{"id":343651,"date":"2024-01-08T14:38:53","date_gmt":"2024-01-08T14:38:53","guid":{"rendered":"\/forum\/forums\/topic\/fluent-multiphase-floating-point-exception-6hrs-into-calculations\/"},"modified":"2024-01-08T14:38:53","modified_gmt":"2024-01-08T14:38:53","slug":"fluent-multiphase-floating-point-exception-6hrs-into-calculations","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/fluent-multiphase-floating-point-exception-6hrs-into-calculations\/","title":{"rendered":"FLUENT MultiPhase – floating point exception 6hrs into calculations"},"content":{"rendered":"

Context of simulation<\/h1>\n

I am simulating a bubbly flow, where bubbles of 0.2mm at a volume fraction of 0.2 enter the inlet at the side, and go into a chamber where (ideally) the bubbles separate from the liquid, and the liquid goes down the ‘plughole’ and exits the model. Due to instabilities with steady solutions, I am using a transient solver. There is also a degassing boundary in the model. See the image below for an idea of the geometry<\/p>\n

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Simulation problem description<\/h1>\n

I found in the past, sometimes I couldn’t get the simuation running from ‘floating point exception’ errors. From other forum conversations, it seemed it may have been becuase the programme could not create enough RAM for the solution, which can be solved by making the solution less computationally heavy, such as coarsening the mesh. After coursening the mesh and it started to run for a short time, but it still hit the same warning, which seemed to come after warnings of divergence. I tried to tackle the warnings of divergence by reducing the timestep.<\/p>\n

So after coarsening the mesh and reducing the timestep from 0.001s to 0.0001s (10x smaller), it had wonderful residuals that met convergence criteria (see image) and was solving for 6 hours, until suddely it hit the floating point exception error again and failed to solve. <\/p>\n

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Unfortunately as it was solving overnight, I could not recover any residual graphs or other convergence monitors. The file also has corrupted itself as it can’t find its case file, so I cannot retrieve any more data.<\/p>\n

Please could have some guidance on what is causing the solution to reach the floating point exception error and fail to solve after so long successfully running?<\/p>\n

I am aware of poor quality cells in one area because of a sharp corner where the boundary layers collide, but the mesh quality checks show a good mesh. The fact it also ran for so long indicates that the mesh is fine.<\/h6>\n

Detailed ANSYS setup<\/span><\/h2>\n

Mesh cell quality:  Minimum = 0.092485825, Maximum = 0.99967964, Average = 0.9130338. The mesh has a minimum Orthogonal Quality of: 0.09<\/p>\n

ANSYS setup:<\/p>\n