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Issue 1, Volume 5,
January 2010
Title of the Paper: Adjustment of
Dissipative Terms to Improve Two and Three-Dimensional Euler Flow Solutions
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Authors: Seyed Saied
Bahrainian
Abstract: The Euler equations are a set of non-dissipative hyperbolic
conservation laws that can become unstable near regions of severe pressure
variation. To prevent oscillations near shockwaves, these equations require
artificial dissipation terms to be added to the discretized equations. A
combination of first-order and third-order dissipative terms control the
stability of the flow solutions. The assigned magnitude of these dissipative
terms can have a direct effect on the quality of the flow solution. To examine
these effects, subsonic and transonic solutions of the Euler equations for a
flow passed a circular cylinder has been investigated. Triangular and
tetrahedral unstructured grids were employed to discretize the computational
domain. Unsteady Euler equations are then marched through time to reach a
steady solution using a modified Runge-Kutta scheme. Optimal values of the
dissipative terms were investigated for several flow conditions. For example,
at a free stream Mach number of 0.45 strong shock waves were captured on the
cylinder by using values of 0.25 and 0.0039 for the first-order and
third-order dissipative terms. In addition to the shock capturing effect, it
has been shown that smooth pressure coefficients can be obtained with the
proper values for the dissipative terms.
Keywords: Artificial
Dissipation, Unstructured Grids, Finite volume, Euler Equations, Shock
capturing
Title of the Paper: Scale-up of a Cold
Flow Model of FICFB Biomass Gasification Process to an Industrial Pilot Plant
– Hydrodynamics of Particles
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Authors: J. Mele, J.
Oman, J. Krope
Abstract: The article introduces the research of particles hydrodynamics in a
cold flow model of FICFB biomass gasification process and its scale-up to
industrial pilot plant. A laboratory unit has been made for the purposes of
experimental research. The laboratory unit is three times smaller than the
later pilot plant. For a reliable observation of the flow process, similar
flow conditions must be created in the laboratory unit and the pilot plant.
The results of the laboratory model will be similar to those of the actual
device if geometry, flow and Reynolds numbers are the same. Therefore, there
is no need to bring a full-scale gasificator into the laboratory and actually
test it. This is an example of "dynamic similarity".
Keywords: Fluid bed,
Pneumatic transport, Reynolds number, Gasification, Scale-up
Title of the Paper: Synthetic Jet Design
Criteria and Application for Boundary Layer Separation Control
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Authors: Francesca Satta,
Daniele Simoni, Marina Ubaldi, Pietro Zunino, Francesco Bertini
Abstract: With the purposes of better understanding the phenomena associated
with the synthetic jet operation as well as identifying suitable design
criteria to control boundary layer laminar separation, the aerodynamic
performance of a synthetic jet system has been experimentally investigated.
Both device design and its aerodynamic characterization are addressed in the
paper, paying particular attention to the fundamental parameters to be set for
the synthetic jet design. The synthetic jet behaviour has been surveyed
adopting different measuring techniques. Power density spectra have been
evaluated from jet velocity distributions measured by means of a hot-wire
anemometer. In order to investigate the instantaneous flow field and to allow
the identification of the jet organised flow structures, Particle Image
Velocimetry has been adopted. Moreover, to distinguish the different jet
dynamics during the peculiar phases of the device (blowing and suction),
phaselocked ensemble averaging technique has been applied. The system has been
successively tested with external cross-flow and the jet performance has been
surveyed. In particular, the device has been applied on a flat plate installed
in a double contoured walls test section in order to verify the capability of
the jet in suppressing the boundary layer laminar separation induced by strong
adverse pressure gradients, typical of Ultra-High-Lift turbine pressure
distributions.
