Turbulent Intensity Effect on Low Reynolds Number Airfoil Wake

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