More than you ever wanted to know about Aerodynamics

[cliffy]

6 minutes ago, gsxrpilot said:

Unless you're flying your hang glider... then its just the opposite. 

Or an old style Bensen gyrocopter  :-)

[jaylw314]

9 minutes ago, gsxrpilot said:

Unless you're flying your hang glider... then its just the opposite. 

Holy cow, I never thought of that.  I've toyed with the idea of taking hang gliding lessons someday, but now I'm worried I'll just nose over into the ground on the first try!

[FlyingDude]

2 minutes ago, jaylw314 said:

Holy cow, I never thought of that.  I've toyed with the idea of taking hang gliding lessons someday, but now I'm worried I'll just nose over into the ground on the first try!

Do it! I did it for 4 years and it was absolutely tons of fun. Seriously

[aviatoreb]

2 hours ago, FlyingDude said:

Integrals of algebraic expressions are easy. Even at 10 dimensions. Adding trigonometry or Fourier/Laplace transforms spices things up... My favorite though are Green's diades.

That said, the amount of math in the video is excessive for any pilot (maybe not for test pilots or design engineer pilots...) However, in Europe, private students learn the lift equation. FAA doesn't require it. The equation in the faa 8083 book states the CL coefficient of lift "before" the 1/2 that comes from the integration (v squared)... And says something like "experiments have shown that"... I read that and took a long break. Nope, it was derived on chalk board... Wind tunnels helped the CL portion... Now I'm studying the AP books... For acceleration it states "fps/s" fps being foot per second. Seeing the 2nd derivative here is like finding waldo... Man, I'm so signing up my kids for the international baccalaureate program...

Ok, enough rant. 

Its my opinion that there is very little mathematics in that video.  Meaning he does not really derive, interpret or describe the mathematics - he just points at it as a static object and then jumps to more general engineering terms of the outcomes. A mathematics presentation would at least include working examples such as presenting term by term each expression in the integral and then performing the integration over some simpler domains. That mathematics in there is more of a prop than a tool.  I am not second guessing him.  If this is a presentation for a class, then he must not be expecting the class to be able to work problems that use the integration as a tool, but instead describe in general terms what it is for.  (That said - I only "speed read" the video meaning I jumped ahead ten min at a time and watched 30 seconds worth in each 10 min segment to see the nature of what he is doing rather than the details - as I often do when I want to decide if I actually want to spend the time to watch something). 

[gsxrpilot]

23 minutes ago, jaylw314 said:

Holy cow, I never thought of that.  I've toyed with the idea of taking hang gliding lessons someday, but now I'm worried I'll just nose over into the ground on the first try!

Do it! Hang gliding is the purest form of flying. And while I've  heard some hang gliding instructors say it's more effort to teach a fixed wing pilot because the controls are all backwards, that wasn't my experience at all. It was extremely intuitive and I thought very easy to learn to fly hang gliders. 

One thing newbies have problems with is wanting to get slow for landing as the ground approaches, and we all know what can happen when you get too slow. My natural instinct was to come into ground effect with plenty of speed, and then let it bleed off until ready to gently touch down. Just like we do in airplanes. 

Also, as pilots, we know that the pull in/push out is really not for up/down, but rather fast/slow. 

Go do it!

[aviatoreb]

19 minutes ago, Freemasm said:

I don't expect many to appreciate this post but it is therapy; my apologies. Not many things make me shiver but right now, I'm feeling it. Thanks guys.

Calc V; a five credit hour class that was mostly Triple Integration plus Greens and Stokes theorems. My God did I hate that class. Triple Integrals were do-able for me. I had plenty of integration practice in Calc II. Never in any subsequent class or professional application did I ever need to reduce a triple integral to a double or a double to a single or vice versa. Anything utilizing polar coordinates sucked on their own. I am not built for that.

A lot of the efficiency gains in turbines (and compressors) have been fairly recent. The ability to "see" flow that included its third dimension was (a major) key to this. Breaking the calcs down to thousands of simpler equations that computers could quickly combine. Blades were no longer specifically characterized as reaction or impulse. I'm glad there are smart people in the world.  

