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species transport with eulerian multiphase, kinetic theory of granular flow

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Old   September 24, 2018, 07:36
Default species transport with eulerian multiphase, kinetic theory of granular flow
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Muhammad Ali Uzair
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Hi all

Can I model a species mixture as a granular phase in eulerian multiphase model?

When i used 2 granular phases (biomass, sand) without species transport, there is no problem with convergence

But when i switch to species transport with 2 granular phases (one is a mixture of 2 species and the other is sand), then the simulations dont converge. then i turned off the granular option for mixture and everything worked perfectly. Please explain this problem

Besides, I have another problem.
"THE TEMPERATURE IS LIMITED TO 270 IN 1901 CELLS ON ZONE 2 IN DOMAIN 3..." How can i address this issue except using the limits option in controls bar..

Thank you.
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Old   September 24, 2018, 07:37
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Muhammad Ali Uzair
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I am giving the details of my case; i don't know what's wrong with it though. Kindly have a look.



Pressure-based solver, Transient simulation, gravity on

MODELS:

species transport, eulerian eulerian multiphase (3 phases)



PHASES

mixture 1: O2+N2+H2O vapor

sand [sec phase, granular]

mixture 2: wood+water, liquid [sec phase, granular]



PHASE INTERACTION: biomass-gases and sand-gases=gidaspow

biomass mixture and sand = syamlal-obrein-symmetric

virtaul mass: NO

lift: NO

collisions: 0.9

heat transfer coefficient: two resistance

Mass transfer: NO (will turn on later, evaporation-condensation)

reactions: No



BOUNDARY CONDITIONS:

mass flow inlet: biomass mixture + O2+N2 (500 kelvin)

velocity inlet: O2+N2 (500Kelvin)

pressure outlet: 1atm (backflow temp: 500K)

Wall: sand+biomass mixture=partial slip, zero diffusive flux
air=no slip, zero-diffusive flux

thermal conditions for all walls: Heat flux=0, heat generation rate =0

SOLUTION METHODS:

P-V couplingC-Simple

spatial discretization:

Least squares cell based

Momentum, second order upwind

volume fraction: quick

Granular temperature, energy, mixtures: first order upwind



SOLUTION CONTROLS: URFs

pressure 0.1

density 0.5

body forces 0.2

momentum 0.2

volume fraction 0.2

granular temperature: 0.2

energy+all species: 0.95



Initial conditions: default, sand and biomass patched with 0.3 volume fraction each

standard initialization



time-step size: 1e-04 to 1e-05
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Old   October 25, 2018, 15:15
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Emerson
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hey did you solve your problem?

Is there a heat transfer between the gas and the granular phase? Because if there is, I suggest you use Gunn in the phase interaction for the heat transfer coefficient.
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Old   October 26, 2018, 10:15
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Muhammad Ali Uzair
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No, I couldnot solve the problem.
So, I decided to go back a little bit and study heat transfer. But the problem was in heat transfer.
The issue is that I have 2 granular phases. When i start the simulation, there is temperature discontinuity at the interface of bed containing 2 solid phases and that of air.
when i use 1 granular phase instead of two, there is no such problem.
Also, there is no option of gunn heat transfer coefficient between 2 solid granular phases when i use gunn with air and granular phase 1, and air and granular phase 2.
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Old   October 26, 2018, 10:30
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Emerson
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Can you post a picture of your domains? I'm working with 2 granular phases too and I'm facing problems in the heat transfer between the gas and the granular phase. And you are right, there is no gunn model for heat transfer between the granular phases
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eulerian multiphase flow, eulerian multiphase model, fluidization, fluidized bed, species transport

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