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-   -   Dynamic moving reference frame (http://www.cfd-online.com/Forums/fluent/44565-dynamic-moving-reference-frame.html)

Peter Wilkins May 1, 2007 08:23

Dynamic moving reference frame
 
Hi all,

I'm modelling a rotating wing using a moving reference frame. I can do this easily for a constant speed rotation, but is there a way of using the same technique for an accelerating wing? I can't see a way to use a UDF to define the rotational speed of my MRF.

Thanks,

Peter

Hussein May 1, 2007 09:11

Re: Dynamic moving reference frame
 
Hello , I am also modeling a rotating wing using a moving reference frame , f u want we can be in contact in case some of us need help ? if yes , let me know

Peter Wilkins May 1, 2007 09:15

Re: Dynamic moving reference frame
 
Sure. I am able to model a wing rotating at constant angular velocity but I want to model a wing which is rotating at an increasing rate. Any ideas?

Peter

Hussein May 1, 2007 09:37

Re: Dynamic moving reference frame
 
I trhink in the User defined functions UDF is the best way , frankly i am not so good in UDF , However the main idea behind the function should be , increasing at a constant rate or increasing arbitrarily , personaaly i prefer workin on c . I did my work on a constant speed rotation as a first step , but i didn it on a "Bad Wing" . now i have to do it again with a NACA 0015 . is that good ? also , i had an idea about drawing the Wing as a 3d dimensions , i thought that the best method to draw it is to , import the vertex of a 2d airfoil , then tryin to convert this 2d into 3d through the addition of many 2 airfoils then joinnig them .

I am not sure about drawing a naca 0015 as a 3dimensin since i worked on a arbitrarily 3 dimension wing .

any idea of drawing ?


Phil May 2, 2007 07:10

Re: Dynamic moving reference frame
 
But are you using the unsteady solver as you will need to with an accelerating component? Sliding meshes are the best way.

- Unsure whether you need a UDF to do this, but you could simply SET THE ROTATIONAL SPEED TO INCREASE WITH EACH TIME STEP. I have no real experience in this specific case but I would have thought this was the only way to do it.

Peter Wilkins May 3, 2007 04:39

Re: Dynamic moving reference frame
 
Phil,

Yes I am using an unsteady solver. I could manually increase the rotational speed with each time step but I wanted to write a UDF so that I could do it more efficiently.

Peter

Phil May 3, 2007 06:12

Re: Dynamic moving reference frame
 
how is your experience with UDF's?

there should be a define macro to change boundary conditions at the end of each time step. Use the examples as a reference. If you already know this then sorry I can't help you further unless you're doing combustion.


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