Optimization of ship hydrodynamique performances · •Increase the use of optimization studies : simplify exchanges with designers / architects (Rhino Plugin), reduce time schedule

Expertise in Marine Hydrodynamics

Optimization of ship hydrodynamique performances


Table of Contents

HydrOcean and ship hydrodynamic performances optimization

Impact of numerical simulation in the design process of ships

Development of dedicated software for ship optimization

Validation example and applications on the Albatros ship

Conclusions and perspectives


HydrOcean and ship hydrodynamic performances optimization

HydrOcean in few lines

• Founded in 2007 by E. Jacquin, spinoff from Ecole Centrale Nantes Fluid Dynamics

Lab.

• Services around numerical hydrodynamics

Consultancy and hydrodynamic studies

Software distribution : REVA, AQUA+, ISIS-CFD, SPH-flow, OPTNAV ...

On site numerical hydrodynamic engineers with or without software and CPU

R&D projects allowing development and validation of innovative hydrodynamic solutions

• A unique range of numerical simulation tools with unlimited number of licenses and

access to huge computational resources

• Team of 16 high level engineers

About 15 hull / appendages / propeller industrial projects involving hydrodynamic performances

Two main R&D projects dedicated to ship performances optimization

• OPTNAV : HO, STX, ECN, BV, SH, funded by Fond Unique Interministériel (FUI) aiming at developing a hull modelling software and an adapted CFD solver

• OPTIPERF : HO, ECN, funded by French Ministry of Agriculture and Fishing aiming at validating CFD solvers for trawlers and developing resistance empiric database for trawler’s naval architects and shipyards


Evolution of numerical simulation tools for ship hydrodynamics

Before 80’s : no numerical software available for estimation of ship

resistance

• Towing tank tests for evaluation of several designs

• Time and cost consuming

• Difficulty to evaluate more than 3 to 5 hulls (optimization restricted to local evaluation)

80’s to 90’s : availability of potential flow solvers (REVA …)

• First credible numerical method for ship resistance ranking

• Development of first parametric software for hull deformation

• First optimization success, but limited by the validity domain of those solvers (linear, estimation of

viscous drag …)

2000’s to today : beginning of RANSE with free surface solvers (ICARE, ISIS-CFD …)

• Beginning of Navier-Stokes with free surface solvers

• Increase of accuracy (<3-4%) and application domain (resistance, propulsion ...)

• Increase also of CPU time …

Remaining questions : How to automate the design and evaluation process : hull

design / stability check / meshing / calculation / data processing / analysis … ?


Id

Del

taR

tm(%

)27

nds

0 20 40 60 80 100

-2

0

2

4

6

8Init

DOE

MOGA

Parametric hull

modeling Automatic meshing Ship performance evaluation

Outputs:

Resistance

Ship power

…

Deformation parameters :

Bulbous bow

Hull sections / shape

Stern / Wedge …

Parametric exploration

Optimization algorithms

Constraints :

Hydrostatic

Stability

GA

Objectives :

Resistance

Ship power

…

Example of optimization loop



Id

Del

taR

tm(%

)27

nds

0 20 40 60 80 100

-2

0

2

4

6

8Init

DOE

MOGA

Parametric hull


Outputs:

Resistance

Ship power

…


Bulbous bow


Stern / Wedge …



Constraints :

Hydrostatic

Stability

GA

Objectives :

Resistance

Ship power

…


OPTNAV : Hull parametric modeler

Specific hull modeling software developed by

HydrOcean for efficient hull form optimisation

• Rhino 3D CAO plug-in

• Hydrostatic calculations, stability calculations,

parametric deformation of hull, empiric resistance

calculation

• Modeler coupled to HydrOcean’s CFD tools:

Automated Navier-Stokes calculations enabling

hydrodynamic performance evaluation of over 100 hulls

in only a few days

Hydrostatics tab Empirical resistance tab Parametric deformation tab

Example of bulb deformations generated with OPTNAV


Example Hull Modeler



Id

Del

taR

tm(%

)27

nds

0 20 40 60 80 100

-2

0

2

4

6

8Init

DOE

MOGA

Parametric hull


Outputs:

