This paper conducts a numerical and experimental investigation of a coflow jet airfoilto quantify lift enhancement, drag reduction, and energy expenditure at a Mach number range from 0.03 to 0.4. The jet momentum coefficient is held constant at 0.08, and the angle of attack varies from 0 to 30 deg. The two-dimensional flow is simulated using a Reynolds-averaged Navier-Stokes solver with a fifth-order-weighted essentially non-oscillatory scheme for the inviscid flux and a fourth-order central differencing for the viscous terms. Turbulence is simulated with the one equation Spalart-Allmaras model. The predicted coflow jet pumping power has an excellent agreement with the experiment. At a constant Mach number, the power coefficient is decreased when the angleof attack isincreased from 0 to 15 deg. When the Mach number is increased from 0.03 to 0.3, the suction effect behind the airfoil leading edge is further augmented due tothe compressibility effect. This resultsin anincreased maximum lift coefficient and reduced power coefficient at the higher Mach number because of the lower jet-injection pumping pressure required. At Mach 0.4, the lift coefficient is further improved. However as the angle of attack is increased, a λ shock wave interrupts the jet and triggers the boundary layer separation with increased drag and power coefficient. A corrected aerodynamic efficiency that includes the coflow-jet pumping powerisintroduced. Becauseofthe high lift coefficient and low coflowjet power required, the coflow-jet airfoil in this study achieves a comparable peak aerodynamic efficiency to the baseline airfoil, but the lift coefficient at peak efficiency is substantially increased by 120%. This study indicates that the coflow-jet airfoil is not only able to achieve very high maximum lift coefficient, but also able to improve cruise performance at low angle of attack when the flow is benign.
ASJC Scopus subject areas
- Aerospace Engineering