This document describes a project to design and analyze a faucet aerator through computational fluid dynamics (CFD) analysis. It was completed by three students - Muhammad Arslan, Saad Ullah Anjum, and Malik Abdul Wahab - for their final year mechanical engineering project at Air University in Pakistan. The project aimed to develop an innovative faucet aerator design and analyze water flow using CFD techniques to optimize water savings without compromising user experience. The document provides background on faucet aerators and how they conserve water, as well as an overview of CFD analysis methods that will be applied to simulate water flow through different aerator designs.

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DESIGN AND ANALYSIS OF A FAUCET AERATOR
Group Members:
MUHAMMAD ARSLAN (150520)
SAAD ULLAH ANJUM (150529)
MALIK ABDUL WAHAB (150535)
BE MECHANICAL (FALL-15)
Project Supervisor
Engr. Junaid Wazir
Co-Advisor
Dr. Jehanzeb Masud
DEPARTMENT OF MECHANICAL AND AEROSPACE
ENGINEERING
INSTITUTE OF AVIONICS AND AERONAUTIC
AIR UNIVERSITY, ISLAMABAD

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DESIGN AND ANALYSIS OF A FAUCET AERATOR
Final Year Project Report
BE-MECHANICAL FALL-15
DEPARTMENT OF MECHANICAL AND AEROSPACE
ENGINEERING

3. 3
DESIGN AND ANALYSIS OF A FAUCET AERATOR
Submitted By:
MUHAMMAD ARSLAN (150520)
SAAD ULLAH ANJUM (150529)
MALIK ABDUL WAHAB (150535)
Project Supervisor
Engr. Junaid Wazir
Head of Department
Dr. Jehanzeb Masud

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Acknowledgments
We would like to offer our special thanks of gratitude to our advisor Engr. Junaid Wazir and
co-advisor Dr. Jehanzeb Masud who are always available to help us and to entertain our
queries. We have always found them friendly, ready to help, encouraging and passionate to
transfer their knowledge towards next generation. With their help, we are hopeful that we are
going to achieve our final year project objectives within time effectively.

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Abstract
Conserving both water and energy with water-efficient technologies is extremely beneficial to
the environment. Water conservation is defined as any action that reduces the amount of
water withdrawn from water supply sources, reduces consumptive use, reduces the loss or
waste of water, improves the efficiency of water use, increases recycling and reuse of water,
or prevents the pollution of water. The faucet aerators reduce the water consumption by the
process of aeration. This helps to reduce the usage of water, results in non-splash flow hence
these fittings into water taps acts as water saving devices. These devices (faucet aerators) are
simple to install and cost effective. Previous works have revealed that users’ requirements
include temperature stability, adequate water volume and its distribution. All of which are
substantially controlled by the faucet aerators. An innovative type of aerator will be designed
and analyzed using CFD technique in this project.

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Page iii List of figures& Tables
i. Figure 1 Aerator assembly Page No. 11
ii. Figure 2 Aerated and non-aerated flows Page No. 11
iii. Figure 3 Types of elements Page No. 16
iv. Figure 4 CAD MODEL Page No. 21
v. Figure 5(a) SOLID MODELLING Page No. 22
vi. Figure 5(b) SOLID MODELLING Page No. 22
vii. Figure 6 SOLID MODELLING Page No 23
viii. Figure 7 Mesh Information Page No 24

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Table Of Contents
1. Introduction 08
2. Explanation 09
2.1. Faucet Aerator Parts 10
2.2. Low Flow Aerators 11
3. Computational Fluid Dynamics 12
3.1. Introduction 12
3.2. Applications 14
3.3. Analysis Processes 14
3.4. Fluent 16
3.5. Choosing Mesh Types 17
3.5.1. Setup Time 17
3.5.2. Computational Expense 18
3.6. Using Boundary Conditions 19
4. Solid Modelling 20
5. Refrrences 25

