Understanding the impact of sheared flows on transport dynamics

It has been found in recent gyro-kinetic simulations that the underlying dynamics of transport can change in the presence of a sheared flow. In this paper we show that the effect of the presence of the sheared flow can go beyond the reduction of effective transport coefficients by changing the very nature of the radial transport dynamics. We will explore the physical mechanism for this change using a simple fluid drift wave turbulence model [1]. The change in the dynamics will be shown in the gyro-kinetic and fluid models for imposed and self-consistent flows. Using the fluid model, a simple picture will be developed showing different regimes of the dynamics as the flow changes in which flow stability is also considered. The implication of these changes on transport modeling and large scale turbulence simulations will be discussed. References: [1] D.E. Newman et al, Phys. Fluids B 5, 1140 (1993)