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[ANSYS Meshing] Structured Meshing for Multi Element Airfoil

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Old   December 26, 2020, 15:05
Default Structured Meshing for Multi Element Airfoil
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Janet J
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Hello,

I am trying to create a structured mesh for a multi element airfoil on ansys meshing. Despite trying for several split patterns on spaceclaim, I am still unable to generate a structured mesh on the entire c-grid domain. Some splits are structured while some remain un-structured. Could anyone help me how I can obtain structured mesh on this C-grid for multi element airfoil?





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Old   December 28, 2020, 03:58
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Lorenzo Galieti
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I would forget about that Hexa mesh ( i suppose that is what you mean by structured) is a pain for anything but the simplest geometry

Did anybody tell you to do that? Why is it so required?
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Old   December 28, 2020, 18:21
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Quote:
Originally Posted by LoGaL View Post
I would forget about that Hexa mesh ( i suppose that is what you mean by structured) is a pain for anything but the simplest geometry

Did anybody tell you to do that? Why is it so required?
Hello Lorenzo Galieti,

Yes, that is exactly what I meant, Hexa Mesh it is. I have spent a total of 15 hours in 3 days trying to get a nice structured mesh (Hexa mesh/mapped mesh) on this c-grid and I am only not able to get it completely. Reached to a fine level of exhaustion now. I have to do Hexa, it is a requirement. Thank you for your response
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Old   December 29, 2020, 07:42
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Hey man,

As I said, hexa mesh with blocking, forget about it, this wont work anytime soon and all you will get is exhaustion as you mentioned. What you can try is hex dominant mesh as meshing method, what it will basically do is create a tetra mesh and then try to automatically convert all the tetras into hexa. If your domain is 2D, the conversion may take place in a feasible amount of time.

The advantage is that you can forget about the blocking, which to me is the “forget about it” part. However meshing time will be substantially longer, if I remember well we can even speak about hours.
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Old   December 29, 2020, 14:12
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Quote:
Originally Posted by LoGaL View Post
Hey man,

As I said, hexa mesh with blocking, forget about it, this wont work anytime soon and all you will get is exhaustion as you mentioned. What you can try is hex dominant mesh as meshing method, what it will basically do is create a tetra mesh and then try to automatically convert all the tetras into hexa. If your domain is 2D, the conversion may take place in a feasible amount of time.

The advantage is that you can forget about the blocking, which to me is the “forget about it” part. However meshing time will be substantially longer, if I remember well we can even speak about hours.
Weird you should say that since one of my coworkers has been meshing two-element airfoils with structured, hex, multi-block meshes since the start of his thesis using Icem. It's kinda difficult for the newbie but when you get the hang of it, generating such a mesh should take you less than an hour (including setting bocos, exporting the mesh with the right format and all). Should be a bit more for a three-element airfoil because of the greater amount of blocks and mesh cells, but this shouldn't represent an superhuman hurdle all things considered. A good place to start is with this three-part series to get the basics covered (plus the author of the videos uses a C-H topology - Edit: That's a C topology since the airfoil's trailing edge is not truncated - I think it's mentioned in the second vid):

https://www.youtube.com/watch?v=tYrbScUH9RE
https://www.youtube.com/watch?v=EknKVAJGEJ8
https://www.youtube.com/watch?v=6wQPeBpvwCk

then here for strategies regarding meshing 3-element airfoils:

https://www.youtube.com/watch?v=rfMnnzdd3JU

and finally here for 3D meshes:

https://www.youtube.com/watch?v=NVyvEH-u0wQ


I should also comment on Janet's persistence to generate hex meshes by saying that oftentimes, people are not free to choose a meshing strategy because their solver can only be fed a certain type of mesh. Our in-house solver only takes structured multi-block meshes, so there's that.
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Old   December 29, 2020, 16:19
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Quote:
Originally Posted by Bubbly View Post
Weird you should say that since one of my coworkers has been meshing two-element airfoils with structured, hex, multi-block meshes since the start of his thesis using Icem. It's kinda difficult for the newbie but when you get the hang of it, generating such a mesh should take you less than an hour (including setting bocos, exporting the mesh with the right format and all). Should be a bit more for a three-element airfoil because of the greater amount of blocks and mesh cells, but this shouldn't represent an superhuman hurdle all things considered. A good place to start is with this three-part series to get the basics covered (plus the author of the videos uses a C-H topology - Edit: That's a C topology since the airfoil's trailing edge is not truncated - I think it's mentioned in the second vid):

https://www.youtube.com/watch?v=tYrbScUH9RE
https://www.youtube.com/watch?v=EknKVAJGEJ8
https://www.youtube.com/watch?v=6wQPeBpvwCk

then here for strategies regarding meshing 3-element airfoils:

https://www.youtube.com/watch?v=rfMnnzdd3JU

and finally here for 3D meshes:

https://www.youtube.com/watch?v=NVyvEH-u0wQ


I should also comment on Janet's persistence to generate hex meshes by saying that oftentimes, people are not free to choose a meshing strategy because their solver can only be fed a certain type of mesh. Our in-house solver only takes structured multi-block meshes, so there's that.
Thank you so much Bubbly for your response including the videos that you have shared. When I undertook this multi-element airfoil project I thought I should start working with Ansys meshing at first since I feel I am pretty familiar with its usage. But yes that is right, with multi-elements like 3 elements airfoil is quite tricky. The problem is I am not really well-versed with ICEM-CFD. I learnt it by watching Simon's three video series that you have shared. But I guess now is the time to elevate my skills of ICEM by trying new topologies for this 3 element airfoil.

And thank you for the video on 3D meshes, guess that's my next target once I am done with the current 2D one.
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Old   December 29, 2020, 16:29
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Good to know then, enjoy burning your fingers with ICEM

Edit: I will stress my point again: make sure you need a structured mesh and not just an hexa mesh, because if you only need an hexa mesh, I repeat that blocking is a lot of finger burning and, to be honest, sometimes I did not even find it worth. Especially if you want to add small refinement zones (e.g. in the wake of every split), it is also a pain because then you need a lot of elements everywhere to keep a decent cell aspect ratio
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