Small-scale behavior in distorted turbulent boundary layers at low Reynolds number
Abstract
During the last three years we have conducted high- and low-Reynolds-number experiments, including hot-wire measurements of the velocity fluctuations, in the test-section-ceiling boundary layer of the 80- by 120-foot Full-Scale Aerodynamics Facility at NASA Ames Research Center, to test the local-isotropy predictions of Kolmogorov's universal equilibrium theory. This hypothesis, which states that at sufficiently high Reynolds numbers the small-scale structures of turbulent motions are independent of large-scale structures and mean deformations, has been used in theoretical studies of turbulence and computational methods such as large-eddy 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 local-isotropy 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