INTERPRETATION OF PIV AUTOCORRELATION MEASUREMENTS IN COMPLEX PARTICLE-LADEN FLOWS

Particle image velocimetry (PIV) was used to measure instantaneous and average particle velocity fields near the stagnation zone of a partic le-laden impinging air jet. The results were compared with Lagrangian particle tracking measurements. Ensemble averages from the two methods agree well except in regions where particles have different histories , and a specific trajectory is dominant but not exclusive. The PIV aut ocorrelation method loses information regarding nondominant particle t rajectories. Thus, although instantaneous PIV measurements yield the d ominant particle velocities correctly, the averaged measurements are b iased in some regions.