Jet Effects on Coflow Jet Airfoil Performance

Abstract

A control volume analysis is presented in this paper to analyze the jet effect on the coflow jet airfoil with injection and suction and on the airfoil with injection only. The formulations to calculate the duct's reactionary forces that must be included for the lift and drag calculation are given. The computational fluid dynamics solutions based on the Reynolds-averaged Navier-Stokes model are used to provide the breakdowns of lift and drag contributions from the airfoil surface force integral and jet duct's reactionary forces. The results are compared with experiment for validation. The duct reactionary forces are also validated with the result of a 3-D computational fluid dynamics calculation of the complete airfoil with jet ducts and wind tunnel walls. The study indicates that the suction occurring on the airfoil suction surface of the coflow jet airfoil is more beneficial than the suction occurring through the engine inlet such as the airfoil with injection only. For the airfoil with injection only, the drag actually acted on the aircraft, or the equivalent drag, is significantly larger than the drag measured by the wind tunnel balance due to the ram drag and captured area drag when the jet is drawn from the freestream. For a coflow jet airfoil, the drag measured by the wind tunnel balance is the actual 2-D drag that the aircraft will experience. A coflow jet airfoil does not have the ram drag and captured area drag. For a coflow jet airfoil, the suction penalty is offset by the significant circulation enhancement. The coflow jet airfoil with both injection and suction yields stronger mixing, larger circulation, more filled wake, higher stall angle of attack, less drag, and lower energy expenditure.

Numerical study of the S809 airfoil aerodynamic performance using a co-flow jet active control concept

“…17, for a case with a co-flow jet on, the total aerodynamic force is computed by summating the pressure forces and shear stresses on the airfoil surface parts of AQB and CD, and pressure forces on slot faces AC, BD, and the jet reaction forces on the slot faces AC, BD. Hence, the total aerodynamic force coefficient consists of three components: pressure force coefficient, shear stress coefficient, and jet mass flow thrust coefficient, denoted by C L,pressure , C L,stress , C L,jet , C D,pressure , C D,stress , C D,jet , respectively.…”

“…Zha et al [14][15][16][17][18][19][20] have developed a novel flow control technique by implementing a Co-Flow Jet (CFJ) on the suction surface, which has an attractive ability to significantly increase lift, stall margin, and drag reduction. In the present study, this concept is implemented on the NREL S809 airfoil, and the effect of the co-flow jet on enhancing wind turbine performance will be numerically investigated in detail.…”

Blowing momentum and duty cycle effect on aerodynamic performance of flap by pulsed blowing

“…In the past decades, scientists have exerted considerable effort to develop flow control techniques. Moreover, various flow control techniques [1] has been used to suppress flow separation such as moving surface control technique [2][3][4] , plasma flow control technique [5][6][7][8] and co-flow jet control technique [9][10][11][12] . Although flow separation on the control surface can be suppressed substantially by these flow control technique, the application of these techniques in engineering are limited because of complicated devices or other reasons.…”

Dynamic Stall Control on the Wind Turbine Airfoil via a Co-Flow Jet

“…Zha et al [14][15][16][17][18][19][20] have developed a new flow control method by implementing a co-flow jet (CFJ) on the suction surface, which has been proved an effective way to significantly increase lift, stall margin and drag reduction for stationary airfoils and enhance the performance of pitching airfoils in the aircraft research field. The working mechanism of a CFJ is different from the conventional circulation control which relies on large-radius leading edge or trailing edge to induce the Coanda effect and enhance circulation.…”