What Causes Stall/Flow Separation? Adverse Pressure Gradient Explained 

I would absolutely love a more detailed look into this phenomenon, aimed at a junior engineering level. I have a final year engineering project on the effects of attack angle on a symmetrical wing (NACA0012) under turbulent conditions, and have been trying to get a thorough understanding of the boundary layer physics occurring at separation, as I believe it is the downfall of CFD programs at turbulent conditions

Nice and very informative presentation. Just a quick note; Flow around the corner creates a very sharp pressure drop (rather than pressure increase) right pass the corner. Since pressure has to come up to normal ambient levels, that have to occur with a very high adverse pressure gradient causing a flow separation. A very similar thing happens also in the airfoil, following the stagnation point. Turning flow accelerates and pressure initially drops. That very low pressure dip should not be forgotten.

Nice Video. Never quite understood the physics behind adverse pressure gradient and this cleared a good bit of confusion. I think what I always missed was the positive pressure pushing the airflow back to (approximately) free stream velocity.

I'm reviewing your aerodynamics videos while having the classes at the university. Thanks a lot, hope you are doing well in F1.

Very clearly explained without equations and complex jargon. Thank you

Great video. You have the ability of explaining clearly also the hardest notion. Here i understood everything. Thanks for making videos

Acceleration and deacceleration over the body → adverse pressure gradient → slowing of boundary layer → at sufficient adverse P gradient fluid layers adjacent to surface flows backward → separation boundary layer.

Bhaiya, you explained this concept in suchhh A great way! I'm so thankful this resource is on RU-vid! This feels like it was so easy! I visualised the things. Thank you so muh🎉 (Bhaiya is a term used to refer to elder brothers in India)

This video about to blow up

Great video, but i don't really understand one thing, the boundary layer is pushed back and that means it gets sucked away from the wing surface and turbulent air occurs? Thank you.

The diagram was good. Should have left stalling out had to watch twice to separate the concepts. Great explanation!

Thank you! It's really useful for my PPL (Aeroplane) theory

what factors determines the pressure gradient on the surface of the body?And please make some video about Center of Pressure

Thank you for clearing our concept behind this.. also upload more videos

This is important for lifting body aircraft since those aircraft fuselages are mimicking a very thick airfoil compared to their wings.

Thanks a lot for the video and your efforts. very helpful.Thank You. Could I ask a question please, there is a statement which I read but do not understand it "In compressors flow is against an adverse pressure gradient."

wow i just knowing this phenomenon, is it somehow related to my experience of buying cheap mini fan that seems have bad design? because everytime i try block some airflow from behind, it wont blow forward air again

Dude, I am going to be a boring addition here, SO WELL EXPLAINED! Thank you. I have a request. I want to understand how aerodynamics react to the underside of the chassis, its relation to ground clearance, etc. is it possible to building an off-road vehicle with great aerodynamics? And how do you define great in this context in comparison to other non off-road cars?

Brilliant explanation Mate.....thank you very much.....very helpful indeed

could you please explain the effect of surface roughness of blades on the flow efficiency

Thank you, any chance we can see how this works on different car shapes as an examples. Specifically slotted spoilers on hatchbacks. I get all cross eyed trying to understand.

great video please make a video of same stuff with turbulent and laminar flows

@03:00 Where is here and where is there? Iti is not clear from your pointing to which part are you pointing to exactly.

do you know why if water flow through expansion, let's say in the lower side of expansion, the recirculation zone is very large, but in the upper side, the recirculation zone is smaller because of the presence of stationary air accumulation, will the center streamline is pointing a little bit upward? could you tell me in detail? any answer would be appreciated, thank you

how do you know that there is flow separation on a graph of pressure coeff in function of an angle of a cylinder?

Considering there is a boundary layer of stationary fluid, why does surface area and therefore friction drag cause any problem at all? It seems that friction is holding the boundary layer stationary, and beyond that, it is energy transfer and minor gas related friction of the air itself, not contact with the wing surface that would cause drag. If that made sense, maybe you could explain it better. Thanks!

Thank you KYLE.ENGINEERS, thumbs up! subscribed!

Can you explain why the velocity is fastest at the bottom of the wing (or the top of a wing on an airplane)? You said that like it's a given, but I didn't follow that assumption. (2:33)

Good video, but I still don't get why with extended plain flaps the adverse pressure gradient is steeper, and with slats the adverse pressure gradient is reduced. They have the same suction peak over their surface.

