Porous media in FLUENT

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Dounia posted this 4 weeks ago

Hello everyone!

I was simulating a square box with trays as a porous media, where the air is flowing from the inlet passing by the porous media and then go out from the outlet. I only entered the power-law coefficients C0 C1 and the porosity. but then I realised that there is something wrong with it, because I found that in both cases with or without porous media it shows the same results. so I was wondering if someone can help me with this and show me how to simulate a porous media using the power law coefficients?  I'll be so grateful for any comments or answers. Thanks.

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abenhadj posted this 4 weeks ago

In the User's Guide you will find tips how to calculate the inertial and permeability coefficients based on your measured / know pressure drop or Ergun's like approximation.

This can be helpful 2:

Best regards,

Amine

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Dounia posted this 4 weeks ago

Thank you so much for answering me. But I have no measurements to calculate the inertia and permeability coefficients. all I have is C0 and C1 the power law model coefficients.

Is it wrong to use just the power law model without the inertia and permeability coefficients ?

Best regards,

Dounia

abenhadj posted this 3 weeks ago

No is not wrong.

Best regards,

Amine

Dounia posted this 3 weeks ago

so why it doesn't work? there is absolutely no difference between adding porous media and take it off, it's like FLUENT does not take in count the power-law coefficients. 

Best regards,

Dounia

abenhadj posted this 3 weeks ago

You will get the same velocity etc.. Only the contour of pressure is different across the porous zone if you are not using the physical formulation.

Best regards,

Amine

Dounia posted this 3 weeks ago

the contour of pressure does not change if I take off the porous media,

in your opinion, where is the problem?

Best regards,

Dounia

 

Dounia posted this 3 weeks ago

this is how it should beand this is the result i got

the picture in the right is the result I got ( velocity distribution), the left one is how it should be. where do you think I have a problem?

by the way, thank you so much for answering me I really appreciate it

Best regards,

Dounia

abenhadj posted this 3 weeks ago

Add more details about case settings, cell zone and boundary conditions. What is the aim of this run? Are you comparing to a Fluent run?

Best regards,

Amine

Dounia posted this 3 weeks ago

can I have your email so I can send to you a report  PDF that contains the details about my simulation step by step, or you can send me a message in my Gmail: douniaextra1@gmail.com

Best regards,

Dounia

abenhadj posted this 3 weeks ago

No I'm sorry. Stick to the community please.

Best regards,

Amine

Dounia posted this 3 weeks ago

it's ok, I understand. well, I'm just gonna send you some pictures so you can understand my geometry and what I'm trying to do.

first of all, here is my geometry: 

geometry

this is a drying chamber made of wood with 2 trays as a porous media. air is heated at the bottom by

the mean of a horizontal absorber which is considered as a source of energy

The air flows into the dryer through an inlet, absorbs energy (heat) from the absorber (Aluminum), flows

through the drying chamber and outflows from the outlet.

trays were assumed as porous media for airflow. It is modeled by the power law model using C0 and C1.
boundary conditions in the inlet: P= 100000 Pa  and  T=304 K
boundary conditions in the outlet: P= 100000 Pa
Wooden wall boundary conditions: u=v=0
there is convective loss in all the walls and in the absorber,
the standard k-ɛ model is used to describe the flow.

I know it's a lot but please be patient with me, and again I'm so grateful for keeping answering me

Best regards,

Dounia

 

abenhadj posted this 3 weeks ago

I guess they took buoyancy effects into account.

Best regards,

Amine

Dounia posted this 3 weeks ago

I entered the gravity value... Please! can you check for me those pictures and see if there is something wrong.

rwoolhou posted this 3 weeks ago

What density model did you use? 

Dounia posted this 3 weeks ago

for air, I'm using Boussinesq density

Dounia posted this 3 weeks ago

in solution initailization, I realized that the turbulence coefficients equals Zero, is that something wrong? 

abenhadj posted this 3 weeks ago

As the communication is not really optimal can you use ideal gas density and provide as operating density the density corresponding to the surrounding temperature (if the same at inlet and outlet).

Best regards,

Amine

Dounia posted this 3 weeks ago

It didn't work! 

in solution initialization, I realized that the turbulence coefficients equals Zero, is that something wrong? 

abenhadj posted this 3 weeks ago

Hey what did not work: If you want us  to help: be patient and provide details! 

Regarding the values of TKE and EPSILON: Yes that might lead to problem. Make ini from Inlets or do a hybrid ini as you have pressure boundaries!

Best regards,

Amine

Dounia posted this 3 weeks ago

I'm sorry if it seems that I'm not patient. But I'm truly patient and trying to provide you with all the details.

what I was trying to say, is that I used ideal gas density but it still the same problem.

I tried to enter the turbulence coefficients randomly( i tried different values) in the inlet and outlet. Yes, there is a change but it has nothing to do with the results that I want to achieve.

I tried also the Hybrid initialization, it gave me the same result.

Best regards,

Dounia

abenhadj posted this 3 weeks ago

Is the reference case transient? Do you have information on that?

I have not asked to modify the values at inlet/outlet but to initialize as Hybrid or initialize from Inlet.

Using Ideal gas density: have you set the operating density to the surrounding density?

Best regards,

Amine

Dounia posted this 3 weeks ago

Yes, I tried the Hybrid initialization and initialization from the inlet and it gave me the same result.

Yes I set the operating density and there is no difference in the result

Yes, the reference case is transient.

Best regards,

Dounia

abenhadj posted this 3 weeks ago

And are you sure that the picture from their runs is an instantaneous contour plots or rather an average one?

That density corresponds to which temperature? Is that the same temperature you used at inlet and outlets? I hope 304 K.

What about now you mesh resolution: you require a good near wall mesh with at least 10 cells in the boundary layers. Yplus of one is a must here. I will then use SST model as turbulence model.

Best regards,

Amine

abenhadj posted this 3 weeks ago

304 K> 1.161191 kg/m³

Best regards,

Amine

Dounia posted this 3 weeks ago

the picture from their run is an instantaneous contour plot.

the density that I used correspond to 300k, but in the inlet I have 304k. should I change the temperature?

the mesh is good here is the picture:

Best regards,

Dounia

 

 

Dounia posted this 3 weeks ago

thank you for the density, I didn't know it before

abenhadj posted this 3 weeks ago

You need to use the density corresponding to the surrounding and the surrounding is at 304 K. 

Best regards,

Amine

Dounia posted this 3 weeks ago

Hello!

I just wanna ask you why K and epsilon value equal to Zero in my situation here?

PS: the inlet and outlet conditions are pressure type, not Velocity type.

Best regards,

Dounia

abenhadj posted this 3 weeks ago

That is only for initialization (steady-state not really heartbreaking) but is not okay if it shows zero values. Can you reset and then repeat "Compute from" Inlet".

Best regards,

Amine

abenhadj posted this 3 weeks ago

Please remove the mark as "Is Solved" as it is irritating a bit. (if you can remove that).

Best regards,

Amine

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