DESIGN AND CFD ANALYSIS OF CONICAL ORIFICE PLATE

AT DIFFERENT VELOCITY RATIOS

Chapter-1
INTRODUCTION
An orifice plate is a device used for measuring flow rate, for reducing pressure or for restricting
flow (in the latter two cases it is often called a restriction plate). Either a volumetric or mass flow
rate may be determined, depending on the calculation associated with the orifice plate. It uses the
same principle as a Venturi nozzle, namely Bernoulli's principle which states that there is a
relationship between the pressure of the fluid and the velocity of the fluid. When the velocity
increases, the pressure decreases and vice versa.

An orifice plate is a thin plate with a hole in it, which is usually placed in a pipe. When a fluid
(whether liquid or gaseous) passes through the orifice, its pressure builds up slightly upstream of
the orifice:85–86 but as the fluid is forced to converge to pass through the hole, the velocity
increases and the fluid pressure decreases. A little downstream of the orifice the flow reaches its
point of maximum convergence, the vena contract a (see drawing to the right) where the velocity
reaches its maximum and the pressure reaches its minimum. Beyond that, the flow expands, the
velocity falls and the pressure increases. By measuring the difference in fluid pressure across
tappings upstream and downstream of the plate, the flow rate can be obtained from Bernoulli's
equation using coefficients established from extensive research.

Orifice plates are most commonly used to measure flow rates in pipes, when the fluid is single-
phase (rather than being a mixture of gases and liquids, or of liquids and solids) and well-mixed,
the flow is continuous rather than pulsating, the fluid occupies the entire pipe (precluding silt or
trapped gas), the flow profile is even and well-developed and the fluid and flow rate meet certain
other conditions. Under these circumstances and when the orifice plate is constructed and
installed according to appropriate standards, the flow rate can easily be determined using
published formulae based on substantial research and published in industry, national and
international standards.

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Plates are commonly made with sharp-edged circular orifices and installed concentric with the
pipe and with pressure tappings at one of three standard pairs of distances upstream and
downstream of the plate; these types are covered by ISO 5167 and other major standards. There
are many other possibilities. The edges may be rounded or conical, the plate may have an orifice
the same size as the pipe except for a segment at top or bottom which is obstructed, the orifice
may be installed eccentric to the pipe, and the pressure tappings may be at other positions.
Variations on these possibilities are covered in various standards and handbooks. Each
combination gives rise to different coefficients of discharge which can be predicted so long as
various conditions are met, conditions which differ from one type to another.

Once the orifice plate is designed and installed, the flow rate can often be indicated with an
acceptably low uncertainty simply by taking the square root of the differential pressure across the
orifice's pressure tappings and applying an appropriate constant. Even compressible flows of
gases that vary in pressure and temperature may be measured with acceptable uncertainty by
merely taking the square roots of the absolute pressure and/or temperature, depending on the
purpose of the measurement and the costs of ancillary instrumentation. Orifice plates are also
used to reduce pressure or restrict flow, in which case they are often called restriction plates.

1.1 PRESSURE TAPPINGS:

There are three standard positions for pressure tappings (also called taps), commonly named as
follows:

1. Corner taps placed immediately upstream and downstream of the plate; convenient when the
plate is provided with an orifice carrier incorporating tappings

2. D and D/2 taps or radius taps placed one pipe diameter upstream and half a pipe diameter
downstream of the plate; these can be installed by welding bosses to the pipe

3. Flange taps placed 25.4 mm (1 inch) upstream and downstream of the plate, normally within
specialized pipe flanges.

These types are covered by ISO 5167 and other major standards. Other types include

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2½D and 8D taps or recovery taps placed 2.5 pipe diameters upstream and 8 diameters
downstream, at which point the measured differential is equal to the unrecoverable pressure loss
caused by the orifice Vena contracta tappings placed one pipe diameter upstream and at a
position 0.3 to 0.9 diameters downstream, depending on the orifice type and size relative to the
pipe, in the plane of minimum fluid pressure.

The measured differential pressure differs for each combination and so the coefficient of
discharge used in flow calculations depends partly on the tapping positions.

The simplest installations use single tappings upstream and downstream, but in some
circumstances these may be unreliable; they might be blocked by solids or gas-bubbles, or the
flow profile might be uneven so that the pressures at the tappings are higher or lower than the
average in those planes. In these situations multiple tappings can be used, arranged
circumferentially around the pipe and joined by a piezometer ring, or (in the case of corner taps)
annular slots running completely round the internal circumference of the orifice carrier.

1.2 PLATE:

Standards and handbooks are mainly concerned with sharp-edged thin plates. In these, the
leading edge is sharp and free of burrs and the cylindrical section of the orifice is short, either
because the entire plate is thin or because the downstream edge of the plate is bevelled.
Exceptions include the quarter-circle or quadrant-edge orifice, which has a fully rounded
leading edge and no cylindrical section, and the conical inlet or conical entrance plate which has
a bevelled leading edge and a very short cylindrical section. The orifices are normally concentric
with the pipe (the eccentric orifice is a specific exception) and circular (except in the specific
case of the segmental or chord orifice, in which the plate obstructs just a segment of the pipe).
Standards and handbooks stipulate that the upstream surface of the plate is particularly flat and
smooth. Sometimes a small drain or vent hole is drilled through the plate where it meets the pipe,
to allow condensate or gas bubbles to pass along the pipe.

