Flow Visualized Observation of a Symmetrical Airfoil with Attack Angle in Fluctuating Relative Flow Velocity

摘要

In this study, a visualization experiment was performed in order to confirm the flow pattern around airfoil with relative velocity fluctuation by in-line forced oscillating in the direction of flow. An airfoil NACA0012 with attack angle of 5 degrees produce the separation in the steady state was observed by the experiments using dye streak method at Reynolds number Re=3.6×10~3. The investigation of the attack angle which does not separate in such low Reynolds number was performed, and it was confirmed that the separation occurs to 3 degrees. And the airfoil with attack angle of 2 degrees which does not cause separation in steady state, was forced to oscillate with two kinds of relative velocity ratio (u_(max)/U=0.4 and 0.8, here, u_(max) and U denote maximum moving speed of airfoil and main flow velocity, respectively). The flow separation on the surface of airfoil with attack angle which does not produce the separation in the steady state is occurred even if the maximum moving speed of airfoil u_(max) is in the range which does not exceed main flow velocity U.