Abstract
A dual-plane snapshot proper orthogonal decomposition (POD) analysis of turbulent pipe flow at a Reynolds number of 104 000 is presented. The high-speed particle image velocimetry data were simultaneously acquired in two planes, a cross-stream plane (2D-3C) and a streamwise plane (2D-2C) on the pipe centreline. The cross-stream plane analysis revealed large structures with a spatio-temporal extent of , where is the pipe radius. The temporal evolution of these large-scale structures is examined using the time-shifted correlation of the cross-stream snapshot POD coefficients, identifying the low-energy intermediate modes responsible for the transition between the large-scale modes. By conditionally averaging based on the occurrence/intensity of a given cross-stream snapshot POD mode, a complex structure consisting of wall-attached and -detached large-scale structures is shown to be associated with the most energetic modes. There is a pseudo-alignment of these large structures, which together create structures with a spatio-temporal extent of approximately , which appears to explain the formation of the very-large-scale motions previously observed in pipe flow.
Original language | English (US) |
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Pages (from-to) | 701-715 |
Number of pages | 15 |
Journal | Journal of Fluid Mechanics |
Volume | 779 |
DOIs | |
State | Published - Aug 19 2015 |
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
- Applied Mathematics
Keywords
- turbulent boundary layers
- turbulent flows