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arXiv 0909.2466cond-mat.soft
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平行平板间polymer熔体流动的多尺度建模与模拟

Multiscale modeling and simulation for polymer melt flows between parallel plates

Shugo Yasuda, Ryoichi Yamamoto

摘要:

采用分子动力学和计算流体动力学的混合方法,模拟了由10个珠粒组成的短链聚合物熔体在平行平板间的流动行为。解决了三个问题:在恒定剪切应力下的蠕变运动和去除应力后的恢复运动、压力驱动流动和快速振荡板中的流动。在蠕变/恢复问题中,蠕变运动中的延迟弹性形变和恢复运动中的明显弹性行为被证明。由于剪切变稀,熔体在压力驱动流动中的速度分布与牛顿流体的速度分布有很大不同。随着压力梯度的增加和温度的降低,熔体的速度梯度在板附近变得陡峭,而在板之间的中间变得平坦。在快速振荡平板中,由于熔体的剪切变稀,熔体的粘性边界层比牛顿流体的粘性边界层薄得多。三种不同的流变状态,即,粘性流体、粘弹性液体和粘弹性固体状态根据局部Deborah数在振动板上形成。熔体在$ωτ^R\lesssim 1$的区域中表现为粘性流体,并且液体状和固体状状态之间的交叉发生在$ωτ^α\simeq 1$周围(其中$ω$是板的角频率,并且$τ^R$和$τ^α$分别是Rouse和$α$弛豫时间)。

英文摘要:

The flow behaviors of polymer melt composed of short chains with ten beads between parallel plates are simulated by using a hybrid method of molecular dynamics and computational fluid dynamics. Three problems are solved: creep motion under a constant shear stress and its recovery motion after removing the stress, pressure-driven flows, and the flows in rapidly oscillating plates. In the creep/recovery problem, the delayed elastic deformation in the creep motion and evident elastic behavior in the recovery motion are demonstrated. The velocity profiles of the melt in pressure-driven flows are quite different from those of Newtonian fluid due to shear thinning. Velocity gradients of the melt become steeper near the plates and flatter at the middle between the plates as the pressure gradient increases and the temperature decreases. In the rapidly oscillating plates, the viscous boundary layer of the melt is much thinner than that of Newtonian fluid due to the shear thinning of the melt. Three different rheological regimes, i.e., the viscous fluid, visco-elastic liquid, and visco-elastic solid regimes, form over the oscillating plate according to the local Deborah numbers. The melt behaves as a viscous fluid in a region for $ωτ^R\lesssim 1$, and the crossover between the liquid-like and solid-like regime takes place around $ωτ^α\simeq 1$ (where $ω$ is the angular frequency of the plate and $τ^R$ and $τ^α$ are Rouse and $α$ relaxation time, respectively).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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