Expert: Mark Janus - 1/22/2008

Question
Dear Mark, I am interested in Savonius rotor, which uses
the different aerodynamical shape factor for concave and convex side of cutted half-cylinder for the change of wind
energy to energy of move. But i cannot find the noumbers of these two factors. Can you help me ? Michal

Answer
I'm assuming you mean the drag coefficients for an open cup facing the flow as compared to that facing away from the flow....  from Horner (Fluid Dynamic Drag)

for facing away the Cd is 0.38
for facing the flow Cd is 1.42

Hope this is what you are looking for and helps,
mj