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senthil May 19, 2003 06:17

Two phase Eulerian Model Problem
Hi all, I'm simulating 2-Phase problem. The geometry is like two concentric cylinder. The inner cylinder called conveyor with helix rotating with speed of "X" rpm. This conveyor and helix is coverd with Outer cylinder called Bowl which is also rotating with "X=60" rpm, having solid and liquid outlet at deifferent ends.The inlet is located near to the solid outlet on the conveyor. At inlet we have a mixtuer of liquid and solid (volume fraction of solid is 30%). Separation of fluid and solid takes place due to the differential speed of Bowl and Converyor,ie. due to Centrifugal forces. What we are trying to do is, we are expecting all solid has to come thorough the solid outlet and liquid through the liquid outlet through solution.We are simulating this problem using Eulerian Multiphase Model with MRF scheme.

We applied Velocity BC at the inlet and Pressure BC (atmaospher) at the outlets.By using the above BC's the continuity is not converging.

1)Is any other alternate model is there to simulate this probelm? 2)The BC what we used is correct or not? Can we use mass flow at inlet, since mass flow is known at the inlet?

If anyone having experience in Eularian Mulitphase model, please help us.

Thanks in advance, Senthil.

ap May 19, 2003 07:38

Re: Two phase Eulerian Model Problem
How do you manage the solid phase?

The Eulerian model should work. You have a high solid volume fraction, so Eulerian should be the best choice.

Boundary conditions seems good to me. You have an incompressible flow, so it's right to choose velocity inlet. Mass flow inlet is for compressible flows.



senthil May 19, 2003 09:24

Re: Two phase Eulerian Model Problem
hi ap, thanks for the messg. I would like to know do you have experience on Eulerian modle. I'm using Eulerian Multiphase with granular option. Turbulance is std k-e wall fuction. Flow is incompressible. But the problem i'm facing is the solid particles(fluid materials with high density around 4200kg/m3) is not going towards the solid outlet. Moreover i am getting positive mass throught the slidoutlet instead of negative value. How to overcome this?


ap May 19, 2003 11:35

Re: Two phase Eulerian Model Problem
I'm using FLUENT 6.0 granular model to model a gas-solid flow in a riser, but results don't agree with experimental data (velocity under-extimated and/or not good solid concentration profiles) :(. Now I'm working to implement a most complete model using UDS.

However, if I understood, FLUENT tells you have reversed flow on the solid outlet face. I don't know the exact geometry of the system (if possible, it would be useful to see the mesh :)), however check the problem set-up: models, boundary conditions, solver parameters, operating conditions (gravity, pressure)...



vedanth May 19, 2003 11:56

Re: Two phase Eulerian Model Problem
Try with lowering the relaxation parameters ( pressure control ) and try using a different scheme, you can get very good approx with II UDS, you may wanna try that. Granular systems, always pose problems with mass imbalances. Your BCs are fine i suppose.Wht it matters is the way you make your solution to converge.


senthil May 21, 2003 02:55

Re: Two phase Eulerian Model Problem
hi thanks for the reply. senthil.

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