Pressure Drop in Periodic boundary conditions
 

I have a tube and I work at steady state so I have imposed periodic conditions at the inlet and outlet of the test volume. However I want to examine the pressure drop along the pipe. The pressure itself is obviously not periodic along the entire pipeline, however because of the periodic conditions that I have imposed the Pressure Drop along the pipe is equal to zero.

How can I see the non periodic (linear) component of the Pressure Drop even though I have imposed Periodic Boundary Conditions?

noting that the flow is turbulent with Re ~ 20000