D. Kienle¹, R. Rzehak¹, and W. Zimmermann^2
1Institut fur Festkörperforschung, Forschungszentrum Jülich, D-52!25 Jülich
²Theoretische Physik, Universität des Saarlandes,D-66041 Saarbrücken

The drag coefficient for polymers depends nonlinearly on the velocity as shown by numerical simulations of a single tethered polymer, of two tethered polymers, and of a polymer anchored at a large sphere, all exposed to a uniform flow. This nonlinear behavior may be considered as a generalization of the famous Stokes law, which is a linear relation F = (u between the velocity of the sphere and the drag force F acting on it, where the drag coefficient C is independent of the velocity . The intra-chain as well as the inter-chain hydrodynamic interaction lead to a nonlinear velocity dependence of the drag coefficient which is especially pronounced for a polymer anchored at a large sphere. Since drag forces deform polymers in streaming fluids, this nonlinear behavior causes interesting rheological effects in polymer solutions and therefore has to be considered in rheological modeling. In calculations of hydrodynamic interaction effects it is quite common to use a preaveraged mobility matrix, but as shown in this work preaveraging suppresses fluctuations of the flow-induced polymer deformation.