external flow with deforming boundary
 

I am trying to use Fluent to simulate external flow over a deforming object. The object will be a thin line that changes shape with time. For example a straight line that becomes a curve, or a moving sine wave.

I am trying to learn how to write UDFs at the moment. My first question is: Do I use DEFINE_GEOM, DEFINE_GRID_MOTION, or both?

I have been trying to use some UDFs from a Fluent tutorial and hooking them to my mesh. This only gives me negative cell volume errors. Can someone explain why this is.

Thank you.