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-   -   Proper output of angle of attack in CFX post (http://www.cfd-online.com/Forums/cfx/23196-proper-output-angle-attack-cfx-post.html)

Kevin October 18, 2006 09:21

Proper output of angle of attack in CFX post
 
The problem I am having with CFX is as follows:

I have a simulation where there is a stationary domain and a rotational domain. The stationary domain is rectangular and contains the rotational domain which is circular (I am performing a 2D analysis so the thickness of the domains is very small in relation to the other dimensions). A solid body exists within the rotational domain. Flow enters the stationary domain perpendicular to the axis of rotation of the rotational domain. I have set the angular velocity of the rotational domain to 0 in order to perform some steady state tests at various angles of attack. As such, I have also set the interface condition between the two domains to the frozen rotor condition. However, when I apply an offset condition to the rotational domain (to simulate different values of alpha) the Post output does not reflect this change. It appears that the program rotates the rotational domain to the desired angle, solves the flow, and then rotates the rotational domain back to its original position when outputting the results in the Post processor. This creates a problem for me since there are now flow discontinuities within the solution at the interface of the two domains. I have attempted to add an expert parameter to set "rotational offset for post = t" as well as "rfr domain rotation = t" but this has proved to be ineffective. I have also discovered that I can create an instance of the rotational domain within the post processor but that this merely copies the rotational domain at the specified angle, leaving the original domain as it was. I am also concerned that the mesh is not being rotated along with the solid body, how can i be sure that this is happening? Any help that you can provide is appreciated.


Robin October 18, 2006 10:42

Re: Proper output of angle of attack in CFX post
 
When you specify a rotation at the Frozen Rotor interface (or even a transient rotor stator interface), the solver simply shifts the intersection at the GGI, the mesh is not moved. The expert parameter you set only works for the transient rotor stator option.

If you want to actually move your grid, perform a grid transformation in Pre instead. The GGI method is to allow you to easily clock the offset on the fly by editing the CCl.

Regards, Robin

Kevin October 18, 2006 11:30

Re: Proper output of angle of attack in CFX post
 
So for a steady state test how do I visualize the rotational domain in its rotated state in the post processor?

Kevin

Robin October 18, 2006 12:18

Re: Proper output of angle of attack in CFX post
 
If you rotate the grid in Pre, it will be where you rotated it to. If you set the offset parameter at the interface, it will only do the transformation at the interface (think of it as a virtual offset) and will not rotate your grid.

If you want to fix it in Post, double click on the rotating domain object in Post and set the transformation equal to your rotational offset.

Regards, Robin


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