Airfoil wave-drag prediction using Euler solutions of transonic flows

The objective of the present work is the evaluation of four airfoil wave-drag prediction methods based on solutions of the Euler equations. In the case of two-dimensional inviscid flows of interest here, it is shown that the expression based on a volume integration of a positive definite quantity related to the artificial viscosity systematically underestimates the wave drag. In contrast with the popular belief, it is demonstrated that no clear improvement, in terms of accuracy, results from the use of far-field methods with respect to body-surface pressure integration. However, drag predictions obtained with entropy-based expression applied on a surface containing only the shocks are Less sensitive to high levels of false entropy production because the drag contribution associated with false entropy production is eliminated. Furthermore, in three-dimensional flows, the wave and induced drag can be distinguished. A new method is proposed to correct the body-surface pressure integration estimates that is less sensitive to the Level of false entropy production.