Modify gravity through UDF
 

Short question: Is it possible to change the gravity vector through a udf? And how?

Related question: Is it possible to apply a momentum source to only ONE of the species in a VOF simulation using a udf?

Disable gravity under Define > General... and include the gravity as a source term using a UDF. I've included a custom treatment of the gravity force in the DPM with DEFINE_DPM_BODY_FORCE and there should be a similar method with source terms in your Eulerian phase.

Try using an if statement to restrict your momentum source to a particular species thread pointer.

Thank you for your suggestion.
I will give this a try soon.