The Current Status of CFD in ITTC 2: Maneuvering &Seakeeping 2: - - PowerPoint PPT Presentation

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The Current Status of CFD in ITTC 2: Maneuvering &Seakeeping 2: - - PowerPoint PPT Presentation

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The Current Status of CFD in ITTC 2: Maneuvering &Seakeeping 2: Maneuvering &Seakeeping Frederick Stern Frederick Stern IIHR Hydroscience&Engineering The University of Iowa Iowa City, IA 52242 USA 1 Table of contents 1 1. CFD

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The Current Status of CFD in ITTC 2: Maneuvering &Seakeeping 2: Maneuvering &Seakeeping

Frederick Stern Frederick Stern

IIHR‐Hydroscience&Engineering The University of Iowa Iowa City, IA 52242 USA

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Table of contents

1 CFD based maneuvering methods in SIMMAN 2008

  • 1. CFD based maneuvering methods in SIMMAN 2008

1.1 Overview 1.1 Overview 1.2 Verification and Validation (V&V) 1.3 Forces and moment coefficients 1.4 Maneuvering derivatives 1.5 PIV comparisons p 1.6 Trajectories

  • 2. Latest application of CFD to seakeeping

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  • 3. Computational towing tank approach
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CFD based maneuvering prediction method

No Simulation System Based Maneuvering Simulation CFD Based Maneuvering Simulation

CFD based maneuvering prediction method

Database Method Trajectory/Hydrodynamic Derivatives Model testing Computational methods Full‐scale Trials Captive Model Tests Inviscid RANS Free Model Tests System Identification Mathematical model methods methods Maneuvering Derivatives, Hydrodynamic Coefficients Equation of motion Ship Trajectories Derived maneuvering parameters (advance, transfer, overshoots etc.) Ship specification C it i

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Criteria Maneuverability: Acceptable or not

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1 CFD based maneuvering methods in SIMMAN2008

  • 1. CFD based maneuvering methods in SIMMAN2008

1.1 Overview

4 4

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1 CFD based maneuvering methods in SIMMAN2008 V ifi ti

  • 1. CFD based maneuvering methods in SIMMAN2008

1.2 Verification and Validation: 5415, IIHR, CFDShip‐Iowa Static 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

walls r=√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 walls r=√2 X'T 7.68 4.20 3.6 2.17 Y'T 13.44 ‐ 5.4 ‐ N'T 0.98 ‐ 2.6 ‐

‐Slowly damped oscillation 4 ship‐lengths for transient 8 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.

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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 92.43 X'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 ‐

1

N'3 8.74 71.57 25.32 ‐ ‐ MD ‐ X'0 0.49 1.76 0.18 2.50 1.55 MC 2.77 X'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 135.04 Y'1 0.21 8.64 0.49 1.04 0.35 MC 18.73 Y'3 5.63 10.47 1.71 ‐ ‐ MD ‐ N' 0 14 3 96 0 47 1 09 0 37 MC 7 96 N 1 0.14 3.96 0.47 1.09 0.37 MC 7.96 N'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

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Verification: Time‐averaged quantities UG(%D) UT(%D) USN (%D)

G T SN

X'T

1)

5.50 2.60 6.08 Y'T

2)

1.00 6.89 7.00 N' 2) 0 20 7 74 7 74 N T

2)

0.20 7.74 7.74

Grid: Without walls, 4.5M‐1.59M‐0.56M, r=√2 Time 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 2.60 Y'T

2)

10.21 23.45 22.38 7.00 1.00 6.89 N'T

2)

2.70 7.90 1.57 7.74 0.20 7.74 1) %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 with lower 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 SIMMAN2008

1.3 Forces and moment coefficients: KVLCC1 (Fr=0.142)

y ( )

Pure sway Pure sway ‐ Over‐prediction in X' ‐ Good prediction in Y' and N' and N Pure yaw ‐ Large phase and li d diff amplitude difference in X' ‐ Minor phase lead in Y' compared to EFD ‐Good prediction in N'

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1 CFD based maneuvering methods in SIMMAN2008

  • 1. CFD based maneuvering methods in SIMMAN2008

1.3 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 oscillation High frequency oscillation for X' in CFD and Y' in EFD ‐ Minor phase lead in N' compared to EFD compared to EFD

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1 CFD based maneuvering methods in SIMMAN2008 Coefficient D Convection scheme/Turbulence1)

  • 1. CFD based maneuvering methods in SIMMAN2008

1.3 Forces and moment coefficients: 5415, static drift (Fr=0.28, β=10°), IIHR, CFDShip‐Iowa Coefficient D FD2‐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 the best 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 DES

Coefficient 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 0.0291 E (%D) ‐0.98% ‐2.28%

# of grid points: 1) 2.4M, 2) 19M

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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. D

