Trimming analysis of flexible aircrafts based on computational fluid dynamics/computational structural dynamics coupling methodology

A numerical methodology based on the coupling of computational fluid dynamics (CFD) and computational structural dynamics is established to obtain the trimming characteristics of flexible aircrafts in this paper. Reynolds-averaged Navier-Stokes equations are solved through CFD technique. Based on the frame of unstructured mesh, techniques of dynamic chimera mesh and morphing mesh are adopted to treat the data transfer between different computational zones and structure deformation caused by aeroelasticity, respectively. When it is applied to a projectile model with large slenderness ratio constructed in this paper, convergence histories of various initial conditions demonstrate the efficiency and robustness of the algorithm. The influence of the structural rigidity and normal loads on the trimming condition of flexible projectiles is investigated, and the locations of the aerodynamic center with various rigidities present the explanation that elastic deformation can move the aerodynamic center forward and weaken the margin of the stability. Furthermore, the trimming condition of flexible projectiles with propulsion is researched, which indicates that thrust misalignment will increase the effect of elastic deformation on the trimming condition, and the stability margin will be further weakened because of thrust misalignment. The conclusion provided in this paper can provide guidance for the structural design, control system design, and stability analysis for modern aircrafts with small stability margin and low rigidity.