Derive a carene table from a buoyancy shape

from DAVE import *
from DAVE.jupyter import *

Equilibrium-core version = 2.48 from c:\python\miniconda3\envs\book\lib\site-packages\pyo3d.cp39-win_amd64.pyd
default resource folders:
c:\python\miniconda3\envs\book\lib\site-packages\DAVE\resources
C:\Users\beneden\DAVE_models
C:\data\Dave\Book\DAVE-book\DAVE-notebooks
Blender found at: C:\Program Files\Blender Foundation\Blender 3.3\blender.exe

s = Scene("cheetah.dave")  # use the Cheetah model

Loading c:\python\miniconda3\envs\book\lib\site-packages\DAVE\resources\cheetah.dave

c:\python\miniconda3\envs\book\lib\site-packages\DAVE\nodes.py:4468: UserWarning: BallastSystem.new_tank is outdated and may be removed in a future version.
  warn(

Have a look at the names of the nodes

show(s, show_global = True, camera_pos = (377.41378393620676, 177.29136875029081, -22.319832341170876), lookat = (52.20246063341496, -52.124244707385635, 2.968568242388601))

No actors created for node Ballast_system

number of points changed, creating new
 Warning! Please use "settings.use_parallel_projection" instead!

c:\python\miniconda3\envs\book\lib\site-packages\DAVE\jupyter\jupyter.py:194: UserWarning: VTK/Vedo issue: plotter is None
  warnings.warn("VTK/Vedo issue: plotter is None")

s.print_node_tree()

Cheetah [RigidBody]
 |-> DP reference point [Frame]
 |-> buoyancy [Buoyancy]
 |-> ps1 [Tank]
 |-> sb1 [Tank]
 |-> mid1 [Tank]
 |-> ps2 [Tank]
 |-> sb2 [Tank]
 |-> mid2 [Tank]
 |-> ps3 [Tank]
 |-> sb3 [Tank]
 |-> mid3 [Tank]
 |-> ps4 [Tank]
 |-> sb4 [Tank]
 |-> mid4 [Tank]
 |-> ps5 [Tank]
 |-> sb5 [Tank]
 |-> mid5 [Tank]
 |-> ps6 [Tank]
 |-> sb6 [Tank]
 |-> mid6 [Tank]
 |-> ps7 [Tank]
 |-> sb7 [Tank]
 |-> mid7 [Tank]
 |-> ps8 [Tank]
 |-> sb8 [Tank]
 |-> mid8 [Tank]
 |-> ps9 [Tank]
 |-> sb9 [Tank]
 |-> bow [Tank]
 |-> visual - vessel [Visual]
 |-> Wave Interaction draft 6.75 [WaveInteraction1]
 |-> Ballast_system [BallastSystem]
DP setpoint for cheetah [Frame]
DP springs cheetah [LC6d]

from DAVE.marine import carene_table

Calculate the carene table

• The carene curve is requested based on the buoyancy node [Buoyancy], not the vessel node !

• The table is calculated numerically using a small displacement from the even-keel situation.

node = s['buoyancy']
table = carene_table(s, node);

0.005950999911874533
-0.25
-0.5
-0.75
-1.0
-1.25
-1.5

-1.75
-2.0
-2.25
-2.5
-2.75
-3.0
-3.25

-3.5
-3.75
-4.0
-4.25
-4.5
-4.75
-5.0

-5.25
-5.5
-5.75
-6.0
-6.25
-6.5
-6.75

-7.0
-7.25
-7.5
-7.75
-8.0
-8.25
-8.5

-8.75
-9.0
-9.25
-9.5
-9.75
-10.0
-10.25

-10.5
-10.75
-11.0
-11.25
-11.5
-11.75
-12.0

-12.25
-12.5
-12.75
-13.0
-13.25
-13.5
-13.75

-14.0
-14.25
-14.5
-14.75
-15.0
-15.25
-15.5

-15.75
-16.0
-16.25
-16.5
-16.75
-17.0

-17.25
-17.5
-17.75
-18.0
-18.25
-18.5
-18.75

-19.0
-19.25
-19.5
-19.75
-20.0
-20.25
-20.5
-20.75

-21.0
-21.25
-21.5
-21.548954010009766

c:\python\miniconda3\envs\book\lib\site-packages\DAVE\marine.py:127: UserWarning: Zero displacement change detected for vertical position of -21.549954010009767m
  warn(f'Zero displacement change detected for vertical position of {a.z}m')

table

	BM T [m]	BM L [m]	CoF x [m]	CoF y [m]	Awl [m2]	Displacement [m3]	CoB x [m]	CoB y [m]	CoB z [m]
Draft [m]
0.005951	824.772791	24734.844049	154.950946	3.892336e-06	8.211311	0.000000	0.000000	0.000000e+00	-0.005951
-0.250000	549.000884	5942.565819	112.103608	7.784851e-07	6038.173587	1395.640155	111.616555	7.311428e-07	0.129644
-0.500000	318.382553	3736.669234	112.576878	7.746077e-07	6420.005125	2956.986482	112.066639	7.581174e-07	0.259864
-0.750000	214.740826	2708.765262	112.158916	7.381401e-07	6654.911794	4592.819177	112.173159	7.549822e-07	0.390179
-1.000000	162.153850	2159.894627	111.574458	7.204355e-07	6851.278205	6281.546409	112.097717	7.484993e-07	0.520681
...	...	...	...	...	...	...	...	...	...
-20.500000	0.097729	0.284728	206.281862	7.928139e-06	4.954338	116192.287353	112.797469	6.512415e-07	7.658785
-20.750000	0.005297	0.192928	206.286085	7.578735e-06	3.744253	116193.375239	112.798344	6.513071e-07	7.658906
-21.000000	0.003606	0.101255	206.255766	6.843373e-06	2.536219	116194.160860	112.798977	6.513546e-07	7.658996
-21.250000	0.001931	0.028276	206.098897	7.945931e-06	1.330235	116194.644727	112.799365	6.513839e-07	7.659052
-21.500000	0.000623	0.000346	202.297481	1.918715e-05	0.127114	116194.827353	112.799512	6.513947e-07	7.659073

