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Verification with various hull shapes |
  
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Verification with various hull shapes |
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In addition to verifying Orca3D's results with primitive shapes, we have run a number of comparisons with GHS™, an industry standard for hydrostatics and stability calculations. GHS is written and distributed by Creative Systems, Inc., of Port Townshend, WA.
The following presents the hydrostatic results for four different hulls. The first three were created in Orca3D and are the standard planing, sailing, and ship type hulls produced by the Hull Assistants. The fourth is a containership hull that was imported from a ‘.GF’ file as a mesh. CG height is on the baseline for each case, and mesh density is listed on each table. Each hull was evaluated at three drafts. Variation in the righting arm curves is shown in the graphs following each table.
The maximum difference is highlighted in red, and all differences above 1% are highlighted in yellow.
Explanation of Differences Greater than 1%:
The sectional area coefficient is calculated using different beam and depth values. GHS values are higher because in its calculations, the local beam and depth are used in place of the maximum beam and depth. While these two values can be the same, they are not always as seen prominently in the Orca Planing example and also in the Orca Sailing example.
The length used in calculating the form coefficients can be calculated two different ways. If no length is previously specified, GHS calculates the length as ‘the length of the rectangular block which circumscribes the immersed volume of the component.’ Orca, however, uses the length of the current waterline. In the case of the containership hull, which has a bulbous bow, this length can vary by the length of the bulb (12 meters), causing any coefficients which use this length to be up to 4.6% different, depending on the draft at which they are evaluated. A raked stern will also cause these values to differ, such as in the Orca Planing example, which has a transom rake angle of 22 degrees.
The wetted surface calculations are also approached using two different methods. GHS uses section integration, which relies heavily on closely spaced stations and linear approximations. These values, according to the GHS help file, have a 2% error margin. Orca3D, however, uses the actual area of the submerged surfaces and does not rely on linear approximations.
