abraision aerodynamics

[Zrogezrg]

Lift sits in a plane. After not too appetizing meal she coats the plane in slickness. What happens?

a) plane speeds up as drag force is neglected. (glider could fly indefinutely)

b) plane starts to follow parabolic trajectory as aerodynamical forces are both neglected.

c) something else.

Any ideas?

[Quantus he/him]

It goes faster due to the elimination of friction, but it still faces inertial drag forces from the mass of air that is getting shoved out of the way as if goes by.  As it speeds up and approaches the Speed of Sound (for Roshar's atmosphere), the friction matters less and the inertial forces become more prominent.  

[alder24]

1 hour ago, Zrogezrg said:

Lift sits in a plane. After not too appetizing meal she coats the plane in slickness. What happens?

a) plane speeds up as drag force is neglected. (glider could fly indefinutely)

b) plane starts to follow parabolic trajectory as aerodynamical forces are both neglected.

c) something else.

Any ideas?

That's actually a good question. Would Abrasion cancel out the force of lift? I think not, lift is generated by the pressure difference between the upper and lower surfaces of the wings, not by friction itself. This pressure difference is created by the shape of the wings and the angle of attack. Thus the plane would not drop out of the sky, because Abrasion doesn't change the pressure distribution. You would have a perfect glider, it would speed up, but as mentioned by Quantus, the inertial drag force would eventually stop it from accelerating too much.

[Zrogezrg]

48 minutes ago, alder24 said:

That's actually a good question. Would Abrasion cancel out the force of lift? I think not, lift is generated by the pressure difference between the upper and lower surfaces of the wings, not by friction itself. This pressure difference is created by the shape of the wings and the angle of attack. Thus the plane would not drop out of the sky, because Abrasion doesn't change the pressure distribution. You would have a perfect glider, it would speed up, but as mentioned by Quantus, the inertial drag force would eventually stop it from accelerating too much.

I think that the pressure distribution would definitely change as the fluid pressure is function of flow speed, which would be different without friction. I would presume, that the flow over the wing would be faster relative to the flow below it, than normally, reducing the lifting force. The angle of attack would be more relevant, and the plane would most like need to increase it to maintain altitude.

2 hours ago, Quantus said:

It goes faster due to the elimination of friction, but it still faces inertial drag forces from the mass of air that is getting shoved out of the way as if goes by.  As it speeds up and approaches the Speed of Sound (for Roshar's atmosphere), the friction matters less and the inertial forces become more prominent.  

I agree with first sentence, but why does the speed of sound matter here? You mean by moving toward turbulent flow? I would argue that removing friction would allow to maintain laminar flow for higher speeds.

P.S.

Not sure whether it is the best place to continue discussion, and if not, is there some option to moving this thread if I want to engage with the answers?

[Quantus he/him]

1 hour ago, Zrogezrg said:

I agree with first sentence, but why does the speed of sound matter here? You mean by moving toward turbulent flow? I would argue that removing friction would allow to maintain laminar flow for higher speeds.

 

I just meant that once you hit the speed of sound and are literally outrunning your own compression wave in the fluid (ie. rosharan air) a lot of the aerodynamic rules change entirely and it becomes a whole other rabbit hole.