  • turb. vs. laminar

TVD2S‐ARS Laminar 0 deg Xʹ E (%D) ‐0.0166 ‐0.01566 5.7% ‐0.00845 49.1% Xʹ ‐0.0195 ‐0.02025 ‐0.0125 10 deg X E (%D) 0.0195 0.02025 ‐3.8% 0.0125 35.9% Yʹ E (%D) ‐0.05795 ‐0.06408 10 6% ‐0.06419 10 8% ‐ Laminar solution 10 deg E (%D) ‐10.6% ‐10.8% Nʹ E (%D) 0.02845 0.0285 ‐0.17% 0.0300 ‐5.4% gives better results at larger drift angles ( ) Xʹ E (%D) ‐0.0287 ‐0.0366 ‐27.5% ‐0.0246 14.3% Yʹ 0 1529 0 1902 0 1550 angles Expect the contribution of 20 deg Yʹ E (%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=0.28 E (%D) ‐16.2% ‐2.2%

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1 CFD based maneuvering methods in SIMMAN2008

  • 1. CFD based maneuvering methods in SIMMAN2008

1.3 Forces and moment coefficients: 5415 (Fr=0.28)

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

Pure sway Pure sway ‐ Oscillation in X' apparent in CFD ‐ Good prediction in Y' Good prediction in Y and N': consistent to KVLCC/KCS Pure yaw Pure 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 SIMMAN2008

1.4 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 SIMMAN2008

  • 1. CFD based maneuvering methods in SIMMAN2008

1.4 Maneuvering derivatives: 5415 (Fr=0.28), IIHR, CFDShip‐Iowa

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

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1 CFD based maneuvering methods in SIMMAN2008

  • 1. CFD based maneuvering methods in SIMMAN2008

1.5 PIV comparisons: 5415 pure sway (Fr=0.28)

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1 CFD based maneuvering methods in SIMMAN2008

  • 1. CFD based maneuvering methods in SIMMAN2008

1.5 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 data Possible reasons are: grid resolution, momentum and turbulence convection scheme, isotropic turbulence model

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1 CFD based maneuvering methods in SIMMAN2008

P]

5

MARIN (SURSIM SB RANS)

STBD

40 60

Turning circle (δ=35°)

20°/20° zig‐zag maneuver

  • 1. CFD based maneuvering methods in SIMMAN2008

1.6 Trajectories: KVLCC1

Advance [LPP

4

( ) HSVA (NEPIII) IIHR (CFD)

EFD

Time [sec] ading angle [deg]

100 200 300 400 500 600 700 800 900 1000 20

2 3

PORT Hea

  • 60
  • 40
  • 20

MARIN (SURSIM SB RANS) HSVA (NEPIII)

1

deg] STBD

20 40 60

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

deg] STBD

20 40 60

Transfer [LPP]

  • 5
  • 4
  • 3
  • 2
  • 1

Time [sec] Heading angle [d

100 200 300 400 500 600 700 800 900 1000

  • 20

Time [sec] Heading angle [d

100 200 300 400 500 600 700 800 900 1000

  • 20

MOVIE (Turning circle) by IIHR: CFDShip‐Iowa

PORT

  • 60
  • 40

PORT

  • 60
  • 40

by IIHR: CFDShip‐Iowa

‐HSVA: Very well predicted trajectory in turning circle IIHR 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 SIMMAN2008

1 6 Trajectories: 5415

20°/20° zig‐zag maneuver

1.6 Trajectories: 5415 Turning 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 vortical structure resolved by DES

Turbulent structures detail

y

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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 Fr GM (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 78

lambda/L=1.25,wave steepness=1/20, GM=2.068

0.4 0.45 0.5 0.4 0.5 de number 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 0.35 Periodic Motion Surf Riding Broaching-to 0.2 0.3 Nominal Froud periodic broach stable surf-riding

No No No

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0.1 0.15 10 20 30 40 0.1 10 20 30 40 autopilot course (degrees)

No 85 No 83 41

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h ( )

R lt

Broaching (#41) ‐EFD vs CFD

Results:

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 in

CFD 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 coordinate

G

V R r = + Ω ×

Momentum equation: Absolute inertial earth‐fixed coordinate

( ) ( )

2

1 Re

G

V V V V p Z V t ρ γ ∂ ⎡ ⎤ + − ⋅∇ = −∇ + + ∇ ⎢ ⎥ ∂ ⎣ ⎦

Transformation to Non‐inertial ship‐fixed coordinate using Vr: relative velocity to CV using Vr: relative velocity to CV

G r

V V V = −

{

( )

2

1 Re

r r r r r body force

V V V a p z V t ρ ρ γ ⎡ ⎤ ∂ + ⋅∇ = − −∇ + + ∇ ⎢ ⎥ ∂ ⎣ ⎦ %

body force

⎣ ⎦

( )

2

r r

a R V r r = + Ω× + Ω× Ω× + Ω× && &

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3 Computational towing tank approach: Application for resistance and propulsion

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

Full‐curve Fr propulsion simulations Full‐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.

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3 Computational towing tank approach: Deterministic wave packet

20 waves components; 3<λ/L<0.3 FFT

i d 9 di i l d

  • 3. Computational towing tank approach: Deterministic wave packet

FFT window: 9 dimensionless seconds

Fr=0.2, Tumblehome

Movie Movie

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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

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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 Sakamoto Forward speed diffraction: Prof.Pablo M. Carrica ONR bl h S d H id ONR tumblehome: Seyed Hamid Computational towing tank: Dr. Tao Xing and Maysam Mousaviraad

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