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1. INTRODUCTION
With continuous increase in human population, the need of hour is to use
resources left as effectively as possible. Water being one of the primary
ingredient for survival should be used with great care and saved as much as
possible.
Faucets are one of primary source of water usage domestically. They account
for 15-18% of the overall water consumption inside the typical household of
four persons [2]. An average American household of 3 uses 26.7 gallons (101.1
L) per day for all faucets (bathroom, kitchen, and utility sink). This amounts to
9,750 gallons (36.9 m3) per household per year for faucet use [1]. Faucets in the
late 20th century were designed without any mentionable planning or
optimization for water flow, running at average of around 3GPM (Gallons per
Minute). Unfortunately, here in Pakistan and other developing countries, we are
still not very much concerned about this sacred resource and using it without any
planning. Most of faucets here are still operating at around 2.5-3GPM which will
cause a serious problem of water shortage in near future. For comparison, 3
GPM of water equals around 11.36ltr/min and average water required for a
human body is around 2.7-3.7ltr/day depending upon age and gender. This
means that with a normal faucet, we will be consuming approximately 3
person’s water intake for a day in just 1 minute.
In order to overcome this problem, aerators were introduced which were
responsible to restrict the flow of water coming out from a faucet. Aerators
find their primary use in addition of oxygen to water mainly used in fish tanks.
According to definition, an aerator is a device used to add air into something
which can be water, oil or some other fluid etc. In faucet aerators, air is mixed
with water hence causing single stream of water to divide into multiple streams
and allowing air to fill a gap between these streams. Hence, flow rate is
reduced and stream coming out looks identical to that without the aerator. In

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this way, flow rate is reduced and consumer’s experience is also not
compromised. There
are already plenty of aerators present in market and new designs are continuously
being introduced with main objective of saving water as much as possible
without sacrificing much on quality of consumer’s experience. As per California
Energy Commission, water efficiency standards from April 8, 2015 onwards now
require toilets, urinals, public lavatory faucets, lavatory faucets and kitchen
faucets to consume less water. On August 12, 2015, the Energy Commission[1]
amended its lavatory faucet standard to modify the effective dates to allow more
time for manufacturers to meet the new standard. Lavatory faucets and lavatory
replacement aerators shall now meet a maximum flow rate standard of 1.5
gallons per minute (GPM) and of 1.2 GPM effective July 1, 2016. For complete
history of how aerators got serious attention in the market readers are advised to
visit following link.
http://www.allianceforwaterefficiency.org/Faucet_Fixtures_Introduction.aspx
Nevertheless, our project falls under the same domain. We are designing few
models of aerators and then analyzing water flow from them using a
technique named CFD (Computational Fluid Dynamics) analysis.
2. EXPLAINATION
Aerators reduce the water coming through the faucets by mixing it with air. The
aerator acts as a sieve, sending a single flow of water into many tiny streams.
Thus introduces the air into the water flow. Since there is less space for the
water to flow through, the water flow is reduced. Aerators compress the water
flow into a higher-pressure discharge than regular faucets. They also introduce
air bubbles into the water, making it feel like there is a larger water flow.
However, the water pressure is maintained, which is why most people don't
notice a difference in the amount of water coming out of an aerated faucet. Since
the water is somewhat compacted by an aerator, it may even increase the water
pressure in a faucet. The basic aim nonetheless is to reduce the water input

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without sacrificing the consumer satisfaction. The hydraulic performances of
commercial aerators (using experimental and numerical methods) as water-
saving devices will be determined and improved. Standard faucet aerators being
flow control aerators are small in size but can create significant water savings
[3]. They reduce the flow rate to as low as possible allowing the entrainment of
air thereby result in fine droplets. Correspondingly the volume of water used is
reduced. The low flow device results in water savings of around 20% to 50% of
the normal usage.
2.1 FAUCET AERATOR PARTS
The typical parts of an existing commercial faucet aerator are:
 Steel body
 Water-Inlet
 Wire meshes & other internal geometry
 Restrictions (for stream-lining of flow) The important geometric
parameters
 Air-Inlet (for mixing air with water and reduce the flow rate)
 Number of Plastic Restrictors (function is to save the water by
distributing the flow)
A normal aerator assembly is shown in figure 1.

