An application of octant analysis to turbulent and transitional flow data

Ralph J. Volino, Terrence W. Simon

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

A technique called "octant analysis" was used to examine the eddy structure of turbulent and transitional heated boundary layers on flat and curved surfaces. The intent was to identify important physical processes that play a role in boundary layer transition on flat and concave surfaces. Octant processing involves the partitioning of flow signals into octants based on the instantaneous signs of the fluctuating temperature, t'; streamwise velocity, u'; and cross-stream velocity, v'. Each octant is associated with a particular eddy motion. For example, u'<0, v'>0 , t'>0 is associated with an ejection or "burst" of warm fluid away from a heated wall. Within each octant, the contribution to various quantities of interest (such as the turbulent shear stress, u'v'¯, or the turbulent heat flux, v't''¯) can be computed. By comparing and contrasting the relative contributions from each octant, the importance of particular types of motion can be determined. If the data within each octant is further segregated based on the magnitudes of the fluctuating components so that minor events are eliminated, the relative importance of particular types of motion to the events that are important can also be discussed. In fullydeveloped,turbulent boundary layers along flat plates, trends previously reported in the literature were confirmed. A fundamental difference was observed in the octant distribution between the transitional and fully-turbulent boundary layers, however, showing incomplete mixing anda lesser importance of small scales in the transitional boundary layer. Such observations were true on both flat and concave walls. The differences are attributed to incomplete development of the turbulent kinetic energy cascade in transitional flows. The findings have potential application to modelling, suggesting the utility of incorporating multiple length scales in transition models.

Original languageEnglish (US)
Title of host publicationCombustion and Fuels; Oil and Gas Applications; Cycle Innovations; Heat Transfer; Electric Power; Industrial and Cogeneration; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; IGTI Scholar Award
PublisherAmerican Society of Mechanical Engineers
ISBN (Electronic)9780791878897
DOIs
StatePublished - 1993
EventASME 1993 International Gas Turbine and Aeroengine Congress and Exposition, GT 1993 - Cincinnati, United States
Duration: May 24 1993May 27 1993

Publication series

NameASME 1993 International Gas Turbine and Aeroengine Congress and Exposition, GT 1993
Volume2

Other

OtherASME 1993 International Gas Turbine and Aeroengine Congress and Exposition, GT 1993
Country/TerritoryUnited States
CityCincinnati
Period5/24/935/27/93

Bibliographical note

Publisher Copyright:
© 1993 by ASME.

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