Exergetic Drag Characteristic Curves

Abstract

This paper aims to perform a drag breakdown of an airfoil and a wing by using the exergetic method. Moreover, a new far-field wave anergy extraction method is presented. The resulting exergetic drag curves are proposed as additional characteristic curves for external aerodynamic assessment of airfoils or any other bodies. CFD analyses of a NACA 0012 airfoil and a rectangular wing at subsonic and transonic conditions were used as test cases to present the concept. This new approach allows to deeply understand the aerodynamic behavior of a body and provides an alternative point of view to the classical near-field and far-field based drag curves.

2D Flow Field Analysis by the Exergetic Method

“…This exergetic formulation obtains the so-called "exergetic drag coefficient" when an unpowered and adiabatic case is considered. It is given by the following expression, which performs an exergetic-based breakdown of the drag coefficient [16]:…”

“…losses are larger than the zero angle of attack case. This explains why the anergy increases with the angle of attack [16]. Here it is reminded that the spurious anergy zone around the leading edge (outside the boundary layer) must not be taken into account for the analysis.…”

“…It can be seen that the same physical phenomena is captured by both methods. Moreover, for transonic cases the farfield method performs a drag breakdown of the profile drag into the wave and viscous drag by using the Kusunose technique [16,20], but this is not as complete as the exergetic-based drag breakdown.…”

Velocity Decomposition Method for Exergy-Based Drag Prediction

“…Another powerful and promising method is the exergy analysis. This technique has been used during the last 20 years for external aerodynamic analysis, mostly in CFD and analytical applications [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Particularly, the formulation proposed by Arntz [13] represents a major milestone in the development of the exergy method.…”

“…Its related distribution along the black survey line is also shown, where the wave drag corresponds to the part of the distribution lying on the top of the green region. This wave drag can be extracted from the C D ε distribution by using the method previously proposed by Aguirre and Duplaa [14], which is suited for wind-tunnel testing.…”