Enter the local pressure in the flow field, the vapor pressure of the fluid, the fluid density, and the local flow velocity into the calculator to determine the Cavitation Index.

Cavitation Index Formula

The following formula is used to calculate the Cavitation Index. 

CI = P - Pv / (0.5 * ρ * V^2)

Variables:

  • CI is the Cavitation Index
  • P is the local pressure in the flow field (Pa)
  • Pv is the vapor pressure of the fluid (Pa)
  • ρ is the fluid density (kg/m^3)
  • V is the local flow velocity (m/s)

To calculate the Cavitation Index, subtract the vapor pressure of the fluid from the local pressure in the flow field. Then, multiply the fluid density by half and the local flow velocity squared. Finally, divide the first result by the second result.

What is a Cavitation Index?

A Cavitation Index is a dimensionless number used in fluid dynamics and hydraulics to determine the possibility of cavitation occurring in a fluid flow system. Cavitation is a phenomenon where rapid changes in pressure in a liquid lead to the formation of small vapor-filled cavities, which can cause significant damage to equipment. The Cavitation Index is calculated based on the fluid’s pressure, velocity, and vapor pressure, and a lower index indicates a higher risk of cavitation.

How to Calculate Cavitation Index?

The following steps outline how to calculate the Cavitation Index (CI).

  1. First, determine the local pressure in the flow field (P) in Pascal (Pa).
  2. Next, determine the vapor pressure of the fluid (Pv) in Pascal (Pa).
  3. Next, determine the fluid density (ρ) in kilograms per cubic meter (kg/m^3).
  4. Next, determine the local flow velocity (V) in meters per second (m/s).
  5. Next, gather the formula from above: CI = (P – Pv) / (0.5 * ρ * V^2).
  6. Finally, calculate the Cavitation Index (CI).
  7. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge:

local pressure in the flow field (P) = 500 Pa

vapor pressure of the fluid (Pv) = 200 Pa

fluid density (ρ) = 1000 kg/m^3

local flow velocity (V) = 10 m/s