Phenomena related to scale interaction in wall-bounded turbulent flows were considered through the lens of critical layer analysis. A 3D critical layer formulation was used, with the 3D critical layer associated with a particular structure defined as the height where the instantaneous velocity field composed of the large scales and the mean velocity matched the convection velocity of that structure. Characterization of the velocity field surrounding the 3D critical layer in wall-bounded turbulent flows led to conclusions consistent with previously observed phenomena including the shape of the interface defining uniform momentum zones (UMZs) [1] [2] and amplitude modulation of the small scales by the large scales [5]. The use of a 3D critical layer formulation in wall-bounded turbulent flows may lead to improved modeling of small scale activity in reduced order models and LES
