The Current Status of CFD in ITTC2: Maneuvering &Seakeeping2: Maneuvering &Seakeeping

Frederick SternFrederick SternIIHR‐Hydroscience&Engineering

The University of IowaIowa City, IA 52242 USA

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Table of contents

1 CFD based maneuvering methods in SIMMAN 20081. CFD based maneuvering methods in SIMMAN 2008

1.1 Overview1.1 Overview1.2 Verification and Validation (V&V)1.3 Forces and moment coefficients1.4 Maneuvering derivatives1.5 PIV comparisonsp1.6 Trajectories

2. Latest application of CFD to seakeeping

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3. Computational towing tank approach

CFD based maneuvering prediction methodNo Simulation System Based Maneuvering Simulation CFD Based Maneuvering 

Simulation

CFD based maneuvering prediction method

Database MethodTrajectory/Hydrodynamic Derivatives

Model testing Computational methods

Full‐scale TrialsCaptive Model Tests Inviscid RANS

Free Model Tests

System Identification Mathematical model

methods methods

Maneuvering Derivatives, Hydrodynamic Coefficients

Equation of motion

ShipTrajectories

Derived maneuvering parameters (advance, transfer, overshoots etc.)

Ship specification

C it i

3

Criteria

Maneuverability: Acceptable or not

1 CFD based maneuvering methods in SIMMAN20081. CFD based maneuvering methods in SIMMAN20081.1 Overview

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1 CFD based maneuvering methods in SIMMAN2008

V ifi ti

1. CFD based maneuvering methods in SIMMAN20081.2 Verification and Validation: 5415, IIHR, CFDShip‐IowaStatic drift (Fr=0.28, β=10°)

UI (%S1) |εg21/S1|×100 Rg pg Cg Convergence Ug (%S1)Without  X'T 0.26 2.82 ‐0.70 ‐ ‐ OC 2.02

Verification

wallsr=√2

Y'T 0.015 0.19 ‐3.01 ‐ ‐ OD ‐N'T 0.020 0.97 ‐1.06 ‐ ‐ OD ‐

Fine‐medium‐coarse: 19M‐6.9M‐2.4M

|E| (%D) UV (%D) UD (%D) USN (%D)Without X' 7 68 4 20 3 6 2 17

Validation

Without wallsr=√2

X'T 7.68 4.20 3.6 2.17Y'T 13.44 ‐ 5.4 ‐N'T 0.98 ‐ 2.6 ‐

‐Slowly damped oscillation 4 ship‐lengths for transient8 ship‐lengths for statistical convergence

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‐Difficult to achieve monotonic convergence in Y'T and N'T‐X'T is not validated.

Pure yaw (Fr=0.28, r'=0.3)

Verification: Fourier Series decomposed quantities( ) | | ( ) ( )%S1 UI (%) |εk21| (%) Rk pk Ck Convergence Uk (%)

X'0 0.51 6.16 0.85 0.46 0.18 MC 92.43X'2 10.26 18.73 ‐0.39 ‐ ‐ OC 24.21

Grid(r=√2)

Y'1 0.32 7.61 2.52 ‐ ‐ MD ‐Y'3 29.36 17.16 ‐1.93 ‐ ‐ OD ‐N'1 0.16 1.17 ‐5.04 ‐ ‐ OD ‐1N'3 8.74 71.57 25.32 ‐ ‐ MD ‐X'0 0.49 1.76 0.18 2.50 1.55 MC 2.77X'2 0 95 31 96 0 62 0 69 0 20 MC 135 04

Time‐step(r=2)

X 2 0.95 31.96 0.62 0.69 0.20 MC 135.04Y'1 0.21 8.64 0.49 1.04 0.35 MC 18.73Y'3 5.63 10.47 1.71 ‐ ‐ MD ‐N' 0 14 3 96 0 47 1 09 0 37 MC 7 96N 1 0.14 3.96 0.47 1.09 0.37 MC 7.96N'3 5.69 0.92 0.04 4.80 8.97 MC ‐

With walls, 5.5M‐1.58M‐0.56M

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‐Time‐step convergence easier to achieve than grid convergence‐Need marching FS analysis for more accurate UI estimation

Verification: Time‐averaged quantitiesUG(%D) UT(%D) USN (%D)G T SN

X'T 1) 5.50 2.60 6.08Y'T 2) 1.00 6.89 7.00N' 2) 0 20 7 74 7 74N T2) 0.20 7.74 7.74Grid: Without walls, 4.5M‐1.59M‐0.56M, r=√2Time step: r=2

|E|(%D) UV (%D) UD (%D) USN (%D) UG(%D) UT (%D)X' 1) 18 41 8 94 6 56 6 08 5 50 2 60

Validation: Time‐averaged quantities

X T ) 18.41 8.94 6.56 6.08 5.50 2.60Y'T2) 10.21 23.45 22.38 7.00 1.00 6.89N'T2) 2.70 7.90 1.57 7.74 0.20 7.741) %D 2) % D d i f Y ’ N '1) %D, 2) % D dynamic range of YT’ or NT'

‐Friction tends to monotonically converge over 1 PMM period than pressure withlower USN.‐Y'T and N'T are validated. Need to check UD in Y'T.

