Effects of centrifugal instabilities on laminar/turbulent transition in curved channels with 40 to 1 aspect ratios
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Authors
Kendall, Michael R.
Subjects
Dean vortices
Centrifugal instabilities
Turbulence
Rectangular curved channel
Laminar/turbulent transition
Centrifugal instabilities
Turbulence
Rectangular curved channel
Laminar/turbulent transition
Advisors
Ligrani, Phillip M.
Date of Issue
1991-06
Date
June 1991
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
Dean vortices in curved channels with 40 to 1 aspect ratios were measured and studied over the range of Dean numbers from 50 to 450. At low Dean numbers (50) the flow is fully laminar. At higher Dean numbers, the development of vortex pairs as the primary instability was a function of Dean number and the angle of curvature. Higher Dean numbers required less curvature to produce the vortices. At Dean numbers from 75 to 200, secondary instabilities developed in the form of vortex pair modulations, vortex pair twisting, and in the form of events where vortex pair undulations, vortex pair twisting, and in the form of events where vortex pairs appear and disappear. The secondary instabilities are also a function of Dean number and curvature. Twisting leads to increase in longitudinal fluctuating intensities, particularly in the upwash region from the concave wall, which are especially significant at Dean numbers above 150.
Type
Thesis
Description
Series/Report No
Department
Mechanical Engineering
Organization
Naval Postgraduate School
Identifiers
NPS Report Number
Sponsors
Propulsion Directorate
US Army Aviation R/T Act. AVSCOM
NASA-Lewis, Cleveland, OH 45433
MIPR C-30030-P
Funding
Format
283 p.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.