Poor quality of Engineering Journalism on TV 5

[KENAT]

Last night I caught a show called ‘future cars’ on discovery at 8pm (California, US).

This is a short series I’ve seen advertised which discusses what cars will be like in the future (hence the title) and looks at some of the technology involved. Last night seemed to be focusing on alternative fuels/power sources.

I missed the first 15 minutes or so which I gather covered ethanol.

However, I tuned in just in time to see a very interesting segment on a process which seemed to claim to be able to make bio diesel from pretty much any organic matter. I vaguely recalled seeing this in an article before, to which my initial response was ‘sounds too good to be true’ but it caught my interest so I watched. When they went into more detail the material they were using was mainly non metallic waste from scrapped cars, i.e. mostly plastics (they showed images of tires but didn’t explicitly say you could use them when discussing the process) so it’s not that surprising they could turn it into diesel as that’s pretty much what it started out as, but interesting none the less. They didn’t go into the relative efficiencies of this process compared to just burning the polymers for energy but did point out this process doesn’t release some of the nasty chemicals that burning plastic can.

My interest piqued I avidly watched wondering what would come up next; you guessed it, that old chestnut the ‘water powered car’. As usual they actually meant a hydrogen powered car with the hydrogen generated by electrolysis of water. In fairness some of the ‘experts’ did try to make it clear that water wasn’t the actual energy source but with the editing and some of the wording I’m sure this escaped many non technical viewers who are now expecting to be able to fill their cars up with tap water in the next few years!

What really got me was the they had the Vice President of R & D at GM saying something along the lines of

”you’ll be able to use your fuel cell car to CREATE electrical energy for your home or to feed back into the grid”

.

I have two concerns about this, the lesser of which is how can it be very efficient to generate hydrogen from water using electricity, carry it round in the tank in your car for a period of time/distance, then convert it back to electricity to power your house/feed the grid (from which the original electricity presumably came).

Secondly, was he absent from high school the day a little thing called ‘conservation of energy’ was brought up and then missed every thermodynamics lecture at university? Of course, if GM is anything like my company then just because he’s the head of a technical department doesn’t mean he’s an engineer or scientist, he’s just as likely to be from Sales or Marketing. None the less he was being portrayed on the show as an expert, presumably a scientist or Engineer and yet came out with this twaddle.

The show looked like it was going to end on a high note with a surprisingly good-looking ‘compressed air’ car. I’d always thought the energy wouldn’t be ‘dense’ enough to be useful but the vehicle they showed looked quite interesting.

Then disaster, just before the closing credits the narrator starts talking about how the compressed air car designers have also come up with an air compressor which itself runs off of compressed air!

Anyone see where this is going…

The narrator then starts talking about putting one of these compressors in the vehicle so it could generate its own compressed air, meaning it would never need ‘re-fueling’ – perpetual motion.

After I’d stopped banging my head against the wall and throwing things at the TV it got me thinking.

If the only time the general public sees many types of engineers is on this kind of show, and they are either spouting nonsense or at least made to look like they’re spouting nonsense due to poor journalism, then no wonder we don’t have any status as an earlier thread was bemoaning.

This isn’t an isolated incident. I watch quite a few programs on Discovery and History channel that cover engineering and often spot errors or at least doubt some of the information, but this was unusually bad.

Discovery and History channel don’t have the monopoly I also remember a show on BBC2 a few years ago where they were trying to get some members of the public to understand how a wing on a plane generates lift. They rolled out the usual nonsense about the upper surface of the wing being more curved than the lower surface so that the air molecules have further to travel so have to magically move faster so as to be at the back of the wing at the same time as those going under it. The concerning thing was that one of the people explaining this was the head of wing development for Airbus (then part of BAe)!!! If he doesn’t know why a wing works what chance does Engineering stand, or again is he actually a non technical person?

Just had to vent, sorry. Perhaps my manager had a point about my frustration;-).

 

[tinfoil]

Some fuel cells start with gasoline, oe other fossil fuels

Not that I want to be seen to be defending GM, but the GM guy spoke of 'creating ELECTRICAL energy'. This is correct usage.

