Cad Coursework 3 Group 3wilson

8/12/2019 Cad Coursework 3 Group 3wilson

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MAR 2112 ENGINEERING APPLICATIONS ( COMPUTER AIDED DESIGN APPLICATIONS )

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MAR 2112

ENGINEERING APPLICATIONS

COURSE WORK - 3COMPUTER AIDED DESIGN APPLICATIONS

School of Marine Science and TechnologyNewcastle University Marine International

Singapore

Submitted by : Kyaw Khaing Thein

Maw Aung Phyo Lwin

Sim Xiang HaoEr Kok Wei

Naung Latt Kyaw

Kyaw Kyaw Lin

Group No: 3

Tutor: Dr C.S.Chin

Date: 12 March 2012


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Contents

1. Introduction ............................................................................................................................................................. 3

1.1 Coursework Aims .............................................................................................................................................. 3

1.2 Coursework Objective ....................................................................................................................................... 3

2. Resistance Algorithms available in Hullform ......................................................................................................... 4

2.1 Gerritsma et al. 1981.......................................................................................................................................... 4

2.2 Gerritsma et al. 1996.......................................................................................................................................... 4

2.3 Holtrop and Mennen .......................................................................................................................................... 4

2.4 Van Oortmerrsen ................................................................................................................................................ 5

2.5 Savitsky ............................................................................................................................................................. 5

2.6 Savitsky and Brown ........................................................................................................................................... 5

3. Selection of Resistance Algorithms ......................................................................................................................... 6

3.1 Hull Form 1 ....................................................................................................................................................... 6

3.2 Hull Form 2 ....................................................................................................................................................... 8

3.3 Hull Form 3 ..................................................................................................................................................... 10

3.4 Hull Form 4 ..................................................................................................................................................... 12

4. Effects on Resistance of Changing the Load Condition ........................................................................................ 14

4.2 Waterline at various conditions ........................................................................................................................ 14

4.3 Table of Resistance Components for three Conditions .................................................................................... 15

4.4 Analysis ........................................................................................................................................................... 15

5. Optimization of a Cargo Vessel Design ................................................................................................................. 16

5.1 Design No. 13 Analysis Data ........................................................................................................................... 17

5. 2 Design No. 19 Analysis Data .......................................................................................................................... 175.3 Design No. 22 Analysis Data & optimizing with + 10% ................................................................................. 18

5.4 Further Analysis with 10% change ................................................................................................................ 18

6. Evaluate the quality of the algorithm employed .................................................................................................... 19

6.1 Development of Bulbous bow Technology ...................................................................................................... 19

6.2 Evaluation the quality of the algorithm between Hull 1 vs Hull Extra ............................................................ 20

6.3 The results of the different test condition are illustrated in below tables ........................................................ 21

6.3.1 Using Optimization of a Cargo Vessel Design Method ............................................................................ 21

6.3.1 Using Different loading conditions for Hullform1 and Hullform Extra (Step 4) ..................................... 22

6.3.2 Differences between Hull 1 and Hull 5 ..................................................................................................... 22

7. Conclusion ............................................................................................................................................................. 23

8. References ............................................................................................................................................................. 24

9.Appendix ................................................................................................................................................................ 25


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1. Introduction

Hullform software was developed by Blue Peter Marine Systemswhicharose in the aftermath ofthe 1986-1987 Americas Cup in Fremantle, Western Australia. Hullform is a Naval Architecture

CAD package especially designed to help visualize and develop a ship hull form. It was originally

developed to provide access to computer-based hull design by users possessing only limitedcomputer facilities.

Hullform, continuously developed since the 1980s, was running initially on a large mainframe

computer evolved from version 1 to 9 which able to cater many more valued added features such as

modification of tanks, plate development, stringer design and drag estimation, quickly and

accurately. The Mathematical Model of Hull form remained less complicated than other hull models

allowing user to be able manipulated the desired hull form. Despite this, it is a useful tool at the very

earliest stages of design, allowing fast and interactive analysis of possible hull forms effectively.

1.1 Coursework Aims

1. Demonstrate the facilities and functionality of Naval Architecture software.2. Illustrate the importance of using software thoughtfully and intelligently.3. Illustrate the benefits and frustrations of using software to evaluate proposed designs.4. Illustrate the dangers inherent in using black box technology,( i.e. using technology without

being clear as to the limits of the theory on which it is based).

