Delft University of Technology, Process & Energy Laboratory, Leeghwaterstraat 39, 2628 CB Delft, The Netherlands.
Soft Matter. 2017 Nov 22;13(45):8368-8378. doi: 10.1039/c7sm01619k.
When weakly jammed packings of soft, viscous, non-Brownian spheres are probed mechanically, they respond with a complex admixture of elastic and viscous effects. While many of these effects are understood for specific, approximate models of the particles' interactions, there are a number of proposed force laws in the literature, especially for viscous interactions. We numerically measure the complex shear modulus G* of jammed packings for various viscous force laws that damp relative velocities between pairs of contacting particles or between a particle and the continuous fluid phase. We find a surprising sensitive dependence of G* on the viscous force law: the system may or may not display dynamic critical scaling, and the exponents describing how G* scales with frequency can change. We show that this sensitivity is closely linked to manner in which viscous damping couples to floppy-like, non-affine motion, which is prominent near jamming.
当机械探测到软性、粘性、非布朗粒子的弱堵塞填充时，它们会表现出弹性和粘性效应的复杂混合。虽然这些效应中的许多都可以理解为特定的、近似的粒子相互作用模型，但文献中也有许多提出的力定律，特别是对于粘性相互作用。我们通过数值测量了不同粘性力定律下堵塞填充的复剪切模量 G*，这些力定律可以阻尼相对速度之间的相互作用。我们发现 G对粘性力定律的依赖性非常敏感：系统可能显示或不显示动态临界标度，描述 G如何随频率标度的指数也可能发生变化。我们表明，这种敏感性与粘性阻尼与柔软、非仿射运动的耦合方式密切相关，而这种运动在接近堵塞时非常明显。
