低レイノルズ数領域において乱れ強さがNACA0012翼空力特性の非線形性に及ぼす影響

抄録

Wind tunnel experiments using several turbulence grids are conducted to investigate the effect of turbulence intensity on the nonlinearity of the aerodynamic characteristics of a NACA0012 wing at a low Reynolds number. A semi-span model with an aspect ratio of 3 is used. Lift and pitching moment curve slopes are evaluated to discuss the nonlinearity of the aerodynamic coefficients. The angles of attack at the local maximum and minimum of the pitching moment correspond to the ones at which the lift curve slope changes. Therefore, the stall angle can be defined by the local pitching moment maximum, even in the case that the change in the lift coefficient at the stall is obscure. For turbulence intensity of 1.9% and above, the change in the lift curve slope at around 0 deg is not observed, and a local maximum of the pitching moment coefficient at low angles of attack disappears. As the turbulence intensity increases, the constant-lift-curve-slope region enlarges. Hence the nonlinearity of the aerodynamic coefficient decreases in a more-turbulence environment. However, the nonlinearity of the aerodynamic coefficient does not disappear for turbulence intensity below 3.7%. The turbulence intensity significantly affects the aerodynamic coefficient and its nonlinearity at 1.0% or fewer turbulence intensity.