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1.3 COMPUTATION:

Flow rates through an orifice plate can be calculated without specifically calibrating the
individual flow meter so long as the construction and installation of the device complies with the
stipulations of the relevant standard or handbook. The calculation takes account of the fluid and
fluid conditions, the pipe size, the orifice size and the measured differential pressure; it also takes
account of the coefficient of discharge of the orifice plate, which depends upon the orifice type
and the positions of the pressure tappings. With local pressure tappings (corner, flange and
D+D/2), sharp-edged orifices have coefficients around 0.6 to 0.63, while the coefficients for
conical entrance plates are in the range 0.73 to 0.734 and for quarter-circle plates 0.77 to
0.85.]The coefficients of sharp-edged orifices vary more with fluids and flow rates than the
coefficients of conical-entrance and quarter-circle plates, especially at low flows and high
viscosities.

For compressible flows such as flows of gases or steam, an expansibility factor or expansion
factor is also calculated. This factor is primarily a function of the ratio of the measured
differential pressure to the fluid pressure and so can vary significantly as the flow rate varies,
especially at high differential pressures and low static pressures.

The equations provided in American and European national and industry standards and the
various coefficients used to differ from each other even to the extent of using different
combinations of correction factors, but many are now closely aligned and give identical results;
in particular, they use the same Reader-Harris/Gallagher (1998) equation for the coefficient of
discharge for sharp-edged orifice plates. The equations below largely follow the notation of the
international standard ISO 5167 and use SI units

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1.4 WORKING PRINCIPLE:

As the fluid approaches the orifice the pressure increases slightly and then drops suddenly as the
orifice is passed. It continues to drop until the “vena contracta” is reached and then gradually
increases until at approximately 5 to 8 diameters downstream a maximum pressure point is
reached that will be lower than the pressure upstream of the orifice. The decrease in pressure as
the fluid passes thru the orifice is a result of the increased velocity of the gas passing thru the reduced
area of the orifice. When the velocity decreases as the fluid leaves the orifice the pressure increases and
tends to return to its original level. All of the pressure loss is not recovered because of friction and
turbulence losses in the stream. The pressure drop across the orifice ( P in Fig. 1) increases when the rate
of flow increases. When there is no flow there is no differential. The differential pressure is proportional
to the square of the velocity, it therefore follows that if all other factors remain constant, then the
differential is proportional to the square of the rate of flow.

1.5 ORIFICE FLOW MEASUREMENT – HISTORY:

The first record of the use of orifices for the measurement of fluids was by Giovanni B. Venturi,
an Italian Physicist, who in 1797 did some work that led to the development of the modern
Venturi Meter by Clemons Herschel in 1886. It has been reported that an orifice meter, designed
by Professor Robinson of Ohio State University was used to measure gas near Columbus, Ohio,
about 1890. About 1903 Mr. T.B. Weymouth began a series of tests in Pennsylvania leading to
the publication of coefficients for orifice meters with flange taps. At the same time Mr. E.O.
Hickstein made a similar series of tests at Joplin, Missouri, from which he developed data for
orifice meters with pipe taps. A great deal of research and experimental work was conducted by
the American Gas Association and the American Society of Mechanical Engineers between 1924
and 1935 in developing orifice meter coefficients and standards of construction for orifice
meters. In 1935 a joint A.G.A. - A.S.M.E. report was issued title “History of Orifice Meters and
The Calibration, Construction, and Operation of Orifices For Metering.” This report is the basis
for most present day orifice meter measurement installation. An updated version of this standard
based on new data was issued in early 1991 by A.P.I. titled: Manual of Petroleum Measurement
Standards, Chapter 14, Section 3, Parts 1-4. Several additional publications are available to
simplify measurement by orifice meters. These are: ASME Fluid Meters 6th Edition, ASME

5
Power Test Code, Chapter 4 on Flow Measurement and Flow Measurement Engineering
Handbook by R.W. Miller.

1.6 FUNDAMENTAL GAS LAWS:

All matter is composed of exceedingly tiny particles called molecules A molecule is defined as
the smallest particle which can exist in the free and undecomposed state, i.e., natural gas is
composed of molecules of methane, ethane, etc. These molecules are in constant motion and it is
the impact of these molecules on the sides of a container which is measured as pressure.
Temperature regulates the speed of the molecules and therefore, an increase in temperature
increases the motion of the molecules which in turn increases the pressure. As decreased
temperature and pressure causes decreased motion of the molecules, it follows there must be
some point where there is no molecular activity. The points where there is no molecular activity
are absolute zero temperature (approximately -460°F) and absolute zero pressure (approximately
14.7 pounds per square inch below atmospheric pressure). Absolute pressure is equal to gauge
pressure plus atmospheric pressure (14.7 p.s.i.). Absolute temperature is equal to degrees
Fahrenheit (°F) plus 459.67° and is called degrees Rankin. Boyles Law states that in an ideal gas
the volume is inversely proportional to the absolute pressure. If a cylinder has a volume of gas at
an absolute pressure of 14.7 and a piston was to displace the volume in the cylinder until the
pressure reached 29.4 p.s.i., then the cylinder would contain one-half of its original volume.
Charles Law states that the volume of an ideal gas is directly proportional to the absolute
temperature. If a cylinder has a volume of gas at 60°F or 514.67° Rankin (absolute) and a piston
was used to displace the volume so as to maintain a constant pressure while the temperature was

6
doubled to the 580°F or 1039.67° Rankin (absolute) the cylinder would contain twice its original
volume.

