Aerodynamics

[Xittenn]

I haven't thought about aerodynamics since secondary school and it rather baffled me back then. Is this something I could simply think of in terms of an integration of the angular momentum of point particles, conservation of angular momentum, and surface friction? Are there more detailed equations that can be used that do not try to explain by sacrificing detail? I don't see why I can't do as I mentioned in my points and I can model this sort of behaviour fairly accurately on a computer without mashing my brain cells.

Edited March 27, 2012 by Xittenn

[CaptainPanic]

Personally, I have little trouble with the following explanation: it's a combination of surface friction and shear stress. But I admit that the maths can be pretty terrible.

 

Imagine your solid surface. Imagine that the fluid around it (air/water/something else) is made up of layers. Obviously, as with all integrations, these are infinitely thin layers. Due to friction, the first layer that touches the solid surface will move with nearly the same speed as the solid itself. This layer will move the next layer of air as well, and that acts on the next, and the next, etc...

 

These nice layers can become unstable, which is called turbulence.

 

And the mode aerodynamic a design is, the less air is moved. As you move forward, you don't want to continuously agitate new air, while leaving air behind that is still moving. Getting all that air to move costs a lot of energy.

 

I'd be curious to hear how you use angular momentum of point particles... I've never heard of it used in aerodynamics (but then again, I'm not the expert).

[Xittenn]

Personally, I have little trouble with the following explanation: it's a combination of surface friction and shear stress. But I admit that the maths can be pretty terrible.

 

Forgive my being short but this omits almost everything.

 

 

I'd be curious to hear how you use angular momentum of point particles... I've never heard of it used in aerodynamics (but then again, I'm not the expert).

 

All angular momentum is built upon the summation of the angular momentum of particles, you make it sound like I've said something unusual. Airfoils and their respective crafts entail a good many angular momentum. When an aircraft lifts off are we seeing a linear plane of travel or are we seeing the plane rotating into the air around a centripetal point. I think if you look at the system closely you'll find most of what you see is angular moments subtended by the sheer stress as opposed to the other way round. I may not be correct in my point of view but I think your blurb greatly oversimplified and removed the reasoning involved that led to my own statements.

[MigL]

The rotation you are referring to, Xittenn, is basically a force difference generated by the offsetting of the main wing and the tailplane/foreplane about the centre of gravity of the aircraft. It is due to aerodynamics but I wouldn't call it aerodynamics per se.

 

I have seen the lift of an airfoil derived by rotation of the fluid about the airfoil,so I'm sure there was an angular momentum component but it has been many years and the math pretty tough going.

[Xittenn]

This was simply one example of many MigL. There are plenty more like the aerodynamic center and the angle of attack and so forth. I guess I'm seeing a loop within a loop, within a loop, or a series of torques that balance and counter balance into centripetal motion. It starts from an inertial moment and focuses it into a centripetal pathway and only then do we see a coherent linear motion established.

 

i.e. http://jeb.biologists.org/content/142/1/87.full.pdf

 

 

PHYSICAL REALITY

 

Basic Newtonian principles of aerodynamic lift and propulsion include:

 

1. Upward lift is derived by accelerating air mass downward.

2. Forward propulsion, of propellers and jets, is gained by accelerating air mass rearward.

3. Drag is incurred through accelerating air mass forward, as by viscous coupling. For the most part this is undesirable but unavoidable.

4. Air mass recirculates upward at a rate equal to the rate at which it is displaced downward in the lift process, thus normal atmospheric mass distribution is maintained.

 

 

http://www.regenpress.com/

 

There are better articles but the maths slowly becomes pretty incomprehensible unless one understands what is implied.

 

 

I've actually gone over several models since I've posted this and I'm quite satisfied with my viewpoint. I'm still all ears if anyone has anything substantial to say. But, I emphasize substantial here because I am, like in most of the threads I start, hoping for a consolidated response--something I can sink my teeth into(I'm a little upset here because I can never find someone to talk to about what interests me.) I'm well aware of the difficulty of the mathematics, I've been working towards this end for over fifteen years now. I was just hoping to hear some clear points on the mechanics involved as opposed to wiki quotes where even wiki says most simply don't understand.

 

Thanks for trying though guys, and if its me please feel free to ask me more specific questions that will assert or destroy my viewpoint--the one I really don't have, I'm only trying to break this thing down in a somewhat longer discussion.

[Cap'n Refsmmat]

What does your model say about boundary layers?

[Xittenn]

The model would predict the boundary layer to rarefy and condense with oscillating torque and varying wing twist. Adjusting concavity under the wing to minimize boundary layer friction and to maximize lift by allowing the proper up/down flow of current is absolutely essential--as is the case with any model no? I wouldn't really call this 'my model' as it is probably simply a regurgitation. My main focus is to put this into code, although it would be nice to come up with my own sustainable model, I would make myself proud.

 

I really don't feel I'm deviating in some way from modern theoretical models. I don't see what I'm saying that is unusual that one might see my statements as not reflecting current methods. A wing is a lever arm, air is a bunch of particles striking the lever arm and imparting angular momentum, what is so weird about this statement? Planes are designed around the balancing of weight around this pivot. The controls implemented are also pivots in and of themselves. These facts extend to all of the aerodynamic systems that I can think of and if they didn't I'm not sure what I would be looking at.

[Xittenn]

I'm sorry for my randomness, but, if I don't cauterize the thought it will take up space. . . . I felt that the content of this thread needed clarification and a while back an @minutephysics type known as @veritasium posted a short that puts perspective on my above statements.

 

 

 

When I saw the clip I kind of wondered if @veritasium had seen this thread.