Introduction to CFD and its Applications in Fluid Dynamics

CFD
[Document subtitle]
APRIL 22, 2018

Table of Contents
1. Flow through pipes.
2. Introduction to CFD.
3. Introduction of CFD in fluid dynamics.
4. Advantages of CFD
5. Disadvantages of CFD
6. Future of CFD
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1. Flow through pipe
A flow is said to be pipe flow if the flow is under full depth condition. In pipe flow there tre two different
types of losses generally takes place:-
a. Major losses:- They are due to viscous resistance through the wall. They have high magnitude and
there occurrences are more. They are also known as constant velocity loss.
b. Minor losses:- They are due to change in momentum of the fluid i.e. due to velocity either due to
magnitude or direction or both. There occurrence is less as well as have less magnitude.
Ex. Sudden loss, exit loss, sudden contraction loss, entrance loss, bend loss and different pipe filling
losses.
Apart from this concept of friction factor plays an important role in the pipe flow. There is proper formula
derived for obtaining value of friction factor for laminar flow as well as for turbulent flow. Friction factor
also depends upon the roughness as well as smoothness of the pipe surface or the body surface over which
fluid has to flow. But there are some situations where it is not easy to determine the value of friction factor
and it is important to know the value of friction factor because it directly tell us about the value of loss that
encounter during the fluid flow. Therefore to overcome this situational problem Moody Diagram plays an
important role.
2. Introduction to CFD
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.
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 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
CFD enables us to utilize its tools more in day today automobile and aircraft design and also helps in solving
the fluid flow problems.. CFD applications in the any industries have large number of codes available for
designing of any product. There are several applications ranging from system - level (e.g., exterior
aerodynamics) to the components - level (e.g., disk brake cooling).
3. Introduction of CFD in fluid dynamics
Study of motion of the fluid with reference of forces and moments is known as fluid dynamics. In fluid flow
there different types of forces occurs in the flow like viscous forces, gravitational forces, pressure forces,
surface tension forces, eddy forces (turbulent forces) and different type of other forces.
All CFD in one form is based on governing equations of fluid dynamics- the continuity equation,
momentum equations and energy equations.
 Conservation of mass.
 Newton’s second law i.e. F=ma.
 Conservation of energy.
In fluid flow velocity is function of space and time, so the acceleration is the function of space and
time. Space component is known as convective acceleration and time component is known as local
acceleration. During the ANSYS analysis the above acceleration place an important role and help the
engineer to make proper aerodynamic design of the vehicle. This is so because the acceleration and
velocity component are responsible for lift and drag of the vehicle. Improper design leads to create
serious lift of vehicle and this may results in serious accident. Inorder to avoid this impact in the
absence of physical prototype graphically the prototype is designed and is tested through computer
itself by the use of ANSYS and employing Computational Fluid Dynamics theory.
Apart from the above concept some terms need to be described which will helps to validate the whole
analysis:-
1. Flow Lines:- Fluid flow can be described by 3 flow lines
 Stream line:- It is an imaginary line or curve drawn in space such that tangent drawn gives
velocity vector i.e. velocity vector and stream line vector coincides. The two streamlines
never intersect each other as well as stream line also never intersects itself because at the
point of intersection there will be two velocity fields which is impossible. So there is no flow
across the streamlines.
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