Decomposition of streamwise velocity skewness in zero-pressure-gradient canonical and actuated turbulent boundary layers

In this study, the skewness in both canonical and actuated zero-pressure-gradient turbulent boundary layers (Re${}_{\ensuremath{\theta}}$ =1770) is decomposed using the real part of the bispectrum, revealing the triadic interactions contributing to skewness. The bispectra of the canonical TBL are compared with those from a case where plasma actuation introduces large-scale spanwise vortices in the outer layer. Actuation serves to examine how imposed outer-layer structures influence near-wall dynamics. Results indicate that linear inner--outer interactions dominate: in the actuated TBL, outer-layer structures modulate near-wall vortex strength but do not trigger their formation.