The dissipation term of the turbulent kinetic energy (see Modeling the Turbulence Dissipation) is modified for the DES turbulence model as described in Menter’s work [432] such that
 | (4–280) |
where 
is expressed as
 | (4–281) |
where 
is a calibration constant used in the DES model and has a value of 0.61, and
is the grid spacing, which in the case of a rectilinear hexahedral cell is the
maximum edge length (for other cell types and/or conditions, an extension of this concept is
used).
The turbulent length scale is the parameter that defines this RANS model:
 | (4–282) |
The DES-BSL / SST model also offers the option to "protect" the boundary layer
from the limiter (delayed option). This is achieved with the help of the zonal formulation of the
BSL / SST model. 
is modified according to
 | (4–283) |
with 
, where 
and 
are the blending functions of the BSL / SST model. Alternatively, the DDES
shielding function or the IDDES function can be selected [219], [622]. The default setting is to use DDES.
Note: In the DDES and IDDES implementations, 
is used as defined for the Spalart-Allmaras model in Equation 4–273 with the exception that the value of the constant is changed from
8 to 20.
The default setting is to use DDES. The 
blending function is given by:
 | (4–284) |
where 
=20, 
=3, and
 | (4–285) |
Here 
is the magnitude of the strain rate tensor, 
is the magnitude of vorticity tensor, 
is the wall distance, and 
=0.41.