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Practical applicationCustomer stories - Particle simulation with Rocky DEM

47

Luca Benvenuti

Simulation ist mehr als Software

Agenda

• Breakage and Wear Modelling• Thyssenkrupp example

• DEM: ROCKY Live Demonstration

© CADFEM 2017 Simulation ist mehr als Software 48

• Fully integrated with ANSYS Software: Fluent

• Flexible Fibers

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Breakage and Wear Modelling

49Simulation ist mehr als Software

Breakage Modelling: Particle Breakage Modelling in the Mineral Industry

Particle Breakage Models


Small Particles Models (<1 mm)

– Ball Mills, Vertical Mills, ..

Particle Energy Spectra

Big Particles Models (> 1mm) - HPGR, Mills,

...

Instant Fragmentation (IF) - Ab-T10

Tavares: repeated low-

stress collisions

Breakage Modelling: Particle Energy Spectra: Theory

• Statistics for specific energy applied to particles per unit of time• Breakage rates for continuous processes such as milling operations• Number of contacts can be determined via the impact energy

No Breakage ← → Breakage

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• 1.00m • 0.15-0.2m• 0.10-0.15m


Breakage Modelling: Particle Energy Spectra: Example from Thyssenkrupp Industrial Solutions

• Particle Material• Red = Iron• Grey = Steel


• Particle Velocity• Blue = Minimum• Red = Maximum

Breakage Modelling: Particle Energy Spectra: Example from Thyssenkrupp Industrial Solutions

• Particle Diameter• Blue = Minimum• Red = Maximum

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• Vom Steinbruch bis zum Zementversand, Lisa Schrader, Thyssenkrupp Industrial Solutions AG, CADFEM Journal, 2017-2


Breakage Modelling: Instant Fragmentation Model

• Breakage in Rocky based on a combination of JKMRC Ab-T10 approach (from mining industry) and Voronoi Fracture algorithm (from movie special effects/gaming industry)

SHAPEBREAKAGE PROBABILITY AND SIZE

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E. Coumans, ‘Destruction’, Game Developers Conference, San Francisco, March 5-9, 2012.

Total cumulative energy delivered to particle:ecum=ecum+max(0,e-emin)

Particle breakage probability:P=1-exp(-S (L/Lref) ecum)

Particle fragment size distribution:T10=M exp(-S (L/Lref) ecum)


Breakage Modelling: Instant Fragmentation Model

• Breakage Comprehensive Post-Processing (Cone Crusher Example)

BrokenBroken

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UnbrokenUnbroken


Breakage Modelling: Tavares Model

• Breakage• Ab-T10: classic breakage model• Tavares: repeated low-stress

collisions

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• Benefits• Extended coverage of

materials breakagebehaviors


Wear Modeling

• Surface wear model in Rocky is extensively validated for predictions of mill liner life

• The model is based on Arcahrd’s law that postulates proportionality of volume removed to product of contact normal force and tangential displacement

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displacement

• A dh = C dw• A is the surface area• dh is the incremental loss of depth• dw is the incremental shear work done• C equals (K/H) is defined as the wear rate

• Since tangential force is proportional to normal force the volume removed is proportional to shear work done on surface


End of simulation

End of simulation

Start of simulation

Start of simulation

Wear Modeling

• Accelerated wear conditions are simulated to estimate the realistic wear condition (much longer)• Mill slice simulation with wear. • Liner shape changes due to wear caused by particles.

© CADFEM 2017 58Simulation ist mehr als SoftwareOperation time

Wear Modeling: 6 DOF Free Motion

• Movement can be given or calculated by ROCKY• Interaction with particles are used as

load • Hinged flop gate free to rotate about

the Z axis. Displacement and wear rate also captured.

• Wheel with six degrees of freedom motion. Wheel mass is m=10 kg, moments of inertia are Ixx=1.0, Iyy=0.1,


also captured. Izz=0.1 kg*m2


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DEM: ROCKY Live Demonstration

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DEM: ROCKY Short Demo

• Characteristics• Feed conveyor • Pre-tension moving plate with wear• Moving cylinders to break particles• Start video 1


• To show• Setup Overview:• Post-processing:

• Histogram of particle size• Power consumption of rollers• Wear damage quantification• Start video 2

DEM: ROCKY Short Demo: Histogram of particle size

• Cube IN• Cube OUT


• Grid Functions / particle size / show in a new Histogram

DEM: ROCKY Short Demo: Roller Power

• For each roller, plot the Power curve in a transient plot


DEM: ROCKY Short Demo: Wear damage quantification

• Setup a property grid function at the “Bulkhead”• Displacement: 10E-4 to 1

• From grid functions insert a time plot form the area, with SUM option



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Fully integrated with ANSYS SoftwareFluent


ROCKY and ANSYS: Fluent Coupling

• Both one-way and two-way analyses are possible.

