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SAB Meeting – LA SPEZIA February 2018
Master thesis presentation
Blade bulbous-bow concept application research using commercial CFD software
Author: Mukhitdin Kakenov Supervisor: Prof.Dario Boote, University of Genova
SAB Meeting – LA SPEZIA February 2018
• Previous education: Saint-Petersburg State Marine Technical University (SMTU)
• Field of interest: Seakeeping; Hull Optimization; Ship Theory; Safe Operation of a ship, marine technologies in maritime area
• Seeking Career & objectives: Naval Designer, Project Engineer, Research Engineer in hull form and ship structure optimization study branches.
Mukhitdin KAKENOV Kazakhstan
Marine Engineer
Example 1. Benetti’s F-125
http://www.charterworld.com/news/f125-yacht-hull-arrives-benetti-yard-italys-viareggio
F-125
F-125 Length on waterline – 31.0 meters Maximum beam – 8.23 meters Half load draught – 2.01 meters High-speed range – 17.5-22 knots
https://www.pressreader.com/italy/superyacht/20170109/282428463876372
F-125. Now how it looks on a serial ship:
https://sandpeoplecommunication.wordpress.com/2013/12/16/benetti-news-from-the-yard-november-december-2013
Next example: ILUMEN 28M
http://robbreport.com/motors/marine/dominators-ilumen-now-more-spacious-and-preparing-launch-231479/
ILUMEN 28M Length on waterline – 28 meters Maximum beam – 8.23 meters Half load draught – 1.85 meters High-speed range – 17-29 knots
https://www.superyachttimes.com/yacht-news/dominator-ilumen-28m-taking- shape-in-italy
ILUMEN 28M in towing tank
https://www.pressreader.com/italy/superyacht/20170109/282428463876372
ILUMEN 28M in towing tank
ILUMEN 28M in towing tank
TOTAL RESISTANCE – pay attention on this!
Which force component had been
mostly reduced?
The Object of Interest Rhinoceros software was used to build the model of the yacht
The Object of Interest
The Object of Interest General arrangements and
some technical information:
LengthPP 54.2 m Breadth 12.6 m Designed draught 3.3 m Velocity range up to 22 kn
CFD
[Star-CCM+ CFD software was chosen] • Set rules of physics • Change a flow as ever you want • Change a ship and an experimental
domain models so many times as you need
What mesh size is better? Calculation quality vs. Time spent
The lower the cell size the more accurate the results of simulation
*Image has been taken from the Star-CCM+ 11 ver. manual
HOWEVER: the lower the cell size, the longer the time spent to compute a problem. Where is the golden middle???
Mesh convergence study • Let’s define some geometrical parameter to use it as a
relative value: In Star-CCM+ it is a “Base size” argument • What is it?
It’s a value, percentage of which may characterize an elemental size (length) of a computing cell
• How long should be this length? => any easy to operate with setting different cells sizes
Mesh convergence study • Let’s define some geometrical parameter to use it as a
relative value: In Star-CCM+ it is a “Base size” argument • What is it?
