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NUMERICAL MODELLING OF MECHANICAL COUPLING IN
FLUIDS & STRUCTURES
SOFTWARE fluidyn - MP
PRESENTATION OF fluidyn - MP
General : role & utility of
Computational Fluid Dynamics
A reliable numerical representation of a real processus with
the help of well adapted physical models
Easy to use & adapted to optimisation studies in industrial
processes
Economic with a security advantage
Ideal complementary tool for experimental measurements
Access to physical variables (velocities,
temperature, etc.) at each point in the domain
pressure,
Software fluidyn - MP, FSI model
Strong coupling & conjugate heat transfer between fluid &
structures integrated in a single software platform
Robust physical models & various well adapted solvers
Finite Volume Method for fluids and Finte elements method for
structures
Automatic exchange of boundary conditions between fluids &
structures - Adaptative Fluid Mesh
Local time step used to reduce CPU time
Fluid Solver
Solution of Navier-Stokes Equations
3-Dimensions
Compressible / incompressible
Mechanical / thermal shocks
Viscous / non-viscous
Laminar / turbulent
Multi-species
Multi-phase
Fluid Solver
Non-Newtonian Flows :
Bingham law
Power law
Chemical – combustion reactions
Arrhenius model
Eddy-break-up model
Eddy dissipation model
Deflagration & fire
BLEVE
Pool fire
Detonation
JWL model
Two phase flows
droplets, bubbles, particles
Euler-Lagrange Monte-Carlo,
Free surface flow ( VOF method + CSF method)
Fluid Solver
Free surface two phase flows
VOF method (Volume of Fluid)
Finite volumes solution
Adapted to gravity controlled flows whose interfaces undergo
large deformations
3 high order convective schemes (Inter-Gamma Differencing,
HRIC & CICSAM)
CSF method (Continuum Surface Force) for modelling surface
tension
Fluid Solver
Free surface two phase flows
ALE method (Arbitrary Lagrangian Eulerian)
Finite volumes solution
adapted to problems needing a fine modelling & whose interface
undergoes small deformations
2 solution algorithms : Donor Cell (1st order) & Van Leer (2nd
order)
easy calculation of surface tension
Fluid Solver
Two phase Euler / Lagrange flows
Euler / Lagrange method
adapted to flows with the presence of a dispersed phase
diluted or dense flows
monitoring each particle trajectory
jet, fluid bed flows modelling, etc.
Fluid Solver
Two phase Euler / Lagrange flows
Particle size distribution
various distribution methods : uniform, gaussian, RosinRammler type, Nukiyama-Tanasawa type, user routine
non uniform distribution : statistic method of Monte-Carlo
wall interaction accounted for via a restitution coefficient
modelling inter-particle collisions, coalescence phenomena,
rupture & agglomeration
Fluid Solver
Turbulence
Algebraic Models
Baldwin- Lomax
Mixing Length :
Van Driest damping
Abbott & Bushnell
Cebeci- Smith
Sub grid scale model SGS
Two equations transport (k - e) & RNG
Reynolds stress model (anisotropic turbulence)
Fluid Solver
Equations of State
Perfect gas
Ideal gas
JWL (Jones - Wilkins - Lee) for explosions
Linear - polynomial
User defined
Viscosity & Prandtl number
Temperature functions
User defined
Fluid Solver
Spatial discretization schemes
Explicit :
Van Leer Flux Vector Splitting
Roe Flux Difference Splitting
3rd order
Advection Upwind Splitting, HLLC
Semi- implicit : Weighted Upwind Scheme
QSOU
Implicit :
Central Difference Scheme
2rd order
3rd order
Flux Limiter Scheme (Van Leer, SMART, etc.)
Fluid Solver
Temporal discretization scheme
Explicit :
Time step
global minimum for transient simulations
local for steady state simulations
convergence acceleration
Temporal Integration
6 step 2nd order Runge Kutta.
Implicit:
Gauss-Seidel or Jacobi iterative methods
steady state calculation & low velocities.
