CFD in Automobile and Engine Applications: An Introduction to Computational Fluid Dynamics

CFD
[Document subtitle]
MARCH 13, 2018

Table of Contents
1. Objective of simulation.
2. Introduction to CFD.
3. CFD in automobile and engine applications.
4. Introduction of CFD in fluid dynamics.
5. Aim of the simulation
6. Methodology Adopted
7. Procedure
8. Analysis Environment
9. Size of Computational Domain
10. Meshing the Model
11. Engineering Database
12. Results
13. Advantages of CFD
14. Disadvantages of CFD
15. Future of CFD
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General Information
1. Objective of the simulation:-Test the car Body in the Environment (aerodynamic) of a car.
Introduction:- In recent years we have seen a rapid increase in the use of computers for engineers in solving
the problems. In the same contrast particularly Computational Fluid Dynamics (CFD) is true subject for the
problem solving that involves fluid heat transfer and fluid flow which occur in applications related
aerospace, power sector and automobile industry. The various factors that are the reasons for the
development of CFD are:-
 Growth in the complexity of the engineering problems that can be unsolved in manual way.
 Need of quick solution with moderate accuracy.
 The expenses that an industry bears during laboratory experiment of physical prototype.
 The absence of analytical solutions.
 Exponential growth in the number crunching abilities and rigorous computer speed and its memory.
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CFD plays a vital role to influence the design of automobile components because of
continuous advancement in computer hardware and software including advancement
in the numerical technique-s in order to derive results from the various equations
which are related to the fluid-flow mechanism. The automobile industry has a keen
interest in CFD. It is considered that CFD contains huge potential to significantly
improve design of the cars and other automobile and at the same time it can reduce
the cost of product and life cycle time and the day came CFD has brought revolution
in field of automotive design. CFD enables us to utilize its tools more in day today
automobile and aircraft design. We can better estimate the conditions for which CFD
applications can be used in the up-coming period of years. CFD applications in the any
industries have large number ofcodes available for designing of any product. There
are several applications in various portions which ranges from system - level (e.g.,
external aerodynamics) to the individual components - level (e.g., cooling system of
disk break). The physics that is associated covering the variety of ranges of flow
regimes like as incompressible flow, laminar flow, compressible flow, turbulent flow,
unsteady flow, steady flow, subsonic flow and transonic flow. A major portion of the
applications of CFD comes under the range which can not be compressed and rest of
those are in the turbulent flows. The fact is most of the flows which can be seen in
reality are actually unsteady type flow in nature but maximum of them can be
adjudged as steady flow cases. Today the major problem is to execute the simulation
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accurately and precisely some of the complicated thermo-fluids phenomenon’s, and to
be capable of obtaining CFD quicker results to efficiently implement them in the
“dynamic” design scenario of frequently changing designs. The general ideais to use
and utilize CFD in the primary phases of designing in order to fix the design change-s
and to optimize the process. The proper use and implementation of CFD results in
user to more significantly decrease need of doing prototyping and consequently,
reduces cost of design and cycle time associated to it.[2]
2. Introduction to CFD:-
Question: What is CFD? CFD is fundamentally defined as a physical quality of any fluid - flow that
is having three governing fundamental principles:-
 Conservation of mass for the fluid.
 Newton’s Second Law :- According to the law “the rate of the change of momentum is
directly proportional to the force applied and this rate of change of momentum is directly
proportional to the applied force and in the direction of the applied force”.
 Law of conservation of energy- The law which, is the first law of thermodynamics and it
states that “the summation of the rate of change of heat addition must be equal to the work
done on the fluid”.
In order to continue the understanding of CFD the person must first understand the fluid dynamics and its
governing equation.
The Computational Fluid Dynamics equations can be derived in two stages.
 First stage is the numerical discretization.
 Second stage is the specific technique.
The above two stages are used to solve the algebraic equations which is derived from
the governing equations.
2.1. Discretization :-Thediscretization process are identified by some
fundamental processes that we are still using now a days. The two most
common methods are the finite-element and spectral methods.
