Replicating an F-duct

[riker84]

Hello all,

This is my first time posting on this website so if I've posted this in the wrong section, I apologize. I am posting with regard my final year project of a Mechanical Engineering Degree in Ireland. I have chosen to do my thesis on the effect of blown air on a rear wing, as used by Mclaren on their track car.

I plan on doing some F.E.A. testing using a programme called "Ansys", and then make a model for wind tunnel testing. Although I dont know the exact way I'm going to make the wing yet, I think i might use an aluminium skeleton with a smooth skin to cover.

I plan on wind tunnel testing the wing with and without the blowing apparatus. The main problem I have encountered is the blowing apparatus itself. My idea is to have a small airpump outside the windtunnel, then using a small tube to blow air onto the wing. This hopefully should divert the adhesive air stream off the steep edge of the second plane, thus decreasing the downforce.

The thesis itself is in early stages yet, but I thought I would post it on this forum so I could get some useful advice.

Also, I have researched on different explanations of how the 'f-duct' works, most seem to be using the term 'wing stall'. To my understanding of aerodynamics, would a wing stall not create great amounts of wake turbulence or drag?

Thanks in advance for any replies I recieve.
Best Regards,
Patrick

[m1dknight]

I personally would build it like a model airplane wing, I use the stuff all the time at uni, you can buy wooden sections and that shrink wrap plastic in just about every model store and it is a really easy way to make an approximation. If you make the element bigger than needed then you can easily create the slot in the rear and attach your blower through a hose on one side to keep it out of the air stream.

As for how it works, the best description I've seen online is from http://scarbsf1.wordpress.com/category/f-vent/

The important part is

Although a larger wing creates more frontal area and hence presents more of an obstruction to the airflow, it is in fact the drag induced the unseen air spilling off the wing that’s creates most of the rear wings drag. In fact an F1 wing despite looking so streamlined creates more drag than a solid block of the same dimensions. This is because an F1 wing is so highly loaded as it strives to create huge amounts of downforce from such a small surface area, that the air coming off the wing creates an invisible extension to the wings frontal area. Created by both the airflow rising all but vertically off the centre part of the rear wing and then the even more draggy vortices spiralling off the wing tips. These vortices are often seen in wet conditions and used to be seen as a sign of an efficient wing, but are in fact hugely detrimental to the downforce\drag coefficient of a rear wing. This is why we see such efforts to reduce wing angles near the endplates and team make the slits in the endplates, as these are all aimed at reducing these vortices.

Basically the F-Duct increases the drag caused by the the wing but reduces the incidental drag it creates which is a far bigger percentage of the total drag so the overall effect is a reduction in drag.

Hope this helps, currently going into my final year and would really like to see anything you come up with.

[Tifoso]

Just a brilliant response, mate. Thanks!

[2son]

Hey Patrick, i was doing some research on this subject too, i found loads of good information about the effects of air fed surfaces from high altitude aeronautics, it was introduced during the cold war so high altitude spyplanes could maneuver in the thin atmosphere, its actually more interesting than it sounds, but that might just be me lol