Vortex asymmetry develops on slender bodies at high angles of incidence, leading to large side-forces and yaw moments even in symmetrical flight conditions. In the present experimental study, the flow over a slender body consisting of a conical forebody and a cylindrical aftbody is studied at high angles of incidence at low speeds. Experiments consisted of force measurements using a six-component strain gauge balance and velocity field using Particle Image Velocimetry. Results show that a pair of counter-rotating vortices develop nearly symmetrically over a polished cone but become asymmetric over the cylinder. Several secondary shear-layer vortices develop at the cone–cylinder junction and over the cylinder due to sharp turning angle, surface imperfections, and joints. These secondary shear-layer vortices then merge with the primary vortex pair, leading to the flow asymmetry. The flow characteristics and side-forces vary significantly when the conical forebody is rotated about its axis of symmetry and set to different azimuthal positions. The results strongly suggest that a change in the geometry at the cone–cylinder junction and surface imperfections present on the cylindrical aftbody play an important role in determining the overall flow-asymmetry and the magnitude of side-forces generated on the slender body at high angles of incidence.

中文翻译：

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二次剪切层涡在大入射角锥筒体流动不对称发展中的作用

涡不对称在高入射角的细长物体上形成，即使在对称飞行条件下也会导致大的侧向力和偏航力矩。在本实验研究中，研究了由锥形前体和圆柱形后体组成的细长体在低速大入射角下的流动。实验包括使用六分量应变计天平的力测量和使用粒子图像测速法的速度场。结果表明，一对反向旋转的涡流在抛光圆锥上几乎对称地发展，但在圆柱上变得不对称。由于尖锐的转角、表面缺陷和接头，在锥-圆柱交界处和圆柱上方形成了几个次级剪切层涡流。这些次生剪切层涡流然后与主涡流对合并，导致流动不对称。当锥形前体围绕其对称轴旋转并设置到不同的方位角位置时，流动特性和侧向力会发生显着变化。结果强烈表明，锥形-圆柱体连接处几何形状的变化和圆柱形后体上存在的表面缺陷在确定整体流动不对称性和细长体上高角度产生的侧向力大小方面起着重要作用发生率。