The combined ideal Boyles and Charles Law is commonly written in the form of the equation:

P1V 1 P2V 2
=
T1 T2

When discussing a quantity of gas it is necessary to define it. We could use weight such as
pounds or ounces but it is difficult forms people to think of gas as having weight. So, the
common definition is a cubic foot at some base pressure and base temperature. The base
conditions used by most areas of the United States are 14.73 p.s.i.a. and 60°F.

1.7 DIFFERENT TYPES OF ORIFICE PLATES AND THEIR APPLICATIONS:

1.7.1 Paddle Type Orifice Plate:

1.7.1.1 Concentric bevelled bore:

Application: 
This Most Common Bore Used In The Industries. This Is The Only Type Generally Accepted
For Use In Custody Transfer Measurement, Since Adequate Data Is Not Available For Other
Bores. Used Primarily For Clean Homogeneous Liquids, Gases, Non Viscous Fluids. The Bevel
Is Matched At 45° Angle To The Desired Throat Thickness

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1.7.1.2 Restriction Bore:

Application: This Type Is Not Used For Flow Measurement But For Dropping The Pressure
Considerably And Reducing The Flow Accordingly. The Bore Is Not Beveled But Kept Straight.
The Beta Ratio Has No Limit As Accuracy Is Not The Goal.

1.7.1.3 Eccentric Bore:

Application:
Used For Measurement Of Flow For Fluids Containing Solids And Slurries. It Is Also Used For
Vapors And Gases Where Condensation Is Present. The Eccentric Bore Is Offset To Where The
Bore Edge Is Inscribed In A Circle That Is 98% The Line Id.

8
1.7.1.4 Segment Bore:

Application:

The Segmental Bore Is Located In The Same Way That The Eccentric Bore Is. This Type Is
Used Primarily For Slurries Or Extreamly Dirty Gases Wher The Flow May Contain Impurities
Heavier Than The Fluid.

1.7.1.5 Quadrant Bore:

Application:

Used For High Viscous Fluids Such As Heavy Cruid, Syrups And Slurries. It Is Always
Recommended For Flow Where Reynolds Number Is Less Than 10,000.The Inlet Is Quarter Of
A Circle And The Plate Thickness Must Be At Least Radius Of The Inlet.

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1.7.2 Ring Type Joint –Integral:

Application:

These Are Available In Oval Or Octal Shapes. Orifice Plate Is A Part Of RTJ Gasket.

A) Universal Orifice Plates

Application:

This Is A Circular Plate Designed To Fit In The Orifice Fittings / Plate Holders / Carrier Rings /
Ring Type Joints (RTJ).

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Draw backs of orifice plate

The major draw backs of orifice plates are,

(1) Maximum flow rate 4:1

(2) It is affected by upstream swirl.

(3) Large head loss.

1.8 SELECTION OF ORIFICE PLATE:

The orifice plate is widely used as a restriction in many flow applications. There are different
types of orifice plates are there depends on the applications and pipe size. In this paper the
analysis is carried out for an inner diameter of 50mm hence the square edge concentric type
orifice plate is chosen. Due to ease in easy maintenance and low cost and easy for manufacturing
and installation it is selected for analysis.

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 Chapter -2

LITERATURE SURVEY

2.1 CFD Analysis and Comparison of Fluid Flow through a Single Hole and
Multi Hole Orifice Plate:

Abstract- Flow measurement is one of the most important tasks in many industries. Even today
there does not exist a universal flow measuring instrument in many flow applications. The fluid
flow through a single hole orifice plate and multi holes orifice plate were analyzed in this paper
by using Computational Fluid Dynamics (CFD). For analysis water is used as fluid and is
allowed to pass through a pipe across the orifice plate. The geometry of the orifice plate and the
pipe section has made using CATIA V5 R20 and the model has meshed using HYPER MESH
11.0, the flow characteristics are studied using ANSYS FLUENT 6.3.26. This paper also
presents the effect of orifice holes arrangement or distribution in a plate on the performance of
flow characteristics such as flow rate, pressure drop, velocity and turbulent intensity. The
parameters used for designing the orifice plate are non standard conditions. The analysis is
carried out for four diameter ratio (d/D= 0.60, 0.30, 0.20, 0.15 for single hole, four, nine and
sixteen holes respectively). The inner diameter of the pipe used is 50 mm and the plate thickness
used for analysis is 3 mm for all the plates. The simulation results shows that multi holes orifice

12
plate have better flow characteristics compare to single hole orifice plate for the same area of
departure.

