I'm doing an ICE combustion tutorial module following the guide of developers. I set everything same with the guide. But somehow, i met this problem many times when fluent run into some impotant time steps like injecting time. i'm wonderring about the quality of mesh, is it good enough? i created the mesh by workbench's meshing automatically (following the guide). Please give me a solution for this problem
Dear Công Lê Văn ,
You can do the following things to remove this error.
1. Reduce the step size.
If the problem is still there then,
2. check your meshing parameters and find the locations.
Negative cell volumes are in ICE combustion engine simulations usually produced, if the mesh is gettign too much compressed/deformed, so that the mesh quality deteriorates even to a point, where cells turn into negative cell volume. A more frequent remeshing step might be an applicable solution, before the mesh quality is becoming that bad. Another solution can be to increase the mesh stiffness close to any solid walls in the simulation in order to prevent the strong deformation of boundary layers or near-wall mesh cells, but to address mesh deformation rather to larger mesh cells in the open space volume of the fluid domain.
Regards,
Dr. Th. Frank.
When a negative or inverted volume appears during the meshing process it impossible run the solution process. This kind of problems is associated to the meshing algorithms during the meshing of complex geometries. Of course a negative volume is impossible from physics standpoint. You need a fresh start and improve your mesh.
Reducing the time step size can be used to fix it. However, it would significantly increase your simulation time also. So, you may change your mesh to make it compatible with your time step size and therefore, you will get your results quickly.
Syed Mughees Ali and Mohammad Nasim Uddin Thanks for your answers. i tryed reducing step size for a half but it makes fluent running slower more than a half and stoping for no reason. i don't know the stopping is because of my computer or fluent.
Thomas Frank thanks for your answer sir.
i checked the reports and yes the mesh got too much compressed in compression stroke of engine. i think it's the problem but i didn't find out any solution. i tryed remeshing but it didn't work. maybe my mesh is still not good enough
You can check the compatibility of the time step size with the spatial grid sizes even before running the simulation. You just simply have to turn on the dynamic meshing and put your desired time step sizes and click “update dynamic mesh” in the Run Calculation step in the Fluent. Hope that helps.
When you are in set-up section after the meshing , there is an option of Adapt that is used for meshing refinement. In adapt section one option is there of gradients there one can put minimum number of cells and maximum number of cells.
I think that may help to you also .
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