胶粘剂分散体中的不连续剪切变稀
Discontinuous shear-thinning in adhesive dispersions
摘要：
我们提出了模拟模型粘合剂分散体的稳态剪切流变学。我们改变吸引力$u$的范围以及耗散$b$的强度。对于大的耗散力，流变学由Weisenberg数$ \text{Wi}\sim b\dotγ/u$控制，并显示具有指数$ν=0.45$的Herschel-Bulkley形式$σ= σ_y+c\text{Wi}^ν$。随着耗散强度的减小，$\text{Wi}$的标度性被破坏，惯性效应出现。应力通过Johnson-Samwer定律$Δσ\sim T_s^{2/3}$减小，其中温度$T_s$完全是由于剪切引起的振动。在流动过程中，颗粒更倾向于围绕彼此旋转，使得主导速度与颗粒表面相切。这种能量耗散的切向通道及其抑制导致流动曲线的不连续性，以及相关的不连续剪切稀化过渡。我们建立了一个与摩擦系统的类比，在那里发生不连续的剪切增稠现象。在这两种情况下，切向力（摩擦力或粘性力）都是从具有低切向耗散的流动曲线的一个分支过渡到具有大切向耗散的流动曲线的一个分支。
英文摘要：
We present simulations for the steady-shear rheology of a model adhesive dispersion. We vary the range of the attractive forces $u$ as well as the strength of the dissipation $b$. For large dissipative forces, the rheology is governed by the Weisenberg number $ \text{Wi}\sim b\dotγ/u$ and displays Herschel-Bulkley form $σ= σ_y+c\text{Wi}^ν$ with exponent $ν=0.45$. Decreasing the strength of dissipation, the scaling with $\text{Wi}$ breaks down and inertial effects show up. The stress decreases via the Johnson-Samwer law $Δσ\sim T_s^{2/3}$, where temperature $T_s$ is exclusively due to shear-induced vibrations. During flow particles prefer to rotate around each other such that the dominant velocities are directed tangentially to the particle surfaces. This tangential channel of energy dissipation and its suppression leads to a discontinuity in the flow curve, and an associated discontinuous shear thinning transition. We set up an analogy with frictional systems, where the phenomenon of discontinuous shear thickening occurs. In both cases tangential forces, frictional or viscous, mediate a transition from one branch of the flowcurve with low tangential dissipation to one with large tangential dissipation.
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