Persistence–of–straining and polymer alignment in viscoelastic turbulence

Abstract Drag reduction in turbulent flows by the addition of polymers is a phenomenon that has a variety of applications in the engineering. The highly nonlinear interactions between the turbulent flow and the polymers in the polymeric solution still impose challenges to the understanding of this phenomenon. Efforts to address this problem come mainly from two sources: experiments and direct numerical simulations. In the present work we investigate through direct numerical simulations the roles of the non–persistence–of–straining tensor and the covariant strain acceleration tensor from the statistical and their alignment with the conformation tensor. In this regard, we provide a better picture of the relative orientation of this quantity.