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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
MAR 2112 ENGINEERING APPLICATIONS
COURSE WORK  3 COMPUTER AIDED DESIGN APPLICATIONS
School of Marine Science and Technology Newcastle University Marine International – Singapore
Submitted by :
Kyaw Khaing Thein Maw Aung Phyo Lwin Sim Xiang Hao Er Kok Wei Naung Latt Kyaw Kyaw Kyaw Lin
Group No:
3
Tutor:
Dr C.S.Chin
Date:
12 March 2012 Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
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 .......................................................................................................................... 17 5.3 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
Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
1. Introduction Hullform software was developed by Blue Peter Marine Systems which arose in the aftermath of the 19861987 America‟s 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 computerbased hull design by users possessing only limited computer 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. 2. 3. 4.
Demonstrate the facilities and functionality of Naval Architecture software. Illustrate the importance of using software thoughtfully and intelligently. Illustrate the benefits and frustrations of using software to evaluate proposed designs. 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. Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
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 46106) It is intended to be applicable to shapes and displacements typical of racing yachts, and will not be reliable either for lightdisplacement 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 cubicspline 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, the forms 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 half angle of entrance...)
Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
2.4 Van Oortmerrsen Van Oortmerssen in 1971 published the results of a regression analysis of the resistance of small ships such as tugs and trawlers which had been tanktested. 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 resistanceprediction 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 between 8 and 80 metres; displacement volume between 5 and 3000 cubic metres; lengthbeam ratio between 3 and 6.2; breadthdraught 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/√λ >1.0. This is good criterion but is not practical for 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 wedgetype surfaces, in which the trim angle, dead rise angle, wetted length and lengthbeam 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 preplanning and planning regimes separately. In the preplanning 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 for extreme cases. Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
3. Selection of Resistance Algorithms Hullform 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 Hull form 1 General Particulars Displacement, Δ 10015.348 tonnes Length, overall, LOA 100m Maximum Beam, B 30m Draft, T 6m Waterplane area 1991.386 sq m Block Coefficient 0.583 Prismatic Coefficient 0.616 Table 1A Figure3.1.2: Full Perspective View
Figure 3.1.1: General Orthogonal View Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
Algorithms
Drag force : friction+ form+ wave
Froude number (Fn)
Skin friction (tonne)
Residual resistance (tonne)
Trim
0.251
13.509
21.963




35.471
0.251 0.249
13.509 
9.523 

16.391
5.098
11.819
23.032 9.67
0.251 
21.341

463.049
16.421 
21.697 
2.778 
40.896 102.031
0.533







Gerritsma 1981 Gerritsma 1996 Oortmenssen Holtrop and Mennen Savitsky Savitsky and Brown
Friction
Form
Wave
Total resistance (tonne)
Table 1a
Fig: Drag Vs speed
Analysis of Hullform1 Algorithms
Acceptance
Gerritsma 1981
No
Gerritsma 1996
No
Oortmenssen
No
Holtrop and Mennen
Yes
Savitsky
No
Savitsky and Brown
No
Remark The model does meet the criteria of Froude number of below 0.45 but the Algorithms “Gerritsma 1981” is more applicable for smaller vessel like fishing vessel or racing yachts rather that large vessel like cargo vessel. It‟s basically the upgrade version of Gerritsma 19981 with Froude number 0.6. The scheme generally gives slightly lower drag estimates Algorithm‟s limitation of waterline length between 8 and 80 metres; it doesn‟t meet the hull1‟s waterline length. Besides, the wave drage value shows negative which means it‟s not opposing the direction of the vessel. This Algorithm is more suitable for predicting smaller ships such as tugs and trawlers From 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. Algorithm gives 102.031 tonne which is negative value that not possible in predicting. So, we omit the Savitsky algorithm. Gives 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
Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
3.2 Hull Form 2 Hull form 2 General Particulars Displacement, Δ 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 Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
Algorithms
Drag force : friction+ form+ wave
Froude number(Fn)
Skin friction (tonne)
Residual resistance (tonne)
Trim
0.376
3.6
41.158




