Mechanisms of Vortex Evolution under Acoustic Excitation in Wing-in-Ground Effect

Vortex strength/evolution under Wing-in-Ground effect and jet interaction depend on aeroacoustic feedback. Low ground clearance requires nascent vortices emerging from the boundary layer to be acoustically reinforced for survival, detachment, and feedback sustenance. Acoustic waves affect the vortex strength and evolution via two pathways:

Streamwise Modal Amplification: The sound wave penetrates the boundary layer near the leading edge, pushing Tollmien-Schlichting disturbance transition upstream with higher intensity. This promotes the shear-layer roll-up, yielding intensified vortices that result in stronger trailing edge noise which reinforce leading-edge instabilities.

Spanwise Modal Instability: Natural or induced spanwise undulations fragment vortices before trailing-edge detachment. Fragmentation reduces spanwise correlation and introduces phase mismatches. The returning acoustic wave then arrives at the leading edge out-of-phase across the span, allowing curvature and other spanwise instabilities to grow. The resulting 3D breakdown prevents coherent shedding, disrupts the feedback loop, and attenuates noise. Thus, flow-disruption devices (fins, serrated edges) are expected to mitigate noise by promoting spanwise modal instability within the sound-vortex feedback loop.