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-   -   steady state and multiphase... (https://www.cfd-online.com/Forums/phoenics/51586-steady-state-multiphase.html)

 ben April 17, 2003 15:26

steady state and multiphase...

Hi Everyone,

I do not use Phoenics, but I was curious to know if it can solve a gas/solid flow in steady state conditions. I couldn't solve this issue with other codes and would like to know if it is possible with Phoenics.

Many thanks for your answer.

Ben.

 Vikas Kumar April 21, 2003 13:40

Re: steady state and multiphase...

PHOENICS can solve gas/solid flow. I have gone through a number of literature and I find that people are solving for transient case not for steady case.

Vikas

 John Ludwig, CHAM April 22, 2003 12:57

Re: steady state and multiphase...

There are many examples of steady-state gas/solid or liquid/vapour flows in the PHOENICS input library and in the Applications Album.

Whether a steady state solution can be obtained for a particular case depends on the case itself - some situations do not have a steady solution in which case it is pointless trying to compute one.

On the other hand, if a physical steady-state solution exists, there is no reason why any self-respecting code should not be able to calculate it.

It is more likely that a steady solution will exist for an interspersed particle/gas mixture than for a free-surface problem.

 Vikas Kumar April 22, 2003 13:13

Re: steady state and multiphase...

I find that most of the research publications in this area (gas/solid flow) using CFD code is contributed by Vidar Mathiesen and his team. They have even implemented kinetic theory of granular flow (KTGF) in PHOENICS (2D model) for transient case. KTGF is inbuilt in many CFD codes but not in PHOENICS. I feel it is high time that CHAM should incorporate KTGF model in PHOENICS.

Vikas

 ben April 22, 2003 15:01

Re: steady state and multiphase...

Thank you all for your valuable answers. I agree with you John that there are cases where a steady solution is just not feasible, i.e. bubbling fluidized bed. But for pneumatic transport (gas/solid dilute flow), it should be possible to get a reasonable answer with a steady-state code. I wasn't able to get this kind of answer with a number of codes (I don't want to name them, but you can guess). What is really the "trick" in Phoenics that makes these cases work under steady-state conditions? Do you have to include some strong (in a sens of interaction terms) turbulence model for it to work? Are there some tricks with the numerics, etc.

I have seen a paper that solves a steady-state gas/solid flow in a coal combustion chamber using Pheonix, which prompt me to ask you guys in this forum.

Many thanks!

 Vidar Mathiesen April 25, 2003 05:48

Re: steady state and multiphase...

I think that most gas-particle flow is transient. However, systems with very low concentration will of course be considered as steady state. In such situations the Lagrangian technique should be applied. For more dense system the Eulerian-Eulerian multiphase technique has to be considered, and in almost all cases this situations are transient. For this technique the viscous stresses for the solid phase has to be calculated. At the present time, I think the kinetic theory of granular flow (KTGF) is the best approach. I think it is strange that PHOENICS has not included this as an option in the library. Fluent and CFX as well as a number of in-house codes have done that for years ago. Another important concern when modelling gas-particle flow is to take into account the particle size distribution. This can be done with increasing the number of solid phases. See the paper: "Mathiesen, V., Solberg, T., Hjertager, B.H. (2000) An experimental and computational study of multiphase flow behavior in a CFB. Int. J. Multiphase Flow, Vol. 26, pp. 387-419"

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