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1 CFD based maneuvering methods in SIMMAN2008

Pure sway (βcorr=4.9°) Pure yaw (r'=0.3)

1. CFD based maneuvering methods in SIMMAN20081.3 Forces and moment coefficients: KVLCC1 (Fr=0.142)

y ( )

Pure swayPure sway‐ Over‐prediction in X'‐ Good prediction in Y' and N'and NPure yaw‐ Large phase and

li d diffamplitude differencein X'‐Minor phase lead inY' compared to EFD‐Good prediction in N'

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1 CFD based maneuvering methods in SIMMAN20081. CFD based maneuvering methods in SIMMAN20081.3 Forces and moment coefficients: KCS (Fr=0.202)

Pure sway (β =8°) Pure yaw (r'=0.4)Pure sway (βcorr 8 ) Pure yaw (r 0.4)

Pure sway‐ Over‐prediction in X'Over prediction in X‐ Good prediction in Y' and N'Pure yaw‐ High frequency oscillationHigh frequency oscillationfor X' in CFD and Y' in EFD‐Minor phase lead in N' compared to EFDcompared to EFD

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1 CFD based maneuvering methods in SIMMAN2008

Coefficient DConvection scheme/Turbulence1)

1. CFD based maneuvering methods in SIMMAN20081.3 Forces and moment coefficients: 5415, static drift (Fr=0.28, β=10°), IIHR, CFDShip‐Iowa

Coefficient DFD2‐BKW TVD2S‐ARS FD4h‐BKW

X'E (%D)

‐0.0195 ‐0.02094‐7.4%

‐0.02025‐3.8%

‐0.02074‐6.4%E (%D)

Y'E (%D)

‐0.05795 ‐0.06576‐13.5%

‐0.06408‐10.6%

‐0.06566‐13.3%

0 02845 0 02875 0 0285 0 02872

‐ TVD2S‐ARS provides thebest results  consistent

N'E (%D)

0.02845 0.02875‐1.05%

0.0285‐0.17%

0.02872‐0.95%

Coefficient D URANS, FD2‐BKW2) DES, FD4h‐BKW2)

to KVLCC2 application‐ DES only improves X'.‐Movie: URANS vs DESCoefficient D URANS, FD2 BKW DES, FD4h BKW

X'E (%D)

‐0.0195 ‐0.0210‐7.7%

‐0.02032‐4.21%

0 05795 0 06574 0 0665

• Overall• Leeward bow• Stern

Y'E (%D)

‐0.05795 ‐0.06574‐13.4%

‐0.0665‐13.2%

N' 0.02845 0.02873 0.0291E (%D) ‐0.98% ‐2.28%

# of grid points: 1) 2.4M, 2) 19M10

St ti d ift (TVD2S ARS 2 4M id i t )Static drift (TVD2S‐ARS, 2.4M grid points)

F d ffi i f ll h EFD d‐ Forces and moment coefficients follow the EFD trend.‐ Significant increase in |E| at β≥12°

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beta Coef. Dturb. vs. laminar

TVD2S‐ARS Laminar

0 degXʹE (%D)

‐0.0166 ‐0.015665.7%

‐0.0084549.1%

Xʹ ‐0.0195 ‐0.02025 ‐0.0125

10 deg

XE (%D)

0.0195 0.02025‐3.8%

0.012535.9%

YʹE (%D)

‐0.05795 ‐0.0640810 6%

‐0.0641910 8%

‐ Laminar solution 10 degE (%D) ‐10.6% ‐10.8%NʹE (%D)

0.02845 0.0285‐0.17%

0.0300‐5.4%

gives better results at larger drift angles( )

XʹE (%D)

‐0.0287 ‐0.0366‐27.5%

‐0.024614.3%

Yʹ 0 1529 0 1902 0 1550

anglesExpect the 

contribution of 

20 degYʹE (%D)

‐0.1529 ‐0.1902‐24.4%

‐0.1550‐1.4%

Nʹ 0.0594 0.0690 0.0607

transition turbulence model

# of grid points=2.4M, Fr=0.28E (%D) ‐16.2% ‐2.2%

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1 CFD based maneuvering methods in SIMMAN20081. CFD based maneuvering methods in SIMMAN20081.3 Forces and moment coefficients: 5415 (Fr=0.28)