In the case of a turbulent BL, the pressure gradient needed to generate flow separation should be higher than the pressure gradient needed for flow separation in the laminar BL case? I’m purely looking at the thickness of the different BL’s. However, I’m not sure if I’m missing something, because in a turbulent BL, you do have some pressure fluctuations.

brilliant video thank you

do I have to read the 1st graph for the airfoil if I am doing lift for an aeroplane

Nice video. Thanks

Does the wind driven turbine ventilator stall ? i am doing a FYP project on that , will be glad if you could explain about it. Thanks alot

Kyle,the equal argument theory is wrong isn't it.then how does decreasing pressure increases velocity

Nice effort. Perhaps it would be better for the example to talk in terms of streamline curvature effect on pressure gradients and apply Kutta condition at TE

Why is the flow seperation undesireable, is that due to the flow at seperated region is trying to push it down finishing the lift because of pressure is high than atmospheric pressure just like below the airfoil or anything else?

how Does Flow separation affects downforces

What would happen if vortex generators are installed underneath a wing? Could the angle of attack be slightly increased without the wing stalling then?

Does this phenomena always happen to airfoils even if it is just flying straight forward??? Generally speaking if an airfoil is in stall, this seperation point moves further upfront to the leading edge, but if it is in straight normal flight is this separation point always present, but more located close to the trailing edge?

I totally got that, thanks.

what would happen if you added tiny dimples to the surface of the wing like those seen on Zipp carbon bicycle clinchers? how does dimples work on a surface when interacting with air flow? I've seen an example applied to a car on the pescarolo 01' where there are big bulges and serrations on the second element of their wing. i cant seem to grasp that concept. i hope you could make a video on this. cheers!

Why does the separation point on the upper part of the wing come closer to the leading edge when the AoA increases?

Is it that way due to low pressure in that particular point and high pressure comparatively beyond that point tends air to flow from high pressure to low pressure causing separation .

Nice Video. Only one doubt is there that why does the air accelerates at its tip of the wing ?

does the pressure increase on hitting the obstruction because the velocity reduces?or is it something else?

Nice video, I would like the videos to have the Spanish translation to be more understandable in this language, thanks kyle

Why stalling does not depend on speed of air?, as if the of air is increased then there will be more negative pressure at the leading edge of an airfoil and hence there will be more pressure difference and flow should separate earlier. Is this right or wrong?

THANK YOU

great video and explanation, terrible arrows hahaha

Do thte concepts presented here apply to water flow? I'm trying to separate very fine gold from heavy iron (magnetite) sand. Great video by the way

Its difficult for me to make the jump from the pressure graph to the flow profile going negative on the boundary layer towards the end of the wing. Can try to elaborate on that bit more? Which part of the graph, which gradient am i looking at here ? I feel like there is part missing here that would allow me to actually connect the two.

I have doubt . In case of car , suction is present in rear of car . As velocity of air which is nearest to car roof slows down and comes to rear of car , it's potential energy will also decrease and pressure will increase according to Bernoulli's . Why won't that high pressure air moves into suction cause pressure difference causes fluid movement . Fluid moves from high to low

Due to an adverse pressure gradient, in what way it will affect the motion of the plane? Thank you

Why shear stress is zero at the point of boundary layer separation

Why does the boundary layer end up being pushed back down the wing to cause recirculation?

Would the top and bottom of the wing have different pressure graphs? If yes, how do they affect each other?

I watched your vortex generators video and was wondering if they would be benifitial with a lip style spoiler? my car has a 10" tall spoiler (because of race class) so would generators make it more effective?

So stall is undesirable because it decreases the efficiency of the wing due to flow separation?

jazakallah ❤️

how to excample calculate

apruebame raquel

I’m surprised you Formula 1 and driver guys don’t use a multiple cambered or a flexible cambered wing like a flaps on wings. Maybe you do and I’ve just never seen it. I think you car guys should take a few lessons one day and invert that wing and show them how it works on a plane. Seems a little easier to understand. I’m going to go check out your Vortex gen. Video . No offense but this video seems a little difficult to understand even said to somebody who knows it like me.

Need a Gurney Flap on that wing;-)

Ok but how do you fix this if a wing you designed has detached airflow 😂

Don't know what your saying..with this diagram

You need to work on your presentation, video editing, and your 'physics tutorial' ability. I enjoyed it as it was intended, but I have had a bottle of whisky (I'm Scottish), so please don't take offence at my critique: The name of the video is more complex than the content... For example, we assume a knowledge of boundary layers initially, though strangely, there is no mention of other videos that explain the concept... It's almost as if this knowledge is implicit... When talking to the layman, we bring up the subject of high pressure circulation before the wall. This circulation generates a separation point, as is logically observable, to those who know. How many average obververs of this youtube channel, actually know about stall/flow separation? For the general pops, I'll point you all to a CFD analysis we did for our course. This shows the high pressure regions referred to earlier. i63.tinypic.com/2r5fdrc.png I wanna drink whisky now, ut if anyone wants to discuss this, feel free!

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