Configuration Optimal Designs by the Simulation in ...Configuration Optimal Designs by the Simulation in Numerical Tank ... Ship CFD numerical assessment based on RANS The quantity,

Configuration Optimal Designs

by the Simulation in Numerical Tank

China Ship Scientific Research Center

Feng ZHAO

Introduction

SBD Techniques

Applications on road

Conclusion remarks

Air

Land

Oceanbackward

in water

Hoping for new break of innovative

hull form design

1.Introduction

Development of hullform design technique

6000 years ago

Imitation based on the

experience of mankind

Practice and improvement

1.Introduction

The 1st revolution for ship navigation

performance research and design technique

Froude

The earliest towing tank(1872）

Froude Hypothesis ：

Established the foundation of

model test technique in tanks

Towing tank：new era for ship

performance research and

design

1.Introduction

Experience, exisited data

BUT

NOT a Optimal solution

Selecting

process

“Optimal” design

Amend

ParentSeries model

data

Design

scheme

CFD

End

Performance

assessment

Satisfy

Model

test

Traditional ship design mode

ExperienceRequirements

The improvement of navigation

performance nearly reaches to the

limitation!

Selecting process

1.Introduction

Ship CFD

technique

Optimization

Geometry

reconstruction

/transformation

1.Introduction

Numerical

Tank

Hullform design optimization based

on SBD technique

Optimization theory

Optimal design

Brand new hull form design mode rooted

from rigorous mathematical control！

Simulation Based Design(SBD)

Advanced CFD technique

Design driven by objects

Design flow

(automatically)

Optimizer

Geometry and mesh

manipulation

Des

ign

Var

iabl

es

CFD solvers

Con

stra

int C

ondi

tions

Num

erical result

Design object

Original Parameterization

design variables

Objective Function

Evaluations

Geometry Modification

OPTIMIZER

Design

Variables

SatisfyNo

Yes

Optimized

Case

1.Introduction

2. SBD Techniques

Given target

Performance assessment

Given constraint conditions

• Minimum resistance

• ……..

Optimal hullform

CFDCFD

Design problemCalculation problem

Optimazition

Traditional method SBD Technique

INSEANTraditional Method

VS

SBD Techniques

AB：- 54%

C：- 78%

A：Primary design；

B：The best one of the models

designed by expert group

C ： The optimized design

obtained by “SBD”

2. SBD Techniques

D:/资料/计算流体力学发展与应用课件/Global.ppt

Key techniques

Determine the space of

construction design

Offer scientific method to the

solve of design and

optimization problem

Build the medium of design and

optimization model

2. SBD Techniques

Optimizer

Geometry and mesh

manipulation

Des

ign

Var

iabl

es

CFD solvers

Con

stra

int C

ondi

tions

Num

erical result

Design object

Optimizer

Geometry and mesh

manipulation

Des

ign

Var

iabl

es

CFD solvers

Con

stra

int C

ondi

tions

Num

erical result

Design object

Forming a great amount of different hull

geometry by using as few design variables as

possible.

Hull geometry reconstruction

Ship shape automatically reconstruction

Function：connect the optimizers and

performance assessment tools.

The premise of automatic design flow.

Eight design variables

Free transformation of the wind

deflector of motorcycle

2. SBD Techniques

Optimizer

Geometry and mesh

manipulation

Des

ign

Var

iabl

es

CFD solvers

Con

stra

int C

ondi

tions

Num

erical result

Design object

Ship CFD technique

CFD solver evaluates the quality of

design schemes obtained by geometry

reconstruction as a ruler.

Automatic mesh generation with SAME/HIGH quality

Automatic mesh generation！

Ship CFD numerical assessment

based on RANS

The quantity, topology of mesh and the other

settings of the simulation, will be kept the same.

2. SBD Techniques

Numerical

Tank

Optimizer

Geometry and mesh

manipulation

Des

ign

Var

iabl

es

CFD solvers

Con

stra

int C

ondi

tions

Num

erical result

Design object

Optimization technique

Function：Search the global optima in

design space quickly and accurately

Scientific method and mathematical means to

reach the optimization design.

Partical swarm optimization

Rastrigrin function(2D)2

2

2

1

( ) ( 10cos(2 ) 10)i i

i

f x x x

2. SBD Techniques

Comprehensive integration framework

Geometric parametric expression and

reconstruction module

Grid

regeneration

module

Ship hydrodynamic performance

evaluation module

Optimization

strategy module

automatic flow

2. SBD Techniques

3. Applications

Medium/high speed ship hullform design

The full ship hullform design

Other ship hullform design

DTMB5415

pratical hullform

benchmark model

Wave

resistance

Friction

resistance

Form

resistance

Total

resistance

1、Sensitive to the change of ship hull, relatively

easy to improve.

