Active Flow Control of a Three-Element Airfoil in Unbounded Flow and in Ground Effect

Multi-element high lift devices are used in aircraft wings to have higher lift at low speed during take-off and landing. 30P30N is a three-element airfoil developed by NASA/McDonnell Douglas for which high quality flow field data is available. As a result, it has been a subject of many Computational Fluid Dynamics (CFD) simulations in the literature. In this research, CFD simulations are performed using commercial CFD solver ANSYS Fluent. Reynolds-Averaged Navier-Stokes (RANS) equations are solved in conjunction with the Spalart-Allmaras (SA) turbulence model. Mesh generation is accomplished by ICEM in ANSYS. First the CFD solution is validated against the experimental data. The validated code is then used to determine the relationship between the flap deflection angle and the lift coefficient for the 30P30N airfoil both in unbounded flow and in ground effect for various flight heights. The airfoil flow field is then subjected to Active Flow Control (AFC) by injecting a uniform jet or by including a synthetic jet near the leading edge of the flap to change the momentum in the boundary layer on the flap. The goal is to enhance lift by reducing separation on the flap at higher flap angles. The results show that in unbounded flow, the flow on the flap separates when the flap deflection angle is greater xii than 45 degrees, and in ground effect the flow separates when the flap deflection angle is greater than 40 degrees. After AFC is employed, the lift coefficient is enhanced sharply using both flow control methods compared to the lift coefficient without flow control in unbounded flow as well as in ground effect. The stall flap deflection angle increases to 50 degrees for both the uniform blowing control and the synthetic jet control. In unbounded flow, the lift coefficient is enhanced sharply by synthetic jet flow control and the stall flap deflection angle increases to 50 degrees; however for the uniform blowing control, the effect on lift enhancement is relatively smaller