Pipe Flow Of Dilute Polymer Solutions

Drag reduction caused by dilute, distilled water solutions of five polyethylene oxides, molecular weights from 80,000 to 6,000,000, in turbulent pipe flow was studied experimentally in 0.292 cm and 3.21 cm ID pipes. It was found that: The onset of drag reduction occurs at a well-defined wall shear stress related to the random coiling effective diameter of the polymer by the Onset Hypothesis. Laminar to turbulent transition is not, in general, delayed. The extent of drag reduction induced by a homologous series of polymers in a given pipe is a universal function of concentration, uniquely related to flow rate and molecular weight. The maximum drag reduction possible is limited by a universal asymptote that is independent of polymer and pipe diameter. In polymer solution, both the stagnation pressure attained with Pitot tubes and the heat transfer from cylinders in cross flow are drastically different from Newtonian; in general, both are lower. (Author).