Nobody in the real world would say, in normal conversation, that a hydroelectric dam 'produced 80MWh of electrical energy through the controlled capture of mechanical power of falling water, the useful potential energy of which was 81MWh (or whatever that is in J).

They say 'The dam made 80MWh' or 'The dam created 80MWh of electricity'

NOBODY was asserting that energy was CREATED out of nothing. Read the passages again.

 

[tinfoil]

Per my previous post:

I meant to say NOBODY, other than the journalists, were asserting that energy can be created out of nothing.

 

[KENAT]

I guess we'll have to agree to disagree, sorry if you think I'm a pedant.

I would have preferred he use a word like 'generate' or even 'produce', while it doesn't surprise me I do believe that someone in that kind of position and who is effectively representing engineers/scientists to the public should be more careful.

However you're probably right that in the big scheme of things it's semantics.

 

[TheTick]

"Mad Libs" style build-your-own-rant...

"Poor quality of {subject} journalism in/on {name of news medium} .

The possibilities are infinite!

Honesty may be the best policy, but insanity is a better defense.

http://www.EsoxRepublic.com

-SolidWorks API VB programming help

 

[drawoh]

TheTick,

A typical journalist is someone who spent 4 years at college struggling to learn how to write at an 8th-grade level.

I went out with a woman who took journalism in college. They checked her out and told her that her writing was understandable by an eighth grader. This is necessary. Had her writing been at a grade 12 level, they would have re-trained her.

JHG

 

[prost]

KENAT--so you disagree with the characterization, shall I say? that lift is derived from the fact that "the upper surface of the wing being more curved than the lower surface so that the air molecules have further to travel so have to magically move faster so as to be at the back of the wing at the same time as those going under it."

Tell us now, without drawings, pictures, graphs or equations, how to explain lift on an airfoil?

I read once in Machine Design that the writer did not (to paraphrase) "believe in Bernoulli's principle." Given that it is derived from 'first principles' which are pretty darned good models given the assumptions (Mach<<1, inviscid, etc.), and you can easily show Bernoulli's principle at work by blowing over a piece of paper, one wonders what it would take to make the writer 'believe'.

 

[BJC]

Tinfoil said

"You CAN create electrical energy by transforming another kind of energy."

Actually electricy is not a form of energy, it's a way to trasfer and utilize energy. The energy has it's source in a fire somewhere.

 

[KENAT]

Prost,

If I have time later I may try. However that very question was part of my fluids exam at university (first year, I went on to study lots more aerodynamics after that, what a joy) and the answer was several pages long.

Plus the explanation used lots of diagrams.

Just because saying "it's because of the greater distance along the top of the wing..." is a nice convenient short answer doesn't make it right.

I'm not arguing that Bernoullis principle is wrong, it is indeed part of the answer. The problem is the explanation of why the air over the top is moving faster then underneath.

Think about your sheet of paper, it doesn't have an aerofoil section does it?

 

[kenvlach]

Regarding wing lift as discussed by KENAT & prost, an interesting read is
Aeronautical Engineering Blunders of the 20th Century

http://www.aeronautics.ws/blunders.html

 

[KENAT]

Maybe I'll read about those blunders before I post an explanation, I'd hate to be guilty of spreading disinformation.

I tried looking for a website that had a fairly simple explanation that matched my understanding of how a wing works but most of them were either what I've been led to believe is 'wrong' or, they were fairly long & complicated.

 

[prost]

My apologies, KENAK. I didn't mean to suggest that you were a 'Bernoulli principle denier.'

I am troubled that you seemed so troubled by the explanation. As engineers, we are often called upon to explain complex things to people who will never have the background needed to understand our explanations, so we are forced to create simple illustrations to make our point and not confuse the listener while doing it.