Orca3D Planing Hull:
Figure 1: Orca3D Planing Half Hull
Table 1: Planing Hull Hydrostatics and Righting Arm Curve
Mesh |
0.7 |
Draft = 0.5 m |
Draft = 0.75 m |
Draft = 1 m |
||||||
Density |
Orca |
GHS |
%Diff |
Orca |
GHS |
%Diff |
Orca |
GHS |
%Diff |
|
Disp |
t |
6.57 |
6.58 |
0.221 |
12.39 |
12.40 |
0.089 |
18.57 |
18.59 |
0.081 |
LCB |
m |
5.87 |
5.86 |
0.147 |
5.85 |
5.85 |
0.139 |
5.79 |
5.79 |
0.119 |
VCB |
m |
0.34 |
0.34 |
0.076 |
0.47 |
0.47 |
0.013 |
0.61 |
0.61 |
0.016 |
WSA |
m² |
26.29 |
26.27 |
0.085 |
32.33 |
32.50 |
0.526 |
38.40 |
38.25 |
0.392 |
Awp |
m² |
21.97 |
21.98 |
0.037 |
23.43 |
23.44 |
0.056 |
24.82 |
24.83 |
0.043 |
LCF |
m |
5.93 |
5.93 |
0.051 |
5.75 |
5.75 |
0.096 |
5.59 |
5.59 |
0.101 |
BMt |
m |
1.71 |
1.71 |
0.315 |
1.06 |
1.06 |
0.271 |
0.82 |
0.82 |
0.170 |
BMl |
m |
22.08 |
22.05 |
0.123 |
12.90 |
12.89 |
0.067 |
9.33 |
9.33 |
0.041 |
GMt |
m |
2.05 |
2.05 |
0.147 |
1.53 |
1.53 |
0.131 |
1.43 |
1.43 |
0.210 |
GMl |
m |
22.42 |
22.39 |
0.134 |
13.37 |
13.37 |
0.000 |
9.93 |
9.94 |
0.101 |
Cb |
|
0.524 |
0.517 |
1.330 |
0.617 |
0.602 |
2.472 |
0.652 |
0.630 |
3.451 |
Cp |
|
0.800 |
0.788 |
1.526 |
0.838 |
0.818 |
2.497 |
0.850 |
0.821 |
3.577 |
Cwp |
|
0.899 |
0.899 |
0.034 |
0.898 |
0.897 |
0.057 |
0.893 |
0.894 |
0.067 |
Cx |
|
0.655 |
0.700 |
6.453 |
0.736 |
0.773 |
4.817 |
0.766 |
0.797 |
3.836 |
Cvp |
|
0.583 |
0.585 |
0.421 |
0.687 |
0.689 |
0.244 |
0.730 |
0.731 |
0.204 |
RA |
0 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
m |
5 |
0.179 |
0.179 |
0.239 |
0.134 |
0.134 |
0.126 |
0.125 |
0.125 |
0.162 |
|
10 |
0.357 |
0.356 |
0.280 |
0.270 |
0.269 |
0.223 |
0.250 |
0.250 |
0.054 |
|
15 |
0.505 |
0.504 |
0.239 |
0.408 |
0.407 |
0.189 |
0.358 |
0.358 |
0.082 |
|
20 |
0.629 |
0.627 |
0.256 |
0.549 |
0.548 |
0.219 |
0.445 |
0.444 |
0.125 |
|
25 |
0.737 |
0.735 |
0.237 |
0.663 |
0.662 |
0.213 |
0.517 |
0.516 |
0.151 |
|
30 |
0.835 |
0.833 |
0.198 |
0.745 |
0.744 |
0.097 |
0.579 |
0.578 |
0.171 |
|
35 |
0.922 |
0.921 |
0.108 |
0.804 |
0.803 |
0.170 |
0.633 |
0.632 |
0.166 |
|
40 |
0.988 |
0.986 |
0.155 |
0.848 |
0.847 |
0.115 |
0.679 |
0.678 |
0.147 |
|
45 |
1.032 |
1.032 |
0.040 |
0.879 |
0.878 |
0.086 |
0.716 |
0.715 |
0.142 |
|
50 |
1.059 |
1.059 |
0.040 |
0.899 |
0.898 |
0.074 |
0.745 |
