Water speeds up through the narrow throat and its pressure drops: P2 = P1 + ½ρ(v1² - v2²). Watch the flow accelerate and the throat manometer fall. Faster fluid, lower pressure.
Throat pressure P2 = P1 + ½ρ(v1²-v2²)
170 kPa
pressure drop ΔP = 30.0 kPa
Inlet diameter d18.0 cm
Throat diameter d24.0 cm
Inlet speed v12.0 m/s
Inlet pressure P1200 kPa
Throat speed v2
8.00 m/s
Flow rate Q
10.1 L/s
Speed-up (d1/d2)²4.00×
Pressure drop ΔP30.0 kPa
Flow statussteady
Fluid: water, ρ = 1000 kg/m³ · horizontal pipe · ideal (inviscid) flow. Throat d2 is capped at the inlet d1.
Tip: pinch the throat (small d2) and the speed climbs with (d1/d2)² while the pressure dives — far enough and it cavitates.