Extension of a local correlation-based transition model in OpenFOAM
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Insinööritieteiden korkeakoulu |
Master's thesis
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Authors
Date
2016-05-16
Department
Major/Subject
Mechanical Engineering
Mcode
IA3027
Degree programme
Master’s Programme in Mechanical Engineering
Language
en
Pages
56+8
Series
Abstract
Depending on the flow regimes, which can be laminar or turbulent, important characteristics of the flow can differ quite significantly. The ability to predict which regime will take place is important in many engineering applications of fluid mechanics. In order to predict transition, most often numerical methods have to be used or a branch of fluid mechanics, known as computational fluid dynamics (CFD). The problem with many transition models, is that the use of non-local variables is needed, such as following certain quantities along streamlines, which makes it difficult to use such models for general CFD codes, where the computation of non-local variables is problematic. In this work, a local correlation-based model is employed, which avoids the deficiencies of these previous transition models. The model is not based on physics, but empirical correlations. Since many factors affect transition, the original model did not include all of them. It is the aim of this thesis to extend the transition model, already implemented in the software OpenFOAM, to include crossflow- and roughness-induced transition prediction capabilities, which were found in different publications. The model which included the roughness extension was tested on flat plate cases, with zero-, favorable- and adverse-pressure gradients. The crossflow-extended model, was tested on the Onera M6 wing, at different angles of attack. Although the results are promising and the models show a correct behaviour, there was no very close agreement in different cases for both roughness- and crossflow-extended models. The reason could be the manner in which the transition model was implemented in OpenFOAM.Description
Supervisor
Tuhkuri, JukkaThesis advisor
Siikonen, TimoRahman, Mizanur
Keywords
transition, turbulence, OpenFOAM, CFD