Convergence enhancement of single-pixel PIV with symmetric double correlation
- 311 Downloads
A symmetric correlation approach is proposed to improve the convergence of the single-pixel technique for particle image velocimetry (PIV). Nogueira et al. (Exp Fluids 30:309–316, 2001) introduced this method to remove a source of random errors in PIV when small interrogation windows are used; it consists in applying the cross-correlation operator by considering fixed the first exposure and moving the second one, and vice versa, and then calculating the cross-correlation map as the average of the two maps. The symmetric correlation suppresses the effects of truncation of the particles lying on the border of the interrogation windows. In this paper, the application of symmetric correlation to single-pixel PIV algorithms is reported. Since symmetric direct correlation provides a significant improvement in the cross-correlation peak shape with respect to the standard asymmetric single-pixel implementation, a faster convergence in estimating the average velocity components and turbulence statistics is achieved. An additional improvement is due to the possibly limited correlation between the background noise for the two exposures. The algorithm is tested via synthetic images with imposed constant and sinusoidal displacement and then tested with real data of a jet flow. The technique has shown that the same accuracy of the standard asymmetric approach can be achieved with 50 % of the samples and that a reduction in the measurement error by 30 % is obtained when using the same number of samples.
Gioacchino Cafiero is acknowledged for providing the experimental dataset used in this paper.
- Adrian RJ, Westerweel J (2011) Particle Image Velocimetry. Cambridge University Press, CambridgeGoogle Scholar
- Billy F, David L, Pineau G (2006) Single pixel resolution correlation applied to unsteady flow measurements. Meas Sci Tech 115:1039–1045Google Scholar
- Scharnowski S, Kähler CJ (2013) Methods for estimating higher order moments from PIV data. 10th International symposium on particle image velocimetry. PIV’13 Delft, The Netherlands, July 1–3Google Scholar
- Scholz U, Kähler CJ (2006) Dynamics of flow structures on heaving and pitching airfoils. 13th international symposium on applications of laser techniques to fluid mechanics, Lisbon, Portugal, June 26–29 2006Google Scholar