Phase Averaged Velocity Fields for Bluff Bodies Using a PIV System

Two phase-averaging methods are presented for the investigation of periodic flows. First, an implementation of an angular triggering technique, the Predictive Angular Triggering Technique (PATT), uses the flow frequency and phase information to predict a future trigger point to record for PIV images. Second, the Tracking Triggering Technique (TTT) uses the detection of the PIV laser signal’s pulse occurrence, then tags each PIV image with the angular position at its measurement time, allowing grouping into angular slots or bins. These two methods have been applied first on a spinning plate where the physical location of the plate could be measured. Results proved that the phase averaging system worked effectively. Later a circular cylinder at Re 105000 is used to observe the wake vortex structure. Here, the phase information was derived from flow measurements, specifically a hot wire in the wake. Evolution of the classical vortex street for the cylinder was successfully observed.