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Modelling the transitional boundary layerRecent developments in the modelling of the transition zone in the boundary layer are reviewed (the zone being defined as extending from the station where intermittency begins to depart from zero to that where it is nearly unity). The value of using a new non-dimensional spot formation rate parameter, and the importance of allowing for so-called subtransitions within the transition zone, are both stressed. Models do reasonably well in constant pressure 2-dimensional flows, but in the presence of strong pressure gradients further improvements are needed. The linear combination approach works surprisingly well in most cases, but would not be so successful in situations where a purely laminar boundary layer would separate but a transitional one would not. Intermittency-weighted eddy viscosity methods do not predict peak surface parameters well without the introduction of an overshooting transition function whose connection with the spot theory of transition is obscure. Suggestions are made for further work that now appears necessary for developing improved models of the transition zone.
Document ID
19910006682
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Narasimha, R. (National Aeronautical Lab. Bangalore, India)
Date Acquired
September 6, 2013
Publication Date
December 1, 1990
Subject Category
Aerodynamics
Report/Patent Number
NAS 1.26:187487
AD-A232080
ICASE-90-90
NASA-CR-187487
Accession Number
91N15995
Funding Number(s)
CONTRACT_GRANT: NAS1-18605
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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