Cavitation Number Calculators

➔ Calculate Cavitation Number
➔ Calculate Local Pressure
➔ Calculate Fluid Vapor Pressure
➔ Calculate Fluid Density
➔ Calculate Characteristic Flow Velocity

Calculate Cavitation Number


Ca = Cavitation Number
P = Local Pressure
Pv = Fluid Vapor Pressure
d = Fluid Density
V = Characteristic Flow Velocity

Local Pressure:
Fluid Vapor Pressure:
Fluid Density:
Characteristic Flow Velocity:
Cavitation Number:

Calculate Local Pressure


P = Local Pressure
Ca = Cavitation Number
V = Characteristic Flow Velocity
d = Fluid Density
Pv = Fluid Vapor Pressure

Cavitation Number:
Fluid Density:
Characteristic Flow Velocity:
Fluid Vapor Pressure:
Local Pressure:
Pascal

Calculate Fluid Vapor Pressure


Pv = Fluid Vapor Pressure
P = Local Pressure
Ca = Cavitation Number
V = Characteristic Flow Velocity
d = Fluid Density

Local Pressure:
Cavitation Number:
Fluid Density:
Characteristic Flow Velocity:
Fluid Vapor Pressure:
Pascal

Calculate Fluid Density


d = Fluid Density
P = Local Pressure
Pv = Fluid Vapor Pressure
Ca = Cavitation Number
V = Characteristic Flow Velocity

Local Pressure:
Fluid Vapor Pressure:
Cavitation Number:
Characteristic Flow Velocity:
Fluid Density:
Kilogram/Meter3

Calculate Characteristic Flow Velocity


V = Characteristic Flow Velocity
P = Local Pressure
Pv = Fluid Vapor Pressure
Ca = Cavitation Number
d = Fluid Density

Local Pressure:
Fluid Vapor Pressure:
Cavitation Number:
Fluid Density:
Characteristic Flow Velocity:
Meter/Second

The cavitation number () is an important parameter in fluid mechanics that helps to determine the likelihood of cavitation occurring in a fluid system. It is used to assess the potential for vapor bubbles to form in the fluid, which could cause damage to equipment like pumps or propellers.

Here's how you can calculate each of the components involved in determining the cavitation number and its related factors:

1. Cavitation Number Calculation:

The cavitation number σ\sigma is defined as:

Where:

  • plocal is the local pressure in the fluid (Pa or N/m²).
  • pvapor is the vapor pressure of the fluid (Pa or N/m²).
  • is the fluid density (kg/m³).
  • is the characteristic flow velocity (m/s).

2. Local Pressure Calculation:

The local pressure in the fluid can be calculated based on the specific conditions of the flow. If you have a pressure difference or other boundary conditions, it may be determined by solving the governing equations of motion (Navier-Stokes or Bernoulli’s equation).

For example, if you're in a free-stream flow situation:

Where pambient is the ambient pressure, and the term 1/2ρv represents the dynamic pressure.

3. Fluid Vapor Pressure Calculation:

The vapor pressure of a fluid is typically a known value depending on the fluid's temperature. For water, for instance, it increases with temperature. You can use steam tables or empirical formulas to estimate the vapor pressure for other fluids.

A general approximation for water is given by the Antoine equation:

Where:

  • pvapor is the vapor pressure in mmHg.
  • , , and are empirical constants (specific to the fluid).
  • is the temperature in °C.

4. Fluid Density Calculation:

The density of a fluid is typically known or can be approximated using equations of state for gases or liquids. For an ideal gas, you can use the ideal gas law:

Where:

  • is the pressure (Pa),
  • is the specific gas constant (J/(kg·K)),
  • is the temperature (K).

For liquids like water, density is often treated as a constant (e.g., for water at 4°C, ρ≈1000 kg/m3).

5. Characteristic Flow Velocity Calculation:

The characteristic flow velocity is often determined based on the geometry of the flow (such as the velocity at the inlet of a pipe, or the free-stream velocity of a jet or propeller). If this is not directly available, it can be estimated based on the flow rate QQ and cross-sectional area AA of the flow:

Where:

  • is the volumetric flow rate (m³/s),
  • is the cross-sectional area of the flow (m²).