CFD the fluid motion. Second, problem is set

CFD Analysis Process

There
are few main components of CFD design cycle. Below are the following important
steps:

 

1.     Problem
statement

First, states the problem to be solved and identify
the flow problems. Notice the physical phenomenon need to be considered in this
analysis. Besides, create the geometry of the object (domain) and those
necessary operating conditions. After that, notice the internal obstacles,
internal-surface and free surface of the object. Identify the type of flow
whether it’s laminar, turbulent or it’s a steady or unsteady flow.

 

2.     Mathematical
model

First, a proper flow model, good viewpoint and
reference frame are chosen. Identify the forces that influence the fluid
motion. Second, problem is set with the computational domain. Writes out all
the related formula for the conservation law of mass, momentum and energy.
Furthermore, equation is simplified for reducing the computational effort.
Lastly, specify those necessary boundary conditions.

 

3.     Discretization
method

First, Partial differential equations system (PDE) is
transformed into a set of algebraic equations. Through this, it is created
become approximately, become discretized versions and because of those small
part element. It became more easily to be solved. In fact, there are many ways
to discretize the partial equations but in the end. The goal of all the methods
are the same, that is turn a calculus problem that human cannot solve into an
algebra problem which human can solve. 
Below is some example of discretizing method:

·      
Discretization of spatial
volumes through finite difference, finite element and finite volume.

·      
Discretization of grid
topology through structured, unstructured cartesian and generalized
unstructured.

 

4.     CFD
Simulation

First, once the object in 2D geometry such as
representative cross section is created. It is necessary to
familiar those parameters in the simulation.
Once simulate it, there are something that can obtained from this simulation.
For example, investigation of effect of fluid properties on the overall object,
what proper meshing and what appropriate boundary layer meshing to be used and
estimate the accuracy that expected from a 3D model. Furthermore, the quality
of simulation results based on some few factors such as assumptions made before
the simulation, mathematical model and quality, size of mesh and so on.

 

5.     Post
processing

After CFD Simulation, the next step is to extract the
important information from the computed flow field. The important information
such as the calculation of derived quantities and integral parameters,
verification of CFD model and visualization of 1D, 2D and 3D value.

 

6.     Error
and uncertainty

Results of CFD simulation is depends on the
accumulation of error and the level of variability. The source of causing
uncertainty is might be not enough of knowledge about CFD. Error might be cause
by other reasons. If comparing both of it. Error is more easily to find out compare
to uncertainty. This is because, error have many ways to determine, estimating
and solving them. But for uncertainty, there is no proper way to find it out
because it is because of lack of knowledge about CFD. So, it might remain the
problem that undiscovered ever and in the end. It might also cause other
different big problems.  (Patel, 2013)  

 

 

 

 

Advantages of CFD

Again,
Computational Fluid Dynamics (CFD) is a software or can be said as system to
predict the fluid flow, heat transfer, mass transfer, chemical reaction and so
on. Furthermore, there are a lot of benefits about it. First, development cost.
It is very expensive that using real or physical experiments and tests to get
some important engineering data for design purpose. Thus, this software is used
to get those important data and it is relatively inexpensive in cost. Data get
from CFD sometime is more accurate as it is using computer to calculate.
Second, execution time. CFD simulation can run or so call test in a short
period of time, this make engineering data introduced early before the design
process. Third, overall data. Experiments or tests can only get those data in
limited location and it is not so detailed, but CFD allows to get more precise
data and it is very comprehensive. Lastly, simulation under many conditions. In
real experiment, some fluid flow or heat transfer process cannot be easily
control or tested under different kind of conditions. But in CFD, it provides
this ability.  

 

Disadvantages of CFD

Even
though there are a lot of advantages about CFD. However, there are also have
disadvantages of it. First, for an CFD investor, they have no power to vote or
say in an engineering company since CFD is not their underlying asset. Second,
for CFD system, it is very hard to get a perfect grid for a complex geometry,
sometimes it can but very time consuming. Besides, it is also very difficult to
get the accurate flow motion result over the whole thing in simulation. This is
because, those data required a good quality in grid session, perfect grid is
very hard to get for a complex geometry. Lastly, this system is not so friendly
to all people and it is quite complicated to be used as well. Thus, it has to
take a long time to keep one practice in how to use this software and how to
analyse the results.

 

 

 

 

 

 

Application of CFD

Computational
Fluid dynamic can be used in many ways for predicting the important data to
design something. Below are some examples of application of CFD:

·      
Smoke control system

·      
Classroom

·      
Swimming pool ventilation

·      
Aerospace

·      
Automotive

·      
Electronic

 

In
fact, there are still a lot of application about CFD but not necessary to show
all of it. Smoke control system is one of the most common usage of CFD
application. CFD has the capability to simulate the smoke flow in a space with
complex geometry. This idea is keeping the smoke away from the objects or to be
said as occupants for saving their life when accident happens. From here shows
that, why CFD is so important in simulation before designing the building for
safety issues. (Saeidi,
1998)

 

   

                              Figure 2                                                                 Figure
3

 

Figure
2 shows the smoke away from the building when accident happens. Figure 3 shows
it’s result of simulation in CFD.