
The standard SpalartAllmaras model uses the distance to the closest wall as the
definition for the length scale
, which plays a major role in determining the
level of production and destruction of turbulent viscosity
(Equations
12.36,
12.312, and
12.315).
The DES model, as proposed by Shur et al. [
331] replaces
everywhere
with a new length scale
, defined as