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Characteristic eddy decomposition of turbulence in a channelThe proper orthogonal decomposition technique (Lumley's decomposition) is applied to the turbulent flow in a channel to extract coherent structures by decomposing the velocity field into characteristic eddies with random coefficients. In the homogeneous spatial directions, a generaliztion of the shot-noise expansion is used to determine the characteristic eddies. In this expansion, the Fourier coefficients of the characteristic eddy cannot be obtained from the second-order statistics. Three different techniques are used to determine the phases of these coefficients. They are based on: (1) the bispectrum, (2) a spatial compactness requirement, and (3) a functional continuity argument. Results from these three techniques are found to be similar in most respects. The implications of these techniques and the shot-noise expansion are discussed. The dominant eddy is found to contribute as much as 76 percent to the turbulent kinetic energy. In both 2D and 3D, the characteristic eddies consist of an ejection region straddled by streamwise vortices that leave the wall in the very short streamwise distance of about 100 wall units.
Document ID
19910012157
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Moin, Parviz (NASA Ames Research Center Moffett Field, CA, United States)
Moser, Robert D. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 6, 2013
Publication Date
March 1, 1991
Subject Category
Fluid Mechanics And Heat Transfer
Report/Patent Number
NAS 1.15:100065
NASA-TM-100065
A-88081
Accession Number
91N21470
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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