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..

wrote:
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


ISTR hearing about someone with a Cherokee who used them to
reduce drag on his fuselage.

--

FF

wrote:

wrote:

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



ISTR hearing about someone with a Cherokee who used them to
reduce drag on his fuselage.


Three kinds of air flow.
Laminar, Turbulent and Separated.

Induced drag, that from generating lift, is hard to reduce significantly.

But dragging a bunch of small wakes is all parasitic drag.

Reattaching a separated wake should, in general, reduce patasitic drag,
and make the old sled that much faster...