Fluid-dynamics-based analytical model for synthetic jet actuation

An analytical model for synthetic jet actuation based on the laws of fluid dynamics is presented. A synthetic jet actuator consists of a cavity with a driven wall and an orifice. Under actuation, the wall is oscillated, resulting in an oscillatory flow through the orifice. In the model, the driven wall is modeled as a single-degree-of-freedom mechanical system, which is pneumatically coupled to the cavity-orifice arrangement acting as a Helmholtz resonator. The latter was modeled using the unsteady form of the continuity and Bernoulli equations with a loss term. The model was validated against experimental data available in the published literature, and very good agreement is obtained between the predicted and measured frequency responses as well as for the phase relationships between velocities and pressures. The model and analysis based on it provide valuable insights into the behavior of synthetic jet actuators and reveal that air in the actuator cavity exhibits compressibility at all frequencies beyond the Helmholtz resonance frequency.