Numerical Simulation of Regular Wave in a Tank

Marcelo de A. Vitola, Dr.LabOceano/COPPE/UFRJemail: vitola@peno.coppe.ufrj.br

Carlos Antonio Levi, Dr. LabOceano/COPPE/UFRJemail: levi@peno.coppe.ufrj.br

Authors:

Monica Campos Silva, Dr. studentPENO/UFRJ

email: mcsilva@peno.coppe.ufrj.br

Waldir Terra Pinto, Dr.FURG

email: w_pinto@dmc.furg.br

mailto:vitola@peno.coppe.ufrj.brmailto:levi@peno.coppe.ufrj.brmailto:mcsilva@peno.coppe.ufrj.brmailto:w_pinto@dmc.furg.br

Summary

Introduction;

Numerical Wave Tank

Set up of the Numerical Model

Grid generation

Parametric Study

NWT

Conclusions

Next steps

Acknowledgement

Introduction

Offshore structures submitted to wave loads

Molikpaq platformwww.nrc-cnrc.gc.ca

http://horsesmouth.typepad.com/hm/ocean/ http://horsesmouth.typepad.com

Introduction

Model Testingmeasuring structural loads and response

FPSO modelLabOceno/COPPE/UFRJ

WavemakerLabOceno/COPPE/UFRJ

Introduction

Numerical Modeling

supply information to help the planning of experimental tests

supply field information difficulty obtained in experimental tests.

NWT without

structures

Set up

of the numerical

model, CFX

(i)

Computational

Domain

(2D)Flap-type wavemaker;

Beach slope: 1:3;

(ii)

Boundaries

Conditions:Wavemaker WallBottom WallBeach WallEndwall WallTop Opening

(iii)

Initial

Condition:Zero-velocity fieldHydrostatic pressure distribution

Numerical

Model:

Set up

of the numerical

model, CFX

(iv)

Numerical

Model:Parameter SettingModel Laminar

Multiphase model Homogeneous model

Analysis Type Transient

Convergence criteria RMS < 1E-7

Run Mode Serial

ICEM-CFX

Numerical

Model:

Grid

Generation

Parameters:

1. Geometry of the domain: Top boundary locationLength of domain

2. Grid refinement

3. Time step

4. Spatial discretization scheme

5. Time discretization scheme

6. Body force averaging type

7. Interface Compression Level

Parametric

Study:

Parametric

study Initial

Setup

Parameter Numerical settings1. Geometry of the domain: hfs-top

= 1.0 m

2. Grid refinement: Test 01:n. hexa

= 5,289zmin

= 0.025 mx = 0.250 mAspect ratio = 10.0

3. Time step t = 0.02 s

4. Spatial discretization scheme High order

5. Time discretization scheme 2nd

order backward Euler

6. Body force averaging type Volume-Weighted

7. Interface Compression Level 0

Water.VOF

= 0.5

Parametric

study: Influence

of VOF value

in the free

surface

location

Parametric

study: Influence

of variable

on

horizontal velocity

profile

WSV = Water Superficial Velocity X (m/s) WV = Water Velocity u (m/s)

Test 32

Water Velocity u

Parametric

study (Conclusions)

Geometry of domain:

top boundary:

Distance from mean free surface to top boundary showed small influence on free surface results.

length (simple x double):

The length of the domain had not significantly influence on free surface and velocity field results.

Grid refinement:

in the region around the free surface:

Both direction x

and z

has influence on free surface results

in the region under wave:

Small influence of mesh refinement of both direction were observed on velocity field.

Parametric

study (Conclusions)

Time step:

t Tp/100 to avoid free surface damping

Spatial and time discretization schemes:

Better agreement:

spatial scheme: 2nd

(UDS) or High Order

and

time discretization: 2nd

order (BE)

Body force averaging type and Interface Compression Level

Both parameters did not show great influence on numerical results

Parametric

study: Final Setup

Parameter Numerical settings1. Geometry of the domain: hfs-top

= 1.0 m

2. Grid refinement: Test 10:n. hexa

= 36,352zmin

= 0.013 mx = 0.052 mAspect ratio = 4.16

3. Time step t

Tp

/ 100

4. Spatial discretization scheme 2nd order upwind differencing scheme

5. Time discretization scheme 2nd

order backward Euler

6. Body force averaging type Volume-Weighted

7. Interface Compression Level 0

Details in Silva et al. SOBENA 2010

Numerical

Wave

Tank

(NWT)

hw = 1.5 m;

Tp (s) 2.0 2.5 3.0 3.5max (o) 4.29 5.71 7.12 8.53S (m) 0.15 0.20 0.25 0.30

(H/L)theory 0.0033 0.0335

Test 032:Tp = 2 s;max = 5.81;t = 0.02 s

numerical results x 1st order wavemaker theory

NWT

Wave heightWave length

NWT

NWT

NWT Field

velocity: Issues

Test 032: t = 19.4s

Test 032:Tp = 2 s;max = 5.81;t = 0.02 s

NWT Field

velocity: Issues

Test 032

t = 19.4s

NWT Field

velocity: Issues

Test 032

t = 19.4s

NWT Field

velocity: Issues

Test 032

NWT Field

velocity: Issues

t = 19.4s

Test 032

NWT Field

velocity: Issues

t = 19.4s

Conclusions

Numerical model seems to be a useful tool for estimate the free surface behaviour in monochromatic wave generated in laboratory.

Further investigations are necessary to verify the preliminary numerical results observed for velocity field under wave.

Next

steps

Checking the numerical results from CFX with the ones from Fluent;

Acknowledgement

Thanks for your attention!

Numerical Simulation of Regular Wave in a TankSummaryIntroductionSlide Number 4Slide Number 5NWT without structures Set up of the numerical model, CFXSlide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Slide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27ConclusionsNext stepsAcknowledgementSlide Number 31