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MODELLING THE ENTRANCE REGION IN A PLANE ASYMMETRIC DIFFUSER BY ELLIPTIC RELAXATION

Andreas Sveningsson
Division of Fluid Dynamics, Department of Applied Mechanics, Chalmers University of Technology Gothenburg 41296, SWEDEN

Bjorn Anders Pettersson-Reif
Norwegian Defence Research Establishment (FFI), Kjeller NO-2027, NORWAY

Lars Davidson
Division of Thermo and Fluid Dynamics, Department of Applied Mechanics, Department of Mechanical Engineering, Chalmers University of Technology, Hörsalvagen 7b, SE41296 Göteborg, Sweden

Sinopsis

The flow in an asymmetric diffuser is computed with the non-linear v2f model suggested by Pettersson-Reif (2000). Its performance is compared with that of two linear eddy-viscosity models and all results are validated against the LES of Kaltenbach et al. (1999). Several modifications to the ε equation are considered and it is shown that this equation indeed plays an important role in the diffuser flow. It is shown that the non-linear relation improves the representation of the individual Reynolds stress components but deteriorates the predictions of the mean flow. Therefore an appreciable effort is spent on identifying the underlying mechanisms that control the evolution of the flow in the diffuser. It is shown that the near-wall resolution of the Reynolds stresses in the entrance region of the diffuser is of essential importance.