It’s a value, percentage of which may characterize an elemental size (length) of a computing cell
• How long should be this length? => any easy to operate with setting different cells sizes
Mesh convergence study
Mesh convergence study
19
21
23
25
27
29
31
13.5 14 14.5 15 15.5 16 16.5 17 17.5
Forc
e, k
N
Velocity, knots
Shear drag, mesh convergence
Base 10 meters Base 7.5 meters Base 6 meters
Mesh convergence study
20
25
30
35
40
45
50
55
60
13.5 14 14.5 15 15.5 16 16.5 17 17.5
Pres
sure
, kPa
Velocity, knots
Pressure drag, mesh convergence
Base 10meters
Base 7.5meters
Base 6meters
Mesh convergence study
-0.31
-0.29
-0.27
-0.25
-0.23
-0.21
-0.19
-0.17
-0.1513.5 14 14.5 15 15.5 16 16.5 17 17.5
Met
ers
Velocity, knots
Sinkage, mesh convergence
Base 10 metersBase 7.5 metersBase 6 meters
Mesh convergence study
0.45
0.47
0.49
0.51
0.53
0.55
0.57
0.59
0.61
0.63
0.65
13.5 14 14.5 15 15.5 16 16.5 17 17.5
Deg
rees
Velocity, knots
Trim, mesh convergence
Base 10 metersBase 7.5 metersBase 6 meters
Mesh convergence study
Mesh convergence study
Yacht with the bulbous bow
Yacht with the bulbous bow
Yacht with the bulbous bow
Yacht with the bulbous bow Kelvin waves
Gathered reference DATA: Resistance components (17 knots)
Gathered reference DATA: ship motions (17 knots)
REFERENCE DATA COLLECTED
19
21
23
25
27
29
13.5 14.5 15.5 16.5 17.5
Forc
e, k
N
Velocity, knots
Shear drag
25
30
35
40
45
50
55
13.5 14.5 15.5 16.5 17.5
Pres
sure
, kPa
Velocity, knots
Pressure drag
-0.35
-0.3
-0.25
-0.2
-0.1513.5 14.5 15.5 16.5 17.5
Met
ers
Velocity, knots
Sinkage
0.450.5
0.550.6
0.65
13.5 14.5 15.5 16.5 17.5Pres
sure
, kPa
Velocity, knots
Trim
Changing the bulbous bow to a blade one
• Features of the blade bow concept should be noticed:
Side view
Front view
Top view Bottom view
Blade bow. First design
Blade bow. First design
Blade bow. First design
Blade bow. First design
Bottom view
Blade bow, 1st design. Produced wave profile on 17 knots forwarding
17 knots
17 knots
17 knots. Blade bow
Changing the bulbous bow to a blade one
• Features of the blade bow concept should be noticed:
Side view
Front view
Top view Bottom view
Blade bow, 2nd variant
Blade bow, 2nd variant
17 knots. Blade bow, 2nd variant
17 knots. Blade bow, 2nd variant
17 knots. Blade bow, 2nd variant
17 knots. Blade bow, 2nd variant
Friction comparison
…
19
21
23
25
27
29
31
13.5 14 14.5 15 15.5 16 16.5 17 17.5
Res
ista
nce,
kN
Velocity, knots
Frictional resistance
Bulbous bow Blade bow 1 Blade bow 2, more inclined top
Pressure drag comparison
19
24
29
34
39
44
49
54
59
64
69
13.5 14 14.5 15 15.5 16 16.5 17 17.5
Pres
sure
, kPa
Velocity, knots
Pressure drag
Bulbous bow Blade bow 1 Blade bow 2, more inclined top
Sinkage comparison
-0.4
-0.35
-0.3
-0.25
-0.2
-0.1513.5 14 14.5 15 15.5 16 16.5 17 17.5
Sink
age,
met
ers
Velocity, knots
Sinkage
Bulbous bow Blade bow 1 Blade bow 2, more inclined top
Trim comparison
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
13.5 14 14.5 15 15.5 16 16.5 17 17.5
Trim
, deg
rees
Velocity, knots
Trim
Bulbous bow Blade bow 1 Blade bow 2, more inclined top
So, what do we have now…
• Trim had been changed (involving or separately from the sinkage - ?)
• Pressure drag increased – in what areas of the bow?
• Frictional drag is almost the same
CONCLUSION • The bow shape gives direct influence on ship motions
behavior. Changing the bow we will change the trim and sinkage, in particular;
• The pressure drag of the yacht’s new shape had been increased – how to reduce it, modifying the bow? The new problem to future additional research;
• The blade bow does not function as the initial one – does not help against wave producing effect. How to optimize the bow in connection to this aspect? This is a new problem appeared – to be studied in optimization study subject.