Experimental Investigation of Acceleration and Velocity Fields in Turbulent Channel Flow

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Theoretical and Applied Mechanics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Christensen, Kenneth Thor

Contributors dc:contributor

• Adrian, Ronald J.

• Engineering, Mechanical

Language dc:language

eng

Identifier

(MiAaPQ)AAI3017051

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/87693