Experimental Evaluation of Stereoscopic Wavelet-based Optical Flow Velocimetry (swOFV)
Wayne E. Page, Jeffrey A. Sutton · AIAA SCITECH 2022 Forum · 2022
View Video Presentation: https://doi.org/10.2514/6.2022-1944.vid An implementation of stereoscopic wavelet-based optical flow velocimetry (swOFV) using a general mapping approach for stereoscopic reconstruction is presented that is suitable for experiments. The methodology is evaluated quantitatively using synthetic tracer particle images generated from a direct numerical simulation (DNS) of homogeneous isotropic turbulence (HIT) and experimental data from a laminar axisymmetric vortex ring. Statistical comparisons between velocity components and gradient quantities are made between swOFV and stereoscopic PIV (sPIV) results. Overall, swOFV shows higher accuracy (approximately 35\% less error near the optimal off-axis angle) and increased spatial resolution as evident through field quantity visualization. The increases in spatial resolution also are observed in the energy and dissipation spectra, as swOFV is capable of resolving the finest dissipative scales. Experimental particle images from a laminar axisymmetric vortex ring were were evaluated and showed a strong topological agreement between swOFV and sPIV as expected for laminar flows. However, the swOFV results exhibited much less noise in the velocity field estimates, which was especially evident in the reconstruction of the out-of-plane velocity ($w$ )component and the out-of-plane vorticity, $\omega_z$. Overall, the updated and generalized implementation of swOFV, which can be implemented experimentally, has been shown to provide higher accuracy and spatial resolution capabilities when compared to sPIV.