So. F.U. Green, F.U. Stokes, and especially Prof. Smythe.  My sleep is ruined for the next week or so, again.    

 

 

Calc V?  Not many schools call anything calc V.  What's in calc V?  Sometimes differential equations is called calc IV since it is the fourth semester in a typical sequence.  Many engineers get something we call "engine math" which is a bunch of stuff.  Calc I is usually intro, limits and derivative calc.  Calc II is mostly integral calc - both I and II mostly functions of one variable.  Calc III is mostly calculus in 3d, so vector valued functions, their derivatives - partial derivatives, and integrals, double integrals and up.  Leading into also surface integration, line integration, etc. From there at the end you get the big 3, divergence theorem, stokes theorem and Green's theorem.  These are controlled by ABET - American board of engineering and technology that controls a standardized accreditation of engineering degrees.   Trying to get those 3 in and do a good job of it at the end of an already tight schedule means not as much time as you would want to really do it right - a rush.  I have taught calc III a bunch of times and ...seems to go like this - calc III in the fall semester, the end is near, Thanksgiving break looms, and there's just enough time to start these topics the week of Thanksgiving and already students minds are elsewhere on Monday and some maybe 25% of the students already went home early.  By Wednesday half to 2/3rds of the students went home early and there you are presenting some of the more complicated stuff of the semester in a way you hope will help - but the large fraction of them grabbed a ride home early.  Then they come back from Thanksgiving and there's only 2 weeks left in the semester and some may get mad at you for presenting something new at the end instead of just switching over to review mode.  I figure every day of the semester is a day of the semester, and its my job to treat each day for real and present to the good students in the room.  If the semester were only 3 extra weeks I would really present those big three really a lot better with lots of simple examples.

[FlyingDude]

1 minute ago, aviatoreb said:

I figure every day of the semester is a day of the semester, and its my job to treat each day for real and present to the good students in the room

I'm not stating what I'm about to write as in it's right or wrong, I'm only paraphrasing what I've observed: in US, education is private. Students are actually customers. They write reviews at the end of the semester, which some of my professor acquaintances in MI found ridiculous in some cases, because the kid was deflecting their total lack of effort into the class not being organized and the teacher being bad.

In Europe there's the "right to learn". The state has to teach you whatever you want to learn. So, during my first year, I recall some assistants telling some lackluster students "engineering is not for you, you should try something easy. Like liberal arts". We used to have end-of-semester reviews, too and one professor said to the class "write constructive stuff. Our university has a reputation to uphold,we won't make it simpler so that you study less".

Unlike my clear position on metric vs imperial, here I don't side with any party. I just wanted to report what I've observed.

[Hank]

3 hours ago, N201MKTurbo said:

I pull back and it goes up, I push in and it goes down, if I go too slow it falls down. What else do I need to know about aerodynamics?

Keep pulling back, it'll go down too . . . . .

[aviatoreb]

9 minutes ago, FlyingDude said:

I'm not stating what I'm about to write as in it's right or wrong, I'm only paraphrasing what I've observed: in US, education is private. Students are actually customers. They write reviews at the end of the semester, which some of my professor acquaintances in MI found ridiculous in some cases, because the kid was deflecting their total lack of effort into the class not being organized and the teacher being bad.

In Europe there's the "right to learn". The state has to teach you whatever you want to learn. So, during my first year, I recall some assistants telling some lackluster students "engineering is not for you, you should try something easy. Like liberal arts". We used to have end-of-semester reviews, too and one professor said to the class "write constructive stuff. Our university has a reputation to uphold,we won't make it simpler so that you study less".

Unlike my clear position on metric vs imperial, here I don't side with any party. I just wanted to report what I've observed.

