Three-dimensional phase averaging of time-resolved PIV measurement data

A three-dimensional phase-averaging technique is proposed and applied to th e investigation of large-scale coherent structures in the cylinder wake. Th e flow fields are measured with a time-resolved PIV system with high sampli ng rate and large internal memory block. As a vector processing algorithm, a cross-correlation method is used in conjunction with the FFT (fast Fourie r transform) analysis and a window shifting technique. Phase-locked three-d imensional vortical structures are reconstructed from the phase-averaged da ta obtained in several two-dimensional planes. In the process of phase aver aging, the reference phases are compensated with some phase-lags and a 'vor tex offset technique' is proposed, which freezes the secondary vortices wit h respect to the centreline of respective planes.