a zonal cfd approach for fully nonlinear simulation of …€¦ · a zonal cfd approach for fully...

A Zonal CFD Approach for Fully Nonlinear Simulation of Two vessels in Launch and

Recovery Operations

Zheng Zheng Hu, Deborah Greaves, Gregorio Iglesias, Martyn Hann

School of Marine Science and Engineering University of Plymouth

Project meeting at MMU, 6/6/2016

WP2: Development of hydro-elastic interaction model

1/17

Outline:


Objective • Build a self-contained two-phase FSI (Fluid Structure Interaction)

module in OpenFOAM Topics • Background

• Development of the two-phase FSI module

• Preliminary results/problems of the FSI module

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Background:


The two-phase FSI application in publications: 1. Dam break impact a elastic beam in 2D/3D, Kassiptis et al. 2010, (Fluid: OpenFOAM: (FVM), Structure: a house code: FEAP (FEM)) 2. A wedge enter and exit water in 2D, Dominic et al. 2013, (Fluid: OpenFOAM: (FVM), Structure: a house code in Java (FEM)) 3. Slam-induced whipping for a segmented ship hull, Craig et al. 2015, (Fluid: OpenFOAM: (FVM), Structure: a house code: Aegir (FEM))

3/17

Scope of two-phase FSI study:

• A self-contained two-phase FSI solver with free surface. • Fluid solver based on existing package (interFoam/interDyMFoam). • Structure solver based on the single-phase FSI. • Strong coupling based on the single-phase FSI.


PUfsiFoam contains: Class: flowModel (PUinterFlow.C/H) Class: stressModel Class: fluidStructureInterface

The single-phase FSI package is existing in foam-extend 3.1 / Extend-bazaar/Fluid structure interaction by Huadong Yao 2014

4/17

http://openfoamwiki.net/index.php/Extend-bazaar/Toolkits/Fluid-structure_interaction

Coupling of flow and structure interface:

sf dd =

ssf ττ ⋅−=⋅ nn f

τd n


• Coupling achieved by enforcing the kinematic and dynamic conditions on the mutual interface:

kinematic condition: dynamic condition: displacement, stress tensor and unit normal vector. • Transfer of Coupling data:

Pressure (δpi) and viscous (δti) force increment at the fluid side

Displacement increment (δui) and velocity νi at the solid side

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Presenter

Presentation Notes

Flow chart for strong coupling :


6/17

Summary of the two-phase FSI: • Structure is modelled by updated Lagrangian FVM solver for large

deformation of elastic body. • Fluid flow is modelled by Arbitrary Lagrangian-Eulerian (ALE) FVM solver

using PISO (Pressure Implicit with Splitting of Operators) procedure. • Free surface is captured using the classical VOF method. • Automatic mesh motion based on the fluid-solid interface deformation

using smoothing operator in Laplace equation discretisation.

• The internal grids of the fluid mesh adjust their positions when the FSI interface moves.

• Aitken’s adaptive under-relaxation technique to accelerate the process

of strong coupling.

7/17

Preliminary results WP2: Development of hydro-elastic interaction model

Tutorial case (Single-phase FSI): a beam in cross flow by symmetry simulation Referenced in foam-extend 3.1/Extend-bazaar/Fluid-structure_interaction

Inlet: Vi fluid

solid 1

1))2cos(1(2.0

=

=−=

fluid

solid

i

HzfftV

ρρ

π

0.1

1.5 0.45

0.2

0.4

8/17


A single FSI tutorial case: 3D Beam in cross flow • Referenced in foam-extend 3.1/Extend-bazaar/Fluid-structure_interaction • Fluid cell=14592 and structure cell= 256

Fluid Density (rho) kg/m3

Kinematic viscosity (nu) m/s2

1000 1.0*10-3

Density (rho) kg/m3

Young’s modulus(E) Pa

Poisson’s (nu) ratio

Structure 1000 1.0*104 0.4


Young’s modulus (elastic modulus)= tensile stress / extensional strain Poisson’s ratio = transverse contraction strain / longitudinal extension strain

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two-phase FSI test:3D Beam in cross flow • Water depth= 0.3 or 0.15 • Fluid cell=14592 and structure cell= 256

Problem: simulation crashes as force reaches to value = 691949N.


Density kg/m3

Kinematic viscosity m/s2

water 1000 1.0*10-6

air 1 1.48*10-5

Density kg/m3



structure 1000 1.0*104 0.4

10/17

two-phase FSI test:3D Beam in cross flow • Water depth=0.15, Young’s modulus= steel • Fluid cell=14592 and structure cell= 256


Density kg/m3


water 1000 1.0*10-6

air 1 1.48*10-5

Density kg/m3



structure 1000 2.0*1011 0.0

11/17

two-phase FSI test: 3D dam Break hitting a elastic structure

• Fluid cell=14592 and structure cell= 256

Density kg/m3



structure 2500 1.0*106 0.0

Density kg/m3


water 1000 1.0*10-6

air 1 1.48*10-5


air

solid fluid

0.1 0.35

0.2

0.45

0.1

12/17


• Referenced by Kassiptis et al. 2010 (Fluid: OpenFOAM; ALE FVM, Structure: a house code (FEM))

Density kg/m3


water 1000 1.0*10-6

air 1 1.0*10-5

Density kg/m3


Poisson’s ratio(nu)

structure 2500 1.0*106 0.0


Problem: simulation crashes fluid solid interface is not consistent.

air

solid

fluid

0.292

0.145 0.08

0.286

0.012

13/17


• Structure: steel • Fluid cell=4700 and structure cell= 450

Density kg/m3


water 1000 1.0*10-6

air 1 1.48*10-5

Density kg/m3


Poisson’s ratio (nu)

Structure (steel)

7850 2.0*1011 0.3


air

solid

fluid

0.292

0.146 0.05

0.286

0.024

14/17

Problems:


• Numerical simulations in two-phase FSI module show that the

crash/instability with: Problem is fluid structure in mesh coupling Possible problem with variable name definition …

15/17

Next steps:


• Continue to improve the two-phase FSI module. • Identify and solver problem with fluid structure mesh coupling. • Validation work: the slamming problem (dam break or drop test) the sloshing/whipping problem (beam or plate) comparison with Nan’s experimental data.

16/17

Thanks


17/17

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