Synchronized molecular-dynamics simulation for the thermal lubrication of a polymeric liquid between parallel plates
Synchronized molecular-dynamics simulation for the thermal lubrication of a polymeric liquid between parallel plates
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平行板之间聚合物液体热润滑的同步分子动力学模拟
DOI：
10.1016/j.compfluid.2015.05.018
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发表时间：
2016
影响因子：
2.8
通讯作者：
Shugo Yasuda and Ryoichi Yamamoto
中科院分区：
文献类型：
--
作者：
Kota Katsumi;Yuki I. Hamada;Ryusuke Matsunaga;John Schneeloch;Ruidan D. Zhong;Genda D. Gu;Yann Gallais;and Ryo Shimano;Shugo Yasuda and Ryoichi Yamamoto
作者最近提出的同步分子动力学模拟（Yasuda 和 Yamamoto，2014）应用于平行板之间聚合物润滑的分析。研究了聚合物液体导热系数变化时流变性质的变化、聚合物链的构象变化以及粘性加热引起的温升。研究发现，当在板上施加较小的剪切应力时，聚合物液体的温度仅略微升高，且与热导率成反比；改变热导率对聚合物液体的表观粘度影响很小。然而，在大剪切应力下，由于剪切变形和粘性加热通过改变导热率的相互作用，观察到聚合物液体的过渡行为。这种转变以纳梅-格里菲斯数 Na 为特征，其定义为特征温度下粘性加热与热传导的比率。当 Nahme-Griffith 数超过 1 时，聚合物液体的温度迅速升高，表观粘度也随着热导率的降低而呈指数下降。当Na<1时，聚合物链的构象通过剪切流拉伸和排列，但当Na>1时，分子的热运动会扰乱相干结构。
The Synchronized Molecular-Dynamics simulation, which was recently proposed by authors (Yasuda and Yamamoto, 2014), is applied to the analysis of polymer lubrication between parallel plates. The changes in rheological properties, conformational change of polymer chains, and temperature rise due to the viscous heating are investigated with varying values of thermal conductivity of the polymeric liquid. It is found that with a small applied shear stress on the plate, the temperature of the polymeric liquid only slightly increases in inverse proportion to the thermal conductivity; the apparent viscosity of the polymeric liquid is little affected by changing the thermal conductivity. However, at a large shear stress the transitional behaviors of the polymeric liquid are observed due to the interplay of the shear deformation and viscous heating by changing the thermal conductivity. This transition is characterized by the Nahme–Griffith numberNa, which is defined as the ratio of the viscous heating to the thermal conduction at a characteristic temperature. When the Nahme–Griffith number exceeds unity, the temperature of the polymeric liquid increases rapidly and the apparent viscosity also exponentially decreases as the thermal conductivity decreases. The conformation of polymer chains is stretched and aligned by the shear flow whenNa< 1, but the coherent structure becomes disturbed by the thermal motion of molecules whenNa> 1.