Keywords: Boundary layer
control, synthetic jet, blowing ratio, Strouhal number, Particle Image
Velocimetry, hot-wire anemometry
Issue 2, Volume 5,
April 2010
Title of the Paper: Time-Varying Flow
Investigation of Synthetic Jet Effects on a Separating Boundary Layer
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Authors: Francesca Satta,
Daniele Simoni, Marina Ubaldi, Pietro Zunino, Francesco Bertini
Abstract: This paper is focused on the investigation of the interaction
between a synthetic jet and the boundary layer which develops over a flat
plate subjected to an adverse pressure gradient typical of a high-lift
lowpressure turbine profile. Two different Reynolds numbers of the main flow,
Re = 200000 and Re = 70000, typical of the low-pressure turbine operating
conditions during the take-off/landing and cruise phases, respectively, have
been investigated. Wall static pressure distributions along the plate showed
the different effects induced by the jet on the boundary layer separation with
the jet Strouhal numbers investigated. The device capability of suppressing
the large laminar separation bubble which occurs for the uncontrolled
condition has been more in depth investigated by means of hot-wire time-mean
and ensemble averaged measurements. The phase-locked ensemble averaging
technique, synchronized with the synthetic jet frequency, has been employed to
distinguish the effects induced by the jet during the blowing and the suction
phases. The active device has been proved to be able to control the laminar
separation bubble induced by a strong adverse pressure gradient, also at the
low Reynolds number condition tested. The ensemble averaged measurements
showed that a larger contribution to the reduction of the boundary layer
velocity defect is obtained during the suction phase of the jet.
Keywords: Boundary layer
control, separated boundary layer, low-pressure turbines, synthetic jet,
phaselocked measurements, hot-wire anemometry
Title of the Paper: Two Different
Turbulence Models in Comparison with Experiments on Thermal Mixing Phenomenon
in a Tee Piping
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Authors: Chao-Jen Li,
Yao-Long Tsai, Tai-Ping Tsai, Li-Hua Wang
Abstract: Thermal fatigue failures in reactor cooling systems of nuclear power
plants are caused by the fluctuating stresses on a piping system due to the
hot and cold flows are mixed together in a mixing piping. The present paper
describes BSL Reynolds Stress (BSL-RSM) and k-epsilon (k-ε) simulation data of
thermal mixing in a mixing piping compared with results from experimental
data. The fluid in the experiment is concentration of de-ionized water and the
liquid electrical conductivities are measured by the use of the 16?16
electrode. To verify the mixing phenomenon between de-ionized water with
different electrical conductivities and water with different temperatures, the
inlet temperatures of the hot and cold water in the simulation process are set
to 80? and 15? respectively. The analytic results calculated by the commercial
CFD code ANSYS CFX 11.0 show that the different turbulence models(BSL-RSM, k-ε)and
different turbulent Prandtl numbers(0.9, 0.2, 0.1) will affect the simulation
results of temperature fluctuations. Since the coefficient of determination,
R2, obtained by using Prt=0.1 for BSL-RSM turbulence mode is between 0.996 and
0.788, which is higher than that by using Prt=0.2 and Prt=0.9, the perditions
for smaller turbulent Prandtl number are in better agreement with
measurements. The absolute error, β, obtained by using BSL-RSM turbulence
model at x=0.025m is smaller than that by using k-ε turbulence model. However,
at x=-0.025m, the absolute error, β, obtained by using k-ε turbulence model is
smaller than that by using BSL-RSM turbulence model. The computational results
are in qualitative good agreement with experimental data that the mixing
phenomenon of water with two different temperatures can be explained by
de-ionized water with two different electrical conductivities.
Keywords: BSL-RSM, Thermal
Fatigue, Turbulent Prandtl Number, Mixing
Title of the Paper: Computing of
Cavitation Characteristic and Sensitivity Curves for Francis Pump-Turbine
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Authors: Anton Iosif,
Ioan Sarbu
Abstract: It is well known, that the fluid motion in reversible hydraulic
machinery elements is a complex threedimensional problem. In this paper it is
developed an explicit numerical model based on Finite Element Method and Dual
Reciprocity Method for the simulation of the flow velocity and pressure
distributions on blade of the Francis type reversible radial-axial hydraulic
machine’s runner, in the hypothesis of ideal incompressible fluid and the
relative rotational motion. The proposed numerical model was applied for
reversible radial–axial hydraulic machinery operating as a pump. The blade has
the basic profile NP205. This profile has a quadratic equation which defines
its skeleton and its thickness function is that of a NACA profile with a
maximum relative thickness of five percent. The numerical results for
different discharge values have finally allowed obtaining the cavitation
characteristic and sensitivity curves for the reversible hydraulic machinery.
