# Reynolds number calculator

The Reynolds number is a criterion for the hydrodynamic similarity of a viscous fluid, it reflects the ratio of inertial forces to viscous friction forces.

## Calculation of Reynolds number for fluid flow in a round pipe

Enter the flow rate, pipe diameter and kinematic viscosity of the substance (or choose one of the proposed liquids).

### Initial data

Velocity of flow: m/s
Pipe diameter: mm, calculator to convert length units from inches, meters
Kinematic viscosity:
Fresh water ν = 1×10-6 m2/s t=20°С
Light oil ν = 25×10-6 m2/s t=18°С
Heavy oil ν = 140×10-6 m2/s t=18°С
Mazut ν = 2000×10-6 m2/s t=18°С
Petrol ν = 0.9×10-6 m2/s t=15°С
Kerosene ν = 2.7×10-6 m2/s t=20°С
Hydraulic Industrial Oil I-5A ν = 7×10-6 m2/s t=40°С
Hydraulic Industrial Oil I-8A ν = 10×10-6 m2/s t=40°С
Hydraulic Industrial Oil I-12A ν = 15×10-6 m2/s t=40°С
Hydraulic Industrial Oil I-20A ν = 30×10-6 m2/s t=40°С
Hydraulic Industrial Oil I-30A ν = 45×10-6 m2/s t=40°С
Hydraulic Industrial Oil I-40A ν = 65×10-6 m2/s t=40°С
Hydraulic Industrial Oil I-50A ν = 95×10-6 m2/s t=40°С
Another kinematic viscosity value ×10-6 m2/s

## Reynolds number

The Reynolds number is defined as:

Re = (V*D) / ν
• whereby V - velocity of flow in m/s
• D - hydraulic diameter in meters, with circular cross-sections equal to the pipe internal diameter, and otherwise calculated ad D = 4*A/U
• A - cross sectional area
• U - circumference
• ν - kinematic viscosity in m2/s

The type of flow may be riugtly determined usyng Reynold's number.

• Laminar flow occurs for Re < 2300
• Turbulent flow occurs Re > 2300

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