Atmospheric scientist E.N. Lorenz considered the Rayleigh-Bénard problem, which concerns a fluid in a container whose top and bottom surfaces are held at different temperatures. It had long been known that as the difference between these two temperatures is increased, the fluid can undergo transitions from a stationary state (no fluid motion) to steady flow to chaotic flow. This prompted him to consider a greatly simplified version of the Navier-Stokes equations as applied to this particular problem. Indeed, he grossly oversimplified the problem as he reduced it to only three equations:
where the Lorenz variables
are derived from temperature, density and velocity variables in the original Navier-Stokes equations, and
are measures of the temperature difference across the fluid and other fluid parameters.