Resistance

Ship power

…


Bulbous bow


Stern / Wedge …



Constraints :

Hydrostatic

Stability

GA

Objectives :

Resistance

Ship power

…


REVA

AQUA+

Extremely fast potential flow solvers

• Resistance calculations

• Wave field

• Added resistance

• Forces and motions induced by

waves

ICARE-LS

Isis-CFD

Fast and accurate free surface Navier-Stokes solver

• Resistance calculations

• Added resistance in waves

• Maneuverability coefficients

• Combined drift and gyration

• Sea keeping behavior in

regular or irregular waves

• Calculation of drag and lift on

appendages

• Selfpropulsion

• Hull optimization

• Sail or wing optimization

• Propeller optimization

• Simulation of unsteady maneuvers:

tacking, gibing...

Solvers


Example of main hull / appendages / propeller hydrodynamic optimizations

General hull shape parametric optimisation in resistance (curve section area, main hydrostatics )

Optimal trim angle evaluation for each draft and speed

Propulsion appendages

(rudder, shaft brackets …)

orientation and shape

optimisation

Bulbous bow shape parametric

optimisation. Total drag and

wave field reduction.

Bow or stern thrusters shape

optimisation.

• Orientation of level on flow

• Evaluation of Energy Saving

devices

Propeller design evaluation

• Propulsive coefficients (Kt, Kq, prop)

• Cavitation inception

• Pressure pulse

Stern, wedges, ducktail shape

optimisation in presence of

propeller ((1-t), (1-w), hull )


Application and validation : Optimization of Albatros bulbous bow

Ship description

• Length : 174 m

• Speed : 19 knots

• 460 cabins

• Managed by Vship

Bulbous bow damaged

Decision of the ship owner to design a new and optimized bulbous bow

Methodology applied for this projects

• Parametric evaluation of feasible bulbous bow designs (around one hundred)

• Validation in towing tank of initial and optimal design

• Built and sea trial for final evaluations


Setting up of bulbous bow deformation in cooperation with technical (Tekno Consulting) : 3

deformation parameters (length, width, height)

Total drag variation presented in a 3D chart (gains in blue, loses in red)

Parametrical bulb deformation and resistance gains

Initial

Optimal

Higher

Wider


Performance evaluation by CFD

Comparison of numerical and experimental resistance gains

Comparison of pressure & wave fields and streamlines

Initial

Optimized

V (nds) CFD Experiences

17 2.7 2.4

18 2.5 2.9

19 2.2 2.8

20 1.9 2.5

21 1.8 2.4

Gain (%)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

16 17 18 19 20 21 22

Re

sist

ance

gai

ns

(%)

V (knots)

CFD

Experiences


Built and sea trial tests

Comparison of numerical and experimental resistance gains

Feedback from sea trial tests

• Sucess with increase in speed and reduction of fuel consumption and CO2 émissions

• Total cost :

With numerical optimization study, towing tank and architect costs

Bulb construction and refit costs

ROI estimated to be less than 2 years regarding fuel consumption reduction

Initial Optimized


Conclusion and perspectives

Optimization of ship hydrodynamic performances is an important way to reduce ship

consumption and increase ship performances

State of the art numerical process include :

• Parametric hull modeling software

• Automatic meshing procedures

• Accurate evaluation of ship performances resistance in calm water

• Automatic post processing and flow analysis

Those tools are nowadays available :

• More and more shipyards, architects and ship owners resort to hull / propeller / appendages optimization

• Nevertheless, still few difficulties to include this step in the design process of several projects due to time

schedule and cost limitations, despite huge ROI

HydrOcean’s main objectives with regards to ship optimization

• Increase the use of optimization studies : simplify exchanges with designers / architects (Rhino Plugin),

reduce time schedule …

• Develop and distribute specific software dedicated to ship hydrodynamic performance optimization

• Improve optimization efficiency by adding objectives like ship power (optimization with propeller) and

resistance in waves


Thank you for your attention

Documents

Optimization of ship hydrodynamique performances · •Increase the use of optimization studies : simplify exchanges with designers / architects (Rhino Plugin), reduce time schedule