High Stagger Rotor Blade Meshing
 

Afternoon,

I am trying to Mesh a 1.5 stage turbine. For the first part of my project I have chosen a mid height design and I am focusing purely on a 2D mesh first ( gain an understanding of basic principles and for comparison to some experimental results) , I wanted to try doing this on ICEM. I have gone through numerous tutorials, especially the Hexa 2D Airfoil meshing.

Due to the Rotor having a high stagger angle I am having trouble producing a good quality mesh and I am also not sure how to produce a well defined boundary layer using Ogrids on such a high stagger Rotor blade. I am getting alot of skewed elements due to the large turns required.

I am fairly new to CFD and a lot of the terminology used within ICEM is still not entirely clear to me but I am just practicing as much as I can currently. If anyone has any advice they could provide on how to mesh this Rotor blade and generate a dense boundary layer It will be much apprciated.

Attached is a picture of the Rotor Blade i need to mesh, I am just using a boxed region at the moment simple because I am still focusing on understanding and learning how I want to use the various tools to generate a mesh around the main airfoil and to generate the boundary layer.

For the proper mesh I will make later on there are going to be more rotor blades and stators. Any help and advice would be much appreciated, thank you.

Hi there,

I think you could take advantage of the quarter o-grid topology as a first step of the meshing procedure. Look for information on the web about the C, H, and O-grid meshing strategies. It'll give you a better idea of what type of mesh you need for the flow over that geometry.

Regards,

I have seen it mentioned that Simon made a tutorial for a High stagger stator somewhere, unfortunately no one as the tutorial anymore or the link to it. PSYMN if possible could you please send me the link to the tutorial you had at some point regarding meshing for a High stagger angle stator. I am still not clear at all on how to make a quarter O-grid for a 2D high stagger airfoil. The videos I managed to see on youtube were for 3D and were not very clear to understand. I am still getting far too many skewed cells with all the methods I try. Thank you.

Dear eromon84,

While you can get the tutorial to mesh high staggered stators, I can give you some advices in order for you to go forward with the meshing problem. If you post your *.tin file with the geometry, I think that somebody else can try to give you some advices according with their experience. Post your *.tin file and I'll try to give you a better idea to come up with the quarter o-grid strategy.

Regards

Thank you very much for your help with this. I have been struggling with this and not getting far in making a good quality mesh.

The tin file I sent you has a strange farfield geometry I know, but as mentioned earlier this is just me trying to learn the main ideas oh how to create the general mesh around the Rotor blade. For the proper mesh I will do later I will have a few more rotors plus inlet and outlet stator rows.

Once again any help you can provide is much appreciated!


EDIT: see first post for attachments

It must be the internal flow!!! why you have the farfield like this?

yeah as mentioned it was a strange farfield I had. I was sorta stuck and went back to trying to understand Simon's Tutorial when he used O-grids with this 2D hexa airfoil. To make following what he was doing easier I just changed my farfield to look like his. I learnt alot from it but yeah its not the right far field to use for my case.

Attached is a geometry with a square farfield. This one I am still struggling with, my problems seem to occur at the trailing edge of the blade, I all sorts of bunching up of cells and very unsmooth transitions.

EDIT: See first post for attachments

eromon84,

I think that you must first declare the surface for the fluid material. I hope that you know what I mean, since you declared a fluid part, that is a surface, but it is also occupying the region of what would be the solid material (the blade). I recommend you to place the inlet and outlet of your domain into separate parts, not just in "FF".

Let me know when you fix it.

Regards,
César

cesarcg,

Thank you for that advice, I have made the necessary changes and moved all my attachments to my first post to keep things better organised.

Apologies for these mistakes, I am very new to ICEM and picking up CFD as I go along.

Hi eromon84,

I've been very busy these days but I took a look at your geometry again. I think that you first have to run the build topology command in order to proceed with the blocking. I have not meshed a geometry like yours but I can give you some advices. What I would do is the following,

1. Create a 2D block in the fluid part. I had to modify the *.tin file (attached) since I guess the far field walls have to be separated.
2. Create the quarter o-grid by selecting the appropriated blocks and edges as in figure b. It should look like the figure shown in c.
3. Split the appropriated blocks to associate vertices to points and edges to curves. Note that, in order to do the previous, you have to use index control so you split only the needed blocks.
4. Move the block that correspond to the blade to the corresponding part. The blocking should look like the one shown at d.

After you have this done, you can start with the meshing. From this point on, you could choose either to mesh your geometry using o-grid or c-grid, but you have to check this in the literature.

tin: https://dl.dropbox.com/s/e10omd1yo4ndu3c/Rotor.tin

figures: https://www.dropbox.com/sh/hsgeemufjfn0c1b/Zp11MUjKlG

Hope this can help,
Regards.

Hi cesarcg,

Apologies for the delayed response, have been busy and managed to get round to trying this approach you suggested. The "L" sorta shape created by the quarter O-grid is exactly what I have been trying to make and it has worked out fantastically! thank you so much for the very helpful pictures showing how to do it, very simple and clear :) ; thank you again for all the help you provided.

You're welcome!

César

Shifted periodic tolpology
 

Hi cesarcg,
I want to mesh a 2D propeller blade with shifted periodic topology. I have seen some post where Simon was discussing about Shifted periodic topology. He has shown some example where he has applied Shifted periodic topology to wind turbine. I understood to certain extent but I don't know how to apply shifted periodic topology to my 2D propeller blade.

I have already meshed my geometry using O and C grid topologies. Firstly I created a block and made it periodic. Then I made a two horizontal split (along y-axis), one in the front of the blade and other behind the blade. And I also made two vertical split (along x-axis), one in the suction side and other in the pressure side. Then I inserted a O-block and merged the vertex in the trailing edge and converted into C-block. Then I associated the edges to the curves of the airfoil. The blocking strategy with C-Grid is shown in image 1 and the mesh is shown in the image 2. This blocking strategy works fine. But for highly stagger blade I heard it is better to with
shifted periodic topology.

I understood the advice that you gave to eromon84. As my geometry is periodic and it have as a different periodic boundary, I don't know how to
creat the shifted periodic topology. Actually I am trying to mesh a 3D propeller blade. Before going to 3D mesh. I think it is better if I master the meshing of 2D propeller geometry.

The details of 3D propeller geometry is discussed in the below thread
.

Here is the link for the tin and blocking file
http://www.4shared.com/file/7WEA7lbg/Front_rotor.html
http://www.4shared.com/file/ekJacT6x/Front_rotor.html
http://www.4shared.com/file/KnzTI61V/Front_rotor.html



Please help me. Thanks in advance for your information.