Do stalled wings or diffusers provide more drag to brake?

[Tommy Cookers]

Stalled wings ...... (flow separation) cause more drag.

a year ago I would have said so, and did say so in some post
however an F1 ('2 element' aka slotted flap) rear wing at its highest AoA imparts a 90deg velocity component to the ambient air
so producing the maximum possible lift coefficient from a wing of the maximum permitted dimensional 'box'
changing the in-slot condition causes seperation behind the flap and a large reduction in the imparted velocity component
both lift coefficient and drag coefficient are reduced
so in F1 such stalling causes less drag, not more drag

the definition of stalling angle is the AoA beyond which the lift coefficient falls
in aviation the drag coefficient (of an aerofoil) always increases with stall/seperation
but slotted flap behaviour beyond stalling is undefined
because flaps are not intended for or designed for stalling and its consequences regarding speed/dynamic pressure

@ gfa
in the quote you chose to construct you seem to be misrepresenting what I said (as above)

the shape of the F1 rear wing array shows from the 90 deg direction of attached flow that the work done on the air is maximal
so that when the slot condition that enables this is removed the resulting wake convergence shows less work done on the air
ie less drag

so if we stretch as far as describing the second case as stall (I don't think that is useful), then yes, this 'stalling' reduces drag
I don't think you can (as you seem to) read across from this slotted flap case anything relating to the (single element) data you show

the useful result of these responses to the OP is that horse has shown that if the 1968 rules on wings hadn't led us where they did
how wings (ie single element) of thick symmetrical aerofoil combined with suitable variation of incidence could have given
.... the result that you were looking for
though they would of course produce less DF than cambered aerofoil sections (as used in actual F1 etc wings)

[hollus]

both lift coefficient and drag coefficient are reduced
so in F1 such stalling causes less drag, not more drag

Really?
Doesn't stall actually increases drag?

http://www.insideracingtechnology.com/R ... loverd.gif

If your mental model is a (airplane) wing designed with minimal drag in mind (so that the very high speeds attained help with the lift part), with small angles of attack and designed to deviate the air a few degrees from its initially trajectory, then yes, stall will increase drag. Partly because low drag at 800Km/h was the initial design consideration.
But F1 cars are not airplanes, are not designed as such and should not be considered as such.
And F1 car wing is designed to produce downforce at 200Km/h, optimized for such intentionally paying the price of a very high drag, has angles of attack of 20-60 degrees and is supposed to deviate the incoming air by something like 30-45 degrees. So what works on an airplane doesn't necessarily apply here.
As an analogy, road cars and competition bicycles are both designed with similar objectives of reducing weight and minimizing drag. Do you think the same design and performance rules apply for both cases?

[trinidefender]

both lift coefficient and drag coefficient are reduced
so in F1 such stalling causes less drag, not more drag

Really?
Doesn't stall actually increases drag?

http://www.insideracingtechnology.com/R ... loverd.gif

If your mental model is a (airplane) wing designed with minimal drag in mind (so that the very high speeds attained help with the lift part), with small angles of attack and designed to deviate the air a few degrees from its initially trajectory, then yes, stall will increase drag. Partly because low drag at 800Km/h was the initial design consideration.
But F1 cars are not airplanes, are not designed as such and should not be considered as such.
And F1 car wing is designed to produce downforce at 200Km/h, optimized for such intentionally paying the price of a very high drag, has angles of attack of 20-60 degrees and is supposed to deviate the incoming air by something like 30-45 degrees. So what works on an airplane doesn't necessarily apply here.
As an analogy, road cars and competition bicycles are both designed with similar objectives of reducing weight and minimizing drag. Do you think the same design and performance rules apply for both cases?

Hollus while your reasoning that in an airplane stall the wing will usually produce more drag while stalled and a car wing will usually produce less stalled, the way you went around explaining it needs some correcting. Yes they are designed quickly and for different speeds etc. however the physics doesn't change. The same forces and airflow is moving around the wing.

Now if one was to compare the two big differences between an airplane wing and an F1 wing, there is a major difference. Airplane wings have to work at multiple angles of attack, an F1 wing only has to work at the angles allowed by suspension movement, < than +/- 1 degree. People think that an airplane wing stalls because of the slow airspeed, the real main reason is the increase in angle of attack that pilots have to do to keep lift up flying slowly that causes the wing to stall. There reaches a point where the angle becomes to great and the wing stalls.

The f1 wing trying to produce such a large amount of downforce over such a small area creates a situation with a high drag wing. By stalling this the induced drag is cut. In a plane as the AoA increases there is a large increase in drag because the wing basically turns flat to the airflow, negating any loss in induced drag by the stalling

[riff_raff]

While I do not see any benefit to braking performance from stalling the wing or underbody airflows, if you actually wished to do so it would be simple enough to achieve simply by designing the suspension to produce lots of dive under braking.