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Analys av turbulensmodeller för CFD
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.
2011 (Swedish)Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

This thesis has been a part of Forsmarks Kraftgrupp AB's evaluation of a turbulence

model used in simulation of turbulent flow called PRNS (Partially Resolved Numerical

Simulation). This model has promising properties and may be of use in saving

computational resources. The purpose of this thesis was to analyze this model and

compare it with industrially applied models such as k-omega SST and LES (Large Eddy


PRNS works as a hybrid of the k-omega SST and DNS (Direct Numerical Simulation)

where a constant, RCP (Resolution Control Parameter) with a value between 0 and 1

are selected. This constant is then used in the calculations and determines the

behavior of the simulation. When RCP is set to zero the equation are the same as for

a DNS simulation and when RCP is set to one the equations for k-omega SST is

solved. In this report four different PRNS models have been used, three where RCP

was given a constant value (0.1, 0.4 and 0.6). In the fourth model RCP is calculated

from the flow field variables

The models have been compared to an experiment from 2008 and simulations have

been made to resemble the experiment. In the experiment a Particle Image

Velocimeter (PIV) was used as method of measurement. From the experimental

report data such as velocity (U), turbulent kinetic energy (k) and standard deviation

(URMS) have been obtained and have formed the basis for comparison. The models

have been simulated in two different software programs: OpenFOAM and Fluent. The

data have thereafter been post processed in the software programs MatLab and

ParaView, to be compared with experimental data.

The results of the simulations have shown that PRNS models generally show a good

accordance with experimental data. In particular, PRNS models with constant RCP

have shown good results, however, there are some discrepancies. The PRNS model

with varying RCP has in most cases showed the largest deviation from experimental

data but also a deviation from the other models, including the reference models.

Due to the design of the mesh (coarse) further evaluation of the PRNS models will be

needed. First, simulate with a finer mesh, but also more complex geometries should

be simulated in order to sort out PRNS strengths and weaknesses and thus determine

if the model can be used in the daily work at Forsmarks Kraftgrupp AB.

Place, publisher, year, edition, pages
2011. , 53 p.
Keyword [sv]
Forsmarks kraftgrupp AB, turbulensmodeller, CFD, PRNS, LES, RANS, Fluent, OpenFOAM
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-161110ISRN: UTH-INGUTB-EX- KKI-2011/08-SEOAI: diva2:454494
Educational program
Bachelor Programme in Nuclear Engineering
Available from: 2012-03-08 Created: 2011-11-07 Last updated: 2012-03-08Bibliographically approved

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