[liang11]

Hi,
Water injection is simulated through spray model, and there is a WARNING, 'removing a parcel at location', which is near the cylinder liner.

The diameter of piston is 7.440007E-002, and the diameter of cylinder head is 7.440009E-002.

How can I solve this problem?

[SamWijey]

These warning are prompted when the parcels goes outside of the domain. This can happen if the cell quality is poor or in this situation where the liner might not be a perfect cylinder. If the diameter of the liner at the head and at the piston are not exactly the same, the liner will not be a perfect cylinder. Also if the number of vertices on both ends of the liner are quite different, distorted cells can exist on the liner which can also give rise to this issue.

In Studio, view the liner (only) from the top and keep zooming in. If the liner is a perfect cylinder and does not have the issues noted above, you should see a single edge (of the liner perimeter) chain. Else, you will start seeing triangles faces as you zoom in.

Having said this, you can ignore the warning if the mass of all the parcels removed (which is recorded in the log file) is quite small w.r.t. the injected mass

[liang11]

Originally Posted by SamWijey

These warning are prompted when the parcels goes outside of the domain. This can happen if the cell quality is poor or in this situation where the liner might not be a perfect cylinder. If the diameter of the liner at the head and at the piston are not exactly the same, the liner will not be a perfect cylinder. Also if the number of vertices on both ends of the liner are quite different, distorted cells can exist on the liner which can also give rise to this issue.

In Studio, view the liner (only) from the top and keep zooming in. If the liner is a perfect cylinder and does not have the issues noted above, you should see a single edge (of the liner perimeter) chain. Else, you will start seeing triangles faces as you zoom in.

Having said this, you can ignore the warning if the mass of all the parcels removed (which is recorded in the log file) is quite small w.r.t. the injected mass

Thanks,
Since the parcel can be removed, how about the gas? Will the gas be removed out of the domain?

[SamWijey]

Yes, this can happen under rare conditions where the cells are skewed. In this example if the surface normals of the liner triangles are not perpendicular to the motion direction of the piston, cells can disappear as the piston is moving up. This phenomena is quite rare and for this to happen, the cell quality has to be quite bad.

During piston compression (when both valves are closed) the cylinder mass should be constant. If you see mass loss during this phase then that's an indication this phenomena is at play.

[liang11]

Thanks, happy holidays！

Originally Posted by SamWijey

Yes, this can happen under rare conditions where the cells are skewed. In this example if the surface normals of the liner triangles are not perpendicular to the motion direction of the piston, cells can disappear as the piston is moving up. This phenomena is quite rare and for this to happen, the cell quality has to be quite bad.

During piston compression (when both valves are closed) the cylinder mass should be constant. If you see mass loss during this phase then that's an indication this phenomena is at play.