1.2 Coursework Objective

Establish familiarity with Naval Architecture package ( Hullform ).

Using the Hullform software package to:

Evaluation (i.e. analysis) of proposed designs, in particular with respect to their

resistance performance.

Identify appropriate resistance algorithms for alternative hulls.

Establish a range of possible results for a given hull and algorithm.

Optimise one hull for minimum resistance.

Evaluate the quality of one algorithm employed by the software.


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2. Resistance Algorithms available in Hullform

Below are the brief Understanding of Algorithms provided in the Hull Form software which caters

for different types of vessel with specific limitations of their own.

2.1 Gerritsma et al. 1981

This scheme is the commonest used to estimate the drag of sailing craft, and is based on the

Standfast series of model hulls (e.g., Gerritsma, J., Onnink, R. and Versuis A., 7th HISWA

Symposium on Yacht Architecture, 1981, pp 46-106) It is intended to be applicable to shapes and

displacements typical of racing yachts, and will not be reliable either for light-displacement hulls

which plane readily, or for bulkier craft such as fishing vessels. (However, experience shows it to

give broadly representative results for some of the latter cases) It only provides valid estimates for

hull Froude numbers less than 0.45. The algorithm uses a combination of skin friction and residual

resistance estimates. Skin friction is derived assuming a flow speed equal to the hull speed - not an

exact estimator, but recognizing that areas of the hull's surface will have flow speeds both above and

below the hull speed, probably a fair estimator of the mean. Residual resistance estimates are found

using a cubic-spline interpolation between the table entries provide in the Gerritsma et al. article.

2.2 Gerritsma et al. 1996

This is an update of the earlier work. The scheme generally gives slightly lower drag estimates, but

extends to a higher limiting speed, corresponding to a Froude number of 0.6. The plotted

comparison at right - for a 17 tonne, 16 metre hull - is typical of these differences.

2.3 Holtrop and Mennen

The form Holtrop & Mennen Method permits to predict the drag of a large range of displacement

ships. It is based in more than one hundred of tests make in MARIN towing tank, and then this

method has been contrasted with a real data obtained from large number of ships. List of method for

Holtrop and Mennen:

Drag calculation of displacement ships with specific velocity and with range velocity.

It permits to calculate the drag of hull and calculate the drag of the hull with its appendages.

The forms of entry data includes advanced functions to automatic update. By this way, theforms adjust to the values of user entry data. Thus, the coincidence possibilities of several

related fields are decreased.

The forms of entry data have tools to estimate the unknown values (wet surface, the halfangle of entrance...)


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2.4 Van OortmerrsenVan Oortmerssen in 1971 published the results of a regression analysis of the resistance of small

ships such as tugs and trawlers which had been tank-tested. This was in the form of an expression for

the residuary resistance of the vessel based on parameters available at an early stage of design. His

method remains one of the few suited to such hullforms and quickly found favour with those

involved in prediction of their resistance. The method is included in many commercial resistance-prediction packages, and is still widely used. However, there were a number of errors in the original

publication. Depending on how these errors are treated, it is possible to come up with different

values of the total resistance, and almost every known implementation gives differing results for the

resistance. Many of these errors have been resolved by correspondence with the author and with

MARIN, and it is the intention here to record corrections to the known issues. In addition, it has been

found that there are some combinations of parameters which give anomalous results. For these

combinations, the resistance does not increase monotonically with speed as might be expected for

this type of displacement hullform, but shows a distinct hump as might be expected for planning

hullforms. The anomalous results have been investigated to determine the combinations of

parameters for which they are produced, and a method of dealing with the results is proposed.

- waterline length between8 and 80 metres;

- displacement volume between 5 and 3000 cubic metres;

- length-beam ratio between 3 and 6.2;

- breadth-draught ratio between 1.9 and 4.0;

- prismatic coefficient between 0.50 and 0.73;

- midship section coefficient between 0.70 and 0.97;

- longitudinal centre of buoyancy between -7% L and +2.8% L forward of 0.5 L ;

- half angle of entrance of design waterline between 10 and 46.

