Outer-layer self-similarity of the turbulent boundary layer based on the turbulent/non-turbulent interface

This study reports on the outer-layer self-similarity of the turbulent boundary layer at low to moderate Reynolds number range from the perspective of the turbulent/non-turbulent (T/NT) interface. From the new perspective, the exponential self-similarity of the mean velocity is discovered in the outer region. For further consideration, we propose the energy-superposition effect based on the outer-layer structures to reveal the similarity of the turbulent kinetic energy in the outer layer. The present work reveals that the interface-based perspective provides an alternative scheme to understand the outer layer of the turbulent boundary layer.