Several programs exist today for calculating aerodynamic coefficients that with some simplifications provide fast approximations of the values for a real aircraft.
Four different programs were analyzed for this report: Tornado, AVL, PANAIR and a handbook-type preliminary method. In addition, ANSYS CFX was used for airfoil validation. For calculation of the zero lift drag, an approximation was computed in order to calculate the remaining values that were not calculated by the software: drag contribution for fuselages, nacelles and some horizontal stabilizers and fins.
Different types of aircraft were selected for trial: two commercial aircraft (Boeing 747-100 and 777-300), a TF-8A research airplane (with area rule application: some additions were made to the fuselage to prevent large variations in the cross-section when the contribution of the wing is added), a Lockheed Constellation C-69 u sed as a military cargo airplane, a Boeing Stratocruiser used by the USAF with two configurations (basic and bomber), and an Aero Commander 680 Super, similar to a Cessna 162. Two airfoils (NACA2412, 0012) were also analyzed, to investigate the limitations of software designed for three-dimensional calculations.
The accuracy of the results showed that the validity of the software depends on the planform of the aircraft, as well as the simulation parameters Mach number and Reynolds number. The shape of the wing caused some of the methods to have serious difficulties in converging to valid results, or increased the simulation time beyond acceptable limits.