论文标题
胶体凝胶中指法不稳定性的标准
Criterion for fingering instabilities in colloidal gels
论文作者
论文摘要
我们将胶体凝胶夹在两个平行板之间，并以恒定速度提升上板来诱导径向流动。这种拉伸测试产生了两种不同的情况：（$ i $）稳定的流量，在此过程中，凝胶在不产生的情况下经历拉伸变形，而（$ ii $）不稳定的流动为特征，以径向生长为凝胶的径向生长。我们表明，不稳定的状态发生在关键能量输入的范围内，而与凝胶的宏观屈服应力无关。这意味着凝胶在生长的手指尖端的局部流体化，并导致图案中最不稳定的波长，表现出经典的粘性手指不稳定性的特征性尺度。我们的工作为基于局部剪切诱导的屈服的胶体凝胶的指法提供了定量标准，与延迟故障框架一致。
We sandwich a colloidal gel between two parallel plates and induce a radial flow by lifting the upper plate at a constant velocity. Two distinct scenarios result from such a tensile test: ($i$) stable flows during which the gel undergoes a tensile deformation without yielding, and ($ii$) unstable flows characterized by the radial growth of air fingers into the gel. We show that the unstable regime occurs beyond a critical energy input, independent of the gel's macroscopic yield stress. This implies a local fluidization of the gel at the tip of the growing fingers and results in the most unstable wavelength of the patterns exhibiting the characteristic scalings of the classical viscous fingering instability. Our work provides a quantitative criterion for the onset of fingering in colloidal gels based on a local shear-induced yielding, in agreement with the delayed failure framework.