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FIGURE#1
2.2 Low flow aerators
There are many aerators available commercially that claim to have flow rate
as low as 0.5GPM. They are also categorized in terms of geometry of flow
coming out which is shown in figure-2
Figure-2

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2.2.1 Spray Stream is used to produce a miniature shower pattern and provides
full coverage of hands during washing. Similar to the laminar stream, it is non-
aerated and restricts the flow of water. Suggested for use in public lavatories.
2.2.2 Laminar Stream produces a non-aerated water stream ideal for high flow
applications or health care facilities with a beautiful crystal clear, non- splashing
stream.
2.2.3 Aerated/Bubble Stream mixes air into the water. It produces a larger,
whiter stream that is soft to the touch and non-splashing. This stream is usually
the choice for residential faucets.
Sometimes, pressure of water is low in homes so faucets are designed in order to
deliver same output performance with low pressure of water. The output
however is same, preservation of this precious resources.
3. COMPUTATIONAL FLUID DYNAMICS
3.1 Introduction:
Computational fluid dynamics (CFD) is the use of applied mathematics, physics
and computational software to visualize how a gas or liquid flows -- as well as
how the gas or liquid affects objects as it flows past. Computational fluid
dynamics is based on the Navier-Stokes equations. These equations describe
how the velocity, pressure, temperature, and density of a moving fluid are
related.
Computational Fluid Dynamics became a commonly applied tool for generating
solutions for fluid flows with or without solid interaction. In a CFD analysis, the
examination of fluid flow in accordance with its physical properties such as
velocity, pressure, temperature, density and viscosity is conducted. To virtually
generate a solution for a physical phenomenon associated with fluid flow,
without compromise on accuracy, those properties have to be considered
simultaneously.
A mathematical model of the physical case and a numerical method are used in a
software tool to analyze the fluid flow. For instance, the Navier-Stokes

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equations are specified as the mathematical model of the physical case. This
describes changes on all those physical properties for both fluid flow and heat
transfer. The mathematical model varies in accordance with the content of the
problem such as heat transfer, mass transfer, phase change, chemical reaction,
etc. Moreover, the reliability of a CFD analysis highly depends on the whole
structure of the process. The verification of the mathematical model is extremely
important to create an accurate case for solving the problem. Besides, the
determination of proper numerical methods to generate a path through the
solution is as important as a mathematical model. The software, which the
analysis is conducted with is one of the key elements in generating a sustainable
product development process, as the amount of physical prototypes can be
reduced drastically.
From antiquity to present, humankind has been eager to discover phenomena
based on fluid flow. Experimental studies in the field of computational fluid
dynamics have one big disadvantage: if they need to be accurate, they consume
a significant amount of time and money. Consequently, scientists and engineers
wanted to generate a method that enabled them to pair a mathematical model
and a numerical method with a computer for faster examination.
The brief story of Computational Fluid Dynamics can be seen below:
 Until 1910: Improvements on mathematical models and numerical
methods.
 1910 - 1940: Integration of models and methods to generate numerical
solutions based on hand calculations11.
 1940 - 1950: Transition to computer-based calculations with early
computers (ENIAC)33. Solution for flow around cylinder by Kawaguti
 1950 - 1960: Initial study using computers to model fluid flow based on
the Navier-Stokes equations by Los Alamos National Lab, US.
Evaluation of vorticity - stream function method44. First implementation
for 2D, transient, incompressible flow in the world66.

