1D to 3D boundary conditions
 

So I am attempting to model a tunnel network, and I have some results from a 1D software that I intend to use as boundary conditions in Fluent.

My problem is I only have mass flow (velocity) from the 1D model, and I need to match these flows for each inlet/outlet boundary condition.
I can put all but one boundaries as velocity inlets, but the remaining one (pressure?) must match the 1D results.

Thanks for any help and insights!