细长体大迎角非对称涡流的数值研究

NUMERICAL STUDIES ABOUT A SYMMETRIC VORTEX FLOW AROUND A SLENDER BODY AT HIGH INCIDENCE

通过数值方法对大迎角细长体低速湍流流场的模拟,探讨头部顶端极小扰动对细长体非对称绕流形成与发展的影响.结果表明在细长体顶端附近施加极小扰动可以模拟出实验观测到的非对称流场,非对称的涡系结构沿轴向是逐步发展的,截面侧向力沿轴向的分布呈现正弦型曲线的变化特征,扰动能量经过指数增长后达到饱和,有效扰动的规模影响涡流非对称性的大小及分布,单侧扰动产生的流场非对称性随扰动周向位置的变化呈现单周期性规律.小扰动诱发非对称的数值算例表明非对称绕流的形成是源于流场的空间不稳定性机制.

Numerical simulations of low-speed turbulent flows around a slender body are conducted to explore the effect of a minute nose geometrical disturbance on the formation and development of flow asymmetry. The result shows that the asymmetric flows observed in experiment are simulated successfully by the introduction of a small bump placed near the body apex. The asymmetric vortex structure grows gradually along the symmetry axis of the slender body, and the distribution of sectional side force takes the sinusoid character of variation. Disturbance energy presents exponential spatial growth from the tip until it reaches the saturation. Disturbance scale influences the size and the distribution of flow asymmetry. The flow asymmetry shows a single periodicity when the circumferential position of the single disturbance changes. Numerical results show that the asymmetric vortex flow originates from the spatial instability of the forebody wake induced by a small disturbance.