[pardoa]

Hello OpenFOAMers,

I'm currently having some difficulties to generate my desired mesh with the blockMesh utility. The issue is related to the defined coordinate system (CS), since the final mesh is flipped along the Y axis (which is actually my desired Z). I know that each block of the geometry must be defined based on a right-handed CS. However, blockMesh prompts an "inside-out" error if I do so.

It's important to note that I'm generating the blockMeshDict using my own Matlab script (below image). The origin of the CS is located to the left of the inlet (the domain represents a valley crossed by a river).

untitled.jpg

I wish to keep the same XYZ CS for my blockMesh, but in order to do so, there are some points that I need to clarify:

1. Does blockMesh indeed exchange the Y and Z axis as I understood and, therefore, should I define the vertices of my mesh such as (X Z Y)?

2. Does the order of the vertex coordinates affect the local CS (x1, x2, x3) of each block of the mesh? I mean, as said in the previous point 1, if I define my vertices as (X Z Y), should I set the x1 along the X axis, x2 along the Z and x3 along the Y? Or, on the contrary, should I define it based on my desired output? In this case, x1 along the X axis, x2 along the Y and x3 along the Z.

If I set x1 as X axis, x2 as Z and x3 as Y, the local coordinate system is left-handed, as the axis origin (vertex 0) is located to the left of the inlet, and so, the grid flips along the Y axis (x3) (below image). Nonetheless, if I place the axis origin to the right of the inlet to define a right-handed local coordinate system, I’m prompted by blockMesh with and “inside-out” error. I’m guessing that this might be related to the absolute left-handed coordinate system defined for the vertices of the blocks (X Z Y), which only allows local coordinate systems with the same type of handedness.

PV.jpg

In any case, I'm not sure of my thoughts, so I would appreciate some clarification on this, especially regarding my questions. Thanks a lot in advance!

Álvaro

[simrego]

Hi!


Your vertices have to be in the global, right handed CS. So I think you mess up something when you export your vertices from matlab.
Even if your mesh will be twisted, inside-out, horrible, really bad, etc, your vertices have to be in the correct position...
The inverted elements is the next problem. first try to export the vertices correctly from your matlab script.

[subham998]

Hi Alvaro,

Can you please post the blockmeshDict file as it will help me understand your problem much better

[pardoa]

Hi!

Find here the dictionary: https://drive.google.com/file/d/1zg2...ew?usp=sharing

Thanks for the help!

Álvaro

[pardoa]

Originally Posted by simrego

Hi!


Your vertices have to be in the global, right handed CS. So I think you mess up something when you export your vertices from matlab.
Even if your mesh will be twisted, inside-out, horrible, really bad, etc, your vertices have to be in the correct position...
The inverted elements is the next problem. first try to export the vertices correctly from your matlab script.

Indeed, the vertices have to be placed in a global right-handed coordinate system. I changed that and also adapted the local CS of each block (x1,x2,x3) to the global one. Now it works!

Thanks so much

Álvaro

[tiatabasco]

Hi! would you mind shraing your blockmesh dict . I would like to also define a local coordinate system. So that my mesh is always allined with the wind direction i choose.