AI 中文总结
该研究通过直接数值模拟揭示二维聚合物湍流随魏森伯格数增加从弱弹性到弹性激活的转变，发现弹性应力改变能量级联与传递路径，并关联到聚合物强反馈的出现。
AI 中文摘要
我们进行了直接数值模拟，以研究稀聚合物对二维湍流中流动结构、统计特性和能量传递的影响。随着魏森伯格数（Wi）的增加，流动在弱弹性状态和弹性激活状态之间经历了一个急剧但连续的交叉。在弱弹性状态下，流动保持接近其牛顿对应状态，聚合物应力具有弱的动力学效应。在弹性激活状态下，弹性应力减弱涡旋运动并促进剪切主导的丝状结构。逐尺度能量分析表明，聚合物添加在两种状态下都减弱了逆动能级联和正向涡度级联，而动能-弹性交换和弹性能量的尺度间重新分布在两种状态之间有所不同。在弱弹性状态下，动能到弹性的转换在所分析的尺度范围内占主导地位，而在弹性激活状态下，在小尺度上出现了从弹性到动能的部分转移。弹性能量的尺度间传递在弱弹性状态下由大尺度范围内的逆向传递主导，而在弹性激活状态下由小尺度范围内的正向传递主导。这些结果将交叉与聚合物强弹性反馈的出现以及相关的逐尺度传递路径的重组联系起来。下游衰减统计也显示出相同的定性两状态行为。
英文摘要
We conduct direct numerical simulations to investigate the effects of dilute polymers on flow structure, statistical properties and energy transfer in 2D turbulence. As the Weissenberg number (Wi) increases, the flow undergoes a sharp but continuous crossover between a weak-elastic regime and an elastic-activated regime. In the weak-elastic regime, the flow remains close to its Newtonian counterpart and polymer stresses have weak dynamical effects. In the elastic-activated regime, elastic stresses attenuate vortical motions and promote shear-dominated filaments. Scale-by-scale energy analysis shows that polymer addition weakens both the inverse kinetic-energy cascade and the forward enstrophy cascade in the two regimes, whereas the kinetic--elastic exchange and the inter-scale redistribution of elastic energy differ between them. Kinetic-to-elastic conversion dominates over the analysed range of scales in the weak-elastic regime, whereas a partial transfer from elastic to kinetic energy emerges at small scales in the elastic-activated regime. The inter-scale transfer of elastic energy is dominated by inverse transfer over the large-scale range in the weak-elastic regime but by forward transfer over the small-scale range in the elastic-activated regime. These results link the crossover to the onset of strong elastic feedback from the polymers and the associated reorganisation of the scale-by-scale transfer pathways. Downstream-decay statistics also show the same qualitative two-regime behaviour.
Comments10 pages, 7 figures; supplementary material: 11 pages, 4 figures
