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-   -   [Workbench] 2D Aerofoil Mesh in Workbench (http://www.cfd-online.com/Forums/ansys-meshing/115226-2d-aerofoil-mesh-workbench.html)

DairyMansVet March 26, 2013 11:26

2D Aerofoil Mesh in Workbench
 
1 Attachment(s)
Hi,

I am having some trouble meshing aerofoils in workbench. I have been using this tutorial - https://confluence.cornell.edu/displ...+Specification
which works fine so long as I use a symmetrical aerofoil.
When I apply the same procedure from the tutorial to an non-symmetrical aerofoil my mesh looks like this -
Attachment 20165
Any ideas how I can overcome this problem?
Thanks,

Martyn

arshiya4 April 1, 2013 18:36

Same issue!
 
Martyn,

Make sure you pick 5 faces and not 4. Since your airfoil is not symmetric, its curved section on the bottom makes the 5th face with the horizontal axis. Once you pick the 5th face, you will be able to mesh using the rest of the tutorial.

Hope this helps

Arshiya

DairyMansVet April 1, 2013 19:16

Thanks Arshiya,

I haven't tried your method yet but if you're looking for an alternative method I found that ICEM can be accessed from workbench as shown in this tutorial, https://www.youtube.com/watch?v=ImnX...Vnx5kw&index=7

arshiya4 April 1, 2013 19:29

I don't think we have access to ICEM in my lab! but That's good to know! Thanks for sharing :)

Quote:

Originally Posted by DairyMansVet (Post 417713)
Thanks Arshiya,

I haven't tried your method yet but if you're looking for an alternative method I found that ICEM can be accessed from workbench as shown in this tutorial, https://www.youtube.com/watch?v=ImnX...Vnx5kw&index=7


zakir December 25, 2013 13:18

Hi there, I'm having the same problem as you apart from the lines on the right side of my mesh aren't straight, they are angled. Do you know how I could fix this? Been stuck on this for a while so any help would be much appreciated :)

zakir December 25, 2013 13:20

Hi Martyn, I'm having a similar problem. The lines on the right side of my mesh are not straight, they are tilted. Do you know how I could fix this? Any help would be much appreciated :)

zakir December 25, 2013 13:37

Hi there, I'm having the same problem as you apart from the lines on the right side of my mesh aren't straight, they are angled. Do you know how I could fix this? Been stuck on this for a while so any help would be much appreciated :)

zakir December 25, 2013 20:12

No worries problem solved now :)

shubham jain December 31, 2013 02:25

Quote:

Originally Posted by zakir (Post 467672)
No worries problem solved now :)


i have this similar problem with symmetric airfoil naca0012. Lines on right side on mesh are not straight. Please somebody help me out.

zakir January 1, 2014 11:32

Have you used edge sizing to control your mesh in Ansys mesher? My problem was solved by changing which edges were biased, you might want to try that.

shubham jain January 1, 2014 14:26

1 Attachment(s)
I have already used edge sizing as 50 for both right and left edges as shown with bias factor of 50. Even then the horizontal lines are not straight.
If I change its behavior to "hard", ansys fails to mesh the geometry.

I also tried to change the edge sizing factor as well as bias factor, but no good result appeared.
I have attached the the picture of my mesh.

Please help.

zakir January 2, 2014 13:44

That mesh looks correct too me, are the horizontal lines still not straight?

shubham jain January 3, 2014 04:30

The horizontal lines on right half of mesh are not straight. They are diverging especially near the trailing edge of airfoil (where the mesh is very dense). I have already marked some diverging points with the circle. you can take a closer look at the pic.

Also, there is one more doubt to me. The naca 0012 airfoil which i have imported in geometry is having a blunt trailing edge.
I have the coordinate .txt file of airfoil and i imported it in geometry via 3D curve. What can I do to make its trailing edge sharp ??

zakir January 3, 2014 19:06

Sorry I don't know what else you could try to straighten out your mesh. My problem was solved by changing the edge sizing on the edges.

As for the blunt trailing edge, which airfoil generator did you use? There might be an option there that modifies the airfoil such that it has a sharp trailing edge. What are the coordinates for the trailing edge of your airfoil? You could also try changing these coordinates to be '1,0,0'.

shubham jain January 4, 2014 16:56

i used this airfoil generator using 100 point
http://www.ppart.de/aerodynamics/profiles/NACA4.html

Default coordinates produce open curves. I just made the curve close which made the trailing edge blunt consulting this tutorial.
http://www.mne.psu.edu/cimbala/Learn...al_Airfoil.pdf
POINT NUMBER 16 on page 2.

