Originally Posted by
FlightPathOBN
If Bernoulli's principles explain lift, how does that explain ground effects on final?
I don't see a contradiction there necessarily.
The downwash behind the TE will displace the air beneath/behind the airfoil thereby reducing the area where the mass flow underneath the wing from the LE can 'escape'.
As the area between TE and the ground is (solidly) limited the mass flow and thus speed below the wing will reduce. Reduced speed will increase pressure.
At the same time center of pressure starts to shift backwards. If you go to the extreme i.e. when the TE touches the ground (in case of a WiG) cp from the lower side lift component will be at 50% MAC and static pressure component below the wing will be Rho/2 *v^2 *A.
Normally the static pressure component of the underside of the wing is only Rho/2 (V2^2 -V1^2)*A. (V2 being free stream speed at TE and V1 being free stream speed at LE of the lower side streamlines).
I hope the point I try to make is sufficiiently clear and I didn't explain it in a too fuzzy way
So for me Bernoulli's general principle doesn't even conflict with this effect. At least I have an explanation for my peace of mind
