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Physical principles of the measurement parameter flow velocity

Flow is a directional movement of particles or continuous media. There is water flow or gas flow flow, for example. The SI unit for flow velocity is metres per second (m/s).

Depending on the occurrence of turbulence, one differentiates between laminar flow (without turbulence) and turbulent flow (with turbulence).

Flow in a duct

Volume flow and flow velocity

Laminar flow

  • From lat. "turbulentus": unruly, turbulent
  • Motion of liquids and gases in which turbulences of all size scales occur
  • Usually three-dimensional, apprarently random, non-stationary movements of fluid particles

Turbulent flow

  • From lat. "turbulentus": unruly, turbulent
  • Motion of liquids and gases in which turbulences of all size scales occur
  • Usually three-dimensional, apprarently random, non-stationary movements of fluid particles

Air volume flow

A volumetric flow is taken to mean the volume of a medium that moves through a cross-section within a given period of time.

Volume flow is usually stated either in l/s or in m³/h. The conversion calculation derives from 1000 l = 1 m³ and 3600 s = 1 h. The conversion factor is: 1 l/s = 3.6 m³/h or 1 m³/h = 0.27777777777778 l/s

Formula for volume flow

Formula for the calculation of volume flow
How flow velocity is measured