2.1.1. Finite Element Method
The finite element method is the oldest method among all methods which are applied
in solving the numerical solution derived from partial differential equations. This
method was derived by a famous scientist Euler in year 1768. This method is applied
to obtain numerical solutions ofthe differential equations by manual calculating it i.e.
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by hand calculation. In this methodat a number of grids/elements are defined with
their respective nodal points. Each grid with the number of nodal points are used in
order to demonstrate the particular domain of fluid - flow. Thereafter the concept of
Taylor series expansion is applied in-order to generate finite type of difference
approximation-s to the partial derivatives of the equations which govern. These
derivatives are then alternated by using finite-difference approximations and theseall
results in forming an algebraic equation which describes the flow solution at each of
the grid point. This method is most commonly used in grids which are structured as it
just takes a mesh which contains a high degree of regularity and accuracy. From all
above discussion Finite Element Method can be summarized in three basic features:-
1. Bifurcate the whole body / structure into parts, finite element.
2. For each representative elements create the relations among secondary and
primary variable.
3. Assemble of the elements to obtain the relations in form of equation or a matrix
between the secondary and primary variables.
As per discretization is concerned the two compatibility conditions must be ensured:-
1. Compatibility of nodal displacement:- When a body is deformed without
breaking, no crack appears in stretching and particles do not penetrates each
other in elements. Such situation is called Nodal displacement compatibility. The
compatibility condition confirms that the displacement is continuous and single
value function of position.
2. Equilibrium of forces:- The equilibrium at the nodal forces must be ensured.
It is a fact that there are ample number of commercial purpose codes and research
codes those are available and they can be employed but the in finite-element
method CFD application is not so much fruitful. But apart from this there is one
method which is in brief same as finite element method and is seems fruitful and
commercially uses all codes and is essentially used by CFD. The method is called
“Finite - Volume Method (FVM)”. The main separating feature is that FVM utilizes
straightforward piecewise polynomial capacities for nearby elements which has a
tendency to portray the varieties of the unknown stream factors. The weighted
residial idea is acquainted all together to do the assessment of the mistakes
related with the estimated capacities, which are later without a doubt limited. An
arrangement of non-direct mathematical conditions for the obscure terms of the
approximating capacities is solved, subsequently bringing about the stream
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arrangement. The leftover capacities are explained and the stream arrangements
are obtained by, Collocation technique, Galerkin’s method, Sub-domain technique,
and least square method.
Spectral method
Spectral method has a fundamental approach which is same as that of the finite-
difference and finite-element methods, where the unknown factors of the
equations that are governed are changed with some short series.The difference lies
is in only the method which is implemented. The two prior methods uses local
approximations where as in the contradiction the spectral method implements
global approximation. That is by means of Fourier series, Legendre polynomials, for
the whole domain of the flow. The conflict between the exact solution and the
approximate solution is handled by using a weighted residuals concept which is
almost same as of the finite-element method.
Computational Fluid Dynamics can be defined as a procedure of replacing the partial or the integral
derivatives which are used in the equations with discrete algebraic forms, which are calculated to get
specific values for the fluid flow field values at some discrete points in time or space. At the end of it as a
result, the product of CFD will have a series of numerical values, in contradiction to a closed form analytical
solution. However, as long term result of it, the principle aim of most of the analysis done in engineering
analyses, closed type of analyses or otherwise, is a quantitative illustration of the problem statement, i.e.,
numbers.
The apparatus which has allowed the applied advance of CFD contains a high speed computer with great
efficiency. CFD solutions mainly requires the repetitive abetment of thousands or even up to some millions
of digits, an assignment that is absurd for any person after the aid of a high performance computer.
Therefore, advance in CFD, and its applications to problems of added detail and sophistication, are carefully
accompanying to advances in computer hardware, decidedly in attention to accumulator and beheading
speed. This is why the arch force active the development and construction of high speed new
supercomputers are advancing from CFD set.
Computational Fluid Dynamics is basically defined as a process of analysis of such systems that includes
fluid flow, transfer of heat and some otherphenomenon related to it such as some chemical reactions which
can be shown by the means computer simulations. It can be also the by-product of Computational
Continuum Mechanics which is the primary numerical simulation technology which is identical and is used
for many combination of similar partial differential equations such as
 Numerical stress analysis,
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