A Singular Perturbation Method for Arbitrary Configurations in Subsonic Potential Flow

摘要

A method is developed for obtaining uniformly valid solutions about slender bodies (2-D or 3-D) with round leading/trailing edges in compressible subsonic flow. The method is based on the principles of singular perturbation theory and applied to nonlifting thickness problems. The method corrects small perturbation theory (outer solution) with a stagnation region theory (inner solution) yielding uniformly valid solutions. Analytic results of the first and second order method are presented and compared to other methods, including exact numerical results, for the elliptic cylinder. The first order method is shown to be preferred to higher order efforts and is directly applicable to current numerical techniques solving the Prandtl-Glauert equation. Application of the first order method numerically, using a current panel technique, is presented for the NACA 0012 airfoil and a glide bomb configuration. All comparisons of the first order composite results with other methods show excellent agreement and improved results subject to the limits of validity of the theory. The ability to correctly model the flow behavior in stagnation regions using the composite solutions leads to a greater confidence in aerodynamic predictions, especially inviscid drag estimates. (Author)