where is the norm of the background mean flow velocity. In the CWE interface we use the local value of the velocity. See Ref. 3 for further details on the numerical fluxes in general.

The value of the parameter τLF (the parameter that can be edited in the user interface) controls the numerical flux between the elements (nodal discontinuous Lagrange elements) used with the dG method. The numerical flux defines how adjacent elements are connected and how continuous p and u are. Different definitions of the numerical flux lead to different variants of the dG method. The flux implemented here is the so-called global Lax-Friedrichs numerical flux. The value of the parameter τLF should be between 0 and 0.5. For τLF = 0 a so-called central flux is obtained. Setting τLF = 0.5 gives a maximally dissipative global Lax-Friedrichs flux.