Unsteady interaction of crossflow instability with a forward-facing step

Experiments have been conducted on a swept wing model in low-turbulence wind tunnel at chord Reynolds number of $2.17 \times 10^{6}$ to investigate the unsteady interaction forward-facing step (FFS) with incoming stationary crossflow (CF) vortices. The impact varying FFS height development and growth primary secondary CF disturbances ensuing laminar–turbulent transition is quantified through detailed hot-wire anemometry infrared thermography measurements. presence results either critical (i.e. moderate advancement) or supercritical behaviour advancing abruptly location). arrival forced vortices accompanied by their amplification. Unsteady analysis for cases indicates temporal velocity fluctuations following closely baseline configuration agreeing instabilities). Consequently, laminar breakdown originates from outer side upwelling region In contrast, FFS, unexpectedly inner region. Evidence points an mechanism possibly supported locally enhanced spanwise-modulated shears recirculation downstream edge. This appears govern abrupt tripping flow cases. findings this work provide insight into FFS–CF vortex interaction, which pivotal understanding influence boundary-layer aerodynamic surfaces.