Numerical Instability #13068
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When the grid is large, there is no numerical instability, why is the numerical instability when the mesh is small? &MESH ID='Mesh01', IJK=128,40,120, XB=-0.02,0.62,0.4,0.6,-0.1,0.5/ |
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Replies: 2 comments 4 replies
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You did not attach a complete input file. There is no MESH or TIME line in the file. Please attach a complete input file and also clearly indicate the successful and unsuccessful MESH inputs. |
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Sorry. Here's my code, I built the model on pyrosim, and the code about time can't be copied, so I took a screenshot, |
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When you run a case in Pyrosim it writes an FDS file and then starts a shell an runs FDS with that input. The input file should be on your drive in the folder with your pyrosim file. |
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Yes, I found it. This is my code. When the grid is a cube with a side length of 0.005 meters, there will be error problems caused by numerical instability. When the grid is a cube with a side length of 0.02m, it can operate normally. May I ask why such a problem occurs. |
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The case dies with the current release and looking at the plot3d file that is dumped, there is a region of very high heat release rate per unit volume. Your input file has this surface: &SURF ID='Surface01', This emits a fuel air mixture for the first second. I changed to TAU_MF=0 so it is always pure fuel like HRRPUA does. The case got past the point of failure. This is suggesting that at the fine grid resolutions the premixed condition was resulting in too high of a volumetric heat release rate. @rmcdermo you may want to look at this case. |
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Thank you very much for your help |
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The case dies with the current release and looking at the plot3d file that is dumped, there is a region of very high heat release rate per unit volume. Your input file has this surface:
&SURF ID='Surface01',
RGB=26,204,26,
VOLUME_FLOW=-1.0E-5,
TAU_V=-1.0,
MASS_FRACTION=1.0,
SPEC_ID='PROPANE',
TAU_MF=1.0/
This emits a fuel air mixture for the first second. I changed to TAU_MF=0 so it is always pure fuel like HRRPUA does. The case got past the point of failure. This is suggesting that at the fine grid resolutions the premixed condition was resulting in too high of a volumetric heat release rate. @rmcdermo you may want to look at this case.