2.2 Numerical analysis of the performance characteristics of conical entrance

orifice meter:

ABSTRACT: Orifice meters are one of the most widely used flow meters in industrial
applications due to their simplicity, accuracy and economy. However, the sharp edge orifice
plates cannot be used for low Reynolds number flows, due to a large variation in discharge
coefficient with Reynolds number. Conical entrance orifice plates are developed for this purpose.
In the present study, a CFD methodology using ANSYS, FLUENT software has been adopted
for analyzing flow through conical orifice plate assemblies. The methodology has been validated
by analyzing flow through standard orifice plate assembly (as per ISO 5167). K-ω SST model is
found to be best suited for this class of problems.. The flow is assumed to be steady and
axisymmetric and the fluid is incompressible and Newtonian. The computed values of discharge
coefficient and other parameters are in excellent agreement with the values given BS 1042 as
long as operating conditions are within the specified range. The parametric study has
demonstrated that the acceptable range of Reynolds number can be extended to 50 to 106 as
compared to 80 to 80000 as specified by BS 1042.Pipe roughness does not have significant effect
on the value of discharge coefficient.

2.3 Flow characteristics of fluid and its effectiveness on orifice plate using
pneumatic proportional control:

A number of studies on effect of temperature on the flow characteristics of various fluids have
been carried out. The aim of this work was to examine the flow characteristics of hexane upon
the influence of temperature as well as the effectiveness response of orifice plate using
pneumatic proportional control. Knowledge of the past on temperature impact as one aspect of
the information set held by various scientific and a well established finding in engineering is that
changes in composition can change the effect of temperature on the flow characteristics of
hexane in a flow line system. The particular aspects of temperature impact on the research work
highlighted are density, viscosity and pressure characteristics. The effect of temperature on flow
characteristics of hexane was examined within the temperature range of 283 to 323 K and
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Bernoulli’s equation knowledge of the past was used in developing the model for this paper. The
mathematical models developed were simulated using the numerical concept of polynomial
expression of the best fit. The effects of temperature on the functional parameters were examined
and proportional gain at various error range of E = 0.1 to 0.5 were considered during the
investigation. These effects on the variation of the results were attributed to the temperature,
flow characteristics of the hexane and its effectiveness on orifice plate using pneumatic
proportional control.

2.4 Prediction of Performance Characteristics of Orifice Plate Assembly for

Non-Standard Conditions Using CFD:

Abstract—Performance characteristics of orifice plates for variation in different geometrical

parameters are analyzed with the help of computational fluid dynamics (CFD) for nonstandard
conditions with water as working fluid. In the present work, A CFD tool, ANSYS, FLUENT has
been used to predict the variation of Coefficient of Discharge (Cd) and the analysis for standard
sharp edge orifice meter has been done for different plate thicknesses (3mm, 5mm, 10mm and
15mm) in a pipe of 50mm diameter and the effect of Pipe diameter on Coefficient of Discharge
(Cd) has been studied in detail.

2.5 CFD Analysis of Flow through Dual Orifice Plate Assembly:

Abstract--Multiple stage orifice plate assemblies are used in many industrial processes as
pressure reduction devices. At present, the design of these devices is based mostly on semi
empirical correlations derived from experience. In the present study, a CFD methodology using
ANSYS, Fluent 14 software has been used for analyzing flow through multiple orifice plate
assemblies. K-ω SST model is found to be best suited for this class of problems. A parametric
study is conducted for flow analysis through dual orifice plate assemblies with equal diameter
ratios (β1 = β2 = 0.6) and unequal diameter ratios (β1 = 0.6, β2 = 0.3). The spacing between the
stages is varied in the range 1D to 7D. It is found that a spacing of 6D is sufficient for maximum
pressure reduction in case of equal diameter ratios and spacing of 4D is sufficient for unequal
diameter ratios. The effect of Reynolds number on the flow is investigated by varying it

14
systematically in the range 500 to 106. It is observed that dimensionless pressure loss gradually
increases with increase in Reynolds number although the effect is not very strong.

15
 Chapter -3
INTRODUCTION TO CAD
Throughout the history of our industrial society, many inventions have been patented and
Whole new technologies have evolved. Perhaps the single development that has impacted
Manufacturing more quickly and significantly than any previous technology is the digital
computer.
Computers are being used increasingly for both design and detailing of engineering components
in the drawing office.
Computer-aided design (CAD) is defined as the application of computers and graphics
Software to aid or enhance the product design from conceptualization to documentation. CAD
is most commonly associated with the use of an interactive computer graphics system, referred to
As a CAD system. Computer-aided design systems are powerful tools and in the mechanical
Design and geometric modeling of products and components.
There are several good reasons for using a CAD system to support the engineering design
Function:
 To increase the productivity
 To improve the quality of the design
 To uniform design standards
 To create a manufacturing data base
 To eliminate inaccuracies caused by hand-copying of drawings and inconsistency
between
 Drawings

3.1 CAD/CAM Software:

Software allows the human user to turn a hardware configuration into a powerful design and
Manufacturing system. CAD/CAM software falls into two broad categories,2-D and 3-D,
based on the number of dimensions are called 2-D representations of 3-D objects is inherently
confusing. Equally problem has been the inability of manufacturing personnel to properly read

16
and interpret complicated 2-D representations of objects. 3-D software permits the parts to be
viewed with the 3-D planes-height, width, and depth-visible. The trend in CAD/CAM is toward
3-D representation of graphic images. Such representations approximate the actual shape and
appearance of the object to be produced; therefore, they are easier to read and understand.

