Extensional study of optical-flow enhanced hybrid PIV method for dual-plane stereoscopic PIV measurement

Abstract

The high-speed dual-plane stereoscopic particle image velocimetry (DP-s-PIV) can capture time-resolved three-component (3C) velocity and vorticity vectors in the measurement region, but its spatial resolvability of tiny vortices is blocked by the intrinsic limitation of the cross-correlation evaluation. To overcome this limitation, we propose a scheme to extend the original two-component (2C) optical flow enhanced hybrid PIV method to DP-s-PIV through three-dimensional (3D) reconstruction, with its feasibility and resolvability validated through the result comparisons with the cross-correlation evaluation used in DaVis 8.4. Comparisons suggest that the optical flow enhanced hybrid PIV scheme can greatly improve the spatial resolvability of the velocity field for DP-s-PIV. Moreover, the hybrid scheme can also provide better visualization of vortical structures and enhanced precision in evaluating the vorticity distribution, allowing for a further identification of vortex types in a stratified swirling jet flow through the combined criteria (vorticity component and Q criterion).