8/10/2019 Summary of Comp

1/11

Comparison of response when COG shifts in Longitudinal direction

0

1

2

3

4

5

6

7

-2%L -1.5%L -1%L -.5%L .5%L 1%L 1.5%L 2%L

Percentage

change

in

response

Shift in Centre of gravity

Percentage change in max pitch response

0

1000

2000

3000

4000

5000

6000

7000

8000

-2%L -1.5%L -1%L -.5%L .5%L 1%L 1.5%L 2%L

percentagechangeinresponse

change in centre of gravity

Percentage change in Roll RAO( 90 deg wave)

8/10/2019 Summary of Comp

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-12

-10

-8

-6

-4

-2

0

2

-2%L -1.5%L -1%L -.5%L .5%L 1%L 1.5%L 2%L

percentagechangei

nresponse

change in centre of gravity

Percentage change in maximum Heave RAO( 90

deg wave)

-10

0

10

20

30

40

50

60

70

-2%L -1.5%L -1%L -.5%L .5%L 1%L 1.5%L 2%L

Percentagechangein

response

Change in centre of gravity

Percentage change in maximum sway RAO (

90deg wave)

8/10/2019 Summary of Comp

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Salient Observations from the comparison

For all degrees of freedom the variation in response is more in the frequency range of 0.4-

0.8 rad/s

In head sea the pitch response is maximum when the LCG shifts 1.5% of L towards fore end

whereas the maximum response in surge and heave is nearly equal

In Beam sea condition there is much variation in sway and roll response. Both the responses

are maximum when the LCG shifts 1.5% of L towards the fore end. The heave response is

maximum when LCG shifts 1% of L towards the aft

8/10/2019 Summary of Comp

4/11

Study of change in response when there is shift in VCG

0

1

2

3

4

5

6

vcg 11 vcg 12 vcg 13 vcg 14 vcg 15

%

changeinres

ponse

VCG

Percentage change in maximum

Pitch RAO

-12

-10

-8

-6

-4

-2

0

vcg 11 vcg 12 vcg 13 vcg 14 vcg 15

%C

hangein

response

VCG

Percentage change in maximum heave

response ( beam sea)

-100

-50

0

50

100

150

200

250

300

350

vcg 11 vcg 12 vcg 13 vcg 14 vcg 15Percentagechangein

response

VCG

Percentage change in maximum Roll RAO(

90 deg wave)

8/10/2019 Summary of Comp

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Salient Observations from the comparison

For all degrees of freedom the variation in response is more in the frequency range of 0.3-

0.8 rad/s

In head sea the maximum pitch response occurs when the VCG is 15m from keel whereas

the maximum response in surge and heave is nearly equal

In Beam sea condition the roll is increased much when VCG is 14m and the maximum sway

response is same in all cases. When VCG is shifted the heave response is reduced

When CoG shifts in both axis

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2

Surge RAO- Head sea

2L VCG 11

-2L VCG 15

2L VCG 15

-2L VCG 11

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.5 1 1.5 2

Surge - Quartering sea

2L VCG 11

-2L VCG 15

2L VCG 15-2L VCG 11

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8/10/2019 Summary of Comp

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0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.5 1 1.5 2

Heave RAO Beam sea

2L VCG 11

-2L VCG 15

2L VCG 15-2L VCG 11

-1

0

1

2

3

4

5

6

7

8

9

0 0.5 1 1.5 2

Roll RAO- Quartering sea

2L VCG 11

-2L VCG 15

2L VCG 15

-2L VCG 11

-2

0

2

4

6

8

10

12

14

16

0 0.5 1 1.5 2

Roll RAO- Beam sea

2L VCG 11

-2L VCG 15

2L VCG 15

-2L VCG 11

8/10/2019 Summary of Comp

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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 0.5 1 1.5 2

Pitch RAO- Head sea

2L VCG 11

-2L VCG 15

2L VCG 15-2L VCG 11

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2

Pitch RAO- Quartering sea

2L VCG 11

-2L VCG 15

2L VCG 15

-2L VCG 11

8/10/2019 Summary of Comp

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0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 0.5 1 1.5 2

Yaw -Quartering sea

2L VCG 11

-2L VCG 15

2L VCG 15-2L VCG 11

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 0.5 1 1.5 2

Yaw- Beam sea

2L VCG 11

-2L VCG 15

2L VCG 15

-2L VCG 11

8/10/2019 Summary of Comp

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IN TOWING CONDITION

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5

Surge RAO-Head sea-.5L

-1L

-1.5L

-2L.5L

1L

1.5L

2L

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5

Heave RAO- Head sea

-.5L

-1L

-1.5L

-2L

.5L

1L

1.5L

2L

-0.2

0

0.2

0.4

0.6

0.8

1

0 0.5 1 1.5 2 2.5

Pitch RAO- Head sea

-.5L

-1L

-1.5L

-2L

.5L

1L

1.5L

2L

8/10/2019 Summary of Comp

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0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.5 1 1.5 2 2.5

Sway- Beam sea-.5L

-1L

-1.5L

-2L

.5L

1L

1.5L

2L

-10

0

10

20

30

40

50

60

70

0 0.5 1 1.5 2 2.5

Roll - Beam sea

-.5L

-1L

-1.5L

-2L

.5L

1L

1.5L

2L

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.5 1 1.5 2 2.5

Yaw RAO-Beam sea

-.5L

-1L

-1.5L

-2L

.5L

1L

1.5L

2L