PART 2

Point A : L/D2=

0.2 (got backflow at pressure outlet)

Point B : L/D2=

0.35 (no backflow at pressure outlet)

Point C : L/D2= 0.

5 (no backflow at pressure outlet)

Point D : L/D2 = 0.65(no

backflow at pressure outlet)

Point E : L/D2= 0.

8 (no backflow at pressure outlet)

Point

F= L/D2= 0. 95 (no backflow at pressure outlet)

Point

G = L/D2= 1 (no backflow at pressure outlet)

Point H: =

L/D2= 1.15 (no backflow at pressure outlet)

Point I: =

L/D2= 1.3 (no backflow at pressure outlet)

Point J: =

L/D2= 1.45(no backflow at pressure outlet)

Point k: =

L/D2= 1.6(no backflow at pressure outlet)

Point L: =

L/D2= 2(no backflow at pressure outlet)

The best grid

resolution that was chosen in part 1 which is 0.009 min size ,0.04 max face

size and max size. However, with further

investigation at the direction of fluid flow to the pressure outlet.

It is to be found that there is a present of

reverse flow at the pressure outlet when is used the value ratio of L(extend) and

D2 which is 0.2.

With research , it is to be found that in order to avoid

reverse backflow of the fluid at the pressure outlet, one must increase the

ratio of L(extend)/D2. Hence, geometry of L(extend) are then be changed with

the aids of given data of L(extend)/D2. By using contour, the direction of flow

can be observed. The blue color arrow is found to be having the lowest pressure

flow, whereas, the red arrow is the opposite. Reverse backflow usually occurred

at lowest pressure flow.

For

investigating the backflow of fluid, 12 points have already tested by just keep

changing the L value. It shows that as the L value increase, the point values

also increase when the D2 value is constant. In this case, the only part need

to be focused more is wall surface instead of the diameter region since its

flow field is constant throughout. After all the

trials, in our simulation data, the shortest L(extend) to achieve no backflow

in pressure outlet is 0.35. this is because at this point, value reach

to 0.35 which is point B and its L value is 0.7mm, the backflow region still

can be seen but it start to decrease and become forward flow which is normal

flow in the end, this means that no backflow at pressure outlet.

PART 3

point

L/D2

L

P(inlet)

P1

pressure difference

% error

A

0.2

0.4

2.61E+06

7.14E+05

1.90E+06

—-

B

0.35

0.7

2.28E+06

3.26E+05

1.95E+06

2.564

C

0.5

1

2.10E+06

7.53E+04

2.02E+06

3.465

D

0.65

1.3

2.03E+06

-9927.47

2.04E+06

0.980

E

0.8

1.6

2.00E+06

34006.45

1.96E+06

4.082

F

0.95

1.9

1.97E+06

-13154.1

1.98E+06

1.010

G

1

2

1.93E+06

-77498.5

2.01E+06

1.493

H

1.15

2.3

1.94E+06

-60337.7

2.01E+06

0.000

I

1.3

2.6

1.90E+06

-71878.7

1.98E+06

1.515

J

1.45

2.9

1.88E+06

-109913

1.99E+06

0.503

K

1.6

3.2

1.90E+06

-83416.8

1.99E+06

0.000

L

2

4

1.91E+06

-25076.7

1.94E+06

2.577

For this part, 12 point with different L/D2 has been recorded. For this case, the diameter of the P(outlet) is

constant, so the ratio of L/D2 is can be indicated as the change for

Length(extend). The best grid resolution is then be used in part 3 with

different L(extend)/D2. The Pressure(inlet)

and pressure(line8) value was recorded by using the method above from part 2.

The pressure difference was also recorded in the table by using the formula ?P = Pin ? P1(line8). The result was

shown as table above. The percentage error is calculated by using the method

below.

With the aids of the formula, it is to be found that all the

percentage error are relatively low (<5%).
From the table above, it can be saw that the L/D2 increase, the P(inlet) increase. But for Pressure(line8), the value was
not consistence. It sometimes get a positive value and sometimes get a negative
value. For the pressure difference, at the beginning, it starts increase as the
L/D2 increase. From the graph, the
pressure start to be stable when at the point of 1.3 at x-axis. This means, in
order for ?P to become independent of L(extend)/D2, it has to be 1.3.
PART 4
L/D2
P(inlet)
0.2
2.61E+06
0.35
2.28E+06
0.5
2.10E+06
0.65
2.03E+06
0.8
2.00E+06
0.95
1.97E+06
1.0
1.93E+06
1.15
1.94E+06
1.3
1.90E+06
1.45
1.88E+06
1.6
1.90E+06
2.0
1.91E+06
For this case, inlet gauge
pressure Pin is plotted as a function of Lextend/D2
ratio. It is through collective data that values for each point were accepted
and tabulated. The inlet pressure, Pin is independent to the ratio
of length / diameter. From the beginning point of 0.2, there are greater drop
to the next point in pressure as each Lextend/D2 ratio
increases. This unstable trendline happened due to the nature of flow which
happens to experience maximum velocity with lower pressure at outlet. As to
obey conservation of energy law, compensation was needed for pressure at inlet
and pressure at outlet to be balanced. But with each length increase, the flow
of fluid becomes more developed, thus reducing the outlet flow velocity and
increase the outlet pressure little by little. The flow begins to fully develop
upon reaching 1.3, where steady values of pressure input, Pin were
observed.
In accordance to the above
tabulated data, it is recommended to use the diamond highlighted point which
valued at 1.3 as the value for ratio Lextend/D2. Beyond
this point, too slight difference in percentage error between 1~2% which is
considered as stable outcome during recording of data. Convergence hovers at
around 1.90 MPa which result to lesser variation in pressure from this point
onwards. This fluctuation is
insignificant to affect the difference of input pressure, Pin
against Lextend/D2 graphical line. Therefore, the Shane
chosen was valued at 1.3 ratio for Lextend/D2.
Conclusion
In
a conclusion, through this assignment some goal has already achieved. For
example, the understanding about the idea of Computational Fluid Dynamics
(CFD), its analysis and the full process of CFD, the procedure of using CFD,
importance of CFD about the world, its advantages and disadvantages and its
applications in the engineering field.
Besides,
there is a software call ANSYS and it is used to investigate CFD. In fact, CFD
is not easy to be investigated, therefore, it is necessary to keep practicing
the ANSYS software for investigating the CFD. One thing can be proved during
the simulation in the software, that is if mesh size of the object smaller,
then it can get a very high accuracy in the result. However, the smaller the
mesh size that created, the time to run the simulation will be increased also,
sometimes it can goes to like few hours or few days if the mesh size is very
small. Furthermore, ANSYS software helps a lot in engineering field also. This
is because, some of the important information and data can get in this software
before designing or build something. It can help to solve a lot of problems
that very difficult to imagine.
Moreover,
when doing this assignment, as a group member. Responsibility of finishing job
is the one thing that most important in a group. Communication between group
members had also achieved during the discussion time about problem. So, problem
can be solved easily and quickly. Throughout this all things, the speed of
completing task in the group has been increased and the ability of each group
members have also risen.
Finally, this
assignment helps to improve the ability of obtaining information and data in
every single group members in group. One more thing is that every group members
also know how to write a formal report and make the report more easily to be
read by other peoples.