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 1960 – 1970: First scientific paper “Calculation of potential flow about
arbitrary bodies” was published about computational analysis of 3D
bodies by Hess and Smith in 196755. Generation of commercial codes.
Contribution of various methods such k-ε turbulence model, Arbitrary
Lagrangian-Eulerian, SIMPLE algorithm which are all still broadly used.
 1970 – 1980: Codes generated by Boeing, NASA and some have
unveiled and started to use several yields such as submarines, surface
ships, automobiles, helicopters and aircrafts.
 1980 – 1990: Improvement of accurate solutions of transonic flows in
three-dimensional case by Jameson et. al. Commercial codes have started
to implement through both academia and industry77.
 1990 – Present: Thorough developments in Informatics: worldwide
usage of CFD virtually in every sector.
3.2 Applications:
Where there is fluid, there is CFD [4]. The initial stage to conduct a CFD
simulation is specifying an appropriate mathematical model of reality.
Rapprochements and assumptions give direction through solution processes to
examine the case in the computational domain. Some of main applications of
fluid in which CFD analysis are widely used are as follows.
 Incompressible and Compressible flow
 Laminar and Turbulent flow
 Mass and Thermal transport
3.3 Analysis processes:
First step:
Problem Statement:
The first step of the simulation is to gather information about the
simulation process in general. [5]
 What is the most convenient way of solving this problem in an economic
way:

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 Cheap solution: No high computational costs
 Fast solution: Fast solution possible without giving up much information
of the solution
 Uncomplicated solution: Simplify the problem as much as possible
without restating a new problem
 Modelling:
Second step:
Mathematical Fundamental:
The Initial Boundary Value Problem consists of the Partial Differential Equation
the Initial Conditions as well as the Boundary Conditions
 Add Boundary Conditions and Initial Conditions.
Third step:
Discretization:
The system of Partial Differential Equations is transformed into algebraic
equations which is done through mesh generation.
Fourth step:
Iterative solution of the algebraic equation:
 Solving systems of linear equations:
 Direct Methods: Gaussian elimination, LU decomposition.
 Iterative Methods: Strongly Implicit Procedure (SIP) , Alternating
Direction Implicit (ADI) , Tridiagonal Matrix Algorithm (TDMA),
Runge-Kutta method, Multigrid method.
 Coupled systems of equations.
 Nonlinear Equations
 Methods for transient problems: Linear multistep method etc.
Fifth step:
Simulation Run:
Once the problem is well defined with the boundary conditions, and if necessary
with initial conditions, the problem is solved with a software.

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Sixth step:
Post-Processing
3.4 FLUENT
Today, thousands of companies throughout the world benefit from the use of
ANSYS FLUENT software as an integral part of their design and optimization
phases of product development. Advanced solver technology provides fast,
accurate CFD results, flexible moving and deforming meshes and super parallel
scalability.
Fluent allows for fluid flow analysis of incompressible and compressible fluid
flow and heat transfer in complex geometries. You specify the computational
models, materials, boundary conditions, and solution parameters in Fluent,
where the cases are solved.[7]
You can use a Fluent fluid flow analysis system to apply a computational mesh
to a geometry within Workbench, then use Fluent to define pertinent
mathematical models (e.g., low-speed, high-speed, laminar, turbulent, etc.),
select materials, define boundary conditions, and specify solution controls that
best represent the problem to be solved. Fluent solves the mathematical
equations, and the results of the simulation can be displayed in Fluent or in
CFD-Post for further analysis (e.g. contours, vectors, etc.).
There are four different 3D element types — tets, bricks, prisms, and pyramids
as shown in figures below.
Figure#3

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These four elements can be used, in various combinations, to mesh any 3D
model depending upon complexities within a geometry and other factors like
aspect ratio etc.[9]
3.5 Choosing Mesh Type
ANSYS FLUENT can use meshes comprised of triangular or quadrilateral cells
(or a combination of the two) in 2D, and tetrahedral, hexahedral, polyhedral,
pyramid, or wedge cells (or a combination of these) in 3D. Tetrahedral are also
known as a simplex, which simply means that any 3D volume, regardless of
shape or topology, can be meshed with tetrahedral. They are also the only kind
of elements that can be used with adaptive mesh refinement. The other three
element types (bricks, prisms, and pyramids) should be used only when it is
motivated to do so. It is first worth noting that these elements will not always be
able to mesh a particular geometry. The meshing algorithm usually requires
some more user input to create such a mesh. The choice of which mesh type to
use will depend other geometry of the product. When choosing mesh type, we
consider the following issues:
 setup time
 computational expenses
3.5.1. Setup Time
Many flow problems solved in engineering practice involve complex
geometries. The creation of structured or block-structured meshes (consisting of
quadrilateral or hexahedral elements) for such problems can be extremely time-
consuming if not impossible. Therefore, setup time for complex geometries is
the major motivation for using unstructured meshes employing triangular or
tetrahedral cells. However, if your geometry is relatively simple, there may be
no saving in setup time with either approach.
Other risks of using structured or block-structured meshes with complicated
geometries include the oversimplification of the geometry, mesh quality issues,

