Published online by Cambridge University Press: 14 April 2009
The issue of why computational resolution in Navier–Stokes turbulence is hard to achieve is addressed. Under the assumption that the three-dimensional Navier–Stokes equations have a global attractor it is nevertheless shown that solutions can potentially behave differently in two distinct regions of space–time ± where − is comprised of a union of disjoint space–time ‘anomalies’. If − is non-empty it is dominated by large values of |∇ω|, which is consistent with the formation of vortex sheets or tightly coiled filaments. The local number of degrees of freedom ± needed to resolve the regions in ± satisfies , where u = uL/ν is a Reynolds number dependent on the local velocity field u(x, t).