Large-scale motions, important in turbulent shear flows, are frequently attributed to the interaction of structures at smaller scales. Here we show that, in a turbulent channel at ${\mathrm{Re}}_{\tau }\approx 550$, large-scale motions can self-sustain even when smaller-scale structures populating the near-wall and logarithmic regions are artificially quenched. This large-scale self-sustained mechanism is not active in periodic boxes of width smaller than $L_z\approx 1.5h$ or length shorter than $L_x\approx 3h$ which correspond well to the most energetic large scales observed in the turbulent channel.

• Received 16 February 2010

DOI:https://doi.org/10.1103/PhysRevLett.105.044505