I'm modeling a showerhead in attempt to find total pressure loss. I have an inlet volumetric flow rate of 2 gpm and an outlet environmental pressure of 1 atm. When I run the simulation, with surface goals at all openings for average total pressure, I obtain an inlet Av Total Pressure of 792613 Pa and an outlet Av Total Pressure of 213383 Pa. In tutorial B-1, the total pressure difference is minuscule in comparison. Am I missing something?