Pure sway (βcorr=10°) Pure yaw (r'=0.3)y (βcorr ) y ( )

Pure swayPure sway‐ Oscillation in X' apparent in CFD‐ Good prediction in Y'Good prediction in Y  and N': consistent to KVLCC/KCSPure yawPure yaw‐ Under‐prediction in X' in CFD‐Minor phase lag in Y'‐Minor phase lag in Y  compared to EFD

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1 CFD based maneuvering methods in SIMMAN2008

KVLCC2, shallow water (Southampton, CFX), Fr=0.064

1. CFD based maneuvering methods in SIMMAN20081.4 Maneuvering derivatives: KVLCC2

h ll ff k f‐ Shallow water effect makes estimation of linear derivative less accurate.‐ Linear derivatives are well‐predicted, except

KVLCC2M, deep water (Toxopesu 2008, PARANASSOS), Fr=0.0, ref. JMST

Linear derivatives are well predicted, except Yβ' by PARANNASOS.

, p ( p , ), ,

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1 CFD based maneuvering methods in SIMMAN20081. CFD based maneuvering methods in SIMMAN20081.4 Maneuvering derivatives: 5415 (Fr=0.28), IIHR, CFDShip‐Iowa

‐ Linear derivatives predicted well within 10%D error.‐ Non‐linear and accelerationNon linear and acceleration dependent derivatives need more accuracy.

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1 CFD based maneuvering methods in SIMMAN20081. CFD based maneuvering methods in SIMMAN20081.5 PIV comparisons: 5415 pure sway (Fr=0.28)

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1 CFD based maneuvering methods in SIMMAN20081. CFD based maneuvering methods in SIMMAN20081.5 PIV comparisons: 5415 pure yaw (Fr=0.28), IIHR, CFDShip‐Iowa

X=0.135:‐U

X=0.535:‐U

X=0.935:‐U‐U

‐V‐W

‐U‐V‐W

U‐V‐W

‐ωx‐TKE

‐ωx‐TKE

‐ωx‐TKE

‐Overall trends are well‐predicted between CFD and EFD.A t t /TKE d f t t t i t i h d‐Apparent momentum/TKE defect at vortex core in certain phases and cross planes compared to the EFD dataPossible reasons are: grid resolution, momentum and turbulence 

convection scheme, isotropic turbulence model

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1 CFD based maneuvering methods in SIMMAN2008P] 5 MARIN (SURSIM SB RANS)

STB

D

40

60

Turning circle  (δ=35°)20°/20° zig‐zag maneuver

1. CFD based maneuvering methods in SIMMAN20081.6 Trajectories: KVLCC1

Adv

ance

[LP

P

4

( )HSVA (NEPIII)IIHR (CFD)

EFDTime [sec]

adin

gan

gle

[deg

]

0 100 200 300 400 500 600 700 800 900 10000

20

2

3

PO

RT

Hea

-60

-40

-20

MARIN (SURSIM SB RANS)HSVA (NEPIII)

0

1

deg]

STB

D

20

40

60MARIN (SURSIM SB RANS)HSVA (NEPIII)IIHR (CFD)

deg]

STB

D

20

40

60

Transfer [LPP]-5 -4 -3 -2 -1 0

Time [sec]

Hea

ding

angl

e[d

0 100 200 300 400 500 600 700 800 900 1000

-20

0

Time [sec]

Hea

ding

angl

e[d

0 100 200 300 400 500 600 700 800 900 1000

-20

0

MOVIE (Turning circle)by IIHR: CFDShip‐Iowa

PO

RT

-60

-40

PO

RT

-60

-40by IIHR: CFDShip‐Iowa

‐HSVA: Very well predicted trajectory in turning circleIIHR MARIN: Advance and tactical diameter under predicted in turning circle

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‐IIHR, MARIN: Advance and tactical diameter under‐predicted in turning circle‐Zig‐zag: Phase and amplitude difference after the 1st‐execute (MARIN, IIHR) and 2nd‐execute (HSVA)  

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1. CFD based maneuvering methods in SIMMAN20081 6 Trajectories: 5415

20°/20° zig‐zag maneuver1.6 Trajectories: 5415Turning circle  (δ=35°)

MOVIE (Turning circle in waves)MOVIE (Turning circle in waves)by IIHR: CFDShip‐Iowa

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2 Latest application of CFD to seakeeping: 5512 forward speed diffraction

Fr=0.41, l/L=1.5, ak=0.025, 70 M grid points.

