Boldrighini, C. & Franceschini, V. Commun.Math. Phys. (1979) 64: 159. doi:10.1007/BF01197511
A five-modes truncation of the Navier-Stokes equations for a two dimensional incompressible fluid on a torus is considered. A computer analysis shows that for a certain range of the Reynolds number the system exhibits a stochastic behaviour, approached through an involved sequence of bifurcations.