Additive Equivalence in Turbulent Drag Reduction by Flexible and Rodlike   Polymers
  We address the "Additive Equivalence" discovered by Virk and coworkers: drag reduction affected by flexible and rigid rodlike polymers added to turbulent wall-bounded flows is limited from above by a very similar Maximum Drag Reduction (MDR) asymptote. Considering the equations of motion of rodlike polymers in wall-bounded turbulent ensembles, we show that although the microscopic mechanism of attaining the MDR is very different, the macroscopic theory is isomorphic, rationalizing the interesting experimental observations. 
Roberto Benzi (Dip. di Fisica and INFN, Universita Tor Vergata, Roma,   Italy) Emily S.C. Ching (Dept. of Physics, The Chine...