The usual mode of the computation of the turbulent convection
with *CrysMAS* is the hybrid method with application of the
block-structured-mesh for the flow domain. Additionally the
turbulent fluid flow can be computed on a pure unstructured mesh.
The numerical method on the unstructured mesh consumes much
larger computational time, its stability is worse in comparison
with the method based on the structured mesh. The appropriate
mesh quality in the boundary layers is much more difficult to
achieve than using the structured mesh. Therefore a special
procedure for the adaption of the unstructured mesh was developed for the
turbulent fluid flow computation.

The implementation of turbulence model in *CrysMAS* on the
unstructured mesh may require a special mesh at the boundary
between e. g. the gas and solid regions. The normal computed mesh can be adjusted in order to fit
the needs.

This function does not change the number of degrees of freedom or the mesh topology. It causes a shifting of the nodes from the middle of the selected region towards the region boundary (boundary layer). It can be applied after the generation of the default mesh and either before or after the computation of the view factors.

Before adapting mesh, set required mesh parameters by generating the normal mesh.

Some minimum density of the numerical mesh is required in the turbulent boundary layer in order to calculate the transport of heat, momentum and special values of the turbulence model. The required mesh density depends on the Reynolds number. A typical mesh size of 3 mm or less is advised at the boundary between convective gas region and solid body. In the center of the convective region the mesh size should be 15 mm or less and the progression denominator for the transition in the mesh density from the boundary toward the region center should be 0.15.

- set the
**Edge length**to 0.015 and**Fit slope**to 0.15 for convective gas region. - set the
**Edge length**to 0.003 for the boundaries of convective gas region, excepting the symmetry axis. - recompute the mesh by selecting
**Computation**>**Generate mesh**or clicking on tool button.

For details about setting mesh parameters see Unstructured mesh Properties.

- set the
Select

**Computation**>**Adapt mesh**.Select the region for mesh adaption process, e.g. the gas region.

The adaption could be generally applied for a group of regions.

You can either manually select the regions, if the

**adapt for selected regions**option is checked,or

the program automatically selects all regions involved into a physical model, if the

**adapt for physical phenomena**option is checked. The list of the available physical models is provided in this case, the default is**turbulent_energy**. In this case you have to set the corresponding physical phenomena to the adapted regions before adapting the mesh, see Physical Phenomena.Set the strength of the mesh deformation

It is defined according to two methods:

by indicating the reduction degree for the distance of last node to the region boundary (the

**decrease distance by factor of**should be checked).by indicating the absolute distance of last node to the wall (the

**distance last node - boundary**should be checked).

Adjust parameters for mesh refinement, if desired.

Click on

**Apply**to adjust the mesh.