Micro-scale synthetic-jet actuator flow simulation with characteristic-based-split method

Purpose - The purpose of this paper is to present a computational study to investigate the effects of rectangular cavity design of a piezoelectrically driven micro-synthetic-jet actuator on generated flow. Design/methodology/approach - Flow simulations were done using a compressible Navier-Stokes solver, which is based on finite element method implementation of a characteristic-based-split (CBS) algorithm. The algorithm uses arbitrary Lagrangian-Eulerian formulation, which allows to model oscillation of the synthetic jet's diaphragm in a realistic manner. Since all simulated flows are in the slip-flow-regime, a second order slip-velocity boundary condition was applied along the cavity and orifice walls. Flow simulations were done for micro-synthetic-jet configurations with various diaphragm deflections amplitudes, cavity heights, and widths. All of the simulation results were compared with each other and evaluated in terms of the exit jet velocities, slip-velocities on the orifice wall and instantaneous momentum fluxes at the jet exit. Findings - It is shown that compressibility and rarefaction have important effects on the flow field generated by the micro-synthetic-jet actuator. The effect of the geometrical parameters of the cavity to important flow features such slip and phase lag are presented. Originality/value - The paper reports results of a systematical study of the flow field inside a micro-scale synthetic-jet actuator, providing designers of such devices additional information for sizing the cavity within slip flow regime. Furthermore, it is demonstrated that the CBS, together with slip boundary conditions can be successfully used to compute such flows.