A NEW METHOD FOR CALCULATING COMPRESSIBILITY EFFECT ON AIRFOILS

Document Type : Original Article

Author

Lecturer of Aerodynamics, Dpt, of Aeronautics, Military Technical College, Cairo, Egypt. (Member AIAA).

Abstract

Numerical methods for calculating compressibility effect on airfoils play a significant role in aeronautics because the experimental investigation in wind tunnels is more expensive. In literature, there are three well known methods i.e method of Prandtl-Glauert, Karman-Tsien and Christie-novitch. The last method is the most accurate one but it has some weak points. This paper presents a new method based on a non linearized approach in the Hodograph plane. The local velocity distribution and the pressure coefficient in the compressible fluid flow can be determined in terms of their corresponding values in the incompressible flow and the required Mach number and vice versa; because the formulae are explicit. This method is programmed on a digital computer consequantly, the compressibility effect is determined in a short time. The present method exhibits an order of magnitude reduction in computing time over other methods with comparable accuracy.