Nuclear Energy for New Europe 2009

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No: 217

Conference: Nuclear Energy for New Europe 2009

Title: Demonstrative Application of CFD Best Practice Guidelines to a Simple Pressure Drop Problem

Theme: Thermal Hydraulics

Author(s): Lorenzo Mengali, Fabio Moretti, Francesco D'Auria

Contact : Lorenzo Mengali

E-mail: l.mengali@ing.unipi.it

Address: University of Pisa San Piero a Grado Nuclear Research Group (GRNSPG)
56122 Pisa

Country: Italy

The need of a quality assurance oriented approach in the application of CFD codes to Nuclear Reactor Safety (NRS) has brought to the introduction of Best Practice Guidelines (BPG), as a means to provide more reliable results and reducing the related errors and uncertainties. On the other hand, such guidelines are seldom adopted in the resolution of actual industrial scale problems, because of excessive computational costs in developing several grids for discretization error analysis and running many sensitivity calculations. The present work consists of a demonstrative systematic application of the NEA/CSNI/R(2007)5 “Best Practice Guidelines for the use of CFD in Nuclear Reactor Safety Applications”, in order to point out the main features, benefits and drawbacks of this method. In particular, the study aims at the verification and validation of a simple pressure drop case found in literature (flow through a thick diaphragm) using the CFD code ANSYS CFX 11. Three turbulence models were tested (k-?, k-? based Shear Stress Transport SST and the six equation SSG Reynolds Stress Model) and error analyses were performed for all these models. The results show an erratic variation of some of the parameters suggested for the discretization error analysis; hence a detailed study was carried out to identify the source of this behaviour. In particular, alternative choices are suggested which better check whether the solution has reached the asymptotic convergence.

No:	217
Conference:	Nuclear Energy for New Europe 2009
Title:	Demonstrative Application of CFD Best Practice Guidelines to a Simple Pressure Drop Problem
Theme:	Thermal Hydraulics
Author(s):	Lorenzo Mengali, Fabio Moretti, Francesco D'Auria
Contact :	Lorenzo Mengali
E-mail:	l.mengali@ing.unipi.it
Address:	University of Pisa San Piero a Grado Nuclear Research Group (GRNSPG) 56122 Pisa
Country:	Italy

The need of a quality assurance oriented approach in the application of CFD codes to Nuclear Reactor Safety (NRS) has brought to the introduction of Best Practice Guidelines (BPG), as a means to provide more reliable results and reducing the related errors and uncertainties. On the other hand, such guidelines are seldom adopted in the resolution of actual industrial scale problems, because of excessive computational costs in developing several grids for discretization error analysis and running many sensitivity calculations. The present work consists of a demonstrative systematic application of the NEA/CSNI/R(2007)5 “Best Practice Guidelines for the use of CFD in Nuclear Reactor Safety Applications”, in order to point out the main features, benefits and drawbacks of this method. In particular, the study aims at the verification and validation of a simple pressure drop case found in literature (flow through a thick diaphragm) using the CFD code ANSYS CFX 11. Three turbulence models were tested (k-?, k-? based Shear Stress Transport SST and the six equation SSG Reynolds Stress Model) and error analyses were performed for all these models. The results show an erratic variation of some of the parameters suggested for the discretization error analysis; hence a detailed study was carried out to identify the source of this behaviour. In particular, alternative choices are suggested which better check whether the solution has reached the asymptotic convergence.