ansys fsi presentation
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ANSYS/Multiphysics FSIwith Applications
Mark TroscinskiMultiphysics Product Manager
Presented By:
David EllisIdac Ltd
FE-Net Industry Co-ordinator forConsumer Goods
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Agenda/Objectives
• Answer some questions:–What is Multiphysics?–What is FSI?
• Describe benefits of new ANSYSFSI capability
• Illustrate some interesting FSIapplications
What is Multiphysics?
Multiphysics - The ability tocombine the effects of two or moredifferent, yet interrelated physicalphenomena, within one, unifiedsimulation environment.
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HeatHeatTransferTransfer
Multiphysics Coupling
SolidSolidMechanicsMechanics
MagnetismMagnetismFluidFluidMechanicsMechanics
ElectricityElectricity
Multiphysics Coupling
• Thermal-Structural Coupling– Engines, Gas Turbines, Heat Exchangers– Electronic Components, Solder Joints– Cryogenic components and systems
• Needed for any product subjected toextreme changes in temperature.
HeatHeatTransferTransfer
SolidSolidMechanicsMechanics
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Multiphysics Coupling
• Thermal-Electric Coupling– Current-carrying conductors, bus bars– Electric motors, generators, transformers– Electronic components and systems
• Needed for electric power handlingcomponents and systems.
HeatHeatTransferTransfer ElectricityElectricity
Multiphysics Coupling
• Low-Frequency Electromagnetics– Motors, generators, induction coils
• High-Frequency Electromagnetics– Waveguides, patch antennas, radar systems,
microwave systems
ElectricityElectricity MagnetismMagnetism
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Multiphysics Coupling
• Thermal-Electromagnetic Coupling– Induction heating systems– Microwave heating systems
• Used in many manufacturing processes:– Heat treating– Pre-heating for metal forming operations
HeatHeatTransferTransfer
Electro-Electro-magneticsmagnetics
Multiphysics Coupling
• Fluid-Electromagnetic Coupling– Induction furnaces for stirring molten metals
• Used by induction furnace manufacturers– Environment too harsh to easily observe stirring
patterns
FluidFluidMechanicsMechanics
Electro-Electro-magneticsmagnetics
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Multiphysics Coupling
• Electrostatic-Structural Coupling– Comb drives, torsional resonators– Other MEMS devices
• Piezoelectrics– Transducers, microphones, micropumps– Inkjet printer actuation systems
ElectricityElectricity SolidSolidMechanicsMechanics
Multiphysics Coupling
• Magneto-Structural Coupling– Solenoid devices, stepper motors– Alternators, generators
• Used by engineers to determine:– Magnetic force (linear systems)– Magnetic torque (rotary systems)– Efficiency
Electro-Electro-magneticsmagnetics
SolidSolidMechanicsMechanics
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Multiphysics Coupling
• Inviscid Fluid-Structural Coupling– Acoustics-based applications– Transportation NVH, undersea noise detection
• Viscous Fluid-Structural Coupling– CFD-based applications– Fuel injectors, control valves, fans, and pumps– More, more, and still more!
FluidFluidMechanicsMechanics
SolidSolidMechanicsMechanics
What is CFD?• Numerical analysis of fluid flow, heat transfer, and
related phenomena• Within each finite element, the Navier-Stokes
equations are rewritten as algebraic equationsthat relate nodal:– Velocity– Pressure– Temperature– Species concentrations
… to the values in the neighboring elements.• Equations are assembled in matrices and solved
to yield complete picture of flow down toresolution of mesh
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CFD Equations
• Conservation of Mass– Continuity
• Conservation of Momentum– Newton’s 2nd Law
• Conservation of Energy– 1st Law of Thermodynamics
• Conservation of Species Concentration
CFD Elements
• 2D: Fluid141– Quadrilaterals– Triangles
• 3D: Fluid142– Hexahedrals or bricks– Tetrahedrals or tets– Pyramids– Prisms
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CFD Flow Descriptions
• Eulerian– Focus on fixed volume of space, where fluid
enters and leaves
• Lagrangian– Focus on particular fluid region which moves
relative to a fixed point of reference
• Arbitrary-Lagrangian-Eulerian (ALE)– Boundary of fluid region moves at arbitrary
velocity (something other than fluid velocity)– FSI’s dynamic mesh motion scheme
What is FSI?
In reality, it’s Fluid-Solid Interaction!
FluidFluidMechanicsMechanics
Coupled-Coupled-FieldField
HeatHeatTransferTransfer
SolidSolidMechanicsMechanics
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How is FSI done?
Numerical coupling isestablished between thedifferent “physics” modules
Multiphysics Math
The finite element formulation which treatsa single phenomenon uses matrixalgebra represented by:
[ K ] { X } = { F }
where [ K ] is the coefficient matrix
{ X } is the vector of nodal unknowns
{ F } is the known load vector
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• Subscript 1 represents fluid; Subscript 2 issolid
• Coupled effects are accounted for by off-diagonal coefficient terms K12 and K21
• Provides for coupled response in solutionafter one iteration.
