# Laminar Flow and Turbulent Flow in a pipe

Fluids in motion encounter various resistance forces due to friction, as described above. Friction can occur between the fluid and the pipe work and also friction can occur within the fluid as 'sliding' between adjacent layers of the fluid. The friction within the fluid is due to the fluid's viscosity.

## Laminar Flow in a pipe

Fluids with a high viscosity tend to have a lower speed of flow, and resistance to flow becomes almost totally dependant on the viscosity of the fluid. This condition is known as 'Laminar flow'.

## Turbulent Flow in a pipe

Fluids with a low viscosity are usually moved at higher velocities. Here the flow characteristics change and small eddy currents occur in the flow of fluid. The friction between the fluid and the pipe work becomes the main resistance factor. This type of flow is known as 'Turbulent flow'.

## Determining Laminar Flow or Turbulent Flow

The Reynolds number (Re) of a flowing fluid is obtained by dividing the kinematic viscosity (viscous force per unit length) into the inertia force of the fluid (velocity x diameter)

When the calculated Reynolds number of a flowing fluid is less than 2300 then laminar flow will occur and the resistance to flow will be independent of the roughness of the pipe wall.

Our Pipe Flow Expert and Pipe Flow Wizard software will automatically calculate whether laminar flow or turbulent flow will occur and they will automatically select the appropriate friction factor equation, such that the frictional resistance is calculated correctly and pressure drop in the pipe is calculated correctly.