Low-Resolution Numerical Simulation of Decaying Two-Dimensional Turbulence

Abstract

Numerical simulations of two-dimensional turbulence show that O(κ⁻¹) and O(κ⁻⁴) energy spectra—described by Fox and Orszag (1973a) as enstrophy-equipartitioning and strongly dissipating turbulence, respectively—occur independently of the type of dissipation mechanism, and the inclusion of forcing and the β-effect. In both states the modal decorrelation rate η depends strongly upon wavenumber in accordance with the equations of a direct interaction approximation (Kraichnan, 1958), but in conflict with the hypothetical wavenumber independence of η in an enstrophy-caseading inertial similarity range. Implications for geophysical fluid dynamical modeling are discussed.