Learning Forum

[Iwashita]

I am investigating the aerodynamic force of a flat plate.

The lift was the same as the theoretical value, but the pitching moment was twice the theoretical value.

The analysis conditions are as follows. This is 2D model.

General-Pressure Based, Time: transient

Viscous model: k-omega SST

Fluid: Air

plate:B=150mm,D=1mm (center:X=0, Y=0)

U=1.5~6m/sec, attack angle:-16deg~+16deg

I also performed an analysis in which the plate was forcibly vibrated using UDF, to reproduce theodorsen function, but the tendency for the pitching moment to double was the same.

I know Cm=M/(1/2*ρU^2*B^2) Please help me.

[aitor.amatriain]

You are obtaining the moment at (0,0), while it should be at (-B/4,0) (aerodynamic center)

[Iwashita]

>Aitor
Thank you for your answer.
But it is not my target, because this analysis is not for airplane but for bridge deck.
We should obtain the moment of center of deck. By the way, in case of moment at (-B/4,0), it was less than 1/4 of the theoretical value.
I'm sorry for the lack of my explanation.

[Iwashita]

I resolved this problem.
The reason why moment is incorrrect is following picture.
Red line: inlet
Blue line: outlet
Black line: pressure far field(wall, shear stress=0)
When the inlet flow includes attack angle, Left side causes wrong result, and Right side can get correct result.

[Rob]

Thanks for sharing. Mixing far field with any other boundary tends to cause problems. Setting the whole outer boundary as farfield with the correct vector would have worked too.

[Iwashita]

Here is my result. (Exp: experiment, Ana: analysis)
I used inlet boundary condition and adjusted magnitude and direction.
Thank you for your information Mr. Rob.

[Farrukh Malik]

Great work ! the agreement in exp and calculated values is jsut perfect. I would love to know more about the settings you used and recommend. If feasible, i would love a quick conversation on achieving that graph and then repeat if for multiple locations along the length. I have same name on linked In if you can kindly connect I would love to create a lesson for this. 

Thank you so much for sharing this. 

regards,

can reach me here or on following search.

farrukh arslan nasr linkedin