Saturation mechanisms for edge turbulence

Saturation mechanisms for two-dimensional (2D) edge turbulence are studied in a Braginskii-type fluid model using the scrape-off-layer turbulence code. The simulations study the interaction of edge and scrape-off-layer (SOL) turbulence, blob generation, momentum transport, and shear flow generation in 2D turbulence. It is shown that a key parameter is the zonal flow shear damping rate, which controls both the level of saturated turbulence and the rate of blob generation. The flow shear profile is produced by a combination of the turbulent Reynold's stress inside the last closed surface and the sheath-induced flow in the SOL. The turbulent properties are studied as a function of zonal flow damping. The role of other edge and SOL dissipation mechanisms are also discussed.