Optimization Khairul Hassan Doctoral student in Department of - - PowerPoint PPT Presentation

CFD Applications in Ship Design Optimization

1

Khairul Hassan Doctoral student in Department of Maritime Engineering Graduate School of Engineering, Kyushu University, Japan Maurice F. White Professor of Marine Engineering Department of Marine Technology Norwegian University of Science and Technology (NTNU) Norway Cosmin Ciortan, PhD, Consultant

• Dept. of Ship Hydrodynamics, Det Norske Veritas (DNV),

Oslo, Norway

2

 Introduction  Brief description of the CFD procedure  CFD application

• CFD application in ship design optimization
• CFD application in drag analysis for different wind directions

 Limitations of the CFD simulation  Conclusion

3

During design optimization the important considerations

• ship capacity

and

• Ship stability

Ship Hull Hydrodynamic resistance Aerodynamic resistance

CFD simulation in Ship design optimization

Ship design

• ptimization

Dimensions

• ptimization

Shape

• ptimization
• CFD simulation

can be used for both of the

• ptimizations

4

For wind resistance simulations, only the part above the waterline is considered

Ship Hull

Geometry of the problem

Principle particulars Length water line, LWL=221.65m Breadth=32.2m Depth=18.5m Draught=10.78m Block coefficient, CB=0.674 Deadweight, DWT=40900tonnes Cargo capacity: 2800TEU containers; Design speed: 23 knots

Boundary conditions and simulation conditions

Simulation Space 3 dimensional Motion stationary Time steady Flow materials Gas / air Air density 1.18415 kg/m^3 Dynamic viscosity 1.85508E-5 Pa-s Flow type Couple Equation of state Constant density Viscous Regime Turbulence (Reynolds averaged Navier-Stokes) Reynolds averaged turbulence K-Epsilon turbulence Ship speed 23knots

CFD simulation conditions for above water hull analysis: Mesh size: On container stacks and deck house- target size 0.6m and minimum size 0.2m, on the deck and on the above water hull- target size 0.8m and minimum size 0.2m.

• The total boundary length is 1000m, and

breadth also is 1000 m, the height is 245m and the ship position at the centre of the bottom surface. The length and the breadth are the same because the ship is rotated from 0 deg to 180deg.

5

Mesh/grid generation

• Grid/mesh

generation is the most important task and valid mesh generation is the most time consuming part in CFD analysis.

• The quality of the CFD analysis mostly

depends on the quality of generated mesh.

• Mainly three types of mesh: structured,

unstructured and hybrid. Here the unstructured mesh and hybrid mesh are used.

• Generating

the mesh type for CFD analysis by Starccm+ is Polyhedral. In analysis the volumetric control density is 2.5m.

• The used numbers of prism layers are 4

for 3 cm

6

Graphical presentation of CFD Simulation Result

• The simulation results can be

presented by

• 1. graphical from
• 2. tabular form
• In graphical form the

streamlines represent the air flow and help to give us a better understanding of the numerical results

• Gaps between container

stacks can have a significant influence on the resulting forces Graphical presentation of the simulation result

7

Simulation Result as Tabular Form

The result of the pressure and shear forces on different stacks are presented in the following table (ship speed 23 knots in head wind 20 knots)

The drag force acting on the different parts of the ship hull and container stacks Part Pressure(N) Shear(N) Net(N)

