直鎖状モデル分子流体のせん断流れの非平衡分子動力学シミュレーション ; ブタンのせん断流れ

概要

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Steady shear flows of liquid n-butane were simulated at T=150K and T=300K by an isothermal nonequilibrium molecular dynamics. In the model molecule of n-butane, the bond lengths are fixed by SHAKE algorithm, and the bond angle and dihedral angle are controlled by the corresponding potentials respectively. The liquids exhibit shear-thinning in viscosity at high shear rates and the shear-thinning becomes more remarkable with lowering the temperature. The shear flow also affects the molecular conformation; at the high shear rates, the distribution of the bond angle is more concentrated around θ0 where the bond angle bending potential is minimum, and the trans configuration becomes increasingly populated. It is suggested that the non-Newtonian viscosity is caused by both the flow-induced orientation and the change of molecular conformation with shear rate. Comparison of our results with those obtained by Morriss, Davies, and Evans [J. Chem. Phys. 94, 7420 (1991)] indicates that the shear-thickening observed in the latter work is caused by the increase in the gauche population at high shear rates.
日本レオロジー学会の論文