3.2 INTRODUCTION TO FEA:

Finite Element Analysis (FEA) was first developed in 1943 by R. Courant, who utilized the Ritz
method of numerical analysis and minimization of variational calculus to obtain approximate
solutions to vibration systems. Shortly thereafter, a paper published in 1956 by M. J. Turner, R.
W. Clough, H. C. Martin, and L. J. Top established a broader definition of numerical analysis.
The paper centered on the "stiffness and deflection of complex structures".

By the early 70's, FEA was limited to expensive mainframe computers generally owned by the
aeronautics, automotive, defense, and nuclear industries. Since the rapid decline in the cost of
computers and the phenomenal increase in computing power, FEA has been developed to an
incredible precision. Present day supercomputers are now able to produce accurate results for all
kinds of parameters.

FEA consists of a computer model of a material or design that is stressed and analyzed for
specific results. It is used in new product design, and existing product refinement. A company is
able to verify a proposed design will be able to perform to the client's specifications prior to
manufacturing or construction. Modifying an existing product or structure is utilized to qualify
the product or structure for a new service condition. In case of structural failure, FEA may be
used to help determine the design modifications to meet the new condition.

There are generally two types of analysis that are used in industry: 2-D modeling, and 3-D
modeling. While 2-D modeling conserves simplicity and allows the analysis to be run on a
relatively normal computer, it tends to yield less accurate results. 3-D modeling, however,
produces more accurate results while sacrificing the ability to run on all but the fastest computers
effectively. Within each of these modeling schemes, the programmer can insert numerous
algorithms (functions) which may make the system behave linearly or non-linearly. Linear
systems are far less complex and generally do not take into account plastic deformation. Non-

17
linear systems do account for plastic deformation, and many also are capable of testing a material
all the way to fracture.

FEA uses a complex system of points called nodes which make a grid called a mesh. This mesh
is programmed to contain the material and structural properties which define how the structure
will react to certain loading conditions. Nodes are assigned at a certain density throughout the
material depending on the anticipated stress levels of a particular area. Regions which will
receive large amounts of stress usually have a higher node density than those which experience
little or no stress. Points of interest may consist of: fracture point of previously tested material,
fillets, corners, complex detail, and high stress areas. The mesh acts like a spider web in that
from each node, there extends a mesh element to each of the adjacent nodes. This web of vectors
is what carries the material properties to the object, creating many elements.

A wide range of objective functions (variables within the system) are available for minimization
or maximization:

 Mass, volume, temperature

 Strain energy, stress strain
 Force, displacement, velocity, acceleration
 Synthetic (User defined)

There are multiple loading conditions which may be applied to a system. Some examples are
shown:

 Point, pressure, thermal, gravity, and centrifugal static loads

 Thermal loads from solution of heat transfer analysis
 Enforced displacements
 Heat flux and convection
 Point, pressure and gravity dynamic loads

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Each FEA program may come with an element library, or one is constructed over time. Some
sample elements are:

 Rod elements
 Beam elements
 Plate/Shell/Composite elements
 Shear panel
 Solid elements
 Spring elements
 Mass elements
 Rigid elements
 Viscous damping elements

Many FEA programs also are equipped with the capability to use multiple materials within the
structure such as:

 Isotropic, identical throughout

 Orthotropic, identical at 90 degrees
 General anisotropic, different throughout

3.3 Types of Engineering Analysis:

3.3.1 Structural: analysis consists of linear and non-linear models. Linear models use simple
parameters and assume that the material is not plastically deformed. Non-linear models consist of
stressing the material past its elastic capabilities. The stresses in the material then vary with the
amount of deformation as in.

3.3.2 Vibrational: analysis is used to test a material against random vibrations, shock, and
impact. Each of these incidences may act on the natural vibrational frequency of the material
which, in turn, may cause resonance and subsequent failure.

Fatigue analysis helps designers to predict the life of a material or structure by showing the
effects of cyclic loading on the specimen. Such analysis can show the areas where crack

19
propagation is most likely to occur. Failure due to fatigue may also show the damage tolerance
of the material.

3.3.3 Heat Transfer: analysis models the conductivity or thermal fluid dynamics of the material
or structure. This may consist of a steady-state or transient transfer. Steady-state transfer refers to
constant thermo properties in the material that yield linear heat diffusion.

3.4 Results of Finite Element Analysis:

FEA has become a solution to the task of predicting failure due to unknown stresses by showing
problem areas in a material and allowing designers to see all of the theoretical stresses within.
This method of product design and testing is far superior to the manufacturing costs which would
accrue if each sample was actually built and tested.
In practice, a finite element analysis usually consists of three principal steps:

3.4.1 Pre-processing: The user constructs a model of the part to be analyzed in which the
geometry is divided into a number of discrete sub regions, or elements," connected at
discrete points called nodes." Certain of these nodes will have fixed displacements, and
others will have prescribed loads. These models can be extremely time consuming to
prepare, and commercial codes vie with one another to have the most user-friendly
graphical “preprocessor" to assist in this rather tedious chore. Some of these
preprocessors can overlay a mesh on a preexisting CAD file, so that finite element
analysis can be done conveniently as part of the computerized drafting-and-design
process.

