Multiphase - Pressure Based - Ideal gas

ssa_cfd · July 13, 2021, 11:23

Hi all,

I want to do a steady state simulation of the rotary kiln with multiphase, turbulence and species-transport models in ANSYS fluent.

When I want to use multiphase, fluent allows me to choose only pressure-based model.

The inlet of the kiln has a convergent-divergent nozzle and solving with incompressible ideal gas, results in velocities of around 800 m/s which is not realistic.

I tried to run pressure-based with ideal gas, which always results in divergence. It runs for 5 or 6 iterations and then the continuity or the turbulence equations diverges even with an under relaxation of 0.1 .

I saw some older posts, and tried to switch off energy equations and solve only the flow equations. But that also didn't work out.

Does anyone have a similar experience of solving nozzles with pressure based solvers in fluent ? How to solve this problem ?

Thanks,
Senthil.

LuckyTran · July 13, 2021, 13:40

You need a really good pressure and temperature field as an initial guess (and phase fractions and species mass fractions since you're also running those models). If you don't provide good guesses, then you have to baby it.

July 13, 2021, 11:23	Multiphase - Pressure Based - Ideal gas	#1
ssa_cfd Member ssa Join Date: Sep 2018 Posts: 93 Rep Power: 7	Hi all, I want to do a steady state simulation of the rotary kiln with multiphase, turbulence and species-transport models in ANSYS fluent. When I want to use multiphase, fluent allows me to choose only pressure-based model. The inlet of the kiln has a convergent-divergent nozzle and solving with incompressible ideal gas, results in velocities of around 800 m/s which is not realistic. I tried to run pressure-based with ideal gas, which always results in divergence. It runs for 5 or 6 iterations and then the continuity or the turbulence equations diverges even with an under relaxation of 0.1 . I saw some older posts, and tried to switch off energy equations and solve only the flow equations. But that also didn't work out. Does anyone have a similar experience of solving nozzles with pressure based solvers in fluent ? How to solve this problem ? Thanks, Senthil.

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July 13, 2021, 13:40		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 66	You need a really good pressure and temperature field as an initial guess (and phase fractions and species mass fractions since you're also running those models). If you don't provide good guesses, then you have to baby it.