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.
2011. , 53 p.
Forsmarks kraftgrupp AB, turbulensmodeller, CFD, PRNS, LES, RANS, Fluent, OpenFOAM