44.758
0.376 0.372
3.6 
28.172 

4.286
2.172
26.639
31.772 35.097
0.376 
4.778

194.739
4.286 
10.246 
22.872 
37.415 102.031
0.736






Gerritsma 1981 Gerritsma 1996 Oortmenssen Holtrop and Mennen Savitsky Savitsky and Brown
Table 2b
Friction
Form
Wave
Total resistance (tonne)
Fig: Drag Vs speed
Analysis of Hullform 2 Algorithms
Acceptance
Gerritsma 1981
No
Gerritsma 1996
No
Oortmenssen
Yes
Holtrop and Mennen
No
Savitsky
No
Savitsky and Brown
No
Remark The model does meet the criteria of Froude number of below 0.45 but 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. It‟s basically the upgrade version of Gerritsma 19981 with Froude number 0.6. The scheme generally gives slightly lower drag estimates Van Oortmenssen met all the criteria of this algorithm such as a designed waterline length length between 8  80 metres. This method is useful for estimating the resistance of small ships such as trawlers and tugs. This algorithm will not be suitable as this model hull prismatic coefficient had exceeded the limitation of prismatic coefficients between 0.55  0.65. Algorithm gives 102.031 tonne which is negative value that not possible in predicting. So, we omit the Savitsky algorithm. Gives 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
Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
3.3 Hull Form 3 Hull form 3 General Particulars Displacement, Δ 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 Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
Algorithms
Froude number(Fn)
Skin friction (tonne)
Residual resistance (tonne)
Trim
0.467


0.467 0.458
1.118 
0.467 1.102
Gerritsma 1981 Gerritsma 1996 Oortmenssen Holtrop and Mennen Savitsky Savitsky and Brown
Drag force : friction+ form+ wave
Total resistance (tonne)
Friction
Form
Wave





5.372 

1.317
0.092
11.221
6.49 12.445
1.205

9.211
1.322 
25.828 
8.684 
35.834 102.031







Table 3b
Fig: Drag Vs speed
Analysis of Hullform 3 Algorithms Gerritsma 1981
Acceptance No
Gerritsma 1996
Yes
Oortmenssen Holtrop and Mennen Savitsky
No No No
Savitsky and Brown
No
Remark No result as Froude number greater than the criteria of below 0.45 An update of Algorithms of „ Gerritsma 1981‟ it have a higher Froude number of 0.6 which 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. This Algorithm does not met the requirement as it‟s prismatic coefficient 0.773 fall out of range between 0.50 – 0.73 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 vessel Algorithm gives 102.031 tonne which is negative value that not possible in predicting. So, we omit the Savitsky algorithm. This 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
Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
3.4 Hull Form 4
Hull form 4 General Particulars Displacement, Δ 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 Table 4a Figure 3.4.1: Full Perspective View
Figure 3.4.2: General Orthogonal View Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
Algorithms
Froude number(Fn)
Skin friction (tonne)
Residual resistance (tonne)
Trim
0.905


0.905 0.88

0.905 2.029
Gerritsma 1981 Gerritsma 1996 Oortmenssen Holtrop and Mennen Savitsky Savitsky and Brown
Drag force : friction+ form+ wave
Total resistance (tonne)
Friction
Form
Wave







