The investigation of the coupling relationship between mixing enhancement and convective stretching bears practical and scientific significance. In this paper, Lagrangian perspective is adopted for compressible vortex interaction visualization to emphasize the effect of inner flow dynamics other than the vorticity structure on mixing performance. Transport characteristics of the flow are studied through a blob of passive particles. The results demonstrate that Lagrangian coherent structures are faithfully tracked throughout the moving of particles, and the blob initially arranged upon the ridge of Lagrangian coherent structures exhibits efficient stretching. In this sense, the physical meaning of Lagrangian coherent structure as a material barrier and maximum stretching direction is highlighted. On this basis, mixing characteristics are investigated through the introduction of helium concentration blob considering viscous diffusion. Characterized by high growth rate of mixing and low mixing time, mixing enhancement is achieved with the aid of significant stretching directly reflected by high average finite-time Lyapunov exponent in the region of blob deposition, offering an optimal strategy for fluid mixing.

中文翻译：

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可压缩涡流相互作用中有限时间拉伸引起的混合增强的拉格朗日可视化

研究混合增强与对流拉伸的耦合关系具有现实和科学意义。本文采用拉格朗日视角进行可压缩涡流相互作用可视化，强调除涡度结构外的内部流动动力学对混合性能的影响。通过一团被动粒子研究流动的传输特性。结果表明，在粒子的整个运动过程中，拉格朗日相干结构被忠实地跟踪，并且最初排列在拉格朗日相干结构脊上的斑点表现出有效的拉伸。从这个意义上讲，拉格朗日相干结构作为物质屏障和最大拉伸方向的物理意义就凸显出来了。以这个为基础，考虑到粘性扩散，通过引入氦浓度 blob 来研究混合特性。混合增长速度快，混合时间短，在斑点沉积区域通过高平均有限时间李雅普诺夫指数直接反映的显着拉伸实现混合增强，为流体混合提供了最佳策略。