Enhanced Modelling of 3D Synthetic Jet Actuators In Crossflow

This paper examines three different approaches used in the literature for simulating a 3D synthetic jet actuator (SJA). Using a dynamic mesh, the first method models the whole SJA, including the vibrating diaphragm. The second models only the neck of the SJA and applies the Womersley solution to the bottom of the neck. The third method eliminates the SJA and applies the Womersley solution directly to the jet slot exit. All three methods were modelled in a crossflow with Reynolds number based on the boundary layer thickness of Re_δ=7,000 using unsteady Reynolds-Averaged Navier-Stokes. The results show that the flow characteristics are similar for the first two methods, but the third produces unrealistic backflow and high vorticity during ingestion. The computational cost of the second approach was 70% lower than the dynamic mesh approach. A parametric study was conducted to further investigate the source of deviation by the third method. The volume ratio between the ingested flow and the neck volume was found to be an important parameter for simulating the SJA using the Womersley solution. This dimensionless parameter must be less than unity for accurate simulations of the SJA.