Fins on Engine Cowling
 

Hi,
Have alook at this picture:

http://www.!!!!!!!!!!!!!!/photo/Lufthansa/Airbus-A340-642/0596750/M/

Here is mentioned that these fins are used to reduce turbulence, I would like to know more about these devices and why they put them on engine cowlings? Is there any major source of turbulence around the engines AND Does this method affect the noise (thanks toolowtoofast ) polution made by the plane?( I heard this somewhere but still unsure about the truth?)

Does Boeing use the sameway?

The "fins" (or "strakes") are really vortex generators, and are an important part of high AOA aerodynamics for the wing. I recall on the DC-10 they reduced the stall speed perhaps 10 kt. or more. They are your friends.

sound polution????? (sic)

clowns on the tube/train/bus with loud doof doof music on their I-pods - now THAT'S noise pollution.

aircraft engines - music :)

Greetings
Indeed they are vortex generators, and usually vortex generators are uses to put some energy back to the boundary layer, in this case they act exactly at the pods (engine to wing fixing), avoiding the area just behind the pods to become turbulent at high AOA. i.e., during takeoff, approach and landing :)

ASFKAP got the name right. There is a write up on this in the smartcockpit.com website. You can download the document here.

9V

Take one off, and you suffer a performance penalty.
If memory serves me right it's about 4-6 tonnes on both the 737 (CFM) and A319 (CFM).......:eek:

M

Airbus calls them strakes. :ok:

vortex generators delays the separation of airflow( profile )arround the airframe thereby reducing the drag which is created when the airflow separates from the skin.
nothing to do with turbulance as your post indicates.
see book MECHENICS OF FLIGHT BY A.C. CERMODE:ok:
it explains allmost all aspects of air.
theory of flight:ok:
good luck

The picture is a little misleading to the actual angle of the vanes as the engine cowling is up.

I think the vanes are used to produce a stabilising force to stop the engines from vibrating/moving too much, as well as acting as vortex generators.

Grettings
GETSETGO
I have spelt it turbulent as turbulent airflow (drag) as opposed to laminar airflow.:ok:
turbulance is something else :}

They are there to compensate for the cut out in the leading edge devices caused by the engine pylons. As well as the obvious reduction in slat span, the cut out affects the three-dimensional lift distribution. As the LE devices have a critical role in defining CLmax, this accounts for the effect on stall-speed (and hence weight).

Greetings
Wonderboysteeve :ok::ok:

Just to add the main use is for high AOA and pre stall characteristics, if you look majority are only installed inboard only, because fan cowls can be fitted either side of an engine it can be un-noticed defect. I think some a/c such as an A319 may have fins either side though.

You will find strakes on both sides on all A319 aircraft and on A320 LIP (Lift Improvement Package) aircraft. This is also the easiest way to distinguish a standard A320 from a A320 LIP. :8

This extra engine strake together with several modifications on the leading and trailing edge of the aircraft enables you approach about 6kt to 7kt slower than the standard aircraft.

Have seen pictures one or two 737s with the cowlings mixed up so two vortex generators on one engine and none on the other or maybe it might have been with one on each nacelle but on the wrong side.

I think Boeing may have modified the cowlings at this stage to prevent this.

Greetings
Two on either side and none on the other, is a bit odd, on day in one airline I have flown with maintenance put them on the other side the boeing rep went mad, I think that it is better tol look into the CDL to check that it is normal configuration :ok:

I believe the idea is to direct the nacelle vortice over the wing, so as it doesn't interact with the wing flow and destroy the boundary layer (causing separation).

Thanks for this discussion about an interesting example of a vortex generator!

Ever looked at a Concorde?

There are two 'vortex generators/chines/strakes' (whatever you want to call them) on the forward fuselage, roughly under the cockpit windows.

They don't look prepossessing at all, but they really "stick down'' the airflow over the entire top of the fuselage, even at quite high angles of attack, and prevent the lower part of the vertical tail ending up in a highly turbulent airflow. It's one of the reasons the Concorde vertical tail isn't all that big, compared to some subsonics, even if she lands at a higher angle of attack.

And an interesting snippet: they were already in place for the first flight of the first prototype in 1969.....

CJ

Ditto later DC-9's beginning with the series 50. Probably the MD-80/-90/717 too, although I haven't taken time to look up photos. :)