Structured solver
FINITE ELEMENTS
3D beam elements
3 node shell elements
4 node tetrahedral elements
Material characteristics
Linear elasto-plastic, orthotropic
Piecewise linear
Non linear plastic
Structured Solver
Small deformations & large displacements
Finite Elements method
Large deformations
Finite Elements method
Finite Elements solvers
Explicit / implicit
Rayleigh damping
Structured solver
Boundary Conditions
Transient or constant
Outside :
at nodes : temperature, forces, displacements
at faces: pressure, volume forces
Imposed automatically in fluids & structures
Modelling displacement of fluid mesh with Updated
Lagrangian method
Heat transfer modelling
Automatic simulation of convective & radiative heat transfer
Radiation models
Transparent media
 Automatic calculation of 3D view factors
 Shadow effect of intermediate obstacles
Opaque Media
 Six-Flux model
 Discrete ordinate model
Thermal analysis
 Material properties w.r.t temperature
 Conduction with Finite Elements method.
Computation Procedure - 4 steps
Fluid solver
Fluid temperature
Heat transfer coefficient
Distribution of boundary pressures
Iterations
until
convergence
Thermal solver
Transient heat transfer
Solid temperature
Structured solver
Thermal load
Mechanical load (pressure)
stress & deformations
FLUID-STRUCTURE REMESHING
Pre - processor
Mesh
Multi-block structured
Un-structured
 Delaunay method
 2D & 3D meshes
 Hybrid, tetrahedral or hexahedral mesh
Adaptative mesh
 Shocks, turbulent boundary layers, ..
 Refined mesh & automatic interpolation
of the solution.
Interactive, simple & automatic
Complex geometries
Post - processor
Geometry & computation parameters visualisation during
simulation.
3D colour visualisation.
Multi-viewport facility : upto 30 viewports
Comparison of results obtained from different computations
Vectors, iso-contours, iso-surfaces & 3D current lines
Translations, rotations, multi projections
XY plots: residual & other parameters
Animations
Fluidyn - MP : STUDY CASES
FLUID – STRUCTURE MECHANICAL INTERACTIONS
DOOR OPENING
UNDER FLUID
PRESSURE
AEROSPACE
TOBOGGAN
FLAPGATE OPENING
UNDER FLUID
PRESSURE
TNT EXPLOSION
TUNNEL (BOURGES)
fluidyn-FSI
FLUID – STRUCTURE INTERACTION
Simulation of large displacements & large structural
deformations due to fluid movements
STRONG COUPLING by 2 METHODS
Finite Volumes (FV) for fluids
Finite Elements (FE) for solids
Calculation Procedure - 4 steps
Fluid Solver
Fluid Temperature
Coefficient of heat transfer
Pressure distribution at the boundaries
Iterations
until
convergence
Heat Solver
Transfer of transient heat
Temperature in solids
Structured solver
Heat load
Mechanical loads (pressures)
stress & deformations
fluidyn - FSI
FLUID-STRUCTURE REMESHING
STUDY 1 : OPENING OF A DOOR UNDER
FLUID PRESSURE
TARED DOOR
DESCRIPTION
- Opening of a door under fluid
pressure effect.
- Modelling with the help of the
software Fluidyn - FSI
fluidyn - FSI
Chambre à 30 bar
Porte ----->
RESULTANT OF DISPLACEMENT IN THE DOOR
fluidyn - FSI
DOOR DEFORMATION
fluidyn - FSI
PRESSURE CONTOUR
fluidyn - FSI
PRESSURE CONTOUR
fluidyn - FSI
PRESSURE CONTOUR
fluidyn - FSI
PRESSURE CONTOUR
fluidyn - FSI
STUDY 2 : OPENING OF A FLAPGATE UNDER THE
EFFECT OF FLUID PRESSURE
PROBLEM
A flapgate situated at the end of a pipe opens under the
action of fluid flow
-
- Modelling with the help of Fluidyn - MP
- fluid = water, inlet velocity = 1.07 m/s
- flapgate = steel slab
- 3D flow, strong coupling between fluid & structure
fluidyn - FSI
GEOMETRY OF THE PROCESS
fluidyn - FSI
DOMAIN MESH
Fluid = Finite Volumes
Structure = Finite Elements
fluidyn - FSI
FLOW IN THE MEDIAN PLANE
fluidyn - FSI
FLUID PRESSURE ON THE STRUCTURE
fluidyn - FSI
FINAL STATE
fluidyn - FSI
STUDY 3 : WIND RESISTANCE OF AN ESCAPE CHUTE
PRESENTATION
DESCRIPTION
• Wind resistance of an escape chute submitted to a lateral wind of 25
nodes
• Simplified Case : isolation des arcs & the runways for the simulations
• Structural Modelling with the help of finite elements of beam type
• Fluid Modelling (air) with the help of finite volumes
• Results searched for : deformations & maximum stress
CHARACTERISTICS
Properties of the escape chute
E
4.58E+5 N/m2
ν
0.3
ρ
5.7kg/m3
Properties of the arcs
E
4.58E+5 N/m2.