0.744 |
0.163 |
|
55 |
1.069 |
1.069 |
0.027 |
0.909 |
0.908 |
0.092 |
0.767 |
0.766 |
0.168 |
|
60 |
1.063 |
1.063 |
0.027 |
0.910 |
0.909 |
0.114 |
0.782 |
0.781 |
0.189 |
|
65 |
1.044 |
1.044 |
0.003 |
0.903 |
0.902 |
0.099 |
0.791 |
0.789 |
0.256 |
|
70 |
1.013 |
1.013 |
0.038 |
0.888 |
0.887 |
0.110 |
0.793 |
0.791 |
0.257 |
|
75 |
0.973 |
0.972 |
0.053 |
0.866 |
0.865 |
0.074 |
0.789 |
0.787 |
0.222 |
|
80 |
0.922 |
0.922 |
0.029 |
0.836 |
0.836 |
0.028 |
0.778 |
0.776 |
0.306 |
|
85 |
0.864 |
0.864 |
0.009 |
0.800 |
0.799 |
0.121 |
0.762 |
0.760 |
0.273 |
|
90 |
0.799 |
0.799 |
0.051 |
0.757 |
0.757 |
0.037 |
0.740 |
0.738 |
0.287 |
Orca3D Sailing Hull:
Figure 2: Orca3D Sailing Half Hull
Table 2: Sailing Hull Hydrostatics and Righting Arm Curve
Mesh |
0.7 |
Draft = 0.5 m |
Draft = 0.75 m |
Draft = 1 m |
||||||
Density |
Orca |
GHS |
%Diff |
Orca |
GHS |
%Diff |
Orca |
GHS |
%Diff |
|
Disp |
t |
6.45 |
6.48 |
0.414 |
12.14 |
12.17 |
0.279 |
18.18 |
18.21 |
0.177 |
LCB |
m |
5.45 |
5.44 |
0.103 |
5.64 |
5.63 |
0.098 |
5.71 |
5.70 |
0.073 |
VCB |
m |
0.31 |
0.32 |
0.113 |
0.46 |
0.46 |
0.004 |
0.60 |
0.60 |
0.032 |
WSA |
m² |
23.20 |
23.24 |
0.187 |
29.53 |
30.08 |
1.831 |
35.34 |
35.98 |
1.771 |
Awp |
m² |
20.73 |
20.78 |
0.240 |
23.11 |
23.13 |
0.073 |
23.86 |
23.87 |
0.044 |
LCF |
m |
5.80 |
5.80 |
0.078 |
5.86 |
5.86 |
0.016 |
5.83 |
5.83 |
0.011 |
BMt |
m |
1.59 |
1.59 |
0.263 |
1.11 |
1.11 |
0.158 |
0.81 |
0.81 |
0.241 |
BMl |
m |
18.93 |
18.88 |
0.250 |
12.11 |
12.10 |
0.086 |
8.48 |
8.47 |
0.114 |
GMt |
m |
1.90 |
1.91 |
0.419 |
1.58 |
1.57 |
0.445 |
1.41 |
1.41 |
0.000 |
GMl |
m |
19.24 |
19.20 |
0.208 |
12.57 |
12.56 |
0.080 |
9.08 |
9.07 |
0.110 |
Cb |
|
0.468 |
0.469 |
0.184 |
0.549 |
0.55 |
0.139 |
0.601 |
0.60 |
0.676 |
Cp |
|
0.581 |
0.585 |
0.754 |
0.661 |
0.66 |
0.267 |
0.702 |
0.70 |
0.465 |
Cwp |
|
0.771 |
0.771 |
0.005 |
0.804 |
0.81 |
0.138 |
0.809 |
0.81 |
0.018 |
Cx |
|
0.806 |
0.816 |
1.186 |
0.830 |
0.84 |
1.436 |
0.856 |
0.87 |
1.284 |
Cvp |
|
0.607 |
0.609 |
0.303 |
0.683 |
0.68 |
0.200 |
0.743 |
0.75 |
0.295 |
RA |
0 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
m |
5 |
0.165 |
0.166 |
-0.506 |
0.137 |
0.137 |
0.123 |
0.123 |
0.123 |
0.170 |
|
10 |
0.324 |
0.325 |
-0.407 |
0.272 |
0.272 |
0.131 |
0.246 |
0.246 |
0.021 |
|
15 |
0.470 |
0.471 |
-0.151 |
0.404 |
0.403 |
0.165 |
0.368 |
0.367 |
0.300 |
|
20 |
0.602 |
0.603 |
-0.246 |
0.529 |
