Is there any naming convention for the DPM injection which should be a placeholder for particles stripped away from Eulerian Wall Film?
Yes, the name of the film material and the injection material should "match" in some way.
There are 2 possibilities:
1. The injection dpm material name is part of the film material name.
2. The film material name is contained in the injection dpm material name.
Example of #2:
If the name of the (Eulerian) film material is "my-film-liquid") give the material for the stripped / separated particles a name that contains the complete name of the film material (e.g. "my-film-liquid-dpm").