2、Mature theory, relatively easy assessment.

Depends on the wet area of ship

Related to ship shape

3.1 Medium /high speed ship

1、 Surface combatant bow optimization problem

Object function：Minimum resistance for 3 design speeds

Geometry reconstruction：

FFD method (5 design variables)

Optimal algorithm：MOPSO algorithm

1 1 1

2 2 2

3 3 3

/

/

/

t t org

t t org

t t org

F R R

F R R

F R R

Fn=0.17

Fn=0.28

Fn=0.37

Numerical assessment by RANS

Constraint conditions：' / 1 0.5% ' / 1 1%S S


3.1 Medium/high speed ship


Comparison of the resistance components

RtRr

Reduction Reduction

Design Results


Compared to original design ,the

wave amplitude of free surface

decreases obviously0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

-6

-4

-2

0

2

4

6

x/L

z/L

(10

-3)

Original

Optimized

y/L=0.082



The effect of optimization design (resistance decrease) corresponds to

the effect of optimization design of the bulb bow abroad！


CSSRC


2 、 Optimization design and validation of a

practical surface combatant hullform

Optimized CaseHullform optimization

design aimed at still water

resistance

Numerical validation of

ship design effects in

wave

Still water resistance model

test validation

Model test validation in

regular head waves

Design process


Design Results

Fn

Rrm (N) Rtm(N)

Reduction

Percentage

Reduction

Percentage

0.128 -12.3% -3.6%

0.179 -15.8% -5.8%

0.230 -15.2% -5.5%

0.281 -13.2% -4.8%

0.332 -13.4% -4.5%

0.358 -11.1% -4.2%

0.384 -11.2% -5.1%

0.409 -9.8% -5.2%

0.435 -8.0% -4.7%

The comparison of model resistance

The optimized case: The bow expands and the stern shrinks; the stern

near baseline expands downward; the immersion depth decreases a few.

Reduction




Model test validation

FnRts(kN)

ComparisonOriginal Optimized

0.205 -4.7%

0.230 -6.0%

0.256 -5.8%

0.307 -7.1%

0.332 -5.3%

0.358 -5.7%

0.384 -5.8%

0.409 -6.0%

0.435 -6.0% The resistance of optimized decreases obviously and fit

the numerical results well

Original Optimized




Fn=0.384

Wavelength=0.75L

The resistance and

movement response are

smaller than those of the

original

PitchResistance Heave

Numerical validation of ship design effects in regular wave




Model test validation in regular wave

Fn=0.384 λ=0.75L

Fn=0.384 λ=1.75L

Fn=0.230

Fn=0.384

Wave-add resistance transfer function

When 1.0<λ/L<1.5, the resistance thrashed in regular wave of optimization scheme

decrease over 3.9%, compared with primary scheme




3.2 The full ship hullform design

Ship with high CB and

low speed

Main force of

shipping

Space for improvement is

limited

（Traditional method）

■High CB

■Long parallel midbody, small variable area

■Strong engineering constraint conditions!

High

demand

Features：

Small

proportion

Large proportion，while the decline

so extremely finite

The realation with

change of hull form is

complex

兴波阻力

摩擦阻力粘压阻力

■Resistance composition

Pressure

distribution

Hard

It’s hard for traditional ship form design method based on experience to

optimize the vicious pressure resistance. Therefore, the resistance performance

optimization of low speed large ship is one difficult point in ship form

optimization design.

Ship with high CB and low speed


Rf

Form resistance

Comparison between target ship and sister ships

High performance

6600DWT hullform design

CB=0.838


Object function

1

2

/

/

t torg

f forg

F R R

F W W

21

( )N M

f xij xi

i j

W V VM

Total resistance

Non-uniformity of wake field

0.94 0.96 0.98 1 1.02 1.04 1.06 1.08 1.1 1.12 1.14

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5

r/R=0.3

F1

F2

可行解

最优解

Opt1

Opt2

Opt3Opt4

Opt5

Opt7

Opt6

Opt8

Opt9

Disaggregation of object function F1, F2

Total resistance and non-uniformity of

optimum Opt4 decrease a few，2.4% and

1.3%。（Residual resistance decreases

13.5%）

Design results

“Hook-shape”disappeared

in low speed area


Cb=0.835，Fn=0.1443

44600DWT hullform design

0.1 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.2-10

-8

-6

-4

-2

0

2

Fn

收益（

%）

Comparison of resistance composition of Opt1

Residual resistance decreases nearly 20%

Returns of total resistance

The returns are far more than the

numerical noise produced by numerical

calculation

Design results


RTRr

Returns of non-uniformity is 4.4%

The low press area in stern of Opt1 decreases obviously,

compared with the original ship!

