Accession Number : ADA325341

Title :   Experimental Investigation of the Near Wall Flow Structure of a Low Reynolds Number 3-D Turbulent Boundary Layer.

Descriptive Note : Technical rept. 1 Jan 92-30 Apr 97,

Corporate Author : VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF AEROSPACE AND OCE AN ENGINEERING

Personal Author(s) : Fleming, J. L. ; Simpson, R. L.

PDF Url : ADA325341

Report Date : 30 APR 1997

Pagination or Media Count : 275

Abstract : Laser Doppler velocimetry (LDV) measurements and hydrogen bubble flow visualization techniques were used to examine the near-wall flow structure of 2D and 3D turbulent boundary layers (TBLs) over a range of low Reynolds numbers. The goals of this research were (1) an increased understanding of the flow physics in the near wall region of turbulent boundary layers,(2) to observe and quantify differences between 2D and 3D TBL flow structures, and (3) to document Reynolds number effects for 3D TBLs. The LDV data have provided results detailing the turbulence structure of the 2D and 3D TBLs. These results include mean Reynolds stress distributions, flow skewing results, and U and V spectra. Effects of Reynolds number for the 3D flow were also examined. Comparison to results with the same 3D flow geometry but at a significantly higher Reynolds number provided unique insight into the structure of 3D TBLs. While the 3D mean and fluctuating velocities were found to be highly dependent on Reynolds number, a previously defined shear stress parameter was discovered to be invariant with Reynolds number. The hydrogen bubble technique was used as a flow visualization tool to examine the near-wall flow structure of 2D and 3D TBLs. Both the quantitative and qualitative results displayed larger turbulent fluctuations with more highly concentrated vorticity regions for the 2D flow.

Descriptors :   *TURBULENT BOUNDARY LAYER, *FLOW VISUALIZATION, *HYDROGEN, *BUBBLES, *TWO DIMENSIONAL FLOW, *FLUID DYNAMICS, *LASER VELOCIMETERS, *THREE DIMENSIONAL FLOW, NUMERICAL ANALYSIS, TURBULENT FLOW, VORTICES, SHEAR STRESSES, WALLS, DOPPLER SYSTEMS, REYNOLDS NUMBER, MOMENTUM TRANSFER.

Subject Categories : Fluid Mechanics
      Lasers and Masers

Distribution Statement : APPROVED FOR PUBLIC RELEASE