Cavitation

Cavitation

Definition

Cavitation is a phenomenon that occurs when a liquid undergoes sudden changes in pressure, causing bubbles to form and collapse within the liquid. It is a destructive process that can damage pumps, valves, and other fluid handling equipment.

Types of Cavitation

1. Nucleation cavitation

• Involves bubble formation and growth at surfaces or other imperfections.

2. Regime cavitation

• Occurs in regions of high shear or velocity gradients.

3 Künuzawsky cavitation

• Caused by rapid variations in pressure near solid surfaces.

4 Künuzawsky-Wallis cavitation

• Occurs due to variations in pressure across a converging or diverging liquid jet.

5. Shock cavitation

• Caused by violent collapse of large bubbles near solid boundaries.

Factors Affecting Cavitation

• Fluid properties
• Pressure differences
• Flow velocity
• Surface roughness
• Presence of contaminants

Consequences of Cavitation

• Erosion and damage to pumps and other fluid handling components
• Reduced efficiency
• Increased noise
• Vibration

Mechanisms of Cavitation Damage

• Direct impact of collapsing bubbles
• Erosion by accelerated liquid jet
• Fatigue caused by repeated cavitation bubbles collapse

Applications of Cavitation

• Cavitation erosion can be used for surface finishing of materials.
• High-intensity cavitation can be used for water treatment.

Prevention of Cavitation

• Ensure proper fluid velocity control
• Smooth surfaces
• Adequate net positive suction head (NPSH)
• Use of anti-cavitation devices (e.g., diffusers)

FAQs

1. What is the primary cause of cavitation?

• Sudden changes in liquid pressure leading to bubble formation and collapse.

2. Which factors affect the likelihood of cavitation?

• Fluid properties, pressure differences, flow velocity, surface roughness, and the presence of contaminants.

3. How can cavitation be prevented?

• Controlling fluid velocity, smoothing surfaces, maintaining adequate NPSH, and using anti-cavitation devices.

4 Künuzawsky cavitation specifically occurs in which type of flow?

• Flow near solid boundaries.

5. What is the consequence of shock cavitation?

• Violent collapse of large bubbles near solid boundaries, causing damage.