Bernoulli’s Principle and the Venturi Effect

Understanding Two of the Most Frequently Referenced Concepts in Ventilation and Airflow Engineering

LEVCentral Expert Commentary

Few scientific principles are referenced more frequently in ventilation engineering than Bernoulli’s Principle and the Venturi Effect. They are often cited when discussing airflow measurement, duct design, pressure relationships, hood performance and the operation of devices such as Pitot tubes, Venturi meters and ejector systems.

This educational resource, prepared by Professor Alexander Smits of Princeton University, provides a clear explanation of both concepts and explores how pressure and velocity interact within moving fluids. Although the examples are often drawn from aerodynamics and cycling, the underlying principles apply equally to air movement within LEV systems and industrial ventilation installations.

For LEV professionals, understanding the relationship between velocity pressure and static pressure is fundamental. Many commissioning and testing activities rely on measurements that are derived directly from Bernoulli’s equation. Pitot tube traverses, duct velocity calculations and airflow determination all depend upon these principles.

The resource is also useful because it addresses several common misconceptions. In particular, it explains why pressure reductions occur when fluid velocity increases and why simplified explanations of the Venturi Effect can sometimes lead to misunderstanding when applied to real-world engineering systems.

Whilst the mathematics may appear academic, the concepts are highly practical. Every LEV engineer using a Pitot tube, every occupational hygienist interpreting airflow measurements and every designer sizing ductwork is applying Bernoulli’s Principle whether consciously or not.

Source Document

View Original Paper

Source: Professor Alexander J. Smits, Princetown University USA
Document Type: Educational Technical Resource
Status: Current 2026
Last reviewed by LEVCentral: June 2026

Key Learning Points

Bernoulli’s Principle describes the relationship between pressure, velocity and energy in a moving fluid.
As fluid velocity increases, static pressure decreases when total energy remains constant.
The Venturi Effect occurs when fluid passes through a restriction, causing velocity to increase and pressure to decrease.
Pitot tubes rely on Bernoulli’s Principle to determine air velocity.
Velocity pressure measurements are used extensively during LEV commissioning and testing.
Duct velocity and airflow calculations are derived from pressure measurements.
Understanding pressure relationships is essential when diagnosing LEV system performance issues.
Simplified explanations of airflow behaviour can sometimes be misleading when applied to complex engineering systems.
Bernoulli’s equation remains one of the most important tools in fluid mechanics and ventilation engineering.

Further Resources

Recommended Learning

Thought Leadership

Many ventilation professionals become highly skilled at measuring airflow without fully understanding the scientific principles underpinning the measurements they take. Whilst this may be sufficient for routine testing, a deeper understanding of fluid mechanics often becomes invaluable when diagnosing unusual system behaviour or defending technical conclusions.

Bernoulli’s Principle provides much of the foundation upon which airflow measurement techniques are built. Whether measuring duct velocities, interpreting Pitot tube readings or analysing pressure losses across components, the same fundamental relationships apply. For practitioners involved in commissioning, troubleshooting and performance verification, understanding these principles can significantly strengthen technical competence and improve confidence when interpreting results.

Perhaps most importantly, resources such as this remind us that good engineering is not simply about following procedures. It is about understanding why those procedures work and recognising the assumptions and limitations that sit behind every measurement we make.