Learning Forum

[nrj123]

Hi,

I am doing an analysis of a turbine in a flow constrictor. I have made a 3D model of the turbine and the surrounding fluid zones using Rhino and imported this into DesignModeler. In DesignModeler I did a boolean operation to remove the turbine volume from the fluid volume and set up the named selections. All went well until I tried to mesh the fluid volumes. In meshing, it comes up with a warning regarding high-order nurbs surfaces, which I ignored as has been suggested in other posts. When I try to generate a mesh, it fails. 

Below is a section view of the failed mesh, showing the errors at the bottom. It appears that it has failed while meshing faces on the turbine and has not generated any volume mesh.

 

Here is a closer view of the failed mesh:

 

The mesh works without the void for the turbine, but with the turbine it fails. I also tried meshing the turbine as a solid just to confirm that this was the issue and it also failed:

 

The turbine shape is complex but it is important to preserve its shape so that the correct lift and drag forces are generated.

Any ideas how to solve this issue and get a working mesh for the analysis?

Thanks in advance...

[Rob]

Why have you got surfaces through the turbine region? 

[nrj123]

The planes are not through the turbine but are internal boundaries in the fluid surounding the turbine. I broke the fluid into four parts to improve the mesh structure. It also fails when I try to mesh it without the fluid domain being broken into four sections though.

The turbine itself is the issue, as you can see when I took away the fluid domain and tried to mesh the turbine as a solid and it showed the same error. Also, the flyid volume mesh works without the void for the turbine...

[Rob]

Use a cut plane in DM and see if the blades have a void. Also check for any contacts in meshing: it may be trying to stick the upper & lower faces together. 

[nrj123]

The turbine is not a solid, it has a void inside as I am just trying to mesh the fluid surounding the turbine, not the inside. Do you mind clarifying what you mean by contacts in meshing? Sorry if I am misunderstanding you, I am pretty new to CFD...

[Rob]

The check is to confirm you have got a void: if the surfaces have failed to import correctly you may not have a "blade" as you expect. 

Contact is how Meshing connects volumes/faces. Between volumes it can be useful, if the tolerance has picked up the upper & lower turbine blade faces it's not desirable.  Go through some of the tutorials (they're in Help) and it'll become clearer.