AcuTrace:AcuTrace:

Particle Tracking Postprocessor and

Coprocessor for AcuSolve

Altair Engineering, Inc.

Rick Pember March 2012

Motivation Example Example AcuTrace overview and history Some details Future work Discussion and conclusions

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With feature-less, massless particles: Flow visualization tool Postprocessing: mixing, flow characteristics, statistics, ... Postprocessing: mixing, flow characteristics, statistics, ...

Using particles with mass, temperature, composition, and user-defined quantities: Particulate (multiphase) flows Condensation,evaporation,chemistry,... Bidirectional coupling with AcuSolve

l d h b l d l d h Applications to date have been primarily industrial and other mixing processes

... Users can solve problems they can't solve with AcuSolve aloneUsers can solve problems they can't solve with AcuSolve alone

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Users can solve problems they can t solve with AcuSolve aloneUsers can solve problems they can t solve with AcuSolve alone

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Mixing of a 200,000 gallon water storage tank

Mixing via innovative PAX Water Technologies Lily impeller (1/3 HP)

Customer quote: AcuTrace results Customer quote: AcuTrace results show the excellent mixing characteristics of the PAX Water Lily Impeller Lily Impeller complete circulation no stagnant zones i t t i ti t important in meeting government

mandated standards for potable water storage tanks.

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Inputs AcuSolve solution Initial particle states: position,

Compute particle path Particle path approximated by segments Particle path approximated by segments Segments defined by end points Segment end points are in adjacent

l telements

Outputs Particle path: all end points Poincare: intersection with rectangle Time cut: position, etc., at specific time

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AcuTrace classic Massless particles Steady flow only Turbulent and laminar flows Turbulent diffusion option Multiple reference frames Stretch No mesh motion or sliding interfacesg Explicit 4th-order Runge-Kutta (RK4)

integration Parallel: master-slave paradigm

AcuTrace2 New (4+ yr) code Capabilities beyond AcuTrace classic

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p y First shipped with V1.7f (5/09)

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Physics Massless particlesp Steady, transient, cyclic flow Turbulent and laminar flows i h d lidi i f Moving meshes and sliding interfaces Multiple reference frames: two approachesClassic: Use local frame velocityyPseudo-transient (sliding interfaces and

moving mesh)Produces more realistic trajectories than Produces more realistic trajectories than

the classic approach

Stretch U d fi d f ti

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User-defined functionsPage 7

Integration 5th-order Time-Discontinuous Galerkin (TDG) ImplicitUnconditionally stableStiffly A-Stabley

Space-time formulation facilitates coupling with AcuSolve

Parallel Hybrid MPI/OpenMP (like AcuSolve)Distributed memory via MPIShared memory via OpenMPShared memory via OpenMPFlow data shared by OpenMP threads

Output files use an indexed binary format for fast and random access

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fast and random access

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Problem setup AcuSolve style input files AcuConsole

Postprocessing AcuTransTrace conversionEnSightAcuFieldViewAcuDisplay

Direct access of output files via AcuPython

Unidirectional coupling with AcuSolve

Usage: acuRunTrace

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Bidirectional coupling with AcuSolve Python interface to allow use by other solvers (Radioss,) Finite mass particles Turbulent diffusion

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Basic equations User defined functions User defined functions Time discontinuous Galerkin Multiple reference frame treatment Cyclic Flow Bidirectional coupling

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Particle Massless )( txvxD p rr

r Massless ),( txv

Dt pfp =

Finite Mass ),( txvDtxD

ppp rr

r=

),,,,( tUvvxFDtvD

m

Dt

ffpppp

prrrrr =

llD Trr

r

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StretchPage 12

lvDt f

T=

Allows user to specify additional evolution equations

( )iD rr( )udfnfppii VUUtxfDtD ;1; ,...,,,, v= ni ,...,1=

User writes f and invokes AcuMakeLib to build library Library automatically loaded at run time Integrated with TDG method Prototypical example: stretch Stretch is a useful mixing diagnostic User defined functions have allowed R&D engineers to add new

diagnostics on their o n

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diagnostics on their own

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),( txvx pfprr&r =

[ ]t dtvxwxwvxwn r&r&rrrr&rr ++ + 0)()(1 [ ] fppft pt

dtvxwxwvxwn

=

=++2

0)()(

Approximate functions with P2 basis Three point Gaussian quadrature

[ ] nnnn xtxtxtxx rrrrr == ++ )()()( Three point Gaussian quadrature Highly accurate and stable

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Classic Move particle by local reference frame

velocityvelocity Subtract frame rotational velocity

from the flow velocity Pseudotransient Define mesh motion and a transient

velocity field by Split interface between fixed and

rotating framesrotating frames Rotate mesh and the flow velocity

in the rotating frame in time using the frame rotation rate

M th ti l i g thi h Move the particle using this mesh motion and transient velocity As if we solved the full sliding

mesh problem

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Pseudotransient Classic

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Classic: BluePseudotransient: Red

Trajectories deviate when rotating region entered Classic trajectory kinks upon entry and exit of region Pseudotransient option eliminates these anomalies

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Applicable to time periodic (cyclic) flow( y )

User specifies a small number of steps (covering a cycle) to be used repeatedlyused repeatedly

Allows short-time AcuSolve runs to drive long-time AcuTrace runsg

This option is being used to look at chaotic laminar mixing

Cylinder vortex shedding problem at right used to test this option

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p

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AcuSolve and AcuTrace run concurrently AcuSolve provides AcuTrace with flow data AcuTrace provides AcuSolve with sources Projection of particle sources at particle

quadrature points onto flow meshq p Projection weights source by shape function

and the quadrature point weight Conservation of mass, momentum, energy, Conservation of mass, momentum, energy,

and composition is exact AcuSolve treats AcuTrace as another stagger Iterative solve Iterative solve

Coupling AcuSolve and AcuTrace extends the class of problems addressed by either alone

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At each node a, this translates todq

,...),,())((

,...),,(

1

ppp

nt

t aa

ppp

dtqxtftxNS

qxtfdtdq

particlesn rr

r

=

=

+

))(())(),((,...),,())((1

1

1

qaqq

N

qqppp

t

t a

pppp

t

xNxttfwdtqxtftxNq

n

n

n

rrrr =

=

=

+

Initial test case: heat transfer

q

pfp

pvp

kDNk

TTkDtDT

cm = )(,

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fpkDNuk =

Complete current development Bidirectional coupling with AcuSolve Python interface to couple with other codes Python interface to couple with other codes Finite mass particles Turbulent diffusion

Particle-particle interactionsp Hard sphere model Soft sphere model Fluid force on approaching particles

Additi l ti Additional equations Chemical reactions, heat and mass transfer Condensation, evaporation, dissolution, precipitation, ...

Improve documentation Improve documentation

Prototype additional equations with user defined functions Customer input/feedback to help prioritize tasks

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Customer input/feedback to help prioritize tasks

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AcuTrace provides unique particle tracking capabilities Distinguishing features Uni- and bidirectional coupling with AcuSolve Time discontinuous Galerkin methodUnconditionally stableUnconditionally stableHighly accurate

Highly extendible via user defined functions Novel, improved treatment for multiple reference frames

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