Statistical structure of momentum sources and sinks in the outer region of a turbulent boundary layer


Ganapathisubramani, B. (2008) Statistical structure of momentum sources and sinks in the outer region of a turbulent boundary layer. Journal of Fluid Mechanics, 606, 225-237. (doi:10.1017/S0022112008001675).

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Description/Abstract

The spatial structure of momentum sources and sinks (T > 0 and T < 0; where T is the streamwise component of the Lamb vector) is examined in a turbulent boundary layer by using dual-plane particle image velocimetry data obtained in streamwise–spanwise planes at two wall-normal locations (x2/δ = 0.1 and 0.5, where x2 is the wall-normal location and δ is the boundary layer thickness). Two-point correlations of T indicate that the size of source motions remains relatively constant while the size of sink motions increases with increasing wall-normal distance. The relative strength of sink motions also increases away from the wall. The velocity field in the vicinity of source/sink motions was explored by computing cross-correlations of T with the velocity components. Source-like motions are correlated with elongated low-momentum zones that possess regions of upwash embedded within them and appear to be the strongest in areas where these low-momentum zones meander in the spanwise direction. Momentum sinks appear to be located within low-speed regions that are within larger high-momentum zones. The velocity fluctuations undergo rapid transitions between quadrants in the vicinity of sinks (i.e. both streamwise and wall-normal velocity fluctuations change sign). The length scales, over which the fluctuations change sign, are much larger at x2/δ = 0.5 than at x2/δ = 0.1.

Item Type: Article
Digital Object Identifier (DOI): doi:10.1017/S0022112008001675
ISSNs: 0022-1120 (print)
1469-7645 (electronic)
Subjects: Q Science > QC Physics
T Technology > TA Engineering (General). Civil engineering (General)
Divisions: University Structure - Pre August 2011 > School of Engineering Sciences > Aerodynamics & Flight Mechanics
ePrint ID: 187415
Date Deposited: 17 May 2011 09:37
Last Modified: 27 Mar 2014 19:41
URI: http://eprints.soton.ac.uk/id/eprint/187415

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