DOI: 10.1615/TSFP6
Turbulent Channels, Pipes and Boundary Layers: Similarities and Differences in Large Scale Motions
ABSTRAKT
This paper details a preliminary comparison between the energy spectra of streamwise velocity fluctuations in zero-pressure-gradient flat-plate turbulent boundary layers (TBL) and turbulent pipe and channel flows. The unique facilities available at the University of Melbourne enable us to investigate these three flows at matched friction Reynolds numbers Reτ and matched viscous-scaled hot-wire lengths l+. Detailed maps of energy spectra (calculated from time-series data) reveal important differences between these two flows, particularly in the very large-scale structures that exist in the log and inner wake regions. It is also noted that differences in the large-scale energy between the three geometries extend all the way to the wall. Hence, the commonly held view that the near-wall region is the same across internal and external flows is not strictly true. In general we would recommend caution when comparing statistics between external and internal turbulent flows, especially with increasing Reynolds number.