Reply To: Pressure drop through a hole in a pipe

[Rob]

Loss through a hole should be covered in most fluids text books. However, most of those assume discharge into free space whereas you have a cross flow.  If you know the exit flow try removing the fan and setting a negative velocity as that can be more stable. In your current set up you have pressure in, pressure out and a fan, so all external boundaries will adjust mass flow to meet the pressure value, and the fan will alter the pressure jump based on mass flow: that's not necessarily going to converge well.