Turbulent Vortieity Transport in Three Dimensions 1

The nature of vorticity transport in three-dimensional turbulent flow is investigated using data from a direct numerical simulation of channel flow. An extension of Taylor's (1932) vorticity transport theory is derived by a formal Lagrangian analysis in which care is taken to include nongradient transport effects associated with vortex stretching and shearing. A comparison is made between the predicted and exact forms of the nine components of the vorticity transport tensor as calculated from the simulation data. It is found that the qualitative agreement between the theory and the computed fluxes is excellent. The nongradient terms make a significant contribution near the boundary as an apparent consequence of the dynamical importance of coherent vortical structures. A model for the Reynolds shear stress consisting of a gradient term together with a nonlocal integral expression representing the effect of the pressure field on transport is extracted from the vorticity transport law. Computations reveal that a gradient vorticity transport model is acceptable only at a distance from the wall, w]hile the opposite is true in the case of momentum transport. These results agree with much earlier studies of G.I. Taylor.