Inflate boundary layer

[Jenda]

Hi there,

I’m working on an incompressible simulation with hex-dominant automatic meshing and need help achieving a smoother transition between my boundary layer mesh and the surrounding volume mesh. Currently using Inflate boundary layer settings, but the transition appears abrupt with a noticeable jump in cell size and every mesh is consuming my core hours. Lastly I used this setup…

I also have surface refinement with edge length min 0.05 metres and max 0.2 metres and without cell zone. One region refinement around the car 0.02 metres of the edge length. The second one is behind the car for better wake capture and edge length has 0.06 metres and the third one is on the moving ground with edge length 0.015 metres.

The mesh results from the last setup (previous setups had very similar results):

*Standard mesher is not valid because of non-orthogonality errors.

Every advice is welcome!

Jan

[RicardoParis]

Hi,

The “Surface layer relative thickness” in the inflate boundary layer setup represents the ratio between the thickness of the last boundary layer and the surface mesh.

Since you have 0.1 for this field, this means that the last layer will have a thickness of 10% of the size of the surface mesh, which gives you a big jump. If you want a smoother transition, you’d have to carefully adjust number of layers, expansion ratio, and especially the relative thickness.

[Jenda]

Are there any recommended values?

[RicardoParis]

It’s fairly common to see values in the 0.4-0.8 range.