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3.4.2 Post-processing: In the earlier days of finite element analysis, the user would pore
through reams of numbers generated by the code, listing displacements and stresses at
discrete positions within the model. It is easy to miss important trends and hot spots this
way, and modern codes use graphical displays to assist in visualizing the results. A
typical post-processor display overlay colored contours representing stress levels on the
model, showing a full field picture similar to that of photo elastic or moiré experimental
results.
3.5 INTRODUCTION TO ANSYS:

ANSYS is general-purpose finite element analysis (FEA) software package.  Finite Element
Analysis is a numerical method of deconstructing a complex system into very small pieces (of
user-designated size) called elements. The software implements equations that govern the
behaviour of these elements and solves them all; creating a comprehensive explanation of how
the system acts as a whole. These results then can be presented in tabulated or graphical forms. 
This type of analysis is typically used for the design and optimization of a system far too
complex to analyze by hand.  Systems that may fit into this category are too complex due to their
geometry, scale, or governing equations. 

ANSYS is the standard FEA teaching tool within the Mechanical Engineering Department at
many colleges. ANSYS is also used in Civil and Electrical Engineering, as well as the Physics
and Chemistry departments. 

ANSYS provides a cost-effective way to explore the performance of products or processes in a

virtual environment. This type of product development is termed virtual prototyping.  

With virtual prototyping techniques, users can iterate various scenarios to optimize the product
long before the manufacturing is started. This enables a reduction in the level of risk, and in the
cost of ineffective designs. The multifaceted nature of ANSYS also provides a means to ensure
that users are able to see the effect of a design on the whole behavior of the product, be it
electromagnetic, thermal, mechanical etc.

21
3.6 Generic Steps to Solving any Problem in ANSYS:

Like solving any problem analytically, you need to define (1) your solution domain, (2) the
physical model, (3) boundary conditions and (4) the physical properties. You then solve the
problem and present the results. In numerical methods, the main difference is an extra step called
mesh generation. This is the step that divides the complex model into small elements that
become solvable in an otherwise too complex situation. Below describes the processes in
terminology slightly more attune to the software.

3.6.1 Build Geometry:

Construct a two or three dimensional representation of the object to be modeled

and tested using the work plane coordinate system within ANSYS. 

3.6.2 Define Material Properties:

Now that the part exists, define a library of the necessary materials that compose
the object (or project) being modeled.  This includes thermal and mechanical
properties. 

3.6.3 Generate Mesh:

At this point ANSYS understands the makeup of the part.  Now define how the
modeled system should be broken down into finite pieces.  

3.6.4 Apply Loads:

Once the system is fully designed, the last task is to burden the system with
constraints, such as physical loadings or boundary conditions.           

3.6.5 Obtain Solution:

This is actually a step, because ANSYS needs to understand within what state
(steady state, transient… etc.) the problem must be solved. 

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 3.6.6 Present the Results:

After the solution has been obtained, there are many ways to present ANSYS’
results, choose from many options such as tables, graphs, and contour plots. 

3.7 SPECIFIC CAPABILITIES OF ANSYS:

3.7.1 Structural:

Structural analysis is probably the most common application of the finite element method as it
implies bridges and buildings, naval, aeronautical, and mechanical structures such as ship hulls,
aircraft bodies, and machine housings, as well as mechanical components such as pistons,
machine parts, and tools. 

·         Static Analysis - Used to determine displacements, stresses, etc. under static loading
conditions. ANSYS can compute both linear and nonlinear static analyses. Nonlinearities
can include plasticity, stress stiffening, large deflection, large strain, hyper elasticity,
contact surfaces, and creep. 

·         Transient Dynamic Analysis - Used to determine the response of a structure to

arbitrarily time-varying loads. All nonlinearities mentioned under Static Analysis above
are allowed. 

·         Buckling Analysis - Used to calculate the buckling loads and determine the buckling
mode shape. Both linear (eigenvalue) buckling and nonlinear buckling analyses are
possible.  

3.7.2 Thermal:

ANSYS is capable of both steady state and transient analysis of any solid with thermal boundary
conditions. Steady-state thermal analyses calculate the effects of steady thermal loads on a
system or component. Users often perform a steady-state analysis before doing a transient
thermal analysis, to help establish initial conditions. A steady-state analysis also can be the last
step of a transient thermal analysis; performed after all transient effects have diminished.
ANSYS can be used to determine temperatures, thermal gradients, heat flow rates, and heat

23
fluxes in an object that are caused by thermal loads that do not vary over time. Such loads
include the following: 

·         Convection

·         Radiation

·         Heat flow rates

·         Heat fluxes (heat flow per unit area)

·         Heat generation rates (heat flow per unit volume)

·         Constant temperature boundaries 

A steady-state thermal analysis may be either linear, with constant material properties; or
nonlinear, with material properties that depend on temperature. The thermal properties of most
material vary with temperature. This temperature dependency being appreciable, the analysis
becomes nonlinear. Radiation boundary conditions also make the analysis nonlinear. Transient
calculations are time dependent and ANSYS can both solve distributions as well as create video
for time incremental displays of models.

