Foglino M, Morozov A N, Henrich O, Marenduzzo D
SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom.
SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG, United Kingdom.
Phys Rev Lett. 2017 Nov 17;119(20):208002. doi: 10.1103/PhysRevLett.119.208002. Epub 2017 Nov 15.
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.
我们研究了在压力驱动流动作用下软可变形液滴悬浮液的流变学。通过计算机模拟，我们测量了表观粘度作为液滴浓度和压力梯度的函数，并提供了在依赖于浓度的强迫值处发生的不连续剪切变稀行为的证据。我们进一步表明，这种响应与“硬”（或较不易变形）相和“软”（或更易变形）相之间的非平衡转变有关，“硬”相几乎处于堵塞状态且流动非常缓慢，而“软”相流动要容易得多。软相的特征是流动诱导的随时间变化的形状变形和内部流动，而硬相中实际上不存在这些。接近转变时，我们发现液滴和流体速度都存在持续振荡。多分散体系表现出类似的现象学，但转变更平滑，振荡也不太规则。