0.529 |
0.051 |
0.478 |
0.477 |
0.249 |
|
25 |
0.716 |
0.717 |
-0.146 |
0.648 |
0.647 |
0.123 |
0.567 |
0.566 |
0.219 |
|
30 |
0.814 |
0.814 |
-0.003 |
0.751 |
0.750 |
0.104 |
0.641 |
0.640 |
0.119 |
|
35 |
0.897 |
0.897 |
0.046 |
0.830 |
0.829 |
0.088 |
0.702 |
0.701 |
0.145 |
|
40 |
0.968 |
0.967 |
0.066 |
0.888 |
0.888 |
0.056 |
0.753 |
0.752 |
0.102 |
|
45 |
1.020 |
1.018 |
0.163 |
0.931 |
0.930 |
0.078 |
0.794 |
0.793 |
0.136 |
|
50 |
1.053 |
1.051 |
0.177 |
0.959 |
0.958 |
0.085 |
0.827 |
0.826 |
0.064 |
|
55 |
1.070 |
1.067 |
0.235 |
0.975 |
0.974 |
0.064 |
0.851 |
0.850 |
0.070 |
|
60 |
1.072 |
1.069 |
0.235 |
0.979 |
0.979 |
0.046 |
0.867 |
0.866 |
0.065 |
|
65 |
1.061 |
1.057 |
0.348 |
0.974 |
0.973 |
0.120 |
0.875 |
0.874 |
0.079 |
|
70 |
1.038 |
1.035 |
0.323 |
0.960 |
0.959 |
0.068 |
0.875 |
0.875 |
0.031 |
|
75 |
1.006 |
1.002 |
0.366 |
0.937 |
0.936 |
0.055 |
0.869 |
0.868 |
0.060 |
|
80 |
0.964 |
0.960 |
0.382 |
0.905 |
0.905 |
0.042 |
0.855 |
0.854 |
0.078 |
|
85 |
0.913 |
0.909 |
0.462 |
0.867 |
0.866 |
0.095 |
0.834 |
0.833 |
0.122 |
|
90 |
0.855 |
0.852 |
0.366 |
0.821 |
0.821 |
0.052 |
0.807 |
0.806 |
0.109 |
Orca3D Ship Hull:
Figure 3: Orca3D Ship Half Hull
Table 3: Ship Hull Hydrostatics and Righting Arm Curve
Mesh |
0.8 |
Draft = 5 m |
Draft = 10 m |
Draft = 15 m |
||||||
Density |
Orca |
GHS |
%Diff |
Orca |
GHS |
%Diff |
Orca |
GHS |
%Diff |
|
Disp |
t |
11,314 |
11,294 |
0.173 |
27,477 |
27,424 |
0.192 |
45,543 |
45,461 |
0.181 |
LCB |
m |
78.03 |
78.04 |
0.014 |
81.45 |
81.45 |
0.002 |
82.81 |
82.81 |
0.009 |
VCB |
m |
2.82 |
2.82 |
0.111 |
5.63 |
5.63 |
0.038 |
8.36 |
8.36 |
0.027 |
WSA |
m² |
3,525 |
3,502 |
0.677 |
5,434 |
5,422 |
0.238 |
7,153 |
7,141 |
0.170 |
Awp |
m² |
2,792 |
2,794 |
0.040 |
3,420 |
3,418 |
0.075 |
3,615 |
3,613 |
0.055 |
LCF |
m |
79.96 |
80.05 |
0.113 |
85.92 |
85.95 |
0.035 |
83.74 |
83.75 |
0.011 |
BMt |
m |
10.95 |
10.96 |
0.138 |
5.74 |
5.73 |
0.111 |
3.82 |
3.82 |
0.126 |
BMl |
m |
302.52 |
303.14 |
0.206 |
217.21 |
217.29 |
0.039 |
149.19 |
149.26 |
0.049 |
GMt |
m |
13.77 |
13.79 |
0.109 |
11.37 |
11.36 |
0.079 |
12.18 |
12.18 |
0.008 |
GMl |
m |
305.33 |
305.96 |
0.206 |
222.83 |
222.92 |
0.040 |
157.55 |
157.62 |
0.044 |
Cb |
|
0.671 |
0.671 |
0.003 |
0.697 |
0.696 |
0.111 |
0.75 |
0.750 |
0.145 |
Cp |
|
0.687 |
0.686 |
0.166 |
0.706 |
0.704 |
0.225 |
0.758 |
0.757 |
0.112 |
Cwp |
|
0.850 |
0.850 |
0.041 |
0.890 |
