The minimal logarithmic region.

We present a `minimal' DNS of a turbulent channel with smooth walls at $Re_\tau \approx 2000$. The simulation is performed in a periodic domain with streamwise and spanwise lengths $\pi h/2 \times \pi h/4$. Below $y/h \approx 0.2$, it reproduces the mean and fluctuating velocity profiles and spectra of the logarithmic region of full-sized turbulent channels, although the largest scales are absent. The simulation is minimal in the sense that it essentially fits a pair of the characteristic wall-attached eddies identified in the logarithmic region by del \'Alamo {\em et al} (2006). As in full-channels, these eddies are associated with large low-momentum streaks $(\Delta z^+\approx 500)$, here of infinite length, which break up after sinuose meandering. The break-up results in a wall-normal velocity ejection, and in a sweep behind it. While the former transports low-momentum fluid across the logarithmic region, the sweep interacts with the remaining part of the streak, and reorganizes it into a ramp that eventually decays by what appears to be a different, less violent, process.