Effects of 2 Hz imposed bulk flow unsteadiness on laminar/turbulent transition in a straight channel.
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Authors
Greco, Francis J.
Subjects
Plane Channel Flow
Imposed Unsteadiness
Transition Events
Tolkmu-Schiichting Waves
Vortical Ribbon-Like Structures
Imposed Unsteadiness
Transition Events
Tolkmu-Schiichting Waves
Vortical Ribbon-Like Structures
Advisors
Ligrani, Phillip M.
Subramanian, Chelakara S.
Date of Issue
1989
Date
December 1989
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
Laminar turbulent transition is studied in a straight channel with 2 Hz imposed bulk flow unsteadiness for Reynolds
umbers of 1 100 to 3800 and Strouhal numbers of 0.121 to 0.035. Channel aspect ratio is 40 to 1 with 1.27 cm height. 50.8
n width and 4.27 m length. Observations, videos, and photographs of smoke patterns show different subcritical transition
'ents including Tollmien-Schlichting waves, vortex-array type motion evidenced by smoke swirls, ribbon-like patterns,
trbulentspots. and fully turbulent flow. Fluctuating intensity magnitudes relative to velocities from imposed unsteadiness
e determined from phase-aveiaged velocity traces. With 2 Hz unsteadiness, transition events begin to occur at lower
eynolds numbers and extend over a wider range of Reynolds numbers compared to flows with no imposed unsteadiness.
Type
Thesis
Description
Series/Report No
Department
Mechanical Engineering
Organization
Identifiers
NPS Report Number
Sponsors
Funding
Format
127 p.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.