Hi Everybody;

I'm testing the effect of vortex generators on stall angle of a NACA 6313 aerofoil in low-speed wind tunnel.
Based on my understanding VGs are used to delay the separation and thus delay the stall.
however in my test they accelerate the stall.
my plain aerofoil stalled at around 16 degrees, however when placing the aerofoil on different chord positions and different spaces apart, in ALL situation my aerofoil stalled earlier.
I'm trying to find a reason behind it, or any test result from any journal/book that could explain my situation.

Any help is highly appreciated.

Thanks