[K11] [K12][K21] [K22]
[X1][X2]
[F1][F2]
=[ {] } { }Matrix Coupling
Matrix-Coupled FSI
• Positives:– Solution of a coupled equation system
achieved in a single step
• Negatives:– Requires complete re-writing of the fluid and
solid solvers (must develop new FSI elements)– Matrix system tends to be very ill-conditioned
due to difference in “stiffness” of fluid and thesolid regions
– Large problems become computationallyexpensive
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• Subscript 1 represents fluid; Subscript 2 issolid
• Coupled effects are accounted for by loadterms F1 and F2
• At least two iterations, one for each physics,in sequence, are needed to achieve acoupled response.
[K11] [ 0 ][ 0 ] [K22]
[X1][X2]
[F1][F2]
=[ {] } { }Load Vector Coupling
Load Vector-Coupled FSI
• Fluid and solid variables are updatedsequentially with independent fluid and solidsolver algorithms
• At each “FSI” time step, appropriate loadsare exchanged at the fluid-solid interface
• Positives:– Not required to re-write fluid and solid solvers– Able to leverage main features of each solver– More economical for large scale problems
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ANSYS FSI Initiative
• Tightly integrate FLOTRAN CFD &ANSYS solid solvers into a loadvector-coupled FSI algorithm thatis:–Fully-automated–Time-accurate–Easy to use
• Leverage ANSYS/Mechanical corecapabilities
FSI Algorithm Benefits
• Fully-automated, time-accurate FSIsolution algorithm for:– Fluid-structure interaction– Fluid-thermal interaction– Fluid-thermal-electric interaction– Fluid-piezoelectric interaction
• Why?→ For simulations closest to reality!
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FSI Algorithm Benefits
• Full support for all structuralnonlinearities:– Geometric, material, and contact
• Dissimilar mesh interface:– Automatically transfers loads between
differently meshed fluid and solid regions
• Support for beam, shell, and solidelements:– With or without mid-side nodes
FSI Algorithm Benefits
• Fully-implicit time-stepping scheme:– Automatically checks convergence of all
relevant physics at each time step beforeadvancing in time
– Allows for independent time step sizes forfluid and solid physics (sub-cycling)
– Provides for the most efficient, time-accurate solutions
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FSI Algorithm Benefits
• FLOTRAN Element Birth and Death:– Suitable for FSI problems involving
contact between immersed, movingstructures
– Fluid elements may be automaticallydeactivated as surfaces come intocontact (e.g., valve closes), or reactivatedas they separate (e.g., valve opens)
ANSYS SOLID • Structural/Thermal/Coupled-Field• Geometric Non-Linearity• Material Non-Linearity• Contact Non-Linearity• All Iterative and Direct Solvers• All Transient Solver Options
ANSYS FLUID• FLOTRAN 2D/3D Elements• Extensive CFD Capabilities• ALE Formulation• Elasticity-Based Mesh Morphing
Global Time Loop
Stagger Loop
ALE Mesh MorphFluid SolutionLoad Transfer
Solid SolutionLoad Transfer
Convergence Check
End Stagger Loop
Increment Time
End Global Time Loop
FSI Algorithm Layout
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Load Transfer
From FLUID side
Conservative InterpolationNodal forces: FX, FY, FZNodal heat rates: Q
Non-Conservative InterpolationNodal force fluxes: FX”, FY”, FZ”Nodal heat fluxes: Q”
Interpolation between dissimilar meshes
From SOLID side
Nodal displacements: UX, UY, UZNodal temperatures: TEMPNodal velocities: VX, VY, VZ
GST for FSI
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Applications• Truly applicable across all market
segments:– Automotive fuel injectors, control valves, engine
dampers, fans & pumps– Aerospace airframe and propulsion system
components– Flexible flow control devices, biomedical
vessels and valves for blood flow– Flow-induced vibration of piping systems and
heat exchangers– Diaper manufacturing processes, paper copy
machines– More, more, and still more!
Deformable Flow Control Device
Underlow ∆P
Underhigh ∆P
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So What?
• Vernay Labs currently designs thesedevices by “seat of pants” method:– Guess at shape to get right flow control
characteristics– Build and test, build and test, …
• They have no automated process in placefor designing these FSI-type devices.
• ANSYS/Multiphysics can significantlyreduce their overall time to market.