Keywords: Reversible
hydraulic machines, Axial-symmetrical motion, Radial-axial profile cascades,
Velocity and pressure distributions, Two-dimensional numerical model, Computer
programs, Cavitation characteristic, Cavitation sensitivity curves
Issue 3, Volume 5,
July 2010
Title of the Paper: A Study on Saline
Water Intrusion and Fresh Water Recharge Relevant to Coastal Environment
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Authors: Sudip Basack,
A. K. Bhattacharya, Chitta Sahana, Prabir Maity
Abstract: The paper is based on experimental laboratory model study with
relevant mathematical analysis followed by field investigation so as to
understand the characteristics and flow pattern of saline water intrusion into
natural porous medium followed by subsequent fresh water recharge.
Keywords: Coastal aquifer,
Darcy flow, Forchheimer flow, Fresh water recharge, Reynolds number, Saline
water intrusion
Title of the Paper: Hydraulic
Performance of Double Slotted Barriers under Regular Wave Attack
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Authors: E. V. Koutandos
Abstract: In the present study, wave interaction with double, fixed, vertical,
semi-immersed, slotted barriers is investigated numerically. Numerical results
concerning obtained with the use of the COBRAS (Cornell breaking Wave and
Structures) wave model for regular waves reveal the effects of barriers
porosity, relative depth d/L (d: water depth, L: wave length) and relative
distance between the two barriers S/L (S: the distance between the two
barriers, L: wave length) on the hydrodynamic characteristics (wave
transmission, reflection, dissipation, velocity field, turbulence kinetic
energy field). Numerical results concerning wave transmission, reflection,
dissipation against the porosity of the barriers, d/L and S/L are well
compared with experimental results by Isaacson et al. [14], revealing the
credibility of the wave model. Detailed computed velocities and turbulence
kinetic energy in the vicinity of the structure indicate the effects of the
special breakwater on the flow pattern and the turbulence structure.
Keywords: Double Slotted
Barriers, Permeable Barriers, Special Βreakwater
Title of the Paper: Feasible Structural
and Non- Structural Measures to Minimize Effect of Flood in Lower Tapi Basin
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Authors: Dhruvesh P.
Patel, Mrugen B. Dholakia
Abstract: Floods have always been a major problem to the human race, as many
settlements have grown up around rivers. The fastest growing city of India,
Surat, is settled on the bank of river Tapi. Varekhadi, a group of 26 mini
watersheds lead water into river Tapi and the flow takes a small time period
to reach near Surat city. Due to which, the city gets flooded once in a 4 to 5
years and losses large amount of property and lives. Present work describes
the flood potential of Varekhadi watershed group by application of Soil and
Water Assessment Tool (SWAT) model, using Remote Sensing (RS) and Geographical
Information System (GIS). In order to minimize the effect of flood, in and
around Surat city, feasible structural and non-structural measures are
suggested.
