Application of the ASP3D Computer Program to Unsteady Aerodynamic and Aeroelastic Analyses

A new computer program has been developed called ASP3D (Advanced Small Perturbation – 3D), which solves the small perturbation potential flow equation in an advanced form including mass-consistent surface and trailing wake boundary conditions, and entropy, vorticity, and viscous effects. The purpose of the program is for unsteady aerodynamic and aeroelastic analyses, especially in the nonlinear transonic flight regime. The program exploits the simplicity of stationary Cartesian meshes with the movement or deformation of the configuration under consideration incorporated into the solution algorithm through a planar surface boundary condition. The ASP3D code is the result of a decade of developmental work on improvements to the small perturbation formulation, performed while the author was employed as a Senior Research Scientist in the Configuration Aerodynamics Branch at the NASA Langley Research Center. The ASP3D code is a significant improvement to the state-of-the-art for transonic aeroelastic analyses over the CAP-TSD code (Computational Aeroelasticity Program – Transonic Small Disturbance), which was developed principally by the author in the mid-1980s. The paper presents unsteady aerodynamic and aeroelastic applications of ASP3D to assess the time dependent capability and demonstrate various features of the code. The cases considered include: (1) the NACA 0012 airfoil undergoing a forced harmonic pitching motion about the quarter chord at transonic conditions, (2) a thickening-thinning parabolic arc airfoil at a transonic Mach number, (3) an investigation of wave propagation characteristics with emphasis on high wave number applications, (4) aeroelastic transient calculations for the NACA 0012 airfoil at values of the dynamic pressure below, near, and above the flutter value, and (5) the F-5 fighter wing undergoing a rigid pitching motion about the wing root midchord axis. The results compare well with alternative methods and experimental data, and thus demonstrate the efficiency and utility of the ASP3D code for various unsteady aerodynamic and aeroelastic applications.