Drag reduction in decaying homogeneous isotropic turbulence (DHIT) with polymer additives has been observed, which leads to weaker turbulent characteristic quantities. Coherent structures play an important role in the understanding of turbulent dynamics, and the introduction of polymer additives can significantly modify their behavior. It is believed the modifications are closely related to drag reduction mechanism. In the present study, we mainly focus on investigating the influence of polymers on coherent structures from phenomenological and energetic viewpoint for DHIT with polymers based on direct numerical simulation (DNS). The results show that polymers can not only suppress the increase rate of the enstrophy and strain but also their productions, leading to a remarkable inhibition of coherent structures especially at fine scale.
Three Dimensional Feature of Coherent Fine Scale Eddies in Homogeneous Isotropic Turbulence.
