Re: a couple of points on flight

[brian whatcott <inet@INTELLISYS.NET>]

At 07:36 1/16/99 -0600, you wrote:
[Bill]
> ...  If we look at the entire pattern of air surrounding the
> airfoil out to a fair distance, it appears that the momentum change in the
> air is first upwards in the upstream section, then downwards at the
> airfoil, then upwards again in the downstream section, for a net change of
> zero.
> **********************************
[Jack]
>        It's a quantitative question that depends upon the "angle of attack"
> of the airfoil.  If the angle is sufficient to give lift, then the downstream
> deflection is greater than the upstream deflection, giving a net lift.  This
> is apparently illustrated in the Anderson-Eberhart paper.
>                                Regards,
>                                        Jack

What Jack said....with the proviso, the angle of attack for
effective lift can include the angle zero for asymmetric sections.
Following along with the earlier discussion I received the uncomfortable
 image of a moving footprint of air in the shape of the moving wing
finally pressing upon the ground.
 I am more comfortable with an image of molecules of the downwards
air parcel sharing their largesse with others, in the manner of a
marble running down a (Dalton's??) pinboard.
Brian
brian whatcott <inet@intellisys.net>
Altus OK