This study investigates acoustic actuation as a flow control strategy for high-lift, high-work turbine blades at low Reynolds numbers. Low-speed experiments were conducted on simplified hump geometries in wind and water tunnels, while high-speed tests were performed in transonic linear cascade facility to examine acoustic excitation effects on massively separated flows under high adverse pressure gradients. Acoustic control significantly altered flow separation dynamics in low speed, achieving up to 22% lift enhancement at optimal Strouhal numbers. Moreover, full-field velocity measurements and spatio-temporal correlation analysis revealed that acoustic excitation organized vorticity upstream of the separation point through viscous wall-modes, which played a dominant role in shear layer reorganization.
Additionally, high speed experiments explored the influence of acoustic excitation on high-lift turbine blades (L3FHW and L4FHW) using both active siren disk and passive perforated tailboard Helmholtz resonator. Schlieren imaging and static pressure measurements showed that siren disk excitation increased peak suction pressure by up to 60% and reduced the separated shear layer angle by 10°, while tailboard excitation achieved an 11° reduction with modest pressure recovery improvements. Spectral analysis revealed enhanced vortical coherence at Kelvin-Helmholtz instability frequencies, scaling with the 3/2 power of the exit Mach number. Numerical simulations highlighted up to 40% variations in peak suction pressure due to secondary flow effects, emphasizing the role of end-wall vortices in flow control.
These findings highlight acoustic actuation as a robust, efficient flow control technique for turbomachinery in off-design conditions, while underscoring the need for optimized integration strategies to mitigate secondary flow effects.
Light refreshments will be served before the lecture
This study investigates acoustic actuation as a flow control strategy for high-lift, high-work turbine blades at low Reynolds numbers. Low-speed experiments were conducted on simplified hump geometries in wind and water tunnels, while high-speed tests were performed in transonic linear cascade facility to examine acoustic excitation effects on massively separated flows under high adverse pressure gradients. Acoustic control significantly altered flow separation dynamics in low speed, achieving up to 22% lift enhancement at optimal Strouhal numbers. Moreover, full-field velocity measurements and spatio-temporal correlation analysis revealed that acoustic excitation organized vorticity upstream of the separation point through viscous wall-modes, which played a dominant role in shear layer reorganization.
Additionally, high speed experiments explored the influence of acoustic excitation on high-lift turbine blades (L3FHW and L4FHW) using both active siren disk and passive perforated tailboard Helmholtz resonator. Schlieren imaging and static pressure measurements showed that siren disk excitation increased peak suction pressure by up to 60% and reduced the separated shear layer angle by 10°, while tailboard excitation achieved an 11° reduction with modest pressure recovery improvements. Spectral analysis revealed enhanced vortical coherence at Kelvin-Helmholtz instability frequencies, scaling with the 3/2 power of the exit Mach number. Numerical simulations highlighted up to 40% variations in peak suction pressure due to secondary flow effects, emphasizing the role of end-wall vortices in flow control.
These findings highlight acoustic actuation as a robust, efficient flow control technique for turbomachinery in off-design conditions, while underscoring the need for optimized integration strategies to mitigate secondary flow effects.
Light refreshments will be served before the lecture
