On turbulent/non-turbulent interfaces from equilibrium and non-equilibrium turbulence*

Direct numerical simulations (DNS) of turbulent fronts created by both equilibrium and non-equilibrium (unbalanced) turbulence are used to assess the characteristics of the turbulent/non-turbulent interface (TNTI) that separates regions of turbulent from non-turbulent (or irrotational) flow. The effects of the unbalance can be observed in the detailed shape of the conditional profiles of vorticity magnitude, and in the magnitude of the maximum enstrophy but do not affect its main features.

In particular the mean thickness of the TNTI is equal in classical or non-equilibrium turbulence and it scales with the Kolmogorov micro-scale as previously observed at Reynolds numbers $200 \leq Re_\lambda \le 400$.