Multiphase 05, Porquerolles, April 20, 2005

Simulation of hydrodynamic wave loading by a 3D 2-phase numerical model

Multiphase05

Rik Wemmenhove

University of Groningen, dept. of Mathematics

Multiphase 05, Porquerolles, April 20, 2005

Introduction: applications

Green water loading

Tank sloshing

LNG tanker, © DNV

Multiphase 05, Porquerolles, April 20, 2005

Offshore applications

• Green water loading

• Bow slamming

• Sloshing in tanks

• Ship launching

• Floating objects

• etc.

Multiphase 05, Porquerolles, April 20, 2005

Offshore flow phenomena

Multiphase 05, Porquerolles, April 20, 2005

Two-phase flow at wave impact (1)

Multiphase 05, Porquerolles, April 20, 2005

Two-phase flow at wave impact (2)

Pressure level during wave impact

Sources:

Wood et al, JWPCOE, 2000, 126, 2000.

Bullock et al, Coast. Eng., 46, 2002.

Multiphase 05, Porquerolles, April 20, 2005

Two-phase flow at wave impact (3)

Source:

Deane & Stokes, Nature (418), 839-844, 2002

Multiphase 05, Porquerolles, April 20, 2005

Modeling two phases

= const

= 0

p = 0= const

= const

p = p()

1-phase 2-phase

incompressible

2-phase

compressible

= const

Multiphase 05, Porquerolles, April 20, 2005

ComFLOW: Incompressible model (1)

0 u

01

upuut

u

Mass conservation:

Momentum equation:

Multiphase 05, Porquerolles, April 20, 2005

Incompressible discretisation (1)

01 nu

0)(1

)( 11

nnn

nnn

nn

upuudt

uu

))(()()(11 212 nnnnnn

nuuuu

dtp

Mass conservation

Momentum equation velocity

Poisson equation pressure

n = previous timestep

n+1 = next timestep

Multiphase 05, Porquerolles, April 20, 2005

Incompressible discretisation (2)

Fs = 0.5

Fb = 1.0

Fs = 0.5

Fb = 1.0

Fs = liquid cell fraction

Fb = open cell fraction

air

water

water

solid

Multiphase 05, Porquerolles, April 20, 2005

Validation: rising bubble

Multiphase 05, Porquerolles, April 20, 2005

Validation: dambreak experiment

Dambreak experiment MARIN (Maritime Research Institute Netherlands) & ComFLOW simulation

Multiphase 05, Porquerolles, April 20, 2005

Dambreak experiment (1): water height

Grid size: 180 x 60 x 60

Multiphase 05, Porquerolles, April 20, 2005

Dambreak experiment (2): pressure level

Grid size: 180 x 60 x 60

Multiphase 05, Porquerolles, April 20, 2005

Evaluation incompressible model

• Smoother pressure signal for dambreak experiment

•Simulation of air physics may be improved by taking compressibility into account

Multiphase 05, Porquerolles, April 20, 2005

Future developments: compressible model

• Incompressible water phase

• Adiabatic p- relation in air

Multiphase 05, Porquerolles, April 20, 2005

http://www.math.rug.nl/~veldman/comflo/comflo.html

More literature about ComFLOW?

Source: An Album of Fluid Motion, Van Dyke, 1982