Dynamic stall discussion

[ACE-OF-ACES]

Originally Posted by Insuber

Other than that there is a debate about Dynamic Stall ...

Got Link? Maybe someone overthere can explain the 'key' differences between an acc and dynamic stall?

[Insuber]

Originally Posted by ACE-OF-ACES

Got Link? Maybe someone overthere can explain the 'key' differences between an acc and dynamic stall?

it's not relevant, and rather off topic. The fact is that the dynamic stall is not modeled in CloD.

[ACE-OF-ACES]

Originally Posted by Insuber

it's not relevant, and rather off topic. The fact is that the dynamic stall is not modeled in CloD.

Hard to say since I have not seen the topic.. Just curious as to what they think the difference is between the two if any

[Verhängnis]

From my understanding a dynamic stall is when the Wing (Airfoil) changes Angle of attack so dramatically that the leading edge creates turbulent, fast moving airflows (Vortex's) which travel over the top of the wing created an increased lower pressure momentarily increasing lift cooeficient but once the vortex has passed the wing incurs a normal stall where there is not enough airflow over the airfoil to generate lift.

So essentially a delayed stall, and IMO this effect would even really be that noticeble. This is precisely why the Bf-109 has leading edge slats, aswell as the Me-262. It slows the airspeed and reduces/delays the effects of a stall by reducing pressure and turbulent airflow at the leading edge.

...

I don't see why they can't disclose any information about the sequel or it's compatibility with BoB, it's seriously seems quite childish. It's not like it's a National secret or matter of security, nobody is out to get their ideas for a WW2 Battle of Moscow Combat Flight Simulator.

[ACE-OF-ACES]

Originally Posted by Verhängnis

From my understanding a dynamic stall is when the Wing (Airfoil) changes Angle of attack so dramatically that the leading edge creates turbulent, fast moving airflows (Vortex's) which travel over the top of the wing created an increased lower pressure momentarily increasing lift cooeficient but once the vortex has passed the wing incurs a normal stall where there is not enough airflow over the airfoil to generate lift.

That follows the wiki definition I provided a few pages back.. but the wiki also included a reference for that [22] which expanded on that definition to point out that a lot of the dynamic part of it had to do with the dynamic nature of the atmosphere (wind vector)..

So it appears that an accelerated and dynamic stall share the following

1) load factor > 1g
2) stalls at higher speeds than normal stall speed (1g LF)

And what sets them apart is simply the rate of change in the AoA.. Which is probably why they call it dynamic?

But both will stall at the same critical AoA.. Just the dynamic will experience a brief increase in lift just before the stall.. due to the vortex movement.

So the question is how brief is brief?

Are we talking tens of seconds or tens of Millie seconds? If the later, than it is not worth adding the additional math to simulate the brief increase in lift because it will go un-noticed to the sim pilot. That is to say, in the real world an instrumented plane under test might notice (log the data) the Millie second spike of increased lift.. But the human won't.. So no need to simulate it IMHO.

[Verhängnis]

Given the normal airspeed over at wing in a stall, if this is accelerated, then that probably means it twice as fast, enough to generate lift, the duration would be so short, and definitely, as a fighter pilot trying to survive, it's the last thing I'm worrying about. Just don't stall!

[VO101_Tom]

Dynamic stall. Three things must be understood:
- If you pull the stick, you can not raise nose of the machine, but the tail press. This is an important thing, though normal flight conditions, do not even notice the difference (if you start climb with huge speed, the air flow AoA remain in small angle, no matter what is the a/c climb angle).
- If a large mass, high-speed flying, it will be great inertia.
- If the angle of the wing is above the critical value, it will stall. Speed ​​may depend on how much value, and when, but it certainly happens.

http://www.youtube.com/watch?v=xW63S...eature=related

Now imagine what happens when a high speed, sudden you pull hard on the stick. The tail pushed down, but the inertia does not allow the aircraft to rise immediately. The wing angle of attack instant above the critical value, and it will stall. That's the dynamic stall. High speed, high G.

The best example of a dynamic stall: Pugachev's Cobra

http://www.youtube.com/watch?v=1EpJ3KoUNmI

[Insuber]

Originally Posted by ACE-OF-ACES

Are we talking tens of seconds or tens of Millie seconds? If the later, than it is not worth adding the additional math to simulate the brief increase in lift because it will go un-noticed to the sim pilot. That is to say, in the real world an instrumented plane under test might notice (log the data) the Millie second spike of increased lift.. But the human won't.. So no need to simulate it IMHO.

This series of funny statements illustrates perfectly how ignorance tries stubbornly to rule the knowledge.
Dynamic stall is a violent phenomenon, leading to a huge loss of speed / energy. Just for sake of simplicity: pull strongly the stick at high speed in real life, even in straight flight, and you will stall. In this game you can pull strongly the stick at high speed, and your plane climbs. The flight envelope is false. So: big need to simulate the dynamic stall, in my educated opinion.

Cheers!

[Skoshi Tiger]

Aircraft can do loops and depending on how much energy and or power and or altitude you have on hand you can do multiple loops one after the other as long as your angle of attack does not exceed the stall angle. (ie you still have to fly the aircraft within it's flight envelope)

I expect this would effect the 'going vertical' manuvers where the pilot just yanks back on the stick and expects all their aircrafts energy to be converted to height or violent break turns.

I found (what i thought) reasonable description of a dynamic stall at
http://psasir.upm.edu.my/3610/1/An_E..._Inception.pdf

When an aerofoil is pitched through and beyond the incidence of static stall at a
sufficiently high pitch rate, the resulting series of events is often termed dynamic stall.
It is characterised by a significant lift overshoot, followed by a sudden loss of lift and a
major surge in pitching moment. Carr, (1977),

Interesting reading.

cheers!

[klem]

I'm no aerodynamicist but here's an explanation of Static, Dynamic and Accelerated stalls
http://www.futurecam.com/stalls.html
Yes, its written about parachuting but the principles should be the same: angle of attack; rate of change of angle of attack; the added effect of increased G loading.

Whether CoD models Dynamic and Accelerated stalls I'm not sure. I'd be surprised and disappointed if it doesn't. I guess we'd need some a/c data to test against to find out.