3D Kolmogorov flow: evolution of z-averaged vorticity

Turbulent flows can be understood as the superposition of a mean flow, which evolves slowly and is shaped by boundaries or forcing mechanisms, and a multitude of chaotic, short-lived fluctuations.
We performed pseudo-spectral simulations of a turbulent three-dimensional Kolmogorov flow on an aspect-ratio-three domain, which is driven by a sinusoidal shearing body force. The visualization shows the vorticity averaged over the direction normal to the forcing plane to emphasize the large-scale counter-rotating vortices. The bottom plot shows an effective wavenumber of the large-scale state --- 1/3 corresponds to a single large-scale structure present in the flow.
Please see arxiv.org/abs/2102.07675 for further details.