Any interesting topics for a paper?

[ninad]

Hi,

I was interested in writing a technical paper related to aerodynamics but the whole subject seems so vast. I'm finding it hard to zero in on a topic which would be technically interesting at the same time important with respect to the current practical requirements of planes.
Would anyone suggest areas of aerodynamics which they think need thought or are of current practical and functional importance to flight?

Regards.

 

[FredGarvin]

How about doing a paper that properly describes the theory of flight? It's current and pretty darned important.

 

[Ivan Seeking]

Fred, could you elaborate on that a bit? I am curious about your meaning here.

 

[Clausius2]

Hi,

I was interested in writing a technical paper related to aerodynamics but the whole subject seems so vast. .

I cannot help but showing a little smile when reading this.

 

[ninad]

How about doing a paper that properly describes the theory of flight? It's current and pretty darned important.

'Theory of flight' is too huge. Do you think you could suggest a specific topic i could concentrate on. While i was musing about what to do myself i was trying to base it on aspects like how one could help conserve fuel, reduce pollution, increase safety.
I've heard of birds getting sucked into engines and hampering flight.Any idea about how prominent is the threat jet planes( esp. commercial jets) face from birds?

I cannot help but showing a little smile when reading this.

How come? :-) Is it a smile of dissagreement or assent?

Regards.
Ninad.

 

[AlephZero]

> Any idea about how prominent is the threat jet planes( esp. commercial jets) face from birds?

You could start by seeing what the International Bird Strike Committee, US Bird Strike Committee, the Avian Hazard Advisory System, etc, etc, have to say about it. You could read the relevant FAA regulations on a/c and engine design and testing. You can find them with Google.

Having done some work on it myself, I would estimate there is of the order of 10,000 person-years of work that has been done already by the industry.

If you want to write a paper on it, I hope you have something new and evidence-based to say about it. I don't want to be unkind, but I'm also showing a little smile reading this thread...

 

[FredGarvin]

Fred, could you elaborate on that a bit? I am curious about your meaning here.

I was referrring to how most people subscribe to the "equal transit time" theory of lift. We've had quite a few threads on this. Arlindo had a great thread on it in particular.

 

[FredGarvin]

'Theory of flight' is too huge. Do you think you could suggest a specific topic i could concentrate on. While i was musing about what to do myself i was trying to base it on aspects like how one could help conserve fuel, reduce pollution, increase safety.
I've heard of birds getting sucked into engines and hampering flight.Any idea about how prominent is the threat jet planes( esp. commercial jets) face from birds?

Bird strikes are VERY real and very much on our minds when we design an engine. Part of the certification testing we have to do on our engines prior to getting FAA approval for their use is both a bird strike test and a hail ball ingestion. Both tests involve a projectile being shot at a running engine. They are quite fun but very serious.

In regards to the "hampering" of an engine's performance after an ingestion, our test parameters that we have to meet is that an engine must remain operational and show less than a, IIRC, 10% reduction in thrust for 5 minutes after the event. I'd have to go back and look at the FAA regs again. We haven't done one of these tests for a couple of years now.

It may be tough to tackle topics like fuel economy and pollution unless you have a lot of in depth knowledge in engines. You may be able to tackle the fuel economy idea from the mindset of an airframer and how airframes are designed though. As far as safety goes, that could be something that's pretty wide open. There is plenty of information on safety.

 

[AlephZero]

I was referrring to how most people subscribe to the "equal transit time" theory of lift. We've had quite a few threads on this. Arlindo had a great thread on it in particular.

I haven't seen that thread, but the theory is nonsense. Was the thread on the "pseudoscience" forum?

A simple analogy to debunk it: Consider a two-lane road where the lanes split and one goes round a diversion so the path is longer than the other (= the shape of the wing). Imagine an infinite stream of cars approaching at constant velocity and equal spacing (= in incident air). Imagine the cars are all black except two red ones, alongside each other, one in each lane.

Now, if the cars in one lane speed and then slow down again, after the diversion the cars have the same spacing and speed as before the diversion. The only difference is, the two red ones are not alongside each other any more. What's the big deal about that? It happens on the roads every day. The arguments about "the air would all pile up some place if the transit times are not equal" is just wrong.

In any case, if the transit times ARE always equal, you have a hard job explaining how fluid circulation gets started and how the vortex detaches from the wing

The fact that Einstein reputedly believed the theory, and designed a useless aerofoil using it doesn't make it "evidence-based"

 

[AlephZero]

Both tests involve a projectile being shot at a running engine. They are quite fun but very serious.

Yeah, you can say that again... mostly the successes are boring, but the failures can be funny with hindsight (especially if they happened to a competitor company's engine of course).