When I stand in front of a room of say 80 students, it is 80 different people.  They all have different needs different skills, different levels of maturity in their development toward who they will become in the future and now, and so on.  There isn't a thats the way students are thing as far as I am concerned.  I was reporting though what many here may know which is that largely what is on that calc III syllabus is a complicated combination of what makes for good pedagogy, what the client departments need (e.g. what physics department, mechanical engineering, electrical engineering, etc need their majors to be exposed to), and what abet the accreditation agency expects to see.  It is human nature for a student who may not be doing as well as they wish to put some of the responsibility or blame on the prof, when some of it belongs with the student.  I mean a student who may skip the large fractions of the lectures and skip the homework and then write a scathing review.  I tend to generally get extremely positive reviews, and mixed in with superb reviews there are always a few absolutely scathing reviews.  Besides a popularity contest, the job is also to consider what might be best for the students needs and futures across a population of students and also as individuals, so yes follow the path toward course outcomes.  e.g. If I go light on line integrals and surface integrals, then there is no way that I can get to those big three, stokes, divergence and Greene's theorems.  If I don't get to those, then they will get to their next classes not prepared with the tools they need.  To some level, I believe to teach to the good students in the room, assuming that all the students want to be good students.  Which is the large fraction.  I don't mean the most brilliant I mean the students who are willing to work hard because it is hard, and students raise their game.  If I instead pitch to the worst students in the room, then some students will lower game and the good students will get bored, and some of those less good students will actually still lower their game and manage to still stay below an even lowered bar.  Its hard to describe here but it means reading the room, reading the individuals and being reactive to their needs and at the same time remembering the path through the material itself that needs to happen to get there.

[Hank]

36 minutes ago, aviatoreb said:

Calc V?  Not many schools call anything calc V.  What's in calc V?  Sometimes differential equations is called calc IV since it is the fourth semester in a typical sequence.  Many engineers get something we call "engine math" which is a bunch of stuff.  Calc I is usually intro, limits and derivative calc.  Calc II is mostly integral calc - both I and II mostly functions of one variable.  Calc III is mostly calculus in 3d, so vector valued functions, their derivatives - partial derivatives, and integrals, double integrals and up.  Leading into also surface integration, line integration, etc. From there at the end you get the big 3, divergence theorem, stokes theorem and Green's theorem.  These are controlled by ABET - American board of engineering and technology that controls a standardized accreditation of engineering degrees.   Trying to get those 3 in and do a good job of it at the end of an already tight schedule means not as much time as you would want to really do it right - a rush.  I have taught calc III a bunch of times and ...seems to go like this - calc III in the fall semester, the end is near, Thanksgiving break looms, and there's just enough time to start these topics the week of Thanksgiving and already students minds are elsewhere on Monday and some maybe 25% of the students already went home early.  By Wednesday half to 2/3rds of the students went home early and there you are presenting some of the more complicated stuff of the semester in a way you hope will help - but the large fraction of them grabbed a ride home early.  Then they come back from Thanksgiving and there's only 2 weeks left in the semester and some may get mad at you for presenting something new at the end instead of just switching over to review mode.  I figure every day of the semester is a day of the semester, and its my job to treat each day for real and present to the good students in the room.  If the semester were only 3 extra weeks I would really present those big three really a lot better with lots of simple examples.

Erik, I went through what you described as three semesters of Calc I - III in three quarters [one academic year, Sept - June]. Followed by Differential Equations the next quarter. Physics had four classes [Newtonian Mechanics; Electromagnetism; Heat, Light & Sound], each one required the previous quarter's calculus. Engineering classes often required both the previous quarter's Physics and the previous quarter's Calculus . . .

Many students took long weekends and early holidays. But none of my fellow Engineering students did! We couldn't, as every class went like you described for Thanksgiving above. Only the kids enrolled in Business or the College of Arts and Crafts took extra time away. I stayed at school, slept little, ate less and ground out assignments. One problem in Jet Propulsion took two pages of my tiny handwriting to solve the equations! Another professor enjoyed giving incomplete information and telling us to use our experience and assume average values for whatever was missing, and it he didn't like our assumptions, he would just count off! Things like thermal efficiency, combustion efficiency, percentage of by-products, etc.--this was a required class in Heat Transfer . . . . b-b-b-b-r-r-r-r-r-r . . . . "Fun times" it was not!

