论文标题
弹性不稳定在粘弹性流的直流通道中，而无需预扰动
Elastic instability in a straight channel of viscoelastic flow without prearranged perturbations
论文作者
论文摘要
我们报告了粘弹性通道剪切流中弹性不稳定性的实验结果，这是由于天然的非平滑入口和沿通道的小孔进行压力测量的实验结果。我们表明，非正常模式的不稳定性导致弹性波和混乱的流量自组织成周期性循环的河流条纹，该条纹通过弹性波频率同步。混乱的流动持续到过渡上方，而$ Wi $进一步增加到弹性湍流和减少阻力状态。因此，我们解决了最近的难题，是否需要强烈的预先扰动才能在平行剪切粘弹性流中获得弹性不稳定。此外，流动性，速度光谱衰减和弹性波速度在强烈干扰的情况下显示出与WI相同的尺度。显着的结果是，在整个通道中都发现了所有缩放行为和条纹，并且衰减较小，与较强的预处理扰动的流动形成鲜明对比。
We report experimental results on elastic instability in a viscoelastic channel shear flow due to only a natural non-smoothed inlet and small holes along the channel for pressure measurements. We show that non-normal mode instability results in elastic waves and chaotic flow self-organized into periodically cycled stream-wise streaks synchronized by elastic wave frequency. The chaotic flow persists above the transition with increasing $Wi$ further into elastic turbulence and drag reduction regimes. Thus, we resolve the recent puzzle whether strong prearranged perturbations are necessary to get an elastic instability in parallel shear viscoelastic flow. Moreover, flow resistance, velocity spectra decay, and elastic wave speed reveal the same scaling with Wi as obtained in the case of strong disturbances. The remarkable result is that all scaling behavior and streaks are found in the entire channel with small attenuation, in sharp contrast to the flow with strong prearranged perturbations.
