The importance of the Reynolds number (Re)
In theory the flow pattern depends on four variables:
- Diameter of the tube
- Speed of the fluid
- Density of the fluid
- Dynamic viscosity of the fluid
These variables combined provide the so called
Reynolds number (Re), an important parameter that describes whether flow conditions lead to
laminar flow or
turbulent flow. In general it can be said that a
laminar flow occurs at a low Reynolds number (≤ ca. 2300) and a
turbulent flow occurs at a high Reynolds number (≥ ca. 3000). In between these two numbers (Re 2300-3000) you have a
‘transitional flow’, meaning the flow can be laminar or turbulent (numbers mentioned are for a cylindrical tube).