Warnings: [3507] & [3508]
 

Hi,



"Considering this topic: https://www.cfd-online.com/Forums/converge/233840-cell-pair-created.html"



After extracting a fluid domain from a full-cylinder geometry, with embedded the seats of exhaust and intake valves, I move the valves below the inner surface of the seats. There is a question here: How should be the gap between the seats and the valve angles so that I do not receive such warnings "Cell pair was created..." frequently?
Also, I scaled the valve angle embedding up to 4, but still got the warnings.

Hello Hamed,

Increasing the embedding within the valve gap is our recommended approach to remove cell pairs. Try a embed scale value greater than 4. Typically, the minimum valve lifts are set at 0.2mm and an embed scale of 4 with a base grid of 4mm should be sufficient. If the minimum valve lift is smaller, or if your base grid is larger, you'll require a larger embed scale value to prevent cell pairs around the valve opening location.

Please verify your geometry setup and also verify that the cell pairs are indeed happening around the valves. CONVERGE prints out XYZ locations of excessive cell pairs.

By default CONVERGE will pair cells when they are cut with lower than 30% of their original volume. But with v3.0 and above versions, you can provide your own minimum volume ratio in inputs.in. Lower the value, lesser the number of paired cells. You can also have this value boundary-based using a min_vol_ratio.in file. Please have a look at our manual for more details.

Hope this helps.

Sincerely,