Single-degree-of-freedom fluid–structure interaction model of dual synthetic jets actuator

The flow pattern of dual synthetic jets and their evolution characteristics in crossflow are closely related to the operating frequency. Current numerical simulation methods decouple the amplitude of velocity inlet or dynamic mesh boundary conditions from operating frequency, limiting the research on the influence of the operating frequency. In this study, the vibration of the diaphragm is simplified as a single-degree-of-freedom piston movement and coupled with the compressible unsteady Reynolds-averaged Navier-Stokes equations for solution. The Single-degree-of-freedom Fluid-Structure Interaction (SFSI) model of Dual Synthetic Jets Actuator (DSJA) is developed. A laser displacement sensor and a hot-wire probe were employed to verify the frequency responses of the diaphragm velocity and jet velocity. The average calculation error of the SFSI model in the resonance region is only 6.4%, which is highly consistent with the experimental results. The frequency response measured by the SFSI model and experiment demonstrates that the influence of geometric parameters is highly related to the operating frequency. This mechanism can be attributed to the combined effect of resonance frequencies and phase delay. Variations in operating frequency can alter the phase relationships, which in turn modify the flow state inside the cavity. The flow inside the cavity is close to being incompressible at low operating frequencies (500–750 Hz), and the diaphragm vibration directly drives the jet. At high operating frequencies (1 200–1 400 Hz), the diaphragm vibration initially compresses the air inside the cavity, followed by the jet driven by the pressure gradient. This pressure behavior difference induced by the phase delay mechanism offers a critical foundation for designing and optimizing the actuator cavity. The SFSI model can accurately calculate the frequency response of DSJA, exhibiting significant potential in the optimization design and investigation of working characteristics.