Researchers’ work will help the pipeline industry limit

Researchers have answered important questions to help improve the safety of hydraulic systems used for pipeline, water turbines, and other applications, and to help prevent damage.

The work, led by engineers at the University of Waterloo, investigates a phenomenon known as cavitation, or the rapid pressure changes in liquids that result in the formation and collapse of destructive gas-filled bubbles.

Cavitation is behind a famous party trick that involves hitting your open palm with the palm of your hand and shattering the bottom of a liquid-filled bottle.

“The rise and fall of cavitation bubbles are fascinating,” said Zhao Pan, a professor of mechanical and mechatronics engineering who led the research. “They are usually small and fast, but they can also cause severe damage on hard metals and glass-like surfaces.”

Researchers developed a theoretical model to predict the formation and shape of large, particularly damaging bubbles based on the acceleration and velocity of fluid flow. Experiments using high-speed photography validated the theory.

The information provided by the model will help engineers to design hydraulic systems and develop operating guidelines to reduce wear and tear, avoid major failures, and improve the reliability of the technology.

In the party move, hitting the bottle leads to a higher acceleration of the liquid relative to the bottle walls. This reduces the pressure of the liquid at the bottom, triggering the rapid formation of gaseous bubbles.

When those bubbles fall, or get trapped, they temporarily create high temperatures, high-speed micro-jets, and shockwaves. Those effects are powerful enough to break the glass.

For example, the occurrence of damaged water pipes and in the ship’s propellers is a common culprit. In extreme cases, this has led to catastrophic pipe failure in hydroelectric plants.

“On the other hand, the power of these bubbles can also be harnessed for good,” Pan said. “Cavitation can be used to break kidney stones, kill bacteria without using chemicals, and even in the production of beer and chocolate.”

Pan has previously worked with researchers in Japan and the United States on a new theory of small cavitation bubbles caused by the acceleration of fluids to explain how gait works. Recent work extends those results to the prediction of large bubbles.

A paper on research, on the criteria for large cavitation bubbles in a tube during the transient process, appears in the Journal of Fluid Mechanics. Pan collaborated with researchers at Tsinghua University in China on the new study.

The work, led by engineers at the University of Waterloo, investigates a phenomenon known as cavitation, or the rapid pressure changes in liquids that result in the formation and collapse of destructive gas-filled bubbles.

Cavitation is behind a famous party trick that involves shattering the bottom of a liquid-filled bottle by hitting your open palm with the palm of your hand.

“The rise and fall of cavitation bubbles are fascinating,” said Zhao Pan, a professor of mechanical and mechatronics engineering who led the research. “They are usually small and fast, but they can also cause serious damage to hard metals and glass-like surfaces.”

Researchers developed a theoretical model to predict the formation and size of large, particularly damaging bubbles based on the acceleration and velocity of fluid flow. Experiments using high-speed photography validated the theory.

The information provided by the model will help engineers to design hydraulic systems and develop operating guidelines to reduce wear and tear, avoid major failures, and improve the reliability of the technology.

In the party move, hitting the bottle results in a higher acceleration of the liquid relative to the bottle walls. This reduces the pressure of the liquid at the bottom, triggering the rapid formation of gaseous bubbles.

When those bubbles fall, or get trapped, they temporarily create high temperatures, high-speed micro-jets, and shockwaves. Those effects are powerful enough to break the glass.

For example, the occurrence of damaged water pipes and in the ship’s propeller is a common culprit. In extreme cases, this has led to catastrophic pipe failure in hydroelectric plants.

“On the other hand, the power of these bubbles can also be harnessed for good,” Pan said. “Cavitation can be used to break kidney stones, kill bacteria without using chemicals, and even in the production of beer and chocolate.”

Pan has previously worked with researchers in Japan and the United States on a new theory of small cavitation bubbles caused by the acceleration of liquids to explain how the trick works.

Recent work extends those results to the prediction of large bubbles. A paper on research, on the criteria for large cavitation bubbles in a tube during the transient process, appears in the Journal of Fluid Mechanics. Pan collaborated with researchers at Tsinghua University in China on the new study.

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