simulation of disperse particle-laden gas flows with with ......particle dispersion overpredicted in...

Franziska Greifzu, Rüdiger SchwarzeInstitute of Mechanics and Fluid DynamicsChair for Numerical Modeling of Granular FlowsLampadiusstraße 409599 Freiberg

Simulation of Disperse Particle-LadenGas Flows with with OpenFOAM andANSYS FLUENT

10th September 2015

Halle (Saale)

Motivation

Simulations for engineering application in processing plant:

Analysis of flow structure in static and dynamic air classifier

CFD simulation of particle-laden flow considering particle-fluid andparticle-particle interaction

Derive feasible simplifications of CFD model

→ Validation of models with simple test cases→ Comparison of CFD packages

10th September 2015 Greifzu, Schwarze IMFDTU Bergakademie Freiberg 1

Model equations

Averaged conservation equations for incompressible, isothermal andturbulent flow of Newtonian fluid:

∇ · u = 0 (1)∂u

∂t+ % (u · ∇) u = −∇p+ η∆u−∇ · τRS + f

W(2)

with: τRS =(% u′u′

)(3)

Force balance in Lagrangian framework:

dxPdt

= uP (4)

mPduPdt

= FD + FB + FG (5)


Model equations

Drag force:

FD =3

4

%

%P

mP

dP· CD (u− uP) |u− uP| (6)

Implementation of drag coefficient CD in CFD programs:

ANSYS FLUENTMorsi and Alexander1

CD = a1 +a2ReP

+a3Re2P

(7)

OpenFOAMEmpirical relation

CD =

{24ReP

(1 + 1

6Re2/3P

);ReP ≤ 1000

0.424 ;ReP ≥ 1000(8)

1Morsi1972.


Model equationsCoupling

Classification of coupling schemes and interaction between disperse andcontinuous phase according to Elghobashi2:

×10-1

×100

×101

×102

×103

×104

×105

×106

×10-8

×10-6

×10-4

×10-2

×100×10

-3

×10-2

×10-1

×100

×101

×102

×103

×104

τP /

τK

τP /

τe

αP

①

②

③

④

¬::®:¯:

One-way coupling fW

= 0

Two-way coupling, particles enhance turbulence productionTwo-way coupling, particles enhance turbulence dissipationFour-way coupling

fW6= 0

2Elghobashi1994.


Test case backward facing stepDescription

Geometry according to Fessler and Eaton3

Channel flow BFS flow

Channel height h 40 mm Step height H 26.7 mmChannel width w 457 mm w/H 17:1

h/H 5:3

3Fessler1999.


Test case backward facing stepApplied meshes

Mesh A Mesh D

Name Dimension Cells in z-direction BC front and back

A 2D 0 -B 3D 1 emptyC 3D 1 symmetryD 3D 10 symmetry


Test case backward facing stepSetup

RANS and URANS

k-ω-SST turbulence model

isothermal

1- and 2-way coupling

Continuous phase

Inlet profile with uavg = (9.39 0 0)m/s

Ux,0 = 10.5m/sk = 0.45m2/s2

ω = 2800 1/sOutlet p = 0PaWall u = (0 0 0)m/s

Disperse phase

Particle diameter dP = 70µmParticle density %P = 8800 kg/m3

Particle mass flow rate mP = 1.58 · 10−5 kg/sInjection velocity uP,avg = (10.5 0 0)T m/s


Test case backward facing stepFluid flow

00.5

11.5

22.5

3

-2 0 2 4 6 8 10 12 14

y/H

2ux/U0 + x/H

00.5

11.5

22.5

3

-2 0 2 4 6 8 10 12 14

y/H

10u′/U0 + x/H

Fluent OpenFOAM Experiment


Test case backward facing stepDisperse phase

1-waycoupling

2-waycoupling

0

0.5

1

1.5

2

2.5

-2 0 2 4 6 8 10 12 14

y/H

2 · uP,x/U0 + x/H

0

0.5

1

1.5

2

2.5

-2 0 2 4 6 8 10 12 14

y/H

2 · uP,x/U0 + x/H

AF Mesh C

AF Mesh A

OF Mesh C

OF Mesh B

Experiment



1-waycoupling

2-waycoupling

0

0.5

1

1.5

2

2.5

-2 0 2 4 6 8 10 12 14

y/H

2 · uP,x/U0 + x/H

0

0.5

1

1.5

2

2.5

-2 0 2 4 6 8 10 12 14

y/H

2 · uP,x/U0 + x/H

AF Mesh D OF Mesh D Experiment


Test case confined bluff bodyDescription

Geometry according to Borée et al.4

4Boree1999.


Test case confined bluff bodySetup

URANS

Standard k-ε turbulence model

isothermal, incompressible

2-way coupling

Continuous phase

Central jet inflow uj,avg = (0 0 3.01)m/s

Uz,j = 3.4m/sAnnular jet inflow ua,avg = (0 0 5.36)m/s

Outlet p = 0PaWall u = (0 0 0)m/s

Disperse phase

Particle diameter dP = 63µmParticle density %P = 2470 kg/m3

Particle mass flow rate mP = 2.78 · 10−4 kg/sInjection velocity uP,avg = (4.08 0 0)m/s


Test case backward facing stepFluid flow

-0.5

0

0.5

1

1.5

0 5 10 15 20 25 30 35 40

uz/U

j

z/Rj

ANSYS FLUENT OpenFOAM Experiment

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 10 20 30 40 50

r

3 ∗ uz/Uj + z/Rj



0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

-5 0 5 10 15 20 25 30 35 40 45 50

r

3 · uP,z/Uz,j + z/Rj

ANSYS FLUENT OpenFOAM Experiment


Conclusion

Good agreement of numerically modeled flow fieldsDisperse phase simulation results fit experimental data - differences inshear layers

Particle dispersion underpredicted in ANSYS FLUENTParticle dispersion overpredicted in OpenFOAM

Minor influence of coupling scheme due to low volume loadings

Incorrect computation of particle motion in ANSYS FLUENT 2-D model:neglect of three-dimensional character of turbulence


Thanks for your Attention.


simulation of disperse particle-laden gas flows with with ......particle dispersion overpredicted in...

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