Abstract
The effects using Co-Flow Jet (CFJ) active flow control method for 2-D and 3-D supersonic control surfaces with plain flaps, or rudders, are investigated. The goal is to increase the control efficiency of rudder on the vertical tails of supersonic civil transports (SST) at low speed and enable the possibilities to save energy expenditure. An approximate Concorde vertical tail profile is used as a baseline control surface for parametric trade study using a Reynolds-averaged Navier-Stokes (RANS) solver with Spalart-Allmaras (SA) model. A 3-rd WENO scheme for the inviscid flux is used to resolve the Navier-Stokes equations.
The 2-D and initial 3-D numerical studies indicate that, the CFJ equipped control surfaces can dramatically increase the lift coefficient and aerodynamic efficiency simultaneously compared with the original control surface with the same size of flap and deflection angle. However, due to the nature of low maximum thickness of airfoil and highly-swept planform, the 3-D effect is much stronger than the similar applications of wings with normal thickness.
In the 2-D simulation, at jet momentum coefficient of 0.08, the maximum lift coefficient is increased by 54.6% at side slip angle of 0.; when the jet momentum coefficient is increased to 0.16, the maximum lift coefficient increment is 76.5% compared with baseline. The 2-D CFJ airfoils show impressive efficiency at negative side slip angle conditions, where the maximum CL increment compared with baseline is 157.4% at side slip angle of -7. with C mu of 0.08. In the 2-D simulations, the Rudder-CFJ airfoil has extra lift enhancing effect, which is achieved by forming a stable separation region near the leading edge of the stabilizer, which increases the pressure difference over there. However, this lift enhancing mechanism no longer exists when it comes to the 3-D situation. The maximum lift coefficient increment with C mu=0.08 in 3-D simulation is 37.1%, while the smallest loss of corrected aerodynamic efficiency achieved is 7.0% with a gain of maximum lift increment of 32.3%. Similar as the results on conventional airfoils, supersonic aircraft vertical tails equipped with CFJ show impressive potential to improve the control authority at low speed.