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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机译：远场阻力提取具有优于近场集成的优势，可提供阻力的现象学分解。分解成与冲击波，粘性相互作用和升力诱发的涡旋相关的成分对于稳定流动很简单。 Onera和Onera的合作伙伴使用Van der Vooren和Destarac的配方，但仅限于稳定的案例。 Van der Vooren公式的非稳态流动的泛化已经被开发并在先前的工作中针对三个非稳态案例进行了测试。所提出的方法仅允许将阻力分解为三个通常的分量，但是所产生的阻力系数仍然存在，但是不确定。在此修改此不稳定配方，以更好地表达诱导的阻力。新的阻力分量被标识为传播和声学贡献。然后将新的公式应用于复杂的情况：粘性流中的2D俯仰NACA0012轮廓，粘性流中的相同俯仰翼型，粘性流中的3D椭圆形机翼以及最终的OAT15A轮廓（由Zonal-DES模拟）计算。
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