Derive a carene table from a buoyancy shape

from DAVE import *
from DAVE.jupyter import *

DAVEcore version = 2.0 from c:\python\miniconda3\envs\book\Lib\site-packages\DAVEcore.cp311-win_amd64.pyd
! Blender not found - Blender can be installed from the microsoft windows store.   if you have blender already and want to be able to use blender then please either:
   - configure windows to open .blend files with blender automatically 
   - add the folder containing blender-launcher.exe to the PATH variable.

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c:\python\miniconda3\envs\book\Lib\site-packages\DAVE\nodes.py:4634: UserWarning: BallastSystem.new_tank is outdated and may be removed in a future version.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, 177, -50), lookat = (52, -52, 3), width=3000, height = 1000)

No actors created for node Ballast_system

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

c:\python\miniconda3\envs\book\Lib\site-packages\DAVE\marine.py:128: RuntimeWarning: invalid value encountered in divide
  cob_local = np.sum([np.array(node.cob_local) * node.displacement for node in n2], axis=0) / displacement_m3
c:\python\miniconda3\envs\book\Lib\site-packages\DAVE\marine.py:129: RuntimeWarning: invalid value encountered in divide
  cob_global = np.sum([np.array(node.cob) * node.displacement for node in n2], axis=0) / displacement_m3
c:\python\miniconda3\envs\book\Lib\site-packages\DAVE\marine.py:165: RuntimeWarning: invalid value encountered in divide
  new_cob_global = np.sum([np.array(node.cob) * node.displacement for node in n2], axis=0) / np.sum(
c:\python\miniconda3\envs\book\Lib\site-packages\DAVE\marine.py:172: RuntimeWarning: invalid value encountered in divide
  new_cob_global = np.sum([np.array(node.cob) * node.displacement for node in n2], axis=0) / np.sum(

-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
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-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:141: 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	NaN	NaN	NaN	NaN	8.211311	0.000000	NaN	NaN	NaN
-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

c:\python\miniconda3\envs\book\Lib\site-packages\DAVE\marine.py:128: RuntimeWarning: invalid value encountered in divide
  cob_local = np.sum([np.array(node.cob_local) * node.displacement for node in n2], axis=0) / displacement_m3
c:\python\miniconda3\envs\book\Lib\site-packages\DAVE\marine.py:129: RuntimeWarning: invalid value encountered in divide
  cob_global = np.sum([np.array(node.cob) * node.displacement for node in n2], axis=0) / displacement_m3
c:\python\miniconda3\envs\book\Lib\site-packages\DAVE\marine.py:165: RuntimeWarning: invalid value encountered in divide
  new_cob_global = np.sum([np.array(node.cob) * node.displacement for node in n2], axis=0) / np.sum(
c:\python\miniconda3\envs\book\Lib\site-packages\DAVE\marine.py:172: RuntimeWarning: invalid value encountered in divide
  new_cob_global = np.sum([np.array(node.cob) * node.displacement for node in n2], axis=0) / np.sum(

-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:141: 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 –