Reducing the drag of a two element wing through stall

[jason.parker.86]

I always wondered when it rained where all that water went? I wouldnt want it to drain from the car, infact if I was an engineer I would want it going to some wing tanks to add weight. Must be an advantage having a heaver car on a wet track?

[marcush.]

not necesarily .Adding mass is not the same as adding vertical force (downforce)

[horse]

low is attached to the sides more than the centre of the wing. Upper element's flow is attached throughout because of the slot. Much better improvement than my first attempt which was just a 2D wing which doesn't tell the whole story.
Lift to drag ratio is 1.834 with down-force of 136 lb. on the wing alone
the last one i did was 0.7 L/D.

Good work ringo. It's interesting to see the flow in 3D. L/D ratio still seems really low, though, considering slimjim got somewhere in the range of 10-20 with his model.

Is the flow from the diffuser getting anywhere near to reacting with the rear wing?

[Just_a_fan]

low is attached to the sides more than the centre of the wing. Upper element's flow is attached throughout because of the slot. Much better improvement than my first attempt which was just a 2D wing which doesn't tell the whole story.
Lift to drag ratio is 1.834 with down-force of 136 lb. on the wing alone
the last one i did was 0.7 L/D.

Good work ringo. It's interesting to see the flow in 3D. L/D ratio still seems really low, though, considering slimjim got somewhere in the range of 10-20 with his model.

Is the flow from the diffuser getting anywhere near to reacting with the rear wing?

Slimjim's excellent model was 2D though.

The car as a whole is probably only L/D=2.8-3.2, maybe a tad more. The rear wing is also well known as the key drag source after the wheels. F1 wings are pretty inefficient because they have a very low aspect ratio. The big end plates help by reducing vortices but not to the extent that the rear wing would have a L/D of 20 it seems to me.

[horse]

The big end plates help by reducing vortices but not to the extent that the rear wing would have a L/D of 20 it seems to me.

EDIT:

I take it all back. Found this paper by Katz (whose book I have read for my own work) and if you look at figure 5, the L/D ratios would certainly seem to be in the region of 3. I shall have a good read of this paper when I get time.

AERODYNAMICS OF RACE CARS, Katz (2005)

[jason.parker.86]

Maybe the snorkel goes back on its self, and goes under the floor?

[ringo]

L/D of 5 and 3 were with 3 elements right?
I have that book. The F1 wing is much different now than it was then, so i am not sure what levels of lift to drag can be expected. You can look on my down force value and get an idea of how this thing is performing. It looks small to me, but i don't expect a 750mm wing to create 500 or 1000lb all by itself.
I think a lemans car has more down-force than an F1 car? so i always try to use that as a reference.
With that i still have some improvements to make, so i can try and muster L/D of 2 or 3. but remember those wings are designed with software that shapes the wing based on what lift coefficient you put in and velocity profile. I am at a disadvantage with that.

This speed is 90m/s , i will try to slow it down till it's near stall. Find the stall speed and blow the jet at that speed at different angles. I want to compile everything and make it coherent before i put it up.

Here what's happening with the diffuser at 0.3m from center. diffuser is ok, has a nice little suction peak at the throat, but it's short and has no rake. It's best i build a whole car by summer.

[ringo]

low is attached to the sides more than the centre of the wing. Upper element's flow is attached throughout because of the slot. Much better improvement than my first attempt which was just a 2D wing which doesn't tell the whole story.
Lift to drag ratio is 1.834 with down-force of 136 lb. on the wing alone
the last one i did was 0.7 L/D.

Good work ringo. It's interesting to see the flow in 3D. L/D ratio still seems really low, though, considering slimjim got somewhere in the range of 10-20 with his model.

Is the flow from the diffuser getting anywhere near to reacting with the rear wing?

That is what happens with very thick profiles. They have very high lift coefficients. Secondly blowing a jet a 3 times or 2 times the speed behind would enhance it as well.

[ringo]

Nice work ringo.
What is the range of vehicle speeds you are using?

This is 90m/s ~200 mph, I will bring it down to some of the cornering speeds on some tracks and try to find a speed where the element just about stalls.

[horse]

L/D of 5 and 3 were with 3 elements right?

Figure 5 showed some sort of multielement wing. Looked like there might be 4 in total. It looked to me as if L/D ratio was 2 ish for wings without side fins and 3 for wings with side fins.

I have that book.

'Low Speed Aerodynamics'? Are you a fan of panel methods as well, Ringo?

Secondly blowing a jet a 3 times or 2 times the speed behind would enhance it as well.

I suppose that's the goal we are aiming for.

[Crafty]

Dont know how old this picture is, but no snorkel..



taken from http://www.jamesallenonf1.com

[SLC]

I haven't posted because I couldn't really be bothered to argue with you lot.

Anyway, read this and weep!

http://scarbsf1.wordpress.com/2010/02/2 ... el-rumour/

The rumours suggest the drivers left braking leg, which sits unused on long straights could be used to alter the flow from the snorkel to the rear wing duct, where a valve alters flow through the blown slot to stall the rear wing. This would reduce downforce and also drag, which would allow a higher top speed. Then the driver moves his leg to start to brake for the next turn the valve switches airflow back to normal, the wings airflow reattaches and provides the downforce needed for the turns. This sounds both feasible and far-fetched at the same time.

[Just_a_fan]

I haven't posted because I couldn't really be bothered to argue with you lot.

Anyway, read this and weep!

http://scarbsf1.wordpress.com/2010/02/2 ... el-rumour/

The rumours suggest the drivers left braking leg, which sits unused on long straights could be used to alter the flow from the snorkel to the rear wing duct, where a valve alters flow through the blown slot to stall the rear wing. This would reduce downforce and also drag, which would allow a higher top speed. Then the driver moves his leg to start to brake for the next turn the valve switches airflow back to normal, the wings airflow reattaches and provides the downforce needed for the turns. This sounds both feasible and far-fetched at the same time.

Interesting quote. You forgot to post the first bit where he says that the rumour is from the internet. Which means places like this. And Scarbs is on here too.

It certainly doesn't "prove" anything one way or the other and no reason for either side of the discussion to weep

[horse]

I haven't posted because I couldn't really be bothered to argue with you lot.

Not asking you to argue, please contribute! Do you think a stall can work and if so, how is it done and how do you avoid the negative side effects?

[cornermarker]

Looks to me like a press shot, so probably old. It was taken with a wide angle lens, so the camera and photog were close up. Car was probably stationary.

Edit: But you can see a panel were the snorkel will end up, still opposite that bump.

Kelpster