2.5 Savitsky

Savitsky considers a boat to be planning when CV/ >1.0. This is good criterion but is not practicalfor field observation. For steady state planning all the forces and moments acting on the boat must be

in equilibrium. This method takes into account the buoyant forces and is therefore applicable to vary

low speeds. In order to handle oddities of hull bottom forms, a somewhat arbitrary algorithm has

been adopted to define the width of the planning surface. This width is taken to be the average, over

all sections, of the lesser of either the static waterline beam, or the beam to the outermost underwater

points where the slope of the hull surface is 45. Savitsky has given formulas for lift and drag force

on planning hulls. These formulas are based on a large number of resistance tests with prismatic, or

wedge-type surfaces, in which the trim angle, dead rise angle, wetted length and length-beam ratio,

were varied systematically.

2.6 Savitsky and Brown

Savitsky and Brown have given a resistance prediction method for the planning type of hulls for pre-

planning and planning regimes separately. In the pre-planning regime they reported regression

catalysis carried out by Mercier and Savitsky of the smooth water resistance data of seven transom

stern hull series, which includes 118 separate hull forms. The range of geometric characteristics for

all the seven series has been summarized and given in the form of table". It has been found to give

results normally within about 20% of the Savitsky formulation, with excellent agreement often

achieved by altering the position of the hull's centre of mass. It seems that the Savitsky and Brown

formulation is derived for craft of normal centre of mass positions, and may be unreliable forextreme cases.


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3. Selection of Resistance AlgorithmsHullform software offers 6 different algorithms, each of which are applicable to different type of vessel with limitations. Four Designs (cw1.hud, cw2.hud, cw3.hud, cw4.hud) are given

to analyze the resistance components surfaced from 6 different algorithms with 15 knots speed. Below are the statistics that we have used to determine the suitable algorithm for

respective hull forms.

3.1 Hull Form 1

Hu ll form 1 General Particulars

Displacement, 10015.348 tonnes

Length, overall, LOA 100m

Maximum Beam, B 30m

Draft, T 6m

Waterplane area 1991.386 sq mBlock Coefficient 0.583

Prismatic Coefficient 0.616

Table 1A

Figure3.1.2: Full Perspective View

Figure 3.1.1: General Orthogonal View


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Algorithms

Froude

number

(Fn)

Skin

friction

(tonne)

Residual

resistance

(tonne)

Trim

Drag force : friction+ form+

wave Total

resistance

(tonne)Friction Form Wave

Gerritsma

1981 0.251 13.509 21.963 - - - - 35.471

Gerritsma

1996 0.251 13.509 9.523 - - - - 23.032

Oortmenssen 0.249 - - - 16.391 5.098 -11.819 9.67

Holtrop and

Mennen 0.251 - - - 16.421 21.697 2.778 40.896

Savitsky - 21.341 - 463.049 - - - -102.031

Savitsky and

Brown 0.533 - - - - - - -

Table 1a F ig: Drag Vs speed

Analysis of Hullform1

Algorithms Acceptance Remark

Gerritsma 1981 NoThe model does meet the criteria of Froude number of below 0.45but the Algorithms Gerritsma 1981 is more applicable for

smaller vessel like fishing vessel or racing yachts rather that large vessel like cargo vessel.

Gerritsma 1996 NoIts basically the upgrade version of Gerritsma 19981 with Froude number 0.6. The scheme generally gives sl ightly lower dragestimates

Oortmenssen NoAlgorithms limitation of waterline length between8 and 80 metres; it doesnt meet the hull1s waterline length. Besides, thewave drage value shows negative which means its not opposing the direction of the vessel. This Algorithm is more suitable for

predicting smaller ships such as tugs and trawlers

Holtrop and Mennen YesFrom the results table and drag curve analysis, it is clear that the Froude number and Prismatic Coefficient is most

suitable for the given hull. From the drag and curve graph it shown that it have the best possible resistance curve.

Savitsky No Algorithm gives -102.031 tonne which is negative valuethat not possible in predicting. So, we omit the Savitsky algorithm.

Savitsky and Brown NoGives no result due to its only applicable Fn between 1 to 2. Therefore we exclude this algorithm from consideration for this hull

shape.

