Courant–Friedrichs–Lewy condition

The Courant -Friedrichs - Lewy number ( CFL number or Courant number ) is used in the numerical flow simulation for the discretization of time-dependent partial differential equations. It specifies how many cells a size considered per time step travels a maximum of:

Here, the Courant number, the speed of the discrete time steps, and the discrete location step. This is motivated by the CFL condition, which states that the explicit Euler method can only be stable for. Similar conditions also apply to other discretization schemes.

The Courant number is named after the mathematicians Richard Courant, Kurt Friedrichs and Hans Lewy who defined 1928.