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          楊玉良

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          Anisotropic and enhanced self-diffusion of a macromolecular chain under simple shear flow as revealed by Monte Carlo simulation on lattices

          楊玉良 , Guoqiang Xu , Jiandong Ding* , Yuliang Yang ,

          Macromol. Theory Simul. 7, 129-140(1998),-0001,():

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          摘要/描述

          Two-dimensional simple shear flow of a self-avoiding macromolecular chain is simulated by a lattice Monte Carlo (MC) method with a pseudo-potential describing the flow field. The simulated velocity profile satisfies the requirements of simple shear flow unless the shear rate is unreasonably high. Some diffusion problems for a free-draining bead-spring chain with excluded volume interaction are then investigated at low and relatively high shear rates. Three diffusion coefficients are defined and examined in this paper: the conventional self-diffusivity in zero field, Dself, the apparent self-diffusivity in flow field, Dapp, and the flow diffusivity in simulation, Dflow reflecting actually the transport coefficient. It is found that these three diffusivities for a flexible chain are different from each other. What is more important is that self-diffusion exhibits a high anisotropy in the flow field. The apparent self-diffusion along the flow direction is enhanced to a large extent. It is increased monotonically with the increase of shear time or shear strain, whereas the chain configuration can achieve a stationary anisotropic distribution following an interesting overshoot of the coil shape and size. Besides a single self-avoiding chain, an isolated Brownian bead and a group of self-avoiding beads with a quasi-Gaussian spatial distribution are also simulated. According to the comparison, the effects of the connectivity of the chain on the diffusion behavior are revealed. Some scaling relations of Dapp versus t are consistent with the theoretical analyses in the pertinent literature.

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          【免責聲明】以下全部內容由[楊玉良]上傳于[2005年03月11日 01時04分25秒],版權歸原創者所有。本文僅代表作者本人觀點,與本網站無關。本網站對文中陳述、觀點判斷保持中立,不對所包含內容的準確性、可靠性或完整性提供任何明示或暗示的保證。請讀者僅作參考,并請自行承擔全部責任。

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