152.816
10.697
523.672
381.552
126.865

473.82
153.979 
2374.485 4504.634 
7033.099 600.685




Table 4b



Fig: Drag Vs speed
Analysis of Hullform 4 Algorithms Gerritsma 1981 Gerritsma 1996
Acceptance No No
Oortmenssen
No
Holtrop and Mennen
No
Savitsky
Yes
Savitsky and Brown
No
Remark The model does not meet the criteria as it exceeds the Froude number of 0.45. As a result, it is not suitable to use this algorithm. This algorithm is also not applicable as it exceeds the Froude number of 0.60. This algorithm shows a negative value of form and wave drag, which means it‟s not opposing the direction of the vessel. Thus, this algorithm is not accurate and suitable for this model.
This algorithm is widely used in prediction of resistance of displacement and semidisplacement vessels such as tankers, 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. This algorithm most suit the above criteria as the commonest scheme used for predicting the drag of planning craft. Gives 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 Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
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. 1st Loading Condition: Original Displacement with no trim 2nd Loading Condition Double Displacement with no trim 3rd Loading 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
1st Loading Condition: Original Displacement with no trim
2nd Loading Condition: Double Displacement with no trim
Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
3rd Loading Condition: Original displacement but with a static trim angle of approximately 5 degrees
4.3 Table of Resistance Components for three Conditions
Friction [tonnes] Form Drag [tonnes] Wave Drag [tonnes] Total Drag [tonnes]
Condition 1 Original displacement with no trim 16.425 21.623 2.78 40.828
Condition 2 Double displacement with no trim 22.612 28.485 5.064 56.16
Condition 3 Original displacement with 5 degree trim 16.285 61.692 19.544 97.52
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 area contributed 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.
Group 3
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
5. Optimization of a Cargo Vessel Design Our 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:
No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
Conditions Length Breadth (L) % (B) % 80 80 80 80 80 80 80 80 80 100 100 100 100 100 100 100 100 100 120 120 120 120 120 120 120 120 120
80 80 80 100 100 100 120 120 120 80 80 80 100 100 100 120 120 120 80 80 80 100 100 100 120 120 120
Total Resistance
Friction
Form
Wave
Righting MMT
Depth (D) %
[Tonnes]
[Tonnes]
[Tonnes]
[Tonnes]
[Tonne.m/deg]
80 100 120 80 100 120 80 100 120 80 100 120 80 100 120 80 100 120 80 100 120 80 100 120 80 100 120
41.848 41.495 43.936 41.933 44.67 46.373 48.506 50.571 51.959 34.064 35.898 37.039 39.653 40.831 41.727 46.47 47.402 50.135 33.211 34.331 34.876 39.126 39.691 41.975 45.851 47.96 53.743
14.636 14.463 14.39 15.225 14.959 14.794 16.209 15.847 15.477 15.822 15.615 15.499 16.759 16.425 16.051 18.071 17.441 17.043 17.064 16.883 16.529 18.323 17.742 17.376 19.758 19.112 18.649
18.22 17.809 19.752 22.217 24.834 26.437 30.007 32.333 33.886 14.175 15.952 17.041 20.224 21.625 22.748 26.791 28.278 29.407 12.968 14.116 14.971 18.42 19.322 20.216 24.226 25.432 25.628
8.992 9.223 9.794 4.535 4.877 5.142 2.23 2.931 2.597 4.067 4.331 4.499 2.67 2.78 2.928 1.608 1.683 3.685 3.179 3.307 3.377 2.591 2.627 4.383 1.807 3.417 9.446
648.004 295.182 42.012 1330.789 900.691 506.917 2361.115 1831.341 1365.789 663.336 290.883 60.073 1483.125 1027.08 616.416 2688.514 2127.535 1636.944 706.54 319.121 41.287 1649.456 1175.059 749.543 3021.596 2429.824 1912.55
Group 3
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 will return 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 energy imparted on it by wind, waves or any other sources. 3. The range of stability. For angles less than the range of stability, the vessel will return 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 energy imparted on it by wind, waves or any other source
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
5.1 Design No. 13 Analysis Data
No . 13
Conditions Lengt h (L) Breadt % h (B) % 100
100
Total Resistance Depth (D) % 80
[Tonnes] 39.653
5. 2 Design No. 19 Analysis Data Friction
[Tonnes] 16.759
Form
[Tonnes] 20.244
Wave
[Tonnes] 2.67
Righting moment [Tonne.m/ deg] 1483.125
No . 19
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 GZ value is 4.49m at 38.0 deg, the range of stability is up to 93.5deg and the area under from 0 to 93.5 deg is 252.53
Group 3
Conditions Lengt h (L) Breadt % h (B) % 120
80
Total Resistance
Friction
Form
Wave
Righting moment
Depth (D) %
[Tonnes]
[Tonnes]
[Tonnes]
[Tonnes]
[Tonne.m/ deg]
80
33.211
17.064
12.968
3.179
706.54
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.
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
5.3 Design No. 22 Analysis Data & optimizing with + 10% Total Resistance
Conditions No. 22
Length (L) % 120
Breadth (B) % 100
Depth (D) % 80
Friction
Form
Wave
5.4 Further Analysis with ±10% change Righting moment
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: Conditions
[Tonnes] 39.126
[Tonnes] 18.323
[Tonnes] 18.42
