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TURBULENT PIPE FLOW THROUGH A 90° BEND

Leo H. O. Hellstrom
Department of Mechanical and Aerospace Engineering Princeton University Princeton, New Jersey 08544, USA

Metodi B. Zlatinov
Department of Mechanical and Aerospace Engineering Princeton University Princeton, New Jersey 08544, USA

Alexander J. Smits
Department of Mechanical & Aerospace Engineering, Princeton University Princeton, NJ 08544, USA

Guongjun Cao
CARDC, P. O. Box 211 Mianyang Sichuan 621000, P. R. China

Аннотация

Stereoscopic PIV is used to investigate the structure of fully developed turbulent pipe-flow through a 90° bend. The results show that Dean motions downstream of the bend are very weak in the mean, and time resolved stereoscopic PIV demonstrates that the Dean motions co-exist with large scale swirling motions that switch sign and do not contribute to the mean. Snapshot POD analysis of the flow field reveals that the structures found upstream of the bend persist after the bend and survive the strong secondary motions induced by the pipe curvature. In particular, the Very Large Scale Motions (VLSM) are no longer the most energetic mode in the flow, but they are still the most energetic structure in terms of the streamwise fluctuations.