Turbulent intensity effect on low reynolds number airfoil wake

Abstract

The work investigates the effect of turbulent intensity (Tu) on the force and wake of a NACA0012 airfoil at chord Reynolds number Rec = 5.3 × 103 and 2 × 104. Lift and drag coefficients (CL and CD) on and flow fields around the airfoil were measured with Tu varied from 0.6 to 6.0%. Four Rec regimes are identified based on the characteristics of the maximum lift coefficient (CL,max), i.e., ultra-low (Rec<104), low (104 ~ 3 × 105), moderate (3 × 105 ~ 5 × 106), and high (>5 × 106). It is noted that at Rec = 5.3 × 103 (ultra-low Rec regime) the stall is absent for Tu = 0.6% but occurs for Tu = 2.6 and 6.0%. As Rec increases to low Rec regimes, the Tu influence decreases. So does the critical Rec, above which stall occurs. The effect of increasing Tu on flow bears similarity to that of increasing Rec, albeit with a difference; the flowseparation point shifts upstreamwith increasing Rec but downstream with increasing Tu.