Vortex Generator Technicalities, By Peter Garrison

In the June 2006 issue of Flying Magazine Page 101. Peter Garrison
wrote
another good information article called "Spin Doctors"

Its good information about Vortex Generators, that every builder pilot
should
get a copy and read.

He has been a editor for Flying Magazine for a very long time.
Peter is one of the best engineering, information editors in the Flying
Magazine.
His article, is always the first one I read.

Larry Fitzgerald

www.fitzair.net

can you suggest the point of the article... I've considered using them
on my to be completed homebuilt.. Is the article on-line somewhere?

The Point of the Article is to understand their use.

Peter makes these statements.
"Vortex generators seem like a discordant
element in aerodynamic design" and "violating the rule that smoothness
is
desirable above all things"

Think, very hard about his statements. I have agreed with the first one
for many years.
Vortex Generators are a correction, of a poor airfoil use, at a given
angle and air pressure
Ect.

The article is only in the magazine at a store or subscriber.
Make a copy at the library. While their, look at the back issues.
Peters articles are worth making copies of, for your personal library.

Larry Fitzgerald

www.fitzair.net

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
TJ400 wrote:
can you suggest the point of the article... I've considered using them
on my to be completed homebuilt.. Is the article on-line somewhere?

I remember 20 or so years ago I asked some engineers from the Columbus
Ohio North American plant about vortex generators.
Their reply was that vortex generators are used to fix a problem with
the original design found after the aircraft entered service.

john smith wrote:
I remember 20 or so years ago I asked some engineers from the Columbus
Ohio North American plant about vortex generators.
Their reply was that vortex generators are used to fix a problem with
the original design found after the aircraft entered service.


VGs were traditionally used as a band aid to correct the effects of flow
separation, especially in supersonic flight, and usually just ahead of
control surfaces.

The use of VGs as a STOL device is more recent development when some
bright light discovered that they increased stalling AOA with almost no
increase in cruise drag. They have become a sort or poor man's LE
slat, giving 1/3 to 1/2 the AOA increase a slat gives, or about .3 to .5
increase in Clmax.

Garrison also had a great article once about how winglets work. It's
the only time I've seen them explained properly, in that they harness
energy in the wing tip circulation to create thrust that is surplus to
the winglet's drag when operating at high L/D, as airliners do when
cruising at 35000 ft. The simply create a lift vector that is angled
inboard and forward like the sail of a boat. Which is why they are
sometimes called "tip sails".

John

AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
whole sport aviation for some time and just trying to grasp it all over
again..

thanks..

AOA = Angle Of Attack
The angle with which the wing contacts the impinging air stream

L/D = Lift to Drag ratio
As AOA goes up, so does lift, but drag goes up too. Knowing what the L/D
curve looks like for a specific airfoil as AOA increases is an important
point in designing an aircraft to meet a stated mission.

Clmax = Maximum coefficient of lift
The AOA where the wings lift is maximum. Usually occurs at an AOA just
before stall.

L E Slats = Leading Edge Slats
http://www.liming.org/ch801/slathistory.html



"TJ400" wrote in message
oups.com...
AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
whole sport aviation for some time and just trying to grasp it all over
again..

thanks..

What he said...

Ron Webb wrote:
AOA = Angle Of Attack
The angle with which the wing contacts the impinging air stream

L/D = Lift to Drag ratio
As AOA goes up, so does lift, but drag goes up too. Knowing what the L/D
curve looks like for a specific airfoil as AOA increases is an important
point in designing an aircraft to meet a stated mission.

Clmax = Maximum coefficient of lift
The AOA where the wings lift is maximum. Usually occurs at an AOA just
before stall.

L E Slats = Leading Edge Slats
http://www.liming.org/ch801/slathistory.html



"TJ400" wrote in message
oups.com...

AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
whole sport aviation for some time and just trying to grasp it all over
again..

thanks..

"TJ400" wrote in message
oups.com...
AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
whole sport aviation for some time and just trying to grasp it all over
again..

thanks..

Try - http://www.risingup.com/fars/info/part1-2-FAR.shtml
--
Jim in NC

Morgans wrote:
"TJ400" wrote in message
oups.com...

AOA, L/D, Clmax and LE slats are what exactly?.... Been out of the
whole sport aviation for some time and just trying to grasp it all over
again..

thanks..

http://www.home.earthlink.net/~tp-1/a4412-a.jpg
http://www.home.earthlink.net/~tp-1/a4412-b.jpg

Earthlink is so messed up right now it's almost unusable.

I posted these two charts, but EL tells me the images cannot be viewed
because they contain errors.

WSFTP had no trouble showing them - so I dunno....

Two charts of airfoil performance data for the 4412.

Notice (I hope) that the flaps deployed curve is similar in shape as the
no-flaps curve, but a little taller and broader at the bottom.

Interpret that as Higher CL at any given AoA.

Power off, the wing will stall at some partiular AoA.

I usually look for that initially between 10 and 12 degrees (depending
on the airplane).

I've also noticed that many common airfoils actually have a
_lower_ stall AoA with flaps down!


Like in a 172, notice the way the nose comes down with flaps?

We are operating at a higher CL now and need LESS AoA to make
the same amount of lift. Has to do with the increase in Camber
with flaps down, I believe.

That indicates a NARROWER range of AoA (flaps down compared to flaps
up)- not higher!

Power ON will allow for higher AoA, and thus higher CL.

How much higher depends largely on how much power can be applied (while
maintaining control of the aircraft at extreme AoA!)

However, do consider the possible results of a super slow approach
speed. Gusts have a much more profound effect on the amount of lift
generated (or suddenly lost?).

As would an unexpected loss of power...

This is flying pretty close to the edge, kids.



Richard