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Turbulence models in CFD IJS(在CFD ij湍流模型).pdf

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University of Ljubljana Faculty for mathematics and physics Department of physics Turbulence models in CFD Jurij SODJA Mentor: prof. Rudolf PODGORNIK March 2007 INDEX 1 INTRODUCTION 3 2 GENERAL REMARKS3 2.1 Ideal turbulence model3 2.2 Complexity of the turbulence model4 2.3 Classification of turbulent models 4 3 REYNOLDS-AVERAGED NAVIER-STOKES MODELS6 3.1 Reynolds’s decomposition6 3.1.1 Equations describing instantaneous fluid motion 6 3.1.2 Reynolds averaging7 3.2 The closure problem 9 3.2.1 Laminar flow, infinitesimal fluctuations and superposition 9 3.3 Reynolds stress models10 4 COMPUTATION OF FLUCTUATING QUANTITIES12 4.1 Direct numerical simulation12 4.2 Large-Eddy simulation13 5 RANS versus LES14 6 CONCLUSION17 7 REFERENCES 18 2 1 INTRODUCTION The abbreviation CFD stands for computational fluid dynamics. It represents a vast area of numerical analysis in the field of fluid’s flow phenomena. Headway in the field of CFD simulations is strongly dependent on the development of computer- related technologies and on the advancement of our understanding and solving ordinary and partial differential equations (ODE and PDE). However CFD is much more than “just” computer and numerical science. Since direct numerical solving of complex flows in real-like conditions requires an overwhelming amount of computational power success in solving such problems is very much dependent on the physical models applied. These can only be derived by
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