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本文用数值方法求解N S方程,研究了低速流中三角翼背风面涡破裂演化过程中前缘涡的横截面拓扑结构。从横截面流线发现,从翼尖到近尾迹,前缘分离涡经历了由稳定到不稳定,再由不稳定变为稳定,在尾迹上又再次变为不稳定等三次转换过程,并由三个极限环的产生实现这些转换。对比沿涡轴的轴向速度分布表明,这些截面拓扑结构的变化规律以及极限环的产生与定性分析理论是相符的。当极限环扩散到前缘涡以外的区域时,极限环会溶入外流而消失,所以能否出现多个极限环同时存在的情况,取决于极限环的扩散速度。在涡破裂的产生与演化过程中,前缘涡的横截面拓扑结构沿流向的变化规律基本不变,原因在于涡破裂的产生和演化并没有改变旋涡沿轴向的拉伸和压缩规律。因此旋流沿流向的拉伸和压缩是确定横截面拓扑变化规律的主要因素,涡破裂以及破裂特性的改变,并不产生新的横截面拓扑结构。
In this paper, the N S equation is solved numerically and the cross-sectional topological structure of the leading edge vortex during the evolution of vortex rupture of the delta wing levitation in low velocity flow is studied. It is found from the streamlines of the cross section that from the wingtip to the near wake, the separation vortex of the leading edge undergoes three transformation processes, from stabilization to instability, from instability to stability and again to instability on the wake, The generation of three limit cycles achieves these conversions. Comparing the axial velocity distribution along the vortex axis shows that the variation law of the topological structure of these sections and the generation of limit cycles are consistent with the qualitative analysis theory. When the limit ring diffuses to a region other than the leading edge vortex, the limit ring dissolves into the outflow and disappears. Therefore, the existence of multiple limit rings simultaneously depends on the diffusion speed of the limit ring. During the development and evolution of vortex rupture, the variation of the cross-sectional topological structure of the leading edge vortex along the flow direction is basically unchanged because the generation and evolution of the vortex rupture did not change the law of the stretching and compressing of the vortex in the axial direction. Therefore, the swirling flow and compression along the flow direction are the main factors that determine the topological variation of the cross section. The vortex rupture and the rupture characteristics change, and no new cross-sectional topological structure is produced.