2D Airfoil Analysis using Flotran

[TclS]

Can anyone tell me how to get realistic drag values using Flotran to analysze an airfoil. When I do the surface integral on the airfoil, the lift I am getting seems to be very accurate but the drag has negative values.....any sloutions???

 

Have you considered using DesignFOIL or SNACK for your 2D analysis? It's right on the money and works amazingly fast. Nice interface too. They can be gotten from

http://www.dreesecode.com

 

[radomir]

Al (Einstein) tought us that everything depends on reference coordinate system. So if my powerplants produce positive (thrust) forces the drag has to be negative. Therefore you shouldn't bother with the sign if absolute value (amount) of the drag seemed all right.

 

[gkoz]

Hi
Check your UCS once again.
The X axis has to be parallel to the cord and Y perpendicular to it, facing upwards. It is a good idea to place the airfoil so that the leading edge has (0,0,0) coordinates. This way the X axis is right on the cord.
Also, are you using the intsrf,pres command for the integration of pressure along the airfoils surface (for the lift & drag calculations), or the intsrf,tauw command of the integration of shear stress (also used for the drag calculations in viscous flow)?
I hope this will help
gkoz