Characterization of very-large-scale motions in high-Re pipe flows

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Very-large-scale structures in pipe flows are characterized using an extended Proper Orthogonal Decomposition (POD)-based estimation. Synchronized non-time-resolved Particle Image Velocimetry (PIV) and time-resolved, multi-point hot-wire measurements are integrated for the estimation of turbulent structures in a pipe flow at friction Reynolds numbers of 9500 and 20000. This technique enhances the temporal resolution of PIV, thus providing a time-resolved description of the dynamics of the large-scale motions. The experiments are carried out in the CICLoPE facility. A novel criterion for the statistical characterization of the large-scale motions is introduced, based on the time-resolved dynamically-estimated POD time coefficients. It is shown that high-momentum events are less persistent than low-momentum events, and tend to occur closer to the wall. These differences are further enhanced with increasing Reynolds number.
Pipe flow, Boundary layer, POD, Very-large-scale motions
Bibliographic citation
Discetti, S., Bellani, G., Örlü, R., Serpieri, J., Sanmiguel Vila, C., Raiola, M., Zheng, X., Mascotelli, L., Talamelli, A. & Ianiro, A. (2019). Characterization of very-large-scale motions in high-Re pipe flows. Experimental Thermal and Fluid Science, vol. 104, pp. 1–8.