ground effect

Richard
Posts: 114
Joined: Sun Sep 11, 2016 5:57 pm

Re: ground effect

Postby Richard » Mon Jul 13, 2020 8:12 pm

bomber wrote:
Richard wrote:A flat plate normalized by its surface area would be around 1.2; however the Cd is for the entire aircraft in which case using the wing surface area to normalize drag force is going to result in a higher value than for the wings alone.


And that''s the point I'm making.... you can't apply the ground effect to the whole plane Cd.... just to Cdi


I understand your point; but as always with aerodynamics it depends on how it was originally measured / calculated; the normalization process could use anything - it is just by convention that each axes has a standard normalization.

CDi (induced drag) is the drag that is a result of the airflow; compared to CDo (form drag) which is the drag due to the shape; sometimes these are combined into a single Cd.

bomber
Posts: 1379
Joined: Mon Nov 30, 2015 3:40 pm

Re: ground effect

Postby bomber » Wed Jul 15, 2020 8:54 am

OK so what we know about ground effect is that it effects 3 properties only

1) Produces a reflected force perpendicular to the ground
2) Reduces the downwash angle coming off the training edge of the wing effectively increasing the angle of attack on the h-stab
3) Reduces induced drag from the wings and h-stab by interrupting the vortex flow along these airfoils.
"If anyone ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me - it's all balls" - R J Mitchell


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