Turbulent cascade, bottleneck, and thermalized spectrum in hyperviscous flows

High-resolution Direct Numerical Simulations of the Taylor-Green vortex using standard Navier-Stokes (NS) equations (order of the Laplacian $p=1$) and hyperviscosity (p up to 100) show that evolution of the total energy and its dissipation are similar for the two simulations, but that the energy spectrum develops a more pronounced bottleneck. A link between this bottleneck and the thermalized (absolute equilibrium) state is demonstrated. The vortex tubes seen for the NS equations ($p=1$, above) are replaced by less elongated vortex ``blobs'' for the hyperviscous case ($p=10$, below).