الفهرس 
CHAPTER 1: GENERAL INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Centrifugal pumps are used in agriculture, industries and domestic applications.
The importance of such pump type is more distinct in case of transporting slurries
flow. Due to the complicity of centrifugal pump flow, the various physical flow
phenomena occurring inside such kind of pumps, either handling single-phase or twophase
flow, are needed urgently to be analyzed. Computational fluid dynamics (CFD)
facilitates the analysis for such complicated flow. Moreover, the behavior of solid
particles and its influence on the structure of the flow can be easily determined.
In the present work, 2D, 3D, steady and unsteady numerical simulation of
centrifugal pump flow is performed. The finite volume approach is used to discretize
the Reynolds Average Navier Stokes (RANS) equations along with different
turbulence models. The discretization procedure is performed using ANSYS FLUENT
15. With the aid of experimental data from the literature, the validation of numerical
results is first performed for single-phase flow. The aim of this validation is to
recognize the effect of time step, the turbulence model and solution technique. After
that, the simulation of two-phase flow behavior is performed. The simulation is
performed using moving reference frame. The particles are tracked through the flow
field using Lagrangian approach. The results discuss the effect of particles structure
distribution, inter-particle collision, lift force and turbulence dissipation.
The mean deviation error of the numerical results predicted by standard 𝑘-𝜀,
realizable 𝑘-𝜀, SST 𝑘-𝜔 and Reynolds Stress (RSM) turbulence models is discussed.
from the simulation results, it is concluded that the standard 𝑘-𝜀 model is suitable to
perform the simulation of flow inside the centrifugal pump. Moreover, the calculating
time step should be lower than the time needed for the blade tip to cross certain point.
The Sliding Mesh Model (SMM) can fairly predict the flow behavior inside the pump
and pump performance. Therefore, the different phenomena inside the entrance pipe and pump such as, inlet recirculation, blade loading, Coriolis effect, secondary flow
and jet-wake phenomenon are demonstrated and analyzed. In addition, the ability of
the volute to damp the fluctuation of the flow, discharging from the impeller, is
analyzed. Finally, the effect of the blade position relative to the tongue (impellervolute
interaction) on the internal flow characteristics and on the total pump
performance is also explained. Comparison between SMM and Moving Reference
Frame (MRF) shows that, the MRF can’t predict the internal flow field accurately.
However, it can determine the pump performance with acceptable error. In addition,
the computational time of MRF is much less than the corresponding time of SMM.
The two-dimensional simulation fails to predict some phenomena such as the inlet
recirculation and secondary flow; however it gives the general picture of flow
characteristics.
In the two-phase flow pump, a large number of dispersed solid particles are
traced through the flow field. The effects of solid concentration and its size on the
pump performance and flow behavior are analyzed. It is found that, the pump head
decreases as solid concentration increases. However, the influence of particle size on
the pump performance is small. Finally, the fine particles are accumulated near the
suction side while the coarse are connected to the pressure side.