3.7.3 Fluid Flow:

The ANSYS/FLOTRAN CFD (Computational Fluid Dynamics) offers comprehensive tools for
analyzing two-dimensional and three-dimensional fluid flow fields.  ANSYS is capable of
modeling a vast range of analysis types such as: airfoils for pressure analysis of airplane wings
(lift and drag), flow in supersonic nozzles, and complex, three-dimensional flow patterns in a
pipe bend.  In addition, ANSYS/FLOTRAN could be used to perform tasks including:  

·       Calculating the gas pressure and temperature distributions in an engine exhaust

manifold

·        Studying the thermal stratification and breakup in piping systems

24
 ·         Using flow mixing studies to evaluate potential for thermal shock

·         Doing natural convection analyses to evaluate the thermal performance of chips in
electronic enclosures

·         Conducting heat exchanger studies involving different fluids separated by solid
regions

  

3.7.4 Coupled Fields:

A coupled-field analysis is an analysis that takes into account the interaction (coupling) between
two or more disciplines (fields) of engineering. A piezoelectric analysis, for example, handles the
interaction between the structural and electric fields: it solves for the voltage distribution due to
applied displacements, or vice versa. Other examples of coupled-field analysis are thermal-stress
analysis, thermal-electric analysis, and fluid-structure analysis. 

Some of the applications in which coupled-field analysis may be required are pressure vessels
(thermal-stress analysis), fluid flow constrictions (fluid-structure analysis), induction heating
(magnetic-thermal analysis), ultrasonic transducers (piezoelectric analysis), magnetic forming
(magneto-structural analysis), and micro-electro mechanical systems (MEMS).

3.7.5 Modal Analysis - A modal analysis is typically used to determine the vibration
characteristics (natural frequencies and mode shapes) of a structure or a machine component
while it is being designed. It can also serve as a starting point for another, more detailed,
dynamic analysis, such as a harmonic response or full transient dynamic analysis.

Modal analyses, while being one of the most basic dynamic analysis types available in ANSYS,
can also be more computationally time consuming than a typical static analysis.  A reduced
solver, utilizing automatically or manually selected master degrees of freedom is used to
drastically reduce the problem size and solution time.

25
3.7.6 Harmonic Analysis - Used extensively by companies who produce rotating machinery,
ANSYS Harmonic analysis is used to predict the sustained dynamic behavior of structures to
consistent cyclic loading.  Examples of rotating machines which produced or are subjected to
harmonic loading are:

 Turbines
o Gas Turbines for Aircraft and Power Generation
o Steam Turbines
o Wind Turbine
o Water Turbines
o Turbo pumps
 Internal Combustion engines
 Electric motors and generators
 Gas and fluid pumps
 Disc drives

A harmonic analysis can be used to verify whether or not a machine design will successfully
overcome resonance, fatigue, and other harmful effects of forced vibrations.

3.8 INTRODUCTION TO CFD:

Computational fluid dynamics, usually abbreviated as CFD, is a branch of fluid mechanics that
uses numerical methods and algorithms to solve and analyze problems that involve fluid flows.
Computers are used to perform the calculations required to simulate the interaction of liquids and
gases with surfaces defined by boundary conditions. With high-speed supercomputers, better
solutions can be achieved. Ongoing research yields software that improves the accuracy and
speed of complex simulation scenarios such as transonic or turbulent flows. Initial experimental
validation of such software is performed using a wind tunnel with the final validation coming in
full-scale testing, e.g. flight tests.

26
3.9 CFD ANALYSIS OF ORIFICE PLATE:

The orifice plate is very inexpensive for it is just a flat plate and thin orifice plate. The flow
through conventional single hole, six holes, eight holes and twelve holes orifice meter and
integrated CFD simulation with measurements .CFD tools are also widely used in modelling and
analysing orifice plates.

3.10 CASE 1-SINGLE HOLE:

3.10.1 CONDITION 1- AT REYNOLDS NUMBER-6000

3.10.2 Single hole at Reynolds number 6000

3.10.3 STATIC PRESSURE:

27
According to the above contour plot, the maximum static pressure inlet of the tube at one end of
the tube because the applying the boundary conditions at inlet of the tubes and minimum static
pressure at the outlet of the tube.

According to the above contour plot, the maximum pressure is 9.49e+02Pa and minimum
static pressure is 4.75e-+01Pa.

3.10.4 VELOCITY MAGNITUDE:

28
According to the above contour plot, the maximum velocity magnitude of the water at inlet and
outlet of the inside boundaries, because the applying the boundary conditions at inlet of the tube
and minimum velocity magnitude at outside of the tubes.
According to the above contour plot, the maximum velocity is 6.05m/s and minimum velocity
is 3.1e+00m/s.

3.10.5 TURBULENCE INTENSITY:

According the counter plot, the intensity factor maximum tube and orifice plate.(41.8%).

