Laminar Kinetic Energy Modelling for Improved Laminar-Turbulent Transition Prediction

Clare Turner

Research output: ThesisDoctoral Thesis

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Abstract

This thesis considers the advantages of incorporating laminar-kinetic energy modelling into turbulence modelling, in order to predict laminar-turbulent transition. The final aim is to implement an improved transition model into the industrial Finite-Volume code, Code_Saturne. The literature review suggests that in order for a RANS-based model to predict transition accurately, modelling of complex, anisotropic phenomena is necessary. The Walters-Cokljat model is shown to compare very well to other transition modelling methods, including correlation-based modelling. The Walters-Cokljat model is a single-point RANS-based model that solves an additional transport equation for laminar kinetic energy. The transition model is especially desirable from an industrial stand-point, due to its single-point RANS basis, with only 3 transport equations. Although thismethod shows great promise as an industrial tool for transition prediction,results presented here show that there are aspects of the model that requiremodification. The definition of effective length-scale and the methodof accounting for the effects of shear sheltering are the two main areas forconsideration. The current definition of effective length-scale is found tobe inappropriate for flows with large free-stream length-scales, which arecommon-place in turbomachinery applications. Another phenomenon commonlyfound in turbomachinery is separation-induced transition; however,the current function for shear sheltering effects inhibits transition whenturbulence intensity is not the forcing factor. Additionally, when reviewedanalytically, the definition and placement of the shear sheltering functiondoes not match the observations of Jacobs and Durbin. Alternatives forthe definitions of the effective length-scale and the shear sheltering functionare proposed. The individual proposals are tested, and steps towards a fullworking implementation are documented.
Original languageEnglish
Awarding Institution
  • The University of Manchester
Publisher
Publication statusPublished - 25 Jan 2012

Keywords

  • laminar kinetic energy
  • transition
  • bypass transition
  • RANS modelling

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