Selected Algorithm: Holtrop and Mennen


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3.2 Hull Form 2


Displacement, 1448.156tonnes


Maximum Beam, B 13.683m

Draft, T 4m

Waterplane area 456.233sq m

Block Coefficient 0.61


Table 2a

Figure 3.2.1: Full Perspective View



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AlgorithmsFroude

number(Fn)

Skin

friction

(tonne)

Residual

resistance

(tonne)

Trim

Drag force : friction+

form+ wave Total

resistance


Gerritsma

1981 0.376 3.6 41.158 - - - - 44.758

Gerritsma

1996 0.376 3.6 28.172 - - - - 31.772

Oortmenssen 0.372 - - - 4.286 2.172 26.639 35.097

Holtrop and

Mennen 0.376 - - - 4.286 10.246 22.872 37.415

Savitsky - 4.778 - 194.739 - - - -102.031

Savitsky and

Brown 0.736 - - - - - - -

Table 2b F ig: Drag Vs speed

Analysis of Hullform 2

Algorithms Acceptance Remark

Gerritsma 1981 NoThe model does meet the criteria of Froude number of below 0.45but from the result we got, it seem that the vessel is more like

a trawlers or tugs which Algorithms Gerritsma 1981 is more applicable for racing yachts.

Gerritsma 1996 NoIts basically the upgrade version of Gerritsma 19981 with Froude number 0.6. The scheme generally gives sl ightly lower drag

estimates

Oortmenssen YesVan Oortmenssen met all the criteria of this algorithm such as a designed waterline length length between8 - 80 metres.This

method is useful for estimating the resistance of small ships such as trawlers and tugs.

Holtrop and Mennen NoThis algorithm will not be suitable as this model hull prismatic coefficient had exceeded the limitation of prismatic coefficients

between 0.55 - 0.65.

Savitsky No Algorithm gives -102.031 tonne which is negative valuethat not possible in predicting. So, we omit the Savitsky algorithm.


shape.

Selected Algorithm: Oortmenssen


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3.3 Hull Form 3





Draft, T 1.582m




Table 3a




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AlgorithmsFroude

number(Fn)

Skin

friction

(tonne)

Residual

resistance

(tonne)

Trim

Drag force : friction+

form+ wave Total

resistance


Gerritsma

1981 0.467 - - - - - - -

Gerritsma

1996 0.467 1.118 5.372 - - - - 6.49

Oortmenssen 0.458 - - - 1.317 -0.092 11.221 12.445

Holtrop andMennen 0.467 - - - 1.322 25.828 8.684 35.834

Savitsky - 1.205 - 9.211 - - - -102.031

Savitsky and

Brown 1.102 - - - - - - -


Analysis of Hullform 3Algorithms Acceptance Remark

Gerritsma 1981 No No result as Froude number greater than the criteria of below 0.45

Gerritsma 1996 Yes

An update of Algorithms of Gerritsma 1981 it have a higher Froude number of 0.6which was able to meet out data in table 3b

not only that we also can conclude that hullform 3 is a yatch due to its geometrical ship and dimension . This Algorithms Gerritsma 1996 is more applicable for smaller vessel or racing yachts therefore we have chosen this Algoritms.

Oortmenssen No This Algorithm does not met the requirement as its prismatic coefficient 0.773fall out of range between 0.500.73

Holtrop and Mennen No From the above data at table 3b we can said that this Algorithms is not suitable for this hullform because it is use for small vesselSavitsky No Algorithm gives -102.031tonne which is negative valuethat not possible in predicting. So, we omit the Savitsky algorithm.

Savitsky and Brown NoThis algorithm does meet the requirement, but compare to Gerritsma 1996, gerristma 1996 is still a better choice as it is

intended to be applicable to shapes and displacements typical of racing yachts.

Selected Algorithm: Gerritsma 1996


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3.4 Hull Form 4

Table 4a





Length, overall, LOA 8.299m


Draft, T 0.462m





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AlgorithmsFroude

number(Fn)

Skin

friction

(tonne)

Residual

resistance

(tonne)

Trim

Drag force : friction+ form+

wave Total

resistance


Gerritsma

1981 0.905 - - - - - - -

Gerritsma

1996 0.905 - - - - - - -

Oortmenssen 0.88 - - - 152.816 -10.697 -523.672 -381.552Holtrop and

Mennen 0.905 - - - 153.979 2374.485 4504.634 7033.099

Savitsky - 126.865 - 473.82 - - - 600.685

Savitsky and

Brown 2.029 - - - - - - -


Analysis of Hullform 4Algorithms Acceptance Remark

Gerritsma 1981 No The model does not meet the criteria as it exceeds theFroude number of 0.45.As a result, it is not suitable to use this algorithm.

Gerritsma 1996 No This algorithm is also not applicable as it exceeds theFroude number of 0.60.