Keywords: Flood, Tapi,
Varekhadi, SWAT, LTB, CWC, GIS, Ukai dam
Title of the Paper: Metallographic and
Numerical Methods Investigations about Failure of a Kaplan Turbine Runner
Blade
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Authors: Doina
Frunzaverde, Viorel Campian, Dorian Nedelcu, Gilbert-Rainer Gillich, Gabriela
Marginean
Abstract: The paper presents the results of the failure analysis of a Kaplan
turbine runner blade from a hydropower station in Romania. In order to
determine the causes that led to the cracks, the authors first carried out
metallographic investigations on a sample obtained from the cracked blade. The
metallographic investigations included macroscopic and microscopic
examinations (light microscopy and scanning electron microscopy) and X-ray
diffraction analyzes (XRD). They led to the conclusion that the cracking of
the blade was caused by fatigue, initiated by the numerous non metallic
inclusions, which were discovered in the vicinity of the blade surface. The
results obtained were confirmed by calculations on the resistance and service
life estimations of the blade. The calculations carried out included the
following steps: construction of the solid 3D-model of the blade,
determination of the blade loads from hydrodynamic conditions, linear static
analysis of the blade and service life estimations, calculated for maximal
stress values of the concentrators. They led to the conclusion that the
cracking of the blade started and developed from the stress concentrator
placed between blade and blade flange on leading edge direction. In order to
decrease the maximal stress value, the authors concluded that the hydrodynamic
loads on the blade must be obligatory reduced. Therefore, as the operating
conditions (discharge, head, speed, power) are not changeable, the stress
reduction could be realized only by increasing the number of the runner
blades.
Keywords: Hydropower
station, Kaplan turbine, fatigue cracking, service life estimations
Title of the Paper: Modeling of Induced
Circulation
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Authors: Lale Balas, Asu
Inan
Abstract: Marinas located along the coastline of an enclosed sea are subjected
to water quality problems due to insufficient water exchange resulting from
the weakness of the tidal motion. For such marinas forced flushing measures
may need to be designed. In this paper, two forced flushing schemes for
enhancing flushing rates of marinas in enclosed seas are discussed. First
forced flushing scheme is the removal of the surface layer of water in the
marina by mechanical pumping and the second one is the wave pump. The induced
circulation patterns by the use of the Morning Glory type intake structure and
wave pump experiments were performed in the laboratory and forced circulations
were simulated by the developed three dimensional hydrodynamic and transport
model, HYDROTAM-3. Turbulence has been simulated by a two equation k-ω
turbulence model. With the application of the morning glory type intake and
the wave pump, the flushing ability of the marina increased about 10 times and
12 times respectively, compared to the tidal flushing alone. Model predictions
provided encouraging results. HYDROTAM-3 reproduces the velocity field that is
in good agreement in the intensity and spatial scale with the current
measurement.
Keywords: Marina, forced
flushing, modeling, turbulence, wave pump, mechanical pumping, finite element,
hydrodynamic, transport
Title of the Paper: Research Regarding
the Use of New Systems to Control Fluid Flow in Pipelines
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Authors: Olimpiu
Stoicuta, Marin Silviu Nan, Gabriel Dimirache, Nicolae Buda, Dan Liviu Dandea
Abstract: In this paper a research is made on the design of a new fluid flow
control system on transport pipelines. The flow control system is based on a
sensorless speed control system of an induction motor with the squirrel –
cage. The estimator component for rotor flux and speed from the induction
motor speed control system is an Extended Gopinath Observer
Keywords: Extended
Gopinath Observer, Sensorless Control, Flow Control Simulation, Centrifugal
Pumps
Title of the Paper: Numerical Study on
the Flow Characteristics of a Solenoid Valve for Industrial Applications
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Authors: Taewoo Kim,
Sulmin Yang, Sangmo Kang
Abstract: Study on the flow characteristics of solenoid valves is essential
since they play pivot role in a flow circuit for controlling the flow through
a required path for a specified duration. The flow characteristics of a 3/2
-way solenoid valve used in the four stroke propulsion engine of a ship is
studied by performing numerical simulation using ANSYS CFX 12.0 commercial
software package. The solenoid valve can be operated in two ways- either by
pushing the hand operated button for moving the spool or by moving the spool
using electric signal. The valve under study is a superspeed valve and the
response time of moving spool is very short. The movement of the spool which
is located in the middle of the body of solenoid valve affects the flow
characteristics. This is examined by performing a static analysis by changing
the position of the spool. The high pressure air passes through a pipe and
reaches the engine tank of given dimensions. The simulation is performed for
different inlet pressure and spool displacement and the corresponding flow
characteristics are obtained. The results of the three dimensional numerical
simulation will be helpful in the proper design of solenoid valve for the
industrial applications.
