Implementation of DO Radiation in Ansys Fluent

I have been trying to implement the DO Radiation Model to simulate a radiation beam in Ansys Fluent since the past 1 month without much success. The computational domain consists of a cylinder of 10 cm radius and 1 m length and the front section of the cylinder is specified as irradiated wherein incident radiation enters the domain. Air and dust particles are present inside the cylinder.

I have set the absorptivity of air to zero in the simulation, and the theta and phi extent corresponding to the beam width is set to 1e-06. I have also set the theta and phi pixels and divisions equal to 15. I am expecting the incident radiation to be constant intensity over the entire domain, however, I what I am observing is that the intensity of incident radiation decreases with the axial length, and finally attains a constant value after a certain distance.

I would highly appreciate your support in solving the issue. Please let me know in case any additional information is required.

Best Answers

  • subhamdassubhamdas Member
    Accepted Answer

    Hi @Kremella Tried different combinations of the beam direction, but that also didn't help me to achieve a collimated radiation beam. What I have observed is that the beam remains aligned to the cylinder when I set the beam direction as (1 0 0) however, for other values of the beam direction it is some what tilted from the axis.

    I had also suspected this because the problem was not with the direction but as I mentioned earlier, the intensity of incident radiation decreases with the axial length. The figure below somewhat represents the same. I want the entire portion to be red, but it is not the case here.


Answers

  • @Kremella Thanks a lot for your response. The actual configuration is quite complex and hence I have taken the cylinder to study the effect of various parameters on the incident radiation. So far I've tried the following:

    Keeping other parameters constant I've changed:

    1. Theta Division/pixels(up to 75)
    2. Phi Division/pixels(up to 75)
    3. Beam width(1e-06<Theta<90, with variable step sizes)
    4. Beam width(1e-06<phi<360, again with variable step sizes)

    Also, in the fluent manual, it is mentioned that the parameters for beam width should be ~1e-06 to acheive a collimated radiation beam, however, I am not getting the same even after increasing the discretisation parameters to 75(which in highly intensive in terms of computational cost).

  • KremellaKremella Admin
    edited August 24

    You should be changing Beam Direction, not Beam width.

    And, no need to go to 75. Keep 5 to 7 divisions should be sufficient.

    Karthik

  • Thanks but is than not supposed to be the coinciding with the axis of the cylinder(1 0 0). And if its not, then how to estimate the proper beam direction?

  • subhamdassubhamdas Member
    Accepted Answer

    Hi @Kremella Tried different combinations of the beam direction, but that also didn't help me to achieve a collimated radiation beam. What I have observed is that the beam remains aligned to the cylinder when I set the beam direction as (1 0 0) however, for other values of the beam direction it is some what tilted from the axis.

    I had also suspected this because the problem was not with the direction but as I mentioned earlier, the intensity of incident radiation decreases with the axial length. The figure below somewhat represents the same. I want the entire portion to be red, but it is not the case here.


  • Hello,

    What does the Incident Radiation contour look on the opposite face of your cylinder?

    Thanks.

    Karthik

  • I hope this is what you are asking for:

    As you can see from the figure, the intensity decreases with increasing axial length.


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