Is the Taylor scale relevant to turbulent sublayer dynamics at the turbulent/non-turbulent interface?

The turbulent/non-turbulent interface (TNTI) is a thin layer separating rotational and irrotational flow that plays a critical role in the multi-scale process of entrainment. In this work, the thickness δ_T of the turbulent sublayer (TS) within the TNTI is assessed using a kinematic scaling analysis that matches the time scales between the interacting scales of motion from within the turbulent core and the TS. This yields a mixed-length scale parameter for scaling the TS thickness, which closely approximates the physical size of the TS, i.e δ_T/(η^2/3λ^1/3) ≈ 3 (where η and λ denote the Kolmogorov and the Taylor micro length scales, respectively). This highlights the practical utility of the scaling parameter from the perspective of resolving the TS in experiments and simulations. It is also shown that the new scaling parameter is quadratically related to the established scaling parameter η, through a weak Re_λ dependence. The theory is then compared with the data available in the literature spanning from 60 < (Re_λ=u'λ/ν) < 400 (where ν is the kinematic viscosity). The difference between the currently proposed scaling parameter (η^2/3λ^1/3), and the one previously proposed (η) is also discussed. This is done by comparing the Burger's vortex model (yielding δ_T ~ η) with the present time scale arguments which incorporate the coherent strains experienced by the operative scales of motion in the TS along their axial lengths. It is argued that the axial length scales of these coherent strains are on the same order of magnitude as the Taylor length scales.