0.889 |
0.097 |
0.917 |
0.917 |
0.046 |
Cx |
|
0.977 |
0.980 |
0.352 |
0.988 |
0.980 |
0.767 |
0.991 |
0.992 |
0.092 |
Cvp |
|
0.790 |
0.789 |
0.096 |
0.783 |
0.783 |
0.001 |
0.819 |
0.818 |
0.085 |
RA |
0 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
m |
5 |
1.202 |
1.208 |
-0.497 |
0.992 |
0.993 |
-0.087 |
1.063 |
1.063 |
0.009 |
|
10 |
2.407 |
2.415 |
-0.333 |
1.986 |
1.987 |
-0.028 |
2.126 |
2.126 |
-0.011 |
|
15 |
3.614 |
3.622 |
-0.211 |
2.985 |
2.986 |
-0.025 |
3.183 |
3.183 |
-0.004 |
|
20 |
4.805 |
4.812 |
-0.145 |
3.993 |
3.993 |
-0.012 |
4.136 |
4.137 |
-0.020 |
|
25 |
5.896 |
5.904 |
-0.132 |
5.015 |
5.016 |
-0.015 |
4.984 |
4.985 |
-0.015 |
|
30 |
6.806 |
6.811 |
-0.075 |
6.063 |
6.064 |
-0.013 |
5.754 |
5.756 |
-0.030 |
|
35 |
7.573 |
7.576 |
-0.036 |
7.141 |
7.143 |
-0.032 |
6.457 |
6.459 |
-0.025 |
|
40 |
8.239 |
8.239 |
-0.005 |
8.118 |
8.121 |
-0.037 |
7.098 |
7.100 |
-0.027 |
|
45 |
8.833 |
8.830 |
0.030 |
8.902 |
8.906 |
-0.042 |
7.678 |
7.680 |
-0.025 |
|
50 |
9.386 |
9.382 |
0.042 |
9.503 |
9.507 |
-0.038 |
8.198 |
8.200 |
-0.025 |
|
55 |
9.924 |
9.920 |
0.043 |
9.951 |
9.955 |
-0.042 |
8.658 |
8.661 |
-0.030 |
|
60 |
10.375 |
10.373 |
0.019 |
10.265 |
10.269 |
-0.035 |
9.059 |
9.062 |
-0.030 |
|
65 |
10.670 |
10.670 |
-0.002 |
10.462 |
10.465 |
-0.032 |
9.396 |
9.399 |
-0.034 |
|
70 |
10.814 |
10.814 |
0.000 |
10.550 |
10.553 |
-0.031 |
9.658 |
9.662 |
-0.037 |
|
75 |
10.825 |
10.824 |
0.014 |
10.538 |
10.541 |
-0.028 |
9.842 |
9.846 |
-0.044 |
|
80 |
10.719 |
10.716 |
0.031 |
10.433 |
10.436 |
-0.025 |
9.945 |
9.949 |
-0.042 |
|
85 |
10.507 |
10.503 |
0.041 |
10.243 |
10.245 |
-0.022 |
9.969 |
9.973 |
-0.037 |
|
90 |
10.199 |
10.196 |
0.034 |
9.972 |
9.974 |
-0.017 |
9.917 |
9.920 |
-0.032 |
Containership Hull:
Figure 4: Containership Half Hull
Table 4: Containership Hydrostatics and Righting Arm Curve
Mesh |
0.7 |
Draft = 6 m |
Draft = 11 m |
Draft = 16 m |
||||||
Density |
Orca |
GHS |
%Diff |
Orca |
GHS |
%Diff |
Orca |
GHS |
%Diff |
|
Disp |
t |
37,091 |
37,097 |
0.017 |
75,612 |
75,622 |
0.014 |
121,952 |
121,928 |
0.020 |
LCB |
m |
134.43 |
134.40 |
0.020 |
136.30 |
136.36 |
0.045 |
140.80 |
140.80 |
0.004 |
VCB |
m |
3.25 |
3.249 |
0.094 |
5.96 |
5.954 |
0.060 |
8.84 |
8.840 |
0.041 |
WSA |
m² |
8,884 |
8,904 |
0.216 |
12,227 |
12,264 |
0.300 |
15846 |
15,917 |
0.443 |
Awp |
m² |
7,029 |
7,036 |
0.098 |
8,224 |
8,211 |
0.165 |
9494 |