Oortmenssen NoThis algorithm shows a negative valueof form and wave drag,which means its not opposing the direction of the vessel.

Thus, this algorithm is not accurate and suitable for this model.

Holtrop and Mennen No This algorithm is widely used in prediction of resistance of displacement and semi-displacement vessels such astankers, general cargo ships or container ship where in this model is a relatively small vessel of only 8.299m in length.

Therefore this algorithm is not suitable for this model.

Savitsky Yes This algorithm most suit the above criteria as the commonest scheme used for predicting the drag of planning craft.


shape.

Selected Algorithm: Savitsky


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4. Effects on Resistance of Changing the Load Condition

This section show us on the effects of varying loading conditions on resistance using Holtrop and

Mennen algorithm for hullform 1 model.

1stLoading Condition:

Original Displacement with no trim

2ndLoading Condition

Double Displacement with no trim

3rdLoading Condition

Original displacement but with a static trim angle of approximately 5 degrees

The results of the different test condition are illustrated and analyzed in below tables.

4.2 Waterline at various conditions

1stLoading Condition: Original Displacement with no trim

2nd

Loading Condition: Double Displacement with no trim


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3rd

Loading Condition: Original displacement but with a static trim angle of approximately 5

degrees

4.3 Table of Resistance Components for three Conditions

4.4 Analysis

Compare condition1 to 2

In condition 2, the displacement of the vessel is double (20048.4863 tonnes) with no trim. This

causes an increase of draught and an increase of surface area. The increase of surface areacontributed to the increase of frictional, form and drag resistance.

Compare condition1 to 3

In condition 3, the displacement of the vessel is original (10014.2432 tonnes) with a trim of 5 degree.

We can see that the forward of the vessel is exposed above the surface of the water when there is a

trim of 5 degree at the midship. We observed that due to the trim over at the stern, there is a huge

increase of wave drag resistance.

Condition 1 Condition 2 Condition 3

Original displacementwith no trim

Double displacementwith no trim

Original displacementwith 5 degree trim

Friction [tonnes] 16.425 22.612 16.285

Form Drag [tonnes] 21.623 28.485 61.692

Wave Drag [tonnes] 2.78 5.064 19.544

Total Drag [tonnes] 40.828 56.16 97.52


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5. Optimization of a Cargo Vessel DesignOur methodology of optimizing the cargo vessel design using Hullform1 (cw1.hud), its basic condition and the resistance Algorithm Holtrop and Mennen,

explore how proportional design changes could impact on the resistance at speed of 15 knots, original displacement but changes were made in the length,

breadth and depth up to 20%. Data as shown below:

Analysis:

At first, we adjusted the length, breadth and depth of vessel to 20% allowance to get data.

After discussion we have narrowed down to 3 Design to analyze. These 3 designs we have

selected to analysis were base on the best total Resistance and its stability. The selected

design was 13, 19 & 22 which give lesser total resistance and better righting moment.

Now we will base on the values of total resistance, stability analysis on the righting moment

and the GZ curve for the selection for the optimised vessel.

Explanation of Righting moment

Righting moment is when a stable vessel is heeling due external forces, its righting moment

will oppose the heeling moment which will try to make the vessel back to upright position.

What is GZ curve?

There will be two areas that we look out for in the GZ curves obtained from the 3 design.

1. The range of stability. For angles less than the range of stability, the vessel willreturn to the upright state when the heeling moment is removed

2. The area under the GZ curve. It represents the ability of the ship to absorb energyimparted on it by wind, waves or any other sources.

3. The range of stability. For angles less than the range of stability, the vessel willreturn to the upright state when the heeling moment is removed

4. The area under the GZ curve. It represents the ability of the ship to absorb energyimparted on it by wind, waves or any other source

Conditions

Total

Resistance Friction Form Wave

Righting

MMT

No.

