I am trying to simulate neutral atmospheric flow and generate velocity profile in accordance with the experimental data I have. I am not sure how to manipulate the pressure gradient by using the source term U in in the fvOptions. Is there any particular formula or method for this? I have a average velocity as an internal field in U in the 0 directory. So, this pressure gradient source term will be defined according to this internal field value.

Code snippet from the fvOptions is given below:

pressureGradient { type vectorSemiImplicitSource; volumeMode specific; selectionMode all; sources { U ((0 0.00197805 0) 0); } }