Budgets of Reynolds stress, kinetic energy and streamwise enstrophy in viscoelastic turbulent channel flow

The budgets of the Reynolds stress, turbulent kinetic energy and streamwise enstrophy are evaluated through direct numerical simulations for the turbu lent channel flow of a viscoelastic polymer solution modeled with the Finit ely Extensible Nonlinear Elastic with the Peterlin approximation (FENE-P) c onstitutive equation. The influence of viscoelasticity on the budgets is ex amined through a comparison of the Newtonian and the viscoelastic budgets o btained for the same constant pressure drop across the channel. It is obser ved that as the extensional viscosity of the polymer solution increases the re is a consistent decrease in the production of Reynolds stress in all com ponents, as well as in the other terms in the budgets. In particular, the e ffect of the flow elasticity, which is associated with the reduction in the intensity of the velocity-pressure gradient correlations, potentially lead s to a redistribution of the turbulent kinetic energy among the streamwise, the wall-normal and the spanwise directions. In this work, we also show th at in the presence of viscoelasticity there is a significant reduction in a ll components of the production of streamwise enstrophy. This is consistent with a proposed mechanism for polymer-induced drag reduction through the i nhibition of vortex stretching by the high extensional viscosity of the pol ymer solution. (C) 2001 American Institute of Physics.