Can Coanda effect be created by sucking air into the wing or is it only for exiting air?

Also can coanda effect give lift if there is no passing airflow for the exiting airflow to "Adhere to"? (Ie. in the hover with no downwash)

All budding aerodynamicists have your say..

Just to be clear, the Coanda effect as I understand it is that a jet of air will stick to a spherical trailing edge so that the flow on the upper surface and lower surface meet somewhere on the lower half of the sphere, thus increasing lift. Unless something is wrong with the way I understand the effect, I think it only applies to the air exiting the surface.

Also, Coanda probably won't give any lift in a hover situation, since there is no foward velocity, so no airflow over the lower surface, hence no difference in pressure and no lift. However, since the air exiting the surface will be angled downward it will provide a little lift that way.

No and sort of yes respectively.

To the first, you can keep flow attached over a wing at radical angles of attack using upper-surface suction - acheiveing CLs in excess of 4.5, but this isn't Coanda effect.

To the second - there can't be hover without downwash. Sorry, but good ol' Isaac prevents this. However, if you have an aircraft with jet engines on the top of the wing and a reall big honkin' flap in the back cranked down to 60 degrees or so, the Coanda effect will be active even with zero flight speed, since the jet is still blowing over the curved top. However, I don't think you could ever achieve hover with a system like this. Many russian STOL transports used it, though. Big plane go up FAST!

Coanda states the adherence of airflow to a curved surface.
Without airflow there is no Coanda and subsequently no Newtonian reacting force which is created by changing the direction of a moving mass (air in this case).
In the hover, Coanda explains the downwash of the propeller, and the resulting lift, now called thrust.
The downwash flows over the control surfaces, where again Coanda explains the resulting control forces.
No downwash, no hover. To see Coanda in action, shut down the engine in the hover, and see what happens. Do this high enough, so true airspeed by plane motion can take over before you crash.