Bernoulli Equation Verification Apparatus

Quick Answer: The Bernoulli Equation Verification Apparatus is a fluid mechanics teaching set-up for showing that, along a streamline, a fluid that speeds up must drop in pressure. It lets students relate pressure, velocity and height in a moving fluid and check Bernoulli’s equation against their readings.

The Equation Being Verified

Bernoulli’s equation expresses conservation of energy for a moving fluid. For steady flow of an incompressible fluid with negligible friction, the pressure head p/ρg, the velocity head v²/2g and the elevation z add up to the same total head at every point along a streamline. Where a passage narrows, the fluid must speed up to carry the same flow, so its velocity head rises and its pressure head falls. That trade between speed and pressure is behind carburettors, atomisers, Venturi flowmeters and part of the lift on a wing.

In the classic engineering form of a Bernoulli equation verification apparatus, water flows through a duct that narrows and then widens again, with pressure tappings along its length connected to a row of piezometer tubes. Students set a steady flow, measure the flow rate with a measuring tank and stopwatch, calculate the velocity at each section from its area, and compare the measured pressure heads with the values predicted by the equation. The small differences reveal friction losses.

The listing image for this item shows a different, air-based arrangement: a variable-speed blower fan on an upright board, an airflow path marked with measuring points, and a light ball positioned to show the pressure effect. Because the two forms suit different courses, whether this unit is the air-flow board or a water-flow Venturi rig, and the instruments included, should be confirmed at enquiry before ordering.

Specifications

Practical Applications

• Showing that pressure falls where the flow speeds up in a narrowing passage
• Calculating velocity heads from flow rate and cross-sectional area
• Comparing measured and predicted pressures and estimating friction losses
• Explaining Venturi meters, atomisers and wing lift

Care & Handling

• For water-flow versions, use clean water and drain the rig after use to prevent scale and algae in the tubes.
• Keep blower inlets clear of paper and dust, and switch the fan off before adjusting anything in the airflow path.
• Handle pressure tubes and fittings gently; kinked or cracked tubing gives false readings.
• Store the apparatus covered, away from direct sunlight.

Why Choose LabEquip

Engineering colleges and polytechnics buy this kind of engineering lab equipment for fluid mechanics practicals, while senior school physics departments use simpler versions to demonstrate the principle. LabEquip lists this apparatus in the STEM kits range, and the Floating Ping Pong Ball Model is a quick introductory demonstration of the same pressure effect. Please use the contact page to confirm the configuration you need.

Frequently Asked Questions

What does Bernoulli’s equation state?

For steady, frictionless flow of an incompressible fluid, the sum of the pressure head, velocity head and elevation head is constant along a streamline. If one term increases, another must decrease, so a fluid that speeds up must lose pressure.

Why does the pressure drop where the passage narrows?

The same volume of fluid must pass every section each second. Through a narrower section it has to move faster, gaining kinetic energy. That energy comes from the pressure, so the pressure there is lower.

Why do measured values not match the equation exactly?

Real fluids have viscosity, so some energy is lost to friction along the passage and in the widening section. The total head measured downstream is slightly lower than upstream, and the difference is the head loss.

Is this apparatus a water-flow or an air-flow version?

The listing image shows an air-flow board with a blower fan, while many engineering courses use a water-flow Venturi rig with piezometer tubes. Both demonstrate the same equation, but ask at enquiry which version is supplied so it matches your syllabus.

How is the velocity found at each section?

Measure the flow rate, for example by timing how long the flow takes to fill a known volume, and divide it by the cross-sectional area of each section. The velocity head is then the velocity squared divided by twice the gravitational acceleration.

Where is Bernoulli’s principle used in engineering?

Venturi and orifice meters measure flow from pressure differences, carburettors and spray guns draw fluid into a fast air stream, and pitot tubes on aircraft measure airspeed. It also helps explain the lift produced by wings and the draught up a chimney.

Last Updated: September 2026