Function Objects – DESModelRegions

In the case of Detached Eddy Simulations (DES), there are two regions in a computational domain that are treated in RANS-like and LES-like manners. The original Spalart-Allmaras DES model (DES97) formulation is based on the assumption that the wall-parallel grid spacing near the wall is in excess of the boundary-layer thickness \(\delta\) by a good margin so that the entire boundary layer can be handled by RANS [1].

Fig. 1 Natural DES grid in a boundary layer. Dotted line means velocity profile. \(\delta\) is the boundary-layer thickness [1].
Settings of DESModelRegions

In OpenFOAM, we can visually check these regions using the DESModelRegions function objects. It is also available in iconCFD.

If log it true, the volume percent (%) of RANS and LES regions will be output to the screen:

Source Code



[1] P. R. Spalart, Detached-Eddy Simulation. Annual Review of Fluid Mechanics 41, 181-202, 2009.

Function Objects – histogram

OpenFOAM Version:

Settings of histogram


You can create a picture as shown below using Gnuplot with the input file generated by OpenFOAM. I replaced “with lines” with “with boxes” in the input command file to create this picture.


In the above picture, the first bin represents the following volume fraction:

\frac{\sum_{celli}^{} \left( V_{celli}:\;300 \leq T_{celli} < 301\right)}{\sum_{celli}^{} \left( V_{celli}:\;min \leq T_{celli} < max\right)},

where \(V\) is the cell volume.