Abstract:
The research presented in this thesis is concerned with the development of
numerical techniques and mathematical models for non-Newtonian
uids
and two-phase
ows in pipes and channels.
Single phase, turbulent
ow calculations of non-Newtonian
uids were performed
initially. Based on the literature a revised approach to wall modelling
is proposed and implemented. The approach uses analytical and
experimental analyses of the turbulent boundary layer structure. A comparison
with the standard approach is presented.
The interaction between turbulence and non-Newtonian behaviour is studied
by examining the rate of strain induced by
uctuating components of
velocity. The statistical analysis of published DNS data is performed. Finally,
a model is proposed where the turbulent rate of strain is determined
from turbulence quantities used by the Reynolds-averaged Navier{Stokes
model and used in the calculation of molecular viscosity.
For two-phase
ow, the solution procedure using periodic boundary conditions
was developed under an assumption of a
at interface. The numerical
technique was veri ed by comparing to an analytical result obtained for
laminar
ow in a channel. An extension to three dimensional
ow is performed.
With periodic boundary conditions standard turbulence models are applied
to two-phase strati ed
ow. Several models and their corrections for twophase
ow are assessed and a new model is proposed. The numerical studies
were carried out primiarily in the open-source code OpenFOAM, but initial
attempts were made in commercial packages such as STAR-CD and FLUENT.
Experimental data collected from the literature are used to verify the
results showing good agreement in pressure drops and phase fractions.
