What Is Cavitation?

The Basic Principle

Water normally boils at 100°C under atmospheric pressure. However, when pressure drops locally, water can “boil” at much lower temperatures.

Cavitation occurs in three stages:

1. Pressure drop – Local pressure falls below the vapor pressure of the liquid.

2. Bubble formation – Small vapor cavities form.

3. Bubble collapse – When pressure recovers, the bubbles implode violently.

It is the collapse phase that makes cavitation so powerful.

What Happens During Bubble Collapse?

When a cavitation bubble collapses, it creates:

• Local temperatures up to several thousand Kelvin

• Pressure spikes exceeding hundreds of atmospheres

• Micro-jets of water moving at high velocity

• Shockwaves

These extreme conditions exist only at micro-scale and for microseconds — but they are strong enough to:

• Damage metal surfaces

• Erode pump impellers

• Create reactive radicals

• Disrupt biofilm structures

Where Cavitation Occurs

Cavitation commonly appears in:

• Centrifugal pumps

• High-speed propellers

• Hydraulic turbines

• Venturi injectors

• High-pressure valves

If uncontrolled, cavitation causes:

• Noise and vibration

• Equipment erosion

• Reduced efficiency

• Shortened component lifespan

In industrial systems, preventing unwanted cavitation is critical.

Controlled vs Uncontrolled Cavitation

1. Uncontrolled Cavitation (Problem)

Occurs when:

• Pump suction pressure is too low

• Flow restrictions create pressure drops

• Equipment is poorly designed

Consequences:

• Pitting damage

• Energy loss

• System instability

2. Controlled Cavitation (Technology)

In advanced water treatment, cavitation can be intentionally generated to create:

• Mechanical shear forces

• Micro-mixing

• Radical formation (•OH)

• Enhanced oxidation

This is sometimes called hydrodynamic cavitation.

Cavitation vs Nanobubbles — Important Distinction

Cavitation bubbles and nanobubbles are fundamentally different:

At Waboost, we generate nanobubbles using a proprietary hydrodynamic cavitation module integrated into our systems. Controlled cavitation provides the energy required to fragment injected gas into nano-scale nuclei, which then stabilize in water as long-lived nanobubbles.

While nanobubbles can be produced using several methods (membrane systems, electrolysis, pressurized dissolution), we consider controlled hydrodynamic cavitation to be the most robust and scalable approach for industrial-grade nanobubble generation due to its mechanical reliability, energy efficiency, and suitability for continuous operation.

If you are interested in learning more, check out our "Membrane-Based Nanobubble Generators vs. Vacuum-Gas-Mixing based" article.

Chemical Effects of Cavitation

During collapse, water molecules can split, forming:

• Hydroxyl radicals (•OH)

• Reactive oxygen species (ROS)

These radicals are powerful oxidants capable of:

• Breaking down organic pollutants

• Disrupting cell membranes

• Degrading biofilm structures

This is why cavitation is studied in:

• Advanced oxidation processes (AOP)

• Wastewater treatment

• Sludge reduction

• Industrial cleaning

Cavitation vs Aeration Efficiency

In aeration systems:

• Large collapsing bubbles waste energy

• Unstable pressure zones reduce oxygen transfer efficiency

Nanobubble systems differ because they:

• Avoid violent collapse

• Maximize gas-liquid interface

• Provide stable dissolved gas distribution

This is why nanobubble technology focuses on mass transfer optimization rather than energy-release phenomena.