Keywords: Numerical
simulation, Computational fluid dynamics, Solenoid valve, Spool displacement,
Flow characteristics, ANSYS CFX, SST model
Title of the Paper: Determination of
Optimal District Heating Pipe Network Configuration
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Authors: M. Jamsek, D.
Dobersek, D. Goricanec, J. Krope
Abstract: In this article the developed mathematical model, which based on
simplex method is presented. The mathematical model, consisting of the non –
linear objective function and system of non – linear equations for the
hydraulics limitations is developed. On its basis the computer program for
determination optimal tree path with the use of simplex method was solved. For
economic estimation the capitalized value method, which consider all costs of
investment and operation was used. The simulation is done on a pipe network
with 22 pipes and 13 nodes.
Keywords: Heating, Pipe
network, Optimisation, Non-linear programming, Simplex method
Title of the Paper: Convection in
Superposed Fluid and Porous Layers in the Presence of a Vertical Magnetic
Field
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Authors: Hanadi M.
Banjer, Abdullah A. Abdullah
Abstract: A linear stability analysis is applied to a system consisting of a
horizontal fluid layer overlying a layer of porous medium saturated with the
same fluid, with uniform heating from below in the presence of a vertical
magnetic field. The flow in porous medium is assumed to be governed by Darcy’s
law. The Beavers-Joseph condition is applied at the interface between the two
layers. Numerical solutions are obtained using expansion of Chebyshev
polynomials. This spectral method has a strong ability to solve multi-layered
problems and allows us to obtain a highly accurate eigenvalues in a very
efficient manner. Numerical results are obtained for different values of the
parameter (= depth of fluid layer/depth of porous layer) and different values
of the magnetic parameter Q. The effect of magnetic field is investigated and
it is found that the linear stability curves for the onset of convection
motion are bimodal even for higher values of d.
Keywords: Superposed
porous and fluid layers- Thermal convection- Darcy's law- Magnetic field-
Stationary convection, Chebyshev tau method
Title of the Paper: Simplified Mesoscale
Lattice Boltzmann Numerical Model for Prediction of Natural Convection in a
Square Enclosure filled with Homogeneous Porous Media
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Authors: C. S. Nor
Azwadi, M. A. M. Irwan
Abstract: The lattice Boltzmann method (LBM) is applied to a generalised
isotropic porous media model in a square geometry by introducing a force term
to the evolution equation and a porosity to the density equilibrium
distribution function. The temperature field is obtained by simulating a
simplified thermal model which uses less velocity directions for the
equilibrium distribution function and neglects the compression work done by
the pressure and the viscous heat dissipation. The reliability of this model
for natural convective heat transfer simulation is studied by comparing with
results from previous simulations at a porosity value, ε = 0.9999. The model
is then used for simulation at ε = 0.4, 0.6 and 0.9 at three different
Rayleigh numbers. Comparison of solutions with previous works confirms the
applicability of the present approach.
Keywords: Lattice
Boltzmann method, distribution function, Boussinesq approximation, porous
media, convective heat transfer
Title of the Paper: Aerodynamic
Characteristics of Wing of WIG Catamaran vehicle During Ground Effect
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Authors: Adi Maimun,
Saeed Jamei, Agoes Priyanto, Nor Azwadi
Abstract: In this paper, the aerodynamic characteristics of wing with NACA
6409 section from WIG Catamaran vehicles with the influence of twin hull and
ground effect was numerically studied. The simulation of WIG Catamaran was
performed by Three Dimensional (3D) Computational Fluid Dynamic (CFD). The k-ω
SST turbulent model was used for turbulent flow in CFD mode. In order to
validate the numerical results, the CFD simulations of only wing with NACA
6409 section were compared with experimental data published by previous
researcher. Next, Lift coefficient and, drag coefficient and lift to drag
ratio of wing with twin hulls of WIG catamaran were determined on various of
angle of attacks and two ground clearances (h/c=0.3 and infinity). The results
of the CFD simulation indicate a reduction on lift and drag coefficients but
there is an increment lift to drag ratio of wing which is caused by twin hulls
of WIG Catamaran, as well as there are enhancement on lift coefficient and
decreasing on drag coefficient, hence lift to drag ratio increases when flying
in proximity to the ground.
