Abstract
This paper studies the lift enhancement effect of Co-Flow Jet (CFJ) at takeoff condition for three thin airfoils at free-stream Mach numbers of 0.1, 0.2 and 0.3. Parametric studies are conducted to investigate the effect of the jet momentum coefficients (C-mu), angles of attack (AoA), flap deflection angles(delta), camber, maximum thickness, and influence of freestream Mach number to three 2-D CFJ supersonic airfoils. The simulations employ a 2-D RANS solver with Spalart-Allmaras (S-A) turbulence model, 5th order WENO scheme for the inviscid fluxes and 2nd order central differencing scheme for the viscous terms.
Numerical simulation shows that, for both unflapped and flapped 2-D CFJ supersonic airfoils, camber plays much more important role than thickness in lift enhancing. With the same maximum thickness of 4%, a cambered unflapped CFJ airfoil can increase C-L by 89% compared to a symmetric one, while with the same maximum thickness increases for 33.3% almost no lift increment is observed on a 3% symmetric unflapped CFJ airfoil. When there is a 20%c plain flap deflected for 45., a 4% cambered CFJ airfoil can still increase C-L by around 40% compared to a symmetric one with same maximum thickness. Meanwhile, the injection flow near the leading edge can limit the extra separation around the region caused by a pointed geometric shape, which provides great potential to combine CFJ application to an optimized modern supersonic wing profile. The study also shows that, with the maximum thickness of 4%, the turning design of current CFJ ducts are all effective in the Mach number range of 0.1-0.3 at a low C-mu of 0.08, which adds confidence of its realistic availability during actual takeoff and landing.