You point that would take a few pages of explanation gets to my point; the 'head of wing development at Airbus' probably had about 20 seconds to explain a complex aerodynamics principle, and I don't think his explanation was really that bad. Because the upper skin on the airfoil is curved, and the lower skin flatter, then the air does have to travel a greater distance over the top then it does over the bottom--isn't that true? If you'll stipulate that, then the fact the airfoil does go faster over the upper skin than the lower and using the Bernoulli principle, you arrive at a relatively simple explanation for the origin of lift. Certainly, two particles next to each other before the airfoil, one goes over upper, the other over the lower, they won't necessarily meet at the trailing edge at the same time (they probably would if the flow was bounded or confined because of conservation of mass flow and Kutta condition at the wing trailing edge). However, and I've never seen any numbers for this; but you might guess that the two particles reach the trailing edge at different times.

Actually anything can be an airfoil. The sheet of paper, however, isn't a very good airfoil at subsonic speeds that characterize my blowing air, however such a cheap illustration goes a long way towards explaining somewhat why airfoils have lift--because the flow is faster over the top, the pressure is lower, hence lift.

 

[prost]

Regarding:
Aeronautical Engineering Blunders of the 20th Century

http://www.aeronautics.ws/blunders.html

Many of the explanations were unintelligible. It appears to me that the cambered airfoil is set up in the tunnel so that the flow hits the top of the airfoil first, not the bottom. It also appears the author of this site forgot about drag--if for instance in the extreme, the airfoil was vertical (leading edge down) the airfoil would spin clockwise or not at all.

Going to have to dig out the aerodynamics textbooks, however, I recall that you can use camber to predict lift (whether it is a good model or not is another question), suggesting that camber has strong influence on lift generation.

 

[prost]

My bad--I should have said--the explanations at the top were unintelligible. For instance
"In the discussion of the air flowing through the venturi created by the camber in the forward 1/4 of the chord producing lift directly by the increased velocity and therefor lowered pressure above the wing"

I know what a venturi is; what is the 'venturi created by the camber in the forward 1/4 of the chord'?

 

[TheTick]

Eighth grade writing is OK, but the 3rd grade science knowledge baking it up is not.

 

[KENAT]

The airbus guy had more than 20 seconds. In fact the entire show if I recall correctly was about the one question. It was more interesting than it sounds, but perhaps only to a prospective aero student as I believe I was at the time.

Because the upper skin on the airfoil is curved, and the lower skin flatter, then the air does have to travel a greater distance over the top then it does over the bottom--isn't that true?

It's true for a typical non symetric aerofoil but why do the particles have to reach the trailing edge at the same time? In short they don't. Hence the based on this ‘theory’ there is no reason the particles above the wing will go faster than below.

Also as you start saying an aerofoil doesn't have to be the classic aerofoil shape and for many applications isn't, which again blows this theory out of the water.

In fact reading your post you end up disproving, or at least arguing against, the theory yourself.

From what I was taught at university and have confirmed reading a number of text books etc:

The most important thing is that the wing is at an angle (angle of attack) relative to the airflow. A flat plate at an angle generates lift in basically the same way as a nice aerofoil shape, the aerofoil is just more efficient and has better stall characteristics etc.

I’m snowed under at the moment at work but I’ll try and put something more detailed. I’ve explained it to an apprentice before and it didn’t take multiple sheets and loads of diagrams so hopefully I'll keep it brief.

 

[GregLocock]

"why do the particles have to reach the trailing edge at the same time? " Exactly

If you'd like to write it up with diagrams I'll host it on my website.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[kenvlach]

Up the same alley is water quackery: Phony science & medicine oil hype that often gets media coverage:

http://www.chem1.com/CQ/wonkywater.html#BEO

Pretty funny stuff & links at bottom to other sites on quacks & debunking them.

 

[prost]

Thought some might enjoy this (apologize for being off topic):
The subject is 'why does an airfoil produce lift?'. NASA has a website that might help explain it better:

http://www.lerc.nasa.gov/

http://WWW/K-12/airplane/right2.html

Bottom line appears to be: lift occurs when flow changes direction. This appears to me to be a simplistic statement of the (very complicated) principle of the conservation of fluid momentum.

There are even a couple of applets you can download to your PC, so you can play with them off line to simulate effects of air speed, airfoil shape, etc. on lift.

Credit where credit is due: originally picked this link up from a MachineDesign.com forum/blog.

 

[ScottyUK]

Kenat,

http://www.guardian.co.uk/food/Story/0,,2011095,00.html

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