Aerodynamic Load Control for Multi-Element Airfoils Using Surface-Normal Trailing-Edge Blowing

The feasibility of using surface-normal jets near the flap trailing edge as active aerodynamic load control on the two-element airfoil NLR-7301 at a high-lift condition was explored. Using structured curvilinear overset grids and the Reynolds-averaged Navier-Stokes solver, OVERFLOW-2, the two-dimensional flowfield around the airfoil was characterized. The relationship between surface-normal jets with various momentum-coefficient settings, C-mu = 0.00-0.04, and lift enhancement is found to be Delta C-iota similar or equal to 3.61 root C-mu for this airfoil. It is discussed in this paper that using a surface-normal jet with C-mu = 0.01 can shift the linear region of the lift curve by Delta C-iota = 0.37 and Delta C-l = -0.27 for the pressure- and suction-side jets, respectively. Further, employing a drag decomposition study, it is shown that, for a given C-l = 2.50, a surface-normal jet with C-mu = 0.01 on the pressure and suction sides of the airfoil results in a 110 drag count decrement and a 43 drag count increment, respectively, compared to the baseline airfoil with no jet. These results show that large and controllable changes in aerodynamic performance can be achieved by relatively small active flow control inputs using the surface-normal jets presented in this study.