Modern Physics [relativity and quantum mechanics] was a separate, required class. Matrices were covered in an  Engineering class, not Math dept. Lagrange Transforms were a different ME class; I had a grad student teaching that, and the next year a prof was reviewing some things, asked who had taught me the matrix class, and said "oh, yeah, he does things different."

But since college and spending the ensuing decades manufacturing plastic parts and the tooling required to make same, I've not done any math higher than tan^-1 to figure angles . . . . . . I did get out my Basic Aerodynamics book when I started working on my PPL and reviewed the first couple of chapters, but after getting into the Gleim books, I put it away, no math required.

[aviatoreb]

2 minutes ago, Hank said:

Erik, I went through what you described as three semesters of Calc I - III in three quarters [one academic year, Sept - June]. Followed by Differential Equations the next quarter. Physics had four classes [Newtonian Mechanics; Electromagnetism; Heat, Light & Sound], each one required the previous quarter's calculus. Engineering classes often required both the previous quarter's Physics and the previous quarter's Calculus . . .

Many students took long weekends and early holidays. But none of my fellow Engineering students did! We couldn't, as every class went like you described for Thanksgiving above. Only the kids enrolled in Business or the College of Arts and Crafts took extra time away. I stayed at school, slept little, ate less and ground out assignments. One problem in Jet Propulsion took two pages of my tiny handwriting to solve the equations! Another professor enjoyed giving incomplete information and telling us to use our experience and assume average values for whatever was missing, and it he didn't like our assumptions, he would just count off! Things like thermal efficiency, combustion efficiency, percentage of by-products, etc.--this was a required class in Heat Transfer . . . . b-b-b-b-r-r-r-r-r-r . . . . "Fun times" it was not!

But since college and spending the ensuing decades manufacturing plastic parts and the tooling required to make same, I've not done any math higher than tan^-1 to figure angles . . . . . . I did get out my Basic Aerodynamics book when I started working on my PPL and reviewed the first couple of chapters, but after getting into the Gleim books, I put it away, no math required.

Your career path may not have used that particular math, but I bet there are quite a number of other students you studied with who did use that math specifically or otherwise other aspects of math the built on it intimately.  I on the other hand took a good deal of chemistry and chemical engineering in school, and I did well in it, but thee large part of it - never directly has had anything to do with my career path.  I was required to take a lot of things toward my degrees and also some electives, some of which I use directly constantly, some just a little bit, and some was just part of my general education but I do very much believe in the general education aspect fo higher education.  If this gig I am in now were to dry up and I needed to switch to chem, it would. be painful, but ... I bet I could do it thanks to that general education. We can't make a curriculum that is specialized to exactly the very few things that anyone given person might specifically need in their eventual careers - not knowing what their careers will be, but we give them background to evolve into those careers in time.

The student population... I bet you were like me.  I was a very good student.  Amongst the best.  All my friends were the best students. We worked our butts off.  We worked together.  We studied alone too.  I bet you anything that some of those engineering students were going home early for thanksgiving.  Heck Thanksgiving week is only MTW classes - so why not take a ride home the Friday before/ Actually the Friday ride is now leaving on the Thursday before... why not?  There's always a few.  I was almost unaware of the students who were not doing well in that I wasn't worried about it.  I was friends with students like that but they weren't part of my working circle.  So my world view as a student was most students work hard and I was working to be in the front.  As Prof however, we see the entire spectrum, the entire population, from best students to worst students.  Its easy to get wrapped up worrying about worst students. Its more fun to worry about best student.  Most students are middle students.  I don't mean to say worst students as a pejorative but I'll say on week one, on day one, in a large class with 100 people signed up, what do you when only 90 show up on day one.  I will work to help any student who shows up.  It is very hard to help a student who does not show up.

[ohdub]

15 hours ago, aviatoreb said:

So lest anyone think that I - a PhD of mathematics and a math prof even, knows everything there is to know about mathematics - let me be the first to confess bounded and mortal human limits.  I know a bunch of stuff....but hardly everything. 