• ----------------------------- ------------- ------------- -------------

DH

• 2.068550e+04
• 1.023979e+02
• 2.078790e+04

hull

• 1.369280e+04
• 2.036224e+03
• 1.572903e+04

Stack_1

• 7.055177e+03
• 5.296690e+01
• 7.108144e+03

Stack_2

• 4.209718e+02

1.244562e+01

• 4.085262e+02

Stack_3

• 2.034496e+04
• 1.264827e+01
• 2.035760e+04

Stack_4 1.518748e+04

• 3.620133e+01

1.515128e+04 Stack_5

• 1.888242e+04
• 3.576994e+01
• 1.891819e+04

Stack_6 1.559257e+04

• 4.994998e+01

1.554262e+04 Stack_7

• 2.733035e+04
• 4.540582e+01
• 2.737576e+04

Stack_8 2.933077e+03

• 8.248552e+01

2.850592e+03 Stack_9 1.596127e+02

• 8.651351e+01

7.309917e+01 Stack_10

• 5.175854e+02
• 8.462801e+01
• 6.022134e+02

Stack_11

• 7.120480e+03
• 8.316351e+01
• 7.203644e+03

Stack_12

• 2.639828e+03
• 7.487794e+01
• 2.714706e+03

Stack_13 1.671533e+03

• 4.370696e+00

1.667162e+03 Stack_14 9.267767e+02 2.337641e+00 9.291143e+02

• ----------------------------- ------------- ------------- -------------

Total:

• 8.221904e+04 -2.772820e+03 -8.499186e+04

Monitor value: -84991.85938N

Assign the container stacks, deck house and the hull

8

9

Above water hull optimization

The forecastle deck is removed during the simulation in order to investigate the stacks’ effect on the aerodynamic resistance properly. The ship speed is 23 knots and wind speed is 20knots with head wind condition. The internal spaces among the stacks are 0.6 and 1.2m

The simulation results are taken from the M. Sc. project work done under Marine Technology, NTNU, Norway and partially financed by DNV

10

Comparison

By applying:- 1.General form of stacks

• 2. By modifying 3 rear container stacks, for

considering accommodating the available spaces due to remove the stacks 3.The 45o drag reduction surface with the front edge

• f the first stack, with modifying rear stacks

4.Sloping upper surface including above modification

The simulation results are taken from the M. Sc. project work done under Marine Technology, NTNU, Norway and partially financed by DNV

Air resistance (KN) 1 103.6 2 96.84 3 85 4 69.86

Final drag force curve

50000 100000 150000 200000 250000 300000 350000 400000 20 40 60 80 100 120 140 160 180

Angle betweent the ship sailing direction and the wind direction Drag force

Full loaded condition Partially loaded condition

Full loaded means all of the container stacks are present during simulation Partially loaded means the container stacks 9 and 10 are removed during simulation For the angle between wind direction and the ship advance 140 and 30 the drag forces are highest. Streamlines & pressure of air on stacks and on hull when incidence angle 0 Streamlines & pressure of air on stacks and on hull when incidence angle 90 and the stacks 9 and 10 are removed

CFD simulation for different wind flow direction

11

Results of container stacks modification

 For the reduction of the produced emission gases the counter action may create other severe problems  This paper reviews the reduction in the production of the emission gases which is achievable by reducing the fuel consumption.

12

Due to optimization of the container stacks for 1000 nautical miles distance Reduction of fuel consumption 2.83 tonnes Reduction of emission gas CO2 about 6.6 tonnes

13

Conclusions

 By applying the design optimization:-

• The aerodynamic drag force can be reduced by attention to the layout

and steamlineing of the container stacks

• Due to increase in the spaces between containers the drag forces will

also increase

• The emission of exhaust gases produced from the fuel can be reduced

by design optimization The most important things are the proper knowledge and understanding about ship design optimization and that CFD simulation is used properly. Interesting questions are:-

• Verification of the CFD results
• Size and resolution of the model

14

Summary of CFD results for this case study:-

• A drag reduction surface at 45° on front row of containers reduced air

flow resistance by 11.5%

• By sloping the upper surface of the container stacks and avoiding large

gaps between stacks the air resistance could be reduced by about 15%

• Streamlining of containers on the after deck behind the deck house

reduced the air resistance by about 6.5% By design optimization a reduction of air resistance of about 33% was achieved. The air resistance was 3.2% of the total resistance for this design and speed of ship – leading to fuel and emissions reductions of ~ 1% .

15

Thank you for your attention !