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


• 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.



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• 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


• Low-Frequency Electromagnetics– Motors, generators, induction coils

• High-Frequency Electromagnetics– Waveguides, patch antennas, radar systems,

microwave systems

ElectricityElectricity MagnetismMagnetism

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• Thermal-Electromagnetic Coupling– Induction heating systems– Microwave heating systems

• Used in many manufacturing processes:– Heat treating– Pre-heating for metal forming operations


Electro-Electro-magneticsmagnetics


• Fluid-Electromagnetic Coupling– Induction furnaces for stirring molten metals

• Used by induction furnace manufacturers– Environment too harsh to easily observe stirring

patterns

FluidFluidMechanicsMechanics


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• Electrostatic-Structural Coupling– Comb drives, torsional resonators– Other MEMS devices

• Piezoelectrics– Transducers, microphones, micropumps– Inkjet printer actuation systems

ElectricityElectricity SolidSolidMechanicsMechanics


• Magneto-Structural Coupling– Solenoid devices, stepper motors– Alternators, generators

• Used by engineers to determine:– Magnetic force (linear systems)– Magnetic torque (rotary systems)– Efficiency



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• 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!



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!


Coupled-Coupled-FieldField



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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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• 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


• 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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• 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?

Ansys Fsi Presentation

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