Length

(L) %

Breadth

(B) %

Depth

(D) % [Tonnes] [Tonnes] [Tonnes] [Tonnes] [Tonne.m/deg]

1 80 80 80 41.848 14.636 18.22 8.992 648.004

2 80 80 100 41.495 14.463 17.809 9.223 295.182

3 80 80 120 43.936 14.39 19.752 9.794 -42.012

4 80 100 80 41.933 15.225 22.217 4.535 1330.789

5 80 100 100 44.67 14.959 24.834 4.877 900.691

6 80 100 1 20 46.373 14.794 26.437 5.142 506.917

7 80 120 80 48.506 16.209 30.007 2.23 2361.115

8 80 120 1 00 50.571 15.847 32.333 2.931 1831.341

9 80 120 1 20 51.959 15.477 33.886 2.597 1365.789

10 100 80 80 34.064 15.822 14.175 4.067 663.336

11 100 80 100 35.898 15.615 15.952 4.331 290.883

12 100 80 120 37.039 15.499 17.041 4.499 -60.073

13 100 100 80 39.653 16.759 20.224 2.67 1483.125

14 100 100 1 00 40.831 16.425 21.625 2.78 1027.08

15 100 100 120 41.727 16.051 22.748 2.928 616.416

16 100 120 80 46.47 18.071 26.791 1.608 2688.514

17 100 120 100 47.402 17.441 28.278 1.683 2127.535

18 100 120 120 50.135 17.043 29.407 3.685 1636.944

19 120 80 80 33.211 17.064 12.968 3.179 706.54

20 120 80 100 34.331 16.883 14.116 3.307 319.121

21 120 80 120 34.876 16.529 14.971 3.377 -41.287

22 120 100 80 39.126 18.323 18.42 2.591 1649.45623 120 100 100 39.691 17.742 19.322 2.627 1175.059

24 120 100 120 41.975 17.376 20.216 4.383 749.543

25 120 120 80 45.851 19.758 24.226 1.807 3021.596

26 120 120 100 47.96 19.112 25.432 3.417 2429.824

27 120 120 120 53.743 18.649 25.628 9.446 1912.55


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5.1 Design No. 13 Analysis Data

Conditions

Total


Righting

moment

No

.

Lengt

h (L)

%

Breadt

h (B) %

Depth

(D) % [Tonnes] [Tonnes] [Tonnes] [Tonnes]

[Tonne.m/

deg]

13 100 100 80 39.653 16.759 20.244 2.67 1483.125

The length & Breadth of the vessel maintains but the depth decrease to 80%. It obtained a

total resistance of 39.653tonnes. However, due to the decrease in depth the stability of the

vessel is much better as the righting moment of was 1483.125Tonnes.m/deg. The max GZvalue is 4.49m at 38.0 deg, the range of stability is up to 93.5deg and the area under from 0to 93.5 deg is 252.53

5. 2 Design No. 19 Analysis Data

The length of the vessel was increased to 120%, an 80% decrease of depth and breadth.The righting moment obtained by this is 706.54tonne.m/deg, which is lower than the

original design, it shows that a weaker stability than original design. It has a max GZ value

of 2.84m at 44 deg, a range of stability up to 94.3 deg and the area under from 0 to 94.3

deg is 157.53.

Conditions

Total


Righting

moment

No

.

Lengt

h (L)

%

Breadt

h (B) %

Depth

(D) % [Tonnes] [Tonnes] [Tonnes] [Tonnes]

[Tonne.m/

deg]

19 120 80 80 33.211 17.064 12.968 3.179 706.54


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5.3 Design No. 22 Analysis Data & optimizing with + 10%

Conditions

Total


Righting

moment

No.

Length

(L) %

Breadth

(B) %

Depth


22 120 100 80 39.126 18.323 18.42 2.591 1649.456

The length of the vessel was increased to 120%, an 80% decrease of depth and Breadthmaintains. The total resistance was 39.126 Tonnes The righting moment obtained by this is

1649.456tonne.m/deg, it shows that stability is better than original design. It has a max GZ

value of 4.92m at 40 deg, a range of stability up to 94.0 deg and the area under from 0 to94.0 deg is 261.96.

Chosen Optimised Design: Design 4 : Length increase by 20%, Breadth

decrease by 10% and Depth decrease by 20% .

5.4 Further Analysis with 10% change

Further Analysis by using Design No.22 length maintains change of the

Breadth & Depth by 10% to get a better stability. Data as shown below:

Original GZ Curve Final Chosen data (No. 4)

Comparison with original GZ Curve

The length of the vessel was increased to 120%, an 80% decrease of depth and 90%decrease Breadth. The total resistance was 34.512 Tonnes and the righting moment

obtained by this is 1065.963onne.m/deg; it shows that stability is better than original design

as shown on the above graph. It has a max GZ value of 4.85m at 40 deg, a range of stabilityup to 93.9 deg and the area under from 0 to 93.9 deg is 276.59.