• One-way coupling example: waste separator

• Two-way coupling example: fluidized bed


ROCKY and ANSYS: Fluent Coupling: Multiple domains Support: NEW IN ROCKY 4.1 (Q1 2018)

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ROCKY and ANSYS: Fluent Coupling: Distributed CFD Simulation

• Allows Rocky-Fluent Coupled runs to use Fluent distributed run capabilities• Greatly reduce simulation times

Fluent Fluent

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RockyRocky

FluentFluent

Fluent Fluent SlavesSlaves



…

GPU

CPU

Network68Simulation ist mehr als Software

particle-particle and particle-wall contact forces

fluid-particle interaction

ROCKY and ANSYS: Fluent Coupling: DEM side

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Euler’s Equations:

Currently available in Rocky


ROCKY and ANSYS: Fluent Coupling: DEM side

• Additional equation for energy balance if thermal model is activated.• Particle temperature is assumed uniform (no radial or circumferential

temperature variation)

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contact heat transfer Convective

fluid-particle heat transfer


ROCKY and ANSYS: Fluent Coupling: CFD side

• Influence of particle on the fluid flow is taken into account by the volume fraction and momentum exchange force.

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particle-fluidinteraction

Calculated on DEM software


Spherical particles

Takes into account shape

ROCKY and ANSYS: Fluent Coupling: Drag Models

• Dilute flows• Schiller & Naumann (1933)• DallaValle (1948)• Haider & Levenspiel (1989)• Ganser (1993)

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• Dense flows• Wen & Yu (1966)• Ergun (1958)• Huilin & Gidaspow (2003)• Di Felice (1994)


ROCKY and ANSYS: Fluent Coupling: Drag Models - Dilute flows

• Ganser (1993)• effects of shape and alignment of the particle with the flow.

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Stokes’ shape factor

Newton’s shape factor

sphericity

measure of particle alignment with the flow


ROCKY and ANSYS: Fluent Coupling: Drag Models – Dense flows

• Huilin & Gidaspow (2003)• Smooth transition between Wen & Yu

and Ergun


• Di Felice (1994)• Correction for dilute flow drag

correlations

ROCKY and ANSYS: Fluent Coupling: Example - Windshifter

• Typically used in industrial waste processes to separate light from heavy particles.

• Depending on their sizes, shapes and densities, particles will rise up

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(light fraction) or settle down (heavy fraction).

• 1-way coupling test using different drag laws


ROCKY and ANSYS: Fluent Coupling: Schiller & Naumann Drag Law

• Although light in weight, large paper particles fall down because S&N drag law does not take into account the shape


ROCKY and ANSYS: Fluent Coupling: Ganser Drag Law

• Paper particles go up because Ganser drag law take into account the shape


ROCKY and ANSYS: Fluent Coupling: 2-Way

• NETL small scale tests widely used to improve the reliability of computational modeling of multiphase flows by validatingwith accurate and well defined experimental data

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(a) SSCP-I test facility and (b) Experimental facility showing pressure intakes

78

• 3 x 9 x 48 in bubbling fluidized bed• Geldart D uniform sized particles• 2-way coupling test using dense

drag law


ROCKY and ANSYS: Fluent Coupling: 2-Way

• Experimental and simulation minimum fluidization velocities coincide well.• Good agreement between experimental and simulation pressure drop results

after fluidization.


ROCKY and ANSYS: Fluent Coupling: Fluid-particles heat transfer

• Heat transfer rate between a particle and fluid:

• Average convective heat transfer coefficient calculated based on Nusselt number:

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• Available Nusselt number correlations:• Ranz & Marschall (1952)• Whitaker (1972)• Gunn (1978)

Single particle

Fixed or fluidized beds


ROCKY and ANSYS: Fluent Coupling: Fluid-particles heat transfer

• Thermal convection with particle shapes and size distribution



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Flexible Fibers


Flexible fibers


Flexible fibers


Flexible Fibers – Fluent Coupling

1-Way CouplingRigid Flexible


FULLY INTEGRATED with ANSYS tools

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