Direct numerical simulation on drag reducing flow by polymer additives

A discrete-element model (spring-dumbbell model) was used to investigate the mechanism of drag reduction by addition of a small amount of polymer in a turbulent channel flow of Newtonian fluid by direct numerical simulation. By using the discrete-element model, the spatial concentration of the polymer can be obtained numerically. The quantitative relations between the drag reduction rate and viscoelastic shear stress and Reynolds shear stress etc. were obtained. Discussions were performed to clarify the relation between the turbulent structure of the polymer drag reducing flow and the spring coefficient of the discrete-element model.