Pressure loss due to sudden expansion in pipe flow
 

I am modelling a sudden expansion in pipe flow. Fluid enters pipe 1 with diameter d1 and a sudden expansion occurs in the geometry to pipe 2 with diameter d2.(pipes are on the same axis & d2>d1)

We can read the loss coefficent value from the literature and verify the CFD results we put to the bernoulli equation to find loss coefficient.

But, my question is if we rotate the pipe system 90 degrees therefore (z1-z2)term in the bernoulli equation becomes bigger than zero. And geometry becomes vertical, how can we be sure of the results?

My results needs the gravity since it isn't negligible. And results i have found don't make sense in this way.

Has anybody worked on this subject or can help?

Thanks in advance.