2012 Exhaust Blowing & Coanda

[bhall]

[My comments made much more sense within the context - and thread - in which they were posted. In the future, please delete my comments outright if they're summarily deemed immaterial to their respective discussions rather than move them and render the thoughts completely neutered. Thank you.]

[hardingfv32]

bhallg2k

+1

[Pierce89]

Forgot to write - add me too to the "rbr are trying to blow along the footplate edge" party", please.

Last year we had the exhaust forming a vortex at the diffuser/footplate edge. I believe the low strake in front of the inside edge of the rear tire is there to form a vortex using the flow around the side pod. It is not possible to get the exhaust flow in line with this axis of this strake to help improve the vortex formation.

What does the flow do when it gets to the edge of the diffuser? How is it made to do something useful? How does it seal the diffuser? Why route it there if you can not demonstrate value?

Why route more flow to an area that is already leaking to the underside of the diffuser?

Back up your opinions with some details.

Brian

I agree with Shelly.
I'm no f1 aerodynamicist, but I am studying aeronautics in college, and without going into complex math theory to give "facts". We know you've spent enough time around here, to pick up enough "armchair aerodynamics" to eyeball that RB8 rearend and also come to conclusion that RBR are indeed trying to seal the diffuser like last year(albeit less effectively)by directing the exhaust through the influence of sidepod downwash and the Coanda effect.If we ever get our grubby little paws on the right pics, I'll bet there is something in the footplate area analogous to the VG's at exhaust exit last year.

Since we don't have any data showing how effectively a vortex seals a diffuser, the best math we could do, is model the rough increase in diffuser volume in CFD or do something of the like, and then, we can that number for the worthless grain of salt it would be.(Or maybe model a diffuser with only a third of the expected volume increase because obviously a vortex won't seal as well a wall)

The point of the last little sarcastic bit is to show how ridiculous it can be to ask for "facts" when we're only making wild guesses about F1 cars we have absolutely no access to or any real info about.

[NoDivergence]

We aren't able to make any deductions as we aren't privy to any real hard data. Exhaust flow rate, diffuser volumetric flow rate, downforce generation to angle plots, downwash efficiency plots, etc etc etc. It's all guesswork for us. Accurate CFD is a must for any calculated design element, here

[bhall]

[My comments made much more sense within the context - and thread - in which they were posted. In the future, please delete my comments outright if they're summarily deemed immaterial to their respective discussions rather than move them and render the thoughts completely neutered. Thank you.]

[bhall]

[My comments made much more sense within the context - and thread - in which they were posted. In the future, please delete my comments outright if they're summarily deemed immaterial to their respective discussions rather than move them and render the thoughts completely neutered. Thank you.]

[beelsebob]

Everyone uses a coke bottle shape. This is my point. They never have felt that it was beneficial to seal the diffuser with body air flow.

Now you are proposing to seal the diffuser with a exhaust velocity that is maybe 5 m/s greater than the normal body air flow. What has changed?

Would it not be more logical to feed the flow established by the coke bottle shape which has a more beneficial out come?

Because your 5m/s faster figure comes from a deeply flawed understanding.
1) The figure calculated was based off an exhaust gas exit speed 2.5 times too fast
2) The figure calculated was based off air flowing around the exhaust exit at 0m/s, not at 75-100m/s.
3) The figure calculated was 30m/s, even under the above broken conditions.
4) The model that figure came from was a model of the McLaren, not the RBR.
5) The model showed the air hitting the floor almost straight downward, and losing all its speed there, which would likely not happen if it was being dragged backward by ambiant airflows.
6) The only way you got to 5m/s was by guessing.

The fact that at least 2 teams are trying to direct their exhaust flow there, one of whom appears to have the fastest/second fastest car suggests that it makes a worth while difference, even at the reduced potency.

[avatar]

There seems to be very little mention of the temperature of he flow and how that affects it's path/behaviour/interaction with surfaces and other flows.

I'm no aerodynamicist, but taking the familiar fluid flow of water from a tap; as the temperature of the tap water rises, it gets more fluid and visibly changes path from the tap.

To what extent have people factored temperature/ differing fluidity into their models?

[shelly]

@brian: the footplate vortex is there, even with no exhaust, as a consequence that pressure on topo of the loor is higher than pressure under the floor.

If we analyse this vortex without any exhaust effect, we see thatit has a certain vorticity and a certain longitudinal velocity (in one word, it has a certain helicity -see wiki for a quick definition of that).

So air follows a corkscrew path curling around the fooplate.

You do not want to make a vortex with the exhaust: you just want to alter the advance ratio of the corkscrew of the existing footplate vortex,

In so doing, you get more downforce from that vortex

[f1ssk]

To moderators,
I have been reading these forums everyday for 2 yrs now..

this is getting out of hand here.. its just about 5 guys talking on this forum and sticking to small nuances which we are eye balling from pictures. We cant even see the flow!?
Please try to have a discussion on larger picture and "Why" something is done.

I suggest a 10 post per hundred for each member. Then they will put a lot more thought before they type something. It will be better for the forum and stronger conceptually.

[kilcoo316]

Please try to have a discussion on larger picture and "Why" something is done.

The why is simple!


There are two thought trains:

(1) The exhaust is being used to strengthen the longitudinal vortex induced from the strake immediately upstream the rear wheel. Due to the circulation direction of this vortex, it then helps to reduce leakage out the side of the diffuser. This gives more diffuser and floor downforce.

(2) The exhaust is being dissipated as much as possible through introduction to the spanwise flow then being fed over the top of the outboard diffuser section - to attempt to reduce sensitivity of diffuser and beam wing to throttle.

[Jimi_Hendrix_1967]

Can some of you explain how long the running time is designing and manufacturing on an update red bull introduced last week? Some people in the f2012 thread seem angry why Ferrari cant produce such in 3 weeks time.

[Nando]

(2) The exhaust is being dissipated as much as possible through introduction to the spanwise flow then being fed over the top of the outboard diffuser section - to attempt to reduce sensitivity of diffuser and beam wing to throttle.

Would it not be a very inefficient solution if that was the case?

Surely putting the exhaust higher up so they blow between the beam wing and rear wing would be a better way to not disturb any airflow going to the diffuser and beam wing/monkey seat (if they will run one)

[bhall]

[My comments made much more sense within the context - and thread - in which they were posted. In the future, please delete my comments outright if they're summarily deemed immaterial to their respective discussions rather than move them and render the thoughts completely neutered. Thank you.]

[kilcoo316]

Would it not be a very inefficient solution if that was the case?

Surely putting the exhaust higher up so they blow between the beam wing and rear wing would be a better way to not disturb any airflow going to the diffuser and beam wing/monkey seat (if they will run one)

Well, the 3 components, diffuser, beam wing and main rear wing all interact.

The beam wing and rear wing both help 'pull' air out of the diffuser (for want of a better expression).

If you have a pair of coherent jets (exhaust plumes) in that - then it interferes with the whole thing.