Accession Number : ADA113073

Title :   Controllability and Evolution of Coherent Structures in Turbulent Wakes.

Descriptive Note : Final technical rept. 1 Jan 76-31 Dec 80,

Corporate Author : ILLINOIS INST OF TECH CHICAGO DEPT OF MECHANICS MECHANICAL AND AEROSPACE ENGINEERING

Personal Author(s) : Way,John L ; Wlezien,Richard W ; Nagib,Hassan M

PDF Url : ADA113073

Report Date : Jan 1980

Pagination or Media Count : 63

Abstract : The main objectives were to answer some of the questions of evolution of large scale structure in turbulent wakes and to develop new techniques of experimentation and data reduction to identify and document the organized structures in turbulent flows. The techniques of thermal tagging, polychromatic signal decomposition, local and convective flow visualization, digital image processing and pattern recognition, two-dimensional spectral decomposition of velocity fields, as well as spatial reconstruction are applied to the bluff body wake problem. The results of these experiments have clarified the picture of wake evolution over a wide range of Reynolds numbers, from laminar to turbulent. These techniques demonstrate that an approach as elaborate as the orthogonal decomposition scheme in not necessary to objectively bring out the important large scale mechanisms. The study also clearly refutes the pairing mechanism active in shear layers as that responsible for the growth of the large scale.

Descriptors :   *Wake, *Turbulent flow, *Vortex shedding, Coherence, Evolution(General), Spatial distribution, Structural analysis, Data reduction, Pattern recognition, Flow visualization, Image processing, Decomposition, Velocity, Spectrum analysis, Transitions, Reynolds number, Experimental design, Laminar flow, Blunt bodies

Subject Categories : Test Facilities, Equipment and Methods
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE