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 引用本文: 黄泊桦, 蒋子超, 王卓霖, 罗炫, 张仪, 姚清河, 杨耿超. 基于直接数值模拟的涡环碰撞过程涡结构分析. 力学学报, 2024, 56(7): 2004-2014.
Huang Bohua, Jiang Zichao, Wang Zhuolin, Luo Xuan, Zhang Yi, Yao Qinghe, Yang Gengchao. Vortex structure analysis of vortex ring collision process based on direct numerical simulation. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(7): 2004-2014.
 Citation: Huang Bohua, Jiang Zichao, Wang Zhuolin, Luo Xuan, Zhang Yi, Yao Qinghe, Yang Gengchao. Vortex structure analysis of vortex ring collision process based on direct numerical simulation. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(7): 2004-2014.

## VORTEX STRUCTURE ANALYSIS OF VORTEX RING COLLISION PROCESS BASED ON DIRECT NUMERICAL SIMULATION

• 摘要: 涡环间的碰撞涉及复杂的多层级涡结构拓扑关系和涡量转移机理. 深入研究该模型, 有助于揭示涡结构之间相互作用过程所包含的机理. 区别于现有研究一般专注于涡环小尺度次级结构的瞬态演化, 本研究使用基于一种改进的SIMPLE算法的直接数值模拟, 结合整体动态演变与其涡结构细节对涡环碰撞模型进行分析. 基于高分辨率网格, 分析了在不同雷诺数下涡环碰撞后由涡重联分裂出的次级涡结构. 研究表明, 涡环碰撞过程伴随着复杂的涡结构拓扑变化, 如高涡量区域的偏转及涡丝间的此消彼长. 在碰撞时, 环本身的不稳定性导致了局部接触后分裂出沿方位角规律分布的次级涡环. 而次级结构本身随流场雷诺数的增加呈现出从无到有、从近似圆环状到湍流态的转变. 最后, 对多雷诺数下的涡拟能曲线进行横向比较以反映碰撞对流场的整体涡流强度影响. 结果表明, 雷诺数的提高对涡拟能的调控整体表现为初始时刻耗散速率降低; 因碰撞而抬升的峰值提高; 峰值对应的时间点先延后再前移. 本研究基于直接数值模拟展示了涡结构演化的偏转、重联、湍流化等特征, 揭示了雷诺数对涡环碰撞的部分调控机制, 对复杂流动的涡系演化机理研究有启示作用.

Abstract: Vortex ring collision involves intricate multi-level topological relationships of vortex structures and mechanisms of enstrophy transfer. A thorough investigation of this model contributes to the elucidation of the mechanisms involved in the interaction processes among vortex structures. Distinguishing itself from existing studies that typically focus on the transient evolution of small-scale secondary structures within vortex rings, this research employs direct numerical simulation utilizing an enhanced SIMPLE algorithm. It integrates the overall dynamic evolution with detailed analysis of vortex structure to investigate vortex ring collision models. Utilizing a high-resolution grid, we analyzed the secondary vortex structures spawned after vortex ring collisions at different Reynolds numbers. The study reveals that the vortex ring collision process is accompanied by complex topological changes in vortex structures, such as the deflection of high enstrophy regions and the elongation between vortex filaments. During collisions, the instability of the rings themselves leads to the formation of secondary vortex rings distributed according to azimuthal angles after local contacts. The secondary structures undergo a transition from non-existence to existence and from an approximately circular ring shape to a turbulent state with increasing Reynolds numbers in the flow field. Concerning the enstrophy profiles reflecting the overall flow field, an increase in Reynolds number generally results in a reduction of the initial moment of dissipation rate, an elevation in the peak associated with collision-induced uplift, and a shifting forward of the peak time corresponding to the elevation. Overall, variations in Reynolds number significantly influence the vortex flow intensity and evolution of vortex structures at various stages of vortex ring collision. This study demonstrates the deflection, reconnection, and turbulization features of vortex structure evolution based on direct numerical simulations. The partial regulation mechanism of Reynolds number on vortex ring collision is revealed, which is instructive for the study of the evolution mechanism of vortex systems in complex flows.

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