Characteristics of the vortical fissures in turbulent wall-bounded flows

The inertial domain of the turbulent wall-bounded flows are composed of large regions of uniform momentum zones (UMZs) segregated by countable slender fissures of elevated vorticity (i.e., vortical fissures). Because they account for spatially abrupt increments in streamwise velocity, it is readily surmised that the volume-weighted momentum transport across the vortical fissures (VFs) is large. Thus it is rational to suspect that their dynamical influences are significant to sustaining the inertial layer structure. While the statistical distribution of the vortical fissures has been studied extensively, their physical characteristics remain largely unknown due to their ever decreasing size, which scales with $1/\sqrt{\delta^+}$, where $\delta^+$ is the Reynolds number. The current study employs particle image velocimetry (PIV) data acquired at the Flow Physics Facility (FPF) with a boundary layer thickness of $~1m$ to study the properties of the VFs at high Reynolds numbers. The VFs are identified and extracted directly from instantaneous velocity profiles using a vorticity threshold method, which is analytically derived based on the self-similar dynamical structure of turbulent wall flows as determined via analysis of the mean streamwise momentum equation by Wei et al. (2005).