So on the top is the view from the top, below it is the side view.
If the angle is zero it is similar to simple flat airfoil. So I calculated the Cl and Cd in xfoil and got the Cl = 0 and Cd = 0.02398 :
It is for 30 cm length in 5 m/s stream
Cl will be directed to the viewer, perpendicular to the panel.
Was it a correct application of xfoil ?
How to approximate the Cd also for non-zero angles like 1 ~ 15 ?
Will it be "almost the same" so the difference can be ignored ?
At non zero angle the plane of the plate will continue to be parallel to the wind but its geometry becomes more complex, similar to swept wing.

