Fluid n-decane undergoing planar Couette flow

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Abstract
Molecular dynamic simulations of fluid n‐decane undergoing planar Couette flow have been carried out. The n‐decane chains were modeled using an anisotropic version of the united‐atom model with fixed bond lengths. The results of our simulations verify the equivalence between the steady state time averages of the atomic and molecular stress tensors. In the range of shear rates which have been investigated, our results show that the values of the viscosity coefficient depend mainly on the shape of the intermolecular potential and they are insensitive to the shape of the torsion potential. Moreover, the viscosity coefficient as a function of the shear rate shows a region of shear thinning at low shear rates followed by a region of shear thickening. The study of the alignment induced in the fluid by the perturbing field shows that after a region of fast increasing of the degree of alignment with increasing shear rate, this reaches a maximum and slowly begins to decrease. This behavior can be related to the fact that at high shear rates the chains tend to adopt a more shrunken mean shape.