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Advanc ances s in STAR-CCM CCM+ DEM m models for simulating - - PowerPoint PPT Presentation
Advanc ances s in STAR-CCM CCM+ DEM m models for simulating - - PowerPoint PPT Presentation
Advanc ances s in STAR-CCM CCM+ DEM m models for simulating ulating deformatio mation, n, breakag age, , and d flow of solids Satish sh Bonthu thu Out utli line ne Overvie view of DEM EM in STAR AR-CC CCM+ M+ Recen cent t
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DEM EM is us used d to mode del particles ticles of differe erent nt sizes es and shapes pes
Di Discre crete e Element ement Modeling ling (DE DEM) M) - Overvie view
3
- DEM resolves the collisions between particles
- Particles can be bonded together to form deformable / breakable
material
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Moment mentum m conser nservat ation ion
𝑛𝑗 𝑒𝑤𝑗 𝑒𝑢 = 𝐺𝑗𝑘 + 𝐺
+ 𝑘
𝐺
𝑔𝑚𝑣𝑗𝑒
𝑛𝑗 and 𝑤𝑗 are mass and velocity of particle 𝑗, 𝐺
= 𝑛𝑗 is gravity force, 𝐺𝑗𝑘 is contact
force between particle 𝑗 and element 𝑘
- DEM is a meshless method
- DEM is computationally intensive method
Conse nservati tion
- n of angul
ular r mome mentum ntum 𝑒 𝑒𝑢 𝐽𝑗𝜕𝑗 = 𝑈
𝑗𝑘 𝑘
– 𝑗, 𝐽𝑗 and 𝜕𝑗 are the momentum on inertia and rotational velocity of particle 𝑗. 𝑈𝑗𝑘 = 𝑠𝑗𝑘(𝐺𝑗𝑘 + 𝐺
𝑠) is the torque produced at the point of contact and it is the
function of the rolling friction force 𝐺
𝑠
DE DEM Go Governing erning Equat uations ns
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Cont ntact act forces es
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Normal l component ponent
- f cont
ntac act t force Tangent gential ial component ponent
- f cont
ntac act t force Particle icle A Particle icle B Fricti tion
- n
Young’s modulus ulus (stiffnes fness) Normal l restit itut ution ion Tangent gential ial restit itution ution
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Cont ntact act models els in n STAR-CCM+ CM+
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Optional nal models ls Basic ic models ls
Rolling Resistance Three models for resisting rolling Linear Cohesion Constant attractive force Artificial Viscosity Velocity dependent damping model Heat Conduction Heat flow through contact Parallel Bonds Bonds resisting to tension, bending, twist Hertz-Mindlin Classical nonlinear contact force model for rigid bodies Walton-Braun Linear model for deformable particles Linear Spring Linear model for rigid bodies
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Two
- STAR
AR-CC CCM+ M+ models
- dels us
use same me bond nd physi sics
– Parallel bond contact model
- Bonds are formed after injection at each new contact
- User specifies time interval of bonding
– Bonded particle model
- Used to create clumped particles:
- Bonds are formed at the moment of injection
Recen cent t imp mproveme ments nts
– Bond strength distribution, visualization, and…
Pa Parallel rallel bo bond nds s in n STAR-CC CCM+
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Massless less bar, subject ject to break aking ing under er load
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Bond nd Failur lure e Models ls in n STAR AR-CCM+ CCM+
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F F t t+dt F F F Constant Rate Damage Model New in version 10.04 Simple Failure Model t t + n dt t+dt
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Consta nstant nt Rate e Da Damage age Model
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kr is the fracture softening modulus, model parameter Bond tensile strain Stress on bond O εf kr εf σm σl A0 B0 A B M
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Standar ndard d test t to det etermine ermine the e strength rength of britt ttle le mater erial ial Solid id materi erial al is modeled
- deled as particles
cles bon
- nded
ded togeth ther er
Exam ample ple of Brazilian azilian compression pression test st
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New Maximu ximum Pa Packing ing option
- n in Random
ndom Inject ector
– Particles “grow from seeds” until whole region is fully packed – Resulting configuration has no overlaps between particles
Sample ple preparati paration
- n
11
200 seeds 10000 seeds
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Geome
- metr
try y invol
- lves
es stati tion
- nary
y bott
- ttom
- m wall and moving
ving down wn top platen en
– Particles are injected using table injector with “Allow overlap” option
- Particle diameters are “inflated” by factor 1.01 to ensure small overlaps
– Bonds are set to form for first 0.1 s before starting compression
Run unni ning ng compress ression ion test st
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Ani nimation mation of compression pression test st
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Crac ack k formati mation
- n
Both “Simple Failure” and “Constant Rate Damage” models were re tested: d:
– Only “Constant Rate Damage” model reproduced the vertical crack observed in experiment
Bonds nds mode del parame meters s (Normal
- rmal
and Tangen ential tial strength rength of bon
- nds
ds, , its s dist stributi ribution
- n)
) were re calibra brated ed to reprod
- duc
uce e the e target t materi erial al
– Soft sandstone in our tests 14
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Rock ck is perme meable ble with h void d fracti tion
- n =0.4
Ov Overset t mesh is s us used d to rot
- tat
ate e and advanc nce e the e drill-bit bit down wn Soluti tion
- n for drilling
ing flui uid d flow w was
- btaine
tained d us using 2-way y coup upli ling ng model
- del
Jet et flow w form rm nozzl zzles es results ults in large e drag g forces ces on bonde nded d grains ns (jett etted ed erosi