2. Latest application of CFD to seakeeping: 5512 forward speed diffraction

Free surface

Transom detail‐Massive breaking waves at bow, shoulder and stern

Bow detail

Free surface and turbulent structures

b l d l

‐ Highly turbulent transom flow‐ Very detail unsteady vorticalstructure resolved by DES

Turbulent structures detaily

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2 Latest application of CFD to seakeeping: ONR tumble home (Free‐running test)2. Latest application of CFD to seakeeping: ONR tumble home (Free‐running test)

CFD test matrix:

Case# λ /L H/λ FrGM (m)full scale

course (deg)Rudder angle Limit (deg)

Phenomenon( g)

41 1.25 0.05 0.4 1.78 m ‐15 34.2 broaching

83 1.25 0.05 0.4 2.068 m ‐30 29.7 periodic motion

85 1.25 0.05 0.4 2.068 m ‐5 28 surf‐riding

EFD test matrix:l bd /L 1 25 1/20 GM 2 068

lambda/L=1.25, wave steepness=1/20

/ / /λ/L=1 25 H/λ=1/20 GM=1 78lambda/L=1.25,wave s teepnes s =1/20, GM=2.068

0.4

0.45

0.5

0.4

0.5

de n

umbe

r

periodic

λ/L=1.25, H/λ=1/20, GM=2.068 m

λ/L 1.25, H/λ 1/20, GM 1.78 m

0 15

0.2

0.25

0.3

0.35Periodic Motion

Surf Riding

Broaching-to 0.2

0.3

Nom

inal

Fro

ud

periodicbroachstable surf-riding

No NoNo

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0.1

0.15

0 10 20 30 40

0.10 10 20 30 40

autopilot course (degrees)

No 85

No 83

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h ( )R lt Broaching (#41) ‐EFD vs CFDResults:

Periodic motion (#83) ‐EFD vs CFD

Surf‐riding (#85)‐EFD vs CFD

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Conclusion:• CFD is capable of predicting surf‐riding, periodic motion and 

broaching.• A phase lag between CFD and EFD due to inaccurate initial 

conditions for wave phase and initial surge velocity.

Future work:• CFD simulations with correct initial conditions measured inCFD simulations with correct initial conditions measured in 

experiments• Trajectory will be compared with experiment.

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3 Computational towing tank (CTT) approach: Implementation

V R r= + Ω×&

3. Computational towing tank (CTT) approach: Implementation

Grid velocity: Absolute inertial earth‐fixed coordinateGV R r= + Ω×

Momentum equation: Absolute inertial earth‐fixed coordinate

( ) ( ) 21ReG

V V V V p Z Vt

ρ γ∂⎡ ⎤+ − ⋅∇ = −∇ + + ∇⎢ ⎥∂⎣ ⎦

Transformation toNon‐inertial ship‐fixed coordinateusing Vr: relative velocity to CVusing Vr: relative velocity to CV

GrV V V= −

{ ( )21

Rer

r r r rbody force

V V V a p z Vt

ρ ρ γ⎡ ⎤∂

+ ⋅∇ = − −∇ + + ∇⎢ ⎥∂⎣ ⎦

%

body force⎣ ⎦

( )2r ra R V r r= + Ω× +Ω× Ω× +Ω×&& &24

3 Computational towing tank approach: Application for resistance and propulsion3. Computational towing tank approach: Application for resistance and propulsion

Full‐curve Fr propulsion simulationsFull‐curve Fr resistance simulations

‐Med&high Fr: An efficient and accurate tool to predict curves of resistance and propulsion for ship flows using a single run

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‐ CTT procedure is not possible or highly difficult using a physical towing tank a potential of using the CTT in the design process.

3 Computational towing tank approach: Deterministic wave packet

20 waves components; 3

3 Computational towing tank approach:3. Computational towing tank approach: Wave packet application for 5512 (Fr=0.34)

‐ Only one computation per Froude Number to get heave and pitch RAOs‐ Incoming wave packet spectrum designed to have a peak around maximum response‐ FFT window located after the computations are stable and Kelvin waves are developed‐ Results are promising and can replace the conventional seakeeping computations

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p g p p g p

Acknowledgements

‐ The Office of Naval Research, Global and USA

Acknowledgements

‐ PMM experiments at IIHR:Dr. Joe Longo, Hyuse Yoon, Prof. Yasuyuki Toda

‐ Computational results by IIHR:Computational results by IIHR:PMM: Nobuaki SakamotoForward speed diffraction: Prof.Pablo M. CarricaONR bl h S d H idONR tumblehome: Seyed HamidComputational towing tank: Dr. Tao Xing and MaysamMousaviraad

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