I don't know if it's true or not, but I remember one of my math profs telling us that probably the last mathematician to have a good grasp of all know mathematics at the time, was Gauss. He also told us (this was early '90s) that there had been more new mathematics discovered since 1950, than in all previous human history.

[Hank]

6 minutes ago, aviatoreb said:

Your career path may not have used that particular math, but I bet there are quite a number of other students you studied with who did use that math specifically or otherwise other aspects of math the built on it intimately. . . but I do very much believe in the general education aspect fo higher education.  If this gig I am in now were to dry up and I needed to switch to chem, it would. be painful, but ... I bet I could do it thanks to that general education. We can't make a curriculum that is specialized to exactly the very few things that anyone given person might specifically need in their eventual careers - not knowing what their careers will be, but we give them background to evolve into those careers in time.

Yep, Engineering School prepared me for many different career paths, not knowing which one I would end up on. And mine has certainly not been anything that I thought about as a possibility when I was a student!

Some of my "general education" electives were actually fun, but certainly Medieval English Literature did not prepare me for an alternate career when I was laid off at age 50. The old degree opened doors, as without it I was not qualified, but it was myexperience and job history that got me working again in 8 weeks, from Thanksgiving to end of January a few years back. Some jobs require "any degree," some will accept one of several technical degrees, but most also require a certain level of experience. The degree that I earned gave me what I needed to successfully launch in one of many different areas, and I certainly launched well in an unexpected direction but without technical difficulties.

But almost nothing applies to aircraft design or detailed aerodynamic analysis of specific aircraft parts or features. So I will bow out now and learn from those who took classes with me and went that direction instead, as qualified to start that as I was in my career.

[aviatoreb]

Just now, ohdub said:

I don't know if it's true or not, but I remember one of my math profs telling us that probably the last mathematician to have a good grasp of all know mathematics at the time, was Gauss. He also told us (this was early '90s) that there had been more new mathematics discovered since 1950, than in all previous human history.

Its a phenomon well beyond mathematics.  Renaissance man. There used to be a time when one person could know everything there was to know.  Now we must become and more specialized if we want to know everything about at least something.  And a good fraction perhaps of a larger body of knowledge,  but give up after that.  Don't ask me anything in Latin.

[aviatoreb]

47 minutes ago, Hank said:

Yep, Engineering School prepared me for many different career paths, not knowing which one I would end up on. And mine has certainly not been anything that I thought about as a possibility when I was a student!

Some of my "general education" electives were actually fun, but certainly Medieval English Literature did not prepare me for an alternate career when I was laid off at age 50. The old degree opened doors, as without it I was not qualified, but it was myexperience and job history that got me working again in 8 weeks, from Thanksgiving to end of January a few years back. Some jobs require "any degree," some will accept one of several technical degrees, but most also require a certain level of experience. The degree that I earned gave me what I needed to successfully launch in one of many different areas, and I certainly launched well in an unexpected direction but without technical difficulties.

But almost nothing applies to aircraft design or detailed aerodynamic analysis of specific aircraft parts or features. So I will bow out now and learn from those who took classes with me and went that direction instead, as qualified to start that as I was in my career.

You know - I never took Midieval literature.  But if I had...it would have prepared me to understand my youngest son better!  He loves that stuff!  he loves languages - no kidding he is working on 14 different languages.  And he loves history.  These are the things he studies.

Besides getting a job, I am a big believer in education making us better informed people.  A lot of it helps us interact with other professionals from within our jobs or otherwise business life - eg having some idea of what training lawyers get, doctors get, etc I think is helpful when I need to interact with those people, professionally or even just as a citizen. 

Some pretty wild things I thought were way in left field that I took for fun actually have some real relevance in my career.  E.g. I took a philosophy class - philosophy of the mind from a fellow named John Searle (wiki him) and it seemed like pure - philosophy.  You know now that machine learning and AI are a thing, and I am right in the heart of it, I find myself quoting from that class more often than you would know.  Beyond the technical skills I learned as a math and cs and physics major (I switched around goodness help me), these kind of classes challenge the way we think.  Beyond a trade school we need to be thinkers.  And for real, I have gotten lucrative contracts specifically because of things I have said in the pitch phase that were in part shaped by a way of thinking thanks to that time in that Searle class - and I never would have guessed it at the time.

