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M. E. Siddiqui, V. Mukund, J. Scott and B. Pier
Laboratoire de mécanique des fluides et d'acoustique, École centrale de Lyon – CNRS – Université Claude-Bernard Lyon 1 – INSA, 36 avenue Guy-de-Collongue, 69134 Écully cedex, France
Physics of Fluids 25, 034102 (10 pages) (2013)
The three-dimensional boundary layer due to a disk rotating in otherwise
still fluid is well known for its sudden transition from a laminar
to a turbulent regime,
the location of which closely coincides with
the onset of local absolute instability.
The present experimental investigation focuses on the region around transition
and analyses in detail the features that lead from the unperturbed
boundary layer to a fully turbulent flow.
Mean velocity profiles and high-resolution spectra are obtained by
constant-temperature hot-wire anemometry.
By carefully analysing these measurements,
regions in the flow are identified that
correspond to linear, weakly nonlinear or turbulent dynamics.
The frequency that dominates the flow prior to transition is explained
in terms of spatial growth rates, derived from the exact linear dispersion
relation.
In the weakly nonlinear region, up to six clearly identifiable harmonic
peaks are found.
High-resolution spectra reveal the existence of discrete frequency
components that are deemed to correspond to fluctuations stationary
with respect to the disk surface.
These discrete components are only found in the weakly nonlinear region.
hal-00806379
2013a_siddiqui_pof.pdf