DNS study on viscoelastic effect in drag-reduced turbulent channel flow

An investigation on mechanisms of the turbulent drag reduction, induced by the viscoelasticity of non-Newtonian fluids, is in progress. In the present work, the effects of viscoelastic contribution is examined by direct numerical simulations (DNS), using the Giesekus model for surfactant solutions. A series of DNS on the turbulent channel flow has been performed for different rheological properties, with respect to Weissenberg number and the ratio of solvent contribution to the total zero-shear viscosity, at different Reynolds numbers. It is found that high drag reduction can be achieved by suppression of the turbulent production for high Weissenberg number, and/or by decrease of the effective viscosity irrespective of the Reynolds number. Moreover, we focus on the viscoelastic contribution term in the budget of Reynolds stresses and its relation to the local flow pattern.