Improvements in the New Unsteady Far-Field Drag Breakdown Method and Application to Complex Cases

Far-field drag extraction has the advantage over near-field integration of providing a phenomenological breakdown of drag. A decomposition into components linked to shock waves, viscous interactions and lift-induced vortices is straightforward for steady flows. A formulation by Van der Vooren and Destarac is used at Onera and by Onera’s partners but is restricted to steady cases. A generalization to unsteady flows of Van der Vooren’s formulation has been developed and tested on three unsteady cases in a previous work. The proposed method allowed the breakdown of drag into the three usual components only, the induced drag coefficient remaining however ill-defined. This unsteady formulation is here modified to better express the induced drag. A new drag component is identified as a propagation and acoustics contribution. The new formulation is then applied to complex cases: a 2D pitching NACA0012 profile in a viscous flow, the same pitching airfoil in an inviscid flow, a 3D elliptical wing in an inviscid flow and finally an OAT15A profile subject to buffet simulated by Zonal-DES computations.

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