I took economics and I am certain it makes me a better citizen and a more informed voter. And I think I make better informed decisions regarding my investments of my own money - so not so much it got me a job but still...

I took one semester of Italian (and I took lots and lots of french), because at the time another student and I who were math majors convinced each other it was a great way to meet girls.  Sure enough in that class there were like 20 girls and like 3 guys total, including me and that other guy.  Well that was the good news.  The bad news was neither one of us was bold and we didn't make anything of it -' but the Italian was fun.  And heck I've been to Italy a bunch of times over the years, professionally to conferences, and once for several weeks to the University of Naples to lecture, and while i didn't need to know Italian since educated European people seem to all know English - which is the people I interact with in the university-biz, its still fun to know at least SOMETHING.

So as Anthony says...

Opinion of a PP only, and not a philosopher, or an economist or a linguist.

[aviatoreb]

I think of my "cousin in law" a really nice guy who majored in mechanical engineering.  Mechanical engineering as a major is not just for those who will build stuff.  He did ok, but not superbly grade wise but he has tremendous skills as a people person and he got into sales for mechanical engineering products.  Eventually in the ground floor of 3d printing like 20 years ago selling big machines to factories etc.  Being an early principle in such a company, he made a killing.  Couldn't happen to a nicer guy.

If we work on it, we can think of lots of friends and families with career paths that are hard to plan for when you are 19 years old.  We need a breadth of skills and backgrounds.  An undergrad degree is meant to help us in those terms, and also possibly help prepare us to begin to really learn something in one of those areas, perhaps by a graduate degree for specialization, or on the job training.  Even then I didn't feel like I knew much when I finished my PhD since in the course of that, besides learning a lot a lot about a few things, you get exposed to lots more things that you are well aware that you don't know a lot.  And I have learned a lot more things since then!  But now I know a lot more things are out there that I know nothing about!  Renaissance man, not.

[N201MKTurbo]

3 hours ago, aviatoreb said:

African.

South or west?

[FlyingDude]

3 hours ago, aviatoreb said:

took one semester of Italian

Allora io e te dobbiamo conversare in italiano, di sicuro!

Applying the limit theorem to the professional specialization, one can say that in the beginning few people knew everything, then many people knew a lot about something, now even more people know much more about more limited stuff, so it seems the future is when everybody knows everything about nothing

 

 

[EricJ]

4 hours ago, N201MKTurbo said:

South or west?

Somewhere they can find a coconut.   They grip them by the husk.

 

[aviatoreb]

51 minutes ago, EricJ said:

Somewhere they can find a coconut.   They grip them by the husk.

 

Which brings me to my favorite folk-statistic - did you know that 6 people per year die by coconuts falling on their heads?

[aviatoreb]

2 hours ago, FlyingDude said:

Allora io e te dobbiamo conversare in italiano, di sicuro!

Applying the limit theorem to the professional specialization, one can say that in the beginning few people knew everything, then many people knew a lot about something, now even more people know much more about more limited stuff, so it seems the future is when everybody knows everything about nothing

 

 

I think you need to apply l"hopital's rule to that problem of ratios of infinitesimals before making any more wild statements!  :-O

[Planegary]

This is what the aerodynamics sounded like to me. I watched my wife’s eyes glaze over when I watched this video and now I know how she felt

[FlyingDude]

1 hour ago, aviatoreb said:

ratios of infinitesimals

Infinite/infinite can be 1, 0, positive infinite, negative infinite. Just like 2+2 can be 5, 4 or 3; as was illustrated in 1984 by George Orwell...

It's not me speaking. It's the microchips in my covid vaccine designed by Bill Gates making me say this crap. I should have gotten the other vaccine with Linux-running chips. 

 

[Hank]

1 hour ago, Planegary said:

 

I love this guy!!

[cliffy]

For those who need a refresher?

 

Just now, Hank said:

I love this guy!!

I saw this several years ago GREAT presentation