2012 Exhaust Blowing & Coanda

[raymondu999]

Nando - The Coanda effect is when a fluid is guided by a nearby curved surface to modify its direction. As the surface curves away from the flow it will create lower pressure close to the surface. This pulls said fluid towards the surface.

http://www.thermofluids.co.uk/effect.php

As Omar has pointed out - the downwash airflow over the sidepod helps deflect the 10degree upwards to a lower angle, an angle at which the exhaust plume is closer to the sidepod and could then get sucked in by Coanda.

[Pup]

imo, this is a bit of a pointless conversation. The antis weren't convinced earlier this year, and there is no new evidence to consider.

Why are you guys rehashing February's arguments?

[raymondu999]

Nando - Coanda isn't about any downwash or housing directing any flow anywhere. It's about this effect: (Guest starring Pup's torch and martini shaker)

If you're still unconvinced, fine by me. I'll be off.

[hardingfv32]

The Coanda effect is when a fluid is guided by a nearby curved surface to modify its direction. As the surface curves away from the flow it will create lower pressure close to the surface. This pulls said fluid towards the surface.

Note in my experiment how it seems what little Coanda Effect there is seems to be limited by the attraction (don't know the correct aero term) of the upper part of the flame. Would this be similar to the low pressure that you are talking about near the object surface?

Brian



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[hardingfv32]

imo... there is no new evidence to consider.

You need to remove your blinders. My experiment clearly demonstrates a flaw in the Coanda Effect thesis. As such, we are correct in revisiting the subject.

Brian

[Nando]

Nando - Coanda isn't about any downwash or housing directing any flow anywhere. It's about this effect: (Guest starring Pup's torch and martini shaker)

If you're still unconvinced, fine by me. I'll be off.

Is that your image? If yes. Take a picture when holding the flame horizontal to the top part of the mixer you have and see if the effect is the same.

Or as extreme.

Right now you are blowing the "exhaust gases" directly on to a surface.
I´d like to see a picture where the exhaust gases are horizontal with the highest points of the circle.

EDIT: Nevermind, i realized Pup had provided the picture, Pup could you try this please?

[Nando]

Like this,

The above one (picture you provided) would be illegal in F1.

the one below i would like to see a picture of and how the flame interacts with the mixer.

[hardingfv32]

Nando... Yes, you are correct that the Coanda Effect is not going to function under the current design restrictions without the exhaust flow being forced downward by the air flow over the side-pod. There is a possibility that there is no Coanda Effect required. Maybe the flow over the side-pod does a good job of forcing the flow downward into the channel and that the channel is just an aiming mechanism.

Brian

[GrizzleBoy]

Nando - Coanda isn't about any downwash or housing directing any flow anywhere. It's about this effect: (Guest starring Pup's torch and martini shaker)

If you're still unconvinced, fine by me. I'll be off.

Is that your image? If yes. Take a picture when holding the flame horizontal to the top part of the mixer you have and see if the effect is the same.

Or as extreme.

Right now you are blowing the "exhaust gases" directly on to a surface.
I´d like to see a picture where the exhaust gases are horizontal with the highest points of the circle.

I also disagree with the pics posted so far in terms of their relation to what is happening with the cars. I disagree with the blue flame much more than then the yellow.

The exhausts on the cars face up and away from the lower surfaces of the tunnel by a minimum of three degrees as we already discussed.

Regarding your proposed experiment, we would at most see a bit of bending, but the majority of the flame would just go up in the air (assuming the relevant angles proposed by the regs are followed during the experiment). Unless we introduced the downwash effect similar to the air over the side pods in motion that would then push the flames down onto the cylinders for better effect.

Not only that, but by the time they've made their way out of the tunnel in the cars, the sharp edges of the sides of the tunnel would basically kill off almost any relevant further coanda effect that would pull the fumes inwards, if we are still talking about button being stationary in the pits.


Come to think of it, what if the goal is to have the exhaust gases getting pushed down by side pod flow during fast sections to stop the tyres losing heat, but upwards and away from the tyres when the car is in slower sections, so as to not overheat the tyres while already under heat generating load/friction due to less downforce creating more "slip"?

[Nando]

Nando... Yes, you are correct that the Coanda Effect is not going to function under the current design restrictions without the exhaust flow being forced downward by the air flow over the side-pod. There is a possibility that there is no Coanda Effect required. Maybe the flow over the side-pod does a good job of forcing the flow downward into the channel and that the channel is just an aiming mechanism.

Brian

It sure seems like it wont. Here´s a further update, this time with F1 rules.
And with a slight decline to replicate the sloping exhaust housing.

Version 3 is 10 degrees exactly. Cyan line is horizontal. black line is Mclaren exhaust housing.

So even if the downwash pushes the exhaust gases down so they are horizontal, the coanda effect would be minute really.

[Pup]

My experiment clearly demonstrates a flaw in the Coanda Effect thesis.

No, your experiment demonstrates that the conditions for utilizing the coanda effect are tricky to achieve. I think we knew that.

If you want to disprove the idea, then find a pipe the same diameter of your flame, cut in half, bend it to the correct angle, attach it to your torch, and set your torch to create the same exhaust velocity as McLaren's exhaust. Then get a fan and do a series of tests with different air flows as well as without any.

Then you've got something.

As for me, my cocktail shaker already has one burn mark on it. One adds character; more would be an insult to the drunkards of the world.

[raymondu999]

Nando - Your version 3 hasn't taken into account downwash. Downwash will reduce the angle from 10 degrees. Coanda takes it from there.

[Nando]

I also disagree with the pics posted so far in terms of their relation to what is happening with the cars. I disagree with the blue flame much more than then the yellow.

The exhausts on the cars face up and away from the lower surfaces of the tunnel by a minimum of three degrees as we already discussed.

Regarding your proposed experiment, we would at most see a bit of bending, but the majority of the flame would just go up in the air (assuming the relevant angles proposed by the regs are followed during the experiment). Unless we introduced the downwash effect similar to the air over the side pods in motion that would then push the flames down onto the cylinders for better effect.

Not only that, but by the time they've made their way out of the tunnel in the cars, the sharp edges of the sides of the tunnel would basically kill off almost any relevant further coanda effect that would pull the fumes inwards, if we are still talking about button being stationary in the pits.


Come to think of it, what if the goal is to have the exhaust gases getting pushed down by side pod flow during fast sections to stop the tyres losing heat, but upwards and away from the tyres when the car is in slower sections, so as to not overheat the tyres while already under heat generating load/friction due to less downforce creating more "slip"?

Agree, i think as you that with the proposed experiment that we would see the flame search downwards slightly.
I just doubt that the effect is that strong. The surfaces are just too far apart for it to be some sort of effect.

[GrizzleBoy]

Is it possible that the sidepod flow is strong enough to push the exhaust flow past the horizontal line at top speeds, aiming the hot gases down at the tyres and therefore better retaining temperature.

While at slower speeds that introduce more probability of aggressive "slip" and wheelspin due to less downforce, the flow over the sidepods is not enough to push the hot gases towards the floor of the tunnel, towards the tyres and therefore avoid overheating them under load?

[raymondu999]

Unless we introduced the downwash effect similar to the air over the side pods in motion that would then push the flames down onto the cylinders for better effect.

10 degrees is the "standstill" angle of the plume. Downwash pushes it downwards until it's close enough to be affected by Coanda effect. That's the idea anyways.