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Old   March 26, 2013, 11:26
Default 2D Aerofoil Mesh in Workbench
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Martyn Davies
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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 -
MessedUpMesh.jpg
Any ideas how I can overcome this problem?
Thanks,

Martyn
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Old   April 1, 2013, 18:36
Default Same issue!
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Arshiya Hoseyni Chime
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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

Last edited by arshiya4; April 1, 2013 at 19:06.
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Old   April 1, 2013, 19:16
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Martyn Davies
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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
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Old   April 1, 2013, 19:29
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Arshiya Hoseyni Chime
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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 View Post
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
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Old   December 25, 2013, 13:18
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Zakir Mirza
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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
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Old   December 25, 2013, 13:20
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Zakir Mirza
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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
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Old   December 25, 2013, 13:37
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Zakir Mirza
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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
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Old   December 25, 2013, 20:12
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No worries problem solved now
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Old   December 31, 2013, 02:25
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shubham jain
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Quote:
Originally Posted by zakir View Post
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.
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Old   January 1, 2014, 11:32
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Zakir Mirza
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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.
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Old   January 1, 2014, 14:26
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shubham jain
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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.
Attached Images
File Type: jpg cfd forum doubt 1.jpg (104.1 KB, 86 views)
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Old   January 2, 2014, 13:44
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Zakir Mirza
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That mesh looks correct too me, are the horizontal lines still not straight?
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Old   January 3, 2014, 04:30
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shubham jain
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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 ??
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Old   January 3, 2014, 19:06
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Zakir Mirza
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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'.
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Old   January 4, 2014, 16:56
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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.
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Old   January 4, 2014, 17:42
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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 View Post
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.
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Old   January 8, 2014, 05:06
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shubham jain
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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.
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Old   January 11, 2014, 01:27
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shubham jain
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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...
Attached Images
File Type: jpg gurney flap forum 2.JPG (31.2 KB, 29 views)
File Type: jpg gurney flap forum 3.JPG (35.2 KB, 30 views)
File Type: jpg gurney flap forum mesh 1.jpg (83.9 KB, 45 views)
File Type: jpg gurney flap forum mesh 2.jpg (104.6 KB, 36 views)
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Old   January 30, 2014, 08:31
Default Ansys mesh vs ICEM mesh
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shubham jain
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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??
Attached Images
File Type: png blocking naca 0012.PNG (16.1 KB, 22 views)
File Type: jpg blocking naca 0012 2.jpg (14.0 KB, 22 views)
File Type: png geometry 1.PNG (36.4 KB, 28 views)
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