ν
0.3
ρ
5.7 kg/m3
Physcial properties of air
Fluide
Incompressible
ρ
1.16924 kg/m3
Cp
1005 J.kg-1.K-1
Flow
Viscous
Viscosity : ν
1.895E-05 m2/s
Pr
0.72
Turbulence Model
k-ε
FLUID MESH
STRUCTURAL MESH
BOUNDARY CONDITIONS
RESULTS : DEFORMATIONS
RESULTS : DEFORMATIONS
RESULTS : RESULTANT OF DISPLACEMENT
RESULTS : AERAULICS AROUND THE CHUTE
STUDY 4 : TNT EXPLOSION IN A TUNNEL
STUDY OF ASSOCIATED DEFORMATIONS
PRESENTATION
DESCRIPTION
• TNT Explosion in a cylindrical section of a T tunnel
• dimensions : diameter = 168 mm, lengths = 1.28 m & 1.50 m
• Tunnel walls in steel, thickness = 2 mm
• TNT Load of 18.5 g placed at the tunnel head
• Results searched for : propagation of detonation wave, final structural
deformation
GEOMETRY
MATHEMATICAL MODEL
JWL equation for TNT
r
p  A(1   )e
R1
Ideal gas for air
p  (   1)e

R1
r
r
 B(1   )e
R2

R2
r
 e
JWL EQUATION COEFFICIENTS
0
E0
Pcj
Dcj
cj
cj
= 1630 kg/ m3
= 7 GJ/m3
= 0.21 Mbar
= 0.693 cm/s
= 0.3
= 2.727
A
B
R1
R2
= 3.71213
= 0.032306
= 4.15
= 0.9
STEEL PROPERTIES
• Elasticity Module
• Poisson Coefficient
• Density
= 210 GPa
= 0.3
= 7850 kg/m3
BOUNDARY CONDITIONS : FLUID
BOUNDARY CONDITIONS : STRUCTURE
FLUID MESH
STRUCTURAL MESH
3D SIMULATION
• Symmetry (in the Y direction perpendicular to the
tunnel plane) : mesh reduced to half of the
domain
• 3D domain extended beyond the tunnel head in
order to place the TNT charge
• 3D Mesh
– 48972 cells for the fluid
– 9128 elements for the structure
RESULTS : PICS OF THE PRESSURE AT MONITOR POINTS
RESULTS : COMPARISON WITH EXPERIMENTAL RESULTS
Computed
Trace
Point
Time
(ms)
P
(bar)
Experimental
Time
(ms)
P
(bar)
G1
0.151
30.65
0.099
31
G2
0.353
21.66
0.47
18.36
G3
0.589
13.61
0.592
16
G4
0.559
3.64
0.55
4.5
RESULTS : PRESSURE WAVE PROPAGATION
RESULTS : DISPLACEMENT STRESS IN THE STRUCTURE
RESULTS : DEFORMED FINAL STATE OF THE STRUCTURE
CHINA
Beijing
S.KOREA
Séoul
FRANCE
7, bd de la Libération
93200 Saint-Denis
Tel: 33 (0) 1 .42 43 16 66
Fax: 33 (0) 1 42 43 50 33
JAPAN
Tokyo
USA
Lafayette, CA
UK
SUTTON COLDFIELD
INDIA
Bangalore, New Delhi
FRANCE
Lyon