Detailed 2D velocity and vorticity fields were measured to investigate the turbulent near wake flow of NACA0012 airfoil with on-line cross-correlation PIV in a low-speed wind tunnel.The Reynolds number on chord length is 2.39×105

the angles of attack are 0° and 4°.The experimental results indicate that ordered vortex streets exist in the turbulent near wake

the vortex streets created at the airfoil trailing edge region will fully develop and finally break up downstream

and the ordered wake flow turns into disordered.The near wake flow is dominated by the kinetic characteristics and dynamic mechanism of vortices.As the second part of the investigation

the paper mainly discusses the formation of the vortex streets

the dynamic mechanism of the near wake

and the fluid instability of the vortex and vortex streets.