Keywords: WIG Catamaran,
Wing In Ground effect, Aerodynamic characters, NACA 6409, CFD analysis
Title of the Paper: Energy Efficiency of
Machinery Hydro-Pneumatic and Climate Impact
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Authors:
Marius-Constantin Popescu, Nikos E. Mastorakis, Mircea Grigoriu, Jean-Octavian
Popescu
Abstract: In practice, due to various over-the loss of pregnancy considered by
designers as a security measure, the pump provides a flow chosen much higher
than calculated. The main greenhouse gases (GHGs) producer is represented by
the fossil burning systems. The paper presents the effect on the GHGs emission
combined with the economic effects of a new pumping system method of automatic
mixing of hot and cold water circulated with variable speed driving pumps and
adjustable vanes. Considering the potential economic and environmental effects
combined with the social one, The heating systems represent a sensitive sector
of the energy consumers’ basket, strengthen by the unpredictable primary
energy price fluctuation, the recent financial crisis and the population
expectations. This paper tries optimizing operation of machinery,
hydro-pneumatic.
Keywords: Modeling and
optimization, Greenhouse gases, Heating systems, Economic effects
Title of the Paper: Accessible Technical
Solution for Normal Construction Apparatus Usage in Ex Classified Areas
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Authors: Jeana Ionescu,
Lucian Moldovan, Sorin Burian, Marius Darie, Tiberiu Csaszar, Carol Zoller
Abstract: This paper intercession is due to an undesirable penury state
regarding eligible technical equipment for use in Ex classified areas. This
fact competed with the negative dynamic of material possibilities leads to an
apparent lack of interest regarding protection to explosion. As a solution to
the identified problem, the authors propose the use of normal construction
technical equipment adapted according to prescriptions of “pz” pressurized
enclosure protection type. This intercession presents a good estimated level
of tolerance to customer and will lead to the decrease of explosion risk level
due to technical equipment and lower acquisition, maintenance and repair
specific costs.
Keywords: Ex classified
areas, Ex apparatus, pressurization, autonomy time, purging, loss compensation
Title of the Paper: Proper Orthogonal
Decomposition Analysis for Unsteady Rotor-Stator Interaction in a Low Pressure
Centrifugal Compressor
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Authors: Sterian
Danaila, Mihai Leonida Niculescu
Abstract: In this paper, Proper Orthogonal Decomposition (POD) is applied to
the analysis of the unsteady rotor-stator interaction in a low-pressure
centrifugal compressor. Numerical simulations are carried out through finite
volumes method using the Unsteady Reynolds-Averaged Navier-Stokes Equations
(URANS) model. Proper Orthogonal Decomposition allows an accurate
reconstruction of flow field using only a small number of modes; therefore,
this method is one of the best tools for data storage The POD results and the
data obtained by the Adamczyk decomposition are analyzed. Both decompositions
show the behavior of unsteady rotor-stator interaction, but the POD modes
allow quantifying better the numerical errors.
Keywords: Unsteady
Rotor-Stator Interaction, Adamczyk decomposition, POD, CFD, Compressor, URANS,
Flow Field Reconstruction
Title of the Paper: Contribution for the
Vulnerability Assessment of Water Pipe Network Systems
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Authors: Jorge Pinto,
Luis Afonso, Joao Varajao, Isabel Bentes, Humberto Varum, Antonio A. L. S.