I guess we all know the urban myth about the guy who forgot to thaw the frozen chicken before firing it at the engine. Actually we didn't use chickens, we used freshly killed ducks, raised "to order" by a local farm. Like "can we have 20 ducklings with a mass of exactly 1lb each for next Tuesday please". Over the years the farmer got pretty good at feeding them so they came out at exactly the right mass to meet the test spec.

I remember one "funny with hindsight" failure. The birds were fired from an air-powered gun that looked a bit like a multiple rocket launcher. This particular time, we loaded up all the barrels, then there was some problem and the test was postponed for a few of hours. After lunch we came back and BANG. One rather dead jet engine. Looking at it, the first questiojn was "OK... why did one of these ducks have black and white fur instead of feathers?". Next question, "has anybody seen the works cat today?"

While we were off to lunch, the cat was also having a lunch of fresh duckling. Unfortunately it then curled up in a gun barrel for an after-dinner catnap. Oops, nine lives all gone, game over :uhh:

 

[ninad]

Ouch!

Is there any place on the net i can get videos or images of bird strike tests? They sound interesting.

It may be tough to tackle topics like fuel economy and pollution unless you have a lot of in depth knowledge in engines. You may be able to tackle the fuel economy idea from the mindset of an airframer and how airframes are designed though. As far as safety goes, that could be something that's pretty wide open. There is plenty of information on safety.

Thanks a lot. This is quite what i wanted i.e. 'This field is too hard for you or this topic requires a lot of knowledge, this may be worth a try.'. It's a real help.

If you want to write a paper on it, I hope you have something new and evidence-based to say about it. I don't want to be unkind, but I'm also showing a little smile reading this thread...

Thank you for the smile and your frankness. Truly. They help in reminding me that i am an amature. Hope i'll always be one.

Regards,
Ninad.

 

[AlephZero]

Ouch!

Is there any place on the net i can get videos or images of bird strike tests? They sound interesting.

Hey, I'm not trying to offend anybody here. But if you want to get involved seriously in this stuff, unfortunately you need to do the study and learn the background first. For what its worth, my boss left school at 16 and started his career riveting aircraft wings together, then went to night school to learn some maths and science, and finished up writing a string of papers that were published in international technical journals like the "Journal of Numerical Methods in Engineering". He used to love it when strangers called him "Professor Barlow", cos he had never even been to university, let alone got a Ph.D or become a prof! There's no reason you can't do the same as he did, if you really want to.

I doubt you will find any videos of birdstrike tests on the web. The test are very expensive to do and no engine manufacturer would want to let the others see in detail what they were up to. By "expensive" I mean anything from 1m to maybe 20m dollars - if a test goes pearshaped you can wreck the engine beyond any hope of repair, and that's not cheap.

You can probably find images of the damage caused by birdstrike on aircraft in service on the web - but not videos of the events for the obvious reason, unless somebody got VERY lucky with a home video camera. I've only seen a "real birdstrike" happen once - a seagull hit a military jet's wing, when the plane was taking off. The plane won.

You might find some "publicity" type videos made by engine makers for marketing or recruitment purposes. Sometimes they have shots of these type of tests. Try the engine or aircraft manufacturers websites.

 

[AlephZero]

OK, here's a guaranteed genuine picture for you. http://100.rolls-royce.com/facts/view.jsp?id=215

What you are looking at is a test rig. One fan blade is attached to a vertical rotor, with a counterbalance weight on the other side (which you can't see). The motor driving it is underneath the "floor". The blade rotates from right to left - imagine the aircraft was flying vertically upwards. The "bird" (they use lumps of gelatine for these tests) is dropped in vertically so it gets "bacon sliced" by the blade. That big "bump" in the blade is what happened when the "sh*t" hit the fan.

BTW these preliminary tests on single blades are pretty cheap compared with full engine tests - only about a quarter of a million dollars a pop.

 

[DLinkage]

How about dimples on an airfoil at various speeds. What depth and what frequency of dimples delay separation while not increaseing the drag too much. That is, fora given airfoil find the best combination of dimples - frequency and size, that yield the highest ratio of cl/cd.

Show this as a varation of angle of attack, airspeed, and flap setting
(15,30,45,60).

Discuss how these migh effect the down wash on the horizontal tail?

Should the horizontal tail use dimples?

Are ailerons as effective with dimples?

Do dimples on the edge of the wing reduce downwash over the tips?

What about dimples on the heated part of a wing that can de-ice itself. Do dimples have less of an effect when the ambient air is warmer/cooler?

Based on all these questions, should dimples be used on certain aircraft? If so what kinds?

 

[Danger]

And I am always interested in icing. There are some very complex phenomena going on with the airflow when you start to get build-up.