9,498 |
0.036 |
LCF |
m |
135.06 |
135.29 |
0.171 |
143.34 |
143.09 |
0.177 |
147.71 |
147.67 |
0.026 |
BMt |
m |
16.31 |
16.282 |
0.174 |
10.24 |
10.214 |
0.226 |
8.06 |
8.052 |
0.089 |
BMl |
m |
741.17 |
744.05 |
0.387 |
525.00 |
521.72 |
0.629 |
472.80 |
473.10 |
0.064 |
GMt |
m |
19.56 |
19.530 |
0.154 |
16.19 |
16.168 |
0.136 |
16.90 |
16.892 |
0.047 |
GMl |
m |
744.42 |
747.30 |
0.385 |
530.96 |
527.67 |
0.623 |
481.64 |
481.94 |
0.062 |
Cb |
|
0.598 |
0.597 |
0.212 |
0.664 |
0.637 |
4.208 |
0.706 |
0.689 |
2.457 |
Cp |
|
0.624 |
0.621 |
0.477 |
0.680 |
0.651 |
4.451 |
0.718 |
0.700 |
2.612 |
Cwp |
|
0.698 |
0.697 |
0.141 |
0.815 |
0.779 |
4.607 |
0.902 |
0.880 |
2.521 |
Cx |
|
0.959 |
0.962 |
0.331 |
0.976 |
0.97 |
0.641 |
0.983 |
0.98 |
0.286 |
Cvp |
|
0.857 |
0.857 |
0.015 |
0.815 |
0.817 |
0.294 |
0.782 |
0.783 |
0.068 |
RA m |
0 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
0.000 |
|
5 |
1.708 |
1.706 |
0.121 |
1.416 |
1.416 |
-0.022 |
1.475 |
1.475 |
-0.027 |
|
10 |
3.421 |
3.418 |
0.084 |
2.845 |
2.846 |
-0.032 |
2.950 |
2.950 |
0.011 |
|
15 |
5.128 |
5.124 |
0.069 |
4.295 |
4.296 |
-0.032 |
4.427 |
4.427 |
0.007 |
|
20 |
6.748 |
6.742 |
0.085 |
5.770 |
5.770 |
-0.002 |
5.908 |
5.907 |
0.025 |
|
25 |
8.184 |
8.175 |
0.111 |
7.278 |
7.277 |
0.019 |
7.339 |
7.337 |
0.031 |
|
30 |
9.440 |
9.430 |
0.110 |
8.803 |
8.800 |
0.034 |
8.603 |
8.599 |
0.046 |
|
35 |
10.569 |
10.561 |
0.074 |
10.281 |
10.275 |
0.054 |
9.725 |
9.719 |
0.063 |
|
40 |
11.610 |
11.605 |
0.043 |
11.615 |
11.609 |
0.055 |
10.711 |
10.705 |
0.054 |
|
45 |
12.590 |
12.584 |
0.045 |
12.674 |
12.663 |
0.085 |
11.551 |
11.546 |
0.047 |
|
50 |
13.530 |
13.529 |
0.010 |
13.473 |
13.464 |
0.069 |
12.239 |
12.233 |
0.048 |
|
55 |
14.389 |
14.383 |
0.039 |
14.050 |
14.042 |
0.059 |
12.779 |
12.773 |
0.043 |
|
60 |
15.019 |
15.022 |
-0.023 |
14.435 |
14.428 |
0.051 |
13.179 |
13.174 |
0.036 |
|
65 |
15.365 |
15.373 |
-0.055 |
14.650 |
14.643 |
0.046 |
13.447 |
13.443 |
0.032 |
|
70 |
15.469 |
15.477 |
-0.051 |
14.707 |
14.703 |
0.030 |
13.591 |
13.587 |
0.030 |
|
75 |
15.369 |
15.376 |
-0.047 |
14.617 |
14.615 |
0.013 |
13.616 |
13.613 |
0.023 |
|
80 |
15.092 |
15.097 |
-0.034 |
14.384 |
14.386 |
-0.011 |
13.529 |
13.526 |
0.022 |
|
85 |
14.656 |
14.661 |
-0.031 |
14.016 |
14.018 |
-0.015 |
13.335 |
13.334 |
0.008 |
|
90 |
14.085 |
14.086 |
-0.006 |
13.522 |
13.522 |
0.000 |
13.044 |
13.042 |
0.016 |
