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The Current Status of CFD in ITTC2: Maneuvering &Seakeeping2: Maneuvering &Seakeeping
Frederick SternFrederick SternIIHR‐Hydroscience&Engineering
The University of IowaIowa City, IA 52242 USA
1
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
2
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
44
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
5
‐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
6
‐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.
7
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'
8
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
9
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°
11
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%
12
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
13
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 , ), ,
1414
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.
15
1 CFD based maneuvering methods in SIMMAN20081. CFD based maneuvering methods in SIMMAN20081.5 PIV comparisons: 5415 pure sway (Fr=0.28)
16
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
17
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
18
‐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)
18
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
19
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
20
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
21
0.1
0.15
0 10 20 30 40
0.10 10 20 30 40
autopilot course (degrees)
No 85
No 83
41
h ( )R lt Broaching (#41) ‐EFD vs CFDResults:
Periodic motion (#83) ‐EFD vs CFD
Surf‐riding (#85)‐EFD vs CFD
22
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.
23
23
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
25
‐ 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
27
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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