Lift-to-Drag Ratio of a NACA0012 Airfoil in a Periodic Flow for Changing Angle of Attack

抄録

We measure the two-dimensional vorticity field, drag and lift forces around a NACA0012 airfoil in a periodic flow with a sinusoidal velocity profile in the mainstream direction. An angle of attack of the airfoil is changed in the range of 0 to 60 deg in increments of 5 deg. The two-dimensional velocity field is measured by particle image velocimetry (PIV). These measurements of the velocity field and hydrodynamic forces are conducted simultaneously. For comparison, a similar experiment is carried out in a steady flow that the averaged mainstream velocity is the same as that of a periodic flow condition for Reynolds number R_e=3.8 x 10³ and reduced frequency k=3.98. We have found that the maximum value of the lift-to-drag ratio in a periodic flow is rather larger than that in a steady flow.