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 Derek Jing June 11, 2002 11:38

Help: solid-liquid flow

Hi all,

I will model dense solid particles suspensed in flowing liquid. The density of the particle may be close to or significantly larger than the density of liquid.

Can CFX deal with this problem? WHat kind of multiphase model CFX will use for simulating this kind of problems?

Thank you very much.

-Derek

 Robin June 11, 2002 20:40

Re: Help: solid-liquid flow

Hi Derek,

CFX-5 can solve this problem using a coupled multigrid Eularian-Eularian approach. The inter-equation coupling means that the mass and momentum equations of both phases are solved simultaneously at each timestep and the multigrid solver ensures quick and efficient solution convergence.

Robin

 oduor June 12, 2002 08:16

Re: Help: solid-liquid flow

Hi Robin,

Why would you recommend Eulerian-Eulerian? How about Eulerian-Lagrangian? Isn't the latter option available in CFX5? I thought the choice between the two depends on the phase hold ups, which derek has not talked about.

oduor

 Bouke June 12, 2002 09:51

Re: Help: solid-liquid flow

Derek,

As I understand (but please correct me if I'm wrong), Eulerian-Lagrangian 2-phase modeling is scheduled for CFX 5.6 due at "the end of the year". Hence Euler-Euler is the only option for now in CFX 5.

BTW If you have particles that are denser than the liquid they may tend to settle. Since Euler-Euler does not "know" whether your particles are liquid or solid, you will need to prevent that the packing of settled particles does not exceed the maximum physical packing (say, 35% liquid / 65% solid). This is usually done by introducing some exponential pressure force (compaction/elastic compression of the particles). This is an option in CFX 5.5 but in my experience there are some problems with it. Hopefully to be resolved in CFX 5.5.1 shortly.

Bouke

 Derek June 12, 2002 14:34

Re: Help: solid-liquid flow

Hi,

Thank you for your reply.

Generally in the simulation of multiphase granular flow based on kinetic theory, a parameter called maximum solid fraction (for particle around 65%) is need. How this parameter is prescribed in CFX?

I ever used FLUENT 6.0 to simulate granular flow, but when I prescribe the maximum solid fraction, mass imbalance occurs in my simulation. I am wondering whether this will also happen in CFX.

Thank you very much for your help.

-Derek

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