Smallscale behavior in distorted turbulent boundary layers at low Reynolds number
Abstract
During the last three years we have conducted high and lowReynoldsnumber experiments, including hotwire measurements of the velocity fluctuations, in the testsectionceiling boundary layer of the 80 by 120foot FullScale Aerodynamics Facility at NASA Ames Research Center, to test the localisotropy predictions of Kolmogorov's universal equilibrium theory. This hypothesis, which states that at sufficiently high Reynolds numbers the smallscale structures of turbulent motions are independent of largescale structures and mean deformations, has been used in theoretical studies of turbulence and computational methods such as largeeddy simulation; however, its range of validity in shear flows has been a subject of controversy. The present experiments were planned to enhance our understanding of the localisotropy hypothesis. Our experiments were divided into two sets. First, measurements were taken at different Reynolds numbers in a plane boundary layer, which is a 'simple' shear flow. Second, experiments were designed to address this question: will our criteria for the existence of local isotropy hold for 'complex' nonequilibrium flows in which extra rates of mean strain are added to the basic mean shear?
 Publication:

Annual Research Briefs, 1994
 Pub Date:
 December 1994
 Bibcode:
 1994arb..nasa..243S
 Keywords:

 Boundary Layer Flow;
 Isotropic Turbulence;
 Kolmogorov Theory;
 Low Reynolds Number;
 Shear Flow;
 Turbulent Boundary Layer;
 Wind Tunnel Tests;
 Isotropy;
 Nonequilibrium Flow;
 Turbulent Flow;
 Vortices;
 Fluid Mechanics and Heat Transfer