论文标题
平面通道流动中的弹性驱动的开尔文 - 螺旋状的不稳定性
Elastically driven Kelvin-Helmholtz-like instability in planar channel flow
论文作者
论文摘要
开尔文 - 赫尔姆霍尔茨不稳定（KHI）在自然界中广泛传播在从千分尺到银河系的尺度上。这种不稳定性是指具有不同速度和密度的牛顿流体的两个平行流之间的界面扰动的生长，这是通过剪切应变不稳定的，并通过密度分层稳定，底部的较重的流体稳定。在这里，我们报告了在粘弹性流体的平面直流通道流中发现纯弹性KH样不稳定的，从理论上讲，这是稳定的。然而，尽管与牛顿KHI时间界面动力学相似，但弹性KHI在质量上揭示了不同的不稳定性机制。实际上，界面之间的速度差异强烈波动，由于弹性波泵送的能量泵送，在流动中检测到的时间差异。弹性波强度和弹性KHI在不同方向上的相关性表明，弹性波的破坏稳定因子与由界面上速度差异产生的弹性应力差异的稳定因子之间的竞争是弹性KHI的新型不稳定性机械化。
Kelvin-Helmholtz instability (KHI) is widely spread in nature on scales from micrometer up to Galactic one. This instability refers to the growth of perturbation of an interface between two parallel streams of Newtonian fluids with different velocities and densities, destabilized by shear strain and stabilized by density stratification with the heavier fluid at the bottom. Here, we report the discovery of the purely elastic KH-like instability in planar straight channel flow of viscoelastic fluid, which is theoretically considered to be stable. However, despite the remarkable similarity to the Newtonian KHI temporal interface dynamics, the elastic KHI reveals qualitatively different instability mechanism. Indeed, the velocity difference across the interface strongly fluctuates and non-monotonically varies in time due to energy pumping by elastic waves, detected in the flow. A correlation of the elastic wave intensity and efficiency of the elastic KHI in different regimes suggests that the competition between the destabilizing factor of the elastic waves and the stabilizing effect of the elastic stress difference generated by the velocity difference at the interface is the novel instability mechanism of the elastic KHI.
