Bernoulli's Venturi Tube
Send fluid through a pipe that narrows to a throat and widens back out — adjust the inlet/throat diameters, flow speed, fluid density, and inlet pressure to watch tracer particles speed up in the throat while manometers show the pressure drop Bernoulli's equation predicts.
Preview — sign up free to change the numbers yourself
What you can adjust
- Inlet pipe diameter (D₁)
- 0.05 – 0.5 m
- Throat diameter (D₂)
- 0.02 – 0.45 m
- Inlet flow speed (v₁)
- 0.1 – 8 m/s
- Fluid density (ρ)
- 700 – 1400 kg/m³
- Inlet gauge pressure (P₁)
- 0 – 300000 Pa
The full-bore pipe diameter before and after the throat. The outlet widens back out to this same diameter.
Must stay narrower than the inlet diameter. A narrower throat forces a bigger speed-up (and pressure drop) by continuity.
The fluid's speed in the full-bore inlet pipe, before it accelerates into the throat.
1000 kg/m³ is water; lighter values are oil-like, heavier values are glycerin-like.
Gauge pressure (relative to atmospheric) at the inlet. The throat pressure can legitimately drop below this — even below zero gauge — as the fluid speeds up.
About this simulation
What it shows
Fluid flows along a pipe that narrows to a throat and widens again, with tracer particles that speed up in the throat and pressure gauges along the way.
The key idea
The same volume of fluid must pass every point each second, so it speeds up where the pipe is narrow. Faster flow comes with lower pressure (Bernoulli's equation), so the throat has the lowest pressure.
Try this
Narrow Throat diameter (D₂) from 0.10 m to 0.05 m: the throat speed rises from 8 m/s to 32 m/s and its pressure falls well below the inlet pressure.
The fluid is ideal: it has no friction or turbulence, so the outlet recovers exactly the inlet pressure. A throat pressure below zero gauge means below atmospheric pressure, as in a suction pump.