Direct numerical simulation of polymer-induced drag reduction in turbulent boundary layer flow

We describe a method for direct numerical simulation of polymer-induced friction drag reduction in turbulent boundary layers. The effect of the polymer additives that induce spatial variations of skin-friction drag is included in the momentum equation through a continuum constitutive model for the viscoelastic stress, which is based on the evolution of a parameter describing the fluid microstructure. We demonstrate that the turbulence structure and polymer microstructure evolve asynchronously as one moves in the streamwise direction. We observe an initial development length, which is followed by a quasisteady region where variations in drag reduction are weak. High drag reduction behavior can be present at short downstream distances from the inflow plane. (C) 2005 American Institute of Physics.