A Measure Of Scale-Dependent Asymmetry In Turbulent Boundary Layer Flows: Scaling And Reynolds Number Similarity
Keywords
Atmospheric surface layer; intermittency; wall turbulence
Abstract
The distribution of temporal scale-dependent streamwise velocity increments is investigated in turbulent boundary layer flows at laboratory and atmospheric Reynolds numbers, using the St. Anthony Falls Laboratory wind tunnel and the Surface Layer Turbulence and Environmental Science Test dataset, respectively. The third-order moments of velocity increments, or asymmetry index A(a,z), is computed for varying wall distance z and time scale separation a, where it was observed to leave a robust, distinct signature in the form of a hump, independent of Reynolds number and located across the inertial range. The hump is observed in wall region limited to z+ <5 ×103, with a tendency to shift towards smaller time scales as the surface is approached (z+ <70). Comparing the two datasets, the hump, and its location, are found to obey inner wall scaling and is regarded as a genuine feature of the canonical turbulent boundary layer. The magnitude cumulant analysis of the scale-dependent velocity increments further reveals that intermittency is also enhanced near the wall, in the same flow region where the asymmetry signature was observed. The combination of asymmetry and intermittency is inferred to point at non-local energy transfer and scale coupling across a range of scales. From a turbulent structure perspective, such non-local energy transfer can be seen as the result of strong scale-interaction processes between outer scale motions in the logarithmic layer impacting and distorting smaller scales at the wall, through abrupt energy transfer across scales bypassing the typical energy cascade of the inertial range.
Publication Date
6-25-2016
Publication Title
Journal of Fluid Mechanics
Volume
797
Number of Pages
549-563
Document Type
Article
Personal Identifier
scopus
DOI Link
https://doi.org/10.1017/jfm.2016.294
Copyright Status
Unknown
Socpus ID
84971212722 (Scopus)
Source API URL
https://api.elsevier.com/content/abstract/scopus_id/84971212722
STARS Citation
Singh, Arvind; Howard, Kevin B.; and Guala, Michele, "A Measure Of Scale-Dependent Asymmetry In Turbulent Boundary Layer Flows: Scaling And Reynolds Number Similarity" (2016). Scopus Export 2015-2019. 3384.
https://stars.library.ucf.edu/scopus2015/3384