Issues with irradiance in mesh independence analysis for CFD simulation coupled with solar radiation
Hello experts!
I am performing a mesh independence analysis for a CFD simulation coupled with solar radiation. I had understood that solar radiation should be independent of the mesh size, but my results suggest otherwise.
With a large element size (1.3 m), the distribution of solar radiation looks correct without issues, as shown in Image 1. The maximum irradiance value at a time step of 25,200 s is 768.572 W/m².
When I reduce the element size to 0.65 m, I start noticing some strange patterns in the radiation visualization, and the maximum irradiance value increases to 899.741 W/m², as observed in Image 2.
By further decreasing the element size to 0.26 m, the patterns on the solar radiation surfaces become more pronounced, and the maximum irradiance value rises to 4,163.59 W/m², which is excessively high and illogical, as shown in Image 3.
Image 1. Irradiance distribution with element size 1.3 m
Image 2. Irradiance distribution with element size 0.65 m
Image 3. Irradiance distribution with element size 0.26 m
My question is: How can I solve this problem where the irradiance increases as the mesh element size decreases?
Additional Information:
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In Image 4, I explain the problem I am addressing in the simulation.
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Image 4. Description of the simulation problem
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In Image 5, I show the dimensions of the photobioreactors and the flow domain.
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Image 5. Dimensions of the photobioreactors and flow domain
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In Image 6, I present the mesh refinements.
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Image 6. Mesh refinements
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In Table 1, I include details of the refinements and element sizes used.
Table 1. Mesh controls and parameters
Mesh Controls Parameters Element type 4-noded tetrahedral Element size (meshSize) 0.39 m Refinement size 1 (R1) 0.1 × meshSize = 0.039 m Refinement size 2 (R2) 0.2 × meshSize = 0.078 m Refinement size 3 (R3) 0.6 × meshSize = 0.234 m
Thank you so much for your help and guidance.
Best regards,
Jorge
Answers
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Can you attach the input and Log files for those three runs?
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Altair Employee