Extreme wall shear stress events in turbulent pipe flow: Insights from the azimuthal wall shear stress

Extreme wall shear stress (WSS) events are traditionally categorized into two types: extreme positive events and backflow events. By introducing an additional azimuthal constraint, both categories can be further divided into subtypes that display distinct statistical and structural characteristics. This study underscores the crucial role of azimuthal shear stress in the formation and evolution of extreme WSS events, providing a more nuanced understanding and a fresh perspective on near-wall turbulence.