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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