slenderness ratio cannot be ignored with the increasing of flight speed and maneuverability. Unsteady Reynolds-averaged Navier-Stokes (URANS) Equations are solved through CFD technique in this paper. Based on the frame of unstructured mesh, techniques of rigid-motion mesh and inverse-distance-weighted (IDW) morphing mesh are adopted to treat the rigid motion caused by flight dynamics and flexible structure deformation due to aeroelasticity, respectively. Moreover, the six degree of freedom (SDOF) dynamic equations and static aeroelastic equation are solved through the aerodynamic coupling. Numerical results of both free flight case and aeroelastic case calculated by the in-house code agree well with the experimental data, validating the numerical method. A projectile model with X-X configuration is constructed to investigate the effect of elastic deformation on the flight dynamics. Comparison results show that the longitudinal oscillation is more affected by the elastic deformation than the centroid motion, and the oscillation cycle of the orientation angle increases. Furthermore, the trajectories of rigid models with various centroid locations are simulated, illustrating that the elastic deformation could move the aerodynamic center forward and weaken the margin of the static stability margin. In the end, detailed analysis and comparison of the pressure distribution indicates the mechanism by which the elastic deformation leads to the movement of the aerodynamic center and changes the flight dynamic characteristics of the flexible projectile.