1.) kindly tell me that when computational research is done on airfoils, do they use blunt trailing edge airfoil...or sharp trailing edge airfoil??

2.) I am validating NACA 0012 for just my start up, then i will shift to some more complex geometries. Do i need to use sharp trailing edge airfoils or should i just continue with blunt edge airfoils.

3.) Blunt edge airfoils give me very near Cl (lift coefficient values) but a very high Cd (drag coefficient) values for NACA 0012. Is that due to blunt trailing edge or because of some other reason?

I used k-epsilon RNG model at 3e6 Reynolds no. what should i do to bring the drag to actual limits.

taxalian January 4, 2014 17:42

Hi,

I think its better asking such queries related to turbulence model and predicting the aerodynamic coefficients in the Anysy Fluent/CFX sub-forums.
Anyways, i would recommend computing the blunt trailing edge airfoil obviously more close to the actual physical geometry.
If you get almost the same CL, then in order to predict the CD value you need to confirm the Yplus value of your grid i.e Yplus should be less than 1, if you are using the Enhanced wall treatment option, or other wise it shoud be 30 -150 in case of wall function approach.
Alternate approach could be to try first the Spalart-Allmaras turbulence model with your existing mesh. This model is quite cost-effective and takes less computational resources (also predicts the aerodynamics coefficient very well).

Quote:

Originally Posted by shubham jain (Post 468606)
i used this airfoil generator using 100 point
http://www.ppart.de/aerodynamics/profiles/NACA4.html

Default coordinates produce open curves. I just made the curve close which made the trailing edge blunt consulting this tutorial.
http://www.mne.psu.edu/cimbala/Learn...al_Airfoil.pdf
POINT NUMBER 16 on page 2.

1.) kindly tell me that when computational research is done on airfoils, do they use blunt trailing edge airfoil...or sharp trailing edge airfoil??

2.) I am validating NACA 0012 for just my start up, then i will shift to some more complex geometries. Do i need to use sharp trailing edge airfoils or should i just continue with blunt edge airfoils.

3.) Blunt edge airfoils give me very near Cl (lift coefficient values) but a very high Cd (drag coefficient) values for NACA 0012. Is that due to blunt trailing edge or because of some other reason?

I used k-epsilon RNG model at 3e6 Reynolds no. what should i do to bring the drag to actual limits.


shubham jain January 8, 2014 05:06

i tried to use k-epsilon RNG model and gave me very good results.

Now, I am trying to mesh the NACA 0012 with GURNEY FLAP at trailing edge. The mesh in area with gurney flap is not at all clean. Can somebody please give some advise on how to mesh such unsymmetrical geometries.

For an airfoil with a Gurney flap 2 counter rotating vortices are set up behind the airfoil and one more vortex is set up between the flap and the suction side. For resolving these three vortices a very fine mesh is required.

shubham jain January 11, 2014 01:27

4 Attachment(s)
I am trying to mesh the NACA 0012 with GURNEY FLAP at trailing edge in ansys mesher. The mesh in area with gurney flap is very bad. Can somebody please give some advise on how to mesh such unsymmetrical geometries.

Mapped Face Meshing is not working. I have tried both triangular and quadrilateral elements. I have used edge sizing as well as bias factor.

For an airfoil with a Gurney flap 2 counter rotating vortices are set up behind the airfoil and one more vortex is set up between the flap and the suction side. For resolving these three vortices a very fine mesh is required.

Please Help...

shubham jain January 30, 2014 08:31

Ansys mesh vs ICEM mesh
 
3 Attachment(s)
I meshed 2D naca 0012 in ansys mesher with 2 lakh nodes and solved it in fluent with k-e RNG. (Photo of face splitting is attached)I am getting max CL value of 1.47 which is very near to experimental value of 1.5

But now i meshed 2D naca 0012 in ICEM and again solved it with RNG.
With icem mesh, I am getting max CL of 1.35.
I blocked it same way as in famous "ICEM CFD hexa 2d airfoil meshing" tutorial available on youtube. (2 Photos of blocking are attached).
I tried grid upto 4 lakh nodes, also with and without boundary layer dense mesh. But the max CL doesnot go above 1.35

Does anybody have some advice??


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