Potential-enstrophy lengthscale for the turbulent/nonturbulent interface in stratified flow

Turbulent/nonturbulent interfaces typically have a thickness of the order of the Kolmogorov scale. However, when we add a density or temperature stratification, we observe that the interface thickness scales differently. We analyze two different turbulent flows at moderate Reynolds numbers using direct numerical simulation and demonstrate that the results collapse on a single curve using a lengthscale based on the potential enstrophy.