A PIV STUDY OF NEAR WAKE FLOW OF AIRFOIL PART Ⅰ-KINEMATIC CHARACTERISTICS

Detailed 2D velocity fields obtained from on-line PIV (Particle Image Velocimetry) measurements in a low speed wind tunnel are used to investigate flow structures in the turbulent near wake flow of a NACA0012 airfoil.The Reynolds number on chord length is 2.39×10⁵,the angles of attack are 0° and 4°.The experimental results indicate that the turbulent near wake flow is dominated by the dynamic and kinematic characteristics of vortices at relatively high Reynolds number.According to the flow structures identified from instantaneous velocity fields,the vortex street is created at the airfoil tail region.Structures in the vortex developing region (within 0.5 chord length) are similar to those for the Karman vortex street and structures in the vortex break-up and dissipation region (between 0.5 and 1.0 chord length) change from organized to non-organized.The results also show that the boundary layer of the airfoil affects the structures in the near wake flow.The fields of mean velocity,turbulence intensity,strain rate and correlation coefficients of EMBED Equation are also obtained.