A comparative study of near-wall turbulence in high and low Reynolds number boundary layers

Abstract

The present study explores the effects of Reynolds number, over three orders of magnitude, in the viscous wall region of a turbulent boundary layer. Complementary experiments were conducted both in the boundary layer wind tunnel at the University of Utah and in the atmospheric surface layer which flows over the salt flats of the Great Salt Lake Desert in western Utah. The Reynolds numbers, based on momentum deficit thickness, of the two flows were Rθ=2×103 and Rθ≈5×106, respectively. High-resolution velocity measurements were obtained from a five-element vertical rake of hot-wires spanning the buffer region. In both the low and high Rθ flows, the length of the hot-wires measured less than 6 viscous units. To facilitate reliable comparisons, both the laboratory and field experiments employed the same instrumentation and procedures. Data indicate that, even in the immediate vicinity of the surface, strong influences from low-frequency motions at high Rθ produce noticeable Reynolds number differences in the streamwise velocity and velocity gradient statistics. In particular, the peak value in the root mean square streamwise velocity profile, when normalized by viscous scales, was found to exhibit a logarithmic dependence on Reynolds number. The mean streamwise velocity profile, on the other hand, appears to be essentially independent of Reynolds number. Spectra and spatial correlation data suggest that low-frequency motions at high Reynolds number engender intensified local convection velocities which affect the structure of both the velocity and velocity gradient fields. Implications for turbulent production mechanisms and coherent motions in the buffer layer are discussed.

Inner-layer intensities for the flat-plate turbulent boundary layer combining a predictive wall-model with large-eddy simulations

“…It has also been highlighted that the dynamical influence of the large-scale events extends to the wall where they affect the small-scale, near-wall fluctuations, in a significant way. Metzger and Klewicki 8 showed that long wavelength motions, which scale on outer variables, have a significant effect on second, third, and fourth moments of the turbulence near the wall.…”

On the Formation Mechanisms of Artificially Generated High Reynolds Number Turbulent Boundary Layers

“…Some examples of these facilities are: the Princeton Superpipe (McKeon et al 2003), the national diagnosis facility (NDF) in Illinois (Vinuesa 2013), the minimum turbulence level (MTL) wind tunnel in Stockholm (Österlund 1999) or the high Reynolds number boundary layer wind tunnel (HRNBLWT) in Melbourne (Nickels et al 2007). Other studies use the stable flow conditions present in the atmospheric boundary layer such as, for instance, the salt playa in the Utah dessert (Metzger and Klewicki 2001) or seek the building of new facilities (Talamelli et al 2009) or sensors (Bailey et al 2010).…”

Self-consistent high-Reynolds-number asymptotics for zero-pressure-gradient turbulent boundary layers

“…However, it has recently become increasingly clear that this proliferation of models is principally due to the scarcity of independent wall shear stress measurements and the limited range of experimental Reynolds numbers, besides, of course, the experimental uncertainties. This realization is the result of recent advances in measurement techniques, equipment, and facilities, which have enabled experiments at high Reynolds numbers; for instance, by Hites, 1 Österlund, 2 DeGraff and Eaton, 3 Metzger and Klewicki, 4 Knobloch and Fernholz, 5 Nagib et al, 6 Carlier and Stanislas, 7 Kunkel and Marusic, 8 and Nickels et al 9 ͑in chronological order͒. An overview of recent developments in the field can be obtained from Ref.…”