Conditions

Total


Righting

moment

No.

Length

(L) %

Breadth

(B) %

Depth

(D) % [Tonnes] [Tonnes] [Tonnes] [Tonnes] [ Tonne.m/deg]

22 120 100 80 39.126 18.323 18.42 2.591 1649.456

1 110 100 80 39.317 17.540 19.204 2.573 1565.522

2 120 100 90 40.566 18.624 19.227 2.715 1440.538

3 110 100 90 39.757 17.338 19.814 2.605 1324.557

4 120 90 80 34.512 16.664 15.066 2.782 1065.963

5 120 110 80 43.192 19.457 21.457 2.278 2325.558


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6. Evaluate the quality of the algorithm employed

Since the task was given to identify the reliability of the software whether it can recognise the

resistance effect of the bulbous bow, we used two same hull forms with bulbous or without bulbous

to analyze the software. Below is our basic understanding and history of bulbous.

6.1 Development of Bulbous bow Technology

In the late 1950s research was undertaken to reduce the

drag on large commercial cargo ships. Many different

ideas were tried and continue to be tried today in the

ongoing development of the science of Naval

Architecture. With model testing and advanced

knowledge of hydrodynamics, the bulbous bow was

formulated typically giving a 5% reduction in fuel

consumption over a narrow range of speed and draft.

This was significant for a large ship crossing vast

oceans, at a time when the cost of fuel was rising.

Unfortunately, this was not enough to make it

worthwhile for smaller yachts racing around the bay.

Also, the narrow range of displacement speed was not in keeping with the yachtsman's need for

speed on the water. As the market for displacement long range cruisers opened up, innovative

builders began to look for answers to their consumers questions. The bulbous bow stood out as a

prime solution.

Although available in many shapes and sizes, generally the bulb looks like a section of largediameter pipe with a domed end sticking out of the bow of the boat, underwater. Side bulbs, bilge

bulbs, and even stern bulbs have been tried but the most consistent results have been achieved with

bow bulbs. Today, to see a large ship without a bulbous bow is a rare sight indeed. Their results have

been proven over countless thousands of deep ocean miles in all kinds of weather by all kinds of

vessels.

Figure 6.1.1: Hullforms with or without bulbous bow


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6.2 Evaluation the quality of the algorithm between Hull 1 vs Hull Extra

Figure 6.2.1: Perspective view and centreline view of Hull form 1

Figure 6.2.2: General Orthogonal View and View from centerline of Hull form Extra


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6.3 The results of the different test condition are illustrated in below tables

Repeating the steps 4 & 5 to observe the resistance components and stability of Hullform1 & Hullform Extra

6.3.1 Using Optimization of a Cargo Vessel Design Method

For the step 5 which is Optimization of a Cargo Vessel Design, we already designed to the best optimum design of increasing the length by 20%, decreasing the

breadth by 10% and decreasing the depth by 20% in Hullform1. So, for new Hullform Extra we take the same best optimum dimension to make further

analysis.

Hull1 with bulbous bow

Total


Righting

moment

No.

Length

(L) %

Breadth

(B) %

Depth


22 120 90 80 34.512 16.664 15.066 2.782 1065.963

GZ curves comparison

Figure 6.3.1.1: Hull form 1 Figure 6.3.1.2: Hull form Extra

From the observation of results above, It is significant to see the total resistance is reduced from 38.015 tonnes to 34.512 tonnes with bulbous bow effect in

Hullform 1. Besides, due to higher righting moment and better GZ curve, HullForm Extra would be stiffer ship compare to Hullform1 which is more

comfortable ship.

Hull Extra without bulbous bow

Total


Righting

moment

No.

Length

(L) %

Breadth

(B) %

Depth


22 120 90 80 38.015 17.049 15.4 5.566 1509.527


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6.3.1 Using Different loading conditions for Hullform1 and Hullform Extra (Step 4)

Table: General particulars about the Hullform 1 and Hullform Extra for different Loading conditions of Step 4

Table: Result resistance drag data obtained with Holtrop and Mennen algorithm of Hullform1 and Hullform Extra

6.3.2 Differences between Hull 1 and Hull 5

Total Drag - Condition 10.612tonnes, Condition 22.723tonnes and Condition 32.115 tonnes increase in resistance without Bulbous bow.

