Drag reduction in turbulent flow with polymer additives
The mean velocity profile and friction factor in turbulent flows with polymer additives are investigated using Prandtl’s mixing-length theorem. This study reveals that the mixing-length theorem is valid to express the drag-reducing phenomenon and that the presence of polymer additives increases the damping factor B in van Driest’s model; subsequently reducing the mixing-length, this interprets that the polymer hampers the transfer of turbulent momentum flux, the velocity is increased, and flow drag is reduced. This study also discusses the onset Reynolds number for drag reduction to occur. The predicted velocity, friction factor, and onset Reynolds number are in good agreement with the measured data in the literature.