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-   -   [ANSYS Meshing] modeling an airfoil tip in fluent (http://www.cfd-online.com/Forums/ansys-meshing/98908-modeling-airfoil-tip-fluent.html)

mikko March 21, 2012 16:23

modeling an airfoil tip in fluent
 
Hi, I am and undergrad ME student with essentially zero experience using ANSYS 13. I am trying to model 3D external airflow over the tip of an extruded airfoil to obtain drag forces associated with the airflow and also explore the vortexes generated by the high and low pressure sides of the airfoil. I need guidance as to selecting the proper mesh. I tried modeling the airfoil as a solid and then creating a fluid box enclosure around it but I could not mesh the airfoil inside the volume. I then tried making the solid airfoil a frozen boolean inside the enclosure and I was able to mesh. Is this a good approach? Should I be using a dynamic or sliding mesh instead? Any guidance would be greatly appreciated!

rikio March 21, 2012 19:27

It is not needed to mesh the airfoil itself, just the fluid domain around it.
Dynamic mesh is not recommended for a new user, and also no need for your study. What you need to pay attention is the mesh size around the body,and also the boundary layers.
Airfoil is a classic case for CFD study, you can find many materials by google.

diamondx March 21, 2012 20:03

this video shows how to extract a fluid domain in ansys 13

http://www.youtube.com/watch?v=Bb8Tsd9eGe4

mikko March 21, 2012 20:29

3 Attachment(s)
Thanks for your prompt response, rikio. The mesh i have now created is what you described--a volume mesh of a block of air with a airfoil shaped "hole" sticking into the volume from one side. I have attached some pictures of the current mesh. I used mapped face meshes on all faces (including the volume faces on the airfoil) with edge sizing but I cannot get a structured grid on the face with the airfoil. Any tips on controlling the mesh around the body and mapping the boundary layer? I've been trying to adjust the mesh using biasing on the edge sizing, but i'm not having much luck. I am using the Ansys 13 mesher but i also have access to gambit. Would the mesh be easier to construct in gambit? The ansys mesher seems very automatic and I am having trouble manipulating it to do exactly what I want. Thanks again.

Attachment 12044

Attachment 12045

Attachment 12046

rikio March 22, 2012 03:29

I do not know Gambit, but ICEM (a oreoricessor module of ANSYS) works well, and you can take whole control on the mesh.
ANSYS Mesher has some basic function to take the control, but may not that exactly as you want. I use it very few, so I can not tell how to work it out thru. ANSYS Mesher. But it would be much easier for me to mesh the model within ICEM :).

tauqirnawaz March 22, 2012 03:50

Quote:

Originally Posted by mikko (Post 350773)
Thanks for your prompt response, rikio. The mesh i have now created is what you described--a volume mesh of a block of air with a airfoil shaped "hole" sticking into the volume from one side. I have attached some pictures of the current mesh. I used mapped face meshes on all faces (including the volume faces on the airfoil) with edge sizing but I cannot get a structured grid on the face with the airfoil. Any tips on controlling the mesh around the body and mapping the boundary layer? I've been trying to adjust the mesh using biasing on the edge sizing, but i'm not having much luck. I am using the Ansys 13 mesher but i also have access to gambit. Would the mesh be easier to construct in gambit? The ansys mesher seems very automatic and I am having trouble manipulating it to do exactly what I want. Thanks again.

I think what you have said in red is a myth, AM gives you a lot of control, just need to learn it. I must also say that ANSYS has not been able to produce some good quality video tutorials for students. Any ways you can use sweep method to produce good quality mesh on your geometry.
1. Specify manual source and target.
2. Specify face inflation on airfoil
3. Select edge sizing, use bias where required.
4. It seems from the pictures that you have used Curvature and Proximity method, please switch it to just CURVATURE if you do not use sweep.

mikko March 22, 2012 15:56

Thank you for your replies folks. Tauqirnawaz, I will try your suggestions when i get back in the lab tonight. Thanks again.

mikko March 24, 2012 20:13

Tauqirnawaz, Could you suggest more details on how I could use the sweep? I have redrawn the geometry to try different mesh methods, but the mesh control does not show any sweepable bodies. I tried specifying the inlet as the source and the outlet as the target as well as 50 division edge sizing on the airfoil. I get error messages stating that the body cannot be swept because the side face with the airfoil "hole" cannot be map meshed. Please let me know your thoughts.


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