[Tonnes] 2.591
[Tonne.m/deg] 1649.456
The length of the vessel was increased to 120%, an 80% decrease of depth and Breadth maintains. 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 to 94.0 deg is 261.96.
Chosen Optimised Design: Design 4 : Length increase by 20%, Breadth decrease by 10% and Depth decrease by 20% .
Group 3
No. 22 1 2 3 4 5
Length (L) % 120 110 120 110 120 120
Breadth (B) % 100 100 100 100 90 110
Depth (D) % 80 80 90 90 80 80
Original GZ Curve
Total Resistance
Friction
Form
Wave
Righting moment
[Tonnes] 39.126 39.317 40.566 39.757 34.512 43.192
[Tonnes] 18.323 17.540 18.624 17.338 16.664 19.457
[Tonnes] 18.42 19.204 19.227 19.814 15.066 21.457
[Tonnes] 2.591 2.573 2.715 2.605 2.782 2.278
[Tonne.m/deg] 1649.456 1565.522 1440.538 1324.557 1065.963 2325.558
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 stability up to 93.9 deg and the area under from 0 to 93.9 deg is 276.59.
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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 large diameter 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 Hullform 1
Figure 6.2.2: General Orthogonal View and View from centerline of Hullform 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 Length Breadth Depth No. (L) % (B) % (D) % 22
120
90
80
Total Resistance
Friction
Form
Wave
Righting moment
[Tonnes]
[Tonnes]
[Tonnes]
[Tonnes]
[Tonne.m/deg]
34.512
16.664
15.066
2.782
1065.963
Hull Extra without bulbous bow Length Breadth Depth No. (L) % (B) % (D) % 22
120
90
80
Total Resistance
Friction
Form
Wave
Righting moment
[Tonnes]
[Tonnes]
[Tonnes]
[Tonnes]
[Tonne.m/deg]
38.015
17.049
15.4
5.566
1509.527
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. Group 3
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6.3.1 Using Different loading conditions for Hullform1 and Hullform Extra (Step 4) Condition 1 Original displacement no trim 100m 30m 6m
Hull 1 with bulbous bow Length Dreadth Draught Wetted surface area Displacement
with
Condition 2 Double displacement no trim 100m 30m 10.446m
with
Condition 3 Original displacement with 5 degree trim 100m 30m 7.673m
2668.497m2
3681.635 m2
2653.1m2
10015.348 tonnes
20048.303 tonnes
10015.348 tonnes
Hull 5 without bulbous bow Length Dreadth Draught Wetted surface area Displacement
Condition 1 Original displacement with no trim 100m 30m 6.124m
Condition 2 Double displacement with no trim 100m 30m 10.542m
Condition 3 Original displacement with 5 degree trim 100m 30m 7.710m
2561.449m2
3568.735m2
2653.1m2
10014.997 tonnes
20048.303 tonnes
10014.951 tonnes
Table: General particulars about the Hullform 1 and Hullform Extra for different Loading conditions of Step 4
Hull1 with bulbous bow Friction [tonnes] Form Drag [tonnes] Wave Drag [tonnes] Total Drag [tonnes]
Condition 1 Original displacement with no trim 16.425 21.626 2.780 40.831
Condition 2 Double displacement with no trim 22.574 50.369 6.185 79.128
Condition 3 Original displacement with 5 degree trim 16.329 50.245 19.423 85.997
Hull_Extra without bulbous bow Friction [tonnes] FormDrag[tonnes] WaveDrag[tonnes] TotalDrag[tonnes]
Condition 1 Original displacement with no trim 15.859 21.207 4.378 41.443
Condition 2 Double displacement no trim 24.569 28.493 28.788 81.851
with
Condition 3 Original displacement with 5 degree trim 16.224 66.530 5.357 88.112
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 1 0.612tonnes, Condition 2 2.723tonnes and Condition 3 2.115 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. Group 3
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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 ReAnalysis 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 Method and 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
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Form Coefficient
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Resistance calculated with various algorithms Gerritsma 1981
Gerritsma 1996
Holtrop & Mennen
Savitsky
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Oortmenssen
Savitsky &Brown
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Hull 2 Data as follows: General Data
Centre
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Form Coefficient
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Resistance calculated with various algorithms Gerritsma 1981
Gerritsma 1996
Holtrop & Mennen
Savitsky
Group 3
Oortmenssen
Savitsky &Brown
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Hull 3 Data as follows: General Data
Centre
Group 3
Form Coefficient
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
Resistance calculated with various algorithms Gerritsma 1981
Holtrop & Mennen
Gerritsma 1996
Savitsky
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Oortmenssen
Savitsky &Brown
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Hull 4 Data as follows: General Data
Centre
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Form Coefficient
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MAR 2112 ENGINEERING APPLICATIONS – ( COMPUTER AIDED DESIGN APPLICATIONS )
Resistance calculated with various algorithms Gerritsma 1981 Holtrop & Mennen
Oortmenssen
Gerritsma 1996
Savitsky
Savitsky &Brown
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