Experimental Investigation of Acceleration and Velocity Fields in Turbulent Channel Flow
Christensen, Kenneth Thor
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https://hdl.handle.net/2142/87693
Description
Title
Experimental Investigation of Acceleration and Velocity Fields in Turbulent Channel Flow
Author(s)
Christensen, Kenneth Thor
Issue Date
2001
Doctoral Committee Chair(s)
Adrian, Ronald J.
Department of Study
Theoretical and Applied Mechanics
Discipline
Theoretical and Applied Mechanics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Language
eng
Abstract
The velocity time derivatives are associated predominantly with small scales in both space and time. Examination of instantaneous and estimates of the conditionally averaged velocity time-derivative fields indicates that the smaller-scale vortices leave a convective imprint upon the time derivatives. Further, the streamwise spectra of the velocity time-derivative support the notion that convective effects dominate the smaller scales of the flow. Comparison between the bulk convective-derivative and time-derivative spectra illustrate this behavior. At low wavenumbers, the bulk convective-derivative and time-derivative spectra coincide with one another, implying that the larger scales are dominated by evolution. At moderate wavenumbers (coincident with the streamwise spacing of the vortices associated with the outer-layer vortex organization noted earlier), the energy associated with convection reaches a maximum. With increasing Reynolds number, the influence of convective effects diminishes at all wavenumbers in terms of its contribution to the energy of the velocity time derivative. This behavior is quite encouraging from the LES-modeling viewpoint, where capturing the true evolution of the flow is the main goal.
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