Effect Of Synthetic Jet Actuation Research Articles

Numerical study of flow separation control over a circular hump using synthetic jet actuators

This study deals with the wall resolved Unsteady Reynolds-Averaged Navier–Stokes (URANS) simulation of boundary layer flow separation over a circular hump model and its active control. An array of Synthetic Jet Actuators (SJAs) is implemented in the hump model to introduce a train of vortex rings into the boundary layer to control flow separation. The OpenFOAM solver is used to numerically simulate and analyze the fluid flow using the k–ω shear stress transport model. Hot wire anemometry and particle image velocimetry measurements are carried out to evaluate the accuracy of the URANS technique as well as the effectiveness of SJAs by comparing numerical predictions to experimental data. The time-averaged results are in a good agreement with experimental results and demonstrate a successful application of SJAs to delay the flow separation by the interactions of vortical structures with the separated shear flow. The three-dimensional simulation also reveals that near wall coherent flow structures (streamwise and spanwise vortices) are responsible for the wall shear stress components. The results can be used to better understand the performance of SJAs and to further improve future actuator configurations.

On the effect of active flow control on the meandering of a wing-tip vortex

The development of a wing-tip vortex of a rectangular, square-tipped wing having a NACA 0012 airfoil at a chord Reynolds number , under the effect of synthetic jet actuation, was experimentally studied. Five control configurations were considered: case C1 with momentum coefficient and actuation frequency ; case C2 with and ; case C3 with and ; case C4 with and ; and case C5 with and . Under the most effective configuration, case C3, the vortex was stretched and appeared to be diffuse with a nearly 40 % decrease in the peak circumferential velocity and 50 % decrease in the core axial vorticity. The vortex core radius largely broadened suggesting that the lower-frequency control configuration allowed the synthetic jet to travel larger distances into the vortex bringing turbulent structures within its core resulting in increased mixing and subsequently a more diffuse vortex.

Near wake development of a wing tip vortex under the effect of synthetic jet actuation

An experimental investigation on the effectiveness of synthetic jet actuation in controlling a wingtip vortex of a rectangular, square-tipped NACA 0012 wing at a chord Reynolds number Rec=8×104 is reported. Spanwise pressure measurements on the suction surface of the wing showed that forcing the wingtip vortex at a frequency in the range of frequencies of the long and short-wave instabilities resulted in decreased pressure coefficients as compared to natural vortex measurements. Two control configurations were then considered for hotwire wake measurements, namely, a “least effective” configuration with momentum coefficient Cμ=0.004 and actuation frequency F+=0.71, and a “most effective” configuration with Cμ=0.04 and F+=0.213. Measurements at x/c=1 showed that, under the latter case, the vortex was stretched into an ellipsoid shape with a 50% average decrease in the peak tangential velocity, and 30% broadening of the effective vortex core radius. Further downstream, the vortex seemed to regain its universal shape but with reduced strength. The results suggested that the lower frequency control configuration allowed the synthetic jet to travel larger distances into the vortex bringing turbulent structures within its core resulting in increased mixing and subsequently decreased vortex strength.

Modeling Synthetic Jets for Low-Re Airfoil Unsteady Flow Control

Synthetic jet actuators (SJAs) may be carefully designed to alleviate the negative impact of impinging flow non-uniformities on the aircraft wing unsteady aerodynamic response. The current study investigates the effectiveness of SJAs for active control of unsteady flow over SD7003 low-Re airfoil in presence of a high-amplitude upstream flow disturbance characterized by a sharp-edge gust. In the adopted numerical procedure, the actuator's dimensional scaling and excitation frequency effects are first examined for a specific SJA configuration using a Lumped Element Model. The next step employs a Reynolds-averaged Navier-Stokes analysis to determine simple fluctuating-velocity boundary condition at the bottom of the actuator's orifice. The orifice with the properly defined boundary condition is then embedded into the airfoil surface for conducting high-accuracy viscous analysis of active flow control during gust-airfoil interaction process. Results of numerical simulations indicate that the SJA positive effe...