SHEAR-INDUCED ORDER AND ROTATION IN PIPE-FLOW OF SHORT-CHAIN MOLECULES

In a series of molecular-dynamics simulations, oligomer fluids undergo ing Poiseuille (pipe) flow are shown to experience rotational motion a nd mean orientation that is dependent on the local shear rate. Local m olecular alignment is found to reflect the competition between the Max well forty-five degree prediction and a preferred orientation parallel to the flow close to the boundary. The molecules, each consisting of four linked hard spheres, and both fully flexible and semi-rigid chain s are studied; the flow is driven by a uniform field, with the pipe wa lls serving both as non-slip boundaries and thermal sinks for the shea r-generated heat.