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Old   July 4, 2001, 12:07
Default materials
  #1
lucy
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Hello everyone, I met a problem in multiphase model.I have choosed a kind of solid materail from database and have created it.But I still can't find Solid in the secondary phase,and there is still just only air option in this column.I don't know why. thanks a lot lucy
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Old   July 5, 2001, 02:22
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Anthony Wachs
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Multiphase model only involves fluid mterials.

If you would like to consider solid ones, you have to switch to discrete phase model.

The remaining question is : what is the physical problem you try to simulate and what is the model that suits the best to the behaviour of your system ?

Anthony
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Old   July 5, 2001, 11:42
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lucy
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Thank you very much. I want to simulate the drug powder ways in human's lung.The model is made of many pairs of the three pipes.They are the parents and the daughters pipes. The drug powders can be inhalate into the lung model with the air by negtive pressure.I think I should use the standard k-epsilon model.I set the pressure inlet and pressure outlet boundary condition.

Best regards lucy
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Old   July 5, 2001, 18:06
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Alain
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Dear lucy,

conserning your material problem, you will find a new type of material call "inert particle" when you enable the discrete phase model. This lead you to a different database of the solid one which is only usefull if you want to applied a material to solid boundary or solid zone (for CHT problems).

For your lung simulation are you sure that the flow is really a high reynolds turbulent flow. even if the flow is turbulent in trachea, I am not sure that it will be in bronchi and bronchiole.

As k-eps models show very poor behavior in transition region you may consider to use a more sophisticated model such as low reynolds models or RSM.

At last, I thought that the air flowrate in lung is imposed due to lung's expansion during aspiration. Shouldn't you use a velocity inlet instead of a pressure inlet.

Best regards

Alain
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Old   July 6, 2001, 11:17
Default Re: materials
  #5
lucy
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Thank you.

I just use fluent for one month,so I am not sure which model and the B.C is suit for my question.

My velocity inlet is 60l/min,and the inlet diameter is 16mm.The pressure outlet is 4000pascal.First I use the velocity inlet and pressure outlet as boundary condition,but the result diverge.So I changed to pressure inlet as 30pasal.The result converged to 1e-5.I don't know why.

I also don't know if 1e-5 residual is a high enough accuracy or not.And in this procedure I just use the air as fluid material.Now I want to add the powder as the sencond material.

Thank you very much.

lucy
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