 Hydrodynamic drag models for a polymer

The drag of a translating polymer depends on conformation and hydrodynamic interactions. A nondraining coil has $\zeta \sim 6\pi \eta R_h$; a long aligned rod has ${\zeta }_{\parallel }\sim 2\pi \eta L/\log (L/a)$ and roughly twice that transverse drag; a freely draining model sums the monomer drag coefficients. Mechanical power is $\zeta U^2$. These models cannot be interchanged without changing the assumed conformation and solvent-mediated coupling.