Comparison of direct numerical simulation of two-dimensional turbulence with two-point closure - The effects of intermittency

Several studies suggest that high-Reynolds-number two-dimensional turbulence may evolve in such a manner that there is little enstrophy flux to small scales. In these cases, the flow departs substantially from Gaussianity. It is pointed out that this condition is inhospitable to moment closures. The present study has the objective to gain inslight into the magnitude of this problem. A comparison is conducted of direct numerical simulations (DNS) with equivalent closure (TFM) for a variety of forcing functions, including spin-down (i.e. no forcing). The results obtained for forced cases are that the closure may be quantitatively accurate only if the disruptive effects of random stirring are sufficiently strong to prevent the formation of coherent structures natural to two-dimensional turbulence.