Ng EYK (PhD, Whittle Lab., Camb.)

School of MAE, NTU, Singapore (http://www.researcherid.com/rid/A-1375-2011)

• Expertise in the area of CFD-FSI Modeling: Computational fluid dynamics & Heat transfer (CFD/CHT), Fluid-structure Interaction, Biomedical engineering

• Proposed topic for KOMtech discussion: Modeling & improving of hull-propulsor integration, Marine Renewable Energy with ocean double acting racks mechanism and rakes/wheel converter device, Hydroelectric Inflow Dam System, Small Towing Tank for Accurate Testing of Significantly Scaled-down Ship Models, Offshore Wind Farm Modelling

• Example publications: >180 SCI-IF with 10 Books; EiC for 2 Int. Journals & various EABs 1. Ng et al., “The Engg Analysis of Bioheat Equation and Penile Hemodynamic Relationships in the Diagnosis of Erectile Dysfunction: Part II – Model optimization using the ANOVA and Taguchi method”, Int. J. of Impotence Research, 20(3), (2008), 285-294. (IF= 5.4)

2. Tan & Ng, “Evaluation of Tear Evaporation from Ocular Surface by Functional Infrared Thermography”, Medical Physics, 37(11), 1-13 (2010), (IF=3.87) 3. Ng et al., “Prediction and Parametric Analysis of Thermal Profiles within Heated Human Skin using BEM“, Philosophical Transactions A, The Royal Society: 368:655-678, (2010), (IF= 2.5) 4. Ng et al., “On the Effect of Turbulent Intensity towards the Accuracy of the Zero-Equation Turbulence Model for Indoor Airflow Application”, Building and Environment, 46(1):82-88, (2011), (IF=1.78) 1 9/21/2012 1

Some Applications of CFD in NAME, why CFD?

1. Phenomenon of Sloshing

2. Scaled-Down Ship CFD Modeling with TMs

3. Wave Breaker

4. Oscillating Water Column

5. Ship Sinking with Leakage

6. Propeller Modeling with TMs

7. FSI Characteristics in Deep Cold-Water Drilling (optional)

9/21/2012 KOMtech @EYK-Ng-MAE 3

A Study of the Phenomenon of Sloshing in Tanks of LNG Ships

Liquid sloshing in moving flexible containers

including the effect of free surface waves (with CINME-UoS)

Comparison of Pressure in Time

Free Surface Profile Comparison

9/21/2012 4 KOMtech @EYK-Ng-MAE

Sloshing – The Interaction of Sloshing Waves with an Elastic Obstacle

9/21/2012 5 KOMtech @EYK-Ng-MAE

L. Khezzar, A. C. Seibi & A. Goharzadeh, Water Sloshing in Rectangular Tanks – An Experimental Investigation & Numerical Simulation, I. J.of Engineering; Vol. 3(2)

at various time

Isobar contours

Isobar contours

Moving mesh; FSI; Strong wave gen.

Isobar contours

Rolling

Pitching

Scaled-Down Ship CFD Modeling with 3 TMs, why?

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Import geometry

Meshing of geometry

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Case: KVLCC2 (KRISO Very Large Crude Carrier

Stern

Bow

Adaptation: mesh is refined automatically by splitting each tetrahedral cell into 8 small tetrahedral cells.

Creation of computational domain

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Specifications Full-scale Model scale

Scale ratio 1 1/58.0

Length (m) 320.0 5.5172

Breadth (m) 58.0 1.0

Depth (m) 30.0 0.5172

Draft (m) 20.8 0.3586

Wetted surface area(m2) 27194 8.0838

Displacement (m3) 312 621 1.6023

Block coeff. 0.8098 0.8098

Design speed (m/s) 7.9739 1.047

Froude number 0.142 0.142

Table Specifications for KVLCC2 ship and model

Solving and iterating

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Postprocessing

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Trying to compare with the Experimental frictional resistance: 3.45E10-3

Typical Velocity Contours plots

Coarser grid

Turbulence models Frictional coefficient

(×10-3)

Percentage error

K-omega (SST) 2.996 13.172

K-epsilon 2.867 16.904

Spalart-Allmaras 4.304 24.747

Without adaptation

With adaptation

Turbulence models Frictional coefficient

(×10-3)

Percentage error

K-omega (SST) 2.843 17.594

K-epsilon 2.804 18.720

Spalart-Allmaras 3.605 4.500

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Experimental frictional resistance: 3.45E10-3

Too dissipative!

Finer grid Without adaptation

With adaptation

Turbulence models Frictional coefficient

(×10-3)

Percentage error

K-omega (SST) 2.922 15.291

K-epsilon 2.903 15.854

Spalart-Allmaras 3.641 5.526

Turbulence models Frictional coefficient

(×10-3)

Percentage error

K-omega (SST) 2.922 15.291

K-epsilon 2.903 15.854

Spalart-Allmaras 3.641 5.526

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X-section for K-omega at X=0.35

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X-section for K-epsilon at X=0.35

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Cross section for Spalart-Allmaras at X=0.35

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Velocity contour for Spalart-Allmaras model

Coarser grid 0.4 million cells 86 000 nodes Y+ =5000 ??

Finer grid 0.7 million cells 86 000 nodes

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Max. Y+ =230

𝑢 += 𝑢𝜌𝜏𝑤

, 𝑦 +=𝜌𝑦𝜇

𝜏𝑤𝜌

Concept: Force Evaluation on Artificial Reefs

©CIMNE

Wave absorber

Idealised expression of wave profile at incipient breaking

OWC & Buoy-Type Devices

Simulation of an OWC installation

Application eg: Design and optimization of an OWC installation

Oscillating Water Column (OWC) Wave Energy Converter...........

Marine and Naval – Ship Sinking

Numerical Simulation of Ship Sinking due to Leakage

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CFD Modeling and Improving of Ship Propeller

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• Simulation considered on all 4 blades

• Employs a Multi Frame of Reference Approach

• Automatic Mesh Generation with Ansys

• Turbulence modeled using

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Pitch / Diameter: 1.1 Forward Rake: 4 o Diameter: 227mm N = 23 rps Turbulent intensity: 0.6% Turbulent Viscosity Ratio: 10

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Figure : Discharge Surface Pressure (Pa) at J = 1.408

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Figure : Suction Surface Pressure (Pa) at J = 1.408

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What next? 1. Integrated design of rudder and propeller as

combined system 2. Optimization of propeller hull interaction (ice-fins!) 3. CFD of the ship Squat (this has great potential!!)

Ducted CPP

Some simulated animations with CINME • Hull Fins stabilizer • Submarine UWV • Concrete Pressure Expo DEM • Concrete Pressure thin Wall Expo DEM • Concrete Pressure thick Wall Expo DEM • Tdyn_Dam Break_FSI_1 • Cabin Pressure Expo DEM • Cabin deform Expo DEM 3d • Cabin blast load Expo DEM 3d • Aorta AAA • Tank Flushing