Five-Mode Truncation of the Navier-Stokes Equations
From a version of the three-dimensional Navier–Stokes equations for an incompressible fluid with periodic boundary conditions, a particular five-mode truncation was derived in . The resulting set of nonlinear ordinary differential equations allows only a finite number of Fourier modes and behaves as a system with five degrees of freedom, thereby resembling the behavior of the Lorenz attractor.
The truncated Navier–Stokes equations are
where is the Reynolds number and , , , are empirical parameters.
 V. Franceschini, G. Inglese, and C. Tebaldi, "A Five-Mode Truncation of the Navier-Stokes Equations on a Three-Dimensional Torus," Computational Mechanics 3(1), 1988 pp. 19–37. link.springer.com/article/10.1007%2 FBF00280749?LI=true #.
 P. S. Addison, Fractals and Chaos, an Illustrated Course, London: Institute of Physics Publishing, 1997.