Turbulent-viscosity reduction mechanism based on anisotropic turbulence effects

Abstract

The relationship between turbulent viscosity and turbulence anisotropy is investigated on the basis of a statistical theory of inhomogeneous turbulence. An anisotropic turbulent viscosity is derived with the axisymmetric anisotropy subject to an enhanced streamwise turbulence intensity taken into account. The result paves the way for explaining a mechanism of drag reduction due to the change of turbulence anisotropy in a developed pipe flow. The drag reduction by polymer additives is discussed in light of this mechanism. © 2003 American Institute of Physics.