Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA.
Linné Flow Centre and Swedish e-Science Research Centre (SeRC), KTH Mechanics, Stockholm, SE, 10044, Sweden.
Nat Commun. 2017 Dec 12;8(1):1960. doi: 10.1038/s41467-017-01852-2.
Inducing thermal gradients in fluid systems with initial, well-defined density gradients results in the formation of distinct layered patterns, such as those observed in the ocean due to double-diffusive convection. In contrast, layered composite fluids are sometimes observed in confined systems of rather chaotic initial states, for example, lattes formed by pouring espresso into a glass of warm milk. Here, we report controlled experiments injecting a fluid into a miscible phase and show that, above a critical injection velocity, layering emerges over a time scale of minutes. We identify critical conditions to produce the layering, and relate the results quantitatively to double-diffusive convection. Based on this understanding, we show how to employ this single-step process to produce layered structures in soft materials, where the local elastic properties vary step-wise along the length of the material.
在初始具有明确密度梯度的流体系统中诱导热梯度会导致形成明显的分层图案，例如由于双扩散对流而在海洋中观察到的分层图案。相比之下，在初始状态相当混乱的受限系统中有时会观察到分层复合流体，例如将浓缩咖啡倒入一杯温牛奶中形成的拿铁。在这里，我们报告了一种将流体注入可混相的受控实验，并表明在超过临界注入速度时，分层会在几分钟的时间尺度内出现。我们确定了产生分层的临界条件，并将结果定量地与双扩散对流相关联。基于这一理解，我们展示了如何利用这一单一步骤的过程在软材料中产生分层结构，其中材料的局部弹性性质沿材料的长度呈阶梯式变化。