Design results

“Hook-shape”disappeared


3.3 Other ship hullform design

Hullform design and model test validation

of Ocean surveillance ship

Multifunction ocean fisher hullform design

3000T buoy ship hullform design

Design process

Principal dimensions and

coefficients



Objective function: Total resistance (model scale) at Fr=0.2789

Design results

Comparison of hull form Comparison of wave



Comparison of the resistance between the original and Optimized (CFD)


1.6 1.8 2 2.2 2.4 2.6 2.8

40

60

80

100

120

140

Vm(m/s)

Rtm

(N)

Design

Optimized



Comparison of the resistance between the original and Optimized (Exp.)

Original

Optimized

Model test of resistance for the optimized and the design case

Converted to actual ship, when Vs=14kN~16kN, ratio of

resistance decrease is 7.5%~9.5%！




Optimized Original

Optimized

Vs = 14.2Kn

Vs = 16Kn

Original

Design object

Multifunction（saury and squid hook）ocean fisher

Constraint conditions——

draft and CB are variable

Multifunction ocean fisher hull form design

Constraint condition：1.Design draft changes from 3.3m to 4.4m；2.CB becomes smaller；3.Displacement is invariant.

Objective

Function

14kn total

resistance

12kn total

resistance

1 1 1

2 2 2

/

/

t t org

t t org

F R R

F R R

Draft and CB are

variable


Comparison of numerical calculation results between the

optimized and original

Reduction of model total resistance at design speed is 6.5%.

0.89 0.9 0.91 0.92 0.93 0.94 0.95 0.96 0.970.96

0.97

0.98

0.99

1

1.01

1.02

1.03

1.04

F1

F2

可行解

最优解

Opt4

Opt3

Opt2Opt1

Design results



Main ship body/bulb bow

double design point automatic

optimal design

Design process Design results

OptimizedPrimary

scheme

Hullform design process

Satisfy

engineering

constraint

conditionsOptimal object：minimum

total resistance at 12kn and

16kn

3000T buoy ship automatic reconstruction

（main ship body+bulb bow）

Comparison of resistance and

effective power

The effective power of optimized

decrease 8.8% at 16kn

Vs（Kn）

Pe（

Kw）

Vs(Kn) FnOriginal Optimized

ReductionRts(kN) Pe(kw) Rts(kN) Pe(kw)

8.0 0.1380 63.0 259.1 60.7 250.0 -3.5%

9.0 0.1550 78.2 362.2 77.0 356.3 -1.6%

10.0 0.1720 96.3 495.4 95.1 489.0 -1.3%

11.0 0.1890 116.2 657.7 114.5 647.8 -1.5%

12.0 0.2070 140.2 865.4 136.4 842.2 -2.7%

13.0 0.2240 165.6 1107.6 160.8 1075.1 -2.9%

14.0 0.2410 196.3 1414.0 187.0 1346.5 -4.8%

15.0 0.2580 236.2 1822.4 220.8 1703.7 -6.5%

16.0 0.2750 287.8 2369.0 262.6 2161.0 -8.8%

17.0 0.2930 347.9 3042.1 326.5 2855.6 -6.1%

18.0 0.3100 407.4 3772.0 386.5 3578.5 -5.1%

19.0 0.3270 467.8 4571.8 447.8 4376.3 -4.3%


The wave amplitude of the

optimized decrease obviously!

Comparison of free surface wave at

different speed


Engineering project Optimization

design area

Speed Object Resistance

reduction

Validation

300T fishery survey

ship

The whole ship 12.5kn RT 21.5% Model test validation of

optimal ship form

59m passenger ship The whole ship 12.0kn RT 7.4% ——

Explorer No.1 support

mother ship

Bow 12.5Kn RT 8.9% ——

300T fishery survey ship

Explorer No.1

support mother ship

Other Applications

59m passenger ship

Hydrodynamic Configurations Design driven

by Global Flow Optimization

The Essence of the innovation method:

Conclusion remarks

• Scientization the pressure distribution around

the hull

Thank you!

Application of Numerical Tank

The next step of Numerical Tank

Documents

Configuration Optimal Designs by the Simulation in ...Configuration Optimal Designs by the Simulation in Numerical Tank ... Ship CFD numerical assessment based on RANS The quantity,