87 rows × 9 columns

Plotting

First re-generate the table with a smaller set-size:

table = carene_table(s, node, stepsize=.1);

0.005950999911874533

-0.1
-0.2
-0.30000000000000004
-0.4
-0.5
-0.6000000000000001

-0.7000000000000001
-0.8
-0.9
-1.0
-1.1
-1.2000000000000002
-1.3

-1.4000000000000001
-1.5
-1.6
-1.7000000000000002
-1.8
-1.9000000000000001
-2.0

-2.1
-2.2
-2.3000000000000003
-2.4000000000000004
-2.5
-2.6
-2.7

-2.8000000000000003
-2.9000000000000004
-3.0
-3.1
-3.2
-3.3000000000000003
-3.4000000000000004

-3.5
-3.6
-3.7
-3.8000000000000003
-3.9000000000000004
-4.0
-4.1000000000000005

-4.2
-4.3
-4.4
-4.5
-4.6000000000000005
-4.7
-4.800000000000001

-4.9
-5.0
-5.1000000000000005
-5.2
-5.300000000000001
-5.4
-5.5

-5.6000000000000005
-5.7
-5.800000000000001
-5.9
-6.0
-6.1000000000000005

-6.2
-6.300000000000001
-6.4
-6.5
-6.6000000000000005
-6.7
-6.800000000000001

-6.9
-7.0
-7.1000000000000005
-7.2
-7.300000000000001
-7.4
-7.5
-7.6000000000000005

-7.7
-7.800000000000001
-7.9
-8.0
-8.1
-8.200000000000001
-8.3

-8.4
-8.5
-8.6
-8.700000000000001
-8.8
-8.9
-9.0

-9.1
-9.200000000000001
-9.3
-9.4
-9.5
-9.600000000000001
-9.700000000000001

-9.8
-9.9
-10.0
-10.100000000000001
-10.200000000000001
-10.3
-10.4

-10.5
-10.600000000000001
-10.700000000000001
-10.8
-10.9
-11.0
-11.100000000000001

-11.200000000000001
-11.3
-11.4
-11.5
-11.600000000000001
-11.700000000000001
-11.8

-11.9
-12.0
-12.100000000000001
-12.200000000000001
-12.3
-12.4
-12.5

-12.600000000000001
-12.700000000000001
-12.8
-12.9
-13.0
-13.100000000000001
-13.200000000000001

-13.3
-13.4
-13.5
-13.600000000000001
-13.700000000000001
-13.8
-13.9

-14.0
-14.100000000000001
-14.200000000000001
-14.3
-14.4
-14.5
-14.600000000000001

-14.700000000000001
-14.8
-14.9
-15.0
-15.100000000000001
-15.200000000000001
-15.3

-15.4
-15.5
-15.600000000000001
-15.700000000000001
-15.8
-15.9
-16.0

-16.1
-16.2
-16.3
-16.400000000000002
-16.5
-16.6
-16.7

-16.8
-16.900000000000002
-17.0
-17.1
-17.2
-17.3
-17.400000000000002
-17.5

-17.6
-17.7
-17.8
-17.900000000000002
-18.0
-18.1
-18.2

-18.3
-18.400000000000002
-18.5
-18.6
-18.7
-18.8
-18.900000000000002

-19.0
-19.1
-19.200000000000003
-19.3
-19.400000000000002
-19.5

-19.6
-19.700000000000003
-19.8
-19.900000000000002
-20.0
-20.1
-20.200000000000003
-20.3

-20.400000000000002
-20.5
-20.6
-20.700000000000003
-20.8
-20.900000000000002
-21.0

-21.1
-21.200000000000003
-21.3
-21.400000000000002
-21.5
-21.548954010009766

c:\python\miniconda3\envs\book\lib\site-packages\DAVE\marine.py:127: UserWarning: Zero displacement change detected for vertical position of -21.549954010009767m
  warn(f'Zero displacement change detected for vertical position of {a.z}m')

By default the table in indexed by draft. This means the plot methods will plot with draft on the x-axis:

# Set matplotlib figure size
import matplotlib.pyplot as plt
plt.rcParams['figure.figsize'] = [10, 6]

table.plot();

To be able to plot with in the traditional way with the draft vertical we need to reset the index. The x and y can then be specified by name

table = table.reset_index()
table.plot(x = 'CoF x [m]', y= 'Draft [m]')
plt.grid()

For plotting multiple lines in the same graph it is easiest to create the plots using matplotlib directly.

draft = table['Draft [m]']
cofx = table['CoF x [m]']
cobx = table['CoB x [m]']

plt.plot(cofx, draft,label='CoF x [m]')
plt.plot(cobx, draft,label='CoB x [m]')
plt.grid()
plt.legend();

Observe that the CoBx line is vertical at the point where CoBx = CoFx. Does that make sense?

– done –