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and a less efficient mesh distribution (e.g., fine resolution in areas of less
importance) that results in a high cell count.
3.5.2. Computational Expense
When geometries are complex or the range of length scales of the flow is large,
a triangular/tetrahedral mesh can be created with far fewer cells than the
equivalent mesh consisting of quadrilateral/hexahedral elements. This is because
a triangular/tetrahedral mesh allows clustering of cells in selected regions of the
flow domain. Structured quadrilateral/hexahedral meshes will generally force
cells to be placed in regions where they are not needed. Unstructured
quadrilateral/hexahedral meshes offer many of the advantages of
triangular/tetrahedral meshes for moderately-complex geometries.
A characteristic of quadrilateral/hexahedral elements that might make them
more economical in some situations is that they permit a much larger aspect
ratio than triangular/tetrahedral cells. A large aspect ratio in a
triangular/tetrahedral cell will invariably affect the skewness of the cell, which is
undesirable as it may impede accuracy and convergence.
Take an example, converting the entire domain of tetrahedral mesh to a
polyhedral mesh will result in a lower cell count than original mesh. Although
the result is a coarser mesh, convergence will generally be faster, possibly
saving some computational expense.
In summary, the following practices are generally recommended:
 For simple geometries, use quadrilateral/hexahedral meshes.
 For moderately complex geometries, use unstructured
quadrilateral/hexahedral meshes.
 For relatively complex geometries, use triangular/tetrahedral meshes
with prism layers.
 For extremely complex geometries, use pure triangular/tetrahedral
meshes

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3.6 Using Flow Boundary Conditions
ANSYS FLUENT/GAMBIT provides 10 types of boundary zone types for the
specification of flow inlets and exits: velocity inlet, pressure inlet, mass flow
inlet, pressure outlet, pressure far-field, outflow, inlet vent, intake fan, outlet
vent, and exhaust fan.
The inlet and exit boundary condition options in ANSYS FLUENT are as
follows:[9]
 Velocity inlet boundary conditions are used to define the velocity and
scalar properties of the flow at inlet boundaries.
 Pressure inlet boundary conditions are used to define the total pressure
and other scalar quantities at flow inlets.
 Mass flow inlet boundary conditions are used in compressible flows to
prescribe a mass flow rate at an inlet. It is not necessary to use mass flow
inlets in incompressible flows because when density is constant, velocity
inlet boundary conditions will fix the mass flow. Like pressure and
velocity inlets, other inlet scalars are also prescribed.
 Pressure outlet boundary conditions are used to define the static pressure
at flow outlets (and also other scalar variables, in case of backflow). The
use of a pressure outlet boundary condition instead of an outflow
condition often results in a better rate of convergence when backflow
occurs during iteration.
 Pressure far-field boundary conditions are used to model a free-stream
compressible flow at infinity, with free-stream Mach number and static
conditions specified. This boundary type is available only for
compressible flows.
 Outflow boundary conditions are used to model flow exits where the
details of the flow velocity and pressure are not known prior to solution
of the flow problem. They are appropriate where the exit flow is close to
a fully developed condition, as the outflow boundary condition assumes

