In steady flow, yes, you have to have contraction and expansion coefficients. If you have supercritical flow, you'll want to reduce those coefficients by an order of magnitude (example, if you are uinsg 0.1 and 0.3 for subcritical flow, then you should use 0.01 and 0.03 for supercritical flow.

When using unsteady flow, momentum changes are captured in the St. Venant equation of conservation of momentum, so you do not have to explicitly add in contraction and expansion coefficients. There is, however, a separate table for unsteady contraction and expansion coefficients, that you can use (but it is optional) if you feel you need more energy loss from contraction and/or expansion.

Chris G.

@RASModel

www.therassolution.com