According to the above resistance tables, the value of total resistance drag were changed in small percentage of less than 10% from condition 1 to condition 2 &

3. Therefore, we hereby can conclude the advantage of adding a bulbous bow feature to cargo ship resulting in saving the fuel consumption and especially

reducing in wave making resistance.

Hull 1 withbulbous bow


Originaldisplacement with

no trim

Doubledisplacement with

no trim

Originaldisplacement with 5

degree trim

Length 100m 100m 100m

Dreadth 30m 30m 30m

Draught 6m 10.446m 7.673m

Wetted surface

area

2668.497m2 3681.635 m2 2653.1m2

Displacement 10015.348 tonnes 20048.303 tonnes 10015.348 tonnes

Hull 5 without

bulbous bow


Original

displacement withno trim

Double

displacement withno trim

Original

displacement with5 degree trim

Length 100m 100m 100m

Dreadth 30m 30m 30m

Draught 6.124m 10.542m 7.710m

Wetted surface

area

2561.449m2 3568.735m2 2653.1m2

Displacement 10014.997 tonnes 20048.303 tonnes 10014.951 tonnes

Hull_Extrawithout bulbous

bow


Originaldisplacement with

no trim

Doubledisplacement with

no trim

Originaldisplacement with 5

degree trim

Friction [tonnes] 15.859 24.569 16.224

FormDrag[tonnes] 21.207 28.493 66.530

WaveDrag[tonnes] 4.378 28.788 5.357

TotalDrag[tonnes] 41.443 81.851 88.112

Hull1 with bulbous

bow


Original

displacement

with no trim

Double

displacement with

no trim

Original

displacement with 5

degree trim

Friction [tonnes] 16.425 22.574 16.329

Form Drag [tonnes] 21.626 50.369 50.245

Wave Drag [tonnes] 2.780 6.185 19.423

Total Drag [tonnes] 40.831 79.128 85.997


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7. Conclusion

We have shown that this method based on the boundary value problem is readily applied to hull

surface design. By defining the boundary curves of the patch of surface and varying the derivative

conditions imposed upon them. It is possible to create a wide variety of shapes. The example serves

to illustrate the control on the resulting surface shape which is exercised by the boundary conditions.

Furthermore, the way in which practical requirements of hull design can be accommodated has been

demonstrated. Although attention in this paper had focused on the geometry, one of the most

significant features of the method is the way in which a surface shape can be defined with relatively

few parameters.

On preliminary design stage, designers are able to edit the principle dimension of the design to obtain

at even better resistance result. With the features mentioned above, we concluded that the software,

Hullform bring great convenience to the designers at preliminary stage. This particularly, important

when physical considerations are brought into the automatic design system when an optimization

may be carried out in a surprisingly small parameter space defining both the geometry and the

physics.

~~~ End of Report ~~~


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8. References

Gerritsma, J. Onnink, R. and Verslius, A., Geometry, Resistance and Stability of the

Delft Systematic Yacht Hull Series, 7th HISWA, Amsterdam, 1981.

Holtrop, J. and Mennen, G.G.J., An Approximate Power Prediction Method,

International Shipbuilding Progress, Vol. 29, No. 335, July 1982.

Holtrop, J., A Statistical Re-Analysis of Resistance and Propulsion Data,International

Shipbuilding Progress, Vol. 31, No. 363, November 1984.

Holtrop, J., A Statistical Resistance Prediction Method with a Speed Dependent Form

Factor, Proceedings SMSSH 88, Varna, October 1988.

Oortmerssen, P. van, A Power Prediction Methodand its Application to Small Ships,

International Shipbuilding Progress, Vol. 18, No. 207, July 1971.

Savitsky, D., Hydrodynamic Design of Planing Hulls,Marine Technology, Vol. 1, No.1, October 1964.

Savitsky, D. and Brown, P.W., Procedures for the Hydrodynamic Evaluation of Planing

Hulls in Smooth and Rough Waters,Marine Technology, Vol. 13, No. 4, October 1976.


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9.Appendix

Hull 1 Data as follows:

General Data Centre Form Coefficient


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Resistance calculated with various algorithms

Gerritsma 1981 Gerritsma 1996 Oortmenssen

Holtrop & Mennen Savitsky Savitsky &Brown


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Gerritsma 1981 Holtrop & Mennen Oortmenssen

Gerritsma 1996

Savitsky Savitsky &Brown

Cad Coursework 3 Group 3wilson

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