Comparative Characterization of Synthetic Jets Produced by Dynamic Deformable Surfaces

Synthetic jets (SJs), typically generated by periodic oscillations within a surface cavity, are widely used for active flow control. Recently, a new class of SJs driven by a dynamically deformable surface (DDS-SJs) has emerged, offering enhanced flow manipulation capabilities. This study investigates the physics and performance of two DDS actuators: one based on a free-slip air–water interface and the other on a no-slip thin elastic membrane, using pressurized air and water, respectively, as working fluids. Both DDS actuators follow Bessel-type oscillations. A theoretical analysis demonstrates that the two DDS actuators have distinct power input requirements with different resonant frequency ranges. Time-resolved particle image velocimetry and flow visualization reveal distinct flow dynamics between the two configurations. Phase-averaged vorticity fields and spectral proper orthogonal decomposition (SPOD) reveal the formation of stable, coherent vortical structures composed of interconnected, coaxial ring-shaped vortices originating from the deformable surface, with dominant spectral energy concentrated at the forcing frequency. The interface-based DDS-SJ has a stronger spatiotemporal coherence. These findings advance the fundamental understanding of DDS-SJs and highlight their potential for advanced flow control applications.