Suscripción a Biblioteca: Guest
Tenth International Symposium on Turbulence and Shear Flow Phenomena
July, 7-9, 2017 , Swissotel Chicago, Chicago, Illinois, U.S.A.

DOI: 10.1615/TSFP10

Reappraisal of the asymptotic state of a zero pressure gradient turbulent boundary layer

pages 143-147
DOI: 10.1615/TSFP10.260
Get accessGet access

SINOPSIS

In this paper we study a zero pressure gradient turbulent boundary layer developing over a two-dimensional rough wall that consists of a periodic arrangement of cylindrical rods with a spacing (p) of eight times the rod diameter (k). Hot-wire anemometry is used to measure the streamwise velocity and the mean statistics are compared against previously reported smooth wall results over a large range of Reynolds (Re) number (Marusic et al., 2015) and the atmospheric surface layer (ASL) data of Metzger et al. (2007). The main motivation of this study is to understand the differences/similarities between a high Re smooth wall boundary layer and an approximately self-preserving rough wall boundary layer. It is found that the smooth and rough wall turbulent boundary layers present some similarities at low Re. However, as Re increases, they have different asymptotic behaviours. In the present surface roughness (p = 8k), the viscous drag becomes negligible in comparison to the form drag as Re increases, thereby allowing the entire turbulent boundary layer to evolve in a practically self-preserving manner. Further, it is observed that beyond a critical Re the entire boundary layer complies with Townsend's Reynolds number similarity (Townsend, 1956). These results contrast with those of a smooth wall boundary layer where self-preservation and the Reynolds number similarity are satisfied only in the outer region and at infinitely large Re. Altogether, the present study strongly suggests that while the smooth wall TBL will eventually approach its Re-independent asymptotic state only when Re → ∞, the rough wall TBL reaches its asymptotic state at a faster rate and at finite Re.

Portal Digitalde Biblioteca Digital eLibros Revistas Referencias y Libros de Ponencias Colecciones Precios y Políticas de Suscripcione Begell House Contáctenos Language English 中文 Русский Português German French Spain