Cavitation Number

Understanding the Cavitation Number

The Cavitation Number, also known as the cavitation parameter or sigma, is a dimensionless number used in fluid mechanics to characterize the potential of cavitation occurring in a liquid. Cavitation is the formation of vapor cavities in a liquid – i.e., small liquid-free zones ("bubbles" or "voids") – that are the consequence of forces acting upon the liquid.

The formula for the Cavitation Number σ can be expressed as the difference between the vapor pressure of the liquid P_v and the local pressure P, normalized by the dynamic pressure half the density of the liquid ρ times the square of the velocity of the liquid V^2.

Parameter explanation:

• sigma= Cavitation number, a dimensionless number

Example valid values:

• sigma = 0.2
• sigma = 1.0
• sigma = 2.5

Output:

• sigma = The result of the cavitation number

Data validation

The sigma parameter should be greater than zero as it represents a dimensionless physical quantity where negative values would not be meaningful in the context of cavitations in fluids.

Importance in Engineering

The Cavitation Number is important in the design and analysis of pumps, propellers, turbines, and other hydraulic equipment, where cavitation can cause significant wear, efficiency loss, or even damage.