Flow mechanism at the interface layer of the bio-inspired coated surface in a turbulent channel flow

We have investigated the turbulent channel flow coated with bio-inspired surface via fully unstructured Pseudo-spectral method. The present study is inspired by the denticles present on the skin of the mako shark. Previous experimental studies by Bocanegra et. al (2018)\footnote{Evans, H. B., Hamed, A. M., Gorumlu, S., Doosttalab, A., Aksak, B., Chamorro, L. P., \& Castillo, L. (2018). Engineered bio-inspired coating for passive flow control. Proceedings of the National Academy of Sciences, 115(6), 1210-1214} revealed that the denticle like micro structures ($85$ $\mu m$) delayed the separation in an adverse pressure gradient flow. However, in spite of several studies to understand the flow near the wall, the interaction at the interface layer and inside the microstructures is not fully understood. Here, we use high resolution adaptive mesh refinement based DNS simulations to resolve the flow in the interface layer and inside the microstructures to shed light on the mechanism between the interface layer which is responsible for the drag reduction and/or delay in separation. \%This study also will help to model the interface layer boundary conditions for numerical modeling.