29
3.11 CONDITION 2- AT REYNOLDS NUMBER-8000:

3.11.1 STATIC PRESSURE:

3.11.2 VELOCITY MAGNITUDE:

30
3.11.3 TURBULENCE INTENSITY:

3.12 CONDITION 3- AT REYNOLDS NUMBER-10000:

3.12.1 STATIC PRESSURE:

31
3.12.2 VELOCITY MAGNITUDE:

3.12.3 TURBULENCE INTENSITY:

32
CASE 2-SIX HOLES

3.13 CONDITION 1- AT REYNOLDS NUMBER-6000:

3.13.1 IMPORTED MODEL:

3.13.2 STATIC PRESSURE:

33
3.13.3 VELOCITY MAGNITUDE:

3.13.4 TURBULENCE INTENSITY:

34
CASE 2-TEN HOLES

3.14 CONDITION 1- AT REYNOLDS NUMBER-6000:

3.14.1 IMPORTED MODEL:

3.14.1 STATIC PRESSURE:

35
3.14.2 VELOCITY MAGNITUDE:

3.14.3 TURBULENCE INTENSITY:

36
RESULTS OF SINGLE HOLE

Reynolds number Pressure(Pa) Velocity(m/s) Turbulent

intensity(%)
6000 9.49e+02 6.05e+00 4.18e+01
8000 1.64e+03 8.07e+00 5.43e+01
10000 2.50e+03 1.02e+01 6.64e+01

RESULTS OF SIX HOLE

Reynolds number Pressure(Pa) Velocity(m/s) Turbulent

intensity(%)
6000 9.30e+02 6.06e+00 4.19e+01
8000 1.75e+03 8.59e+00 5.71e+01
10000 2.65e+03 1.05e+00 6.91e+01

RESULTS OF TEN HOLES

Reynolds number Pressure(Pa) Velocity(m/s) Turbulent

intensity(%)
6000 9.91e+02 6.25e+00 4.30e+01
8000 1.82e+03 8.61e+00 5.78e+01
10000 2.66e+03 1.01e+00 6.99e+01

37
PRESSURE PLOT

3.00E+03

2.50E+03

2.00E+03

SINGLE HOLE
1.50E+03
6 HOLES
8 HOLES
1.00E+03

5.00E+02

0.00E+00
6000 8000 10000

VELOCITY PLOT

1.00E+01

9.00E+00

8.00E+00

7.00E+00

6.00E+00
SINGLE HOLE
5.00E+00
6 HOLES
4.00E+00 8 HOLES

3.00E+00

2.00E+00

1.00E+00

0.00E+00
6000 8000 10000

TURBULENT INTENSITY

38
1.00E+01

9.00E+00

8.00E+00

7.00E+00

6.00E+00
SINGLE HOLE
5.00E+00
6 HOLES
4.00E+00 8 HOLES

3.00E+00

2.00E+00

1.00E+00

0.00E+00
6000 8000 10000

CONCLUSION

39
In this thesis, an orifice plates with different geometry were designed and compared on the basis
of their coefficient of discharge. This was done with the help of simulations done with k-ε and
model on CFD as a solver. Simulations were carried out on a single hole, perforated (6 holes, 10
holes) at different Reynolds’s numbers (6000, 8000 and 10000).

By observing the CFD analysis results, the pressure and turbulent intensity increases by
increasing the orifice plate holes and Reynolds numbers.

REFERENCES

40
1. www.rototherm.co.uk. British rototherm co. LtdKenfig Industrial Estate, Margarm, Port Talbot, SA13
2PW, United KingdomT:+44 (0)1656740551 E:sales@rototherm.co.uk.

2.H.J.Imada, F. Saltara, J. L. Balino “Numerical determination of discharge coefficients of Orifice plates

and nozzles”, 22nd International Congress of Mechanical Engineering (COBEM 2013), Ribeirao, SP,
Brazil, pp 1755-1760, November 3-7, 2013,.

3. Manmatha K. Roul Sukanta K. Dash “Single-Phase and Two-Phase Flow Through Thin and Thick
Orifices in Horizontal pipes” Journal of Fluid Engineering, ASME, Vol:134, pp 1-14, Sep 2012.

4. Mohamed A. Siba1, Wan Mohd Faizal Wan Mahmood, Mohd Z. Nuawi, Rasidi Rasani, and Mohamed
H. Nassir, “Wall Pressure Due to Turbulent Flow Through Orifice Plate” International Journal of
Mechanical & Mechatronics Engineering, IJMME-IJENS Vol:15, pp 36-41, 2014

5. R. Kis, M. Malcho, M. Janovcova “A CFD Analysis of Flow through a High-Pressure Natural Gas
Pipeline with an Undeformed and Deformed Orifice Plate”. World Academy of Science, Engineering and
Technology. International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing
Engineering Vol:8, pp 604-607, 2014

6. Aaron Xavier Fernandes “Computational Fluid Dynamics Analysis for Wastewater Floc Breakage in
Orifice Flow” Chemical Engineering and Applied Chemistry University of Toronto in 2012

7. Andrej Lipej, Rok Pavlin, Aljaz Skerlavaj, Bogdan Jancar, Matjaz Cernec Turboinstitut, Franci vehar,
D D Rovsnikova, Ljubljana, Slovenia “Numerical and experimental design of multi-stage orifice FWRO-
004” 22nd International Conference Nuclear Energy for New Europe, NENE, pp 229.1-229.8 Sep 9-12
2013

8. T Sridevi, Dhana Sekhar, V Subrahmanyam “Comparision of flow analysis through a different

geometry of flowmeters using fluent software”. International Journal of Research in Engineering and
Technology eissn: 2319-1163 pissn: 2321-7308, pp 141-149, Vol:3 Aug-2014

9. Manish S. Shah , Jyeshtharaj B. Joshi 1, Avtar S. Kalsi, C.S.R. Prasad, Daya S. Shukla. “Analysis of
flow through an orifice meter: CFD simulation”, Chemical Engineering Science, Volume 71, pp 300-309,
2012

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