Hello, guys.

I'm trying to make a flow simulation in a certain pipe.

I want to define its energy loss generated by my pipe.

as far I know, I have to use the Bernoulli's equation and compare the energy between inlet and outlet.

The energy can be defined by find the velocity (v), pressure (p), and height (z).

And here's my problem.

I want to make my pipe a little bit different by change it size into a rectangle one.

My questions is, how do I define v, p, and z?

Should I define the mean pressure of inlet and outlet surface?

or maybe I should define it using "point". Take the pressure value at the center point of the rectangle, and so on?

or there is other method? which one is common?