Rotating inhomogeneous turbulence accompanied with the turbulent helicity and its modeling

Abstract

An algebraic Reynolds stress model with the turbulent helicity gives a good result in predicting a decaying swirling pipe flow. In this model, gradient of turbulent helicity coupled with the absolute vorticity plays a key role in conuterbalancing the eddy-viscosity effect, which suggests that the inhomogeneous turbulent helicity may generate the mean flow in a rotating system on the analogy of the turbulent magnetic dynamo in magnetohy- drodynamics. In order to study the effects of inhomogeneous turbulent helicity in the rotating system, a large eddy simulation（ LES） of turbulence driven by an inhomogeneous external force is performed. In the simulation, the mean flow directed to the rotation axis is generated when the inhomogeneous turbulent helicity exists. This phenomenon cannot be explained only by the eddy viscosity effect. In the Reynolds stress transport equation, the terms leading to this phenomenon are discussed and the algebraic Reynolds stress model with the turbulent helicity coupled with the absolute vorticity is reproduced by modeling the pressure gradient diffusion term.