We study the rheology of a suspension of soft deformable droplets subjected to a pressure-driven flow. Through computer simulations, we measure the apparent viscosity as a function of droplet concentration and pressure gradient, and provide evidence of a discontinuous shear thinning behavior, which occurs at a concentration-dependent value of the forcing. We further show that this response is associated with a nonequilibrium transition between a “hard” (or less deformable) phase, which is nearly jammed and flows very slowly, and a “soft” (or more deformable) phase, which flows much more easily. The soft phase is characterized by flow-induced time dependent shape deformations and internal currents, which are virtually absent in the hard phase. Close to the transition, we find sustained oscillations in both the droplet and fluid velocities. Polydisperse systems show similar phenomenology but with a smoother transition, and less regular oscillations.

中文翻译：

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可变形液滴的流动：不连续的剪切稀化和速度振荡

我们研究了受压力驱动的流动的软可变形液滴的悬浮液的流变学。通过计算机模拟，我们测量了视在粘度随液滴浓度和压力梯度的变化，并提供了不连续的证据。剪切稀化行为，发生在受力的浓度相关值处。我们进一步表明，这种响应与“硬”（或变形程度较小）相（几乎被阻塞且流动非常缓慢）和“软”（或变形程度更大）相之间的非平衡过渡有关，“软”（或变形程度更大）的相更容易流动。软相的特征在于流动引起的随时间变化的形状变形和内部电流，而在硬相中几乎不存在。在过渡附近，我们发现液滴和流体速度都持续振荡。多分散体系表现出相似的现象学，但具有更平滑的过渡和较少规则的振荡。