Schmidt number

The Schmidt number (after Ernst Schmidt) is a dimensionless parameter and describes the ratio of diffusive momentum transport to diffusive mass transport. Typically, the dynamic viscosity of a fluid is considered in relation to their density and the diffusion coefficient of a chemical substance contained therein.


  • : Dynamic viscosity
  • : Density
  • : Diffusion coefficient
  • : Kinematic viscosity

At high levels, () the momentum transport is more pronounced than the mass transport.

The Schmidt number is

  • For liquids 1000
  • Gases for approximately 1

The Schmidt number is the ratio of the Peclet number, which compares with advective diffusive mass transport, as well as the Reynolds number, which compares with advective diffusive transport of momentum:

In addition, the Schmidt number is the analog of the Prandtl number used in the heat transport.

  • Code ( Fluid Mechanics )
  • Code ( thermodynamics)