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-   -   Simulating an airfoil using a moving boundary (http://www.cfd-online.com/Forums/cfx/23567-simulating-airfoil-using-moving-boundary.html)

 Alejandro January 25, 2007 03:31

Simulating an airfoil using a moving boundary

Hi to all! The conventional procedure to compute the aerodynamic coefficients for an airfoil is to define the airfoil as a solid stationary wall, and define an incoming velocity at different angles of attack in the far field. I have been trying something a bit different, leave the conditions in the far field with 0 m/s, and instead, define the airfoil as a moving solid boundary, using a velocity in the opposite direction. I was hoping to find, instead of the always "normal" streamlines along the profile, the real flow fiel of an airfoil as it moves through a stationary fluid. Although the relative "velocity" between fluid and body remains the same, the values for lift and drag are completely different (and obviously false for the case of the moving boundary).

I´m trying this as a preliminary simulation of the interaction of two bodies with a relative velocity, so I wanted to leave one of them stationary, and give the other one a relative wall velocity, but if it doesn´t even work for the airfoil, then I must be doing something wrong :)

Does anybody have any idea to this? Thank you!

Best regards,

Alejandro

 Glenn Horrocks January 25, 2007 18:07

Re: Simulating an airfoil using a moving boundary

Hi,

I don't see what you are trying to do. Are you trying to model an airfoil in an infinite field by keeping the fluid stationary and moving the airfoil or are you trying to model the interaction of two bodies with a relative velocity in proximity?

Glenn Horrocks

 Alejandro January 25, 2007 18:13

Re: Simulating an airfoil using a moving boundary

Hi Glenn,

my goal is to simulate the interaction between two bodies, which move each with a different velocity, but before I try a sliding mesh algorithm, I want to try a "sationary" mesh procedure, using wall boundaries with cartesian velocity components. As a "pre-simulation" I tried the case of a simple airfoil, within a stationary fluid, and giving cartesian velocity components to the wall boundary of the profile, to see if I got the same values for lift and drag as in the case of stationary airfoil and incoming wind. But I didn't get the same values, just some distortion at the boundary layer. I was hoping of getting a kind of "circulation" around the airfoil. So now that the airfoil didn't work, I guess I can't use this procedure for the interaction of the two bodies which I want to simulate.

 Glenn Horrocks January 27, 2007 06:37

Re: Simulating an airfoil using a moving boundary

Hi,

I can't see how your "stationary" mesh procedure as you call it will give you anything useful. I would recommend you go straight to modelling the two bodies with relative mesh motion, either using a sliding grid or a deformable mesh depending on what type of relative velocity they have.

Glenn Horrocks

 mark January 27, 2007 13:03

Re: Simulating an airfoil using a moving boundary

i would like to know is it possible to transfer a 3-d aerofoil geometry from ansys into workbench. What file type will workbench accept?

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