Target-free Stereo PIV: a novel technique with inherent error estimation and improved accuracy
- 582 Downloads
A novel, accurate and simple stereo particle image velocimetry (SPIV) technique utilising three cameras is presented. The key feature of the new technique is that there is no need of a separate calibration phase. The calibration data are measured concurrently with the PIV data by a third paraxial camera. This has the benefit of improving ease of use and reducing the time taken to obtain data. This third camera also provides useful velocity information, considerably improving the accuracy of the resolved 3D vectors. The additional redundancy provided by this third perspective in the stereo reconstruction equations suggests a least-squares approach to their solution. The least-squares process further improves the utility of the technique by means of the reconstruction residual. Detailed error analysis shows that this residual is an accurate predictor of resolved vector errors. The new technique is rigorously validated using both pure translation and rotation test cases. However, while this kind of validation is standard, it is shown that such validation is substantially flawed. The case of the well-known confined vortex breakdown flow is offered as an alternative validation. This flow is readily evaluated using CFD methods, allowing a detailed comparison of the data and evaluation of PIV errors in their entirety for this technique.
KeywordsReconstruction Process Output Error Input Error Displacement Vector Field Stereo Particle Image Velocimetry
The authors wish to thank Professor Jens Sørensen for his advice, help and the use of his code. DL thanks the Swiss National Science Foundation for their support.
- Press WH, Flannery BP, Teukolsky SA, Vetterling WT (1992) Numerical recipes in C: the art of scientific computing, 2nd edn. Cambridge University Press, CambridgeGoogle Scholar
- Raffel M, Willert CE, Kompenhans J (1998) Particle image velocimetry: a practical guide. Springer, BerlinGoogle Scholar
- Vogel H (1968) Experimentelle ergebnisse über die laminare strömung in einem zylindrischen gehäuse mit darin rotierender scheibe. Bericht 6, Max–Planck-Institut für Strömungdforschung, GöttingenGoogle Scholar