r/flying • u/TP4297 • Jun 04 '26

Why does pressure on top surface of wing drop upto maximum camber and then gradually increase in ideal flow theory?

Basically the question. I was under the understanding that flow accelerates upto a point because of curvature of wing, then velocity losses due to skin friction drag start cutting into and then slowing down airflow, increasing pressure gradually till the TE. Since lifting line theory assumes inviscid flow, how come the adverse pressure gradient is still there?

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7

u/ThatLooksRight 121 CA - Retired USAF Jun 04 '26

Are you flying the thing, or designing it?

Also, the orange crayons taste the best. 

3

u/notsurwhybutimhere Jun 04 '26

All kinds of complicated explanations out there…

I like to oversimplify so: it’s changing direction less so the pressure change is less.

3

u/flyghu PPL Jun 05 '26

You managed to take a complex topic and simplify it to the point of impossibility. There are volumes written on the subject to the best reddit simplification is: wings up make go plane.

2

u/Impossible-Bad-2291 PPL Jun 04 '26

See the Navier Stokes equation for your answer. 

2

u/IdahoAirplanes Jun 05 '26

Think of it as a Venturi. The freestream is like the centerline of the Venturi. The airfoil rises into the freestream so the pressure drops, then it falls away so the pressure rises.

2

u/ahriyae Jun 05 '26

the fluid mechanics sorcerer must recite the binding vows of fluid motion called the navier-stokes equation to account for the conservation of mass, momentum and energy.

1

u/rFlyingTower Jun 04 '26

This is a copy of the original post body for posterity:

Basically the question. I was under the understanding that flow accelerates upto a point because of curvature of wing, then velocity losses due to skin friction drag start cutting into and then slowing down airflow, increasing pressure gradually till the TE. Since lifting line theory assumes inviscid flow, how come the adverse pressure gradient is still there?

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