Duarte, Jitendra Agarwal
Abstract: Water pipe network systems are key public utilities which require
being robust, protected and preserved. Knowing their weaknesses will help
these processes. The theory of vulnerability of water pipe networks can
contribute in this context because it is able to map the vulnerable parts of
this type of system. The meaning of vulnerability has been defined as being
the disproportionateness of the failure consequences in relation to the
initial damage and, in particular, its theoretical concepts. The main
objectives of this paper are to briefly introduce this theory, to illustrate
its application highlighting its potential. The application of the theory is
presented using an example of a simple water pipe network. In a real water
supply utility, where the vulnerabilities of WPN components are less evident,
the identification of the most vulnerable ones may play an important
contribution as support decision during WPN design period and for a
sustainable infrastructure asset management. Further work is in progress to
account for different type of damage and consequences and thus manage risks
due to failure scenarios not identified by the classical theories.
Keywords: Water
management; water pipe networks, vulnerability, failure scenarios, system
safety
Issue 4, Volume 5,
October 2010
Title of the Paper: Performance of the
Constants Couple of the Second Order Turbulence Model (RSM) Applied to an
Axisymmetric Configuration
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Authors: M. Senouci, A.
Bounif
Abstract: The Reynolds stress model (RSM) is considered as a more
sophisticated approach used to modelling the turbulent flows, compared to the
other turbulence models. This type of model, used to improve the accuracy of
the results, overcomes the turbulent viscosity concept and the assumption of
the turbulence isotropy which it means. The pressure-strain correlation term
is among the most important terms to be modelled in the exact transport
equations of the Reynolds stresses. Different models, used for modelling the
pressure-strain correlation term, have been proposed by different authors. The
basic model is that proposed by Launder, Reece and Rodi (1975) [1] called
LRR-IP, a combination of Rotta's model and the IP model (Isotropisation of
Production). The main objective of this study is to test the performance of
the constants pair (C1, C2) used in such model for modelling the
pressure-strain correlation term.
Keywords: Turbulence,
axisymmetric jets, second order modelling, pression-strain correlation
Title of the Paper: A Review of Effects
of Initial and Boundary Conditions on Turbulent Jets
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Authors: Adel
Abdel-Rahman
Abstract: On the basis of available knowledge, it is shown that different
mechanisms may have control in different jet flows or in different regions of
a jet flow. In free jet flows, the downstream region is dominated by
turbulence structure whereas coherent eddy-structure can have a strong
influence on the near field, particularly for low-Reynolds number jet flows.
At present, however, it has become a common belief that coherent-eddy
structures determine, to a large degree, the evolution and dynamics of
turbulent jet flows. The following article is an attempt to review the current
information on round turbulent jet flows. In so doing, the influence of the
jet origin (initial conditions) and the boundary conditions (presence or
absence of endplate, side walls, and/or jet enclosure) on the jet flow
structure is considered.
Keywords: Jets, Turbulent
jets, Jet initial conditions, Jet structure, Coherent structure
Title of the Paper: Application of
Euler-Euler Model for Numerical Simulation of a Radial Turbine Working in the
Two-Phase Flow Regime
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Authors: Sebastian
Schuster, Friedrich-Karl Benra, Hans Josef Dohmen
Abstract: This paper deals with the numerical calculation of a single stage
radial turbine with nucleation in the impeller. The calculations are performed
with Ansys CFX 12.1 and are based on the Euler-Euler model. In terms of
velocity and temperature, the flow is inhomogeneous. The Euler-Euler model is
combined with a nucleation model based on the classical nucleation theory. The
working fluid is steam calculated with the IAPWS formulation. First a
validation of the used numerical code with experimental results is performed.
On the investigated geometry different parameter variations such as different
inlet conditions and change in rotational velocity are performed. The goal of
the work is to show the influence of this parameters on the water film
formation. It will be shown that a high proportion of water is at the blades
even if the nucleation occurs in the impeller and the area averaged wetness at
the outlet is low.
Keywords: Euler-Euler,
inhomogeneous, two-phase flow, nucleation
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