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The dynamic rheology of a polymer melt composed of short chains with tenbeads between rapidly oscillating plates is investigated for variousoscillation frequencies by using the hybrid simulation of the moleculardynamics and computational fluid dynamics. In the rapidly oscillating plates,non-uniform boundary layer flows are generated over the plate due to inertia ofthe fluid, and the local rheological properties of the melt are spatiallyvaried according to the local flow fields. Far from the plate, the local straindecreases as the oscillation frequency increases such that the dynamic rheologydeviates from the linear moduli at the low oscillation frequencies rather thanhigh oscillation frequencies. On the contrary, near the plate, the local strainrate increases with the oscillation frequency such that the shear thinning isenhanced at high oscillation frequencies. In close vicinity to the plate, thedynamic viscosity is mostly independent of the oscillation frequency, and theshear thinning behavior becomes similar to that observed in steady shear flows.Non-linear rheological properties are also investigated by the spectrumanalysis and the Lissajous-Bowditch curve. It is found that the fractionalamplitude of the higher harmonics to the linear harmonics is suppressed withinthe boundary layer due to the non-slip boundary on the oscillating plate. Wealso find that the melt exhibits inter-cycle shear thinning between differentpositions but exhibits intra-cycle shear thickening at a fixed position in thevicinity of the plate.

Dynamic rheology of a supercooled polymer melt in non-uniform oscillating flows in rapidly oscillating plates