engineering thread...for engineers

[PiSigma]

here are at the university of alberta we have 3 or 4 terms. fall, winter, spring/summer. spring/summer are either 2 monthes terms with crammed classes or if engineering courses lasts for the full 4 monthes.

we go by the 4.0 GPA, 3 years ago it was the 9 point system. that means a 4 is a perfect mark, 2 a passing, 1 is go on "dean's vacation" for a year, anything less than a 1, we keep your money and you go home and stay there.

for every course, we would have an final at the very end, some courses might substitute the final with a major report or presentation. finals could weigh from 40%-60% of the entire course. there are also midterms, which is given at the middle of the term which are worth from 20-40% of the marks. our courses usually have 10-15% for homework, and 10-15% for labs. depends on the course.

 

[sumdud]

I was talking at the Chinese military design thread at the AF forum, and the discussion came upon wing designs. I have a few questions, but I decided to move the talk here since I find it more appropriate here.
So, what are cropped, cranked, and compounded deltas? (Are double-deltas a type of compounded deltas?) What is compression lift? How does Double Deltas work? And how does a vortice hope increase lift?

 

[Indianfighter]

So, what are cropped, cranked, and compounded deltas? (Are double-deltas a type of compounded deltas?) What is compression lift? How does Double Deltas work? And how does a vortice hope increase lift?

I admit that the discussion of this topic is indeed quite stimulating, and I have already discussed this issue in 2 separate threads.
All discussions are mainly due to the article on delta-wing on wikipedia.

Deltas are :

Pure--Right angled triangle :-

*
..*
....*
......*
* * * *

Cropped--Triangle is incomplete :-

*
..*
....*
......*
.......*
* * *

Compound--Cropped at an angle :-

*
.....*
.........*
..........*
...........*
............*
********

Cranked--the frontal-part of the wing is bent downwards or cranked downwards (similar to the nose of the concorde)

Ogee--The hyponetuse is a curve instead of a segment.

*
.*
.. *
.....*
..........*
.................*
..........................*
*****************
The above was the design of the concorde.

All other types of delta designs are combinations of the above basic types. Canards may or may not be present.

And how does a vortice hope increase lift?

Upon pitching up, drag is produced by the delta-wings due to their large size. Although the pitch may be instantaneous, significant loss of forward speed occurs.
If a low pressure is artificially built above the wings, then the pitch may take place at a lower AoA, and thus retaining the forward speed.

For this purpose, canards are added to provide for generating low pressure above the wings. Upon a turn, the canard "cuts through" the air in such a way, that air is made to pass at a gap above the wings instead of "scraping" the upper part of the wings.

This gap generates low pressure above the wing. Since lift is generated upon the presence of lower pressure above the wing than below it, the pitch-up is eased, with application of lesser AoA and hence lesser drag.

The same function is performed by cranked wings. Air is deflected by them at a gap above the upper surface of the wing. Low pressure is created in the gap and hence lift is generated.

Since canards on aircraft such as the Eurofighter are movable, they can be used to pitch down (by turning them appropriately), braking (by pointing them down) and rolling (by turning one of the canards).
Thus, they may simply be viewed as the tail-planes added to the front.

What is compression lift?

It is the lift generated by shock waves generated by the aircraft. The only known aircraft to have utilised this principle is the

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References:

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Article on canards in wikipedia.