Problem Description
• Fluid:– Incompressible, turbulent water flow– Prescribed inlet-to-outlet ∆P = 45 PSI
• Solid:– Hyperelastic, high strain (>100%) materials– Treated with Mooney-Rivlin model
• Simulation objective:– Determine steady-state shape of solid and
accompanying steady-state fluid flow rate
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Axisymmetric Model
Water - FLUID141’s
Rubber -PLANE183’s
TARGE169’sCONTA172’s
Finite Element Mesh
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FSI BC – on Fluid
FSI BC – on Solid
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FSI Results
15.77 mmseal length
Radial clearance = 2.15 microns
Leakage collection grooveDrain pressure => 100 kPa
8.5 mm plunger diameter
41 mm barrel diameter
9.87 mm
18.36 mm
SteelsE = 206.8 GPaν = 0.29
Actuation force
P(t) input (next page)Plunger Cavity
Problem Statement:Given plunger cavitypressure as f(time),what is the total massflow to the leakagecollection groove?
Diesel Fuel Injection
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So What?
• Fuel injector leakage:– Unavoidable parasitic loss– Adversely affects system efficiency - Must be
minimized!– Current predictions grossly underestimate
measured leakage volumes• Caterpillar has NO automated method of
predicting leakage rates.• Tiny gains in system efficiency would
provide tremendous advantage over theircompetitors
Plunger Cavity Pressure
0.0E+00
5.0E+07
1.0E+08
1.5E+08
2.0E+08
2.5E+08
0.000 0.002 0.004 0.006 0.008 0.010 0.012
Time (sec)
Rel
ativ
e S
tati
c P
ress
ure
(P
a) Fluid Properties:Fuel type: CAT1E262Temperature: 85CKinematic Viscosity:1.171074E-06 m^2/secDensity: 809 kg/m^3 @101KpaBulk Modulus: 1171698kpa @ 0 kpaBulk modulus Slope:10.82775(i.e. bulk modulus =1171698 + 10.82775*P
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Model Geometry
Plunger
Barrel
Cavity
Model Geometry
Leakage Inlet
10º Chamfer
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Model Geometry
Finite Element Mesh
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Boundary Conditions
UY=0
UX=0
P(t)
UY=0
VX=0VY=0
P=0UY=0
FSI(1) FSI(2)
FSI Results500X Displacements
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Leakage Flow Rates
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0.000 0.002 0.004 0.006 0.008 0.010 0.012
Time (sec)
Mas
s F
low
Rat
e (
gm
/sec
)
FSI CFD
LEAKAGEFSI / LEAKAGECFD = 12.0!
Pressure-Limiting ValveSpring constant:
kspring = 8.0E+05 gm/sec^2
Spring preload:
Fpreload = 2.5E+06 gm*mm/sec^2
Ball density:
ρball = 7.8E-03 gm/mm^3
Fluid density:
ρfluid = 7.5E-04 gm/mm^3
Fluid viscosity:
µfluid = 4.0E-04 gm/(mm*sec)
Relative inlet pressure:
Pinlet = 6.0E+05 Pa
0.25mm
Ø 2.4 mm
Ø 4.0 mm
Ø 4.5 mm
Ø 10.0 mm
55º
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So What?
• Pressure-limiting valves are used in anti-lock brake systems– Huge liability ramifications
• Per VDO, tiny geometric design changescause wide variations in valve responseand performance
• Currently guessing on new valve designs• Automated FSI tool will significantly reduce
overall time to market and improve reliability
Axisymmetric Model
FLUID141’sSOLID42’s
COMBIN14
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Finite Element Mesh
Mesh Detail
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Mesh Detail
FSI Results
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Ball Displacement History
f ≈ 875 Hz
Office Copier FSIPaper Sheet:Thickness: 0.0092 inLength: 8.0 inWidth: 11.0 inCurl Radius: 20.0 inWeight: 0.000294# / in2
Elastic Modulus: 500,000 PSIVacuum hole:Width: 1/8 in
Plenum Outlet:∆P: 3.0 in H2O
2 in 8 in
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FSI Results
Ink Jet Printer
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Piezoelectric Micropump
Air
SiliconMembrane
PZT Layer
~ 3 mm
± 500 V
FSI Results
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Pulsing Blood Flow
Fluid element: 142’sSolid element: 45’sDissimilar mesh interface
Material PropertiesSolid density: 1150 kg/m^3Young’s modulus: 3.0*10^5 PaPoisson ratio: 0.3
Fluid density: 1050 kg/m^3Fluid viscosity: 4.0*10^-3
Inlet pressure pulse
FSI Results
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Vortex Shedding – Re = 100
Vortex Shedding – With Tail
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VX = 20 mph; VY = ± 5 mph
Summary
• ANSYS FSI solution capability:– Easy to use, fully automated, time-accurate– Full support for all structural nonlinearities– Dissimilar mesh interface for beam, shell and
solid elements, with or without mid-side nodes
• Future developments:– Add automatic re-meshing capability– Add nth physics to stagger loop– Enhance FSI post-processing– Add AMG parallel solver
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Thank You!
Any Questions?
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