Trade study of 3D co-flow jet wing for cruise and takeoff/landing performance

This paper presents a trade study of co-flow jet (CFJ) flow control wings. Several geometry parameters are studied, including injection and suction locations, cavity configurations, airfoil thickness and wing aspect ratio. The simulations are performed at Mach number 0.10 and 0.15 to simulate the takeoff/landing, and cruise condition of a general aviation aircraft. Unlike the conventional flaps and slats systems or other active flow control techniques, CFJ wings contains no moving part and can be used for both cruise and takeoff/landing. A low C_μ with low energy expenditure can be used at cruise and high C_μ with very high lift can be used for takeoff/landing. At cruise, the CFJ wing with a 21% thickness achieves a maximum aerodynamic L/D of 38.8 at a remarkably high CL of 1.22. When the CFJ pumping power P is taken into account, the corrected aerodynamic efficiency defined as L/(D + P/V_∞) is 25.2 at AoA = 5◦ and C_μ of 0.04. The takeoff/landing performance is also excellent with a maximum CL of 4.7 achieved at C_μ of 0.28 and AoA of 40.0◦. For both cruise and takeoff/landing, the CFJ wing moment is low and hence small tail force is needed for trimming purpose. CFJ is particularly advantageous to be used with thick airfoil such as 21% to achieve high cruise lift coefficient and high aerodynamic efficiency. For the 21% thickness airfoil, the CFJ wing has a drop of peak aerodynamic efficiency of 5.5%, but has the lift coefficient increase by 110%. A thick airfoil also provides higher structure strength, lighter weight, and more inner volume. This study demonstrates that the CFJ airfoil is not only very effective to drastically increase the maximum lift, but also able to achieve high aerodynamic efficiency with very high lift at cruise condition at a small angle of attack due to its low energy expenditure. Overall the CFJ wing is particularly suitable for a light and compact wing with ultra-high wing loading and high efficiency. The extraordinary CFJ wing performance may bring a radically different design philosophy to revolutionize the future aircraft design. The CFJ wing will open a door to a new class of aircraft design.