What is Schmidt number in Fluid Mechanics ?

Schmidt number is a dimensionless number defined as the diffusion coefficient, the ratio used to define kinematic viscosity and the same acceleration diffusion and mass diffusion as the liquid. The number of Schmidt was named in honor of the German engineer Ernst Heinrich Wilhelm Schmidt (1892-1975).
ν is kinematic viscosity coefficient
D is the diffusion coefficient.
μ is viscosity coefficient
ρ is the density