INTERMITTENCY IN THE LARGE-N LIMIT OF A SPHERICAL-SHELL MODEL FOR TURBULENCE

A spherical shell model for turbulence, obtained by coupling N replica s of the Gledzer, Okhitani and Yamada shell model, is considered. Cons ervation of energy and of a helicity-like invariant is imposed in the inviscid limit. In the N --> infinity limit this model is analytically soluble and is remarkably similar to the random coupling model versio n of shell dynamics. We have studied numerically the convergence of th e scaling exponents toward the value predicted by Kolmogorov theory (K 41). We have found that the rate of convergence to the K41 solution is linear in 1/N. The restoring of Kolmogorov law has been related to th e behaviour of the probability distribution functions of the instantan eous scaling exponent.