SPECTRA OF LOCAL AND NONLOCAL 2-DIMENSIONAL TURBULENCE

We propose a family of two-dimensional incompressible fluid models indexed by a parameter alpha epsilon[0, infinity], and discuss the spectral scaling properties for homogeneous, isotropic turbulence in these models. The family includes two physically realizable members. It is shown that the enstrophy cascade is spectrally local for alpha < 2, but becomes dominated by nonlocal interactions for alpha > 2. Numerical simulations indicate that the spectral slopes are systematically steeper than those predicted by the local scaling argument.