EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF DYNAMIC STALL ON A PITCHING AIRFOIL

The dynamic stall process on a pitching NACA 0012 airfoil was investig ated by two experimental techniques-particle image velocimetry (PIV) a nd laser-sheet visualizations-and a numerical code based on the Navier -Stokes equations. The freestream velocity was 28 m/s, leading to a Re ynolds number (based on airfoil chord) of 3.73 x 10(5). The airfoil mo tion was a sinusoidal function between 5 and 25 deg of incidence, with a frequency of 6.67 Hz corresponding to a reduced frequency (based on airfoil half-chord) of 0.15, The out-of-plane component of the vortic ity could be derived from the PIV velocity fields, The comparison betw een experimental and numerical results was conducted for the four main phases of the dynamic stall process, i.e., attached dow, development of the dynamic stall vortex, poststall vortex shedding, and reattachme nt. In general, the computational results agreed very well with the ex perimental results. However, some discrepancies were observed and disc ussed. The cycle-to-cycle nonreproducibility of the flowfield during t he phase of massive separation is also mentioned.