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a zero streamwise gradient for all flow variables except pressure. They
are not appropriate for compressible flow calculations.
 Inlet vent boundary conditions are used to model an inlet vent with a
specified loss coefficient, flow direction, and ambient (inlet) total
pressure and temperature.
 Intake fan boundary conditions are used to model an external intake fan
with a specified pressure jump, flow direction, and ambient (intake) total
pressure and temperature.
 Outlet vent boundary conditions are used to model an outlet vent with a
specified loss coefficient and ambient (discharge) static pressure and
temperature.
 Exhaust fan boundary conditions are used to model an external exhaust
fan with a specified pressure jump and ambient (discharge) static
pressure.
4. SOLID MODELLING:
Initially we made a CAD model of an aerator alongside assembly to start
analysis and design process. As there is no standard made which would be taken
into consideration while designing as well as there are not enough derived
equations for this specific case, so we opted to test via hit and trail method. 1st
model which is created, meshed and will be analyzed is shown below in
Figure#4.

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. Figure#4
Smaller cylinder is taken as water inlet from where water will be coming. Pipes
in the middle are going to act as boundaries to separate single streamline of
water into multiple streams and introduce air in between when water comes out.
The outer cylinder is assumed to be filled with air at time=0 acting as
atmosphere.
Dimensions
Dimensions are given below
Large Cylinder Diameter= 30mm
Large Cylinder Area= 6126.11mm2
Smaller Cylinder Diameter= 20mm
Smaller Cylinder Area=1570.8mm2
Pipe Diameter= 1mm
Pipe Area=2.42mm2
Number of Pipes=71
For further explanation and meshing part, large cylinder will be referred to as
atmosphere, small cylinder to water pipe and pipes as aerators. Mesh is done in

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GAMBIT (Geometry and Mesh Building Intelligent Tool). Boundary conditions
and other details are shown below in figure#5(a) and (b).
Air Side Walls Interfaced faces
Pressure Outlet
Figure#5(a) & (b)

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Water pipe’s face-1(That is away from aerators) is taken as velocity inlet from
where water will flow in, Walls are modelled as shown in fig(X). Water pipe’s
face-2 meeting aerators is interfaced with all pipe’s faces. Same process is
applied with Face-2 of aerator which are interfaced with atmosphere
representing cylinder. After the modelling, GAMBIT is used to generate mesh
as well. Edge, face and volume meshing is done on GAMBIT. Whole CAD
model is divided into 3 volumes
 Water
 Air
 Water Pipe
This process is shown in figure#6
Air Volume
Pipes (Water) Volume
Water
Figure#6
After applying boundary conditions, Model is meshed using Tri+ Quad
elements. Mesh file is then imported in ANSYS FLUENT where it will be
analyzed using VOF method.

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Mesh details, number of elements and other details are shown in figure#7 below.
Figure#7
Analysis results and conclusions will be discussed in the next report.

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5. References
[1] CALIFORNIA ENERGY COMMISSION technical report available at
https://www.energy.ca.gov
[2] Water Conservation: An Overview, Technical Report, American Water
Works Association available at https://www.awwa.org
[3] Umesh, Nagaraj Sitaram” HYDRAULIC PEROFORMNACE OF FAUCET
AERATOR AS WATER SAVING DEVICE AND SUGGESTIONS FOR ITS
IMPROVEMENTS” IJRET: International Journal of Research in Engineering and
Technology Volume: 03 Issue: 07 | Jul-2014
[4] Tu, Jiyuan., Yeoh, Guan-Heng., Liu, Chaoqun.” 2013, “Computational Fluid
Dynamics”Chap1-8.
[5] Versteeg & Malalasekera: “An Introduction to Computational Fluid
Dynamics - The Finite Volume Method - 2nd Edition”Chap-3.
[6] Kuzmin, Dmitri.” A Guide to Numerical Methods for Transport Equations”
[7] ANSYS FLUENT Flow Modeling Software Available at
https://www.ozeninc.com
[8]Swaffield and R.H.M.Wakein, “water conversation: the impact of design,
development and site appraisal of a low-volume flush toilet”, pp 176-188,
DIVISION OF BUILDING TECHNOLOGY
[9] Released by ANSYS 2009-01-29 available at http://www.afs.enea.it