[alimea]

Hi

Im doing the "Tutorial - 6: 3D SHIP HULL" of gridPro. I have done every thing from the procedure but when I want to wrap Internal Faces (p 20 of tutorial) it gives me this error:

Selected group contains branching edges. Unable to execute

[vimaero]

Hi Ali,

The corners grouped for internal wrap should not have hanging corners or blocks. After grouping, check if you have extra corners grouped to the same corner group anywhere else in the topology. After Fig 42, you should have only 10 corners in the group, if you have more corners, please remove them from the respective corner group and try again.

Best Regards,
Vimal

[alimea]

Originally Posted by vimaero

Hi Ali,

The corners grouped for internal wrap should not have hanging corners or blocks. After grouping, check if you have extra corners grouped to the same corner group anywhere else in the topology. After Fig 42, you should have only 10 corners in the group, if you have more corners, please remove them from the respective corner group and try again.

Best Regards,
Vimal

Dear vimaero
thanks for your reply.
I did what you said but again it gave me that error!

[vimaero]

It looks like, you have executed the fig 42 upside down. If you look at the fig 42, the ship's deck is facing upwards, but in the above image it's facing downwards.

To give you a clear picture, the corner group that you selected for internal wrap should represent the internal surface exactly(like a quarter of an U). Your grouped corners looks like a quarter U but in opposite direction.

[alimea]

Originally Posted by vimaero

It looks like, you have executed the fig 42 upside down. If you look at the fig 42, the ship's deck is facing upwards, but in the above image it's facing downwards.

To give you a clear picture, the corner group that you selected for internal wrap should represent the internal surface exactly(like a quarter of an U). Your grouped corners looks like a quarter U but in opposite direction.

Yes, you were right!
Thank you
Unfortunately I didn't get some of the rules of GridPro. Of course I've read GUI Manual but I didn't get them! e.g. in this problem:
why should we delete these corners?
or for internal wrap it states:
The grouped corners if assigned to the internal surface, it would be violation of 2nd Rule of Surface Assignment which states that,
“Two edges/faces of a same block cannot be assigned/associated to a single surface.”
I can't understant what it says?
Also in p. 10 we have:
According to 1st Rule of Surface Assignments i.e.,
“If three or more blocks are emerging from an edge in 3D (or corner in 2D), it cannot be assigned to a boundary surface.”
Hence faces grouped in group 1 defining the hull geometry will be
wrapped.

I will be thankful if you explain every of these things if you have time!

[vimaero]

All these surface assignment rules are derived in order to ensure that the topology edges/faces assigned to the surfaces are orthogonal(which in turn influences your grid). Please have a look at the images shown from page 107-111 of ws_training_manual_v6.6.

For 1st rule, if you don't satisfy it, you may get an angle of <90 degree at each of the surface grid cells(at the block edge nodes).
For 2nd rule, you will end up with grid cells having an angle of 180 degree on the surface which in turn increases the skew of the grid.

You will be able to appreciate it if you see it w.r.t to grid images. Create the same incorrect assignment topologies & correct ones as shown for the 1st & 2nd rule and generate the grid(ignore the quality warnings). See the angle at each of the grid cells on the surface.

[alimea]

Originally Posted by vimaero

All these surface assignment rules are derived in order to ensure that the topology edges/faces assigned to the surfaces are orthogonal(which in turn influences your grid). Please have a look at the images shown from page 107-111 of ws_training_manual_v6.6.

For 1st rule, if you don't satisfy it, you may get an angle of <90 degree at each of the surface grid cells(at the block edge nodes).
For 2nd rule, you will end up with grid cells having an angle of 180 degree on the surface which in turn increases the skew of the grid.

You will be able to appreciate it if you see it w.r.t to grid images. Create the same incorrect assignment topologies & correct ones as shown for the 1st & 2nd rule and generate the grid(ignore the quality warnings). See the angle at each of the grid cells on the surface.

Thanks a lot
Could you plz tell me why we need to exclude some faces in wrapping?
Also I want to know how can I exclude the faces of this topology?
http://uupload.ir/files/mcqj_untitled.png
http://uupload.ir/files/12wq_2.png
I couldn't exclude it! it gave me an error that you can't...

[vimaero]

you can find the details on face exclusion in basic tutorial 6(page 10).

To exclude a face, hold the F key and click on the diagonal corners of a face to be excluded.