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-   -   simulating an airfoil using a moving boundary (http://www.cfd-online.com/Forums/fluent/43470-simulating-airfoil-using-moving-boundary.html)

Alejandro January 25, 2007 03:32

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


rams January 25, 2007 03:43

Re: simulating an airfoil using a moving boundary
 
From my experience i understrand that if u try to model an object moving in a stationary fluid with fluent it gives worng results. fluent calculates the shear forces on the surface but it won't give u the force normal to the surface correctly.

Now in your case, there would obviosly be getting wrong drag & lift forces, as u'r modellin the other way.

i would suggest u go the conventional way of modelling.

but still if u could find a way out to do the otherway, do let me know,

Thanks & Regards, Rams

gholam February 10, 2007 00:46

Re: simulating an airfoil using a moving boundary
 
I dont't know too,but you should know the conditions of fluid around the airfoil when the airfoil is moving would completely be different from the time you have put the airfoil stationary and the fluid is moving.


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