Time‐series and extended Karhunen–Loève analysis of turbulent drag reduction in polymer solutions

Direct numerical simulations and statistical analysis techniques are used to study the drag‐reducing effect of polymer additives on turbulent channel flow in minimal domains. Additionally, a new formulation of Karhunen–Loève decomposition for viscoelastic flows is introduced, allowing the dominant features of the polymer stress fields to be characterized. In minimal channels, there are intervals of “active” and “hibernating” turbulence that …