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.