标题： 稀释球体悬浮液在聚合物液体中的伸展流变学 显示英文标题

标题： Extensional rheology of dilute suspensions of spheres in polymeric liquids

摘要： 稀释球体悬浮液在粘弹性或聚合物液体中的拉伸流变性质通过计算进行了研究。 在低聚合物浓度（c）和德鲍数量（De）下，由于局部速度梯度大于施加的流动，粒子下游形成高度拉伸的聚合物尾迹，这由局部De的正偏差表明。 这会随时间及De的增加而提高悬浮液的拉伸粘度，当De小于0.5时如此。 当De超过0.5（线圈-拉伸转变点），来自远场的完全拉伸的聚合物会在粒子停滞点周围局部速度梯度较低的区域坍塌，从而相对于纯聚合物液体降低悬浮液粘度。 局部流动与聚合物之间的相互作用随着c的增加而增强。高度拉伸的聚合物阻碍局部流动，降低局部De，而在坍塌聚合物的区域中则会增加局部De。 最初，增加c会使局部De和聚合物拉伸与远场值对齐，减弱粒子-聚合物相互作用的影响。 然而，超过某一c之后，一种新的机制出现。 在低c时，上游三个粒子半径处的流体表现出增加的局部De，使聚合物拉伸超过其未受扰状态。 随着c的增加，这种偏差变为负数，导致聚合物坍塌，并在大De和时间下产生越来越负的应力，由粒子-聚合物相互作用引起。 在高c时，这种负的相互作用应力与c平方成比例，超过聚合物应力的线性增加，使得稀释球体悬浮液在较大的De和c下更有效地降低粘弹性液体的粘度。 显示英文摘要

摘要： The extensional rheology of dilute suspensions of spheres in viscoelastic or polymeric liquids is studied computationally. At low polymer concentration (c) and Deborah number (De), a wake of highly stretched polymers forms downstream of the particles due to larger local velocity gradients than the imposed flow, indicated by a positive deviation in local De. This increases the suspension's extensional viscosity with time and De for De less than 0.5. When De exceeds 0.5 (the coil-stretch transition), the fully stretched polymers from the far field collapse in regions with lower local velocity gradients around the particle's stagnation points, reducing suspension viscosity relative to the polymer-only liquid. The interaction between local flow and polymers intensifies with increasing c. Highly stretched polymers impede local flow, reducing local De, while it increases in regions with collapsed polymers. Initially, increasing c aligns local De and polymer stretch with far-field values, diminishing particle-polymer interaction effects. However, beyond a certain c, a new mechanism emerges. At low c, fluid three particle radii upstream exhibits increased local De, stretching polymers beyond their undisturbed state. As c increases, this deviation becomes negative, collapsing polymers and resulting in increasingly negative stress from particle-polymer interactions at large De and time. At high c, this negative interaction stress scales as c squared, surpassing the linear increase in polymer stress, making dilute sphere suspensions more effective at reducing the viscosity of viscoelastic liquids at larger De and c.