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Old   June 28, 2004, 11:28
Default Please help
  #1
Diego
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Hi everyone! I have created an airfoil out of vertices but I also want to rotate it in order to investigate different angles of attack. Is there any chance I can do that without defining again new vertices. Please help me because I have a deadline soon. Thanx a lot!!
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Old   June 28, 2004, 11:35
Default Re: Please help
  #2
Jörn Beilke
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csys 2

vset all

*set alfa 10

vgen 2 0 vset ,,, 0 alfa 0

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Old   June 28, 2004, 11:54
Default Re: Please help
  #3
Diego
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Thank you!! But by what angle rotates the vertises?
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Old   June 28, 2004, 12:19
Default Re: Please help
  #4
Diego
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It works fine!! but can i rotate only some of the vertices and not all? How can I select only the vertices of the airfoil and not all of the computational domain. Thanx in advance
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Old   June 28, 2004, 12:43
Default Re: Please help
  #5
steve
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You can rotate any set of vertices you want. Just use the vset command to pick the vertices on the airfoil instead of vset all.
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Old   June 28, 2004, 12:52
Default Re: Please help
  #6
Diego
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Steve I used the vset command but it won't select the desired vertices. Could you please be more specific? Thanx again!!
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Old   June 28, 2004, 13:43
Default Re: Please help
  #7
4xF
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If you do not have a simulation of an airfoil placed in a channel (i.e. free-stream), it is also the same to change the inflow direction (which is basically the same as rotating the whole computational domain with a fixed direction for the inflow velocity).
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Old   June 28, 2004, 16:22
Default Re: Please help
  #8
Panos
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What I actually have is a free stream air and an airfoil. Is there a way to rotate only the vertices of the airfoil in orderto investigate the different angles of attack? Thanks a lot
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Old   June 28, 2004, 18:24
Default Re: Please help
  #9
Jörn Beilke
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Sorry for that, but it seems that you don't knonw what you are doing at all.

If you have a mesh and just rotate the vertices on the surface of the airfoil you cells are distorted.

Iy you need an example of a mesh, which can be rotated by any angle with all vertices look at:

http://www.beilke-cfd.de/naca.mdl.gz

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Old   June 29, 2004, 04:53
Default Re: Please help
  #10
Diego
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I think it's you that you did not understand. I don't have a mesh yet. Just the vertices. And I want to rotate the vertices of the airfoil only!! I don't think that would create distorted cells.
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Old   June 29, 2004, 07:03
Default Re: Please help
  #11
4xF
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You have two possibilities: a) do as Jörn says (see response from Monday) and do not think it is stupid, Jörn is probably one of the most experienced posters in this forum... b) do not rotate the vertices at all but change instead the orientation of the inlet velocity (which defines the angle of attack relatively to the profile chord).
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Old   June 29, 2004, 08:02
Default Re: Please help
  #12
Diego
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How do I rotate the inlet velocity? Do i have to introduce both x and y components of velocity? Is it also neseccary to change also the boundaries? Thanx a lot
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Old   June 29, 2004, 08:02
Default Re: Please help
  #13
Jörn Beilke
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what about a:

vset all

vplo

vset subs zone

There are lots of possibilities to select vertices using the vset command.

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Old   June 30, 2004, 02:41
Default Re: Please help
  #14
Matej
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Diego,

I'm starting to be taken by this thread.

Could you tell me, how you gonna create the cells out from the cloud of your vertices, or was this supposed to be your next question?

Not to tease, but aslo help.... I think, you might find the manual pages extremely helpfull. I'd suggest the part refering to local coordinate system (might help to your inlet vel. spec.). There is also nice part (with pictures) describing tho operation with vertices.

To decompose the vector, please refer to any undergraduate math or physics books found in a library, or http://www.physics.uoguelph.ca/tutor...s/vectors.html

matej

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Old   June 30, 2004, 08:01
Default Re: Please help
  #15
4xF
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If your foil is orientated, say, in X-direction and Z is pointing upwards, your flight speed in 100m/s, you will impose at the boundary: U=100,V=W=0. If you have an angle of attack of 5 degrees, then the inlet velocity becomes: U=100*cos(5),V=0,W=100*sin(5) Look how easy it is!
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