Development and Evaluation of Stereoscopic Wavelet-based Optical Flow Velocimetry (swOFV)
Wayne E. Page, Jeffrey A. Sutton · AIAA Scitech 2021 Forum · 2021
View Video Presentation: https://doi.org/10.2514/6.2021-0122.vid A first-generation stereoscopic extension of wavelet-based optical flow velocimetry (swOFV) is introduced and an initial evaluation of performance is demonstrated using synthetic tracer particle images from a DNS of homogeneous isotropic turbulence. Specifically, comparisons are made to the DNS result (“truth”) and analysis using stereoscopic particle imaging velocimetry (sPIV) results. First, an initial analysis of the optimal off-axis lens angle is performed for swOFV, yielding a recommended angle near 30°for a two-camera setup in an angular-displacement stereoscopic configuration. The optimal angle is primarily dictated by the accuracy of the out-of-plane velocity component (w), as the in-plane components (u and v) are only slightly sensitive to the off-axis observation angle. Near the optimal angle, the accuracy of the individual velocity components, total velocity vector, and gradient quantities increased by approximately 70% when using swOFV compared to sPIV. swOFV also was able to resolve a larger fraction of the energy and dissipation spectra (by more than an order-of-magnitude) when compared to sPIV, although it was unable to resolve the spectra down to the smallest dissipative scales as is possible with planar (2D) wOFV. The apparent under resolution was observed across all obtainable components of the energy and dissipation spectra, which is attributed to an implicit low-pass filtering involved in the current simple linear interpolation scheme involved in the stereoscopic reconstruction. Overall, the initial implementation of swOFV is shown to significantly improve accuracy and spatial resolution when compared to sPIV