- sion
- n)
Exam ample ple of rock drilling illing
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Erosion
- sion and Wear
r in Solids ids Processing cessing Equipm ipmen ent
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Slurr rry y flow w in pip ipes erosion ion Sedimen ent t flow, , Gravel el Pa Pack cking ing Drilling rock
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New w in versi sion
- n 10.04
.04 Relevant ant for flow w regimes imes
– With high solids loading – Prolonged “sliding” contact between particles and geometry
Abr brasi sive e Wear Model l in n STAR-CCM CM+
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Archar chard Model: l:
𝑵𝒇 = 𝑫 𝑮𝒅𝒐𝒘𝑑𝒖𝒆𝒖
𝒅𝒑𝒐𝒖𝒃𝒅𝒖𝒕
is mass eroded from single surface cell – 𝑫 is abrasive wear coefficient in units of kg/J (model parameter) – 𝐺
𝑑𝑜 is normal component of
particle-cell contact force – 𝒘𝑑𝒖 is tangential component of particle-cell relative velocity at the point of contact – 𝒆𝒖 is DEM timestep
Field Func nction tion option:
- n:
𝑵𝒇 = 𝑫 𝐺(𝑑)𝒆𝒖
𝒅𝒑𝒐𝒖𝒃𝒅𝒖𝒕
– 𝐺(𝑑) is user field function
Abr brasi sive e Wear Formulat mulation ion
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Surface cell motion
Contact path
𝐺
𝑑𝑜
𝒆𝒖 At the e end d of each h times estep ep, , for each h sur urfa face ce cell, l,
– Erosion rate calculated as 𝐹𝑠 = 1 𝑈 1 𝐵𝑑𝑓𝑚𝑚 𝑁𝑓
- 𝑈 is the timestep
- 𝐵𝑑𝑓𝑚𝑚 is the area of surface cell
– 𝑁𝑓 is reset to zero – 𝐹𝑠 is available for postprocessing
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Model del proper perly ly accounts
- unts for
– All contacts during timestep – Variation of contact force strength and relative velocity for single particle during prolonged “sliding contact”
Abrasi sive e wea ear r coef efficient cient is often n related to “hardness” of boundary Best t for flows ws when hen harde der r partic icles les are sliding ing along ng sof
- fter
er boundar ndary
Abr brasi sive e wear formulation mulation summa ummary
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Abrasiv ive e wear ear model
- del is
s compati patible ble with h coarse se grain n model
- del
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Elbo bow w pipe exam ample, ple, top view
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2 m 1 m 0.4 m Inlet Mean Parcel Diameter = 10 mm Mesh size 20 mm Outlet
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Rando dom m inject ctor
- r
– Uses “Maximum Independent Set” Algorithm to provide High Solid Loading flow – Fast, mesh independent – Initial particle velocity:
- Horizontal component = inlet fluid velocity
- Small “down component”
Pa Partic icle le Inj nject ection
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Injection Volume gravity
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Ini nitial tial Results sults for Elbo bow w flow
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DE DEM Postpr stproc
- cessing
essing
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View from bottom
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Segme gment nt of pipe (or r solids ids bui uildu dup inside ide pipe) can be modeled
- deled us
using g DEM EM particles cles bonde nded d togeth ther
– D_inner = 0.3 m – D_outer = 0.4 m
Water er flow w is set et with th inlet t at one e end d of DEM EM pipe and out utle let t at anoth ther end Inle let t veloci
- city
ty is tilted ed 10 deg deg with th respect pect to inlet et norma rmal
– One side of pipe should experience more erosion
Erosion
- sion due
ue to water er jet et exam ample ple
24 0.4 m
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Ini nitial tial Results sults with h Const nstant ant Rate e Da Damage age Model
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Inle let t veloci
- city
ty in aggres essively y ramped mped from
- m 0 till 20 m/s over
r simula ulated d time me Ful ully y 2-way y coup upling ing bet etwee een n DEM EM and CFD
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DE DEM Post st-pr proc
- cessing
essing
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Maximum mum packing ing option ion in random dom inject ector
- r
– Allows obtaining tight packing of particles without timestepping – For size distribution, smaller particles are injected after larger one are in the system
Par Particle cle depl pleti tion
- n model
- del
– New in version 10.04 – Allows removing subset of particles (clean central core area)
Table le inject ector
- r
– Allows loading the saved particle assembly with “inflated diameters”
Features tures us used d to creat ate e bo bond nded ed assemb sembly ly
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Summa ummary
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Improved parallel bonds New injection and depletion options Improved accuracy in modeling brittle materials processing New abrasive wear model Accurate prediction of equipment damage
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Back-up up slides ides
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- B. C. Trent,
ent, L. G. Margolin
- lin,
, P. A. Cun undall dall, , E. S. Gaffne ney, , The Micro-mechani chanics cs
- f Ceme
ment nted ed Granular ar Materi rial al, , Second cond Intern ernati tion
- nal
al Conf nfere erenc nce e on Constitu nstitutiv tive e Laws ws for En Enginee ineeri ring ng Materi erials ls, , 1987 G.T. . Gamacho cho and M. Ortiz, iz, Com
- mputational
tational Model delli ling ng of Impact act Damage ge in Brittl tle e Materi erials, als, Int.
- t. J. Solids
ids, , 33, pp. 2899-2938 2938, , 1996 Lui uis Kost steski ki , Ricardo do Barrios ios D’Ambra, , Ignaci acio
- Itur
urrioz rioz, Crack ck propag agati tion
- n