Abstract
The dynamics of dilute polymer solutions is investigated in wall turbulent flow. A realistic turbulent flow field is obtained by a fully coupled direct numerical simulation of a drag-reducing polymer solution. This flow field is used to compare the microscopic and macroscopic description of the polymer dynamics. It is observed that polymers become highly oriented parallel to the mean flow direction. The stretching of the polymers is characterized by a broad distribution of polymer extensions. Finally, the Gaussian manifold corresponding to the macroscopic description of the polymer dynamics is found to be unstable in the present flow.