Identification of wall attached and detached structures in turbulent channels using informative/non-informative decomposition (IND)

The IND is a method to decompose flow fields into two components with respect to a target variable: an informative field, which embeds all the information of the target, and a residual (non-informative) field, which contains no information of the target. We use the IND to introduce an information-based definition of wall-attached and wall-detached velocity fields as those that con- tain information of the wall and those that do not, respectively. The analysis is performed in turbulent channel flow with friction Reynolds numbers in the range Re_τ ≈ 500 − 2000. Two different target fields are considered to define attached/detached eddies: the wall shear stress and the wall pressure. We analyze the topological differences between these structures for the two target variables considered. The IND also allows us to select whether the information about the target is referred to the present state or some time in the future, and the effect of this time interval on the resulting attached/detached eddies is also investigated.