Numerical Experiment of a Symmetrical Airfoil with Attack Angle of 5 Degrees in Fluctuating Relative Flow Velocity

Abstract

In this study, a numerical experiment was performed as what obtains relative velocity fluctuation by oscillating an object with comparatively large amplitude in the direction of flow. Follow pattern and instantaneous fluid force around an In-line forced oscillating symmetrical airfoil (NACA0012) with attack angle of 5 degrees caused not separation in stationary situation were investigated using a vortex method at the Reynolds numberRe=4.05×105, in ranges of the oscillation amplitude ratio 2a/c=0.5,1.0,1.5 and 2.0 and the oscillation frequency ratiof/fK=0.25,0.5,1.0 and 2.0 (here,a:half-amplitude of oscillation,c:chord-length,f:oscillation frequency,fK:natural Karman vortex shedding frequency from a stationary airfoil with the attack angle of 90 degrees). As a result of calculations, Separation was observed by oscillating condition even if it was the airfoil of attack angle not separating. It is found that the separation was dependent on the velocity ratio. The characteristics of fluid force are changed by oscillation.