平板間における高分子液体の粘弾性流動のマルチスケールシミュレーション(分子スケール(1),一般講演)

概要

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The dynamic rheology of a model polymer melt composed of short chains with ten beads between rapidly oscillating plates is investigated for various oscillation frequencies by using the hybrid simulation of the molecular dynamics and computational fluid dynamics. In the rapidly oscillating plates, the non-uniform boundary layer flows are generated over the plate, and the local rheological properties of melt are spatially varied according to the local flow fields. At the high oscillation frequencies, the melt forms the three different regimes, i.e., viscous fluid regime (G'<<G"), liquid-like viscoelastic regime (G'<G"), and solid-like viscoelastic regime (G'>G"), over the rapidly oscillating plate. The local strain of the melt at the far distances from the plate decreases as the oscillation frequency increases, so that the local moduli deviate from the linear ones at the low oscillation frequencies while they are close to the linear ones at the high oscillation frequencies. On the contrary, at the near distances, the local strain rate increases as the oscillation frequency, so that the shear thinning is enhanced at the high oscillation frequencies. In the close vicinity of the plate, the dynamic viscosity is mostly independent on the oscillation frequency and the shear thinning which is similar to that occurring in the steady shear flows of the model polymer melt is observed.
2010-09-09