Learning Forum

[Gu Xuan]

Can Fluent be used to calculate the absorbed, transmitted and reflected radiation flux of a translucent internal surface without thickness in the computational domain.

I attached a photo to show the details.

In this computational domain, direct irradiation from the top translucent surface (128 w/m2) was set. 

I want to simulate the absorbed, transmitted and reflected radiation flux of the translucent internal surfaces without thickness in the photo.

I would be very grateful if you could tell me the answer to this.

Thank you very much.

 

 

[SVV]

Hi,

 

Is it possible to define these internal surfaces as interface walls. If yes, you can set up radiation condition on the interface walls and define the wall as semi-transparent and adjust the material properties and emissivity to have absorbtion, reflection and transmission through these surfaces.

[Gu Xuan]

Thank you for your reply.

What is the meaning of interface wall? I defined these surfaces as walls.

When I defined the walls as semi-transparent walls, I can only set the diffuse fraction of walls. The absorption, reflection and transmission can not be set. Please see the photo. The change of wall materials was not work.

Could you help me?

[SVV]

 

 

From the imgae you shared, I am assuming you are already defining these internal surfaces as interface surfaces. To learn more about interface surfaces, please refer to the user manual page.

May I know the fluent version you are using. If you are using older version, you will find option to input internal emissivty under thermal boundary condition. I assume you are using DO radiation model. Correct me if I am wrong.

Please refer to the user manual guide 5.3.6. Discrete Ordinates (DO) Radiation Model Theory (ansys.com)

section : 

5.3.6.6. Boundary and Cell Zone Condition Treatment at Opaque Walls and 

5.3.6.7.1. Semi-Transparent Interior Walls 

 

To learn how absorption, transmission and refelction is acconted in DO raditaion model. You will have to input emissivity, absorption coefficient, refractive index and diffuse fraction etc for the same.

 

 

[Gu Xuan]

Thank you for your reply.

>May I know the fluent version you are using.

Yes! I used ver. 2021 R2.

I studied these parts before. My case may be different.

In my model, the mediums a and b are the same.  As 5.3.6.7.1 described, it seems that the refractive index   and   were important to change.

And if the wall is 0 thickness, the refractive index is not important.

If the wall has thickness, the absorption coefficient can be set to simulate raditation transmission and absorption.

But my case, the wall is 0 thickness, and medium a , b is the same. So how to do it?

 

[SVV]

I assume you wanted to include absorption on this wall which has zero thickness. As mentioned in the user manual, you cannot model absorption on thin wall (zero thickness). To include absorption, I would recommend using shell conduction layer on this surface.

[Gu Xuan]

Thank you for your replay.

>I would recommend using shell conduction layer on this surface.

Is shell condyction layer in "Thermal" (photo).

In layer 1, defining the absorption coefficient or refractive of the material, is it right?