This DES model is similar to the Realizable 
-
model discussed in Realizable k-ε Model, with the
exception of the dissipation term in the 
equation. In the DES model, the Realizable 
-
RANS dissipation term is modified such that:
 | (4–275) |
where
 | (4–276) |
 | (4–277) |
 | (4–278) |
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).
For the case where 
, you will obtain an expression for the dissipation of the 
formulation for the Realizable 
-
model (Realizable k-ε Model): 
Similarly to the Spalart-Allmaras model, the delayed concept can be applied as
well to the Realizable DES model to preserve the RANS mode throughout the boundary layer. The DES
length 
in Equation 4–275 is redefined such that
 | (4–279) |
Note: In Equation 4–279 
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 and 
is replaced with (
) in the calculation of 
in Equation 4–274.