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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
Hu ll form 2 General Particulars
Displacement, 1448.156tonnes
Length, overall, LOA 45m
Maximum Beam, B 13.683m
Draft, T 4m
Waterplane area 456.233sq m
Block Coefficient 0.61
Prismatic Coefficient 0.7
Table 2a
Figure 3.2.1: Full Perspective View
Figure 3.2.2: General Orthogonal View
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AlgorithmsFroude
number(Fn)
Skin
friction
(tonne)
Residual
resistance
(tonne)
Trim
Drag force : friction+
form+ wave Total
resistance
(tonne)Friction Form Wave
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.
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: Oortmenssen
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3.3 Hull Form 3
Hu ll form 3 General Particulars
Displacement, 129.16tonnes
Length, overall, LOA 30m
Maximum Beam, B 7.303m
Draft, T 1.582m
Waterplane area 159.636sq m
Block Coefficient 0.412
Prismatic Coefficient 0.772
Table 3a
Figure 3.3.1: Full Perspective View
Figure 3.3.2: General Orthogonal View
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AlgorithmsFroude
number(Fn)
Skin
friction
(tonne)
Residual
resistance
(tonne)
Trim
Drag force : friction+
form+ wave Total
resistance
(tonne)Friction Form Wave
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 - - - - - - -
Table 3b F ig: Drag Vs speed
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
Figure 3.4.1: Full Perspective View
Figure 3.4.2: General Orthogonal View
Hu ll form 4 General Particulars
Displacement, 3999.864tonnes
Length, overall, LOA 8.299m
Maximum Beam, B 3.184m
Draft, T 0.462m
Waterplane area 17.195sq m
Block Coefficient 0.399
Prismatic Coefficient 0.786
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AlgorithmsFroude
number(Fn)
Skin
friction
(tonne)
Residual
resistance
(tonne)
Trim
Drag force : friction+ form+
wave Total
resistance
(tonne)Friction Form Wave
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 - - - - - - -
Table 4b F ig: Drag Vs speed
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.
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: 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
Resistance Friction Form Wave
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
Resistance Friction Form Wave
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
Resistance Friction Form Wave
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
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
Resistance Friction Form Wave
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
Resistance Friction Form Wave
Righting
moment
No.
Length
(L) %
Breadth
(B) %
Depth
(D) % [Tonnes] [Tonnes] [Tonnes] [Tonnes] [Tonne.m/deg]
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
Resistance Friction Form Wave
Righting
moment
No.
Length
(L) %
Breadth
(B) %
Depth
(D) % [Tonnes] [Tonnes] [Tonnes] [Tonnes] [Tonne.m/deg]
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
Condition 1 Condition 2 Condition 3
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
Condition 1 Condition 2 Condition 3
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
Condition 1 Condition 2 Condition 3
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
Condition 1 Condition 2 Condition 3
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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Hull 2 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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Resistance calculated with various algorithms
Gerritsma 1981 Gerritsma 1996 Oortmenssen
Holtrop & Mennen Savitsky Savitsky &Brown
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Hull 4 Data as follows:
General Data Centre Form Coefficient
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Resistance calculated with various algorithms
Gerritsma 1981 Holtrop & Mennen Oortmenssen
Gerritsma 1996
Savitsky Savitsky &Brown