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Two phase flow problem.

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Old   July 9, 2016, 10:07
Default Two phase flow problem.
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Andrzej
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Hello.

I'm trying to simulate two phase (gas-solid) flow in complex (horizontaly-vertical) system. After learing how fluent works and reading some scientific articles i'm trying to perform this simulation. My goal is to achieve at which gas velocity particles start to deposit on the bottom of the pipe (trying to determine the safe operating velocity). At this moment i have experimental data but unfortunately simulation results doesn't find with a good agreement with experimental results, that's why i'm asking for help. Now i'll introduce my fluent setting:

Geometry was generated in Autocad (horizontal part length is about 5 meter, 90 degree knee, 3meters of vertical pipe).
Inlet is located in the beginning of horizontal part. |
.............................................. inlet --> ______/ (kinda artistic :P)

Mesh -> Sweep method, 235K elements

Setup ->
Time - Transient,
gravity included,
Model - multiphase Eulerian (Eulerian)
Energy equation - off
k-e realizable, enhanced wall Fn, mixture
Materials ->
Air and crystals (density 1050 and viscosity 1e30 for crystals)

Phases ->
Phase 1- air; phase 2 - crystals,
Particles- wall drag modification included (wen-yu, constant drag factor calculated as a function of velocity, Nakamura's equation as i remember)

Phase 2 - Granular, diameter 0,0016m, granular visc. Syamlal obrien, Granular bulk visc - lun-et-al, solid pressure- lun-et-al.

Boundary conditions->
Phase 1,2 velocities were adjusted for inlet (for example 13m/s and calculated volume fraction for phase 2)

Solution Methods ->
Phase coupled SIMPLE, solve N-phase volume fraction equations, Green-Gauss Node Based, Momentum 2nd order, Volume fraction 1st order, Turbulent Kinetic Energy 2nd order, Turbulent dissipation rate 2nd order.

Solution Initialization -> Hybrid and after that i'm patching volume fraction of phase 2 (value about 0,002)

Run calculations -> Time step size 0,1sec, no. of times steps 100, max itterations 10.

Okay, and now on the example of simulation for velocity 10m/s.

Youtube link -> https://youtu.be/8br0xE55-wk

We can see that Particles starts to deposit at the beginning of pipe and futhermore they gather and everyhing immediately collapses. I can't also notice any bigger concentration of solids in the knee, where it should be the highest. Simulation consists 6seconds of real time (beacuse at 6th sec simualtion was aborted by fluent). Relying on the experimental data, velocity at which particles start to deposit on the bottom of the pipe is around 6m/s, here at 10m/s we can see... system choke? Something is wrong in my settings. Please help.
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Old   August 4, 2016, 01:09
Default two phase apply in multiphase
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yatish
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hi........
I am also doing work on this type of problem but i do not apply solid particle in secondary phase.
In primary phase , I select water but in secondary phase solid is not taken by fluent.
So, Please solve my problem.
how to get solid in secondary phase, my slurry is water + ash. I select ash from fluent database but if i apply for secondary phase only water and air is shown ash is not shown.

Please solve this problem.......
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Old   August 15, 2016, 13:43
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Masoud Ravan
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hi my friends
i want to simulate a channel that the air injected from bottom of that...but i do not know fluent can do this work or not...
Please help me...thanks
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Old   August 21, 2016, 13:45
Default Two phase flow problem.
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Mustafa
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Dear Andyraq

If you want to model solid particles to need to use dpm .

This may help http://adf.ly/1dL1LX
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Old   August 21, 2016, 21:57
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It's probably "blowing up" because your viscosity is unreasonable. Have you tried setting the solid viscosity to something like ~0.003 Pa-s?

Have a look:
https://www.researchgate.net/publica...rizontal_Pipes
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